The Research Of One-Step Preparation Of Ethylene Glycol Though Ethylene Catalyzed By TS-1

Currently EG is industrially produced via traditional oil ethylene route which has two steps:oxidation of ethylene to ethylene oxide (EO) and the following hydrolysis of EO to EG. Epoxidation of ethylene is commercially operated over silver-based catalysts with oxygen or air as oxidants and the single-pass ethylene conversion is about 4-8%. In order to keep the high conversion of EO should be operated at a high molar ratio of H2O/EO(15～20) for the hydrolysis of EO to EG, thus causing the high energy consumption in the following purification steps.The green catalyst system TS-1/H2O2 is used to catalytic conversion of ethylene to ethylene glycol in this paper. TS-1 was prepared by using a modified hydrothermal method, and the attention was specially paid to the effect of crystallization time on the contents of the framework Ti species.The results shown that with the crystallization time increase non-framework titanium species gradually transform into framework Ti species, especially when the crystallization time is 24h, the relative crystallinity of TS-1 samples reach the highest point. The optimum Si/Ti molar ratio of the TS-1 samples is 50, if add more titanium source the amount of non-framework Ti species will be increased and mostly are anatase TiO2.The reaction conditions for the conversion of ethylene to EG were optimized by varying a parameter at once when the others were fixed. The optimized conditions for tank reactor were 60℃,1.0mol/LH2O2, 1wt %catalyst and relative high ethylene pressures. Under such conditions, the H2O2 utilization efficiency and the selectivity to EG could be as high as 85% and 94%, respectively.Additional rate measurements indicated that the acidity of titanium hydroperxo species, rather than H2O2 or the intrinsically weakacidity of TS-1 sieves, should be responsible for the ring-opening process ofoxirane reactionintermediates.TS-1 powder was mixed with silica aerogel to improve its mechanical strength for the use in a flowing fixed-bed reactor. The optimized conditions contained a temperature of 50℃, an ethylene pressure of 3.0MPa, n(C2H4)/n(H2O2) ratio of 2.5, and space velocities of H2O2 and ethylene of 0.08h-1 and 0.2h-1, respectively. The H2O2 conversion and EG selectivity were both above 96% even after reaction for 200 h under these optimized conditions.