Hydrogenation Of Dimethyl Oxalate Research Articles

Effect of Copper Nanoparticles Dispersion on Catalytic Performance of Cu/SiO2 Catalyst for Hydrogenation of Dimethyl Oxalate to Ethylene Glycol

Cu/SiO2 catalysts, for the synthesis of ethylene glycol (EG) from hydrogenation of dimethyl oxalate (DMO), were prepared by ammonia‐evaporation and sol‐gel methods, respectively. The structure, size of copper nanoparticles, copper dispersion, and the surface chemical states were investigated by X‐ray diffraction (XRD), transmission electron microscopy (TEM), temperature‐programmed reduction (TPR), and X‐ray photoelectron spectroscopy (XPS) and N2 adsorption. It is found the structures and catalytic performances of the catalysts were highly affected by the preparation method. The catalyst prepared by sol‐gel method had smaller average size of copper nanoparticles (about 3‐4 nm), better copper dispersion, higher Cu+/C0 ratio and larger BET surface area, and higher DMO conversion and EG selectivity under the optimized reaction conditions.

Vapor-phase hydrogenation of dimethyl oxalate over a CNTs–Cu–SiO2 hybrid catalyst with enhanced activity and stability

Hybrids containing carbon nanotubes (CNTs) have attracted considerable attention in heterogeneous catalysis. In this study, a CNTs–Cu–SiO2 hybrid fabricated by urea-assisted gelation is disclosed to display excellent activity and outstanding long-term stability in the vapor-phase hydrogenation of dimethyl oxalate (DMO). Appropriate hybridization of CNTs with Cu–SiO2 results in enhanced Cu dispersion, which is suggested to be one of the key factors in determining the catalytic performance of copper catalysts. Furthermore, the growth of Cu nanoparticles (NPs) during the catalyst activation, DMO hydrogenation and severe aging tests is distinctively inhibited by incorporating CNTs into Cu–SiO2, leading to remarkably enhanced catalytic stability. The adsorption and activation of hydrogen on this particular hybrid catalyst are also influenced by the CNTs introduction.

Solvent feedstock effect: the insights into the deactivation mechanism of Cu/SiO2 catalysts for hydrogenation of dimethyl oxalate to ethylene glycol

The variation of the supports on the Cu/SiO2 catalyst plays an important role in the catalytic performance for hydrogenation of dimethyl oxalate. The loss of silica in the form of tetramethoxysilane from the support under the reaction conditions is responsible for the deactivation of the Cu/SiO2 catalyst.

Cover Picture: Remarkable Improvement of Catalytic Performance for a New Cobalt‐Decorated Cu/HMS Catalyst in the Hydrogenation of Dimethyloxalate (ChemCatChem 1/2013)

Cover Picture: Remarkable Improvement of Catalytic Performance for a New Cobalt‐Decorated Cu/HMS Catalyst in the Hydrogenation of Dimethyloxalate (ChemCatChem 1/2013)

Chemoselective synthesis of ethanol via hydrogenation of dimethyl oxalate on Cu/SiO2: Enhanced stability with boron dopant

The long-term stability and activity of catalysts are vital for vapor-phase selective hydrogenation of dimethyl oxalate to synthesize ethanol. Boron has been widely employed as a modifier for transition-metal catalysts mainly to, improve selectivity and stability. We introduced boron species by impregnation into silica-supported copper catalysts prepared by an ammonia evaporation hydrothermal method and investigated their catalytic activity and thermal stability for hydrogenation of dimethyl oxalate. The effect on activity mainly depends on the amount of boron and an optimal Cu/B molar ratio of 3 was obtained. The characterization of the catalysts shows that boron-modified Cu/SiO2 facilitates the dispersion of copper species, enhances the metal–support interaction, and suppresses the growth of copper particles during dimethyl oxalate hydrogenation.

In situ IR study of dimethyl oxalate hydrogenation to ethylene glycol over Cu/SiO2 catalyst

The mechanism of dimethyl oxalate hydrogenation to ethylene glycol over Cu/SiO2 catalyst was investigated by in situ Fourier transform infrared (FTIR) spectroscopy. It was found that dimethyl oxalate and methyl glycolate proceeded via dissociative adsorption on Cu/SiO2 catalyst, and four main intermediates, CH3OC(O)(O)C-M (1655 cm−1), M-C(O)(O)C-M (1618 cm−1), HOCH2(O)C-M (1682 cm−1) and CH3O-M (2924-2926 cm−1), were identified during the reaction. It was concluded that dimethyl oxalate hydrogenation to ethylene glycol mainly proceeded along the route: dimethyl oxalate → CH3OC(O)(O)C-M → methyl glycolate → HOCH2(O)C-M → ethylene glycol. Finally a schematic reaction network was proposed.

Remarkable Improvement of Catalytic Performance for a New Cobalt‐Decorated Cu/HMS Catalyst in the Hydrogenation of Dimethyloxalate

Remarkable Improvement of Catalytic Performance for a New Cobalt‐Decorated Cu/HMS Catalyst in the Hydrogenation of Dimethyloxalate

Efficient low-temperature selective hydrogenation of esters on bimetallic Au–Ag/SBA-15 catalyst

Gold (Au)–silver (Ag) bimetallic catalyst supported on ordered mesoporous silica SBA-15 exhibits unprecedentedly high activity and superior stability for the selective hydrogenation of dimethyl oxalate to methyl glycolate at a low temperature of 418K. By contrast, monometallic Au/SBA-15 and Ag/SBA-15 catalysts are almost inactive under identical conditions. A combined tuning of particle dispersion and its surface electronic structure is shown as a consequence of the changes in the size and valence band structure of Au and Ag, which leads to significantly enhanced synergy. Considerably reduced apparent activation energies indicate that special active sites with the ability to activate substrate molecules more efficiently are generated in Au–Ag alloy nanoparticles. The Au–Ag bimetallic catalyst also displays excellent activity for the selective hydrogenation of some other unsaturated or saturated esters and acetic acid.

Hydrogenation of Dimethyl Oxalate Using Extruded Cu/SiO2 Catalysts: Mechanical Strength and Catalytic Performance

In this work, the extrusion process of Cu/SiO2 catalysts prepared by the ammonia-evaporation (AE) method has been investigated and optimized in order to obtain materials with convenient catalytic and mechanical properties for their application in the gas-phase hydrogenation reaction of dimethyl oxalate (DMO) to ethylene glycol (EG). Thereby, a variety of Cu/SiO2 extrudates were prepared with different Cu loading. It has been observed that a special microstructure including defects, flaws, and discontinuities plays a significant role on the mechanical strength. Larger CuO grains may act as fracture origins, which negatively affect the mechanical strength. The 20Cu/SiO2 extrudate with high Cu dispersion and high porosity is optimized for hydrogenation of DMO to EG, achieving a 98% conversion of DMO and 85% selectivity of EG under the liquid hourly space velocity (LHSV) of 1.0 h–1.

Effect of copper loading on texture, structure and catalytic performance of Cu/SiO2 catalyst for hydrogenation of dimethyl oxalate to ethylene glycol

Cu/SiO2 catalysts prepared by a convenient and efficient method using the urea hydrolysis deposition-precipitation (UHDP) technique have been proposed focusing on the effect of copper loading. The texture, structure and composition are systematically characterized by ICP, FT-IR, N2-physisorption, N2O chemisorption, TPR, XRD and XPS. The formation of copper phyllosilicate is observed in Cu/SiO2 catalyst by adopting UHDP method, and the amount of copper phyllosilicate is related to copper loading. It is found the structure properties and catalytic performance is profoundly affected by the amount of copper phyllosilicate. The excellent catalytic activity is attributed to the synergetic effect between Cu0 and Cu+. DMO conversion and EG selectivity are determined by the amount of Cu0 and Cu+, respectively. The proper copper loading (30 wt%) provides with the highest ratio of Cu+/Cu0, giving rise to the highest EG yield of 95% under the reaction conditions of p = 2.0 MPa, T = 473 K, H2/DMO = 80 and LHSV = 1.0 h−1.

Cu/SiO2 hybrid catalysts containing HZSM-5 with enhanced activity and stability for selective hydrogenation of dimethyl oxalate to ethylene glycol

A novel type of hybrid catalysts composed of Cu/SiO2 and H-form ZSM-5 (HZSM-5) zeolite, prepared using urea-assisted gelation method, displayed excellent catalytic activity and stability for the selective hydrogenation of dimethyl oxalate (DMO) to ethylene glycol (EG). The content and SiO2/Al2O3 ratio of HZSM-5 significantly influenced the performance of hybrid catalysts. An unprecedentedly high EG space time yield of 1.50gg-cat−1h−1, with DMO conversion of 99.5% and EG selectivity of 94.8%, were obtained on a hybrid catalyst containing 3wt% of HZSM-5 with SiO2/Al2O3=38. The characterizations of N2 physisorption and N2O chemisorptions revealed that both specific surface area and copper dispersion were promoted by introducing HZSM-5 zeolite into the Cu/SiO2 catalyst. Moreover, X-ray Auger electron spectroscopy and in situ Fourier transform infrared spectroscopy of chemisorbed CO demonstrated that the surface Cu+ site concentration of the catalysts containing HZSM-5 was higher than those without HZSM-5. The results indicated that the introduction of HZSM-5 zeolite changed the crystallization behaviors of cupric phyllosilicate precursor, essentially improving copper dispersion and enhancing copper–silica interaction. Furthermore, the specific zeolitic cages and negatively charged framework of HZSM-5 zeolite incorporated into Cu/SiO2 entities might also be beneficial for accommodation and stabilization of highly dispersed cuprous species, which act as efficient active sites for the activation of ester groups.

Highly-Dispersed Copper-Based Catalysts from Cu–Zn–Al Layered Double Hydroxide Precursor for Gas-Phase Hydrogenation of Dimethyl Oxalate to Ethylene Glycol

The highly-dispersed copper-based catalysts for the gas-phase hydrogenation of dimethyl oxalate to ethylene glycol (EG) were prepared from a Cu–Zn–Al layered double hydroxide (LDH) precursor. Powder X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), N2 adsorption–desorption, H2 temperature programmed reduction (H2-TPR) and H2–N2O titration indicated that the composition, texture, and structure of resulting copper-based catalysts were profoundly affected by the calcination temperature of LDH precursor. Moreover, the as-synthesized catalyst calcined at 600 °C was found to exhibit a superior catalytic hydrogenation performance with an EG yield of 94.7 % to the other catalysts calcined at 500 and 700 °C, which should be mainly attributed to the presence of the highly-dispersed active metallic copper species over metal oxide matrix.

Thermodynamic Analysis of Indirect Ethanol Synthesis from Syngas

The dependence of chemical equilibrium constant on the reaction temperature and pressure and the feed molar ratio were theoretically calculated for indirect ethanol synthesis from syngas through the coupling of CO with methyl nitrite (MN) to dimethyl oxalate (DMO) and the hydrogenation of DMO to ethanol. It shows that the coupling process and the hydrogenation of DMO to ethanol are highly favorable at all temperatures and pressures, especially at low temperature. The hydrogenation of DMO to ethylene glycol (EG) and the further reaction of ethanol with H2 to high alcohol are thermodynamically favorable at low temperatures, below 630 and 450 K, respectively. Additionally, high reaction pressure is facilitated to EG and high alcohol formation. Accordingly, moderate reaction temperature (up 538 K) and low reaction pressure (below 1 MPa) are beneficial to ethanol production.

Effect of feedstock solvent on the stability of Cu/SiO2catalyst for vapor-phase hydrogenation of dimethyl oxalate to ethylene glycol

The lifetime (200 h) of a Cu/SiO(2) catalyst under DMO-ethanol feedstock is 20 times longer than that (10 h) of the catalyst under DMO-methanol feedstock without any modification of the catalyst. The stabilization effect of ethanol on the active centers can effectively slow down the agglomeration of copper particles during the hydrogenation process.

Remarkable enhancement of Cu catalyst activity in hydrogenation of dimethyl oxalate to ethylene glycol using gold

The performance of an SBA-15-supported Cu catalyst for hydrogenation of dimethyl oxalate to ethylene glycol is markedly promoted with Au. A key genesis of the high activity of the catalyst is ascribed to the formation of Cu–Au alloy nanoparticles which stabilize the active species and retard their agglomeration during the hydrogenation process.

Hydrogenation of dimethyl oxalate to ethylene glycol on a Cu/SiO2/cordierite monolithic catalyst: Enhanced internal mass transfer and stability

AbstractThe design and application of a Cu/SiO2‐based monolithic catalyst for hydrogenation of dimethyl oxalate (DMO) to ethylene glycol (EG) is presented. The catalyst was dip‐coated on cordierite with highly dispersed Cu/SiO2 slurry prepared by ammonia evaporation method. This structure guarantees high dispersion of copper species within the mesopores of silica matrix in the form of copper phyllosilicate. The catalyst is low cost, stable, and exhibits high activity in the reaction of hydrogenation of DMO, achieving a 100% conversion of DMO and more than 95% selectivity to EG. Notably, STYEG over the monolith is significantly enhanced compared to the packed bed Cu/SiO2 catalysts in both forms of pellet and cylinder. It is primarily due to the relatively short diffusive pathway of the thin wash‐coat layer and high efficiency of the active phase derived from the monolithic catalyst. Theoretical results indicated that the internal mass transfer is dominated on the catalysts of pellet and cylinders. Moreover, the monolithic catalyst possessed excellent thermal stability compared to the pellet catalyst, which is attributed to the regular channel structure, uniform distribution of flow. © 2011 American Institute of Chemical Engineers AIChE J, 2012

Ag/MCM-41 as a highly efficient mesostructured catalyst for the chemoselective synthesis of methyl glycolate and ethylene glycol

A novel highly efficient heterogeneous Ag/MCM-41 catalyst was prepared by ammonia-evaporation deposition-precipitation method and displayed outstanding methyl glycolate (MG) selectivity (up to 99%) and ethylene glycol (EG) selectivity (up to 99%) in the chemoselective gas-phase hydrogenation of dimethyloxalate (DMO). Systematic characterizations have been carried out to elucidate the bulk and surface physicochemical properties of the catalysts. It is shown that the silver loading, the calcination temperature, the surface hydroxyl group amount and the pretreatment atmosphere all have great influences on the catalytic performance of DMO hydrogenation reaction. The best catalytic performance could be achieved over the Ag/MCM-41 catalyst with 10wt.% silver loading after calcined at 673K. Much higher catalytic activity could be obtained via the MCM-41 supported silver catalyst with large amount of surface hydroxyl groups. The argon pretreated Ag/MCM-41 catalyst with less subsurface oxygen species exhibited much higher DMO conversion and MG selectivity compared with H2 and air pretreated samples. Under the optimized reaction conditions, 99% yield of MG and EG could be obtained over the optimized Ag/MCM-41 catalyst.

Ruthenium-catalysed hydrogenation of esters using tripodal phosphine ligands

The synthesis of a new tripodal phosphine ligand, N(CH 2PEt 2) 3, N-TriPhos Et is reported, and the use of tripodal ligands of this type, N(CH 2PR 2) 3 (R = Ph, Et), in conjunction with ruthenium for the catalysed hydrogenation of dimethyl oxalate (DMO) is reported and contrasted with catalysis using the MeC(CH 2PPh 2) 3 (TriPhos Ph) ligand. A different order of reaction with respect to the DMO substrate is found, and the rate is slower. A study of the kinetics and mechanism of the hydrogenation of DMO with Ru(acac) 3/TriPhos Ph is described, along with the effect of different additives to the system. The performance of Ru(acac) 3/TriPhos Ph/Zn system with unactivated ester substrates is probed and found to proceed significantly slower. Finally, based upon experimental observations, a mechanism is proposed for ester hydrogenation using ruthenium catalysts with tripodal phosphine ligands.

Highly active and selective Cu/SiO2 catalysts prepared by the urea hydrolysis method in dimethyl oxalate hydrogenation

Abstract Cu/SiO2 catalysts have been successfully prepared via urea hydrolysis method. The catalysts have been systematically characterized by X-ray diffraction, high-resolution transmission electron microscopy, N2-physisorption and H2 temperature-programmed reduction. The results demonstrated the presence of copper nanoparticles and their high dispersion on the SiO2 support. Catalysts with different copper loadings were prepared, and their performances in the hydrogenation of dimethyl oxalate to ethylene glycol were studied. A 100% conversion of dimethyl oxalate and maximum 98% selectivity of ethylene glycol were reached with 15.6 wt.% copper loading at 200 °C and 2 MPa. Furthermore, under the same reaction conditions, the catalyst can maintain the selectivity of 90% when the reduction temperature reduced from 350 °C to 200 °C. The high activity and selectivity over the catalyst may be ascribed to the homogenously distribution of copper nanoparticles on the large surface.

The influence of B-doping on the catalytic performance of Cu/HMS catalyst for the hydrogenation of dimethyloxalate

The influence of boron introduction on the performance of 20 wt.% Cu/HMS catalysts for the catalytic hydrogenation of dimethyloxalate was systematically investigated. It is shown that the boron loading, boron source and the preparation method all have great effect on the catalytic behaviors of the catalyst. Characterization methods including N 2-physisorption, X-ray diffraction, H 2-temperature-programmed reduction, N 2O titration, NH 3 temperature-programmed desorption, and X-ray photoelectron spectroscopy were carried out to elucidate the structure evolution of the catalyst with the introduction of boron. Experimental results showed that the B 2O 3 modified catalyst prepared via the ammonia-evaporation-induced synthesis method exhibited the highest conversion and ethylene glycol selectivity because of the higher metallic copper surface area and copper dispersion. The optimum Cu/B mole ratio, which strongly affects the surface composition of the catalyst, was found to be 2/1. 100% DMO conversion and 98% EG selectivity could be obtained over the CuB/HMS(2/1) catalyst under 2.5 h −1 liquid hour space velocity, which is almost four times higher than that of the one without boron introduction.