Study On The Performance Of Polyvinylpolypyrrolidone Supported Catalyst

Carboxylic esters are widely applied of plasticizers,cosmetics,preservatives,medications,and paints.They are mainly synthesized by esterification of acids with alcohols.Sulfuric acid as a traditional homogenous catalyst for esterification reaction has drawbacks such as equipment corrosion,difficult to separate and environmental pollution.In contrast,heterogeneous catalysts are very important for esterification reaction due to their ease of separation and excellent performance.Thus,developing a new heterogeneous catalyst is a crucial task for esterification reactions.Among the developed heterogeneous catalysts for esterification reactions,the supported ionic liquid has many advantages.Such as high reusability and easy to separate.In this paper,a novel supported ionic liquid catalyst with high catalytic activity,[PVPP-BS]HSO₄,waspreparedbythereactionofSO₃H-functionalized polyvinylpolypyrrolidone?PVPP-BS?with H₂SO₄.The catalyst was characterized by FT-IR,TGA and FE-SEM and applied in the synthesis of butyl butyrate,tributyl citrate and methyl benzoate.The catalytic activity of the supported ionic liquid in the synthesis of butyl butyrate was carefully investigated.Under the optimized conditions of alcohol to acid molar ratio of1.7:1,catalyst amount of 8 wt.%,reaction temperature of 120°C and reaction time of 3 h,the conversion of butyl butyrate reached 95.9%.The catalytic activity of[PVPP-BS]HSO₄remained satisfactory for the synthesis of butyl butyrate after 6 cycles.Its catalytic activity in the synthesis of tributyl citrate?TBC?was studied.The optimized conditions in the single factor experiments are n-butanol to citric acid molar ratio 5:1,catalyst amount of 6 wt.%,reaction temperature of 115°C and reaction time of 5 h.Based on these conditions,a Box-Behnken response surface method was used to establish a mathematical model with the yield of TBC as the response value.Then,the process was optimized.The results showed that the optimal conditions for this esterification are n-butanol to citric acid molar ratio of 5.2:1,catalyst amount of 6.6 wt.%,reaction temperature of 120°C and reaction time of 5.5 h.Under optimized conditions,the conversion of citric acid and the yield of TBC were 97.5%and 92.9%,respectively.Moreover,the catalyst could be reused 5 times without a noticeable decrease in its activity.The[PVPP-BS]HSO₄ catalytic activity in the synthesis of methyl benzoate via conventional-heating and microwave-assisted methods were also studied.When the conventional-heating method was used,the optimized conditions were alcohol to acid molar ratio of 4:1,catalyst amount of 4 wt.%,reaction temperature of 75°C and reaction time of 2 h.The conversion of benzoic acid was 64.2%.Whereas,the microwave-assisted method optimized conditions were alcohol to acid molar ratio of 4:1,reaction temperature of 130°C,catalyst amount of 4 wt.%and reaction time of 60 min.Under this conditions,the conversion of benzoic acid reached the maximum of 85.5%.