Hydrogen adsorption isotherm

Figure 5.19 Hydrogen adsorption isotherm at room temperature (left) and at liquid nitrogen temperature (right) on metal organic frameworks (MOFs).

Fig. 2. Nitrogen adsorption isotherms at —196°C. and hydrogen adsorption isotherms at 23°C.

Figure 9.46 Hydrogen adsorption isotherm at 77 K and X-ray crystal structure of MOF-177 (reproduced with permission of The Royal Society of Chemistry).

Figure 9. Hydrogen adsorption isotherms for active carbon fiber Busofit-M8 (a), wood-based cardon WAC 3-00 (b) and different temperatures (1 - 77, 2 -153, 3 - 193, 4 - 293 K) experimental data - points, calculated data (Dubinin-Radushkevich equation) - lines.

Fig. 5. Hydrogen adsorption isotherms at 293 K with platinum-gold/Aerosil catalysts V, Pt 98, Au 2 mol %, 1.0 wt % metal 0.516 g catalyst A, Pt 90, Au 10 mol %, 0.9 wt % metal, 0.510gcatalyst , Pt 67, Au 33 mol %,0.9wt % metal, 0.500g catalyst O.Pt 15, Au 85 mol %, 1.0 wt % metal, 0.450 g catalyst standard pretreatment (cf. text). Filled symbols, amount of adsorbed hydrogen remaining after pumping at 293 K for 30 min, after equilibration at indicated pressure. Catalyst samples identified from corresponding symbols above. Within the limits of experimental accuracy, no adsorption could be detected on a Pt 0, Au 100 mol %, 1.0 wt % catalyst, using a 0.500 g sample (20).

Figure 2.9 Hydrogen adsorption isotherm of MOF-5 with low specific surface area (triangles) [88], of MOF-5 prepared by BASF (circles) [13] and of MOF-5 prepared avoiding exposure to air (square) [91] (data corrected to give the wt% storage capacity as defined in Eq. (2.2)).

Hydrogen adsorption isotherms on single wall nanotubes at 77K. From E. Poirier, R. Chahine, P. Benard, G. Dorval-Douville, L. Lafi and P.A. Chandonia, Langmuir 22, 8784 (2006). 

The hydrogen capacity of a large variety of microporous activated carbons and activated carbon fibres has been measured in a wide pressure range at room temperature [117]. The hydrogen adsorption isotherms of the samples at 293 K and up to 70 MPa have similar shapes and are of type I according to foe lUPAC classification. Fig. 27 shows the amount of hydrogen adsorbed (in wt%) in the studied samples at 10 MPa and 70 MPa vs foe Dubinin Radushkevich (DR) micropore volume measured by nitrogen or CO2 adsorption. 

The equilibrium constant Khj is related to the hydrogen adsorption isotherm. At high hydrogen coverage h 1 and we have ... 

Figure 2. Hydrogen adsorption isotherm on smooth Pt in 2 Af H2SO4 (Bold and Breiter ). Dotted lines indicate isotherms expected for the Langmuir isotherm C4(Ph2) = /(l 0) with...

Figure 10.26. Hydrogen adsorption isotherms on activated carbon, CECA AC35 (BET surface area 1000 m /g, from Lamari et ai., 2000, with permission).

The slopes of the isotherms for the various substances are approximately identical in the central part and close to the slope of the hydrogen adsorption isotherm. On iridium the methanol adsorption isotherms are satisfedby the Freundlich equation, where the power in the equation of the isotherm is close to that in the isotherm for hydrogen adsorption on iridium. The adsorption isotherms for methanol and hydrogen on rhodium are the same in nature. These results lead to the conclusion that the dependence of 0 andc is determined not by the nature of the adsorbed substance but by the nature and character of inhomogeneity in the catalyst surface. 

By integration of the hydrogen region of I, curves [15], obtained in sulfuric acid and zinc sulfate and cadmium sulfate solutions at 28, 40, and 60 C, hydrogen adsorption isotherms were plotted with 6 against log p (p = pressure), from which it was seen that they obey a logarithmic isotherm equation ... 

Thomas[116] suggested that a slope of about 60 mV may be caused by various mechanisms, in particular, by a slow recombination under the condition that the hydrogen adsorption isotherm is logarithmic. However, for low surface coverages, which are always observed in the case of mercury[117], the logarithmic isotherm is not applicable and hence this explanation for a 60 mV slope cannot be correct. 

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