Destruction Of Nitrogen Monoxide Research Articles

Experimental and numerical studies on NOx emission characteristics in laminar non-premixed jet flames of ammonia-containing methane fuel with oxygen/nitrogen oxidizer

The study investigated the formation characteristics of nitrogen oxides (NOx) in non-premixed coflow methane jet flames experimentally and numerically. Ammonia was added to the fuel stream, while varying the oxygen ratio in the oxygen/nitrogen oxidizer stream. In the coflow jet flame experiment using pure oxygen oxidizer, NOx emissions increased monotonically with respect to the mixing ratio of ammonia. When using oxygen/nitrogen oxidizers, NOx emissions reached a maximum at an oxygen ratio of 0.7, with non-monotonic changes occurring in response to variations in the oxygen ratio. Depending on the ammonia addition, increasing NOx emissions appeared in the two ranges of either relatively low or high ratio oxygen in the oxidizers. However, a reversal phenomenon of decreasing NOx emissions was noted within the section between the two ranges of the oxygen ratio. To elucidate the characteristics of NOx formation under various conditions of fuel and oxidizer compositions, 1-D and 2-D numerical simulations were conducted using a detailed chemical kinetics (GRI-Mech 3.0). The 2-D simulation results for pure oxygen and oxygen/nitrogen oxidizers provided reasonable predictions of trends in experimentally measured NOx emissions with the ammonia addition. Moreover, the cause of the reversal phenomenon was successfully explained through a comparative analysis of reactions leading to production and destruction of nitrogen monoxide (NO), based on the results of the 1-D and 2-D simulations. The results provide fundamental information to help in the design of oxygen-enriched combustor.

Microwave-assisted hydrothermal synthesis of monoclinic nitrogen-doped titania photocatalyst and its DeNOx ability under visible LED light irradiation

Nitrogen-doped titania (TiO2−xNy) nanoparticles with monoclinic phase were successfully prepared by a microwave-assisted hydrothermal process. The obtained TiO2−xNy powders showed high specific surface area, fine particle size, and excellent photocatalytic ability for the oxidative destruction of nitrogen monoxide under irradiation of monochromatic LED light with various wavelengths.

MICROWAVE-ASSISTED HYDROTHERMAL SYNTHESIS OF NITROGEN-DOPED TITANIA NANOPARTICLES

Nitrogen-doped titania ( TiO 2-x N y) nanoparticles with excellent visible-light-reactive photocatalytic activity were successfully prepared by a microwave-assisted hydrothermal process. The obtained TiO 2-x N y powders showed high specific surface area, fine particle size and excellent photocatalytic ability for the oxidative destruction of nitrogen monoxide under irradiation of both visible-light (λ > 510 nm) and UV light (λ > 290 nm).

Improvement of thermal stability of nitrogen doped titania photocatalyst by addition of surfactants during solvothermal treatment

The TiO2−xNy nanocrystals with beige color were prepared by homogeneous precipitation-solvothermal process in TiCl3-hexamethyleneamine-alcohol solutions with the addition of various surfactants, such as sodium dodecylbenzenesulfonate (SDBS), n-hexadecylamine (HAD), and n-hexadecyltrimethylammonium chloride (HTAC) at 190 °C for 10 h. The phase composition, crystallinity, microstructure, specific surface area, nitrogen doped amount, and photocatalytic activity of titania powders greatly changed depending on pH value and other reaction conditions. The TiO2−xNy powders prepared by solvothermal treatment with surfactant additives followed by calcination in air at 400 °C showed smaller particle size, larger BET specific surface area and higher photocatalytic activity than those without surfactant. The TiO2−xNy powders showed excellent visible-light absorption, thermal stability and photocatalytic activity for nitrogen monoxide destruction under irradiation of both visible-light and UV-light irradiation. About 40% and 60% nitrogen monoxide could be continuously removed with the residence time of 1.9 min by the TiO2−xNy photocatalyst under irradiation of visible-light (λ > 510 nm) and UV-light (λ > 290 nm), respectively.

Promotion of Photocatalytic Activity of Titania by the Combination with Nitrogen-doped Titania

Titania/nitrogen-doped titania (TiO2/TiO2-xNy) composite was prepared by mechanical milling in liquid medium and the phase composition, specific surface area, photo chemical properties, and photocatalytic activities were characterized. TiO2/TiO2-xNy composites showed excellent photocatalytic ability for the oxidative destruction of nitrogen monoxide and acetaldehyde. It is suggested that the doped nitrogen in TiO2-xNy acts as the acceptor of photoinduced holes on TiO2 to depress the recombination of the electron-hole and improve the photocatalytic activity.

Visible-light induced photocatalytic activity of TiO 2− xA y (A = N, S) prepared by precipitation route

Nitrogen doped or nitrogen/sulfur co-doped titania photocatalyst TiO 2− x A y (A = N, S) which can be excited by visible light were prepared by mixing aqueous TiCl 3 solutions with various nitrogen sources such as hydroxylamine (NH 2OH), hexamethylenetetramine (HMT, C 6H 12N 4), urea ((NH 2) 2CO) and thiourea ((NH 2) 2CS) followed by hydrothermal treatment at 190 °C. The titania powders prepared using hydroxylamine consisted of rutile crystals with non-homogeneous size distribution. The nitrogen doped titania powders prepared using hexamethylenetetramine consisted of mainly mono-size spherical brookite crystals, whereas those using urea and thiourea consisted of belt-like rutile particles. The TiO 2− x A y (A = N, S) powders showed excellent visible-light absorption and photocatalytic ability for the oxidative destruction of nitrogen monoxide under irradiation of visible light. The effect of reaction solvents on the phase composition, specific surface area and photocatalytic activity was also characterized.

Visible-light-induced photocatalytic activity of TiO 2− xN y prepared by solvothermal process in urea–alcohol system

Nitrogen-doped anatase, rutile and brookite titania photocatalyst TiO 2− x N y which can be excited by visible light were prepared by mixing aqueous TiCl 3 solutions with urea ((NH 2) 2CO) and various type of alcohols followed by solvothermal treatment at 190 °C. The phase composition, crystallinity, microstructure and specific surface area of titania powders greatly changed depending on the pH and type of solvents. Violet, yellowish and grayish TiO 2− x N y with excellent visible light absorption and photocatalytic activity were prepared. The TiO 2− x N y powders prepared in urea–methanol solution showed excellent photocatalytic ability for the oxidative destruction of nitrogen monoxide under irradiation of visible light λ > 510 nm.

Synthesis of excellent visible-light responsive TiO2 − xNyphotocatalyst by a homogeneous precipitation-solvothermal process

Anatase, brookite and rutile type nitrogen-doped titania nanocrystals (TiO2−xNy) which are beige in color were successfully prepared by a ‘Homogeneous Precipitation–Solvothermal Process’ (HPSP) in TiCl3–hexamethylenetetramine (C6H12N4) aqueous and alcohol solutions. The phase composition, crystallinity, microstructure, specific surface area, nitrogen doping amount and photocatalytic activity of titania powders greatly changed depending on pH, temperature and the type of treatment alcohols. The TiO2−xNy powders showed excellent visible-light absorption and photocatalytic activity for nitrogen monoxide destruction under irradiation by both visible-light and UV-light. The beige titania powders prepared in TiCl3–hexamethylenetetramine alcohol solutions at 190 °C for 2 h possessed higher specific surface areas than those in aqueous solution. About 39 and 83% nitrogen monoxide could be continuously removed by the anatase TiO2−xNy photocatalyst under irradiation of visible-light (λ > 510 nm) and UV-light (λ > 290 nm), respectively.

Phase-compositional control and visible light photocatalytic activity of nitrogen-doped titania via solvothermal process

Nitrogen-doped titania nanoparticles consisted of pure anatase, rutile and brookite phases were successfully prepared by a solvothermal process in TiCl 3–HMT (hexamethylenetetramine, C 6H 12N 4)-alcohol mixed solution. The powders were yellow or beige and showed excellent visible light absorption and photocatalytic ability for the oxidative destruction of nitrogen monoxide under irradiation of visible light of wavelength >510 nm.

Mechanochemical synthesis of SrTiO3−xFxwith high visible light photocatalytic activities for nitrogen monoxide destruction

Download options Please wait... Supplementary files XRD patterns and thermogravimetry analysis curves of experimental samples DOC (111K) Article information DOI https://doi.org/10.1039/B303420H Article type Paper Submitted 26 Mar 2003 Accepted 09 Jul 2003 First published 22 Jul 2003 Download Citation J. Mater. Chem., 2003,13, 2348-2352 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Mechanochemical synthesis of SrTiO3−xFx with high visible light photocatalytic activities for nitrogen monoxide destruction J. Wang, S. Yin, Q. Zhang, F. Saito and T. Sato, J. Mater. Chem., 2003, 13, 2348 DOI: 10.1039/B303420H To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Search articles by author Jinshu Wang Shu Yin Qiwu Zhang Fumio Saito Tsugio Sato

Preparation of nitrogen-doped titania with high visible light induced photocatalytic activity by mechanochemical reaction of titania and hexamethylenetetramine

Nitrogen-doped yellowish rutile titania was prepared by a mechanochemical method. The samples were prepared by high-energy ball milling of a P-25 titania powder with various amounts of hexamethylenetetramine (HMT) under different milling conditions at around room temperature. The effects of the reaction conditions on the phase composition, particle size, specific surface area, amount of nitrogen-doping, microstructure and photocatalysis of nitrogen monoxide destruction were investigated in detail. The high mechanical energy accelerated the transformation of the phase from anatase to rutile, while the presence of HMT decreased the phase transformation. Residual HMT and by-products could be removed by post-milling calcination in air at 400 °C. The nitrogen-doped yellowish titania possessed two absorption edges at around 400 and 550 nm and showed excellent photocatalytic ability for nitrogen monoxide oxidation under visible light irradiation. Irradiation with visible light of wavelength >510 nm allowed nearly 37% nitrogen monoxide to be continuously removed by the nitrogen-doped titania prepared by planetary ball milling of a P-25 titania–10 wt% HMT mixture at 700 rpm for 120 min followed by calcination in air at 400 °C.

Synthesis of HTaWO 6/(Pt, TiO 2) nanocomposite with high photocatalytic activities for hydrogen evolution and nitrogen monoxide destruction

HTaWO 6/(Pt, TiO 2) nanocomposite was synthesized by successive intercalation reactions of HTaWO 6 with Pt(NH 3) 4 2+, C 3H 7NH 2/heptane mixed solution and TiO 2 acidic sol, followed by UV irradiation. The height of TiO 2 and Pt pillar is less than 0.51 nm. The host HTaWO 6 was white and possessed band gap energy of 3.11 eV, whereas the HTaWO 6/(Pt, TiO 2) nanocomposite was yellow and showed broad reflection over 400–600 nm together with that corresponding to the host layer, and possessed both excellent hydrogen evolution and nitrogen monoxide destruction photocatalytic activities even under visible light irradiation ( λ>510 nm). The HTaWO 6/(Pt, TiO 2) possessed higher photocatalytic activity than those of undoped HTaWO 6, commercial titania powder (Degussa P-25), fibrous titania and Pt-doped fibrous titania.