Preparation of Hierarchically Trimodal-Porous ZSM-5 Composites through Steam-assisted Conversion of Macroporous Aluminosilica Gel with Two Different Quaternary Ammonium Hydroxides  

作　　者：Zhao Tianbo Wang Jia Xu Xin Wang Guijie 

机构地区：[1]School of Chemistry,Beijing Institute of Technology [2]China Coal Information Institute

出　　处：《China Petroleum Processing & Petrochemical Technology》2015年第1期48-58,共11页中国炼油与石油化工（英文版）

基　　金：the financial support by the National Natural Science Foundation of China (No. 20973022 and No. 11472048)

摘　　要：This article presents a detailed structural study of a new spherical Mg Cl2-supported Ti Cl4 Ziegler-Natta catalyst for isotactic propylene polymerization, and researches on the relationship between catalyst structure and polymer properties. The spherical support with the chemical composition of CH3CH2 OMg OCH(CH2Cl)2 has been synthesized from a new dispersion system and is used as the supporting material to prepare Ziegler-Natta catalyst. The XRD analysis indicates that the catalyst is fully activated with δ-Mg Cl2 in the active catalyst. The far-IR spectrometric results confirm again the presence of δ-Mg Cl2 in the active catalyst. Textural property of the active catalyst exhibits high surface area coupled with high porosity. The high activity in propylene polymerization is mainly ascribed to the full activation and the porous structure of the catalyst. Scanning electron microscopy/energy dispersive spectrometer mapping results indicate a uniform titanium distribution throughout the catalyst particles. Particle size analysis shows that the catalyst has a narrow particle size distribution. The perfect spherical shape, uniform titanium distribution and narrow particle size distribution of the catalyst confirm the advantage of polymer particles production with less fines. The solid state 13 C NMR and mid-IR spectroscopic analyses indicate that there exists strong complexation between diisobutyl phthalate and Mg Cl2, which leads to the high isotacticity of polypropylene.The hierarchically structured ZSM-5 composites （HZC） with trimodal pores （macropores/mesopores/micropore）were synthesized by transforming the skeleton of the macroporous aluminosilica gel into ZSM-5 pure phase crystalsthrough steam-assisted conversion method. The monolithic aluminosilica gel was used not only as the silicon and aluminumsources, but also as a structural support. The synthesis parameters, such as the composition of the precursor solution, the Si/Al feed ratios of the support gel, the time for impregnation of the support with the synthesis mixture and the structure-directingagents （SDAs） with different crystallization temperatures, were investigated. The textural properties of the resultingsamples were characterized by means of the Fourier transform infrared （FT-IR） spectroscopy, X-ray powder diffractometry（XRD）, scanning electron microscopy （SEM） and N2 adsorption-desorption isotherms. The experimental results indicatedthat the HZC could be manufactured with quaternary ammonium hydroxide as SDA without seeding and additional sourcesof silicon or aluminum, the Si/Al feed ratio of the support and pretreatment time had a significant effect on the morphologyof the products using tetrapropyl ammonium hydroxide （TPAOH） as SDA. Furthermore, the textural properties varied fromthe macroporous aluminosilica gel when different SDAs at different crystallization temperatures were also discussed.

关 键 词：ZSM-5 composites hierarchically trimodal-porous steam-assisted CONVERSION method MACROPOROUS aluminosilicagel quaternary ammonium hydroxide 

分 类 号：TQ426[化学工程] TQ325.14