摘要
以酸化粘土矿物蒙脱土为载体 ,采用浸渍蒸发法制备了蒙脱土负载的ZnCl2 固体酸催化剂 ,并以苯与苄基氯的苄基化反应评价了其催化性能 .考察了催化剂制备条件、苄基化反应条件和催化剂的再生性能 ,比较了负载前后催化剂的活性 .利用XRD ,TG DTA和FT IR等技术对催化剂的结构和表面酸性进行了表征 .结果表明 ,较适宜的催化剂制备条件为 :原矿土经 30 %硫酸酸化处理 4h ,ZnCl2 负载量为 2 0mmol/ g,催化剂于 2 5 0～ 35 0℃焙烧活化 .过量的苯和较高的反应温度有利于提高苄基氯的转化率 ,催化剂与苄基氯的用量比为 1 5 g/mol.产物二苯甲烷的收率最高可达 83 5 %.表征分析表明 ,蒙脱土酸化处理后层状结构遭到破坏 ,比表面积增大 ,负载和活化处理使ZnCl2 与蒙脱土载体的羟基之间发生了化学键合 ,提高了蒙脱土表面的总酸量 ,从而提高了催化剂的催化活性 .
Supported Lewis reagents have been extensively explored and used as solid acid catalysts in green organic synthesis. In this paper, the clay-supported zinc chloride catalyst was prepared by the impregnation-evaporation method using acid-treated clay minerals (montmorillonite) as the support. The effects of catalyst preparation conditions and reaction parameters on the performance of the catalyst for the benzene benzylation with benzyl chloride were investigated. The structure and surface acidity of the clay-supported ZnCl 2 catalyst were characterized by XRD, nitrogen adsorption, TG-DTA and FT-IR techniques. The results reveal that the optimal H 2SO 4 concentration and time for clay treatment is 30% and 4 h, respectively. The suitable ZnCl 2 loading, calcination temperature, catalyst/benzyl chloride ratio and reaction time are 2 mmol/g, 250～350 ℃, 1.5 g/mol and 4 h, respectively. Under the optimal conditions, the highest diphenylmethane yield of 83.5% over the clay-supported ZnCl 2 catalyst is obtained. Compared with the acid-treated clay and pure ZnCl 2, the clay-supported ZnCl 2 catalyst shows the highest catalytic activity. The clay-supported ZnCl 2 catalyst can be regenerated with stable benzylation activity by repeated thermal activation. The XRD results indicate that after acid treatment the layer structure of the clay is destroyed and the catalyst surface area is increased. Calcination activation results in chemical interaction between the clay support and ZnCl 2. The TG-DTA analysis shows that heating at 480～574 ℃ results in the decomposition and removal of active species from the catalyst surface. The pyridine-adsorbed FT-IR spectra reveal that there is a remarkable increase in total number of acid sites on ZnCl 2/montmorillonite catalyst surface, thus, the catalyst performance is strengthened.
出处
《催化学报》
SCIE
EI
CAS
CSCD
北大核心
2003年第8期579-584,共6页
基金
国家自然科学基金 (2 970 6 0 11)
浙江省自然科学基金资助项目 (2 0 10 5 7/2 990 0 5 )
关键词
粘土
蒙脱土
氯化锌
固体酸催化剂
苯
苄基氯
烷基化
二苯甲烷
clay, montmorillonite, zinc chloride, solid acid catalyst, benzene, benzyl chloride, benzylation, diphenylmethane
