Catalytic Activity For NO Decomposition Research Articles

Excellent catalytic activity for NO decomposition on Rhn supported on grain-boundary terminations of the MgO (0 0 1) surface

In the present study, we first propose the grain-boundary termination of the MgO (001) surface (referred as GB@MgO(001)) as the substrate to support a series of Rhn clusters to trap and dissociate NO. Using van der Waals density functional theory calculations, we have studied the interaction between the Rhn (n = 1 ∼ 8) cluster and the MgOΣ5(210)GB@MgO(001) and the properties of the adsorption and dissociation of NO on Rhn/GB@MgO(001) systems. The Rhn clusters can tightly bond to the GB@MgO(001), with interfacial interactions comparable to those at the Rhn/MgO-nanotube interface. Stable quasi-two-dimensional Rhn clusters provide more active sites to NO. Moreover, NO dissociation is activated, with all the complete reaction paths occur below the reference state, indicating the possibility of the NO decomposition. An extremely small energy barrier of 0.037 eV was obtained for NO dissociating on the square-Rh4/GB@MgO(001) system. Molecular dynamic (MD) calculations reveal that NO can be completely decomposed at 527 K without obvious structure distortions of the complex. The adsorption of NO yields a change in the total magnetic moment of the Rhn/GB@MgO(001) system, but it has a minimal impact on the adsorption energy of NO. Our results also show that the optimal Rhn clusters that are good at trapping and dissociating NO are not the most stable structures, but rather clusters of relatively low dimension that are bound to the substrate with a moderate strength. As a result, the modification and tuning of the substrate structure can effectively enrich the structure of Rh cluster catalyst and improve its physical properties so that it can potentially play a greater role in other redox reactions, which motivates us to continue designing various types of GB@MgO(001) for different purposes.

Waste eggshell to valuable Co3O4/eggshell material as an efficient catalyst for catalytic decomposition of N2O under simulated real tail gases

Co3O4 shows excellent catalytic activity for N2O decomposition, in which it is urgently needed to develop novel efficient catalysts/supports with cheap and environmentally-friendly properties. Herein, Co3O4 nanoparticles decorated eggshell catalysts (Co3O4/eggshell-GR, Co3O4/eggshell-IM, and Co3O4/eggshell-DP) were prepared using simple grinding, impregnation, and deposition-precipitation methods, where waste eggshells were used as an effective support and reaction-promoter. The results indicated that the preparation methods significantly influenced the catalytic activity of Co3O4/eggshell catalysts; the highest activity was obtained over the Co3O4/eggshell-DP. The activity of Co3O4/eggshell-DP was comparable to that of pure Co3O4. More importantly, its specific activity was about 7.3 times that of Co3O4 at 400 °C. The examined Co3O4/eggshell-DP also displayed outstanding stability and anti-poisoning property in NO, O2, and/or H2O-containing atmospheres. It was also verified that the excellent activity of Co3O4/eggshell-DP correlated with the unique structure of the eggshell and the close incorporation between CaCO3 and Co3O4. The Co3O4/eggshell-DP catalyst owned abundant Co3O4 nanoparticles, more Co3+ species, and excellent redox performance, promoting the conversion of N2O at a lower temperature. The presence of abundant surface basic sites and a larger amount of oxygen vacancies also facilitated the catalytic efficiency of Co3O4/eggshell-DP.

Analysis of N2O reduction by components of red mud in bubbling fluidized bed

Circulating fluidized bed (CFB) technology is developing rapidly, but there is no effective treatment measure for N2O emission. Based on the catalytic theory of metal oxides for N2O, the catalytic performance and apparent activation energy of red mud and its main components for N2O decomposition in gas mixture were measured in a bubbling fluidized bed. The decomposition rate and catalytic rate of different materials were compared. The properties of the materials were similar to those of red mud. The main oxides of red mud were proportioned, and the N2O decomposition experiment was carried out by changing their proportions. The decomposition effect of N2O by various materials in coal-fired process was tested. It is found that all kinds of additives can accelerate the decomposition of N2O with different degrees, but the effect on NO is not significant. When the initial amount of N2O is the same, the catalytic activity of red mud for N2O decomposition is higher than that of single oxide and mixed oxide with different proportions in red mud. The order of catalytic activity for N2O decomposition is: Red mud > CaO > Al2O3 > Fe2O3 > SiO2 > MgO ≈ TiO2. For ammonia injection process, all additives can promote the decomposition of N2O and NO. Compared with other materials, red mud has stronger N2O decomposition ability, lower recovery rate and better economic performance. Iron-containing components can accelerate N2O decomposition, but increase the emission of NO. As a bed material and additive, Al2O3 can achieve better balance between N2O and NO.

Taming the Redox Property of A0.5Co2.5O4 (A = Mg, Ca, Sr, Ba) toward High Catalytic Activity for N2O Decomposition

Nitrous oxide (N2O) originating from the combustion of fossil fuels causes serious environmental issues. The design and construction of a catalyst with high performance for the removal of N2O remains challenging. Herein, a series of alkaline-earth metal-modified A0.5Co2.5O4 (A = Mg, Ca, Sr, Ba) catalysts were initiated by a hydrothermal protocol, and their catalytic activities for N2O decomposition were systematically investigated by experimental and density functional theory calculation. The results reveal that the doping of alkaline-earth metals significantly affects the morphology, structure, active oxygen species, oxygen vacancy, and redox property and thereafter the catalytic activity of A0.5Co2.5O4 for N2O catalytic decomposition. The introduction of alkaline-earth metals (A = Ca, Sr, Ba) considerably promoted the reduction of Co3+ to Co2+, thereby improving the electron-donating ability and oxygen vacancy number and thereafter weakening the Co–O bond. As a result, the catalytic activity of N2O decomposition distinctively enhanced. Among them, Ba0.5Co2.5O4 shows optimal N2O decomposition performance by virtue of its outstanding active oxygen species and excellent redox property. However, the doping of Mg suppresses the electron-donating ability of Mg0.5Co2.5O4 and thereafter the catalytic activity for N2O decomposition. Therefore, this work may shine light on the understanding of N2O decomposition over alkaline-earth metal-modified Co-based oxides.

Promotion effect of rare earth elements (Ce, Nd, Pr) on physicochemical properties of M-Al mixed oxides (M\u2009=\u2009Cu, Ni, Co) and their catalytic activity in N2O decomposition

A series of M-AlOx mixed oxides (M = Cu, Co, Ni) with the addition of high loadings of rare earth elements (REE, R = Ce, Nd, Pr; R0.5M0.8Al0.2, molar ratio) were investigated in N2O decomposition. The precursors were prepared by coprecipitation and subsequent calcination at 600 °C. The obtained mixed metal oxides were characterized by X-ray diffraction with Rietveld analysis, N2 sorption, and H2 temperature-programmed reduction. Depending on the nature of REE and the initial M-Al system, R cations could be separately segregated in oxide form or coordinated with the transition metal cations and form mixed structures. The addition of Ce3+ consistently led to nanocrystalline CeO2 mixed with the divalent oxides, whereas the addition of Nd3+ or Pr3+ resulted in the formation of their respective oxide phases as well as perovskites/Ruddlesden–Popper phases. The presence of REE modified the textural and redox properties of the calcined materials. The rare earth element-induced formation of low-temperature reducible MOx species that systematically improved the N2O decomposition on the modified catalysts compared to the pristine M-Al materials by the order of Co > Ni > Cu. The Ce0.5Co0.8Al0.2 catalyst revealed the highest activity and remained stable (approximately 90% of N2O conversion) for 50 h during time-on-stream in 1000 ppm N2O, 200 ppm NO, 20 000 ppm O2, 2500 ppm H2O/N2 balance at WHSV = 16 L g−1 h−1.

The correlation of NO chemisorption adsorption with its directly catalytic dissociation pathway on β-MnO2(1 1 0) and (1 0 1) surfaces

MnO2-based oxide catalysts have recently drawn so much attention owing to its good catalytic activity for NOx direct catalytic decomposition at low-temperature. As the reaction mechanism of NO direct catalytic decomposition on different MnO2 surfaces is not yet clear, it is important to understand the influence of different crystal surfaces of β-MnO2 on catalytic activity for NO decomposition. The correlation of NO chemisorption with its dissociation pathways on β-MnO2(110) and (101) surfaces are investigated based on density functional theory (DFT) with Vienna Ab-initio Simulation Package (VASP). The calculation results have shown that NO prefers to be adsorbed on β-MnO2(110) instead of β-MnO2(101) surface. The analysis results of density of states and differential charge density indicate that the interaction between NO and β-MnO2(110) surface is stronger and the adsorbed NO had more charge transfer with β-MnO2(110) surface. The effective activation energies of the possible NO dissociation pathways on the β-MnO2(110) and (101) surfaces are 2.57 and 3.07 eV, respectively. The lower energy barrier on β-MnO2(110) must be associated with the bridge adsorption of NO and more electrons transfer from NO to the surface, which is conducive to the breaking of N-O bond.

Investigation of Different Apatites-Supported Co3O4 as Catalysts for N2O Decomposition

Two types of apatite supports including hydroxyapatite (HAP) and fluorapatite (FAP) were prepared by the co-precipitation method. Supported Co catalysts with the above carriers were synthesized from Co(NO3)2·6H2O via the impregnation method. The catalytic activity for N2O decomposition was investigated using a continuous flowing microreactor system. The catalytic results demonstrated that the Co/HAP exhibited more excellent catalytic activity as well as the impurity gas (H2O, O2, and NO) resistance capability than the Co/FAP in the temperature range of 300–600 °C. Furthermore, the physicochemical properties of Co/HAP and Co/FAP were determined by several relevant characterization methods. The obtained experimental results revealed that Co/HAP possessed larger specific surface area, more ion-exchanged Co2+ and stronger oxygen desorption capacity than Co/FAP, which are the key factors for high N2O decomposition activity. Moreover, compared with Co/FAP, Co/HAP has not only more basic content, but also higher basic site density, which may be also conducive to enhance the electron donating ability of Co2+, thereby promoting the N2O catalytic decomposition.

Preparation and evaluation of iron nanoparticles embedded CNTs grown on ZSM-5 as catalysts for NO decomposition

Due to their high activity and selectivity, single-atoms based catalysts for oxygen removal and wastewater treatment have received enormous attentions in academia and industry. The present work sought to extend the single-atom catalyst concept to NO decomposition. A series of catalysts with highly dispersed iron nanoparticles embedded in carbon nanotubes grown on a ZSM-5 zeolite were prepared using an induced growth method, by pyrolysing melamine and ferric nitrate precursors impregnated on ZSM-5 at 900 °C. The catalysts were then tested for their catalytic activity in NO decomposition using a fixed-bed reactor operating at 300 °C and were shown to be able to completely decompose NO under the test conditions. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), BET, Raman and temperature-programmed oxidation (TPO) were used to study the effects of molar ratio of ferric nitrate to melamine on the active species, sample structures and NO decomposition mechanism. An increase in the molar ratio of melamine to iron nitrate led to an improvement to the dispersibility of iron nanoparticles and enhancement of NO decomposition. The use of ZSM-5 increased the dispersion of iron, thus enhancing the catalytic decomposition of NO. The characterisation of the used catalysts revealed that it was possible to regenerate the catalytic activity by doping and pyrolysing the deactivated catalysts with melamine, with no significant difference to that of the fresh catalysts.

N2O catalytic decomposition on electrodeposited Rh-based open-cell metallic foams

The present article reports on Rh-containing hydrotalcite (HT) derived catalysts coated on the surface of open-cell FeCralloy foams. The structured catalysts were prepared by in situ synthesis of Rh/Mg/Al HT precursors through electrodeposition followed by calcination. For comparison purposes, powder catalysts with analogous compositions were obtained by coprecipitation. The catalytic activity in N2O decomposition (deN2O) over structured and pelletized catalysts was investigated in absence and presence of inhibitors (O2 + NO) by keeping similar Rh loading and reaction conditions. Furthermore, stability of the structured catalysts was investigated.A Rh/Mg/Al HT-derived film uniformly coated the surface of the foam. The deN2O performance over both structured and pelletized catalysts was comparable for constant Rh loading in the catalytic bed, though lower activation energy was obtained for the structured catalyst. The coating was stable after a 24 h test at 475 °C in presence of O2 and NO, while rhodium oxide was reduced to Rh0 (2.0 ± 1.1 nm). Due to a low amount of active phase in the thin catalytic coating, the conversion steadily decreased during the first 20 h of time-on-stream from 60 until a constant 51% reaching stable level.

Direct Decomposition of N2O over C-Type Cubic Yb2O3-Co3O4 Catalysts

Abstract (Yb1−xCox)2O3−δ catalysts with cubic (C-type) rare-earth sesquioxide structure were synthesized by a co-precipitation method. The introduction of Co2+/3+ ions into the Yb2O3 lattice resulted in an improved catalytic activity for N2O decomposition, due to the enhanced redox properties and increased amount of active sites. Among the prepared catalysts, (Yb0.90Co0.10)2O3−δ exhibited the highest activity for the decomposition of N2O, which was completely converted to N2 and O2 at 500 °C. Moreover, (Yb0.90Co0.10)2O3−δ also showed high durability in the presence of H2O, O2, or CO2.

N2O decomposition and reduction on Co-MOR, Fe-MOR and Ni-MOR catalysts: in situ UV–vis DRS and operando FTIR investigation. An insight on the reaction pathways

Co-, Fe- or Ni-exchanged Na-MOR (Si/Al = 9.2) were prepared by ion-exchange method. The catalytic activity for N2O decomposition in the absence or in the presence of NO and for N2O reduction with CH4 in the absence of O2(CRN2O), or in the presence of O2(SCRN2O) was investigated. The catalytic measurements were performed in a flow apparatus with GC analysis of reactants and products. On Fe-MOR, in situ FTIR and UV–vis characterization evidenced coordinatively unsaturated sites (c.u.s.) Fe2+ arising from two families of Fe3+ dimers with different reducibility. Characterization and catalytic results combined with operando FTIR experiments gave an insight into the transition metal ion (tmi) species working during N2O abatement and into the reaction pathways.For N2O decomposition the activity order was Co-MOR > Fe-MOR in the absence of NO and Fe-MOR ≥ Co-MOR in the presence of NO, whereas Ni-MOR was always inactive. The decomposition occurred via redox mechanism passing through the formation of activated surface oxygen species, Oads*. The quasi-oxidic character of this activated oxygen in the Fe3+-O(1+δ)−---Fe(2+δ)+ intermediates with respect to the oxyl character of that in Co3+O‒ intermediates accounted for the lower activity and for the activity enhancement by NO addition to the feed of Fe-MOR with respect to Co-MOR. In Ni-MOR, both isolated or dimeric Ni2+ species were unable to be oxidized by N2O yielding Oads*.For N2O reduction, (CRN2O) and (SCRN2O), the activity order was Fe-MOR > Ni-MOR > Co-MOR. On all catalysts operando FTIR experiments revealed CHxOy intermediates (methoxy, formaldehyde and two types of formate species). The investigation of surface species changing the addition order of the reactants evidenced that the formation of CHxOy intermediates was favored on Co-MOR by pre-saturation with N2O, that yielded Co3+O− able to activate CH4, whereas on Ni-MOR by pre-saturation with CH4, that reduced Ni2+ dimers to Ni+ dimers, able to activate N2O. On Fe-MOR, the Fe2+ dimers formed during activation behaved as Co2+, whereas the Fe2+ dimers formed by reduction with CH4 behaved as Ni+ dimers.The formation and the stability of Oads* surface species were key factors for N2O decomposition and reduction pathways. These factors were affected by the mobility of the tmi electrons, that depends on the oxidation state, nuclearity and location in MOR framework of tmi.

Design of bimetallic Rh-M catalysts for N2O decomposition: From DFT calculation to experimental study

To understand the second doped metal influence on catalytic activity for N2O decomposition, the mechanisms of N2O decomposition over Rh-M(M = Co, Ni and Cu) bimetallic catalysts were investigated by density functional theory (DFT). Co doped into Rh catalyst can increase the activity for N2O decomposition due to the decrease of the activation energy of rate-determining step while Ni and Cu present contrary performance. A series of corresponding RhM catalysts supported on SBA-15 was prepared and applied in N2O catalytic decomposition. The catalytic activity trend of Rh-M catalysts for N2O decomposition is determined as Rh7Co1/SBA-15 > Rh/SBA-15 > Rh7Ni1/SBA-15 > Rh7Cu1/SBA-15, which is in consistency with the corresponding DFT calculation results.

Rh 2 O 3 /monoclinic CePO 4 composite catalysts for N 2 O decomposition and CO oxidation

CePO4 (in particular, monoclinic CePO4) has been rarely used to make supported catalysts. Herein, monoclinic CePO4 nanoparticles were prepared by calcining hexagonal CePO4 nanorods (prepared by precipitation) in air at 900 °C. Monoclinic CePO4 nanowires were prepared by calcining hexagonal CePO4 nanowires (prepared by hydrothermal synthesis at 150 °C) in air at 900 °C. Both monoclinic CePO4 materials were used to support Rh2O3 by impregnation using Rh(NO3)3 as a precursor (followed by calcination). The catalytic performance of Rh2O3/monoclinic CePO4 composite materials in N2O decomposition and CO oxidation was investigated. It was found that Rh2O3 supported on monoclinic CePO4 nanowires was much more active than Rh2O3 supported on monoclinic CePO4 nanoparticles. The stability of catalysts as a function of reaction time on stream was studied in both reactions. The influence of co-fed CO2, O2, and H2O on the catalytic activity in N2O decomposition was also studied. These catalysts were characterized by employing N2 adsorption–desorption, ICP-OES, XRD, TEM, XPS, H2-TPR, O2-TPD, and CO2-TPD. The correlation between physicochemical properties and catalytic properties was discussed.

Comparison between unsupported mesoporous Co3O4 and supported Co3O4 on mesoporous silica as catalysts for N2O decomposition

Mesoporous Co3O4 (meso-Co3O4) and Co3O4 nanoparticles supported on mesoporous silica SBA-15 (Co/SBA-15) were prepared by hydrothermal synthesis and an impregnation method, respectively. Although the as-prepared meso-Co3O4 had mesopores and a higher surface area comparable to that of Co/SBA-15, its catalytic activity for N2O decomposition was much lower than that of Co3O4/SBA-15. The low catalytic activity of meso-Co3O4 mainly stems from the drastic decrease of the meso-Co3O4 surface area under the reaction condition used. On the other hand, Co/SBA-15 maintained its high surface area and mesopores with the aid of a robust silica support. This finding indicates that Co3O4 supported by a support is much more stable and efficient than meso-Co3O4 under N2O decomposition reaction conditions.

N2O decomposition on CoOx, CuOx, FeOx or MnOx supported on ZrO2: The effect of zirconia doping with sulfates or K+ on catalytic activity

Zirconia doped with sulfates or K+ were prepared by impregnation with (NH4)2SO4, or KNO3 aqueous solutions. MeOx/ZrO2 and MeOx/doped-ZrO2 catalysts (Me=Co, Cu, Fe or Mn) were prepared by wet impregnation of zirconia and doped-zirconia supports. The effect of doping on MeOx properties was studied by XRD, UV–vis DRS, H2-TPR and FTIR and the influence of doping on the catalytic activity for N2O decomposition was investigated under ideal conditions (N2O in He) and under real reaction conditions (addition of NO, O2, and water vapour to the reactant mixture).Characterization results indicated that all samples contained mainly dispersed Men+ species interacting with the support. In MeOx/sulfated-ZrO2 the doping with electron-withdrawing sulfates stabilized the Men+ oxidation state. In CoOx/K-ZrO2 samples the doping with electron-releasing K+ increased the poly-nuclear CoOx reducibility. FTIR characterization suggested that the electron-donor capacity of Co2+ site had the order CoOx/sulfated-ZrO2<CoOx/ZrO2<CoOx/K-ZrO2.Catalytic results showed that dispersed Men+ are the active site for N2O decomposition on MeOx/ZrO2. The “twin peak pattern” of catalytic activity versus tmi d-electron number suggests that formation and stability of the intermediate Me(n+1)+O- surface complex, requiring the mobility of Men+ oxidation state, are key factors for activity. Because the electron-withdrawing sulfates lowered the electron-donor capacity of tmi, hindering the formation of Me(n+1)+O-, the effect of sulfate-doping was to decrease the deN2O activity in MeOx/sulfated-ZrO2. Conversely, because the electron-releasing potassium cation increased electron-donor capacity of Co2+, yielding an easier formation of the intermediate surface complex, the effect of K-doping was to increase the deN2O activity in CoOx/K-ZrO2.From an applied viewpoint, cobalt supported on ZrO2 and K-doped ZrO2 systems, that were affected by reversible inhibitory effect in real reaction conditions, are interesting catalysts for N2O abatement and for simultaneous abatement of N2O and NO with hydrocarbons.

Effect of precursor synthesis on catalytic activity of Co3O4 in N2O decomposition

Series of precursors was prepared by precipitation of cobalt nitrate in aqueous solutions using various precipitation agents (NH3·H2O, NaOH, Na2CO3) and reactions conditions (OH/Co molar ratio, aging time). Powder XRD showed different phase composition of the obtained precursors, in which β-Co(OH)2, CoII–CoIII layered double hydroxide, and basic cobalt carbonate were identified. Only Co3O4 spinel-like oxide was found in products after heating at 500°C in air but different N2O conversions were observed over the examined oxide catalysts. Especially the catalysts obtained from β-Co(OH)2 precursors showed high catalytic activity in N2O decomposition. The correlation between methods of preparation, phase composition of precursors, catalytic properties of the related oxide catalysts, and the role of the cobalt ions as catalytic active sites is discussed.

Investigation of potassium doped mixed spinels CuxCo3−xO4 as catalysts for an efficient N2O decomposition in real reaction conditions

The influence of copper in the mixed spinel CuxCo3−xO4 on the catalytic activity in N2O decomposition was investigated under ideal and real reaction conditions. A strong dependency of the catalytic activity on the amount of Cu in CuxCo3−xO4 catalysts was observed. Decreasing the amount of Cu increases the catalytic activity. Aiming for improved activity the influence of doping with alkaline (earth) metals was investigated. The use of potassium as dopant allowed a further increase of the catalysts activity. High activity was found for K-Cu0.25Co2.75O4 and full conversion was already reached at 330°C under ideal conditions. The effect of O2, NO and H2O in the gas mixtures on the decomposition of N2O was evaluated. Overall, full N2O decomposition could be reached at temperatures as low as 490°C in realistic reaction conditions. Additionally, stability tests emphasise stable activity for at least 60h. Furthermore, no irreversible deactivation even in the presence of NO, O2 and H2O was found. The catalysts were fully characterised by means of XRD, elemental analysis, TGA, TPR and N2-physisorption. TPD-O2 measurements were performed to investigate the influence of the catalyst composition on oxygen vacancies to elucidate the nature of active sites.

Catalytic decomposition of N2O over NixCo1–xCoAlO4 spinel oxides prepared by sol-gel method

NixCo1–xCoAlO4 spinel oxides with different compositions were prepared by sol-gel method and further modified with K2CO3 by incipient impregnation. The NixCo1–xCoAlO4 spinel oxides were characterized by means of nitrogen physisorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), and temperature-programmed reduction by hydrogen (H2-TPR); the effect of preparation parameters such as composition, mother liquid pH value, and potassium loading on their catalytic activity in N2O decomposition was investigated. The results show that the K/Ni0.15Co0.85CoAlO4 catalyst prepared with a pH value of 3 and a K/(Ni+Co) molar ratio of 0.1 is most active for N2O decomposition; over it, N2O can be completely decomposed into nitrogen and oxygen at 450°C in the presence of oxygen. K-modified catalysts exhibit high catalytic activity, good reducibility and resistance towards water, as K species may be able to weaken the surface metal-oxygen bonds.

Hierarchical Fe-, Cu- and Co-Beta zeolites obtained by mesotemplate-free method. Part I: Synthesis and catalytic activity in N2O decomposition

Two series of BEA zeolites (Beta and Beta/meso) have been prepared. A first series of the samples was obtained by a conventional aging of parent zeolite gel, while the second series (Beta/meso) was prepared by mesotemplate-free method. In this method Beta nanoparticles are aggregated under acidic conditions with the formation of micro-mesoporous material. Both series (Beta and Beta/meso) were doped with Fe, Cu and Co by ion-exchange method and tested as catalysts of N2O decomposition. The Cu-Beta catalyst was found to be the most active in the process of N2O decomposition conducted in inert gas atmosphere. However, in the process performed under conditions similar to those prevailing in waste gases emitted from nitric acid plants (one of the main sources of N2O emission) higher reaction rate was found for the Cu-Beta/meso catalyst.

Effect of RhOx/CeO2 Calcination on Metal-Support Interaction and Catalytic Activity for N2O Decomposition

The effect of the calcination conditions on the catalytic activity for N2O decomposition of 2.5% RhOx/CeO2 catalysts has been investigated. Ramp and flash calcinations have been studied (starting calcinations at 25 or 250/350 °C, respectively) both for cerium nitrate and ceria-impregnated rhodium nitrate decomposition. The cerium nitrate calcination ramp has neither an effect on the physico-chemical properties of ceria, observed by XRD, Raman spectroscopy and N2 adsorption, nor an effect on the catalysts performance for N2O decomposition. On the contrary, flash calcination of rhodium nitrate improved the catalytic activity for N2O decomposition. This is attributed to the smaller size of RhOx nanoparticles obtained (smaller than 1 nm) which allow a higher rhodium oxide-ceria interface, favoring the reducibility of the ceria surface and stabilizing the RhOx species under reaction conditions.