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1.
New luminescent inorganic–organic hybrid materials incorporating the luminescent zinc(II) complex ZnL2 (λem = 457 nm and Φem = 4.4% reference values for ZnL2; HL = chelating ligand resulting from the reaction between salicylaldehyde and 3-aminopropyltriethoxysilane), covalently bonded to different types of mesoporous silica hosts (namely MCM-41, MCM-48 and SBA-15), were prepared via both the methods of grafting post-synthesis (GPS) and one-pot synthesis (OPS). The products obtained, which form the GPS [(GPS)(Zn/MCM-41), (GPS)(Zn/MCM-48), (GPS)(Zn/SBA-15)] and the OPS [(OPS)(Zn/MCM-41), (OPS)(Zn/MCM-48), (OPS)(Zn/SBA-15)] series, contain the ZnL2 guest covalently bonded to the silica framework through silicon–oxygen bonds formed when the silane group is placed at the periphery of the Zn(II) coordination sphere. GPS and OPS materials were characterized by powder X-ray diffraction, N2 adsorption/desorption, thermogravimetric analysis (TGA) and UV/vis spectroscopy. For the new mesoporous materials the emission quantum yield (EQY) was measured by means of an integrating sphere combined with a spectrofluorimeter. The ZnL2 loading (measured by the ZnL2/SiO2 ratio calculated from TGA data) for MCM-41 appears to be independent of the synthesis procedure, whereas, for both MCM-48 and SBA-15, the ZnL2/SiO2 ratio of the materials obtained via OPS is about four times higher than products obtained from GPS. The ZnL2 loaded GPS and OPS series show λem maxima at about 485 and 455 nm, respectively. Moreover, with reference to EQY (GPS)(Zn/SBA-15) and (OPS)(Zn/SBA-15), although featuring ZnL2/SiO2 ratios of 0.13 and 0.45, respectively, they showed similar EQY values: 2% and 5%. On the contrary, (GPS)(Zn/MCM-41) and (OPS)(Zn/MCM-41) which give similar ZnL2/SiO2 ratios (0.09 and 0.14) exhibit very different EQY, i.e. 2% and 22%, respectively.  相似文献   

2.
By extended X-ray absorption fine structural (EXAFS) spectroscopy, copper oxide clusters with a square-plane structure are found in the channels of mesoporous molecular sieve MCM-41. Bond distances of Cu–O and Cu–Cu are 1.90 and 2.80 Å, respectively. Oxidation of naphthalene at 723 K for 4 h in MCM-41 leads to structural perturbation of the clusters (e.g., Cu–O: −0.02 Å and Cu–Cu: +0.02 Å) with little change in their coordination numbers.  相似文献   

3.
This study focuses on the MCM-41 material (Mobil Composition of Matter). The MCM-41 nanomaterial presents higher physical properties such as pore sizes, surface areas and pore volumes. This material is usually synthesized by using laboratory reagents as silicate sources and aluminium source. These laboratory reagents are still expensive and toxic for large scale production. The main aim of this work is to resolve this problem and to replace these expensive laboratory reagents by more cost effective ones. The volclay and Algerian bentonite low-cost mass clay materials are used as silicate and acuminate sources separately by adopting an alkaline fusion process to extract both silicon and aluminium (1 kg of silicium and aluminium from volclay and Algerian bentonite cost around 0.03 and 0.01 € whereas the same amount of silicon from ludox and aluminium from sodium aluminates cost around 350 €). The synthesis of MCM-41 from bentonite was carried out by the hydrothermal method using the supernatants of bentonite (in the form of sodium silicate and sodium aluminate). On the basis of the data obtained from powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and N2 adsorption and desorption, the results revealed that the properties of MCM-41 synthesized from Algerian bentonite and volclay separately depend on both elemental composition and mineral phase contents of the used bentonite. Pure and highly ordered hexagonal mesoporous MCM-41 with uniform pore sizes and a high specific surface area have been successfully synthesized without any phases which exist in natural bentonite. The Algerian bentonite was chosen because of its low cost compared to volclay, another commercial clay source.  相似文献   

4.
《Solid State Sciences》2012,14(2):250-257
CO2 adsorption properties on Mg modified silica mesoporous materials were investigated. By using the methods of co-condensation, dispersion and ion-exchange, Mg2+ was introduced into SBA-15 and MCM-41, and transformed into MgO in the calcination process. The basic MgO can provide active sites to enhance the acidic CO2 adsorption capacity. To improve the amount and the dispersion state of the loading MgO, the optimized modification conditions were also investigated. The XRD and TEM characteristic results, as well as the CO2 adsorption performance showed that the CO2 adsorption capacity not only depended on the pore structures of MCM-41 and SBA-15, but also on the improvement of the dispersion state of MgO by modification. Among various Mg modified silica mesoporous materials, the CO2 adsorption capacity increased from 0.42 mmol g−1 of pure silica SBA-15 to 1.35 mmol g−1 of Mg–Al–SBA-15-I1 by the ion-exchange method enhanced with Al3+ synergism. Moreover, it also increased from 0.67 mmol g−1 of pure silica MCM-41 to 1.32 mmol g−1 of Mg–EDA–MCM-41-D10 by the dispersion method enhanced with the incorporation of ethane diamine. The stability test by 10 CO2 adsorption/desorption cycles showed Mg–urea–MCM-41-D10 possessed quite good recyclability.  相似文献   

5.
The pyrolytic conversion of pure lignin at 600 °C in flowing helium over five catalysts is described and compared to the control bed material, sand. Product distribution as char, liquid, and gas are described as well as the composition of the liquid and gas fractions. The catalysts examined were HZSM-5, KZSM-5, Al-MCM-41, solid phosphoric acid, and a hydrotreating catalyst, (Co/Mo/Al2O3). The sand yielded a liquid phase that was 97% oxygenated aromatics and a gas phase that was CO (18 vol%), CO2 (16 vol%), and CH4 (12 vol%). HZSM-5 was the best catalyst for producing a deoxygenated liquid fraction yielded almost equal amounts of simple aromatics (46.7%) and naphthalenic ring compounds (46.2%). The gas phase over this catalyst consisted of CO (22 vol%), CO2 (14 vol%), H2 (12 vol%), and CH4 (10 vol%). The Co/Mo/Al2O3 hydrotreating catalyst yielded a liquid consisting of 21% aromatics, 4% naphthalenics, and 75% oxygenated aromatics and a gas phase that was rich in hydrogen: H2 (18 vol%), CO2 (16 vol%), CO (12 vol%), and CH4 (8 vol%).  相似文献   

6.
The formation process and morphology of BTDA-TDI/MDI co-polyimide (P84, CAS#: 58698-66-1) asymmetric flat sheet membranes have been studied. Experimental results indicated that the weight ratio of H2O and N-methyl-2-pyrrolidone (NMP, CAS#: 872-50-4) at cloud point curve (above critical point) was a constant (7.66/92.34 (w/w)) for the P84/NMP/H2O system. For two different casting solutions (21 wt.% P84 in pure NMP; 15 wt.% P84 in H2O/NMP: 6.0/94.0 (w/w)), the approaching ratio α strongly dominated the formation of finger-like structure rather than the viscosity of casting solution. The formation of finger-like structure in P84 co-polyimide asymmetric membranes was due to the hydrodynamically unstable viscous fingering developed when the casting solution was displaced by a polymer-lean phase. Three types of membrane morphologies, finger-like structure, transition structure and sponge-like structure can be expected with various approaching ratio α of casting solutions. The critical approaching ratio α* was initially defined to describe the sharp change of membrane morphology from finger-like to sponge-like structure. The casting temperature also influenced the membrane morphology. For some casting solutions (e.g. 15 wt.% P84 in H2O/NMP: 6.4/93.6 (w/w)), the membrane morphology changed from sponge-like to finger-like structure with an increase in casting temperature. Meanwhile, the critical approaching ratio α* also increased with an increase in casting temperature.  相似文献   

7.
Measurements of thermophysical properties (vapour pressure, density, and viscosity) of the (water + lithium bromide + potassium acetate) system LiBr:CH3COOK = 2:1 by mass ratio and the (water + lithium bromide + sodium lactate) system LiBr:CH3CH(OH)COONa = 2:1 by mass ratio were measured. The system, a possible new working fluid for absorption heat pump, consists of absorbent (LiBr + CH3COOK) or (LiBr + CH3CH(OH)COONa) and refrigerant H2O. The vapour pressures were measured in the ranges of temperature and absorbent concentration from T = (293.15 to 333.15) K and from mass fraction 0.20 to 0.50, densities and viscosities were measured from T = (293.15 to 323.15) K and from mass fraction 0.20 to 0.40. The experimental data were correlated with an Antoine-type equation. Densities and viscosities were measured in the same range of temperature and absorbent concentration as that of the vapour pressure. Regression equations for densities and viscosities were obtained with a minimum mean square error criterion.  相似文献   

8.
A highly accurate P, V, T,x model is developed for aqueous chloride solutions of the binary systems, viz. (LiCl + H2O), (NaCl + H2O), (KCl + H2O), (MgCl2 + H2O), (CaCl2 + H2O), (SrCl2 + H2O), and (BaCl2 + H2O). The applied ranges of temperature, pressure, and concentrations for the systems (LiCl + H2O), (NaCl + H2O), (KCl + H2O), (MgCl2 + H2O), (CaCl2 + H2O), (SrCl2 + H2O), and (BaCl2 + H2O) are (273 K to 564 K, 0.1 MPa to 40 MPa, and 0 to 10 molal), (273 K to 573 K, 0.1 MPa to 100 MPa, and 0 to 6.0 molal), (273 K to 543 K, 0.1 MPa to 50 MPa, and 0 to 4.5 molal), (273 K to 543 K, 0.1 MPa to 40 MPa, and 0 to 3.0 molal), (273 K to 523 K, 0.1 MPa to 60 MPa, and 0 to 6.0 molal), (298 K to 473 K, 0.1 MPa to 2 MPa, and 0 to 2.0 molal) and (273 K to 473 K, 0.1 MPa to 20 MPa, and 0 to 1.6 molal), respectively. Comparison of the model with thousands of experimental data points concludes that the average deviation over the above T, P, m range is 0.020% to 0.066% in density (or volume) for these systems, which indicates high accuracy. From this model, various volumetric properties, such as the apparent molar volume at infinite dilution and isochores of fluid inclusions, can be calculated, thus having a wide range of geological applications, such as reservoir fluid flow simulation and fluid-inclusion study. A computer code is developed for this model and can be downloaded from the website: www.geochem-model.org/programs.htm and online calculations is made available on: www.geochem-model.org/models.htm  相似文献   

9.
The relative structural and dynamic properties of hydrogen-bonding between Pyrimidine (Pmd) + H2O and Pmd + D2O, and 4-Methylpyrimidine (Mpmd) + H2O and Mpmd + D2O are investigated experimentally by linear Raman spectroscopy using Raman difference spectroscopic (RDS) technique. The focus has been given to the ring breathing mode (ν1). The effect of methylation on the Pmd ring has been studied in terms of wavenumber shift (Δν), peak-position and linewidth variation with mole fraction of the solvent. The wavenumber shift has been calculated by assuming the Voigt profile of the Raman band. In order to explain our experimental results, we have optimized single Pmd and 4Mpmd molecules and their various complexes with H2O and D2O in the stoichiometric ratio of 1:1, 1:2, 1:3 and 1:4 by employing DFT/B3LYP functional with 6-311+G(d,p) basis set using Gaussian software. There is a good correspondence between experimental and theoretical results. Our result reveals that with RDS technique, Δν of a band up to 1/100th of the FWHM can be measured precisely.  相似文献   

10.
With the aid of differential phonon spectrometrics (DPS) and surface stress detection, we show that HI and NaI solvation transforms different fractions of the HO stretching phonons from the mode of ordinary water centred at ∼3200 to the mode of hydration shell at ∼3500 cm−1. Observations suggest that an addition of the H  H anti-hydrogen-bond to the Zundel notion, [H(H2O)2]+, would be necessary as the HO bond due H3O+ has a 4.0 eV energy, and the H  H fragilization disrupts the solution network and the surface stress. The I and Na+ ions form each a charge centre that aligns, stretches, and polarize the O:HO bond, resulting in shortening the HO bond and its phonon blue shift in the hydration shell or at the solute-solvent interface. The solute capabilities of bond-number-fraction transition follow: fH = 0, fNa  C, and fI  1  exp(−C/C0) toward saturation, with C being the solute molar concentration and C0 the decay constant. The fH = 0 evidences the non-polarizability of the H+ because of the H  H formation. The linear fNa(C) suggests the invariance of the Na+ hydration shell size because of the fully-screened cationic potential by the H2O dipoles in the hydration shell but the nonlinear fI(C) fingerprints the I  I interactions at higher concentrations. Concentration trend consistency between Jones–Dole’s viscosity and the fNaI(C) coefficient may evidence the same polarization origin of the solution viscosity and surface stress.  相似文献   

11.
Pyrolysis of corncob with and without catalyst was investigated using thermogravimetry analyzer coupled with Fourier transform infrared spectroscopy (TGA–FTIR). The effects of two completely different catalysts, acid catalyst (MCM-41) and base catalyst (CaO), on the formation characteristics and composition of pyrolysis vapor were studied. The results show that these two catalysts give different product distributions. For catalytic run with MCM-41, the molality of carbonyl compounds decreases 10.2%, while that of phenols, hydrocarbons and CH4 increases 15.32%, 4.29% and 10.16% compared with non-catalytic run, respectively. The increase of phenols exhibits in a wide temperature range from about 295 °C to 790 °C in the catalytic run with MCM-41 catalyst. However, the use of CaO in pyrolysis of corncob leads to a huge change of product distribution. The molality of acids decreases 75.88%, while the molality of hydrocarbons and CH4 increases 19.83% and 51.05% compared with non-catalytic run, respectively. CaO is very effective in deacidification and the conversion of acids promotes the formation of hydrocarbons and CH4. Catalytic pyrolysis of corncob with CaO shows two main weight-loss stages. The first stage is from 235 °C to 310 °C with a weight loss of 31%. The second stage is from 650 °C to 800 °C with a weight loss of 21%.  相似文献   

12.
The important zinc borate of 2ZnO · 3B2O3 · 3H2O has been synthesized and characterized by means of chemical analysis, XRD, FT-IR, and DTA–TG techniques. The molar enthalpies of solution of H3BO3(s) in HCl · 54.561H2O, of ZnO(s) in the mixture of HCl · 54.561H2O and calculated amount of H3BO3, and of 2ZnO · 3B2O3 · 3H2O(s) in HCl · 54.604H2O were measured, respectively. With the use of the standard molar enthalpies of formation for ZnO(s), H3BO3(s), and H2O(l), the standard molar enthalpy of formation of ?(5561.7 ± 4.9) kJ · mol?1 for 2ZnO · 3B2O3 · 3H2O(s) was obtained. Thermodynamic properties of this compound were also calculated by a group contribution method.  相似文献   

13.
By a simple DTA system, the glass transition temperatures of the quaternary ammonium type ionic liquid, {N,N-diethyl-N-methyl-N-(2-methoxyethyl) ammonium iodide, [DEME][I] + H2O} mixtures after quick pre-cooling were measured as a function of water concentration (x mol% H2O). Results were compared with the previous results of {[DEME][BF4] + H2O} mixtures in which double glass transitions were observed in the water concentration region of (16.5 to 30.0) mol% H2O. Remarkably, we observed the double glass transition phenomenon in {[DEME][I] + H2O} mixtures too, but the two-Tgs regions lie towards the water-rich side of (77.5 to 85.0) mol% H2O. These clearly reflect the difference in the anionic effect between BF4- and I? on the water structure. The end of the glass-formation region of {[DEME][I] + H2O} mixtures is around x = 95.0 mol% H2O, and this is comparable to that of {[DEME][BF4] + H2O} mixtures (x = 96.0 mol% H2O).  相似文献   

14.
Water activities in the ternary system (CaCl2 + SrCl2 + H2O) and its sub-binary system (CaCl2 + H2O) at T = 298.15 K have been elaborately measured by an isopiestic method. The data of the measured water activity were used to justify the reliability of solubility isotherms reported in the literature by correlating them with a thermodynamic Pitzer–Simonson–Clegg (PSC) model. The model parameters for representing the thermodynamic properties of the (CaCl2 + H2O) system from (0 to 11) mol  kg−1 at T = 298.15 K were determined, and the experimental water activity data in the ternary system were compared with those predicted by the parameters determined in the binary systems. Their agreement indicates that the PSC model parameters can reliably represent the properties of the ternary system. Under the assumption that the equilibrium solid phases are the pure solid phases (SrCl2  6H2O and CaCl2  6H2O)(s) or the ideal solid solution consisting of CaCl2  6H2O(s) and SrCl2  6H2O(s), the solubility isotherms were predicted and compared with experimental data from the literature. It was found that the predicted solubility isotherm agrees with experimental data over the entire concentration range at T = 298.15 K under the second assumption described above; however, it does not under the first assumption. The modeling results reveal that the solid phase in equilibrium with the aqueous solution in the ternary system is an ideal solid solution consisting of SrCl2  6H2O(s) and CaCl2  6H2O(s). Based on the theoretical calculation, the possibility of the co-saturated points between SrCl2  6H2O(s) and the solid solution (CaCl2  6H2O + SrCl2  6H2O)(s) and between CaCl2  6H2O(s) and the solid solution (CaCl2  6H2O + SrCl2  6H2O)(s), which were reported by experimental researchers, has been discussed, and the Lippann diagram of this system has been presented.  相似文献   

15.
《Fluid Phase Equilibria》2005,231(2):138-149
Reactive canonical Monte Carlo (RCMC) method was performed to simulate the chemical reaction equilibrium of ammonia synthesis in two important porous materials: MCM-41 pores and pillared clays. First, our results were compared with those in slit pores in the literature. Then, the effect of other factors such as pore size, pressure and temperature on the chemical equilibrium was investigated. A parameter of the absolute increase of ammonia mole fraction in the pores against that in the bulk phase, Δabs, is introduced to describe the effect of confinement on the chemical equilibrium. The yield of ammonia increases with the decrease of pore size, but this increase becomes pronounced at pore sizes of 1.5 nm for MCM-41 pores and 1.02 nm for pillared clays. The yield of ammonia also increases with pressure. In addition, the maximum ammonia mole fraction is attained at 100 bar and 573 K in both MCM-41 pores and pillared clays. When the feed mole ratio of N:H of the bulk phase declines from 4:13 to 4:15, the yield of ammonia in the pore phase also decreases. In addition, the effect of porosity in pillared clays on the chemical equilibrium was simulated.  相似文献   

16.
New Schiff base (H2L) ligand is prepared via condensation of o-phthaldehyde and 2-aminobenzoic acid in 1:2 ratio. Metal complexes are prepared and characterized using elemental analyses, IR, solid reflectance, magnetic moment, molar conductance, 1H NMR, ESR and thermal analysis (TGA). From the elemental analyses data, the complexes were proposed to have the general formulae [MCl(L)(H2O)]·2H2O (where M = Cr(III) and Fe(III)); [M(L)]·yH2O (where M = Mn(II), Ni(II), Cu(II) and Zn(II), y = 1–2) and [M(L)(H2O)nyH2O (where M = Co(II) (n = y = 2), Co(II) (n = y = 1), Ni(II) (n = 2, y = 1). The molar conductance data reveal that all the metal chelates were non-electrolytes. IR spectra show that H2L is coordinated to the metal ions in a bi-negative tetradentate manner with NOON donor sites of the azomethine-N and carboxylate-O. The 1H NMR spectral data indicate that the two carboxylate protons are also displaced during complexation. From the magnetic and solid reflectance spectra, it was found that the geometrical structure of these complexes are octahedral (Cr(III), Fe(III), Co(II) and Ni(II)), square planar (Cu(II)), trigonal bipyramidal (Co(II)) and tetrahedral (Mn(II), Ni(II) and Zn(II)). The thermal behaviour of these chelates showed that the hydrated complexes losses water molecules of hydration in the first step followed immediately by decomposition of the ligand molecule in the subsequent steps. The biological activity data show that the metal complexes to be more potent/antibacterial than the parent Shciff base ligand against one or more bacterial species.  相似文献   

17.
Reaction of Zn(NO3)2·6H2O with p-aminobenzoic acid in a 1:2 molar ratio under ethanol medium at room temperature affords a new three dimensional (3D) coordination polymer [Zn(PABA)2]·H2O (1) (PABA = p-aminobenzoic acid). Single-crystal X-ray diffraction reveals that 1 crystallizes in the orthorhombic system, space group P212121, a = 7.614(2), b = 11.133(3), c = 16.869(4). 1 adopts a 3D open framework with H2O molecules in the cavities. PABA, acting as bridging ligand as well as coordinating ligand, adopts a different coordination mode to bridge Zn atoms and form the 3D supramolecular structure which is further stabilized by N–H?O, O–H?O hydrogen bonding and π–π stacking interactions. Powder second-harmonic generation (SHG) efficiency measurement with Nd:YAG laser (1064 nm) radiation shows that the SHG efficiency of 1 is equivalent to KDP crystal. The present work also demonstrates that the framework of 1 is retained after removal of the guest H2O molecules, and the H2O molecules can be reintroduced into the framework, indicating that this complex may also be used to generate porous materials.  相似文献   

18.
The molar enthalpies of solution of 2MgO · 2B2O3 · MgCl2 · 14H2O in approximately 1 mol · dm−3 aqueous hydrochloric acid (HCl) and of MgCl2 · 6H2O(s) in aqueous (approximately 1 mol · dm−3 HCl + MgCl2 + H3BO3) at T=298.15 K were determined. From a combination of these results with measured enthalpies of solution of boric acid (H3BO3) in HCl(aq) and of magnesium oxide (MgO) in aqueous (HCl + H3BO3) solution, together with the standard molar enthalpies of formation of MgO(s), H3BO3(s), MgCl2 · 6H2O(s) and H2O(l), the standard molar enthalpy of formation of −(8812 ± 3) kJ · mol−1 of 2MgO · 2B2O3 · MgCl2 · 14H2O was obtained. Thermodynamic properties of this compound were also calculated by group contribution method.  相似文献   

19.
The tert-butyl alcohol (TBA) and dimethyl sulfoxide (DMSO) are two small molecules geometrically very similar, but having different polar groups. Taking into account the intermolecular interactions in the TBA/H2O and DMSO/H2O systems, especially in the water-rich region of concentration, the ultrasonic speeds (high accuracy resonance method at the frequency 7.5 MHz) and densities in pseudo-binary mixtures of the system: (TBA + H2O + DMSO) with the ratio (TBA + DMSO)/H2O = 1/25 have been measured. From these data, various thermodynamical parameters such as adiabatic compressibility, molar volume, thermal expansivity, and the deviation from reference system have been calculated. In addition, the isobaric molar heat capacity to convert adiabatic compressibility to the isothermal one has been measured. All these parameters have been discussed to explain solute–solvent and solute–solute interactions, especially the effect of the complexation process between TBA and DMSO molecules. The composition dependence of these deviations functions was interpreted in the light of the mixing schemes in the aqueous solutions of TBA and DMSO.  相似文献   

20.
The solubility and the density in the aqueous ternary system (Li2SO4 + MgSO4 + H2O) at T = 308.15 K were determined by the isothermal evaporation. Our experimental results permitted the construction of the phase diagram and the plot of density against composition. It was found that there is one eutectic point for (Li2SO4 · H2O + MgSO4 · 7H2O), two univariant curves, and two crystallization regions corresponding to lithium sulphate monohydrate (Li2SO4 · H2O) and epsomite (MgSO4 · 7H2O). The system belongs to a simple co-saturated type, and neither double salts nor solid solution was found. Based on the Pitzer ion-interaction model and its extended HW models of aqueous electrolyte solution, the solubility of the ternary system at T = 308.15 K has been calculated. The predicted solubility agrees well with the experimental values.  相似文献   

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