摘要
沸石的酸催化反应中的一个很难避免的副反应就是催化剂的结炭。结炭使催化剂表面生成一些分子量很大、贫氢并且极不活泼的“焦炭”物质,使得催化剂中毒,活性下降。众多的研究认为:沸石结构、表面酸性质及Si/Al比等都对结炭反应有重要影响。但关于结炭机理的研究报道不多,且已有的结果矛盾很多。
Various intermediates and coke forwation during the reaction of 1-hexene on faujasites with different framework Si/Al ratios were studied by UV-VIS and IR. After the admission of adsorbate l-hexene at room temperature, allyl carbonium ions were immediately formed in the zeolite cavities. At elevated temperature (>100℃), polyenic carbocations and low-ring aromatics could be detected. Further elevation of temperature to >150℃ resulted in coke formation as shown by the strong absorption bands at around 1600cm-1 on IR spectra and 225, 265, 425 nm on UV-VIS spectra, indicating that the polyenic carbocations and low-ring aromatics are the important precursors of coke. Absorption bands related to coke are weakened with increasing the framework Si/Al ratio of faujasite.
基金
国家自然科学基金
