Eficiencia de la cáscara de huevo como catalizador para la obtención de biodiesel a partir de la grasa de pollo.

Abstract

The objective of this research work is to evaluate the efficiency of eggshell as a basic heterogeneous catalyst based on calcium oxide (CaO) applied in the process of transesterification of chicken fat to obtain biodiesel, an alternative proposed for the circular economy of the poultry sector. Eggshell, having a high percentage of calcium carbonate (CaCO3), is subjected to a calcination process for its conversion into calcium oxide (CaO), a compound that has demonstrated a catalytic nature in processes where heterogeneous alkaline catalysts are applied. To obtain it, three tests were carried out at different time and temperature conditions, 3 hours at 800 ºC; 4 hours at 900 ºC; 5 hours at 1000 ºC, these were subjected to manual agitation using 80 cm crucible tongs every 10 seconds at 1 hour intervals since the muffle reached its established temperature. The chicken fats obtained were treated to eliminate impurities and subsequently subjected to a wet rendering process for a higher percentage of oil extraction. This oil entered an esterification process in order to reduce free fatty acids to prevent saponification. Characterization analyses were performed which determined an acid index (AI) of 0.7005 mg NaOH/g ≤ 1, free fatty acids (FFA) of 0.304% ≤ 2.54%, demonstrating optimal conditions for subsequent transesterification. According to the catalyst characterization, the X-ray diffraction (XRD) analysis presented a 90% similarity to pattern 00-048-1467 at 900 °C conditions for 4 h, of treatment with CaO patterns when comparing their intensity peaks. The images taken by scanning electron microscope (FEM-SEM) showed cubic crystalline species of high porosity with a particle size ≤ 5 µm and agglomerations of about 50 µm in length, in addition, with the help of an energy dispersive X-ray spectroscopy (EDS) sensor, the mass composition of 67.6728% oxygen and 51.6298% calcium was determined. For the experimental model of the transesterification process, the catalyst loading by weight (2%, 3% and 4%) and the methanol-oil molar ratio (6:1, 9:1 and 12:1) were evaluated as independent variables at conditions of 65°C and 300 rpm, with the objective of determining the optimum conditions to maximize the yield in obtaining biodiesel. The results showed that the highest conversion (96.3%) was achieved with 3% catalyst and 9:1 molar ratio, confirming the feasibility of the agro-industrial waste revalorization process. The ANOVA analysis resolved with a p-value of 0.0009, validating the efficiency of the catalyst obtained for obtaining biodiesel with the experimental design determined.