Selective O-methylation of catechol using dimethyl carbonate over calcined Mg-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, along with small amounts of catechol carbonate and C-alkylated products. At 573 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 selectivity decreased markedly with a concomitant increase in the selectivity of veratrole, An optimum value of the strength of acid-base pair sites involved in the adsorption of DMC and catechol makes hydrotalcite-based oxides better catalysts compared to alumna and basic MgO. It is possible that the nature of alkylating agent also can affect the product selectivity along with the experimental factors and the acid-base properties of the catalysts. (C) 2001 Elsevier Science B.V. All rights reserved.