Hydrogenation Of Dimethyl Oxalate Research Articles

β-Cyclodextrin promoted the formation of copper phyllosilicate on Cu-SiO2 microspheres catalysts to enhance the low-temperature hydrogenation of dimethyl oxalate

The formation of copper phyllosilicate is critical to the hydrogenation performance of Cu-SiO2 catalysts. A series of Cu-SiO2 microsphere catalysts modified with β-cyclodextrin (β-CD) prepared by the hydrothermal method were fabricated in this work. The results showed that Cu–β-CD complexes were favored to form during the hydrothermal process, which could promote the synthesis of copper phyllosilicate. Meanwhile, the introduction of an appropriate amount of β-CD also promoted the uniform dispersion of CuO species and reduced the size of copper nanoparticles. This could increase the ratio of Cu+/Cu0 after reduction. Thereby the synergistic effect between Cu0 and Cu+ and the stability of the catalyst could be enhanced. Eventually, the modified Cu-SiO2 microsphere catalyst exhibited better catalytic activity for hydrogenation of dimethyl oxalate to ethylene glycol. The dimethyl oxalate conversion of 99.9 % and ethylene glycol selectivity of 97.5 % could be obtained at a low temperature of 453 K. This work has considerable reference value for the subsequent construction of copper species on the catalyst surface.

Enhanced Effect of the Mesoporous Carbon on Iron Carbide Catalyst for Hydrogenation of Dimethyl Oxalate to Ethanol

AbstractDue to the low activity of bulk Fe5C2 catalyst in the hydrogenation of dimethyl oxalate to ethanol, a supported Fe5C2 catalyst was designed and prepared with mesoporous carbon as the carrier. For a comparison, two iron carbide catalysts supported on activated carbon and microporous carbon were also prepared. Based on the characterization results of IR, XRD, H2‐TPR, CO‐TPD, XPS and MES, the oxygen‐containing functional groups (especially COOH group) on the surface of the carbon supports inhibit the formation of iron carbides, which are regarded as the active sites and play the key role in the hydrogenation of dimethyl oxalate to ethanol. However, the mesoporous carbon exhibits a more positive effect on the dispersion of iron particles than the other two carbon supports. As a result, the as‐prepared mesoporous catalyst presents an excellent activity (the ethanol yield of 85.8 %) and stability in the hydrogenation of dimethyl oxalate. This work suggests a practical strategy in fabricating a supported iron carbides catalyst for the chemosynthesis of ethanol via DMO hydrogenation from syngas.

Boron-doped lamellar porous carbon supported copper catalyst for dimethyl oxalate hydrogenation

Doping heteroatoms on carbon materials could bring some special advantages for using as catalyst support. In this work, a boron doped lamellar porous carbon (B-LPC) was prepared facilely and utilized as carbon-based support to construct Cu/B-LPC catalyst for dimethyl oxalate (DMO) hydrogenation. Doping boron could make the B-LPC own more defects on surface and bigger pore size than B-free LPC, which were beneficial to disperse and anchor Cu nanoparticles. Moreover, the interaction between Cu species and B-LPC could be strengthened by the doped B, which not only stabilized the Cu nanoparticles, but also tuned the valence of Cu species to maintain more Cu+. Therefore, the B-doped Cu/B-LPC catalyst exhibited stronger hydrogenation ability and obtained higher alcohols selectivity than Cu/LPC, as well as high stability without decrease of DMO conversion and ethylene glycol selectivity even after 300 h of reaction at 240 °C.

Probing the structure sensitivity of dimethyl oxalate partial hydrogenation over Ag nanoparticles: A combined experimental and microkinetic study

Silver nanoparticles of different sizes have been synthesized to study their catalytic performance in dimethyl oxalate (DMO) partial hydrogenation to methyl glycolate (MG). Then, a detailed microkinetic analysis based on the results of DFT calculations has been performed to elucidate the origin of the observed size-dependent kinetics, where tabulated thermodynamic properties of gas-phase species are used to ensure the thermodynamic consistency of the reaction. Calculated results show that the turnover frequency for DMO consumption is much higher on Ag(211) than on Ag(111), suggesting the stepped surface dominates the kinetics. The hydrogenation of DMO on the two surfaces occurs along the same dominant reaction pathway, and the rate-determining step for the partial and deep hydrogenation of DMO is DMO and MG dissociation, respectively. The finding that the MG selectivity increases while the DMO hydrogenation activity decreases with the Ag nanoparticle size reveals the structure sensitivity of DMO partial hydrogenation.

Synthesis of methyl glycolate via low‐temperature hydrogenation of dimethyl oxalate over an efficient and stable Ru/activated carbon catalyst

AbstractBACKGROUNDSyngas to dimethyl oxalate (DMO) followed by hydrogenation to methyl glycolate (MG) is considered to be an environmentally friendly and economical route. However, the catalyst with super performance and low cost for this route is still challenging. In this work, a simple and low‐lost fabrication method was developed to prepare a Ru/activated carbon (AC) catalyst and was used for DMO hydrogenation to MG under mild reaction conditions.RESULTSThe Ru/AC catalyst showed the best performance in the low‐temperature hydrogenation of DMO to MG compared to Ru/SiO2 and Ru/Al2O3. A series of characterization results showed that the super catalytic properties of Ru/AC catalyst might be attributed to the higher dispersion of Ru on support and its smallest nanoparticles size, weak surface acidity and electron‐deficient state of Ru species. The key parameters such as Ru loading, temperature, weight hourly space velocity, and pressure, were comprehensively investigated. MG selectivity of 94.6% with DMO conversion of 97.2% were obtained over the 4.0 Ru/AC catalyst at 90 °C. The 4.0Ru/AC catalyst showed excellent stability and there was no obvious deactivation after 1032 h test.CONCLUSIONSThe Ru/AC catalyst is effective for the DMO hydrogenation to MG under mild conditions and has great promise for industrial applications because of its low cost, simple preparation, high efficiency, and long life. © 2022 Society of Chemical Industry (SCI).

Enhanced catalytic stability of Cu-based catalyst for dimethyl oxalate hydrogenation

Using mesoporous silica with different structures and morphologies as support, a series of copper-based catalysts was prepared for dimethyl oxalate (DMO) hydrogenation to ethylene glycol (EG). The results showed that the structure and morphology of supports had a significant effect on the catalytic stability of Cu-based catalysts. The Cu-based catalyst prepared by using MS-3 with hexagonal prism-like structure as support, exhibited excellent catalytic activity and enhanced stability (DMO conversion of ∼100%, EG selectivity up to 98%, and stability over 400 h). The enhanced catalytic performance of Cu/MS-3 catalyst could be attributed to the strong interaction between copper species and MS-3 support. MS-3 with narrowed pore size and larger specific surface area was not only beneficial to the dispersion and limitation of Cu nanoparticles, but also conducive to the formation of copper phyllosilicate structures from the copper ammonia complex and the silicon support, which provides a large number of stable active copper species. These attributes collectively promote the catalytic stability of Cu-based catalyst for DMO hydrogenation.

Ambient-pressure synthesis of ethylene glycol catalyzed by C 60 -buffered Cu/SiO 2

Bulk chemicals such as ethylene glycol (EG) can be industrially synthesized from either ethylene or syngas, but the latter undergoes a bottleneck reaction and requires high hydrogen pressures. We show that fullerene (exemplified by C 60 ) can act as an electron buffer for a copper-silica catalyst (Cu/SiO 2 ). Hydrogenation of dimethyl oxalate over a C 60 -Cu/SiO 2 catalyst at ambient pressure and temperatures of 180° to 190°C had an EG yield of up to 98 ± 1%. In a kilogram-scale reaction, no deactivation of the catalyst was seen after 1000 hours. This mild route for the final step toward EG can be combined with the already-industrialized ambient reaction from syngas to the intermediate of dimethyl oxalate.

Fullerenes make copper catalysis better.

Ethylene glycol can be reliably produced by mild hydrogenation of dimethyl oxalate.

Effect of Surface Hydroxyl Content of Support on the Activity of Cu/ZSM-5 Catalyst for Low-Temperature Hydrogenation of Dimethyl Oxalate to Ethylene Glycol

Effect of Surface Hydroxyl Content of Support on the Activity of Cu/ZSM-5 Catalyst for Low-Temperature Hydrogenation of Dimethyl Oxalate to Ethylene Glycol

Insights into a New Formation Mechanism of Robust Cu/SiO2 Catalysts for Low-Temperature Dimethyl Oxalate Hydrogenation Induced by a Chelating Ligand of EDTA

The Cu/SiO2 catalyst has been widely used in dimethyl oxalate (DMO) hydrogenation due to its low cost and high efficiency. However, the reaction temperature of DMO hydrogenation is higher than the Hüttig temperature of Cu, and the smaller Cu particles are easier to agglomerate. Therefore, there is much interest in constructing a catalyst with a small particle size and strong stability. In the present work, the effect of introducing EDTA on Cu/SiO2 catalysts is systematically investigated. It not only was beneficial to form smaller copper nanoparticles (CuNPs) but also to enhance the stability of Cu species by introducing a suitable amount of EDTA. Furthermore, the surface Cu species were more evenly dispersed, and the number of active sites was increased with the introduction of EDTA; subsequently, the synergistic effect between Cu+ and Cu0 was enhanced. The best performance of 0.08E-Cu/SiO2 had been achieved in the DMO hydrogenation to ethylene glycol (EG), and the DMO conversion and EG selectivity reached 99.9% and 97.7%, respectively. Above all, the 0.08E-Cu/SiO2 catalyst exhibited a high level of stability during the 1200 h life test at 180 °C.

Mesoporous Cu Catalysts for Dimethyl Oxalate Selective Hydrogenation: Impact of the Cu/Al interface on the Textural Properties and Catalytic Behavior

AbstractIn this paper, mesoporous monometallic Cu catalysts reinforced by the Al3+ dopants with different chemical features were successfully synthesized by controlling the preparation process. The N2‐Adsorption/Desorption, XRD, H2‐TPR, SEM, TEM, H2‐TPD and XPS were conducted to explore the structure evolution of the as‐synthesized samples focusing on the interface effect between Cu nano‐particles (NPs) and Al3+ dopants. It is found that the precipitants used for preparing precursors show drastically effect on the Al3+ chemical form and Cu/Al bonding manners of the as‐synthesized CuAl catalysts, further determining the resultant physicochemical properties and catalytic behavior in dimethyl oxalate (DMO) hydrogenation. In gas‐phase DMO hydrogenation, 98.0 % ethylene glycol (EG) and 90.0 % ethanol (EtOH) yield from DMO selective hydrogenation can be achieved over the CuAl catalyst by regulating the reaction temperature. The correlation between the catalytic behavior and physicochemical features shows that the surface Cu+ sites generated in the Cu/(hydr)oxide interface should be essential for DMO selective hydrogenation in presence of the adequate Cu0 sites. Additionally, the Cu−O−Al patterns in the Cu/Al interface intend to promote more electron transferred from the Al3+ dopants to Cu species through the O bridging, facilitating the CuAl(O) stronger Cu/Al interaction than that of the CuAl(C) catalyst in form of Cu−Al−OH mode. Thus, the Cu NPs growth of the CuAl(O) catalyst was effectively retarded, favoring enhanced catalytic stability.

Stable ethanol synthesis via dimethyl oxalate hydrogenation over the bifunctional rhenium-copper nanostructures: Influence of support

Addition of oxophilc rhenium to decorate small copper nanoparticles has been validated to be an efficient method to prepare a low-copper catalyst for the direct synthesis of ethanol via dimethyl oxalate (DMO) hydrogenation process, and herein we investigated the impact of supports on the catalytic performance of ReCu catalysts. A series of materials including activated carbon (AC), Al2O3, SiO2, TiO2 and ZrO2 were utilized as the support and as prepared Re2Cu5 catalysts were evaluated. The results exhibited that the Re2Cu5/ZrO2 catalyst possesses the highest DMO hydrogenation activity and ethanol yield (∼93%), which may be due to its lowest Cu0/Cu+ ratio (0.13), smallest Cu particle size (∼0.84 nm) a relative high reduction degree (59%). The CO adsorption behavior characterized by in situ IR spectroscopy showed that a strong metal-support interaction creates an electron deficient environment of Cu nanoparticle, resulting in a lower Cu0/Cu+ ratio that enhances the activation of CO bond in the DMO molecular.

Ni-Modified Ag/SiO2 Catalysts for Selective Hydrogenation of Dimethyl Oxalate to Methyl Glycolate.

Ni-modified Ag/SiO2 catalysts containing 0~3 wt.% Ni were obtained by impregnating Ni species onto Ag/SiO2 followed by calcination and reduction. The catalysts’ performance in the hydrogenation of dimethyl oxalate (DMO) to methyl glycolate (MG) was tested. Ag-0.5%Ni/SiO2 showed the highest catalytic activity among these catalysts and exhibited excellent catalytic stability. The effects of the Ni content on the structure and surface chemical states of catalysts were investigated by XRF, N2-sorption, XRD, TEM, EDX-mapping, FT-IR, H2-TPR, UV–vis, and XPS. The better catalytic activity and stability of Ni-modified Ag/SiO2 (versus Ag/SiO2) are ascribed to the improved dispersion of active Ag species as well as the higher resistance to the growth of Ag particles due to the presence of Ni species.

Influence of Pd‐Doping on The Efficiency of In2O3/ZrO2 Catalysts Used for Hydrogenating Dimethyl Oxalate to Ethanol

AbstractA co‐precipitation method followed by an impregnation method was used to synthesize the xPd‐In2O3/ZrO2 catalysts that could be used for the hydrogenation of dimethyl oxalate to ethanol. The results indicated that xPd‐In2O3/ZrO2 exhibited excellent catalytic activity during the hydrogenation of dimethyl oxalate to ethanol. It was found that Pd−doping could improve the performance of the catalysts. 100 % conversion and 84 % ethanol selectivity could be achieved using the 0.5 % Pd‐In2O3/ZrO2 catalyst. In‐depth charact‐erization of the xPd‐In2O3/ZrO2 catalyst revealed the occurrence of hydrogen spillover and the formation of oxygen vacancies on the surface of the catalyst. The improvement in the catalytic activity can be attributed to the increase of activated hydrogen concentration during the process of hydrogen spillover in the presence of Pd and the enhancement of activation capacity (toward dimethyl oxalate) of the catalyst caused by the formation of oxygen vacancies.

Atomic ruthenium stabilized on vacancy-rich boron nitride for selective hydrogenation of esters

Constructing and taming metal–support interaction of atoms and/or clusters has emerged as a promising protocol to maximize the catalytic performance of noble metal-based materials. Here, we report atomic ruthenium (Ru) with the oxidized state immobilized on defect-rich hexagonal boron nitride (d-BN) nanosheets and the essential interfacial electronic effect on Ru deduced from B- and N-vacancies for superior selective hydrogenation of esters. Experimental results indicate that strong electronic interplay exists between vacancies and atomic Ru species. Unlike defect-free commercial hexagonal BN (h-BN), d-BN can highly stabilize the active Ru species in atomic scale with oxidation state, and the obtained Ru/d-BN significantly increases the catalytic activity and durability. Specifically, the turnover frequency of Ru/d-BN is more than one order of magnitude higher than that of the conventional optimized Ag/SiO2 catalyst for the selective hydrogenation of dimethyl oxalate to methyl glycol. Systematic characterizations show that the Ru on B- and N-vacancies, and the defective BN serves as electron acceptor. The findings demonstrate the overall electronic effect on the electron-rich feature of Ru on d-BN, such that the electronic metal–support interactions cause the Ru species to favor the adsorption and selective scission of C–O bonds in esters, revealing a highly efficient hydrogenation catalysis.

Effect of calcination temperature on the Cu–ZrO2 interfacial structure and its catalytic behavior in the hydrogenation of dimethyl oxalate

The 5 wt% Cu/ZrO2 catalysts showed satisfying performance in DMO hydrogenation to EG via simply tuning the calcination temperature. The synergistic effect of the Cu0–Cu+–ZrO2 interface in activating H2 molecules and carbonyl bonds was elucidated.

Synthesis of methyl glycolate by hydrogenation of dimethyl oxalate with a P modified Co/SiO2 catalyst

A P-modified Co/SiO2 catalyst exhibited excellent performance in selective hydrogenation of dimethyl oxalate to methyl glycolate.

Study on performance of Ag-modified layered copper silicate catalyst for hydrogenation of dimethyl oxalate to methyl glycolate

Methyl glycolate (MG) is a high value-added chemical intermediate and widely used in the fields of medicine, chemical industry, fodder and dyes. A series of CuAg/SiO2 catalysts were prepared by sol-gel method for hydrogenation of dimethyl oxalate to MG. The structure of catalysts was characterized by XRD, N2-physical adsorption, FT-IR, TEM, H2-TPR, and XPS, and the influence of Ag loading on catalytic performance was investigated. The 5Ag-Cu/SiO2 catalyst with Ag loading of 5% exhibited the best catalytic performance with DMO conversion of 83.7% and MG selectivity of 72.2%. The characterization results showed that introducing appropriate amount of Ag not only improved the dispersion of copper species, but also increased the content of Cu+, thereby improving the catalytic activity of CuAg/SiO2 catalysts. In addition, the electron transfer between Ag and Cu could effectively stabilize Cu+, and eventually improved the stability of the catalyst.

Highly selective hydrogenation of dimethyl oxalate to methyl glycolate and ethylene glycol over an amino-assisted Ru-based catalyst.

A Ru/NH2-MCM-41 catalyst was prepared via a coordination-assisted strategy for chemoselective hydrogenation of dimethyl oxalate with a high selectivity of methyl glycolate (ca. 100%) and ethylene glycol (>90%) at reaction temperatures of 343 K and 433 K, respectively. The amino groups help to anchor and form stable electron-rich Ru active sites, which accounts for the excellent CO bond activation and hydrogenation selectivity.

K+-induced formation of granular and dense copper phyllosilicate precursor converts dimethyl oxalate to ethylene glycol in absence of H2

The reducibility of heterogeneous Cu-based precursor greatly influences the activity and stability of the final catalysts because the excessive reduction to metallic Cu significantly deactivates the catalysts. Herein, we develop a crystallization inhibition strategy to fabricate the granular and densely stacked copper phyllosilicate precursor which possesses stronger resistance to H2 reduction. The reduction-resistant CuSiO3 precursor contains more abundant Cu+ species and oxygen deficiencies, which was verified by O2-TPD, TGA, O XPS and Cu XAES measurements, and is beneficial for methanol dehydrogenation and dimethyl oxalate (DMO) adsorption. A high yield of 85.4% of ethylene glycol (EG) was achieved from DMO hydrogenation at 240 °C, with methanol as both the solvent and hydrogen supplier. The delicately designed synthesis of specific Cu precursor with unique properties resulted in an excellent multi-functional Cu catalyst for coupled methanol dehydrogenation and DMO hydrogenation to EG.