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Koichi Yuzaki Takayoshi Yarimizu Kenji Aoyagi Shin-ichi Ito Kimio Kunimori 《Catalysis Today》1998,45(1-4):129-134
The study of catalytic decomposition of nitrous oxide to nitrogen and oxygen over Rh catalysts supported on various supports (USY, NaY, Al2O3, ZrO2, FSM-16, CeO2, La2O3) showed that the activities of Rh/Al2O3 and Rh/USY (ultrastable Y zeolite) catalysts were comparable to or higher than the other catalysts reported in the literatures. The catalytic activity of N2O decomposition was sensitive not only to the Rh dispersion but also to the preparation variables such as the Rh precursors and the supports used. A pulsed N2O experiment over a Rh/USY catalyst suggested that the catalytic N2O decomposition occurs on oxygen-covered surface and that O2 may be freed on collision of N2O molecules with the adsorbed oxygen atoms. 相似文献
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采用正交试验设计方法设计和浸渍法制备分子筛RPSA负载Co、K、Ba和Sr催化剂,使用微型反应器评价催化剂用于直接分解N2O的催化活性,考察活性组分对催化剂活性的影响。采用XRD、H2-TPR和NH3-TPD等方法对催化剂进行表征。结果表明,金属Co和K对催化剂活性影响显著,Co对提高催化剂活性有促进作用,Co含量增加,催化剂活性提高,而K对催化剂活性有抑制作用。催化剂表征结果显示,Co物种主要以Co3O4形式存在于载体表面,催化剂的组成和配比影响催化剂活性、氧化还原性能和酸性,催化剂强酸的存在有利于催化剂活性的提高。 相似文献
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Jian Lin Lin Li Xiaoli Pan Xiaodong Wang Yu Cong Tao Zhang Shaomin Zhu 《American Institute of Chemical Engineers》2016,62(11):3973-3981
N2O, as a green propellant alternative to N2H4, shows potential application in satellite propulsion system. The state of Ir species and the reaction behaviors on Ir/Al2O3 in the oxidative environment during N2O decomposition were identified here. Two types of Ir sites existed in this catalyst and affected the process of N2O decomposition. The strong Ir sites facilitated the dissociative adsorption of N2O to form N2 and adsorbed O atoms with adsorption heat of as high as 281 kJ/mol, which promoted the desorption of adsorbed O atoms and favored the self‐sustaining decomposition of N2O by raising the catalyst bed temperature. The other Ir sites interacted weakly with O atoms but facilitated their combination to form O2. The Ir/Al2O3 catalyst then exhibited an excellent performance in initiating the decomposition of N2O at low temperature of 200°C and good stability in 0.1 N microthruster for orbit adjustment and attitude control of satellite. © 2016 American Institute of Chemical Engineers AIChE J, 62: 3973–3981, 2016 相似文献
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CePO_4(in particular,monoclinic CePO_4)has been rarely used to make supported catalysts.Herein,monoclinic CePO_4 nanoparticles were prepared by calcining hexagonal CePO_4 nanorods(prepared by precipitation)in air at 900℃.Monoclinic CePO_4 nanowires were prepared by calcining hexagonal CePO_4 nanowires(prepared by hydrothermal synthesis at 150℃)in air at 900℃.Both monoclinic CePO_4 materials were used to support Rh_2O_3 by impregnation using Rh(NO_3)_3 as a precursor(followed by calcination).The catalytic performance of Rh_2O_3/monoclinic CePO_4 composite materials in N_2O decomposition and CO oxidation was investigated.It was found that Rh_2O_3 supported on monoclinic CePO_4 nanowires was much more active than Rh_2O_3 supported on monoclinic CePO_4 nanoparticles.The stability of catalysts as a function of reaction time on stream was studied in both reactions.The influence of co-fed CO_2,O_2,and H_2O on the catalytic activity in N_2O decomposition was also studied.These catalysts were characterized by employing N_2 adsorption–desorption,ICP-OES,XRD,TEM,XPS,H_2-TPR,O_2-TPD,and CO_2-TPD.The correlation between physicochemical properties and catalytic properties was discussed. 相似文献
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Ru/TiO2 and Ru/Al2O3 were prepared by wet impregnation of TiO2 and Al2O3, and tested in the catalytic decomposition of dichloromethane (DCM). Ru/TiO2 catalyst presents the higher activity than Ru/Al2O3 catalyst, with 50% and 90% conversion occurring at 235 and 267 °C, respectively. Moreover, the higher stability on Ru/TiO2 catalyst is observed, which can be related to ready removal of Cl species produced during DCM decomposition. The chlorine uptake on Ru/TiO2 catalyst is estimated at 240 °C to be 0.36 mmol Cl/gcat, while on Ru/Al2O3, the value is 1.46 mmol Cl/gcat. 相似文献
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《Applied catalysis. B, Environmental》2005,55(1):57-64
The behaviour of Rh/γ-AlO3–sepiolite monolithic systems in the N2O decomposition reaction using catalysts with rhodium contents between 0.2 and 0.8 wt.% were analysed. The observed increase of the catalytic activity with the metal loading was related to an enhancement in the number of active sites. The SEM–EDX results showed that rhodium was mainly located on the alumina particles. The variation of the reaction rate values with the inlet N2O and O2 concentrations, suggested an apparent first order equation with respect to N2O and zero order for O2. The presence of NH3 traces or water vapour in the feed decreased the catalytic activity, probably due to the competitive adsorption of NHx or OH species. The ammonia oxidation reaction took place, producing N2O as a secondary product. The monolithic catalysts developed operate with a low pressure drop achieving a N2O conversion higher than 90% at 773 K in the presence of oxygen, ammonia or water vapour in the stream. 相似文献
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The room temperature decomposition of N2O over prereduced Rh‐based catalysts (Rh supported on ceria, zirconia and titania–alumina) is studied as a function of the oxygen content in the feed. Results indicate that Rh supported on titania–alumina shows lower degree of inhibition by gaseous oxygen on this reaction, attributed to the role of the metal particle–support interface region in the reaction. The effect of Rh loading and of the reaction temperature are consistent with the hypothesis. This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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Sung Su Kim Sang Jin Lee Sung Chang Hong 《Journal of Industrial and Engineering Chemistry》2012,18(4):1263-1266
The decomposition of N2O in the presence of oxygen was studied on Rh/CeO2 and Rh/La2O3–CeO2 catalysts prepared by wet impregnation method. The conversion of N2O decomposition increased as the Rh loading increased, and the Rh-chloride catalyst showed a poor activity than the Rh-nitrate catalyst. XPS and IC/ICP analysis confirmed that the Rh-chloride catalyst's low activity caused since Rh-chloride catalyst had the some RhCl3 species. N2O decomposition rate over Rh/La2O3–CeO2 catalysts decreased as the La loading increased due to the SMSI effect between Rh and CeO2. H2 TPR confirmed that the activity and reducibility of the catalyst were closely related. 相似文献
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Fly ash (FA), an industrial waste material, has been treated by physical and chemical methods. These materials were then employed as supports for preparation of Ru-based catalysts for H2 generation from ammonia decomposition. The physicochemical properties of the supports and Ru-based catalysts were characterised using several techniques. The results revealed that the surface area of FA could be enhanced and thus improved the dispersion of Ru particles, resulting in higher catalytic activity. Ru/FA-800 exhibits the highest conversion due to higher surface loading of Ru, stronger NH3 adsorption and least acid sites. 相似文献
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A series of KW/γ-Al2O3 catalysts with varying K/W mole ratio were prepared for the synthesis of methanethiol from carbon disulfide and methanol, and characterized by N2 adsorption–desorption, XRD and NH3/CO2-TPD techniques. Experimental results showed that the acidic and basic property of the catalyst plays a key role on the catalytic performance. It is shown that the conversion of CH3OH is chiefly related to the acid sites, while the base sites of catalysts are favorable for the selectivity toward CH3SH and hydrocarbons, but the strong base sites will restrain the selectivity toward CH3SH. When the K/W mole ratio is K/W = 2/1 and the reaction temperature is at 603 K, the conversion of CH3OH and the selectivity toward CH3SH are 98.3 and 56.2%, respectively. 相似文献
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铜锌掺杂的六铝酸盐分解N2O催化性能研究 总被引:2,自引:1,他引:1
采用共沉淀法制备了Cu和Zn取代六铝酸盐(LaCuxZn1-xAl11O19-δ,x=0、0.2、0.4、0.5、0.6、0.8、1.0)催化剂,通过XRD和BET等技术对催化剂进行表征,利用微型固定床反应器考察催化剂对N2O的分解活性。结果表明,以(NH4)2CO3为沉淀剂制备的催化剂在1 200 ℃焙烧4 h,可以形成完整的六铝酸盐晶型,Cu和Zn能够取代Al3+进入六铝酸盐晶体结构。LaCuxZn1-xAl11O19-δ催化剂对N2O分解有较好的催化活性,其中,LaCu0.8Zn0.2Al11O19-δ活性较好。在LaCuxZn1-xAl11O19-δ六铝酸盐中,Cu为N2O催化分解的主要活性元素,Zn有助于提高催化剂的稳定性,但由于六铝酸盐的特殊结构,Zn在催化剂中的作用较小。 相似文献
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Fong-Chang Sheu Cheng-Tsung Hong Wen-Long Hwang Cheng-Jec Shih Jung-Chung Wu Chuin-Tih Yeh 《Catalysis Letters》1992,14(3-4):297-304
A series of alumina aluminum borate (AAB) with various Al/B molar ratios were prepared by the coprecipitation method. The supported rhenium oxide catalysts with various contents of Re2O7 were also prepared by the impregnation method with perrhenic acid. The catalytic activity and stability of Re2O7/AAB catalysts for the reaction of propylene metathesis were tested in a fixed-bed microreactor. It was found that Re2O7/AAB is more active, stable and regenerable than Re2O7/Al2O3 for propylene metathesis. The optimum Al/B molar ratio was found to be in the range of 4–10. 相似文献
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In this study, fresh and aged Pd/(OSC–Al2O3) and Pd/(Al2O3–OSC–La2O3) metallic monoliths (OSC material Ce0.75Zr0.25O2) were used to find out the effect of La2O3 on the catalyst behaviour in dynamic oxygen storage capacity (OSC) measurements. In addition, the interaction of CO, NO and
O2 reaction compounds over the studied catalysts was investigated in order to understand the effect of La2O3 in the oxidation and reduction reactions in lean automotive exhaust gas conditions. A FT-IR gas analyser was used to analyse
the product gas composition. The presence of La2O3 on fresh and aged catalysts had negative effect on both the dynamic OSC and the activity of the catalyst. The reason for this
is the different washcoat compositions between the studied catalysts which could explain the differences in BET surface areas. 相似文献
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以RPSA分子筛为载体,采用浸渍法制备了一系列以Co为主活性组分和碱土金属为助剂的CoM/RPSA(M=Mg、Ca、Sr和Ba)催化剂,考察了含硫和含氧条件下直接催化分解N2O的性能。采用X射线衍射、热重-质谱联用系统、NH3-TPD和N2O-TPD等方法对催化剂进行了表征。XRD结果表明,Co物种主要以Co3O4尖晶石形态存在。NH3-TPD和N2O-TPD结果表明,碱土金属的种类影响催化剂酸性和对反应物N2O的吸附-脱附性能,催化剂活性与催化剂酸性及其对反应物N2O的吸附-脱附性能有关。催化剂活性评价结果显示,CoSr/RPSA催化剂的N2O分解活性较好,N2O转化率达到95%时的反应温度为471 ℃。 相似文献
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The oxidation states of Rh in NaY supported catalysts have been studied by temperature programmed reduction (TPR). After calcination of the exchanged catalyst to 380°C, both RhO2 and Rh2O3 are identified, besides small amounts of RhO+ and Rh3+. Quantitative reduction is possible for samples calcined at temperatures not exceeding 500°C. Re-oxidation of the reduced samples leads to formation of RhO2 and Rh2O3, with negligible protonolysis to Rh3+. The dioxide prevails after re-oxidation at 320°C, but the sesquioxide after oxidation at 500°C. In the temperature regime where both oxides coexist the reduction of NO with propane is catalyzed even at an O2/C3H8 ratio of 10. Total oxidation of propane reaches 80% at 350°C. 相似文献
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《Applied catalysis. B, Environmental》2009,85(3-4):433-439
The co-production of hydrogen and carbon nanotubes (CNTs) from the decomposition of ethanol over Fe/Al2O3 at different temperatures and feeding rates of ethanol was investigated systematically. The results indicated that Fe/Al2O3 was a quite active catalyst for the co-production of hydrogen and CNTs and that its activity and stability depended strongly on the Fe loading. Among all catalysts tested, 10 mol% Fe/Al2O3 was the most effective catalyst based on the ratio of hydrogen production, the total H2 yield, and the quality of the CNTs formed. The efficiency of hydrogen production from ethanol decomposition over 10 mol% Fe/Al2O3 reached a maximum of ∼80% at 800 °C and the yield of CNTs with well-oriented growth and uniform diameter was 141%. In addition, the reaction of hydrogen and CNTs co-produced from ethanol decomposition was proposed. 相似文献
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E. A. Belopukhov A. S. Belyi M. D. Smolikov D. I. Kir’yanov T. I. Gulyaeva 《Catalysis in Industry》2012,4(4):253-260
Benzene hydroisomerization is among the promising processes converting benzene into methylcyclopentane (MCP), which is an environmentally friendlier, octane boosting component of motor fuels. Benzene hydroisomerization into MCP over the Pt/MOR/Al2O3 (MOR = mordenite) catalytic system is reported here. The dependence of the yield of the target product on the acidic properties of the support and platinum precursor ([Pt(NH3)4]Cl2 or H2PtCl6) have been investigated in order to optimize the catalyst composition. The acidic properties of the surface have been altered by introducing 30–95 wt % alumina into the support. Catalytic activity has been measured in the hydroisomerization of cyclohexane and a benzene (20 wt %) + n-heptane (80 wt %) mixture in a flow reactor at 250–350°C, 1.5 MPa, H2: CH = 3: 1, a cyclohexane LHSV of 6 h?1, a mixed feedstock LHSV of 2 h?1, a catalyst bed volume of 2 cm3, and catalyst pellet sizes of 0.25–0.75 mm. The most efficient catalyst for cyclohexane and n-heptane isomerization and benzene hydroisomerization is the platinum-containing catalyst (0.3 wt % Pt) whose support consists of 30 wt % MOR and 70 wt % Al2O3. The highest yield of the target products of isomerization in the presence of this catalyst is attained in the temperature range from 280 to 310°C, which is thermodynamically favorable for MCP formation from benzene. This indicates that this catalyst is promising for the hydroisomerization of benzene-containing gasoline fractions. Use of H2PtCl6, a readily available chemical, as the platinum precursor is favorable for commercialization of the catalyst and ensures price attractiveness in its industrial-scale manufacturing. 相似文献
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研究了不同含量的银对Pd/Al2O3催化分解NO反应活性的影响。结果表明,低温下,Pd/Al2O3催化剂对NO的分解反应活性不高;反应温度达到720 ℃时,NO分解活性迅速上升。O2-TPD研究表明,Pd/Al2O3上氧的脱附速率也是在720 ℃左右达到最大值,因此,在温度低于720 ℃时,氧从催化剂表面的脱附是NO分解反应的速率控制步骤。Pd/Al2O3中添加适量的Ag对NO分解反应有促进作用。O2-TPD研究表明,这种促进作用与Pd表面氧物种的起始脱附温度向低温移动有关。 相似文献
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