Influence of the binder on the n-octane hydroisomerization over palladium-containing zeolite catalysts

The influence of the binder on the properties and performance of palladium-containing zeolite catalysts in the n-octane hydroisomerization was studied. Three different framework zeolites were used as catalysts: mordenite, beta, and ZSM-5 with or without binder. To characterize the catalysts, surface area measurements, temperature-programmed desorption of ammonia, atomic absorption spectroscopy, inductively coupled plasma emission spectrophotometry, hydrogen chemisorption, and solid-state Al-27 NMR were used. Catalytic performance of the zeolites was strongly influenced by the binder because its presence modified both zeolite acidity and porosity. A decrease in the strong acidity of the zeolites could be observed when the samples were agglomerated, due to a solid-state ion exchange between the zeolite protons and bentonite sodium. The neutralization of some zeolite acid sites caused a decrease in the n-octane conversion for mordenite (from 90.5 to 53.8 mol %) and ZSM-5 (from 78.4 to 71.2 mol %) zeolites. The binder modified the porosity of the zeolite providing meso- and macropores, which allow a higher formation of branched isomers for mordenite (from 27.3 to 48.9 mol %) and ZSM-5 (from 14.3 to 35.4 mol %). Activity of beta zeolite was modified by the presence of extraframework aluminum species (EFAL) formed during the agglomeration process, improving both n-octane conversion (from 22.9 to 88.7 mol %) and branched isomer selectivity (from 48.7 to 77.5 mol %).