Conversion of m-cresol, which is a representative of phenolic compounds, has been studied over different zeolites at different reaction temperatures (400oC � 600oC) using a micro-pulse reaction system. At the reaction temperature of 400oC, all of the reactant in a pulse was trapped forming carbonaceous deposits (or coke) on the catalyst. When the reaction temperature increased, total output, including aromatics, m-cresol and other phenolic products, increased. Correspondingly, the coke amount decreased as the reaction temperature increased. Moreover, the temperature programmed oxidation of the spent catalyst showed that the fraction of coke burned off at low temperature (below 550oC) decreased significantly with reaction temperature, while the fraction burned off at high temperature (above 550oC) increased.Even though all of the reactant in a pulse was trapped at 400oC and formed coke, significant water was produced. This result indicates that dehydration reaction and condensation of m-cresol might form a surface pool of phenolic compounds. Temperature programmed reaction of the spent catalyst after pulsing m-cresol at 400oC was carried out in He to study the reaction of the phenolic pool. Upon further heating of the spent catalyst, cracking of the phenolic pool produced aromatics (benzene and toluene) and methane while there was no phenolic product produced. Isomerization, transalkylation of m-cresol produced different phenolic products. At low temperature, these products were trapped again by the zeolite, forming the phenolic pool. However, as the reaction temperature increased, adsorption of these phenolic products decreased, leading to a larger release of products.The HY zeolite trapped the phenolic compounds more effectively than HZSM-5, leading to enhanced coke formation and faster catalyst deactivation.

Conversion of m-cresol over HY and HZSM-5 zeolites

247th National Meeting (2014)

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