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?.