Application of snail shells as a heterogeneous catalyst for rapeseed oil butyl esters production

Abstract

ABSTRACT Synthesis of fatty acid butyl esters using snail shells is attractive and increases the share of renewable resources because the snail shells are a waste of the food industry and 1-butanol can be obtained from renewable resources. Chemical and instrumental analysis methods (XRDA, FT-IR, EDS) were used for the evaluation of the chemical composition of snail shells. It was found that composition slightly depends on the kind and growing conditions, but in all the cases the main component in raw shells is CaCO3. After calcination for 5 h at a temperature of 850 °C, almost pure CaO (93.69 ± 0.43% %) is formed, which is used as a catalyst in the triglyceride transesterification process. SEM studies showed that the structure of the shells becomes porous after calcination, which increases the efficiency of the process. The Response surface methodology was used for the optimization of rapeseed oil transesterification with 1-butanol. It was found that the optimum transesterification conditions when the reaction temperature is 110°C are the following: 1-butanol-to-oil molar ratio of 10.6:1, a snail shell content of 7.53 wt%, and a reaction time of 10.77 h. Under these conditions, the 99.25 wt% yield of rapeseed butyl esters was obtained.