Optimization of the Production of Methyl Ester from Used cotton Seed Oil: A Statistical Approach Using Box-behnken Design

Methyl ester is the name given to monoalkyl esters of vegetable and animal oils. Since methyl ester has fuel properties that are comparable to those of diesel fuel, it is becoming more popular as a substitute fuel for use in diesel engines. The amount of free fatty acids (FFA) in the oil determines how methyl ester is produced. In this study, the titration method was used to calculate the FFA values of the crude cottonseed oil (CCSO) and one-time Used Cottonseed Oil (UCSO), with values ۰.۵۶ % and ۱.۲۶ %, respectively. The UCSO is transformed into methyl ester by employing a heterogeneous alkali catalyzed transesterification reaction. It involves the addition of methanol to bleach and degummed UCSO in the presence of heterogeneous catalysts CaO-blend derived from calcinated eggshells and coconut shell blend. Reaction variables including the methanol-to-oil ratio, reaction temperature, reaction time and catalyst concentration control the transesterification process. The Box-Behnken design was employed to optimize the aforementioned parameters using the response surface methodology (RSM). Numerous factors that affect the generation of biodiesel have been plotted using the response surface plot and contour plot. An optimized UCSO methyl ester yield of ۹۲.۰۰ % was obtained at a ۱:۱۰.۸۰ molar ratio, ۲.۵ wt. % catalyst concentration, ۸۰ minute reaction time, and ۶۰ °C reaction temperature. The experimental yield was ۹۲.۱۰ %, as determined by the optimized yield based on these parameters. This shows that the response surface methodology is a successful strategy for increasing the yield. The regression model proved successful, as observed by the error values between the predicted and actual outcomes being less than ۱ % UCSOME conversion. For this study, adequate precision was ۸.۹۵۱۸. As a result, the model can be utilized to explore the design space. Each succeeding cycle of reuse produced ۹۱.۶۰ %, ۸۵.۵۰ %, ۸۱.۶۰ %, ۷۸.۶۰ %, ۷۴.۲۰ %, and ۷۲.۸۷ % of the biodiesel. The measurements for viscosity, density, and flash point of UCSO were ۳۳-۳۶ mm۲/s at ۳۱۱ K, ۹۱۱-۹۱۶ kg/m۳ at ۲۸۸ K, and ۵۰۴-۵۱۰ K, respectively. UCSO methyl ester (UCSOME) had a viscosity between ۳.۶ and ۳.۷ mm۲/s and a density between ۸۷۵ and ۸۸۰ at ۳۱۱ K. While the flash points of the UCSOME are measured at ۴۳۵–۴۴۰ K as opposed to ۵۰۴-۵۱۰ K. The saponification value of cottonseed oil was ۱۸۸.۳۲ mg/g while that of biodiesel was ۱۶۵.۸۷ mg/g. Thus, biodiesel fatty acid methyl ester possesses a distinctive FTIR absorption of carbonyl (C=۰) stretching vibrations near ۱۷۴۰-۱۷۴۴ cm-۱ and C-O bending vibrations in the range of ۱۱۹۶ cm-۱.

Keywords:

Monoalkyl ester , Transesterification , Vegetable Oil , Biodiesel , Free fatty acids