| Chloroacetic acid is one of the basic chemical products,which is widely used in medicine,pesticide,activator and many other fields.Batch process is widely used to produce chloroacetic acid in China.There are many problems of current MCA processes,such as long production cycle,high consumption of raw maternals,poor product quality,heavy environmental pollution and low automation.The aim of this thesis is to develop a new process of chloroacetic acid with high efficiency and low consumption.The specific work includes:1)The kinetic data of chloroacetic acid synthesis under oil bath and microwave heating were measured,and the effects of reaction parameters on the synthesis of chloroacetic acid were studied.For oil bath heating:The effects of reaction temperature,catalyst dosage and chlorine flow rate on chlorination production were studied.The amount of catalyst showed maximum influence on the reaction rate of acetic acid chlornnation and the maximum MCA concentration.In actual production,the amount of acetic anhydride should not be less than 10%(wt),and the reaction time should be 3-4 hours.The best temperature control strategy is keeping high temperature(120 C)in the early stage(0-4h)and low temperature(l 10 C)in the later stage(>4h),and the optimum chlorine flow rate is 300 ml/min.For microwave heating:The effects of reaction temperature,catalyst dosage and microwave power on the chlornnation process were studied.The experimental data showed that microwave could enhance the chlorination process,increase the reaction rate and the selectivity of chloroacetic acid.The reaction rate and maximum yield of chloroacetic acid synthesized by microwave were higher than that of oil bath,and microwave heating had better selectivity than oil bath heating.The advantage of microwave heating was more obvious at 100-110 0C.The optimum conditions for synthesis of chloroacetic acid under microwave irradiation are acetic acid:acetic anhydride = 100:15,reaction temperature 100-110 C,microwave power 200 W,and chlornne flow slightly excessive.2)Establishment of kinetic model of MCA synthesis by oil bath and microwave.A formula for descrnbimg the loss of acetyl chloride was proposed.It is found that the fitting accuracy can be effectively improved by introducing the correction term of acetyl chloride concentration.The comparison of multiple correction terms models shows that the Quasi-First-Order series model with volume correction term,acetyl chloride concentration correction term and competition factor correction term is the best.For oil bath,the activation energies of chloroacetic acid,dichloroacetic acid and trichloroacetic acid were found to be Ea1= 50.02kJ/mol Ea2 = 53.96kJ/mol,Ea3= 68.15kJ/mol respectively.The corresponding activation energies under microwave heating was Ea,= 49.95kJ/mol Ea2= 55.15kJ/mol,Ea3=53.12kJ/mol ·The simulation results showed that microwave can improve both the chlorination efficiency and the selectivity of chloroacetic acid synthesis.3)Study on the simulation and optimization of chloroacetic acid process.The Aspen Plus computer model of both intermittent chlorination process and acetic acid continuous chlorination process with an annual output of 20,000 tons of MCA was established according to the operating parameters from a real plant.By analyzing the exergy balance of the process,the exergy loss of the operation unit was determined,and the key to the energy loss of the system was found out.To optimal processes were proposed based the comprehensive analysis of the real process.The calculation results showed that compared with batch process,the consumption of acetic acid of proposed process was decreases by 30.66%and the unavailable useless heavy component decreases by 97.49%. |
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