Study On Synthesis Of Ethylene Glycol Monoethers In Semi-batch Reactor

Ethylene glycol ether is one of important derivatives of ethylene oxide. It is of excellent performance as solvent and detergent, which is widely used in industrial applications, such as in coatings, paints, inks, resins and so on. Ethylene glycol monoethers is synthesized from ethylene oxide and low molecular alcohol (methanol, ethanol, butanol) in the presence of catalyst in industry. Ethoxylation is a special kind of chemical reaction and is highly exothermic reaction. In addition, ethylene oxide is a very reactive, flammable and explosible reactant. So the requirement of security for the plant is very high. The new technique of continuous catalytic distillation had been proposed in our laboratory in order to develop a green energy-saving technique for synthesis of ethylene glycol monoethers. In order to understand the feasibility of the new technique and establish the kinetic equations, semi-batch reactor is particularly used in this work for the synthesis of ethylene glycol monoethers, aimming at establishing an important foundation on the development of the new catalytic distillation technique.The main study, the adopted method and the obtained results in this work are as follows:1. The experimental study of low molecular alcohol ethoxylation is carried out and the optimum process conditions are determined.The effects of process conditions, such as stirring rates, the amount of catalyst, the feed ratio of substrate to ethylene oxide, the reaction temperature and pressure, on the selectivity of ethylene glycol monoethers are investigated in a 2L semi-batch reactor. As a result, the optimum operation parameters are obtained. The optimum operation parameters of synthesis of ethylene glycol monobutyl ether are as follows: the amount of catalyst is 0.2%, the reaction temperature is 373 K, the feed ratio of substrate to ethylene oxide is 3 and the pressure is 0.35 MPa. In these conditions, the selectivity of ethylene glycol monobutyl ether of 81.36% can be achieved. The optimum operation parameters of synthesis of ethylene glycol monomethyl ether are as follows: the amount of catalyst is 0.5%, the reaction temperature is 353 K, the feed ratio of substrate to ethylene oxide is 2.5 and the pressure is 0.40 MPa. In these conditions, the selectivity of ethylene glycol monomethyl ether of 82.87% can be achieved. This study can provide the necessary data and efficient theoretical guidance for the process of industrial production.2. The reaction kinetic study of synthesizing ethylene glycol monoethers catalyzed by a new type of solid base is carried out and the kinetic equations are established.Firstly, the experimental data of kinetic are measured in a 2L semi-batch reactor. Secondly, a kinetic model of general utility for interpreting ethoxylation behavior is established by supposing the reaction rate of all steps being approximately identical based on the reaction mechanism. Thirdly, the calculation method of ethylene oxide concentration in liquid is established. Based on the suggested approach, the concentration of ethylene oxide in liquid can be estimated from the temperature and pressure of reactor, the partial pressure of nitrogen, the amounts of ethylene oxide introduced and the composition of substrate in reaction mixtures. Finally, the kinetic equations of n-butanol and methanol ethoxylation are obtained. The activation energy of n-butanol ethoxylation is 73061 J·mol-1, the pre-exponential factor is 7.232×10~6 m~3·mol-1·s-1; the activation energy of methanol ethoxylation is 60161J·mol-1, the pre-exponential factor is 5.232×10~7 m~3·mol-1·s-1. The data obtained in this study can provide theoretical foundation for the development and scale-up of the new technique of synthesizing ethylene glycol monoethers.3. The study of simulation for the industrial reactor is performed and the mathematical model and simulation method of semi-batch reactor are proposed.Firstly, the whole reaction process is divided into three stages according to the characteristic of the industrial reactor: the stage of trial introduction for ethylene oxide, the stage of reaction with constant pressure and the aging stage. Secondly, the mathematical model of reaction process is established based on the suggested kinetic equation. Thirdly, with three reactor series, these three stages are simulated respectively by means of RBatch module in Aspen plus simulation software. The profiles during the reaction process of molar fraction of ethylene oxide in liquid and vapor, reactor pressure and product composition are obtained through simulation. Finally, the simulation results are compared with that of industrial and the good agreement verified the reasonableness and reliability of kinetic equation obtained and the method proposed. This study can provide model support for the operation of the industrial reactor and give theoretical guidance to ensuring the safe operation of the plant.