共查询到20条相似文献,搜索用时 15 毫秒
1.
Thin palladium composite membranes were prepared by modified electroless plating method on a-alumina supports and a dense Pd/α-Al2O3 composite membrane with high hydrogen flux, good selectivity for hydrogen was obtained. It was tested in a single gas permeation system for hydrogen permeance and hydrogen selectivity over mtrogen. The hydrogen permeance of the corresponding membrane was ashigh as 2.45×10^-6mol·m^-2·s^-1.Pa^-1 and H2/N2 selectivityover700 at 623K and a pressure difference of 0.1MPa. The-main resistance of the composite membrane to H2 permeation lies in the aluminum ceramic support rather than the thin Pd layer. 相似文献
2.
《分离科学与技术》2012,47(14):2877-2889
Abstract Palladium acetate vapor was sublimed at a reduced pressure and was evacuated through the porous wall of an α-alumina support tube of 1.8 mm i.d. and 2.4 mm o.d. Due to chemical vapor deposition (CVD), a thin palladium membrane was formed in macropores of the support. The membrane part was about 50 mm in length and was used without any pretreatment. The palladium membrane, prepared at a maximum CVD temperature of 400°C, showed hydrogen permeance and selectivity to nitrogen higher than 10?6 mol·m?2·s?1·Pa?1 and 1000 at 300–500°C, respectively. Even after the permeation temperature was repeatedly varied between 100 and 300°C in a hydrogen atmosphere, the membrane exhibited no hydrogen embrittlement. The amount of palladium deposited in pores of the support tube was 22 g/m2 of the outer surface of the tube. The thickness of the palladium membrane calculated from this value was 4.4 μm. 相似文献
3.
A novel photocatalytic deposition method for the preparation of a thin tubular palladium membrane is presented in this paper.
The membrane is prepared on a porous asymmetric TiO2 support by photocatalytic reaction of palladium ion, followed by electroless plating. Gas permeation results show that the
membrane exhibits increased hydrogen permeance with the increase of temperature. The hydrogen permeance and selectivity to
nitrogen at 773 K are about 1.43×l0−6 mol m−2 s−1 Pa−1 and 17, respectively, when the pressure in the feed side is 0.1 MPa. The activation energy of hydrogen permeation is 11.06
kJ/mol at the temperature range of 573–773 K. 相似文献
4.
G. Ya. Akimov V. M. Timchenko É. V. Chaika 《Refractories and Industrial Ceramics》1997,38(7-8):310-314
The physicomechanical properties of a ceramics composed of ZrO2+3 mol.% Y2O3 and fabricated by cold isostatic pressing (CIP) at up to 0.8 GPa with sintering at 1440–1620°C are described. It is shown
that the material with a low content of admixtures sinters only at 1620°C at a pressure of 0.6–0.8 GPa and possesses a density
of 6.0 g/cm3, an ultimate bending strength of 900 MPa, and a fracture toughness of 8 MPa·m1/2. For the material with a high content of admixtures sintered at 1550°C and pressed at a pressure of 0.6 GPa the same parameters
are 5.95 g/cm3, 700 MPa, and 12 MPa·m1/2. It is established that CIP promotes sintering of Y-PSZ ceramics. CIP has the best effect on the mechanical properties of
high-purity materials.
Translated from Ogneupory i Tekhnicheskaya Keramika, No. 8, pp. 17–21, August, 1997. 相似文献
5.
Thin, defect‐free palladium, palladium/copper and palladium/silver hydrogen absorbing membranes were microfabricated. A dual sputtering technique was used to deposit the palladium alloy membranes of only 1 μm thickness on a nonporous silicon substrate. Advanced silicon etching (ASE) was applied on the backside to create a mechanically stable support structure for the thin films. Performance evaluation was carried out for different gases in a temperature range of 20 °C to 298 °C at a constant differential pressure of 110 kPa at the two sides of the membrane. The composite membranes show an excellent permeation rate of hydrogen, which appears to be 0.05 Pa m3 s–1 and 0.01 · 10–3 Pa m3 s–1 at 20 °C for the microfabricated 23 % silver and the 53 % copper composite membranes, respectively. The selectivity to hydrogen over a gas mixture containing, in addition to hydrogen, carbon monoxide, carbon dioxide and nitrogen was measured. The mass spectrometer did not detect any CO2 or CO, showing that the membrane is completely hydrogen selective. The microfabricated membranes exhibit both high mechanical strength (they easily withstand pressures up to 4 bar) and high thermal stability (up to 650 °C). 相似文献
6.
The H–D isotopic exchange between H2 and D2 and between H2S and D2 was carried out at 80°C in a recycling reactor over a series of presulfided Mo/Al2O2 catalysts containing different amounts of nickel. Whatever the pretreatment procedure, it was found that the promoter had
no significant effect on the rate of H–D exchange or on the amount of exchangeable hydrogen present on the catalysts.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
7.
Cellulose, one of the important components of biomass, was gasified in supercritical water to produce hydrogen-rich gas in
an autoclave which was operated batch-wise under high-pressure. K2CO3 and Ca(OH)2 were selected as the catalysts (or promoters). The temperature was kept between 450°C and 500°C while pressure was maintained
at 24–26 MPa. The reaction time was 20 min. Experimental results showed that the two catalysts had good catalytic effect and
optimum amounts were observed for each catalyst. When 0.2 g K2CO3 was added, the hydrogen yield could reach 9.456 mol·kg−1 which was two times of the H2 amount produced without catalyst. When 1.6 g Ca(OH)2 was added, the H2 yield was 8.265 mol·kg−1 which is lower than that obtained using K2CO3 as catalyst but is still 1.7 times that achieved without catalyst. Comparing with the results obtained using K2CO3 or Ca(OH)2 alone, the use of a combination of K2CO3 and Ca(OH)2 could increase the H2 yield by up to 2.5 times that without catalyst and 25% and 45% more than that obtained using K2CO3 and Ca(OH)2 alone, respectively. It was found that methane was the dominant product at relatively low temperature. When the temperature
was increased, the methane reacts with water and is converted to hydrogen and carbon dioxide.
__________
Translated from Journal of Chemical Engineering of Chinese Universities, 2007, 21(3): 436–441 [译自: 高校化学工程学报] 相似文献
8.
Co–BaCO3 catalysts exhibited high catalytic performance for oxidative dehydrogenation of ethane (ODE) using CO2 as oxidant. The maximal formation rate of C2H4 was 0.264 mmol · min−1 · (g · cat.)−1 (48.0% C2H6 conversion, 92.2% C2H4 selectivity, 44.3% C2H4 yield) on 7 wt% Co–BaCO3 catalyst at 650 °C and 6000 ml. (g · cat.)−1. h−1. Co–BaCO3 catalysts were comparatively characterized by XRF, N2 isotherm adsorption-desorption, XRD, H2-TPR and LRs. It was found that Co4+–O species were active sites on these catalysts in ODE with CO2. The redox cycle of Co–O species played an important role on the catalytic performance of Co–BaCO3 catalysts. On the other hand, the co-operation of BaCO3 and BaCoO3 was considered to be one of possible reasons for the high catalytic activity of these catalysts. 相似文献
9.
Chunrui Wu Shouhai Zhang Fajie Yang Chun Yan Xigao Jian 《Frontiers of Chemical Engineering in China》2008,2(4):402-406
The novel thermal stable composite nanofiltration membranes were prepared through the interfacial polymerization of piperazine
and trimesoyl chloride on the poly (phthalazinone ether) ultrafiltration substrate. The effects of polymerization and testing
conditions on membrane performance were studied. The surface morphologies of the substrate and the composite membranes were
observed by means of scanning electron microscopy (SEM) and atomic force microscopy (AFM). The separation properties of membranes
for dyes and salts were tested. The composite membranes show good thermal stability. The rejection for Na2SO4 was kept over
96%, while the flux reached 400 L·m−2·h−1 when it was tested at 1.0 MPa and 80°C. When tested at 1.0 MPa and 60°C, the rejection of the composite membrane for dyes
was kept at high level, and the flux reached 180–210 L·m−2·h−1, while the rejection for NaCl was lower than 20%.
__________
Translated from the Journal of Functional Materials, 2007, 38(12): 2025–2027, 2031 [译自: 功能材料] 相似文献
10.
Lionel Fabre Guy Flèche Patrick Fuertes Pierre Gallezot Alain Perrard 《Catalysis Letters》2000,68(1-2):41-44
Water solutions of glucono-δ-lactone and glucono-γ-lactone in equilibrium with gluconic acid were hydrogenated with molecular
hydrogen in the presence of a commercial carbon-supported ruthenium catalyst (5% Ru/C, Engelhard Escat 40). Reactions were
conducted batchwise on 20 wt% solutions under 100 bar pressure in the temperature range 80–140°C. Reaction rates were unexpectedly
high at moderate temperatures (e.g., 0.58 mol h-1 g
Ru
-1
at 100°C) because lactones were probably the reactive species. The selectivity to sorbitol at total conversion was larger
than 99% at temperatures lower than 100°C. Kinetic study was done at different temperatures, pressures and concentrations.
Modelling of the reaction kinetics showed that the reaction followed a rate law corresponding either to the Langmuir–Hinshelwood
mechanism without H2 dissociation, or to the Horiuti–Polanyi mechanism.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
11.
《分离科学与技术》2012,47(1-4):487-504
Abstract In recent years, there has been increased interest in developing inorganic and composite membranes for in-situ separation of hydrogen to achieve an equilibrium shift in catalytic membrane reactors. The productivity of these membrane reactors, however, is severely limited by the poor permeability and selectivity of available membranes. To develop a new class of permselective inorganic membranes, electroless plating has been used to deposit palladium thin-films on a microporous ceramic substrate. A palladium thin-film coating was deposited on a microporous ceramic disk (α-alumina, φ 39 mm × 2 mm thickness, nominal pore size 150 nm and open porosity ≈ 42%) by electroless deposition. The film was evaluated by SEM and EDX analysis. A steady-state counter-diffusion method, using gas chromatographic analysis, was used to evaluate the permeability and selectivity of the composite palladium membrane for hydrogen separation at temperatures from 373 to 573 K. The pressure on the high pressure side of the membrane ranged from 170 to 240 kPa and the low pressure side was maintained at 136 kPa. The measured hydrogen permeabilities at 573 K were found to be 1.462×10?9 mol·m/m2·s·Pa0.778, and 3.87×10?8 mol · m/m2 · s · Pa0.501 for palladium film thicknesses of 8.5 and 12 μm, respectively. The results indicate that the membrane has both high permeability and selectivity for hydrogen and may find applications in high temperature hydrogen separation and membrane reactors. 相似文献
12.
Lu Lu Hongfeng Xu Hong Zhao Shaomin Zhu Ruiming Ren 《Journal of Applied Electrochemistry》2012,42(4):201-207
Pt/C–RuO2·xH2O catalyst was successfully prepared through the deposition of hydrated RuO2·xH2O on Pt/C catalyst for a proton exchange membrane fuel cell (PEMFC). The Pt/C and Pt/C–RuO2·xH2O catalysts were compared using physical and electrochemical techniques. The ON–OFF cycling test results showed sudden cell
failures after 1,850 and 1,160 cycles for Pt/C–RuO2·xH2O and Pt/C, respectively. Nearly 11.2% of the cell voltage of Pt/C–RuO2·xH2O was lost after 1,160 cycles, compared with 26.3% for Pt/C. The charge transfer resistances of Pt/C–RuO2·xH2O and Pt/C increased from 0.5217 and 0.5366 Ω to 0.5732 and 0.7261 Ω, respectively. The remaining electrochemical active surface
area of Pt was about 30.6% in Pt/C and about 68.9% in Pt/C–RuO2·xH2O after the ON–OFF test. The mean particle size of Pt/C significantly increased from 4.6 to 8.9 nm, whereas that of Pt/C–RuO2·xH2O increased from 4.3 to 6.3 nm. Therefore, the long-term durability of Pt/C–RuO2·xH2O in a PEMFC was much better than that of Pt/C. 相似文献
13.
The catalytic dehydro-aromatization reaction over Mo/HZSM-5 catalyst was drastically stabilized by the co-addition of 5.4%
H2 and 1.8% H2O to methane feed at 750 °C, 0.3 MPa and methane space velocity of 3000 mL g−1 h−1, suppressing the coke formation effectively, compared with single hydrogen or steam addition. 相似文献
14.
A nozzle, fabricated from nickel, molybdenum, iron, palladium, and quartz was utilized to produce longer chain hydrocarbons,
C
m
H
n
(m ≥ 3, n≤ m) from C2 (ethane, acetylene) and C1 (methane) reactants at nozzle temperature range 1000–1150°C. The conversion of ethane was close to 100% at T
noz = 1000°C, while that of methane reached 20% at T
noz = 1150°C. The contact time in the nozzle is in the 10-3–10-2 s range. The reactions are first and higher order in reactant pressure. The reaction mechanism involves the formation of
free radicals at the nozzle surface followed by gas‐phase reactions.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
15.
Masakoto Kanezashi Takanori Sasaki Hiromasa Tawarayama Tomohisa Yoshioka Toshinori Tsuru 《Journal of the American Ceramic Society》2013,96(9):2950-2957
The sol–gel method was applied to the fabrication of amorphous silica membranes for use in hydrogen separation at high temperatures. The effects of fabrication temperature on the hydrogen permeation properties and the hydrothermal stability of amorphous silica membranes were evaluated. A thin continuous silica separation layer (thickness = <300 nm) was successfully formed on the top of a deposited colloidal silica layer in a porous glass support. After heat treatment at 800°C for an amorphous silica membrane fabricated at 550°C, however, it was quite difficult to distinguish the active separation layer from the deposited colloidal silica layer in a porous glass support, due to the adhesion of colloidal silica caused by sintering at high temperatures. The amorphous silica membranes fabricated at 700°C were relatively stable under steam atmosphere (500°C, steam = 70 kPa), and showed steady He and H2 permeance values of 4.0 × 10?7 and 1.0 × 10?7 mol·m?2·s?1·Pa?1 with H2/CH4 and H2/H2O permeance ratios of ~110 and 22, respectively. The permeance ratios of H2/H2O for membranes fired at 700°C increased drastically over the range of He/H2 permeance ratios by factors of ~3–4, and showed a value of ~30, which was higher than those fired at 500°C. Less permeation of water vapor through amorphous silica membranes fabricated at high temperatures can be ascribed to the dense amorphous silica structure caused by the condensation reaction of silanol groups. 相似文献
16.
The sub- and supercritical water extractions of Athabasca oil sand bitumens were studied using a micro reactor. The experiments
were carried out in the temperature range of 360–380 °C, pressure 15–30 MPa and water density 0.07–0.65 g/cm3 for 0–2 hrs. The extraction conversion of bitumens increased with solvent power and temperature. A maximum conversion of
24% was obtained after 90 min extraction at the supercritical condition. Hydrogen and carbon mono-oxide were not detected
in sub-critical region but in the supercritical region. The supercritical condition was favorable to the hydrogen formation
for bitumen extraction. The extraction products were upgraded relative to the original bitumens due to direct hydrolysis of
low-energy linkage and H2 formed by water gas shift reaction in supercritical condition. 18% of initial sulfur in bitumen can be removed at maximum
conversion condition. The asphaltene contents of the residue were significantly higher than that of original bitumen due to
preferential extraction of aromatic compounds in supercritical condition. 相似文献
17.
Maryam Ghoreishi Amiri Ali Morsali Fahime Bigdeli 《Journal of Inorganic and Organometallic Polymers and Materials》2011,21(1):195-200
A new 1D supramolecular involving two different ligands, {[Zn(GB)2]·(μ-bpe)3}
n
(ClO4)2n
·nH2O (GB = 2-guanidinobenzimidazole and bpe = 1,2-bis(4-pyridyl)ethylene, has been synthesised, characterized by elemental analysis,
IR-, 1H NMR-, 13C NMR spectroscopy. The thermal stability of compound {[Zn(GB)2]·(μ-bpe)3}
n
(ClO4)2n
·nH2O was studied by thermal gravimetric and differential thermal analyses. The single crystal X-ray analysis shows that the complex
is a one-dimensional polymer involving macrocycle rings as a result of non-covalent bridging bpe ligands via N–H···N and N···N
interactions, N–H···bpe···bpe···H–N, with the basic repeating {[Zn(GB)2](μ-bpe)3}(ClO4)2·H2O units and by connecting [Zn(GB)2]2+ nodes. ZnO nanoparticles were obtained by calcination of compound {[Zn(GB)2]·(μ-bpe)3}
n
(ClO4)2n
·nH2O at 500 °C in air. The nanoparticles were characterized by X-ray diffraction and scanning electron microscopy. 相似文献
18.
Thapanon Settheeworrarit Chaveng Pakawatchai Santi Maensiri Jumras Limtrakul Apinpus Rujiwatra 《Journal of Inorganic and Organometallic Polymers and Materials》2006,16(3):231-239
Summary The inorganic–organic hybrid [VIV
4O10VV
2O4] (C6H14N2)·H2O polymeric framework was prepared under mild hydrothermal conditions from a mixture of DABCO and V2O5 in deionized water with a 1:1:450 mole ratio, at neutral pH. The reaction was carried out at 180 °C for 3 days under autogenous pressure yielding phase pure crystals product. The crystal structure was studied using both powder and single crystal X-ray crystallography, revealing the structure to be of the ({UuDd}:T*)α′ type in the SP+T class and Z-T subclass. The presence of the organic cation was confirmed by FT-IR spectrum and chemical composition analysis. The structure was thermally stable up to over 400 °C, and showed ferromagnetic character at room temperature with the maximum molar susceptibility of 8.26 × 10−3 emu/mol−1 at zero applied field. 相似文献
19.
《分离科学与技术》2012,47(13):2128-2137
Silver-doped methyl-modified silica membranes (Ag/M-SiO2) have been prepared using the sol-gel method by adding AgNO3 solution to a methyl-modified silica sol. The influence of silver-doping on the physical and chemical structures, thermal stability of –CH3 groups, and gas permeation performance for the silica membranes were investigated. The metallic silver results from the reduction of AgNO3 which can be completely transformed after calcined above 200°C. The Si–CH3 vibrational bands disappear completely when the calcination temperature is increased to 600°C, which mineralized when the calcination temperature is further increased to 750°C. The doping of silver nanoparticles has nearly no influence on the chemical structure of the methyl-modified silica materials and the thermal stability of –CH3 groups, but can make the mean pore size, total pore volume, H2 permeability, and H2/CO2 selectivities of the silica membranes increase. When operated at 200°C and a pressure difference of 0.35 MPa, the H2 permeance and H2/CO2 selectivity of Ag/M-SiO2 membrane with the AgNO3/tetraethylorthosilicate molar ratio of 0.08 is 8.99 × 10?6 mol · m?2 · Pa?1 · s?1 and 10.22, respectively. After hydrothermal treatment and regeneration, the Ag/M-SiO2 membranes show a smaller change in gas permeances and H2/CO2 permselectivities than the methyl-modified silica membranes without silver-doping. 相似文献
20.
A. A. Vostrikov D. Yu. Dubov S. A. Psarov M. Ya. Sokol 《Combustion, Explosion, and Shock Waves》2008,44(2):141-149
A study was made of the conversion of single spherical coal particles of diameter 1–5 mm in a supercritical H2O/O2 fluid with an oxygen mass fraction of 0–6.6% in a semibatch reactor at a pressure of 30 MPa and a temperature of 673–1023
K. A decrease in the particle mass was observed in two parallel processes: gasification of coal with water and oxidation of
coal with oxygen. An activation energy 19 ± 7 kJ/mole and a pre-exponential factor 10−2±0.4 sec−1 were obtained under the assumption of zero order for the concentration H2O and an Arrhenius dependence for the rate of gasification with water. The oxidation with oxygen at a temperature above 780
K was found to be limited by the rate of O2 diffusion to the coal organic matter. Below 780 K, the rate of heterogeneous oxidation with oxygen is described by a first-order
reaction for the concentration of O2 and a zero-order reaction for the concentration of H2O with an activation energy of 150 ± 27 kJ/mole and a pre-exponential factor of 107.6±1.9 cm3/(g · sec).
__________
Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 2, pp. 23–31, March–April, 2008. 相似文献