Will I qualify for 72-hour visa-free transit?

I am traveling from LAX to PEK with layover and then to BKK Thailand on Nov 26-27, 2015. Then I fly back from BKK to PEK on Dec 4, arriving at 12:45am. I will be in Beijing until my flight back to LAX on Dec 6 at 3:00pm. Will the time I am in Beijing qualify for the free transit? If so, do I need to apply for this ahead of time or when I arrive at the PEK airport? Thank you!