Zn-Modified CuCr2O4 as Stable and Active Catalyst for the Synthesis of 2,6-Dimethylpyrazine: Valorization of Crude Glycerol Obtained from a Biodiesel Plant

Modified CuCr2O4 catalysts were investigated for vapor phase conversion of crude glycerol and 1,2-propanediamine (1,2-PDA) to synthesize 2,6-dimethylpyrazine (2,6-DMP). The addition of Zn not only enhanced the activity of CuCr2O4 but also improved the stability of the catalyst. The introduction of Zn into the CuCr2O4 matrix increased the copper metallic surface area of the catalyst. The rate of 2,6-DMP is found to be dependent on the Cu metal surface area. Diffuse reflectance infrared Fourier transform spectroscopic data revealed that a high fraction of Lewis-acid-base pair sites are responsible for the selective formation of 2,6-DMP. A direct correlation between 2,6-DMP rate and the surface Cu is established.