Res. Chem. Intermed. , Vol. 29, No. 2, pp. 137– 146 (2003) Ó VSP 2003. Also available online - www.vsppub.com Hydrothermal preparation of CuO – ZnAl 2 O 4 catalyst for phenol ortho-alkylation with methanol: effect of the calcination temperature on the catalytic performance W. MI ´ STA, M. ZAWADZKI and H. GRABOWSKA Catalysis Department, Institute of Low Temperature and Structure Research, Polish Academy of Sciences, 50– 950 Wrocaw 2, P.O. Box 1410, Poland Received 20 August 2002; accepted 13 November 2002 Abstract —The effect of heat-treatmenton 10 wt% CuO–ZnAl 2 O 4 catalytic activity in methylation of phenol and the degree of interaction of CuO active phase with support spinel phase were investigated. The CuO–ZnAl 2 O 4 sample was subjected to heat-treatment up to 1000 ± C. The thermal products were characterized by X-ray diffraction (XRD) analysis, nitrogen adsorption–desorption at ¡196 ± C and temperature-programmed desorption (TPD-MS) of CO 2 . Additionally, the reducibility of copper phases was investigated by temperature-programmed reduction (TPR). XRD patterns of the fresh catalyst sample (calcined at 600 ± C) indicated the presence of a mixture of poorly crystallized CuO and ZnAl 2 O 4 spinel phase. The presence of two reducible copper species has been found on fresh CuO–ZnAl 2 O 4 catalystby TPR analysis. After subsequentcalcinationsin air at elevatedtemperatures some CuO disappeared with appearance of CuAl 2 O 4 phase. The catalytic results revealed that the CuO addition to ZnAl 2 O 4 increases the activity in ortho-methylation of phenol. Subsequent heat-treatment up to 900 ± C causes partial deactivation of copper centers, which is the result of transformation of CuO to the inactive CuAl 2 O 4 phase. Keywords: Copper oxide-zinc aluminate spinel; hydrothermal synthesis; phenol methylation; TPR; CO 2 TPD-MS. INTRODUCTION Methylation of phenol in the gas phase conducted in the presence of catalysts is performed for obtaining ortho-cresol, 2,6-xylenol and other alkylated phenols. Alkylphenols are substrates for further production of, among other products, agro- chemicals, dyes, antioxidants, avoring agents, emulsiers, non-ionic detergents, pharmaceuticals, plastics, including important polyoxyphenylene resins used in pro- duction of housings for electrical equipment and of pipes resistant to high pressure and temperature.