141-78-6Relevant articles and documents
Activated carbon aerogel supported copper catalysts for the hydrogenation of methyl acetate to ethanol: Effect of KOH activation
Hou, Xiaoxiong,Zhao, Jinxian,Liu, Junjie,Han, Yahong,Pei, Yongli,Ren, Jun
, p. 9430 - 9438 (2019)
Methyl acetate (MA) hydrogenation is crucial for indirect ethanol synthesis through syngas (CO + H2). In our work, activated carbon aerogel supported copper (Cu-ACA) catalysts have been prepared by a conventional impregnation method. The surface area and functional groups of the ACA soared after KOH activation. The highest surface area achieved for the ACA was 2562 m2 g-1. The anchoring effect of micropores and external oxygen-containing groups (OCGs) significantly enhanced the metal-support interaction in catalysts, facilitating the high dispersion of Cu and an enhancement in surface Cu+ species, both of which improved the catalytic activity of catalysts. Cu-ACA-A4 showed the most outstanding catalytic performance, with a MA conversion of 95.2% and an ethanol selectivity of 62.2%, close to the carbon equilibrium selectivity of 66.7%.
ESI-MS Insights into Acceptorless Dehydrogenative Coupling of Alcohols
Vicent, Cristian,Gusev, Dmitry G.
, p. 3301 - 3309 (2016)
Acceptorless dehydrogenative coupling (ADC) reactions catalyzed by a series of Ru and Os complexes were studied by ESI-MS. Important ethoxo, 1-ethoxyethanolate, and hydride intermediates were intercepted in the ADC of ethanol to ethyl acetate. Collision-induced dissociation (CID) experiments were applied as a structure elucidation tool and as a probe of the propensity of the reaction intermediates to evolve acetaldehyde, ethyl acetate, and H2, relevant to the catalytic cycle. The key mechanistic step producing ethyl acetate from the 1-ethoxyethanolate intermediates was documented. Energy-dependent CID experiments demonstrated the importance of a vacant coordination site for efficient production of ethyl acetate. The versatility and potential broad applicability of ESI-MS and its tandem version with CID was further illustrated for the ADC reaction of alcohols with amines, affording amides. A mechanism related to that found for the ester synthesis is plausible, with the key step involving formation of a hemiaminaloxide intermediate.
THERMAL DECOMPOSITION OF PEROXIDE DERIVATIVES OF POLYFLUORINATED β-KETOESTERS
Rakhimov, A. I.,Chapurkin, V. V.,Val'dman, A. I.,Val'dman, D. I.,Saloutin, V. I.,et al.
, (1990)
The thermal flow microcalorimetric method was used to determine the kinetic parameters for the thermal decomposition of peroxide derivatives of polyfluorinated β-ketoesters and the decomposition products were established.
Total oxidation of ethanol over Au/Ce0.5Zr0.5O2 cordierite monolithic catalysts
Topka, Pavel,Klementová, Mariana
, p. 130 - 137 (2016)
The aim of this work was to propose the methods for gold introduction during the preparation of monolithic catalysts and to investigate their effect on catalyst properties. Two types of catalysts were prepared: (i) monoliths washcoated with gold/ceria-zirconia powder, and (ii) gold deposited on the monoliths washcoated with ceria-zirconia powder. An important part of the work was the characterization of the catalysts, in particular Au particle size and redox properties. Catalytic performance and selectivity were evaluated using ethanol gas-phase oxidation. It was shown that the enhanced reducibility of the catalysts with higher Au dispersion leads to improved catalytic performance.
Iodide-induced differential control of metal ion reduction rates: synthesis of terraced palladium-copper nanoparticles with dilute bimetallic surfaces
King, Melissa E.,Personick, Michelle L.
, p. 22179 - 22188 (2018)
Metal nanoparticles possessing a high density of atomic steps and edge sites provide an increased population of undercoordinated surface atoms, which can enhance the catalytic activity of these materials compared to low-index faceted or bulk materials. Simply increasing reactivity, however, can lead to a concurrent increase in undesirable, non-selective side products. The incorporation of a second metal at these reactive stepped features provides an ideal avenue for finely attenuating reactivity to increase selectivity. A major challenge in synthesizing bimetallic nanomaterials with tunable surface features that are desirable for fundamental catalytic studies is a need to bridge differences in precursor reduction potentials and metal lattice parameters in structures containing both a noble metal and a non-noble metal. We report the use of low micromolar concentrations of iodide ions as a means of differentially controlling the relative reduction rates of a noble metal (palladium) and a non-noble metal (copper). The iodide in this system increases the rate of reduction of palladium ions while concurrently slowing the rate of copper ion reduction, thus providing a degree of control that is not achievable using most other reported means of tuning metal ion reduction rate. This differential control of metal ion reduction afforded by iodide ions enables access to nanoparticle growth conditions in which control of palladium nanoparticle growth by copper underpotential deposition becomes possible, leading to the generation of unique terraced bimetallic particles. Because of their bimetallic surface composition, these terraced nanoparticles exhibit increased selectivity to acetaldehyde in gas phase ethanol oxidation.
Kinetics of ethanol dehydrogenation into ethyl acetate
Men'Shchikov,Gol'Dshtein,Semenov
, p. 12 - 17 (2014)
The kinetics of gas-phase dehydrogenation of ethanol into ethyl acetate over a copper-zinc-chromium catalyst has been investigated in a flow reactor at pressures of 10-20 atm and temperatures of 230-290 C. For the process occurring under kinetic control, the rate constants of two reactions and the adsorption constants of five components have been determined using the Langmuir-Hinshelwood model. A kinetic model has been developed for the process. This model provides means to design a reactor for dehydrogenation of ethanol into ethyl acetate in different regimes.
Acetic acid hydrogenation over supported platinum catalysts
Rachmady,Vannice
, p. 322 - 334 (2000)
The kinetic behavior of acetic acid hydrogenation over platinum supported on TiO2, SiO2, η-Al2O3, and Fe2O3 was studied in a differential, fixed-bed reactor at 423-573 K, 100-700 torr hydrogen, and 7-50 torr acetic acid. The interaction of acetic acid with the oxide support played a major role in determining the kinetics of the reaction, and platinum served as a source of mobile, activated hydrogen atoms. During hydrogenation at low conversions, carbon-containing products consisted of about 50% CO and 50% CH4 over Pt/SiO2; 50% ethanol, 30% ethyl acetate, and 20% ethane over Pt/TiO2 reduced at 473 or 773 K; 40% CH4, 10% ethane, 8% ethanol, 4% ethyl acetate, 33% CO, and 5% CO2 over Pt/η-Al2O3; and 80% acetaldehyde and 20% ethanol over Pt/Fe2O3. Pt/TiO2 catalysts were the most active, with activities and turnover frequencies being ≤ 2 orders of magnitude larger than those for the other catalysts. The apparent reaction order with respect to H2 varied between 0.4 and 0.6, while that with respect to acetic acid was 0.2-0.4. This study provided evidence that acetic acid hydrogenation over supported Pt catalysts can be described by a Langmuir-Hinshelwood-type mechanism invoking two sites, one on the metal to activate H2 and one on the oxide to molecularly adsorb acetic acid. The kinetic rate expression derived from this reaction model fitted the data well with thermodynamically consistent parameters.
Acetic acid hydrogenation to ethanol over supported Pt-Sn catalyst: Effect of Bronsted acidity on product selectivity
Rakshit, Pranab Kumar,Voolapalli, Ravi Kumar,Upadhyayula, Sreedevi
, p. 78 - 90 (2018)
Gas phase hydrogenation of acetic acid was investigated over a series of SiO2-Al2O3 supported platinum-tin (Pt-Sn) catalysts. The active metals were impregnated over the support using incipient wetness technique and the resulting catalyst samples were characterized by Transmission electron microscopy, Hydrogen pulse chemisorption, BET surface area analyzer, Powder X-Ray diffraction, NH3-Temperature programmed desorption and H2-Temperature programmed reduction methods. Acetic acid hydrogenation reaction was carried out in an isothermal fixed bed catalyst testing unit. The results revealed that bimetallic Pt-Sn catalyst forms Pt-Sn alloy upon reduction which favors acetic acid hydrogenation to ethanol compared to competing side product CH4. The magnitude of Pt-Sn alloy formed per unit mass of catalyst depends upon the Pt/ Sn molar ratio in the calcined catalyst sample. 3 wt% Pt- 3 wt% Sn on SiO2-Al2O3 was found to be the optimum catalyst loading, resulting in 81% acetic acid conversion with 95% ethanol selectivity at 2 MPa and 270 °C. Further increase in ethanol selectivity would require prevention of esterification of acetic acid with ethanol, which leads to formation of ethyl acetate as by-product. The effect of catalyst acidity on acetic acid conversion and ethanol selectivity was studied and it was observed that proton donating capability of the support leads to the formation of ethyl acetate as by-product which, in turn, reduces ethanol selectivity. The ethanol synthesis reaction and esterification reaction over Bronsted acid sites takes place in series. The rate of esterification reaction was found to be highly dependent on the Bronsted acid density of the catalysts. Other catalyst parameters have little role on ethyl acetate yield.
Role of the Cu-ZrO2 Interfacial Sites for Conversion of Ethanol to Ethyl Acetate and Synthesis of Methanol from CO2 and H2
Ro, Insoo,Liu, Yifei,Ball, Madelyn R.,Jackson, David H. K.,Chada, Joseph Paul,Sener, Canan,Kuech, Thomas F.,Madon, Rostam J.,Huber, George W.,Dumesic, James A.
, p. 7040 - 7050 (2016)
Well-defined Cu catalysts containing different amounts of zirconia were synthesized by controlled surface reactions (CSRs) and atomic layer deposition methods and studied for the selective conversion of ethanol to ethyl acetate and for methanol synthesis. Selective deposition of ZrO2 on undercoordinated Cu sites or near Cu nanoparticles via the CSR method was evidenced by UV-vis absorption spectroscopy, scanning transmission electron microscopy, and inductively coupled plasma absorption emission spectroscopy. The concentrations of Cu and Cu-ZrO2 interfacial sites were quantified using a combination of subambient CO Fourier transform infrared spectroscopy and reactive N2O chemisorption measurements. The oxidation states of the Cu and ZrO2 species for these catalysts were determined using X-ray absorption near edge structure measurements, showing that these species were present primarily as Cu0 and Zr4+, respectively. It was found that the formation of Cu-ZrO2 interfacial sites increased the turnover frequency by an order of magnitude in both the conversion of ethanol to ethyl acetate and the synthesis of methanol from CO2 and H2.
A green approach to ethyl acetate: Quantitative conversion of ethanol through direct dehydrogenation in a Pd-Ag membrane reactor
Zeng, Gaofeng,Chen, Tao,He, Lipeng,Pinnau, Ingo,Lai, Zhiping,Huang, Kuo-Wei
, p. 15940 - 15943 (2012)
Pincers do the trick: The conversion of ethanol to ethyl acetate and hydrogen was achieved using a pincer-Ru catalyst in a Pd-Ag membrane reactor. Near quantitative conversions and yields could be achieved without the need for acid or base promoters or hydrogen acceptors (see scheme).
