Bio-glycerol utilization: Synthesis of 2,6-dimethylpyrazine over MxOy–MCr2O4 (M = Mg, Fe, Co, Ni, Cu and Zn) catalysts

• A mechanism proposed for 2,6-dimethylpyrazine and 6-hydroxymethyl-2-methylpyrazine.
• A pair of acid–base sites is involved in dehydrocyclization reaction.
• Copper in conjunction with copper chromite are selective for 2,6-dimethylpyrazine.

The MxOy–MCr2O4 (M–Cr–O; M = Mg, Fe, Co, Ni, Cu and Zn) mixed oxides obtained from their respective M(II)–Cr(III) hydrotalcite precursors have been examined for vapour phase dehydrocyclization of bio-glycerol and 1,2-propanediamine. The physico-chemical properties of the calcined M–Cr–O are characterized by various adsorption and spectroscopic methods. The high 2,6-dimethylpyrazine rate of Cu–Cr–O is rationalized by a combined effect of copper species in close proximity to the CuCr2O4. The kinetic studies demonstrated that glycerol undergoes dehydration to hydroxyacetone (75%) on acidic sites and dehydrogenation to produce dihydroxyacetone on basic sites (25%) at low GHSV. However, a reverse trend has been observed at higher GHSV. Fe2O3–Cr2O3 is found to be active for 2,6-dimethylpiperazine and copper in the vicinity of CuCr2O4 is highly selective for 2,6-DMP formation.

Figure optionsDownload high-quality image (82 K)Download as PowerPoint slide