Do I need a visa for one overnight in Beijing for less than 24 hours transit?

I will be travelling to Ulaan Baatar via Beijing in a few days. I will not be able to make the same day connection and will need to overnight in Beijing for less than 24 hours until my flight leaves the following morning. Do I need a visa and can I leave the airport to stay in a hotel? If I can't leave the airport, is there any place to sleep (or hotel within) the Beijing Airport? Thank you.