Mesoporous Beta Zeolite-Supported Ruthenium Nanoparticles for Selective Conversion of Synthesis Gas to C 5 –C 11 Isoparaffins

Mesoporous beta (meso-beta) zeolites prepared by post-treatment of H-beta with NaOH aqueous solution were studied as supports of Ru catalysts for Fischer–Tropsch (FT) synthesis. The size and volume of the mesopores increased with the concentration of NaOH. The Brønsted acidity declined because Na + ions were exchanged into the meso-beta during the post-treatment, and a further ion exchange of the meso-beta with NH 4 + followed by calcination, forming H-meso-beta, could recover the Brønsted acidity. The use of H-meso-beta or meso-beta instead of H-beta or Na-beta as the support for FT synthesis decreased the selectivities to CH 4 and heavier hydrocarbons (C 12 + ) and increased that to C 5 –C 11 hydrocarbons. The C 5 –C 11 selectivity depended on the concentration of NaOH used for meso-beta preparation. Under an optimum NaOH concentration, a C 5 –C 11 selectivity of 77%, significantly higher than the maximum expected from Anderson–Schulz–Flory distribution (∼45%), was attained with a ratio of isoparaffins to n -paraffins being 2.7. The mesoporosity and the unique acidity of the meso-beta probably contribute to the selective hydrocracking of the primary heavier hydrocarbons formed on Ru nanoparticles into gasoline-range liquid fuels.