Selective catalytic reduction with NH3 (NH3-SCR) is the most efficient technology to reduce the emission of nitrogen oxides (NOx) from coal-fired industries, diesel engines, etc. Although V2O5-WO3(MoO3)/TiO2 and CHA structured zeolite catalysts have been utilized in commercial applications, the increasing requirements for broad working temperature window, strong SO2/alkali/heavy metal-resistance, and high hydrothermal stability have stimulated the development of new-type NH3-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 VOx, MnOx, CeO2, and Fe2O3 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.

Selective Catalytic Reduction of NOx with NH3 by Using Novel Catalysts: State of the Art and Future Prospects.

Highly visible-light active C- and V-doped TiO2 for degradation of acetaldehyde

SiO2/V2O5/TiO2 catalysts were synthesized for removing elemental mercury (Hg0) from simulated coal-combustion flue gas. Experiments were carried out in fixed-bed reactors using both pellet and powder catalysts. In contrast to the SiO2-TiO2 composites developed in previous studies, the V2O5 based catalysts do not need ultraviolet light activation and have higher Hg0 oxidation efficiencies. For Hg0 removal by SiO2-V2O5 catalysts, the optimal V2O5 loading was found between 5 and 8%, which may correspond to a maximum coverage of polymeric vanadates on the catalyst surface. Hg0 oxidation follows an Eley-Rideal mechanism where HCI, NO, and NO2 are first adsorbed on the V2O5 active sites and then react with gas-phase Hg0. HCI, NO, and NO2 promote Hg oxidation, while SO2 has an insignificant effect and water vapor inhibits Hgo oxidation. The SiO2-TiO2-V2O5 catalysts exhibit greater Hg0 oxidation efficiencies than SiO2-V2O5, may be because the V-O-Ti bonds are more active than the V-O-Si bonds. This superior oxidation capability is advantageous to power plants equipped with wet-scrubbers where oxidized Hg can be easily captured. The findings in this work revealed the importance of optimizing the composition and microstructures of SCR (selective catalytic reduction) catalysts for Hg0 oxidation in coal-combustion flue gas.

Development of silica/vanadia/titania catalysts for removal of elemental mercury from coal-combustion flue gas.

Methods of sequestering carbon dioxide (CO2) are provided. Aspects of the methods include precipitating a storage stable carbon dioxide sequestering product from an alkaline-earth-metal-containing water and then disposing of the product, e.g., by placing the product in a disposal location or using the product as a component of a manufactured composition. Also provided are systems for practicing methods of the invention.

Methods of sequestering CO2

We investigated the influence of Ce on the catalytic activity of V/Sb/Ce/Ti and its deactivation due to SO2. We studied the properties of the catalyst using physio-chemical techniques, including transmission infrared spectroscopy (IR), NH3 and SO2 temperature programmed desorption (TPD), X-ray photoelectron spectroscopy (XPS), H2 temperature programmed reduction (H2-TPR), and thermal gravimetric analysis (TGA). The catalysts V/Sb/Ti and V/Sb/Ce/Ti showed an excellent NOx conversion and N2 selectivity in the temperature range of 200–400 °C. Increasing Bronsted acid sites and the NH3 adsorption positively affected the efficiency of the catalyst. The Ce4+ ratio increased upon the addition of Sb and V to Ce/Ti. The catalyst V/Sb/Ce/Ti was prepared by controlling the Ce4+ ratio and exhibited an excellent activity upon increasing the Ce4+ ratio. The V/Sb/Ti (or V/W/Ti) showed one route in which NH4HSO4 formed by converting SO2 into SO3 upon the injection of SO2 in the selective catalytic reduction (SCR) reaction. In addition to this route, the reaction in the presence of V/Sb/Ce/Ti can proceed via a second route, in which Ce2(SO4)3 is formed in the reaction of Ce with SO2 and O2. Thus, V/Sb/Ce/Ti can inhibit the formation of NH4HSO4 due to the consumption of SO2 in the formation of Ce2(SO4)3. Therefore, V/Sb/Ce/Ti was found to have excellent SO2 resistance compared to V/Sb/Ti (or V/W/Ti).

The role of ceria on the activity and SO2 resistance of catalysts for the selective catalytic reduction of NOx by NH3

TiO 2 -SiO 2 with various compositions prepared by the coprecipitation method and vanadia loaded on TiO 2 -SiO 2 were investigated with respect to their physico-chemical characteristics and catalytic behavior in SCR of NO by NH 3 and in the undesired oxidation of SO 2 to SO 3 , using BET, XRD, XPS, NH 3 -TPD, acidity measurement by the titration method and activity test. TiO 2 -SiO 2 , compared with pure TiO 2 , exhibits a remarkably stronger acidity, a higher BET surface area, a lower crystallinity of anatase titania and results in allowing a good thermal stability and a higher vanadia dispersion on the support up to high loadings of 15 wt% V 2 O 5 . The SCR activity and N 2 selectivity are found to be more excellent over vanadia loaded on TiO 2 -SiO 2 with 10–20 mol% of SiO 2 than over that on pure TiO 2 , and this is considered to be associated with highly dispersed vanadia on the supports and large amounts of NH 3 adsorbed on the catalysts. With increasing SiO 2 content, the remarkable activity decrease in the oxidation of SO 2 to SO 3 , favorable for industrial SCR catalysts, was also observed, strongly depending on the existence of vanadium species of the oxidation state close to V 4+ on TiO 2 -SiO 2 , while V 5+ exists on TiO 2 , according to XPS. It is concluded that vanadia loaded on Ti-rich TiO 2 -SiO 2 with low SiO 2 content is suitable as SCR catalysts for sulfur-containing exhaust gases due to showing not only the excellent de-NO x activity but also the low SO 2 oxidation performance.

TiO2-SiO2 and V2O5/TiO2-SiO2 catalyst: Physico-chemical characteristics and catalytic behavior in selective catalytic reduction of NO by NH3

An object of the present invention is to provide a new method for treating an exhaust gas, which can effectively treat an exhaust gas containing a nitrogen oxide and metal mercury over a long term, and also can be applied to treatment of a large volume of an exhaust gas. As a means of achieving this object, a method according to the present invention for treating an exhaust gas comprises performing a reaction of changing metal mercury into mercury halide in the presence of a halogen compound and treatment of a nitrogen oxide, using a Ti—V-containing catalyst, upon treatment of an exhaust gas containing a nitrogen oxide and metal mercury.

Method for treating exhaust gas

PROBLEM TO BE SOLVED: To provide a new exhaust gas treatment method capable of efficiently treating an exhaust gas containing nitrogen oxides and metal mercury over a long period of time and also adaptable to the treatment of a large volume of the exhaust gas. SOLUTION: In this exhaust gas treatment method for treating the exhaust gas containing nitrogen oxides and metal mercury, a mercury halogenating catalyst is used in the presence of a halogen compound to convert metal mercury to mercury halide. This mercury halide is trapped by an absorbing liquid to be removed from the exhaust gas and the nitrogen oxides are subsequently treated using a denitration catalyst. COPYRIGHT: (C)2005,JPO&NCIPI

Exhaust gas treatment method

A catalyst for exhaust gas treatment that excels in capability of removing nitrogen oxides and organic halogenated compounds and durability, being low in the ratio of SO2 oxidation; titanium oxide suitable for preparation of this catalyst; and a method of treating an exhaust gas containing nitrogen oxides and/or organic halogenated compounds with the use of the catalyst. There is provided a titanium oxide, or catalyst for exhaust gas treatment, of 50 to 200 m2/g BET specific surface area whose intensity (Ia) of peak ascribed to anatase crystal existing between 2θ=24.7° and 25.7° in powder X-ray diffractometry ranges from 15 to 145% of the intensity (Ib) of peak ascribed to anatase crystal existing between 2θ=24.7° and 25.7° in powder X-ray diffractometry with respect to standard specimen composed of a mixture of 15 mass% of pure anatase type titanium dioxide and 85 mass% of pure rutile type titanium dioxide. In the case of titanium oxide, the BET specific surface area may be in the range of 85 to 250 m2/g (others identical with those of the catalyst).

Titanium oxide, catalyst for exhaust gas treatment and method of purifying exhaust gas

PROBLEM TO BE SOLVED: To provide a catalyst for treating exhaust gas which is particularly effective for treating exhaust gas comprising a hydrocarbon and has a particularly excellent capability of removing a hardly decomposable organic compound such as a saturated hydrocarbon present in exhaust gas as an odorous component, and an apparatus for treating exhaust gas using the catalyst. SOLUTION: The catalyst for treating exhaust gas is comprised of a support comprising a solid acid having acid strength (Ho) of -5.6 to -3.0 in an amount not lower than 0.25 mmol/g (mmol per 1 gram of the support). COPYRIGHT: (C)2008,JPO&INPIT

Ryoji Kuma

Papers

TiO2-SiO2 and V2O5/TiO2-SiO2 catalyst: Physico-chemical characteristics and catalytic behavior in selective catalytic reduction of NO by NH3

Method for treating exhaust gas

Exhaust gas treatment method

Titanium oxide, catalyst for exhaust gas treatment and method of purifying exhaust gas

Catalyst and method for treating exhaust gas