Brian, you know more about phase change than me!
But I have seen stuff on TV ( heheh yeh laugh) about propane being used in R-12 and R134A(?) setups( the "freon" substitute). And they showed that the lubricant used in most automotive A/C systems does react with Propane/Butane and can eat away seals... now whether this is as big of a problem as the show claimed, who knows...
I personally will use a chemical MEANT for the job instead of a chemical meant to BURN
