Selective O-methylation of catechol using dimethyl carbonate over calcinedMg-Al hydrotalcites

Methylation of catechol with dimethyl carbonate as an alkylating agent has been carried out over calcined Mg-Al hydrotalcites in the temperature range 523-623 K. Guaiacol and veratrole were obtained as the major products, alo ng with small amounts of catechol carbonate and C-alkylated products. At 57 3 K, the total O-selectivity was 96.1% with a guaiacol selectivity of 84%. At higher DMC/catechol molar ratios and longer contact times, guaiacol sele ctivity decreased markedly with a concomitant increase in the selectivity o f veratrole, An optimum value of the strength of acid-base pair sites invol ved in the adsorption of DMC and catechol makes hydrotalcite-based oxides b etter catalysts compared to alumna and basic MgO. It is possible that the n ature of alkylating agent also can affect the product selectivity along wit h the experimental factors and the acid-base properties of the catalysts. ( C) 2001 Elsevier Science B.V. All rights reserved.