Procedure to secure a "72 hour Visa Free Transit" at Guangzhou Baiyun for 16 hours transit

I am an American citizen. I will have a "16 hours" Transit at "Guangzhou Baiyun Intl. AP" enroute to "Los Angeles" coming from "Dhaka" with a confirmed ticket/seat from "China Southern Airlines". What is the procedure/chances to secure a "72 hour Free Transit" at "Guangzhou Baiyun Intl. AP", so that I can go out of Airport to a hotel and can explore a "Guangzhou city tour"?