Катализаторы на основе высокомодульного цеолита типа MOR

Abstract

This paper is dedicated to synthesis of MOR-type zeolite specimens in Na- and H-form of high phase purity and having crystallinity degree of nearly 100% with molar ratio of SiO2/Al2O3 = 15-24 in deep-decationated form, and investigation of their properties. To obtain chemically homogeneous silica-alumina hydrogel, mixing of crystal-forming components was implemented with reaction mass being continuously stirred. The stirring was still continuing during the process of crystallization. Crystallization was conducted at a temperature of 150-160 ºС. The compositions of oligomers were quantified by high-performance liquid chromatography. The conversion of the initial olefin, its composition and amount of its isomers, the amount of low molecular weight oligomers (with a molecular weight less than the dimers) as well as the number of dimer were measured by gas-liquid chromatography. The dimer fraction was extracted by reaction mixture distillation under reduced pressure and analyzed by nuclear magnetic resonance (NMR) ¹H, ¹³C, IR- and mass spectrometry methods. By method of temperature-programmed ammonia desorption it was found that with zeolite module increasing there was an increase in strength of zeolite acid sites. For evaluation of catalytic properties of the derived H-form of MOR-type zeolite specimens with various modules, model reaction of a-methylstyrene dimerization was used. It was found that with zeolite module increasing there was an increase in cyclic dimers formation selectivity from 20 to 52%. The α-methylstyrene conversions on MOR-type zeolite specimens were investigated at a temperature of 80 ºС with a 10% catalyst in nitrogen atmosphere. The catalyst was calcinated prior to the reaction at a temperature of 300 ºС during 2-3 hours with rare gas current in the reaction flask. Implementation of the method developed makes it possible to expand the raw materials base, simplify the synthesis and reduce the cost of powdery mordenite type zeolite.