Direct Oxidation Of Benzene To Phenol And Propane To Propylene By N₂O Over Fe-based New Type Zeolites

As one of the major air pollutants, N2O is harmful to natural environment and human health. Recycling of the waste N2O generated in the industrial production of adipic acid has very significant economic and social benefits to the turning waste into treasure and reducing the environmental hazards. In this thesis, one-step oxidation of benzene to phenol and propane to propene with N2O have been investigated in details over iron impregnated new type Al-rich Beta and ZBM-10intergrowth zeolites, respectively. The effects of different pretreatments on the catalyst performances were studied systematically. Moverover, the catalyst structures were characterized by a comibination of low-temperature nitrogen adsorption, XRD, UV-vis diffuse reflectance spectroscopy and EPR. The main findings are summarized as follows:(1) For the one-step oxidation of benzene to phenol with N2O, the catalyst evaluation conditions were established as:atmospheric pressure,330℃, C6H6:N2O=1:1, GHSV4000h-1, the optimized Fe content of0.1wt%.(2) The thermal and hydrothermal treatments at different temperatures have great influences on the Fe-Beta catalyst performances. In contrast to the conventional Fe-Beta with Si/Al=19, the aluminum-rich Fe-Beta with Si/Al=4has better benzene conversion up to19%. UV-vis and EPR spectroscopic results reavel that a large amount of non-framework isolated Fe3+ions was formed on the Al-rich Fe-Beta catalyst, which could enhance the catalyst activity.(3) For one-step oxydehydrogenation of propane to propene with N2O, Fe-ZBM-10catalyst is more efficient than Fe-Beta and Fe-Al-COE-2catalysts. In the conditions of N2O:C3H8=1:1, GHSV10000h-1and500℃, the thermal treatments, static and dynamic hydrothermal treatments have great influences on the catalyst performances. Under the optimized dynamic hydrothermal treatment at850℃, propane conversion maintains40%and propene selectivity reaches60%. UV-vis and EPR spectroscopic results reavel that more non-framework isolated Fe3+ions were formed on Fe-ZBM-10catalyst after dynamic hydrothermal treatment. This could be advantageous for increase of propene selectivity.