Using a mixture of NO + O2 as the oxidant enabled the direct selective oxidation of methane to dimethyl ether (DME) over Pt/Y2O3. The reaction was carried out in a fixed bed reactor at 0.1 MPa over a temperature range of 275–375 °C. During the activity tests, the only carbon‐containing products were DME and CO2. The DME productivity (μmol gcat?1 h?1) was comparable to oxygenate productivities reported in the literature for strong oxidants (N2O, H2O2, O3). The NO + O2 mixture formed NO2, which acted as the oxygen atom carrier for the ultimate oxidant O2. During the methane partial oxidation reaction, NO and NO2 were not reduced to N2. In situ FTIR showed the formation of surface nitrate species, which are considered to be key intermediate species for the selective oxidation. 相似文献
AbstractThree novel dammarane-type saponins, 2α,3β,12β,20(S),24(S)-pentahydroxydammar-25-ene-3-O-β-D-glucopyranosyl-(1→2)-β-D-glucopyranosyl-20-O-β-D-glucopyranoside (1, namely gypenoside J1), 2α,3β,12β,20(S),25-pentahydroxydammar-23-ene-3-O-β-D-glucopyranosyl-(1→2)-β-D-glucopyranosyl-20-O-β-D-glucopyranoside (2, namely gypenoside J2) and 2α,3β,12β,20(S)-tetrahydroxydammar-25-en-24-one-3-O-β-D-glucopyranosyl-(1→2)-β-D-glucopyranosyl-20-O-β-D-xylopyranosyl-(1→6)-β-D-glucopyranoside (3, namely gypenoside J3) along with one known gypenoside (gypenoside LVII) were isolated from the aerial parts of G. pentaphyllum using various chromatographic methods. Their structures were elucidated on the basis of IR, 1D- (1H and 13C), 2D-NMR spectroscopy (HSQC, HMBC and COSY), and mass spectrometry (ESI-MS/MS). Their activity was tested using CCK-8 assay. These four compounds showed little anti-cancer activity with IC50 values more than 100?μM against four types of human cancer lines. The effects of them against H2O2-induced oxidative stress in human neuroblastoma SH-SY5Y cells were evaluated and they all showed potential neuroprotective effects with 3.64–18.16% higher cell viability than the H2O2-induced model group. 相似文献
In this study, factors affecting the crystal structure of flame-synthesized Y 2 O 3 :Eu particles were inves- tigated, especially the particle size effect and its interaction with Eu doping concentration. Polydisperse Y 2 O 3 :Eu (size range 200 nm to 3 m) powder samples with Eu doping concentrations from 2.5 mol% to 25 mol% were generated in either H 2 /air or H 2 /O 2 substrate-free flames. The crystal structure of the powder samples was determined by powder X-ray diffraction (XRD), which was complemented... 相似文献
The procedure of microphase adsorption–spectral correction is applied to the interaction of eosine Y (EO) to the micelles of cetyl trimethyl ammonium bromide (CTAB). The Langmuir aggregation of EO on CTAB occurs owing to microelectrostatic attraction. The results have shown that at pH 3.8, monomeric and micellar aggregates have the structure EO5·CTAB2 and (EO5·CTAB2)39. The adsorption constant of an aggregate is 7.01·105, its molar absorption coefficient is = 8.8·104 liters·mole–1·cm–1 at 550 nm. Application of the aggregation of EO on CTAB gives satisfactory results for quantitative determination of cation surfaceactive agents (surfactants). 相似文献
In univariate Padé approximation we learn from the Froissart phenomenon that Padé approximants to perturbed Taylor series exhibit almost cancelling pole–zero combinations that are unwanted. The location of these pole–zero doublets was recently characterized for rational functions by the so‐called Froissart polynomial. In this paper the occurrence of the Froissart phenomenon is explored for the first time in a multivariate setting. Several obvious questions arise. Which definition of Padé approximant is to be used? Which multivariate rational functions should be investigated? When considering univariate projections of these functions, our analysis confirms the univariate results obtained so far in [13], under the condition that the noise is added after projection. At the same time, it is apparent from section 4 that for the unprojected multivariate Froissart polynomial no conjecture can be formulated yet.