Continuous hydrogenation of CO2-derived ethylene carbonate to methanol and ethylene glycol at Cu-MoOx interface with a low H2/ester ratio

Emerging catalysts for the ambient synthesis of ethylene glycol from CO2 and its derivatives

Ethylene glycol (EG), a useful chemical raw material, has been widely applied in many aspects of modern society. The conventional preparation of ethylene glycol mainly uses the petroleum route at high temperatures and pressure. More and more approaches have been developed to synthesize EG from CO₂ and its derivatives under mild conditions. In this review, the ambient synthesis of EG from thermocatalysis, photocatalysis, and electrocatalysis is highlighted. The coal-to-ethylene glycol technology, one of the typical thermal catalysis routes for EG preparation, is relatively mature. However, it still faces some problems to be solved in industrialization. The recent progress in the development of coal-to-ethylene glycol technology is introduced. The main focus is on how to realize the preparation of EG under mild conditions. The strategies include doping promoters, modification of supports, design of catalysts with special structures, etc. Furthermore, the emerging technological progress of photocatalytic and electrocatalytic ethylene glycol synthesis under ambient conditions is introduced. Compared with the thermal catalytic reaction, the reaction conditions are milder. However, there are still many problems in large-scale production. Finally, we propose future development issues and related prospects for the ambient synthesis of EG using different catalytic routes.

Enhancement of Cu+ stability under a reducing atmosphere by the long-range electromagnetic effect of Au

In conventional thermocatalytic reactions under a reducing atmosphere, stabilization of the active Cu⁺ component and inhibition of over-reduction into metallic Cu⁰ are extremely challenging. In this study, Au@Cu₂O core-shell nano-catalysts with different Cu₂O shell thicknesses were synthesized, and the effect of the Au nano-core on Cu⁺ stability under a reducing atmosphere and the catalytic performance of Cu⁺ in the ethynylation of formaldehyde were investigated. The Au nano-core facilitates Cu₂O dispersion and leads to an increase of 0.2-0.5 eV in electron binding energies of Cu₂O and Cu₂C₂ in the range of 27-55 nm, attributed to the long-range electromagnetic effect of Au NPs. Specifically, active Cu⁺ centers exhibit high stability under a reducing atmosphere due to the long-range electromagnetic effect of the Au nano-core. In the ethynylation of formaldehyde as a probe reaction, Cu⁺/(Cu⁰ + Cu⁺) on Au@Cu₂O catalysts remained at 88-91%. The catalytic performance in the ethynylation of formaldehyde revealed that the introduction of an Au nano-core into Cu-based catalysts increased the TOF from 0.37 to 0.7 h^-1, and decreased the activation energy from 42.6 to 38.1 kJ mol^-1. Additionally, the Cu⁺/(Cu⁰ + Cu⁺) ratios and the catalytic performance in the ethynylation of formaldehyde (BD yield = 65%, BD selectivity = 95%) on Au@Cu₂O catalysts remained constant after nine cycles, while pure Cu₂O readily deactivated due to the dramatically reduced Cu⁺/(Cu⁰ + Cu⁺) ratios and carbyne deposition. In summary, Cu⁺ in Cu-based catalysts showed high catalytic activity and stability during the ethynylation of formaldehyde due to the long-range electromagnetic effect of the Au nano-core.

Model-Based Analysis for Ethylene Carbonate Hydrogenation Operation in Industrial-Type Tubular Reactors

Hydrogenation of ethylene carbonate (EC) to co-produce methanol (MeOH) and ethylene glycol (EG) offers an atomically economic route for CO2 utilization. Herein, aided with bench and pilot plant data, we established engineering a kinetics model and multiscale reactor models for heterogeneous EC hydrogenation using representative industrial-type reactors. Model-based analysis indicates that single-stage adiabatic reactors, despite a moderate temperature rise of 12 K, suffer from a narrow operational window delimited by EC condensation at lower temperatures and intense secondary EG hydrogenation at higher temperatures. Boiling water cooled multi-tubular reactors feature near-isothermal operation and exhibit better operability, especially under high pressure and low space velocity. Conduction oil-cooled reactors show U-type axial temperature profiles, rendering even wider operational windows regarding coolant temperatures than the water-cooled reactor. The revelation of operational characteristics of EC hydrogenation under industrial conditions will guide further improvement in reactor design and process optimization.

Synthesis of cyclohexanol and ethanol via the hydrogenation of cyclohexyl acetate with Cu2Znx/Al2O3 catalysts

The Cu2Zn1.25/Al2O3 catalyst exhibited 93.9% conversion and 97.2% selectivity to ethanol with 97.1% selectivity to cyclohexanol for the hydrogenation of cyclohexyl acetate due to the abundant weak acid sites and the highest ratio of Cu+/(Cu0 + Cu+).