Acid-catalyzed ethanol dehydration on zeolite is shown to proceed via a covalent ethoxy group (C2H5O) as a stable intermediate, which was directly observed by IR spectroscopy.

Adsorption and reactions of 2-methylpropene (isobutene) on mordenite were investigated between 150 and 300 K by infrared (IR) spectroscopy. The methyl groups of isobutene interacted with the acidic OH groups of mordenite below 160 K, which was converted to the strongly interacted π-bonded isobutene to the acidic OH groups (π-complex). Above 200 K, the π-bonded isobutene dimerized even under evacuation condition. The stable 2,4,4-trimethyl-2-pentoxy species was identified by FT-IR by comparison with the spectra of the adsorbed C8 olefins. The expected monomeric reaction intermediate, the 2-methyl-2-propoxy (tert-butoxy) species, was not observed. This is probably due to the rapid migration and reaction of the adsorbed isobutene molecules.

The adsorption of alkanes and alkenes on zeolites is investigated by comparing the adsorption characteristics for three types of zeolite: ferrierite, ZSM-5, and mordenite. The activation energy for the diffusion of propane and n-butane on ferrierite and the heat of adsorption of C 2 -C 4 alkanes and alkenes on zeolites and silica are estimated based on Fourier transform infrared spectroscopy, and the diffusion processes in the micropores are elucidated by comparing the results with previously reported activation energies for n-butene diffusion. The adsorption of 1-butene on mordenite is also examined. The structure and process of experimentally observable adsorption is found to differ depending on the type of zeolite and adsorbing molecule, reflecting differences in the sizes of molecules and pores. This differing behavior is utilized to interpret the elementary adsorption processes of alkanes and alkenes on zeolites.

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