A novel V 2 O 5 -MoO 3 /TiO 2 /Al 2 O 3 metal wire-mesh-honeycomb catalyst prepared by electrophoretic deposition (EPD) was investigated for the selective catalytic reduction (SCR) of NO with NH 3 . The effects of reaction temperature, space velocity and NH 3 /NO ratio on the SCR activity were evaluated. The experimental results show that V 2 O 5 -MoO 3 /TiO 2 /Al 2 O 3 catalyst can achieve satisfied NO removal effect at 350degC; the increase of the space velocity will make NO conversion ratio reduce, except 400degC. NH 3 /NO ratio has a little influence on NO removal efficiency, which raises slowly with the increasing NH 3 /NO ratio. At the same time, body structure and surface character of catalyst prepared were characterized by XRD, SEM and XPS. Combining characterization with the results of activity test, the relation between catalyst structure and catalysis performance was analyzed. The results of characterization show that the active component is uniformly distributed on the catalyst carrier as a single layer and high SCR activity is attributed to the strong interaction between TiO 2 and V 2 O 5 .
Abstract Accelerating propane dehydrogenation in propane aromatization is vital because it is the first and rate control step. In this study, we introduced Cr to Ga/ZSM‐5 by tuning its impregnation sequence and amount, which was expected to accelerate the dehydrogenation step and improve aromatization performance. The impregnation sequence of Cr on catalyst not only affected the interaction between Ga and ZSM‐5, but also tuned the amount of dehydrogenation active species Cr 3+ . Due to the plenty of Cr 3+ species and strong interaction between Ga species and ZSM‐5, 2Cr/GaZ5 catalyst accelerated the dehydrogenation step and improved the aromatization process. More light hydrocarbons were preferred to be produced and were further converted into BTX on 2Cr/GaZ5 catalyst. Excessive Cr on catalyst caused the formation of Cr 2 O 3 particles with worse dispersion. The aggregated Cr 2 O 3 decreased the strong acidity of catalyst, which could not further promote propane conversion and decreased the aromatization ability of catalyst.
Reduction process is a key step to fabricate metal-zeolite catalysts in catalytic synthesis. However, because of the strong interaction force, metal oxides in zeolites are very difficult to be reduced. Existing reduction technologies are always energy-intensive, and inevitably cause the agglomeration of metallic particles in metal-zeolite catalysts or destroy zeolite structure in severe cases. Herein, we disclose that zeolites after ion exchange of ammonium have an interesting and unexpected self-reducing feature. It can accurately control the reduction of metal-zeolite catalysts, via in situ ammonia production from 'ammonia pools', meanwhile, restrains the growth of the size of metals. Such new and reliable ammonia pool effect is not influenced by topological structures of zeolites, and works well on reducible metals. The ammonia pool effect is ultimately attributed to an atmosphere-confined self-regulation mechanism. This methodology will significantly promote the fabrication for metal-zeolite catalysts, and further facilitate design and development of low-cost and high-activity catalysts.
Zeolite P1, a significant conversion product of fly ash, is predominantly utilized for the removal of metal ions, adsorption of carbon dioxide, and capture of aromatic compounds. Despite its diverse applications, its role as a catalyst remains underexplored in the scientific community. Traditionally, mordenite (MOR) zeolites are considered typical dimethyl ether (DME) carbonylation catalysts, whose Brønsted acid sites located on the 8-membered rings (8-MR) are the key active sites for this reaction. This conventional approach underscores the importance of specific zeolite structures in facilitating catalytic processes. H-P1 zeolite was synthesized through a template-free approach in this paper. When applied to DME carbonylation, this zeolite exhibited an impressive selectivity of up to 93% for methyl acetate (MA), suggesting its potential as a highly effective catalyst. This promising outcome hints at a new frontier for the application of the P1 zeolite, potentially revolutionizing its role in catalysis and expanding its utility beyond traditional adsorption processes. The findings suggest that the P1 zeolite could be a versatile material in the realm of catalytic chemistry, offering new pathways and methodologies for various chemical reactions.
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