Development of CaO supported on modified geopolymer catalyst for transesterification of soybean oil to biodiesel

Heterogeneous base catalysts, CaO supported on modified geopolymer (Geo), were developed and characterized as low-cost catalyst for biodiesel production from the transesterification of soybean oil. Geo was modified and synthesized by facile method, meta-kaolin and fumed silica were employed as sources of silica, alumina and, foaming agent (Al metal). The modified Geo was then compared to the conventional Geo without foaming agent (unfoamed-Geo). The catalysts, CaO with various loadings supported on Geo, were prepared by applying microwave radiation and subsequent calcination in air at 600 degrees C. The addition of Al metal during the synthesis of a geopolymer resulted in larger pore size. The results from CO2-TPD and XPS suggested that the calcium species dispersed with strong interactions in the aluminosilicate network of the geopolymer structure leading to strong basicity of the catalysts. The reactivity results showed that the fatty acid methyl ester (FAME) yield of 30%CaO/Geo was 93.12 +/- 0.48%, larger amount than that of 30%CaO/unfoamed-Geo (70.87 +/- 0.22%). Moreover, 30% CaO/Geo could be reused for at least 3 runs, suggesting a promising catalyst for cost-effective biodiesel production.

Automated summary

By adding Al metal during the synthesis of geopolymer, a modified Geo with larger pore size was obtained, exhibiting strong basicity of the catalysts due to strong interaction of calcium species with the aluminosilicate network. Experimental results showed that the catalyst based on CaO/Geo achieved a FAME yield of 93.12%, significantly higher than that of unfoamed Geo. The 30% CaO/Geo catalyst could be reused for at least 3 runs, demonstrating its potential as a cost-effective catalyst for biodiesel production.