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1.
A novel catalyst based on copper-silver was developed to solve the contradiction between the high conversion temperature of Cu-based catalyst and low N 2 selectivity of Ag-based catalyst during selective oxidation of ammonium gas. The Cu-Ag-based catalyst (Cu 5 wt.%-Ag 5 wt.%/Al 2O 3) displayed a relatively low complete conversion temperature (<320 °C) with a high N 2 selectivity (>95%). Increasing loading of Cu and Ag decreases N 2 selectivity. The low N 2 selectivity of Ag-based catalyst is possibly related to the formation of Ag 2O crystals. Improvement of N 2 selectivity of Ag-based catalyst was obtained by doping Cu to decrease crystallized Ag 2O phase. The temperature programmed reaction (TPR) data show that N 2O is the main byproduct of oxidation of ammonia at temperature lower than 200 °C. Two bands of nitrate species at 1541 and 1302 cm −1 were observed on Ag 10 wt.%/Al 2O 3 at the temperature higher than 250 °C, which indicates the formation of NO x during the selective catalytic oxidation of ammonia. No nitrate species was observed on Cu 10 wt.%/Al 2O 3 and Cu 5 wt.%-Ag 5 wt.%/Al 2O 3, while only one nitrate species (1543 cm −1) existed on Cu 10 wt.%-Ag 10 wt.%/Al 2O 3. We proposed that mixing Ag with Cu inhibited the formation of NO x during the selective catalytic oxidation of ammonia over Cu-Ag/Al 2O 3. 相似文献
2.
The influence of NO 2 on the selective catalytic reduction (SCR) of NO with ammonia was studied over Fe-ZSM5 coated on cordierite monolith. NO 2 in the feed drastically enhanced the NO x removal efficiency (DeNOx) up to 600 °C, whereas the promoting effect was most pronounced at the low temperature end. The maximum activity was found for NO 2/NO x = 50%, which is explained by the stoichiometry of the actual SCR reaction over Fe-ZSM5, requiring a NH 3:NO:NO 2 ratio of 2:1:1. In this context, it is a special feature of Fe-ZSM5 to keep this activity level almost up to NO 2/NO x = 100%. The addition of NO 2 to the feed gas was always accompanied by the production of N 2O at lower and intermediate temperatures. The absence of N 2O at the high temperature end is explained by the N 2O decomposition and N 2O-SCR reaction. Water and oxygen influence the SCR reaction indirectly. Oxygen enhances the oxidation of NO to NO 2 and water suppresses the oxidation of NO to NO 2, which is an essential preceding step of the actual SCR reaction for NO 2/NO x < 50%. DRIFT spectra of the catalyst under different pre-treatment and operating conditions suggest a common intermediate, from which the main product N 2 is formed with NO and the side-product N 2O by reaction with gas phase NO 2. 相似文献
3.
Reaction mechanism of the reduction of nitrogen monoxide by methane in an oxygen excess atmosphere (NO–CH 4–O 2 reaction) catalyzed by Pd/H-ZSM-5 has been studied at 623–703 K in the absence of water vapor, in comparison with the mechanism for Co-ZSM-5. Kinetic isotope effect for the N 2 formation in NO–CH 4–O 2 vs. NO–CD 4–O 2 reactions was 1.65 at 673 K and decreased with a decrease in the reaction temperature. In addition, H–D isotopic exchange took place significantly in NO–(CH 4+CD 4)–O 2 reaction. These results are in marked contrast with the case of Co-ZSM-5, for which the C–H dissociation of methane is the only rate-determining step, and show that the C–H dissociation is slow but not the only rate-determining step in the case of Pd/H-ZSM-5. A reaction scheme was proposed, in which the relative rates of the three steps ((i)–(iii) below) vary depending on the reaction conditions. Further, in contrast to Co-ZSM-5, NO x–CH 4–O 2 reaction was much slower than CH 4–O 2 reaction for Pd/H-ZSM-5; the presence of NO x retards the reaction of CH 4 over the latter catalyst, while it accelerates the reaction over the former. It is suggested that CH 4 is activated directly by the Pd atoms in the case of Pd/H-ZSM-5, but by NO 2 strongly adsorbed on Co ion for Co-ZSM-5. The reaction order of the NO–CH 4–O 2 reaction with respect to NO pressure was consistent with this mechanism; 1.05 for Pd/H-ZSM-5 and 0.11 for Co-ZSM-5. 相似文献
4.
The selective catalytic reduction of nitrogen oxides (NO x) with ammonia over ZSM-5 catalysts was studied with and without water vapor. The activity of H-, Na- and Cu-ZSM-5 was compared and the result showed that the activity was greatly enhanced by the introduction of copper ions. A comparison between Cu-ZSM-5 of different silica to alumina ratios was also performed. The highest NO conversion was observed over the sample with the lowest silica to alumina ratio and the highest copper content. Further studies were performed with the Cu-ZSM-5-27 (silica/alumina = 27) sample to investigate the effect of changes in the feed gas. Oxygen improves the activity at temperatures below 250 °C, but at higher temperatures O 2 decreases the activity. The presence of water enhances the NO reduction, especially at high temperature. It is important to use about equal amounts of nitrogen oxides and ammonia at 175 °C to avoid ammonia slip and a blocking effect, but also to have high enough concentration to reduce the NO x. At high temperature higher NH 3 concentrations result in additional NO x reduction since more NH 3 becomes available for the NO reduction. At these higher temperatures ammonia oxidation increases so that there is no ammonia slip. Exposing the catalyst to equimolecular amounts of NO and NO 2 increases the conversion of NO x, but causes an increased formation of N 2O. 相似文献
5.
A multi-component NO x-trap catalyst consisting of Pt and K supported on γ-Al 2O 3 was studied at 250 °C to determine the roles of the individual catalyst components, to identify the adsorbing species during the lean capture cycle, and to assess the effects of H 2O and CO 2 on NO x storage. The Al 2O 3 support was shown to have NO x trapping capability with and without Pt present (at 250 °C Pt/Al 2O 3 adsorbs 2.3 μmols NO x/m 2). NO x is primarily trapped on Al 2O 3 in the form of nitrates with monodentate, chelating and bridged forms apparent in Diffuse Reflectance mid-Infrared Fourier Transform Spectroscopy (DRIFTS) analysis. The addition of K to the catalyst increases the adsorption capacity to 6.2 μmols NO x/m 2, and the primary storage form on K is a free nitrate ion. Quantitative DRIFTS analysis shows that 12% of the nitrates on a Pt/K/Al 2O 3 catalyst are coordinated on the Al 2O 3 support at saturation. When 5% CO2 was included in a feed stream with 300 ppm NO and 12% O2, the amount of K-based nitrate storage decreased by 45% after 1 h on stream due to the competition of adsorbed free nitrates with carboxylates for adsorption sites. When 5% H2O was included in a feed stream with 300 ppm NO and 12% O2, the amount of K-based nitrate storage decreased by only 16% after 1 h, but the Al2O3-based nitrates decreased by 92%. Interestingly, with both 5% CO2 and 5% H2O in the feed, the total storage only decreased by 11%, as the hydroxyl groups generated on Al2O3 destabilized the K–CO2 bond; specifically, H2O mitigates the NOx storage capacity losses associated with carboxylate competition. 相似文献
6.
The catalytic properties of cobalt containing ZSM-5 zeolites prepared by various methods were compared. TPR, XRD, N 2-BET, XPS, FTIR and UV–vis spectroscopy were used for characterizing the samples. Well-dispersed cobalt oxide-like species and isolated Co 2+ ions in charge compensation positions were found in the zeolite. Catalysts prepared using a single step cation exchange method showed high activity for N 2O decomposition in a temperature range 300–550°C, in the presence of 0–5% O 2, and high stability in the presence of 10% H 2O to the feed. UV–vis spectra and TPR experiments indicated the presence of some cobalt oxides, not detected by DRX, in a Co-ZSM-5 catalyst containing 3.76 wt% Co, prepared by a solid-state reaction procedure. The N 2O conversion over this catalyst was strongly affected by addition of both O 2 and H 2O to the feed. 相似文献
7.
A quaternary catalyst library of 56 samples comprising all combinations of four elements, viz. Ag, Co, Cu, In, with six equally spaced atomic fraction increments from 0 to 1 was prepared by impregnation of a proprietary mesoporous alumina support. Catalytic properties of the library were tested in the selective catalytic reduction (SCR) of NO x by propane under lean conditions in the temperature range 400–500 °C. The catalytic data acquired by a parallel 64-channel microreactor system with automated time-of-flight mass spectrometric analysis have been evaluated regarding selectivity–compositional relationships, synergistic effects for NO x conversion, and efficiency of propane utilization. Full conversion of NO x is achieved over Ag–Co combinations at 450 °C with N 2 selectivities of more than 90% and reductant utilization of 20% in a feed of 1500 ppm NO, 1500 ppm propane and 5 vol.% O 2 (space velocity of 36,000 cm 3 g cat−1 h −1). For the single-component catalysts Ag/Al 2O 3, Co/Al 2O 3, Cu/Al 2O 3, and In/Al 2O 3, the state of the elements on the mesoporous alumina was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). Cobalt forms a spinel-like cobalt aluminate phase whereas copper and indium are present as oxides with small sizes not detectable by XRD. Silver occurs in both metallic state and as Ag 2O, and forms Ag n clusters of at least two different sizes, predominantly with diameters of about 30 nm. The conclusions are consistent with the reducibility of the single-component catalysts samples by H 2. Surface area measurements and pore size distributions revealed reasonable modifications of the textural properties. The main pore size of the alumina support is decreased from 7 to ca. 5 nm after loading of the active components. 相似文献
8.
Reaction activities of several developed catalysts for NO oxidation and NO x (NO + NO 2) reduction have been determined in a fixed bed differential reactor. Among all the catalysts tested, Co 3O 4 based catalysts are the most active ones for both NO oxidation and NO x reduction reactions even at high space velocity (SV) and low temperature in the fast selective catalytic reduction (SCR) process. Over Co 3O 4 catalyst, the effects of calcination temperatures, SO 2 concentration, optimum SV for 50% conversion of NO to NO 2 were determined. Also, Co 3O 4 based catalysts (Co 3O 4-WO 3) exhibit significantly higher conversion than all the developed DeNO x catalysts (supported/unsupported) having maximum conversion of NO x even at lower temperature and higher SV since the mixed oxide Co-W nanocomposite is formed. In case of the fast SCR, N 2O formation over Co 3O 4-WO 3 catalyst is far less than that over the other catalysts but the standard SCR produces high concentration of N 2O over all the catalysts. The effect of SO 2 concentration on NO x reduction is found to be almost negligible may be due to the presence of WO 3 that resists SO 2 oxidation. 相似文献
9.
Catalytic performance of Sn/Al 2O 3 catalysts prepared by impregnation (IM) and sol–gel (SG) method for selective catalytic reduction of NO x by propene under lean burn condition were investigated. The physical properties of catalyst were characterized by BET, XRD, XPS and TPD. The results showed that NO 2 had higher reactivity than NO to nitrogen, the maximum NO conversion was 82% on the 5% Sn/Al 2O 3 (SG) catalyst, and the maximum NO 2 conversion reached nearly 100% around 425 °C. Such a temperature of maximum NO conversion was in accordance with those of NO x desorption accompanied with O 2 around 450 °C. The activity of NO reduction was enhanced remarkably by the presence of H 2O and SO 2 at low temperature, and the temperature window was also broadened in the presence of H 2O and SO 2, however the NO x desorption and NO conversion decreased sharply on the 300 ppm SO 2 treated catalyst, the catalytic activity was inhibited by the presence of SO 2 due to formation of sulfate species (SO 42−) on the catalysts. The presence of oxygen played an essential role in NO reduction, and the activity of the 5% Sn/Al 2O 3 (SG) was not decreased in the presence of large oxygen. 相似文献
10.
The reaction between hydrogen and NO was studied over 1 wt.% Pd supported on NO x-sorbing material, MnO x–CeO 2, at low temperatures. The result of pulse mode reactions suggest that NO x adsorbed as nitrate and/or nitrite on MnO x–CeO 2 was reduced by hydrogen, which was spilt-over from Pd catalyst. The NO x storage and reduction (NSR) cycles were carried out over Pd/MnO x–CeO 2 in a conventional flow reactor at 150 °C. In a storage step, NO was removed by the oxidative adsorption from a stream of 0.04–0.08% NO, 5–10% O 2, and He balance. This was followed by a reducing step, where a stream of 1% H 2/He was supplied to ensure the conversion of nitrate/nitrite to N 2 and thus restore the adsorbability. It was revealed that the NSR cycle is much more suitable for the H 2–deNO x process in excess O 2, compared to a conventional steady state reaction mode. 相似文献
11.
The lean selective catalytic reduction of NO x by methane over protonic palladium loaded ZSM-5, FER and MOR, as well as, on bimetallic Pd–Pt-HMOR was examined. Special emphasis was paid on the combined effects of water and SO 2 in the feed stream. Under dry conditions and in the absence of SO 2, the degree of NO x conversion at 450°C decreases as follows: Pd-HZSM-5>Pd-HMOR>Pd-HFER. Sulfur dioxide alone has no apparent effect on the activity for NO x reduction, but the coexistence of water and SO 2 inhibits both NO x and methane conversions. The extent of inhibition by water and SO 2 on NO x reduction is Pd-HFER>Pd-HZSM-5>Pd-HMOR. Acid mordenite doped with low levels of Pt and Pd leads to an active catalyst that is more tolerant to the presence of either water or SO 2 than the corresponding monometallic Pt- and Pd-HMOR. Nevertheless, NO x reduction is also inhibited at temperatures below 450°C when SO 2 and water are both present. TPD experiments of water over calcined samples of protonic Pd supported pentasil zeolites, Pd/γ-Al 2O 3 and Pt–Pd-HMOR with and without pretreatment in SO 2+O 2 indicate that sulfation of the surface increases water chemisorption by the support. Therefore, the observed decrease of NO x reduction on Pd-loaded zeolite catalysts when SO 2 and H 2O coexist in the feed stream may be due to enhanced water inhibition and presumably active site poisoning. 相似文献
12.
Pt-based catalysts have been prepared using supports of different nature (γ-Al 2O 3, ZSM-5, USY, and activated carbon (ROXN)) for the C 3H 6-SCR of NO x in the presence of excess oxygen. Nitrogen adsorption at 77 K, pH measurements, temperature-programmed desorption of propene, and H 2 chemisorption were used for the characterization of the different supports and catalysts. The performance of these catalysts has been compared in terms of de-NO x activity, hydrocarbon adsorption and combustion at low temperature, and selectivity to N 2. Maximum NO x conversions for all the catalysts were achieved in the temperature range of 200–250°C. The order of activity was, Pt-USY>Pt/ROXNPt-ZSM-5Pt/Al 2O 3. At temperatures above 300°C only Pt/ROXN maintains a high activity caused by the consumption of the support, while the other catalysts present a strong deactivation. Propene combustion starts at the same temperature for all the catalytic systems (160°C). Complete hydrocarbon combustion is directly related to the acidity of the support, thus determining the temperature of the maximum NO x reduction. The support play an important role in the reaction mechanism through the hydrocarbon activation. N 2O formation was observed for all the catalysts. N 2 selectivity ranges from 15 to 30% with the order, Pt/ROXN>Pt-USYPt/Al 2O 3>Pt-ZSM-5. The catalytic systems exhibit a stable operation under isothermal conditions during time-on-stream experiments. 相似文献
13.
Pt-USY was used for the selective catalytic reduction of NO x with hydrocarbons in the presence of excess oxygen. The catalyst was prepared by an ion-exchange method and characterized by XRD, TEM, CO chemisorption, and Ar adsorption at 87 K. The platinum particle size distribution was found to be broad (2–20 nm), with no apparent sintering of the active phase during the HC-SCR process after 25 h time-on-stream. Generally, large metal clusters (>15 nm) are situated at the external surface of the zeolite, while the smaller ones are located in the pores of the support. Pt-USY shows an excellent activity in the deNO x reaction (molar NO x conversion 90% at 475 K) with propene as the reductant in 5 kPa O 2, as well as stable operation during time-on-stream. Propane only yields a low NO x conversion compared to propene. The presence of high oxygen contents (5–10 kPa O 2) slightly inhibits the reaction. No significant decrease in deNO x activity was observed at high space velocities (up to 100,000 h −1). The presence of SO 2 and H 2O in the feed stream did not significantly affect the deNO x activity. Pt-USY performs better under lean-burn conditions than other Pt-catalysts supported on e.g. ZSM-5, Al 2O 3, or SiO 2. The selectivity to N 2 was similar to the other Pt-based catalysts (30%), the other major product being N 2O. 相似文献
14.
A series of 1 wt.%Pt/ xBa/Support (Support = Al 2O 3, SiO 2, Al 2O 3-5.5 wt.%SiO 2 and Ce 0.7Zr 0.3O 2, x = 5–30 wt.% BaO) catalysts was investigated regarding the influence of the support oxide on Ba properties for the rapid NO x trapping (100 s). Catalysts were treated at 700 °C under wet oxidizing atmosphere. The nature of the support oxide and the Ba loading influenced the Pt–Ba proximity, the Ba dispersion and then the surface basicity of the catalysts estimated by CO 2-TPD. At high temperature (400 °C) in the absence of CO 2 and H 2O, the NO x storage capacity increased with the catalyst basicity: Pt/20Ba/Si < Pt/20Ba/Al5.5Si < Pt/10Ba/Al < Pt/5Ba/CeZr < Pt/30Ba/Al5.5Si < Pt/20Ba/Al < Pt/10BaCeZr. Addition of CO 2 decreased catalyst performances. The inhibiting effect of CO 2 on the NO x uptake increased generally with both the catalyst basicity and the storage temperature. Water negatively affected the NO x storage capacity, this effect being higher on alumina containing catalysts than on ceria–zirconia samples. When both CO 2 and H 2O were present in the inlet gas, a cumulative effect was observed at low temperatures (200 °C and 300 °C) whereas mainly CO 2 was responsible for the loss of NO x storage capacity at 400 °C. Finally, under realistic conditions (H 2O and CO 2) the Pt/20Ba/Al5.5Si catalyst showed the best performances for the rapid NO x uptake in the 200–400 °C temperature range. It resulted mainly from: (i) enhanced dispersions of platinum and barium on the alumina–silica support, (ii) a high Pt–Ba proximity and (iii) a low basicity of the catalyst which limits the CO 2 competition for the storage sites. 相似文献
15.
Conversion of NO x with reducing agents H 2, CO and CH 4, with and without O 2, H 2O, and CO 2 were studied with catalysts based on MOR zeolite loaded with palladium and cerium. The catalysts reached high NO x to N 2 conversion with H 2 and CO (>90% conversion and N 2 selectivity) range under lean conditions. The formation of N 2O is absent in the presence of both H 2 and CO together with oxygen in the feed, which will be the case in lean engine exhaust. PdMOR shows synergic co-operation between H 2 and CO at 450–500 K. The positive effect of cerium is significant in the case of H 2 and CH 4 reducing agent but is less obvious with H 2/CO mixture and under lean conditions. Cerium lowers the reducibility of Pd species in the zeolite micropores. The catalysts showed excellent stability at temperatures up to 673 K in a feed with 2500 ppm CH 4, 500 ppm NO, 5% O 2, 10% H 2O (0–1% H 2), N 2 balance but deactivation is noticed at higher temperatures. Combining results of the present study with those of previous studies it shows that the PdMOR-based catalysts are good catalysts for NO x reduction with H 2, CO, hydrocarbons, alcohols and aldehydes under lean conditions at temperatures up to 673 K. 相似文献
16.
The NO x storage and reduction functions of a Pt–Ba/Al 2O 3 “NO x storage–reduction” catalyst has been investigated in the present work by applying the transient response and the temperature programmed reaction methods, by using propylene as the reducing agent. It is found that: (i) the storage of NO x occurs first at BaO and then at BaCO 3, which are the most abundant sites following regeneration of catalyst with propylene; (ii) the overall storage process at BaCO 3 is slower than at BaO; (iii) CO 2 inhibits the NO x storage at low temperatures; (iv) the amount of NO x stored up to catalyst saturation at 350 °C corresponds to 17.6% of Ba; (v) the reduction of stored NO x groups is fast and is limited by the concentration of propylene in the investigated T range (250–400 °C); (vi) selectivity to N 2 is almost complete at 400 °C but is significantly lower at 300 °C due to the formation of NO which can be tentatively ascribed to the presence of unselective Pt–O species. 相似文献
17.
The release and reduction of NO x in a NO x storage-reduction (NSR) catalyst were studied with a transient reaction analysis in the millisecond range, which was made possible by the combination of pulsed injection of gases and time resolved time-of-flight mass spectrometry. After an O 2 pulse and a subsequent NO pulse were injected into a pellet of the Pt/Ba/Al 2O 3 catalyst, the time profiles of several gas products, NO, N 2, NH 3 and H 2O, were obtained as a result of the release and reduction of NO x caused by H 2 injection. Comparing the time profiles in another analysis, which were obtained using a model catalyst consisting of a flat 5 nmPt/Ba(NO 3) 2/cordierite plate, the release and reduction of NO x on Pt/Ba/Al 2O 3 catalyst that stored NO x took the following two steps; in the first step NO molecules were released from Ba and in the second step the released NO was reduced into N 2 by H 2 pulse injection. When this H 2 pulse was injected in a large amount, NO was reduced to NH 3 instead of N 2. A only small amount of H2O was detected because of the strong affinity for alumina support. We can analyze the NOx regeneration process to separate two steps of the NOx release and reduction by a detailed analysis of the time profiles using a two-step reaction model. From the result of the analysis, it is found that the rate constant for NOx release increased as temperature increase. 相似文献
18.
Performance of NO x traps after high-temperature treatments in different redox environments was studied. Two types of treatments were considered: aging and pretreatment. Lean and rich agings were examined for a model NO x trap, Pt–Ba/Al 2O 3. These were done at 950 °C for 3 h, in air and in 1% H 2/N 2, respectively. Lean aging had a severe impact on NO x trap performance, including HC and CO oxidation, and NH 3 and N 2O formation. Rich aging had minimal impact on performance, compared to fresh/degreened performance. Deactivation from lean aging was essentially irreversible due to Pt sintering, but Pt remained dispersed with the rich aging. Pretreatments were examined for a commercially feasible fully formulated NO x trap and two model NO x traps, Pt–Ba/Al 2O 3 and Pt–Ba–Ce/Al 2O 3. Pretreatments were done at 600 °C for 10 min, and used feed gas that simulated diesel exhaust under several conditions. Lean pretreatment severely suppressed NO x, HC, CO, NH 3 and N 2O activities for the ceria-containing NO x traps, but had no impact on Pt–Ba/Al 2O 3. Subsequently, a relatively mild rich pretreatment reversed this deactivation, which appears to be due to a form of Pt–ceria interaction, an effect that is well known from early work on three-way catalysts. Practical applications of results of this work are discussed with respect to NO x traps for light-duty diesel vehicles. 相似文献
19.
A series of sulfated zirconia supported Pd/Co catalysts was synthesized by the sol–gel method and examined for NO x reduction by methane. The NO conversion increased up to a Co/S ratio of 0.43, and then decreased at a higher Co loading (Co/S = 0.95). Sulfate content was also essential for obtaining high selectivity to molecular nitrogen. A catalyst loaded with 0.06 wt.% Pd, 2.1 wt.% Co and 2.1 wt.% S (Pd/Co-SZ-2) exhibited remarkable performance under lean conditions and displayed stability in a long-term durability test using a synthetic reaction mixture containing 10% water vapor. This catalyst exhibited the highest sulfur retention most probably as cobalt sulfide. Besides, the catalytic oxidation of NO to NO y groups was confirmed by FT-IR, in agreement with the general mechanism for the SCR of NO by hydrocarbons. In the absence of oxygen in the feed stream, the catalyst was highly active for NO reduction with methane. IR stretching bands assigned to N 2O and adsorbed nitro groups were identified upon adsorbing NO on Pd/Co-SZ-2. This indicates that under rich conditions disproportionation of NO to N 2O and NO 2 occurs and confirms that the formation of NO 2 species is an essential step for NO reduction by CH 4. 相似文献
20.
NO x reduction with NO 2 as the NO x gas in the absence of plasma was compared to plasma treated lean NO x exhaust where NO is converted to NO 2 in the plasma. Product nitrogen was measured to prove true chemical reduction of NO x to N 2. With plasma treatment, NO as the NO x gas, and a NaY catalyst, the maximum conversion to nitrogen was 50% between 180 and 230 °C. The activity decreased at higher and lower temperatures. At 130 °C a complete nitrogen balance could be obtained, however between 164 and 227 °C less than 20% of the NO x is converted to a nitrogen-containing compound or compounds not readily detected by gas chromatograph (GC) or Fourier transform infrared spectrometer (FT-IR) analysis. With plasma treatment, NO 2 as the NO x gas, and a NaY catalyst, a complete nitrogen balance is obtained with a maximum conversion to nitrogen of 55% at 225 °C. For γ-alumina, with plasma treatment and NO2 as the NOx gas, 59% of the NOx is converted to nitrogen at 340 °C. A complete nitrogen balance was obtained at these conditions. As high as 80% NOx removal over γ-alumina was measured by a chemiluminescent NOx meter with plasma treatment and NO as the NOx gas. When NO is replaced with NO2 and the simulated exhaust gases are not plasma treated, the maximum NOx reduction activity of NaY and γ-alumina decreases to 26 and 10%, respectively. This is a large reduction in activity compared to similar conditions where the simulated exhaust was plasma treated. Therefore, in addition to NO2, other plasma-generated species are required to maximize NOx reduction. 相似文献
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