Catalytic Reduction Method Research Articles

Electrocatalytic reduction of nitrate to ammonia over activated carbon-supported copper-iron bimetallic catalyst synthesized by hydrothermal co-precipitation method

Ammonia synthesis via electrocatalytic reduction of nitrate is a promising approach for green ammonia production. However, this process limited by multiple reaction pathways and NO3− adsorption over electrocatalyst surface. Herein, copper-iron bimetallic catalysts with different atom ratios of Cu/Fe (Cu/Fe = 10/0, 7/3, 5/5, 3/7 and 0/10) and activated carbon as supporter (CuFeOx/AC) were synthesized through hydrothermal co-precipitation method for catalytic reduction of nitrate. Synergistic effects between the Cu and Fe were observed in the copper-iron bimetallic catalysts and an appropriate atom proportion of Cu/Fe was benefit to accelerate the adsorption and electrocatalytic kinetics of nitrate reduction to *NO2 and *NO2 hydrogenation to·NH3 through electron redistribution. The catalyst of 7Cu3FeOx/AC presented the best catalytic performance in nitrogen electroreduction reaction for ammonia synthesis, with an NH3 yield rate of 2091 μg h−1 mgcat−1 and a faradaic efficiency of 76 % at −0.8 V vs. reversible hydrogen electrode. The 7Cu3FeOx/AC also exhibited excellent cycle ability and long-term durability whose NH3 yield rates maintained as high as 1476 and 2326 μg h−1 mgcat−1 after 9 cycles and 10 h durability measurement, respectively. The nitrate reduction behavior over 7Cu3FeOx/AC proceeded with a series of deoxygenation reactions as follows: NO3− → *NO3 → *NO2 → *NO → *NOH → *NH2OH →·NH3. With the above excellent properties, the 7Cu3FeOx/AC may prove to be a promising electrocatalyst for ammonia synthesis via nitrogen electroreduction reaction.

Compositional and Fabrication Cycle Optimization of Ceria-Zirconia-Supported Mo-Based Catalysts for NH3-SCR NOx Reduction

The reduction of nitrogen oxides (NOx), critical pollutants from stationary to mobile sources, mainly relies on the selective catalytic reduction (NH3-SCR) method, employing ammonia to reduce NOx into nitrogen and water. However, conventional catalysts, while effective, pose both environmental and operational challenges. This study investigates ceria-zirconia-supported molybdenum-based catalysts, exploring the effects of zirconium doping and different catalyst synthesis techniques, i.e., co-precipitation and impregnation. The catalytic performance of the differently prepared samples was significantly influenced by the molybdenum incorporation method and the zirconium content within the ceria-zirconia support. Co-precipitation at higher temperatures resulted in catalysts with better structural attributes but slightly lower catalytic activity compared to those prepared via impregnation. Optimal NOx reduction (close to 100%) was observed at a 15 mol% zirconium doping level when using the impregnation method.

Effect of samarium doping on the activity and sulfur resistance of Ce/MnFeOx catalyst for low-temperature selective catalytic reduction of NOx by ammonia

The self-made MnFeOx catalysts doped with cerium and samarium were prepared by impregnation method for low-temperature selective catalytic reduction by NH3. In this work, the surface properties of the series of MnFe-based catalysts were studied. The results indicate Sm-modified catalyst have superior low-temperature SCR activity; NOx conversion maintained at nearby to 100% at 90–240 °C. In addition, The N2 selectivity of Sm doping remains above 80% in the range of 60–150 °C. In SO2 poisoning test, the NOx conversion can be remained >90% after 10 h of reaction. The XPS, NH3-TPD and H2-TPR results show the catalyst with Sm doping enhances the acid sites and oxidation catalytic sites of mixed oxides serves for improving oxygen vacancies and transfer electrons. In situ DRIFTS results show that NOx is more easily adsorbed on the surface after Sm doping, which provided favorable conditions for the NH3-SCR reaction to proceed. The reaction at the catalyst surface will follow the L-H reaction mechanism by transient reaction test.

Investigation of iron oxide supported on activated coke for catalytic reduction of sulfur dioxide by carbon monoxide

In view of the low utilization rate of by-product in limestone-gypsum wet flue gas desulfurization process, a method of catalytic reduction of SO2 to elemental sulfur was proposed. In this work, supported iron catalyst using activated coke as supporter was prepared and characterized. Moreover, the performance of SO2 reduction using CO as reducing agent at various Fe loadings, temperatures, gaseous hourly space velocities and CO/SO2 molar ratios was studied. Research shows that, compared with other metals, the highest catalytic activity is achieved over Fe-based catalyst. The iron sulfide is the main active component during the catalytic reduction reaction, hence the catalyst needs to be presulfided before use. The micropores of activated coke become more abundant after loading Fe, whereas excessive increase of Fe loading may bloke the mesopores and weaken the catalytic activity. Higher reaction temperature, lower GHSV and a stoichiometric molar ratio are conducive to the improvement of SO2 conversion and S yield. The catalytic performance at lower temperatures was further improved by loading Co. When the Co loading is 4 wt%, the SO2 conversion rate reaches 90.9% at 400 °C because loading Co enhances the redox performance of the catalyst surface. The findings are instructive for the development of cost-effective carbon-based catalysts for resource recovery of sulfur.

Enhanced low-temperature selective catalytic reduction (SCR) activity and H2O and SO2 resistance of flower-like SmMnOx and SmMnOx-rGO catalysts

Reed flower-like SmMnOx and cauliflower-like SmMnOx-rGO catalysts were successfully synthesized by a coprecipitation-coupled solvothermal method for selective catalytic reduction (SCR) of NOx. The NOx conversion of the two catalysts is more than 90% in the temperature range of 75–200 °C, and the N2 selectivity of SmMnOx-rGO is above 90%. Moreover, both of them exhibit more than 62% of resistance to H2O and SO2 at a very low temperature of 100 °C, much superior than the fluffy spherical SmMnOx prepared by coprecipitation method. The strong synergy between Mn and Sm endowed by the flower-like structure contributes to a low degree of crystallization, a high ratio of (Mn3++Mn4+)/Mn, more chemisorbed oxygen species, strong redox ability, and more Lewis acid sites, hence effectively enhancing low-temperature SCR activity and resistance to H2O and SO2. In addition, the decreased ratio of Mn4+/Mn after rGO doping hinders the side reaction of NH3 oxidation, thus enhancing the N2 selectivity of rGO-doped SmMnOx catalyst.

Broadening active temperature window for NH3-SCR on tungsten-promoted MnCeOx nanorod catalysts

xW/MnCe nanorod catalysts with various tungsten contents were synthesised using the incipient wetness impregnation method for selective catalytic reduction (SCR) of nitrogen oxides with NH3 (i.e. NH3-SCR reaction). Tungsten addition considerably widened the active temperature window and enhanced the SO2/H2O tolerance of the catalysts. The optimum catalytic performance was achieved when the tungsten content was 15 wt% with NOx conversion being ≥ 80% in the range of 175–450 °C. The MnCe nanorods approximately retained their morphology after tungsten loading. Microcrystalline WO3 formed when the W content was 15%, resulting in increments in the amount of Ce3+ and Mn4+, which is in favour of the NH3-SCR reaction on the catalyst surface. Moreover, the broad active temperature windows of the tungsten-modified MnCe nanorod catalysts were related to the balance between the redox and acidic properties. Tungsten addition enhanced the acidity of the MnCe catalyst while suppressing its reducibility. Both the Brønsted and Lewis acid sites are active, and the formation of reactive bridging nitrate species promote the performance of 15 W/MnCe catalyst. Overall, this study provided an easy method of adjusting the active temperature window of Mn–Ce nanorod catalysts through W modification.

Rational fabrication of Ti0.69Zr0.31O2 modified Au-loaded halloysite core-shell catalyst for highly efficient reduction of 4-nitrophenol and dye pollutants

Catalytic reduction method can reductively degrade some highly toxic and harmful pollutants and transform them into useful chemical resources with low toxicity and easy biodegradability, owning the advantages of environmental friendliness, economic effectiveness and mild conditions. This study reported the rational fabrication of the HNTs-Au@Ti0.69Zr0.31O2 hollow tubular core-shell catalyst for facile reductive degradation of aqueous 4-nitrophenol and azo dye pollutants. The catalyst employed the interfacial reaction strategy for aminopropyl-functionalization of halloysite nanotubes as core, amino electrostatic adsorption and in situ redction of ultrasmall Au nanoparticles with good dispersibility, and sol-gel deposition of Ti0.69Zr0.31O2 shell. The obtained HNTs-Au@Ti0.69Zr0.31O2 catalyst manifested superior catalytic performance and atom utilization efficiency of Au active sites for reduction of 4-nitrophenol, methylene blue and methyl orange in comparison to those control samples. The integration of TiO2 and ZrO2 within Ti0.69Zr0.31O2 shell enriched the porosity of the catalyst, and generated the extraordinary interfacial chemical effect on Au NPs with improved surface electronic state. The interlayer-embedded Au nanoparticles were effectively solidified and avoided from agglomeration and loss, where the reactive electron migration rate from BH4- to target pollutants upon Au surfaces was elevated for prominent catalytic reaction rate. The unique structural characteristics and synergistic enhancement effect of catalyst components created excess catalytic active sites at the hybrid interface surrounded Au nanoparticles due to the strong metal-carrier chemical effect, and contributed to the construction of the high-performance catalytic system, which endowed the HNTs-Au@Ti0.69Zr0.31O2 catalyst with remarkable catalytic capability, reusability and structural stability. The reaction mechanism and structure-property relationship were finally proposed.

Experimental parameters for the preparation of Mn/TiO2 catalysts by ultrasonic spray pyrolysis method for selective catalytic reduction of NOx at low temperature

Mn/TiO2 series selective catalytic reduction (SCR) catalysts with regular spherical shape could be obtained by ultrasonic spray pyrolysis method. The investigation of experimental parameters, such as decomposition temperature and the type and flow rate of carrier gas, showed that a high and stable NOx conversion at 70% could be achieved at 180 °C when the ultrasonic spray pyrolysis temperature was 500 °C and N2 was used as a carrier gas with a flow rate of 2 L/min. The physical and chemical properties of the catalysts were characterized by X-ray diffraction, SEM, and H2-TPR, revealing that a regular spherical structure, a small amount of Mn2O3 crystals, and high redox ability were the important factors affecting the activity of the catalyst. With these properties, Mn(0.5)/TiO2 (500 °C, N2, 2 L/min) exhibited more than 90% conversion at 240 °C with N2 selectivity above 96%.

NiO and Co3O4 nanoparticles decorated La0.8Sr0.2MnO3-based electrodes for electrochemical NOx removal in solid electrolyte cells

Solid electrolyte cells (SECs) have great application prospect for nitrogen oxides (NOx) removal due to no required reductant addition in contrast to the conventional selective catalytic reduction (SCR) method. Perovskites are the potential electrode materials in SECs but their reaction activity is insufficient at the intermediate-low temperature. Herein, NiO and Co3O4 nanoparticles are decorated on the La0.8Sr0.2MnO3-based electrode to improve the electrode activity. A variety of characterizations were conducted to analyze the electrode properties, and the electrode performance was systematically evaluated. The results show that the decorated NiO and Co3O4 nanoparticles both improved the electrode performance significantly and the NiO-modified electrode had a better performance. Compared with the unmodified electrodes, the surface NiO nanoparticles decreased the area-specific polarization resistance by 63.1% to 81.7 Ω cm2 while the NO conversion was increased by 85.9% to 59.3% at 1.4 V in 1000 ppm NO, 700 ℃. The electrochemical impedance spectra revealed that the nanoparticles not only promoted the species adsorption, dissociation and diffusion processes but facilitated the charge transfer between electrode and electrolyte. The first-principle calculation confirmed that the decorated NiO nanoparticles decreased the energy gap of electrodes and promoted the electron transfer between electrode and NO molecule, in agreement well with the experimental results. This work presented a new way to increase the NOx removal performance of SECs and offered guidance for the future construction of high-performance electrodes.

Effect of Cu loading on the performance and kinetics of Cu/SAPO-34 catalysts for selective catalytic reduction with NH3

A series of X%Cu/SAPO-34 (X = 1.0, 2.0, 4.0 and 6.0) catalysts were prepared by ultrasonic impregnation method for selective catalytic reduction (SCR) of NOx with ammonia. The effect of different Cu loadings on the selective catalytic reduction of NO by molecular sieve catalysts was examined on a fixed-bed reactor. Catalyst physicochemical properties were characterized and analyzed using XRD, TEM, NH3-TPD, H2-TPR, and in situ DRIFTS. Catalysts were used in reaction kinetics studies from the perspective of transient and steady-state kinetics. Cu/SAPO-34 catalyst with 4% Cu loading had the best denitrification efficiency and wide activity window. Copper species were highly dispersed on the catalyst surface. Cu/SAPO-34 catalyst with 4% Cu loading had rich acidic sites and excellent redox performance. Cu/SAPO-34 catalysts with 4% Cu loading possess minimal activation energy and were lower than commercial catalysts. According to the results of in situ IR, transient and steady-state analysis, the Cu/SAPO-34 catalyst with 4% Cu loading in the NH3-SCR reaction process was mainly E-R mechanism, and there was L-H mechanism.

Glucose-derived zirconium-containing mesoporous composite for efficient catalytic transfer hydrogenation of furfural to furfuryl alcohol

Meerwein-Ponndorf-Verley (MPV) reaction has been widely acknowledged to be a mild catalytic transfer hydrogenation method for selective reduction of biomass-derived furfural to furfuryl alcohol. Herein zirconium-containing mesoporous composite catalyst was developed through the combination of sol-gel process and soft templating method, in which naturally abundant glucose and F127 triblock copolymer were used as the ligand and pore-forming agent, respectively. The hydroxyl groups in glucose molecules were demonstrated to be coordinated with zirconium ion during hydrolysis-condensation of zirconium precursor, leading to the even dispersion of zirconia nanoparticles in the composite catalyst. The composite catalyst was proven to be highly efficient for catalyzing MPV reduction of furfural with the maximum furfuryl alcohol yield of 93.4% at 180 °C within 180 min in 2-propanol, which served as both solvent and reductant. The composite also showed a good reusability. After five consecutive reaction cycles, furfuryl alcohol yield was slightly reduced from 93.4% to 77.7%, but it could be recovered to 92.8% after the reused composite was regenerated with dilute alkali solution. Batch experiments and systematic characterizations demonstrated that the excellent catalytic performance of composite catalyst was determined by multiple factors mainly including the stronger Lewis acidity, a considerable amount of basic site and the rich mesoporous structure. This study provides a facile strategy to prepare multifunctional composite catalysts using naturally abundant carbohydrates as the feedstocks for lignocellulosic biorefinery.

V2O5-WO3 catalysts treated with titanium isopropoxide using a one-step co-precipitation method for selective catalytic reduction with NH3

Selective Catalytic Reduction (SCR) of nitrogen oxides (NOx) is the most effective way to reduce NOx emissions. However, the most used catalysts for this purpose, V2O5-WO3/TiO2 (VWTi) hybrid system, have limited applicability owing to its narrow operating temperature range (300–400 °C). Therefore, catalysts with abundant active sites are needed to extend the temperature range to more acceptable values (200–400 °C). The number of active sites depends on the catalyst synthesis method. The aim of this study is to increase the dispersion of V-OH and W-OH through a one-step process, this is achieved by treating the TiO2 support with titanium isopropoxide (TTIP) and simultaneously incorporating the V-OH and W-OH. This synthesis method used here is expected to enhance the interaction between the support and V-OH and W-OH by increasing the number of catalytically active sites. This process is simple and could be applied for the catalyst manufacturing process in the industrial scale. The optimal performance observed for the catalysts prepared at a TTIP loading of 5 wt% using a one-step method is due to its higher catalytic activity at lower temperatures, the observed results could be explained based on the formation of abundant V-OH and W-OH functional groups and the V4+/V5+ ratio (≈1). The scope of this study is to develop a new catalyst for selective catalytic reduction of nitrogen oxides.

Effect of metal elements doping on the CePO4 catalysts for selective catalytic reduction of NO with NH3

A series of Metals doped M-CePO4 (M=Zr, Co, Mo, Cu) catalysts were prepared via the coprecipitation method for selective catalytic reduction of NO with NH3 (NH3-SCR). The results showed that the NOx conversion of M-CePO4 were higher than that of CePO4, especially the Mo-CePO4 catalysts exhibited the best low-temperature activity and N2 selectivity, the Mo-CePO4 catalysts can reach about 99% at 300 °C and excellent 70 h long stability with the coexistence of SO2 and H2O. The effect of metal elements doping on physiochemical properties of catalysts were characterized by XRD, BET, Raman, TEM, XPS, H2-TPR and NH3-TPD. SEM and TEM analysis. The results showed that part of M ions doped into CePO4 lattice resulted in lattice shrinkage. More importantly, the MOx species could not only increased the relative content of Ce3+ and surface adsorption oxygen (O′) of M-CePO4 catalysts, but also increased the specific surface area of the catalysts. It could provide more reaction sites for active gas to promote the activation of NH3 and enhance oxidation–reduction performance. The in-situ DRIFTS results suggested that NH3 were adsorbed on both Lewis and Bronsted acid sites which can easily react with NOx gas. The NO species were adsorbed on Mo-CePO4 in the form of bidentate nitrate. The main reactants of Mo-CePO4 catalysts were NH3 linked to Lewis acid sites and bidentate nitrate species on the catalytic surface. The Eley–Rideal and Langmuir–Hinshelwood mechanisms coexisted in the SCR reaction route.

Highly active MnOx supported on the MgAlOx oxides derived from LDHs for low temperature NH3-SCR

A series of novel highly dispersed MnOx on the MgAlOx support derived from layered double hydroxides (LDHs) were successfully prepared by incipient wetness impregnation method for low-temperature selective catalytic reduction of NOx with ammonia (NH3-SCR). The physicochemical properties and the catalytic performance of the prepared samples with different Mn precursor salt (acetate, nitrate and sulfate) and varying calcination temperatures of MgAlOx support were systematically investigated. The optimal catalyst, MgAlOx calcined at 800 °C with impregnating manganese acetate (denoted as MnA/MgAlOx-800), exhibited superior denitration performance, with NOx conversion over 80 % in the temperature range of 100–300 °C as well as remarkable resistance against H2O. The proper supports MgAlOx not only provided large specific area for the dispersion of the Mn, but also supplied more adsorption sites for reactant molecules. It was also found that the interaction between Mn species and MgAlOx support induced the higher concentration of Mn4+ and chemisorbed oxygen species. As suggested from in situ DRIFTs analysis, Lewis acid sites promoted the adsorption and activation of NH3, which facilitated the NH3-SCR reaction to proceed. Furthermore, E-R mechanism was proposed in the SCR reaction, evidenced by in situ DRIFTS study.

Effect of MnOx/α-Fe2O3 Prepared from Goethite on Selective Catalytic Reduction of NO with NH3

A low-cost goethite and manganese acetate were used to prepare a MnOx/α-Fe2O3 composite catalyst by simple impregnation method for novel high-efficiency selective catalytic reduction (SCR) of NO with NH3, and its denitration performance of composite catalyst under different conditions was investigated in a thermal fixed-bed catalytic reaction system. The results showed that MnOx/α-Fe2O3 with Mn/Fe molar ratio of 0.1 and calcination temperature of 400 °C had the best low-temperature catalytic activity and wider reaction temperature window compared with α-Fe2O3. It achieved over 90% NO conversion efficiency with a space velocity of 72,000 h−1 at 200~350 °C and possessed a good resistance of H2O and SO2. Characterization by XRD, BET, H2-TPR, and NH3-TPD revealed that the main reason for the high catalytic activity of MnOx(0.1)/α-Fe2O3(400) was that the addition of Mn changed phase types of catalyst and valence composition of Fe, resulting in a larger specific surface area, more acidic sites, and higher redox performance.

Synthesis and characterization of SiO2-NiO xerogel nanocomposite prepared by sol–gel method for catalytic reduction of p-nitrophenol

This manuscript describes the preparation and characterization of silica-nickel oxide (SiO2-NiO) xerogel nanocomposite and its catalytic application in the hydrogenation of p-nitrophenol. Hydrochloric acid and ammonium hydroxide were used as the acid and base catalyst, respectively during the synthesis of SiO2-NiO. The Fourier Transformation Infra-Red spectroscopic results supported the formation of the silica xerogel skeleton structure with corresponding characteristic peaks of siloxane linkage. The surface of SiO2-NiO xerogel nanocomposite was observed to be porous along with some irregular cracks. The X-Ray diffraction analysis showed that the SiO2-NiO xerogel nanocomposite was amorphous in nature. The synthesized xerogel nanocomposite was employed as a catalyst for the hydrogenation of p-nitrophenol with sodium borohydride in water. The rate of hydrogenation of p-nitrophenol was observed to be increased with the increased amount of catalyst as well as the temperature. The maximum reduction rate of p-nitrophenol was found as high as 0.26 min-1.

Insights to sulfur-resistant mechanisms of reduced graphene oxide supported MnOx-CeOy catalysts for low-temperature NH3-SCR

The MnOx-CeOy/rGO catalysts were prepared by a facile hydrothermal method for selective catalytic reduction (SCR) of NO with NH3. Compared with MnOx-CeOy catalyst, the optimal MnOx-CeOy/rGO(0.1) catalyst not only shows an excellent low-temperature catalytic activity (60–180 °C), but also exhibits a better sulfur-resistant performance in the presence of 100 ppm SO2+5 vol% H2O at 160 °C. The in-situ DRIFTS results show that more NH4+ on Brønsted acid sites and NH3 on Lewis acid sites, as well as NH4HSO4 are detected on MnOx-CeOy catalyst during SCR reaction with SO2, while the adsorbed NHx species over MnOx-CeOy/rGO(0.1) catalyst can be quickly activated and consumed via Eley-Rideal (E-R) reaction pathway. The highly dispersed Ce sites can effectively protect more Mn active sites from sulfation, and the Mn sites with stronger acidity and abundant oxygen vacancy defects promote the oxidative dehydrogenation of NH3 to form NH2, thus enhancing the sulfur resistance of MnOx-CeOy/rGO(0.1) catalyst.

Self-assembled biomineralized MnOx for low temperature selective catalytic reduction of NOx

A self-assembled biomineralized MnOx materials was prepared by a simple liquid phase co-precipitation method for selective catalytic reduction (SCR) of nitrogen oxides (NOx). Biomineralized MnOx exhibited great SCR performance (achieve > 99% NOx conversion at 100 °C) and high N2 selectivity (exceed 70% at 75–200 °C). The effects of biomineralized materials on physiochemical properties of catalyst were investigated by various characterization methods. X-ray diffraction (XRD) and scanning electron microscopy (SEM) results showed that the crystal structure and the morphologies of MnOx and biomineralized MnOx are remained the same. In order to eliminate the effect of specific surface area, the rate of specific reaction for biomineralized MnOx was calculated to be about twice than that of MnOx. In-situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) analyze intermediates during SCR, and speculated that biomineralized MnOx catalyst may mainly follow the Langmuir-Hinshelwood(L-H) mechanism below 200 ℃. The above excellent N2 selectivity can be attributed to the fast NOx specific reaction rate, form Mn-O-C and Mn-C-N structure, provide abundant oxygen vacancies, and high Mn3+/Mn atomic ratio on the catalyst surface. Moreover, biomineralized MnOx possessed a better catalytic cycle performance due to the synergistic effect between biomass and Mn species. Therefore, a reasonable preparation method is proposed to realize the industrial application of biomineralized manganese oxide.

The Enhanced Performance of Ce-Cu/Tio2 Catalyst Synthesized by Ice Melting Method for Selective Catalytic Reduction of Nox with Nh3

The Enhanced Performance of Ce-Cu/Tio2 Catalyst Synthesized by Ice Melting Method for Selective Catalytic Reduction of Nox with Nh3

Production and characterization of AG based catalyst for HC-SCR system

In this study, Ag-Cu-Ce/TiO2 catalyst was produced by using impregnation method for hydrocarbon-selective catalytic reduction (HC-SCR) system. In this system, as a reducing agent ethyl alcohol and urea solution mixture was used. The NOx conversion efficiency of the system with using synthesized catalyst was analyzed. Chemical and structural properties of the used catalyst were examined by SEM, BET and XRD analyzes. In the SCR test system, the experiments were conducted in different temperatures ranged from 200 C to 300 C in constant gas hourly space velocity (GHSV) (30000 h-1). The tests were carried out by using 2 cylinders, V-type diesel engine with constant speed (3000 rpm) under 3 different loads (1 kW, 3 kW and 5 kW). These tests identified the effects of produced catalyst on NOx conversion rate of SCR system. In result, NOx conversion rates were measured between 66 % and 93 %. In 1 kW load, at 300 C, SV= 30000 h-1, 100% ethyl alcohol spraying the NOx conversion rate was reached approximately to 93% which is the highest point.