Methylation Of 2-methylnaphthalene In A High-pressure Fixed-bed Flow Reactor

2,6-dimethylnaphthalene(2,6-DMN)is a precursor of 2,6-naphtalene dicarboxylic acid in the manufacture of high performance polyester resins such as polyethylene naphalate polymer(PEN).PEN is too expensive to expand its market completely because of few effective processes for 2,6-DMN commercialization.Therefore,it has become an important subject to find an efficient process for 2,6-DMN synthesis to promote application of PEN.A shape-selective zeolite catalytic process for 2,6-DMN synthesis by methylation of 2-methylnaphthalene was implemented in this paper.The methylation of 2-MN over HZSM-5(SiO₂/Al₂O₃=83)was investigated in a fixed-bed flow reactor under the pressure of 3MPa.The main influence factors of reaction performance have been taken into account.For example,temperature,WHSV and molar ratio of feed flow. The feed flow has three components,2-MN,methanol and 1,3,5-TMB。According to the conclusion,the optimized reaction conditions under 3MPa is WHSV=2h^-1,temperature360℃and molar ratio of feed flow=1:2:5.After the comparison of HZSM-5 and HM,hydrothermal treatments were employed on HM zeolite under different temperatures.Hydrothermal treatment is an important modified way for catalysts,can better the catalytic performance.Campared the reaction capability over HM with different hydrothermal treatment temperature,500℃was the best.Acid leaching was employed over the HM zeolite which had been hydrothermal treated, increased the percents of meso-pore structure.Consolidate with the effect of 1,2,4-TMB as solvent,we better the conversion of 2-MN and selectivity of 2,6-DMN.The reaction implemented in the air of H2,the catalyst showed a slower deactivation velocity,kept the stability of reaction.After 5h reaction,the conversion of 2-MN was 27.1%,the selectivity of 2,6-DMN was 48.8%and the yield of 2,6-DMN was as high as 5.1%.