(401bg) Synthesis of Various Water Adsorbents with Controllable Adsorption Properties for Application of Water Adsorption Chiller

Adsorption chiller is a type of refrigeration system, operating on the basic principle of heat removal by evaporation of liquid refrigerants (e.g., water, ammonia, and alcohol) and consequent adsorption in porous materials. It has been considered and gaining great interest as an environment-friendly and energy-efficient system, owing to its several advantages such as utilization of renewable heat, low electric capacity, and the use of non-Freon-gas-type refrigerants [1-3]. Many research institutes and private companies, including Mycom, Nishiyodo, Mitsubishi Plastics, Zeopower, Invensor, SorTech, and Shanghai Jiao Tong University, have developed adsorption chillers. The key to the development of adsorption chillers with high efficiency and good performance is the development of suitable adsorbents that can adsorb as much refrigerant as possible at room temperature and desorb the refrigerant easily using low-temperature heat during the regeneration step. When water is used as refrigerant in this chiller, nanoporous materials with high water uptake under 9 ~ 12 Torr at room temperature and with remarkable desorbing capability under 353 K are highly desirable to generate chilled water (~283 K). However, it is hard to control the chemical properties of the adsorbent materials in such a way as to achieve the desired performances in both sides. Furthermore, the feasibility of mass production and low production costs for the adsorbent are also required.

In this work, we have synthesized various types of water adsorbent such as zeolite derivatives, mesoporous silica and activated carbon which show large difference of water adsorption amount (so called, ‘dynamic sorption amount’) between conditions of adsorption step and desorption-regeneration step of water adsorption chiller. Water sorption isotherms of the synthesized adsorbents were measured using volumetric sorption analyzer, and dynamic sorption amounts of the samples were also measured using gravimetric sorption analyzer for several cycles of conversion between adsorption and regeneration steps. According to the results of the sorption analysis, all the synthesized adsorbent exhibited significantly larger dynamic sorption amount than previous commercial water adsorbents such as regular-density silica gel and AQSOA^TM FAM series adsorbents. Synthesis methods of the present water adsorbents are quite simple and low-cost, so that we could synthesize the water adsorbents in large-scale batch. In addition, we developed precise methods for pelletizing the adsorbents and coating the adsorbents on aluminum metal surface for the application of water adsorption chiller. Detail results for the synthesis, the adsorption measurement, the palletization, and the coating of the synthesized adsorbents will be presented in the conference.

[1] F. Meunier, Journal of Heat Recovery Systems 6 (1986) 491.

[2] K.C. Ng et al., Applied Thermal Engineering 21 (2001) 1631.

[3] K. Cho et al., J. Nanosci. Nanotechnol. 17 (2017) 5869.