摘要
本文采用＂原位＂红外光谱结合ＸＰＳ和ＸＲＤ比较了ＣｕＣｒＫ、ＣｏＣｒＫ和ＣｕＣｏＣｒＫ三种催化剂在２．５ＭＰａ，２７０℃条件下，ＣＯ_２＋Ｈ_２合成醇的中间体及其演变过程；初步探讨了Ｃｕ－Ｃｏ催化剂中活性金属的作用、氧化物的作用、以及甲醇合成机理和碳链增长机理。研究结果表明，Ｃｕ是最主要的合成甲醇活性组分，Ｃｏ能够导致ＣＯ_２离解吸附，而碳链增长则需要二者的协同作用。吸附在金属表面的甲酸盐是甲醇合成的中间体，ＣＯ插入表面其它基团是碳链增长的关键步骤，一定量的氧化物的存在对Ｃｕ基催化剂合成甲醇活性是必不可少的，能够起到稳定表面甲酸盐的作用。
Methanol synthesis from CO_2 and H_2 has been studied extensively in recent years.All kinds of means have been used for the characterization of the reaction intermediates.For almost all catalysts the same intermediates were found. The final conclusion is widely divergent,Most arguments are focused on the methanol synthesis via CO as the intermediate or not,In the past, the study on the hydrogenation of CO_2 was aimed at methanol synthesis,less attention was paid to higher alcohol synthesis. In previous paper, we reported C_1- C_6 alcohol synthesis from CO_2 and H_2 using alkalipromoted Cu-Co-Cr catalysts,In this paper,we use″in situ″FTIR,XPS and XRD to investigate the function of the active metals of catalysts,the mechanism of methanol synthesis and the growth of carbon chain.The catalysts used in this work were prepared via homogeneous citrate complexes.The″in situ″IR ce11,.constructed from stainless steel with NaCl window, can work under reaction conditions.In this study,pressure of 2.5 MPa,temperature of 270℃,and space velocity of 3600 ml/gcat·h were used.The experimetal results reveal that Cu is most suitable for CO_2hydrogenation to methanol;Co can cause the dissociative adsorption of CO2;the synthesis of C_2￣+alcohols needs a synergy between Cu and Co.The formate on the surface of metals is an intermediate for methanol synthesis, while the insertion of surface CO into surface groups is the key step of the growth of carbon chain. Oxide in the catalysts can stabilize the surface formate on metals,The active phase is Cu metal for methanol synthesis,and Cu-Co alloy for C2+alcohol synthesis.
出处
《分子催化》
EI
CAS
CSCD
1995年第1期37-43,共7页
Journal of Molecular Catalysis(China)
基金
山西省自然科学基金
