INFRARED SPECTROSCOPIC INVESTIGATIONS RELATING TO COKE FORMATION ON ZEOLITES .1. ADSORPTION OF HEXENE-1 AND N-HEXANE ON ZEOLITES OF TYPE-Y

The adsorption of hexene-1 and n-hexane on HY, CaY, and Pt CaY has been studied by means of the transmission technique at various temperatures. Especially elucidated was the interaction between the functional OH groups on the internal and external surface and hexene-1 or n-hexane. Primarily not only at low but also at high temperatures a linear surface species is formed, which starts to rearrange at higher temperatures (T ≥ 400 K) to branched species with tertiary carbon atoms. Further heating is accompanied by the appearance of a coke" band at 1585 cm-1. By dynamic and static adsorption experiments the importance of the gas phase and of the surface OH groups with bands at 3640 and 3740 cm-1 has been proved for the formation of coke. The influence of the external OH groups (3740 cm-1) on coke formation is very low below 773 K and the Ca(OH)+ (3585 cm-1) groups do not participate at all in the coking reaction. The highest activity for coking is shown by the OH groups in the supercages (3640 cm-1). © 1979."