Transit from 12 hours in Beijing

Giovanni, there is no such thing as "temporary free visa". You are actually looking for a temporary entry permit to be allowed to exit the airport during your layover in Beijing.

First of all and the most important detail is that your itinerary is eligible for 24 hour visa free transit and you don't need any kind of visa.

Anyway, to be allowed to exit the airport, you will have to apply for a temporary entry permit at 24 hour visa free transit counter upon your landing in Beijing. You have to be aware that the issuing of a temporary entry permit always depends on discretion of immigration authorities and in general they tend to issue one in case if you have a hotel booking confirmation or a tour booking confirmation or similar. If you just apply without presenting the above mentioned, your chances are very slim.