There is a September 2013 paper (pdf) on this topic by Ryan D. Griffiths, Pablo Guillen, and Ferran Martinez i Coma:
We propose a game theoretical model to assess the capacity of Catalonia to become a recognized, independent country with at least a de facto European Union (EU) membership. Support for Catalan independence is increasing for reasons pertaining to identity and economics. Spain can avoid a vote for independence by effectively ‘buying-out’ a proportion of the Catalan electorate with a funding agreement favorable to Catalonia. If, given the current economic circumstances, the buying-out strategy is too expensive, a pro-independence vote is likely to pass. Our model predicts an agreement in which Spain and the European Union accommodate Catalan independence in exchange for Catalonia taking a share of the Spanish debt. If Spain and the EU do not accommodate, Spain becomes insolvent, which in turn destabilizes the EU. The current economic woes of Spain and the EU both contribute to the desire for Catalan independence and make it possible.
My worry however is this. If Catalan took away its share of the Spanish debt, or even more than its share, I don’t think this would help the Spanish fiscal situation. For similar reasons, I have never been convinced that the debt-to-gdp ratio is such an important variable. I myself put greater stress on the ability of a government to rule its territory, command the wealth and allegiance of its subjects, and continue to generate a more or less stable political equilibrium. Every developed country has the wealth to pay off its debts, if at least it has the political willingness to do so. If you view fiscal stability in this kind of macro public choice framework, the unwilling loss of a major piece of wealthy, high status territory is a much, much bigger fiscal blow than can be offset by a marginal improvement in the debt-to-gdp ratio. Besides, which part of Spain might be then next in line with demands for greater autonomy?
I am entirely fine with the idea of a Catalonian independence referendum in normal economic times, however, as I do not in general wish to maintain nation-states on those who are truly unwilling. I am very happy for instance that Estonia is no longer part of Russia/USSR, and in turn one can see that an Estonian independence referendum would pass in either good economic states or bad. If the same is true for Catalonia, we should all be willing to wait.