Study About Direct Amination Reaction Of Isobutylene To Tert-butylamine On HZSM-5

As an important organic chemical raw material and pharmaceutical intermediates, there are many methods to prepare tert-butylamine such as hydrolysis of tert-butylurea, hydrolysis of N-tert-butylacetamide or N-tert-butylbenzamide, direct amination of haloalkane, direct amination of tert-butanol, direct amination of methyl tert butyl ether, direct amination of isobutylene, etc.. Therein, the direct amination of isobutylene to prepare tert-butylamine has obtained many attentions, because of high efficient atom economy and environmental friendly process. Zeolite molecular sieve is widely used as catalysts in many reactions, because of the acid nature and ordered microporous structure of zeolites. American Air Product and Chemicals Inc. and-German BASF both found that zeolites (ZSM-5and BEA, respectively) had good catalytic performance in direct amination of isobutylene.To father study the effect of zeolites and reaction conditions on isobutylene conversion, the properties of zeolites, such as acidity, channel structure, mental modification and the reaction conditions, such as temperature, pressure, ammonia/isobutylene molar ratio of feedstock and WHSV were studied by taken HZSM-5zeolite as catalysts. Meanwhile, the catalyst was characterized by XRD, NH3-TPD and N2-adsorption and desorption. The following results were obtained:1. For direct amination reaction of isobutylene, HZSM-5with high Si/Al ratio zeolites has better performance than that with low Si/Al ratio. HZSM-5zeolites with large or few amount of acid site were not beneficial to the reaction. The HZSM-5zeolite with appropriate strength and amount of acid sites has good catalytic performance.2. The hierarchical zeolites with high surface area barely showed better catalytic performance. It was demonstrated that the step of molecular diffusion was not the reaction control step. The conculsion that the HZSM-5zeolite with appropriate strength and amount of acid sites has good catalytic performance was confirmed again.3. Compared with untreated zeolites, metal-treated HZSM-5(Li, Zn, La, Ce) did not show better catalytic performance in the direct amination of isobutylene. Thus, the further studies are required.4. Through standard thermodynamic calculations, it was found that low temperature, high pressure and high ammonia/isobutylene molar ratio are favorable to the direct amination of isobutylene, and this conclusion was confirmed by experimental results.5. The conversion of isobutylene and selectivity of tert-butylamine can be up to5.0%and100%, respectively, when the amination conditions were temperature260℃, pressure7.5MPa, ammonia/isobutylene molar ratio1.5and isobutylene weight hourly space velocity2.8h"1. And the catalyst was still active after14days.