Preparation of diesters using acidic mesoporous catalysts

Abstract

SBA-15 and FSM-16 catalysts, which contained propyl sulfonic, aryl sulfonic or aluminium, were synthesized by hydrothermal method. The synthesized materials were characterized by X-ray powder diffraction, nitrogen sorption analysis, scanning electron microscopy, sulfur elemental analysis and ammonia temperature programmed desorption techniques. When comparison between synthetic catalysts, the FSM-16-PrSO3H was the best efficient catalyst. Catalytic performances of FSM-16-PrSO3H were studied via estrification of adipic acid with 2-ethyl hexanol. The optimum condition on lubricating oil additive preparation was carried out over catalyst amount of 3%wt. of the reaction mixture at 100 oC for 5 hrs. with stirring speed 150 rpm. and molar ratio of alcohol to carboxylic acid as 2. The reaction mixtures exhibited highest 2-ethyl hexyl adipate esters yield as 96.2% with 86.0% of diester and 14.0% of monoester selectivities. An increasing in the 2-ethyl hexanol to adipic acid molar ratio resulted in an improvement of the diester yield and selectivity. The molecular size of diacid was significantly affected, when the number of carbon in the linear alkyl chain of dicarboxylic acid was increased, the diester yield and the diester selectivity were decreased due to the enhacement of steric effect. The FSM-16-PrSO3H was used for two times to examine its reusability. It was indicated that the catalyst can be reused without losing catalytic activity when using hexane as washing agent.