Catalonia has a great economy that can support itself independently. The Catalan economy is responsible for more than half of Spain's total startup investment. Millions of tourists choose Catalonia out of the Spanish areas to visit. These are important elements that show the ability of Catalonia to succeed as a sovereign nation. 
Catalonia pays to the Spanish government in taxes much more than it receives in benefits. The Spanish government has also been unwilling to negotiate giving more autonomy to Catalonia.
Some people say the question is not whether Catalonia can succeed independently from Spain, but whether Spain can support itself without Catalonia.