Comparative study of Nickel-based perovskite-like mixed oxide catalysts for direct decomposition of NO

Direct NO decomposition over conventional and mesoporous Cu-ZSM-5 and Cu-ZSM-11 catalysts: Improved performance with hierarchical zeolites

Catalytic activities for direct NO decomposition were investigated over C-type cubic Y2O3–Tb4O7–ZrO2 prepared by a coprecipitation method. The NO decomposition activity was enhanced by partial substitution of the yttrium sites with terbium in a (Y0.97Zr0.03)2O3.03 catalyst, which shows high NO decomposition activity. Among the catalysts synthesized in this study, the (Y0.67Tb0.30Zr0.03)2O3.33 catalyst exhibited the highest NO decomposition activity; NO conversion to N2 was as high as 67% at 900℃ in the absence of O2 (NO/He atmosphere), and a relatively high conversion ratio was observed even in the presence of O2 or CO2, compared with those obtained over conventional direct NO decomposition catalysts. These results indicate that the C-type cubic Y2O3–Tb4O7–ZrO2 catalyst is a new potential candidate for direct NO decomposition.

Cu–ZSM-5, Cu–ZSM-11, and Cu–ZSM-12 catalysts for direct NO decomposition

Catalytic activities for direct NO decomposition were investigated on C-type cubic Y2O3–ZrO2 and Y2O3–ZrO2–BaO prepared by coprecipitation. Introduction of excess oxide anions in the Y2O3 lattice was achieved by partial substitution of the Y3+ sites with Zr4+, and high NO decomposition activity was obtained for the (Y0.97Zr0.03)2O3.03 catalyst. In addition, the catalytic activity was further enhanced by partial substitution of the Y3+ sites in the Y2O3–ZrO2 solid solution with Ba2+, and the (Y0.89Zr0.07Ba0.04)2O3.03 catalyst exhibited the highest NO decomposition activity among the samples prepared; NO conversion to N2 reached 90% at 1173 K in the absence of O2 (NO/He atmosphere), and a relatively high conversion ratio was observed even in the presence of O2, H2O, or CO2, compared with the activities of conventional direct NO decomposition catalysts. These results indicate that the C-type cubic Y2O3–ZrO2–BaO catalyst is a new potential candidate for direct NO decomposition.

Effect of Mn content on physical properties of CeO x–MnO y support and BaO–CeO x–MnO y catalysts for direct NO decomposition

Catalytic Activity of Cu-Beta Zeolite in NO Decomposition: Effect of Copper and Aluminium Distribution

Oxidative coupling of methane over Ba-doped Y2O3 catalyst—Similarity with active site for direct decomposition of NO

Support and particle size effects on direct NO decomposition over platinum

The catalytic performance of Ba–Y2O3 prepared by a coprecipitation method for the direct decomposition of NO was investigated. Although Y2O3 catalyzed NO decomposition, its activity was increased by addition of Ba. The maximum NO decomposition activity was achieved on Ba–Y2O3 with 5 wt % Ba loading. XRD measurements revealed the formation of a solid solution of Ba and Y2O3 as well as BaCO3 small particles, when Ba loading was increased up to 5 wt %. From the comparison between the amount of CO2 desorption measured by temperature-programmed desorption of CO2 (CO2-TPD) and the NO decomposition activity of Ba–Y2O3, highly dispersed Ba species, which is initially present as BaCO3 small particles, on the catalyst surface act as catalytically active sites for NO decomposition. On the basis of in situ observation of surface species formed during NO decomposition by Fourier transform infrared (FT-IR) spectroscopy, we proposed that highly dispersed Ba species plays a role for the formation and adsorption of nitrite (NO2−) as reactive species for NO decomposition over Ba–Y2O3 catalyst.

The direct catalytic decomposition of NO into N2 and O2 with high activity and N2 selectivity at low temperature under excess oxygen is a challenge. Herein, we report a new approach for the direct decomposition of NO into N2 and O2 by microwave catalysis over MeOx‐Cu‐ZSM‐5 (Me=Mn, Ni) under excess oxygen. We observed that the microwave direct catalytic decomposition of NO over MeOx‐Cu‐ZSM‐5 under excess oxygen is highly efficient, and the NO conversions are 94.3 % over MnO2‐Cu‐ZSM‐5 at 300 °C and 92.3 % over Ni2O3‐Cu‐ZSM‐5 at 350 °C. Meanwhile, the N2 selectivity remains more than 98 %. Importantly, the apparent activation energies of MnO2‐Cu‐ZSM‐5 and Ni2O3‐Cu‐ZSM‐5 are as low as 15.5 and 25.7 kJ mol−1, which suggests a significant microwave catalytic effect. Furthermore, microwave irradiation exhibits a microwave selective effect. The oxygen concentration has almost no influence on the activity of catalytic decomposition of NO over MeOx‐Cu‐ZSM‐5 under microwave irradiation.

Cerium-iron mixed oxides were prepared by a glycothermal method, and NO decomposition reactions over these oxides and barium catalysts supported on them were examined. Although Ce–Fe mixed oxides (Ce–Fe(x), x = Fe/(Ce + Fe) molar ratio) exhibited only low activities for the direct decomposition of NO into N2 and O2, Ba catalysts supported on these mixed oxides are active for this reaction. The highest NO conversion was achieved with 3 wt% BaO/Ce–Fe(0.02). The NO conversion on this catalyst increased with increasing reaction temperature, and NO conversion was 51% at 800 °C. The high activity of this catalyst was maintained for more than 10 h and a relatively high NO conversion (23%) was obtained even in the presence of 5% oxygen. The XRD results indicated the formation of Ce–Fe(x) solid solutions with a cubic fluorite structure. The CO2-TPD results indicated NO decomposition activities of the catalysts were correlated with their basicities.

Direct decomposition of NO into N 2 and O 2 over La(Ba)Mn(In)O 3 perovskite oxide

Selective catalytic reduction of NO with hydrocarbon on Cu 2+-exchanged pillared clay: An IR study of the NO decomposition mechanism

The growing concerns for the environment and increasingly stringent standards for NO emission have presented a major challenge to control NO emmissions from electric utility plants and automobiles. Catalytic decomposition of NO is the most attractive approach for the control of NO emission for its simplicity. Successful development of an effective catalyst for NO decomposition will greatly decrease the equipment and operation cost of NO control. Due to lack of understanding of the mechanism of NO decomposition, efforts on the search of an effective catalyst have been unsuccesful. Scientific development of an effective catalyst requires fundamental understanding of the nature of active site, the rate-limiting step, and an approach to prolong the life of the catalyst. Research is proposed to study the reactivity of adsorbates for the direct NO decomposition and to investigate the feasibility of two novel approaches for improving catalyst activity and resistance to sintering. The first approach is the use of silanation to stabilize metal crystallites and supports for Cu-ZSM-5 and promoted Pt catalysts; the second is utilization of oxygen spillover and desorption to enhance NO decomposition activity. An innovative infrared reactor system will be used to observe and determine the dynamic behavior and the reactivity of adsorbates during NO decomposition, oxygen spillover, and silanation. A series of experiments including X-ray diffraction, temperature programmed desorption, temperature programmed reaction, X-ray photoelectron spectroscopy will be used to characterized the catalysts. The information obtained from this study will provide a scientific basis for developing an effective catalyst for the NO decomposition under practical flue gas conditions.

The growing concerns for the environment and increasingly stringent standards for NO emission have presented a major challenge to control NO emissions from electric utility plants and automobiles. Catalytic decomposition of NO is the most attractive approach for the control of NO emission for its simplicity. Successful development of an effective catalyst for NO decomposition will greatly decrease the equipment and operation cost of NO control. Due to lack of understanding of the mechanism of NO decomposition, efforts on the search of an effective catalyst have been unsuccessful. Scientific development of an effective catalyst requires fundamental understanding of the nature of active site, the rate-limiting step, and an approach to prolong the life of the catalyst. Research is proposed to study the reactivity of adsorbates for the direct NO decomposition and to investigate the feasibility of two novel approaches for improving catalyst activity and resistance to sintering. The first approach is the use of silanation to stabilize metal crystallites and supports for Cu-ZSM-5 and promoted Pt catalysts; the second is utilization of oxygen spillover and desorption to enhance NO decomposition activity. An innovative infrared reactor system will be used to observe and determine the dynamic behavior and the reactivity of adsorbates during NO decomposition, oxygen spillover, and silanation. A series of experiments including X-ray diffraction, temperature programmed desorption, temperature programmed reaction, X-ray photoelectron spectroscopy will be used to characterized the catalysts. The information obtained from this study will provide a scientific basis for developing an effective catalyst for the NO decomposition under practical flue gas conditions.