Vapor phase synthesis of methylpyrazine using aqueous glycerol and ethylenediamine over ZnCr2O4 catalyst: Elucidation of reaction mechanism

A novel method has been developed for the synthesis of methylpyrazine (MP) by using aqueous glycerol and ethylenediamine (EDA) over Zn–Cr catalyst derived from hydrotalcite precursors. The X-ray diffraction analysis of the oven-dried Zn–Cr samples synthesized at various pH ranging from 7 to 11 showed hydrotalcite phase whereas the calcined catalysts displayed ZnO and ZnCr2O4 phases. The cyclisation activity of Zn–Cr catalyst prepared at pH ~ 9 demonstrated 99.4% conversion of EDA and 94% of glycerol with ~ 72% selectivity to MP at a reaction temperature of 400 °C. This process demonstrates direct utilization of bio-glycerol for the synthesis of MP.

Graphical abstractA novel and highly economical method has been developed for the synthesis of 2-methylpyrazine by using glycerol and ethylenediamine over Zn–Cr catalysts derived from hydrotalcite precursors.Figure optionsDownload full-size imageDownload as PowerPoint slideResearch Highlights► Bio-glycerol is a byproduct that is formed in large amounts (about 10%) during bio-diesel production by transesterification of oils. ► Generation of alternate fuels is important but utilization/safe disposal of the byproducts obtained in the process is equally important. ► Synthesis of methylpyrazine is so far reported using ethylenediamine and 1,2-propylene glycol. ► Here we report on synthesis of methylpyrazine using glycerol and EDA and a reaction mechanism has been proposed. ► This method could be extended to synthesize methylpyrazine using bioglycerol the byproduct obtained in the biodiesel production.