MECHANISM OF ALKYKLATION OF PHENOL WITH METHANOL ON ACID ZEOLITES

MARÍA EUGENIA SAD; CRISTINA LILIANA PADRÓ; CARLOS RODOLFO APESTEGUÍA

Genova, Italy

Congreso; 6th world congress on Catalysis by Acids and Bases; 2009

The gas-phase alkylation of phenol with methanol has been widely studiedon acid catalysts but knowledge regarding the reaction mechanism and theexact requirements of acid site density and strength to efficiently promotethe selective formation of cresols is still needed. A variety of products suchas cresols, anisole, xylenols and methylanisoles are formed frommethylation of phenol on acid catalysts [1,2]. Cresols are formed by bothdirect C-alkylation of phenol with methanol and conversion of anisolepreviously formed by O-methylation of phenol. But cresols can in turnreact with methanol on acid sites to produce dialkylated compounds(xylenols, methylanisoles). In this work, we performed a detailed study onthe effect of the pore microstructure and the nature, density, and strength ofsurface acid sites on product distribution for the methylation of phenol withmethanol on acid zeolites (zeolites HZSM5, HBEA and HMCM22). Wepropose a reaction mechanism that interprets the primary and secondaryreaction pathways leading from phenol to mono- and dialkylated productsand also explains the unique high para-selectivity obtained on HMCM22.