Hydrodeoxygenation of Anisole with Pt Catalysts

Abstract

Pt catalysts supported on neutral\nand acid materials, namely SiO₂, γ-Al₂O₃, Na-Beta, and NaH-Beta,\nwere studied in the anisole deoxygenation reaction. The main objective\nwas to compare different supports for this reaction and determine\nthe conditions that maximize the selectivity to deoxygenated products.\nThe reactions were carried out in a fixed-bed reactor at atmospheric\npressure by varying the temperature between 200 and 500 °C. Depending\non reaction conditions, benzene, and in lesser amounts toluene and\nxylenes, were obtained as deoxygenated products. Also, n-methylanisoles\nand n-methylphenols were produced in low amounts. The effects of space\ntime, temperature, and H₂/anisole ratio on the catalytic\nperformance were analyzed in a wide range of values, which thus made\nit possible to obtain detailed information regarding the changes in\nselectivity and activity upon changes in the operational variables.\nAnisole deoxygenation to benzene requires both the metallic and the\nacid functions. Acid and metal sites promoted demethylation needed\nto allow the deoxygenation reaction to occur. The acid sites also\npromote transalkylation reactions, which led to undesired oxygenated\nproducts, and on the other hand, the acidity catalyzed the alkylation\nof aromatic rings with the −CH₃ fragments coming\nfrom demethylation, thus improving the carbon balance. Coke formation\nfollows a series-type mechanism, formed mainly from the anisole. It\nis possible to regenerate these catalysts by burning the coke with\nair at 350–400 °C. The catalysts supported on the beta\nzeolite worked under a mass transfer controlled regime.