康塔公司的一部分吸附资料？ QCI_PowderTech_27(主要介绍氩吸附等温线在表征 分子筛 孔道分布方面的优点,低温氩分子在分子筛孔道内扩散速度快,故氩吸附比氮吸附需要时间短,同时对仪器要求较低) title: QUANTACHROME ANNOUNCES A NEW METHOD FOR ZEOLITE CHARACTERIZATION introduction: Physical adsorption in materials consisting of micropores, as for instance in zeolite etc. occurs at relative pressures substantially lower than in case of adsorption phenomena in mesopores, but spans several orders of magnitude in relative pressure. In particular the characterization of zeolites with nitrogen at 77.4 K is difficult, because the filling of pores of dimension 0.5 - 1 nm occurs at relative pressures of 10-7 to 10-5, where the rate of diffusion and adsorption equilibration is very slow. Hence, it is of advantage to analyze zeolites consisting of such narrow micropores by using argon as adsorptive at liquid argon temperature (87.3 K). Argon fills micropores of dimensions 0.5 – 1nm at much higher relative pressures (i.e., at relative pressures 10-5 to 10-3) compared to nitrogen, which leads to accelerated diffusion and equilibration processes and thus also to a reduction in analysis time. In Figure 1 the different pore filling ranges for argon adsorption at 87.3 K and nitrogen adsorption at 77.4 K is illustrated based on sorption data obtained on a faujasite-type zeolite. QCI_PowderTech_29(在测试等到温线时,需测试不同相对压力下的吸附量,本文介绍了通过提高液体的饱和蒸气压,降低平衡时间的方法) title: Elevated Saturation Vapor Pressure of Liquid Nitrogen introduction: From the analysis of nitrogen gas sorption isotherms obtained at the boiling temperature of nitrogen, (i.e. 77.35 K), important quantities like the specific su**ce area, pore volume, pore size, and pore size distribution can be derived. The sorption isotherm is measured as a function of pressure until the saturation pressure P0 of the bulk fluid is achieved. However the thickness of the adsorbed film and the pore filling (condensation) pressure is related to the difference in chemical potential Δμ = μ- μo of the adsorbate film (μ) and the chemical potential of the bulk liquid (μo), which is related to the pressures P and P0 of the vapor in equilibrium with the adsorbed film and the saturated liquid, respectively, by μ - μo = RTlnP/P0, where R is the universal gas constant and T is the temperature. Hence, the adsorbed amount is measured as a function of the ratio P/P0 and the accurate monitoring of the saturation pressure is crucial in order to ensure the highest accuracy and precision for pore size and su**ce area analysis. QCI_PowderTech_34(nova的广告,当然广告也分有用的广告和讨厌的广告) title: Some Aspects of Quantachrome’s NOVA (NO Void Analysis) Technology introduction: To generate accurate gas sorption data using the conventional volumetric static methods, it is necessary to introduce a non-adsorbing gas such as helium prior to every analysis. The helium is used to measure void (free space) volumes, apply gas non-ideality corrections, and define void volume zones (at room temperature and at liquid nitrogen temperature if this is the temperature at which the adsorption experiment is performed). The helium void volume measurement procedure is based on various assumptions: (i) helium is not adsorbed/ absorbed on/into the adsorbent (ii) helium does not penetrate into regions which are inaccessible for the adsorptive (typically nitrogen). However, these pre-requisites are not always fulfilled and the use of helium for dead-space calibrations has been, therefore, under discussion for many years. Many researchers confirmed that some microporous solids adsorb significant amounts of helium even at ambient temperatures [1], and further evidence for helium absorption was discovered recently [2]. It is also well know that at these low temperatures and low pressures (e.g., at the temperatures of liquid nitrogen, 77.35 K, and liquid argon, 87.27 K) nitrogen and argon molecules can ( in contrast to helium) not enter the most narrow micropores of adsorbents due to diffusion limitations. As a consequence, such nitrogen and argon sorption isotherms are affected by a systematic void volume error. QCI_PowderTech_36(主要介绍了对于不同吸附材料,吸附等温线和脱附等线测试孔道颁布的差别) title: COMMENTS ON THE PROPER SELECTION OF ADSORPTION OR DESORPTION BRANCHES FOR MESOPORE SIZE ANALYSIS introduction: The occurrence of adsorption/desorption hysteresis generates a problem for the pore size analysis of mesoporous materials. The question whether the adsorption or desorption branch of a hysteretic isotherm should be taken for pore size analysis has been discussed for many decades. QCI_PowderTech_37(利用氢吸附测试吸附等温线) title: Hydrogen Adsorption: Experiment and Application introcution:In light of recent growing interest in hydrogen storage and fuel cell applications it is important to develop adequate and accurate methods for the characterization of porous materials that are designed for hydrogen applications such as H2 storage and separation. A number of studies have been published on modeling and on experimental data of physical adsorption of H2 on various porous materials [e.g., 1, 2]. Due the fact that hydrogen is supercritical at room temperature (where storage applications will be performed) significant amount of hydrogen can only be stored at elevated pressures. However, hydrogen adsorption experiments performed at subatmospheric pressures can still provide important information about the hydrogen storage potential of an adsorbent. Porous materials concentrate gas molecules, such as hydrogen, in their micropores due to the enhanced gas-solid interaction potential between the walls of such pores. Magnitude of this potential and capacity for hydrogen adsorption, at given temperature and pressure conditions, strongly depend on pore sizes, and so-called ultramicropores (pore sizes < 7 Å) are here most important. Hence, information about ultramicropore sizes and their distribution can be obtained if microscopic approaches are applied to analyze hydrogen adsorption data (see section 3). [ ]查看更多0个回答 . 4人已关注
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