Phase equilibria in the H2/CO2 system at temperatures from 220 to 290 K and pressures to 172 MPa

Phase equilibria in the system H₂/CO₂ have been studied experimentally using a vapor-recirculating apparatus. Measurements of vapor and liquid phase compositions were made for ten temperatures ranging from 220 to 290 K and pressures to 172 MPa. The mixture critical line and the pressure-temperature trace of the three-phase region solid-liquid-vapor have been located. The three-phase region and the critical line intersect at T ? 234.8 K and P ? 198 MPa to form an upper critical end point. Experimental results have been compared with previous studies and with predictions of three equations of state, Peng-Robinson, Redlich-Kwong and Deiters. Expressions have been derived for temperature dependent critical parameters that account for quantum effects in H₂, in calculations for H₂/X systems using the Peng-Robinson equation.