Novel ammonia sorbents “porous matrix modified by active salt” for adsorptive heat transformation: 1. Barium chloride in various matrices

Novel composite materials BaCl2/vermiculite, BaCl2/γ-Al2O3 and BaCl2/(carbon Sibunit) have been synthesised by impregnation of the three porous matrices with barium chloride and studied as ammonia sorbents. Isosters of ammonia sorption are measured at T = 15–80 °C and P = 0.7–9 bar. It was found that a modification of the host matrices by the salt increases the ammonia uptake due to a chemical reaction between ammonia and barium chloride. The enthalpy and entropy of ammonia sorption by the salt confined to the mesopores of alumina and Sibunit are significantly smaller with regard to those for the bulk salt. This indicates that the salt confinement to the small pores allows tuning its sorption properties. In the large vermiculite pores the properties remain unchanged. Based on the experimental isosteric charts, the feasibility of the new materials for adsorptive heat transformation has been analyzed. For composite BaCl2/vermiculite the coefficient of performance (COP) for ice making and air conditioning cycles calculated from the ammonia sorption data can reach 0.6 which seems quite encouraging from a practical point of view.