Mass Transfer And Reacion Kinetics Of Alkyl Polyglucosides Synthesis With One-step Method

Surfactant,which is known as an industrial monosodium glutamate,is a kind of essential assistant for daily life and industrial production.As a non-ionic surfactant,alkyl polyglucosides(APGs)are by far the most important sugar-based surfactant.Glycosylation of Fisher process(one-step method)between D-glucose and fatty alcohol is the oldest known method for manufacturing of APGs.The complex composition of final mixture results from the competition between many element reactions.The complexity of the reaction process clearly restricted the study of reaction kinetics.It is very interesting and valuable to study the reaction kinetics of one-step method.In this paper,a kinetics model is proposed based on the analysis of reaction mechanism?The reaction process is simulated with this model,accompanied with the liquid-solid mass transfer model.The main work and important results are summarized as follows.(1)A special sample instrument is designed,and an analysis method is established.A special sample instrument is designed based on the reaction properties.The problems,such as sample occlusion,and liquid coherence,are solved with this method.The sample accuracy is ensured.The component concentration is measured with its content in unit mass of 1-dodecanol.Gas chromatography is used to analyze the sample.Polysaccharose is extracted from the system using ethanol and water respectively.The content of polysaccharose is determined using phenol-sulphuric acid method.The alcohol extraction and water extraction time is four hours and three hours respectively.(2)The reaction process of one-step method is studied,and the kinetics model structure is established.The reaction between D-glucose and fatty alcohol follows the liquid mechanism.D-glucose is reacted with 1-dodecanol to form monoglucoside.The formed monoglucoside can be reacted with D-glucose further to form diglucoside.The main by-products are disaccharide and polysaccharide.The place where the side reaction takes place is the solid phase.The experiments results show that the reaction temperature,the catalyst system,the catalyst content,and the ratio of D-glucose and fatty alcohol,all can influence reaction time and reaction selectivity.The conclusions can explain the experiment results successfully.D-glucose solubility in 1-dodecanol,1-decanol and 1-octanol from 343.15 K to 393.15 K is determined respectively to study the reaction kinetics.Modified UNIQUAC model,S-UNIFAC model,and mS-UNIFAC model are applied to predict the solubility data,and the interaction parameters are determined.In the three models,the modified UNIQUAC model shows better prediction accuracy.Some kinetics aspects of the glycosylation of D-glucose to polyglucosides,catalyzed by dodecylbenzene sulfonic acid,are examined.A detail reaction pathway is proposed.Using several assumptions,a kinetics model at low catalyst concentration is derived.Several batch experiments are carried out to study the reaction kinetics.A comparison between the simulated results and the experimental data shows that the agreements are in general satisfactory.(3)A liquid-solid mass transfer model is proposed.A single solid particle mass transfer is proposed from boundary layer theory and turbulence structure theory respectively.The models based on the two theories are similar in structure.The particle size,the Reynolds number,and the Schmitt number can influence the mass transfer process.The particle size exponents of particle shape coefficient and particle size decreasing rate are integrated,and the mass decreasing rate of this single solid particle is obtained.Under some reasonable assumptions,the mass transfer model for the whole D-glucose solid phase is obtained.The mass transfer model parameters are determined with the evolution of D-glucose concentration in liquid phase.Experiments are conducted to investigate the influence of particle size distribution,stirring speed,temperature,and the content of solid phase on the mass transfer process.The influence of temperature and stirring speed on mass transfer can be correlated with Sherwood number,Reynolds number,and the Schmitt number.The solubility of D-glucose under different glucoside concentration at different temperature is determined.The solubility data can be correlated with different quadratic polynomials.(4)A reaction kinetics study under high catalyst concentration is conducted.The solubility of D-glucose in 1-dodecanol is very low.It is almost impossible to study the reaction kinetics under high catalyst concentration.In this paper,the heterogeneous reaction results,accompanied with the liquid-solid mass transfer model,are applied to determine the kinetics model parameters under high catalyst concentration.The influence of temperature on reaction is studied,and the activation energy for the different step is determined.The influence of catalyst concentration on reaction is studied,and the reaction constants under high catalyst concintration are determined.The bulk transformation coefficients under different conditions are calculated with the kinetics model and mass transfer model.The results show that,the mass transfer rate is important for the one-step reaction process,and the method to intensify the mass transfer process is necessary to increase the reaction rate.The average polymerization degree of products under different conditions is simulated with the models proposed in this paper.