Synthesis Of ZSM-5/Cordierite Mononlith Catalysts And Study On Their Catalytic Performance Of Toluene Alkylation With Methanol

P-xylene（PX）is an important intermediate in the industrial production process.Due to the increasing demand of PX,the extraction and separation of PX from the naphtha and pyrolysis gasoline directly has been unable to meet the demand.As the third technology of producing PX,more and more attention has been paid to the process of methanol alkylation of toluene with methanol.But the application and research of this technology is limited because of the catalyst powder with high pressure drop and deposition in the alkylation reaction.In the recent decades,with the continuous research of the monolith catalyst technology,the advantages of the monolith catalyst which brings new hope for the alkylation and remedies the defects of the powder catalyst.How to combine the alkylation with monolith catalyst effectively?Aiming at these problems,this paper explores the application method which the monolith catalyst used in the alkylation reaction of toluene with methanol,with the perspective of catalyst preparation and characterization,activity evaluation and resistance to coke formation.The main research contents and results are as follows:In-situ hydrothermal synthesis method is used to synthesize ZSM-5/cordierite monolithic catalyst,and the effects of n（Si O₂）/n（Al₂O₃）ratio,amount of tetra-propyl ammonium hydroxide（TPAOH）,crystallization condition and aging temperature on the deposition of ZSM-5 cordierite monolithic catalyst were investigated,The results showed that the loading amount of ZSM-5increases first and then decreases with the increase of n（Si O₂）/n（Al₂O₃）ratio,and the ZSM-5particle becomes uniform and compact;when template content increase,the load amount also increases first and then decreased,but the particle size becomes smaller decreasing from 4.08μm to 0.247μm.When molar ratio of TPAOH and Si O₂ is ranged from 0.169 to 0.242,the ZSM-5loading changed a little;with the increase of the crystallization temperature or crystallization time,the deposition of ZSM-5 on the surface of the supporter increases as well,but the particle size becomes smaller and loading uniform gets unstable;the increase of aging time does not change the load amount,and makes the particle small and compact.By regulating n（Si O₂）/n（Al₂O₃）ratio,amount of tetra-propyl ammonium hydroxide（TPAOH）,crystallization condition and aging temperature,the ZSM-5 loading can be controlled between 6%and 37%,and the diameter of crystal particle size is ranged from 250nm to 5μm.To understanding the performance of ZSM-5/Cordierite Monolithic Catalyst synthetized by in-situ hydrothermal synthesis method,In this paper,monolithic catalyst which has the load from20%to 25%,the particle size from 1μm to 4μm and the uniform load support surface is applied to toluene alkylation with methanol.Consider Toluene conversion rate and selectivity of para-xylene as the evaluation index in the reaction,and under the condition that toluene/methanol molar ratio is 2:1,the liquid space velocity is 2h^-1,the carrier gas flow（H₂）is40ml/min and the reaction temperature is 480℃,the catalytic performances of the purchased ZSM-5 catalyst,in-situ hydrothermal synthesis catalyst and monolithic catalyst are investigated.By the means of TG,explore the effect of particle catalyst and monolithic catalyst on the coke formation.The results show that under the unmodified conditions the three kinds of catalyst can get toluene conversion between the 22%and 29%.monolithic sample which has the highest catalyst selectivity of para-xylene can reach 50%,and the synthesis particle one gets 36%while the purchased one has only 30%.After modified by Mg,monolithic catalyst has a higher selectivity.And the selectivity reaches 68.54%,while the conversion rate of toluene is 18.76%.Combined with the analysis of TG,the coking type of monolithic catalyst is graphitic carbon.as the concentration of modified solution increasing,the coking reduces.The loss decreases from7.38%to 4.63%.Monolithic catalyst synthetized by in-situ hydrothermal synthesis method has not only higher PX selectivity,but also better resistance to carbon deposition.