Oligomerization of ethene on ZSM-5 catalyst

Oligomerization of ethene over ZSM5 catalyst was investigated on a fixed bed micro-reactor. The catalytic performance of HZSM-5 zeolite was markedly affected by the reaction conditions. Moderate reaction conditions can suppress secondary reactions and enhance the production of propene and butene. A slow deactivation accompanied by changes in the product distributions was observed along with the reaction time, which can be attributed to the coke deposition in the HZSM-5 pores during reaction. The conversion of ethene decreased gradually from initial 96.2% to 41.1% after 6h reaction, whereas the selectivity to propene and butene was increased during this period. Hydrogen transfer reaction was restrained at high space velocity, resulting in an increase of the selectivity to olefins. On the basis of the product distributions under different ethene conversions, a reaction pathway for ethene oligomerization was proposed. With the increase of the reaction temperature, ethene conversion increased first, reached a maximum value of 88.0% at 500℃, and then dropped; paraffins are dominated in the main product LPG. Raising the pressure of reaction system could promote the oligomerization of ethene, which was beneficial to ethene conversion, but unfavorable for yielding propene or butene.