Hydrodeoxygenation of Anisole with Pt Catalysts

Abstract

Pt catalysts supported on neutral and acid materials, namely SiO2, γ-Al2O3, Na-Beta, and NaH-Beta, were studied in the anisole deoxygenation reaction. The main objective was to compare different supports for this reaction and determine the conditions that maximize the selectivity to deoxygenated products. The reactions were carried out in a fixed-bed reactor at atmospheric pressure by varying the temperature between 200 and 500 °C. Depending on reaction conditions, benzene, and in lesser amounts toluene and xylenes, were obtained as deoxygenated products. Also, n-methylanisoles and n-methylphenols were produced in low amounts. The effects of space time, temperature, and H2/anisole ratio on the catalytic performance were analyzed in a wide range of values, which thus made it possible to obtain detailed information regarding the changes in selectivity and activity upon changes in the operational variables. Anisole deoxygenation to benzene requires both the metallic and the acid functions. Acid and metal sites promoted demethylation needed to allow the deoxygenation reaction to occur. The acid sites also promote transalkylation reactions, which led to undesired oxygenated products, and on the other hand, the acidity catalyzed the alkylation of aromatic rings with the -CH3 fragments coming from demethylation, thus improving the carbon balance. Coke formation follows a series-type mechanism, formed mainly from the anisole. It is possible to regenerate these catalysts by burning the coke with air at 350-400 °C. The catalysts supported on the beta zeolite worked under a mass transfer controlled regime.