Selective catalytic reduction pore size

Copper ions exchanged microporous molecular sieves, in particular Cu-ZSM-5, are active catalysts for the selective catalytic reduction of NO and N2O with hydrocarbons in the presence of O2 (HC-SCR). It has been reported that the catalytic activity may be controlled by intra-crystalline diffiisivity and by geometry-limited diffusion depending on the hydrocarbon molecular size and the zeolite pore size [1]. Therefore, it is of interest to prepare Cu-Al-MCM-41 mesoporous molecular sieves and to compare their activity with that of Cu-ZSM-5. 

It appears interesting to investigate vanadia doped sulfated Ti-pillared clay for the selective catalytic reduction of NO by anmionia and to compare their performance with sulfated Ti-pillared clay and vanadia doped Ti-pillared clay. In this work, all the catalysts were synthesized under identical conditions and were characterized by different techniques. These techniques included surface area measurement, pore size distribution, X-ray diffraction. X-ray photoelectron spectroscopy, TPD-NH3 and chemical analysis of Ti retained by the clay. The catalysts were then tested in the selective catalytic reduction of NO by ammonia in the presence of oxygen at different temperatures. 

Influence of catalyst preparation, composition, and structure on activity and selectivity. There is an extensive literature some of which has been covered incidentally already. An excellent review has been published by Ripperger and Saum. Much of the work relates to the catalysts as oxides and so will not be covered in detail in this Report. Variables that influence catalytic properties include preparation e.g., method and order of addition of active components), pretreatment (drying and calcination,pre-reduction sulphiding,composition (e.g., concentration and ratio of active components and the type of support), distribution of active components in catalyst particles,particle size, " and surface area and pore size distribution. 

The Co-HEU synthetic zeolite has been used for selective redirction of NO by CH4 in the presence of excess O2 [99K1]. These data were compared to those obtained when irsing Co-MFI or Co-FER. On the basis of the overall catalytic resrtlts, the importance of zeolite pore size as a structural parameter irtfluencing the activity of intrazeolitic Co ions for NO reduction by CH4 was stressed. According to [03G1], the characterization of Co-HEU by powder-XRD, N2-BET, and wet-chemical methods does not provide adeqirate information for the hypothesis that intrazeolitic Co ions were responsible for the observed catalytic behavior. 

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