Acta Phys. -Chim. Sin. ›› 2021, Vol. 37 ›› Issue (5): 2009101.doi: 10.3866/PKU.WHXB202009101

Special Issue: CO2 Reduction

• ARTICLE • Previous Articles     Next Articles

Understanding the Role of Cu/ZnO Interaction in CO2 Hydrogenation to Methanol

Congming Li1,*(), Kuo Chen1, Xiaoyue Wang1, Nan Xue2, Hengquan Yang2,*()   

  1. 1 Key Laboratory of Coal Science and Technology, Ministry of Education and Shanxi Province, Taiyuan University of Technology, Taiyuan 030024, China
    2 School of Chemistry and Chemical Engineering, Shanxi University, Taiyuan 030006, China
  • Received:2020-09-30 Accepted:2020-10-30 Published:2020-11-06
  • Contact: Congming Li,Hengquan Yang E-mail:licongming0523@163.com;hqyang@sxu.edu.cn
  • About author:Email:hqyang@sxu.edu.cn (H.Y.)
    Email: licongming0523@163.com (C.L.)
  • Supported by:
    the National Natural Science Foundation of China(21676176);Major Scientific and Technological Project of Shanxi Province of China(20201102005);the Foundation of State Key Laboratory of Coal Conversion(J20-21-610);the Fund of State Key Laboratory of Catalysis in DICP, China(N-15-05)

Abstract:

Using renewable green hydrogen and carbon dioxide (CO2) to produce methanol is one of the fundamental ways to reduce CO2 emissions in the future, and research and development related to catalysts for efficient and stable methanol synthesis is one of the key factors in determining the entire synthesis process. Metal nanoparticles stabilized on a support are frequently employed to catalyze the methanol synthesis reaction. Metal-support interactions (MSIs) in these supported catalysts can play a significant role in catalysis. Tuning the MSI is an effective strategy to modulate the activity, selectivity, and stability of heterogeneous catalysts. Numerous studies have been conducted on this topic; however, a systematic understanding of the role of various strengths of MSI is lacking. Herein, three Cu/ZnO-SiO2 catalysts with different strengths of MSI, namely, normal precipitation Cu/ZnO-SiO2 (Nor-CZS), co-precipitation Cu/ZnO-SiO2 (Co-CZS), and reverse precipitation Cu/ZnO-SiO2 (Re-CZS), were successfully prepared to determine the role of such interactions in the hydrogenation of CO2 to methanol. The results of temperature-programmed reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS) characterization illustrated that the MSI of the catalysts was considerably affected by the precipitation sequence. Fourier transform infrared reflection spectroscopy (FT-IR) results indicated that the Cu species existed as CuO in all cases and that copper phyllosilicate was absent (except for strong Cu-SiO2 interaction). Transmission electron microscopy (TEM), X-ray diffraction (XRD), and N2O chemical titration results revealed that strong interactions between the Cu and Zn species would promote the dispersion of Cu species, thereby leading to a higher CO2 conversion rate and improved catalytic stability. As expected, the Re-CZS catalyst exhibited the highest activity with 12.4% CO2 conversion, followed by the Co-CZS catalyst (12.1%), and the Nor-CZS catalyst (9.8%). After the same reaction time, the normalized CO2 conversion of the three catalysts decreased in the following order: Re-CZS (75%) > Co-CZS (70%) > Nor-CZS (65%). Notably, the methanol selectivity of the Re-CZS catalyst was found to level off after a prolonged period, in contrast to that of Co-CZS and Nor-CZS. Investigation of the structural evolution of the catalyst with time on stream revealed that the high methanol selectivity of the catalyst was caused by the reconstruction of the catalyst, which was induced by the strong MSI between the Cu and Zn species, and the migration of ZnO onto Cu species, which caused an enlargement of the Cu/ZnO interface. This work offers an alternative strategy for the rational and optimized design of efficient catalysts.

Key words: Cu/ZnO-SiO2 catalysts, Metal-support interaction, CO2 hydrogenation, Methanol

MSC2000: 

  • O643