Of course it is not possible. If that were possible everybody would create their own private network with a huge amount of lumens in it, then transfer all these to his account on the Stellar public network and be instantaneously rich.
The lumens in your private network are not real lumens, they're just your own pet lumens, play money, for all that matters (unless your network becomes very popular and start to be used by hundreds of people, in this case you'll probably need a new name for the native currency there).
