Flying in and out of Shanghai with different airlines and separately booked tickets

I am a Belgian citizen and will arrive in Shanghai Pudong airport on October 26th in the afternoon. My return flight with the same airline will departure from Hong Kong the week after. I will leave Shanghai on 29 around noon (within the 72 hours limit) from Honqiao airport with a separately booked ticket fro a local airline. Do I require a visum and if not how can I be sure that I pass the passport control (what kind of documents do I need to have with me?)?