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1.
Adsorption of H2 on multiwalled carbon nanotubes was measured at 77 K by a volumetric method. Adsorption and desorption isotherms are largely reversible. The adsorption capacity increased remarkably after receiving heat treatment at 400 °C and being pressed into pellets. The isotherms show typical feature of supercritical adsorption and were satisfactorily modeled by the model that applied for usual supercritical adsorption. The maximal adsorption capacity of hydrogen under the condition tested is less than 0.5 wt%. 相似文献
2.
R. A. Shutilov I. V. Grenev O. V. Kikhtyanin V. Yu. Gavrilov 《Kinetics and Catalysis》2012,53(1):137-144
The H2 sorption properties of the aluminophosphate zeolites AlPO-5, AlPO-31, AlPO-11, AlPO-36, and AlPO-8 at 77 K have been investigated.
A series of H2 adsorption isotherms has been obtained for cylindrical micropore channels in the aluminophosphate zeolites. The absolute
values of the amount adsorbed α(P) for the mesoporous aluminophosphate materials and the effective density of adsorbed H2 in the micropore space β*(P, d) have been determined. It has been demonstrated experimentally that the sorbate density depends on the size of the micropore
channel of the zeolite d. Hydrogen sorption isotherms have been calculated from experimental isotherms. A procedure allowing β*(P, d) to be estimated for intermediate d values is presented. 相似文献
3.
A. Gil 《Adsorption》1998,4(3-4):197-206
The micropore structure of four microporous materials (two zeolites, ZSM-5 and Y-82; an activated carbon and an alumina pillared clay) and their binary physical mixtures (50-50 wt%) have been examined by nitrogen adsorption at 77 K. Various micropore sizes have been considered from the stages on the micropore filling mechanism in the microporous materials. The application of the Dubinin-Astakhov (DA) equation to characterize and obtain the adsorption potential distributions of the microporous materials is presented. 相似文献
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Dihydrogen adsorption at 77 K on a number of fine-particle carbon materials, activated carbons, and carbon nanotubes has been investigated. The micropore structure parameters of these materials have been determined using a volumetric comparative method and nonlocal density functional theory (NLDFT). These data processing methods lead to different values of textural parameters. This difference is attributed to the presence of specific sorption sites on the surface of real carbon materials. The pore size range in which the NLDFT method is applicable to the C-H2 system has been determined. A comparison between the hydrogen sorption properties of different carbon nanotubes is presented. 相似文献
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《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1982,38(11):1109-1113
Infrared spectra of polycrystalline C6F6 are analyzed in the 200 cm−1 to 4000 cm−1 region. The vibrational frequencies agree well with liquid data although many of the bands are split. Mutual exclusion between infrared active and Raman active fundamentals is found. 相似文献
7.
有机胺修饰具有较大孔径介孔材料的二氧化碳吸附性能 总被引:2,自引:0,他引:2
以非离子表面活性剂P123为模板剂,正硅酸甲酯为硅源,通过加入不同的扩孔剂制得具有较大孔径的SBA-15类介孔材料,并采用粉末X射线衍射(XRD)、低温氮气吸附-脱附、扫描电镜(SEM)、傅里叶变换红外(FTIR)光谱等手段对所得样品进行了表征.加入扩孔剂可以明显增大介孔材料的孔容和孔径,而异辛烷为扩孔剂的扩孔效果明显优于四氯化碳.经四乙烯五胺(TEPA)镀饰后,这些样品均表现出良好的CO2吸附性能.其中对于除去模板剂后再镀胺的样品,其CO2吸附能力与介孔材料孔道结构关系不大,而对于未除模板剂的原粉镀胺样品,CO2吸附能力则随孔道的变大而增强.此外,通过吸附等温线和CO2-程序升温脱附(TPD)手段比较了温度和压力对CO2吸附的影响,发现在较高温度下吸附时CO2的吸附能力随压力的变化存在显著差别,因而在这类TEPA修饰的介孔材料上可通过变压吸附的途径来实现对环境气流中CO2的吸附和分离. 相似文献
8.
在酸性条件下,以三嵌段非离子表面活性剂P123为模板剂,四氧基硅烷(TEOS)预水解后与3-巯基丙基三乙基硅(MPTES)共聚,合成了具有不同巯基官能团比例x[n(MPTES)/n(TEOS+MPTES)]的功能化介孔材料(SBA-SH-x),其结构和性能经FT-IR,元素分析,SEM,TEM,小角X-ray和N2吸附-脱附表征。结果表明:x10%,SBA-SH-x为六方p6mm介观结构;10%x15%,SBA-SH-x为立方Ia3d介孔结构;x20%,SBA-SH-x为无序结构。SBA-SH-x在水溶液中吸附Hg2+的研究结果表明:SBA-SH-10和SBA-SH-15对Hg~(2+)吸附性能较好。 相似文献
9.
The luminescence properties of the 2,5-diphenyloxazole (PPO) at 77 K are very sensitive to complex formation with hydroxyl-containing solvents. At the triplet level complex formation affects the internal conversion to the ground state as shown by adding large salt concentration in ethanol solutions. Salt addition induces an increase in the phosphorescence quantum efficiency and a blue-shift of this emission. 相似文献
10.
Yu. K. Dolgikh V. K. Ryabchuk L. L. Basov S. G. Grenishin 《Reaction Kinetics and Catalysis Letters》1986,32(1):45-50
Photoinduced adsorption (PIA) of oxygen molecules on AgBr films at 77 K has been experimentally observed and investigated. Lifetimes of PIA centers and desorption activation energies of O2 molecules have been determined. The process is suggested to compete with the ionic step of AgBr photolysis.
- () - AgBr 77 K. - O2. , , - AgBr.相似文献
11.
The cocondensation of atomic carbon with o, m and p-tolualdehyde at 77K results in deoxygenation to the o, m and p-tolylmethylenes which possess sufficient energy to rearrange to benzocyclobutene and styrene. 相似文献
12.
Frost RL Erickson KL Weier ML Leverett P Williams PA 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(4):607-612
Raman spectroscopy at 298 and 77K has been used to study the structure of likasite, a naturally occurring basic copper(II) nitrate of formula Cu3NO3(OH)5.2H2O. An intense sharp band is observed at 3522 cm(-1) at 298 K which splits into two bands at 3522 and 3505 cm(-1) at 77 K and is assigned to the OH stretching mode. The two OH stretching bands at 3522 and 3505 provide estimates of the hydrogen bond distances of these units as 2.9315 and 2.9028 angstroms. The significance of this result is that equivalent OH units in the 298 K spectrum become two non-equivalent OH units at 77 K suggesting a structural change by cooling to liquid nitrogen temperature. A number of broad bands are observed in the 298 K spectrum at 3452, 3338, 3281 and 3040 cm(-1) assigned to H2O stretching vibrations with estimates of the hydrogen bond distances of 2.8231, 2.7639, 2.7358 and 2.6436 angstroms. Three sharp bands are observed at 77 K at 1052, 1050 and 1048 cm(-1) attributed to the nu1 symmetric stretching mode of the NO3 units. Only a single band at 1050 cm(-1) is observed at 298 K, suggesting the non-equivalence of the NO3 units at 77 K, confirming structural changes in likasite by cooling to 77 K. 相似文献
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K. Noble A.B. Seddon M.L. Turner P. Chevalier I.A. Mackinnon 《Journal of Sol-Gel Science and Technology》2000,19(1-3):807-810
We report the preparation of polysiloxane-modified mesoporous silica gels derived from the acid catalysed hydrolysis of tetraethoxysilane (TEOS) and oligomeric silanol terminated polydimethylsiloxane (PDMS) in the presence of the non-ionic surfactant, octaethylene glycol monohexadecyl ether. The gels were characterised using thermal gravimetric analysis (TGA), infra-red (IR) spectroscopy, X-ray diffraction (XRD) and 29Si solid state cross-polarisation (CP) magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy. TGA and IR spectroscopy showed the loss of surfactant after calcination and a decrease in the Si–OH band at 950 cm–1 indicated further condensation had occurred. This was confirmed by the increase in Q4 at –110 ppm, in 29Si MAS NMR spectroscopy, which also showed that calcination had led to the redistribution of PDMS forming a T species. XRD data showed ordering within the structure, with an initial d-spacing of 45 Å, decreasing to 35 Å after calcination. 相似文献
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The isothermal luminescence at 77 K of gamma-irradiated high density polyethylene, both with and without introduced admixtures (n-hexane, naphthalene) has been measured. The spectrum of emitted light was recorded and found to be identical with that of added compound. A reaction mechanism responsible for the isothermal luminescence consistent with the experimental results is proposed. 相似文献
18.
H G?rner 《Journal of photochemistry and photobiology. B, Biology》1990,5(3-4):359-377
The emission spectra of nucleic acids, pyrimidine and purine nucleotides, nucleosides and bases and a series of pyrimidine derivatives were obtained using UV light excitation in glasses (ethanol and 2:1 mixtures of ethylene glycol and water (EG-H2O); also partly in butyronitrile and 2-methyltetrahydrofuran) at 77 K. The quantum yields of fluorescence phi f and phosphorescence phi p of some 30 compounds are presented; for several substituted uracils they are reported for the first time. The values cover a range from phi f = 0.0002 and phi p = 0.001 for uracil in ethanol to phi f = 0.50 for guanosine in acidic ethanol and phi p = 0.095 for guanosine-5'-monophosphate in EG-H2O (pH 6-7). The phosphorescence lifetime tau p at 77 K ranges from about 0.3 s (uracil moiety) to 3 s (adenine moiety). The measured tau p, phi f and phi p values are compared with those available in the literature. 相似文献
19.
Frost RL Kristof J Rintoul L Kloprogge JT 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2000,56(9):1681-1691
The Raman spectra of urea and urea-intercalated kaolinites have been recorded at 77 K using a Renishaw Raman microprobe equipped with liquid nitrogen cooled microscope stage. The NH2 stretching modes of urea were observed as four bands at 3250, 3321, 3355 and 3425 cm(-1) at 77 K. These four bands are attributed to a change in conformation upon cooling to liquid nitrogen temperature. Upon intercalation of urea into both low and high defect kaolinites, only two bands were observed near 3390 and 3410 cm(-1). This is explained by hydrogen bonding between the amine groups of urea and oxygen atoms of the siloxane layer of kaolinite with only one urea conformation. When the intercalated low defect kaolinite was cooled to 77 K, the bands near 3700 cm(-1) attributed to the stretching modes of the inner surface hydroxyls disappeared and a new band was observed at 3615 cm(-1). This is explained by the breaking of hydrogen bonds involving OH groups of the gibbsite-like layer and formation of new bonds to the C=O group of the intercalated urea. Thus it is suggested that at low temperatures two kinds of hydrogen bonds are formed by urea molecules in urea-intercalated kaolinite. 相似文献
20.
Adsorption kinetic studies are conducted to investigate the potential to use chiral mesoporous materials nanoporous guanosine monophosphate material-1 (NGM-1) and nanoporous folic acid material-1 (NFM-1) for the enantiomeric separation of l- and d-valine. A pseudo-second-order (PSO) kinetic model is applied to test the experimental adsorption equilibrium isotherms, according to both the Langmuir and Freundlich models and the characteristic parameters for each model are determined. The calcined versions of both NGM-1 and NFM-1 fit the Langmuir model with maximum sorption capacities of 0.36 and 0.26 g/g for the preferred adsorption enantiomers, d-valine and l-valine, respectively. Experimental results and the analysis of adsorption models suggest a strong adsorbate–adsorbent interaction, and the formation of a monolayer of tightly packed amino acid on the internal mesopore surface for the preferred enantiomers. 相似文献