Study On Process Intensification Of Chlorination Of 1,3-dichloro-2-butuene

Persistent by-products such as 1,2,3,3-tetrachloro butane (TCBd) and 1,2,2,3,4-pentachloro butane (PCB) were obtained in the process of chlorination 1,3-dichloro-2-butene(DCB) with Cl₂ to produce 2,3,4-trichloro-2-butene(TCB). Lots of by-product were produced for the use of inefficient catalysts and backward agitator in the chlorination of DCB in the Chinese large chemical factory, which serious environmental pollution and it is difficult to obtain goals of energy saving as well as emission reduction, presently.To develop process intensification, for which purpose of low consumption, high yield, environmental protection, is guarantee of sustainable development of chemical industry. Both gas-liquid mass transfer and reaction selectivity have influence heavily in consumption and yield in the process of reaction DCB with Cl₂.DCB distillation liquid (≥93 wt%) and chlorine (industrial grade) are supplied by Chinese large chemical factory for situ experiments in this work. To enhance the gas-liquid mass transfer between Cl₂ and DCB and improve the selectivity of TCB, effects of catalysts and agitator on process intensification were investigated, and then effects of reaction time, reaction temperature and flow rate of chlorine on DCB chlorination process were studied.First of all, effects of metal chloride catalysts (ZnCl₂, CuCl, FeCl₃, AlCl₃), ionic liquid catalysts ([Bmim]Cl, [Bmim]PF₆, [Bmim]BF₄), inhibitors (aniline, phenol, nitrogen and oxygen free radicals piperazine pyridine alcohols, ethylene diamine) on DCB chlorination were investigated. The results showed that the yield of TCB decrease in the presence of metal chlorides or ionic liquids, and the yield of TCB increase in the presence of inhibitors compared with blank experiment.Secondly, the effect of straight blade turbine agitator, 4cm disc agitator, 5cm disc agitator on Cl₂-DCB flow field and power were simulated with CFD software MixSim2.0.2, and effect of agitators on DCB chlorination were studied under the conditions of the chlorine eccentric jet. The results showed that 5cm disc agitator have a better gas-liquid mass transfer effect than the other agitators.Finally, effects of the reaction time, temperature, chlorine flow rate on DCB chlorination were investigated. The results showed that reactions to form TCB and TCBd are parallel reactions, PCB is the poly-chloride from TCB continuous reaction. Lower temperature and smaller chlorine flow conditions are useful for the formation of TCB.The optimum conditions obtained were volume of DCB 600 mL, chlorine flow rate 0.01m³/h, temperature 278 K, piperidine nitroxides alcohol 0.015 mol, 5cm disc agitator (rotational speed 100 rpm), reaction time 4 hrs; and the content of TCB was 80.5%, which increased 5.4% comparing with small experiment of original process.