Mesoporous Carbon-Based Rhodium Catalysts for Benzene Hydrogenation

Abstract

Two different carbons, namely CAS-P-500 and CRH-P-500, were prepared from apricot stones and rice husk by H₃PO₄-activation at 500 ºC and H₃PO₄/precursor (wt/wt) impregnation ratio of 2:1 followed by water washing and desilication by NaOH solution respectively. Elemental analyses of both samples using X-ray fluorescence spectroscopy and VARIO ELEMENTAR III elemental analyzer detected up to 1% of remained phosphorus and about 88% of carbon. SEM characterization and nitrogen adsorption data revealed that highly mesoporous materials were obtained. According to BJH scheme calculations, N₂ BET-surface area and pore volume for CAS-P-500 reached the values of 2030 m²/g and 1.64 cm³/g, while for CRH-P-500: 1690 m²/g and 1.95 cm³/g respectively. Activated carbons CAS-P-500 and CRH-P-500 were used as catalyst supports for the conversion of small amounts of benzene into cyclohexane to obtain cleaner gasoline. According to Euro-3 standards, gasoline should contain less than 1% of benzene, since the incomplete combustion of gasoline, which contains benzene, leads to formation of benzopyrene- a powerful carcinogen in exhaust gases. The activity of rhodium catalysts based on the CAS-P-500 and CRH-P-500 allow complete conversion of benzene into cyclohexane at 40 atm and 80oC temperature and is comparable to those of based on conventional carbons: “Sibunit”, etc.