No, sir! Big mistake. I'm surprised you're making it. To join the EU, all existing members must accept the new member. This is why Macedonia can't join, Greece is blocking it. Spain will block Catalonia from joining, France too because a little part of it, historically, was part of Catalonia, and Italy too, will probably puts it veto to prevent the Northern League from following the same path.
The € will remain the de facto currency, but it would be terribly dangerous for Catalonia because it will not have any say in European policies. In case of trouble, their fate would be worse than Greece as it would be illegal for the ECB to help them in any way.
I was in Barcelona on the 11th, there were huge crowds in the streets, most of them good looking people, but I'm not sure they fully understand what's at stake.