Optimization of Process Variables in the Synthesis of Tributyl Citrate Using a Polyvinylpolypyrrolidone-Supported Brønsted Acidic Ionic Liquid Catalyst

Song Wang,Linlin Xu,Chengcheng Tian,Yinyan Guan,Lanlan Xu

doi:10.1155/2018/1953563

Song Wang, Linlin Xu + Show 3 more

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https://doi.org/10.1155/2018/1953563

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Abstract

A polyvinylpolypyrrolidone- (PVPP-) supported Brønsted acidic ionic liquid catalyst ([BsPVPP]HSO4) was synthesized by the reaction between SO3H-functionalized PVPP and H2SO4. The prepared catalyst was characterized by IR, XRD, FESEM, TG, and DSC. The catalytic activity of [BsPVPP]HSO4 in the preparation of tributyl citrate (TBC) by the esterification reaction between citric acid and n-butanol was investigated. Response surface methodology (RSM) was applied to optimize the process variables of the esterification reaction. The variables, including the reaction time, the n-butanol-to-citric acid mole ratio, the reaction temperature, and the catalyst amount, were optimized by a Box-Behnken design. Under optimized conditions, with a n-butanol-to-citric acid mole ratio of 5.2 : 1 and a reaction temperature of 120°C, the TBC yield reached 92.9% within 5.5 h in the presence of 6.6 wt% of catalyst; this result is in good agreement with the values predicted by the mathematical model. Moreover, the catalyst could be recycled four times with high catalytic activity.

Highlights

Tributyl citrate (TBC) is usually applied as a thermally stable, high-performance, and nontoxic plasticizer in toys, medical products, biodegradable polymers, and food additives [1,2,3,4]
To optimize the reaction conditions for [BsPVPP]HSO4-catalyzed esterification reaction of n-butanol with citric acid, a three-level and four-factorial Box-Behnken design was designed to investigate the influences of the reaction conditions on the TBC yield
The results indicate that both the citric acid conversion and the TBC yield increased when the temperature increased from 105°C to 115°C

Summary

Introduction

Tributyl citrate (TBC) is usually applied as a thermally stable, high-performance, and nontoxic plasticizer in toys, medical products, biodegradable polymers, and food additives [1,2,3,4]. Metal oxide and zeolitesupported catalysts have attracted more and more attention [7,8,9,10] These heterogeneous catalysts have some disadvantages, including low product selectivity, high mass transfer resistance, and rapid deactivation during the esterification reaction. Because of their excellent thermal stability, negligible volatility, and tunable acidity, acidic ionic liquids (ILs) have been utilized as environmental friendly reagents for organic reactions [11,12,13,14,15,16,17]. Heterogeneous polymer-supported catalysts had been developed to solve these problems because of their environmentally friendly characteristics, such as excellent chemical stability, efficient recover ability, and recyclability [21,22,23,24] These properties make polymer-supported ILs suitable candidates for catalytic reactions.

Experimental Approach

Catalyst Preparation

Results and Discussion

Conclusion