Influence of acid-base sites on ZnO-ZnCr2O4 catalyst during dehydrocyclization of aqueous glycerol and ethylenediamine for the synthesis of 2-methylpyrazine: Kinetic and mechanism studies

The physicochemical characteristics of ZnO-ZnCr2O4 (Zn-Cr-O) mixed oxides were determined by adsorption and spectroscopic methods. The catalytic activities of Zn-Cr-O was investigated for dehydrocyclization of ethylenediamine and aqueous glycerol to synthesize 2-methylpyrazine (2MP). Reductive pre-treatment was required for better 2MP yields and rate of 2MP was dependent upon strong basicity of Zn-Cr-O. Product distribution revealed that cyclocondensation of glycerol and ethylenediamine followed by homo-coupling of 2-pyrazinylmethanol occurred on moderate acid and strong base sites. On the contrary weak to moderate acidic and base sites were inefficient for homo-coupling of 2-pyrazinylmethanol. Role of acid-base properties was examined by pyridine and 2,6-dimethylpyridine poisoning studies. (C) 2013 Elsevier B.V. All rights reserved.