Catalysts For Direct Decomposition Research Articles

Novel cobalt‐doped ZrSnO4 catalysts for direct nitrous oxide decomposition

AbstractNovel ZrSn1−xCoxO4−δ catalysts for the direct decomposition of nitrous oxide (N2O) were synthesized using a co‐precipitation method. Metastable ZrSnO4 with an α‐PbO2‐type structure was used as the mother solid because of its interstitial open spaces derived from its lattice distortion that may be effective for N2O adsorption. The doping of Co2+/3+ into the ZrSnO4 lattice improved the N2O decomposition activity, likely owing to the enhancement of the redox properties and the increase in the number of oxygen vacancies. Among the prepared catalysts, Zr1.17Sn0.73Co0.10O4−δ exhibited the highest activity decomposing N2O completely decomposed at 550°C. In addition, the Zr1.17Sn0.73Co0.10O4−δ catalyst showed high durability in the presence of CO2, O2, and H2O vapor.

Metal-porphyrin: a potential catalyst for direct decomposition of N(2)O by theoretical reaction mechanism investigation.

The adsorption of nitrous oxide (N2O) on metal-porphyrins (metal: Ti, Cr, Fe, Co, Ni, Cu, or Zn) has been theoretically investigated using density functional theory with the M06L functional to explore their use as potential catalysts for the direct decomposition of N2O. Among these metal-porphyrins, Ti-porphyrin is the most active for N2O adsorption in the triplet ground state with the strongest adsorption energy (-13.32 kcal/mol). Ti-porphyrin was then assessed for the direct decomposition of N2O. For the overall reaction mechanism of three N2O molecules on Ti-porphyrin, two plausible catalytic cycles are proposed. Cycle 1 involves the consecutive decomposition of the first two N2O molecules, while cycle 2 is the decomposition of the third N2O molecule. For cycle 1, the activation energies of the first and second N2O decompositions are computed to be 3.77 and 49.99 kcal/mol, respectively. The activation energy for the third N2O decomposition in cycle 2 is 47.79 kcal/mol, which is slightly lower than that of the second activation energy of the first cycle. O2 molecules are released in cycles 1 and 2 as the products of the reaction, which requires endothermic energies of 102.96 and 3.63 kcal/mol, respectively. Therefore, the O2 desorption is mainly released in catalytic cycle 2 of a TiO3-porphyrin intermediate catalyst. In conclusion, regarding the O2 desorption step for the direct decomposition of N2O, the findings would be very useful to guide the search for potential N2O decomposition catalysts in new directions.

New insights into intermediate-temperature solid oxide fuel cells with oxygen-ion conducting electrolyte act as a catalyst for NO decomposition

The environmental problems and supply of clean and economical energy is grand global challenges. Direct decomposition of nitrogen oxides (NOx) is the most ideal and effective approach for NOx removal by catalysis, which has the great potential to alleviate the air pollution. On the other hand, solid oxide fuel cells (SOFCs) are one of the cleanest, most efficient chemical-to-electrical energy conversion systems. Here we reported a new electrochemical system to combine the traditional catalyst for direct decomposition of NOx with an electric generation process through a SOFC. By nano-sized La0.4Ba0.6Mn0.8Mg0.2O3–δ (LBMM), an effective catalyst widely used for NOx decomposition, adopting an anode-support SOFC configuration, which consisted with the conventional NiO-samarium doped ceria (SDC) anode, and thin film SDC electrolyte, we demonstrated that complete decomposition of NOx and a peak power density of 25mWcm−2 at 600°C when Ar containing 5% NO and 5% O2 was fed to the cathode and 10% H2 was used the fuel. The effect of the ratio between NO and O2 was found to be critical for the NO conversion and SOFC performance. The dependence of temperature and gas composition on NO conversion was also investigated.

Fabrication and Characterization of Bimetallic Mordenite-Zeolite Catalysts for Low Temperature Direct Decomposition of N2O Emitted from Nitric Acid Plants∗

Abstract In this research, the mordenite based catalysts for direct decomposition of N2O have been prepared and characterized for their direct decomposition performance at the operating temperature of 300–550 °C commonly encountered in the nitric acid plants tail gases. The zeolite catalyst was prepared by 2 steps: 1. Precursor wet ion exchange, 2. Precursor impregnation. The bi-metallic catalyst thus prepared shows an excellent N2O decomposition performance. The total conversion efficiency of Pt-Fe-MOR catalyst has been achieved at 390 °C. XPS analysis confirmed platinum on mordenite supports in two forms: PtO and PtO2 species interact with oxygen ions at the metal/support interface. Deposition of Pt as a promoter on the surface of Fe-mordenite results in a considerable enhancement of catalytic activity.

Direct Decomposition of N2O Emitted from Nitric Acid Plant Tail Gases Using Noble Metal Supported Mordenite-Zeolite Catalysts∗

Abstract Mordenite based catalysts for direct decomposition of N2O have been successfully prepared and their direct decomposition performance characterized at the operating temperature of 300–400 °C commonly encountered in the nitric acid plants tail gases. The catalyst was prepared in 2 steps: 1. Precursor wet ion exchange, 2. Precursor impregnation. In addition to the previous contribution, it is shown here that the bimetallic Rh-, Pd-, Ir-Fe-MOR catalysts thus prepared exhibited an excellent N2O decomposition performance: total conversion efficiency of Rh-Fe-MOR catalyst has been achieved at 400 °C and between 7500 h−1 and 10 000 h−1 space velocity.

TiO 2 promoted Ir/Al 2O 3 catalysts for direct decomposition of N 2O

TiO 2 promoted Ir/Al 2O 3 catalysts (Ir/TiO 2–Al 2O 3) were successfully used in direct decomposition of N 2O with high catalytic activities and good thermal stabilities. Application of different characterization techniques revealed that the activity enhancement was closely correlated with the properties of the support material. Iridium was highly dispersed over the binary system of TiO 2–Al 2O 3, due to the nanoscale rough surface and strong interaction between iridium and the support induced by TiO 2 addition. Enhanced capability of reversible oxygen adsorption was detected on the TiO 2 promoted sample, which also promoted the catalyst for N 2O decomposition.

Metal Exchanged ZSM-5 Zeolite Based Catalysts for Direct Decomposition of N2O

Co+Pt/ZSM-5 and Ag+Pt/ZSM-5 type catalysts were prepared by ion exchange method followed by calcination. These Co and Ag based catalysts, promoted by a small amount of Pt have been studied for their catalytic activity towards N2O decomposition. Both the catalysts show high catalytic activity, however, cobalt–platinum based catalyst shows relatively better activity at higher temperature. At 550 °C almost 100% conversion of N2O is achieved over Co+Pt/ZSM-5 with a maximum of 0.08479 mmole of N2O decomposed per gram of the catalyst per unit time. These catalytic materials have been characterized for their structure, composition, morphology and other details, using XRD, SEM, EDX, ICP, BET techniques. Much improved catalytic activity for the bimetallic zeolite than the mono-metal containing compositions clearly demonstrate the synergistic effect of these transition metals, while high surface area of ZSM-5 is also responsible for the improved N2O decomposition activity.

Potassium-doped Co3O4 catalyst for direct decomposition of N2O

Direct decomposition of nitrous oxide (N2O) on K-doped Co3O4 catalysts was examined. The K-doped Co3O4 catalyst showed a high activity even in the presence of water. In the durability test of the K-doped Co3O4 catalyst, the activity was maintained at least for 12h. It was found that the activity of the K-doped Co3O4 catalyst strongly depended on the amount of K in the catalyst. In order to reveal the role of the K component on the catalytic activity, the catalyst was characterized by XRD, XPS, TPR and TPD. The results suggested that regeneration of the Co2+ species from the Co3+ species formed by oxidation of Co2+ with the oxygen atoms formed by N2O decomposition was promoted by the addition of K to the Co3O4 catalyst.

Advantage of radiolysis over impregnation method for the synthesis of SiO2 supported nano-Ag catalyst for direct decomposition of N2O

Abstract Two SiO 2 supported Ag catalysts with 5 wt% Ag in each were prepared by impregnation and radiolysis methods. These catalysts were characterized by BET surface area, temperature programmed reduction (TPR) and X-ray diffraction techniques. TPR results indicate the presence of metallic silver in the catalyst prepared by radiolysis method whereas Ag + precursor is formed in the catalyst prepared by impregnation method. The Ag particle size as calculated from the XRD patterns, in the catalyst prepared by radiolysis method is relatively smaller compared to that of the impregnated catalyst. The two catalysts are tested for decomposition of N 2 O and it is observed that the catalyst prepared by radiolysis gives higher conversion and better N 2 selectivity. These results suggest that radiolysis method yields metallic Ag nanoparticles directly without any reduction treatment and that the catalyst exhibits good activity in N 2 O decomposition.

Direct decomposition of nitric oxide into nitrogen and oxygen over C-type cubic Y2O3–ZrO2 solid solutions

Abstract C-type cubic yttria–zirconia (Y2O3–ZrO2) solid solutions were found to exhibit high activity in NO direct decomposition. Effects of Zr4+ substitution for Y3+ in (Y1−xZrx)2O3+x solid solutions were studied on the catalytic activity in the direct decomposition of NO. Among several compositions investigated in this study, the highest NO conversion was observed for (Y0.94Zr0.06)2O3.06. On this catalyst, NO conversion was enhanced with increasing the reaction temperature, and at 1000 °C, NO direct conversion into N2 attained the value of 44%. This result suggests that the C-type cubic yttria–zirconia solid solutions are also the potential candidates for the NO direct decomposition catalysts at elevated temperatures.

Alkali-doped Co 3O 4 catalysts for direct decomposition of N 2O in the presence of oxygen

Direct decomposition of nitrous oxide (N 2O) on various metal oxide catalysts was examined in the presence of oxygen. The NiO and Co 3O 4 catalysts showed high activities. Whereas the activity of the NiO catalyst was only slightly affected by the preparation conditions, the activity of the Co 3O 4 catalyst severely depended on the preparation conditions. It was found that the sodium content remaining in the precursor was the determining factor for the catalyst activity. Therefore, the effects of alkali doping on the performance of the Co 3O 4 catalysts were examined by using the catalysts prepared by impregnation of commercial CoCO 3 with alkali nitrates and subsequent calcination at 400 °C for 4 h. The alkali-doped Co 3O 4 catalysts showed higher activities than pure Co 3O 4. Strontium, calcium and barium ions had also favorable effects, but alkaline earth metals required higher concentration to exert the effects than that required by alkali metals.

Study of Ag/La0.6Ce0.4CoO3 catalysts for direct decomposition and reduction of nitrogen oxides with propene in the presence of oxygen

Perovskite-type oxide La0.6Ce0.4CoO3 and its doped Ag catalysts were prepared and their catalytic performances were evaluated for the direct decomposition of NO and the selective reduction of NO with propene in the presence of oxygen. A noticeable enhancement in activity was achieved by doping Ag and the optimum Ag loading was 1%. The effects of H2O, SO2, CO2 and O2 on the performances of Ag/La0.6Ce0.4CoO3 catalysts for NO decomposition were also investigated. The resistance against H2O and SO2 appears satisfactory. The inhibition by CO2 is strong, although it is reversible. Oxygen did not inhibit the NO decomposition reaction but significantly promoted it. Compared with other perovskite-type oxides reported previously, higher conversions were obtained over the present catalysts for the NO reduction by propene. We speculate that the decomposition of NO is the predominant process even in the presence of propene. The catalysts were characterized by N2-adsorption, XRD, XPS and NO-TPD and some explanations were put forward.

99/01312 Thermodynamic analysis of high temperature fuel cells: methane reforming : Call, F. W. AES (Am. Soc. Mech. Eng.), 1996, 36, 305–311

We are developing direct decomposition catalysts to decompose the NOx involved in high temperature exhaust gases to N2 and O2 without any reductants such as urea and plan to bring this technology into practice in the 21st century. We expect to create very simple deNOx systems using direct decomposition catalysts applicable to a wide range of fields (co-generation, boilers, automobiles and so on) after overcoming the technical difficulties. Perovskite catalyst and zeolite catalyst are the most promising materials for direct decomposition catalysts. This study focuses on seeking and designing novel NOx direct decomposition catalysts having high activities through theoretical studies using computational chemistry and experimental studies using surface-science techniques.

99/01314 Tin-based oxide anode for lithium-ion batteries with low irreversible capacity : Wan, K. et al. J. Power Sources, 1998, 75, (1), 9–12

We are developing direct decomposition catalysts to decompose the NOx involved in high temperature exhaust gases to N2 and O2 without any reductants such as urea and plan to bring this technology into practice in the 21st century. We expect to create very simple deNOx systems using direct decomposition catalysts applicable to a wide range of fields (co-generation, boilers, automobiles and so on) after overcoming the technical difficulties. Perovskite catalyst and zeolite catalyst are the most promising materials for direct decomposition catalysts. This study focuses on seeking and designing novel NOx direct decomposition catalysts having high activities through theoretical studies using computational chemistry and experimental studies using surface-science techniques.

Catalytic activity of perovskite-type oxide catalysts for direct decomposition of NO: Correlation between cluster model calculations and temperature-programmed desorption experiments

The relationship between NO decomposition activity on lanthanum transition metal oxide catalysts (transition metal=Cr, Mn, Fe, Co and Ni) and their oxygen desorption properties was investigated by using catalytic activity measurements, temperature-programmed desorption (TPD), X-ray photoelectron spectroscopy (XPS) and molecular orbital calculations. The NO decomposition activity correlated with both the amount of O 2 desorbed and the temperature of O 2 desorption. The variations in the temperature of O 2 desorption during TPD could be explained by electronic interaction with the transition metal. The variations in the O1s photoline observed by XPS could be explained by the variations in the charge of the surface oxygen species, which was affected by the electronic interaction with the transition metal. Molecular orbital techniques are powerful tools in NO decomposition catalyst research.

ChemInform Abstract: Comparative Study of Nickel‐Based Perovskite‐Like Mixed Oxide Catalysts for Direct Decomposition of NO.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Fundamental study on the NO x direct decomposition catalysts

We are developing direct decomposition catalysts to decompose the NO x involved in high temperature exhaust gases to N 2 and O 2 without any reductants such as urea and plan to bring this technology into practice in the 21st century. We expect to create very simple deNO x systems using direct decomposition catalysts applicable to a wide range of fields (co-generation, boilers, automobiles and so on) after overcoming the technical difficulties. Perovskite catalyst and zeolite catalyst are the most promising materials for direct decomposition catalysts. This study focuses on seeking and designing novel NO x direct decomposition catalysts having high activities through theoretical studies using computational chemistry and experimental studies using surface-science techniques.

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

The mixed oxides LaNiO 3, La 0.1Sr 0.9NiO 3, La 2NiO 4 and LaSrNiO 4 were prepared and used as catalysts for the direct decomposition of NO. The catalysts were characterized by means of XRD, XPS, O 2-TPD, NO-TPD and chemical analysis. By comparing the physico-chemical properties and catalytic activity for NO decomposition, a conclusion could be drawn as follows. The direct decomposition of NO over perovskite and related mixed oxide catalysts follows a redox mechanism. The lower valent metal ions Ni 2+ and disordered oxygen vacancies seem to be the active sites in the redox process. The oxygen vacancy plays an important role favorable for the adsorption and activation of NO molecules on one hand and on the other hand for increasing the mobility of lattice oxygen which is beneficial to the reproduction of active sites. The presence of oxygen vacancies is one of the indispensable factors to give the mixed oxides a steady activity for NO decomposition.

Silver-promoted Cobalt Oxide Catalysts for Direct Decomposition of Nitrogen Monoxide

Abstract Silver as a catalyst additive showed an excellent effect to improve the catalytic activity of cobalt oxide for the decomposition of nitrogen monoxide below 773 K. Reaction inhibition by oxygen was very much relieved by using Ag–Co oxide catalysts.

Excessively Copper Ion-exchanged ZSM-5 Zeolites as Highly Active Catalysts for Direct Decomposition of Nitrogen Monoxide

Abstract Repeated ion exchange of the ZSM-5 zeolite using aqueous copper(II) acetate solution was found to bring about excess loading of copper ions above 100% of exchange level. The catalytic activities of the resulting Cu-ZSM-5 zeolites for direct decomposition of nitrogen monoxide were very high and increased with increasing exchange level. The activity did not decrease even after 30 h of continuous service.