Study on heterogeneous catalysts from calcined Ca riched hydrotalcite like compounds for biodiesel production


ÇAKIRCA E. E., AKIN A. N.

SUSTAINABLE CHEMISTRY AND PHARMACY, vol.20, 2021 (SCI-Expanded) identifier identifier

Abstract

Ca riched Hydrotalcite like compounds (HLCs) were synthesized by co-precipitation method to obtained Ca-Mg-Al mixed metal oxides with a view to produce biodiesel via methanolysis of microalgae. For this purpose, hydrotalcite-like catalysts containing Ca+2, Mg+2 and Al+3 metals were prepared with a molar ratio (x value) of Al+3/(Ca+2 + Mg+2 + Al+3) at 0.33. Ca/Mg molar ratio in the hydrotalcite like compounds was determined as 0, 0.5, 1, 2. Also, Mg-free CaAl HLCs was prepared at x = 0.33 value. The calcination process was carried out at 800 degrees C. Obtained catalysts were characterized by BET, XRD, TGA, FTIR, SEM and ICP-OES techniques. The basicity of the all catalysts were investigated by using TPD/CO2 technique and Hammett indicators. With increase in calcium amount on the HLCs, some evident features were observed such as high basicity and increase in basicity range with H_ values above 15, increase in pore diameter up to 18.37 nm, low pore volume and high catalytic activities. XRD analysis demostrated that the desired Ca-Mg-Al active metal oxide forms were formed after calcination. Catalytic activities of all the catalysts were examined in terms of conversion of microalgae oil to biodiesel and achieved up to 90% FAME yield under mild reaction conditions: 338 K for 5 h, methanol/microalgae oil molar ratio 6:1 and 3% catalyst amount. These results showed that the molar ratio of Ca-Mg in HLCs were significantly effective on the HLCs structure and catalytic activity.