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123-73-9Relevant articles and documents
Redox mechanism for selective oxidation of ethanol over monolayer V2O5/TiO2 catalysts
Kaichev, Vasily V.,Chesalov, Yuriy A.,Saraev, Andrey A.,Klyushin, Alexander Yu.,Knop-Gericke, Axel,Andrushkevich, Tamara V.,Bukhtiyarov, Valerii I.
, p. 82 - 93 (2016)
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.
Study of acetaldehyde condensation chemistry over magnesia and zirconia supported on silica
Ordomsky,Sushkevich,Ivanova
, p. 85 - 93 (2010)
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.
Magnetic core-shell Fe3O4?Cu2O and Fe3O4?Cu2O-Cu materials as catalysts for aerobic oxidation of benzylic alcohols assisted by TEMPO and: N -methylimidazole
Liu, Xiaoming,Lu, Chunxin,Senthilkumar, Samuthirarajan,Shen, Zhongquan,Xu, Binyu,Zhong, Wei
, p. 26142 - 26150 (2020)
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.
Supported bimetallic AuPd clusters using activated Au25 clusters
Lee, Kee Eun,Shivhare, Atal,Hu, Yongfeng,Scott, Robert W.J.
, p. 259 - 265 (2017)
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.
Copper(II)-catalysed aerobic oxidation of primary alcohols to aldehydes
Gamez, Patrick,Arends, Isabel W. C. E.,Reedijk, Jan,Sheldon, Roger A.
, p. 2414 - 2415 (2003)
[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.
Selective oxidation of crotyl alcohol by Au: X Pd bimetallic pseudo-single-atom catalysts
Chivers, Brandon A.,Scott, Robert W. J.
, p. 7706 - 7718 (2020)
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.
Kinetics and Mechanism of Electron Transfer Reactions: Oxidation of Crotyl Alcohol by Peroxomonosulfate in Aqueous Acidic Medium
Sharma, Priyamvada,Sailani, Riya,Meena, Anita,Khandelwal
, p. 335 - 342 (2018)
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.
Aldol Condensation of Acetaldehyde over Titania, Hydroxyapatite, and Magnesia
Young, Zachary D.,Hanspal, Sabra,Davis, Robert J.
, p. 3193 - 3202 (2016)
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.
Effect of the ZrO2 phase on the structure and behavior of supported Cu catalysts for ethanol conversion
Sato,Volanti,Meira,Damyanova,Longo,Bueno
, p. 1 - 17 (2013)
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.
Vinylation of phenol by acetaldehyde: A new reaction for the synthesis of o-vinylphenol
Parfenov, Mikhail V.,Pirutko, Larisa V.,Soshnikov, Igor E.,Starokon, Eugeny V.,Kharitonov, Alexander S.,Panov, Gennady I.
, p. 59 - 62 (2016)
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.