Not interchangeable with R12.
Probably should be disposed of properly.
"Since R11 has highest potential to cause the depletion of ozone layer, as per the Montreal Protocol, its use and production has to be stopped completely in the phase manner. R-11 is now being replaced by other environment friendly refrigerants, of which the most common is R-123."
Found this:
https://www.brighthubengineering.com...-replacements/