Catalonia or Catalunya formed part of the Kingdom of Aragón, one of the two kingdoms that originated Spain in the XVth Century. The other is the Kingdom of Castille. Although different they became united thanks to the fusion of their crowns, and gave the identity of the idea of modern spanish (different people of different cultures, with same roots and similar ways of life who love the idea of a country that means all of it and represents all the hispanics culture).
There also exists some Extremist Independent movements grounded in pseudo-theories who represent a small minority, whose supporters are in most people with little education. In any case the situation can't be compared to other movements as the Scotish, Belgian or even Welsh.