Biodiesel Production from Waste Cooking Oil Catalyzed by a Bifunctional Catalyst

The objective of this study was to prepare bifunctional catalysts based on iron and CaO and test them in the biodiesel production using waste cooking oil (WCO) as feedstock. Two iron precursors were studied, Fe₂O₃ and Fe(NO₃)₃·9H₂O. The identified crystalline phases were Ca₂Fe₂O₅ and CaFeO₃. Surface morphology and textural properties (distribution of active species, specific surface area, size, and pore volume) were also analyzed. Additionally, thermal stability was studied and 800 °C was established as the optimum calcination temperature. The density of both acidic and basic sites was higher with the catalyst prepared with Fe₂O₃ than with that prepared with Fe(NO₃)₃·9H₂O. The latter, however, leads to reach equilibrium in half of the time than with the former. This was ascribed to the ratio of acidic to basic sites, which is higher with the catalyst prepared with the precursor salt. This ratio not only affects the overall cost of the process by affecting the time at which equilibrium is reached but also by dictating the methanol/oil molar ratio at which the equilibrium is reached sooner. The prepared bifunctional catalyst allowed us to produce biodiesel with 90% of methyl ester content at atmospheric pressure, reaction temperature of 60 °C, reaction time of 2 h, with 12:1 M ratio of methanol/WCO, 10 wt % of Fe over CaO, and a catalyst loading of 5 wt %. This catalyst can be used at least 3 times. The so-obtained biodiesel met the European norm EN-14214 regarding viscosity and density.

Efficient Synthesis of Diethyl Carbonate by Mg, Zn Promoted Hydroxyapatite via Transesterification Reaction

Transesterification of propylene carbonate (PC) and ethanol is a potent non-phosgene route for the synthesis of diethyl carbonate (DEC). In the present study, hydroxyapatite was synthesized and modified using Zn and Mg (Zn/HAP and Mg/HAP). Modified hydroxyapatite was used as catalyst for the synthesis of DEC. The thermal analysis of the catalytic precursor was studied using thermogravimetric-differential thermal analysis. The structural analysis, surface morphology, and nature of active sites over the catalyst surface were studied using techniques such as Fourier transform infrared spectroscopy, X-ray diffraction, N2 adsorption-desorption, scanning electron microscopy, and CO2 temperature-programmed desorption. Effects of reaction conditions like reaction temperature, reaction time and ethanol/PC molar ratio on DEC yield were also studied. The effects of Mg and Zn on HAP were found to be promotional for the synthesis of DEC using PC and ethanol. Mg/HAP was found to be the best among the three catalysts studied owing to its high basicity. Maximum DEC yield of 52.1 % was obtained in 5 h at 433 K using Mg/HAP catalyst.