(558ae) Apparent Kinetic Rate Expressions of Light Olefins Alkylation of Isobutane Using a PtSO4ZrTiSO/SiO2 Meso-Structured Catalyst

The apparent path of reactions in solid acid alkylation of ethylene and propylene with isobutane was studied at different temperatures and concentrations in a batch (slurry) reactor at a total pressure of 1.4 MPa. A regenerated PtSOxTiZr/SiO2 catalyst was used to study the reaction network in the presence of hydrogen. Different operating conditions were explored to obtain 230 experimental data points. Samples of liquid, gas and solid phases were taken at different contact times, gases and liquids were analyzed by GC-MS techniques. Solid were extracted with CS2 to remove some of not desorbed hydrocarbons. The complexity of the corresponding reaction network was overcome using an apparent heterogeneous kinetic rates model that represents the alkylation, hydrogenation, isomerization, cyclization, dimerization and dehydrogenation of adsorbed species. Coke on catalyst was characterized before and after reaction. Adsorption studies demonstrated that in this catalyst there is accessible active sites located in the wall of mesopores and in the intersection micro-macropores with different activity and selectivity. It was found that in presence of Pt, at low hydrogen partial pressure and low concentration of olefins, the mechanism of primary alkylation seems to be controlled primary by on-surface rates of reaction on these two sites because micropore do not play any role. The main reactions follow an order one respect to the olefins and isobutane of other intermediates. The in-series-parallel set of reactions produce alkylate and dimers, which desorb and C10+ species that do not desorb and form soluble and insoluble type of coke. Catalyst, with Pt incorporated, suffered 10 times lower deactivation in presence than in absence of hydrogen and 4 times lower main alkylation rates of reactions.