Conversion of 4-ethylphenol to light aromatics on the Cr₂O₃/Al₂O₃ modified by phosphoric acid

With the goal of conversion of alkylphenols to light aromatics (benzene and toluene), Cr₂O₃/Al₂O₃ catalysts were prepared and their hydrogenation performance was investigated using 4-ethylphenol as a model compound. With the increase of LHSV, H₂/oil, reaction pressure and temperature, the dealkylation rate, the total selectivity of aromatics, and the selectivity of light aromatics first rose and then dropped. The conversion of 4-ethylphenol was obviously influenced by the reaction temperature. Cr₂O₃/Al₂O₃ was modified with different concentrations of phosphoric acid. As the increase of the amount of phosphoric acid, the general amount of weak and medium acids on the catalyst increased, and the strength of acid was first enhanced and then weakened. The amount of weak acid increased significantly under a high value of the amount of phosphoric acid. Compared with the unmodified catalyst, the conversion of 4-ethylphenol on the catalysts modified by 8% phosphoric acid is higher than 99.5%, while the dealkylation rate of 4-ethylphenol increased by 9.4%, reaching to 74.4%, and the selectivity to light aromatics (benzene and toluene) increased by 4.0%, reaching to 57.0%. Conversion of 4-ethylphenol to light aromatics was achieved in high selectivity. Furthermore, the total selectivity of aromatics was as high as 80.4%, which meant that most of the aromatic rings was not broken. The path of hydrogenation reaction of 4-ethylphenol on Cr₂O₃/Al₂O₃ was proposed and the reaction mechanism was discussed.