Application of response surface methodology for optimization of biodiesel production parameters from waste vegetable oil using N-(2-hydroxy) propyl-3-trimethyl ammonium chitosan chloride-based catalyst

Catalysts play a crucial role in the transesterification reaction involved in the production of biodiesel. It is vitally important to conduct research on catalysts with high efficiency, competitive pricing, and ease of manufacture. Chitosan (CS) is one of the biodegradable and sustainable polymers used in a variety of fields due to its wide availability, low environmental impact, and diverse functional group composition. This study involved the synthesis of N-(2-hydroxy) propyl-3-trimethyl ammonium chitosan chloride (HTCC) via the interaction of CS with glycidyl trimethylammonium chloride (GTMAC). Then, an alkaline catalyst based on a polymer can be easily constructed for use in biodiesel production by combining HTCC with sodium metasilicate (SMS). Epichlorohydrin (ECH) was used as a chemical linker between the HTCC chains to make SMS more stable in the polymer. The synthesized polymer-based catalyst was successfully identified using techniques including Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDX), thermogravimetric analysis (TGA), and the Brunauer-Emmett-Teller (BET) technique. Response surface methodology (RSM) was applied to analyze the effect of various experimental conditions on the percentage of fatty acid methyl ester (FAME) produced in a batch reactor. The molar ratio of methanol/waste vegetable oil (WVO), amount of catalyst, and reaction time were considered in order to maximize the %yield of FAME. Highest FAME yield of 97.74% was achieved via optimizing the following parameters: 9:1 molar ratio of methanol/WVO, 3.5 wt.% catalyst amount, and 1.5 h reaction time. The HTCC-based solid catalysts shown excellent catalytic activity for the transesterification of WVO. In addition, these catalysts displayed excellent reusability for up to 5 consecutive runs without experiencing a substantial activity drop.