Study On The Deactivated Titanosilicate Zeolite As A Catalyst For Cracking Of Butene

Catalytic cracking of C₄⁼to produce C₃⁼is an important channel of high value-utilized of low-value hydrocarbon.The significant direction for developing C₄⁼catalytic cracking is to obtain high selectivity of olefin products,especially the target product C₃⁼,meanwhile to reduce non-olefin by-products,the heart of which lies in the development of efficient catalysts.This paper developed the deactivated TS-1 as an efficient catalyst for catalytic cracking of C₄⁼to produce C₃⁼,further explored the real active center of deactivated TS-1 for C₄⁼catalytic cracking and regulated its acid property.Finally,the support was introduced into the deactivated TS-1 to develop into a new and efficient catalyst for cracking of C₄⁼.Three aspects of the research results will be mentioned below:1.The physicochemical properties and intrinsic catalytic capacity of fresh titanosilicate zeolite（MTS-1）and deactivated titanosilicate zeolite（De-TS-S and De-TS-D）were compared systematically,the result showed that De-TS possessed a certain number of Br（?）nsted acid sites,the acid strength of which is distinctly weaker than Si-（OH）-Al of ZSM-5,and obtained well reaction performance of C₄⁼catalytic cracking.By pickling process which can remove selectively silicon-titanium binary mixture,potassium ion（K⁺）exchange,combined with some characterization techniques,such as UV-visible spectrum（UV-Vis）and Vacuum infrared spectrum（IR）,it was found that the active center of De-TS for C₄⁼catalytic cracking is the silanol group adjacent to the titanium hydroxyl group.2.The acid properties of the active center on De-TS are regulated by nitric acid pickling,K⁺exchange and phosphorus（P）modification,it was found that the pickling process effectively increased accessibility of acid sites on De-TS-D,thus improved markedly its catalytic performance.Both K⁺exchange and P modification also played an important role in reducing and weakening the density and intensity of the medium strong/strong acid sites on De-TS,hence decreased the generation of non-olefin by-products,especially C₃-C₅alkanes and increased the selectivity of olefin products,especially the target product C₃⁼for C₄⁼catalytic cracking.3.The influence of three kinds of supports（ɑ-Al₂O₃,SiO₂and pseudoboehmite）was investigated for C₄⁼catalytic cracking,it was found that three kinds of supports all don’t have the capability and affect the reaction performance of active component（De-TS-S）for C₄⁼catalytic cracking.Different De-TS catalysts were prepared by physical mixing and extrusion into strips of three kinds of supports and De-TS-S,and the De-TS catalyst with high efficiency for C₄⁼catalytic cracking was obtained by appropriate K⁺exchange.