摘要
采用固体离子交换法制备了Cu(Ⅰ ) /沸石双功能羰基化催化剂 ,以CO ,吡啶和NH3 为探针分子 ,用原位FT IR和TPD方法研究了活性中心的性质和作用机理 .结果表明 ,在Cu(Ⅰ ) /Hβ沸石双功能催化剂中存在固体酸和金属羰基两类活性中心 ,其中B酸中心的数量可以用Cu+ 交换来进行调变和控制 ,而金属羰基活性中心则分布在两类不同的位置上 ,分别构成Cu+ 与Cu+ (CO)以及Cu+ (CO)与Cu+ (CO) 2 两个可逆的动态平衡 ,平衡移动时伴随着CO的吸收和释放 .本文的研究结果支持两类活性中心协同催化的机理 ,即固体酸中心使醇质子化形成正碳离子后 ,金属羰基活性中心协同催化 。
The Cu(Ⅰ)/Hβ catalysts for carbonylation of alcohol and CO were prepared carefully by solid state ion exchange technique. The relative amount of acid sites to metal carbonyl active sites in the catalysts can be adjusted by changing the ratio of Hβ to CuCl added. When there is no CuCl added, the 3?610 cm -1 peak of B acid predominates. With increasing the added amount of CuCl, the intensity of the 3?610 cm -1 peak decreases. When the ratio of CuCl reaches 4 7%, the peak at 3?610 cm -1 disappears completely and there are no B acid centers under these conditions. It is demonstrated that there are two kinds of Cu(Ⅰ) sites. By heating and evacuating, Cu +(CO) at S Ⅰ sites and Cu +(CO) 2 at S Ⅱ sites can be reversibly transformed to Cu + and Cu +(CO), respectively. However, Cu +(CO) at S Ⅱ sites is reluctant to evacuation and heating. The two equilibriums at S Ⅰ and S Ⅱ sites are: S Ⅰ: Cu ++COCu +(CO); S Ⅱ: Cu +(CO)+COCu +(CO) 2. These equilibriums can be moved reversibly by changing the temperature and pressure. At the same time, adsorption or release of CO is accompanied, from which the CO for carbonylation reaction is originated. The starting alcohol is protonized at acid sites and transformed into carbonium ions, from which the carboxylic acids are synthesized or their esters are finally produced by cooperative catalysis of the adjacent bifunctional catalytic sites.
出处
《催化学报》
SCIE
CAS
CSCD
北大核心
2000年第2期113-116,共4页
基金
国家自然科学基金!(29676025)
广东省自然科学基金!(950823)
汕头大学工业催化学科"211工程"项目资助
关键词
氯化亚铜
HΒ沸石
双功能催化剂
羰基化反应
cuprous chloride, Hβ zeolite, carbonylation, bifunctional catalyst, carbon monoxide, adsorption
