Synthesis of advanced MgAl-LDH based geopolymer as a potential catalyst in the conversion of waste sunflower oil into biodiesel: Response surface studies

Novel geopolymer was synthesized based on natural silica resources and synthetic MgAl- layered double hydroxides (MgAl-LDH) nanostructure as advanced potassium loaded heterogeneous catalysts in the transesterification of sunflower waste cooking oil. The synthetic geopolymer was characterized by different techniques to identify its structural, chemical, and morphological properties. The transesterification behavior and the optimization processes were evaluated based on the response surface morphology in conjunction with central composite rotatable design. Based on the improvised design tests, the best experimental conditions with 94.6% biodiesel yield is 4 h, 4 wt, % catalyst dosage, methanol/oil ratio of 15:1, and a temperature of 120 degrees C. The predicted optimum conditions regarding to the second order polynomial-model are 5 h as reaction time, 5.4 wt, % as catalyst loading, 117.5 degrees C as temperature, and 16.4:1 as methanol/oil molar ratio achieving biodiesel yield of 96.12%. The catalyst is of significant stability and reused effectively in fie transesterification cycles and the obtained biodiesel showed properties close to that of the international standards.