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71-36-3Relevant articles and documents
Manganese containing copper aluminate catalysts: Genesis of structures and active sites for hydrogenation of aldehydes
D?rfelt, Christoph,Hammerton, Michelle,Martin, David,Wellmann, Alexander,Aletsee, Clara C.,Tromp, Moniek,K?hler, Klaus
, p. 80 - 90 (2021)
Copper aluminate spinel (CuO.CuAl2O4) is the favoured Cr-free substitute for the copper chromite catalyst (CuO.CuCr2O4) in the industrial hydrogenation of aldehydes. New insights in the catalytic mechanism were obtained by systematically studying the structure and activity of these catalysts including effects of manganese as a catalyst component. The hydrogenation of butyraldehyde to butanol was studied as a model reaction and the active structure was characterised using X-ray diffraction, temperature programmed reduction, N2O chemisorption, EXAFS and XANES, including in-situ investigations. The active catalyst is a reduced spinel lattice that is stabilised by protons, with copper metal nanoparticles grown upon its surface. Incorporation of Mn into the spinel lattice has a profound effect on the spinel structure. Mn stabilises the spinel towards reduction of CuII to Cu0 by occupation of tetrahedral sites with Mn cations, but also causes decreased catalytic activity. Structural data, combined with the effect on catalysis, indicate a predominantly interface-based reaction mechanism, involving both the spinel and copper nanoparticle surface in protonation and reduction of the aldehyde. The electron reservoir of the metallic copper particles is regenerated by the dissociative adsorption and oxidation of H2 on the metal surface. The generated protons are stored in the spinel phase, acting as proton reservoir. Cu(I) species located within the spinel and identified by XANES are probably not involved in the catalytic cycle.
Step mechanism of 1-butanol formation in the course of liquid-phase catalytic hydrogenation of 2-butyne-1,4-diol
El'chaninov,Pyatnitsyna,El'chaninov
, p. 585 - 589 (2015)
Exhaustive hydrogenation of 2-butyne-1,4-diol to 1,4-butanediol on suspended palladium and Raney nickel catalysts under atmospheric pressure at 40 C was studied with the aim to determine the mechanism of 1-butanol formation. The previously unknown pathway of 1-butanol synthesis is realized under these conditions. The content of 1-butanol precursors in hydrogenation catalyzates was estimated by gas-liquid chromatography. The graphic dependence of the content of the intermediates and 1-butanol on time was found. The possibility of increasing the hydrogenation selectivity on Raney Ni catalysts with respect to the target product was revealed.
Transhalogenation Catalysed by Haloalkane Dehalogenases Engineered to Stop Natural Pathway at Intermediate
Beier, Andy,Damborsky, Jiri,Prokop, Zbynek
, p. 2438 - 2442 (2019)
Haloalkane dehalogenases (HLDs) are α/β-hydrolases that convert halogenated compounds to their corresponding alcohols. The overall kinetic mechanism proceeds via four steps: (i) binding of halogenated substrate, (ii) bimolecular nucleophilic substitution (SN2) leading to the cleavage of a carbon-halogen bond and the formation of an alkyl-enzyme intermediate, (iii) nucleophilic addition of a water molecule resulting in the hydrolysis of the intermediate to the corresponding alcohol and (iv) release of the reaction products – an alcohol, a halide ion and a proton. Although, the overall reaction has been reported as irreversible, several kinetic evidences from previous studies suggest the reversibility of the first SN2 chemical step. To study this phenomenon, we have engineered HLDs to stop the catalytic cycle at the stage of the alkyl-enzyme intermediate. The ability of the intermediate to exchange halides was confirmed by a stopped-flow fluorescence binding analysis. Finally, the transhalogenation reaction was confirmed with several HLDs and 2,3-dichloropropene in the presence of a high concentration of iodide. The formation of the transhalogenation product 3-iodo-2-chloropropene catalysed by five mutant HLDs was identified by gas chromatography coupled with mass spectrometry. Hereby we demonstrated the reversibility of the cleavage of the carbon-halogen bond by HLDs resulting in a transhalogenation. After optimization, the transhalogenation reaction can possibly find its use in biocatalytic applications. Enabling this reaction by strategically engineering the enzyme to stop at an intermediate in the catalytic cycle that is synthetically more useful than the product of the natural pathway is a novel concept. (Figure presented.).
Hydrogen transfer reactions relevant to Guerbet coupling of alcohols over hydroxyapatite and magnesium oxide catalysts
Young, Zachary D.,Davis, Robert J.
, p. 1722 - 1729 (2018)
Hydrogenation and dehydrogenation reactions were performed over hydroxyapatite (Ca10(PO4)6(OH)2, HAP) and magnesia (MgO) to explore their role in the reaction network for the Guerbet coupling of ethanol to butanol. In particular, the dehydrogenation of benzyl alcohol at 633 K and the hydrogenation of ethene and acetone at 473 K using both H2 and ethanol as a hydrogen source were studied. The H2-D2 exchange reaction at room temperature and the Guerbet coupling of ethanol at 613-673 K in the presence of D2 were also performed. Although there was no consequence of adding D2 to the Guerbet coupling of ethanol in terms of rate or selectivity, incorporation of deuterium into product butanol was only observed over MgO. This was attributed to the rapid exchange of H2-D2 that can occur over MgO but not over HAP. Hydrogenation of acetone occurred with ethanol as a sacrificial hydrogen donor via an MPV-like reaction whereas hydrogenation with H2 was not observed. Hydrogenation of ethene with H2 or ethanol was not observed above background. Comparing the rate of benzyl alcohol dehydrogenation to the rate of ethanol coupling over HAP and MgO suggests that the MPV-like hydrogen transfer reaction over HAP is mostly responsible for generating intermediate acetaldehyde during the Guerbet reaction instead of direct dehydrogenation.
Isotopic transient analysis of the ethanol coupling reaction over magnesia
Birky, Theodore W.,Kozlowski, Joseph T.,Davis, Robert J.
, p. 130 - 137 (2013)
Isotopic transient analysis of ethanol coupling to butanol over MgO in a fixed-bed reactor at 673 K revealed a surface coverage of adsorbed ethanol equivalent to about 50% of the exposed MgO atomic pairs. DRIFTS of ethanol reaction at 673 K confirmed that the surface was populated primarily with adsorbed ethoxide and hydroxide, presumably from the dissociative adsorption of ethanol. The coverage of reactive intermediates leading to butanol was an order of magnitude lower than that of adsorbed ethanol, and about half the surface base sites counted by adsorption of CO2. The intrinsic turnover frequency for the coupling reaction at 673 K determined by isotopic transient analysis was 0.04 s-1, which is independent of any assumptions about the nature of the active sites. Although the ethanol coupling reaction appears to involve aldol condensation of an aldehyde intermediate, the high coverage of ethanol under steady-state conditions apparently inhibits unproductive CC coupling reactions that deactivate the catalyst at high temperature.
A green process for the production of butanol from butyraldehyde using alcohol dehydrogenase: Process details
Jadhav, Swati B.,Harde, Shirish,Bankar, Sandip B.,Granstroem, Tom,Ojamo, Heikki,Singhal, Rekha S.,Survase, Shrikant A.
, p. 14597 - 14602 (2014)
Depletion of energy sources has drawn attention towards production of bio-butanol by fermentation. However, the process is constrained by product inhibition which results in low product yield. Hence, a new strategy wherein butanol was produced from butyraldehyde using alcohol dehydrogenase and NADH as a cofactor was developed. Butyraldehyde can be synthesized chemically or through fermentation. The problem of cofactor regeneration during the reaction for butanol production was solved using substrate coupled and enzyme coupled reactions. The conventional reaction produced 35% of butanol without regeneration of cofactor using 300 μM NADH. The process of substrate coupled reaction was optimized to get maximum conversion. NADH (30 μM) and 100 μg per ml of alcohol dehydrogenase (320 U mg-1) could convert 17.39 mM of butyraldehyde to butanol using ethanol (ratio of butyraldehye to ethanol 1:4) giving a maximum conversion of 75%. The enzyme coupled reaction under the same conditions showed only 24% conversion of butyraldehyde to butanol using the glutamate dehydrogenase-l-glutamate enzyme system for the regeneration of cofactor. Hence, substrate coupled reaction is suggested as a better method over the enzyme coupled reaction for the cost effective production of butanol. This journal is the Partner Organisations 2014.
Tuning the selectivities of Mg-Al mixed oxides for ethanol upgrading reactions through the presence of transition metals
Quesada, Jorge,Faba, Laura,Díaz, Eva,Ordó?ez, Salvador
, p. 167 - 174 (2018)
The effect of the presence of reduced Co and Ni (chosen as representative metals because of their good activity for dehydrogenation reactions) on the catalytic performance of basic mixed oxide (Mg-Al) for ethanol condensation is studied in this work. This effect has been studied both in absence and in presence of hydrogen, and considering the different steps of this complex reaction. Globally, best results were obtained with Co/MgAl, under reducing atmosphere, at mild temperature (below 600 K). At these conditons, 1-butanol production rates are up to eight times higher than the obtained with Mg-Al under inert atmosphere. Co has a marked activity in the dehydrogenation step, that prevails over its less relevant activity in aldolization and hydrogenation reactions. This result indicates the relevant role of this first reaction step. DRIFT spectroscopy analyses were carried out to support the experimental results and to identify the role of hydrogen and metals on the oligomerization and permanent adsorption processes, which can produce the deactivation of the catalyst.
Kinetics of complexation between cyclodextrin and alcohol by ultrasonic relaxation method: β-cyclodextrin solutions with 1-butanol and 2-methyl-2-propanol
Nishikawa, Sadakatsu
, p. 1003 - 1007 (1997)
The ultrasonic absorption coefficients over frequency range from 1.0 to 220 MHz were measured in aqueous β-cyclodextrin solutions with 1-butanol and 2-methyl-2-propanol at 25 °C. A clear single relaxational absorption with a relaxation frequency from 5 to 20 MHz was observed in a solution with 1-butanol, while the relaxational absorption was found in a lower frequency range in a solution with 2-methyl-2-propanol. The cause of the relaxation was attributed to a perturbation of a chemical equilibrium associated with complexation between β-cyclodextrin (host) and alcohol (guest). The rate and equilibrium constants for the complexation were determined from the concentration dependence of the relaxation frequency for the solution with 1-butanol. The standard volume change of the reaction was also obtained from the maximum absorption per wavelength. These results were compared with those for complexation between β-cyclodextrin and 1-propanol, and were considered in relation to the alcohol molecular structure. It was found that the rate of complex formation is almost independent of the guest molecule, and, therefore, the equilibrium constant for the complexation is controlled by the rate of departure of the guest molecule from the host. From this fact, the rate parameters for a solution with 2-methyl-2-propanol were estimated, and the calculated ultrasonic relaxation parameter was compared with the experimental data.
Synthesis and Characterization of Ru-Loaded Anodized Aluminum Oxide for Hydrogenation Catalysis
Vandekerkhove, Annelies,Negahdar, Leila,Glas, Daan,Stassen, Ivo,Matveev, Serguei,Meeldijk, Johannes D.,Meirer, Florian,De Vos, Dirk E.,Weckhuysen, Bert M.
, (2019)
Anodized aluminum oxides (AAOs) are synthesized and used as catalyst support in combination with Ru as metal in hydrogenation catalysis. SEM and TEM analysis of the as-synthesized AAOs reveal uniform, ordered nanotubes with pore diameters of 18 nm, which are further characterized with Kr physisorption, XRD and FTIR spectroscopy. After impregnation of the AAOs with Ru, the presence of Ru nanoparticles inside the tubular pores is evidenced clearly for the first time via HAADF-STEM-EDX. The Ru?AAOs have been tested for catalytic activity, which showed high conversion and selectivity for the hydrogenation of toluene and butanal.
Multiproduct steady-state isotopic transient kinetic analysis of the ethanol coupling reaction over hydroxyapatite and magnesia
Hanspal, Sabra,Young, Zachary D.,Shou, Heng,Davis, Robert J.
, p. 1737 - 1746 (2015)
The Guerbet coupling of ethanol into butanol was investigated using multiproduct steady-state isotopic transient kinetic analysis (SSITKA) in a comparative study between stoichiometric hydroxyapatite (HAP) and magnesia (MgO) catalysts at 613 and 653 K, respectively. The steady-state catalytic reactions were conducted in a gas-phase, fixed-bed, differential reactor at 1.3 atm total system pressure. Multiproduct SSITKA results showed that the mean surface residence time of reactive intermediates leading to acetaldehyde was significantly shorter than that of intermediates leading to butanol on both HAP and MgO. This finding may suggest that the dehydrogenation of ethanol to acetaldehyde is fast on these surfaces compared with C-C bond formation. If adsorbed acetaldehyde is a key reaction intermediate in the Guerbet coupling of ethanol into butanol, then SSITKA revealed that the majority of adsorbed acetaldehyde produced on the surface of MgO desorbs into the gas-phase, whereas the majority of adsorbed acetaldehyde on HAP likely undergoes sequential aldol-type reactions required for butanol formation. Adsorption microcalorimetry of triethylamine and CO2 showed a significantly higher number of acid and base sites on the surface of HAP compared with those on MgO. Diffuse reflectance infrared Fourier transform spectroscopy of adsorbed ethanol followed by stepwise temperature-programmed desorption revealed that ethoxide is more weakly bound to the HAP surface compared with MgO. A high surface density of acid-base site pairs along with a weak binding affinity for ethanol on HAP may provide a possible explanation for the increased activity and high butanol selectivity observed with HAP compared with MgO catalysts in the ethanol coupling reaction.
