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Improved theories for calculating adsorption energy distributions of porous solids

Subject Area Technical Chemistry
Term from 2017 to 2023
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 343864554
 
Final Report Year 2023

Final Report Abstract

The energetic heterogeneity of classical and state-of-the-art porous solids holds a key position in their evaluation and application in processes such as adsorption, heterogeneous catalysis or gas storage. Methods for the evaluation of experimental adsorption isotherms of gases or liquids on porous solids based on the solution of the adsorption integral equation are already widely used today, e.g. in commercial devices for gas adsorption volumetry, but so far do not provide reliable information on the adsorption energy distributions (AED) of the surfaces of porous solids. In particular, the error of the AED cannot be estimated. The main goal of the project was the calculation of trustworthy AED. For this purpose, a general regularization procedure in the proper sense for solving the adsorption integral equation with Langmuir kernel was developed for the first time in the project. It is shown that for a given choice of the regularization parameter, the approximation error of the AED also vanishes when the error level of the total isotherm vanishes. This means that the quality of the approximation can now be estimated as a function of the error level, which was not possible before. The developed method can be modified for other kernels, insofar as the adsorption integral equation can be transformed into a convolution. The results were verified using gas- and liquid-phase adsorption data, independent experimental methods, and Monte Carlo simulations to better evaluate the information content of AED.

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