Fritz Blatter

Selective oxidation of propylene by O2 with visible light in a zeolite

Propylene and O2 loaded into zeolite BaY were found to react upon irradiation with green or blue light in a single photon process. In situ monitoring by FT-infrared spectroscopy showed that allyl hydroperoxide is the predominant product at −100°C. At room temperature, acrolein, propylene oxide, and allyl hydroperoxide were observed in comparable amounts. The aldehyde and epoxide are shown to emerge from secondary thermal chemistry of the allyl hydroperoxide photoproduct. The selectivity in terms of the hydroperoxide photoproduct is very high (98% at room temperature) even at high propylene conversion. Diffuse reflectance spectra show that access to the mild oxidation path is made possible by a zeolite-induced shift of the propylene O2 charge-transfer absorption from the UV into the visible region.

Oxidation of propane to acetone and of ethane to acetaldehyde by O2 in zeolites with complete selectivity

Oxidation of propane by O2 to acetone was observed in solvent-free BaY and CaY under irradiation with visible light as well as under dark thermal conditions. The reaction was monitored in situ by FT-infrared spectroscopy. In the case of the photochemical oxidation, isopropyl hydroperoxide was detected as reaction intermediate. No byproduct was observed even upon > 50% conversion of the alkane. Ethane was oxidized completely selectively to acetaldehyde in CaY under irradiation with blue light.

Selective photooxidation of abundant hydrocarbons by O2 in zeolites with visible light

Summary Selective oxidation of small alkenes and of toluene by O2 has been accomplished by irradiation of the reactants in zeolite Y with visible light. Products are industrially important compounds like benzaldehyde (from toluene) and acrolein (from propylene). The key to these tightly controlled reactions is an unprecedented stabilization of hydrocarbon•O2 excited charge-transfer states by the ionic environment of the zeolite matrix cage.