24 Hour Direct Transit Visa on outbound flight & 72 Hour Visa Free transit on inbound flight ?

I have a return ticket from London to Ulaanbaater in Mongolia via Beijing. On the outbound flight I have a 18 hour stop over in Beijing and on the return flight I have a 52 hour stop over in Beijing. Can i apply for a 24 Hour Direct Transit China on the outbound and a 72 hour free transit in China on the return?