The MSDS available from Jobo USA website has always disclosed the composition of Protectan as propane/butane.

The approach is to displace the oxygen in air with some inert gas. Propane and related compounds have the advantage of liquifying at room temperature under pressure -- this allows a larger quantity to fit within the can. The obvious disadvantage is the inflammable nature. Nitrogen, argon or other noble gasses should work well. You don't need a super high purity grade -- as long as you greatly reduce the amount of oxygen in the bottle, the lifetime of oxygen-sensitive photochemicals will be extended. Argon probably wasn't selected for the photo trade because of its expense. Propane/butane doesn't sound nice for wine and might impart a flavor, hence the selection of argon.

Another consideration is the container. Many plastics, even those used for some bottles intended for photochemicals, are permeable to oxygen. I have had the best results keeping B+W developers using glass bottles. The disadvantage of glass is the weight, breakability and possibility of injury from broken glass. Another approach is to limit the amount of oxygen by using full bottles -- either use smaller bottles, or add marbles. The smaller bottles will work if the material is impermeable to oxygen -- if the material is permeable to oxygen, the higher surface area to volume ratio of a small bottle will increase the oxygen reaching the photochemicals.