Transit on separate tickets at Beijing Capital Airport

I arrive at PEK T3 on Qatar from Doha at 14.55 then travel on to Hong Kong on a separate ticket on Cathay (T3) .Cathay have just changed my flight with a departure at 18.35. Will I have enough time? will I be able to use the transit system (I presumably need to collect and resubmit my baggage as well) I am on Business Class for both flights if that makes a difference. Can you advise please.