The summer I lived there (1988), the Catalan referred to themselves as Catalan, and corrected you if you called them Spanish. They referred to the rest of Spain as Spain, as if where they were wasn't Spain. And they practically *spat* upon the Spanish language. That fact was crucial to my doctoral research so I looked into it... Franco has a lot to answer for.
So they have always *been* culturally separate, like the Basque in both France and Spain.
That said, I'm agin national boundaries in general, so I am agin increasing the number of them.
Also, I don't know whether states can secede from that union legally or not. Spain is a recent pastiche of a lot of smaller cultures, like Andalusia and all.
But even if they can't, riot police throwing old ladies down stairs (I conflate, I know) is not the answer to an illegal vote. Voting is peaceful behavior and should not be answered with violence. Barricades? Disposing of ballot boxes? There is a lot they could have done without violence to the individuals.
And *having* committed that high-enous act, now, even the Catalan who weren't for separation are more against Spain now than they were, which is not helpful for unity either.
And if you get the high-enous reference, bully for you.