This work investigates the synthesis and performance of double salts for H-2/CO2 separation. A series of NaMg double salts were prepared based on xMg(NO3)(2): yNa(2)CO(3): zH(2)O and characterised. The best sorbents reached CO2 uptake of 17.9 wt% at 0.62 MPa and 375 degrees C. The NaMg double salts preferentially sorbed CO2 as determined by breakthrough tests. The NaMg double salts were packed in a sorbent bed and tested for H-2/CO2 separation at the back end of a water gas shift reactor. The space velocity had the largest impact on the performance of the sorbent bed, as increasing the space velocity from 2.16 x 10(-3) to 9.51 x 10(-3) s(-1) sped up the breakthrough time by 84%. Increasing the feed gas pressure from 0.3 to 0.6 MPa reduced the breakthrough time by -45%. The NaMg double salt sorbents were exposed for over 1000 h of continuous temperature including 28 cycles of sorption and desorption, and proved to be stable during changes of operating conditions such as flow rates and pressures. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.