摘要
测过了吡啶、己烯和1,5-己二烯在NaY,CaY,HY和 USY等沸石上的微分吸附热和相应的红外谱图。结果表明,烯烃吸附热的大小是由沸石表面酸中心的性质和吸附质分子的性质共同决定的。沸石表面的酸性强,气体分子中的活性部位(如双键)多,则吸附热大。当1,5-己二烯吸附时,吸附分子可以占据两个活性中心,分步打开两个或一个双键。通过分子内或分子间的活化,发生异构或聚合反应。因此,吸附初始阶段的量热曲线上出现双峰,整个微分吸附热曲线呈波浪状。
The differential heat of adsorption and IR spectra for pyridine, he-xene and 1,5-hexadiene adsorbed on USY, HY, CaY and NaY zeolites were measured with a SETARAM microcalorimeter and IR spectrophoto-meter. The values of heat of adsorption for alkene depend on the acidity of the zeolites, and the properties and structure of the adsorbates. The B acid sites are much more effective than the L acid sites for activating the π-bonds of alkenes.One molecule of 1,5-hexadiene could be adsorbed on two adjacent acid sites of the zeolite surface. After one π-bond of hexa-diene molecule broken down to meet the surface protonation, another π-bond would be opened successively. Thus the 1,5-hexadiene molecules activated by intra- and inter-molecular interaction would be isomerized or polymerized on the zeolite surface. Therefore, there were two peaks on the calorimetric curves for each dose during the initial adsorption measurement and the curves of differential heat of adsorption of 1,5-hexadiene on zeolites were wave in shape.
