Ortho-alkylation of phenol derivatives with methanol over magnesium oxide catalysts. 1. Characterization of promoted magnesium oxide catalysts

Cr- and Pt-promoted magnesium oxide catalysts were used to catalyze ortho-a lkylation of phenol derivatives in the presence of excess methanol. The cha racteristic properties of the MgO surface measured by XRD, SEM, BET, and TP D suggest that Cr exists as fine chromium oxide particles on the MgO surfac e, while a Pt and MgO interaction causes an increase of the BET surface are a as well as of surface acid and base amounts. Cr/MgO shows a specialty for ortho-alkylation of phenol derivatives with methanol without forming O-alk ylated products, i.e.. anisole or methylated anisole. The catalytic activit y and the stability of Cr/MgO are improved by the addition of a fairly smal l amount of Pt. The effect of Pt can be explained by the Pt and MgO interac tion which increases both the acid and base amounts. A mechanism involving the reaction of phenol derivatives and methanol adsorbed simultaneously on acid-base pair sites is proposed.