Hi, I intend to get the trans Mongolian express from Moscow thru Mongolia and into China to Beijing.

I understand it takes about 10 hours from the border (Erlian) to BJ. I intend to then transfer straight to BJ airport and fly to Seoul Korea. I will be in China less than 24 hours, can i use a transit visa? The reason for no stopover is that i was 3 weeks in China including BJ only 2 months ago. Thanks