Novel zeolite Na-X synthesized from fly ash as a heterogeneous catalyst in biodiesel production

Several studies have been carried out on the production of biodiesel using different heterogeneous catalysts but this study has been able to demonstrate the prospect of utilizing South African class F fly ash as a raw material for zeolite synthesis subsequently applied as a solid base catalyst in the production of biodiesel. A novel faujasite zeolite material synthesized from South African class F fly ash and denoted as FA/Na-X was ion exchanged with potassium to obtain the South African class F fly ash based zeolite FA/K-X. This heterogeneous catalyst was used in the conversion of sunflower oil with methanol to yield fatty acid methyl esters. Different characterization techniques were employed to give more information about this zeolite material. The FA/Na-X and the ion exchanged FA/K-X were applied as catalysts in biodiesel synthesis via transesterification reactions. A high quality biodiesel with a yield of 83.53% was obtained at reaction conditions of methanol:oil ratio of 6:1, catalyst amount of 3% (w/w) of oil and reaction temperature of 65 °C after 8 h.

A solid basic Bronsted catalyst such as a basic zeolite can be used for transesterification reactions following the Eley–Rideal (ER) mechanism where the alcohol is adsorbed on the catalyst site and the formed catalytic specie (homogeneous alkoxides ion) on the surface of the catalyst attacks the positively polarized carbon triglyceride in the liquid phase.Figure optionsDownload high-quality image (75 K)Download as PowerPoint slideHighlights
► This study has been able to uniquely demonstrate the utilization of South African Class F fly ash as a raw material for zeolite synthesis.
► South African class F fly ash transformed into a zeolite Na-X phase and exchanged with potassium proved to be suitable for use as a heterogeneous catalyst in biodiesel production.
► The reaction conditions and methyl ester yields in this study were obtained under less rigorous conditions than studies previously reported.