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1.
(CuO)1–z(La2O3)z/2 based catalysts with 0.0z1.0 supported on -Al2O3 have been prepared in situ and the phases formed have been identified by XRD, SEM and TEM/EDS studies. The catalyst with z=0.5 exhibited the best catalytic activity for oxidation of CO (T 50=295 and 390C with degrees of conversions of 93 and 92% at 450C under rich and lean conditions, respectively) and C3H6 (291 and 414C; 93 and 83%) and reduction of NO (405C; 60 and 0%). This catalyst contained appreciable amounts of the perovskite phase LaAl1–xCuxO3 and the enhanced catalytic properties are ascribed to the presence of this phase. Addition of Pd to this catalyst implied that the degree of conversion of NO increased and that the light-off temperatures for all involved gas species decreased. Ageing experiments revealed that LaAl1–xCuxO3 decomposed and that Cu containing Pd particles were formed during this procedure which in turn deteriorated the catalytic properties of the catalyst.  相似文献   

2.
Vapor phase hydroformylation of ethylene was studied with silica-supported metal catalysts. A cobalt metal catalyst derived from Co2(CO)8 gave propanal and its derivatives in as high selectivity of about 36% as Rh/SiO2 catalyst under the reaction conditions of 1.1 MPa of a gas-mixture of ArCOC2H4H2 = 1333 at 423–503 K. On the other hand, conventional cobalt catalysts derived from cobalt nitrate, chloride, or acetate, and other noble metal catalysts (Pd/SiO2 and Ir/SiO2) produced mainly ethane.  相似文献   

3.
The promotion of Ag/-Al2O3 by adding alkali metals (Li, Na, K, Cs) for selective catalytic reduction of NO with C3H6 was studied in this work. The activity of NO reduction was enhanced by addition of Cs to Ag/-Al2O3 in the presence of excess oxygen and SO2. The stability and growth of silver oxide particles were promoted and the dispersion of silver particles on -Al2O3 was improved by the addition of 0.5 wt% Cs and 1 wt% Cs to 2 wt% Ag/-Al2O3, respectively. The results were confirmed by H2 TPR, UV-Vis DRS, TEM, and XPS.  相似文献   

4.
Poly[1-methyl-1-[3-(3-pyridinyl)propyl]-1-sila-cis-pent-3-ene], poly[1-phenyl-1-[3-(3-pyridinyl)propyl)-1-sila-cis-pent-3-ene], and poly[1-phenyl-1-(4-pyridinyl)-1-sila-cis-pent-3-ene] were synthesized by the anionic ring-opening polymerization of 1-methyl-1-[3-(3-pyridinyl)propyl]-1-silacyclopent-3-ene, 1-phenyl-1-[3-(3-pyridinyl)propyl]-1-silacyclopent-3-ene, and 1-phenyl-1-(4-pyridinyl)-1-silacyclopent-3-ene, respectively. These are the first polycarbosilanes which contain heterocyclic pyridine units as side-chain substituents. These polymers were characterized by1H,13C, and29Si NMR as well as by IR and UV spectroscopy. The molecular weight distributions were determined by gel permeation chromatography, glass transition temperatures, by differential seanning calorimetry: (DSC) and thermal behavior, by thermogravimetric analysis. (TGA).  相似文献   

5.
H. He  H.X. Dai  K.Y. Ngan  C.T. Au 《Catalysis Letters》2001,71(3-4):147-153
The physico-chemical properties of passivated -Mo2N have been investigated. The material showed high activities for NO direct decomposition: nearly 100% NO conversion and 95% N2 selectivity were achieved at 450C. The amount of O2 taken up by -Mo2N increased with temperature rise and reached 3133.9 molg–1 at 450C; we conclude that there formation of Mo2OxNy occurred. This oxygen-saturated -Mo2N material was catalytically active: NO conversion and N2 selectivity were 89 and 92% at 450C. We found that by means of H2 reduction at 450C, Mo2OxNy could be reduced back to -Mo2N and the oxidation/reduction cycle is repeatable; such a behaviour and the high oxygen capacity (3133.9 molg–1) of -Mo2N suggest that -Mo2N is a promising catalytic material for automobile exhaust purification.  相似文献   

6.
Two sex pheromone components, 3(Z),6(Z),9(Z)-nonadecatriene (3Z,6Z,9Z-19 H), and 3(Z),6(Z),9(Z)-eicosatriene (3Z,6Z,9Z-20 H), have been positively identified, and a third component, 6(Z),9(Z)-nonadecadiene (6(Z),9(Z)-19 H) has been tentatively identified from abdominal tip extracts of female spring cankerworm moths,Paleacrita vernata Peck (Lepidoptera Geometridae). The pheromone components were identified by a combination of gas chromatography, electroantennography, mass spectrometry, chemical tests, comparison with standards, and field testing. Only 3Z,6Z,9Z-20 H exhibited significant attractant activity when tested alone, and it was potentiated by the other two components. The attractive blend was an 821 ratio of 3Z,6Z,9Z-20H/3Z,6Z,9Z-19H/6Z,9Z-19H. However, the two-component blend of 3Z,6Z,9Z-20 H and 6Z,9Z-19 H (81 ratio) was as attractive as the three-component blend in further field tests. A series of related compounds, the diene monoepoxides available from epoxidation of C19 and C20 3Z,6Z,9Z-trienes, some of which have been found in the pheromone blends of other moth species, were tested as behavioral antagonists. The attraction of male moths to synthetic lures was suppressed by the addition of 6Z,9Z-cis-3,4-epoxy-nonadecadiene to the lures. Additional experiments were performed to determine the effects of lure dosage, trap height, and trap design on the numbers of male moths captured.Issued as NRCC 30711.  相似文献   

7.
F. Gracia  W. Li  E.E. Wolf 《Catalysis Letters》2003,89(3-4):235-242
From EXAFS (extended X-ray absorption fine structure) analysis, gold was found to have mainly oxygen in its nearest coordination shell in the fresh Au/-Al2O3 catalyst prepared by AuCl3 impregnation and vacuum drying at room temperature. After thermal treatment under helium, chlorine appeared within the nearest neighbors of gold and more chlorine showed up as the treatment temperature was increased from 323 to 473K. No reduced Au species was observed up to 473K under He. However, the gold became reduced during CO oxidation at 373K and above. The precursor AuCl3 was found to deposit on -Al2O3 via bonding to surface hydroxyl groups. This catalyst showed nearly 100% CO conversion at 573K, but a very low activity at 373 K under the conditions used in this study. Neither the residual chlorine nor the extent of reduction can explain the low activity at lower temperatures.  相似文献   

8.
To study the influence of steam on the solid state reaction between MeO (Me = Ni, Co, Cu or Fe) and Al2O3, MeO/-Al2O3 and MeO/-Al2O3 model catalysts were kept in either N2/20% O2 or N2/O2/30% H2O at 500–1000°C. The samples were subsequently analyzed with RBS and FTIR. Surprisingly, nickel, cobalt and copper volatilized when MeO/-Al2O3 or MeAl2U4/-Al2O3 samples were annealed in the presence of 0.3 atm steam at 1000°C. Especially copper was found to volatilize very rapidly in the presence of steam, even at a temperature as low as 800°C. FTIR spectra of steam-treated NiO/-Al2O3 samples showed the incorporation of hydroxyl groups in the nickel oxide layer. This observation and an excellent agreement with thermochemical calculations support our conclusion that the volatile species are metal hydroxides. The solid state reaction of MeO with-Al2O3 was found to proceed at a much higher rate in the presence of 0.3 atm steam at 500–800°C, presumably as a result of an enhanced surface mobility of Me and Al ions along the grain boundaries and the surfaces of the internal pores of the-Al2O3 support, when steam is present.  相似文献   

9.
The catalytic activity and selectivity of three PdO-MoO3/-Al2O3 catalysts containing about 2% Pd and 2% Mo were studied for the reduction of NO by h2 in the presence of varying amounts of oxygen at temperatures from 50 to 550 °C. The results are compared with those for PdO/-Al2O3, PdO-MoO3/-Al2O3 containing 2% Pd and 20% Mo, and a commercial Pt-Rh catalyst. In the absence of oxygen, the conversion of NO to N2 and N2O is higher on the three catalysts than it is on PdO/-Al2O3 at 500 and 550 °C. In the presence of oxygen, the yields of N2 and N2O are generally lower on two of the PdO-MoO3/-Al2O3 catalysts than on PdO/-Al2O3.  相似文献   

10.
A series of Al2O3-SnO2 catalysts with the mole ratio of Al2O3 to SnO2 equal to 1:1, 1 0.5, 1 0.1, 1 0.05 and 1 0.01 were characterized by31P NMR of adsorbed trimethyl phosphine (TMP) and119Sn MAS NMR spectroscopy. It was found from31P NMR that no Brønsted acid sites exist in these samples. Pure SnO2 shows two different types of Lewis acid sites; in the mixed oxide samples a Lewis peak characteristic of pure Al2O3 is always seen, together with either one or two other Lewis peaks, depending on the Sn concentration.119Sn CP/MAS NMR spectra of the highest Sn-content sample show one narrow line at –603 ppm superimposed on a very broad line, indicating a strong interaction between Al and Sn oxides.  相似文献   

11.
Anisotropic oxidation of crystallites of vanadyl pyrophosphate ((VO)2P2O7) has been demonstrated by Raman spectroscopy with samples having different microstructures. Oxidation of these samples by O2 produced X1 phase,- and-VOPO4 phases. The relative peak intensity of the X1 phase to the other phases correlated well with the ratio of the (100) plane to the side planes (surface area-basis). This correlation showed that the (100) plane was oxidized to X1 phase and the side planes to- and-VOPO4. For example, thin plate-like (VO)2P2O7, of which the (100) fraction is 98%, was oxidized almost exclusively to X1 phase. But when it was fractured into small plates to increase the side planes and then oxidized,- and-VOPO4 were detected in addition to the X1 phase. These results are consistent with our previous conclusion that the (100) plane of (VO)2P2O7 is selective, but side planes are non-selective for catalytic oxidation ofn-butane.  相似文献   

12.
Barthos  R.  Lónyi  F.  Engelhardt  J.  Valyon  J. 《Topics in Catalysis》2000,10(1-2):79-87
Protonated pyridine (PyH+) was not found on ZrO2 (Z) or ZrO2–TiO2 (ZT), but was detected on sulfated oxides (ZS, ZTS) by IR spectroscopy. In contrast, ZrO2–SiO2 samples containing about 30–80 mol% ZrO2 showed Brønsted acidity both in nonsulfated (ZS) and sulfated (ZSS) forms. The total acidity was determined by NH3TPD. Introduction of sulfate ions increased the sitespecific catalytic activity (TOF) in the conversion of cyclopropane or nhexane. The effect of sulfate ions was more significant on samples rich in zirconia. Results suggest that Zr is homogeneously distributed in ZS samples rich in silica. Zirconiabound dimeric sulfate, generating strong acidity, could not be formed in these preparations due to the absence of fairly large ZrO2 domains.  相似文献   

13.
Laboratory bioassays and field tests demonstrated that a Swiss population ofS. multistriatus responded much more strongly to - than to -miltistriatin in combination with 4-methyl-3-heptanol and -cubebene. High concentrations of brevicomin appeared to replace -multistriatin in evoking a response byScolytus species, but this effect can be explained by the fact that the brevicomin was contiminated with small amounts of -multistriatin. Frontalin, another bicyclic ketal, showed no biological activity. Field tests indicated thatS. pygmaeus aggregates to the same attractant mixture asS. multistriatus. S. scolytus also responded preferentially to this mixture, but the relative amounts of -multistriatin to 4-methyl-3-heptanol do not appear to be as important as forS. multistriatus.  相似文献   

14.
The sulphidation of a CoMo/Al2O3 hydrotreating catalyst was studied under pressure and flow conditions close to industrial practice. The sulphiding mixture contained equal amounts of H2S and CH4 diluted in hydrogen under 3.9 MPa total pressure. The oxidic precursor was flushed by the reagent gas at 40°C for 10 h, then the temperature was raised to 400°C within 2 h. Mass variation was continuously recorded by means of a suspension magnetic balance, and the gas phase was analysed by mass spectrometry. Sulphur contents were also determined at intermediate temperatures by chemical analyses. Thus, mass variations due to the presence of adsorbed species or to the formation of CoMo sulphides could be distinguished. The rapid gain in mass noted at 40°C was mostly due to adsorption of H2S over the oxidic solid, since it increased with H2S partial pressure. At this stage, however, a small amount of the reactive oxygen was already exchanged for sulphur. Upon raising the temperature, the mass decreased due to a combination of desorption and sulphiding steps. Above 140°C, H2S consumption was evidenced, together with water production, and the rate of sulphiding increased with the H2S partial pressure. At 300°C, the mass variation was close to that expected for complete transformation into Co9S8 and MoS2. Above 350°C, the mass further increased due to the replacement of adsorbed water by H2S. At 400°C, an important excess mass was observed at all H2S partial pressures. Thus, the adsorption sites on the metal sulphides are essentially saturated by H2S species under practical conditions.  相似文献   

15.
Summary Asymmetrically disubstituted poly(2-isopropoxy-5-methoxy-1,4-phenylene-vinylene), PIMPV, was prepared in thin films via organic-soluble precursor polymer method. These polymer films could be easily stretched up to 7 times, and the drawn films of the PIMPV could be doped with FeCl3 and I2 to give conductivities of 26.9 and 11.3 Scm-1, respectively. The third-order nonlinear optical susceptibility of the polymer was determined using third harmonic generation(THG) method at 1907 nm, fundamental wavelength. Measured (30) (-3: , , ) value was 3.7x10-12 esu.  相似文献   

16.
ESR and XPS are used to study the Mo-based catalysts MoO3/K2CO3/SiO2 and K2MoO4/SiO2 prepared with two kinds of precursors, (NH4)6Mo7O244H2O and K2MoO4. The catalytic properties of the catalysts for methanethiol synthesis from high H2S-containing syngas are explored. The activity assay shows that the two catalysts have much the same activity for the reaction. By the ESR characterization of both functioning catalysts, the resonant signals of oxo-Mo(V) (g=1.93), thio-Mo(V) (g=1.98) and S (g=2.01 or 2.04) can be detected. In the catalyst MoO3/SiO2 modified with K2CO3, as increasing amounts of K2CO3 are added, the content of oxo-Mo(V) increases, but thio-Mo(V) decreases. The XPS characterization indicates that Mo has mixed valence states of Mo4+, Mo5+ and Mo6+, and that S includes three kinds of species: S2– (161.5 eV), [S–S]2– (162.5 eV) and S6+ (168.5 eV). Adding K2CO3 promoter to the catalysts, the Mo species of high valence state is easily sulphided and reduced to Mo2S and oxo-M(V), and the derivation of [S–S]2– and S2– species from S is promoted simultaneously. The methanethiol synthesis is favored if the mole ratio of (Mo6+ + Mo5+)/Mo4+ 0.8 and S2–/[S–S]2– is kept at a value of about 1.  相似文献   

17.
Males of the redbanded leafroller,Argyrotaenia velutinana (Walker) (Lepidoptera: Tortricidae), were studied for their behavioral responses in laboratory olfactometers and in the field to the 3 components of the female-produced sex pheromone:cis-11-tetradecenyl acetate (c11–14Ac),trans-11-tetradecenyl acetate (t11–14Ac), and dodecyl acetate (12Ac). Dodecyl acetate, when evaporated with c11–14Ac (8%trans) in the field, modified the behavior of feral males nearby the chemical source, causing an increase in the frequency of landing and close approach to the pheromone dispenser. Apparently, an inflight behavioral modification concerning landing or not landing occurs within 60 cm of the source and is mediated by 12Ac. In laboratory olfactometers, c11–14Ac (8%trans) demonstrated a lower threshold for male activation than pure c11- and t11–14Ac and blends of the two isomers. Additionally, over a wide range of dosages, males responded with optimum wing-fanning response to c11–14Ac (8%trans) compared to pure c11–14Ac, c11–14:Ac (30%trans), and pure t11–14Ac, suggesting that thecistrans ratio rather than absolute amounts of either isomer, is a crucial factor in eliciting male response. When presented with c11–14Ac (8%trans) (11), dodecyl acetate caused a significant prolongation of wing-fanning over c11–14Ac (8%trans) alone and resulted in a greater percentage of males moving upwind to the source. Since the increase in wing-fanning and orientation occurred at higher concentrations of the 3-component mixture, the effect of 12Ac in the laboratory may reflect the close-range role of 12Ac in the field.  相似文献   

18.
Three-arm star polyisobutylene ionomers (¯Mn=8800) with terminal SO3 M (M=K or Ca2) groups were synthesized and their mechanical properties investigated. Compression molded films displayed high elongations, i.e., -1000% for Ca2 ionomers with lower values for the K counterions. Strain induced crystallinity was observed at higher elongations. Mechanical properties in general compared favorably with conventional covalently linked rubbery networks and were comparable and in some cases superior to EPDM-based ionomers carrying randomly distributed SO3 M groups.For the first two parts see Proceedings, 28th IUPAC Macromolecular Symposium, Amherst, MA, July 11–16, 1982, p. 905 and 906  相似文献   

19.
Mudcrack-free oxide films of Ir x Ti1–x O2 (0 < x 1) on titanium substrates were obtained, and the effects of the oxide composition on the rate of oxygen-evolution reaction were investigated. At x 0.6, Ir-rich grains appear on the mudcrack-free surface. In the purely single-phase region (0 < x 0.5), the pseudo-capacitive charge is proportional to the surface composition, x s, and the exchange-current density for the oxygen-evolution reaction increases linearly with x s at 0.2 x s 0.5, with an extrapolated intercept at x s 0.15, below which the oxides are inactive.  相似文献   

20.
The enantioselective hydrogenation of ethyl pyruvate to (S)-ethyl lactate over cinchonine- and -isocinchonine-modified Pt/Al2O3 catalysts was studied as a function of modifier concentration and reaction temperature. The maximum enantioselectivities obtained under the applied mild conditions were 89% ee using cinchonine (0.014 mmoldm–3, 1 bar H2, 23°C, 6% AcOH in toluene), and 76% ee in the case of -isocinchonine (0.14 mmoldm–3, 1 bar H2, –10°C, 6% AcOH in toluene). Since -isocinchonine of rigid structure exists only in anti-open conformation these data provide additional experimental evidence to support the former suggestion concerning the dominating role of anti-open conformation in these cinchona-modified enantioselective hydrogenations.  相似文献   

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