共查询到20条相似文献,搜索用时 15 毫秒
1.
Hiroyuki Kamata Shun-ichiro Ueno Naoki Sato Toshiyuki Naito 《Fuel Processing Technology》2009,90(7-8):947-951
Mercury oxidation by hydrochloric acid over the metal oxides supported by anatase type TiO2 catalysts, 1 wt.% MOx/TiO2 where M = V, Cr, Mn, Fe, Ni, Cu, and Mo, was investigated by the Hg0 oxidation and the NO reduction measurements both in the presence and absence of NH3. The catalysts were characterized by BET surface area measurement and Raman spectroscopy. The metal oxides added to the catalyst were observed to disperse well on the TiO2 surface. For all catalysts studied, the Hg0 oxidation by hydrochloric acid was confirmed to proceed. The activity of the catalysts was found to follow the trend MoO3 ~ V2O5 > Cr2O3 > Mn2O3 > Fe2O3 > CuO > NiO. The Hg0 oxidation activity of all catalysts was depressed considerably by adding NH3 to the reactant stream. This suggests that the metal oxide catalysts undergo the inhibition effect by NH3. The activity trend of the Hg0 oxidation in the presence of NH3 was different from that observed in its absence. A good correlation was found between the NO reduction and the Hg0 oxidation activities in the NH3 present condition. The catalyst having high NO reduction activity such as V2O5/TiO2 showed high Hg0 oxidation activity. The result obtained in this study suggests that the oxidation of Hg0 proceeds through the reaction mechanism, in which HCl competes for the active catalyst sites against NH3. NH3 adsorption may predominate over the adsorption of HCl in the presence of NH3. 相似文献
2.
Great depression of the formation N2O in the selective catalytic reduction of NO by NH3 (NH3-SCR) has been studied by combining a V2O5-WO3/TiO2 (VWT) catalyst with a Fe-exchanged ZSM-5 zeolite (FeZ). At temperatures > 400 °C, N2O formation was significant over VWT but < 5 ppm over FeZ/VWT catalysts with the FeZ ≥ 8%. Unfortunately, all these FeZ-promoted catalysts disclosed a decrease in deNOxing performances, due to an enhanced NH3 oxidation into NO. At temperatures > 350 °C, the chemically-combined VWT-based FeZ systems could facilitate both N2O reduction with NH3 and N2O decomposition, thereby suppressing N2O emissions in NH3-SCR reaction. 相似文献
3.
《Journal of Industrial and Engineering Chemistry》2014,20(4):1577-1580
CeO2–CuO catalyst prepared by citric acid method was investigated for selective catalytic reduction of NO with NH3. The activity of the CeO2 catalyst was enhanced about 8–27% in the temperature range of 125–225 °C at a space velocity of 28,000 h−1 by the addition of Cu. It was found that the state of Cu species had great impact on the SCR performance of CeO2–CuO catalyst. Cu2+ can enhance the low temperature activity of SCR reaction, while CuO would promote NH3 oxidation before SCR reaction at high temperature, which would cause the decrease of its high temperature SCR activity. 相似文献
4.
Chuanmin Chen Wenbo Jia Songtao Liu Yue Cao Bing Zhao Jianqiao Wang 《Korean Journal of Chemical Engineering》2018,35(3):637-644
CuCl2-SCR catalysts prepared by an improved impregnation method were studied to evaluate the catalytic performance for gaseous elemental mercury (Hg0) oxidation in simulated flue gas. Hg0 oxidation activity of commercial SCR catalyst was significantly improved by the introduction of CuCl2. Nitrogen adsorption, XRD, XRF and XPS were used to characterize the catalysts. The results indicated that CuCl2 was well loaded and highly dispersed on the catalyst surface, and that CuCl2 played an important role for Hg0 catalytic oxidation. The effects of individual flue gas components on Hg0 oxidation were also investigated over CuCl2-SCR catalyst at 350 oC. The co-presence of NO and NH3 remarkably inhibited Hg0 oxidation, while this inhibiting effect was gradually scavenged with the decrease of GHSV. Further study revealed the possibility of simultaneous removal of Hg0 and NO over CuCl2-SCR catalyst in simulated flue gas. The mechanism of Hg0 oxidation was also investigated. 相似文献
5.
Ni(0.4)-MnOx catalyst was prepared by citrate combustion, which showed high catalytic performance for NH3-SCR reaction. After the resistance tests of SO2 and H2O, Ni(0.4)-MnOx-SH showed better NH3-SCR activity than that of Ni(0.4)-MnOx, when the temperature was > 240 °C. The characterizations suggest that Ni(0.4)-MnOx-SH has more acid sites for ammonia adsorption and far weaker oxidation capacity for NH3, which resulted in the high catalytic activity at middle-temperature. 相似文献
6.
The effects of regeneration on the activities and structure of CeO2 catalysts for NH3-SCR of NOx have been studied in this article. CeO2 catalyst is deactivated by SO2 for NH3-SCR of NOx in a 200 h long-term operation at 350 °C due to the formation of sulfates, and its NOx conversion decreases from 100% to 83% gradually. However, sulfates can be removed from sulfur-poisoned CeO2 catalysts under high temperature thermal treatment in air. After regeneration, NOx conversion of sulfur-poisoned CeO2 catalyst is recovered to about 100% at 350 °C. Moreover, the regeneration temperature is related to the nature of the sulfates formed on the sulfur-poisoned CeO2 catalysts. 相似文献
7.
Hong-Soon Kim Kwang-Seo Cha Byoung-Kwan Yoo Tae-Gong Ryu Young-Seak Lee Chu-Sik Park Young-Ho Kim 《Journal of Industrial and Engineering Chemistry》2010,16(1):81-86
The chemical hydrogen storage (hydrogen reduction) and release (water-splitting oxidation) properties of the Cu-added Fe/Ce/Zr mixed oxide medium were investigated. The media with Cu content ranging from 0 to 5 wt% were prepared by a co-precipitation method using urea as a precipitant. The hydrogen reduction and the water-splitting oxidation on the medium were tested by temperature programmed reduction/oxidation (TPR/TPO) and repeated isothermal redox cycles at 550 °C for reduction and 350 °C for oxidation. The initial reduction rates and oxidation rates of the media increased with increasing the amount of the Cu additive. In addition, the reactivity of the medium for water-splitting oxidation was enhanced as the CeO2/ZrO2 ratio increased. Especially, the Fe-based mixed oxide medium with Cu/CeO2/ZrO2 contents of 3/30/10 wt% (Cu(3%)-Fe-CeO2/ZrO2(3/1)) showed superior performance in chemical hydrogen storage and release. As the results of isothermal redox cycles using the medium, the total amount of hydrogen evolved in water-splitting oxidation was maintained at ca. 8.5 mmol g?1-medium (ca. 1.8 wt% hydrogen storage amounts on the basis of the total medium) over 15 repeated redox cycles. 相似文献
8.
The effects of mercury oxidation on V2O5–WO3/TiO2 SCR catalyst's physical and chemical properties have been investigated. Both fresh catalyst and mercury exposed catalyst have been examined by BET, XRD, XPS and catalytic activity measurements. Mercury oxidation promoted the V5 + species transforming to the V4 + species and consumed the lattice oxygen on the surface of catalyst. In addition, the NO conversion of mercury exposed catalyst decreased in the range of 200 °C to 300 °C. It suggested a competitive relationship between gaseous NH3 and adsorbed mercury on the catalyst surface in that temperature range. 相似文献
9.
Chong Wang Xinping Wang Na Xing Qing Yu Yijing Wang 《Applied Catalysis A: General》2008,334(1-2):137-146
Zr-based zeolite catalysts were investigated for the first time in selective catalytic reduction of NO by hydrocarbon (HC-SCR). Highly dispersed zirconium species, especially the amorphous ultrafine zirconium oxide in the catalyst, considerably enhanced the activity for selective catalytic reduction of NO by acetylene (C2H2-SCR), both by accelerating the NO oxidation to NO2 and enlarging the NO2 adsorption capacity of the catalyst under the reaction conditions. Thus a durable and active Zr/HZSM-5 catalyst giving 89% of NO conversion to N2 at 350 °C in 1600 ppm NO, 800 ppm C2H2, and 9.95% O2 in helium was obtained. For the C2H2-SCR of NO, it was suggested that acidic sites with strong acidity on the Zr-based HZSM-5 catalysts are indispensable to initiate the aimed reaction via the route of NO oxidation to NO2, which explains the higher activity for the reaction obtained over the Zr/HZSM-5 catalyst sample with lower SiO2/Al2O3 ratio. The zirconium species could only functioned in the presence of protons in the C2H2-SCR of NO, so a synergistic effect between the zirconium species and protons of the Zr/HZSM-5 catalyst was proposed. 相似文献
10.
Mei-Yu Chen Ching Yu Chiu Chia-Ta Chia J.F. Lee J.J. Bian 《Journal of the European Ceramic Society》2010,30(2):335-339
A-site deficient perovskite compounds, La(2?x)/3NaxTiO3 (0.02 ≤ x ≤ 0.5) and Nd(2?x)/3LixTiO3 (0.1 ≤ x ≤ 0.5) microwave ceramics, were investigated by Raman scattering. Nd(2?x)/3LixTiO3 (0.1 ≤ x ≤ 0.5) was also investigated by extended X-ray absorption fine structure (EXAFS) measurement. The Raman shifts of the E (239 cm?1) and A1 (322 cm?1) modes of La(2?x)/3NaxTiO3 were found to decrease with x. However, the E (254 cm?1) and A1 (338 cm?1) of Nd(2?x)/3LixTiO3 were found to blueshift with x, which was caused by Li substitution. The redshift of the A1 (471 cm?1) phonon of Nd(2?x)/3LixTiO3 (0.1 ≤ x ≤ 0.3) indicates that O–Ti–O bonding forces lessen with Li concentration, which is consistent with the EXAFS result that Ti–O bond lengths increase for 0.1 ≤ x ≤ 0.3. For x > 0.3, the EXAFS result shows that Ti–O bond lengths decrease. Moreover, Ti–O bond lengths show strong correlation with the microwave dielectric constants of Nd(2?x)/3LixTiO3. 相似文献
11.
《Catalysis communications》2007,8(1):43-48
Pure oxides of ceria (CeO2) and zirconia (ZrO2) were prepared by precipitation method and a catalyst comprising of 25 mol% of CeO2 and 75 mol% of ZrO2 (25CZ) mixed metal oxide was prepared by co-precipitation method and also a catalyst with 25 wt% of 25CZ (25 mol% of CeO2 and 75 mol% of ZrO2) and 75 wt% SBA-15(25/25CZS) was prepared by precipitation–deposition method. Aqueous NH3 solution was used as a hydrolyzing agent for all the precipitation reactions. These catalysts were characterized by X-ray diffraction and nitrogen adsorption–desorption techniques for the confirmation of SBA-15 structural intactness. All these catalysts were found to be effective for the oxidative dehydrogenation of ethylbenzene (ODHEB) to styrene in the presence of CO2 and also it was observed that there was a sequential enhancement in the catalytic activity from individual oxides to mixed oxides followed by supported mixed oxide catalysts. Of the catalysts studied in this work, the supported 25/25CZS catalyst exhibited the superior activity, which was about 10–20 times higher than the activity of bulk single oxides in terms of turn over frequency. 相似文献
12.
《Catalysis communications》2007,8(11):1675-1680
CeO2–K catalysts supported on porous alumina substrate have been prepared by using a novel water-immiscible solvent. The advantage of this method is to load the catalyst onto the filter surface by one-time coating and prevent depositing the catalyst into the porous structure of support materials. The catalytic activities of the supported catalysts were evaluated by TPR system and the results showed that the pure CeO2 displayed a poor catalytic activity for soot oxidation, while the addition of K element into CeO2 would result in the formation of CeO2–K solid solution and significant enhancement of catalytic activity. Nevertheless, the variation of K content had a limited effect on soot ignition temperature. The catalyst with a Ce:K molar ratio of 1:2 exhibited an ignition temperature of about 330 °C and the oxidation rates of about 0.16 and 0.28 mg min−1 cm−2 at temperatures of 370 and 390 °C, respectively. 相似文献
13.
Vapor-phase catalytic dehydration of 2,3-butanediol was investigated over metal oxides such as CeO2, La2O3, Yb2O3, ZrO2, Al2O3, TiO2, ZnO, Fe2O3, NiO, and Cr2O3. In the dehydration of 2,3-butanediol, 3-buten-2-ol was preferentially produced over monoclinic ZrO2 along with major by-products such as butanone and 3-hydroxy-2-butanone. Over ZrO2 calcined at 900 °C, 3-buten-2-ol was produced with a maximum selectivity of 59.0% at 300 °C without producing 1,3-butadiene. 相似文献
14.
Zr-doped MnOx/CeO2–TiO2 for high temperature stability was investigated in terms of its dispersion and oxidation state. Aggregation of cerium oxide was observed in MnOx/CeO2–TiO2, but the Zr-doped catalyst was well dispersed. An increase of the Mn4 +/Mn3 + ratio was confirmed with a Zr addition through valence state analysis. De-NOx efficiency of the catalyst was increased to 40–45% by Zr addition at low temperature (150–200 °C). The substitution of Zr led the catalyst to improve the de-NOx efficiency, with a high dispersion and MnO2 ratio. 相似文献
15.
Carbon-supported catalyst with vanadium(V) sulfate (V2O3(SO4)2) as active component was prepared, characterized and tested for SO2 and NO catalytic removal. Result shows that this catalyst is very active towards SO2 oxidation and selective catalytic reduction of NO with NH3 in the low temperature range of 100–250 °C. 相似文献
16.
《Catalysis communications》2007,8(11):1815-1819
We report for the first time the use of CexZr1−xO2 solid solutions as supports for Ru catalysts to be implemented in the catalytic wet air oxidation of 2-chlorophenol. Such catalytic systems appeared to be very efficient, even at low temperature (393 K) and low pressure (3 MPa), and exhibited a great advantage over Ru/CeO2 or Ru/ZrO2. 相似文献
17.
《Catalysis communications》2007,8(8):1274-1278
Potassium nitrate catalysts supported on different oxides (CeO2, Ce0.5Zr0.5O2 and ZrO2) were prepared for diesel soot combustion. The ageing treatment was performed at 800 °C for 24 h and the catalytic activity was evaluated by a temperature-programmed oxidation technique. The results demonstrated that, compared with CeO2 and ZrO2, Ce0.5Zr0.5O2 presented good redox properties, a high surface area and available potassium-holding capacity at an elevated temperature. For aged K/Ce0.5Zr0.5O2, the combustion temperature of soot particle was 359 °C under tight contact conditions and 455 °C under loose contact conditions. Thus, ceria–zirconia mixed oxides were considered as good candidate supports for diesel soot oxidation catalysis. 相似文献
18.
《Catalysis communications》2007,8(3):612-618
A new bimetallic catalyst (Ag–Co/CeO2) was studied for simultaneously catalytic removal of NO and CO in the absence or presence of O2. CeO2 prepared by homogeneous precipitation method was optimized as supports for the active components. The addition of Ag on CeO2 greatly improved the catalytic activities in the lower temperature regions (⩽300 °C), and the introduction of Co on CeO2 increased the activities at higher temperatures (⩾250 °C). The bimetallic Ag–Co/CeO2 catalyst combined the advantages of the corresponding individual metal supported catalysts and showed superior activity due to the synergetic effect. The effect of support, temperature, loading amount, GHSV and oxygen on catalysis was investigated. NO and CO could be completely removed in the temperature range of 200–600 °C at a very high space velocity of 120 000 h−1. No deactivation was observed over 4% Ag–0.4% Co/CeO2 catalyst even after 50 h test. 相似文献
19.
The introduction of transition metals in Mn/TiO2 catalysts played significant roles in oxidative abstraction of hydrogen from adsorbed ammonia during the selective catalytic reduction (SCR). Thermodynamic calculation studies showed that the SCR performance was in accordance with the ammonia oxidation with transition metals, and the reaction tendency for the ammonia oxidation was decreased in the following order: CuO > Co3O4 > NiO > Fe2O3 > Cr2O3 > ZnO > La2O3 > CeO2 > ZrO2. In addition, Mn/TiO2 catalyst doped metal (Fe and Cu) oxides enhanced performance for NOx conversion, being approximately 100% at 453 K. 相似文献
20.
A series of MoO3-doped CeO2–ZrO2 catalysts were investigated for the selective catalytic reduction of NOx by NH3 (NH3-SCR). It was found that the added MoO3 significantly enhanced the activity of CeO2–ZrO2 catalyst for NH3-SCR of NOx in a wide temperature range and the optimum MoO3 loading is 5%. The highly dispersed MoO3 not only resulted in more Lewis acid and Brønsted acid sites formed on the catalyst surface, but also increased the redox property of the catalyst, all of which account for the enhanced SCR activity. 相似文献