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91.
Growing environmental concerns and the need for alternatives for oil
and natural gas resulted in intensive researches on ultra clean coal (UCC).
Therefore, the researches related to practice and application of various methods
to produce UCC become more important. Thermal characterization of chemically
demineralized coals by thermogravimetric analysis method is presented in this
study. The aim of the study is to provide thermal data for HF–HNO3
leaching system used for the production of UCC. Coal samples were first physically
enriched by density separation. Then the enriched portion was chemically demineralized
by using HF and HNO3, respectively. Ash content of coal samples were reduced
to a range of 0.12–0.41% by chemical demineralization process. The petrographic,
ultimate and proximate analyses were carried out to determine main features
of samples. Physically and chemically enriched coal samples were then analyzed
in a TG by two different techniques separately. The first technique covered
thermal characterization of samples under non-isothermal conditions. Characteristic
temperatures for each sample were obtained from the TG and DTG data. The second
technique involved the determination of reactivity of in situ produced chars
of each sample. 相似文献
92.
Tetravalent metal phosphates (M=Zr, Ti, and Sn) were prepared and characterized by XRD, surface properties, and TG-DTA. The cation exchange and sorption behavior of these metal phosphates toward transition metal ions such as Cu(2+), Co(2+), and Ni(2+) have been studied comparatively as a function of temperature and concentration. The adsorption process was found to increases with increase in temperature and concentration. The selectivity order for alpha-titanium and alpha-tin phosphates is Cu(2+)>Co(2+)>Ni(2+), whereas for alpha-zirconium phosphate it is Cu(2+)>Ni(2+)>Co(2+). The ion exchange capacity of alpha-titanium phosphate is greater than those of other phosphates, which is explained on the basis of the surface behavior, disorderness of the system, degree of hydrolysis of incoming guest adsorbate metal ions, and structural steric hindrance of the exchangers during adsorption and sorption. The distribution coefficient, Gibbs free energy, enthalpy, and entropy values indicate that the ion-exchange processes are spontaneous. 相似文献
93.
Itaru Yamashita Youhei Kawabata Tadashi Kato Masakatsu Hato Hiroyuki Minamikawa 《Colloids and surfaces. A, Physicochemical and engineering aspects》2004,250(1-3):485-490
Small angle X-ray scattering (SAXS) is measured for the lamellar phase in aqueous systems of 1-o-β-3,7-dimethyoctyl-D-glucopyranoside (β-Glc(Ger)), which has recently been prepared by us, 1-o-β-decyl-D-glucopyranoside (β-GlcC10), and 1-o-β-octyl-D-glucopyranoside (β-GlcC8). The repeat distance d obtained from the position of the diffraction peak does not follow the swelling law d = 2δhc/hc, where δhc and hc are the thickness and the volume fraction of the hydrophobic layer, respectively. This may result from the fact that δhc increases and, equivalently, the surface area per surfactant molecule (as) decreases with increasing concentration. So we calculate δhc and as from the observed d value at each concentration using the above swelling law. The half-thickness δhc increases in the order β-GlcC8 < β-Glc(Ger) < β-GlcC10 at a fixed concentration. On the other hand, the data on as for β-GlcC10 and β-GlcC8 lie on the same line and the data for β-Glc(Ger) lies above this line. These results suggest that the cross-sectional area of the geranyl chain is larger than that of the glucose headgroup. Existence of water filled defects in bilayer sheets is also discussed based on the SAXS pattern and the concentration dependence of d. 相似文献
94.
We construct diffusions in random velocity fields which present anomalous superdiffusive behavior. The mean square displacement can be made to have any power lawt
for 1<2. Higher moments and characteristic functions are also investigated. 相似文献
95.
Chao Chen Yu-Lin Yang Kun-Lin Huang Zhen-Hua Sun Wei Wang Zhuo Yi Yun-Ling Liu Wen-Qin Pang 《Polyhedron》2004,23(18):3033-3042
With a hydrothermal technique, a layered titanium phosphate with the formula Ti2(H2PO4)(HPO4)(PO4)2 · 0.5C6N2H16 (denoted TP-J2) has been prepared by treating the Ti/H3PO4/H2O/1-methylpiperazine system directly. The as-synthesized products were characterized by powder X-ray diffraction, CP-MAS solid-state 31P NMR spectroscopy, thermogravimetric and differential thermal analyses (TG-DTA). The structure was solved by single-crystal X-ray diffraction analysis and it presents an extended γ-phase intercalated with organic amine. Crystal data: triclinic, , a = 8.106 (2) Å, b = 8.197 (2) Å, c = 11.658 (2) Å. = 78.32 (3)°, β = 80.85 (3)°, γ = 77.90 (3)°, Z = 2. Additionally, the intercalation behavior of TP-J2 with n-alkyl monoamine (n = 2, 3, 4, 6, 8, 10 and 12) was investigated. Owing to the strong brønsted base, N,N′-dimethylpiperazine, resides in the interlayer, it presented unusual features of TP-J2 in contrast with that of γ-Tip. 相似文献
96.
Anyun Zhang Yuezhou Wei Harutaka Hoshi Mikio Kumagai Masayoshi Kamiya Tomozo Koyama 《Radiation Physics and Chemistry》2005,72(6):669-678
The resistance of a novel silica-based N,N,N′,N′-tetraoctyl-3-oxapentane-1,5-diamide (TODGA) polymeric adsorption material (TODGA/SiO2-P) against nitric acid, temperature and γ-irradiation had been investigated. The adsorption property of the treated TODGA/SiO2-P was evaluated by a 3 M HNO3 solution containing 0.01 M Nd(III). It was found that both 3 and 0.01 M HNO3 concentrations did not decrease the stability of TODGA/SiO2-P at 25°C. The quantity of TODGA leaked from TODGA/SiO2-P was equivalent to its solubility in the corresponding HNO3 aqueous solution. The effect of 3 M HNO3 on the leakage of TODGA at 80°C was significantly higher than that in 0.01 M HNO3 as well as in all cases at 25°C. The amount of Nd(III) adsorbed towards the treated TODGA/SiO2-P was determined in the range of 0.143–0.148 mmol/g for the HNO3 concentration effect and 0.142–0.0506 mmol/g for the temperature effect. γ-Irradiation showed a more noticeable destruction effect on TODGA/SiO2-P. The content of TODGA leaked increased with an increase in the γ-irradiation dose (ID) from 1.06 to 3.72 MGy in terms of the linear equation [TODGA]=794.5ID+84.0. The amount of Nd(III) adsorbed onto the irradiated TODGA/SiO2-P decreased rapidly from 0.134 to 0.0438 mmol/g, which was lower than 0.153 mmol/g, the adsorption of fresh TODGA/SiO2-P for Nd(III), according to the equation QNd(III)=−0.0301ID+0.160, showing that a large quantity of TODGA leaked from TODGA/SiO2-P. The adsorbed amount of Nd(III) decreased obviously in this order: the HNO3 concentration effect, temperature effect and γ-irradiation. 相似文献
97.
Mitsuru Ueda Takayoshi Yokoo Takeo Nakamura 《Journal of polymer science. Part A, Polymer chemistry》1994,32(15):2989-2995
A general method for the preparation of aromatic poly (ether-sulfone-amide)s has been developed. Polymerization is based on the palladium-catalyzed polycondensation of aromatic dibromides containing ether sulfone structural units, aromatic diamines, and carbon monoxide. Reactions were carried out in N, N-dimethylacetamide (DMAc) in the presence of palladium catalyst, triphenylphosphine, and 1,8-diazabicyclo [5,4,0]–7–undecene (DBU), and gave a series of poly (ether-sulfone-amide)s with inherent viscosities up to 0.86 dL/g under mild conditions. The polymers were quite soluble in strong acids, dipolar aprotic solvents, and pyridine. Thermogravimetry of the polymers showed excellent thermal stability, indicating that 10% weight losses of the polymers were observed in the range above 470°C in air. The glass transition temperatures of the polymers were around 230°C, which are higher than those of poly (ether-sulfone) analogues. These polymers also showed the good tensile strengths and tensile modulus. © 1994 John Wiley & Sons, Inc. 相似文献
98.
Poly(arylene ether diketone)s were prepared by the aromatic nucleophilicdisplacement reaction of 4,4'-difluorobenzil with different bisphenols in the presence of an-hydrous potassium carbonate in diphenylsulfone at elevated temperature. The polymersobtained had inherent viscosity of 0.51 ~ 0.63 dL/g, and exhibited glass transition temper-ature ranging from 136 ~217℃ mainly depending on the bisphenols used in the polymersynthesis. Thermogravimetry of these polymers showed excellent thermal stability, indi-cating that 10% weight losses of the polymers were observed in the range above 428℃ and438℃ in air and nitrogen, respectively. The mechanical properties of these polymers werealso described and the permeability of five polymers for H_2, O_2 and N_2 was determined at30℃. 相似文献
99.
100.
The ability to separate enzymes, or cells or viruses, from a mixture is important and can be realized by the incorporation of the mixture into a macromolecular solution. This incorporation may lead to a spontaneous phase separation, with one phase containing the majority of one of the species of interest. Inspired by this phenomenon, we studied the theoretical phase behavior of a model system composed of an asymmetric binary mixture of hard spheres, of which the smaller component was monodisperse and the larger component was polydisperse. The interactions were modeled in terms of the second virial coefficient and could be additive hard sphere (HS) or nonadditive hard sphere (NAHS) interactions. The polydisperse component was subdivided into two subcomponents and had an average size ten or three times the size of the monodisperse component. We gave the set of equations that defined the phase diagram for mixtures with more than two components in a solvent. We calculated the theoretical liquid–liquid phase separation boundary for the two-phase separation (the binodal) and three-phase separation, the plait point, and the spinodal. We varied the distribution of the polydisperse component in skewness and polydispersity, and we varied the nonadditivity between the subcomponents as well as between the main components. We compared the phase behavior of the polydisperse mixtures with binary monodisperse mixtures for the same average size and binary monodisperse mixtures for the same effective interaction. We found that when the compatibility between the polydisperse subcomponents decreased, the three-phase separation became possible. The shape and position of the phase boundary was dependent on the nonadditivity between the subcomponents as well as their size distribution. We conclude that it is the phase enriched in the polydisperse component that demixes into an additional phase when the incompatibility between the subcomponents increases. 相似文献