Selective synthesis of p-cresol by methylation of phenol

MARÍA EUGENIA SAD; CRISTINA LILIANA PADRÓ; CARLOS RODOLFO APESTEGUÍA

APPLIED CATALYSIS A-GENERAL

Elsevier

Lugar: Amsterdam, Holanda; Año: 2007 vol. 342 p. 40 - 48

0926-860X

The selective synthesis of p-cresol by gas-phase alkylation of phenol with methanol was studied on SiO2-Al2O3 and zeolites HBeta, HZSM5 and MCM22.  Cresols were formed from phenol alkylation of methanol via two parallel pathways: the direct C-alkylation of phenol and the consecutive transformation of anisole intermediate obtained by O-alkylation of phenol.  Methylation of o- and p-cresol  led  to  the  formation of 2,6- and 2,4-xylenols while anisole produced methylanisoles either by alkylation with methanol or  by  disproportionation. Regarding the cresol isomers distribution, p- and o-cresol were the major products on all the samples while m-cresol formation remained always lower than 6%. SiO2-Al2O3, HBEA and HZSM5  exhibited  similar  initial  p-cresol:o-cresol  ratios,  between  0.6-0.8 In contrast, p-cresol was the predominant product on HMCM22 because the sinusoidal 10-member ring channels of this zeolite were particularly suitable for improving by shape selectivity the formation of p-cresol.  Thus, we report here for the first time that p-cresol yields of 55% and p-cresol:o-cresol selectivity ratios of 4 are obtained on MCM22 by gas-phase alkylation of phenol with methanol at 473 K and contact time of 350 g h/mol.