فهرست نشریات علمی دسترسی آزاد ایران

Optimization of the in situ esterification of rubber seed was investigated in a batch process. Rubber seed is a non-edible seed containing a high vegetable oil content (54.64 ± 1.80%), and therefore, it does not compete with the food sector. The oil in rubber seeds, however, contains a substantial level of free fatty acids, approximately 10.4%. The oil recovery processing step can be reduced by applying in situ esterification. The use of n-hexane as a cosolvent can facilitate oil extraction. Consequently, in situ methanolysis-esterification of rubber seed with n-hexane as a cosolvent was employed to produce a high-yield, low-acid-number methyl ester, which was optimized using a central composite design of the response surface method. The acid number was determined by AOCS Cd 3d-63 titration, and the methyl ester composition was verified using Gas Chromatography-Mass Spectrometry analysis. Optimization of rubber seed in situ esterification resulted in a maximum yield of 89.92 ± 0.99% and a low acid number of 0.45 mg KOH/g at a solution volume of methanol and n-hexane to rubber seed mass ratio of 7:1 mL/g, a methanol volume fraction of 0.44 in the blended methanol-n-hexane solution, and 12.37 wt.% H2SO4 for a reaction time of 5 hours. The methyl ester yield increased and the acid number decreased with increasing reaction time up to 5 hours. Beyond this duration, extending the reaction time did not significantly enhance the methyl ester yield or reduce the acid number. The obtained methyl ester properties complied with the SNI-7182 standard.