Addition of malodorants to lighter gas – The phase equilibrium properties of mixtures of lighter gas and selected substances

Relevant thermodynamic and phase behavior of mixtures created by adding malodorants to lighter gas to discourage its abuse have been studied. The influence of physical factors such as temperature, pressure and concentration of the selected substances with lighter gas is studied. This work represents one component in a larger study examining the feasibility of adding malodorants to lighter gas and focuses on the physical chemistry or chemical engineering aspects of the problem. An initial set of 27 compounds was selected based on deterrent effect (odor) in order to find suitable additives to lighter gas components. The aim is to find substances that not only have the correct physiological effect (discourage abuse) but also the correct physical behavior upon addition to lighter gas (solubility, phase behavior). Specifically the way the malodorant partitions between the vapor and liquid phase is modeled. Furthermore, addition of the malodorants should not affect the normal use of the lighter. Thus of the 27 initial components chosen, nine were found that could be suitable additives. In this work we used the thermodynamic models COSMOtherm – an activity coefficient model – and Cubic-Plus-Association (CPA) – an equation of state – to model the fluid phase and solubility behavior of the mixtures formed by the various additives with butane.