A response surface for an eggshell model shows that for lowconcentrations of catalyst, the conversion of methyl ester de-
creased graph is not showed. This shows that the significant factor is X C, which has a positive effect on transesterification at a confidence level of 95%, as noted in the response surface plot. This is due to the fact that the increase in catalyst concentration implies a higher number of active basic sites in the reaction medium, resulting in higher conversions to methyl esters. The transesterification is a reaction that can be conducted by adding excess methanol, which shifts the chemical equilibrium of the reaction toward the formation of methyl esters, increasing the rate of conversion.However, using high volumes of methyl alcohol complicates the separation process due to the existence of gravity between the phases formed and glycerin ester, increasing their miscibility and promoting the displacement of the balance in the opposite direction toward the formation of mono-, di-, and triglycerides, thereby decreasing the production of methyl esters. Based on the experiments carried out, the best experimental conditions (coded and dependent variables) for transesterification are as follows: 1:9 ( X MR ) and 3 wt.% ( XC ) on the mass of oil sunflower; temperature = 60 °C; time = 3 h; stirring speed during reaction = 1000 rpm, which is obtained after the conversion of triglycerides to methylesters (97.75 ± 0.02% wt.%). The results showed that after calcination process, a mixed oxide
(CaO and CaCO3) has catalytic activity. The higher surface content of Ca for calcined eggshell compared with that of calcined crabwaste (evaluated by XPS), associated to the high basicity characteristics (evaluated by TPD-CO2) explains the better catalytic performance of calcined eggshell