Preparation and characterization of fly ash based mesoporous catalyst for transesterification of soybean oil

• Waste coal fly ash was utilized to synthesis different types of zeolites.
• highly crystalline zeolite was obtained at fly ash/NaOH ratio of 1:1.5.
• The average particle size of the zeolites was found to be about 2–5 μm.
• The zeolite KX resulted in the maximum biodiesel yield of 81.2%.

In this work, waste coal fly ash was utilized to synthesis different types of zeolites. Conventional alkali fusion step followed by hydrothermal treatment was used for zeolite synthesis. The synthesis conditions were optimized to obtain highly crystalline zeolite. The effect of acid treatment and calcination temperature on zeolite formation was investigated. Further, the effect of addition of sodium aluminate (controlling Si/Al ratio) on zeolitization was also studied. highly crystalline zeolite was obtained at fly ash/NaOH ratio of 1:1.5, fusion temperature of 550 °C, hydrothermal temperature of 90 °C and 8 h hydrothermal time. The zeolite obtained was characterized for its structural, morphological and compositional properties. It was found that high Si/Al ratio favors zeolite X and higher concentration of aluminum results in the formation of zeolite A. The average particle size of the synthesized zeolites was found to be about 2–5 μm. The maximum surface area of fly ash based zeolite X and A was found to be 727.2 and 24 m2 g−1 respectively. Maximum biodiesel yield of 81.2% was obtained using synthesized catalyst. The calorific value of the synthesized biodiesel was 39.2 MJ kg−1 and was found competent with commercial biodiesel (38–42 MJ kg−1).