Dual behavior of ZSM-5 as Bronsted acid and electron acceptor in the adsorption of N,N '-diphenylhydrazine

Incorporation of N,N'-diphenylhydrazine into HZSM-5 led to the formation of azobenzene and aniline (70-80 mol-% mass balance). The formation of azoben zene can be followed by the appearance in diffuse reflectance UV/Vis spectr oscopy of a characteristic band (lambda max = 420 nm). IR spectra of the ex tracted solids indicate that some aniline is retained in the zeolite, proba bly due to acid-base interaction with active sites. The products are ration alized by two competing mechanisms: the formation of azobenzene by electron transfer to an oxidizing site, the generation of aniline by proton transfe r from a Bronsted acid site. A long-wavelength diffuse-reflectance band (la mbda max = 800 nm) in the initial stages of the reaction supports the inter mediacy of a radical cation. These results show that acid zeolites can exhi bit a dual behavior against basic substrates with low oxidation potential, serving simultaneously as electron acceptor and Bronsted acid.