A propane engine is basically a gas engine. You can't convert it to a diesel. Totally different technology.
Now, if you mean you want to remove your propane generator and replace it with a diesel, that might be doable if it will fit. But several obstacles to overcome, the biggest is the weight difference.
Bill & Brigitte
06 Windsor PEQ, Cummins 400 ISL
2014 Honda CRV