The effective and stable Cu-C@SiO_2 catalyst for the syntheses of methanol and ethylene glycol via selective hydrogenation of ethylene carbonate

摘要

The co-production of ethylene glycol and methanol via ethylene carbonate hydrogenation derived from CO2 has attracted great concerns because of the promising chemical utilization of CO2 in large-scale. Copper-based catalysts are widely concerned in hydrogenation of ester due to the high catalytic efficiency and low cost, but the stability of copper-based catalyst is poor and needs to be further improved. In this study, the modification Cu-C@SiO2-R catalyst with graphite oxide was prepared by using Cu-3(BTC)(2) as the precursor and ammonia evaporation method, and was applied in ethylene carbonate hydrogenation to synthesis ethylene glycol and methanol. Furthermore, the catalysts were characterized in detail. The results showed that the Cu-C@SiO2-R catalyst was modified with graphite oxide, the average size of Cu particles was 2.9 nm and Cu particles had good dispersion. In addition, both Cu-C@SiO2-R and Cu@SiO2-R catalysts had similar ratio of Cu+/(Cu-0+Cu+). In a batch reactor, under 453 K, 5 MPa, 4 h, the catalytic efficiency was 80.0% EC conversion 92.2% EG and 70.8% MeOH selectivity showing excellent catalytic performance capability of Cu-C@SiO2-R catalyst. In long-term experiment, the Cu-C@SiO2-R catalyst showed excellent stability after using for 264 h. The activity was 0.63 gEC g(cat)(-1) h(-1), and 100.0% EC conversion 99.9% EG and 85.8% MeOH selectivity could be achieved in a fixed bed. After the long-term experiment, the Cu+ /(Cu++Cu-0) ratio in Cu-C@SiO2-R catalyst kept at around 0.48. In contrast, the Cu+/(Cu++Cu-0) ratio in Cu@SiO2-R catalyst decreased sharply from 0.48 to 0.38. The stability of the structure and the balance of valence of Cu were considered to be responsible to the stability of Cu-C@SiO2-R catalyst, because the graphite oxide not only kept the Cu+/(Cu-0+Cu+) ratio stability, but also restrained the aggregation of Cu particles and loss of copper. This work provides an in-depth understanding of the stabilization mechanism of Cu and can be a reference for the industrial application of ethylene carbonate hydrogenation. (C) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.