Hydrogenation Of Dimethyl Oxalate Research Articles

Tuning the product selectivity of dimethyl oxalate hydrogenation over WOx modified Cu/SiO2 catalysts

Product selectivity and reaction pathway are highly dependent on surface structure of heterogeneous catalysts. For vapor-phase hydrogenation of dimethyl oxalate (DMO), “EG route” (DMO → methyl glycolate (MG) → ethylene glycol (EG) → ethanol (ET)) and “MA route” (DMO → MG → methyl acetate (MA)) were proposed over traditional Cu based catalysts and Mo-based or Fe-based catalysts, respectively. Herein, tunable yield of ET (93.7%) and MA (72.1%) were obtained through different reaction routes over WOx modified Cu/SiO2 catalysts, and the corresponding reaction route was further proved by kinetic study and in-situ DRIFTS technology. Mechanistic studies demonstrated that H2 activation ability, acid density and Cu-WOx interaction on the catalysts were tuned by regulating the surface W density, which resulted in the different reaction pathway and product selectivity. What’s more, high yield of MA produced from DMO hydrogenation was firstly reported with the H2pressure as low as 0.5 MPa.

Cobalt-silver catalyst with low metal content for highly efficient synthesis of methyl glycolate through synergistic effect

The Co-Agx/TiO2 catalysts with low mass content of Co and Ag were synthesized through the impregnation method and investigated for dimethyl oxalate (DMO) hydrogenation to methyl glycolate (MG). Remarkably, the Co-Ag0.7/TiO2 catalyst with an Ag concentration of 0.7 wt%, exhibited an impressive yield of MG of ∼94.4 %, surpassing the yields of MG obtained with Co/TiO2 (∼54 %) and Ag0.7/TiO2 (∼69 %) catalysts. Various characterizations elucidated that the exceptional catalytic performance of Co-Ag0.7/TiO2 can be ascribed to the synergy between Co and Ag, resulting in the formation of AgCoO2 as high active site can improve the adsorption and activation of DMO and H2 on catalyst surface. Additionally, the doping of a small amount of Ag regulated the contents of Lewis acidic and Brønsted acidic sites, leading to a high conversion of DMO and selectivity of MG. Furthermore, the excellent MG yield and long-term stability (at least 200 h) facilely obtained over our catalyst under mild reaction conditions guarantee a feasible prospect in the industrial application. This study not only unraveled the superior performance of the Co-Ag synergistic catalyst, but also carried significant implications for developing catalysts with low-content in DMO hydrogenation to MG.

Efficient Descriptor for Designing High-Performance Cu-Based Catalysts for the Hydrogenation of Dimethyl Oxalate to Methyl Glycolate

Efficient Descriptor for Designing High-Performance Cu-Based Catalysts for the Hydrogenation of Dimethyl Oxalate to Methyl Glycolate

Stochastic-Based Optimization Strategy of Dimethyl Oxalate Hydrogenation for Ethylene Glycol Production

Stochastic-Based Optimization Strategy of Dimethyl Oxalate Hydrogenation for Ethylene Glycol Production

Insight into the size-dependent activity in Ag/SiO2 catalyzed hydrogenation of dimethyl oxalate to methyl glycolate

Methyl glycolate (MG) is an important building block for synthesizing biodegradable material of polyglycolic acid. Hydrogenation of coal-based dimethyl oxalate (DMO) to MG is quite promising, where Ag-based catalysts exhibited excellent selectivity. Here, a series of Ag/SiO2-x catalysts with particle sizes of 1.4–13.5 nm were prepared, which showed significant structural sensitivity in DMO hydrogenation. For Ag nanoparticles of 1.4–2.7 nm, the turnover frequency (TOF) was linearly increased with the surface electron density of silver, but when the Ag nanoparticles further enlarged, no significant variation of TOF was observed. Combining DFT calculation and experimental results of the model catalyst, triangular nanoplate, it was deduced that the Ag (111) played a dominant role in DMO hydrogenation to MG, originating from the benefited MG desorption as well as promoted dissociation of H2 and DMO. This understanding about Ag particle size effect may provide guidance for designing efficient catalysts for DMO hydrogenation to MG.

In situ exsolution to fabricate interfacial Ni0/Niδ+ sites for regulating reaction pathways in hydrogenation

Regulating the selectivity of reaction pathways to desirable products via controlling adsorption/activation behaviors towards reactants is significant for the design of excellent catalysts for selective hydrogenation but remains challenging. Exemplified with dimethyl oxalate (DMO) hydrogenation, we herein propose an in situ exsolution strategy for constructing interfacial Ni0/Niδ+ sites by using pre-synthesized Ni phyllosilicate as the precursor to control the reaction pathways of selective hydrogenation. Structural characterizations, including in situ spectroscopic and isotopic studies, and theoretical calculations elucidate that the interfacial Ni0/Niδ+ sites can selectively activate monoester group of DMO via a tilted adsorption configuration and hence boost hydrogen dissociation. With such activation behaviors the reaction pathway is steered to methyl glycolate, other than the pathway to ethylene glycol on the reference active sites where both ester groups are activated and methyl formate is formed via breaking the C–C bond of DMO.

Facile synthesis of Cu@Ag/SiO2 catalysts for the selective hydrogenation of dimethyl oxalate to methyl glycolate

A promising route for producing biodegradable polyglycolic acid material from syngas has garnered increasing attentions. In this route, one of the pivotal issues is developing favorable catalysts for semi-hydrogenation of dimethyl oxalate (DMO) to methyl glycolate (MG). Silver catalysts were reported to be effective but suffered from the high cost. Herein, we prepared small-sized Cu@Ag/SiO2 catalysts with appropriate Ag/Cu ratios by a facile wet impregnation method. This core–shell structure facilitated the intermetallic electronic transference from Cu to Ag. The surface exposure of electron-rich silver species could promote the catalytic activity and MG desorption in the DMO hydrogenation, which achieved high efficiency without compromising the MG selectivity. The optimal catalyst with Ag/Cu mass ratio of 3/2 displayed excellent space time yield towards MG of 47.3 g·gAg−1·h−1. These insights could offer a potential strategy to reduce the silver-based catalyst cost for the semi-hydrogenation of DMO to MG.

A DFT study on the formation mechanism of side product 1,2-propanediol in the hydrogenation of dimethyl oxalate over copper catalyst

The costly separation of 1,2-propanediol (1,2-PDO), an unavoidable byproduct in the hydrogenation of dimethyl oxalate (DMO), significantly hampers the economic viability of coal-to-ethylene glycol (EG) technology. To address this challenge, the formation mechanism of the side product 1,2-PDO on the Cu(111) and Cu2O(111) surfaces during DMO hydrogenation was investigated, which focused on the active sites of copper catalyst and the dominant pathway through density functional theory calculation. The thermodynamics of each elementary step and the adsorption behavior of various species involved in the reaction network along with the local density of states and charge density difference were systematically analyzed. The results indicate that 1,2-PDO is generated more favorably on the Cu2O(111) surface than that on the Cu(111) surface, owing to the Lewis acid-base pairs, i.e. Cu+ us and O– suf sites, present on the Cu2O(111) surface, which strengthens the binding of reactants, products, and reaction intermediates to the substrate. EG reacts primarily with methanol (MeOH) to form 1,2-PDO through Guerbet alcohol condensation reaction through three consecutive steps: alcohol dehydrogenation, aldol condensation, and unsaturated aldehyde hydrogenation. The O– suf sites promote the dehydrogenation of alcohols into aldehydes, the generation of enolates during aldol condensation and the hydrogenation of unsaturated aldehydes, while the Cu+ us sites are responsible for the C–C coupling reaction. These findings may shed light on the mechanism of 1,2-PDO formation over Cu catalyst and provide fundamental knowledge for the development of more efficient catalysts and process optimization.

Highly stable Cu catalyst embedded in N-doped carbon microsphere for hydrogenation of dimethyl oxalate to methyl glycolate

Cu catalyst often subjects to low stability due to chemical state transformation during carbon-oxygen hydrogenation reaction. In the present work, the copper catalysts embedded in N-doped carbon microsphere (Cu@NC) were fabricated by one-pot hydrothermal method and applied in dimethyl oxalate (DMO) hydrogenation to methyl glycolate (MG). The optimized Cu@10NC catalyst exhibited an excellent stability with DMO conversion of 80.1% and MG selectivity of 80.3% during 220 h long-term evaluation under 1.9 MPa, 210 °C, H2/DMO molar ratio of 80 and WHSV of 0.8 gDMO·gCu−1·h−1, beneficial from the stable Cu+ ratio and confinement effect of carbon support during the reaction. The Cu dispersion and Cu+ proportion can be finely controlled by varying the N-doping content due to the enhanced interaction between Cu and carbon microspheres. Particularly, graphitic-N is primarily accountable for Cu dispersion, while pyridinic-N is dominantly responsible for the stabilization of Cu+ species.

Alkaline earth modified activated carbon supported Cu catalysts with enhanced selectivity in the hydrogenation of dimethyl oxalate to methyl glycolate.

In this work, the effect of alkaline earth metal modification on the catalytic performance of activated carbon supported Cu was investigated. The experimental results showed that the introduction of Ca and Sr improved the selectivity of methyl glycolate (MG) during hydrogenation of dimethyl oxalate (DMO) in gas phase. The optimal loading amount of Ca was 0.1 wt%, and under the optimal conditions (temperature 240 °C, pressure 2 MPa, hydrogen-ester ratio of 80, feedstock 15% DMO methanol solution, and WLHSVDMO = 0.9 h-1) the selectivity of MG was as high as 94%, and the conversion of DMO was 97%. The optimal loading of Sr was 0.2 wt% with MG selectivity up to 89% and DMO conversion of 98%. The results of catalyst characterization showed that both Ca and Sr modifications were beneficial to further reduce the particle size of Cu, improve the dispersion of Cu, increase the basicity of the catalyst, and improve the stable presence of Cu+ during the reaction process. Cu+ was beneficial to the stabilization of the MG species, in which Cu+ accounted for more in the Ca-modified catalysts Cu+/(Cu+ + Cu0) = 0.65, and in the Sr-modified ones Cu+/(Cu+ + Cu0) = 0.51. Therefore, both Ca and Sr modified catalysts showed improvement in the selectivity of MG.

Bimetallic nickel molybdenum nitride catalyst with low pressure and reduced hydrogen consumption for hydrogenation of dimethyl oxalate to ethanol: the impact of reduction temperature on catalytic performance

The bimetallic nickel molybdenum nitride (Ni3Mo3N) catalyst exhibits exceptional performance with a high EtOH yield (>97.5%) under low pressure (0.5 MPa) and minimal hydrogen consumption (H2/DMO (mol)) conditions.

Dealuminated Beta zeolite reverses Ostwald ripening for durable copper nanoparticle catalysts.

Copper nanoparticle-based catalysts have been extensively applied in industry, but the nanoparticles tend to sinter into larger ones in the chemical atmospheres, which is detrimental to catalyst performance. In this work, we used dealuminated Beta zeolite to support copper nanoparticles (Cu/Beta-deAl) and showed that these particles become smaller in methanol vapor at 200°C, decreasing from ~5.6 to ~2.4 nanometers in diameter, which is opposite to the general sintering phenomenon. A reverse ripening process was discovered, whereby migratable copper sites activated by methanol were trapped by silanol nests and the copper species in the nests acted as new nucleation sites for the formation of small nanoparticles. This feature reversed the general sintering channel, resulting in robust catalysts for dimethyl oxalate hydrogenation performed with supported copper nanoparticles for use in industry.

Significant effect of In doping on Ni/C catalyst for hydrogenation of dimethyl oxalate to ethanol: Synergistic effect of InNi3 alloy, surface oxygen, and defect sites

The Ni-In/C catalyst, prepared using a one-pot method, demonstrates superior catalytic performance compared to the Ni/C catalyst in the hydrogenation of dimethyl oxalate (DMO) to ethanol (EtOH). The introduction of doping results in the formation of defect sites and InNi3 alloy, enhancing both the adsorption of DMO and the activation of H2. Additionally, the presence of -OH groups (acting as Bronsted acid sites) on the carbon surface activates C-O, thereby effectively promoting the deep hydrogenation of intermediate products to produce EtOH. The catalyst exhibits remarkable industrial potential by achieving high ethanol yield through a straightforward preparation method, while maintaining low Ni content.

Facile and Optimized Ion-Exchange Method for Synthesizing Low-Cost and Stable Cu/SiO2 Catalyst for Hydrogenation of Dimethyl Oxalate to Ethylene Glycol

Facile and Optimized Ion-Exchange Method for Synthesizing Low-Cost and Stable Cu/SiO₂ Catalyst for Hydrogenation of Dimethyl Oxalate to Ethylene Glycol

Interface-enhanced catalytic performance of TiO2-supported Cu and Au for dimethyl oxalate hydrogenation: A comparative microkinetic analysis

The electronic structures of Cu-TiO2 and Au-TiO2 and their catalytic behaviors in the hydrogenation of dimethyl oxalate (DMO) have been studied by the stochastic surface walking-global neural network potential method, density functional theory calculation, and microkinetic analysis. Calculated results indicate that metal clusters on the pristine and oxygen-deficient TiO2 are mostly coordinated to O2c ions, and the defective surface may provide additional oxygen vacancies for Cu6 and Au6 cluster anchoring. It turns out that the interfacial Ti5c and Cuδ+/Auδ- ions provide adsorption and hydrogenation sites for the reaction intermediates with unsaturated O and C atoms, respectively. The turnover frequency for DMO consumption is much higher on Cu-TiO2 than on Au-TiO2, Cu(111), and Cu(211) at 443.15 K and 20 bar of total pressure. Given the satisfactory methyl glycolate (MG) selectivity, the Cu-TiO2 catalyst has the potential to act as an excellent catalyst for the selective MG production.

Superior silicon-free Cu catalyst for dimethyl oxalate hydrogenation: Exploring interaction between Cu and pyridinic-N-rich ultrathin carbon

The hydrogenation of dimethyl oxalate (DMO) is a key step in the economical and eco-friendly synthesis of high value-added alcohols from syngas. In this study, a pyridinic-N-rich ultrathin carbon was employed as a support to construct a silicon-free Cu catalyst for highly efficient DMO hydrogenation. N-doped ultrathin carbon support with a two-dimensional structure provided sufficient anchoring sites for Cu species. More critically, abundant pyridinic-N (72.3%) maintained Cu in an electron-deficient state via electronic interactions between Cu and the carbon support, thereby preserving the vital active sites Cu+ during the hydrogen-rich reaction. The new silicon-free Cu catalyst (Cu/0.1 N-UC) demonstrated an ethanol selectivity that was 1.8 times higher than that of the commonly used Cu/SiO2 catalyst. Additionally, the Cu/0.1 N-UC catalyst displayed superior stability and could convert the primary product to ethylene glycol by adjusting the reaction temperature. This study offers a novel approach for the development of promising silicon-free Cu catalysts for DMO hydrogenation.

Thermodynamics of Dimethyl Carbonate and Ethylene Carbonate Generation During the Conversion of Syngas to Ethylene Glycol

AbstractDespite recent progress in the coal‐to‐ethylene glycol (EG) technology, some indicators show that the obtained products are still different from those produced by the petroleum route method. Therefore, it is of great significance to improve the thermodynamic performance of the system to obtain an enhanced process technology. In this paper, thermodynamic data related to uncommon substances in coal‐to‐EG reactions were estimated using the Benson group contribution method, and the values of the reaction enthalpy, Gibbs free energy, and the equilibrium constant of each reaction in the system were calculated. We systematically analyzed the temperature influence on the main product, DMO (dimethyl oxalate), and the main by‐product, DMC (dimethyl carbonate), in the DMO synthesis reaction and the influence of the DMC content on the spontaneous formation of EC (ethylene carbonate) in the DMO hydrogenation reaction. The obtained results demonstrated that elevated temperatures are favorable for the generation of DMC. In the DMO hydrogenation reaction, the mass fraction of DMC should be less than 0.05678 % when the feeding proportion is based on industrial data. When pure DMO is fed, the mass fraction of DMC should be less than 0.0335 %. Finally, no special treatment is required for EC separation in these cases.

Role of the Cu dopant in the textural and catalytic features of the Co/ZnO catalyst for dimethyl oxalate selective hydrogenation

AbstractBACKGROUNDConverting the syngas‐derived dimethyl oxalate (DMO) intermediate to versatile simple diols (ethylene glycol, EG) has been deemed as a promising chemical synthesis technology, owing to the cheap, widely available raw materials. Nonetheless, finding the optimal catalyst for this route is still challenging. In this work, copper (Cu)‐doped cobalt/zinc oxide (Co/ZnO)‐based CoCu/ZnO catalysts for DMO selective hydrogenation to EG were successfully synthesized by the oxalic co‐precipitation method.RESULTSThe Cu content shows significant influence on Co dispersion and chemical features, further determining the resultant structural and morphology properties of the as‐prepared samples. For DMO gas‐phase hydrogenation, the CoCu20/ZnO catalyst prepared in presence of the 20.0 wt% Cu additive exhibited 100.0% DMO conversion and 93.0% EG yield, superior to that of the other catalysts due to adequate active Co0 sites released adjacent to the Cu species. Moreover, the CoCu/ZnO catalyst showed outstanding thermal stability in DMO‐selective hydrogenation for >200 h.CONCLUSIONSThe H2 activation ability and capability of the surface Co species depends critically on the Cu content, further regulating the reaction pathways of the DMO hydrogenation. © 2023 Society of Chemical Industry (SCI).

Surface Amine Species Promoted Cu/SiO2 Catalysts for the Hydrogenation of Dimethyl Oxalate to Ethylene Glycol

Surface Amine Species Promoted Cu/SiO₂ Catalysts for the Hydrogenation of Dimethyl Oxalate to Ethylene Glycol

Ultra-stable Cu-based catalyst for dimethyl oxalate hydrogenation to ethylene glycol

Dimethyl oxalate (DMO) hydrogenation is a crucial step in the coal to ethylene glycol (CTEG) process. Herein, Cu catalyst supported on fibrous mesoporous silica (Cu/FMS) was synthesized via liquid phase deposition technique and applied for the DMO hydrogenation to EG. The catalyst exhibited a remarkable EG selectivity of 96.95% and maintained its activity without deactivation for 1000 h. Fibers of FMS support and liquid phase deposition technology cooperated to give high dispersion of Cu species in the Cu/FMS catalyst, resulting in a high Cu surface area. The formation of Si—O—Cu during catalyst preparation process increased the Cu+/(Cu0 + Cu+) ratio and enhanced the thermal and valence stability of Cu species. The high Cu+ surface area and Cu stability (thermal and valence stability) of the Cu/FMS catalyst were key factors for achieving superior EG selectivity and ultra-high stability.