- Production of Alcohols from Olefins via One-Pot Tandem Hydroformylation-Acetalization-Hydrogenolysis over Bifunctional Catalyst Merging RuIII-P Complex and RuIII Lewis Acid
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A novel three-step tandem hydroformylation-acetalization-hydrogenolysis was first proposed to produce alcohols (derivatives) from olefins, and the developed unique Ru(III)-complex [Ru(III)-L2] ligated by the ionic diphosphine (L2) proved efficient toward this tandem reaction. In Ru(III)-L2, the strong π-acceptor nature of L2 guaranteed Ru-center remaining in +3 valence state without redox reaction. Hence, Ru(III)-L2 was able to behave as a bifunctional catalyst merging RuIII-P complex and RuIII Lewis acid, which acted not only as a transition metal catalyst responsible for hydroformylation of olefins and hydrogenolysis of (hemi)acetals but also as a Ru3+ Lewis acid in charge of acetalization of aldehydes [to form (hemi)acetals]. The easily performed acetalization served as a bridge step to get through the pathway from aldehydes to alcohols instead of the direct hydrogenation.
- Wang, Peng,Wang, Dong-Liang,Liu, Huan,Zhao, Xiao-Li,Lu, Yong,Liu, Ye
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- POLYMER-BOUND TITANIUM OLEFIN ISOMERIZATION CATALYSTS
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Polystyrene-bound bis(cyclopentadienyl)titanium dichloride has been shown to react with Grignard reagents to form a reactive alkene isomerization catalyst, which converts 1-alkenes primarily into E-2-alkenes at room temperature.The catalyst specificity se
- Bergbreiter, David E.,Parsons, Gregory L.
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- Alkyne hydrogenation using Pd-Ag hybrid nanocatalysts in surface-immobilized dendrimers
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A series of Pd-Ag mixed-metal nanocatalysts were prepared by reduction of Pd-Ag salts in the presence of poly(propylene imine) dendrimers, which were covalently bound to the surface of a silica polyamine composite, BP-1 (polyallylamine covalently bound to a silanized amorphous silica gel). Three different Pd-to-Ag ratios were evaluated (50:50, catalyst 1; 40:60, catalyst 2; 60:40, catalyst 3) with the goal of determining how the amount of Ag effects selectivity, rate and conversion in the selective reduction of alkynes, such as phenylacetylene and 1- or 4-octyne, to the corresponding alkenes. Conditions for the catalysis are reported where there is improved selectivity without a serious reduction in rate when compared with the analogous Pd-only catalysts. Catalyst 2 worked best for phenylacetylene and catalyst 3 worked best for the octynes. The catalysts could be reused seven times without loss of activity.
- Karakhanov, Edward A.,Maximov, Anton L.,Zolotukhina, Anna V.,Yatmanova, Nadezhda,Rosenberg, Edward
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- Production of linear alkane via hydrogenative ring opening of a furfural-derived compound in supercritical carbon dioxide
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A simple method has been described to accomplish the formation of linear alkane with >99% selectivity in supercritical carbon dioxide under very mild conditions using Pd/Al-MCM-41 catalyst. The linear alakne was formed through the hydrogenation and dehydration/hydrogenation of 4-5-(5-(hydroxymethyl)furan-2- yl)but-3-en-2-one, which is an aldol condensation product of 5-hydroxymethyl furfural and acetone.
- Chatterjee, Maya,Matsushima, Keichiro,Ikushima, Yutaka,Sato, Masahiro,Yokoyama, Toshirou,Kawanami, Hajime,Suzuki, Toshishige
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- Catalytic and supported Barton-McCombie deoxygenation of secondary alcohols: A clean reaction
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Secondary alcohols were deoxygenated using a new version of the Barton- McCombie process involving a catalytic amount of supported tin hydride in the presence of trimethoxysilane. The products are then easily separated from the catalyst by a simple filtration avoiding pollution by toxic tin by-products. (C) 2000 ElSevier Science Ltd.
- Boussaguet, Paul,Delmond, Bernard,Dumartin, Gilles,Pereyre, Michel
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- Multifunctional, defect-engineered metal-organic frameworks with ruthenium centers: Sorption and catalytic properties
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A mixed-linker solid-solution approach was employed to modify the metal sites and introduce structural defects into the mixed-valence Ru II/III structural analogue of the well-known MOF family [M 3II,II(btc)2] (M=Cu, Mo, Cr, Ni, Zn; btc=benzene-1,3,5-tricarboxylate), with partly missing carboxylate ligators at the Ru2 paddle-wheels. Incorporation of pyridine-3,5-dicarboxylate (pydc), which is the same size as btc but carries lower charge, as a second, defective linker has led to the mixed-linker isoreticular derivatives of Ru-MOF, which display characteristics unlike those of the defect-free framework. Along with the creation of additional coordinatively unsaturated sites, the incorporation of pydc induces the partial reduction of ruthenium. Accordingly, the modified Ru sites are responsible for the activity of the defective variants in the dissociative chemisorption of CO 2, the enhanced performance in CO sorption, the formation of hydride species, and the catalytic hydrogenation of olefins. The defect engineering in Ru-based metal-organic frameworks (MOFs) at coordinatively unsaturated metal centers (CUS) induces partial reduction of the metal nodes and leads to properties that are absent for the parent MOF, such as dissociative chemisorption of CO2 and enhanced sorption capacity of CO. The modified MOFs offer new perspectives as multifunctional materials whose performance is controlled by design of the defects.
- Kozachuk, Olesia,Luz, Ignacio,Llabres I Xamena, Francesc X.,Noei, Heshmat,Kauer, Max,Albada, H. Bauke,Bloch, Eric D.,Marler, Bernd,Wang, Yuemin,Muhler, Martin,Fischer, Roland A.
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- Controlled Pyrolysis of Ni-MOF-74 as a Promising Precursor for the Creation of Highly Active Ni Nanocatalysts in Size-Selective Hydrogenation
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Metal organic frameworks (MOFs) are a class of porous organic-inorganic crystalline materials that have attracted much attention as H2 storage devices and catalytic supports. In this paper, the synthesis of highly-dispersed Ni nanoparticles (NPs) for the hydrogenation of olefins was achieved by employing Ni-MOF-74 as a precursor. Investigations of the structural transformation of Ni species derived from Ni-MOF-74 during heat treatment were conducted. The transformation was monitored in detail by a combination of XRD, in situ XAFS, and XPS measurements. Ni NPs prepared from Ni-MOF-74 were easily reduced by the generation of reducing gases accompanied by the decomposition of Ni-MOF-74 structures during heat treatment at over 300 °C under N2 flow. Ni-MOF-74-300 exhibited the highest activity for the hydrogenation of 1-octene due to efficient suppression of excess agglomerated Ni species during heat treatment. Moreover, Ni-MOF-74-300 showed not only high activity for the hydrogenation of olefins but also high size-selectivity because of the selective formation of Ni NPs covered by MOFs and the MOF-derived carbonaceous layer.
- Nakatsuka, Kazuki,Yoshii, Takeharu,Kuwahara, Yasutaka,Mori, Kohsuke,Yamashita, Hiromi
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- Mechanism of the isomerization of 1-alkene during iron-catalyzed Fischer-Tropsch synthesis
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The deuterium/hydrogen exchange reaction was conducted under iron-catalyzed Fischer-Tropsch reaction conditions using a mixture of deuterated octane, nonane, decane, tridecane, and pentadecane as the probes. The deuterium/hydrogen exchange did not occur in alkanes under these conditions. Under the same reaction conditions, 1-octene-d16 was used as the probe to study the isomerization of 1-alkene. The 1-octene-d16 was reduced to deuterated octane, and isomerized to deuterated trans-2-octene and cis-2-octene with nearly equal amounts of the two isomers. Products from cracking and isomerization to internal octenes other than the 2-octene isomers did not occur to a measurable extent. When 1-octene-d16 was used as the probe, there was H/D exchange in octenes and octane; the lowest deuterium-containing isomer products were the d11 isotopomers, and there were no d16 isomers in the 2-octenes.
- Shi, Buchang,O'Brien, Robert J.,Bao, Shiqi,Davis, Burtron H.
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- Hydrogenation of dienes by a recyclable poly(ethylene oxide)-rhodium phosphineless catalytic system
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The monocationic complex [(η5-Cp*)2Rh2(μ2-Cl)3]PF6 in poly(ethylene oxide) (PEO) 3350/MeOH has proven to be a very efficient catalyst for 1,7-octadiene, 1,9-decadiene, and 1,5-cyclooctadiene hydrogenation. This system allows perfect product separation and catalyst phase recycling, resulting in thousands of catalytic cycles (TON ≈ 9000). Even at room temperature, turnover frequencies as high as 5000 h-1 are attained (50 bar), which makes this one of the most active catalytic systems for diene hydrogenation. Kinetic studies reveal that the reaction rate is second-order in H2 pressure and first-order in both rhodium and diene concentrations. Typical tests suggest that, despite the reductive reaction conditions, which could lead to colloidal metal dispersion, the reduction of dienes is catalyzed by molecular species.
- Tavares, Aline,Wolke, Silvana I.,da Rosa, Ricardo Gomes
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- Reductive-hydroformylation of 1-octene to nonanol using fibrous Co3O4 catalyst
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This work reports, reductive-hydroformylation of 1-octene to nonanol in the presence of fine fibrous cobalt oxide (Co3O4) nano-catalyst prepared via urea reduction method under phosphine-free and additive free condition. Co3O4 nano-catalyst was prepared by the wet chemical method and was characterized using various instrumental techniques like FEG-SEM, EDS, XRD, TPR and FTIR. The effects of various reaction parameters such as temperature, synthesis gas (CO/H2) pressure/ratio, catalyst loading, solvent and time were studied. The reaction was successfully achieved in tetrahydrofuran (THF) as the solvent medium. This reaction believed to takes place through the generation of HCox(CO)y active catalyst species. The Co3O4 nano-catalyst could be recycled up to three consecutive cycles.
- Bhagade, Sachin S.,Chaurasia, Shivkumar R.,Bhanage, Bhalchandra M.
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- A SIMPLE, EFFICIENT METHOD FOR THE PURIFICATION OF POTASSIUM HYDRIDE AND ITS ROLE IN NEW BOROHYDRIDE CHEMISTRY
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KH can be purified with LiAlH4 in THF providing a highly active material wich quantitatively converts even hindered trialkylboranes to the corresponding borohydrides, borinate esters to dialkylborohydrides and reduces, with a catalytic amount of a trialkylborane, 1-bromoalkanes.
- Soderquist, John A.,Rivera, Isaac
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- Deoxygenation of alcohols by the reactions of their xanthate esters with triethylsilane: An alternative to tributyltin hydride in the Barton-McCombie reaction
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O-Alkyl S-methyl dithiocarbonates derived from primary or secondary alcohols (ROH) react with trialkylsilanes in non-aromatic solvents to give the corresponding hydrocarbons RH in good yields; the reductions are promoted by thiols which act as polarity reversal catalysts.
- Nicholas Kirwan,Roberts, Brian P.,Willis, Colin R.
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- Hypervalent iodine in carbon-carbon bond forming reactions. A new reaction of hypervalent iodine compounds and organolithium reagents
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Hypervalent iodine compounds react with organolithium reagents instantaneously even at -80°C resulting in the formation of hydrocarbons. Our findings indicate that the carbon-carbon bond formation is the result of ligand exchange and second displacement on the carbon bonded to iodine.
- Barton,Jaszberenyi Cs.,Lessmann,Timar
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- Catalytic deoxygenation of octanoic acid over silica- and carbon-supported palladium: Support effects and reaction pathways
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Octanoic acid (OA) deoxygenation was investigated over silica- and carbon-supported palladium catalysts (each containing 5 wt.% Pd) at 235-300 °C and 1 atm in a continuous flow reactor. A commercial Pd/SiO2 (A) catalyst was active for OA decarbonylation (DCN) and hydrodeoxygenation (HDO) at 260 °C under 10% H2; subsequent hydrogenation (HY) and DCN of the primary products, 1-heptene and octanal, respectively, produced n-heptane. Under equivalent conditions, a Pd/SiO2 (B) catalyst prepared using Pd(NO3)2 and Aerosil 300 produced n-heptane with very high selectivity (>99%) via DCN/HY. In contrast, a commercial Pd/C (A) catalyst was highly active and selective to n-heptane (>98%) and CO2 (65%) under these conditions. Moreover, CO2 selectivity and n-heptane yield increased with reaction temperature consistent with direct decarboxylation (DCX). Increasing H2 partial pressure resulted in markedly lower activity and CO2 selectivity; however, Pd/C (A) had negligible activity under He. Pd/C (A) exhibited greater water-gas shift (WGS) activity than Pd/SiO2 (A); however, differences in WGS activity alone cannot explain the observed support effect. A more highly dispersed Pd/C (B) catalyst was more active at 260 °C under H2 than Pd/C (A); however, under 10% H2, it had lower activity, CO2 selectivity (55%), and stability. Pd/C (A) and Pd/C (B) have very similar textural properties, but Pd/C (A) has a much higher Na content. By comparison, Pd supported on high-purity acetylene carbon black exhibited only DCN activity. These results indicate that carbon surface properties (e.g., polar functional groups, alkali metal content) influence the fatty acid deoxygenation performance of Pd/C catalysts.
- Sun, Keyi,Schulz, Taylor C.,Thompson, Simon T.,Lamb, H. Henry
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- Improvement on the catalytic performance of Mg-Zr mixed oxides for furfural-acetone aldol condensation by supporting on mesoporous carbons
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A new procedure for improving the performance of the most common catalysts used in aqueous-phase aldol condensation (Mg-Zr mixed oxides) reactions is presented. This reaction is of interest for upgrading carbohydrate feedstocks. The procedure involves supporting Mg-Zr oxides on non-microporous carbonaceous materials, such as carbon nanofibers (CNFs) or high-surface-area graphites (HSAGs), using either incipient wetness or coprecipitation procedures. The use of HSAGs together with the coprecipitation method provides the best performance. Results obtained for the cross-condensation of acetone and furfural at 323K reveal that the catalyst performance is greatly improved compared to the bulk oxides (96.5 % conversion vs. 81.4 % with the bulk oxide; 87.8 % selectivity for C13 and C8 adducts vs. 76.2 % with the bulk oxide). This difference is even more prominent in terms of rates per catalytically active basic site (four and seven times greater for C8 and C13 adducts, respectively). The improved performance is explained in terms of a more appropriate basic site distribution and by greater interaction of the reactants with the carbon surface. In addition, deactivation behavior of the catalyst is improved by tuning the morphology of the carbonaceous support. An important enhancement of the catalytic stability can be obtained selecting a HSAG with an appropriate pore diameter. With HSAG100 the activity decreased by less than 20 % between successive reaction cycles and the selectivity for the condensation products remained almost unaltered. The decrease is greater than 80 % for the bulk oxides tested at these conditions, with important increases in the selectivity for by-product formation. Copyright
- Faba, Laura,Diaz, Eva,Ordonez, Salvador
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- Hydroconversion of n-hexadecane on Pt/silica-alumina catalysts: Effect of metal loading and support acidity on bifunctional and hydrogenolytic activity
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Bifunctional catalysts based on platinum and amorphous silica-alumina were studied in the hydroconversion of n-hexadecane. The influence of platinum loading and support acidity on activity and selectivity were assessed. The contribution of hydrogenolysis reactions on top of bifunctional hydrocracking was shown to depend not only on metal loading, but also on the effect of support acidity on the intrinsic activity of the platinum sites. The yield of cracking products, and their linear alkane fraction, increased with metal loading, while the isomerization yield was practically independent of the metal content. On a support of high Br?nsted acidity, the rate of formation of methane was proportional to the platinum surface area, indicating that demethylation occurred by metal-catalyzed hydrogenolysis. On the other hand, the methane site-time yield was one order of magnitude lower on a catalyst with negligible Br?nsted acidity. Pt-catalyzed hydrogenolysis was also investigated during selective poisoning of acid sites by co-feeding pyridine and comparing the effect of hydrogen partial pressure on reaction rates. In the presence of pyridine, total hydroconversion activity was reduced by one order of magnitude while rates to methane and linear cracking products remained relatively high. These observations indicate that acid sites do not intervene in the mechanism, but that support acidity affects the hydrogenolytic activity of platinum sites.
- Regali, Francesco,Liotta, Leonarda Francesca,Venezia, Anna Maria,Boutonnet, Magali,J?r?s, Sven
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- Tailorable synthesis of porous organic polymers decorating ultrafine palladium nanoparticles for hydrogenation of olefins
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Two 1,2,3-triazolyl-containing porous organic polymers (CPP-C and CPP-Y) were readily synthesized through click reaction and Yamamoto coupling reaction, respectively. The effects of synthetic methods on the structures and properties of CPP-C and CPP-Y were investigated. Their chemical compositions are almost identical, but their physical and texture properties are different from each other. Ultrafine palladium nanoparticles can be effectively immobilized in the interior cavities of CPP-C and CPP-Y. The interactions between polymers and palladium are verified by IR, solid-state NMR, XPS, and EDS. Their catalytic performances are evaluated by hydrogenation of olefins. Pd@CPP-Y exhibits higher catalytic activity and recyclability than Pd@CPP-C. Hot filtration and the three-phase test indicate that hydrogenation functions in a heterogeneous pathway. (Figure Presented).
- Li, Liuyi,Zhao, Huaixia,Wang, Ruihu
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- N-heterocyclic carbene rhodium complexes and their reactions with H2 andwith co
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The NHC-RhIcomplexes [RhCl(COE)(NHC)] 2 1 and 2 [COE= cyclooctene, NHC in 1 = N,N-bis(2,6-diisopropylphenyl)-imidazol-2-ylidene (IPr) and, in 2, N,N-bis(2,4,6-trimeth-ylphenyl)imidazol-2-ylidene (IMes)] react with H2 in hexaneto give the dimeric, mono-carbene dihydrido species [Rh(H)2-Cl(NHC)] 2 (NHC = IPr (3), IMes (4)). In the presence offurther NHC, the bis-carbene dihydrido species Rh(H)2Cl-(NHC)2 are formed; a crystal structure of the IPr complex 5is analogous to that of the known IMes analogue. The di-hydride-mixed-carbene species Rh(H)2Cl(IPr)(IMes) (5a) wasalso observed but not isolated. A benzene solution of 5 underD2 slowly generates the corresponding dideuteride. Reactions of the mono-carbenes (1/3, or 2/4) with CO in hexaneafford the respective dicarbonyl complexes RhCl(CO)2(NHC)[NHC = IPr (6), IMes (7)] , while CO reactions with the bis-carbene dihydrides give, respectively, the mono-carbonylcomplex RhCl(CO)(IPr)2 (8) and the known IMes analogue. All the complexes are characterized by elemental analysis, 1H and 13C{1H} NMR and IR spectroscopies and, in the caseof 5, by X-ray crystallography. The catalytic activities of 5and the previously reported Rh(H)2Cl(IMes)2 for hydrogenation of COE and 1-octene (and isomerization of the latter) areshowntobepoor. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009.
- Yu, Xiao-Yan,Sun, Hongsui,Patrick, Brian O.,James, Brian R.
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- Synthetic and structural studies of NHC-Pt(dvtms) complexes and their application as alkene hydrosilylation catalysts (NHC = N-heterocyclic carbene, dvtms = divinyltetramethylsiloxane)
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The synthesis and structural characterization of a series of platinum complexes, bearing N-heterocyclic carbenes (NHC) and divinyltetramethylsiloxane (dvtms) as supporting ligands, are described. The reaction of commercially available Karstedt's catalyst
- Berthon-Gelloz, Guillaume,Buisine, Olivier,Brière, Jean-Fran?ois,Michaud, Guillaume,Stérin, Sébastien,Mignani, Gérard,Tinant, Bernard,Declercq, Jean-Paul,Chapon, David,Markó, István E.
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- Fast Halogen Abstraction from Alkyl Halides by Alkyl Radicals. Quantitation of the Processes Occurring in and a Caveat for Studies Employing Alkyl Halide Mechanistic Probes
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Second-order rate constants for halogen atom transfer (kRX) in benzene at 50 deg C were determined for reactions of octyl radical with tert-butyl, isopropyl, and cyclohexyl iodides and bromides and with ethyl iodide, n-butyl bromide, tert-butyl chloride, and carbon tetrachloride using two methods.In method A, an aklyl iodide and tributylstannane were allowed to compete for octyl radical in radical-chain reactions; in method B, an alkyl halide competed with 1-(oxononoxy)-2(1H)-pyridinethione (1) for octyl radical.The values for kRX were calculated from the product distributions, the reactant ratios, and the known rate constants for reaction of tributylstannane or 1 with octyl radical.The possibility that rearranged products can be formed in reactions of alkyl halide mechanistic probes with nucleophiles via a sequence involving radical-chain isomerization that converts the probe halide into a rearranged halide followed by nucleophilic attack on the isomerized halide is discussed as are possible chain-terminating reactions.The conclusion is reached that the percentage of rearranged substitution products formed in reactions of alkyl halide mechanistic probes with nucleophiles can give misleading information about the number of radical-initiating events.
- Newcomb, Martin,Sanchez, Robert M.,Kaplan, Jere
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- Designing highly efficient Rh/CPOL-bp&PPh3 heterogenous catalysts for hydroformylation of internal and terminal olefins
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Vinyl functionalized Biphephos ligand, denoted as vinyl biphephos, has been succesfully synthesized. Copolymerization of vinyl biphephos with tris(4-vinphenyl) phosphane can afford an efficient Porous Organic Polymer (POP), CPOL-bp&PPh3. The ultimately formed Rh/CPOL-bp&PPh3 heterogeneous catalyst showed excellent performance in converting terminal olefins to the corresponding linear aldehydes with high regioselectivity (l/b = 96:4-98:2), activity and stability, even better than the comparable homogeneous Rh + vinyl biphephos system. Notably, isomerizing hydrofromylation of internal olefins (2-heptene, 2-octene, trans-3-hexene) was also performed with high regioselectivity (l/b = 92:8-93:7) using the Rh/CPOL-bp&PPh3 heterogeneous catalyst.
- Li, Cunyao,Xiong, Kai,Yan, Li,Jiang, Miao,Song, Xiangen,Wang, Tao,Chen, Xingkun,Zhan, Zhuangping,Ding, Yunjie
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- Synthesis of phosphorus amidite ligand and investigation of its flexibility impact on rhodium-catalyzed hydroformylation of 1-octene
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A new flexible 2,2′-bis((dipyrrolylphosphinooxy)methyl)-1,1′-(±)-biphenyl ligand (L1) was synthesized, characterized and employed in the hydroformylation of 1-octene. In order to investigate the influence of ligand flexibility on the catalytic performance, its analogue 2,2′-bis (dipyrrolylphosphinooxy)-1,1′-(±)-biphenyl (L3) was also applied in the hydroformylation of 1-octene. With the presence of L1, the aldehyde selectivity was approximately 10% higher than that with the relevant less flexible ligand L3. Theoretical calculation indicated that the olefin-insertion into the Rh-H bond of intermediate III and the CO-insertion into Rh-alkyl bond of intermediate V were favorable in terms of thermodynamics, which were vital to the generation of aldehyde. Meanwhile, the ligand flexibility was indeed improved by adding a methylene between benzene and oxygen atom that connected with P, as the calculation showed the variation of the bite angle ∠P-Rh-P of the intermediates I-VI was 8.7° in L1-system, as for L3-system, the variation was 14.0°. This structural feature might make the olefin-insertion and the CO-insertion occur more easily in the L1-system and resulted in higher aldehyde selectivity.
- Han, Weibiao,Qin, Song,Shu, Xiao,Wu, Qianhui,Xu, Bin,Li, Ruixiang,Zheng, Xueli,Chen, Hua
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- Encapsulated liquid nano-droplets for efficient and selective biphasic hydroformylation of long-chain alkenes
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Aqueous nano-droplets of homogeneous Rh-TPPTS catalyst encapsulated within the cavity of hollow silica nanospheres were fabricated for biphasic hydroformylation of long-chain alkenes, which showed significant reaction rate enhancement effects and improved aldehyde selectivity.
- Zhang, Xiaoli,Wei, Juan,Zhang, Xiaoming
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- Dinuclear Ruthenium Complexes as Active Catalyst Precursors for the Low Pressure Hydroformylation of Alkenes into Aldehydes
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Di-μ-acetato diruthenium complexes catalyse the low pressure hydroformylation of alkenes to give the corresponding aldehydes with high selectivities.
- Jenck, Jean,Kalck, Philippe,Pinelli, Eric,Siani, Michel,Thorez, Alain
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In dimethylformamide or N-methylpyrrolidone the Ni-bipyridyl system catalyses the electrochemical reduction of functionalised or non-functionalised aliphatic halides. High yields of dimeric products are obtained besides primary mono- or di-bromides. Analysis of the reaction products shows the formation of dialkylnickel which can be isolated by coulometry. This species acts as a reducing agent for aliphatic halides.
- Mabrouk, Salah,Pellegrini, Sylvain,Folest, Jean-Claude,Rollin, Yolande,Perichon, Jacques
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- Reducing Alkyl Halides Using a Polymer-Bound Crown Ether/Tin Hydride Cocatalyst
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In this paper the synthesis and application of a novel macromolecular cocatalyst in which both reactive sites are on the same polymer matrix is described.Using this macromolecular cocatalyst, it was found that alkyl halide groups could be conveniently transformed into the corresponding hydrocarbon moiety in moderate yields.
- Blanton, James R.,Salley, Joseph M.
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- DIRECT PHOTOLYSIS AT 185 nm OF 1-ALKENES IN SOLUTION. MOLECULAR ELIMINATION OF TERMINAL HYDROGENS
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Direct irradiations at 185 nm of 1-octene and 2-methyl-1-pentene in pentane gave alkylidene carbenes through the molecular elimination of terminal hydrogens, as well as double-bond migration products via 1,3-shift of allylic hydrogen and radical-derived products.
- Inoue, Yoshihisa,Mukai, Toshio,Hakushi, Tadao
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- High Molecular Weight Hydrocarbons from the Fischer-Tropsch Process with a Pre-oxidized Ruthenium Zeolite Catalyst
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The catalytic performance of zeolite-based ruthenium catalysts in the Fischer-Tropsch reaction depends on the sequence of oxidations/reductions to which they are subjected: with finely divided Ru particles obtained by reducing 3+-exchanged synthetic faujasitic zeolite, methane is the predominant product; but when the zeolite is first oxidised in air at 400 deg C forming crystallites of RuO2 which can then be reduced, longer-chain hydrocarbons are produced at low reaction temperatures (155 deg C).
- Audier, Marc,Klinowski, Jacek,Benfield, Robert E.
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- In Situ Generation and Immobilization of an Activated Rh Complex Catalyst in a Metal–Organic Framework for Hydrogenation at Low H2 Pressure
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Hydrogenation reactions under low-pressure H2 atmosphere are highly relevant from the safety viewpoint, because H2 gas is highly flammable in air and explosions can be triggered by spark, heat, or sunlight. In this work, an Rh complex/MOF hybrid was synthesized and used as catalyst for the hydrogenation of alkene substrates. Thanks to the activation of the Rh complex catalyst during the immobilization process and the intrinsic gas-condensation property of MOFs, the resulting composite showed much higher catalytic activity than the complex catalyst itself. Moreover, the composite can maintain its catalytic activity even at low H2 pressures that cannot support the reaction with the complex catalyst alone. Furthermore, in contrast to the complex catalyst, the composite maintained its catalytic activity even without solvent, and thus provides an environmentally friendly approach to catalysis.
- Takashima, Yohei,Fukuhara, Yoshimasa,Sato, Yasushi,Tsuruoka, Takaaki,Akamatsu, Kensuke
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- The mechanism of polarity-reversal catalysis as involved in the radical-chain reduction of alkyl halides using the silane-thiol couple
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The mechanism by which thiols promote the radical-chain reduction of alkyl halides by a variety of simple silanes, such as Et3SiH and Ph3SiH, has been investigated in detail. Kinetic studies of the thiol-catalysed reduction of 1-bromooctane and of 1-chlorooctane by Et3SiH in cyclohexane at 60°C are consistent with a mechanism that involves reversible abstraction of hydrogen by the thiyl radical from the silane, followed by abstraction of halogen from the octyl halide by the resulting triethylsilyl radical and quenching of the derived octyl radical by the thiol to give octane. On the basis of this mechanism, rate constants for abstraction of hydrogen from Et3SiH by the adamantane-1-thiyl radical (kXSH) and for transfer of hydrogen in the reverse direction (KSiH) were determined as 3.2 × 104 M-1 s-1 and 5.2 × 107 M-1 s-1, respectively, at 60°C. The equilibrium constant kXSH/kSiH is thus 6.2 × 10-4 at 60°C and corresponds to ΔrH ≈ ΔrG = +20.4 kJ mol-1 for abstraction of hydrogen from Et3SiH by 1-AdS, implying that the Si-H bond in the silane is stronger by ca. 20 kJ mol-1 than the S-H bond in the alkanethiol. The silanethiol (ButO)3SiSH was found to be a more effective catalyst than 1-AdSH, because kXSH is greater (1.3 × 105 M-1 s-1) while kSiH is very similar (5.1 × 107 M-1 s-1). The value of kXSH/kSiH is now 2.6 × 10-3 at 60°C and thus the S-H bond in this silanethiol is stronger by ca. 4 kJ mol-1 than that in 1-AdSH. The proposed mechanism for alkyl halide reduction is strongly supported by kinetic studies of the thiol-catalysed H/D-exchange between R3SiH/D and XSH/D and the thiol-catalysed racemisation of (S)-ButMePhSiH, radical-chain processes that provide independent confirmation of the values of kXSH derived from octyl bromide reduction. The value of ΔrH determined in this work indicates that abstraction of hydrogen from Et3SiH by an alkanethiyl radical in cyclohexane solvent is ca. 11 kJ mol-1 less endothermic than implied by the difference in the currently-favoured experimental gas-phase dissociation enthalpies for the Et3Si-H and MeS-H bonds.
- Cai, Yudong,Roberts, Brian P.
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- Kinetics of hydrodeoxygenation of octanol over supported nickel catalysts: A mechanistic study
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The hydrodeoxygenation (HDO) of 1-octanol as a model aliphatic alcohol of bio-oil was investigated in a continuous down-flow fixed-bed reactor over γ-Al2O3, SiO2, and HZSM-5 supported nickel catalysts in the temperature range of 488-533 K. The supported nickel catalysts were prepared by incipient wetness impregnation method and characterized by BET, XRD, TPR, TPD, H2pulse chemisorption, and UV-vis spectroscopy. Characterization of supported nickel (or nickel oxide) catalysts revealed existence of dispersed as well as bulk nickel (or nickel oxide) depending on the extent of nickel loading and the nature of the support. The acidity of γ-Al2O3supported nickel catalysts decreased with increasing the nickel loading on γ-Al2O3. n-Heptane, n-octane, di-n-octyl ether, 1-octanal, isomers of heptene and octene, tetradecane, and hexadecane were identified as products of HDO of 1-octanol. The C7hydrocarbons were observed as primary products for catalysts with active metal sites such as γ-Al2O3and SiO2supported nickel catalysts. However, C8hydrocarbons were primarily formed over acidic catalysts such as pure HZSM-5 and HZSM-5 supported nickel catalyst. The 1-octanol conversion increased with increasing nickel loading on γ-Al2O3, and temperature and decreasing pressure and WHSV. The selectivity to products was strongly influenced by temperature, nickel loading on γ-Al2O3, pressure, and types of carrier gases (nitrogen and hydrogen). The selectivity to C7hydrocarbons was favoured over catalysts with increased nickel loading on γ-Al2O3at elevated temperature and lower pressure. A comprehensive reaction mechanism of HDO of 1-octanol was delineated based on product distribution under various process conditions over different catalysts. This journal is
- Chandra Sekhar Palla, Venkata,Shee, Debaprasad,Maity, Sunil K.
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- Noble metal-free catalytic decarboxylation of oleic acid to n-heptadecane on nickel-based metal-organic frameworks (MOFs)
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Nickel based metal organic frameworks (Ni-MOFs) were successfully synthesized using new conjugated carboxylic acid linkers. These conjugated carboxylic acid linkers were synthesized using mild Heck coupling that led to the incorporation of functional groups not possible by traditional synthetic methods. Control of linker size allows for porosity tuning of the crystalline network and high surface area, that, in theory, results in the increased accessibility to Ni metal centers for catalysis. The resultant crystalline Ni-MOFs displayed BET areas as high as ～314 m2 g-1. To investigate their catalytic activity for conversion of oleic acid to liquid hydrocarbons, Ni-MOFs were grown on zeolite 5A beads that served as catalytic supports. The resultant catalysts displayed heptadecane selectivity as high as ～77% at mild reaction conditions, one of the highest yields for non-noble metal containing catalysts. The catalytic activity correlated to the concentration of acid sites. A slight decrease in catalytic activity was observed after catalysts recycling.
- Yang,McNichols,Davidson,Schweitzer,Gómez-Gualdrón,Trewyn,Sellinger,Carreon
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- DISSOLVING METAL REDUCTIONS WITH SODIUM POTASSIUM ALLOY IN THE PRESENCE OF 18-CROWN-6
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The dissolving metal reduction of organic compounds can be performed in THF utilizing sodium potassium alloy in the presence of a catalytic amount of 18-crown-6.
- Mathre, David J.,Guida, Wayne C.
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- Oligomerization of 1-butene with a homogeneous catalyst system based on allylic nickel complexes
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The oligomerization of 1-butene with a nickel-based catalyst system constitutes an elegant synthesis method for obtaining linear octenes from readily available chemicals. It is well known that the bis-(cyclooctadiene)nickel(0)-complex (Ni(COD)2) can be used in combination with 1,1,1,5,5,5-hexafluoroacetylacetone (hfacac) forming [Ni-1] as a catalyst for the dimerization of 1-butene, which produces a linear octene yield of 75-83% at reaction temperatures between 70-80 °C. We are the first to demonstrate that it is also possible to use allylic nickel complexes in combination with hfacac to produce linear octenes with a selectivity of 70% under very mild reaction conditions and at low catalyst concentrations. Additionally the catalyst can be formed simply by adding the activator hfacac to a solution of the allylic nickel complex. No complicated synthesis or purification is needed.
- Behr,Bayrak,Peitz,Stochniol,Maschmeyer
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- Controlling the performance of a silver co-catalyst by a palladium core in TiO2-photocatalyzed alkyne semihydrogenation and H2 production
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Titanium (IV) oxide (TiO2) having palladium (Pd) core-silver (Ag) shell nanoparticles (Pd@Ag/TiO2) was prepared by using a two-step (Pd first and then Ag) photodeposition method. The core-shell structure of the nanoparticles having various Ag contents (shell thicknesses) and the electron states of Pd and Ag were investigated by transmission electron microscopy and X-ray photoelectron spectroscopy, respectively. The effect of the Pd core and the Ag shell was evaluated by hydrogenation of 4-octyne in alcohol suspensions of a photocatalyst under argon and light irradiation. 4-Octyne was fully hydrogenated to 4-octane over Pd/TiO2, whereas 4-octyne was selectively hydrogenated to cis-4-octene over Pd(0.2)@Ag(0.5)/TiO2. Further increase in the Ag content resulted in a decrease in the conversion of 4-octyne. Pd-free Ag/TiO2 was inactive for hydrogenation of alkyne and induced coupling of active hydrogen species (H2 production). Photocatalytic reactions at various temperatures revealed that the change in selectivity (semihydrogenation or H2 production) can be explained by the difference in values of activation energy of the two reactions. An applicability test showed that the Pd@Ag/TiO2 photocatalyst can be used for hydrogenation of various alkynes to alkenes.
- Fudo, Eri,Imai, Shota,Kojima, Yasumi,Kominami, Hiroshi,Tanaka, Atsuhiro
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- Activation of Reducing Agents. Sodium Hydride Containing Complex Reducing Agents. 15. Reduction and Selective Reduction of Organic Halides
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The reduction of alkyl and vinyl halides with a reducing system composed of NaH, alkoxides, and metal salts ("complex reducing agents", CRA) has been investigated.The reagent system efficiently converts primary, secondary, and tertiary alkyl iodides, bromides, and chlorides to the corresponding hydrocarbons.Alkyl tosylates are less readily attacked, and fluorides are inert.Benzyl, allyl, and vinyl halides are also reduced.The latter react stereospecifically without double bond isomerization.Selective reductions of mixtures of alkyl halides are possible with eitherNi CRA or Zn CRA, and the reagents are inert toward a number of other functional groups, allowing selective reductions to be achieved.Finally, the reduction may be achieved by using catalytic amounts of nickel salts.Possible structures for the complex reducing agents are discussed, as well as suggested mechanisms for halide reductions.
- Vanderesse, Regis,Brunet, Jean-Jacques,Caubere, Paul
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- Engineering active sites on reduced graphene oxide by hydrogen plasma irradiation: Mimicking bifunctional metal/supported catalysts in hydrogenation reactions
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H2 plasma has been used to generate carbon vacancies on reduced graphene oxide to increase its catalytic activity as a hydrogenation catalyst. A relationship between the power of the plasma treatment and the exposure time with the activity of the material was observed for CC double bond hydrogenation. The activity data in the case of 1-octene, showing skeletal isomerization besides hydrogenation, indicate that H2 plasma treatment can introduce hydrogenating and acid sites rendering a bifunctional catalyst that is reminiscent of the activity of noble metals supported on acid supports.
- Primo, Ana,Franconetti, Antonio,Magureanu, Monica,Mandache, Nicolae Bogdan,Bucur, Cristina,Rizescu, Cristina,Cojocaru, Bogdan,Parvulescu, Vasile I.,Garcia, Hermenegildo
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- Promotional effect of Fe on performance of Ni/SiO2 for deoxygenation of methyl laurate as a model compound to hydrocarbons
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Ni/SiO2, Fe/SiO2 and bimetallic FeNi/SiO2 catalysts with different Fe/Ni weight ratios were prepared by incipient-wetness impregnation method for the deoxygenation of methyl laurate to hydrocarbons. It was found that a suitable amount of Fe enhanced the activity of Ni/SiO2 for the deoxygenation of methyl laurate, and FeNi(0.25)/SiO2 with a Fe/Ni weight ratio of 0.25 showed the best activity. Moreover, the addition of Fe to Ni/SiO2 significantly promoted the hydrodeoxygenation pathway to produce more C12 hydrocarbon and suppressed the activity for C-C hydrogenolysis. The effect of Fe on the performance of Ni/SiO2 is ascribed the formation of the NiFe alloy particles, particularly with the Fe-enriched surface at low Fe content, and the existence of oxygen vacancies in Fe oxides. A mechanism is proposed to explain the promoting effect of Fe, which involves the synergism between iron sites with strong oxophilicity and nickel sites with high ability to activate hydrogen. Besides, the effect of reaction conditions and catalyst stability were also investigated.
- Yu, Xinbin,Chen, Jixiang,Ren, Tianyu
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- A new air-stable and reusable tetraphosphine ligand for rhodium-catalyzed hydroformylation of terminal olefins at low temperature
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Tetraphosphine and bisphosphine ligands were synthesized, characterized and employed in Rh-catalyzed hydroformylation of 1-octene and 1-hexene. Conversion of over 97.7% and aldehyde yield of 94.1% were achieved at 60°C, 20?bar. This remarkable performance could also be retained at lower temperature (i.e. 40°C) by prolonging the reaction time. The tetraphosphine ligand-modified Rh catalyst could be reused for at least seven successive runs with catalytic activity and selectivity almost unchanged; the catalyst was separated from the products and recycled directly in homogeneous hydroformylation, indicating that the catalyst might have good stability. 31P NMR and high-resolution mass spectral characterization hinted that the reason for the reusability of the catalyst might be that the tetraphosphine ligand is relatively air-stable and is probably slowly oxidized during the recycling runs. The tetraphosphine ligand has four phosphorus atoms to be partially oxidized and could still coordinate with the Rh center via the unoxidized phosphorus atoms to stabilize the catalyst, based on the multiple chelating modes of the tetraphosphine ligand. Hence, the catalytic activity and selectivity could be retained for a certain number of runs.
- Zhou, Fanding,Zhang, Lin,Wu, Qianhui,Guo, Fuya,Tang, Songbai,Xu, Bin,Yuan, Maolin,Fu, Haiyan,Li, Ruixiang,Zheng, Xueli,Chen, Hua
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- Hydrocarbon production from decarboxylation of fatty acid without hydrogen
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Decarboxylation of oleic acid without hydrogen was carried out using hydrotalcites with three different MgO contents (30, 63 and 70 wt%). Effect of MgO content in hydrotalcites and reaction temperatures on the decarboxylation performance in terms of oleic
- Na, Jeong-Geol,Yi, Bo Eun,Kim, Ju Nam,Yi, Kwang Bok,Park, Sung-Youl,Park, Jong-Ho,Kim, Jong-Nam,Ko, Chang Hyun
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- Decarboxylation of Oleic Acid to Heptadecane over Pt Supported on Zeolite 5A Beads
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The synthesis of Pt supported on zeolite 5A beads for the decarboxylation of oleic acid to heptadecane is demonstrated. The use of a microporous ZIF-67 crystalline layer on zeolite 5A beads not only improved the heptadecane selectivity but also, most importantly, improved the stability of the resultant catalyst. Heptadecane yields as high as ～81% were observed for the fresh catalysts. The catalysts displayed only low to moderate loss of catalytic activity after two rounds of recycle. To our best knowledge, the catalytic performance of these catalysts is superior to those of the state-of-the-art catalysts at mild reaction conditions. In addition, as compared to powders, beads are much easier to recycle, can be fully recovered, and are more amenable for potential scale-up. The resultant catalysts are promising for the catalytic conversion of fatty acid molecules into gasoline/diesel-range hydrocarbons.
- Yang, Liqiu,Tate, Kirby L.,Jasinski, Jacek B.,Carreon, Moises A.
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- The effect of the position of cross-linkers on the structure and microenvironment of PPh3moiety in porous organic polymers
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Three trivinyl functionalization triphenylphosphine (3vPPh3)-based porous organic ligands (3vPPh3-POLs) with cross-linkers in different positions were obtained through solvothermal polymerization. By simply changing the position of the cross-linkers (vinyl groups) attached to the PPh3monomer, the resulting porous organic polymer (POP) materials acquired diverse hierarchical porous structures, and the microenvironment of POPs was sequently regulated. Among the three 3vPPh3-POLs, the BET surface areas ranged from 168 to 1583 m2g?1, while the proportion of micropores changed from 0.0% to 52.0%. Benefiting from the unique structure, Rh ions could be coordinated and dispersed as a single site inm-3vPPh3-POL to form HRh(CO)2(PPh3-POL)2species, which endowed the Rh/m-3vPPh3-POL catalyst with an activity similar to that in the homogeneous system, anl/bratio (the ratio of the linear aldehyde to the branched aldehyde) approximately as high as 10, and stability for a duration of more than 500 h in the hydroformylation of 1-octene.
- Ji, Guangjun,Li, Cunyao,Xiao, Dong,Wang, Guoqing,Sun, Zhao,Jiang, Miao,Hou, Guangjin,Yan, Li,Ding, Yunjie
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- STRONGLY LEWIS ACIDIC METAL-ORGANIC FRAMEWORKS FOR CONTINUOUS FLOW CATALYSIS
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Lewis acidic metal-organic framework (MOF) materials comprising triflate-coordinated metal nodes are described. The materials can be used as heterogenous catalysts in a wide range of organic group transformations, including Diels-Alder reactions, epoxide-ring opening reactions, Friedel-Crafts acylation reactions and alkene hydroalkoxylation reactions. The MOFs can also be prepared with metallated organic bridging ligands to provide heterogenous catalysts for tandem reactions and/or prepared as composites with support particles for use in columns of continuous flow reactor systems. Methods of preparing and using the MOF materials and their composites are also described.
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Paragraph 0166; 0168
(2021/02/26)
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- Steric and Electronic Effects of Phosphane Additives on the Catalytic Performance of Colloidal Palladium Nanoparticles in the Semi-Hydrogenation of Alkynes
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We report on the influence of phosphanes on the catalytic activity and selectivity of colloidal, tetraoctylammonium bromide (TOAB) stabilised palladium nanoparticles (NPs) in the semi-hydrogenation of alkynes to olefins. Full characterisation of the catalytic system (HRTEM, EDX, XPS, IR, NMR) confirmed the formation of spherical particles with a narrow size distribution (1.9±0.5 nm). The catalytic performance of the Pd NPs in the semi-hydrogenation of 1-octyne, 2-octyne and phenylacetylene to the respective olefins and the influences on the selectivity was investigated. The system shows high activities and selectivities at mild conditions (0 °C and 1.0 bar H2 pressure). It was shown that generally, phosphanes lead to an increase of both the reaction rate and selectivity towards the olefin where both steric and electronic effects of the ligand play a crucial role for the catalyst performance. A moderate steric demand of the ligand with a rather weak σ-donating ability turned out to give the highest catalytic performance.
- Staiger, Lena,Kratky, Tim,Günther, Sebastian,Tomanek, Ondrej,Zbo?il, Radek,Fischer, Richard W.,Fischer, Roland A.,Cokoja, Mirza
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p. 227 - 234
(2020/10/14)
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- Catalytic Boration of Alkyl Halides with Borane without Hydrodehalogenation Enabled by Titanium Catalyst
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An unprecedented and general titanium-catalyzed boration of alkyl (pseudo)halides (alkyl-X, X=I, Br, Cl, OMs) with borane (HBpin, HBcat) is reported. The use of titanium catalyst can successfully suppress the undesired hydrodehalogenation products that prevail using other transition-metal catalysts. A series of synthetically useful alkyl boronate esters are readily obtained from various (primary, secondary, and tertiary) alkyl electrophiles, including unactivated alkyl chlorides, with tolerance of other reducing functional groups such as ester, alkene, and carbamate. Preliminary studies on the mechanism revealed a possible radical reaction pathway. Further extension of our strategy to aryl bromides is also demonstrated.
- Wang, Xianjin,Cui, Penglei,Xia, Chungu,Wu, Lipeng
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supporting information
p. 12298 - 12303
(2021/05/07)
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- Metal-Organic Framework-Confined Single-Site Base-Metal Catalyst for Chemoselective Hydrodeoxygenation of Carbonyls and Alcohols
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Chemoselective deoxygenation of carbonyls and alcohols using hydrogen by heterogeneous base-metal catalysts is crucial for the sustainable production of fine chemicals and biofuels. We report an aluminum metal-organic framework (DUT-5) node support cobalt(II) hydride, which is a highly chemoselective and recyclable heterogeneous catalyst for deoxygenation of a range of aromatic and aliphatic ketones, aldehydes, and primary and secondary alcohols, including biomass-derived substrates under 1 bar H2. The single-site cobalt catalyst (DUT-5-CoH) was easily prepared by postsynthetic metalation of the secondary building units (SBUs) of DUT-5 with CoCl2 followed by the reaction of NaEt3BH. X-ray photoelectron spectroscopy and X-ray absorption near-edge spectroscopy (XANES) indicated the presence of CoII and AlIII centers in DUT-5-CoH and DUT-5-Co after catalysis. The coordination environment of the cobalt center of DUT-5-Co before and after catalysis was established by extended X-ray fine structure spectroscopy (EXAFS) and density functional theory. The kinetic and computational data suggest reversible carbonyl coordination to cobalt preceding the turnover-limiting step, which involves 1,2-insertion of the coordinated carbonyl into the cobalt-hydride bond. The unique coordination environment of the cobalt ion ligated by oxo-nodes within the porous framework and the rate independency on the pressure of H2 allow the deoxygenation reactions chemoselectively under ambient hydrogen pressure.
- Antil, Neha,Kumar, Ajay,Akhtar, Naved,Newar, Rajashree,Begum, Wahida,Manna, Kuntal
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supporting information
p. 9029 - 9039
(2021/06/28)
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- Photo-Initiated Cobalt-Catalyzed Radical Olefin Hydrogenation
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Outer-sphere radical hydrogenation of olefins proceeds via stepwise hydrogen atom transfer (HAT) from transition metal hydride species to the substrate. Typical catalysts exhibit M?H bonds that are either too weak to efficiently activate H2 or too strong to reduce unactivated olefins. This contribution evaluates an alternative approach, that starts from a square-planar cobalt(II) hydride complex. Photoactivation results in Co?H bond homolysis. The three-coordinate cobalt(I) photoproduct binds H2 to give a dihydrogen complex, which is a strong hydrogen atom donor, enabling the stepwise hydrogenation of both styrenes and unactivated aliphatic olefins with H2 via HAT.
- Sang, Sier,Unruh, Tobias,Demeshko, Serhiy,Domenianni, Luis I.,van Leest, Nicolaas P.,Marquetand, Philipp,Schneck, Felix,Würtele, Christian,de Zwart, Felix J.,de Bruin, Bas,González, Leticia,V?hringer, Peter,Schneider, Sven
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p. 16978 - 16989
(2021/08/09)
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- Amphiphilic polymeric nanoreactors containing Rh(i)-NHC complexes for the aqueous biphasic hydrogenation of alkenes
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A rhodium(i) complex bearing a monodentate N-heterocyclic carbene ligand has been confined into the core of amphiphilic polymeric core-crosslinked micelles (CCMs). The Rh complex was covalently bound to the polymeric chains by incorporation of a polymerizable unit on the NHC ligand. Nanoreactor Rh-NHCmes@CCM5bhas been evaluated as a catalyst for the aqueous biphasic hydrogenation of styrene and other alkenes. It has shown a high activity with styrene at a low catalytic loading (10?000/1 substrate/Rh ratio), greater than that of an analogous molecular Rh(i) complex, and its evolution to Rh0is slower. This is attributed to several factors, among which the confinement effect and the favourable polyoxygenated environment of the nanoreactor core. Finally, the CCMs could be recycled up to four times with almost no loss of activity over 3 h cycles and the loss of rhodium per cycle was on average lower than 0.6 ppm.
- Allandrieu, Audrey,Coppel, Yannick,Daran, Jean-Claude,Gayet, Florence,Hromov, Roman,Labande, Agnès,Manoury, Eric,Poli, Rinaldo,Ruzhylo, Illia,Sabatier, Cassandra,Sambou, Sasaline Salomon,Wang, Hui
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p. 6811 - 6824
(2021/10/25)
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- Pd, Cu and Bimetallic PdCu NPs Supported on CNTs and Phosphine-Functionalized Silica: One-Pot Preparation, Characterization and Testing in the Semi-Hydrogenation of Alkynes
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Triphenylphosphine stabilized Pd, Cu and PdCu nanocatalysts supported on carbon nanotubes (CNTs) or phosphorus functionalised silica (P?SiO2) were prepared via a one-pot methodology. The series of P?SiO2 supported catalysts evidenced metal particle sizes of metallic nanoparticles (M-NPs) between 1 and 2.4 nm, smaller than their equivalents on CNTs (2.4–2.6 nm). Such a difference in particle size as a function of the support and the metallic composition indicated the more pronounced mediation of the CNTs support during the formation of the M-NPs when compared to the P?SiO2 support. The series of supported catalysts were tested in the semi-hydrogenation of alkynes providing differences in reactivity which might be correlated with the size and composition of the M-NPs and the nature of corresponding support. The carbon supported catalysts displayed in general higher activities than those supported on silica and the bimetallic catalyst PdCu/CNTs were the most selective for the case of alkyl substituted alkynes. This catalyst could moreover be recycled several times without loss of activity nor selectivity.
- Sánchez-Resa, Daniel,Delgado, Jorge A.,Fernández-Martínez, Maria Dolores,Didelot, Chloé,De Mallmann, Aimery,Szeto, Ka? C.,Taoufik, Mostafa,Claver, Carmen,Godard, Cyril
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supporting information
p. 4970 - 4978
(2021/11/10)
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- Enhanced Hydrogenation Catalytic Activity of Ruthenium Nanoparticles by Solid-Solution Alloying with Molybdenum
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We report the hydrogenation catalytic activity application of molybdenum–ruthenium (MoRu) solid-solution alloy nanoparticles (NPs) as catalysts for the hydrogenation of 1-octene and 1-octyne. The solid-solution structure of MoRu NPs was confirmed through scanning transmission electron microscopy (STEM) coupled with energy-dispersive X-ray spectroscopy (EDX), and powder X-ray diffraction (PXRD) measurement. The hydrogenation catalytic activity of these NPs toward 1-octyne and 1-octene in tetrahydrofuran (THF) was tested. The hydrogenation catalytic activity of Ru was enhanced by alloying with Mo at the atomic level. An electronic modification of Ru by a charge transfer from Mo to Ru, which could induce the change in the adsorption energy of reactants resulting in enhanced catalytic activity, was observed by X-ray photoelectron spectroscopy.
- Okazoe, Shinya,Staiger, Lena,Cokoja, Mirza,Kusada, Kohei,Yamamoto, Tomokazu,Toriyama, Takaaki,Matsumura, Syo,Kitagawa, Hiroshi,Fischer, Roland A.
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supporting information
p. 1186 - 1189
(2021/03/16)
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- Chemoselective Hydrogenation of Olefins Using a Nanostructured Nickel Catalyst
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The selective hydrogenation of functionalized olefins is of great importance in the chemical and pharmaceutical industry. Here, we report on a nanostructured nickel catalyst that enables the selective hydrogenation of purely aliphatic and functionalized olefins under mild conditions. The earth-abundant metal catalyst allows the selective hydrogenation of sterically protected olefins and further tolerates functional groups such as carbonyls, esters, ethers and nitriles. The characterization of our catalyst revealed the formation of surface oxidized metallic nickel nanoparticles stabilized by a N-doped carbon layer on the active carbon support.
- Klarner, Mara,Bieger, Sandra,Drechsler, Markus,Kempe, Rhett
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supporting information
p. 2157 - 2161
(2021/05/21)
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- Mild olefin formationviabio-inspired vitamin B12photocatalysis
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Dehydrohalogenation, or elimination of hydrogen-halide equivalents, remains one of the simplest methods for the installation of the biologically-important olefin functionality. However, this transformation often requires harsh, strongly-basic conditions, rare noble metals, or both, limiting its applicability in the synthesis of complex molecules. Nature has pursued a complementary approach in the novel vitamin B12-dependent photoreceptor CarH, where photolysis of a cobalt-carbon bond leads to selective olefin formation under mild, physiologically-relevant conditions. Herein we report a light-driven B12-based catalytic system that leverages this reactivity to convert alkyl electrophiles to olefins under incredibly mild conditions using only earth abundant elements. Further, this process exhibits a high level of regioselectivity, producing terminal olefins in moderate to excellent yield and exceptional selectivity. Finally, we are able to access a hitherto-unknown transformation, remote elimination, using two cobalt catalysts in tandem to produce subterminal olefins with excellent regioselectivity. Together, we show vitamin B12to be a powerful platform for developing mild olefin-forming reactions.
- Bam, Radha,Pollatos, Alexandros S.,Moser, Austin J.,West, Julian G.
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p. 1736 - 1744
(2021/02/22)
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- A study of the mechanism of triglyceride hydrodeoxygenation over alumina-supported and phosphatized-alumina-supported Pd catalysts
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The mechanism of catalytic hydrodeoxygenation (HDO) of fats, vegetable oils, and fatty acids was studied using alumina-supported Pd catalysts and tricaprylin and valeric acid as model reactants. The chemistry of fatty acid/catalyst interaction was studied by quasi-operando Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS). The Pd/γ–Al2O3 catalyst showed good activity in the hydrogenolysis reaction of the ester bonds to convert tricaprylin to caprylic acid, but they were of poor activity in the consecutive hydrodeoxygenation (HDO) of the acid to paraffin. The surface modification of the support alumina by phosphate groups significantly increased the HDO activity of the Pd catalyst and, consequently, the paraffin yield. The activity change was accounted partly for the partial replacement of the weak base Al–OH groups by weak acid P–OH groups but mainly for the partial elimination of Lewis acid (Al⊕) – Lewis base (O?) pair sites on the surface of the support. Both surface Al–OH and P–OH groups were shown to participate in the reaction with carboxylic acid and formed bidentate surface carboxylate species, which further reacted with hydrogen to give paraffin. Carboxylates of less basic surface sites were found to be more prone to HDO reaction than those of strong base sites. Monodentate carboxylates, formed on Al⊕ O? pair sites were of low reactivity. Phosphatizing eliminated most of the Lewis type acid-base pair sites, therefore, reactive bidentate carboxylates represented the most abundant surface intermediate (MASI) during the HDO reaction of triglyceride. The hydroxyl coverage of the carboxylated surface was shown to become somewhat higher under steady-state reaction conditions. The increased hydroxyl coverage implies that C–O bond hydrogenolysis of the surface carboxylate proceeds, regenerating OH groups and forming aldehyde that could be intermediate of paraffin formation.
- Barthos, Róbert,Domján, Attila,Hancsók, Jen?,Lónyi, Ferenc,Mihályi, Magdolna R.,Novodárszki, Gyula,Solt, Hanna E.,Valyon, József,Vikár, Anna
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- Continuous flow hydrogenation with Pd complexes of pyridine-benzotriazole ligands
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The use of continuous flow systems in chemical synthesis provides great advantages in terms of sustainability, efficiency, and safety. The ability to control reaction parameters such as temperature, pressure, and catalyst exposure in flow system enables rapid optimization of reaction conditions. In the present study, palladium complexes of 1-(piridin-2-il)-1H-benzo[d][1,2,3]triazol, N-((1H-benzo[d][1,2,3]triazol-1-il)metil)piridin-2-amin, and (1H-benzo[d][1,2,3]triazol-1-yl)(pyridin-2-yl)methanone ligands were synthesized and characterized. The catalytic activities of complexes are investigated in the hydrogenation of various alkenes such as styrene, cyclohexene, and 1-octene under continuous flow conditions. The complexes showed very high activity at 10-bar H2 pressure and 50°C for short periods of 5–10?min. The catalysts reused for 10 cycles with no significant loss of catalytic activity.
- Y?lmaz, Filiz,Hür, Deniz
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- Synthesis and Reactivity of (N2P2)Ni Complexes Stabilized by a Diphosphonite Pyridinophane Ligand
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A series of (N2P2)NiIIcomplexes (N2P2 =P,P′-ditertbutyl-2,11-diphosphonito[3.3](2,6)pyridinophane) stabilized by a modified tetradentate pyridinophane ligand containing two phosphonite groups were synthesized and characterized. Cyclic voltammetry (CV) studies revealed the accessibility of the NiIoxidation state at moderate redox potentials for these NiIIcomplexes.In situEPR, low-temperature UV-vis, and electrochemical studies were employed to detect the formation of NiIspecies during the reduction of NiIIprecursors. Furthermore, the [(N2P2)NiI(CNt-Bu)](SbF6) complex was isolated upon reduction of the NiIIprecursor with 1 equiv of CoCp2and was characterized by EPR and X-ray photoelectron spectroscopy (XPS). Finally, the (N2P2)NiIIBr2complex acts as an efficient catalyst for the Kumada cross-coupling of an aryl halide with an aryl or alkyl Grignard, suggesting that the N2P2 ligand can support the various Ni species involved in the catalytic C-C bond formation reactivity.
- Fuchigami, Kei,Watson, Michael B.,Tran, Giang N.,Rath, Nigam P.,Mirica, Liviu M.
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supporting information
p. 2283 - 2289
(2021/05/06)
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- Highly active cobalt complex catalysts used for alkene hydrosilylation
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A series of nitrogen phosphine ligands were synthesized, and the hydrosilylation reaction of alkenes catalyzed using MCl2 in the presence of these ligands was investigated. FeCl2/1(N1, N1, N2, N2-Tetrakis[(diphenylphosphino)methyl]ethane-1,2-diamine) showed low catalytic activity. MnCl2/1, CrCl3/1 and NiCl2/1 showed some catalytic activity. The CoCl2/N,P-ligand catalyst system showed high activity as well as excellent selectivity (The selectivity of the β-adduct was ~100%.) in the hydrosilylation reaction. CoCl2/1 showed the highest catalytic activity (~ >99.9% conversion of 1-octene). Additionally, no α-adduct, dehydrogenative silylation product and octane were detected.
- Liu, Yu,Li, Jiayun,Bai, Ying,Peng, Jiajian
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- A New Protocol for Catalytic Reduction of Alkyl Chlorides Using an Iridium/Bis(benzimidazol-2′-yl)pyridine Catalyst and Triethylsilane
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The reduction of alkyl chlorides using triethylsilane is investigated. Primary, secondary, tertiary, and benzylic C-Cl bonds are effectively converted into C-H bonds using an [IrCl(cod)] 2/2,6-bis(benzimidazol-2′-yl)pyridine catalyst system. This catalyst system is quite simple since the tridentate N-ligand can be easily prepared in one step from commercially available reagents.
- Fukuyama, Takahide,Hamada, Yuki,Ryu, Ilhyong
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p. 3404 - 3408
(2021/07/14)
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- Multistep Engineering of Synergistic Catalysts in a Metal-Organic Framework for Tandem C-O Bond Cleavage
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Cleavage of strong C-O bonds without breaking C-C/C-H bonds is a key step for catalytic conversion of renewable biomass to hydrocarbon feedstocks. Herein we report multistep sequential engineering of orthogonal Lewis acid and palladium nanoparticle (NP) catalysts in a metal-organic framework (MOF) built from (Al-OH)n secondary building units and a mixture of 2,2′-bipyridine-5,5′-dicarboxylate (dcbpy) and 1,4-benzenediacrylate (pdac) ligands (1) for tandem C-O bond cleavage. Ozonolysis of 1 selectively removed pdac ligands to generate Al2(OH)(OH2) sites, which were subsequently triflated with trimethylsilyl triflate to afford strongly Lewis acidic sites for dehydroalkoxylation. Coordination of Pd(MeCN)2Cl2 to dcbpy ligands followed by in situ reduction produced orthogonal Pd NP sites in 1-OTf-PdNP as the hydrogenation catalyst. The selective and precise transformation of 1 into 1-OTf-PdNP was characterized step by step using powder X-ray diffraction, transmission electron microscopy, thermogravimetric analysis, inductively coupled plasma mass spectrometry, infrared spectroscopy, and X-ray absorption spectroscopy. The hierarchical incorporation of orthogonal Lewis acid and Pd NP active sites endowed 1-OTf-PdNP with outstanding catalytic performance in apparent hydrogenolysis of etheric, alcoholic, and esteric C-O bonds to generate saturated alkanes via a tandem dehydroalkoxylation-hydrogenation process under relatively mild conditions. The reactivity of C-O bonds followed the trend of tertiary carbon > secondary carbon > primary carbon. Control experiments demonstrated the heterogeneous nature and recyclability of 1-OTf-PdNP and its superior catalytic activity over the homogeneous counterparts. Sequential engineering of multiple catalytic sites in MOFs thus presents a unique opportunity to address outstanding challenges in sustainable catalysis.
- Brzezinski, Carter,Chen, Justin S.,Feng, Xuanyu,Lin, Wenbin,Song, Yang,Xu, Ziwan
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supporting information
p. 4872 - 4882
(2020/04/01)
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- Mononuclear calcium complex as effective catalyst for alkenes hydrogenation
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Hydrogenolysis of the scorpionate-supported calcium benzyl complex [(TpAd,iPr)Ca(p-CH2C6H4-Me)(THP)] (TpAd,iPr= hydrotris(3-adamantyl-5-isopropyl-pyrazolyl)borate, THP = tetrahydropyran) (2-THP) afforded the mononuclear calcium hydrido complex [(TpAd,iPr)Ca(H)(THP)] (3). Under mild conditions (40 °C, 10 atm H2, 5 mol% cat.), complex3effectively catalyzed the hydrogenation of a variety of alkenes, including activated alkenes, semi-activated alkenes, non-activated terminal and internal alkenes. Mononuclear calcium unsubstituted alkyl complex [(TpAd,iPr)Ca{(CH2)4Ph}(THP)] (6), proposed as the catalytic hydrogenation intermediate, was isolated and structurally characterized.
- Shi, Xianghui,Hou, Cuiping,Zhao, Lanxiao,Deng, Peng,Cheng, Jianhua
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supporting information
p. 5162 - 5165
(2020/05/26)
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- The Electronic Properties of Ni(PNN) Pincer Complexes Modulate Activity in Catalytic Hydrodehalogenation Reactions
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Three chloronickel(II) complexes of PNN- pincer ligands with pyrazolyl and diphenylphosphino donors appended to different arms of diarylamido anchors were prepared and fully characterized. The three derivatives (1-OMe, 1-Me, 1-CF3) differ only by the identity of the para-aryl substituent on the pyrazolyl arm with 1-OMe being 310 mV easier to oxidize than 1-CF3. All three complexes are competent catalysts for hydrodehalogenation reactions of 1-bromooctane and a variety of aryl halides in dimethylacetamide using NaBH4 as both base and hydride source. Comparative studies using diverse substrates showed that catalytic activity correlates with electron donor properties; 1-OMe was superior to the other two. Deuterium labeling studies verified NaBD4 as the deuteride source and excluded solvent-assisted radical pathways.
- Wang, Denan,Gardinier, James R.
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p. 4425 - 4434
(2020/10/19)
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- Accelerated Semihydrogenation of Alkynes over a Copper/Palladium/Titanium (IV) Oxide Photocatalyst Free from Poison and H2 Gas
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Selective hydrogenation of alkynes to alkenes (semihydrogenation) without the use of a poison and H2 is challenging because alkenes are easily hydrogenated to alkanes. In this study, a titanium (IV) oxide photocatalyst having Pd core-Cu shell nanoparticles (Pd@Cu/TiO2) was prepared by using the two-step photodeposition method, and Pd@Cu/TiO2 samples having various Cu contents were characterized by electron transmission microscopy, X-ray photoelectron spectroscopy and UV-vis spectroscopy. Thus-prepared Pd@Cu/TiO2 samples were used for photocatalytic hydrogenation of 4-octyne in alcohol and the catalytic properties were compared with those of Pd/TiO2 and Cu/TiO2. 4-Octyne was fully hydrogenated to octane over Pd/TiO2 at a high rate and 4-octyne was semihydrogenated to cis-4-octene over Cu/TiO2 at a low rate. Rapid semihydrogenation of 4-octyne was achieved over Pd(0.2 mol%)@Cu(1.0 mol%)/TiO2, indicating that the Pd core greatly activated the Cu shell that acted as reaction sites. A slight increase in the reaction temperature greatly increased the rate with a suppressed rate of H2 evolution as the side reaction. Changes in the reaction rates of the main and side reactions are discussed on the basis of results of kinetic studies. Reusability and expandability of Pd@Cu/TiO2 in semihydrogenation are also discussed.
- Imai, Shota,Nakanishi, Kousuke,Tanaka, Atsuhiro,Kominami, Hiroshi
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p. 1609 - 1616
(2020/02/15)
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- Selective hydrogenation of terminal alkynes over palladium nanoparticles within the pores of amino-modified porous aromatic frameworks
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Palladium catalysts, based on porous aromatic frameworks, synthesized via Suzuki cross-coupling reaction and further modified with amino groups, were prepared and tested in hydrogenation of several unsaturated compounds. Catalysts obtained were characterized by several techniques including IR spectroscopy, solid-state NMR spectroscopy, low-temperature nitrogen adsorption, transmission electron microscopy, atomic emission spectroscopy and X-ray photoelectron spectroscopy. It was shown that the amino-groups within the structure of aromatic frameworks interact with palladium nanoparticles and enhance their selectivity towards hydrogenation of terminal alkynes.
- Karakhanov, Edward,Maximov, Anton,Terenina, Maria,Vinokurov, Vladimir,Kulikov, Leonid,Makeeva, Daria,Glotov, Aleksandr
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p. 176 - 184
(2019/05/24)
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- Metal-organic frameworks containing nitrogen-donor ligands for efficient catalytic organic transformations
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Metal-organic framework (MOFs) compositions based on nitrogen donor-based organic bridging ligands, including ligands based on 1,3-diketimine (NacNac), bipyridines and salicylaldimine, were synthesized and then post-synthetically metalated with metal precursors, such as complexes of first row transition metals. Metal complexes of the organic bridging ligands could also be directly incorporated into the MOFs. The MOFs provide a versatile family of recyclable and reusable single-site solid catalysts for catalyzing a variety of asymmetric organic transformations. The solid catalysts can also be integrated into a flow reactor or a supercritical fluid reactor.
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Page/Page column 44-47
(2020/06/03)
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- Bidentate NHC-Cobalt Catalysts for the Hydrogenation of Hindered Alkenes
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Herein, we report a series of easily accessible bidentate N-heterocyclic carbene (NHC) cobalt catalysts, which enable the hydrogenation of hindered alkenes under mild conditions. The four-coordinated bidentate NHC-Co(II) complexes were characterized by X-ray diffraction, elemental analysis, ESI-HRMS, and magnetic moment measurements, revealing a distorted-tetrahedral geometry and a high-spin configuration of the metal center. The activity of the in situ formed catalytic system, which was obtained from easily available NHC precursors, CoCl2, and NaHBEt3, was identical with those of well-defined NHC-cobalt catalysts. This highlights the potential utility of this reaction system.
- Wei, Zeyuan,Wang, Yujie,Li, Yibiao,Ferraccioli, Raffaella,Liu, Qiang
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p. 3082 - 3087
(2020/10/02)
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- Photocatalytic Reductive Defluorination of Fluorinated Compounds in Aqueous Alcohol Suspensions of a Metal-loaded Titanium(IV) Oxide
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Selective elimination of the fluorine element in organic fluorinated compounds under mild conditions is desired in order to resolve the environment and energy resource issues. Selective reductive defluorination of fluorine-containing organic compounds in 2-propanol-water suspensions of metal-loaded titanium(IV) oxide (TiO2) photocatalysts is described in this paper. The effects of different types of metal co-catalysts, adsorption behavior of fluorobenzene (FB), stoichiometry, redox balance, scope, chemoselectivity and reaction temperature were examined. Photocatalytic defluorination of FB occurred over platinum-loaded TiO2 at room temperature, and benzene and fluoride ion were produced with a high stoichiometry without degradation of the benzene structure, while hydrogen (H2) production occurred as a competitive electron-consuming reaction. A slight elevation in the reaction temperature greatly accelerated defluorination and suppressed H2 evolution, resulting in FB defluorination free from H2 production at 333 K. Kinetic parameters of FB defluorination and H2 evolution were determined, and the results obtained are explained on the basis of these parameters.
- Fukui, Makoto,Tanaka, Atsuhiro,Kominami, Hiroshi
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p. 3298 - 3305
(2020/05/18)
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- Selective Hydrogenation and Hydrodeoxygenation of Aromatic Ketones to Cyclohexane Derivatives Using a Rh&at;SILP Catalyst
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Rhodium nanoparticles immobilized on an acid-free triphenylphosphonium-based supported ionic liquid phase (Rh&at;SILP(Ph3-P-NTf2)) enabled the selective hydrogenation and hydrodeoxygenation of aromatic ketones. The flexible molecular approach used to assemble the individual catalyst components (SiO2, ionic liquid, nanoparticles) led to outstanding catalytic properties. In particular, intimate contact between the nanoparticles and the phosphonium ionic liquid is required for the deoxygenation reactivity. The Rh&at;SILP(Ph3-P-NTf2) catalyst was active for the hydrodeoxygenation of benzylic ketones under mild conditions, and the product distribution for non-benzylic ketones was controlled with high selectivity between the hydrogenated (alcohol) and hydrodeoxygenated (alkane) products by adjusting the reaction temperature. The versatile Rh&at;SILP(Ph3-P-NTf2) catalyst opens the way to the production of a wide range of high-value cyclohexane derivatives by the hydrogenation and/or hydrodeoxygenation of Friedel–Crafts acylation products and lignin-derived aromatic ketones.
- Bordet, Alexis,Emondts, Meike,Leitner, Walter,Moos, Gilles
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supporting information
p. 11977 - 11983
(2020/06/02)
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- One-pot reductive amination of carboxylic acids: a sustainable method for primary amine synthesis
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The reductive amination of carboxylic acids is a very green, efficient and sustainable method for the production of (bio-based) amines. However, with current technology, this reaction requires two to three reaction steps. Here, we report the first (heterogeneous) catalytic system for the one-pot reductive amination of carboxylic acids to amines, with solely H2 and NH3 as the reactants. This reaction can be performed with relatively cheap ruthenium-tungsten bimetallic catalysts in the green and benign solvent cyclopentyl methyl ether (CPME). Selectivities of up to 99% for the primary amine could be achieved at high conversions. Additionally, the catalyst is recyclable and tolerant for common impurities such as water and cations (e.g. sodium carboxylate).
- Coeck, Robin,De Vos, Dirk E.
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supporting information
p. 5105 - 5114
(2020/08/25)
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- Reversible Formation of Alkyl Radicals at [Fe4S4] Clusters and Its Implications for Selectivity in Radical SAM Enzymes
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All kingdoms of life use the transient 5′-deoxyadenosyl radical (5′-dAdoa ) to initiate a wide range of difficult chemical reactions. Because of its high reactivity, the 5′-dAdo?must be generated in a controlled manner to abstract a specific H atom and avoid unproductive reactions. In radical S-Adenosylmethionine (SAM) enzymes, the 5′-dAdo?is formed upon reduction of SAM by an [Fe4S4] cluster. An organometallic precursor featuring an Fe-C bond between the [Fe4S4] cluster and the 5′-dAdo group was recently characterized and shown to be competent for substrate radical generation, presumably via Fe-C bond homolysis. Such reactivity is without precedent for Fe-S clusters. Here, we show that synthetic [Fe4S4]-Alkyl clusters undergo Fe-C bond homolysis when the alkylated Fe site has a suitable coordination number, thereby providing support for the intermediacy of organometallic species in radical SAM enzymes. Addition of pyridine donors to [(IMes)3Fe4S4-R]+ clusters (R = alkyl or benzyl; IMes = 1,3-dimesitylimidazol-2-ylidene) generates Ra , ultimately forming R-R coupled hydrocarbons. This process is facile at room temperature and allows for the generation of highly reactive radicals including primary carbon radicals. Mechanistic studies, including use of the 5-hexenyl radical clock, demonstrate that Fe-C bond homolysis occurs reversibly. Using these experimental insights and kinetic simulations, we evaluate the circumstances in which an organometallic intermediate can direct the 5′-dAdo?toward productive H-Atom abstraction. Our findings demonstrate that reversible homolysis of even weak M-C bonds is a feasible protective mechanism for the 5′-dAdo?that can allow selective X-H bond activation in both radical SAM and adenosylcobalamin enzymes.
- Brown, Alexandra C.,Suess, Daniel L. M.
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supporting information
p. 14240 - 14248
(2020/09/15)
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- Olefin reaction in the catalyst and the olefin production
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PROBLEM TO BE SOLVED: To provide a catalyst for obtaining an olefin in high selectivity with a vicinal diol as a raw material.SOLUTION: A catalyst for olefination reaction for use in a reaction to produce an olefin by a reaction of a polyol, having two adjacent carbon atoms each having a hydroxy group, with hydrogen comprises: a carrier; at least one oxide selected from the group consisting of oxides of the group 6 elements and oxides of the group 7 elements supported on the carrier; and at least one metal selected from the group consisting of silver, iridium, and gold supported on the carrier.SELECTED DRAWING: None
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Paragraph 0145-0146; 0149
(2020/10/31)
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- Radical dehydroxylative alkylation of tertiary alcohols by Ti catalysis
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Deoxygenative radical C?C bond-forming reactions of alcohols are a long-standing challenge in synthetic chemistry, and the current methods rely on multistep procedures. Herein, we report a direct dehydroxylative radical alkylation reaction of tertiary alcohols. This new protocol shows the feasibility of generating tertiary carbon radicals from alcohols and offers an approach for the facile and precise construction of all-carbon quaternary centers. The reaction proceeds with a broad substrate scope of alcohols and activated alkenes. It can tolerate a wide range of electrophilic coupling partners, including allylic carboxylates, aryl and vinyl electrophiles, and primary alkyl chlorides/bromides, making the method complementary to the cross-coupling procedures. The method is highly selective for the alkylation of tertiary alcohols, leaving secondary/primary alcohols (benzyl alcohols included) and phenols intact. The synthetic utility of the method is highlighted by its 10-g-scale reaction and the late-stage modification of complex molecules. A combination of experiments and density functional theory calculations establishes a plausible mechanism implicating a tertiary carbon radical generated via Ti-catalyzed homolysis of the C?OH bond.
- Xie, Hao,Guo, Jiandong,Wang, Yu-Quan,Wang, Ke,Guo, Peng,Su, Pei-Feng,Wang, Xiaotai,Shu, Xing-Zhong
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supporting information
p. 16787 - 16794
(2020/11/09)
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- One-pot synthesis of aldoximes from alkenes: Via Rh-catalysed hydroformylation in an aqueous solvent system
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Aldoxime synthesis directly starting from alkenes was successfully achieved through the combination of hydroformylation and subsequent condensation of the aldehyde intermediate with aqueous hydroxylamine in a one-pot process. The metal complex Rh(acac)(CO)2 and the water-soluble ligand sulfoxantphos were used as the catalyst system, providing high regioselectivities in the initial hydroformylation. A mixture of water and 1-butanol was used as an environmentally benign solvent system, ensuring sufficient contact of the aqueous catalyst phase and the organic substrate phase. The reaction conditions were systematically optimised by Design of Experiments (DoE) using 1-octene as a model substrate. A yield of 85% of the desired linear, terminal aldoxime ((E/Z)-nonanal oxime) at 95% regioselectivity was achieved. Other terminal alkenes were also converted successfully under the optimised conditions to the corresponding linear aldoximes, including renewable substrates. Differences of the reaction rate have been investigated by recording the gas consumption, whereby turnover frequencies (TOFs) >2000 h-1 were observed for 4-vinylcyclohexene and styrene, respectively. The high potential of aldoximes as platform intermediates was shown by their subsequent transformation into the corresponding linear nitriles using aldoxime dehydratases as biocatalysts. The overall reaction sequence thus allows for a straightforward synthesis of linear nitriles from alkenes with water being the only by-product, which formally represents an anti-Markovnikov hydrocyanation of readily available 1-alkenes.
- Gr?ger, H.,Guntermann, A.,Hinzmann, A.,Jolmes, T.,Panke, D.,Plass, C.,R?sler, J.,Seidensticker, T.,Terhorst, M.,Vogt, D.,Vorholt, A. J.
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supporting information
p. 7974 - 7982
(2020/11/30)
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- A General One-Pot Methodology for the Preparation of Mono- and Bimetallic Nanoparticles Supported on Carbon Nanotubes: Application in the Semi-hydrogenation of Alkynes and Acetylene
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A facile and straightforward methodology for the preparation of monometallic (copper and palladium) and bimetallic nanocatalysts (NiCu and PdCu) stabilized by a N-heterocyclic carbene ligand is reported. Both colloidal and supported nanoparticles (NPs) on carbon nanotubes (CNTs) were prepared in a one-pot synthesis with outstanding control on their size, morphology and composition. These catalysts were evaluated in the selective hydrogenation of alkynes and alkynols. PdCu/CNTs revealed an efficient catalytic system providing high selectivity in the hydrogenation of terminal and internal alkynes. Moreover, this catalyst was tested in the semi-hydrogenation of acetylene in industrially relevant acetylene/ethylene-rich model gas feeds and showed excellent stability even after 40 h of reaction.
- Lomelí-Rosales, Diego A.,Delgado, Jorge A.,Díaz de los Bernardos, Miriam,Pérez-Rodríguez, Sara,Gual, Aitor,Claver, Carmen,Godard, Cyril
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supporting information
p. 8321 - 8331
(2019/06/04)
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- Bimetallic nickel-lutetium complexes: tuning the properties and catalytic hydrogenation activity of the Ni site by varying the Lu coordination environment
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We present three heterobimetallic complexes containing an isostructural nickel center and a lutetium ion in varying coordination environments. The bidentate iPr2PCH2NHPh and nonadentate (iPr2PCH2NHAr)3tacn ligands were used to prepare the Lu metalloligands, Lu(iPr2PCH2NPh)3 (1) and Lu{(iPr2PCH2NAr)3tacn} (2), respectively. Reaction of Ni(COD)2 (where COD is 1,5-cyclooctadiene) and 1 afforded NiLu(iPr2PCH2NPh)3 (3), with a Lu coordination number (CN) of 4 and a Ni-Lu distance, d(Ni-Lu), of 2.4644(2) ?. Complex 3 can further bind THF to form 3-THF, increasing both the Lu CN to 5 and d(Ni-Lu) to 2.5989(4) ?. On the other hand, incorporation of Ni(0) into 2 provides NiLu{(iPr2PCH2NAr)3tacn} (4), in which the Lu coordination environment is more saturated (CN = 6), and the d(Ni-Lu) is substantially elongated at 2.9771(5) ?. Cyclic voltammetry of the three Ni-Lu complexes shows an overall ～410 mV shift in the Ni(0/I) redox couple, suggesting tunability of the Ni electronics across the series. Computational studies reveal polarized bonding interactions between the Ni 3dz2 (major) and the Lu 5dz2 (minor) orbitals, where the percentage of Lu character increases in the order: 4 (6.0% Lu 5dz2) 2 at low temperatures (?30 to ?80 °C) and are competent catalysts for styrene hydrogenation. Complex 3 outperforms 4 with a four-fold faster rate. Additionally, adding increasing THF equivalents to 3, which would favor build-up of 3-THF, decreases the rate. We propose that altering the coordination sphere of the Lu support can influence the resulting properties and catalytic activity of the active Ni(0) metal center.
- Ramirez, Bianca L.,Sharma, Prachi,Eisenhart, Reed J.,Gagliardi, Laura,Lu, Connie C.
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p. 3375 - 3384
(2019/03/21)
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- Hydrogenation of hydrophobic substrates catalyzed by gold nanoparticles embedded in Tetronic/cyclodextrin-based hydrogels
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Hydrogenation of alkenes, alkynes and aldehydes was investigated under biphasic conditions using Au nanoparticles (AuNP) embedded into combinations of α-cyclodextrin (α-CD) and a poloxamine (Tetronic90R4). Thermo-responsive AuNP-containing α-CD/Tetronic90R4 hydrogels are formed under well-defined conditions of concentration. The AuNP displayed an average size of ca. 7 nm and a narrow distribution, as determined by TEM. The AuNP/α-CD/Tetronic90R4 system proved to be stable over time. Upon heating above the gel-to-sol transition temperature, the studied catalytic system allowed hydrogenation of a wide range of substrates such as alkenes, alkynes and aldehydes under biphasic conditions. Upon repeated heating/cooling cycles, the Au NP/α-CD/Tetronic90R4 catalytic system could be recycled several times without a significant decline in catalytic activity.
- Chevry,Menuel,Léger,No?l,Monflier,Hapiot
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p. 9865 - 9872
(2019/07/04)
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- A nickel-iridium alloy as an efficient heterogeneous catalyst for hydrogenation of olefins
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Nickel and iridium supported on SiO2 (Ni-Ir/SiO2) acted as an effective and reusable heterogeneous catalyst for hydrogenation of olefins, and it showed higher activity and selectivity than the monometallic counterparts. The Ni-Ir/SiO2 catalyst has small Ni-Ir alloy and monometallic Ni particles, and the high catalytic performance can be attributed to the isolated Ni atom in the Ni-Ir alloys.
- Bai, Jia-qi,Tamura, Masazumi,Nakagawa, Yoshinao,Tomishige, Keiichi
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supporting information
p. 10519 - 10522
(2019/09/06)
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- Biomolecule-derived supported cobalt nanoparticles for hydrogenation of industrial olefins, natural oils and more in water
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Catalytic hydrogenation of olefins using noble metal catalysts or pyrophoric RANEY nickel is of high importance in the chemical industry. From the point of view of green and sustainable chemistry, design and development of Earth-abundant, less toxic, and more environmentally friendly catalysts are highly desirable. Herein, we report the convenient preparation of active cobalt catalysts and their application in hydrogenations of a wide range of terminal and internal carbon-carbon double bonds in water under mild conditions. Catalysts are prepared on multi-gram scale by pyrolysis of cobalt acetate and uracil, guanine, adenine or l-tryptophan. The most active material Co-Ura/C-600 showed good productivity in industrially relevant hydrogenation of diisobutene to isooctane and in natural oil hardening.
- Pews-Davtyan, Anahit,Scharnagl, Florian Korbinian,Hertrich, Maximilian Franz,Kreyenschulte, Carsten,Bartling, Stephan,Lund, Henrik,Jackstell, Ralf,Beller, Matthias
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supporting information
p. 5104 - 5112
(2019/09/30)
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- Amine-Borane Dehydrogenation and Transfer Hydrogenation Catalyzed by α-Diimine Cobaltates
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Anionic α-diimine cobalt complexes, such as [K(thf)1.5{(DippBIAN)Co(η4-cod)}] (1; Dipp=2,6-diisopropylphenyl, cod=1,5-cyclooctadiene), catalyze the dehydrogenation of several amine-boranes. Based on the excellent catalytic properties, an especially effective transfer hydrogenation protocol for challenging olefins, imines, and N-heteroarenes was developed. NH3BH3 was used as a dihydrogen surrogate, which transferred up to two equivalents of H2 per NH3BH3. Detailed spectroscopic and mechanistic studies are presented, which document the rate determination by acidic protons in the amine-borane.
- Maier, Thomas M.,Sandl, Sebastian,Shenderovich, Ilya G.,Jacobi von Wangelin, Axel,Weigand, Jan J.,Wolf, Robert
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supporting information
p. 238 - 245
(2019/01/04)
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- Involving Single-Atom Silver(0) in Selective Dehalogenation by AgF under Visible-Light Irradiation
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The dehalogenation-arylation and the hydrodehalogenation of various types of organic halides are selectively realized using AgF and visible light without any organic additives under mild conditions. Single-atom silver(0) (denoted as SAAg) serves as the catalytically active center, and the TOF of SAAg reaches 6000 h-1. This elusive activity of Ag is beyond that expected from its ionic, nano, or bulk forms.
- Wu, Wenli,Cui, Enxin,Zhang, Yun,Zhang, Chen,Zhu, Feng,Tung, Chen-Ho,Wang, Yifeng
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p. 6335 - 6341
(2019/07/04)
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- Axial Donor Effects on Oxidatively Induced Ethane Formation from Nickel-Dimethyl Complexes
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Tetradentate pyridinophane ligands have been shown to stabilize uncommon high-valent palladium and nickel organometallic complexes. Described herein are the synthesis and detailed characterization of a series of NiII- and NiIII-dimethyl complexes supported by modified tetradentate pyridinophane ligands in which one or both of the N-methyl substituents were replaced with electron-withdrawing p-toluenesulfonyl groups, thus reducing the amine N atom donicity and favoring the formation of Ni complexes with lower coordination numbers. The corresponding NiII-dimethyl complexes exhibit accessible oxidation potentials, and their oxidation generates NiIII species that were characterized by EPR and X-ray crystallography. Moreover, the NiII-dimethyl complexes exhibit selective ethane formation upon oxidatively induced reductive elimination using various oxidants - including O2 and H2O2, without the generation of any C-heteroatom products. Overall, these results suggest that the (RN4)NiIIMe2 complexes with more weakly donating axial ligands are more reactive toward ethane formation, likely due to destabilization of the corresponding high-valent Ni intermediates and formation of 5- and 4-coordinate conformations for these Ni species.
- Smith, Sofia M.,Rath, Nigam P.,Mirica, Liviu M.
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supporting information
p. 3602 - 3609
(2019/10/11)
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- Bimetallic Co/Al nanoparticles in an ionic liquid: Synthesis and application in alkyne hydrogenation
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Herein, we report the microwave-induced decomposition of various organometallic cobalt and aluminum precursors in an ionic liquid (IL), 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIm]NTf2), resulting in Co/Al nanoalloys with different molar Co/Al ratios. The dual-source precursor system of dicobalt octacarbonyl (Co2(CO)8) and pentamethylcyclopentadienyl aluminum ([AlCp?]4) in [BMIm]NTf2 afforded CoAl nanoparticles (CoAl-NPs) with a molar Co/Al ratio of 1?:?1. Their size and size distribution were determined via transmission electron microscopy (TEM) to be an average diameter of 3.0 ± 0.5 nm. Furthermore, the dual-source precursor system of cobalt amidinate ([Co(iPr2-MeAMD)2]) and aluminum amidinate [Me2Al(iPr2-MeAMD)] in molar ratios of 1?:?1 and 3?:?1 resulted in CoAl-and Co3Al-NPs with an average diameter of 3 ± 1 and 2.0 ± 0.2 nm, respectively. All the obtained materials were characterized via TEM, energy dispersive X-ray spectroscopy (EDX), selected area electron diffraction (SAED), together with high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and (high-resolution) X-ray photoelectron spectroscopy ((HR-)XPS). Phase-pure Co/Al-NPs were not obtained since the concomitant formation of Co-NPs and Al2O3 occurred in this wet-chemical synthesis. The as-prepared Co/Al nanoalloys were evaluated as catalysts in the hydrogenation of phenylacetylene under mild conditions (2 bar H2, 30 °C in THF). In comparison to the monometallic Co-NPs, the Co/Al-NPs showed a significantly higher catalytic hydrogenation activity. The Co-and Co/Al-NPs were also active under harsher reaction conditions (80 bar H2, 80 °C) without the addition of the activating co-catalyst DIBAL-H.
- Schmolke, Laura,Gregori, Bernhard J.,Giesen, Beatriz,Schmitz, Alexa,Barthel, Juri,Staiger, Lena,Fischer, Roland A.,Jacobi Von Wangelin, Axel,Janiak, Christoph
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p. 16583 - 16594
(2019/11/11)
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- Transition metal-free hydrodefluorination of acid fluorides and organofluorines by Ph3GeH promoted by catalytic[Ph3C][B(C6F5)4]
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It has been shown that the germane Ph3GeH converts aryl and aliphatic acid fluorides directly to their corresponding aldehydes without over-reduction via the conversion of Ph3GeH to the germylium cation[Ph3Ge]+ by a catalytic amount of the tritylium salt[Ph3C][B(C6F5)4]. Here, no transition metal catalyst is required and there is no decarbonylation of the acid fluoride, which are advantages over existing methods. The fluorine atoms can also be abstracted from organofluorine compounds using this method.
- Hayatifar, Ardalan,Borrego, Alejandro,Bosek, David,Czarnecki, Matthew,Derocher, Gabriel,Kuplicki, Adam,Lytle, Erik,Padilla, Jonas,Paroly, Charles,Tubay, Gillian,Vyletel, Jackson,Weinert, Charles S.
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supporting information
p. 10852 - 10855
(2019/09/18)
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- Cobalt-Catalyzed Hydrogenations via Olefin Cobaltate and Hydride Intermediates
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Redox noninnocent ligands are a promising tool to moderate electron transfer processes within base-metal catalysts. This report introduces bis(imino)acenaphthene (BIAN) cobaltate complexes as hydrogenation catalysts. Sterically hindered trisubstituted alkenes, imines, and quinolines underwent clean hydrogenation under mild conditions (2-10 bar, 20-80 °C) by use of the stable catalyst precursor [(DippBIAN)CoBr2] and the cocatalyst LiEt3BH. Mechanistic studies support a homogeneous catalysis pathway involving alkene and hydrido cobaltates as active catalyst species. Furthermore, considerable reaction acceleration by alkali cations and Lewis acids was observed. The dinuclear hydridocobaltate anion with bridging hydride ligands was isolated and fully characterized.
- Sandl, Sebastian,Maier, Thomas M.,Van Leest, Nicolaas P.,Kr?ncke, Susanne,Chakraborty, Uttam,Demeshko, Serhiy,Koszinowski, Konrad,De Bruin, Bas,Meyer, Franc,Bodensteiner, Michael,Herrmann, Carmen,Wolf, Robert,Von Jacobi Wangelin, Axel
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p. 7596 - 7606
(2019/08/20)
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- Iridium-Catalyzed Alkene-Selective Transfer Hydrogenation with 1,4-Dioxane as Hydrogen Donor
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The iridium-catalyzed transfer hydrogenation of alkenes using 1,4-dioxane as a hydrogen donor is described. The use of 1,2-bis(dicyclohexylphosphino)ethane (DCyPE), featuring bulky and highly electron-donating properties, led to high catalytic activity. A polystyrene-cross-linking bisphosphine PS-DPPBz produced a reusable heterogeneous catalyst. These homogeneous and heterogeneous protocols achieved chemoselective transfer hydrogenation of alkenes over other potentially reducible functional groups such as carbonyl, nitro, cyano, and imino groups in the same molecule.
- Zhang, Deliang,Iwai, Tomohiro,Sawamura, Masaya
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supporting information
p. 5867 - 5872
(2019/08/26)
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- Titanium-catalyzed hydrosilylation of olefins: A comparison study on Cp2TiCl2/Sm and Cp2TiCl2/LiAlH4 catalyst system
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Hydrosilylation of olefins catalyzed by Cp2TiCl2/Sm (Cp = cyclopentadienyl) under solvent free conditions have been investigated. By using Cp2TiCl2/Sm as catalyst system, β-adducts and hydrogenation products were detected. Hydrosilylation of olefins catalyzed by Cp2TiCl2/LiAlH4 under room temperature has also been studied. The influence of TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) on Cp2TiCl2/Sm and Cp2TiCl2/LiAlH4, respectively, indicated that hydrosilylation of olefins catalyzed with Cp2TiCl2/Sm went through a free radical reaction pathway while a coordination mechanism was applied for Cp2TiCl2/LiAlH4 catalyst system.
- Yang, Xiaoling,Bai, Ying,Li, Jiayun,Liu, Yu,Peng, Jiajian,Li, Tianbo,Lang, Rui,Qiao, Botao
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- The catalytic activity of alkali metal alkoxides and titanium alkoxides in the hydrosilylation of unfunctionalized olefins
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The catalytic activities of titanium alkoxides and alkali metal alkoxides for hydrosilylation of unfunctionalized olefins have been studied. Titanium(IV) alkoxides showed excellent catalytic activity, while alkali metal alkoxides have low catalytic activity for the hydrosilylation of olefins. However, by using titanocene dichloride as an additive, alkali metal alkoxides showed also excellent catalytic property for hydrosilylation. In comparison with titanium alkoxides, no α-adduct was obtained by using alkali metal alkoxides/Cp2TiCl2 as catalysts.
- Yang, Xiaoling,Bai, Ying,Li, Jiayun,Liu, Yu,Peng, Jiajian,Li, Tianbo,Lang, Rui,Qiao, Botao
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- Chemoselective Hydrodeoxygenation of Carboxylic Acids to Hydrocarbons over Nitrogen-Doped Carbon-Alumina Hybrid Supported Iron Catalysts
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The establishment of catalyst systems for the chemoselective hydrodeoxygenation (HDO) of carboxylic acids to hydrocarbons, such as the HDO of long-chain fatty acids to alkanes, is important for biomass to biofuel conversion. As the most abundant and probably the cheapest transition metal on the earth, iron is a promising non-noble-metal alternative to precious metals for large-scale conversion of biomass. However, it usually suffers from unsatisfactory activity. In this work, a nitrogen-doped carbon-alumina hybrid supported iron (Fe-N-C@Al2O3) catalyst is established for chemoselective HDO of carboxylic acids to hydrocarbons. By using stearic acid HDO as the model reaction, n-octadecane and n-heptadecane are produced with yields of 91.9% and 6.0%, respectively. Triglycerides can also be converted into liquid alkanes with a total molar yield of >92%. In addition, the iron catalyst can chemoselectively catalyze the HDO of the carboxylic acid group in the presence of other functional groups such as an aromatic ring. This chemoselectivity has rarely been seen before because the aromatic ring is usually more easily hydrogenated in comparison to HDO of the carboxylic acid group. The characterization results showed that both the formation of a nitrogen-doped carbon-alumina hybrid and the iron loading are important for the Lewis basicity of these catalysts, in order to adsorb the acid substrates. The addition of melamine as the nitrogen precursor during pyrolysis eliminates undesired reactions between the iron precursor and alumina support to form an inactive hercynite phase, leading to the formation of an Fe3C active phase for the hydrogenation of -COOH to -CH2OH and the hybrid of N-C and alumina for the HDO of -CH2OH to -CH3.
- Li, Jiang,Zhang, Junjie,Wang, Shuai,Xu, Guangyue,Wang, Hao,Vlachos, Dionisios G.
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p. 1564 - 1577
(2019/02/03)
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- Hydrosilylation of alkenes catalyzed by Fe powder
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A novel iron-catalyzed hydrosilylation of alkenes process under solvent-free conditions has been reported. The influence of the amount of Fe catalyst, reaction temperature and various alkenes and silanes on the hydrosilylation were investigated. High yields of adduct were obtained in the hydrosilylation of octene with MeCl2H, Me2ClSiH and Ph2SiH2 by using 10 mol% iron powder as a signal catalyst.
- Yang, Xiaoling,Bai, Ying,Li, Jiayun,Dai, Zinan,Peng, Jiajian
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- Preparation of Highly Active Monometallic Rhenium Catalysts for Selective Synthesis of 1,4-Butanediol from 1,4-Anhydroerythritol
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1,4-Butanediol can be produced from 1,4-anhydroerythritol through the co-catalysis of monometallic mixed catalysts (ReOx/CeO2+ReOx/C) in the one-pot reduction with H2. The highest yield of 1,4-butanediol was over 80 %, which is similar to the value obtained over ReOx–Au/CeO2+ReOx/C catalysts. Mixed catalysts of CeO2+ReOx/C showed almost the same performance, giving 89 % yield of 1,4-butanediol. The reactivity trends of possible intermediates suggest that the reaction mechanism over ReOx/CeO2+ReOx/C is similar to that over ReOx–Au/CeO2+ReOx/C: deoxydehydration (DODH) of 1,4-anhydroerythritol to 2,5-dihydrofuran over ReOx species on the CeO2 support with the promotion of H2 activation by ReOx/C, isomerization of 2,5-dihydrofuran to 2,3-dihydrofuran catalyzed by ReOx on the C support, hydration of 2,3-dihydrofuran catalyzed by C, and hydrogenation to 1,4-butanediol catalyzed by ReOx/C. The reaction order of conversion of 1,4-anhydroerythritol with respect to H2 pressure is almost zero and this indicates that the rate-determining step is the formation of 2,5-dihydrofuran from the coordinated substrate with reduced Re in the DODH step. The activity of ReOx/CeO2+ReOx/C is higher than that of ReOx–Au/CeO2+ReOx/C, which is probably related to the reducibility of ReOx/C and the mobility of the Re species between the supports. High-valent Re species such as Re7+ on the CeO2 and C supports are mobile in the solvent; however, low-valent Re species, including metallic Re species, have much lower mobility. Metallic Re and cationic low-valent Re species with high reducibility and low mobility can be present on the carbon support as a trigger for H2 activation and promoter of the reduction of Re species on CeO2. The presence of noble metals such as Au can enhance the reducibility through the activation of H2 molecules on the noble metal and the formation of spilt-over hydrogen over noble metal/CeO2, as indicated by H2 temperature-programmed reduction. The higher reducibility of ReOx–Au/CeO2 lowers the DODH activity of ReOx–Au/CeO2+ReOx/C in comparison with ReOx/CeO2+ReOx/C by restricting the movement of Re species from C to CeO2.
- Wang, Tianmiao,Tamura, Masazumi,Nakagawa, Yoshinao,Tomishige, Keiichi
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p. 3615 - 3626
(2019/07/15)
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