Stopping in Beijing for 18 hours

Hi, I am an Irish citizen. I am going on holidays to Thailand in December with my dad and am stopping off in Beijing for 18 hours and I dont want to stay in the airport for the wait. He has a UK passport so he will be allowed to leave the airport but since I have an Irish passport, I am told I will need a visa. I was wondering which type I would need and how to get it? and how long it will take.

Thanks