Development of Heterogeneous Catalysts for Formation of Biodiesel

Abstract

In present thesis, heterogeneous catalysts for the transesterification of triglycerides have been developed. Four types of catalysts were prepared viz.; (i) KOH impregnated MgO (ii) potassium impregnated mixed oxides of La and Mg (iii) potassium impregnated SiO2 (iv) KNO3 and MgO modified mesoporous SBA-15. These catalysts were characterized by powder XRD, TEM, SEM-EDX, TGA/DTA, FT-IR, Hammett indicators and soluble basicity measurements. In addition to this work, commercially available sodium aluminate has also been evaluated for the transesterification. Potassium hydroxide (5-20 wt.%) impregnated MgO catalysts were prepared by wet-impregnation followed by drying and calcination. Powder XRD and DTA studies support the formation of heterogeneised potassium species over MgO during calcination at 550oC. TEM studies supported that size of these particles are in the range 20-45 nm. Prepared catalysts were used for the transesterification of mutton fat and optimized reaction parameters were the 4 wt.% of MgO-KOH-20 (MgO impregnated with 20 wt.% of KOH), 1:22 molar ratio of fat to methanol, 65oC reaction temperature and 20 min of reaction duration. Potassium impregnated mixed oxides of La and Mg in 1: 1 to 1: 5 atomic ratios were prepared by co-precipitation method. TEM studies of these oxides supported the formation of polygonal, square and hexagonal shaped particles. The catalyst prepared by using 1: 3 atomic ratio of La to Mg was found to have stronger basic sites and better activity towards the transesterification reaction of used cotton seed oil. Under optimized reaction conditions of 1: 54 molar ratio of oil to methanol and 5 wt.% of the catalyst (prepared with La to Mg atomic ratio of 1:3 at pH 10) at 65oC reaction temperature, 96% FAME yield was obtained in 20 min.