The separatists were convicted of sedition over their role in an illegal independence referendum in 2017.
Another three were found guilty of disobedience and fined, but not jailed. All 12 defendants denied the charges.
Large crowds of pro-independence protesters clashed with police at Barcelona's international airport.
Footage showed people attempting to break through a police line blocking one area of the building, while in another, officers hit protesters with batons and attempted to disperse the crowds with gas.
A total of 108 flights were cancelled on Monday, the Spanish airport authority Aena said.