Experimental study of the ammonia adsorption characteristics on the composite sorbent of CaCl2 and multi-walled carbon nanotubes

• A new composite sorbent of CaCl2/MWCNT is prepared for adsorption refrigeration.
• Adsorption capacities of the new composite sorbents are evaluated.
• Chemical reaction steps between CaCl2 and NH3 are investigated and analyzed.
• Additive of MWCNTs can improve the adsorption performance of the chemical sorbent.

A new composite sorbent made of CaCl2 and multi-walled carbon nanotube (MWCNT) was prepared for solid–gas ammonia adsorption refrigeration systems in the paper. The composite sorbent was fabricated by impregnating MWCNTs matrix with CaCl2 to improve the adsorption performance of the chemical sorbent. The ammonia adsorption capacity of the composite sorbent and the MWCNTs matrix were measured using a Rubotherm magnetic suspension balance. Experimental results showed that the maximum adsorption amount of ammonia by the MWCNTs matrix and the composite sorbent are 90.05 mg gCNT−1 and 859.85 mg gsorbent−1 under the experimental conditions. Moreover, the chemical reaction plateaus and steps of the reaction between CaCl2 and NH3 were analyzed and the adsorption capacities of the composite sorbent at different working conditions were evaluated. The results indicated that although the adsorption capacity of ammonia on the pure MWCNTs is relatively low, the addition of MWCNTs into the chemical sorbent can avoid the agglomeration and prevent the adsorption performance attenuation of reactive salt.