T,p Dependence of intradiffusion in binary fluid mixtures with carbon dioxide as one component

Abstract

Intradiffusion coefficients D_ii were measured by the pulsed field gradient NMR technique for five binary systems with carbon dioxide as one component, the second component being benzene, hydrogen, palmitic acid methyl ester, acetic acid or methanol. The studies are limited for most systems to low temperatures because of the onset of crystallisation. They are extended to a maximum pressure of 200 MPa. The concentration dependence of the hydrogen-containing mixtures shows, at the carbon dioxide rich side of the D_ii s. x diagram, a fairly steep increase in diffusivity with hydrogen concentration. The analysis of the methanol/carbon dioxide system is complemented by studies of the hydroxyl proton chemical shift. The x, T, p dependence of the chemical shift is described by a linear association model. These data show clearly that the carbon dioxide molecule does not form any hydrogen bonds with the methanol hydroxyl group.