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Direct Oxidation of Benzene to Phenol by N2O Over Fe-ZSM-5 Catalysts

Author: ChenXi
Tutor: ZhuWeiDong；ZhangFuMin
School: Zhejiang Normal University
Course: Physical and chemical
Keywords: N2O Benzene Phenol Fe-ZSM-5 Mesoporous zeolite
CLC: TQ243.12
Type: Master's thesis
Year: 2010
Downloads: 69
Quote: 0
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Abstract


Phenol is an important organic chemical intermediates and chemical raw materials, mainly used in the manufacture of phenolic resins, bisphenol A and caprolactam. The most important methods of industrial production of phenol cumene, the biggest drawback of the method is that the relatively small acetone byproduct of the production of phenol, while equimolar market demand, and thus the production of phenol the acetone market price constraints. Compared with traditional methods of production of phenol, more economical and environmentally friendly benzene direct catalytic oxidation of phenol (BTOP) new technology gradually by academia and industry attention. Joint research and development of Solutia Inc., USA and Russia Boreskov Institute of Catalysis N2O as the oxidant, Fe-ZSM-5 zeolite as a catalyst for benzene hydroxylation preparation the phenol AlphOx process most attractive. The process can not only make use of waste N2O adipic industrial production can also be phenol production plant with adipic acid production unit to effectively integrate, resulting phenol selectivity, is environment-friendly chemical processes. However, in the trial showed that the continuous operation period of the Fe-ZSM-5 catalyst is poor there is still a certain distance away from the industrialization. This is mainly because the Fe-ZSM-5 is a microporous material, the reactant benzene and the product phenol is passed in the pores of the catalyst is limited, easy to cause catalyst coke due to inactivation. The zeolite after the treatment to enhance the mass transfer performance in the refining industry has been subject to the attention of the researchers, the general method used to produce mesoporous water heat treatment or acid treatment, the removal of the molecular sieve framework Al. Off Al, however, may be partially blocked zeolite channels, not significantly improve the mass transfer properties of the zeolite. A modified method is of recent developments in the alkali treatment, de Si by selective control the molecular sieve to produce the mesoporous and communicates with micropores holding, thereby shortening the diffusion distance of the molecules in the pores of zeolite pores, and can increase the mass of the zeolite transfer performance. Modified after the alkali treatment, the micropores of the material crystal structure and an acidic substantially no change in the generation of the mesoporous conducive to the transfer of the substance, while the micropores as a micro-reactor, not only provides the reactive center or the adsorption sites, and the shape and size of molecules having a selectivity. Thus, the alkali treatment is a the mesoporous zeolitic molecular sieve effective way, however, the Fe-ZSM-5 catalyst modified and applied BTOP catalyzed reaction, the present study uncommon. Therefore, we mainly compare by alkali treatment mesoporous molecular sieves with the parent of Fe-ZSM-5 zeolite catalytic performance in the direct oxidation of benzene to phenol was, the text of the main results are summarized as follows: 1) liquid ion exchange method and isomorphous replace the Fe-ZSM-5 catalysts were prepared on the hydroxylation of benzene. Found that the Fe-ZSM-5 catalysts synthesized by isomorphous substitution after alkali treatment showed high activity and stability. Further investigated the impact of Fe-ZSM-5 catalyst BTOP reactive alkali treatment conditions, such as temperature, time and concentration. The optimal conditions for 0.3MNaOH alkali treatment, 80 ° C, 2h, obtained on this basis the optimum catalyst, at 320 ° C reaction temperature, the initial conversion of benzene was 22.1%, the reaction is still maintained at 20% after 3h . This is the first demonstration of the alkali-treated modified Fe-ZSM-5 in BTOP reactions very effective. Alkali treatment did not change the Fe (Ⅲ) presence status, alkali treatment, however, arising from the mesoporous can significantly improve the mass transfer performance of the molecular sieve, which is an alkali treatment of the Fe-ZSM-5 catalyst modified with superior the BTOP catalytic reaction performance reasons. 2) by an alkali treatment and then steam treatment modified Fe-ZSM-5 catalysts, its activity is not as good as the only alkali-treated modified catalyst, this is because in many Fe species in the process of the water vapor into Fe3 xOy oligomeric particles this was confirmed by TEM and UV-vis characterization. Characterized by N2 adsorption combined with water vapor treatment after the alkali treatment modified Fe-ZSM-5 zeolite, its specific surface area and pore volume have been reduced, which may be the cause BTOP less reactive.

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CLC: > Industrial Technology > Chemical Industry > Basic Organic Chemistry Industry > The production of aromatic compounds > Phenols, aromatic alcohols and their derivatives > Phenols and their derivatives > Benzene series phenol
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