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Adsorbent for water adsorption and desorptionAdsorbent for water adsorption and desorption description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20090130411, Adsorbent for water adsorption and desorption. Brief Patent Description - Full Patent Description - Patent Application Claims
The present invention relates to an adsorbent over which the adsorption and desorption processes of water are facile at the temperature of less than 100° C. and the difference between the adsorption capacity at adsorption condition and the adsorption capacity at desorption condition is high. More particularly, present invention relates to an adsorbent using porous inorganic-organic hybrid materials that have pores of nanometer-size and the pore volume and surface area are very large. An adsorbent that adsorbs and desorbs water has various uses. For example, a dehumidifier can utilize an adsorbent that adsorbs water at low temperature, while desorbs water when it is heated at high temperature. Moreover, a heater may humidify like a humidifier by desorbing adsorbed water, at high temperature, which is adsorbed from outside environment at low temperature, if an adsorbent is used in a heater. Likewise, a cooler, if an adsorbent is incorporated, may decrease the humidity of a room by adsorbing water at low temperature. The adsorbed water may be desorbed to outside by heating at high temperature. Air conditioners and humidity controllers (humidistats) that utilized these concepts are suggested in U.S. Pat. Nos. 6,978,635, 6,959,875 and 6,675,601. However, there is no detailed explanation on the adsorbents used in the equipments. It is said that silica gels, zeolites or ion-exchangers are used in the equipments or it is just stated that adsorbents are used for the equipments. Moreover, the adsorbents have drawbacks of low adsorption capacity, and the desorption temperature is higher than 100° C., leading to the increase of operation costs. Therefore, it is highly desirable to develop an adsorbent that desorbs water even at low temperature and the difference between adsorption capacity and the remaining water after desorption is large. However, there always remain problems of difficult desorption if the adsorption capacity is high; and the difference between adsorption capacity and the remaining water after desorption is small when the adsorption capacity is small. The present invention can be completed by confirming that, by utilizing a hybrid inorganic-organic material having very large surface area, the adsorption capacity is large and most of the adsorbed water can be desorbed at the temperature of 100° C. or below. In the present invention, the hybrid inorganic-organic material, which is used as a water adsorbent, can be defined as a porous coordination compound formed by central metal ions and organic ligands that coordinate to the metal ions. The hybrid inorganic-organic material contains both organic species and inorganic species in the framework structure and means a crystalline compound having pore structure of molecular size or nano size. Hybrid inorganic-organic material is a wide terminology and generally called as porous coordination polymer (Angew. Chem. Intl. Ed., 43, 2334. 2004) or metal-organic frameworks (Chem. Soc. Rev., 32, 276, 2003). Recently, the study on these materials has been newly developed by the combination between molecular coordination bonds and materials science, and these materials have been actively investigated in these days because these materials, due to high surface area and pore of molecular dimensions or nanometers, can be used as versatile nanomaterials. These materials can be synthesized by various methods. Typical synthesis methods include solvent diffusion at room temperature, hydrothermal synthesis at high temperature in the presence of water solvent and solvothermal synthesis using an organic solvent (Microporous Mesoporous Mater., 73, 15, 2004; Accounts of Chemical Research, 38, 217, 2005). The synthesis of a hybrid inorganic-organic material can be executed, similar to the synthesis of inorganic porous materials including zeolites and mesoporous materials, under autogenous pressure in the presence of water or suitable solvents at temperature higher than the boiling point of the solvent used in the synthesis. In other words, the hybrid inorganic-organic material have been synthesized, similar to zeolites and mesoporous materials, during several days at high temperature after loading reactants in a high pressure reactor such as an autoclave. The heat source for high temperature has generally been conventional electric heating. For example, an autoclave containing precursors including metal salts, organic ligands and water or solvent was heated using an electric heater or an electric oven at a constant temperature. However, the methods of the previous embodiments using electric heating are not economical because of the long reaction time. Moreover, the methods do not provide hybrid inorganic-organic material with size less than 500 nm, or more preferably less than 100 nm, because amorphous hybrid inorganic-organic materials are obtained when the reaction duration is decreased in order to obtain small crystal particles. Therefore, in the present invention, hybrid inorganic-organic materials are obtained by using microwave as a heat source in order to overcome the above mentioned problems. As small particles are obtained by microwave heating, the small particles, if used as an adsorbent, have the advantage of easy diffusion. Moreover, the small particles are easy to make a thin film, thick film or membrane. On the other hand, the synthesis by using microwave heating leads to improved performance of water adsorbent because the hydrophobicity and hydrophilicity of adsorbents are improved by the method. Therefore, hybrid inorganic-organic materials can be obtained by using microwave heating under the autogenous pressure after sealing the precursors containing metal salts, organic ligands and solvent such as water or organic solvent. Moreover, the hybrid inorganic-organic materials can be synthesized continuously by the microwave heating. Accordingly, the object of this invention is to develop an adsorbent to have high adsorption capacity for water and to desorb easily the water at relative low temperature; and to develop an adsorbent, having outstanding adsorption capacity and adsorption characteristics, by using hybrid inorganic-organic materials. Therefore, the purpose of this invention is to develop an adsorbent that adsorb and desorb water easily, and has the purpose to control humidity by using the adsorbent thus obtained. Moreover, the present invention has another purpose to provide the preparation method of the adsorbent. The present invention is directed to a water adsorbent, especially to an adsorbent using porous hybrid inorganic-organic materials having pore dimension of nanometer levels. The present invention provides an adsorbent by using hybrid inorganic-organic materials that desorb water easily even at low temperature and the difference between the adsorption capacity at high temperature and the adsorption capacity at low temperature is high. The adsorbent according to the present invention has surface area larger than 1000 m2/g, pore volume larger than 1.0 mL/g, pore dimension of 0.5-2.0 nm and the framework of the adsorbent is composed of both organic species and inorganic species. It is preferable for the adsorbent to have the ratio of (adsorption capacity at 100° C.)/(adsorption capacity at room temperature) is less than 0.2. If the surface area and pore volume are less than the values described above, the efficiency as a water adsorbent is low. Even though the efficiency increases with increasing the surface area and pore volume, the practical limitations attainable by usual methods are about 10000 m2/g and 10 mL/g for surface area and pore volume, respectively. If the pore size is less than 0.5 nm, the time necessary for the adsorption and desorption is long because the adsorption and desorption velocities are low. On the contrary, if the pore size is larger than 2 nm, the structure of the adsorbent becomes unstable and the adsorbent has drawback of low stability. Moreover, an adsorbent reported previously has drawback of inefficient desorption at low temperature because less than 50% of the adsorbed water is desorbed at the temperature of 100° C. or low and because the ratio of (adsorption capacity at 100° C.)/(adsorption capacity at room temperature) is 0.5-1.0. On the other hand, the adsorbent of the present invention desorbs, at the temperature of 100° C. or low, at least 80% of the adsorbed water. The adsorbent of the present invention is specifically metal terephthalates or so, and the metal is Cr, Al, Fe, etc. The preparation method of the present invention for the adsorbent is to add metal precursors, organic materials selected from benzene dicarboxylic acid, benzene tricarboxylic acids, etc. and solvents to a reactor; to seal the reactor; and to heat the reactor to high temperature. The reaction temperature is maintained by microwave heating, and the reaction pressure is maintained as autogenous pressure. Continue reading about Adsorbent for water adsorption and desorption... Full patent description for Adsorbent for water adsorption and desorption Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Adsorbent for water adsorption and desorption patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. 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