Al-Modified Dendritic Fibrous Nanosilica Catalyst: Accurately Regulated Acidity for Tunable Product Distribution in 1-Decene Oligomerization

Olefin oligomerization plays a pivotal role in producing value-added chemicals and functional materials, driving the development of the chemical industry. Acid catalysts are widely utilized in olefin oligomerization, yet precisely controlling acidity remains a significant challenge due to the considerable difficulties in regulating the complex coordination of the active components with the supports. In this study, a series of Al-modified dendritic fibrous nanosilica catalysts (Al-DFNS) were synthesized and applied in the oligomerization of 1-decene to polyalphaolefins (PAOs). Multiple characterizations elucidate that the hydrogen-replaced Al-DFNS (H-Al-DFNS) featured a unique three-dimensional center-radial channel with hierarchical pores, while pulsed-field gradient nuclear magnetic resonance (PFG-NMR) further indicates that the high density of accessible acidic sites and diffusion-limited pore properties lead to much higher catalytic efficiency than diverse siliceous catalysts. Acid distribution measurement and product analysis together reveal that H-Al-DFNS has a well-balanced ratio of Brønsted acid sites (BAS) to Lewis acid sites (LAS). Specifically, high acid strength enhances hydrogen transfer and contributes to high selectivity of trimer and reduced dimer production. Density functional theory (DFT) calculation highlights the crucial role of the stability of carbocation intermediates on acid sites in the oligomerization reaction. The present work provides a reliable strategy for accurately regulated acidity for tunable oligomerization product distribution and initiates the applications of a kind of promising catalytic material in olefin oligomerization.