visa information about transit in Beijing Capital Airport

Hello :
We are four Moroccan citizens who will participate in an international congress in South Korea on October 16th 2014. To go from Rabat to Seoul by air we must have a transit first in Paris, then another of 2 hours 25 minutes’ duration in BJ Airport, (BJ, CN (CAPITAL INTL), TERMINAL 2 ) .
On our return on 21st October 2014 from Seoul to Rabat, we also must have another transit of 11 hours and 35 minutes in the same airport (BJ, CN (CAPITAL INTL), TERMINAL 2 ), before changing the plane to Paris.
So please we want to know if it’s necessary and compulsory for us to have a Chinese visa, knowing that we won’t get out of BJ Airport.
(N.B). Moroccan passports don’t need Korean visa.