Catalonia's planned independence vote will not lead to secession, although the row could be protracted. Spanish and Catalan debt markets have so far been relatively subdued. The reason for this, presumably, is that markets don't expect Catalonia to secede from Spain anytime soon. They're right: Madrid won't allow it. Rather than try to prevent the vote, Rajoy could simply refuse to recognise it; and when it registers a Soviet-style majority for independence on a derisory turnout, congratulate the Catalan government on having conducted a glorified survey of its own supporters. It would then be a declaration of independence which would seem illegitimate and divisive. A messy dispute might result, but with economic and hard power and international recognition vested in Madrid, the outcome would not be in doubt.
Independence vote is 92% (of 43% turnout) in favour. Madrid refuses to recognise the result and Catalonia remains part of Spain.