Is there a way to limit access to the knowledgebase only? For example, I would like to have agents who can log in and create, edit, review and publish KB articles, but I don't want them to have any access to any of our tickets.
Create knowledgebase only Agents?
It sounds like you do not want to limit access to the kb... you want to limit access to the agent to not see tickets. If that's the case then Sure.
Create a department. Give them access to that department. Don't assign tickets to the department or to them. they will not see any tickets.