气相法合成偏二氯乙烯的高稳定CsNO3/SiO2催化剂

用浸渍法制备CsNO₃/SiO₂催化剂,用于气相催化裂解1, 1, 2-三氯乙烷(TCE)制偏二氯乙烯(VDC)反应,考察了反应温度对CsNO₃/SiO₂催化剂失活的影响。研究发现,在较低反应温度( < 350 ℃)时, CsNO₃/SiO₂催化剂容易失活,在较高反应温度(> 400 ℃)时催化剂的活性较高且不易失活。反应后CsNO₃/SiO₂催化剂中CsNO₃物种转变为CsCl,催化剂表面存在积炭。导致催化剂失活的主要原因不是Cs物种转变和积炭,而是含氯反应产物在低温反应时难以从催化剂表面脱附。这些含氯反应产物能够高温脱附,从而使低温反应失活的催化剂再生。CsNO₃/SiO₂催化剂在400 ℃下100 h寿命实验中, TCE转化率和VDC选择性分别稳定为98%和78%,具有较好的工业应用前景。

Highly Stable CsNO3/SiO2 Catalysts for the Synthesis of Vinylidene Chloride Using a Gaseous Phase Method

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 ℃) lead to a rapid deactivation, while high reaction temperatures (> 400 ℃) 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 HCl) 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 ℃) 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 ℃ for 100 h. The TCE conversion and the selectivity to VDC remained stable at 98% and 78%, respectively, showing good prospect for industrial applications.