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The FeV/TiO2 catalyst was prepared by introducing V species to modify the iron-based catalyst' and the structures and performances were compared with the unmodified catalyst. The catalysts were characterized by means of XRD, Raman, BET, UV-Vis-NIR, NH3-TPD and H2-TPR. The results show that FeVO4 exists as the main phase in the catalyst after introducing V, and there were abundant acid sites to guarantee strong surface acidity. The strong interaction between Fe and V species also greatly enhance the redox ability. Therefore, the low-temperature activity is significantly improved and the temperature window is greatly widened. Moreover, the structure of the catalyst is hardly affected by alkali poisoning, and the catalyst could still maintain strong surface acidity after poisoning, resulting in good resistance to alkali metals. [ABSTRACT FROM AUTHOR]

It is still a challenge to develop metal-based monolithic deNOx catalysts with high activity, mass transfer ability and stability. Herein, we proposed a convenient and versatile pathway for the synthesis of novel monolithic deNOx catalysts originating from the in situ immobilization of metal organic framework (MOF) precursors on Fe mesh. Interestingly, the morphology and composition of the catalysts could be modulated by adjusting the synthesis parameters, such as the synthesis time, ligands and precursors, while the characterization results revealed an improvement in oxygen vacancies and Brønsted acid sites led by the strong interaction between the uniformly distributed active Mn–Fe components. As a result, the novel monolithic catalysts demonstrated improved catalytic performance compared with traditional catalysts obtained by hydroxide precursors. This work sheds lights on the advantages of using MOF-derived materials in situ decorated on metal mesh as monolithic catalysts and paves a way to design new monolithic deNOx catalysts with excellent low-temperature catalytic activity for future efforts. [ABSTRACT FROM AUTHOR]

In this work, we have rationally designed and originally developed a novel monolith de-NOx catalyst with nickel foam as the carrier and three dimensional hierarchical MnO2@NiCo2O4 core–shell nanowire arrays in situ grown on the surface via a two-step hydrothermal process with a post calcination treatment. The catalysts were systematically examined by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, elemental mapping, ion sputtering thinning, X-ray photoelectron spectroscopy, inductively coupled plasma atomic emission spectroscopy, H2 temperature-programmed reduction, NH3/NO + O2 temperature-programmed desorption measurements and catalytic performance tests. The results indicate that the nanowire is composed of hollow NiCo2O4 spinel as the core and MnO2 nanoparticles as the shell layer. By ingeniously making the hierarchical Ni–Co oxide nanowires as the support for manganese oxides, the MnO2@NiCo2O4@Ni foam catalyst not only takes advantage of the high surface area of Ni–Co nanowires to achieve high loading amounts as well as high dispersion of manganese oxides, but also makes use of the synergistic catalytic effect between Ni, Co and Mn multiple oxides, and exhibits excellent low-temperature catalytic performance in the end. In addition, with the structure and morphology well maintained under long term steady isothermal operation, the catalyst is able to sustain high NO conversion and exhibits superior catalytic cycle stability and good H2O resistance. Considering all these favorable properties, the MnO2@NiCo2O4@Ni foam catalyst could serve as a promising candidate for the monolith de-NOx catalyst at low temperatures and the rational design of in situ synthesis of 3D hierarchical monolith catalysts also puts forward a new way for the development of environmental-friendly and highly active monolith de-NOx catalysts. [ABSTRACT FROM AUTHOR]

The deactivation issue arising from alkali poisoning over catalysts is still a challenge for the selective catalytic reduction of NO x by NH 3 . Herein, improved NO x reduction in the presence of alkaline metals over phosphate-modified Fe 2 O 3 /TiO 2 catalysts has been originally demonstrated via tailoring the reaction paths by in situ creating alkali-poisoning sites. The introduction of phosphate results in the partial formation of iron phosphate species and makes the catalyst to mainly exhibit the characteristics of FePO 4 , which is responsible for the widened temperature window and enhanced alkali resistance. The tetrahedral [FeO 4 ]/[PO 4 ] structures in iron phosphate act as the Brønsted acid sites to increase the catalyst surface acidity. In addition, the formation of an Fe-O-P structure enhances the redox ability and increases surface adsorbed oxygen. Furthermore, the created phosphate groups (PO 4 3- ) serving as alkali-poisoning sites preferentially combine with potassium so that iron species on the active sites are protected. Therefore, the enhanced NH 3 species adsorption capacity, improved redox ability, and active nitrate species remaining in the phosphate-modified Fe 2 O 3 /TiO 2 catalyst ensure the de-NO x activity after being poisoned by alkali metals through the Langmuir-Hinshelwood reaction pathway. Hopefully, this novel strategy could provide an inspiration to design novel catalysts to control NO x emission with extraordinary resistance to alkaline metals.

Reducing the poisoning effect of alkali and heavy metals over ammonia selective catalytic reduction (NH 3 -SCR) catalysts is still an intractable issue, as the presence of K and Pb in fly ash greatly hampers their catalytic activity by impairing the acidity and affecting the redox properties of the catalysts, leading to the reduction in the lifetime of SCR catalysts. To address this issue, we propose a novel self-protected antipoisoning mechanism by designing SO 4 2- /TiO 2 superacid supported CeO 2 -SnO 2 catalysts. Owing to the synergistic effect between CeO 2 and SnO 2 and the strong acidity originating from the SO 4 2- /TiO 2 superacid, the catalysts show superior catalytic activity over a wide temperature range (240-510 °C). Moreover, when K or/and Pb are deposited on SO 4 2- /TiO 2 catalysts, the bond effect between SO 4 2- and Ti-O would be broken so that the sulfate in the bulk of SO 4 2- /TiO 2 superacid support would be induced to migrate to the surface to bond with K and Pb, thus prohibiting poisons from attacking the Ce-Sn active sites, and significantly boosting the resistance. Hopefully, this novel self-protection mechanism derived from the migration of sulfate in the SO 4 2- /TiO 2 superacid to resist alkali and heavy metals provides a new avenue for designing novel catalysts with outstanding resistance to alkali and heavy metals.

Selective catalytic reduction with NH 3 (NH 3 -SCR) is the most efficient technology to reduce the emission of nitrogen oxides (NO x ) from coal-fired industries, diesel engines, etc. Although V 2 O 5 -WO 3 (MoO 3 )/TiO 2 and CHA structured zeolite catalysts have been utilized in commercial applications, the increasing requirements for broad working temperature window, strong SO 2 /alkali/heavy metal-resistance, and high hydrothermal stability have stimulated the development of new-type NH 3 -SCR catalysts. This review summarizes the latest SCR reaction mechanisms and emerging poison-resistant mechanisms in the beginning and subsequently gives a comprehensive overview of newly developed SCR catalysts, including metal oxide catalysts ranging from VO x , MnO x , CeO 2 , and Fe 2 O 3 to CuO based catalysts; acidic compound catalysts containing vanadate, phosphate and sulfate catalysts; ion exchanged zeolite catalysts such as Fe, Cu, Mn, etc. exchanged zeolite catalysts; monolith catalysts including extruded, washcoated, and metal-mesh/foam-based monolith catalysts. The challenges and opportunities for each type of catalysts are proposed while the effective strategies are summarized for enhancing the acidity/redox circle and poison-resistance through modification, creating novel nanostructures, exposing specific crystalline planes, constructing protective/sacrificial sites, etc. Some suggestions are given about future research directions that efforts should be made in. Hopefully, this review can bridge the gap between newly developed catalysts and practical requirements to realize their commercial applications in the near future.

In this study, halloysites, one of the most abundant clays, with hollow nanotube features were reconstructed by selectively etching silica from the outermost layer of the halloysites associated with unzipping the nanotubes to nanosheets via ball milling, and then, nickel nanoparticles were confined by the resulting defects in the nanosheets to boost charge transfer by a wet impregnation method. The obtained materials were developed as coke-resistant defect-confined Ni-based nanosheet-like catalysts for CO2 reforming of methane (CRM) for the first time. The as-prepared catalyst exhibited good coke and sintering resistance performance in CRM, and especially, there was almost no loss of activity even after a 20 h stability test due to the strong interaction between the Ni nanoparticles and the support. The present investigations may provide a new pathway for the design and application of highly coke-resistant CRM catalysts.

Owing to their advantages of strong mechanical stability, plasticity, thermal conductivity and mass transfer ability, metal foam or meshes are considered promising monolith supports for de-NO x application. In this work, we developed a facile method for the decoration of porous Mn-Co bi-metal oxides on Fe meshes. The block-like structure was derived from in situ coating, and simultaneous nucleation and growth of the Mn-Co hydroxide precursor, while the porous Mn-Co oxides were formed via the calcination process. Moreover, the decoration of the high-purity Co 2 MnO 4 spinel could lead to enhanced reducibility and adsorption behaviors, which are crucial to the catalytic process. Of note is the fact that the Fe mesh used in the synthesis procedure could be substituted by various metal supports including Ti mesh, Cu foam and Ni foam. Driven by the above motivations, metal supports decorated with Mn-Co oxides were evaluated as monolith de-NO x catalysts for the first time. Inspiringly, these catalysts demonstrate outstanding low-temperature catalytic activity, desirable stability and excellent H 2 O resistance. This work might open up a new path for the design and development of high performance de-NO x monolith catalysts.