deN2O Activity Research Articles

N2O Catalytic Decomposition and NH3-SCR Coupling Reactions over Fe-SSZ-13 Catalyst: Mechanisms and Interactions Unraveling via Experiments and DFT Calculations

Simultaneous catalytic elimination of NO and N2O from exhausts is an ideal solution for nitric or adipic acid plants. Herein, Fe-based zeolite catalysts were applied for the NH3–NOx–N2O system. 1% Fe-SSZ-13 performed excellent catalytic activity with 100% conversions for both NOx and N2O at 400–600 °C. Experimental and computational research studies unraveled that NO could significantly improve N2O decomposition by reacting with αO* to generate easily desorbed NO2; furthermore, NO−αO* also can decrease charge density of Fe−αO*, facilitating αO* desorbed from the Fe sites. Besides, NH3 inhibits low-temperature deN2O activity due to strong competitive adsorption with N2O; however, NH3 accelerates N2O decomposition by consuming αO* and simultaneously reduces N2O as a reductant at high temperature. Interestingly, the αO* generated from N2O decomposition would enhance NO oxidation to NO2, which is beneficial to NH3-selective catalytic reduction. This work elaborates fundamental insights for simultaneous abatement of NOx and N2O and provides candidate catalyst for application.

Ir-Catalysed Nitrous oxide (N2O) Decomposition: Effect of Ir Particle Size and Metal–Support Interactions

The effect of the morphology of Ir particles supported on γ-Al2O3, 8 mol%Y2O3-stabilized ZrO2 (YSZ), 10 mol%Gd2O3-doped CeO2 (GDC) and 80 wt%Al2O3–10 wt%CeO2–10 wt%ZrO2 (ACZ) on their stability on oxidative conditions, the associated metal–support interactions and activity for catalytic decomposition of N2O has been studied. Supports with intermediate or high oxygen ion lability (GDC and ACZ) effectively stabilized Ir nanoparticles against sintering, in striking contrast to supports offering negligible or low oxygen ion lability (γ-Al2O3 and YSZ). Turnover frequency studies using size-controlled Ir particles showed strong structure sensitivity, de-N2O catalysis being favoured on large catalyst particles. Although metallic Ir showed some de-N2O activity, IrO2 was more active, possibly present as a superficial overlayer on the iridium particles under reaction conditions. Support-induced turnover rate modifications, resulted from an effective double layer [Oδ−–δ+](Ir) on the surface of iridium nanoparticles, via O2− backspillover from the support, were significant in the case of GDC and ACZ.

Optimization of cesium and potassium promoter loading in alkali-doped Zn0.4Co2.6O4|Al2O3 catalysts for N2O abatement

A series of potassium or cesium doped Zn0.4Co2.6O4|Al2O3 catalysts with different alkali loadings were prepared, characterized with respect to chemical composition (XRF), structure (XRD, RS) morphology (TEM), and the alkali promoter thermal stability. A strong beneficial effect on the deN2O activity of the Zn0.4Co2.6O4|Al2O3 catalyst (decrease in the T50% by about 80 °C) was observed for both promoters at different surface coverages. It was found that in comparison to a rather narrow range of optimal cesium loading (0.5–2 atoms/nm2) a comparable promotional effect of potassium doping was observed for a slightly wider surface concentrations (0.5–3 atoms/nm2). Such difference was attributed to surface dispersion of potassium over the alumina support and the spinel active phase, while cesium was found to be located mainly on the spinel phase. For practical applications, the superiority of potassium over cesium consist in fact that a similar beneficial effect is associated with much higher thermal stability in the temperature range of the catalyst deN2O operation and lower price of the promoter precursor.

Catalytic decomposition of N2O on inorganic oxides: Εffect of doping with Au nanoparticles

The aim of this work is to explore the influence of the support (MxOy: Al2O3, CeO2, Fe2O3, TiO2 and ZnO) on the physicochemical characteristics and the N2O decomposition (deN2O) performance of supported gold nanoparticles (Au/MxOy). Both the bare oxides and the Au/oxide catalysts were characterized by several methods (BET, XRD, SEM, HR-TEM, XPS and H2-TPR) and comparatively evaluated in order to gain insight into the structure-property relationships. A close correlation between the catalytic performance and the redox properties (reducibility and oxygen mobility) of oxide carriers was revealed on the basis of a redox type mechanism, resulting in the following deN2O activity order: Fe2O3>>CeO2>ZnO>TiO2>Al2O3. In contrast, no significant effect of textural/structural characteristics on the deN2O performance was found. Addition of gold to the oxides facilitates the surface oxygen reduction and, consequently, the deN2O performance, without, however, affecting the activity order. When oxygen is in excess in the feed stream (N2O+O2) a slight inhibition was observed for all samples, due to the competitive adsorption of both reactants on the catalyst surface. On the basis of a kinetic analysis the superior performance of Fe2O3-based samples can be attributed to the optimum compromise between the activation energy and the pre-exponential factor under the present conditions.

Influence of preparation method on dispersion of cobalt spinel over alumina extrudates and the catalyst deN2O activity

A series of supported catalysts of the Co3O4 spinel active phase dispersed over alumina extrudates (9×25mm) was prepared by several methods (incipient wetness impregnation with Co(NO3)2 and CoCl2, with glycerol-assisted impregnation with Co(NO3)2, combustion synthesis, and two variants of spray deposition with Co(NO3)2 on pristine and ammonia soaked extrudates). The catalysts were characterized by XRF, XRD, RS, UV–vis, SEM/TEM/EDX, and their catalytic deN2O activity was investigated in the temperature programmed surface reaction (TPSR) mode. The relation between the spinel active phase particle size and its radial dispersion over the alumina extrudate and the deN2O activity was revealed and quantified. For the assessment of the active phase utilization, the N2O concentration profile across the extrudates was calculated using Thiele modulus and compared with the radial distribution of the spinel. It was shown that the dispersion of spinel active phase exhibits optimal profile when the sample is obtained in the presence of the organic components of the precursor mixture (glycerol or urea). The obtained results were discussed in the context of practical implications for the development of an efficient, low-cost catalyst for the N2O abatement.

Enhancing the deN2O activity of the supported Co3O4|α-Al2O3 catalyst by glycerol-assisted shape engineering of the active phase at the nanoscale

A series of supported Co3O4/α-Al2O3 catalyst synthesized by glycerol-assisted method was thoroughly characterized (X-ray micro-tomography, XRD, RS, FTIR, SEM/TEM/EDX, TG/DTA, TPR), and their reactivity was evaluated in N2O decomposition in 5% N2O/He and 1.5% N2O, 1% NOx, 1 vol.% H2O, 2.0 vol.% O2. Their superior catalytic activity in comparison to the benchmark Co3O4/α-Al2O3 catalyst, obtained via incipient wetness impregnation with the aqueous solution, was accounted for by differences in cobalt spinel dispersion on the alumina support, spinel nanoparticle size and faceting. Whereas for the samples prepared from the aqueous solution the spinel active phase exhibits a broad bimodal size distribution (with the maxima for 10–50nm crystallites and 300–600nm agglomerates) in the case of glycerol-assisted synthesis a monomodal distribution is featured by isolated spinel nanocrystallites of 10–30nm. At the same time, the presence of glycerol changes the spinel crystallites morphology from rhombicuboctahedron with abundant exposition of the less favorable (111) planes into the truncated cubic shape with the dominant more active (100) facets. It was shown that the beneficial effect of glycerol is sustained in typical gaseous residuals (H2O, NOx, O2) present in the tail gases of nitric acid plants. The observed effect of glycerol-assisted synthesis was accounted for by complexation of cobalt by glycerol, leading to the formation of an intrapore cobalt glycerolate, which upon calcination is transformed into well dispersed Co3O4 cubic nanocrystals.

N2O decomposition over ceria-promoted Ir/Al2O3 catalysts: The role of ceria

The impact of CeO2 in the Al2O3-20wt% CeO2 support prepared by the co-precipitation method on the Ir particle size, morphology and oxidation state, and in turn on the deN2O catalytic activity (1000ppmN2O) of supported Ir catalysts were investigated in the absence and presence of excess O2 (2vol%) conditions. It was demonstrated that the deN2O activity of Ir/Al2O3 is notably suppressed by the presence of oxygen in the feed stream, namely, the N2O conversion at 600°C is declined to 65% in the presence of oxygen as compared to 100% in the absence of oxygen. A similar detrimental catalytic effect was also observed for the Ir/CeO2 solid. On the contrary, the deN2O performance of CeO2-modified Ir/Al2O3 catalyst is only slightly affected by the presence of oxygen. An extensive characterization study involving surface texture analysis (N2 adsorption-desorption at −196°C), temperature-programmed reduction in H2 (H2-TPR), X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), scanning transmission electron microscopy (STEM), electron energy loss spectroscopy (EELS) and diffuse reflectance infrared Fourier transform spectroscopy of CO adsorption and desorption (CO-DRIFTS) was carried out to gain insight into the origin of the CeO2-induced promotional effect. The characterization results revealed the existence of IrO2 phase (H2-TPR, XRD, HRTEM, EELS and CO-DRIFTS) as well as of very small isolated particles of Ir on the Al2O3, CeO2 and CeO2-Al2O3 supports (STEM) but to a notably different extent. The coexistence of large IrO2 particles of perfect crystallite structure and very small Ir particles located at the Ir-ceria interface was revealed only in Ir/AlCe. The establishment of a certain Irδ+/Ιr0 ratio and oxygen vacant sites (VO) concentration in ceria around very small Ir particles under oxidative reaction conditions seem to largely promote N2O adsorption and subsequent decomposition into N2 and O2 over the CeO2-promoted Ir/Al catalyst. In the case of Ir/Al, a different deN2O decomposition mechanism occurs, where the site reactivity of Irδ+/Ιr0 established under oxidizing conditions is reduced significantly.

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.

Cobalt–zinc spinel dispersed over cordierite monoliths for catalytic N2O abatement from nitric acid plants

A series of monolithic catalysts with the 0.3wt.% loading of the (Co,Zn)Co2O4 spinel active phase dispersed on bare and ceria and zincite washcoated cordierite substrates was prepared by impregnation method: (Co,Zn)Co2O4/cordierite, (Co,Zn)Co2O4/ZnO/cordierite and (Co,Zn)Co2O4/CeO2/cordierite. The catalysts were thoroughly characterized (XRD, RS, SEM/TEM/EDX, XRF), and their catalytic deN2O activity was investigated using model gas mixture (2000ppm N2O/N2), and tail gases (1400±50ppm N2O, 900±100ppm NOx, 0.8±0.2vol.% H2O, 2.0±0.2vol.% O2) of the nitric acid pilot plant. The reported data points correspond to the measurements performed at possibly the closest tail gas composition. Morphological SEM analysis of the monolith cross-sections indicated the segregation of both ZnO and CeO2 washcoats in the form of islands covered by the (Co,Zn)Co2O4 active phase. The catalytic tests revealed that the monolithic catalysts exhibit high catalytic deN2O activity, reaching X>96% at 400°C (model gas) and 450°C (tail gases) for the best (Co,Zn)Co2O4/CeO2/cordierite system. It was also found that the specific reaction rate per cobalt spinel weight loading for the monolithic catalysts is even two orders of magnitude higher than in the case of the optimized bulk spinel phase. Yet, the beneficial effect of ceria, dominant in the model gas mixture, is largely dumped in tail gases at low temperature. It is however restored above 400°C, when the poisoning H2O and NOx molecules are desorbed.

Insights into the twofold role of Cs doping on deN2O activity of cobalt spinel catalyst—towards rational optimization of the precursor and loading

Cobalt spinel catalysts promoted with different cesium loadings from various precursors (Cs2CO3, CsNO3, CH3COOCs, and CsOH) were prepared by incipient wetness impregnation. The catalysts were characterized by XRF, XRD, SEM, XPS and Raman Spectroscopy. The work function studies were used to optimized the surface doping and monitor the retention of surface oxygen. The stability of cesium promoter was evaluated by means of species resolved – thermal alkali desorption method. The catalytic activity of N2O decomposition over the synthesized catalysts was studied by temperature programmed reaction. The role of cesium precursor was evaluated in terms of dispersion and the nature of the counterion. The results show that the most active deN2O catalysts are obtained for cesium carbonate at the narrow loading range of 2–3atoms/nm2 (complete N2O conversion at T<200°C). The twofold promotional effect is discussed in terms of modification of the electronic properties of the spinel catalyst (stimulation of dissociation step: N2O+e=N2+O–) and stability of the surface oxygen species (recombination step: O–=½O2+e).

Catalytic properties in N2O decomposition of mixed cobalt–iron spinels

The effect of introduction of iron in the Co3 − xFexO4 on catalytic activity in N2O decomposition was investigated. The spinel catalysts were characterized by XRD, SEM, RS, BET methods, work function measurements and Mössbauer spectroscopy. Introduction of iron in the Co3 − xFexO4 spinel catalysts at the level of x < 1 leads to preferential substitution of Fe3+ in tetrahedral sites, whereas for x > 1 also octahedral ones are substituted. A strong correlation between deN2O activity (T50%) and work function was observed showing that electronic factor controls the catalytic reactivity of Co–Fe spinels. The results revealed that the active centers for N2O decomposition are cobalt ions and thus even a low level of their substitution by iron leads to substantial decrease of the deN2O activity of the cobalt spinel.

Mechanistic analysis of direct N2O decomposition and reduction with H2 or NH3 over RuO2

The mechanisms of direct N2O decomposition and N2O reduction by H2 or NH3 on RuO2 has been studied by means of steady-state catalytic tests at ambient pressure, transient experiments in a temporal analysis of products (TAP) reactor, and density functional theory (DFT) simulations. Bulk RuO2 is very active for N2O decomposition into N2 and O2, achieving full conversion at 723K. According to the DFT calculations, coordinatively unsaturated ruthenium (Rucus) sites are active for the decomposition and oxygen elimination from the surface is rate-limiting step. When pre-reducing RuO2 with H2, the de-N2O activity in the low-temperature region increases. This is attributed to the higher reactivity of surface oxygen vacancies created by H2 at bridge sites compared to Rucus sites. Co-feeding of hydrogen or ammonia with nitrous oxide strongly accelerates the rate of N2O elimination. TAP studies show that oxygen species formed upon N2O decomposition over RuO2 react with NH3 and H2 yielding N2, NO, N2O, and H2O. Both TAP experiments and DFT simulations show that the N-containing intermediates coming from ammonia adsorb much stronger on the catalyst surface than H-containing intermediates coming from hydrogen. This causes blockage of active sites for N2O decomposition by the former species, accounting for the higher efficiency of H2 as reductant for N2O. The presence of O2 in the feed cancels the reducing effect of H2 or NH3 due to the more favorable re-oxidation of reduced RuO2 by O2 compared to N2O.

Study on the direct decomposition of nitrous oxide over Fe-beta zeolites: From experiment to theory

N 2O direct decomposition over Fe-beta zeolite prepared by wet ion-exchange (WIE) was systematically investigated based on the experimental and theoretical studies in this paper. Both isolated iron ions in the charge compensation positions and highly dispersed FeO x -like crystallite were verified by means of H 2-TPR. Catalytic performances of various Fe-BEA zeolites with diverse iron contents were thereafter studied. The results showed that: (1) the catalytic activity of bare beta zeolite was significantly promoted via ion-exchange; (2) no obvious further increase in deN 2O activity was observed for Fe-beta samples with iron contents higher than 1%. Two kinds of reaction mechanism, with respective formation of oxygen (O 2) or nitrogen oxide (NO x ) intermediate, for the direct decomposition of N 2O over Fe-beta zeolite (noted as Fe-Z) were proposed according to the N 2O-TPD, NO 2-TPD, N 2-TPD, N 2O-TPSR, and in situ DRIFTS investigation and density functional theory (DFT) study. The corresponding energy calculations for O 2-formation mechanism revealed that O 2 desorption was the rate determining step with an energy barrier of 63.20 kcal/mol. Another mechanism with NO formation was also simulated by DFT calculations, whose energy calculations indicated that the formation of Fe-Z-(NO) 2 was the main pathway for NO generation with an energy barrier of 26.92 kcal/mol.

Guidelines for optimization of catalytic activity of 3d transition metal oxide catalysts in N 2O decomposition by potassium promotion

The effect of potassium promotion on deN 2O activity of various 3d electron spinels (Mn 3O 4, Fe 3O 4, Co 3O 4) was investigated by TPSR in conjunction with parallel work function measurements. The results were interpreted in terms of a surface dipole model (K δ+ –O surf δ− ) supported by DFT molecular modelling. The substantial enhancement of deN 2O reactivity of Co 3O 4 and Mn 3O 4 upon K addition (decrease of Δ T 50% by 150 °C) was observed, whereas for Fe 3O 4 the promotional effect was unexpectedly small. The maximum deN 2O activity was found for potassium surface coverage of 2, 6, 8 K atoms/nm 2 for cobalt, iron and manganese spinels, respectively. In each case the optimal level of doping was found for the minimum of the measured work function indicating that this parameter can be use for optimization of the catalyst deN 2O reactivity.

Effect of the preparation method on high-temperature de-N2O performance of Na–CaO catalysts. A mechanistic study

A simple cellulose-templating (CT) method was used to prepare Na–CaO catalysts for high-temperature N2O decomposition to N2 and O2 in excess of NO, O2, and H2O. According to this method, cellulose materials were soaked in aqueous solution of calcium and/or sodium nitrates followed by burning out the template material. Depending on the nature of cellulose template and calcination procedure, the obtained catalysts consisted of regularly shaped particles of 100–400nm. Conventionally prepared Na–CaO reference materials had randomly shaped particles on a micron scale. Compared to the latter catalysts, the CT ones showed higher de-N2O activity and resistance against inhibition by NO and O2, which make them interesting from industrial point of view. Transient analysis of NO interaction with the studied catalysts in the presence and the absence of O2 enabled us to conclude that the superior de-N2O performance of the CT materials is due to improved desorption of surface NOx species acting as inhibitors for N2O decomposition.

Mechanism and micro-kinetics of direct N2O decomposition over BaFeAl11O19 hexaaluminate and comparison with Fe-MFI zeolites

Mechanistic and kinetic aspects of direct N2O decomposition over BaFeAl11O19 hexaaluminate were investigated in the Temporal Analysis of Products (TAP) reactor and compared with those previously determined for Fe-MFI zeolites. The catalysts were chosen due to their de-N2O operation in significantly different temperature regimes. Several micro-kinetic models were evaluated for describing the transient responses of N2O, N2, and O2 obtained in N2O pulse experiments at 823–973K. Thorough discrimination between these models enabled us to conclude that the preferred models of N2O decomposition over BaFeAl11O19 and Fe-MFI zeolites differ in the reaction pathways leading to O2 and N2. Gas-phase N2 and O2 are simultaneously formed over BaFeAl11O19 upon interaction of gas-phase N2O with a bi-atomic surface oxygen (*–O2) species. Contrarily, the formation of O2 over Fe-MFI occurs via a sequence of three elementary heterogeneous steps and limits the overall rate of N2O decomposition. Despite the easy O2 formation, BaFeAl11O19 is less active for N2O decomposition below 973K than the Fe-MFI zeolites due to the low coverage by *–O2. According to our quantitative micro-kinetic analysis, this species is formed when gas-phase N2O reacts with a mono-atomic oxygen (*–O) species. This reaction pathway is strongly influenced by the degree of isolation of iron species. The higher the degree of iron isolation in the catalyst, the lower the de-N2O activity.

Enhanced de‐N2O Performance of Cellulose‐Templated CaO‐Based Catalysts

A simple cellulose-templated method is applied to synthesize CaO-based catalysts with high activity and stability in N2O decomposition in excess of NO, O2, and H2O. Their de-N2O activity and resistance against inhibition by O2 and NO are determined by particle size: the smaller the particles, the better the performance. Application of cellulose and/or other organic templates provides opportunities for tuning particle size.

A comparison between electrochemical and conventional catalyst promotion: The case of N 2O reduction by alkanes or alkenes over K-modified Pd catalysts

In the present work, two different methods of catalyst promotion, the electrochemical promotion (EP) and the conventional promotion (CP), were comparatively applied on a catalytic system of significant environmental and practical importance: the N 2O reduction by hydrocarbons (alkanes and alkenes), in the presence or absence of O 2, over Pd catalysts. A galvanic cell of the type Pd/K + -conducting β″-Al 2 O 3 /Au was constructed for the application of the EP concept whereas the CP concept was investigated via a series of highly dispersed Pd/γ-Al 2O 3 catalysts, conventionally promoted (by impregnation) with K modifier. Given that EP is a straightforward, efficient and in situ way for investigating the effect of a promoter on a catalytic system, the present study is dealing with its prior use as a rapid “research tool” for exploring the effect of K promoter on the catalytic system under consideration. Subsequently, the insight obtained from EP studies is applied to the design of conventional catalysts' composites, i.e. Pd/γ-Al 2O 3 catalysts conventionally promoted by K at loadings indicated from EP studies. For the system investigated, the optimal promoter loading was in the range of ∼ 0.45–0.55, in terms of K-coverage. In this range of K-loadings significant enhancement on de-N 2O activity was obtained under reducing conditions using both methods of K-promotion. However, in the presence of excess oxygen in the reaction mixture the effect of K-promotion was less pronounced, independently of the reducing agent used.

Optimization of Multicomponent Cobalt Spinel Catalyst for N2O Abatement from Nitric Acid Plant Tail Gases: Laboratory and Pilot Plant Studies

The influence of Zn and K promoters on N2O decomposition over Co3O4 was investigated by work function measurement and temperature-programmed surface reaction. The beneficial effect of the promoters resulting in spectacular decrease in the temperature of 50% conversion by 200 °C was found to be essentially of electronic origin. The strong correlation between the catalyst work function and deN2O activity allowed for the optimization of the doping level of both additives. The pilot plant tests in real nitric acid tail gases revealed that the optimized double promoted (Zn, K) cobalt spinel catalyst maintained its remarkable activity in N2O decomposition (conversion >95% at the target temperature of 350 °C) for more than 60 h.

Optimal Hydrocarbon Selection for Catalytic N2O Reduction over Iron-Containing ZSM-5 Zeolite

The selective catalytic reduction of N2O over steam-activated FeZSM-5 zeolite has been investigated at 473-823 K using C1-C3 hydrocarbons (methane, ethane, ethene, ethyne, propane, and propyne). The assessment of the hydrocarbons for nitrous oxide abatement is discussed according to different criteria: (i) de-N2O activity and operation temperature, (ii) hydrocarbon utilization, that is, the selectivity to react with N2O in 02 excess, (iii) emission of CO and CO2, (iv) sensitivity to NO and NH3, and (v) cost. Alkanes are generally more effective reducing agents than unsaturated hydrocarbons. In particular, alkynes require higher temperature to activate N2O and are unselective because of their proneness to react with O2. Ethane is an optimal reductant, featuring a high de-N2O activity, high selectivity, and compared to methane, a lower degree of inhibition by NO.