Alkylation of methylnaphthalene with methanol is one promising technology for producing 2,6-dimethylnaphthalene. When the alkylation is carried out under ambient pressure by using HZMS-5 catalysis, the reaction activity is very low and obvious deactivation of catalyst is observed in a short run.This paper aims at slowing down catalyst deactivation and improving reaction activity of alkylation of methylnaphthalene with methanol by taking advantage of some special properties of supercritical fluids, such as higher solubility than gases and higher diffusivity than liquids. The results indicate that the reaction under supercritical condition will achieve high reaction activity and long catalyst life. When the reaction was carried out at 460 ℃ and 7.0 MPa which is above the critical temperature and pressure of the inert reaction solvent,1,3,5-trimethylbenzene, the reaction activity increased by 3 times and catalyst life was extended by 25 to 30 times than those under ambient pressure and at the same temperature.
