Efficient oligomerization of pentene into liquid fuels on nanocrystalline beta zeolites

Abstract

Light alkenes oligomerization, performed in the presence of heterogeneous acid catalysts, is an interesting alternative for the production of clean liquid fuels. The process, when catalyzed by zeolites, is flexible and can be directed to the formation of oligomers in the gasoline, jet fuel, or diesel range by adjusting the reaction conditions and the zeolite’s structure. Herein we show how reducing the crystal size of large-pore Beta zeolites down to 10–15 nm and controlling the number and strength distribution of their Brønsted acid sites leads to highly active and stable catalysts, selective to true oligomers within the naphtha and, especially, the diesel range. The shorter diffusion path lengths in the smaller crystallites and the reduced Brønsted acid site density of the two nanosized beta zeolites (10–15 nm) synthesized with Si/Al = 15 lead to 1-pentene conversion above 80% during the 6 h time on stream (TOS) at a space time (W/F) of 2.8 g·h·mol–1. This value is higher than the olefin conversion obtained for a commercial nanobeta (30 nm) at a 3-fold space time of 9.1 g·h·mol–1.