Surface Langmuir

G. Suits (ed.), The Collected Works of Irving Langmuir, Surface Phenomena, Vol. 9, Pergamon Press, Oxford, 1962. 

Langmuir surface area micropore volume ° average pore size d = AV JS by Langmuir TOFav = (moles of substrate consumed)/)(moles of M) x time] inside parentheses, the values for the... 

Langmuir, Surface chemistry, in Nobel Lectures. Chemistry 1922-1941, 287-325 and Journal of the American Chemical Society (1932) 2798, cited in Brunauer, The Adsorption of Gases and Vapours, 62. 

Although many kinetic models assume that the catalyst is an ideal Langmuir surface (all sites have identical thermodynamic properties and there are no interactions among surface species), modern surface science has proven that ideality is often not the case. 

Figure 9.30 Plot of saturation H2 uptake versus Langmuir surface area. Reproduced with permission from [212], Copyright (2006) American Chemical Society...

Catalyst sample Langmuir surface area (mVg) Total micropore volume (cmVg)... 

The identity and crystalline purity of the bulk material are determined by PXRD, with the same diffraction pattern as the solvothermal reaction above. Solvent exchange in the pores is confirmed by thermogravimetric analysis and full evacuation is confirmed either by TGA (again, no weight loss until 420°C) or, more rigorously, by gas adsorption (N2,77K, Langmuir surface area of 3909 m2/g). 

Langmuir Surface Layers of Insoluble Materials on Liquids... 

It is seen from the von Szyszkowski-Langmuir surface tension isotherm, Eq. (2.41), that at a given temperature the shape of the surface tension isotherm is determined by only one parameter cOg =cO =cd. The other parameter b enters this equation as a dimensionless variable be, in combination with the concentration. Therefore, the value of b does not affect the shape of surface tension isotherm, and only scales this curve with respect to the concentration axis. It should be noted that this dependence on b is characteristic to all the equations presented above. The dependence of the surface pressure isotherm on the molar area co is illustrated by Fig. 2.1. It is seen, that the lower ro is, hence the higher the limiting adsorption T = 1/co, the steeper is the slope of the n(c)-curve. 

Examples of false obedienee to the Langmuir isotherm abound. These usually arise when adsorption data have not been obtained over a sufficiently wide range of partial pressures a good test is to see if value of Vm evaluated from isotherm data at different temperatures are equal, sinee within the framework of the Langmuir surface model the saturation capacity should not vary with the temperature. It can be difficult to tell, however, in view of experimental error. 

The carboxyhc-type hypercrosslinked resin MN-600 was examined comprehensively by Saha and Streat [388], in comparison with polyacryHc acid C-104E (Purolite), with the aim of evaluating the performance of the resins for trace heavy metal removal. Characterization of these polymers involved scanning electron microscopy, BET and Langmuir surface area measurements, Fourier transform infrared (FTIR) spectroscopy. X-ray photoelectron spectroscopy, elemental analysis, zeta potential... 

Figure 1.9 ThevariationofH2adsorbed(wt%)atsaturationat77KwithBET (a)and Langmuir surface area (b) for porous MOFs, carbons, zeolites, silicas, polymers, and covalent organic frameworks (COFs). Reprinted with permission from K.M. Thomas, Dalton Trans., 9,1487-1505. Copyright (2009) Royal Society of Chemistry...

Chromium has a large contribution to the MOF arena due to the fact that it has created the largest pore-sized metal catalysts yet known. Ferey created a crystal structure for porous chromium terephthalate, MIL-101, with very large pore sizes and surface area. Its zeotype cubic structure has an enormous cell volume ( 702 000 A ), a hierarchy of extra-large pore sizes (30 to 34 A), and a Langmuir surface area for N2 of 5900 300 m This... 

It is seen from the von Szyszkowski-Langmuir surface tension isotherm, that at a given temperature the shape of the surface tension isotherm is determined only by the parameter co, while parameter b enters this equation as a dimensionless variable be. The dependence of the surface pressure isotherm on the molar area CO is illustrated by Fig. 2. For lower co steeper curves 11(c) are obtained. 

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