Alkylation of phenol with methanol over H-ZSM-5, H-Beta, H-Mordenite, H-USY and H-MCM-22
Doctoral Thesis
2003
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University of Cape Town
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Abstract
Alkylphenols are intermediates used in the synthesis of many important substances. The most significant of the commercially important lower alkylphenols are cresols (methyl phenols) and xylenols (dimethyl phenols). The main markets for alkylphenol products are nonionic detergents, phenolic resins, polymer additives and agrochemicals. Of the western world cresol market, 55% originates from synthetic cresols whereas 45% originates from so-called “natural” cresols obtained from coal tars and refinery caustics. The methylation of phenol is the only process specifically developed to produce cresols and xylenols. There are three cresol isomers, namely ortho, para and meta. It is possible to produce a high selectivity to o-cresol by alkylation of phenol with methanol over a basic or a Al2O3 catalyst or a Fe/V catalyst. A mixture of the cresol isomers can be obtained over aluminium oxides with strong acid sites, silica alumina, zeolites, aluminium phosphates and phosphoric acid-Kieselguhr catalysts. However, direct synthesis of high purity m-cresol and p-cresol is desirable due to the high costs of separating these two isomers. Thus to synthesize p-cresol, a m-cresol free or very low m-cresol concentration in the product is desirable for purification reasons and a high p/o-cresol ratio is also desirable in the product for yield reasons since separation of the p- and the o-cresols is economically possible.
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Bibliography: leaves 223-232.
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Moon, G. 2003. Alkylation of phenol with methanol over H-ZSM-5, H-Beta, H-Mordenite, H-USY and H-MCM-22. University of Cape Town.