Hall thrusters are a type of electric propulsion. CO2 is a promising candidate as a propellant of the thruster, advantageous in terms of cost, storage, and in-situ resource utilization. This study is the first to simulate the discharge of a Hall thruster using CO2 propellant using a fully kinetic particle-in-cell model. The code was based on existing code developed for Xe with the collision model applied to CO2. Collisions were selected by mean free path analysis, and the collision model was verified using fluid model with assumed Maxwellian distribution. Simulations applying the collision model evaluated sensitivity of artificial mass ratio. In the validation, thrust performance and the produced ion fraction at a discharge voltage of 200 V were compared with experimental results. Further, by increasing the anode mass flow rate, the effect of background pressure, which is important in the experiment, was estimated, and its sensitivity was analyzed. The CO2 discharge had a high sensitivity of discharge current to anode mass flow rate. This relation was observed in the simulation. The produced ion fraction of CO2+ and CO+ differed partially from the experiment because dissociation and multi-step ionization of CO2 were not included in the model. These results suggest a model including such collisions is needed.