Response surface methodology for the optimum production of biodiesel over Cr/Ca/γ-Al2O3 catalyst: catalytic performance and physicochemical studies

Abstract

Attention continues to be focused on biomass as a very promising alternative source of renewable materials for energy production. This research focused on the use of a heterogeneous base alkaline earth metal oxide incorporated with a transition metal oxide catalyst supported on gamma alumina oxide varied with different temperatures, Cr loading and number of alumina coatings that make the biodiesel easily separated, low cost and environmental friendly. The physicochemical properties of Cr/Ca(10:90)/γ-Al2O3 catalyst calcined at 700 °C investigated by BET surface area and CO2-TPD indicated high surface area, 164.32 m2/g and higher basicity, 3.38 mmol/g, respectively. FESEM-EDX mapping showed the homogeneous distribution of each element presence in Cr/Ca(10:90)/γ-Al2O3 catalyst was well-distributed and indicated that the Cr/Ca has a higher dispersion on the surface of the γ-Al2O3. The response surface methodology was used to optimize the catalytic activity of Cr/Ca/γ-Al2O3 catalyst for transesterification of biodiesel from low-grade cooking oil. The most important variable for biodiesel yield was the calcination temperature of the catalyst followed by the Cr loading and the number of alumina coatings. The experimental value achieved with 93.10% conversion of biodiesel closely agreed with the predicted result from RSM and validated the findings of response surface optimization.