Deolefinization performance of oxalic acid treated USY zeolites and the analysis of catalyst deactivation
The molecular sieve catalytic deolefinization of reformate is a simple route and can significantly reduce the solid waste.Here we investigated the influence of oxalic acid post-treatment on the framework structure,pore structure,and acid properties of USY molecular sieves in detail.The catalytic deolefiniza-tion performance and stability of USY zeolites before and after acid treatment were investigated by using toluene containing trace amounts of styrene as a model feed.The composition of the feeds and products were analyzed by gas chromatography-mass spectrometry.The results showed that the oxalic acid treatment can result in framework-dealumination of USY,thus reduce the acid strength and acid content.Besides alkylation with toluene,or self-dimerization,the styrene can undergo side reactions to generate polycyclic aromatic hydrocarbons to block the zeolite pores,which can cause catalyst deactivation.However,the self-dimerization and side reactions were significantly weakened after modification with oxalic acid,at the same time,the alkylation reaction was significantly enhanced,thus the catalyst life was extended,and the stabi-lity of catalytic deolefinization was significantly improved.
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