Bulk and Confined Benzene-Cyclohexane Mixtures Studied by an Integrated Total Neutron Scattering and NMR Method

Abstract

AbstractHerein mixtures of cyclohexane and benzene have been investigated in both the bulk liquid phase and when confined in MCM-41 mesopores. The bulk mixtures have been studied using total neutron scattering (TNS), and the confined mixtures have been studied by a new flow-utilising, integrated TNS and NMR system (Flow NeuNMR), all systems have been analysed using empirical potential structure refinement (EPSR). The Flow NeuNMR setup provided precise time-resolved chemical sample composition through NMR, overcoming the difficulties of ensuring compositional consistency for computational simulation of data ordinarily found in TNS experiments of changing chemical composition—such as chemical reactions. Unique to the liquid mixtures, perpendicularly oriented benzene molecules have been found at short distances from the cyclohexane rings in the regions perpendicular to the carbon–carbon bonds. Upon confinement of the hydrocarbon mixtures, a stronger parallel orientational preference of unlike molecular dimers, at short distances, has been found. At longer first coordination shell distances, the like benzene molecular spatial organisation within the mixture has also found to be altered upon confinement.