Kinetic studies on the synthesis of fuel additives from glycerol using CeO2–ZrO2 metal oxide catalyst

Document Type: Research Paper

Authors

Department of Chemical Engineering, M. S. Ramaiah Institute of Technology, MSR Nagar, MSRIT Post, Bangalore-560054, Karnataka, India.

Abstract

Highly stable and active CeO2-ZrO2 metal oxide catalyst was synthesized via the combustion method and was further functionalized with sulphate (SO42-) groups. The morphology, surface functionalities, and composition of the metal oxide catalyst were determined by scanning electron microscopy, N2 adsorption and desorption measurement, X-ray diffraction, and Fourier transform infrared spectroscopy. The synthesized catalyst was used for esterification of glycerol with acetic acid. Effects of the process parameters including acetic acid to glycerol molar ratios (3-20), catalyst loadings (1-9 wt.%) and reaction temperatures (70–110°C) on the glycerol conversion and glycerol acetates selectivity were studied. Excellent catalytic activity was observed by using the sulphated metal oxide catalyst resulting in a glycerol conversion as high as 99.12%. The selectivity towards the di and triacetin (fuel additive) formed stood at 57.28% and 21.26% respectively. The reaction rate constants and activation energies were also estimated using a Quasi-Newton algorithm, namely Broyden’s method and Arrhenius equations at 80-110℃. The calculated values were in accordance with the experimental values which confirmed the model. Finally, the developed catalyst could be reused for three consecutive cycle without major loss of its activity. Overall, the findings presented here could be instrumental to drive future research and commercialization efforts directed toward biodiesel glycerol valorisation into fuel additives.

Graphical Abstract

Kinetic studies on the synthesis of fuel additives from glycerol using CeO2–ZrO2 metal oxide catalyst

Highlights

  • Mixed oxide CeO2-ZrO2 catalyst in unsulphated and sulphated forms was used for glycerol acetylation to produce acetins (fuel additives).
  • Both unsulphated and sulphated mixed oxide catalysts were fully characterized.
  • SO42–/CeO2-ZrO2 led to glycerol conversion of 99.12% with selectivity of 57.28% and 21.26% towards di and triacetins, respectively.
  • The activation energy for monoacetin, diacetin, and triacetin formation were 5.34, 16.40, and 43.57 kJ.mol-1, respectively.
  • Regeneration studies indicated the reusability of the catalyst up to three consecutive cycles.

Keywords