Research on Chemical Intermediates - Fe–Cu–ZSM-5 and Ce–Fe–Cu–ZSM-5 solids prepared using solid-state ion exchange method (SSIE) were tested in the NH3–SCR of NO... 相似文献
Two synthetic protocols leading to novel γ-aminophosphonate and phosphine oxide derivatives, by reductive amination of γ-phosphonylketones, are reported. The first method involved a two-step procedure. Imine intermediates were first isolated from the p-toluenesulfonic acid-catalyzed reaction of primary amines with γ-ketophosphonates and phosphine oxides, then reduced with NaBH4 in refluxing ethanol. The second method consists of a one-pot procedure which includes the condensation of γ-ketophosphonates and phosphine oxides with primary amines, in the presence of molecular sieves, followed by reduction with NaBH4. These methods offer significant advantages over prior reports, such as efficiency, generality, and good yields. Furthermore, they are green protocols avoiding hazardous hydrides and solvents. 相似文献
A green and versatile method for the preparation of γ-hydroxyphosphonate and phosphine oxide derivatives in 5?min, is accomplished through the reduction of γ-phosphonylketones with sodium borohydride supported on alumina, at room temperature, under solvent free conditions. 相似文献
Journal of Thermal Analysis and Calorimetry - Thermal decomposition (2 K min?1) of ammonium heptamolybdate tetrahydrate, performed between room temperature and... 相似文献
The essential oils obtained from leaves of two Myrtus communis varieties (baetica and italica), growing wild in North Tunisia, were investigated by GC and GC–MS at their different phenological stages. The highest essential oil yield was observed at the flowering stage with 0.6% (w/w) for italica and 0.4% (w/w) for baetica and 49 compounds were identified. The main essential oil leaf compounds of both myrtle varieties, belonging to the monoterpene class, were α-pinene, 1,8-cineole, limonene and linalool and their percentages showed significant changes during the phenological stages.
A series of catalysts based on Mn-Fe loaded zeolites was prepared by impregnation and their activity in the selective catalytic reduction of NO with ammonia (NH3-SCR) was investigated. The highest catalytic conversion was recorded for MnFe-ZSM-5 (MnFe-Z), followed by MnFe-BEA (MnFe-B) and MnFe-MOR (MnFe-M), while MnFe-FER (MnFe-F) showed a very poor activity over the entire temperature range. In order to evidence a correlation between the structure and acidity of the zeolites and NO conversion, the prepared samples were characterized by various techniques (ICP-AES, N2 physisorption at 77 K, XRD, 27NMR, Raman, FTIR spectroscopy of adsorbed ammonia, H2-TPR, DRS UV–Vis, EPR and XPS). The superior catalytic activity of MnFe-Z at low temperature is attributed to the abundance of Mn4+ concentration as revealed by XPS, the highest NH3-L/NH4+ ratio indicative of the contribution of metals in generating Lewis acidic centers as evidenced by IR-NH3, and the better reducibility of manganese and iron on ZSM-5 which increases the kinetics for red-ox cycles as confirmed in TPR analysis. Fe3Mn3O8 mixed oxide phase is also detected by XRD and XPS and can be associated with the high reducibility of MnFe-Z which generates a high oxidation ability favoring NO to NO2 oxidation. Raman spectroscopy was also used to confirm the existence of a strong synergy between metals and ZSM-5 support revealed by the shift in the signal position and the decrease in band intensities. The results showed that the zeolite framework and acidity generate catalysts with different textural and structural properties which influence the metal dispersion and speciation and hence influence the catalytic performances.
α,β-Ethylenic chiral acetals react regio- and stereoselectively with organolithium reagents. The obtained enol ether may be hydrolyzed into a chiral β-disubstituted aldehyde. 相似文献
In this paper, we consider the efficient estimation of local boiling heat fluxes from transient temperature measurements in
the heater close to the heater surface. For accurate prediction, heat flux estimation is formulated as a transient three-dimensional
(3D) inverse heat conduction problem (IHCP). This inverse problem is ill-posed and cannot be treated straightforwardly by
established numerical methods. In order to obtain a regularized stable solution, a large-scale time-dependent PDE-constrained
optimization problem has to be solved and an appropriate stopping criterion for the termination of the iterative solution
process has to be chosen. Since the boiling heat flux is non-uniformly distributed on the heater surface due to the strong
local activity of the boiling process, the use of a fixed uniform spatial discretization is not efficient. Instead, an adaptive
mesh refinement strategy can be used to obtain an appropriate discretization which significantly reduces the total computational
effort. In this work, we present an automatic algorithm incorporating an adaptive mesh refinement via a heat flux-based a-posteriori
error estimation technique. The suggested algorithm can cope with both spatially point-wise or highly resolved temperature
observations efficiently. It is applied to real measurement data obtained from two different types of pool boiling experiments.
The numerical results show that the computational effort can be reduced significantly for given estimation quality. This adaptive
IHCP solution technique can be also viewed as an efficient soft sensor to deduce unmeasurable local boiling heat fluxes. 相似文献
Research on Chemical Intermediates - The selective catalytic reduction of NO with ammonia (NH3-SCR) in the presence of H2O was studied over a series of Fe-Cu-ZSM-5 catalysts prepared by solid-state... 相似文献
A series of Cr/Al2O3 and Co/Al2O3 catalysts were tested in the selective ammoxidation of ethylene to acetonitrile. Catalysts were prepared either by sol–gel
method or by impregnation with chromium or cobalt acetylacetonate salts. Physicochemical properties of catalysts were accomplished
by several techniques such as chemical analysis, physisorption of N2, X-ray diffraction (XRD), 27Al MAS NMR, UV–Visible diffuse reflectance (DRS) and Raman spectroscopy and temperature programmed reduction of H2 (H2–TPR). Textural analysis reveals that mesoporous materials with pronounced surface areas were obtained using sol–gel procedure
while impregnation of the support produces a moderate decrease of its surface area and pore volume. XRD analysis confirms
the presence of highly dispersed metal species which reside essentially on the surface and measure less than 4 nm. Furthermore,
27Al MAS NMR shows that for xerogels, part of metal species occupies sites on/in A12O3 in close vicinity of octahedral 27Al. This, apparently, is not the case for aerogels. For Cr/Al2O3 catalysts, isolated Cr6+, mono and polychromate species were identified using DRS, Raman Spectroscopy and H2–TPR which seem to play a key role in the ammoxidation of ethylene. Furthermore, for cobalt doped catalysts, CoAl2O4 was identified as active phase on the basis of DRS and H2–TPR results. From the supercritical drying, it results generally better catalysts than catalysts calcined by ordinary procedure
which leads to inactive agglomerated Co3O4 and CoO–Al2O3 phase. 相似文献