Technical Study On Catalytic Hydration Of Ethylene Oxide For Preparing Ethylene Glycol

Ethylene glycol (EG) is an important chemical product. Now a particularly important use of EG is in the production of polyester fibers. At present, the direct hydration for synthesis of EG from ethylene oxide (EO) is universally adopted on large-scale production plant in and out abroad. But the direct hydration has a serious limitation that it wastes massive energy to vaporize the superfluous water in production, which doesn't accord with the demand of energy saving and carbon emission reduction . So all of the global producers of EG are exertting themsevles to exploit the fixed bed reaction technology. We developed a new process of EO catalytic hydtraion to produce EG on series multi-fixed bed reactors. We used the strongly basic anion-exchange resin catalyst S201 which degree of cross linking was 2%, adopted the way of multi-stage feeding and controlling the temperature respectively according to the demand. The heat was effectively removed. The expansion of resin catalyst was resolved and the operating life of catalyst greatly extended by this method. Meanwhile, the kinetics of heterogeneous catalytic hydration of EO was studied and the resin catalyzed process was suitably interpreted for industrialized production of EO catalytic hydration. We also studied thermal stablility of anion exchange resin. The quaternary ammonium anion exchange resin catalysts was nitrified, then it was used to EO catalyze hydration. The main resultes are as follows:We prepared the styrene-divinylbenzen alkaline anion-exchange resin catalyst S201, which degree of cross linking was 2%, and used it into catalytic hydrolysis of ethylene oxide. In the mean time we studied its thermal stability and expandability also. The results showed that S201 had high alkaline capability and fine thermal stability. Both the conversion of EO and the selectivity of EG could reach 99.9% and 96.6%, under the reaction conditions of 358K, the pressure of 1.5MPa, the initial mole ratio of water and EO 6, the space velocity of 1.0 h-1. After 1800 hours, it also had higher activity and its expansive rate was only 6.8%. The kinetics of heterogeneous catalytic hydration to ethylene glycol on anion-exchange resin catalyst S201 in the HCO3- form, was studied in an isothermal integral reactor under the reaction conditions of 343K~363K, the pressure of 1.0~1.5 MPa, the initial mass ratio of water and EO 4~6, the space velocity of 0.5~4h-1.According to the experimental findings the kinetic model was fitted and compared with the kinetic model proposed by the Langmuir. The results showed that the reaction rate to concentration of EO had the 1.5 order reaction, which the activation energy was 23.8kJ/mol and the pre-exponential constant was 2.4×104 mol-0.5·L1.5·(g·h)-1. Compared with the non-catalytic hydration, the anion exchange resin S201 could sharply decrease the activity energy and heighten the reaction rate. A new process of EO catalytic hydtraion to produce EG in series multi-fixed bed reactors was researched. The effects of reactive conditions on multi-stage product yields were particularly studied, than compared to the normal hydration. The results showed that the multi-stage was superior to the single-stage. Both the conversion of EO and the selectivity of EG could reach 99.9% and rised form 96.2% to 98.0%, with the catalyst running 2880 hours, under the reaction conditions of 350K, 348K, 343K, the pressure of 1.0 MPa, the initial mole ratio of water and EO 8, the space velocity of 2.0 h-1. The multi-stage craft settled the expansion of resin and highly increased the operating life of the catalyst.The quaternary ammonium anion exchange resin catalysts(S211) was nitrified, then it was changed into bicarbonate type to catalyze EO hydration.The catalytic behaviors of the resin fore and after nitrified were observed. the result showed that the nitroresin (N211) had a better thermal stability. Both the conversion of EO and the selectivity of EG rised form 89.8% to 99.9% and 94.2% to 95.6%. with the catalyst running 980 hours, under the reaction conditions of 348K, the pressure of 1.0 MPa, the initial mole ratio of water and EO 6, the space velocity of 1.0 h-1. After nitration the loss fact of bsae exchange capacity decreased 51 percent.