I don’t understand why so many people on this thread support Catalonian independence from Spain. It isn’t a right wing nationalist movement - the leaders of the independence movement are to the left of the Spanish government. They want to be free from Madrid so that they can be even more beholden to Brussels and even more open to immigration from Africa and the Middle East. The agitators in Catalonia aren’t any different from the Pro-EU anti-Brexit leftist advocates of Scottish independence from the UK.
It is doubtful the EU would ever agree to let in an independent Catalonia...Spain itself would have veto power over that decision.
Scotland is a bit different since GB is leaving the EU, but any member country struggling with a separatist/independence movement would likely block them.