A comparative study on the catalytic activity of ZnO modified zeolites in the synthesis of alkylpyrazines

The vapor phase condensation reaction of monoethanolamine (MEA) has been carried out over three ZnO-modified zeolite catalysts in the temperature range 280-400 degreesC. Ethylpyrazine was formed as the major product in the cases of ZnO-ZSM-5 and ZnO-FER, whereas pyrazine was formed as the major product in the case of ZnO-MOR. Moreover, we observed with ZnO-MOR a large amount of lower boilers which included methylamine, aziridine, ethylamine and ethylenediamine. The formation of DABCO was appreciable over ZnO-MOR; however, it becomes less probable over the other two catalysts, due to their higher dehydrogenation activity. The stability of these catalyst systems in the conversion of MEA followed the order: ZnO-ZSM-5 > ZnO-MOR > ZnO-FER. (C) 2001 Elsevier Science B.V. All rights reserved.