Role of Metal Oxides in Cu-Based Catalysts with NaBH 4 Reduction for the Synthesis of Methanol from CO 2 /H 2

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Role of Metal Oxides in Cu‑Based Catalysts with ­NaBH4 Reduction for the Synthesis of Methanol from ­CO2/H2 Gang Zhou1,2 · Zhenglong He1,2 · Xiaosu Dong1,2 Received: 6 June 2020 / Accepted: 31 August 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020

Abstract Cu/ZnO catalyst was prepared with ­NaBH4 reduction instead of high temperature ­H2 reduction to relieve the aggregation of Cu species. With the purpose of strengthening the interaction between Cu species and ZnO, some ­Al2O3, ­Y2O3, ­ZrO2 promoters are introduced to promote the synthesis of methanol from ­CO2/H2. The introduction of metal oxide promoters improves the dispersion of Cu species, decreases the onset reduction temperature and increases the quantity of basic sites. The Cu/ZnO/ZrO2 catalyst exhibited the highest ­CH3OH yield of 0.20 g mL−1 h−1 with ­CO2 conversion of 22.8% and ­CH3OH selectivity of 56.2% at 543 K. The catalytic activity is closely correlated to the exposed Cu surface area and a synergistic effect between the Cu species and metal oxides was proposed, which promoted the catalytic conversion of ­CO2 as well as ­H2 and simultaneously facilitated the migration of atomic hydrogen from Cu sites to metal oxides through spillover.

* Xiaosu Dong [email protected] 1



College of Safety and Environmental Engineering, Shandong University of Science and Technology, Qingdao 266590, China



State Key Laboratory of Mining Disaster Prevention and Control Cofounded by Shandong Province and Ministry of Science and Technology, Shandong University of Science and Technology, Qingdao 266590, China

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Graphic Abstract

Keywords  Cu · CO2 hydrogenation · NaBH4 · Metal oxides · Methanol

1 Introduction With the rapid development in modern society, the energy crisis and environmental issues have become enormous threat that the human society faces [1]. Chemical utilization of ­CO2 to methanol has been recognized as one of the most effective and economical methods to offer a way to the green-house gas mitigation and fossil fuel substitution [2, 3]. Catalytic conversion of C ­ O2 to methanol is currently attracting a great scientific and technological concern, and the optimization of catalysts has correspondingly become a key research around the world [4]. Cu-based catalysts prepared by conventional co-precipitation method are generally applied to the synthesis of methanol from C ­ O2/H2 [5, 6]. The preparation of highly dispersed Cu-based catalysts has become a great challenge in view of the low melting point (1083 °C) and Tammann temperature (405 °C) of copper [7, 8]. An attractive technique to reduce the copper-based catalysts with ­NaBH4 has been proposed to restrain the aggregation of Cu particles in reduction process

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[9]. Compared with strong exothermic and high-temperature ­H2 reduction, ­NaBH4 reduction in liquid system is rapid, easily controlled and low reaction temperature. Our previous research has confirmed the superiority of N ­ aBH4 reduction to prepare Cu-based catalyst