Novel approach for synthesis of highly active nanostructured MgO/ZnAl2O4 catalyst via gel-combustion method used in biofuel production from sunflower oil: Effect of mixed fuel

Abstract

A series of MgO/ZnAl2O4 nanocatalysts was prepared in order to conversion of sunflower oil to green fuel through transesterification reaction. The ZnAl2O4 spinel was synthesized using combustion method with different mixtures of urea and citric acid as fuel. MgO was also loaded on the catalysts as the active phase by impregnation method. the physicochemical properties of synthesized MgO/ZnAl2O4 nanocatalysts was evaluated with TGA/DTG, XRD, FESEM, EDX-dot mapping and nitrogen adsorption–desorption technique. XRD patterns of all samples showed crystalline phase of zinc aluminate without any impurities. The porous morphology as well as high degree of active phase dispersion was observed in samples prepared with mixed fuel. Using mixed fuel with urea to citric acid ratio of 0.5 led to create more pores in range of 10–20 nm. It is worth mentioning that the results of the catalytic performance test of the synthesized catalysts revealed that the highest conversion rate of 98.45 % was obtained in the synthesized sample with a ratio of urea to citric acid of 1:2. Furthermore, this sample illustrated superb stability in the reusability examination so that even over after five recovery cycles, the conversion triglyceride just decreased to 91.1 %.