Evaluation of nopol production obtained from turpentine oil over Sn/MCM-41 synthesized by wetness impregnation using the Central Composite Design

A face-centered Central Composite Design (CCD) was used for nopol synthesis from turpentine oil over Sn/MCM-41 catalyst synthesized with sodium silicate as silicon source and incorporating Sn by wetness impregnation using SnCl2.2H2O as metal source. The catalyst was characterized by XRD, NH3-TPD and UV–vis-DRS. The catalyst was used four times without an apparent loss of catalytic activity and with no leaching of Sn. The CCD was constructed from 24 factorial points, eight axial points and seven central points, with time, paraformaldehyde to β-pinene molar ratio, catalyst concentration and solvent to β-pinene ratio as factors. Three response variables were selected (β-pinene conversion, nopol selectivity and nopol yield), and second order models were obtained taking into account all possible effects and identifying the non statistically significant effects. The optimal values found by response surface methodology were 71 %, 99 % and 61 % for conversion, selectivity and yield, respectively. The reactions were carried out under the established optimal conditions and the error varied between 2.14 and 2.63 %. Finally, the assumptions of independence, normality and homoscedasticity for each of the models were satisfactorily validated.