Hydrothermal stability of SAPO-34 for refrigeration and air conditioning applications

Hydrothermal stability is one of the crucial factors in applying SAPO-34 molecular sieve to adsorption refrigration. The SAPO-34 was synthesized by a hydrothermal method using diethylamine as a template. Both a vacuum gravimetric method and an intelligent gravimetric analyzer were applied to analyze the water adsorption performance of SAPO-34. Cyclic hydrothermal performance was determined on the modified simulation adsorption refrigeration test rig. Crystal phase, morphology, and porosity of SAPO-34 were characterized by X-ray diffraction, scanning electron microscopy, and N₂ sorption, respectively. The results show that, water adsorption strength on SAPO-34 is between that on 13X and A type silica gel. During 100-400 Pa, the water uptake on SAPO-34 increases sensitively to pressure, and equilibrium water uptake reaches 0.35 kg/kg, 25% higher than 13X. SAPO-34 shows no significant reduced cyclic water uptake over 60 cycles. Most of the initial SAPO-34 phase is restored, while the regular cubic-like morphology is well maintained, and the specific surface area only decreases by 8.6%.