Arriving to Shanghai, 3 days later going to Hong-Kong for one night on a separate ticket

Hello, i am thinking to arrive from Canada to Shanghai, stay there for 72hrs, then fly to Hong-Kong on a separate confirmed ticket, stay in Hong-Kong only one night, next morning come back to Shanghai, stay there another 72hrs and leave to Canada.

Will this qualify for the free transit visas? Does the fact that my flight to Hong-Kong is on a separate ticket would be a problem? Does the fact that i will stay in Hong-Kong only for one night and in China for 3 day on either direction will be a problem.

Thanks a lot.
Arie.