| Ethylene glycol ether is one of the important chemical products. Because of the existence of hydrophilic groups such as hydroxyl group and hydrophobic alkyl groups, they are the main nonionic surfactants and the good solvent in industry, which are widely used in washing, paints, leather and so on. Currently, the ethoxylation reaction is traditionally carried out in the presence of alkaline catalysts in the batch reactor of ethoxylation reaction in industry. But in this process, broad-range-distributed products are obtained. At the same time, since these catalysts uniformly dissolve in the reaction system, they pose engineering problems such as the separation of the catalyst from the reaction product, the corrosion of the reaction apparatus and environmental pollution which lead to the comproise of the application of the ethylene glycol ether and the development of the ethylene glycol industry.The ethoxylation reaction catalyzed by supported tungstophosphoric acid catalysts was carried out in a fixed-bed reactor for the first time in this paper. By using SiO2, Al2O3, SiO2-Al2O3 and 5A molecular sieve as supports, tungstophosphoric acid was loaded on them by impregnation method and the structure and propertie of the catalysts were investigated by the techniques of XRD, BET, FT-IR, NH3-TPD and Py-IR. The catalytic performance of the supported tungstophosphoric acid catalysts for the ethoxylation of ethanol and ethylene oxide was tested in a fixed-bed reactor. The influence of support on ethoxylation was discussed and the reaction conditions of ethoxylation reaction were discussed. The main results were as follows:(1) The tungstophosphoric acid supported on the supports-had very strong interaction with the supports and was highly dispersed on the supports'surface, and its Keggin structure was maintained. Support had some influence on the ethoxylation acidity of the catalysts, and the HPW/SiO2-Al2O3 catalyst possessed the most acid sites which exhibited the high activity and the high stability.(2) The loading of tungstosphoric acid and the calcined temperature of catalyst had biggish influence on the cataltsts properties. The tungstophosphoric acid was well distributed on the SiO2-Al2O3 support at the loading range of 5%-35%. Increasing tungstophosphoric acid to 20%, the H3PW12O40/SiO2-Al2O3 reached the highest activity. The calcined temperature of catalysts affected the activity and the stability of the catalysts. When the catalyst was calcined at 300℃, the stability of the catalysts was best. (3) The result of the study on the effects of reaction temperature, reaction pressure, LHSV and the molar rate of ethanol and ethylene oxide on ethoxylation reaction showed that the conversion of ethylene oxide was close to 100% and the selectivity of 2-ethoxyethanol was 85.17%, under the reaction temperature of 100℃, reaction pressure of 0.4MPa, molar rate of ethanol and ethylene oxide of 5and LHSV of 5 h-1.(4) The stability of H3PW12O40/SiO2-Al2O3 catalyst for the ethoxylation of ethanol with ethylene oxide was tested in fixed bed reaction. The result showed that the conversion of ethylene oxide remained up to 90% in initial 24h; and then it decreased as the reaction continued; at last it remained about 50% which was maintained. The reason of the deactivation is ascribed to the dissolution of tungstophosphoric acid as revealed by NH3-TPD of the used catalyst.
|
PDF Full Text Request