Separate Tickets for Visa Free Transit

If I buy one ticket from BOS-YUL-PVG round trip on Air Canada, then a separate round trip ticket PVG-HKG on Cathay Pacific, can I still qualify for Free Transit in Shanghai if I am in Shanghai less than 72 hours both times? For example BOS-YUL-PVG (stay 2 days), PVG-HKG (stay 4 days), HKG-PVG (stay 1 day), PVG-YUL-BOS. Thanks