Thermocatalytic Cracking of Natural Feedstocks in Microchannels

Homogenous catalysed transesterification is commonly used for biodiesel production. Although the process has some advantages such as high conversion rates and short reaction time, there are a number of drawbacks: such as soap formation due to free fatty acids in the feedstock, the catalyst is not recoverable; however it must be neutralized for glycerol removal. Even when homogeneous acid or solid catalysts are used, transesterification process is far from being environmentally friendly; this is because the product stream needs thorough washing. This generates a lot of waste water which need to be further treated. Secondly alcohol is still employed in the process, incurring more cost. Alternatively, thermocatalytic cracking of triglycerides using heterogeneous solid-acid catalyst would eliminate the associated drawbacks caused by transesterification and reduce the unit operations as seen from Figures 1 to 2.

Among many heterogeneous solid-acid catalysts, sulphated zirconia is a promising catalyst; it is a super-acid catalyst with H0 =16; that is 104 greater than that of 100 % sulphuric acid, thermally stable and can be used for organic reaction at low temperatures compared to zeolites; however its conventional preparations lead to small surface area and micro-pores, leaching and high Lewis acid sites compared to Bronsted acid sites, therefore restricting its catalytic activity.

Presently, our research has focused on the improvement of its catalytic properties (surface area, increased Bronsted acid sites, and leaching) to produce a high active and selective catalyst via a solvent-free method of preparation for enhancing biodiesel production from triglycerides by thermocatalytic cracking without the use of alcohol at a temperature of 270oC. Interestingly the catalysts were not just active for fatty acid methyl ester but in addition exhibited some selectivity for saturated and unsaturated methyl esters.

The solvent-free method does not only enhance the catalytic properties of the catalyst in addition it is an environmentally friendly process compared to the conventional wet-precipitation method of sulphated zirconia synthesis as shown from Figures 3 to 4. It does not involve any aqueous medium.

For more information please contact Prof Adam Harvey or Dr Jon Lee.

Publication and Conference Papers

• Eterigho, E. J., Lee, J. G. M. and Harvey, A. P. (2011) 'Triglyceride cracking for biofuel production using a directly synthesised sulphated zirconia catalyst', Bioresource Technology, 102, (10), pp. 6313-6316.

• Eterigho, E. J., Lee, J. G. M. and Harvey, A. P. (2011) 'Synthesis, Characterization and Evaluation of two Forms of Sulphated Zirconia for Biofuel Production by Triglyceride Cracking ', Bioenergy III Conference: Present and New Perspectives on Biorefineries Lanzarote, Canary Islands, May 22 - 27.

• Eterigho, E. J., Lee, J. G. M. and Harvey, A. P. (2011) 'Evaluation of Catalytic Activity of Synthesized Sulphated Zirconia for Triglyceride Cracking ', 8th European Congress of Chemical Engineering. Berlin, Germany, September 25 - 29.

• Kasim, F. H., Eterigho, E. J., Lee, J. G. M. and Harvey, A. P. (2011) 'Catalytic Cracking of Triglyceride by Sulphated Zirconia for Fatty Acid Methyl Ester with High Selectivity', 2012 AIChE Annual Meeting. Minneapolis, MN, United States, October 16-21, 2011.