Will 2 hours enough for a connecting flight (Singapore - Beijing - Qiqihar)

We are going to Qiqihar next week from Singapore and will transit at BJ. From SG to BJ we use Singapore Airline while from BJ to Qiqihar we use Air China. We were told we can't take the luggage check-through service, and we were told we need to re-check and we have to go through immigration and custom before pick up your luggage.

We were thinking to have hand carry only, without any luggage, so will 2 hours enough for this connecting flight?

Besides, any possibilities for us to re-check without go through immigration and custom if we only bring hand carry?

Thank you.