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Preparation Of HZSM-5/γ-Al2O3Composite Molecular Sieve Catalyst And Their Catalytic Performance Of Aromatization Reaction

Posted on:2014-12-25Degree:MasterType:Thesis
Country:ChinaCandidate:W LiuFull Text:PDF
GTID:2251330398483135Subject:Chemical Engineering and Technology
Abstract/Summary:PDF Full Text Request
In the chemical industry, aromatics are very basic chemical raw materials, aromatization technology has great significance, because it can transform light alkanes into aromatics including benzene、 toluene and xylene(BTX). In addition, aromatization of light hydrocarbons is also an important technology to improve the octane number of gasoline to produce clean energy.This article uses chemical precipitation method、 aluminum sol impregnation method and half synthetic method, selects aluminum nitrate、aluminum sulfate、 aluminum chloride、 boehmite and aluminum isopropoxide as the source of γ-Al2O3, prepares HZSM-5/γ-Al2O3composite catalyst. XRD, N2adsorption-desorption isotherms and other modern analytical means are used to get the information about the structure of the catalyst including the pore structure、 phase and so on. In the experiment, n-hexane is a model compound, we evaluate the aromatization catalytic performance of the catalyst on Fixed-bed reactor. We investigate the influence of different sources、 introduction amount and introduction methods of γ-Al2O3to the aromatization performance on HZSM-5, and obtain the following results:In the catalysts prepared by three methods, HZSM-5Zeolites skeleton structure is not destroyed and remains intact. Compared with the catalyst prepared by mechanical mixing, their surface areas have varying degree of increase, among them, sol impregnation method increases the sharpest, approximately65m2/g.The addition of y-A12O3will improve n-hexane conversion rate in the aromatization of the catalyst, when the amount is20%, the conversion is highest, but after it the conversion rate declines as the amount increases. Judging from the reaction temperature, when the temperature is500℃, the conversion rate of n-hexane comes to the highest, after it essentially unchanged; Judging from selectivity, the content ofy-Al2O3is higher, selectivity of p-xylene in the aromatization product is better, but the selectivity of benzene and toluene decreased.The composite zeolite catalysts HZSM-5/γ-Al2O3prepared by different methods have different n-hexane aromatization performance. To the n-hexane conversion, chemical precipitation method, the alumina sol impregnation method and half-synthetic catalysts prepared higher than the catalysts prepared by mechanical mixing method; Judging from selectivity, to the xylene selectivity:alumina sol impregnation method> chemical precipitation method> half-synthetic method> mechanical mixing method.
Keywords/Search Tags:HZSM-5, γ-Al2O3, n-hexane, aromatics, aromatizationperformance study
PDF Full Text Request
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