摘要
本文采用“原位”红外光谱与脉冲快速应答技术相结合对Cu/ZnO/Al_2O_3(K)、2.0 MPa、280℃条件下,CO+H_2合成低碳醇反应中间物及其衍变动态过程进行了研究。实验结果表明,在该体系中,反应中间物有表面酰基物种:(1715 cm^(-1))、(1670 cm^(-1))、(1730 cm^(-1))。表面羧酸盐物种:HCOOM(1590与1382cm^(-1))、CH_3COOM(1563与1434 cm^(-1))。这些中间物的衍变动态表明:是由转化而成,表面酰基物种是C_2+OH生成的主要中间体,低碳醇合成反应中碳链的增长是通过及与吸附的CO和H_2作用进一步转化为CH_3COM等更高级的实现的。而表面羧酸盐在此条件下不易形成C_2^+的增链物种。
The synthesis of lower alcohols from CO + H2 is one of the most important subjects in C1 chemistry. At present, there have been many hypotheses about the mechanism of this synthesis based on macro or partly micro experimental results. For the micro experimental proof of the growth of carbon chain in this reaction, there has been few reports up to now. In this paper, by means of the 'in situ' IR spectroscopy fast response technique for a pulse of gas, the formation of the intermediates and the process of their dynamic change on the catalyst surface during the synthesis of lower alcohols from CO+H2have been studied.
The catalyst of Cu/Zn/Al2O3 (K) used in this work was made by coprecipitation method. The 'in situ' IR cell, constructed from stainless steel with NaCl windows, can work under the reaction temperature and pressure. In these experiments, the pressure of 2. 0 MPa, the temperature of 280 ℃and the space velocity of 3000 ml/h were used.
When the reaction gas of CO+H2flowed through the 'in situ' IR cell, the intermediates formed
and adsorbed on the catalyst surface, such as, HCOM(1715 cm-1), HC-O (1670 cm-1),
HCOOM (1590, 1382 cm-1), CH3COM (1730 cm-1) and CH3COOM (1563, 1434 cm-1) were observed. When CO was preadsorbed on the catalyst surface and a pulse of H2 was introduced into the 'in situ' IR cell, the process of dynamic change of the intermediates was observed. It was found that
HCOM is the initial intermediate and can be transformed into HC-O Moreover, both HCOM
and HC-O were further transformed into CH3COM by acting with adsorbed CO and H. At the
same time, it was also found that HCOOM formed on the catalyst surface did not show any change during the whole measurement. Thus, it may be concluded that under our experimental conditions, HCOOM and CH3COOM are not the main intermediates in this synthesis. So it is postulated that the
growth of carbon chain is realized by the reaction of HCOM and HC-O with the adsorbed CO
and H and the subsequent transformation into C2 or C2+ .
出处
《分子催化》
EI
CAS
CSCD
1992年第1期38-43,共6页
Journal of Molecular Catalysis(China)
关键词
表面
中间物
催化剂
Lower alcohols, Surface acyl species, Synthetic gas
