The Alkylation Of Benzene With Methanol Over High-silicon Nano-HZSM-5 Zeolites

Recently,methanol and benzene has a severe problem of overcapacity.Therefore,it is critical to develop some competitive application ways.The alkylation of benzene with methanol generating aromatic hydrocarbons is a prospect application.Because it can not only provide raw materials for PX（1,4-dimethyl-benzene）process,but also can supply additive for high octane number gasoline.In this dissertation,by using a fixed-bed reactor,the catalytic performances of the nano-HZSM-5 zeolite catalysts on the alkylation reaction of benzene with methanol have been investigated,and the catalysts have been characterized.Some results have been achieved as follows:（1）The product distribution of the benzene/methanol alkylation reaction is influenced by the acidity of the HZSM-5 catalysts.The reduction of strong acid can not only favor the production of toluene,xylene and trimethybenezene,but also can suppress the generation of by-products ethylbenzene,propylbenzene,ethyltoluene and C10+ aromatics.This product distribution is good for producting raw materials for PX process.The strong acid content of the middle silicon HZSM-5 catalysts（SiO₂/Al₂O₃=120）can be reduced dramatically through the water vapor treatment,and this catalyst can be used in the benzene/methanol alkylation reaction to producting raw materials for PX process.However,by using the low silicon HZSM-5 catalyst with strong acidity,the conversion of benzene and methanol was high,and the benzene/methanol alkylation reaction tended to producing C8+ aromatics,which is good for producting additive for high octane number gasoline.（2）Reaction conditions（temperature,pressure,space velocity,carrier gas）also influence the product distribution of the benzene/methanol alkylation reaction.The effect of reaction temperature is more obvious than others.The PX raw material demand the percentage of ethylbenzene accounted for C8 aromatic productis less than 20%.When reaction temperature is 550 ℃,the percentage is 13%.（3）During the long-term operation of the benzene/methanol alkylation reaction,the percentage decreased gradually,which is favorable for producing PX raw material.Meanwhile,the reation temperature influences the lifetime of the catalyst.At400℃,the lifetime of the catalyst was 1440 hours,but it changed into 240 hours at 550℃.