Catalysis of Organic..

Ardizzi et al. 7710. The Control of Regio- and Chemo-Selectivity in the Gas-phase, Acid-CatalyzedMethylation of 1,2-Diphenol (Catechol)Mattia Ardizzi, Nicola Ballarini, Fabrizio Cavani, Luca Dal Pozzo,Luca Maselli, Tiziana Monti and Sara RovinettiUniversity of Bologna, Dipartimento di Chimica Industriale e dei Materiali, VialeRisorgimento 4, 40136 Bologna, Italy. INSTM, Research Unit of Bologna. A memberof Concorde CA and of Idecat NoE (6FP of the EU).Abstractfabrizio.cavani@unibo.itThe catalytic properties of materials having either (i) Brønsted-type acidity (Hmordeniteand Al phosphate), or (ii) Lewis-type acidity (Al trifluoride), wereinvestigated in the reaction of gas-phase catechol methylation with methanol. H-mordenite and AlF 3 gave high selectivity to guaiacol (the product of O-methylation)only under mild reaction conditions, that is for very low catechol conversion. In fact,the increase of temperature led to the transformation of guaiacol to phenol andcresols, and to considerable catalyst deactivation. The use of a mildly acidic catalyst,AlPO 4 , instead made it possible to obtain a stable catalytic performance, with highselectivity to guaiacol at 42% catechol conversion.IntroductionPhenol and diphenols (catechol, resorcinol and hydroquinone, the ortho, meta andpara isomers, respectively), are versatile starting material for the synthesis of manycompounds. However, most of the corresponding industrial transformations still havedrawbacks that make the processes environmentally unfriendly, such as:(1) The use of alkylhalides, or dimethylsulphate or acylhalides as co-reactants, withco-production of waste effluents containing inorganic salts, which have to bedisposed.(2) The high number of synthetic steps that sometimes are necessary, withconsequent low overall yield, due to the by-products formed in each step.(3) The use of stoichiometric conditions instead than catalytic, or of such largeamounts of catalyst, often not recoverable, that the process can be regarded as astoichiometric one. Moreover, the use of homogeneous catalysts often impliesthe development of corrosive reaction media, and problems in the purification ofthe product.(4) The use of solvents that may have themselves unfriendly characteristics.Therefore, the development of new processes having lower environmentalimpact represents one important target (1,2). In the present work we report about