Applied Catalysis A: General, Vol.119, No.2, 241-252, 1994
Alkylation of Phenol with Methanol over Magnesium-Aluminum Calcined Hydrotalcites
Vapour phase alkylation of phenol with methanol was carried out in a fixed-bed flow reactor over thermally calcined magnesium aluminium hydrotalcites, with Mg/Al atomic ratios from 3 to 10. The main products were anisole, o-cresol, and 2,6-xylenol. The influence of phenol-to-methanol molar ratio, reaction temperature and contact time on the product yields were examined. The activity of these catalysts was compared with MgO, Al2O3 and physically mixed MgO-Al2O3. Of the catalysts studied, Mg-Al 4.0:1 calcined hydrotalcite (CHT) was the most active. These catalysts are more active than magnesia and gamma-alumina. On the basis of the results obtained, a suitable reaction pathway was proposed. The participation of combined acidic and basic sites in the calcined hydrotalcites for the alkylation of phenol with methanol over magnesium-aluminium calcined hydrotalcites has been suggested. Prior to the reaction, the catalyst precursors were characterised by X-ray powder diffraction and surface area measurements.
Keywords:SYNTHETIC HYDROTALCITE;CATALYTIC ALKYLATION;CONDENSATION;SELECTIVITIES;METHYLATION;ZEOLITES