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Hitherto, adsorption has been traditionally used to study only the porous structure in disordered materials, while the structure of the solid phase skeleton has been probed by crystallographic methods such as x-ray diffraction. Here we show that for carbons density functional theory, suitably adapted to consider heterogeneity of the pore walls, can be reliably used to probe features of the solid structure hitherto accessibly only approximately even by crystallographic methods. We investigate a range of carbons, including commercial activated carbons, activated carbon fibres as well as coal chars prepared in our laboratory, and determine pore wall thickness distributions using argon adsorption. The results are corroborated by x-ray diffraction studies, which yield a parallelism indicator that correlates well with its counterpart determined from the adsorption-based pore wall thickness distributions. Further, characterization of progressively heated carbons using the proposed approach shows clear evidence of thickening of pore walls, confirmed by xrd.

We present simulation results for the packing for single center Lennard Jones models of adsorbed fluids such as methane, carbon dioxide and carbon tetrachloride at high pressure in carbon slit pores. These show a series of packing transitions that are well described by a lattice density functional theory model developed in our laboratory. By contrast, simulations show that these transitions are absent for a three-center model, which provides a more adequate representation of carbon dioxide. Analysis of the simulation results shows that alternations of flat lying molecules and rotated molecules can occur in this case as the pore width is increased. The presence or absence of quadrupoles has negligible effect on these high-density structures.

A novel and simple method for determination of micropore network connectivity of activated carbon using liquid phase adsorption is presented in this paper. The method is applied to three different commercial carbons with eight different liquid phase adsorptives as probes. The effect of the pore network connectivity on the prediction of multicomponent adsorption equilibria was also studied. For this purpose, the Ideal Adsorbed Solution Theory (IAST) was used in conjuction with the modified DR single component isotherm. The results of comparison with experimental data show that incorporation of the connectivity, and consideration of percolation processes associated with the different molecular sizes of the adsorptives in the mixture, can improve the performance of the IAST in predicting multicomponent adsorption equilibria.

The development of regular mesoporous materials, MCM-41, has catalyzed considerable research in modeling adsorption phenomena at this scale. A new model for determining the pore size distribution of micro and mesoporous materials from gas adsorption isotherms is proposed here. The model uses the Dubinin-Rudushkevich (D-R) isotherm with Chen and Yang's correction in the micropore region. For the mesopore region, a recent model of the authors using a molecular-continuum approach for the multilayer region, and the Unilan model for the sub-monolayer region, has been extended. The experimental adsorption data is inverted using regularization to obtain the pore size distribution. The family of model mesoporous adsorbent, MCM-41, was chosen for testing the present model. The model was found to be successful in predicting the pore size distribution of pure as well as binary physical mixtures of MCM-41, with results in agreement with those from the XRD method. It was found that the BJH and the BdB methods under-predict while the Saito-Foley method over-predicts the pore diameter. The pore diameters obtained by the current model and the NLDFT were found to be close to actual pore diameters obtained by XRD.

In the present work the meso- and macro-structural characteristics of the mesoporous adsorbent MCM-41 have been estimated with the help of various techniques. The structure is found to comprise four different length scales: that of the mesopores, the crystallites, the grains and of the particles. It was found that the surface area estimated by the use of small angle scattering techniques is higher, while that estimated by mercury porosimetry is much lower, than that obtained from gas adsorption methods. Based on the macropore characterization by mercury porosimetry, and the considerable macropore area determined, it is seen that the actual mesopore area of MCM-41 may be significantly lower than the BET area. TEM studies indicated that MCM-41 does not have an ideal mesopore structure; however, it may still be treated as a model mesoporous material for gas adsorption studies because of the large radius of curvature of the channels.

In the present work, various theories predicting the critical diameter for the absence of capillary condensation and hysteresis are applied to experimental adsorption isotherms of vapors on regular mesoporous materials. Among the various theories studied, the tensile strength approximation proposed by the authors was found to be the most successful. Reversibility of nitrogen adsorption at 77.4 K was studied on pure MCM-41 of various pore sizes, as well as mixtures of pure MCM-41 samples in a 1:1 ratio. The results of PSD and hysteresis on MCM-41 mixtures are close to that expected from studies of the pure materials. The estimates of hysteresis critical temperature and diameter of MCM-41, HMS, FSM and KIT materials are also provided.