Dimethyl oxalate, with the molecular formula C?H?O?, is a colorless, needle-like crystal at room temperature. The molecule consists of two methyl ester groups linked by an oxalic acid backbone. It is soluble in organic solvents such as ethanol and diethyl ether, and slightly soluble in cold water. its solubility in hot water increases significantly. Dimethyl oxalate can undergo hydrolysis, alcoholysis, ester exchange, and addition reactions, making it an important organic chemical intermediate. It is commonly used in the preparation of ethylene glycol, various pharmaceuticals, pesticides, and dye derivatives, and can also be used as a solvent and analytical reagent.

Selective Hydrogenation of Dimethyl Oxalate to Methyl Glycolate

Methyl glycolate (MG), containing both hydroxyl and ester groups, is an important fine chemical. As it has similar chemical properties to alcohol and ester, MG can undergo various reactions such as carbonylation, hydrolyzation, and oxidation. Thus, the development of a green synthetic method with high efficiency is warranted. The synthesis of MG by catalytic hydrogenation of dimethyl oxalate (DMO) has been proposed as a more economical and environmentally friendly route compared with other catalytic procedures. The hydrogenation of DMO contains the successive hydrogenation of DMO to MG, MG to ethylene glycol (EG), and EG to ethanol (EtOH). To make sure that the hydrogenation of dimethyl oxalate stops at the formation of MG, catalysts with relatively weak hydrogenolysis ability should be used. The catalytic properties and stability of metallic catalysts can be improved by adding a promoter. The promoted catalysts can exhibit superior catalytic performance in many reactions such as catalytic reforming, selective oxidation of alcohols, and selective hydrogenation. Recently, several Ag-containing promoted catalysts were applied in the MG synthesis from selective hydrogenation of dimethyl oxalate. Herein, researchers report Ag-Ni/SiO2 catalysts with several Ni loadings for the vapor-phase hydrogenation of dimethyl oxalate to MG. The catalysts were synthesized by ammonia evaporation with cheap silica sol followed by simple impregnation of an aqueous Ni(NO3)2 solution. The preparation method is different from that in our previous work and leads to better catalytic performance. [1]

To clearly compare the catalytic performance between Ag/SiO2 and Ag-Ni/SiO2 in DMO hydrogenation, the TOF values of all catalysts were measured at the conversion of DMO lower than 30% by regulating the DMO liquid hourly space velocity (LHSV). The dimethyl oxalate conversion data were used to calculate the TOF according to the active metal dispersion. When increasing the content of Ni, both the TOF and DAg values increased first, passing through a maximum, and then decreased at higher Ni contents. Generally, the changes in the structural properties and chemical states of active component might be the key factors affecting the catalytic behavior of Ag-based catalysts in dimethyl oxalate hydrogenation. In our case, the MG yield of Ag-Ni/SiO2 catalysts is well consistent with the surface Ag concentration. In particular, Ag-0.5%Ni/SiO2 had the smallest Ag particle sizes and, hence, the largest number of exposed active sites, thus exhibiting the highest catalytic activity. Furthermore, the hydrogenation of dimethyl oxalate to MG is a structure-sensitive reaction on Ag-Ni/SiO2, and the intrinsic catalytic activity (TOF) increased with the decrease in Ag particle sizes. The catalytic performance of a series of Ni-modified Ag/SiO2 catalysts for the hydrogenation of dimethyl oxalate to MG was investigated. Ag-0.5%Ni/SiO2 with a Ni content of 0.5 wt.% exhibited the best catalytic activity (complete conversion of DMO, 92.5% selectivity to MG).

Recent advances in dimethyl oxalate hydrogenation

Leveraging the rising imperative for green and low-carbon manufacturing, the hydrogenation of dimethyl oxalate (DMO) is a strategically central route that couples two sustainability pillars: carbon circularity and renewable hydrogen utilization. DMO can be synthesized from CO/H2 syngas derived from coal, biomass, natural gas, municipal solid waste, and even CO2via gasification/reforming/reduction pathways, providing a flexible carbon entry point. Selective dimethyl oxalate hydrogenation then upgrades this syngas intermediate into methyl glycolate (MG), ethylene glycol (EG), and ethanol (EtOH)-key molecules for biodegradable polyesters, PET/PEF, refrigerants, and fuel additives. Critically, the process is inherently “power-to-chemicals ready”: green H2 from wind-solar electrolysis can be directly integrated into the hydrogenation step, converting intermittent renewable electricity into stable, high-value products. By uniting diversified carbon feedstocks with renewably sourced hydrogen in a single catalytic platform, dimethyl oxalate hydrogenation delivers high atom-efficiency, lowers lifecycle CO2 emissions, and establishes a scalable pathway from syngas to value-added chemicals. DMO hydrogenation network is characterized by its cascade nature, demanding precise catalytic control over product selectivity. By tuning the hydrogenation degree, a series of high-value chemicals can be obtained. MG, featuring both ester and hydroxyl functionalities, is a crucial intermediate for pharmaceuticals and organic synthesis as well as an excellent solvent.[2]

As a crucial pathway for converting non-petroleum carbon resources into high-value chemicals, dimethyl oxalate hydrogenation technology faces core scientific challenges in overcoming the intrinsic coupling of catalyst activity, selectivity, and stability to achieve efficient conversion at low H2/ester ratios under mild conditions. Dimethyl oxalate hydrogenation is a pivotal process for transforming non-petroleum carbon resources into high-value chemicals such as methyl glycolate, ethylene glycol, and ethanol. Despite its potential for enabling carbon circularity and renewable hydrogen integration, industrial adoption remains hindered by persistent challenges in achieving balanced activity, selectivity, and catalyst stability under mild and energy-efficient conditions. Existing reviews often address catalyst design or process optimization in isolation, lacking a comprehensive perspective. In this review, we provide a systematic overview of recent advances in dimethyl oxalate hydrogenation, with particular emphasis on the intricate cascade reaction mechanisms as well as thermodynamic and kinetic factors that govern product distribution and efficiency. Through an integrated analysis of catalyst structure, reaction networks, and process engineering, we identify key bottlenecks and outline emerging strategies poised to overcome current limitations.

References

[1]Cheng S, Meng T, Mao D, Guo X, Yu J, Ma Z. Ni-Modified Ag/SiO2 Catalysts for Selective Hydrogenation of Dimethyl Oxalate to Methyl Glycolate. Nanomaterials (Basel). 2022 Jan 26;12(3):407. doi: 10.3390/nano12030407. PMID: 35159752; PMCID: PMC8838820.

[2]Zhang, K., Cao, Y., Zhang, T., Gu, J., Shen, S., Zhang, Y., Luo, X., Weng, Y., & Huang, Z. (2025). Recent advances in dimethyl oxalate hydrogenation: integrating catalyst design with reaction engineering for sustainable production of C? oxygenates. Journal of Materials Chemistry A, 13(48), 41462–41487. https://doi.org/10.1039/D5TA06914A