I'll try to find some sources.
I believe I've found the actual opinion poll in independence/a referendum conducted in June
HERE. It also shows the change of opinion over the last few years, which is handy.
Look at this if nothing else.WSJ:
"While the legal steps that Mr. Rajoy is set to take could serve to momentarily rein in Catalan leaders, support for a split with Spain among voters in the region is unlikely to fade. Around 35% of Catalans support independence, according to the most recent poll this past summer by the region’s survey agency."
From another WSJ article:
"According to a poll by Catalonia’s regional government survey agency in June, 35% of Catalans support full-fledged independence, down from a peak in 2013 of around 50%."
BBC:
"Angered by having their autonomy watered down as well as by years of recession and cuts in public spending, Catalans held an unofficial vote on independence in November 2014. More than two million of the region's 5.4 million eligible voters took part and officials declared that 80% had backed secession."
From the same article:
"Opinion polls are hard to come by but the clearest indication before the referendum came in July, when a public survey commissioned by the Catalan government suggested 41% were in favour and 49% were opposed to independence.
We know that 2.2 million voters backed independence in the previous vote in November 2014, and that coalition of separatist parties called Junts pel Si (Together for Yes), with the support of a radical left-wing party, the CUP, won 48% of the vote in 2015 elections."
