Hi ! we carry Norwegian passport and fly from amster. Do we have 18 hrs to get a flight from bei

Hi ! we carry Norwegian passport and fly from Amsterdam to Beijing and wait 18 hrs to catch another flight to Ho Chi Minh ( Vietnam ). We planed to get out to Beijing city for a short city sightseeing and get back to the airport to get a flight to Ho Chi Minh. Is it possible to have 72 hour free transit???