Will arrive Peking Airport 6:10 AM and depart 19hours later-does I need a Police registration

I have only 19 hours time in Peking, (arrive 6:15 in the morning from Bangkok - departure to Munich the next morning 1:30 )
So I doesn't have a Hotel for registration , does I need the registration too , when I only make this day trip into the town and if I need a registration , where can I get this , I assume with the 72h Visa itselfe it is no problem ?!