Effect of dealumination of zeolite catalysts on methylation of 2-methylnaphthalene in a high-pressure fixed-bed flow reactor

摘要

Catalytic performances of various dealuminated zeolite catalysts such as H-mordenite(HM),H-beta(HP),USY and HMCM-22,for methylation of 2-methylnaphthalene(2-MN)were investigated in a high-pressure fixed-bed flow reactor.Methanol and 1,2,4-trimethyl-benzene(TMB)were used as solvents and methylating agents.Dealumination of HM substantially improved 2-MN conversion,2,6-dimethylnaphthalene(2,6-DMN)selectivity and stability.HM after the steam treatment at 550 deg C followed by acid leaching exhibited a high and a steady conversion of 40% with the very high 2,6-/2,7-DMN ratio of 2.4 for 5 h of time on stream.In contrast,the untreated HM showed a severe deactivation,with a conversion of 8.4% and the 2,6-/2,7-DMN ratio of 1.4.On the other hand,Hbeta showed very high and nearly steady conversion,but with reduced selectivity for 2,6-DMN;USY showed initially high conversion but the value decreased and there was no selectivity for 2,6-DMN;and HMCM-22 showed low but steady conversion with low selectivity for 2,6-DMN for 5 h of time on stream.No promotion effect by dealumination on the conversion,stability,or selectivity was observed over Hbeta,USY or HMCM-22.These distinguishing characteristics of these catalysts are discussed based on the differences in their porosity and acidity.