Understanding the Promotional Effect of Silver in Naphtha Reforming over a Ga/ZSM-5 Catalyst to Enhance Liquid Yield

Aromatics are one of the most highly demanded hydrocarbon raw materials for the chemical industry. In the present study, efforts are made to understand the promotional effect of silver together with gallium on ZSM-5 zeolite as a catalyst for the reforming reaction of realistic, full range commercial naphtha feed in a fixed bed reactor at atmospheric pressure and 550 °C temperature. The dual metal system showed a synergic effect to enhance the aromatic selectivity and liquid yield and decrease the off-gas formation. The catalyst samples are prepared by desilication followed by co-impregnation of silver and gallium on to ZSM-5, characterized by X-ray diffraction, N₂ adsorption, NH₃ desorption, pyridine-FTIR, temperature-programmed reduction, and analysis of morphology. It is observed from reduction studies that upon incorporation of silver and gallium, catalyst properties like proton abstraction, reducibility, Lewis and Brönsted acidities, etc. are favorably modified. These results are discussed in detail, and an attempt is made to correlate them with the catalytic reaction results obtained.