Selectivity for CO2 over CH4 on a functionalized periodic mesoporous phenylene-silica explained by transition state theory

Abstract

Periodic mesoporous organosilicas-PMO, CO 2 /CH 4 separation, Transition state theory, DFT Highlights • We study the interaction of functionalized periodic mesoporous phenylene-silica APTMS@Ph-PMO with CO 2 and CH 4 by dispersion corrected periodic density functional theory (DFT). • From a transition state theory based approach using such DFT results, an estimation of initial CO 2 /CH 4 selectivity is presented for a wide temperature range. • At ambient temperatures (298 K), such determined CO 2 /CH 4 selectivity of 32.2 agrees to a value of 26.1 from previous experiments

Biogas Upgrading by Transition Metal Carbides

“…However, materials with a high CO 2 selectivity over CH 4 at standard temperature/pressure operation conditions are needed. There is exhaustive experimental research on promising materials, yet performance regretfully often remains low.…”

“…Materials screening is conveniently first sieved from simulations accurately estimating the interaction of a given material with CO 2 and CH 4 . Among other methods, , density functional theory (DFT) including dispersion (DFT-D) has proven especially useful to size CH 4 interactions with Ni and Co surfaces, nanoporous carbons, zeolites, periodic mesoporous phenylene-silica (PMOs), and metal–organic frameworks (MOFs) . Similar examples are available for CO 2 , and in combination with statistical thermodynamics based approaches, realistic and therefore useful estimates of selectivity and uptake rates are accessible. , …”

“…Further better grounded evaluation of CO 2 selectivity over CH 4 is provided for the temperature range 50–1000 K as based on the estimation of adsorption and desorption rates from harmonic transition state theory (TST) using present DFT-D results, as fully explained in the Supporting Information. Notice that such a theoretical approach has been successfully used to explain the experimental biogas upgrading in PMOs . In short, adsorption rates and for CO 2 and CH 4 depend on the impingement of molecules on the surfaces and therefore on their partial pressures.…”

“…Note that present estimations are given for initial adsorption stages, where adsorbate lateral interactions are disregarded. For CO 2 at medium coverages, these are found not to be repulsive, seen, e.g., on Ni or α-Mo 2 C surfaces.…”

Recent Advances in the Preparation and Applications of Organo‐functionalized Porous Materials

“…demonstrated that amine groups could be functionalized in the PMOs through mononitration with nitric acid in the presence of sulphuric acid, followed by the reduction with tin chloride and HCl. The amine‐functionalized samples showed higher selectivity for the adsorption of CO 2 molecules in comparison with the CH 4 molecules . The same group also manipulated the amine‐functionalized PMOs for the formation of dialkylated amine through the microwave‐assisted approach.…”