科研之友
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摘要
CsNO3/SiO2 catalysts were prepared using an impregnation method, and were applied in the vapor phase catalytic synthesis of vinylidene chloride (VDC) from 1,1,2- trichloroethane (TCE). The influence of reaction temperature on the deactivation of CsNO3/SiO2 catalysts was investigated in detail. It was found that low reaction temperatures (<350 degrees C) lead to a rapid deactivation, while high 'reaction temperatures (>400 degrees C) result in a high and stable catalytic activity. During the dehydrochlorination process, CsNO3 species were transformed into CsCl, and coke was formed and deposited on the catalyst surface. However, the chemical change of the Cs species and deposited coke were not the main reason for the deactivation of CsNO3/SiO2 catalyst. Some chlorine-containing species (organic products or HCI) were formed during the reaction and were difficult to desorb from the catalyst surface, which accounts for the deactivation of CsNO3/SiO2 catalysts at low reaction temperatures. High temperature treatment (550 degrees C) in a non-oxidizing atmosphere could remove the contaminants and regenerate the catalysts completely. The life test of CsNO3/SiO2 catalyst was carried out at 400 degrees C for 100 h. The TOE conversion and the selectivity to VDC remained stable at 98% and 78%, respectively, showing good prospect for industrial applications.
