I WILL ARRIVE BEIJING 31ST JULY AND HAVE 18 HOUR STAY AT AIRPORT. DO I NEED A CHINA VISA FOR THIS?

I MUST COLLECT MY BAGS AFTER CUSTOMS BUT I WONT LEAVE THE AIRPORT. I HAVE ALREADY BAUGHT AN ONGOING TICKET TO SIBERIA WHICH I HAVE PAID FOR. BUT I MUST GET A BOARDING PASS. DO I NEED TO GET A VISA OR CAN I GET ONE IN CHINA WHEN I GO THROUGH CUSTOMS. Thankyou