- Kinetic study of the oxidation of propan-1-ol by alkaline hexacyanoferrate(III) catalyzed by ruthenium trichloride
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The oxidation kinetics of propan-1-ol by alkaline hexacyanoferrate(III) catalyzed by ruthenium trichloride were studied spectrophotometrically. The initial rate method was used for kinetic analysis. The reaction rate shows a fractional order in [oxidant] and [substrate] and a first-order dependence on [RuCl3]. The dependence on [OH-] is complicated. A reaction mechanism involving two active catalytic species is proposed. Each one of these species forms an intermediate complex with the substrate. The attack of these complexes by hexacyanoferrate(III) in rate-determining step produces a radical species which is further oxidized in the subsequent step.
- Mucientes,Poblete,Rodriguez,Santiago
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- Molecular Hydrogen Complexes in Catalysis: Highly Efficient Hydrogen Production from Alcoholic Substrates catalysed by Ruthenium Complexes.
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The complex catalyses the thermal production of hydrogen from a range of different alcoholic substrates with rates corresponding to up to >1000 catalyst turnover h-1; the mechanism of the reaction is discussed and possible reasons for the high efficiency of this catalyst including the fact that loss of hydrogen occurs from a molecular hydrogen complex, are explored.
- Morton, David,Cole-Hamilton, David J.
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- Bulky monophosphite ligands for ethene hydroformylation
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A wide range of monophosphite ligands was investigated in rhodium-catalyzed ethene hydroformylation. A stoichiometric gas mixture CO/H2/ethene 1:1:1 was used, the reaction being thus 100% atom economic. The reaction was found to be very selective and only propanal was formed under the reaction conditions studied. The most efficient catalytic system was L1-modified rhodium, and reaction parameters were optimized for this ligand. Under optimized catalytic conditions, reaction rates 10-15 times higher than those of the triphenylphosphine-modified system were obtained, demonstrating the high suitability of π-accepting ligands for this reaction. Stability tests, resistance toward water and acids in particular, showed the good stability of the selected phosphite L1. Notably, L1 was more stable than cyclic phosphites L6 and L13.
- Tricas, Hugo,Diebolt, Olivier,Van Leeuwen, Piet W.N.M.
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- Formation of C3H6 from the Reaction C3H7 + O2 and C2H3Cl from C2H4Cl + O2 at 297 K
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The generation of conjugate olefins from the reactions of propyl (reaction 1) or chloroethyl (reaction 2) radicals with O2 has been investigated as a function of total pressure (0.4-700 Torr) at 297 +/- 2 K.The experiments were carried out by UV irradiation of mixtures of propane (or ethyl chloride), Cl2, and O2 to generate alkyl radicals.Propylene from reaction 1 was measured by FTIR spectroscopy, while vinyl chloride from reaction 2 was monitored by both FTIR and gas chromatographic analysis.At pressures where the formation of propylperoxy radicals is near the high-pressure limit, the propylene yield from reaction 1 was inversely dependent on total pressure (YC3H6 P-0.68+/-0.03), proving that it is formed via rearrangement of an excited propylperoxy adduct that can also be stabilized by collision.The vinyl chloride yield decreased from 0.3 + /- 0.1 percent at 1 Torr to 0.1 percent at 10 Torr.Because the formation of chloroethylperoxy radicals is in the fall-off region over this pressure range, the vinyl chloride yield cannot be ascribed unambiguously to an addition-elimination process.The propylene yield from reaction 1 is 2-4 times smaller than the ethylene yield from C2H5 + O2 over the pressure range 0.4-100 Torr, while the vinyl chloride yield from reaction 2 is 40 times smaller between 1 and 10 Torr.This is consistent with more efficient stabilization of the excited propylperoxy relative to the ethylperoxy adduct caused by the presence of additional vibrational modes.The markedly smaller ambient temperature vinyl chloride yield from reaction 2 may result from a combination of more efficient stabilization resulting from the lower frequency of the C-Cl bond and reduction of the C-H bond reactivity upon Cl substitution.
- Kaiser, E. W.,Wallington, T. J.
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- The Photochemical Reaction of Benzocinnoline. IV. Comments on the Mechanism of 2,2'-Diaminobiphenyl Formation
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In order to determine the mechanism of 2,2'-diaminobiphenyl formation from benzocinnoline, effect of aldehyde on the reaction was examined.It is proposed that ethanal, which was generated from ethanol in the initial photoreduction, formed an adduct with 5,6-dihydrobenzocinnoline, and that the resulting adduct participated in the subsequent photo-induced 2,2'-diaminobiphenyl formation.
- Inoue, Hiroyasu,Hiroshima, Yukimi,Sakai, Toshihiko,Sakurai, Tadamitsu,Fukuda, Norio
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- A sensitive cataluminescence-based sensor using a SrCO3/graphene composite for n-propanol
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In this paper, we developed a cataluminescence-based sensor using SrCO3/graphene for sensitive and selective detection of n-propanol. The composite was characterized by X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, and gas adsorption. The sensor was coupled with a miniature vaporizing device to detect n-propanol in liquid samples. The experimental results revealed that the SrCO3/graphene sensor exhibited a sensitivity for n-propanol 5.8 times higher than that of pure SrCO3, indicating that the sensitivity of the SrCO3/graphene sensor was increased by adding graphene to SrCO3. The linear range of the sensor was 0.2 to 32 mg L-1 (r = 0.9987) with a limit of detection of 0.08 mg L-1. The sensor showed a rapid response of 2 s and a recovery time of 20 s, respectively. The sensor was used to analyze samples spiked with known concentrations of n-propanol. The concentrations of n-propanol in all samples were well quantified with satisfactory recoveries, indicating that the SrCO3/graphene sensor is a promising candidate for fast, sensitive, selective detection of n-propanol. We also discuss the possible mechanism based on the reaction products.
- Zhang, Qianchun,Meng, Feifei,Zha, Lin,Wang, Xingyi,Zhang, Guoyi
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- Dehydration of 1,3-butanediol over rare earth oxides
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Vapor-phase catalytic dehydration of 1,3-butanediol was investigated over rare earth oxides (REOs) calcined at different temperatures. In the dehydration of 1,3-butanediol over REOs such as Dy2O3, Ho2O3, Er2O3, Tm2O3, Yb2O3, Lu2O3, and Y2O3, 3-buten-2-ol and 2-buten-1-ol were preferentially produced. REOs exhibited different catalytic activities in the dehydration of 1,3-butanediol depending on their crystal structures. CeO2 showed the highest formation rate with the highest selectivity to the unsaturated alcohols among the REOs. Cubic REOs also selectively produced the unsaturated alcohols: cubic Er2O3, Yb2O3, and Lu2O3 showed high formation rate of the unsaturated alcohols. Since the formation rates of the unsaturated alcohols over Er2O3 and CeO2 were suppressed in CO2 and NH3 carrier gas flows more than in H2 flow, it is probable that the acid-base sites play a major role of the formation of the unsaturated alcohols.
- Gotoh, Hiroshi,Yamada, Yasuhiro,Sato, Satoshi
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- Hydrolysis of Aldal Acetals
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Eleven aldal acetals were synthesized, and the kinetics of their hydrolyses in water and in water-acetonitrile were studied as model systems for the hydrolysis of sucrose. α,α'-Diethoxypropyl ether (an aldal acetal) hydrolyzes in water without hemiacetal buildup.The reaction is not subject to general acid catalysis and the value of kD3O(+)/kH3O(+) = 2.44, both results being characteristic of an A1 mechanism.The energy of activation for the hydrolysis of α,α'-diethoxydipropyl ether was 84.98 kJ mol -1 in water and showed no temperature dependency over the range of 15 - 35 deg C.The structural effects for the hydrolysis of aldal acetals parallel those for acetal hydrolysis.
- Su Min Oon,Kubler, Donald G.
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- Thermolysis of Dioxetanes: 3,3-Diethyl-1,2-dioxetane and 3,3-Dimethyl-4-ethyl-1,2-dioxetane
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3,3-Diethyl-1,2-dioxetane (1) and 3,3-dimethyl-4-ethyl-1,2-dioxetane (2) were synthesized in 10percent yield by closure of the corresponding bromo hydroperoxides with base.Thermal decomposition of 1 and 2 produced only the expected cleavage products.Dioxetanes 1 and 2 directly produced high yields of triplet carbonyl products upon thermal decomposition similar to those reported for other alkyl-substituted dioxetanes.The activation parameters of the thermal decomposition of 1 and 2 were determined from Arrhenius plots (for 1, Ea = 24.9 kcal/mol, log A = 13.1, k60 deg C = 6.5*1E-4 s-1, ΔSexcit. = -0.8 eu; for 2, Ea = 24.7 kcal/mol, log A = 12.8, k60 deg C = 3.4*1E-4 s-1, ΔSexcit. = -2.3 eu).Also, trimethyl-1,2-dioxetane (3) and 3,3-dimethyl-1,2-dioxetane (4) were prepared and the activation parameters redetermined (for 3, Ea = 24.9 kcal/mol, log A = 13.0, k60 deg C = 4.5*1E-4 s-1, ΔSexcit. = -1.4 eu; for 4, Ea = 23.4, log A = 12.5, k60 deg C = 1.4*1E-4 s-1, ΔSexcit. = -3.6 eu).The results suggest that a major substituent effect on alkyldioxetane thermolysis is due to 3,3 steric interactions as opposed to 3,4 steric interactions.
- Baumstark, Alfons L.,Dunams, Tambra
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- Regioselective rhodium-diphosphine ligand catalyzed hydroformylation of vinyl acetate
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Rhodium-catalyzed hydroformylation of vinyl acetate with the use of diphosphine ligands was studied. A high regioselectivity (branched:linear of 99:1) and activity (TOF: 4000 h-1) under optimum conditions were achieved by using a 2,2'-bis(diphenylphosphino methyl)-1,1'-biphenyl ligand. The high turnover number (9200) obtained under mild conditions and stability of the catalyst indicates that it would be useful for industrial vinyl acetate hydroformylation.
- Liang, Haoran,Zhang, Lin,Zheng, Xueli,Fu, Haiyan,Yuan, Maolin,Li, Ruixiang,Chen, Hua
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- Dehydration of 1,2-propanediol to propionaldehyde over zeolite catalysts
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Dehydration of 1,2-propanediol has been investigated over a range of zeolite catalysts with different pore structures and acidity. The reaction forms part of a two-step process for the conversion of glycerol to propionaldehyde. The effects of reaction temperature, concentration, space velocity, and SiO 2/Al2O3 ratio have been studied. The medium pore size, unidirectional channel zeolites ZSM-23 and Theta-1 showed high activity and selectivity to propionaldehyde (exceeding 90 wt% at 300-350 °C). Selectivity to the intermolecular dehydration product 2-ethyl-4-methyl-1,3-dioxolane was high at lower temperatures for all the zeolites, but decreased to a low value at higher temperatures and lower GHSV. The results are discussed in relation to the reaction mechanism and zeolite structures. Significant deactivation was observed for higher 1,2-propanediol partial pressures, which was partially mitigated by the addition of steam.
- Zhang, Dazhi,Barri, Sami A.I.,Chadwick, David
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- Rates of Reaction of Hydroxyalkyl Radicals with Molecular Oxygen
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The rate constants for the reactions of a series of hydroxyalkyl radicals with molecular oxygen have been measured at room temperature (296 +/- 4 K) by laser flash photolysis-photoionization mass spectrometry.Measured rate constants are k = (1.17 +/- 0.12) * 1E-11, k = (2.61 +/- 0.41) * 1E-11, k = (1.16 +/- 0.22) * 1E-11, k = 3.82 +/- 0.60) * 1E-12, and k = (3.71 +/- 0.62) * 1E-11, all in units of cm3 molecule-1 s-1.These reactions seem to be at high-pressure limits at experimental pressures (1.3-5.5 Torr of He).Although it has been suggested in previous studies that the reaction mechanisms are different between α- and β-hydroxyalkyl radicals (H atom abstractions and recombinations, respectively), the present rates of reaction involving both α- and β-hydroxyalkyl radicals were found to correlate well with the ionization potentials of the radicals.This results suggests that the rate constants for all these reactions are largely controlled by the long-range forces similar to the reactions of alkyl radicals with molecular oxygen.
- Miyoshi, Akira,Matsui, Hiroyuki,Washida, Nobuaki
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- Hydroformylation of Ethylene Catalysed by Ruthenium Complexes Supported on Zeolite
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Hydroformylation of ethylene is catalysed by zeolite-supported ruthenium compounds and gives propan-1-al and propan-1-ol as major products.
- Jackson, Peter F.,Johnson, Brian F. G.,Lewis, Jack,Ganzerla, Renso,Lenarda, Maurizo,Graziani, Mauro
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- Selective oxidation of: N -buthanol to butyraldehyde over MnCo2O4spinel oxides
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Partial oxidation of n-butanol to butyraldehyde, propionaldehyde and acetaldehyde over MnCo2O4 spinel oxides has been investigated. Physicochemical characteristics of samples, prepared by co-precipitation with different amounts of precipitating agent, were studied by XRD, N2 adsorption-desorption isotherms, FT-IR, SEM and XPS. The ratio between the precipitating agent and the precursors has a considerable influence both on the structure, which is evidenced by XRD, due to switching from a crystalline structure to an amorphous one and on the surface (XPS) by an obvious change in the ratio Co3+/Co2+ and Mn4+/Mn3+ and in the content of oxygen vacancies. The reaction rate is not influenced by the oxygen pressure, emphasizing that n-butanol oxidation occurs through the Mars van Krevelen mechanism. The conversion of n-butanol and yield of butyraldehyde are directly proportional to the cobalt content on the surface, while the propionaldehyde yield is proportional to the Mn4+/Mn3+ ratio.
- Chen, Shaojiang,Mitran, Gheorghita,Seo, Dong-Kyun
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- Highly selective supramolecular catalyzed allylic alcohol isomerization
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A supramolecular tetrahedral assembly Na12[Ga4L6] (L = 1,5-bis-catecholamide naphthalene) has been found to selectively encapsulate monocationic rhodium complexes of the appropriate size and shape. Encapsulation within the chiral environment of the host directly affects the symmetry of the rhodium guest and can be well characterized by NMR spectroscopy. The rhodium complexes were found to be catalytically active for the isomerization of allylic alcohols. Investigations into the catalytic activity of the encapsulated rhodium guests have shown that the constrained cavity of the host exerts a strong influence on the reactivity at the metal center. The supramolecular host prevents substrates of the wrong size and shape from entering the host cavity and reacting with the encapsulated metal center, while substrates of the correct dimensions are allowed ready access. These results suggest that the metal center remains in the active site of the host while reactants and products freely and rapidly access the host cavity. Copyright
- Leung, Dennis H.,Bergman, Robert G.,Raymond, Kenneth N.
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- Simple Enols. 4. Generation of Some New Simple Enols in Solution and the Kinetics and Mechanism of Their Ketonization
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The simple enols -2-hydroxypropene, -3-chloro-2-hydroxypropene, 2,2-dichlorovinyl alcohol, and hydroxypropadiene have been generated from reactive precursors in solution and characterized by NMR spectroscopy.The kinetics of ketonization of 3-chloro-2-hydroxypropene, hydroxypropadiene, and of the previously described (Z)-prop-1-en-1-ol and 2-methylprop-1-en-1-ol were studied by UV spectrophotometry at 15 deg C.It was found that k0 varied with pH according to the equation k0 = kH2O + (kH+10-pH) + (kHO-KW)/10-pH and values of kH2O, kH+, and kHO- were evaluated for these four enols.Solvent isotope effects, kH+/kD+, were determined and the acid-catalyzed ketonization of 3-chloro-2-hydroxypropene and 2-methylprop-1-en-1-ol were studied in water-Me2SO4 mixtures.The kinetics of the acid-catalyzed hydrolyses of the methyl enol ethers that correspond to these enols were also investigated.It is concluded that the kinetic results were best explained by concerted mechanism for the hydronium ion catalyzed and spontaneous ketonization and by a stepwise mechanism for the hydroxide ion catalyzed ketonization.
- Capon, Brian,Siddhanta, Arup K.,Zucco, Cesar
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- Photocatalysis on Native and Platinum-Loaded TiO2 and ZnO Catalysts - Origin of Different Reactivities on Wet and Dry Metal Oxides -
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Substantial differences in photocatalytic reactivity were observed on powdered TiO2 and ZnO, both Pt-loaded and unloaded, in the photocatalytic hydrogenation of CH3CCH and C3H6 in the presence of H2O.Similar reactivity was observed, however, in the photocatalytic oxidation of i-C4H8 and C3H6 by O2 on these same catalysts.Photoluminescence of TiO2 and ZnO in the presence and the absence of H2O and/or O2 indicate that H2O causes a downward band bending to increase the efficiency of recombination of photogenerated electrons and holes, with a greater effect being observed on ZnO than on TiO2.These results, together with the direct detection of reaction intermediates by ESR, are rationalized by differences in the yields of the photogenerated intermediates, i. e., H. (formed from trapped electrons) and OH. (formed from trapped holes).The steady state concentrations of these intermediates depend on the degree of the positively-charged adducts on the surfaces of these oxides.The addition of O2 causes an upward band bending of the oxide and suppresses recombination of photo-generated electrons and holes, by formation of negatively-charged surface adducts.With similar degrees of band bending, TiO2 and ZnO produce almost the same photocatalytic reactivities as are observed for these oxides as dry systems.
- Anpo, Masakazu,Chiba, Katsuichi,Tomonari, Masanori,Coluccia, Salvatore,Che, Michel,Fox, Marye Anne
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- Single Turnover Epoxidation of Propylene by α-Complexes (FeIII-O?)α on the Surface of FeZSM-5 Zeolite
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Single turnover epoxidation of propylene by α-complexes (FeIII-O?)α on the surface of FeZSM-5 zeolite was studied in the temperature range from +25 °C to -60 °C. After extraction, the reaction products were identified by gas chromatography (GC), gas chromatography-mass spectrometry (GC-MS), and nuclear magnetic resonance (NMR). The reaction C3H6 + (FeIII-O?)α was shown to proceed in a similar way as the oxidation of propylene by the enzyme methane mono-oxygenase sMMO, i.e., via the addition of active oxygen over C=C bonds to yield propylene oxide, not affecting a weakly bound allylic hydrogen. This result, together with the previous results on the hydroxylation of methane and other hydrocarbons, shows the (FeIII-O?)α to be the unique functional model of compound Q, the key intermediate of sMMO. In another aspect, the results relate to the low selectivity problem of the silver catalyst in propylene epoxidation and raise doubts about the presently accepted mechanism explaining an adverse effect of allylic hydrogen.
- Panov, Gennady I.,Starokon, Eugeny V.,Parfenov, Mikhail V.,Pirutko, Larisa V.
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- In Situ Study of the Reactivity of RhI(CO)2/SiO2 Derived from Rh6(CO)16 for CO Insertion
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The formation of RhI(CO)2 from Rh6(CO)16 impregnated on SiO2 and its reactivity toward C2H4/H2 have been investigated by in situ infrared spectroscopy.Impregnation of Rh6(CO)16 on partially dehydroxylated SiO2 results in a partially decarbonylated structure exhibiting the terminal and bridging carbonyl bands at 303 K; surface H2O reacts with Rh6(CO)16 to form RhI(CO)2 at 373-423 K.The terminal carbonyls show no reactivity toward C2H4/H2 at 303 K while they begin to react with C2H4/H2 to produce adsorbed acyl and propionaldehyde at 323 K.Under the same condition, the terminal carbonyls are less active for CO insertion than gem-dicarbonyl derived from Rh6(CO)16 and linear CO on the surface of Rh crystallites.The low reactivity of the terminal carbonyls compared to that of linear CO may be attributed to the lack of neighboring Rh sites for adsorbed alkyl, C2H4 and hydrogen.Steady-state ethylene hydroformylation reveals that the Rh is in an oxidized state and that hydrogenation of acyl species is rate limiting at 393 K and 1 MPa.Increasing reaction temperature to 513 K leads to the reduction of oxidized Rh sites, hydrogenation of adsorbed acyl, and an enhancement of propionaldehyde selectivity.
- Srinivas, Girish,Chuang, Steven S. C.
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- The Propylene Oxide Rearrangement Catalyzed by the Lewis Acid Sites of ZSM-5 Catalyst with Controllable Surface Acidity
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The rearrangement of propylene oxide is greatly affected by the acidity of the catalyst. ZSM-5 zeolite with easily regulated surface acidity was used to catalyze the reaction with propionaldehyde as main product. The difference in the ratio of silica to alumina resulted in significant changes in the acidity. The results show that the ratio of the amount of Lewis acid sites (LAS) to the amount of Br?nsted acid sites (BAS) has a great positive influence on the catalytic performance. When the ratio of silica to alumina reaches 50, the ratio of the LAS to BAS reaches the maximum value of 18.6, the catalytic performance is excellent. The in-situ diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) was employed to study the adsorption and reaction behavior of propylene oxide on the ZSM-5 catalyst. Results showed that the epoxy ring of propylene oxide first adsorbs on the Lewis acid site (Al atom with empty electron orbital) of ZSM-5 catalyst to form an intermediate with the bond between C=O and C–O which then converts to the propionaldehyde. The Lewis acid sites is of great importance for the reaction. [Figure not available: see fulltext.].
- Liang, Mengnan,Zhu, Xiangshuai,Ma, Weihua
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- Promoting effect of Al on tethered ligand-modified Rh/SiO2 catalysts for ethylene hydroformylation
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A Rh/SiO2 catalyst with excellent activity and stability for ethylene hydroformylation was developed by modifying with tethered diphenylphosphinopropyl and doped with an Al promoter. The catalyst was characterized by means of N2 adsorption/desorption isotherms, transmission electron microscope, NH3 temperature programmed desorption, Fourier transform infrared spectroscopy and solid-state nuclear magnetic resonance. Experimental results showed that the existence of the Al promoter inhibited the growth of Rh particles, increased the number of exposed Rh atoms, changed the acidity of the catalyst surface, promoted in situ formation of active species that were similar to their corresponding homogeneous counterparts, and enhanced electron density of the P atom in the phosphine ligand.
- Liu, Jia,Yan, Li,Ding, Yunjie,Jiang, Miao,Dong, Wenda,Song, Xiangen,Liu, Tao,Zhu, Hejun
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- Direct formation of propanol from a dilute ethylene feed via reductive-hydroformylation using homogeneous rhodium catalysts at low feed pressures
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This work details a system for the direct production of propanol from a dilute ethylene stream by reductive hydroformylation catalyzed by soluble rhodium complexes coordinated to tri-aryl or tri-alkyl phosphines. Typically, in commercial production, normal alcohols are produced from primary olefins via a two step process consisting of hydroformylation of the olefins to aldehydes, followed by subsequent hydrogenation of the aldehydes to the corresponding alcohols. This work describes a method to produce propanol directly from dilute ethylene feeds. In addition, the partial pressures of the syngas used in these experiments are significantly lower (approximately an order of magnitude) than reported for nearly all of the other rhodium catalyzed reductive- hydroformylation systems (0.7-70 atm vs. ～20-700 atm).
- Rodriguez, Brandon A.,Tenn III, William J.
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- Selective oxidation of propylene to propylene oxide or propionaldehyde over au supported on titanosilicates in the presence of H2 and O2
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Gas phase selective oxidation of propylene to propylene oxide (PO) or propionaldehyde (PA) in the presence of H2 and O2 has been carried out with a propylene conversion in the range of 0.5-3.7% over gold deposited on titanosilicates
- Uphade,Tsubota, Susumu,Hayashi, Toshio,Haruta, Masatake
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- Location of active sites for 3-pentanone formation during ethene hydroformylation on Rh/active-carbon catalysts
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In ethene hydroformylation over Rh/active carbon prepared from RhCl3, 3-pentanone was formed in addition to propanal, which was a common product in the reaction. In the case of propene hydroformylation, however, butanal was exclusively formed and no appreciable formation of ketones was observed. On the catalyst treated with CO at 473 K, both activities for propanal and butanal formation were observed to be higher than those on the catalyst untreated. An approximate linear relation between the activity for propanal formation and that for butanal formation was observed, indicating that the active sites for aldehyde formation can catalyze the reaction for both ethene and propene. On the other hand, the activity for 3-pentanone formation was reduced by the CO treatment. These results indicate that the transformation of active species for 3-pentanone formation into the active species for aldehyde formation was induced by the CO treatment. On the catalyst treated with CO, a value for n/iso- ratio in butanal formed was observed to be higher than that on the catalyst untreated. These results suggest the formation of new active Rh particles in the narrower pores. On the basis of the results obtained, the active species for 3-pentanone formation was thought to be located in the narrow pores, where the formation of reaction intermediates of C7-ketones from propene would be strongly suppressed because of their bulky structure compared with that for 3-pentanone.
- Sakagami, Hirotoshi,Ohta, Naoki,Endo, Shunsuke,Harada, Teruyuki,Takahashi, Nobuo,Matsuda, Takeshi
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- Solvent effects in acid-catalyzed biomass conversion reactions
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Reaction kinetics were studied to quantify the effects of polar aprotic organic solvents on the acid-catalyzed conversion of xylose into furfural. A solvent of particular importance is g-valerolactone (GVL), which leads to significant increases in reaction rates compared to water in addition to increased product selectivity. GVL has similar effects on the kinetics for the dehydration of 1,2-propanediol to propanal and for the hydrolysis of cellobiose to glucose. Based on results obtained for homogeneous Bronsted acid catalysts that span a range of pKa values, we suggest that an aprotic organic solvent affects the reaction kinetics by changing the stabilization of the acidic proton relative to the protonated transition state. This same behavior is displayed by strong solid Bronsted acid catalysts, such as H-mordenite and H-beta.
- Mellmer, Max A.,Sener, Canan,Gallo, Jean Marcel R.,Luterbacher, Jeremy S.,Alonso, David Martin,Dumesic, James A.
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- Acid-Catalyzed Hydrolysis of Vinyl Acetals. Reaction through the Acetal Rather Than the Vinyl Ether Functional Group
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The hydrolysis of three vinyl acetals, 9-methoxy-1-oxacyclonon-2-ene and the cis- and trans-1-propenyl methyl acetals of acetaldehyde, was monitored by 1H NMR spectroscopy in dilute minaral acid solution, and rates of the reactions were also measured in dilute mineral acids and semicarbazide, acetic acid, and cacodylic acid buffers.The NMR spectra showed biphasic changes, which could be assigned to the formation and decay of enol intermediates generated by initial acetal group hydrolysis.Biphasic absorbance changes also appeared in the ultraviolet spectra of thesesubstrates reacting in dilute mineral acid solution, and rate constants for two successive reactions could be evaluated.These rate constants were assigned to the individual reaction steps, and further support for the assigned reaction path was obtained, by comparison with rate constants measured in the buffer solutions, where acetal hydrolysis was the only reaction observed, and also by comparison with rates of ketonization of the enols generated independently from the corresponding trimethylsilyl enol ethers.Solvent isotope effects provided yet more evidence for the assigned reaction path.Estimates of rates of hydrolysis of the vinyl ether groups of these substrates show that these vinyl ether functions are too unreactive to compete with acetal hydrolysis.Simultaneous vinyl ether and acetal hydrolysis, however, does occur in the case of 6-membered cyclic vinyl acetals, such as 2-methoxy-2,3-dihydropyran, and this is probably because intramolecular recapture of the alkoxycarbocationic intermediate slows acetal hydrolysis in the case of these smaller ring compounds.
- Chiang, Y.,Chwang, W. K.,Kresge, A. J.,Yin, Y.
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- Fast Generation and Stabilization of 2-Methylprop-1-en-1-ol with ClO4
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2-Methylprop-1-en-1-ol is rapidly generated and stabilized during the isomerization of 2-methylprop-2-en-1-ol to 2-methylpropanal with ClO4.
- Park, Jeonghan,Chin, Chong Shik
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- Partial Oxidation of Propane over B-P Mixed Oxide Catalysts
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B-P mixed oxide was the active and selective catalyst for partial oxidation of propane.The selectivity and the yield of the partial oxidation products (propionaldehyde, acetone, acetaldehyde, propylene, etc.) were 50percent and 27percent , respectively, under the reaction conditions; T=806 K, P(C3H8)=20 kPa, P(O2)=30 kPa, and W/F=0.67 g h l-1.
- Komatsu, Takayuki,Uragami, Yuji,Otsuka, Kiyoshi
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- Kinetics and mechanism of oxidation of some aliphatic esters by sodium n-bromo-p-toluenesulfonamide
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The kinetics of oxidation of methyl, ethyl, n-propyl, isopropyl, and n-butyl acetates to acetic acid and the corresponding aldehyde by the title oxidant in aqueous HCl medium at 40°C has been studied. The reaction shows first-order with respect to [oxidant] and fractional orders in [H+] and [ester]. An isokinetic relationship was observed with β = 374 K indicating enthalpy as the rate controlling factor. Attempts have been made to arrive at a linear free energy relationship through the Taft treatment. Electron releasing groups in the ester moiety increase the rate with ρ = -9.88. A two-pathway mechanism, consistent with the obs d kinetic data, has been proposed.
- Rangappa,Mythily,Mahadevappa,Gowda
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- Homogeneous Catalysis of the Reppe Reaction with Iron Pentacarbonyl: The Production of Propionaldehyde and 1-Propanol from Ethylene
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The Reppe hydroformylation of ethylene to produce propionaldehyde and 1-propanol in basic solutions containing Fe(CO)5 as a catalyst has been studied under carefully controlled conditions at temperatures ranging from 110 to 140 deg C.Propionaldehyde is the principal product formed when NaOH is used as the base.The rate of reaction is found to increase with ethylene concentration and is second order with respect to Fe(CO)5.The reaction is inhibited by CO.The increase in reaction rate with temperature corresponds to an activation energy of 31 kcal/mol.Infrared spectra indicate that HFe(CO)4- and Fe(CO)5 are present in the solution phase under reaction conditions.The experimental results are shown to be consistent with a mechanism in which the rate-determining step involves a binuclear iron carbonyl derivative.The substitution of (C2H5)3N for NaOH facilitates the reduction of propionaldehyde to form 1-propanol but results in a slower rate for the overall reaction.
- Massoudi, R.,Kim, J. H.,King, R. B.,King, Allen D.
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- Steam-activated FeMFI zeolites as highly efficient catalysts for propane and N2O valorisation via oxidative conversions
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The reaction between C3H8 and N2O over steam-activated FeMFI zeolites leads to high yields towards propene (24%) and propionaldehyde (6%) at 773-798 K.
- Perez-Ramirez, Javier,Kondratenko, Evgueni V.
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- Direct synthesis of isobutyraldehyde from methanol and ethanol on Cu-Mg/Ti-SBA-15 catalysts: The role of Ti
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Herein, Cu-Mg/Ti-SBA-15 catalysts were prepared through the modification of Cu and Mg to mesoporous Ti-SBA-15 zeolites with different Ti/Si ratios and used for the synthesis of isobutyraldehyde (IBA) from methanol and ethanol. The catalysts were characterized via various techniques including XRF, XRD, TEM, N2 sorption, CO2-TPD, FT-IR, and XPS. With an increase in Ti content, CuO was well dispersed accordingly, and the amounts and strength of the basic sites were reduced. However, an excess introduction of Ti led to the accumulation of single TiO2 crystals, inducing a decrease in the surface area and a deviation from the regular pattern such that the binding energies of Cu 2p, Mg 2p, and Si 2p shifted to lower values. This precisely affected the catalytic behaviors of the prepared catalysts synergistically. The catalyst stability was improved with the increasing Ti content accordingly, and over the catalyst with a Ti/Si ratio = 4/15, the IBA selectivity, after 24 h reaction, could still reach 25%, which was the best durability ever reported for IBA synthesis from methanol and ethanol. The catalytic performance test conducted using a regenerated catalyst and IR measurement of the spent catalyst indicated that carbon deposition on the catalyst surface could be depressed to some extent with the increasing Ti content.
- Zhang, Junfeng,Zhang, Meng,Wang, Xiaoxing,Zhang, Qingde,Song, Faen,Tan, Yisheng,Han, Yizhuo
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- FTIR kinetic, product, and modeling study of the OH-initiated oxidation of 1-butanol in air
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A kinetic and product study was conducted on the reaction of OH radicals with 1-butanol in a 480 L indoor photoreactor and in the EUPHORE outdoor smog chamber in Valencia, Spain. Long path in situ FTIR spectroscopy and GC with photoionization detection were used to analyze reactants and products. The reaction products observed were butanal, propanal, ethanal, and formaldehyde. The results supported the probable formation of 4-hydroxy-2-butanone. Propanal, ethanal, and formaldehyde could also be formed in secondary reactions of some of the primary aldehydic products. A detailed atmospheric degradation mechanism was constructed and evaluated against experimental data by chemical box model calculations based on product studies. The difference between modeled and measured formaldehyde concentration was always x developed in this study showed the experimental data generated in a large outdoor smog chamber well and could be used for the purposes of modeling oxidant formation in urban air masses, either in an explicit form or after suitable lumping, in chemical modules applied in chemistry transport models.
- Geiger,Cavalli,Barnes,Becker
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- FTIR studies of iron-carbonyl intermediates in allylic alcohol photoisomerization
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The 532 or 355 nm laser-induced photoisomerization of allylic alcohols to aldehydes catalyzed by [Fe3(CO)12] or [Fe(CO) 4PPh3] in hexane was investigated. The Fourier transform infrared (FTIR) absorption spectra of iron-carbonyl intermediate species such as [Fe(CO)5], [Fe(CO)4(RC3H4OH)], and more importantly the π-allyl iron-carbonyl hydride species [FeH(CO) 3(R-C3H3OH)] (R = H, Me, Ph) were recorded during the catalytic process using [Fe3(CO)12] as the catalytic precursor. When [Fe(CO)4PPh3] was photolyzed with 355 nm, [FeH(CO)3(R-C3H3OH)] was also generated indicating the common occurrence of the species in these two systems. The π-allyl hydride species is long believed to be a key intermediates and its detection here lends support to the π-allyl mechanism of the photoisomerization of allyl alcohols.
- Chong, Thiam Seong,Tan, Sze Tat,Fan, Wai Yip
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- Studies on the autocatalyzed oxidation of amino acids by peroxomonosulfate
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The kinetics of oxidation of six α-amino acids (AA) by peroxomonosulfate (PMS) ion at pH 4.2 and 35°C are investigated once again. The rate of disappearance of peroxomonosulfate at constant [AA] adn [H+] follows the equation d[PMS]t/dt = k1obs[PMS]t + k2obs[PMS]t([PMS]0 - [PMS]t) The experimental results suggest that the hydroperoxide intermediate formed by the reaction between the hydrated form of aldehyde and PMS is more reactive and is responsible for the autocatalysis. The hydroperoxide reacts with the amino acid in the rate-determining step. This observation is contrary to the earlier explanation that the autocatalysis is due to the Schiff's base from amino acid and aldehyde. The effect of H+, the structure of the aldehyde, etc. on the rate constants are discussed.
- Kannan, R. Sayee,Ramachandran
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- Kinetic and mechanistic studies of some aliphatic amines' oxidation by sodium N-bromo-p-toluenesulfonamide in hydrochloric acid medium
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Oxidations of n-propyl, n-butyl, isobutyl, and isoamyl amines by bromamine-T (BAT) in HCl medium have been kinetically studied at 30°C. The reaction rate shows a first-order dependence on [BAT], a fractional-order dependence on [amine], and an inverse fractional-order dependence on [HCl]. The additions of halide ions and the reduction product of BAT, p-toluenesulfonamide, have no effect on the reaction rate. The variation of ionic strength of the medium has no influence on the reaction. Activation parameters have been evaluated from the Arrhenius and Eyring plots. Mechanisms consistent with the preceding kinetic data have been proposed. The protonation constant of monobromamine-T has been evaluated to be 48 ± 1. A Taft linear free-energy relationship is observed for the reaction with ρ* = -12.6, indicating that the electron-donating groups enhance the reaction rate. An isokinetic relationship is observed with β = 350 K, indicating that enthalpy factors control the reaction rate.
- Ananda,Jagadeesha,Puttaswamy,Venkatesha,Vinod,Made Gowda
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- Rate Constants and Mechanism for Reactions of Ketenes with OH Radicals in Air at 299 +/- 2K
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Rate constants for reactions of OH radicals with four kinds of simple ketenes (ketene, methylketene: MK, ethyketene: EK, and dimethylketene: DMK) were measured in 1 atm of air at 299 +/- 2K by use of a competitive reaction method.The photolysis of CH3ONO in air was used to generate OH radicals.The rate constants for OH reactions obtained are (1.8+/-0.2)x10-11, (7.6+/-1.4)x10-11, (11+/-3)x10-11 and (10+/-3)x10-11 cm3 molecule-1s-1 for ketene, MK, and DMK, respectively.The major product was a carbonyl compound; HCHO from ketene, CH3CHO from MK, and CH3COCH3 from DMK; the yield was cca. 80percent, 72+/-17percent, and 70+/-3percent respectively.t is proposed that the reaction proceeded mainly via an OH addition to the olefinic carbons of ketenes and the adduct decomposes to give a carbonyl compound and CO as final products in air.
- Hatakeyama, Shiro,Honda, Shigeo,Washida, Nobuaki,Akimoto, Hajime
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- ON HYDROGEN ACTIVATION IN THE HYDROFORMYLATION OF OLEFINS WITH Rh4(CO)12 OR Co2(CO)8 AS CATALYST PRECURSORS
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In the hydroformylation of ethylene with approximately equimolar H2/D2 mixtures and Rh4(CO)12 or Co2(CO)8 as the catalyst precursor about 50percent of propionaldehyde-d1 was formed.The propionaldehyde-d0/d2 ratio was ca. 3 for rhodium and ca. 2.6 for the cobalt catalyst.On the basis of the results and assuming that there is no rapid M(H)2/M(D)2 scrambling, activation of hydrogen through M(H)2 or M(H)2 (olefin) complexes can be excluded.
- Pino, Piero,Oldani, Felix,Consiglio, Giambattista
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- Epoxidation of propene by gaseous oxygen over silica and Mg-loaded silica under photoirradiation
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Silica was found to promote the photooxidation of propene by molecular oxygen, yielding acetaldehyde, propylene oxide, and propionaldehyde. The yield of and selectivity to propylene oxide were improved significantly by modification of silica with 1 wt% magnesium oxide loading. The product selectivity was affected by the amount of magnesium and the preparation method. Mg K-edge XANES and phosphorescence spectra indicated that the active sites on the Mg-loaded silica for epoxidation of propene are highly dispersed and isolated magnesium oxide species. The photoactive sites on bare silica are briefly discussed.
- Yoshida, Hisao,Tanaka, Tsunehiro,Yamamoto, Muneshige,Yoshida, Tomoko,Funabiki, Takuzo,Yoshida, Satohiro
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- A Striking Effect of H2S Treatment of Catalyst on the Improvement of Acetic Acid Selectivity in High Pressure CO Hydrogenation over Rh-Ir-Mn-Li/SiO2
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A selective synthesis of acetic acid from syngas was investigated.Acetic acid was produced with nearly 70percent selectivity in carbon efficiency over H2S-modified Rh-Ir-Mn-Li/SiO2 catalyst at the expense of the activity.The role of H2S modification was also studied.
- Nakajo, Tetsuo,Arakawa, Hironori,Sano, Ken-ichi,Matsuhira, Shinya
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- Thin-layer Supported Nafion Catalysts for the Partial Oxidation of Light Alkanes
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Thin-layer carbon supported Nafion-H catalysts were found to be active and highly selective for the partial oxidation of C1-C3 alkanes under mild conditions and in the presence of aqueous H2O2.A three phase catalytic membrane reactor (3PCMR) has been used.
- Frusteri, Francesco,Parmaliana, Adolfo,Arena, Francesco,Giordano, Nicola
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- EFFECTS OF VARIOUS PRETREATMENTS OF THE Rh-Y ZEOLITE ON THE CATALYTIC ACTIVITY FOR ETHYLENE HYDROFORMYLATION UNDER ATMOSPHERIC PRESSURE
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The active species for ethylene hydroformylation formed in the Y zeolite are extremely stable under the reaction conditions and the steady activity lasts more than one month.The catalytic activity is remarkably affected by the pretreatment of the catalyst; the He-H2 pretreatment at 338-453 K enhances the activity while the He-CO or He-CO-C2H4 pretreatment at 400 K reduces it.
- Takahashi, Nobuo,Hasegawa, Shuichi,Hanada, Norio,Kobayashi, Masayoshi
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- Syngas conversion to ethanol over a mesoporous Cu/MCM-41 catalyst: Effect of K and Fe promoters
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Transportation fuels such as ethanol can be obtained through thermochemical processing of biomass. Interest in the development of more selective catalysts for the conversion of biomass-derived syngas (H2?+?CO) to ethanol is increasing in both academia and industry. In this work, we have evaluated the performances of K and Fe as metal promoters of a mesoporous Cu/MCM-41 catalyst and their effects on the product selectivity and especially on ethanol formation. The metal loading was 29?wt.% Cu, 2?wt.% Fe and 1.6?wt.%?K. The catalysts were tested at 300?°C, 20?bar and gas-hourly-space-velocities in the range of 1500–30000?mlsyngas/gcat h; under these conditions the syngas conversion level was between 2 and 11%. The non-promoted Cu/MCM-41 catalyst showed interesting selectivity toward oxygenated compounds, mostly methanol. The addition of K as promoter increases the selectivity toward methanol even more, while the addition of Fe as promoter favors the formation of hydrocarbon compounds. When both K and Fe as promoters are incorporated into the Cu/MCM-41 catalyst, the reaction rate to oxygenated compounds is notably increased, especially for ethanol. The space time yield for ethanol for the Cu/MCM-41 catalyst is 0.3?×?10?5 carbon-mol/gcath which increases to 165.5?×?10?5 carbon-mol/gcath for the Cu-Fe-K/MCM-41 catalyst. From XPS analysis, the Cu-Fe-K/MCM-41 catalyst was found to have the following atomic composition: Cu0.34Fe0.08K0.08Si1.00. The promoting effect of both K and Fe, may be related to an increased reaction rate toward CO non-dissociation and CO-dissociation paths, respectively, which is beneficial for the ethanol formation. Further catalytic results, catalyst characterization and discussion of results are presented in this work.
- Lopez, Luis,Montes, Vicente,Ku?ar, Henrik,Cabrera, Saul,Boutonnet, Magali,J?r?s, Sven
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- Tandem hydroformylation/hydrogenation over novel immobilized Rh-containing catalysts based on tertiary amine-functionalized hybrid inorganic-organic materials
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Non-phosphorous rhodium-containing catalysts for direct conversion of olefins to alcohols via tandem hydroformylation/hydrogenation have been designed and synthesized. Interaction between Rh(acac)(CO)2 and tertiary amino groups on the surface of mesoporous hybrid organic-inorganic supports yielded materials which were successfully used in the tandem process. Data obtained for a selected catalyst KN demonstrate that rhodium is in the Rh+1 state highly dispersed on the surface and is bonded with nitrogen atoms both before and after use. Evaluation of the catalytic performance shows high activity (hydroformylation TOF 312 h?1), chemoselectivity and stable hydroformylation yield at least in the first 5 cycles with a decrease in alcohol selectivity. The influence of temperature, reaction time, total pressure, and molar CO/H2 ratio of syngas on oxygenate yields is described. Type of the hydroformylation active sites and possible pathways for the observed decrease in hydrogenation are discussed.
- Gorbunov, Dmitry,Karakhanov, Eduard,Maximov, Anton,Naranov, Evgeny,Nenasheva, Maria,Rosenberg, Edward
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- Enhancing the activity, selectivity, and recyclability of Rh/PPh3 system-catalyzed hydroformylation reactions through the development of a PPh3-derived quasi-porous organic cage as a ligand
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In contrast to heterogeneous network frameworks (e.g., covalent organic frameworks and metal-organic frameworks) and porous organic polymers, porous organic cages (POCs) are soluble molecules in common organic solvents that provide significant potential for homogeneous catalysis. Herein, we report a triphenylphosphine-derived quasi-porous organic cage (denoted as POC-DICP) as an efficient organic molecular cage ligand for Rh/PPh3 system-catalyzed homogeneous hydroformylation reactions. POC-DICP not only displays enhanced hydroformylation selectivity (aldehyde selectivity as high as 97% and a linear-to-branch ratio as high as 1.89) but can also be recovered and reused via a simple precipitation method in homogeneous reaction systems. We speculate that the reason for the high activity and good selectivity is the favorable geometry (cone angle = 123.88°) and electronic effect (P site is relatively electron-deficient) of POC-DICP, which were also demonstrated by density functional theory calculations and X-ray absorption fine-structure characterization.
- Wang, Wenlong,Li, Cunyao,Zhang, Heng,Zhang, Jiangwei,Lu, Lanlu,Jiang, Zheng,Cui, Lifeng,Liu, Hongguang,Yan, Li,Ding, Yunjie
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p. 1216 - 1226
(2021/03/06)
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- Green, homogeneous oxidation of alcohols by dimeric copper(II) complexes
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Three pyrazole derivatives, 3,5-dimethyl-1H-pyrazole (DMPz) (I), 3-methyl-5-phenyl-1H-pyrazole (MPPz) (II), and 3,5-diphenyl-1H-pyrazole (DPPz) (III), were prepared via reacting semicarbazide hydrochloride with the acetylacetone, 1-phenylbutane-1,3-dione, and 1,3-diphenylpropane-1,3-dione, respectively. Complexes 1–3 were isolated by reacting CuCl2·2H2O with I–III, respectively, and characterized by CHNS elemental analyses, FT-IR, UV-Vis, 1H and 13C NMR, EPR spectra, and TGA/DTA. Molecular structures of the pyrazole derivatives I–III and copper(II) complexes 2 and 3 were studied through single-crystal XRD analysis to confirm their molecular structures. Overlapping of hyperfine splitting in the EPR spectra of the dimeric copper(II) complexes 1–3 indicates that both copper centers do not possess the same electronic environment in solution. The copper(II) complexes are dimeric in solid state as well as in solution and catalyze the oxidation of various primary and secondary alcohols selectively. Catalysts 1–3 show more than 92% product selectivity toward ketones during the oxidation of secondary alcohols. Surprisingly primary alcohols, which are relatively difficult to oxidize, produce carboxylic acid as a major product (48%–90% selectivity) irrespective of catalytic systems. The selectivity for carboxylic acid rises with decreasing the carbon chain length of the alcohols. An eco-friendly and affordable catalytic system for oxidation of alcohols is developed by the utilization of H2O2, a green oxidant, and water, a clean and greener solvent, which is a notable aspect of the study.
- Maurya, Abhishek,Haldar, Chanchal
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p. 885 - 904
(2020/12/18)
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- Dual utility of a single diphosphine-ruthenium complex: A precursor for new complexes and, a pre-catalyst for transfer-hydrogenation and Oppenauer oxidation
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The diphosphine-ruthenium complex, [Ru(dppbz)(CO)2Cl2] (dppbz = 1,2-bis(diphenylphosphino)benzene), where the two carbonyls are mutually cis and the two chlorides are trans, has been found to serve as an efficient precursor for the synthesis of new complexes. In [Ru(dppbz)(CO)2Cl2] one of the two carbonyls undergoes facile displacement by neutral monodentate ligands (L) to afford complexes of the type [Ru(dppbz)(CO)(L)Cl2] (L = acetonitrile, 4-picoline and dimethyl sulfoxide). Both the carbonyls in [Ru(dppbz)(CO)2Cl2] are displaced on reaction with another equivalent of dppbz to afford [Ru(dppbz)2Cl2]. The two carbonyls and the two chlorides in [Ru(dppbz)(CO)2Cl2] could be displaced together by chelating mono-anionic bidentate ligands, viz. anions derived from 8-hydroxyquinoline (Hq) and 2-picolinic acid (Hpic) via loss of a proton, to afford the mixed-tris complexes [Ru(dppbz)(q)2] and [Ru(dppbz)(pic)2], respectively. The molecular structures of four selected complexes, viz. [Ru(dppbz)(CO)(dmso)Cl2], [Ru(dppbz)2Cl2], [Ru(dppbz)(q)2] and [Ru(dppbz)(pic)2], have been determined by X-ray crystallography. In dichloromethane solution, all the complexes show intense absorptions in the visible and ultraviolet regions. Cyclic voltammetry on the complexes shows redox responses within 0.71 to -1.24 V vs. SCE. [Ru(dppbz)(CO)2Cl2] has been found to serve as an excellent pre-catalyst for catalytic transfer-hydrogenation and Oppenauer oxidation.
- Mukherjee, Aparajita,Bhattacharya, Samaresh
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p. 15617 - 15631
(2021/05/19)
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- Understanding Ligand-Directed Heterogeneous Catalysis: When the Dynamically Changing Nature of the Ligand Layer Controls the Hydrogenation Selectivity
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We present a mechanistic study on the formation and dynamic changes of a ligand-based heterogeneous Pd catalyst for chemoselective hydrogenation of α,β-unsaturated aldehyde acrolein. Deposition of allyl cyanide as a precursor of a ligand layer renders Pd highly active and close to 100 % selective toward propenol formation by promoting acrolein adsorption in a desired configuration via the C=O end. Employing a combination of real-space microscopic and in-operando spectroscopic surface-sensitive techniques, we show that an ordered active ligand layer is formed under operational conditions, consisting of stable N-butylimine species. In a competing process, unstable amine species evolve on the surface, which desorb in the course of the reaction. Obtained atomistic-level insights into the formation and dynamic evolution of the active ligand layer under operational conditions provide important input required for controlling chemoselectivity by purposeful surface functionalization.
- Baumann, Ann-Katrin,Haugg, Philipp A.,Schauermann, Swetlana,Schmidt, Marvin C.,Schr?der, Carsten,Smyczek, Jan
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supporting information
p. 16349 - 16354
(2021/06/25)
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- Solvent-free oxidation of straight-chain aliphatic primary alcohols by polymer-grafted vanadium complexes
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Oxidovanadium(IV) complexes [VO(tertacac)2] (1), [VO(dipd)2] (2), and [VO(phbd)2] (3) were synthesized by reacting [VO(acac)2] with 2,2,6,6-tetramethyl-3,5-hepatanedione, 1,3-diphenyl-1,3-propanedione, and 1-phenyl-1,3-butanedione, respectively. Imidazole-modified Merrifield resin was used for the heterogenization of complexes 1–3. During the process of heterogenization, the V4+ center in complex 2 converts into V5+, whereas the other two complexes 1 and 3 remain in the oxidovanadium(IV) state in the polymer matrix. Theoretically, calculated IPA values of 1–3 suggest that 2 is prone to oxidation compared with 1 and 3, which was also supported by the absence of EPR lines in 5. Polymer-supported complexes Ps-Im-[VIVO(tertacac)2] (4), Ps-Im-[VVO2(dipd)2] (5), and Ps-Im-[VIVO(phbd)2] (6) were applied for the solvent-free heterogenous oxidation of a series of straight-chain aliphatic alcohols in the presence of H2O2 at 60°C and showed excellent substrate conversion specially for the alcohols with fewer carbon atoms. Higher reaction temperature improves the substrate conversion significantly for the alcohols containing more carbon atoms such as 1-pentanol, 1-hexanol, and 1-heptanol while using optimized reaction conditions. However, alcohols with fewer carbon atoms seem less affected by reaction temperatures higher than the optimized temperature. A decreasing trend in the selectivity(%) of carboxylic acid was observed with increasing carbon atoms among the examined alcohols, whereas the selectivity towards aldehydes increased. The order of efficiency of the supported catalysts is 4 > 6 > 5 in terms of turnover frequency (TOF) values and substrate conversion, further supported by theoretical calculations.
- Chaudhary, Nikita,Haldar, Chanchal,Kachhap, Payal
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- Single-atom Ru catalyst for selective synthesis of 3-pentanone: Via ethylene hydroformylation
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A Ru single-atom (Ru SA) catalyst supported on activated carbon was adopted to synthesize 3-pentanone with 83.3% selectivity via heterogeneous ethylene hydroformylation, while 52.1% ethane selectivity was obtained for Ru nanoparticles (Ru NPs). The atomically dispersed Ru species with oxidation state (Ruδ+) and Ru-C4O coordination structure were identified as the active sites for efficient C-C coupling to generate 3-pentanone, while metallic Ru nanoparticles exhibited high activity for ethylene hydrogenation to ethane. Density functional theory (DFT) calculation revealed that the energy barrier of the direct coupling of C2H5CO? with C2H5? to form 3-pentanone on Ru SA was much lower than that on Ru NPs. As a result, the formation of 3-pentanone over Ru SA was more favourable than propanal, which was admittedly generated via coupling of C2H5CO? and H?. This strategy may provide a potential green route for the one-pot synthesis of 3-pentanone with high atomic economy.
- Dang, Yaru,Jiang, Zheng,Li, Shenggang,Li, Xiao,Lin, Tiejun,Mei, Bingbao,Qin, Tingting,Sun, Yuhan,Tang, Zhiyong,Wu, Bo,Zhong, Liangshu
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supporting information
p. 9038 - 9047
(2021/11/30)
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- METHOD FOR PRODUCING CARBONATE DERIVATIVE
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The objective of the present invention is to provide a method for producing a polycarbonate safely and efficiently even without using a base. The method for producing a carbonate derivative according to the present invention is characterized in comprising the step of irradiating a high energy light to a composition comprising the halogenated methane and the hydroxy group-containing compound in the presence of oxygen, wherein a molar ratio of a total usage amount of the hydroxy group-containing compound to 1 mole of the halogenated methane is 0.05 or more.
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Paragraph 0122-0123
(2022/01/04)
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- Mesoporous silica supported phosphotungstic acid catalyst for glycerol dehydration to acrolein
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Conversion of glycerol to acrolein is a useful reaction for value-added application of biodiesel-derived glycerol and bioenergy development. The high-performance solid acid catalyst is essential to this dehydration reaction. In this paper, tungsten-based heteropolyacids (HPA) were supported on non-ordered mesoporous silica (MSU-x) to increase their dispersion and used as catalysts for glycerol dehydration to acrolein. Aiming to reveal the surface structure of HPA and resulting acidic properties, as well as the relationship between acidic properties and dehydration activity, different loadings of H3PW12O40 were supported on MSU-x (10–50 wt%) and the catalysts were characterized by X-ray diffraction (XRD), BET, SEM/TEM, UV–vis diffuse reflectance spectra (DRS), Raman and FT-IR techniques. Their acidic properties were studied by NH3-Temperature Programmed Desorption (NH3-TPD) and Pyridine adsorption methods. The molecular structure and dispersion of H3PW12O40 supported on the catalysts was revealed. The Keggin unit preserved well but with different hydration level for various loadings. The total acid concentration and respective Br?nsted/Lewis acid identification were calculated. The acrolein yield increased with H3PW12O40 loading until 30 wt% and showed less change with higher loadings. Based on the correlation of acrolein formation rate with acidic properties, the active role of Br?nsted acid and the cooperative role of Br?nsted/Lewis acid sites for glycerol dehydration to acrolein were discussed. This work provides new insight into the structure evolution of heteropolyacids and the catalyst design for the glycerol to acrolein.
- Wang, Zhiheng,Liu, Licheng
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- Chemo- And regioselective hydroformylation of alkenes with CO2/H2over a bifunctional catalyst
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As is well known, CO2 is an attractive renewable C1 resource and H2 is a cheap and clean reductant. Combining CO2 and H2 to prepare building blocks for high-value-added products is an attractive yet challenging topic in green chemistry. A general and selective rhodium-catalyzed hydroformylation of alkenes using CO2/H2 as a syngas surrogate is described here. With this protocol, the desired aldehydes can be obtained in up to 97% yield with 93/7 regioselectivity under mild reaction conditions (25 bar and 80 °C). The key to success is the use of a bifunctional Rh/PTA catalyst (PTA: 1,3,5-triaza-7-phosphaadamantane), which facilitates both CO2 hydrogenation and hydroformylation. Notably, monodentate PTA exhibited better activity and regioselectivity than common bidentate ligands, which might be ascribed to its built-in basic site and tris-chelated mode. Mechanistic studies indicate that the transformation proceeds through cascade steps, involving free HCOOH production through CO2 hydrogenation, fast release of CO, and rhodium-catalyzed conventional hydroformylation. Moreover, the unconventional hydroformylation pathway, in which HCOOAc acts as a direct C1 source, has also been proved to be feasible with superior regioselectivity to that of the CO pathway.
- Hua, Kaimin,Liu, Xiaofang,Wei, Baiyin,Shao, Zilong,Deng, Yuchao,Zhong, Liangshu,Wang, Hui,Sun, Yuhan
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supporting information
p. 8040 - 8046
(2021/11/01)
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- Operando Investigation of Ag-Decorated Cu2O Nanocube Catalysts with Enhanced CO2 Electroreduction toward Liquid Products
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Direct conversion of carbon dioxide into multicarbon liquid fuels by the CO2 electrochemical reduction reaction (CO2RR) can contribute to the decarbonization of the global economy. Here, well-defined Cu2O nanocubes (NCs, 35 nm) uniformly covered with Ag nanoparticles (5 nm) were synthesized. When compared to bare Cu2O NCs, the catalyst with 5 at % Ag on Cu2O NCs displayed a two-fold increase in the Faradaic efficiency for C2+ liquid products (30 % at ?1.0 VRHE), including ethanol, 1-propanol, and acetaldehyde, while formate and hydrogen were suppressed. Operando X-ray absorption spectroscopy revealed the partial reduction of Cu2O during CO2RR, accompanied by a reaction-driven redispersion of Ag on the CuOx NCs. Data from operando surface-enhanced Raman spectroscopy further uncovered significant variations in the CO binding to Cu, which were assigned to Ag?Cu sites formed during CO2RR that appear crucial for the C?C coupling and the enhanced yield of liquid products.
- Herzog, Antonia,Bergmann, Arno,Jeon, Hyo Sang,Timoshenko, Janis,Kühl, Stefanie,Rettenmaier, Clara,Lopez Luna, Mauricio,Haase, Felix T.,Roldan Cuenya, Beatriz
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supporting information
p. 7426 - 7435
(2021/02/26)
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- Oxidation of Propane: Influence of the Nature of Catalyst, Cocatalyst, and Coreductant
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Abstract: Variation of the nature of the components of the catalytic systems comprisinga catalyst [Pd/C, Pd(α,α-bipy)Cl2,RhCl3] and a cocatalyst(FeSO4, CuSO4), as well as acoreductant (H2, CO), allows exerting some control overthe selectivity of the process of propane oxidation with oxygen. In particular,the yield of carbonyl compounds such as acetone and propanal in the presence ofthe Pd/C–FeSO4–H2catalytic systemreached 90%, and that of propyl esters in the presence ofRhCl3–CuSO4–CO catalyticsystem was 64.5%. These differences are supposedly attributable to the changesin the process mechanism depending on the composition of the catalyticsystems. [Figure not available: see fulltext.]
- Chepaikin, E. G.,Menchikova, G. N.,Pomogailo, S. I.
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p. 781 - 786
(2021/08/03)
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- Organic Ligand-Free Hydroformylation with Rh Particles as Catalyst?
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An efficient and organic ligand-free heterogeneous catalytic system for hydroformylation of olefins is highly desirable for both academy and industry. In this study, simple Rh black was employed as a heterogeneous catalyst for hydroformylation of olefins in the absence of organic ligand. The Rh black catalyst showed good catalytic activity for a broad substrate scope including the aliphatic and aromatic olefins, affording the desired aldehydes in good yields. Taking the hydroformylation of ethylene as an example, 86% yield of propanal and TOF of 200 h–1 were obtained, which was superior to the reported homogeneous catalytic systems. In addition, the catalyst could be reused five times without loss of activity under identical reaction conditions, and the Rh leaching was negligible after each cycle.
- Liu, Shujuan,Dai, Xingchao,Wang, Hongli,Wang, Xinzhi,Shi, Feng
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supporting information
p. 139 - 143
(2020/01/03)
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- Highly active and durable WO3/Al2O3catalysts for gas-phase dehydration of polyols
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Gas-phase glycerol dehydration over WO3/Al2O3catalysts was investigated. WO3loading on γ-Al2O3significantly affected the yield of acrolein and the catalyst with 20 wt% WO3loading showed the highest activity. The WO3/Al2O3catalyst with 20 wt% WO3loading showed higher activity and durability than the other supported WO3catalysts and zeolites. The number of Br?nsted acid sites and mesopores of the WO3/Al2O3catalyst did not decrease after the reaction, suggesting that glycerol has continuous access to Br?nsted acid sites inside the mesopores of WO3/Al2O3, thereby sustaining a high rate of formation of acrolein. Dehydration under O2flow further increased the durability of the WO3/Al2O3catalyst, enabling the sustainable formation of acrolein. In addition, the WO3/Al2O3catalyst with 20 wt% WO3loading showed high activity for the dehydration of various polyols to afford the corresponding products in high yield.
- Aihara, Takeshi,Asazuma, Katsuya,Miura, Hiroki,Shishido, Tetsuya
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p. 37538 - 37544
(2020/10/19)
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- Highly Active, Selective, and Recyclable Water-Soluble Glutathione-Stabilized Pd and Pd-Alloy Nanoparticle Catalysts in Biphasic Solvent
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Glutathione-protected Pd, PdAu and PdPt nanoparticles (NPs) show greatly increased reactivity and stability towards the hydrogenation/isomerization of allyl alcohol in a biphasic organic/aqueous solvent mixture compared to single-phase alkanethiol-protected Pd-based NPs. NPs synthesized under aerobic conditions have higher activity compared to those synthesized under nitrogen, with the highest TOF of 676 mole product/mole metal/hour for 75 : 25 PdAu NPs at 20 mL/min H2 flow. 75 : 25 PdAu NPs prepared under nitrogen have a maximum TOF of 507 at 20 mL/min H2 flow, but can be recycled 4 times (9 times at 8 mL/min H2 flow). Ethyl acetate is a better organic phase solvent compared to dichloromethane and chlorobenzene in terms of TOF and recyclability. All of the NPs studied show >80 % selectivity for the isomer product (propanal). The branched, open structure of the glutathione and use of the biphasic solvent provides high catalytic activity, high selectivity, and easy removal of the products in the organic phase for good recyclability of the water-soluble catalysts.
- Bhama, Shekhar,Sibakoti, Tirtha R.,Jasinski, Jacek B.,Zamborini, Francis P.
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p. 2253 - 2261
(2020/03/13)
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- PROCESS FOR PRODUCING METHACRYLIC ACID OR METHACRYLIC ACID ESTERS
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The present invention relates to a process for producing methacrylic acid or methacrylic acid esters. The present invention is directed to a new process for the production of methacrylic acid or alkyl methacrylate starting from Acrolein, which is available from glycerol or propane.
- -
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Page/Page column 16
(2020/03/02)
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- Reduction of Propanoic Acid over Pd-Promoted Supported WOx Catalysts
-
Silica-, titania-, and zirconia-supported tungsten oxide catalysts were synthesized by wetness impregnation techniques. When promoted with Pd, these materials catalyzed the reduction of propanoic acid to 1-propanol at 433 K with a selectivity of up to 92 % (13.5 % conversion) in atmospheric pressure of H2. Over Pd-promoted WOx/TiO2, the observed orders of reaction were 0.2 in H2 and 0.7 in propanoic acid, and the apparent activation energy was 54 kJ mol?1. In situ X-ray absorption spectroscopy of Pd-promoted WOx/SiO2 revealed a slight reduction of the W from +6 to an average oxidation state of about +5 during H2 treatment above 473 K. In situ infrared spectroscopy indicated the catalyst surface was covered mostly by propanoate species during reaction. For comparison, supported phosphotungstic acid was also evaluated as a catalyst under identical conditions, but the resulting high acidity of the catalyst was deleterious to alcohol selectivity.
- Kammert, James D.,Brezicki, Gordon,Miyake, Naomi,Stavitski, Eli,Davis, Robert J.
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p. 314 - 325
(2019/11/28)
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- The design, synthesis and catalytic performance of vanadium-incorporated mesoporous silica with 3D mesoporous structure for propene epoxidation
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V-containing mesoporous silica with 3D structure was prepared by a hydrothermal procedure using NH4VO3 as the vanadium precursor and with varied reaction mixture pH values (pH = 3 and pH = 5). The combined use of DR UV-vis and H2-TPR techniques confirmed the successful incorporation of vanadium into the structure of the mesoporous silica material. The number of acid sites, evidenced by ammonia TPD, strongly correlates with the vanadium content. Propene oxidation with N2O revealed the noticeable activity of the synthesised vanadium-containing mesoporous materials in epoxidation reactions. The activity of the synthesized vanadosilicates is compared with the performance of vanadium-supported catalysts (on mesoporous silica of 3D structures) prepared by wet-impregnation method. On the basis of TOF analysis indicating the activity of particular vanadium ions, it was evidenced that although the presence of isolated V species is crucial in propene epoxidation, the availability of the active species is of paramount importance for proper vanadium utilization.
- Czerepińska, Justyna,Held, Agnieszka,Janiszewska, Ewa,Kowalska-Ku?, Jolanta
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p. 10144 - 10154
(2020/03/26)
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- Tailoring Interfacial Lewis Acid-Basic Pair on ZnO/4Mg1ZrOx Allows Dehydrogenative α-Methylenation of Alcohols with Methanol to Allylic Alcohols
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Allylic alcohols are the essential building blocks widely used in diverse streams of organic inventions for pharmaceuticals, fragrances, agrochemicals and polymers. Currently, allylic alcohols are industrially produced from petroleum-based feedstocks via atom uneconomic processes. More sustainable synthesis route for allylic alcohols is limited. Herein, a methodology for the direct and highly selective production of allylic alcohols has been accomplished by controlled dehydrogenative α-methylenation of alcohols with methanol. This transformation is enabled by interfacial Lewis acid-basic pair on tailor-made ZnO/4Mg1ZrOx mixed oxide. High selectivity (83～92%) of allylic alcohols is the consequence of alcohols acceptorless dehydrogenation to liberation of H2 and Meerwein-Ponndorf-Verley type hydrogen transfer onto C = O bonds of unsaturated aldehydes. Furthermore, the prepared ZnO/4Mg1ZrOx mixed oxide shows good stability after 200 h time on stream test. These observations could additionally allow us to design multifunctional solid acid-basic catalysts for the transformations of renewable oxygenates into value-added chemicals.
- Fu, Aixiao,Jiang, Shifeng,Liu, Qiang,Liu, Xiaoran,Liu, Xiuyun,Mu, Xindong,Sun, Mengqing,Wang, Xicheng,Xu, Guoqiang,Zhao, Lingling
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- Direct Transformation of Glycerol to Propanal using Zirconium Phosphate-Supported Bimetallic Catalysts
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Selective transformation of glycerol to propanal (PA) provides a feasible route towards the sustainable synthesis of high value-added chemicals. In this work, zirconium phosphate (ZrP) was studied as support and Ru and Co as metal sites for glycerol hydrogenolysis in a continuous-flow reactor. It was found that ZrP-supported Co?O species had a moderate selectivity to PA (49.5 %) in glycerol hydrogenolysis. Notably, once Ru species were doped into CoO/ZrP, the resulting catalyst exhibited not only an outstanding catalytic performance for glycerol hydrogenolysis to PA (a selectivity of 80.2 % at full conversion), but also a high stability at least a 50 h long-term performance. The spent catalyst could be regenerated by calcining in air to remove carbonaceous deposits. Characterization indicated that the acid sites on ZrP played a very critical role in the dehydration of glycerol into acrolein (AE), that the distribution of Co was uniform, basically consistent with that of Zr, P and Ru, and that an especially close contact between Co?O and Ru species was formed on Ru/CoO/ZrP catalyst. The further activity tests and characterizations confirmed that there was a strong interaction between the dispersed Co?O species and Ru0 nanoparticles, which endowed Ru sites with high electronic density. This effect could play a role in facilitating the dissociation of H2, and thus in promoting the hydrogenation reaction. Besides, DFT calculations suggested that the Co?O species can adsorb more strongly the C=C bond of the intermediate AE on a highly coordinatively unsaturated Co (Cocus) site and thus lead to preferential hydrogenation at the C=C bond of AE to PA.
- Gong, Honghui,Zhou, Chuan,Cui, Yan,Dai, Sheng,Zhao, Xiuge,Luo, Ruihan,An, Pengfei,Li, Huan,Wang, Haifeng,Hou, Zhenshan
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p. 4954 - 4966
(2020/08/21)
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- Direct transformation of silica from natural resources to form tetramethoxysilane
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A simple and practical method for direct synthesis of tetramethoxysilane (TMOS) from silica (SiO2) and methanol was achieved using a base catalyst and acetal as a dehydrant under carbon dioxide (CO2). The production of TMOS was strongly influenced by the kind of the acetal used, with 2,2-dimeth-oxypropane identified as the most effective dehydrant. We observed that the acetal used enabled the production of a high yield of dimethyl carbonate (DMC), which promoted the TMOS production. DMC is an intermediate product from the reaction of CO2 and methanol, which supported the SiO2 depolymerization process. When the reaction is conducted with 2,2-dimethoxypropane at 260 °C for 24 h, TMOS can be produced in up to 59percent yield. For practical applications, the TMOS synthesis has been developed on a 250 mL and 1 L-scale reaction with constant yield (>50percent) from various silica resources.
- Putro, Wahyu S.,Fukaya, Keisuke,Choi, Jun-Chul,Choi, Seong Jib,Horikoshi, Toshio,Sato, Kazuhiko,Fukaya, Norihisa
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p. 958 - 962
(2020/09/04)
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- Reduction of carbon dioxide at a plasmonically active copper-silver cathode
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Electrochemically deposited copper nanostructures were coated with silver to create a plasmonically active cathode for carbon dioxide (CO2) reduction. Illumination with 365 nm light, close to the peak plasmon resonance of silver, selectively enhanced 5 of the 14 typically observed copper CO2 reduction products while simultaneously suppressing hydrogen evolution. At low overpotentials, carbon monoxide was promoted in the light and at high overpotentials ethylene, methane, formate, and allyl alcohol were enhanced upon illumination; generally C1 products and C2/C3 products containing a double carbon bond were selectively promoted under illumination. Temperature-dependent product analysis in the dark showed that local heating is not the cause of these selectivity changes. While the exact plasmonic mechanism is still unknown, these results demonstrate the potential for enhancing CO2 reduction selectivity at copper electrodes using plasmonics.
- Corson, Elizabeth R.,Subramani, Ananya,Cooper, Jason K.,Kostecki, Robert,Urban, Jeffrey J.,McCloskey, Bryan D.
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supporting information
p. 9970 - 9973
(2020/09/23)
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- Investigating the Origin of Enhanced C2+Selectivity in Oxide-/Hydroxide-Derived Copper Electrodes during CO2Electroreduction
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Oxide-/hydroxide-derived copper electrodes exhibit excellent selectivity toward C2+ products during the electrocatalytic CO2 reduction reaction (CO2RR). However, the origin of such enhanced selectivity remains controversial. Here, we prepared two Cu-based electrodes with mixed oxidation states, namely, HQ-Cu (containing Cu, Cu2O, CuO) and AN-Cu (containing Cu, Cu(OH)2). We extracted an ultrathin specimen from the electrodes using a focused ion beam to investigate the distribution and evolution of various Cu species by electron microscopy and electron energy loss spectroscopy. We found that at the steady stage of the CO2RR, the electrodes have all been reduced to Cu0, regardless of the initial states, suggesting that the high C2+ selectivities are not associated with specific oxidation states of Cu. We verified this conclusion by control experiments in which HQ-Cu and AN-Cu were pretreated to fully reduce oxides/hydroxides to Cu0, and the pretreated electrodes showed even higher C2+ selectivity compared with their unpretreated counterparts. We observed that the oxide/hydroxide crystals in HQ-Cu and AN-Cu were fragmented into nanosized irregular Cu grains under the applied negative potentials. Such a fragmentation process, which is the consequence of an oxidation-reduction cycle and does not occur in electropolished Cu, not only built an intricate network of grain boundaries but also exposed a variety of high-index facets. These two features greatly facilitated the C-C coupling, thus accounting for the enhanced C2+ selectivity. Our work demonstrates that the use of advanced characterization techniques enables investigating the structural and chemical states of electrodes in unprecedented detail to gain new insights into a widely studied system.
- Lei, Qiong,Zhu, Hui,Song, Kepeng,Wei, Nini,Liu, Lingmei,Zhang, Daliang,Yin, Jun,Dong, Xinglong,Yao, Kexin,Wang, Ning,Li, Xinghua,Davaasuren, Bambar,Wang, Jianjian,Han, Yu
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p. 4213 - 4222
(2020/03/04)
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- Synchrotron Photoionization Study of the Diisopropyl Ether Oxidation
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Scientific evidence has shown oxygenates help to reduce dangerous pollutants arising from burning fossil fuel in the automotive sector. For this reason, their use as additives has spread widely. The aim of this work consists in providing a comprehensive identification of the main primary oxidation products of diisopropyl ether (DIPE), one of the most promising among etheric oxygenates. The Cl-initiated oxidation of DIPE is examinated by using a vacuum ultraviolet (VUV) synchrotron radiation at the Advanced Light Source (ALS) of the Lawrence Berkeley National Laboratory (LBNL). Products are identified on the basis of their mass-to-charge ratio, shape of photoionization spectra, adiabatic ionization energies, and chemical kinetic profiles, at three different temperatures (298, 550, and 650 K). Acetone, propanal, propene, and isopropyl acetate have been identified as major reaction products. Acetone is the main primary product. Theoretical calculations using the composite CBS-QB3 method provided useful tools to validate the postulated reaction mechanisms leading to experimentally observed species. The formation of other species is also discussed.
- Giustini, Andrea,Meloni, Giovanni
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- Homogeneous Metal-Complex Catalyst Systems in the Partial Oxidation of Propane with Oxygen
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Abstract: The effect of copper compounds and phosphorus–molybdenum–vanadium heteropoly acids (HPAs) H5PMo10V2O40 and H7PMo8V4O40 used as cocatalysts in the cooxidation
- Chepaikin, E. G.,Menchikova, G. N.,Pomogailo, S. I.
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p. 1260 - 1267
(2020/12/02)
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- The influence of H/D kinetic isotope effect on radiation-induced transformations of hydroxyl-containing compounds in aqueous solutions
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Vicinal diols and its derivatives can be exploited as model compounds for the investigation of radiation-induced free-radical transformations of hydroxyl-containing biomolecules such as carbohydrates, phospholipids, ribonucleotides, amino acids, and peptides. In this paper, for the first time, the prospects of isotope reinforcement approach in inhibiting free-radical transformations of hydroxyl-containing compounds in aqueous solutions are investigated on the example of radiolysis of 1,2-propanediol and 1,2-propanediol-2-d1 aqueous solutions. At an absorbed dose rate of 0.110 ± 0.003 Gy·s?1 a profound kinetic isotope effect (KIE) is observed for the non-branched chain formation of acetone, which is a final dehydration product of predominant carbon-centred radicals CH3·C(OH)CH2OH. In 0.1 and 1 M deaerated solutions at pH 7.00 ± 0.01, the values of KIE are 8.9 ± 1.7 and 15.3 ± 3.1, respectively. A rationale for the fact that a strong KIE takes place only in the case of chain processes, which may occur during free-radical transformations of vicinal diols, is also provided herein based on the results of 2-propanol and 2-propanol-2-d1 indirect radiolysis. Lastly, the lack of KIE is shown in the case of 2-butanone formation from 2,3-butanediol or 2,3-butanediol-2,3-d2. This indicates that the type (primary, secondary) of the β-carbonyl radicals formed as a result of CH3·C(OH)CH(OH)R (R = H, CH3) dehydration determines the manifestation of the effect.
- Bekish, Andrei V.,Nepachalovich, Palina S.,Shadyro, Oleg I.,Shmanai, Vadim V.
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p. 732 - 744
(2020/12/28)
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- Ethylene Hydroformylation in the Presence of Rhodium Catalysts in Hydrocarbon-Rich Media: The Stage of Combined Conversion of Refinery Gases to Oxygenates
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Abstract: The feature of hydroformylation of model gas mixtures with different ethylene, hydrogen, and methane concentrations in the presence of rhodium catalysts have been studied. The effect of the initial pressure in the reactor and the reaction temperature on the reaction rate and selectivity has been determined. It has been shown that ethylene hydroformylation occurs with a high propanal selectivity (up to 99%), with the turnover frequency of the reaction reaching 9500 h–1. It has been proposed that various phosphine ligands should be used to implement alternative methods of separating the catalyst system from the reaction products.
- Gorbunov,Nenasheva,Matsukevich,Terenina,Putilin,Kardasheva, Yu. S.,Maksimov,Karakhanov
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p. 1009 - 1016
(2019/10/19)
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- Chiral geminal disilyl alkane compound, synthesis method and applications thereof
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The present invention discloses a chiral geminal disilyl alkane compound, which is represented by a formula V, wherein * represents a chiral carbon atom in the formula V. The invention discloses a synthesis method of the chiral geminal disilyl alkane compound, wherein the synthesis method comprises: carrying out a reaction in the presence of a reducing agent by using alkyne represented by a formula I, dihydrosilane represented by a formula II and trihydrosilane represented by a formula III as raw materials and using Xantphos-CoBr2 and a chiral CoX2-OIP complex as catalysts under an inert gas to prepare the chiral geminal disilyl alkane compound represented by the formula V. According to the present invention, the method has characteristics of mild reaction condition, simple operation, highatomic economy, no requirement of the addition of any other toxic transition metals (such as ruthenium, rhodium, palladium and the like) salts, high yield and high enantioselectivity, and has great practical value in the synthesis of drugs and materials, wherein the yield is generally 50-85%, and the enantioselectivity is generally 93-99%. The formulas I, II, III and V are defined in the specification.
- -
-
Paragraph 0204; 0205; 0206; 0207; 0209
(2019/01/14)
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- Racemic gem disilyl alkane compound containing four silicon-hydrogen bonds, and sybthesis method and application of compound
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The invention discloses a racemic gem disilyl alkane compound containing four silicon-hydrogen bonds. The compound is as shown in a formula IV. The invention further discloses a synthesis method of the racemic gem disilyl alkane compound. The synthesis method comprises the following step of carrying out a reaction by taking alkyne as shown in a formula I and trihydrosilane as shown in a formula IIas raw materials and taking a chiral CoX-IIP complex as a catalyst in the presence of a reducing agent to obtain the racemic gem disilyl alkane compound containing four silicon-hydrogen bonds, wherein the compound is as shown in the formula IV. The method disclosed by the invention has mild reaction conditions, is simple and convenient to operate and has high atom economy. In addition, the reaction does not need addition of any salts of toxic transition metals (such as ruthenium, rhodium, palladium and the like), and the method has a relatively large practical application value in synthesis of medicines and materials. In addition, the reaction has a medium to excellent yield (51-99%) and high area selectivity (10:1-19:1, most parts larger than 19:1).
- -
-
Paragraph 0263-0268; 0269
(2019/05/15)
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- Visible-light mediated C-C bond cleavage of 1,2-diols to carbonyls by cerium-photocatalysis
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We describe a photocatalytic method for the cleavage of vicinal diols to aldehydes and ketones. The reaction is catalyzed by blue light and a cerium-catalyst and the scope includes aryl as well as alkyl substituted diols. The simple protocol which works under air and at room temperature enables the valorization of abundant diols.
- Schwarz, Johanna,K?nig, Burkhard
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supporting information
p. 486 - 488
(2019/01/10)
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- Hybrid Photo-induced Copolymerization of Ring-Strained and Vinyl Monomers Utilizing Metal-Free Ring-Opening Metathesis Polymerization Conditions
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We introduce the hybrid copolymerization of two disparate monomer classes (vinyl monomers and ring-strained cyclic olefins) via living photopolymerization. The living character of the polymerization technique (metal-free photo-ROMP) is demonstrated by consecutive chain-extensions. Further, we propose a mechanism for the copolymerization and analyze the copolymer structure in detail by high-resolution mass spectrometry.
- Krappitz, Tim,Jovic, Kristina,Feist, Florian,Frisch, Hendrik,Rigoglioso, Vincent P.,Blinco, James P.,Boydston, Andrew J.,Barner-Kowollik, Christopher
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supporting information
p. 16605 - 16609
(2019/10/21)
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- Dinuclear half-sandwich iridium complex containing bisimine ligand and preparation method and application thereof
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The invention belongs to the technical field of synthetic chemistry and relates to a dinuclear half-sandwich iridium complex containing bisimine ligand and a preparation method and application thereof. Pentamethylcyclopentadienyl iridium chloride dimer [(C5Me5)IrCl2]2 is used as a raw material subjected to reaction with pyrrole ring-containing bisimine ligand under alkaline conditions to prepare the finished N,N-coordinated dinuclear half-sandwich iridium complex. The synthetic process herein is simple and green and has good selectivity and high yield; the dinuclear half-sandwich iridium complex herein has stable physio-chemical properties and thermal stability and the like and shows efficient catalytic activity in the reaction where halogenated hydrocarbons are oxidized into correspondingaldehydes.
- -
-
Paragraph 0030; 0031; 0032
(2019/04/17)
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- One-pot synthesis of vanadium-containing silica SBA-3 materials and their catalytic activity for propene oxidation
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V-containing silica SBA-3 mesoporous catalysts were prepared by means of one-pot hydrothermal procedure with NH4VO3 or VOSO4 as vanadium precursors under various acidic medium of the reaction mixture (pH 2-TPR allowed to determine the nature of vanadium species in the studied samples. A successful incorporation of vanadium into the structure of silica SBA-3 was attained for the samples with low V content (5 wt%) exhibited the presence of isolated vanadium and also of polynuclear surface species. The resulting V-bearing samples contain the Br?nsted and Lewis acidic centres evidenced by FTIR spectra of adsorbed pyridine and by catalytic activity for 2-propanol decomposition and cumene cracking. Ammonia TPD allowed to estimate the number and strength of acid sites in regards to the vanadium content. Propene oxidation with N2O revealed noticeable activity of the synthesised V-SBA-3 samples in epoxidation reaction. On the basis of TOF analysis indicating the activity of particular vanadium ions it seems that not all of the introduced V atoms take part in the formation of mild electrophilic oxygen species responsible for propene oxide formation.
- Janiszewska, Ewa,Held, Agnieszka,Nowińska, Krystyna,Kowalak, Stanis?aw
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p. 4671 - 4681
(2019/02/27)
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- Production and testing of technical catalysts based on MnO2 for the abatement of aromatic volatile compounds at the laboratory and pilot plant scales
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Shaping is a crucial step to produce technical catalysts that remains as some sort of dark art for catalytic researchers in academia. This contribution discusses aspects concerning the fabrication of technical catalysts based on MnO2 powders ai
- Baldovino-Medrano, Víctor Gabriel,Kartheuser, Beno?t,Gaigneaux, Eric M.
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- Sustainable hydrocarbon production via simultaneous condensation-hydrodeoxygenation of propionic acid with furfural over red mud-supported noble metal catalysts
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A new catalytic system for single-step alkane synthesis from furans and carboxylic acids was investigated using noble metals-supported red mud (RM) catalysts. Maximum alkane selectivities were 100%, 87%, and 56% over Pt/RM, Pd/RM, and Ru/RM respectively. Potassium doping prolonged the catalyst life by suppressing methanation reaction, decreased coking, and enhancing the stability of noble metals towards oxidation. Five functionalities were accomplished on the modified catalysts: partial reduction of propionic acid on noble metals; moderating coking reactions on K, suppressing methanation on K, ketonization of acid on RM, and condensation-hydrodeoxygenation reaction on RM. Magnetite played significant role in catalyzing ketonization reaction.
- Castille, Antonie,Bessette, Claudie,Thomas, Francois,Etemad, Mania
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- Influence of the structure of trigonal Mo-V-M3rd oxides (M3rd?=?-, Fe, Cu, W) on catalytic performances in selective oxidations of ethane, acrolein, and allyl alcohol
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Crystalline “MoVO”, “MoVCuO”, “MoVFeO” and “MoVWO” catalysts with a trigonal symmetry were successfully synthesized and characterized. The influence of the as-obtained structures on catalytic performances in selective oxidation reactions was investigated. MoVFeO and MoVCuO accomodated Fe and Cu species inside heptagonal channels, while W in MoVWO was incorporated in pentagonal {Mo6O21}6? units. Whereas MoVO and MoVWO showed catalytic activity in the selective oxidation of ethane and acrolein, MoVFeO and MoVCuO performed very poorly in the same reaction, suggesting that the presence of empty heptagonal channels is related to ethane and acrolein activations. In the selective oxidation of allyl alcohol, substantial amounts of acrolein (formed by oxidative dehydrogenation) and propanal (formed by isomerization) were formed as primary products over MoVO and MoVWO, whereas MoVFeO and MoVCuO preferentially promoted the formation of acrolein. It was found that the local crystal structure around the heptagonal channel was related with a modification of the reaction pathway for the selective oxidation of allyl alcohol. Due to the prevention of isomerization over MoVFeO, a high acrylic acid yield of 83.1% from allyl alcohol was achieved at 350 °C over this sample.
- Ishikawa, Satoshi,Murayama, Toru,Katryniok, Benjamin,Dumeignil, Franck,Araque, Marcia,Heyte, Svetlana,Paul, Sébastien,Yamada,Iwazaki, Mizuki,Noda, Nagisa,Ueda, Wataru
-
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- A study of the oxidehydration of 1,2-propanediol to propanoic acid with bifunctional catalysts
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The gas-phase oxidehydration (ODH) of 1,2-propanediol to propionic acid has been studied as an intermediate step in the multi-step transformation of bio-sourced glycerol into methylmethacrylate. The reaction involves the dehydration of 1,2-propanediol into propionaldehyde, which occurs in the presence of acid active sites, and a second step of oxidation of the aldehyde to the carboxylic acid. The two reactions were carried out using a cascade strategy and multifunctional catalysts, made of W-Nb-O, W-V-O and W-Mo-V-O hexagonal tungsten bronzes, the same systems which are also active and selective in the ODH of glycerol into acrylic acid. Despite the similarities of reactions involved, the ODH of 1,2-propanediol turned out to be less selective than glycerol ODH, with best yield to propanoic acid no higher than 13percent, mainly because of the parallel reaction of oxidative cleavage, occurring on the reactant itself, which led to the formation of C1-C2 compounds.
- Bandinelli, Claudia,Basile, Francesco,Cavani, Fabrizio,Concepcion, Patricia,De Maron, Jacopo,Dimitratos, Nikolaos,Lambiase, Barbara,Nieto, Jose Manuel Lopez,Tabanelli, Tommaso
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- New insights for the valorisation of glycerol over MgO catalysts in the gas-phase
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Aqueous glycerol solutions of up to 50 wt% were reacted over magnesium oxide catalysts at temperatures greater than 300 °C, the reactivity of which was compared to catalyst-free reactions. Under catalyst-free conditions, modest levels of dehydration to hydroxyacetone were observed at temperatures >400 °C in a steel reactor tube and >320 °C over silicon carbide. For reactions over MgO, the product distribution becomes more diverse, resulting in the formation of methanol, acetaldehyde, ethylene glycol, 1,2-propanediol and acetic acid. The methanol space-time-yield over MgO catalyst samples (0.5 g) was found to be highest at 400 °C (205 g h-1 kgcat-1) with a 50 wt% solution of glycerol, or with a glycerol concentration of 10 wt%; 255 g h-1 kgcat-1 over 0.1 g of catalyst. Despite the high glycerol conversion achieved, the MgO catalyst was found to be stable over 48 h, following a modest decrease in glycerol conversion during the initial 2 h of reaction. Post-reaction characterisation revealed that the level of coking at high glycerol conversions (>90%) was ≥120 mg gcat-1. The carbon mass balance determined by GC analysis for a typical reaction was 75% and so the carbon lost from catalyst coking only represents a modest quantity of the missing carbon; typically 10%. MgO was also found to promote the formation of high molecular weight products via condensation reactions, which were responsible for the remainder of the missing carbon; ca. 15%. Therefore, the total organic content of the post-reaction mixture and coke was calculated to be 94% of the starting solution. We conclude that the catalyst surface directs the formation of methanol, however, the results indicate that the reaction conditions are crucial to obtain optimum yields.
- Smith, Louise R.,Smith, Paul J.,Mugford, Karl S.,Douthwaite, Mark,Dummer, Nicholas F.,Willock, David J.,Howard, Mark,Knight, David W.,Taylor, Stuart H.,Hutchings, Graham J.
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p. 1464 - 1475
(2019/03/26)
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- Direct Production of Higher Oxygenates by Syngas Conversion over a Multifunctional Catalyst
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Selective synthesis of higher oxygenates (linear α-alcohols and α-aldehydes, C2+OH) from syngas is highly attractive but remains challenging owing to the low C2+OH selectivity and low catalytic stability. Herein we introduce a multifunctional catalyst composed of CoMn and CuZnAlZr oxides that dramatically increased the oxygenates selectivity to 58.1 wt %, where more than 92.0 wt % of the produced oxygenates are C2+OH. Notably, the total selectivity to value-added chemicals including oxygenates and olefins reached 80.6 wt % at CO conversion of 29.0 % with high stability. The appropriate component proximity can effectively suppress the formation of the undesired C1 products, and the selectively propulsion of reaction network by synergetic effect of different components contributes to the enhanced selectivity to higher oxygenates. This work provides an alternative strategy for the rational design of new catalysts for direct conversion of syngas into higher oxygenates with co-production of olefins.
- Lin, Tiejun,Qi, Xingzhen,Wang, Xinxing,Xia, Lin,Wang, Caiqi,Yu, Fei,Wang, Hui,Li, Shenggang,Zhong, Liangshu,Sun, Yuhan
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supporting information
p. 4627 - 4631
(2019/03/07)
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- Hydroformylation of unsaturated esters and 2,3-dihydrofuran under solventless conditions at room temperature catalysed by rhodium: N-pyrrolyl phosphine catalysts
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Rhodium complexes of the type HRh(CO)L3 (where L is an N-pyrrolyl phosphine, such as P(NC4H4)3, PPh(NC4H4)2, or PPh2(NC4H4)) were applied in the hydroformylation of less reactive unsaturated substrates, namely allyl acetate, butyl acrylate, methyl acrylate, 2,3-dihydrofuran and vinyl acetate. Even at room temperature, these catalysts enabled complete substrate conversion and high chemoselectivity towards the corresponding aldehydes. High conversion of vinyl acetate (88% in 6 h) to the branched aldehyde was obtained with HRh(CO)[P(NC4H4)3]3 at 25 °C. An increase of the turnover frequency, TOF, up to 2000 mol mol-1 h-1 was achieved in this reaction under 20 bar of syngas (H2/CO = 1) at 80 °C. The introduction of chiral phosphines, BINAP or Ph-BPE, to this system resulted in the production of a branched aldehyde with enantioselectivity, ee, up to 44 and 81%, respectively. High activity combined with high enantioselectivity was achieved due to the formation of the mixed rhodium hydrides HRh(CO)[P(NC4H4)3](BINAP) and HRh(CO)[P(NC4H4)3](Ph-BPE), identified by the NMR method.
- Alsalahi,Trzeciak
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p. 16990 - 16999
(2019/11/14)
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- Auto-Tandem Catalysis with Ruthenium: From o-Aminobenzamides and Allylic Alcohols to Quinazolinones via Redox Isomerization/Acceptorless Dehydrogenation
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A strategy for the synthesis of quinazolinones via Ru-catalyzed redox isomerization/acceptorless dehydrogenation was proposed and accomplished. In the presence of a commercially available [(p-cymene)Cl2]2, a range of desirable products were obtained with o-aminobenzamides and allylic alcohols as starting materials in moderate to high yields. This strategy is attractive due to high atom efficiency, and minimal consumption of chemicals and energy. (Figure presented.).
- Zhang, Weikang,Meng, Chong,Liu, Yan,Tang, Yawen,Li, Feng
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p. 3751 - 3759
(2018/09/14)
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- Metal-free hypervalent iodine/TEMPO mediated oxidation of amines and mechanistic insight into the reaction pathways
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A highly efficient metal free approach for the oxidation of primary and secondary amines to their corresponding aldehydes and ketones using PhI(OAc)2 in combination with a catalytic amount of TEMPO as an oxidizing agent is described. This protocol is rapid and provides diverse products under milder reaction conditions in excellent yields. In addition, the mechanistic study is well demonstrated by spectroscopic methods.
- Bansode, Ajay H.,Suryavanshi, Gurunath
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p. 32055 - 32062
(2018/09/29)
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- Gas phase glycerol dehydration over H-ZSM-5 zeolite modified by alkaline treatment with Na2CO3
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Modified H-ZSM-5 zeolite catalysts were studied for the dehydration of glycerol to acrolein in gas phase. The modifications were made by alkaline treatment using Na2CO3 solutions in different concentrations, followed by consecutive i
- Lago,Decolatti,Tonutti, Lucas G.,Dalla Costa,Querini
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- Exploring the Reaction Pathways of Bioglycerol Hydrodeoxygenation to Propene over Molybdena-Based Catalysts
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The one-step reaction of glycerol with hydrogen to form propene selectively is a particularly challenging catalytic pathway that has not yet been explored thoroughly. Molybdena-based catalysts are active and selective to C?O bond scission; propene is the only product in the gas phase under the standard reaction conditions, and further hydrogenation to propane is impeded. Within this context, this work focuses on the exploration of the reaction pathways and the investigation of various parameters that affect the catalytic performance, such as the role of hydrogen on the product distribution and the effect of the catalyst pretreatment step. Under a hydrogen atmosphere, propene is produced primarily via 2-propenol, whereas under an inert atmosphere propanal and glycerol dissociation products are formed mainly. The reaction most likely proceeds through a reverse Mars–van Krevelen mechanism as partially reduced Mo species drive the reaction to the formation of the desired product.
- Zacharopoulou, Vasiliki,Vasiliadou, Efterpi S.,Lemonidou, Angeliki A.
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p. 264 - 275
(2017/12/15)
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- MCF Material as an Attractive Support for Vanadium Oxide Applied as a Catalyst for Propene Epoxidation with N2O
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Abstract: Vanadium modified mesocellular silica foams (MCF) materials (V content ca. 3 and 5 wt%) prepared by the impregnation method show mainly isolated or low-polymeric VOx species, which was confirmed by means of Raman spectroscopy and DR UV–Vis. Textural measurements, and also XRD and TEM results indicate that the characteristic mesocellular structural features of MCFs are preserved after vanadium incorporation. The MCF-supported vanadia catalysts exhibit much higher propene conversion and propene oxide productivity when compared to vanadium modified mesoporous silicas of 2D structure, demonstrating that apart from the presence of highly dispersed isolated vanadium species, internal molecular transport within three-dimensional ultra large pores of MCF materials also plays an important role in gas-phase propene epoxidation. Graphical Abstract: [Figure not available: see fulltext.]
- Held, Agnieszka,Kowalska-Ku?, Jolanta,Nowińska, Krystyna,Góra-Marek, Kinga
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p. 2058 - 2068
(2018/05/28)
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- Hexafluoroisopropanol as the Acid Component in the Passerini Reaction: One-Pot Access to β-Amino Alcohols
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A new Passerini-type reaction in which hexafluoroisopropanol functions as the acid component is reported. The reaction tolerates a broad range of isocyanides and aldehydes, and the formed imidates can be reduced toward β-amino alcohols under mild and metal-free conditions. In addition, the imidate products were shown to undergo an unprecedented retro-Passerini-type reaction under microwave conditions, providing valuable mechanistic information about the Passerini reaction and its variations.
- Saya, Jordy M.,Berabez, Rayan,Broersen, Pim,Schuringa, Imme,Kruithof, Art,Orru, Romano V. A.,Ruijter, Eelco
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supporting information
p. 3988 - 3991
(2018/07/15)
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- METHOD FOR PRODUCING PROPIONALDEHYDE
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PROBLEM TO BE SOLVED: To provide a method for producing propionaldehyde that allows propionaldehyde to be produced efficiently from propylene, as a novel production route of propionaldehyde. SOLUTION: A method for producing propionaldehyde comprises the step for bringing a catalyst having titanium oxide carried on mesoporous silica into contact with mixed gas comprising molecular oxygen and propylene to oxidize propylene. SELECTED DRAWING: None COPYRIGHT: (C)2017,JPOandINPIT
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Paragraph 0051; 0052; 0057
(2017/10/10)
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- Facile synthesis of [Ru(η2-O2CO)(pta)(η6-p-cymene)], an outstandingly active Ru(II) half-sandwich complex for redox isomerization of allylic alcohols
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The water-soluble [RuCl2(pta)(η6-p-cymene)] (pta = 1,3,5-triaza-7-phosphaadamantane) was applied as catalyst in the transposition of allylic alcohols, such as oct-1-en-3-ol in aqueous media. The isomerisation of oct-1-en-3-ol to octan-3-one took place only at pH > 10 buffer solutions or in the presence of alkali metal carbonates. The aqueous solution of “in situ” catalyst ([RuCl2(pta)(η6-p-cymene)] + 2 eq Na2CO3) could be reused in the biphasic isomerization of oct-1-en-3-ol for at least five times without a significant loss of the catalytic activity. It was demonstrated that carbonate is not only a base in this reaction but leads to formation of a highly active catalyst, [Ru(η2-O2CO)(pta)(η6-p-cymene)]. This compound was isolated as crystalline solid and characterized in detail (including X-ray diffraction).
- Bolyog-Nagy, Evelin,Udvardy, Antal,Barczáné-Bertók, ágnes,Joó, Ferenc,Kathó, ágnes
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p. 514 - 520
(2016/12/02)
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