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1.
The catalytic activity behavior for the selective catalytic reduction of NO by C3H6 under excess oxygen and the nature of surface species on the active sites of Pt/Al2O3 catalyst after adding a second metal (Fe, Sn, Co, Cr or W) were investigated. It has been found that an important role of
second metals is on TONs of C3H6 and NO conversions and the nature of surface species produced on the catalyst surface at low temperature instead of the catalytic
activity behavior towards the temperature programmed reaction. Although the introduction of each second metal distinctly disturbs
the characteristic of surface species, the reaction mechanism is presumably similar. The observation of few surface species
and the investigation about their reactivity indicate that few mechanisms are simultaneously proceeding at the same reaction
condition. 相似文献
2.
The selective oxidation of hydrogen sulfide in the presence of excess water and ammonia was investigated by using vanadium-bismuth
based mixed oxide catalysts. Synergistic effect on catalytic activity was observed for the mechanical mixtures of V-Bi-O and
Sb2O4. Temperature programmed oxidation (TPO), X-ray photoelectron spectroscopy (XPS), and two separated bed reactivity test results
supported the role of Sb2O4 for reoxidizing the reduced V-Bi-O during the reaction.
This paper is dedicated to Professor Hyun-Ku Rhee on the occasion of his retirement from Seoul National University. 相似文献
3.
Jiangyin Lu Zhen Zhao Chunming Xu Aijun Duan Xiaoning Wang Pu Zhang 《Journal of Porous Materials》2008,15(2):213-220
Several systems of HZSM-5, FeHZSM-5 and CrHZSM-5 zeolite catalysts with different ratios of SiO2/Al2O3 (25,38,50,80, and 150) were prepared and they were characterized by means of X-ray diffraction (XRD), UV–Vis, NH3-TPD and BET techniques. The results indicated that, compared with uncalcined HZSM-5 zeolites, the total acid amounts, acidic
site density and acidic strength of HZSM-5, FeHZSM-5 and CrHZSM-5 zeolite catalysts obviously decreased, while those of weak
acid amounts obviously enhanced with the decrease of SiO2/Al2O3 molar ratio. When the ratio of SiO2/Al2O3 is less than 50, the three systems of HZSM-5, FeHZSM-5 and CrHZSM-5 zeolite catalysts with same ratio of SiO2/Al2O3 gave similar and high isobutane conversions. However, when the ratio of SiO2/Al2O3 was equal to or greater than 80, these three systems of catalysts possessed different altering tendencies of isobutane conversions,
thus their isobutene conversions were different. High yields of light olefins were obtained over the FeHZSM-5 and CrHZSM-5
zeolite catalysts with high ratio of SiO2/Al2O3 (≥80). The ratio of SiO2/Al2O3 has large effects on the surface area, and acidic characteristics of HZSM-5, FeHZSM-5 and CrHZSM-5 zeolites catalysts, and
thus further affect their catalytic performances for isobutane cracking. That is the nature of SiO2/Al2O3 ratio effect on the catalytic performances. 相似文献
4.
Laura Mureşan Graziella Liana Turdean Ionel Cătălin Popescu 《Journal of Applied Electrochemistry》2008,38(3):349-355
Graphite electrodes chemically modified with Prussian Blue (G/PB) were obtained by spreading, on the electrode surface, appropriate
volumes of 100 mM K3[Fe(CN)6] and 100 mM FeCl3 solutions, both containing 10 mM HCl. In order to improve the electrochemical response stability, the potential of G/PB electrodes
was cycled (in the domain where PB exhibits electrochemical activity) in 0.1 M KCl solution (G/PB-K), as well as in 2 mM RhCl3 solution, containing 0.05 M KCl (G/PB-Rh). Compared with G/PB-K, the G/PB-Rh modified electrodes showed: (i) higher relative
stability of the PB electrochemical response; (ii) better analytical parameters for H2O2 amperometric detection; (iii) slightly lower rate constant corresponding to the second order electrocatalytic reaction for
H2O2 amperometric detection; (iv) an electrocatalytic activity not affected by the H2O2 concentration. 相似文献
5.
In this work, the oxidative polycondensation reaction conditions of benzylidene-4′-hydroxyanilene (B-4′-HA) were studied using oxidants such as air O2, H2O2 and NaOCl in an aqueous alkaline medium between 40 and 95 ○C. Oligo-benzylidene-4′-hydroxyanilene was characterized by 1H-NMR, FT-IR, UV-Vis, size exclusion chromatography (SEC) and elemental analysis techniques. The solubility of oligomer using organic solvents such as DMF, THF, DMSO, methanol, ethanol, CHCl3, CCl4, toluene, acetonitrile, ethyl acetate was investigated. According to air O2 oxidant (flow rate 8.5 L/h), the conversion of B-4′-HA was 82.0% in optimum conditions such as [B-4′-HA]0=[KOH]0=0.1015 mol/L at 50 ○C for 25 h. According to the SEC analysis, the number-average molecular weight (Mn), weight-average molecular weight (Mw) and polydispersity index (PDI) values of O-B-4′-HA were found to be 1852 g mol−1, 3101 g mol−1 and 1.675; 2123 g mol−1, 4073 g mol−1 and 1.919; 2155 g mol−1, 4164 g mol−1 and 1.932, using air oxygen, NaOCl and H2O2 oxidants, respectively. Also, Thermo gravimetric analysis (TGA) showed oligo-benzylidene-4′-hydroxyanilene to be unstable against thermo-oxidative decomposition. The weight loss of O-B-4′-HA was found to be 95.87% at 1000 ○C. 相似文献
6.
The sulfur removing capacities of various Zn-Ti-based sorbents were investigated in the presence of H2O and HCl at high-(sulfidation, 650 °C; regeneration, 800 °C) and medium-(sulfidation, 480 °C; regeneration, 580 °C) temperature
conditions. The H2O effect of all sorbents was not observed at high-temperature conditions. At mediumtemperature conditions, the reaction rate
of ZT (Zn/Ti : 1.5) sorbent decreased with the level of H2O concentration, while modified (ZTC, ZTN) sorbents were not affected by the water vapor. HCl vapor resulted in the deactivation
of ZT sorbent with a cycle number at high-temperature due to the production of ZnCl2 while the sulfur removing capacities of ZTC and ZTN sorbents were maintained during 4–5 cyclic tests. In the case of medium-temperature
conditions, ZT sorbent was poisoned by HCl vapor while cobalt and nickel added to ZT sorbent played an important catalytic
role to prevent from being poisoned by HCl due to providing heat, emitted when these additives quickly react with H2S even at medium-temperature conditions, to the sorbents 相似文献
7.
An H2O/dimethyl sulphoxide (DMSO) mixture was used as the coagulation bath of a wet-spun process. The diffusion coefficient of H2O in the protofibers prepared by acrylonitrile homopolymers was determined. It was found that the diffusion coefficient of H2O in the protofibers prepared by homopolymers synthesized by solution polymerization was highest compared with those of homopolymers synthesized by H2O/DMSO mixture suspension polymerization and aqueous suspension polymerization. With an increase of polyacrylonitrile concentration in the dope, the diffusion coefficient of H2O decreased continuously. The diffusion coefficient of H2O increased along with the bath temperature, but the changes of diffusion coefficient values were less prominent as the temperature went beyond 60 ○C. When the DMSO concentration in the coagulation bath was 55%, the value of the diffusion coefficient of H2O was minimal. The diffusion coefficient of H2O increased with increasing jet stretch minus ratio. When the protofiber radius was increased, there was a corresponding increase of the diffusion coefficient of H2O. 相似文献
8.
CO impedes the low temperature (<170 °C) oxidation of C3H6 on supported Pt. Supported Au catalysts are very effective in the removal of CO by oxidation, although it has little propene oxidation activity under these conditions. Addition of Au/TiO2 to Pt/Al2O3 either as a physical mixture or as a pre-catalyst removes the CO and lowers the light-off temperature (T
50) for C3H6 oxidation compared with Pt catalyst alone by ~54 °C in a feed of 1% CO, 400 ppm C3H6, 14% O2, 2% H2O. 相似文献
9.
Sukjeong Choi Kyuchul Shin Jong-Ho Cha Huen Lee 《Korean Journal of Chemical Engineering》2008,25(6):1397-1400
We demonstrate the spectroscopic observation of H2 migration in the binary structure-I (sI) clathrate hydrate. The H2 molecules captured into sI small cage (sI-S) at lower temperature migrate to sI large cage (sI-L) through shared pentagonal
face of 51262 cage. The hexagonal faces of 51262 cage provide the windows essential for creating continuous diffusion paths for H2 molecules. It is essential to realize that the vacant channels formed by the linkage of specific cages can play an important
role in guest diffusion pathways and occupancy occurring in a complex clathrate hydrate matrix. 相似文献
10.
Jun Li Xianyou Wang Qinghua Huang Chunling Dai Sergio Gamboa P. J. Sebastian 《Journal of Applied Electrochemistry》2007,37(10):1129-1135
A series of RuO2 · xH2O/carbon aerogel (CA) composite electrode materials was prepared by a chemical precipitation method. Ultrasonication was used
to accelerate the chemical reaction and improve the dispersion of RuO2 · xH2O particles on the surface and the pores of the aerogel. The structure and morphology of the as-prepared composite were characterized
by N2 adsorption isotherm, X-ray diffraction (XRD), and field emission-scanning electron microscopy (FE-SEM). The results showed
that the CA had a pearly network structure and the composites had a relatively high specific surface area and mesopore volume.
The electrochemical performance of the composite electrodes was studied by cyclic voltammetry, galvanostatic charge/discharge
measurements and electrochemical impedance measurements. The results indicated a substantial increase in the specific capacitance
of the composite. Moreover, the utilization efficiency of RuO2 · xH2O was greatly improved by loading it on the conductive and porous CA due to a significant improvement in the inter-particle
electronic conductivity and the extensive mesoporous network of the composites. 相似文献
11.
Role of some thiadiazole derivatives as inhibitors for the corrosion of C-steel in 1 M H<Subscript>2</Subscript>SO<Subscript>4</Subscript> 总被引:1,自引:0,他引:1
Inhibition of C-steel corrosion by some thiadiazole derivatives (I–VI) in 1 M H2SO4 was investigated by weight loss, potentiodynamic polarization, linear polarization resistance (LPR) and electrochemical impedance
spectroscopy (EIS) techniques. The presence of these compounds in the solution decreases the double layer capacitance, increases
the charge transfer resistance and increase of linear polarization. Polarization studies were carried out at room temperature,
and showed that all the compounds studied are mixed type inhibitors with a slight predominance of cathodic character. The
effect of temperature on corrosion inhibition has been studied and the thermodynamic activation and adsorption parameters
were calculated and discussed. Electrochemical impedance was used to investigate the mechanism of corrosion inhibition. The
adsorption of the compounds on C-steel was found to obey Langmuir’s adsorption isotherm. The synergistic effect brought about
by combination of the inhibitors and KSCN, KI and KBr was examined and explained. The mechanism of inhibition process was
discussed in the light of the chemical structure and quantum-chemical calculations of the investigated inhibitors. 相似文献
12.
A layered LiNi0.8Co0.2O2 solid solution, which is a promising cathode material for secondary lithium batteries, was successfully synthesized by an emulsion drying method. Because electrochemical properties significantly depend on the conditions of the synthesis, the calcination temperature was carefully determined on the basis of X-ray diffraction and TG studies. The prepared cathodes were characterized by means of SEM, BET, X-ray diffraction, Rietveld refinement, cyclic voltammetry and a charge-discharge experiment. From the Rietveld analysis, it was found that powder calcined at 800 °C for 12 h exhibits a well ordered and lower cation mixed layered structure than the others. The cyclic voltammetry experiment shows that phase transformation can be suppressed considerably by increasing the calcination temperature to 800 °C. The highest discharge capacity of 188.4 mA h g−1 was obtained from the sample prepared at 800 °C. Furthermore, a high capacity retention ratio of 88.1% was found for the initial value after 50 cycles at a constant current density of 40 mA g−1 between 2.7 VLi/Li+ and 4.3 VLi/Li+. In the rate capability test, the cathode delivered a higher discharge capacity of 153.1 mA h g−1 at a 4 C (800 mA g−1) rate. 相似文献
13.
Min Kang Jinsoon Choi Yong Tae Kim Eun Duck Park Chee Burm Shin Dong Jin Suh Jae Eui Yie 《Korean Journal of Chemical Engineering》2009,26(3):884-889
A series of V2O5-TiO2 aerogel catalysts were prepared by the sol-gel method with subsequent supercritical drying with CO2. The main variables in the sol-gel method were the amounts of V2O5 and when the vanadium precursor was introduced. V2O5-TiO2 xerogel and V2O5/TiO2 (P-25) were also prepared for comparison. The V2O5-TiO2 aerogel catalysts showed much higher surface areas and total pore volumes than V2O5-TiO2 xerogel and impregnated V2O5/TiO2 (P-25) catalysts. The catalysts were characterized by N2 physisorption, X-ray diffraction (XRD), FT-Raman spectroscopy, temperature-programmed reduction with H2 (H2-TPR), and temperature-programmed desorption of ammonia (NH3-TPD). The selective catalytic reduction of NOx with ammonia in the presence of excess O2 was studied over these catalysts. Among various V2O5-TiO2 catalysts, V2O5 supported on aerogel TiO2 showed a wide temperature window exhibiting high NOx conversions. This superior catalytic activity is closely related to
the large amounts of strong acidic sites as well as the surface vanadium species with characteristics such as easy reducibility
and monomeric and polymeric vanadia surface species.
This work was presented at the 7
th
Korea-China Workshop on Clean Energy Technology held at Taiyuan, Shanxi, China, June 26–28, 2008. 相似文献
14.
Vanadium oxide supported on zirconia modified with WO3 was prepared by adding Zr(OH)4 powder into a mixed aqueous solution of ammonium metavanadate and ammonium metatungstate followed by drying and calcining
at high temperatures. The characterization of prepared catalysts was performed by using FTIR, Raman, and XRD. In the case
of calcination temperature at 773 K, for samples containing low loading V2O5 below 18 wt%, vanadium oxide was in a highly dispersed state, while for samples containing high loading V2O5 equal to or above 18 wt%, vanadium oxide was well crystallized due to the high V2O5 loading on the surface of ZrO2. The ZrV2O7 compound was formed through the reaction of V2O5 and ZrO2 at 873 K, and the compound decomposed into V2O5 and ZrO2 at 1,073 K, these results were confirmed by FTIR and XRD. Catalytic tests for 2-propanol dehydration and cumene dealkylation
have shown that the addition of WO3 to V2O5/ZrO2 enhanced both catalytic activity and acidity of V2O5-WO3/ZrO2 catalysts. The variations in catalytic activities for both reactions are roughly correlated with the changes of acidity. 相似文献
15.
The present paper reports the effects of N2 addition and preheating of reactants on bluff-body stabilized coaxial LPG jet diffusion flame for two cases, namely, (I)
preheated air and (II) preheated air and fuel. Experimental results confirm that N2 addition to the fuel stream leads to an enhancement in flame length, which may be attributed to the reduction in flame temperature.
The soot free length fraction (SFLF) also increases, which might be caused by the decrease in fuel concentration and flame
temperature. The flame length and also the SFLF are observed to be reduced with increasing temperature of reactants and lip
thickness of the bluff body. The NO
x
emission level for all burner configurations are found to be attenuated with nitrogen addition, which can be attributed to
the reduction of the residence time of the gas mixture in the flame. The emission index of NO
x
(EINO
x
) also becomes enhanced with increasing lip thickness and reactant temperature due to an increased residence time and thermal
effect, respectively.
__________
Translated from Fizika Goreniya i Vzryva, Vol. 45, No. 1, pp. 3–10, January–February, 2009. 相似文献
16.
A. A. Konnov 《Combustion, Explosion, and Shock Waves》2008,44(5):497-501
The measurements of NO concentrations in the post-flame zone of different hydrocarbon + O2 + N2 flames at standard temperature and atmospheric pressure available in the literature are compared with predictions of the
original Konnov reaction mechanism and with the same mechanism extended by the reaction of C2O with N2. The goal was to investigate the possible role of this reaction proposed by Williams and Fleming [Proc. Combust. Inst., Vol. 31 (2007), pp. 1109–1117]. This new reaction of C2O with N2 seems to be a reasonable explanation of the deficiencies in the prompt-NO route. Direct comparisons of the experimental measurements
performed in different flames with the modeling strongly suggests that the upper limit of this reaction rate constant is k = 7 · 1011 exp(−17,000/RT) [cm3/(mole · sec)].
__________
Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 5, pp. 3–7, September–October, 2008. 相似文献
17.
Massimo Fabris Cindy Aquino Antony J. Ward Alvise Perosa Thomas Maschmeyer Maurizio Selva 《Topics in Catalysis》2009,52(3):315-321
In this contribution we describe the use of heterogeneous catalysts for the liquid-phase self-metathesis of 1-octene in supercritical
CO2. Our work aims at addressing the mass-transfer problems associated with such reaction systems. By coupling a heterogeneous
supported Re2O7 catalyst with the use of scCO2, the self-metathesis of 1-octene takes place by and large much more rapidly than in traditional solvent media, and furthermore,
by using scCO2 the overall efficiency and sustainability of the transformation can be improved.
相似文献
Maurizio Selva (Corresponding author)Email: |
18.
The maximization of the total surface area of Pt-SnO2/Al2O3 catalyst was studied by using the Taguchi method of experimental design. The catalysts were prepared by sol-gel method. The
effects of HNO3, H2O and aluminum nitrate concentrations and the stirring rate on the total surface area were studied at three levels of each.
L9 orthogonal array leading nine experiments was used in the experimental design. The parameter levels that give maximum total
surface area were determined and experimentally verified. In the range of conditions studied it was found that, medium levels
of HNO3 and H2O concentration and lower levels of aluminum nitrate concentration and stirring rate maximize the total surface area. 相似文献
19.
Jeong Gil Seo Min Hye Youn Kyung Min Cho Sunyoung Park Sang Hee Lee Joohyung Lee In Kyu Song 《Korean Journal of Chemical Engineering》2008,25(1):41-45
An Al2O3-ZrO2 xerogel (AZ-SG) was prepared by a sol-gel method for use as a support for a nickel catalyst. The Ni/AZ-SG catalyst was then
prepared by an impregnation method, and was applied to hydrogen production by steam reforming of LNG. A nickel catalyst supported
on commercial alumina (A-C) was also prepared (Ni/A-C) for comparison. The hydroxyl-rich surface of the AZ-SG support increased
the dispersion of nickel species on the support during the calcination step. The formation of a surface nickel aluminate-like
phase in the Ni/AZ-SG catalyst greatly enhanced the reducibility of the Ni/AZ-SG catalyst. The ZrO2 in the AZ-SG support increased the adsorption of steam onto the support and the subsequent spillover of steam from the support
to the active nickel sites in the Ni/AZ-SG catalyst. Both the high surface area and the well-developed mesoporosity of the
Ni/AZ-SG catalyst improved the gasification of adsorbed surface hydrocarbons in the reaction. In the steam reforming of LNG,
the Ni/AZ-SG catalyst showed a better catalytic performance than the Ni/A-C catalyst. Moreover, the Ni/AZ-SG catalyst showed
strong resistance toward catalyst deactivation. 相似文献
20.
The V/MgO catalysts with different V2O5 loadings were prepared by impregnating MgO with aqueous vanadyl sulfate solution. All of the catalysts were characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). It was observed that the H2S removal capacity with respect to vanadia content increased up to 6 wt%, and then decreased with further increase in vanadia loading. The prepared catalysts had BET surface areas of 11.3 ~ 95.9 m2/g and surface coverages of V2O5 of 0.1 ~ 2.97. The surface coverage calculation of V2O5 suggested that a vanadia addition up to a monomolecular layer on MgO support increased the H2S removal capacity of V/MgO, but the further increase of VO
x
surface coverage rather decreased that. Raman spectroscopy showed that the small domains of Mg3(VO4)2 could be present on V/MgO with less than 6 wt% vanadia loading. The crystallites of bulk Mg3(VO4)2 and Mg2(V2O7) became evident on V/MgO catalysts with vanadia loading above 15 wt%, which were confirmed by a XRD. The TPR experiments showed that V/MgO catalysts with the loading below 6 wt% V2O5 were more reducible than those above 15 wt% V2O5. It indicated that tetrahedrally coordinated V5+ in well-dispersed Mg3(VO4)2 domains could be the active species in the H2S wet oxidation. The XPS studies indicated that the H2S oxidation with V/MgO could proceed from the redox mechanism (V5+ V4+) and that V3+ formation, deep reduction, was responsible for the deactivation of V/MgO. 相似文献