Influence of desilication route of ZSM-5 zeolite in mesoporous zeolite supported calcium oxide catalyst for biodiesel production

Abstract

The application of calcium oxide (CaO) as transesterification catalyst for biodiesel production is restricted as there is a high tendency for the calcium (Ca2+) active species to be leached out during the reaction. To overcome this problem, CaO was supported with mesoporous zeolite. A series of mesoporous zeolite supports were prepared via 3 different desilication routes, which are conventional desilication, desilication in the presence of pore directing agent and surfactant-assisted desilication method. The catalytic efficiency of the synthesized catalyst, which are CaO/Zeo, CaO/Zeo-NaOH, CaO/Zeo-TPAOH and CaO/Zeo-CTAB catalyst, in the transesterification of waste cooking oil (WCO) was evaluated. Results revealed that the surfactant-assisted desilication route demonstrates the partial incorporation of the dissolved Al species into the zeolite framework and thus led to highly crystalline material. An obtained high mesoporosity of the zeolite support through this route caused the high dispersion of CaO species in the pores of zeolite support. As a results, the CaO/Zeo-CTAB catalyst exhibited the best performance with 89% biodiesel yield, due to strong acidic and basic properties together with high surface area. The catalyst also showed the higher resistance against Ca2+ active sites leaching by restraining the agglomeration, due to the stronger interaction between CaO and zeolite. The optimum reaction conditions were found to be 4 wt% catalyst dosage, 4 h reaction time, 5:1 methanol to oil molar ratio and 65 °C reaction temperature. The CaO/Zeo-CTAB catalyst could be reused for 6 consecutive runs without significant loss in biodiesel yield and displayed an excellent tolerance to high free fatty acid (FFA) feedstock. For the final remark, these results suggest that the surfactant-assisted desilication is an efficient route for the production of mesoporous zeolite for catalyst support.