Study On Aromatization And Catalyst Of Methanol-Refinery C₅ Fraction Mixed Raw Material

Aromatization of methanol-C₅ fraction can effectively improve the current situation of overcapacity,low utilization rate and low economic benefit of methanol and C₅ fraction,and produce aromatics with high economic value.In this paper,the effects of reaction conditions such as temperature and raw material ratio on the aromatization of methanol and C₅ fraction were explored,and the type of zeolite and the optimal silicon aluminum ratio were determined.Then the zeolite was treated by acid treatment and metal oxide modification treatment,and its physicochemical properties,aromatization activity and carbon deposition were investigated to obtain the best modified catalyst.Through the research,the following conclusions are obtained:（1）In HY、Hβ、HZSM-5 and HSAPO-11 zeolites investigated,HZSM-5 zeolite has good aromatization performance.The conversion of total C₅ fraction is 33.32%,and the content of aromatics in liquid phase is 19.35%.This is mainly related to the pore structure,pore size and acid center of zeolite.（2）When the reaction temperature is too low,the raw materials can not be fully activated to meet the activation energy required for the reaction,and the conversion is low;When the reaction temperature is too high,the reaction is violent,the side reactions increase,and the catalyst deactivation is accelerated.Under comprehensive consideration,the reaction temperature of 450℃is better.The aromatization reaction results are different with different methanol/C₅ distillation partition ratio.With the increase of the proportion of C₅ fraction in the mixed raw materials,the yield of aromatics increased first and then decreased.The appropriate raw material ratio m（methanol）∶m（C₅ fraction）is 1∶10.（3）Silicon aluminum ratio has a significant effect on the reaction performance.The zeolite with low silicon aluminum ratio has large acid content,easy carbon deposition and deactivation,and weak stability;Compared with zeolite,high silicon aluminum ratio has better aromatization catalytic performance and better stability.The zeolite with silicon aluminum ratio of 85 has the best performance,the conversion of total C₅ fraction is 35.99%,and the content of aromatics in liquid phase is 20.11%.（4）Due to the existence of some amorphous silicon aluminum in the pores of the zeolite,which affects the performance of the zeolite,nitric acid is used to treat it.With the increase of the concentration of nitric acid used,the performance of the catalyst increased first and then decreased.Among them,the catalyst treated with 1.0 mol/L nitric acid showed good catalytic performance,the conversion of total C₅ fraction was60.67%,and the content of aromatics in liquid phase was 43.75%.After long-term operation for 36 h,it was found that the zeolite treated with nitric acid had better stability.（5）13 kinds of metal oxides were selected to modify the zeolite and divided into four groups according to the similarity of their chemical properties.Among them,the catalysts modified by Ba,W,Ni and Zn showed better reaction performance,and the zeolite modified by Zn and Ni had better catalytic performance.The study of Zn modified content shows that the catalyst modified with 1.0 wt%Zn has good catalytic performance.The conversion of total C₅ fraction is 74.53%and the content of aromatics in liquid phase is 56.03%.Among the different Ni loading,the reaction evaluation results of 1.0 wt%Ni catalyst are better,the total C₅ fraction conversion is64.45%,and the aromatics content in the liquid phase is 42.37%.When the mass space velocity was 6.4 h^-1 and the long-term operation was 36 h,it was found that the HZSM-5 zeolite obtained by the treatment of 1.0 wt%Zn supported nitric acid was the best aromatization catalyst and had the best stability.