Isobutane/Butene Alkylation Over Y Type Zeolite Catalyst

Suffering from the dual pressure of gasoline upgrading and environmental protection,environment-friendly solid acid catalyst that is prone to be regenerated is the main development tendency of alkylation catalyst.Therefore,acid zeolite catalyst is one of the most promising alternatives for traditional liquid acid catalyst although it is prone to deactivation rapidly.Under the context,HY zeolite was synthesized in the thesis to analyze influence of physiochemical properties of Y zeolite on isobutane/butene alkylation performance and mechanisms,and on this basis HY zeolite was modified.The particle diameters of synthesized HY zeolite with high relative crystallinity was 200⁴00nm.Alkylation test was conducted under the reaction condition of 75?,2.0MPa,low WHSV and high ratio of isobutane to butene,feeding as industrial raw materials.It is revealed that HY zeolite has better alkylation activity and lifespan despite regeneration property was unsatisfactory.What's worse,the slight fluctuation of ratio of isobutane to butene and WHSV would cause greatly adverse effects.The ratio of Bronsted acid concentration to that of Lewis acid of the HY zeolite was changed by adjusting the mass ratio of parent HY zeolite powder to pseudo-boehmite which functions as binder in the process of catalyst formation.A conclusion can be reached according to the alkylation results that Bronsted acid is beneficial to solid acid alkylation,however Lewis acid may constrain the cracking and hydride transfer ability of catalyst,leading to butene oligomerization.Transition metal Ni was loaded in HY zeolite by impregnating Ni?NO₃?₂,the range of calculated Ni loading was 5%,10%,15%and 20%respectively.Bronsted acid concentration and acid strength was contrarily fortified to a certain extent with Ni loading increasing.It was shown that increasing of Ni loading not only benefit to alkylation activity,stability and selectivity but also contribute to hydro-regeneration of deactivated catalyst.Cracking and oligomerization and self-alkylation coexist in the alkylation process,thus,it is speculated according to the reaction mechanism that C5^C7 species come from cracking of C12+hydrocarbons and C9^C11 origin from cracking of C16+hydrocarbons and electrophilic addition of C5^C7 to butene.Additionally,the carbon number in final oligomers was not simply the multiples of four due to?-scission of carbocation.Butene oligomerization is the leading cause to deactivation of catalyst in the alkylation so that more active and more unstable the butene isomer is,easier the oligomerization be triggered resulting in deactivation.Thus,in spite of high conversion of isobutene,the oligomerization is easier to be evoked and the selectivity to trimethylpentane?TMP?was lower so that isobutene is improper to alkylation.