镧改性β分子筛上的异丁烯水合醚化复合反应  

Complex Reactions of Hydration and Etherification of Isobutene over La-Modified β Molecular Sieve

作　　者：杨伯伦[1] 路士庆[1] 吴江[1] 王华军[1] 

机构地区：[1]西安交通大学化学工程系动力工程多相流国家重点实验室,陕西西安710049

出　　处：《催化学报》2007年第1期73-79,共7页

基　　金：国家自然科学基金重点资助项目(20436040)

摘　　要：采用离子交换法，分别在微波加热和常规加热的条件下，制备了La／β分子筛催化剂，并采用红外光谱、扫描电子显微镜、X射线衍射与能量色散谱进行了表征．考察了不同加热条件下所得的改性β分子筛上La的负载量，La在分子筛表面的分散度以及催化剂对乙醇-水-异丁烯体系水合醚化复合反应的催化性能，并分析了反应机理．与传统加热法相比，微波加热法制得的催化剂上La离子的一次交换度和负载量高，且交换时间大大缩短．La离子的引入使得β分子筛上乙醇与水的转化率提高了10％～20％，而且随着La负载量的增加，催化剂的活性呈明显的上升趋势．反应机理的分析表明，上述水合醚化反应主要发生在β分子筛的表面上，B酸位桥接Al-OH-Si酸性点可能是主要的反应活性点，并且反应过程经历碳正离子中间体的形成步骤．The La/β molecular sieve catalyst was prepared by the ion-exchange method using microwave heating and conventional heating. The catalyst was characterized by infrared spectroscopy, scanning electron microscopy, X-ray diffraction, and energy dispersive spectroscopy. Hydration and etherification reactions of isobutylene with an ethanol-water mixture to produce a fuel mixture were carried out over these catalysts. The effects of the preparation method and La loading on the catalytic performance of La/β catalysts were studied, and the reaction mechanism was proposed. The results indicated that the ion-exchange degree and La loading of the La/β catalyst prepared by the microwave heating method were higher than the one prepared by the conventional heating method, and the ion-exchange time was shorter. The conversion of water and ethanol over the modified La/β molecular sieve catalyst was increased by 10 % -20 % compared with the unmodified Hβ molecular sieve, and the catalyst activity increased with the La loading. The hydration and the etherification mainly occurred on the external surface of the β molecular sieve catalyst. Bridging Al-OH-Si acid sites, i.e. , Broensted acid sites, were the main active sites, and the carbonium ion was formed during the reaction.

关 键 词：Β分子筛 镧 异丁烯 乙醇 水 水合醚化 微波加热 

分 类 号：O643.32[理学—物理化学]