The small disposable propane bottles are useful for catalytic heaters, camp stoves, lanterns, and other portable propane powered camp equipment. They are a much more expensive way to get propane compared to the big tanks on your RV feeding the built in appliances. That is why there is a lot of interest about ways to refill the small disposable bottles. WheeliePete has a YouTube video, NO Pre-Chilling! FULLY Refill a 1lb Propane Bottle (Avoid 600%+ Markup on Propane) Coleman, that is one of the better of its type.
Do take his caveats and precautions to heart. These range from potential legal issues to the general hazards of doing things with combustible gases under pressure.