MONTMORILLONITE CLAY CATALYSIS - CONVERSION OF METHYL BENZOATE AND NH3 INTO BENZONITRILE AND AMIDES

The reaction of methyl benzoate [1] with NH3 was studied over Montmori llonite K10 clay in the temperature range 280-340 degrees C. Benzonitr ile [2], benzoic acid [3], benzamide [4], N-methylbenzamide [5], and m ethanol were formed as products in varying amounts. This reaction was investigated as a function of molar Patio of 1 to NH3, temperature, an d contact time. At 1/NH3=0.5, 320 degrees C, and contact time of 1.96x 10-(3)h the conversion of 1 was 64.7% and the selectivities of 2 and 4 +5 were 59.6 and 20.2, respectively. The clay catalyst was equally act ive for other aromatic and aliphatic esters. At 340 degrees C and 67.2 % conversion of ethyl propionate the selectivity to propionitrile was as 73.3 after 4h reaction. The actual pathways leading to formation of products was studied in detail. ESCA, NK3 adsorption, pyridine adsorp tion, and IR studies, in combination with the catalytic investigation show that NH3 adsorbed on the acidic >AI-OH sites forms ammonium ions [NK4+] which participate in the reaction. The Lewis acid sites are lik ely to be involved in the formation of 2. The clay catalyst undergoes deactivation on continuous use for several hours [23h]. The deactivati on is mainly due to dealumination by water produced in the reaction an d accumulation of organic residue containing an amide group on the sur face of the clay. It was also possible to calculate effective active s ites on the catalyst surface and then a correlation with the turnover of formation of benzonitrile could be established. (C) 1998 Academic P ress.