环状烯烃在USY和NaY上吸附的量热和IR研究

CALORIMETRY AND IR STUDY ON ADSORPTION OF CYCLO-ALKENES ON USY AND NaY ZEOLITES

用量热法测定了部分环状和支链烯烃、烷烃在USY上的吸附热及它们在USY和NaY沸石上的IR谱。在USY上吸附时,六碳环状烯烃分子和多支链烯烃分子扩散阻力比相应烷烃分子的大得多,吸附质分子不能占据全部活性中心。即使在室温下,环状烯烃在USY上吸附打开双键后,所生成的正碳离子也可进行脱氢和骨架重排反应,并生成缺氢化合物及芳香化合物。脱氢是分步进行的。环状正碳离子脱氢生成的环烯正碳离子等在～1500cm^(-1)处有一个强的IR吸收峰。

Differential heats of adsorption of several cyclo- and branched-alkenes and alkanes on USY and NaY zeolites and corresponding IR spectra were measured. In the process of adsorption on USY zeolites, the diffusion resistances of cycloand branched-alkened with 6 carbon atoms were much higher than those of alkanes with similar molecular structures. Therefore, they could not occupy all active sites on USY zeolites. Cyclo-carbonium(et al.) formed by cycloalkenes reacting with H^+ of USY could rearrange their skeletons and dehydrogenate to form hydrogen deficient and aromatic compounds even at room temperature. The dehydrogenation was a stepwise process. Cycloalkene carbonium(et al.) formed by dehydrogenation of cyclocarbonium showed strong IR adsorption peaks at～1500cm^(-1).