Insights into the confinement effect on isobutane alkylation with C4 olefin catalyzed by zeolite catalyst: A combined theoretical and experimental study

Elucidating the confinement effect harbours tremendous significance for isobutane alkylation with C4 olefin. Herein, the confinement effect over zeolite catalysts was elucidated by combining DFT calculations, experiments (using the novel Beta zeolite exposing only external surfaces (Beta-E) and conventional Beta-I zeolite with both external and internal surfaces) and multi-techniques (e.g., TGA-DTG, HRTEM, SEM and XRD). It is found that the main active sites for C4 alkylation reaction are located on internal surface rather than external surface. On the external surface, the hydride transfer reaction does not occur because the H-shared intermediate cannot be formed without the confinement effect. Moreover, the external surface has stronger selectivity for C4 olefin adsorption than isobutane, leading to enhanced oligomerization reactions. Therefore, the suitable micropore with confinement effect is essential for zeolite-catalyzed C4 alkylation. The atomic-scale insights of this work are of great referential importance to the design of highly effective zeolite catalyst.