STUDY ON PREPARATION AND CATALYTIC PERFORMANCE OF LA-MCM-41 MOLECULAR SIEVE UNDER ULTRASONIC-MICROWAVE ENVIRONMENT

摘要

The doping of transition metals or rare earth elements can effectively increase the hydrophobi- city of zeolite and optimise the catalytic performance. MCM-41 is an ideal molecular sieve because of its ordered mesoporous framework, uniform pore size and excellent pore environment. To promote the loading of a La heteroatom on an MCM-41 channel or surface, La-MCM-41 mesoporous material w ith different Si/La ratios were synthesised in laboratory under ultrasonic-microwave environment. In the experiment, tetraethyl orthosilicate was used as a silicon source, cetyltrime- thylammonium bromide as a template and a lanthanum nitrate solution as a source of La ions. XRD and TEM were used to characterise the molecular sieve. The results showed that the molecular sieve had a regular framework structure environment but the products could contain organic compounds produced by side reactions. La ions would randomly enter the framework of the molecular sieve, and form a stable La-MCM-41 molecular sieve catalyst. In addition, taking the synthesis of ketal from propylene glycol and cyclohexanone as an example, the catalytic performance of La-MCM-41 zeolite was analyzed. The optimal conditions included concentration of catalyst, reaction time, reaction temperature and the water-carrying agent were evaluated. The results showed that the molecular sieve has catalytic and repeatability performance for the synthesis of ketal. In conclusion, La-M CM- 41 molecular sieve prepared by ultrasonic- microwave is worthy of popularization and application in industrial environment.