In my experience flying from PUS-PEK-HAN on separate tickets (CA PUS-PEK, VN PEK-HAN) I had to show both ticket itineraries and my hotel reservation with my passport at check in. I had the TIMATIC print out of the TWOV process ready to show the check in agent but didn't need it as there were no issues and the agent seemed very familiar with the process. I consulted the following Master Thread which you can check out if you haven't done so.
China 24, 72, and 144 hour Transit Without Visa ("TWOV") rules master thread