The experimental and MD studies of the sorption processes of organic molecules on the SiO2 surface

In this paper the experimental and molecular dynamics studies have been performed for the adsorption processes of n-butanol and butyl acetate on the SiO2 surface. The experimental measurements of the adsorption/desorption processes of n-butanol and butyl acetate on the SiO2 surface include data from thermokinetic spectrometry. Additionally, the computer molecular dynamics (MD) simulations involved the analysis of temperature, energy, and structural characteristics of the adsorption processes of n-butanol and butyl acetate on the SiO2 surface. Based on the MD simulations of the triple system—surface (SiO2)—carrier gas (Ar)—target molecule (n-butanol, butyl acetate), radial distribution function (RDF) profiles were constructed and analyzed at three temperatures of the system: T = 300, 500, and 700 K. A comparative analysis of the results reveals that the addition of an acetate group enhances the affinity of the butyl acetate molecule towards the SiO2 surface. Consequently, the adsorption process of butyl acetate occurs more completely at higher temperatures compared to n-butanol. In addition, changes in size influence the arrangement of atoms within the butyl acetate molecule relative to the surface atoms of SiO2, leading to the observed "displacement" effect of an identical chain for both molecules (n-butanol and butyl acetate) of the carbon "skeleton" atoms (C1(Q=−3)–C2(Q=−2)–C3(Q=−2)–C4(Q=−1)–O1(Q=−2)). The experimental data on the desorption processes of n-butanol and butyl acetate from the SiO2 surface in the triple system "n-butanol/SiO2/argon" ("butyl acetate/SiO2/argon") yield an Arrhenius activation energy value of 78.83 kJ/mol (87.58 kJ/mol) and a pre-exponential multiplier value of 4.41 × 107 s−1 (1.81 × 1010 s−1).