- Redox mechanism for selective oxidation of ethanol over monolayer V2O5/TiO2 catalysts
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The selective oxidation of ethanol to acetaldehyde and acetic acid over a monolayer V2O5/TiO2 catalyst has been studied in situ using Fourier transform infrared spectroscopy and near-ambient-pressure X-ray photoelectron spectroscopy (XPS) at temperatures ranging from 100 to 300 °C. The data were complemented with temperature-programmed reaction spectroscopy and kinetic measurements. It was found that under atmospheric pressure at low temperatures acetaldehyde is the major product formed with the selectivity of almost 100%. At higher temperatures, the reaction shifts toward acetic acid, and at 200 °C, its selectivity reaches 60%. Above 250 °C, unselective oxidation to CO and CO2 becomes the dominant reaction. Infrared spectroscopy indicated that during the reaction at 100 °C, nondissociatively adsorbed molecules of ethanol, ethoxide species, and adsorbed acetaldehyde are on the catalyst surface, while at higher temperatures the surface is mainly covered with acetate species. According to the XPS data, titanium cations remain in the Ti4+ state, whereas V5+ cations undergo reversible reduction under reaction conditions. The presented data agree with the assumption that the selective oxidation of ethanol over vanadium oxide catalysts occurs at the redox Vn+ sites via a redox mechanism involving the surface lattice oxygen species. A reaction scheme for the oxidation of ethanol over monolayer V2O5/TiO2 catalysts is suggested.
- Kaichev, Vasily V.,Chesalov, Yuriy A.,Saraev, Andrey A.,Klyushin, Alexander Yu.,Knop-Gericke, Axel,Andrushkevich, Tamara V.,Bukhtiyarov, Valerii I.
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- Study of acetaldehyde condensation chemistry over magnesia and zirconia supported on silica
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Aldol condensation of acetaldehyde was investigated over silica supported magnesium and zirconium oxides. The acidic and basic properties of the catalysts were studied by TPD of NH3 and CO2 and IR spectroscopy of adsorbed pyridine and CO2. MgO/SiO2 catalyst was characterized by high content of both basic and acidic sites, while ZrO 2/SiO2 contained mainly Lewis acid sites. All materials studied were shown to catalyze the aldol condensation of acetaldehyde with selectivity to crotonaldehyde of ca. 85%. The activity of the catalysts was found to be in the following order: ZrO2/SiO2 > MgO/SiO2 SiO2. To assess the role of acidic and basic sites in condensation reaction, pyridine and carbon dioxide were used as probe molecules for poisoning of the corresponding active sites during catalytic runs. The results pointed to the key role of Lewis acid sites in acetaldehyde condensation. A concerted mechanism involving Lewis and Br?nsted acid sites of the catalysts is proposed on the basis of in situ IR spectroscopic studies.
- Ordomsky,Sushkevich,Ivanova
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- Magnetic core-shell Fe3O4?Cu2O and Fe3O4?Cu2O-Cu materials as catalysts for aerobic oxidation of benzylic alcohols assisted by TEMPO and: N -methylimidazole
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In this work, core-shell Fe3O4?Cu2O and Fe3O4?Cu2O-Cu nanomaterials for aerobic oxidation of benzylic alcohols are reported with 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) and N-methylimidazole (NMI) as the co-catalysts. To anchor Cu2O nanoparticles around the magnetic particles under solvothermal conditions, the magnetic material Fe3O4 was modified by grafting a layer of l-lysine (l-Lys) to introduce -NH2 groups at the surface of the magnetic particles. With amine groups as the anchor, Cu(NO3)2 was used to co-precipitate the desired Cu2O by using ethylene glycol as the reducing agent. Prolonging the reaction time would lead to over-reduced forms of the magnetic materials in the presence of copper, Fe3O4?Cu2O-Cu. The nanomaterials and its precursors were fully characterized by a variety of spectroscopic techniques. In combination with both TEMPO and NMI, these materials showed excellent catalytic activities in aerobic oxidation of benzylic alcohols under ambient conditions. For most of the benzylic alcohols, the conversion into aldehydes was nearly quantitative with aldehydes as the sole product. The materials were recyclable and robust. Up to 7 repeat runs, its activity dropped less than 10%. The over-reduced materials, Fe3O4?Cu2O-Cu, exhibited slightly better performance in durability. The magnetic properties allowed easy separation after reaction by simply applying an external magnet.
- Liu, Xiaoming,Lu, Chunxin,Senthilkumar, Samuthirarajan,Shen, Zhongquan,Xu, Binyu,Zhong, Wei
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- Supported bimetallic AuPd clusters using activated Au25 clusters
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Bimetallic AuPd nanoparticles on alumina supports were prepared using Au25(SR)18 precursors activated by mild calcination or LiBH4 treatment, followed by selective deposition of Pd via ascorbic acid reduction. Comparison of their catalytic activity for the oxidation of crotyl alcohol showed that bimetallic structure had significantly improved catalysis compared to Pd/Al2O3. In particular, AuPd samples grown from LiBH4-activated Au25 clusters exhibit the highest catalytic activity as well as high selectivity towards crotonaldehyde formation, likely due to their smaller particle sizes as compared to AuPd samples grown from calcined Au25 clusters. X-ray absorption spectroscopy (XAS) at the Au L3-edge, Pd L3-edge and Pd K-edges showed that the resulting bimetallic AuPd nanoparticles had Au-Pd core-shell structures with a 4d-electron poor Pd surface.
- Lee, Kee Eun,Shivhare, Atal,Hu, Yongfeng,Scott, Robert W.J.
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- Copper(II)-catalysed aerobic oxidation of primary alcohols to aldehydes
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[CuBr2(2,2′-bipyridine)] catalyses the selective and very mild aerobic oxidation of primary alcohols to aldehydes in acetonitrile:water (2:1) in the presence of 2,2,6,6-tetramethylpiperidinyl-1-oxy (TEMPO) and a base as cocatalysts.
- Gamez, Patrick,Arends, Isabel W. C. E.,Reedijk, Jan,Sheldon, Roger A.
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- Selective oxidation of crotyl alcohol by Au: X Pd bimetallic pseudo-single-atom catalysts
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AuPd bimetallic single-atom catalysts are being extensively studied as selective catalysts for hydrogenation and oxidation reactions due to their high selectivity. Previous work in our group has shown that alloy and core-shell AuPd nanoparticle catalysts can selectively oxidize crotyl alcohol to crotonaldehyde at room temperature in base-free conditions. In this work, we discuss the synthesis, extensive characterization, and activity for crotyl alcohol oxidation across a series of AuxPd catalysts (x = 4, 3, 2, and 1) made by both co-reduction and sequential reduction strategies, in order to examine whether single-atom systems can lead to improved activity and/or selectivity for this reaction. X-ray absorption spectroscopy data shows that both co-and sequentially-reduced Au4Pd catalysts have very small Pd-Pd coordination numbers, with values of 1.2 ± 0.3 and 1.6 ± 0.3, respectively, which indicates that they are closest to single-atom systems. The co-Au4Pd catalyst, with the lowest Pd-Pd CN, also exhibits the highest selectivity for the selective oxidation of crotyl alcohol to crotonaldehyde. We were further able to enhance the selectivity of the AuPd nanoparticle catalysts by incorporating vinyl acetate as a hydride scavenger. We show in this paper that dispersing Pd in a Au matrix can lead to very selective catalysts while also lowering the amount of Pd needed in the system.
- Chivers, Brandon A.,Scott, Robert W. J.
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- Kinetics and Mechanism of Electron Transfer Reactions: Oxidation of Crotyl Alcohol by Peroxomonosulfate in Aqueous Acidic Medium
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The kinetics and mechanism of oxidation of crotyl alcohol by peroxomonosulfate has been studied, and the species of the peroxomonosulfate are discussed to find out the role of activated species. A plausible reaction mechanism is suggested, and a derived rate law corresponds to all experimental observations. The activation parameters such as energy and entropy of activation have been calculated as 37.21 ± 0.5 kJ mol?1 and ?148.91 ± 2.7 J K?1 mol?1, respectively, by employing the Eyring plot.
- Sharma, Priyamvada,Sailani, Riya,Meena, Anita,Khandelwal
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- Aldol Condensation of Acetaldehyde over Titania, Hydroxyapatite, and Magnesia
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The kinetics of aldol condensation of acetaldehyde were studied over anatase titania (TiO2), hydroxyapatite (HAP), and magnesia (MgO). Reactions were carried out in a fixed-bed reactor with a total system pressure of 220 kPa at temperatures between 533 and 633 K and acetaldehyde partial pressures between 0.05 and 50 kPa. Crotonaldehyde was the only product observed over all three catalysts, and severe catalyst deactivation occurred at acetaldehyde partial pressures of 5 kPa or greater. The aldol condensation reaction over all three catalysts was first order at low acetaldehyde partial pressure and approached zero order at high acetaldehyde partial pressure. No kinetic isotope effect (KIE) was observed with fully deuterated acetaldehyde reacting over TiO2 or HAP, implying that C-H bond activation is not kinetically relevant. These measurements are consistent with a mechanism in which adsorption and desorption steps are kinetically significant during the reaction. Characterization of the catalysts by adsorption microcalorimetry of acetaldehyde and ethanol and diffuse reflectance Fourier transform infrared spectroscopy of adsorbed acetaldehyde, crotonaldehyde, and acetic acid revealed a very high reactivity of these catalysts, even at low temperatures.
- Young, Zachary D.,Hanspal, Sabra,Davis, Robert J.
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- Effect of the ZrO2 phase on the structure and behavior of supported Cu catalysts for ethanol conversion
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The effect of amorphous (am-), monoclinic (m-), and tetragonal (t-) ZrO2 phase on the physicochemical and catalytic properties of supported Cu catalysts for ethanol conversion was studied. The electronic parameters of Cu/ZrO2 were determined by in situ XAS, and the surface properties of Cu/ZrO2 were defined by XPS and DRIFTS of CO-adsorbed. The results demonstrated that the kind of ZrO2 phase plays a key role in the determination of structure and catalytic properties of Cu/ZrO 2 catalysts predetermined by the interface at Cu/ZrO2. The electron transfer between support and Cu surface, caused by the oxygen vacancies at m-ZrO2 and am-ZrO2, is responsible for the active sites for acetaldehyde and ethyl acetate formation. The highest selectivity to ethyl acetate for Cu/m-ZrO2 catalyst up to 513 K was caused by the optimal ratio of Cu0/Cu+ species and the high density of basic sites (O2-) associated with the oxygen mobility from the bulk m-ZrO2.
- Sato,Volanti,Meira,Damyanova,Longo,Bueno
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- Vinylation of phenol by acetaldehyde: A new reaction for the synthesis of o-vinylphenol
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A new catalytic reaction for the single-step synthesis of o-vinylphenol from phenol and acetaldehyde in the gas phase is investigated in this work. A search for an efficient catalyst was made. The best results were obtained with a modified Cr2O3 catalyst supported on γ-Al2O3. The effect of content of Cr2O3 and potassium as a modifying additive was studied. It was shown that the catalyst containing 13% Cr2O3 and 1% K makes it possible to obtain o-vinylphenol with a selectivity of 100% referred to phenol and up to 87% referred to acetaldehyde. The influence of reaction conditions on the activity, selectivity and stability of catalyst operation was elucidated.
- Parfenov, Mikhail V.,Pirutko, Larisa V.,Soshnikov, Igor E.,Starokon, Eugeny V.,Kharitonov, Alexander S.,Panov, Gennady I.
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- Dual Role of the Rhodium(III) Catalyst in C-H Activation: [4 + 3] Annulation of Amide with Allylic Alcohols to 7-Membered Lactams
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[4 + 3] annulation of primary and secondary benzamide and cinnamamide derivatives using allyl alcohol as a coupling partner catalyzed by Rh(III) is reported, where Rh(III) is playing a dual role of an oxidant and a catalyst for C-H activation. The Rh-catalyst oxidizes allyl alcohol to its carbonyl derivative, and the in situ-generated carbonyl compound reacts with benzamide in the presence of the Rh-catalyst, forming the corresponding alkylated products. Mechanistic studies show that AgSbF6 is also playing a dual role. Apart from being a halide scavenger, AgSbF6 catalyzes the cyclization of the alkylated product, forming the desired lactam. The current method has good synthetic application and is useful for synthesizing a few biologically active compounds that can act as the dopamine D3 receptor ligand, including berberine-like analogues. The deuteration study and control experiments helped us to propose the mechanism.
- Sherikar, Mahadev Sharanappa,Devarajappa, Ravi,Prabhu, Kandikere Ramaiah
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- Dinuclear Pathways for the Activation of Strained Three-Membered Rings
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Dinuclear, strain-induced ring-opening reactions of vinylaziridines and vinylcyclopropanes are described. The previously reported [NDI]Ni2(C6H6) complex (NDI = naphthyridine-diimine) reacts with N-tosyl-2-vinylaziridine via C-N oxidative addition to generate a dinickel metallacyclic product. On the basis of this stoichiometric reactivity, the [NDI]Ni2(C6H6) complex is shown to be a highly active catalyst for the rearrangement of vinylcyclopropane to cyclopentene. Notably, 2-phenyl-1-vinylcyclopropane undergoes regioselective activation at the less hindered C-C bond in contrast to the noncatalytic thermal rearrangement. DFT calculations provide insight into the ability of the Ni-Ni bond to stabilize key intermediates and transition states along the catalytic pathway.
- Rounds, Heather R.,Zeller, Matthias,Uyeda, Christopher
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- Selective Oxidation of Allylic and Benzylic Alcohols Using Potassium Ruthenate (K2RuO4) Under Phase-Transfer Catalysis Conditions
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Catalytic amounts of potassium ruthenate in the presence of potassium peroxodisulfate, which quickly regenerates ruthenate during reaction, selectively oxidize allylic and benzylic alcohols in the presence of Adogen 464 as phase-transfer catalyst at room temperature but do not affect saturated alcohols.
- Kim, Kwan Soo,Kim, Sung Jung,Song, Yang Heon,Hahn, Chi Sun
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- Isomerization and dissociation of 2,3-dihydrofuran (2,3-DHF) induced by infrared free electron laser
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We investigated infrared multiphoton dissociation and isomerization reactions of 2,3-dihydrofuran (2,3-DHF), cyclopropanecaboxaldehyde (CPCA) and crotonaldehyde (CA) with free electron laser at Tokyo University of Science (FEL-TUS). From 2,3-DHF as a starting material, CPCA and CA were the main isomerization products. From the measured [CPCA]/[CA] ratio, the equivalent temperature for the vibrationally hot 2,3-DHF was estimated to be 1300-1500 K. From CPCA, both 2,3-DHF and CA were detected as isomerization products. No isomerization reaction from trans-CA to CPCA and 2,3-DHF was recognized and the dissociation to propylene was the dominant process. The experimentally identified reaction pathways are well explainable by quantum chemical calculations at the MP2/cc-pVDZ level.
- Matsubara,Osada,Nakajima,Imai,Nishimura,Oyama,Tsukiyama
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- Systematic Screening for Catalytic Promiscuity in 4-Oxalocrotonate Tautomerase: Enamine Formation and Aldolase Activity
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The enzyme 4-oxalocrotonate tautomerase (4-OT) is part of a catabolic pathway for aromatic hydrocarbons in Pseudomonas putida mt-2, where it catalyzes the conversion of 2-hydroxy-2,4-hexadienedioate (1) to 2-oxo-3-hexenedioate (2). 4-OT is a member of the tautomerase superfamily, a group of homologous proteins that are characterized by a β-α-β structural fold and a catalytic amino-terminal proline. In the mechanism of 4-OT, Pro1 is a general base that abstracts the 2-hydroxyl proton of 1 for delivery to the C-5 position to yield 2. Here, 4-OT was explored for nucleophilic catalysis based on the mechanistic reasoning that its Pro1 residue has the correct protonation state (pKa～6.4) to be able to act as a nucleophile at pH 7.3. By using inhibition studies and mass spectrometry experiments it was first demonstrated that 4-OT can use Pro1 as a nucleophile to form an imine/enamine with various aldehyde and ketone compounds. The chemical potential of the smallest enamine (generated from acetaldehyde) was then explored for further reactions by using a small set of selected electrophiles. This systematic screening approach led to the discovery of a new promiscuous activity in wild-type 4-OT: the enzyme catalyzes the aldol condensation of acetaldehyde with benzaldehyde to form cinnamaldehyde. This low-level aldolase activity can be improved 16-fold with a single point mutation (L8R) in 4-OT's active site. The proposed mechanism of the reaction mimicks that used by natural class-I aldolases and designed catalytic aldolase antibodies. An important difference, however, is that these natural and designed aldolases use the primary amine of a lysine residue to form enamines with carbonyl substrates, whereas 4-OT uses the secondary amine of an active-site proline as the nucleophile catalyst. Further systematic screening of 4-OT and related proline-based biocatalysts might prove to be a useful approach to discover new promiscuous carbonyl transformation activities that could be exploited to develop new biocatalysts for carbon-carbon bond formation. Prozymes: A systematic screening strategy to discover new promiscuous carbonyl-transformation activities in 4oxalocrotonate tautomerase (4-OT) is reported. The N-terminal proline of this enzyme provides a chemical functionality in the active site that might be suitable for enamine catalysis. It is shown that the aldol condensation of acetaldehyde with benzaldehyde is catalyzed by 4-OT.
- Zandvoort, Ellen,Baas, Bert-Jan,Quax, Wim J.,Poelarends, Gerrit J.
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- Primary Deuterium Kinetic Isotope Effects for the Thermal Sigmatropic Rearrangement of 7-Methylocta-1,3(Z),5(Z)-triene
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7-Methylocta-1,3(Z),5(Z)-triene isomerizes to 2-methylocta-2,4(Z),6(Z)-triene over the temperature range 60-115 deg C through a first order process characterized kinetically by the activation parameters log AH = 9.8 and EaH = 21.5 kcal/mol.Parallel kinetic work with the 7-deuterio-7-methyloctatriene establishes the Arrhenius parameters log AD = 10.3 and EaD = 23.5 kcal/mol.Thus AD/AH = 3.2 and (EaD-EaH) = 2.0 kcal/mol, and a substantial tunneling component for the sigmatropic hydrogen migration is evident.
- Baldwin, John E.,Prakash Reddy, V.
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- Pd nanoparticles supported on 1H-benzotriazole functionalized carbon with enhanced catalytic performance towards ethanol oxidation
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Nitrogen functionalized carbon has received widely research interest because of their remarkable performance. In this paper, 1H-benzotriazole functionalized carbon (BTA-C) is fabricated and used as support to immobilize Pd nanoparticles. The physical characterization results demonstrate that the Pd nanoparticles uniformly disperse on the BTA-C. Because of the good effect of BTA functionalization, the as-prepared Pd/BTA-C catalyst has larger electrochemically active surface area contrasted to Pd/C. Meanwhile, the electrochemical test results indicate that the Pd/BTA-C possesses higher activity (more than 1.8 times), lower onset potential (negative 90 mV) and better stability than that of Pd/C counterpart in ethanol oxidation reaction. All results imply that the Pd/BTA-C is a promising candidate electrocatalyst in direct ethanol fuel cells.
- Liu, Yanqin,Wang, Wei,Yang, Yan,Wang, Fengxia,Zhao, Xiaolong,Lei, Ziqiang
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- Solid-state conversion of 1,1-diacetates with N,N′-dibromo-N, N′-1,2-ethanediylbis(p-toluenesulfonamide) to aldehydes
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N,N′-Dibromo-N,N′-1,2-ethanediylbis(p-toluenesulfonamide) can be used for the solid-state conversion of 1,1-diacetates to aldehydes in excellent yields.
- Ghorbani-Vaghei, Ramin,Akbari, Safar-Ali,Zolfigol, Mohammad A.,Mirjalili, BiBi Fatemeh,Bamoniri, Abdolhamid
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- Aerobic Oxidation of Alcohols Catalysed by Cu(I)/NMI/TEMPO System and Its Mechanistic Insights
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Abstract: Homogeneous Cu(I)/NMI/TEMPO catalyst system (TEMPO = 2,2,6,6-tetramethylpiperidine-N-oxyl) has been investigated for its catalysis on the aerobic oxidation of 1-octanol and other alcohols into aldehydes under room temperature. The catalytic species was found to be a Cu(I) centre coordinated by two NMI molecules and other two weakly bound solvent molecules, [Cu(NMI)2(Sol)2]+ (Sol = solvent). When CuI was used, this species could be [Cu(NMI)I(Sol)2]. Not like being speculated previously, NMI in this system acts solely as a ligand and its role coordinated to the copper centre enhanced the electron density on the metal centre which promoted the O2 binding in the catalysis. The labile solvent binding to the Cu(I) centre is essential to ensure both oxygen and substrate binding. The catalyst system is suitable for the oxidation of various alcohols using a simple reaction setup and workup. In particular, the system possesses strong oxidizing capability in quantitative conversion of benzylic alcohols regardless of the substituents on the phenyl ring and allylic alcohols into aldehydes. A plausible mechanism was also proposed for the catalysis. Graphical Abstract: The aerobic oxidation of primary alcohols at room temperature to corresponding aldehydes was achieved by the catalyst composed by Cu(I) and methyl imidazole (NMI) mediated by TEMPO in acetonitrile. The catalytic species is proposed to be such a Cu(I) complex that two of its four coordinating sites are occupied by a strong ligand(s) and the rest two are weakly bound by solvent molecules.[Figure not available: see fulltext.].
- Liu, Zhenzhen,Shen, Zhongquan,Zhang, Ning,Zhong, Wei,Liu, Xiaoming
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- Selective oxidation of ethanol over vanadia-based catalysts: The influence of support material and reaction mechanism
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The catalytic performance of vanadia supported on silica, alumina, zirconia, and titania was investigated in the selective oxidation of ethanol. It was shown that the activity and product distribution strongly depend on the support material, which determines the structure of supported vanadia species. On silica and alumina, low-active V2O5 crystallites were mainly formed regardless of the vanadium content. These catalysts demonstrated high selectivity toward only acetaldehyde. In contrast, monomeric surface vanadia species and polymeric surface vanadia species were mainly formed over TiO2 when the vanadium content did not exceed what is necessary for the ideal monolayer. Over zirconia, both the surface vanadia species and the V2O5 crystallites existed regardless of the vanadium content. It was found that the surface vanadia species are more active in the selective oxidation of ethanol than the V2O5 crystallites. The highest activity was observed for the polymeric vanadia species and, correspondingly, the best catalytic performance was achieved on the monolayer V2O5/TiO2 catalyst. At low temperatures between 110 and 150 °C, this catalyst demonstrated high activity in the oxidation of ethanol to acetaldehyde with the selectivity ranging between 80% and 100%. At temperature near 200 °C, the same catalyst was active in the oxidation of ethanol to acetic acid with the selectivity of approximately 65%. The surface intermediates and the catalyst state were also studied in situ by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. It was shown that under reaction conditions near 100 °C, non-dissociatively adsorbed molecules of ethanol, ethoxide species, and adsorbed acetaldehyde exist on the catalyst surface, while at higher temperatures, V2O5/TiO2 is mainly covered with acetate species. Titanium cations remained in the Ti4+ state, whereas V5+ cations underwent a reversible reduction under reaction conditions. On the basis of the in situ data complemented by the results of kinetic measurements, a reaction mechanism for the selective oxidation of ethanol to acetaldehyde and acetic acid over the monolayer catalysts was proposed.
- Andrushkevich,Kaichev,Chesalov, Yu.A.,Saraev,Buktiyarov
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- Oxidation of Allylic Alcohols by Means of Electrochemical Methodology. Novel Rearrangement of Prenol under Direct Anodic Oxidation Conditions
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Electrochemical oxidation of naturally occurring allylic alcohols is described.Under direct anodic oxidation conditions, prenol 1 was readily oxidized, followed by rearrangement presumably on the surface of the anodic electrode, to give 3-hydroxy-2,2'-dimethyl-1,1'-dimethoxy propane 2 in high yield, whereas geraniol 5 afforded citral 6 under the same conditions.
- Maki, Shojiro,Konno, Katsuhiro,Takayama, Hiroaki
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- A comparative study of Bi2WO6, CeO2, and TiO2 as catalysts for selective photo-oxidation of alcohols to carbonyl compounds
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Several semiconductors based on ceria or bismuth tungstate were tested for selective oxidation of alcohols to carbonyl compounds in a search for photocatalysts more selective than TiO2. Gas-phase selective photo-oxidation of propan-2-ol to acetone and liquid-phase transformation of 2-buten-1-ol (crotyl alcohol) to 2-butenal (crotonaldehyde) were studied as test reactions. In both processes the highest selectivities were achieved with Bi2WO6-based solids. Further studies on crotyl alcohol transformation evidenced the lower adsorption of the aldehyde on these systems which could minimize the decrease in crotyl alcohol yield observed for TiO2 or CeO2 at high conversions. Incorporation of titania (5% molar) to the Bi2WO6 system increased the reaction rate significantly whereas the aldehyde yield remained high.
- López-Tenllado,Murcia-López,Gómez,Marinas,Marinas,Urbano,Navío,Hidalgo,Gatica
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- Sonochemical synthesis of PdO@silica as a nanocatalyst for selective aerobic alcohol oxidation
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Abstract A sonochemical method has been employed for the synthesis of palladium oxide (PdO) nanoparticles deposited on silica nanoparticle. By sonochemical process, the PdO nanoparticles were doped on the surface of silica at room temperature and atmospheric pressure with short reaction time. Silica nanoparticles were used as a supporting material to suppress aggregation and thereby to increase surface area of PdO nanoparticles. Fabricated PdO-doped silica nanoparticle (PdO@SNP) was applied as a nanocatalyst for selective alcohol oxidation reaction in the presence of molecular oxygen. The PdO@SNP composite showed higher catalytic activity and selectivity than unsupported PdO nanoparticle for aerobic alcohol oxidation reaction.
- Seok, Seunghwan,Hussain, Muhammad Asif,Park, Kyun Joo,Kim, Jung Won,Kim, Do Hyun
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- Effect of Cu content on the surface and catalytic properties of Cu/ZrO 2 catalyst for ethanol dehydrogenation
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ZrO2-supported Cu catalysts with different Cu content (5-30 wt.%) were prepared by impregnation method. The effect of Cu content on the structure, surface and catalytic properties of Cu/ZrO2 catalysts in the reaction of ethanol conversion was studied. The physicochemical characterization of the calcined and reduced samples was carried out by: N 2 adsorption-desorption isotherms, N2O titration, XRD, XPS, TPR and DRFTS of CO adsorption. It was observed that the increase of Cu content leads to decrease of the apparent copper metal dispersion caused by the strong agglomeration of the metal particles. The selectivity to different reaction products was connected with the electronic properties of the catalysts defined by the copper particle size and the interface at metal-oxide support. The highest selectivity to ethyl acetate over samples with Cu content ≥10 wt.% was assigned to the high density of basic sites of O2- ions and more heterogeneous distribution of copper species (Cu0/Cu +) defined by DRIFTS of CO adsorption and XPS.
- Freitas,Damyanova,Oliveira,Marques,Bueno
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- In situ X-ray absorption spectroscopic analysis of gold-palladium bimetallic nanoparticle catalysts
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Gold-palladium core-shell nanoparticles have been previously shown to be extremely effective catalysts for a number of oxidation reactions including the aerobic oxidation of alcohols. However, the novel activity and durability of such catalysts are still poorly understood, and there are several putative mechanisms by which oxidation reactions can proceed. Previously we showed that Pd(II) salts in the presence of Au nanoparticles were also effective catalysts for the room temperature oxidation of crotyl alcohol. Herein we show an in situ X-ray absorption spectroscopy (XAS) study at both the Pd-K and Pd-L III edges of Au nanoparticle/Pd(II) salt solutions in the presence of crotyl alcohol. Liquid cells with X-ray permeable windows were used to obtain quick-scan XAS data during the oxidation of crotyl alcohol, allowing for time-resolved Pd speciation information and information about the reaction mechanism and kinetics. XAS measurements definitively show that the first step of this reaction involves Pd reduction onto the Au nanoparticles; in addition, further studies of the stability of the resulting Au-Pd core-shell nanoparticles toward oxygen gas suggests that the role of Au in such catalysts is to prevent the reoxidation of the catalytically active surface Pd atoms. Catalytic crotyl alcohol oxidation measurements were done which validated that the in situ reduction of Pd(II) in the presence of Au nanoparticles did indeed result in catalytically active AuPd bimetallic catalysts.
- Maclennan, Aimee,Banerjee, Abhinandan,Hu, Yongfeng,Miller, Jeffrey T.,Scott, Robert W. J.
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- A rational design of a Pd-based catalyst with a metal-metal oxide interface influencing molecular oxygen in the aerobic oxidation of alcohols
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In a green process for selective oxidation of alcohols, the utilization of molecular oxygen as a primary oxidant is the most critical step. Although many palladium (Pd)-based catalysts have shown potential, the role of different Pd-species in the aerobic oxidation reaction is still a matter of discussion. There have been diverse reports, which describe either Pd0 or Pd2+ as the individual species responsible for the aerobic oxidation of alcohols. Herein we demonstrate that the presence of both Pd0 and Pd2+ species with a Pd-PdO interface stabilized on the surface of reduced graphene oxide (rGO) is important for the oxidation of alcohols. With an optimum Pd2+/Pd0 ratio, the catalyst catalyzes the oxidation of benzyl alcohol in water with oxygen, resulting in a turnover frequency (TOF) of up to 18 000 h-1 with 98% selectivity towards the aldehyde. It is proposed that both metallic Pd and its oxide domains, when co-existing with a phase boundary between them, promote the activation of oxygen. On the other hand, rGO provides surface functionalities for the formation and stabilization of Pd-PdO nanoclusters enabling the catalyst to be both stable and reusable. Using histidine as a scavenger for singlet oxygen, we have also determined the importance of oxygen-activation in the reaction. Furthermore, the catalyst is capable of converting various other alcohols into the corresponding carbonyl compounds. Comparison of various catalysts shows that the Pd-PdO@rGO catalyst is the most efficient in terms of TOF, conversion and selectivity for the oxidation of benzyl alcohol using oxygen compared to the reported Pd-based catalysts, particularly when performed under milder reaction conditions. Therefore, the result on Pd-catalyst designing is believed to be of significance for the further developments in the environmentally benign oxidation processes involving molecular oxygen as the oxidant.
- Meher, Songhita,Rana, Rohit Kumar
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- Kinetic study for oligomerization of acetaldehyde over cation exchange resin
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Several industrially important liquid phase reactions which involve acetaldehyde as the main reactant are practised in the presence of acidic catalyst. However, under these conditions, acetaldehyde also undergoes oligomerization via self-aldol condensation reactions to form multiple side products thereby reducing the selectivity of the desired product. In this work, we investigate the detailed kinetics of oligomerization over a commonly used commercial cation exchange resin, Amberlyst-15 as catalyst. It is found that, crotonaldehyde and subsequent heavy aldols are formed in the reaction. Molecular weight distribution of the oligomers formed during the reaction is verified with Flory's statistical method. Kinetic studies are performed in an autoclave over a temperature range of 343?363 K. The effect of different parameters such as temperature, concentration, catalyst loading, and catalyst reusability is examined. A kinetic model based on Langmuir-Hinshelwood-Hougen-Watson (LHHW) rate expression is proposed to explain acetaldehyde oligomerization in the presence of acidic resin.
- Kamal, Sumit,Mahajani, Sanjay
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- Ferritin-supported palladium nanoclusters: Selective catalysts for aerobic oxidations in water
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Confinement of nanometallic Pd within the core of a hyperthermophilic ferritin cage (from Pyrococcus furiosus) is reported. The resulting nanostructured hybrid catalysts can be used for highly specific aerobic oxidation of alcohols in water. This journal is
- Kanbak-Aksu,Nahid Hasan,Hagen,Hollmann,Sordi,Sheldon,Arends
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- Hydrotalcite-supported gold catalysts for a selective aerobic oxidation of benzyl alcohol driven by visible light
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Hydrotalcite-supported gold nanoparticles are studied as photocatalysts for the aerobic oxidation of benzyl alcohol and its derivatives without additional base under irradiation by visible light. The effects of the solvent, the hydrotalcite constitution and the gold content on the catalytic reaction are studied. The reactions utilizing benzotrifluoride as the solvent yield the best results. When varying the gold content and support, 2 wt% Au/HT-3 exhibits good catalytic activity. Furthermore, the rate of conversion under visible light is far superior to that in the dark. The catalytic activity can be tuned by manipulating the intensity or wavelength of the light. A reaction mechanism is proposed to rationalize these results: the primary reason for the lower activity observed on recycled catalysts is that the basic sites of hydrotalcite are decreased during the reaction in light.
- Yu, Jing,Li, Jingyi,Wei, Huili,Zheng, Jianwei,Su, Haiquan,Wang, Xiaojing
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- An experimental (flash vacuum pyrolysis) and theoretical study of the tautomerism of pyrazolinones at high temperatures
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Flash vacuum pyrolysis experiments were carried out between 500 and 800°C on 3(5)-phenyl- and 3(5)-methylpyrazolinones and on 3(5)-methoxy-5(3)-phenylpyrazole. The origin of the isolated products (mainly indanone, hydroxyalkynes and α,β-unsaturated aldehydes) can be explained as arising from the hydroxy tautomers of pyrazolinones. Temperature effects on the tautomeric equilibrium of 1-phenyl-3-methylpyrazolinone in solution show that the percentage of the CH tautomer increases with the temperature. MP2 ab initio calculations on the model compound, pyrazolinone itself, have been used to rationalize these findings. The problem of the aromaticity of the four tautomers of pyrazolinone has been examined through Schleyer's NICS (nuclear independent chemical shifts) calculations.
- Yranzo, Gloria I.,Moyano, Elizabeth L.,Rozas, Isabel,Dardonville, Christophe,Elguero, Jose
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- Catalytic properties of the antibody H11
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The catalytic activity of the antibody H11 is shown to reside chiefly in its ability to hydrolyze 1-acetoxybutadiene to crotonaldehyde and to promote the cycloaddition of the intermediate enol with N-alkylmaleimides. This conclusion is based upon the demonstration that the enol tautomerizes too rapidly in solution to be a competent intermediate and that under the reaction conditions for H11, no cycloaddition occurs with crotonaldehyde and N-ethylmaleimide. As a first step towards a structural understanding of the chemistry of H11, chemical modification experiments have shown that reactions of acidic amino acids, tyrosine, lysine, and histidine, but not arginine, inhibit the reactions mediated by H11.
- Pitt, Andrew R.,Stimson, William H.,Suckling, Colin J.,Marrero-Tellado, Jose J.,Vazzana, Caterina
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- A kinetic and mechanistic study of the osmium(VIII)-catalysed oxidation of crotyl alcohol by hexacyanoferrate(III) in aqueous Alkaline medium
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The kinetics and mechanism of the osmium(VIII)-catalysed oxidation of crotyl alcohol by hexacyanoferrate(III) in aqueous alkaline medium is studied. The role of the osmium(VIII) catalyst is delineated to account for the experimental observations. A plausible reaction mechanism is suggested. Activation parameters such as the energy and entropy of activation are evaluated by employing the Eyring equation and are found to be 36.833 kJ mol?1 and ?141.518 J K?1 mol?1, respectively.
- Sharma, Priyamvada,Sailani, Riya,Meena, Anita,Khandelwal, Chandra Lata
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- Iodide assisted zeolite catalysed 1,4-addition of water to butadiene monoxide
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Selective 1,4-addition of water to butadiene monoxide can be achieved in a liquid phase catalytic process using ultrastable Y zeolite as Broensted acid, potassium iodide, and an ether solvent. The reaction mechanism could be elucidated based on the occurrence of intermediate reaction products. Iodide is added to the terminal unsaturated carbon atom of a protonated butadiene monoxide molecule. The strong solvent effect observed can be rationalised based on the nucleophilicity of the iodide depending on the basicity of the ether function. With USY zeolite, the 2-butene-1,4-diol selectivity reaches 73.9% at 100% conversion when using 1,2-dimethoxyethane solvent, 2,5-dihydrofuran being the main by-product. With this catalytic system followed by an additional hydrogenation step, butadiene monoxide can be selectively converted into 1,4-butanediol.
- Remans, Thomas J.,Van Oeffelen, Domien,Steijns, Matt,Martens, Johan A.,Jacobs, Pierre A.
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- THE TETRAHYDROPYRANYL ETHER OF (E)-3-BROMO-3-TRIMETHYLSILYL-2-PROPEN-1-OL, A SINGLE SYNTHON FOR THE (E)-β-FORMYLVINYL ANION AND CATION
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The tetrahydropyranyl ether of (E)-3-bromo-3-trimethylsilyl-2-propen-1-ol can serve as a single synthon for both the (E)-β-formylvinyl anion and cation depending upon the manner in which the bromine group is stereospecifically replaced by an alkyl group.
- Miller, R. Bryan,Al-Hassan, Mohamed I.
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Read Online
- Method for preparing crotonaldehyde from ethanol
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The invention relates to a method for preparing crotonaldehyde from ethanol. The method comprises the following steps of firstly, dehydrogenating ethanol into acetaldehyde by using a metal-loaded semiconductor photocatalyst under illumination, then carrying out aldol condensation under base catalysis, and finally dehydrating under a heating condition to form crotonaldehyde. The method starts from ethanol and has the advantages of wide raw material sources, mild reaction conditions and the like.
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Paragraph 0019-0048
(2021/06/13)
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- Rapid, chemoselective and mild oxidation protocol for alcohols and ethers with recyclable N-chloro-N-(phenylsulfonyl)benzenesulfonamide
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Chlorine is the 20th most abundant element on the earth compared to bromine, iodine, and fluorine, a sulfonimide reagent, N-chloro-N-(phenylsulfonyl)benzenesulfonamide (NCBSI) was identified as a mild and selective oxidant. Without activation, the reagent was proved to oxidize primary and secondary alcohols as well as their symmetrical and mixed ethers to corresponding aldehydes and ketones. With recoverable PS-TEMPO catalyst, selective oxidation over chlorination of primary and secondary alcohols and their ethers with electron-donating substituents was achieved. The reagent precursor of NCBSI was recovered quantitatively and can be reused for synthesizing NCBSI.
- Badani, Purav,Chaturbhuj, Ganesh,Ganwir, Prerna,Misal, Balu,Palav, Amey
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supporting information
(2021/06/03)
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- Copper-Containing Catalysts Based on Cerium–Zirconium Oxide Supports in Ethanol Conversion Reaction According to In Situ IR Spectroscopic Data
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Abstract: Copper-containing catalysts based on CeO2–ZrO2 solid solutions were prepared by the Pecini method and studied using a set of physicochemical methods. It was found that the bond strength of oxygen on the catalyst surface, which depends on the properties of supported copper oxide clusters and a ratio between CeO2 and ZrO2 in the support, plays a main role in ethanol conversion. Ethoxy groups, acetate and formate complexes, and condensation products were detected as main surface intermediates formed in the course of ethanol conversion on the catalysts. The decomposition of the formate complexes was the key stage in the formation of hydrogen. Its appearance on the surface of the catalysts was due to the competition between the reactions of formate and acetate complex formation for oxygen with suitable properties.
- Ilichev, A. N.,Korchak, V. N.,Matyshak, V. A.,Sil’chenkova, O. N.
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p. 404 - 417
(2021/06/14)
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- A study on the cataluminescence of propylene oxide on FeNi layered double hydroxides/graphene oxide
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In this work, FeNi layered double hydroxides/graphene oxide (FeNi LDH/GO) was prepared, which exhibits excellent selective cataluminescent performance towards propylene oxide. The selectivity and sensitivity of the cataluminescence (CTL) reaction were investigated in detail. Moreover, the catalytic reaction mechanism, including the intermediate products and the conversion of reactants to products, was discussed based on both the experimental and computational results. Furthermore, the proposed FeNi LDH/GO based CTL sensor was successfully applied for the determination of propylene oxide residue in fumigated raisins, which indicates extensive application potential for rapid food safety evaluation.
- Li, Ming,Hu, Yufei,Li, Gongke
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p. 11823 - 11830
(2021/07/11)
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- Lewis Acidic Boranes, Lewis Bases, and Equilibrium Constants: A Reliable Scaffold for a Quantitative Lewis Acidity/Basicity Scale
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A quantitative Lewis acidity/basicity scale toward boron-centered Lewis acids has been developed based on a set of 90 experimental equilibrium constants for the reactions of triarylboranes with various O-, N-, S-, and P-centered Lewis bases in dichloromethane at 20 °C. Analysis with the linear free energy relationship log KB=LAB+LBB allows equilibrium constants, KB, to be calculated for any type of borane/Lewis base combination through the sum of two descriptors, one for Lewis acidity (LAB) and one for Lewis basicity (LBB). The resulting Lewis acidity/basicity scale is independent of fixed reference acids/bases and valid for various types of trivalent boron-centered Lewis acids. It is demonstrated that the newly developed Lewis acidity/basicity scale is easily extendable through linear relationships with quantum-chemically calculated or common physical–organic descriptors and known thermodynamic data (ΔH (Formula presented.)). Furthermore, this experimental platform can be utilized for the rational development of borane-catalyzed reactions.
- Mayer, Robert J.,Hampel, Nathalie,Ofial, Armin R.
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supporting information
p. 4070 - 4080
(2021/01/29)
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- IBX-TfOH mediated oxidation of alcohols to aldehydes and ketones under mild reaction conditions
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An efficient, practical and facile procedure has been developed for the oxidation of primary and secondary alcohols using IBX-TfOH catalytic system in 1,4-dioxane at ambient temperature. The reaction affords quantitative yields of the corresponding carbonyl compounds without the formation of over oxidized products. The present synthetic protocol is compatible with a variety of substrates having arene, heteroarene and alkene functionalities. The developed synthetic protocol can be used for higher scale reactions as evident by the oxidation of alcohol at 1 g scale in higher yields by a simple filtration process.
- Kumar, Kamlesh,Kumar, Prashant,Joshi, Penny,Rawat, Diwan S
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supporting information
(2020/03/04)
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- Oxidation of crotyl alcohol by N-chloro-4-methylbenzene sulphonamide in acidic medium and in alkaline media in the presence of os(VIII) catalyst-a kinetic pathway
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The kinetic pathway of oxidation of crotyl alcohol by sodium salt of N -chloro-4-methylbenzene sulphonamide (chloramine-T) in acidic and alkaline medium has been studied. The speciation of chloramine-T has been made to suggest a proper and reasonable reaction mechanism. The thermodynamic quantities such as activation energy and activation entropy are evaluated in acidic as well as in catalysed alkaline medium. An anticipated reaction mechanism has been suggested.
- Khandelwal, Chandra Lata,Meena, Anita,Sailani, Riya,Sharma, Priyamvada
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p. 950 - 970
(2020/09/18)
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- MgO?SiO2 Catalysts for the Ethanol to Butadiene Reaction: The Effect of Lewis Acid Promoters
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MgO?SiO2 samples, having the composition of natural talc (NT), were obtained by co-precipitation (CP) and wet kneading (WK) methods. The materials were used as catalysts of the ethanol-to-1,3-butadiene reaction. ZnO, Ga2O3 and In2O3 were tested as promoters. The catalyst WK gave the highest 1,3-Butadiene (BD) yield among the non-promoted catalysts because of the high specific surface area and strong basicity. Results suggested that over the neat WK catalyst the acetaldehyde coupling to crotonaldehyde was the rate-determining process step. Formation of crotyl alcohol intermediate was substantiated to proceed by the hydrogen transfer reaction between crotonaldehyde and ethanol. The crotyl alcohol intermediate becomes dehydrated to BD or, in a disproportionation side reaction, it forms crotonaldehyde and butanol. The promoter was found to increase the surface concentration of the reactant and reaction intermediates, thereby increases the rates of conversion and BD formation. The order of promoting efficiency was Zn>In>Ga.
- Szabó, Blanka,Novodárszki, Gyula,Pászti, Zoltán,Domján, Attila,Valyon, József,Hancsók, Jen?,Barthos, Róbert
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p. 5686 - 5696
(2020/09/22)
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- METHOD FOR PRODUCING CROSS ALDOL CONDENSATE USING AMINE-CARRYING CATALYST
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PROBLEM TO BE SOLVED: To provide a method for producing a cross aldol condensate with improved selectivity of a cross aldol condensate, the target material. SOLUTION: A method for producing a cross aldol condensate has a step of performing a cross aldol condensation reaction of different two substrates in the presence of an amine-carrying catalyst with an amine compound immobilized to a carrier, the substrate containing two compounds selected from aldehyde and/or ketone having α hydrogen. SELECTED DRAWING: None COPYRIGHT: (C)2021,JPO&INPIT
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Paragraph 0033; 0036; 0043
(2021/01/16)
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- Amorphous Nickel Phosphide Nanoparticles for Selective Hydrogenation of Cinnamaldehyde
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Abstract: The selective hydrogenation of α,β-unsaturated aldehydes plays a crucial role in industrial production, and an efficient non-noble metal catalyst for it has been pursued to reduce the cost. Herein, we report an amorphous nickel phosphide for the selective hydrogenation of cinnamaldehyde. Compared to crystalline nickel phosphide, amorphous nickel phosphide showed both high activity and high selectivity to target products. Its catalytic performance was also better than that of commercial Pd/C catalyst. In addition, initial P/Ni ratio was found to be an important factor to affect the activity of amorphous nickel phosphide. High initial P/Ni ratio led to high activity owing to small particles, high surface area and strong metallicity of as-synthesized catalyst. Moreover, excellent catalytic performances of amorphous nickel phosphide were observed in the selective hydrogenation of different α,β-unsaturated aldehydes and ketones. Graphic Abstract: [Figure not available: see fulltext.].
- Liu, Ping,Zhu, Ya-Lu,Zhou, Lei,Zhang, Wei-Hong,Li, Yong-Xin
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p. 2695 - 2702
(2020/03/23)
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- Synthesis of α,β- and β-Unsaturated Acids and Hydroxy Acids by Tandem Oxidation, Epoxidation, and Hydrolysis/Hydrogenation of Bioethanol Derivatives
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We report a reaction platform for the synthesis of three different high-value specialty chemical building blocks starting from bio-ethanol, which might have an important impact in the implementation of biorefineries. First, oxidative dehydrogenation of ethanol to acetaldehyde generates an aldehyde-containing stream active for the production of C4 aldehydes via base-catalyzed aldol-condensation. Then, the resulting C4 adduct is selectively converted into crotonic acid via catalytic aerobic oxidation (62 % yield). Using a sequential epoxidation and hydrogenation of crotonic acid leads to 29 % yield of β-hydroxy acid (3-hydroxybutanoic acid). By controlling the pH of the reaction media, it is possible to hydrolyze the oxirane moiety leading to 21 % yield of α,β-dihydroxy acid (2,3-dihydroxybutanoic acid). Crotonic acid, 3-hydroxybutanoic acid, and 2,3-dihydroxybutanoic acid are archetypal specialty chemicals used in the synthesis of polyvinyl-co-unsaturated acids resins, pharmaceutics, and bio-degradable/ -compatible polymers, respectively.
- Faria, Jimmy,Komarneni, Mallik R.,Li, Gengnan,Pham, Tu,Resasco, Daniel E.,Ruiz, Maria P.,Santhanaraj, Daniel
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supporting information
p. 7456 - 7460
(2020/03/23)
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- Conversion of ethanol to 1,3-butadiene over high-performance Mg-ZrO: X/MFI nanosheet catalysts via the two-step method
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Mg-Zr/MFI nanosheet (NS) catalysts were prepared by a wet impregnation method for ethanol conversion to 1,3-butadiene (1,3-BD) via the two-step method in a dual fixed bed reaction system. Compared with Zr catalysts loaded on MFI(micro) or commercial SiO2, 16%Zr/MFI(NS) gave the better performance, with 42.3% 1,3-BD selectivity and 60.5% total conversion of ethanol and acetaldehyde. Introducing 1.2 wt% Mg to 16%Zr/MFI(NS) improved the 1,3-BD selectivity to 54.7% at the expense of a 6% drop in the catalytic activity. Reaction conditions imposed remarkable influence on the reaction results. When the reaction was conducted at 350 °C, a WHSV of 1.44 h-1 and a 2 : 1 ratio of ethanol to acetaldehyde, the 1,3-BD selectivity reached 74.6% with 41.5% total conversion. Such high performance over 1.2%Mg-16%Zr/MFI(NS) was maintained well in a 7 day (168 h) run without deactivation. The catalysts were characterized by XRD, N2 adsorption, UV-Vis, Raman, and infra-red spectroscopy, NH3-TPD, TEM and TG. The results showed that the Zr species on MFI(NS) are well distributed with the highest dispersion as compared with the microporous MFI and SiO2 supported Zr catalysts. The Zr species preferentially occupied the silanol nests of MFI(NS) and eliminated the Br?nsted acid sites at 4 wt% Zr loading, and afforded abundant Lewis acid sites in the form of Zr(OH)(OSi)3 when the Zr loading was increased to 16 wt%. As a base site, Mg is inactive for MPVO reduction but slightly active for the aldol condensation of acetaldehyde, both of which are much inferior to that of the Lewis acid sites. The 1.2%Mg-16%Zr/MFI(NS) catalyst with hierarchical structures of meso- and micro-pores, abundant weak Lewis acid sites but nearly no Br?nsted acid sites is competent for the two-step ethanol to 1,3-BD conversion process with high activity, selectivity and stability.
- Li, Lin,Li, Xianquan,Pan, Xiaoli,Pang, Jifeng,Wang, Chan,Zhang, Tao,Zheng, Mingyuan
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p. 2852 - 2861
(2020/06/17)
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- Structural activity of unsaturated alcohols and oxidation towards pyrazinium chlorochromate
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The kinetics of oxidation of allyl, crotonyl, styryl carbinol by pyrazinium chlorochromate (PzCC) has been investigated in 60% acetic acid medium.The order was found to be first order with respect to [oxidant], [substrate] and [H+.]. The rate of the oxidant decreased with increase in [PzCC] and increased with increase in the percentage of acetic acid. The addition of sodium perchlorate did not show any change in rate constant. Based on the kinetic results, the mechanism between unsaturated alcohol and chromium (VI) oxidant is proposed. The reactivity of unsaturated alcohols was observed to be allyl alcohol crotonyl alcohol styryl carbinol.
- Anbarasu,Ilavenil
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p. 436 - 441
(2019/06/07)
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- Production and testing of technical catalysts based on MnO2 for the abatement of aromatic volatile compounds at the laboratory and pilot plant scales
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Shaping is a crucial step to produce technical catalysts that remains as some sort of dark art for catalytic researchers in academia. This contribution discusses aspects concerning the fabrication of technical catalysts based on MnO2 powders ai
- Baldovino-Medrano, Víctor Gabriel,Kartheuser, Beno?t,Gaigneaux, Eric M.
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- Ethanol to Butanol Conversion over Bifunctional Zeotype Catalysts Containing Palladium and Zirconium
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Abstract: A study of the kinetics of ethanol conversion in the presence of Zr-containing zeolites BEA doped with palladium particles has revealed the order of formation of the main reaction products. It has been shown that the primary processes are ethanol dehydrogenation to acetaldehyde on Pd sites and ethanol dehydration to diethyl ether on the acid sites of the catalyst. After that, acetaldehyde undergoes the aldol–croton condensation reaction to form crotonal, which is hydrogenated to butanol on the metal sites. Butanol, in turn, is dehydrated into butenes, which undergo hydrogenation to butane. The presence of hydrogen in the gas phase leads to the displacement of ethanol from the metal surface and prevents the formation of surface carbonates and acetates. It has been found that hydrogen significantly accelerates ethanol dehydration owing to a decrease in the activation energy, which can be attributed to hydrogen spillover to the zeolite. The addition of water inhibits all acid-catalyzed reactions owing to competitive adsorption on acid sites and thereby decreases the butanol yield and the ethanol conversion.
- Kots,Zabilska,Grigor’ev, Yu. V.,Ivanova
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p. 925 - 934
(2019/08/20)
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- Length-Selective Synthesis of Acylglycerol-Phosphates through Energy-Dissipative Cycling
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The main aim of origins of life research is to find a plausible sequence of transitions from prebiotic chemistry to nascent biology. In this context, understanding how and when phospholipid membranes appeared on early Earth is critical to elucidating the prebiotic pathways that led to the emergence of primitive cells. Here we show that exposing glycerol-2-phosphate to acylating agents leads to the formation of a library of acylglycerol-phosphates. Medium-chain acylglycerol-phosphates were found to self-assemble into vesicles stable across a wide range of conditions and capable of retaining mono- and oligonucleotides. Starting with a mixture of activated carboxylic acids of different lengths, iterative cycling of acylation and hydrolysis steps allowed for the selection of longer-chain acylglycerol-phosphates. Our results suggest that a selection pathway based on energy-dissipative cycling could have driven the selective synthesis of phospholipids on early Earth.
- Bonfio, Claudia,Caumes, Cécile,Duffy, Colm D.,Patel, Bhavesh H.,Percivalle, Claudia,Tsanakopoulou, Maria,Sutherland, John D.
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supporting information
p. 3934 - 3939
(2019/03/08)
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- Cu2 O/monodentate ligand/TEMPO by catalyzing air production of aldehydes
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The invention discloses a Cu2 O/monodentate ligand/TEMPO by catalyzing air production of aldehydes, characterized in that incendiary as raw materials, air as the oxidizing agent, to the organic solution as the solvent, in the Cu2 S/monodentate ligand/TEMPO under the catalytic action, modifiable is oxidized to obtain corresponding aldehydes; the catalyst of the invention not only has excellent catalytic activity of the catalytic system at the same time recycled; and simplify the catalytic system, the operation is simple, the substrate serviceability is good, high yield, low cost.
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Paragraph 0027; 0028; 0050
(2019/01/08)
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- Stable Carbocation Generated via 2,5-Cyclohexadien-1-one Protonation
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Protonation of a substituted cyclohexadien-1-one (1) leads to the generation of carbocation [3]+, capable of effecting hydride abstraction and oxidation reactions. The molecular structure of [3]+ shows it to be structurally similar to [(p-MeO-C6H4)Ph2C]+. The ability to easily access [3]+ from stable and available precursors, such as 1 and commercially available acids, may allow a wider application of the growing number of trityl-based reactions in organic syntheses.
- Fraser, Craig,Young, Rowan D.
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p. 505 - 509
(2018/02/19)
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- CONVERSION OF ALCOHOLS TO LINEAR AND BRANCHED FUNCTIONALIZED ALKANES
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Embodiments herein concerns the eco-friendly conversion of simple alcohols to linear or branched functionalized alkanes, by integrated catalysis. The alcohols are firstlyoxidized either chemically or enzymatically to the corresponding aldehydes or ketones, followed by aldol condensations using a catalyst to give the corresponding enals or enones. The enals or enones are subsequently and selectively hydrogenated using a recyclable heterogeneous metal catalyst, organocatalyst or an enzyme to provide linear or branched functionalized alkanes with an aldehyde, keto- or alcohol functionality. The process is also iterative and can be further extended by repeating the above integrated catalysis for producing long-chain functionalized alkanes from simple alcohols.
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Page/Page column 9
(2018/03/09)
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- Catalytic Reactions of Homo- and Cross-Condensation of Ethanal and Propanal
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Abstract: Processes of catalytic homocondensation of propanal and its cross-condensation with ethanal and methanal in the presence of aniline and amino acids have been studied. The dependence of the conversion of the reactants and selectivity of the homo/heterocondensation process on the catalyst nature and temperature has been revealed. It has been shown that the maximum acrolein selectivity is reached in the case of using benzoyl-substituted derivatives in water, with the proportion of the products of further condensation decreasing. The selectivity for the ethanal homocondensation product 2-butenal decreases simultaneously as a result of the formation of linear and branched oligomers of successive condensation.
- Martsinkevich,Bruk,Dashko,Afaunov,Flid,Sedov
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p. 1032 - 1035
(2019/01/03)
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- A versatile biobased continuous flow strategy for the production of 3-butene-1,2-diol and vinyl ethylene carbonate from erythritol
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A versatile, tunable and robust continuous flow procedure for the deoxydehydration (DODH) of biobased erythritol toward 3-butene-1,2-diol is described. The procedure relies on specific assets of multistep continuous flow processing. Detailed mechanistic and computational studies on erythritol show that either 3-butene-1,2-diol or butadiene are obtained in high selectivity and yield on demand, as a function of the DODH reagent/substrate ratio and of the process parameters. Short reaction times (1-15 min) at high temperature (225-275 °C) and moderate pressure are reported. 3-Butene-1,2-diol is then further converted downstream into its corresponding carbonate, i.e. 4-vinyl-1,3-dioxolan-2-one (vinyl ethylene carbonate), an important industrial building block. The carbonation step uses a supported organocatalyst, and could be directly concatenated to the first DODH step. This unprecedented procedure also relies on a unique combination of on- and off-line analytical protocols for reaction monitoring and product quantification, and offers a biobased strategy toward important industrial building blocks otherwise petrosourced.
- Tshibalonza, Nelly Ntumba,Gérardy, Romaric,Alsafra, Zouheir,Eppe, Gauthier,Monbaliu, Jean-Christophe M.
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p. 5147 - 5157
(2018/11/26)
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- Environment-friendly method for synthesizing propenyl ketone compound
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The invention discloses an environment-friendly method for synthesizing a propenyl ketone compound. The method comprises the following steps: subjecting an aldehyde compound and allyl bromide to a Barbier reaction in the presence of metal powder, so as to obtain an allyl alcohol compound; and subjecting the allyl alcohol compound to a structural isomerization reaction in the presence of a catalyst, thereby obtaining the propenyl ketone compound. The method disclosed by the invention has the advantages of short synthesis route, mild reaction conditions, simplicity in operation, readily available raw materials, and the like and has relatively high academic research value and market economy significance.
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Paragraph 0019; 0020
(2019/01/04)
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- Aldol condensation among acetaldehyde and ethanol reactants on TiO2: Experimental evidence for the kinetically relevant nucleophilic attack of enolates
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Combinations of rate measurements as functions of reactant pressures, in situ infrared spectroscopy, comparisons of kinetic isotope effects, and rate inhibition effects provide experimental evidence that aldol condensation of acetaldehyde proceeds by kinetically relevant nucleophilic attack of a reactive enolate upon an acetaldehyde molecule over anatase TiO2. Steady-state turnover rates of aldol condensation measured as a function of the pressures of C2H4O, C2H5OH, H2O, and H2 between 503 K and 537 K show that rates reflect a second order dependence on C2H4O pressure and an inverse second order dependence on the C2H5OH pressure at the lowest C2H4O-to-C2H5OH ratios. Infrared spectra obtained in situ show that the exposed cationic Ti-atoms that facilitate aldol addition on TiO2 surfaces are saturated with C2H5OH? species and C2H4O? coverages are much smaller. In addition, aldol rates increase when C2D4O replaces C2H4O as a reactant, which likely reflects an inverse, secondary isotope effect caused by rehybridization of C-atoms at the transition state that forms a C–C bond between two reactive intermediates derived from acetaldehyde. These results suggest that the kinetically relevant step is a bimolecular surface reaction, specifically the nucleophilic attack of an enolate onto a vicinal C2H4O? species. This conclusion is consistent also with aldol condensation rates that decrease with an inverse second order dependence on pyridine (C5H5N) pressure, because C5H5N displaces C2H4O from the two Lewis acid sites involved in the kinetically relevant step (confirmed by in situ FTIR). Comparisons to recent reports on the mechanism of this reaction on anatase TiO2 indicate that the presence of high coverages of C2H5OH? causes nucleophilic attack to become the kinetically relevant step by significantly reducing the number of enolate-acetaldehyde reactant pairs upon the surface.
- Zhang, Hongbo,Ibrahim, Malek Y.S.,Flaherty, David W.
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p. 290 - 302
(2018/04/02)
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- METHODS FOR PRODUCING BUTANOL
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Methods and compositions for producing 1-butanol are described herein. In some examples, the methods can comprise, contacting a reactant comprising ethanol with a catalyst system, thereby producing a product comprising 1-butanol. The catalyst system can comprise, for example, an iridium catalyst and a nickel, copper, and/or zinc catalyst. The nickel, copper, and zinc catalysts can comprise nickel, copper, and/or zinc and a sterically bulky ligand.
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Paragraph 0087-0088
(2017/02/02)
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- Method for synthesizing muscone by utilizing beta-monomethyl methylglutarate
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The invention discloses a method for synthesizing muscone by utilizing beta-monomethyl methylglutarate. According to the method, beta-monomethyl methylglutarate and alpha,omega-dodecanedioic acid monomethyl ester respectively prepared through a heteropoly acid catalytic transesterification method are used as raw materials, and Kolbe electrolysis, acyloin condensation and reduction reaction are performed to prepare the muscone. The method of the present invention has advantages of high raw material utilization rate, mold condition, easy control and environmental protection, and is suitable for industrial production .
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Paragraph 0021; 0022
(2017/12/05)
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- Engineering a Promiscuous Tautomerase into a More Efficient Aldolase for Self-Condensations of Linear Aliphatic Aldehydes
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The enzyme 4-oxalocrotonate tautomerase (4-OT) from Pseudomonas putida mt-2 takes part in a catabolic pathway for aromatic hydrocarbons, where it catalyzes the conversion of 2hydroxyhexa-2,4-dienedioate into 2-oxohexa-3-enedioate. This tautomerase can also promiscuously catalyze carbon–carbon bond-forming reactions, including various types of aldol reactions, by using its amino-terminal proline as a key catalytic residue. Here, we used systematic mutagenesis to identify two hotspots in 4-OT (Met45 and Phe50) at which single mutations give marked improvements in aldolase activity for the self-condensation of propanal. Activity screening of a focused library in which these two hotspots were varied led to the discovery of a 4-OT variant (M45Y/F50V) with strongly enhanced aldolase activity in the self-condensation of linear aliphatic aldehydes, such as acetaldehyde, propanal, and butanal, to yield α,β-unsaturated aldehydes. With both propanal and benzaldehyde, this double mutant, unlike the previously constructed single mutant F50A, mainly catalyzes the self-condensation of propanal rather than the cross-condensation of propanal and benzaldehyde, thus indicating that it indeed has altered substrate specificity. This variant could serve as a template to create new biocatalysts that lack dehydration activity and possess further enhanced aldolase activity, thus enabling the efficient enzymatic self-coupling of aliphatic aldehydes.
- Rahimi, Mehran,van der Meer, Jan-Ytzen,Geertsema, Edzard M.,Poelarends, Gerrit J.
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p. 1435 - 1441
(2017/07/25)
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- A new selective route towards benzoic acid and derivatives from biomass-derived coumalic acid
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The selective production of aromatics from bio-based sources is an area of interest to expand the potential for greener alternatives to petroleum-derived chemicals. A scalable, efficient route to produce bio-based benzoates is demonstrated by carrying out heterogeneous catalytic reactions in non-toxic bio-based solvents at 180°C obtaining yields of up to 100 mol%. This approach extends the 2-pyrone (coumalic acid/methyl coumalate) Diels-Alder platform by utilizing a bioavailable co-reactant ethylene. A detailed investigation using a combination of kinetic experiments, DFT calculations, and multi-dimensional NMR was carried out to determine the detailed reaction network, and the corresponding activation energies for critical steps. Additionally, a series of experiments were conducted to maximize the yields by comparing different solvents, for both coumalic acid and methyl coumalate. Our results show that the choice of solvent was a significant factor when coumalic acid was the reactant (yields 71-92 mol%), while methyl coumalate was only minimally affected by the solvent (yields 95-100 mol%). Interestingly, the reaction network and kinetic analysis showed that the Diels-Alder reactions were not significantly different between coumalic acid and methyl coumalate, with the rate limiting step for both being decarboxylation with an activation barrier of 141 kJ mol-1 compared to 77 kJ mol-1 for the formation of the bicyclic adduct. Finally, the reaction cascade was found to be highly susceptible to by-product formation when as little as 5 vol% water was present in the solvent, which demonstrates that the absence of water is essential for high yielding benzoate production.
- Pfennig, Toni,Carraher, Jack M.,Chemburkar, Ashwin,Johnson, Robert L.,Anderson, Austin T.,Tessonnier, Jean-Philippe,Neurock, Matthew,Shanks, Brent H.
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supporting information
p. 4879 - 4888
(2017/10/23)
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- Manganese-Catalyzed Upgrading of Ethanol into 1-Butanol
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Biomass-derived ethanol is an important renewable feedstock. Its conversion into high-quality biofuels is a promising route to replace fossil resources. Herein, an efficient manganese-catalyzed Guerbet-type condensation reaction of ethanol to form 1-butanol was explored. This is the first example of upgrading ethanol into higher alcohols using a homogeneous non-noble-metal catalyst. This process proceeded selectively in the presence of a well-defined manganese pincer complex at the parts per million (ppm) level. The developed reaction represents a sustainable synthesis of 1-butanol with excellent turnover number (>110 000) and turnover frequency (>3000 h-1). Moreover, mechanistic studies including control experiments, NMR spectroscopy, and X-ray crystallography identified the essential role of the "N-H moiety" of the manganese catalysts and the major reaction intermediates related to the catalytic cycle.
- Fu, Shaomin,Shao, Zhihui,Wang, Yujie,Liu, Qiang
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supporting information
p. 11941 - 11948
(2017/09/07)
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- SELECTIVE REMOVAL OF IMPURITIES IN ACETIC ACID PRODUCTION PROCESSES
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Processes for producing carboxylic acid are included herein. The processes include contacting methanol and carbon monoxide in the presence of a liquid reaction medium under carbonylation conditions sufficient to form a carbonylation product including acetic acid and one or more components selected from acetaldehyde, formic acid and combinations thereof, wherein the liquid reaction medium includes: a carbonylation catalyst selected from rhodium catalysts, iridium catalysts and palladium catalysts; and water in a water concentration in a range of 1 wt.% to 14 wt.% based on the total w eight of the liquid reaction medium; and contacting at least a portion of the carbonylation product or a derivative thereof with an adsorbent at adsorption conditions sufficient to selectively reduce a concentration of one or more components present in the carbonylation product, wherein the adsorbent includes a silicoaluminophosphate (SAPO).
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Paragraph 0087
(2017/07/18)
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- SINGLE-STEP CONVERSION OF N-BUTYRALDEHYDE TO 2-ETHYLHEXANAL
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Disclosed is a method of making and using a titania supported palladium catalyst for the single step synthesis of 2-ethylhexanal from a feed of n-butyraldehyde. This titania supported palladium catalyst demonstrates high n-butyraldehyde conversion but also produces 2-ethylhexanal in an appreciable yield with maintained activity between runs. This method provides a single step synthesis of 2-ethylhexanal from n-butyraldehyde with a catalyst that can be regenerated that provides cleaner downstream separations relative to the traditional caustic route.
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Paragraph 00130; 00151-00153
(2017/08/21)
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- Formation Pathways toward 2- and 4-Methylbenzaldehyde via Sequential Reactions from Acetaldehyde over Hydroxyapatite Catalyst
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Condensation reactions of biomass derived C2 and C4 aldehydes form both ortho- and para-tolualdehydes (2-MB and 4-MB, respectively). The complete reaction network and the detailed mechanisms, however, have not been fully described. H
- Moteki, Takahiko,Rowley, Andrew T.,Bregante, Daniel T.,Flaherty, David W.
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p. 1921 - 1929
(2017/06/13)
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- Role of the surface intermediates in the stability of basic mixed oxides as catalyst for ethanol condensation
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The ethanol condensation catalyzed by mixed oxides is studied in this work, considering not only the activity but also the stability of these materials. Concerning to the activity, different weight hourly space velocities (WHSV) were tested, obtaining the highest conversion and 1-butanol selectivity with Mg-Al, mainly at 673?K and a WSHV of 7.9?h?1. On the other hand, dehydration products, observed with Mg-Zr in relevant amounts, limit the results obtained with this material. Deactivation studies were carried out by combining the measurement of reactant and products in the gas phase and in the catalytic surface using spectroscopic techniques (DRIFT). Good stability was observed with both materials at low temperatures (lower than 673?K), whereas at the highest one, Mg-Zr suffers relevant deactivation justified by the permanent adsorption of aldehydes and oxygenated oligomers on the active sites. It has been demonstrated that Mg-Al mixed oxides are promising catalyst for 1-butanol production from ethanol not only in terms of activity, but also in terms of catalyst stability.
- Quesada, Jorge,Faba, Laura,Díaz, Eva,Ordó?ez, Salvador
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p. 271 - 281
(2017/06/14)
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- Method to oxidize alcohols selectively to aldehydes and ketones with heterogeneous supported ruthenium catalyst at room temperature in air and catalyst thereof
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The present invention relates to a method for selectively oxidizing alcohol by using a heterogeneous catalyst for producing aldehyde and ketone in an organic synthesis process used in the laboratory and chemical industries, and a catalytic system thereof. The method can be used as an intermediate product for synthesizing medicine, scent, fragrance, and precise chemical products, and can use a heterogeneous catalyst at room temperature in air by using the catalytic system and producing alcohol and ketone.COPYRIGHT KIPO 2016
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Paragraph 0021; 0022
(2016/10/07)
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- Characterization of the monolignol oxidoreductase AtBBE-like protein 15 L182V for biocatalytic applications
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Monolignol oxidoreductases from the berberine bridge enzyme-like (BBE-like) protein family (pfam 08031) catalyze the oxidation of monolignols to the corresponding aldehydes. In this report, we explore the potential of a monolignol oxidoreductase from Arabidopsis thaliana (AtBBE-like protein 15) as biocatalyst for oxidative reactions. For this study we employed a variant with enhanced reactivity towards oxygen, which was obtained by a single amino acid exchange (L182V). The pH and temperature optima of the purified AtBBE-like protein 15 L182V were determined as well as the tolerance toward organic co-solvents; furthermore the substrate scope was characterized. The enzyme has a temperature optimum of 50 °C and retains more than 50% activity between pH 5 and pH 10 within 5 min. The enzyme shows increased activity in the presence of various co-solvents (10–50% v/v), including acetonitrile, 2-propanol, 1,4-dioxane, and dimethyl sulfoxide. Primary benzylic and primary or secondary allylic alcohols were accepted as substrates. The enantioselectivity E in the oxidation of secondary alcohols was good to excellent (E>34 to?>200).
- Pils, Sabine,Schnabl, Kordula,Wallner, Silvia,Daniel, Bastian,Macheroux, Peter,Kljajic, Marko,Kupresanin, Nina,Breinbauer, Rolf,Fuchs, Michael,Rocha, Raquel,Schrittwieser, Joerg H.,Kroutil, Wolfgang
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- MICROORGANISMS FOR PRODUCING 4C-5C COMPOUNDS WITH UNSATURATION AND METHODS RELATED THERETO
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The invention provides a non-naturally occurring microbial organism having a butadiene, crotyl alcohol, 2,4-pentadienoate, 3-buten-2-ol, or 3-buten-1-ol, pathway. The microbial organism contains at least one exogenous nucleic acid encoding an enzyme in a pathway. The invention additionally provides a method for producing butadiene, crotyl alcohol, 2,4-pentadienoate, 3-buten-2-ol, or 3-buten-1-ol,. The method can include culturing a butadiene, crotyl alcohol, 2,4-pentadienoate, 3-buten-2-ol, or 3-buten-1-ol-producing microbial organism, where the microbial organism expresses at least one exogenous nucleic acid encoding a pathway enzyme in a sufficient amount, and under conditions and for a sufficient period of time to produce butadiene, crotyl alcohol, 2,4-pentadienoate, 3-buten-2-ol, or 3-buten-1-ol.
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Paragraph 0014; 00100
(2016/01/25)
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- An improved production process of butenal
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The invention relates to an improvement of a crotonaldehyde production technique, which comprises the following steps: steam condensate is added into a condensation tower, an acetaldehyde condensation tower, a 3-hydroxybutyraldehyde dehydration tower and a primary distillation tower are in a water distillation state, tetramethyl ammonium hydroxide is used as a catalyst, the catalyst:acetaldehyde:acetic acid mole ratio is 1:1000:5, the catalyst solution, acetaldehyde and acetic acid are respectively added into the 10th, 11th and 6th tower trays of a bubbling hood condensation tower to generate 3-hydroxybutyraldehyde at the condensation temperature of 42-49 DEG C under the pressure of 0.05 MPa, the tower top condensate completely flows back, the tower bottom 3-hydroxybutyraldehyde enters the dehydration tower and is dehydrated under acidic conditions to generate crude crotonaldehyde, 0.34 part of the tower top distillation product condensate flows back, the rest tower top distillation product condensate and uncondensed gas enter the primary distillation tower to be concentrated, the tower top acetaldehyde gas condensate returns to the condensation tower for cyclic utilization, the crotonaldehyde is recovered from the middle part of the condensation tower, and the supernatant 89% crude crotonaldehyde is refined into 99.3% crotonaldehyde; and the wastewater is introduced into an incinerator to be incinerated, thereby implementing the zero discharge of wastewater and the production green technique.
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Paragraph 0011-0013
(2018/02/04)
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- Synthesis of C4 and C8 Chemicals from Ethanol on MgO-Incorporated Faujasite Catalysts with Balanced Confinement Effects and Basicity
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A new type of catalyst has been designed to adjust the basicity and level of molecular confinement of KNaX faujasites by controlled incorporation of Mg through ion exchange and precipitation of extraframework MgO clusters at varying loadings. The catalytic performance of these catalysts was compared in the conversion of C2 and C4 aldehydes to value-added products. The product distribution depends on both the level of acetaldehyde conversion and the fraction of magnesium as extraframework species. These species form rather uniform and highly dispersed nanostructures that resemble nanopetals. Specifically, the sample containing Mg only in the form of exchangeable Mg2+ ions has much lower activity than those in which a significant fraction of Mg exists as extraframework MgO. Both the (C6+C8)/C4 and C8/C6 ratios increase with additional extraframework Mg at high acetaldehyde conversion levels. These differences in product distribution can be attributed to 1) higher basicity density on the samples with extraframework species, and 2) enhanced confinement inside the zeolite cages in the presence of these species. Additionally, the formation of linear or aromatic C8 aldehyde compounds depends on the position on the crotonaldehyde molecule from which abstraction of a proton occurs. In addition, catalysts with different confinement effects result in different C8 products.
- Zhang, Lu,Pham, Tu N.,Faria, Jimmy,Santhanaraj, Daniel,Sooknoi, Tawan,Tan, Qiaohua,Zhao, Zheng,Resasco, Daniel E.
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p. 736 - 748
(2016/05/09)
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- Versatile PdTe/C catalyst for liquid-phase oxidations of 1,3-butadiene
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A commercial Pd catalyst based on Sibunit carbon support was treated with H6TeO6 in a reducing media to obtain a Te coating on the surface of Pd particles. The PdTe/C catalyst prepared in this way showed the ability to control the radical chain oxidation of 1,3-butadiene by promoting the selective formation of 2-butene-1,4-diol, 4-hydroxybut-2-enal and furan in DMA (total selectivity of 61% and yield of 7%). At the same time, the catalyst induced oxidation of 1,3-butadiene by a non-radical heterolytic mechanism involving the formation of two groups of primary products: (1) crotonaldehyde and methyl vinyl ketone and (2) the products of oxygenation at the 1,4-positions. The compounds of the second group including 1,4-dimethoxy-2-butene and maleic acid dimethyl ester were formed on PdTe centers in MeOH. Increasing the Te concentration in the PdTe/C catalyst forced the conversion of 1,3-butadiene toward 1,4-oxygenation and simultaneously decreased the intensity of secondary oxidation, resulting in the selective formation of derivatives of the 1,4-oxygenation - 1,4-dimethoxy-2-butene and allenic alcohol methyl ether (total selectivity of 84% and yield of 48%).
- Kuznetsova,Zudin,Kuznetsova,Zaikovskii,Kajitani,Utsunomiya,Takahashi
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