Nitrogen-adsorption method

Surface Area Measurements. For a discussion of procs used see above under Fisher Sub-Siever and Nitrogen Adsorption. For AP, the Fisher Sub-Siever is most suitable for samples having surface areas from 0.05 to 0.46sqm/g, and the Nitrogen Adsorption method for finer mat, up to 30000 sqcm/cc (Ref 49)... 

Fig. 3. Plot to calculate surface fractal dimension by nitrogen adsorption method.

The specific surface area of the fresh and used catalysts was measured by nitrogen adsorption method (Sorptometer 1900, Carlo Erba Instruments). The catalysts were outgassed at 473 K prior to the measurements and the Dubinin equation was used to calculate the specific surface area. The acidity of investigated samples was measured by infrared spectroscopy (ATI Mattson FTIR) by using pyridine (>99.5%, a.r.) as a probe molecule for qualitative and quantitative determination of both Bronstcd and Lewis acid sites (further denoted as BAS and LAS). The amounts of BAS and LAS were calculated from the intensities of corresponding spectral bands by using the molar extinction coefficients reported by Emeis (23). Full details of the acidity measurements are provided elsewhere (22). 

The surface area of the catalysts was measured by the conventional B.E.T. nitrogen adsorption method. 

A number of attempts have been made [l], at a national level, to establish standard procedures for the determination of surface area by the BET-nitrogen adsorption method. In addition, the results have been published [2] of an SCI/IUPAC/NPL project on surface area standards. This project brought to light a number of potential sources of error in the determination of surface area by the gas adsorption method. 

The progress in the determination of porosity of various types of materials has arisen over the past ten years from advances in application of new spectroscopy techniques. In the present paper the application of small angle X-ray scattering (SAXS), positronium annihilation lifetime spectroscopy (PALS) and low temperature nitrogen adsorption methods to the characterization of mesoporosity is reviewed using different types of silica gels with chemically modified surface. The results from the three methods are compared and discussed. 

Two mesoporous silica molecular sieves synthesized by using n-octadecyl-ammonium bromide and n-dodecylammonium bromide as a templates were characterized for their pore size distribution by temperature programmed desorption method and low temperature nitrogen adsorption method. The pore size distributions and total pore volumes determined by the two methods agree quite well and are within experimental error. 

Figures 6 and 7 show PSDs calculated from nitrogen adsorption method and-thermo-desorption method.

In both cases the pore distributions are deformed and the location of the pore size distribution peaks differs considerably from those obtained from the nitrogen adsorption method. If is too slow, desorption will be too slow, so that air can mix with the vapour. When p < 1 atm the evapouration from the pores at each measuring temperature is possi-... 

The surface areas of the catalysts were measured by the conventional BET nitrogen adsorption method. Values of 26, 7 and 4 m /g were obtained for the 2, 6 and 10 % PbO/SiOa catalysts, respectively. 

Surface Area Measurement The BET surface area of the samples were measured by low temperature nitrogen adsorption method. 

Research on the fractal characteristics of pore structure of coal particles based on low temperature nitrogen adsorption method... 

Jiang Wenping, et al. 2011. Research on the pore properties of different coal body structure coals and the effects on gas outburst based on the low-temperature nitrogen adsorption method. Journal of China Coal Society, 36(4) 609 14 (in Chinese). 

Qi Lingling, et al. 2012. Study on porosity of coal samples based on low temperature nitrogen adsorption method and mercury porosimetry. Coal Science and Technology, 40(8) 36-39 (in Chinese). 

From the average primary particle diameter, a theoretical total surface area can be calculated, assuming spherical particle shapes. This does not account for the aggregate structure or porosity. Another method to determine surface area (per 100 g of filler) is by measuring the absorption of a gas of small atoms, e.g., nitrogen. The gas penetrates the finest crevices. According to the nitrogen adsorption method developed by Brunauer, Emmett and Teller, one obtains the so-called BET-value of surface area, expressed as m /g. 

The particle size distribution was determined by sedimentation of the ash residue with a Sedigraph 5100. For calcium carbonate filler precipitated onto the surface of fibrils, the specific surface area was determined by oxidising the cellulosic fibres at low temperature (300°C) followed by oxidation for 1 h at 500°C. The specific surface area of the ash residue and reference PCC was determined with the Bmnauer-Emmett-Teller (BET) nitrogen adsorption method. The measurement was carried out with a Micromeritics Gemini 2375 apparatus. 

Figure 1.206 shows the PSD (or UWCSD) calculated using the NMR and TSDC cryoporometry methods, NMR relaxometry (aqueous suspensions), and nitrogen adsorption method. 

Gun ko, V.M., MeMe, S.T., Kozynchenko, O.P. et al. 2011a. Comparative characterisation of carbon and polymer adsorbents by SAXS and nitrogen adsorption methods. J. Phys. Chem. C 115 10727-10735. 

Nanometer size SnOg was prepared with a sol-gel process followed by supercritical fluid drying. Their structure, particle size and spedflc surface area were characterized by XRD, TEM and nitrogen adsorption method. The effect of the preparation parameters is also discussed. 

Under certain conditions, however, the micropores may be closed or reduced in size so that the BET nitrogen adsorption method measures only the exterior surface of the microgel particles. Such a product may thus have a low specific area especially when the process is conducted hot and the precipitate aged at High pH, as done by Acker and Winyall (424). 

Specific surface areas are measured using the nitrogen adsorption method at 77 K, except those marked by ) with the permeation method and ) using the Wagner turbidimeter. 

The most common methods to determine pore size distributions are the A. mercury penetration method, B. nitrogen adsorption method, and C. molecular probe method. 

As is understood from Fig. 2.9, for small pores which have molecular sieving abilities, it is not possible to determine pore size distribution by nitrogen adsorption method. In these cases, the most direct determination of the effective pore size is the molecular probe method. 

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