ALKYLATION OF PHENOL WITH METHANOL OVER MAGNESIUM-ALUMINUM CALCINED HYDROTALCITES

Vapour phase alkylation of phenol with methanol was carried out in a f ixed-bed flow reactor over thermally calcined magnesium aluminium hydr otalcites, with Mg/Al atomic ratios from 3 to 10. The main products we re anisole, o-cresol, and 2,6-xylenol. The influence of phenol-to-meth anol molar ratio, reaction temperature and contact time on the product yields were examined. The activity of these catalysts was compared wi th MgO, Al2O3 and physically mixed MgO-Al2O3. Of the catalysts studied , Mg-Al 4.0:1 calcined hydrotalcite (CHT) was the most active. These c atalysts are more active than magnesia and gamma-alumina. On the basis of the results obtained, a suitable reaction pathway was proposed. Th e participation of combined acidic and basic sites in the calcined hyd rotalcites for the alkylation of phenol with methanol over magnesium-a luminium calcined hydrotalcites has been suggested. Prior to the react ion, the catalyst precursors were characterised by X-ray powder diffra ction and surface area measurements.