Study On Copper-Based Catalysts For The Hydrogenation Of Ethylene Carbonate To Methanol And Ethylene Glycol

The reduction of CO₂ emissions is a worldwide challenge.Targeting at reaching CO₂ emission peak by 2030 and realizing carbon neutrality by 2060 in China,CO₂utilization to produce bulk chemicals shows great potential in solving both the environmental and energy concerns.CO₂ and ethylene oxide to synthesize ethylene carbonate（EC）,with subsequent hydrogenation of EC to methanol and co-production of ethylene glycol（EG）,is one of the most promising routes for industrialization due to the advantages of mild reaction conditions,high CO₂ conversion and good methanol selectivity,which has attracted attention from both academy and industry.The development of efficient catalysts for EC hydrogenation is one of the key issues for the application.In order to address the problems of the high hydrogen to EC ratio in the feed and the low selectivity of methanol in EC hydrogenation,we developed different Cu-based catalysts and explored the effect of doping noble metal and modifying catalyst pore structure and morphology on the catalytic performance for EC hydrogenation.A series of Cu/Si O₂ catalysts prepared by the ammonia evaporation（AE）method and doped Pt by the incipient-wetness impregnation（IWI）method were synthesized,and used in EC hydrogenation.By modulating the Pt amount,the optimal 0.2Pt-Cu/Si O₂ catalyst exhibited the highest catalytic performance with～99%EC conversion,over 98%selectivity to EG and 95.8%selectivity to methanol at the H₂/EC ratio as low as 60 in feed.In addition,0.2Pt-Cu/Si O₂ catalyst showed an excellent stability for150 h on stream.It is demonstrated a proper amount of Pt could promote the reducibility and dispersion of copper,enhanced the surface density of Cu⁺species,and also facilitate the H₂ adsorption and dissociation.This could be due to the strong interaction of Cu and Pt induced by formation of alloyed Pt single atoms on the Cu lattice.Meanwhile,a relatively higher amount of Pt would deteriorate the catalytic activity,which could be due to the surface coverage and aggregation of active species.A series of mesoporous silica（MPS）with different pore sizes were prepared,followed by loading copper species by using deposition precipitation（DP）method.These catalysts were with similar size of copper particles and similar surface distribution of copper species,which allowed us to discuss the effect of pore size on the performance in EC hydrogenation.It is found that the Cu/MPS catalyst with a wide pore size of 28.6 nm achieved the superior catalytic performance with>99%conversion of EC,98.8%selectivity of methanol and 97.6%selectivity of EG at the H₂/EC as low as 50（compared with the typical values of 180–300 in literatures）.Moreover,it is observed that there is a hydrogen enrichment effect of the catalysts with different pore sizes.With the increase in pore size,the concentration of H₂ inside the MPS pores decreased,but the methanol selectivity first increased and then decreased as a volcano-type trend.It could be originated from the enhanced hydrogen partial pressure,which promotes both the EC hydrogenation and the side reactions.These understandings could provide new possibilities in the design of high-performance copper-based catalysts for the hydrogenation of EC.