Dilitihum is used to focus M/AM reactions as described in early TNG.
It's not a power source though... and I would imagine it's possible to replicate, but it's molecular structure could be sufficiently taxing on energy reserves to make it impractical.
Instead, they can recrystalize it for extended use, and of course mine the rest.
Replicators were said that they can make fully powered weapons such as phasers, which happen to contain their own energy source.
It stands to reason a replicator would be able to do this. It uses specific amount of energy which will be turned into matter (phaser) and another smaller portion of it is rearranged into a form used by the weapon which is immediately integrated into the energy storage area upon materialization.