共查询到20条相似文献,搜索用时 15 毫秒
1.
Ye Liu Ping Ning Kai Li Lihong Tang Jiming Hao Xin Song Guijian Zhang Chi Wang 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2017,91(3):490-499
A series of modified porous activated carbon (AC) catalysts prepared by impregnation were investigated for the low-temperature (≤250°C) selective catalytic reduction (SCR) of NO x with NH3 with simultaneous removal of SO2. The effects of various preparation conditions and reaction conditions on NO and SO2 conversions were observed, such as support type, active components, copper loading, calcination temperature and presence of H2O and O2. The modified AC catalysts were characterized by BET, XRD, TG and TPX methods. The activity test results showed that the optimal catalyst is 15% Cu/WCSAC which can provide 52% NO conversion and 68% SO2 conversion simultaneously at 175°C with a space velocity of 30000 h?1, and the optimal calcination temperature was 500°C. The presence of H2O could inhibit NO conversion and promote the SO2 conversion. The effect of O2 (0–5%) was evaluated, and the NO and SO2 conversions were best when the concentration of O2 was 3%. Research demonstrated that Cu/WCSAC catalyst was a kind of potential catalysts due to the amorphous phase, high specific areas and high active ability. 相似文献
2.
Fengxiang Li Junlin Xie De Fang Feng He Kai Qi Pijun Gong 《Research on Chemical Intermediates》2017,43(10):5413-5432
A series of Ce–MnO x /TiO2 catalysts were prepared using a novel sol–gel template method and investigated for low-temperature selective catalytic reduction (SCR) of NO with NH3 at temperatures ranging from 353 to 473 K. The 0.07Ce–MnO x /TiO2 catalyst showed the highest activity and best resistance to SO2 poisoning. The structure and properties of the catalysts were characterized using X-ray diffraction (XRD) analysis, thermogravimetric analysis (TGA), thermogravimetry (TG)–differential scanning calorimetry (DSC)–mass spectroscopy (MS), high-resolution transmission electron microscopy (HRTEM), Brunauer–Emmett–Teller (BET) measurements, H2-temperature-programmed reduction (TPR), and NH3-temperature-programmed desorption (TPD). The superior catalytic activity of the 0.07Ce–MnO x /TiO2 catalyst was probably due to a change in the active components, an increase in surface active oxygen and surface acid sites, and lower crystallinity and larger surface area with Ce doping. Furthermore, the reduction ability also became stronger. The SO2 poisoning resistance of the 0.07Ce–MnO x /TiO2 catalyst improved because doping with Ce can effectively decrease the formation of ammonium salt on the catalyst surface and the sulfation of MnO x . In situ diffuse-reflectance infrared Fourier-transform (DRIFT) spectroscopy experiments indicated that addition of Ce could promote adsorption of NH3 and inhibit generation of some nitryl species. The SCR reactions over the catalysts mainly followed the Eley–Rideal mechanism accompanied with a partial Langmuir–Hinshelwood mechanism. 相似文献
3.
(1.2–8.3)%FeOх/Al2O3 monolith catalysts have been prepared by impregnating alumina with aqueous solutions of iron(III) nitrate and oxalate and have been tested in NH3 oxidation and in the selective decomposition of N2O in mixtures resulting from ammonia oxidation over a Pt–Rh gauze pack under conditions of nitric acid synthesis (800–900°C). In the case of the support calcined at 1200°C, the catalyst is dominated by bulk Fe2O3 particles localized on the Al2O3 surface. The activity of these samples in both reactions decreases with a decreasing active component content, thus limiting the potential of Fe2(C2O4)3 · 5H2O, an environmentally friendlier but poorly soluble compound, as a substitute for Fe(NO3)3 · 9H2O. Decreasing the support calcination temperature to 1000°C or below leads to the formation of a highly defective Fe–Al–O solid solution in the (1.2–2.7)%FeOх/Al2O3 catalysts. The surface layers of the solid solution are enriched with iron ions or stabilize ultrafine FeOх particles. The catalytic activity of these samples in both reactions is close to the activities measured for ~8%FeOх/Al2O3 samples prepared using iron nitrate. 相似文献
4.
Hao Li Guang-Fei Qu Yan-Kang Duan Ping Ning Qiu-Lin Zhang Xin Liu Zhong-Xian Song 《Chemical Papers》2015,69(6):817-826
Ce-Ti-W-O x catalysts were prepared and applied to the NH3-selective catalytic reduction (SCR) reaction. The experimental results showed that the Ce-Ti-W-O x catalyst prepared by the hydrothermal method exhibited higher NO conversion than those synthesised via the sol-gel and impregnating methods, while the optimal content of WO3 and molar ratio of Ce/Ti were 20 mass % and 4: 6, respectively. Under these conditions, the catalyst exhibited the highest level of catalytic activity (the NO conversion reached values higher than 90 %) across a wide temperature range of 225–450°C, with a range of gas hourly space velocity (GHSV) of 40000–140000 h?1. The catalyst also exhibited good resistance to H2O and SO2. The influences of morphology, phase structure, and surface properties on the catalytic performance were investigated by N2 adsorption-desorption measurement, XRD, XPS, H2-TPR, and SEM. It was found that the high efficiency of NO removal was due to the large BET surface area, the amorphous surface species, the change to element valence states, and the strong interaction between Ce, Ti, and W. 相似文献
5.
M. A. Shuvaeva I. V. Delii O. N. Mart’yanov O. A. Bayukov E. I. Osetrov A. A. Saraev V. V. Kaichev N. S. Sakaeva G. A. Bukhtiyarova 《Kinetics and Catalysis》2011,52(6):896-906
The effect of calcination temperature on the state of the active component of iron-containing catalysts prepared by the impregnation of silica gel with a solution of FeSO4 and on their catalytic properties in selective H2S oxidation to sulfur was studied. With the use of thermal analysis, XPS, and Mössbauer spectroscopy, it was found that an X-ray amorphous iron-containing compound of complex composition was formed on the catalyst surface after thermal treatment in the temperature range of 400–500°C. This compound contained Fe3+ cations in three nonequivalent positions characteristic of various oxy and hydroxy sulfates and oxide and sulfate groups as anions. Calcination at 600°C led to the almost complete removal of sulfate groups; as a result, the formation of an oxide structure came into play, and it was completed by the production of finely dispersed iron oxide in the ?-Fe2O3 modification (the average particle size of 3.2 nm) after treatment at 900°C. As the calcination temperature was increased from 500 to 700°C, an increase in the catalyst activity in hydrogen sulfide selective oxidation was observed because of a change in the state of the active component. A comparative study of the samples by temperature-programmed sulfidation made it possible to establish that an increase in the calcination temperature leads to an increase in the stability of the iron-containing catalysts to the action of a reaction atmosphere. 相似文献
6.
Yan-Hua Zhang Hai-Long Zhang Yi Cao Yi Yang Bao-Qiang Xu Ming Zhao Mao-Chu Gong Hai-Di Xu Yao-Qiang Chen 《Chemical Papers》2016,70(10):1370-1379
A series of Co-modified Ce0.5Zr0.5O2 catalysts with different concentrations of Co (mass %: 0, 2, 4, 6, 8, 10) was investigated for diesel soot combustion. Ce0.5Zr0.5O2 was prepared using the coprecipitation method and Co was loaded onto the oxide using the incipient wetness impregnation method. The activities of the catalysts were evaluated by thermogravimetric (TG) analysis and temperature-programmed oxidation (TPO) experiments. The results showed the soot combustion activities of the catalysts to be effectively improved by the addition of Co, 6 % Co/Ce0.5Zr0.5O2 and that the 8 % Co/Ce0.5Zr0.5O2 catalysts exhibited the best catalytic performance in terms of lower soot ignition temperature (Ti at 349°C) and maximal soot oxidation rate temperature (Tm at 358°C). The reasons for the improved activity were investigated by X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), H2 temperature-programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). These results revealed that the presence of Co could lower the reduction temperature due to the synergistic effect between Co and Ce, thereby improving the activity of the catalysts in soot combustion. The 6 % Co catalyst exhibited the best catalytic performance, which could be attributed to the greater amounts of Co3+ and surface oxygen species on the catalyst. 相似文献
7.
D. Yu. Ebert A. S. Savel’eva N. V. Dorofeeva O. V. Vodyankina 《Kinetics and Catalysis》2017,58(6):720-725
FePО4/SiO2 supported catalysts with a different content of iron phosphate are prepared. The properties of the catalyst are changed by the introduction of alkali metal compounds (Na or Cs) on its surface. The samples obtained are characterized by X-ray diffraction, low-temperature nitrogen adsorption, temperatureprogrammed reduction by hydrogen, and temperature-programmed desorption of ammonia. The catalytic properties are investigated in the reaction of gas-phase propylene glycol oxidation. It is shown that the selectivity of methylglyoxal formation on the unmodified catalysts is determined by the state of the supported active component and by its reduction–oxidation ability under the action of a reaction mixture. 相似文献
8.
Jingying Li Xiaolong Tang Fengyu Gao Honghong Yi Shunzheng Zhao 《Chemical Papers》2017,71(10):1921-1928
The poisoning effect of calcium on a commercial De-NO x SCR catalyst (V2O5–WO3/TiO2) and the regeneration process of deactivated catalysts via water or H2SO4 washing were investigated under simulated condition in laboratory. The physicochemical properties of the catalysts were characterized by SEM–EDX, XRD, BET, TPD and FT-IR measurements, and the deactivation mechanism was discussed. The poisoning of calcium was attributed to the coverage of active sites and the reduction of acid sites on the surface of catalyst. The change of V=O bonds on catalyst surface was an important reason, which plays a significant role in the catalytic cycle of SCR. Due to the suction deliquescence of CaO to Ca(OH)2, the catalytic activity of deactivated catalyst can be finitely recovered by water washing. Besides, as the result of the re-exposure of active sites by washing CaO off and the promotional effect of surface sulfation, the process of regeneration via sulfuric acid washing has a favorable effect in the experiment. 相似文献
9.
A series of MoO3 doped Fe2O3 catalysts prepared by the co-precipitation method were investigated in the selective catalytic reduction of NO by NH3 (NH3-SCR). The catalysts displayed excellent catalytic activity from 225 to 400°C and high tolerance to SO2/H2O poisoning at 300°C. To characterize the catalysts the N2-BET, XRD, Raman, NO-TPD, NH3-TPD and in situ DRIFTS were carried out. It was found that the main reason explaining a high NH3-SCR performance might be the synergistic effect between Fe and Mo species in the catalyst that could enhance the dispersion of Fe2O3 and increase NH3 adsorption on the catalyst surface. 相似文献
10.
Zhongxian Song Qiulin Zhang Ping Ning Xin Liu Jinhui Zhang Yancai Wang Lisi Xu Zhenzhen Huang 《Research on Chemical Intermediates》2016,42(10):7429-7445
The Cu/ZSM-5 catalysts prepared by different copper precursors were used for the selective catalytic reduction (SCR) of NO x with NH3. The Cu/ZSM-5 catalyst prepared by the copper nitrate (Cu/ZSM-5-N) presented the best performance among the Cu/ZSM-5 catalysts and showed above 90 % NO x conversion at 225–405 °C. The average particle size of CuO was 5.82, 9.20, and 11.01 nm over Cu/ZSM-5-N, Cu/ZSM-5-S (prepared by copper sulfate), and Cu/ZSM-5-C (prepared by copper chloride), respectively. The Cu/ZSM-5-N catalyst showed the highly dispersed copper species, the strong surface acidity, and the excellent redox ability compared with the Cu/ZSM-5-C and Cu/ZSM-5-S catalysts. The Cu+ and Cu2+ existed in the Cu/ZSM-5 catalysts and the abundant Cu+ over Cu/ZSM-5-N might be responsible for the superior SCR activity. 相似文献
11.
Ezzat Rafiee Mohammad Joshaghani Parvaneh Ghaderi-Shekhi Abadi 《Research on Chemical Intermediates》2018,44(4):2503-2522
Transition metal compounds have emerged as suitable catalysts for organic reactions. Magnetic compounds as soft Lewis acids can be used as catalysts for organic reactions. In this report, the Fe3O4 nanostructures were obtained from Fe2+ and Fe3+-salts, under an external magnetic field (EMF) without any protective agent. The X-ray photoelectron spectroscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy tools were used to characterize these magnetic compounds. The two-dimensional (2-D, it showed nanometric size in the two dimensions, nanorod structure) Fe3O4 compound showed high catalytic activity and stability in N- and C-alkylation reactions. A diverse range of N- and C-alkylation products were obtained in moderate to high yield under green and mild conditions in air. Also the N- and C-alkylation products can be obtained with different selectivity and yield by exposure reactions with EMF. Results of alkylation reactions showed that the presence of Fe(II) and Fe(III) species on the surface of magnetic catalysts (phase structure of magnetic compounds) are essential as very cheap active sites. Also, morphology of magnetic catalysts had influence on their catalytic performances. After the reaction, the catalyst/product(s) separation could be easily achieved with an external magnet and more than 95% of catalyst could be recovered. The catalyst was reused at least four times without any loss of its high catalytic activity for N- and C-alkylation reactions. 相似文献
12.
Preparation of nanocrystalline Fe-doped TiO<Subscript>2</Subscript> powders as a visible-light-responsive photocatalyst 总被引:1,自引:0,他引:1
Nanocrystalline Fe-doped TiO2 powders were prepared using TiOSO4, urea, and Fe(NO3)3 · 9H2O as precursors through a hydrothermal method. The as-synthesized yellowish-colored powders are composed of anatase TiO2, identified by X-ray diffraction (XRD). The grain size ranged from 9.7 to 12.1 nm, calculated by Scherrer’s method. The specific
surface area ranged from 141 to 170 m2/g, obtained by the Brunauer–Emmett–Teller (BET) method. The transmission electron microscopy (TEM) micrograph of the sample
shows that the diameter of the grains is uniformly distributed at about 10 nm, which is consistent with that calculated by
Scherrer’s method. Fe3+ and Fe2+ have been detected on the surface of TiO2 powders by X-ray photoelectron spectroscopy (XPS). The UV–Vis diffuse reflection spectra indicate that the light absorption
thresholds of the Fe-doped TiO2 powders have been red-shifted into the visible light region. The photocatalytic activity of the Fe-doped TiO2 was evaluated through the degradation of methylene blue (MB) under visible light irradiation. The Fe-doped TiO2 powders have shown good visible-light photocatalytic activities and the maximum degradation ratio is achieved within 4.5 h. 相似文献
13.
Ag/Al2O3 is a promising catalyst for the selective catalytic reduction (SCR) by hydrocarbons (HC) of NO
x
in both laboratory and diesel engine bench tests. New developments of the HC-SCR of NO
x
over a Ag/Al2O3 catalyst are reviewed, including the efficiencies and sulfur tolerances of different Ag/Al2O3-reductant systems for the SCR of NO
x
; the low-temperature activity improvement of H2-assisted HC-SCR of NO
x
over Ag/Al2O3; and the application of a Ag/Al2O3-ethanol SCR system with a heavy-duty diesel engine. The discussions are focused on the reaction mechanisms of different Ag/Al2O3-reductant systems and H2-assisted HC-SCR of NO
x
over Ag/Al2O3. A SO2-resistant surface structure in situ synthesized on Ag/Al2O3 by using ethanol as a reductant is proposed based on the study of the sulfate formation. These results provide new insight
into the design of a high-efficiency NO
x
reduction system. The diesel engine bench test results showed that a Ag/Al2O3-ethanol system is promising for catalytic cleaning of NO
x
in diesel exhaust. 相似文献
14.
Chun-guang Gao Yong-xiang Zhao Yin Zhang Dian-sheng Liu 《Journal of Sol-Gel Science and Technology》2007,44(2):145-151
The Ni/ZrO2/SiO2 aerogels catalysts were synthesized via three different routes: (i) impregnation ZrO2–SiO2 composite aerogels with a aqueous solution of Ni(NO3)2, (ii) impregnation SiO2 aerogels with a mixed aqueous solution of Ni(NO3)2 and ZrO(NO3)2 · 2H2O, (iii) one-pot sol–gel procedure from precursors Ni(NO3)2/ZrO(NO3)2 · 2H2O/Si(OC2H5)4. These catalysts were characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), ammonia temperature-programmed
desorption (NH3-TPD), N2 adsorption–desorption isotherms and Fourier transform infrared (FT-IR). The Liquid-phase hydrogenation of maleic anhydride
(MA) was performed over these catalysts. The results revealed that the different preparation routes result in a difference
between the obtained samples, concerning the crystal structure and composition, surface acidity, mixed level of each component,
texture, and catalytic selectivity. 相似文献
15.
Zhe-Shan Zhang Xin-Pu Fu Wei-Wei Wang Zhao Jin Qi-Sheng Song Chun-Jiang Jia 《中国科学:化学(英文版)》2018,61(11):1389-1398
Transition metal catalysts have been considerably used for NH3 decomposition because of the potential application in COx-free H2 generation for fuel cells. However, most transition metal catalysts prepared via traditional synthetic approaches performed the inferior stability due to the agglomeration of active components. Here, we adopted an efficient method, aerosol-assisted self-assembly approach (AASA), to prepare the optimized cobalt-alumina (Co3O4-Al2O3) catalysts. The Co3O4-Al2O3 catalysts exhibited excellent catalytic performance in the NH3 decomposition reaction, which can reach 100% conversion at 600 °C and maintain stable for 72 h at a gaseous hourly space velocity (GHSV) of 18000 cm3 gcat?1 h?1. The catalysts were characterized by various techniques including transmission electron microscope (TEM), scanning electron microscope (SEM), nitrogen sorption, temperature-programmed reduction by hydrogen (H2-TPR), ex-situ/in-situ Raman and ex-situ/in-situ X-ray diffraction (XRD) to obtain the information about the structure and property of the catalysts. H2-TPR and in-situ XRD results show that there is strong interaction between the cobalt and alumina species, which influences the redox properties of the catalysts. It is found that even a low content of alumina (10 at%) is able to stabilize the catalysts due to the adequate dispersion and rational interaction between different components, which ensures the high activity and superior stability of the cobalt-alumina catalysts. 相似文献
16.
T. N. Afonasenko D. A. Shlyapin N. N. Leont’eva T. I. Gulyaeva K. S. Buyal’skaya M. V. Trenikhin P. G. Tsyrul’nikov 《Kinetics and Catalysis》2011,52(6):843-850
The CuO-CeO2/Al2O3 catalysts for the selective oxidation of CO in hydrogen-containing mixtures were prepared by surface self-propagating thermal
synthesis (SSTS) with the use of cerium nitrate Ce(NO3)3, the ammonia complex of copper acetate [Cu(NH3)4](CH3COO)2, and citric acid C6H8O7 as a fuel additive. The effect of the C6H8O7/Ce(NO3)3 molar ratio on the catalyst activity and selectivity for oxygen was studied. The catalyst samples were studied by X-ray diffraction
(XRD) analysis, temperature-programmed reduction (TPR-H2), IR spectroscopy of adsorbed CO, and transmission electron microscopy (TEM). It was found that an increase in the C6H8O7/Ce(NO3)3 ratio resulted in an increase in the degree of dispersion of the resulting CeO2 phase. The greatest amount of dispersed CuO particles, which are responsible for catalytic activity in the oxidation of CO,
was formed at C6H8O7/Ce(NO3)3 = 1. 相似文献
17.
V. A. Matyshak A. N. Il’ichev O. N. Sil’chenkova V. A. Sadykov V. N. Korchak 《Kinetics and Catalysis》2017,58(2):198-210
It has been demonstrated by quantitative spectrokinetic measurements that, on the surface of zirconia stabilized as a tetragonal phase, the rate-limiting step of the selective catalytic reduction of nitrogen oxides (SCR of NO x ) with propylene is the interaction of surface nitrates with C3H6 yielding organic nitro compounds. It is hypothesized that propylene reacts not with the nitrates themselves but with the activated complex NO2 ads whose structure is intermediate between the structures of the monodentate NO3 ? and NO2 species. Deep C3H6 oxidation exerts an adverse effect on the rate of the SCR of NO x with propylene, and the interaction between O2 and NO, which yields NO2 and NO3 ? stimulates further nitrogen reduction to N2. The effect of the reaction between oxygen and O2N?C n H m on the NO x reduction rate is variable and is determined by the C3H6/NO x ratio. A generalized scheme of the SCR of NO x with propylene on the surface of ZrO2 partially stabilized as a tetragonal phase has been developed by comparing experimental data of this study and data available from the literature. 相似文献
18.
The catalytic activity of the colloidal catalyst based on iron(III) hydroxide was studied in the decomposition of H2O2 in a neutral medium (pH 6.7). A colloidal micellar solution of iron(III) hydroxide after preparation was kept at 19–20 °С for 2 or 20 h without additives or with C2H5OH additives. The decomposition of H2O2 under the action of the colloidal catalyst (20 h) proceeds via the first-order reaction with the decay rate constant kd = 1.26?10–4 s–1, whereas the decay rate of the first-order reaction is kd = 0.77?10–4 s–1 for the colloidal catalyst (2 h) prepared in the presence of C2H5OH. 相似文献
19.
T. V. Mironyuk V. L. Struzhko S. N. Orlik G. M. Tel’biz 《Theoretical and Experimental Chemistry》2005,41(2):129-134
We have shown that the activity of cobalt-containing catalysts based on sulfated zirconium dioxide in selective catalytic reduction (SCR) of NO by methane depends on the amount of sulfur and the preparation method. Modification of Fe and Mn improves the catalytic behavior of SO
4
2−
/ZrO2 as a result of the increase in the concentration of active sites.__________Translated from Teoreticheskaya i Eksperimental’naya Khimiya, Vol. 41, No. 2, pp. 121–125, March– April, 2005. 相似文献
20.
A H3PW12O40/ZrO2 catalyst for effective dimethyl carbonate (DMC) formation via methanol carbonation was prepared using the sol–gel method. X-ray photoelectron spectra showed that reactive and dominant (63%) W(VI) species, in WO3 or H2WO4, enhanced the catalytic performances of the supported ZrO2. The mesoporous structure of H3PW12O40/ZrO2 was identified by nitrogen adsorption–desorption isotherms. In particular, partial sintering of catalyst particles in the duration of methanol carbonation caused a decrease in the Brunauer–Emmett–Teller surface area of the catalyst from 39 to 19 m2/g. The strong acidity of H3PW12O40/ZrO2 was confirmed by the desorption peak observed at 415 °C in NH3 temperature-programmed desorption curve. At various reaction temperatures (T?=?110, 170, and 220 °C) and CO2/N2 volumetric flow rate ratios (CO2/N2?=?1/4, 1/7, and 1/9), the calculated catalytic performances showed that the optimal methanol conversion, DMC selectivity, and DMC yield were 4.45, 89.93, and 4.00%, respectively, when T?=?170 °C and CO2/N2?=?1/7. Furthermore, linear regression of the pseudo-first-order model and Arrhenius equation deduced the optimal rate constant (4.24?×?10?3 min?1) and activation energy (Ea?=?15.54 kJ/mol) at 170 °C with CO2/N2?=?1/7 which were favorable for DMC formation. 相似文献