Pilot-scale Experiment And Process Optimization Of Triacetin Systhesis Via Reactive Distillation Technology

Triacetin(TAG),also known as Glyceryl Triacetate,has expanded uses in perfume,coating,pharmacy,cigarette and other fields.So far,the most-used TAG industrial production process is direct esterification of glycerol and acetic acid in the presence of concentrated sulfuric acid.However,glycerol esterification with acetic acid to produce TAG is an exothermic reaction kinetically limited and associated with complex cascade reactions behavior,which results in the TAG production having many problems such as incomplete reaction,low yield of TAG and long reaction time by traditional method of reaction first followed by separation and purification.Therefore,we propose to produce TAG via continuous reactive distillation(RD)technology.This paper focused on the feasibility and optimal design and operation parameters of TAG production by RD technology from glycerol and acetic acid.A novel structured catalytic packing,seepage catalytic packing internals(SCPI),filled with NKC-9 cation exchange resin was used in this study.In the first part,experiments were conducted to determine the kinetics of glycerol and acetic acid esterification reaction in the presence of NKC-9 in a 500 ml batch reactor.When the experimental conditions were set as: 95℃ for reaction temperature,9:1 for AA/G mole ratio.99% conversion of glycerol and 88% yeilds of diester and triester of glycerol were obtained in the experiments.The results indicate that the catalyst has good catalytic performance in the esterification reaction system of glycerol and acetic acid.The kinetic data obtained in the experiments will be used in the reactive distillation process simulation.Second,to verify the feasibility of TAG production by RD with novel catalytic packing SCPI,a series of pilot-scale experiments were conducted to investigate the feasibility of TAG production by RD.Complete glycerol conversion could be easily achieved and the highest purity of TAG in the experiments could reach 81.45%,which validating RD is a potential candidate for TAG production.Third,based on the components analysis of crude products from the reboiler of the pilot-scale RD experiments,experimental study on distillation process of triacetin purifying was carried out.Finally,a rigorous mathematical model based on the chemical kinetics and thermodynamic method was developed and the accuracy of the model was validated by comparing with the experimental data,furthermore the influence of important design and operation parameters on glycerol conversion and TAG purity were studied systematically by using sensitivity analysis tool.The results indicate that the feed position of acetic acid should be located at the bottom of reactive section,a range of 3-4.5 for AA/G mole feed ratio,35 kPa for column head pressure,50 theoretical stages for reactive section and a range of 4-6 for reflux ratio is desirable to get high TAG purity in bottom stream and low energy consumption.