KR100803964B1 - A synthesis method of fe containing porous organic inorganic hybrid materials and water adsorbent using the same - Google Patents

Abstract

A porous organic-inorganic hybrid and a moisture adsorbent using the same are provided to increase the amount of adsorbed moisture and facilitate the desorption of moisture even at a temperature of no more than 100°C, by using an iron-containing porous organic-inorganic hybrid. A moisture adsorbent is formed by using iron-terephthalate or iron-benzene tricarbonate. The moisture adsorbent is produced by heating a reactant mixture solution through electric heating and microwave irradiation. The reactant mixture solution is prepared by an iron precursor such as iron or iron salt, an organic ligand such as terephthalic acid or benzene tricarboxylic acid, a solvent, and a reaction accelerant such as a mixture of hydrofluoric acid and nitric acid. The moisture adsorbent has a surface area of 1,700-10,000 m^2/g and a pore volume of 0.8-10 mL/g. Further, a temperature of heating the reactant mixture solution is 100-250°C.

Description

A synthesis method of Fe containing porous organic inorganic hybrid materials and water adsorbent using the same}

1 is an X-ray diffraction pattern of the iron benzenetricarboxylate organic-inorganic adsorbent obtained in Example 1. FIG.

2 is a nitrogen isothermal adsorption line of the iron benzene tricarboxylate organic-inorganic adsorbent obtained in Example 1;

Figure 3 is a graph showing the water adsorption characteristics of the adsorbents using the iron benzene tricarboxylates of Examples 1 and 2 and zeolite Y of Comparative Example 1, the desorption of the moisture adsorbent is 70 ℃ (Examples 1 and 2) or 200 ℃ (Comparative Example 1), adsorption is the result performed at a relative humidity of 68%,

4 is a graph showing the results of the water desorption test for the adsorbents of Example 1 and Comparative Example 1, Example 1 is 70 ℃, Comparative Example 1 is the water desorption results at 200 ℃.

The present invention relates to an adsorbent which is easy to adsorb and desorption even at low temperatures within 100 ° C., and has a large difference between the amount of adsorption under adsorption conditions and the amount of adsorption under desorption conditions, and more particularly, has a nano-sized pores and has a surface area and pores. It relates to an adsorbent using a porous organic-inorganic hybrid having a very bulky feature.

The porous organic-inorganic hybrid used in the present invention may be defined as a porous organic-inorganic polymer compound formed by combining iron ions, which are core metals, with organic ligands, and include both organic and inorganic substances in a skeleton structure, and have a molecular size or nano size. It means a crystalline compound having a pore structure of.

Such porous organic-inorganic hybrids have a broad meaning and are generally included in the category of porous coordination polymers [Angew. Chem. Intl. Ed., Vol. 43, p. 2334 (2004)], also called metal-organic frameworks [Chem. Soc. Rev., vol. 32, p. 276 (2003).

The research on the porous organic-inorganic hybrids has recently begun to develop by the combination of molecular coordination bonds and materials science, and they have high surface area and molecular size or nano sized pores. It has been actively studied recently because it can be used not only for catalysts and catalyst carriers but also to encapsulate guest molecules smaller than pore size or to separate molecules larger than pore size.

Porous organic-inorganic hybrids can be used for catalysts, catalyst carriers, adsorbents, ion exchange and gas storage as well as for the storage, manufacture and storage of nanomaterials due to their high surface area, highly regular crystal structure and relatively high thermal stability. Cr-MIL-100 (Bulletin of Korean Chemical Society vol.26, p.880), which is used for separation and has a unique characteristic that can be utilized as a nanoreactor, is a MIL-100 structure which is an organic-inorganic hybrid. 2005).

However, in the case of the organic-inorganic hybrid made of Cr as described above, its application is inevitably limited due to the Cr component harmful to the human body, and in particular, the iron-inorganic hybrid having Fe as the central metal, which is not harmful to the human body. Is not well formed by the synthesis method of organic-inorganic hybrid having a Cr component has been developed a new manufacturing method for this.

On the other hand, the adsorbent for easily adsorbing and desorbing moisture has various uses. For example, the dehumidifier may utilize an adsorbent having a desorption characteristic when the moisture is adsorbed at a low temperature and then heated to a high temperature. In addition, if the adsorbent is used in the air conditioner, it adsorbs the outdoor moisture at low temperature during heating and then enters the room and desorbs at the high temperature indoor to take the role of a humidifier. It can be detached from the high temperature outdoor and sent to the outside, so you can get a pleasant indoor atmosphere. Air conditioners and humidity controllers employing this concept have been proposed in US 6978635, 6959875, 6675601, and the like. However, no specific reference is made to the adsorbents used in these devices and only mentions the use of silica gels, zeolites, ion exchange resins or the use of adsorbents. In addition, in the case of such an adsorbent, not only the adsorption amount is low but also a high temperature of 100 ° C. or more is required for desorption, which causes an increase in operating costs.

Therefore, there is a great need for the development of an adsorbent that can be desorbed even at low temperatures and has a large difference in adsorption amount and desorption amount. However, when the amount of adsorption increased, desorption was difficult. When the amount of adsorption was small, there was always a problem that the difference between the amount of adsorption and the amount of desorption was small.

Accordingly, the present invention was intended to develop an adsorbent having a high water adsorption amount and easy desorption even at a relatively low temperature of 100 ° C. or less, for example, 60 to 80 ° C., and an adsorption amount and adsorption by applying a porous organic-inorganic hybrid containing iron. We tried to develop an adsorbent with excellent properties.

Accordingly, an object of the present invention is to provide a moisture absorbent having a high water adsorption amount and easy desorption even at a relatively low temperature.

More specifically, an object of the present invention is to provide a moisture adsorbent using an iron-containing porous organic-inorganic hybrid having a high water adsorption amount and easy desorption even at a relatively low temperature, and having a high surface area and a large pore volume. .

It is another object of the present invention to provide a method for producing an iron-containing porous organic-inorganic hybrid having a high surface area and a large pore volume.

Instead of Cr, a metal material contained in the porous organic-inorganic hybrid, an iron precursor containing an environmentally friendly Fe and an organic ligand are reacted, and a crystallization reaction is performed by heating a mixture with a solvent in the presence of a mixed acid of nitric acid and hydrofluoric acid. When carried out, a high surface area and a large pore volume of the iron-containing porous organic-inorganic hybrid having a surface area higher than 1700 m 2 / g and a pore volume larger than 0.8 ml / g were produced. The present invention was completed by confirming that the water desorption at the temperature is easy and the amount of water adsorption per weight of the adsorbent is very high.

The present invention relates to a water adsorbent, in particular, characterized in that the adsorbent using a porous organic-inorganic hybrid containing an environmentally friendly iron as a metal component.

The present invention provides an adsorbent using a porous organic-inorganic hybrid including iron easily desorption even at low temperatures and the difference between the low temperature adsorption amount and the high temperature adsorption amount, the adsorbent according to the present invention is larger than 1,700 m ² / g It has a surface area, a pore volume of more than 0.8 mL / g, and contains both organic and inorganic substances as constituents of the skeleton, and the iron-containing porous organic-inorganic hybrid is composed of an organic ligand compound capable of coordinating with iron precursors and iron precursors. It is characterized in that it is prepared through the reaction.

If the surface area and pore volume are smaller than the above values, the effect as a moisture adsorbent is not great. The larger the surface area and pore volume is, the better, but the practically practical range in the manufacturing method is about 10000 m ² / g. The upper limit of pore volume is about 10 mL / g. The iron-containing porous organic-inorganic hybrid according to the present invention has a surface area of 1,700 to 2,500 m ² / g and a pore volume of 0.8 to 1.2 mL / g.

In the case of the conventional adsorbent, the ratio of the water adsorption amount at 100 ° C. to the water adsorption amount at room temperature is about 0.5 to 1, and at temperatures below 100 ° C., 50% or less of the adsorbed water desorbs and Although there is a problem in that the desorption property is not good, the adsorbent according to the present invention has a property that 80% or more, more preferably 90% or more of the water adsorbed at a temperature of 100 ℃ or less. After drying for 10 to 30 minutes at a relative humidity of 60 to 80%, the moisture adsorption amount is 0.4 to 0.7 g / g per weight of the adsorbent at a relative humidity of 60 to 80%. Therefore, the moisture adsorbent according to the present invention has a very high water adsorption amount and is easy to desorption even at a low temperature of 100 ° C. or lower, and is suitable for use for controlling humidity due to its high desorption rate compared to a conventional adsorbent.

Hereinafter, a method for preparing an iron-containing porous organic-inorganic hybrid used as an adsorbent according to the present invention will be described in more detail.

Iron-containing porous organic-inorganic hybrid used as the adsorbent according to the present invention

1) preparing a reactant mixture by mixing mixed acids of hydrofluoric acid and nitric acid with iron or iron salts, organic ligands, solvents and reaction accelerators as iron precursors; And

2) heating the reactant mixture to 100 ~ 250 ℃ by electric heating or microwave irradiation;

It is prepared by a manufacturing method comprising a.

The organic ligand is also called a linker, and any organic compound may be used as long as it is an organic compound capable of coordinating with the iron precursor. As such organic _{^{-CO 2 -, -CS 2 -,}} -SO 3 - and any organic material can be used, and also organic substances having a seat that can be coordinated with a seat that can be coordinated, such as -N, as well as potentially It is also possible to have a position to coordinate so that it can be coordinated under the reaction conditions. Representative examples of such organic compounds include terephthalic acid (benzenedicarboxylic acid), naphthalenedicarboxylic acid, benzenetricarboxylic acid, naphthalenetricarboxylic acid, pyridinedicarboxylic acid, bipyridyldicarboxylic acid, formic acid, oxalic acid, malonic acid, Succinic acid, glutaric acid, hexanedioic acid, heptanedioic acid and the like, and anion, pyrazine, bipyridine and the like may be selected from one kind or may be used by mixing two or more kinds. It is preferable to use terephthalic acid or benzenetricarboxylic acid.

Iron-containing porous organic-inorganic hybrid adsorbent according to the present invention is an iron precursor, an organic ligand, a solvent and a reaction promoter, mixed with hydrofluoric acid and nitric acid mixed in a reactor and heated to 100 to 250 ℃ and microwave or The reaction temperature is maintained using electricity, and the pressure can be prepared by maintaining the automatic pressure.

As described above, the method for producing the iron-containing organic-inorganic hybrid according to the present invention is characterized by using a mixed acid of hydrofluoric acid and nitric acid. In particular, the organic-inorganic hybrids containing iron of the present invention showed a significant improvement in crystallinity and a decrease in crystal size compared to the conventional method of synthesis using hydrofluoric acid. Conventional production methods using hydrofluoric acid cannot produce iron-containing organic-inorganic hybrids having surface areas greater than 1,700 m ² / g and pore volumes greater than 0.8 mL / g. Referring to the results of Examples and Comparative Examples, when using the existing hydrofluoric acid, the BET surface area value is 1,590 m 2 / g, and the mixed acid is significantly lower than the BET surface area value of 2,050 m 2 / g, and also in the pore volume. 1.0 ml / g for mixed acids, 0.7 for hydrofluoric acid low as ml / g. In addition, in the case of using a mixed acid, the crystallinity was improved and the yield had the same effect in spite of a very short reaction time (within 2 minutes when using microwave) compared with the case where it was not. However, it is difficult to prepare an organic-inorganic hybrid having sufficient crystallinity when using acid components such as acetic acid and sulfuric acid or salts such as ammonium fluoride and sodium chloride as other acids. In the production method of the present invention, the mixed ratio of nitric acid and hydrofluoric acid in the mixed acid may be used in a molar ratio of 0.1 to 1: 1 to 0.1 to prepare the iron-containing organic-inorganic hybrid as an object of the present invention. If nitric acid or hydrofluoric acid is out of the molar ratio, there is a disadvantage that the yield is lowered and the reaction time is too long.

In addition to the iron precursor and the organic ligand, a suitable solvent is required when preparing a porous organic-inorganic hybrid. As the solvent, one or a mixture of two or more selected from water, an alcohol having 1 to 10 carbon atoms, a ketone having 2 to 10 carbon atoms, and a hydrocarbon having 5 to 20 carbon atoms may be used, and preferably, water is used. good.

The iron precursor and the organic ligand may be used by mixing in a ratio (molar ratio) of 1: 0.1 to 10, and the ratio may be appropriately adjusted according to the type of each iron precursor and the organic ligand. In the present invention, as the iron precursor, iron salts such as iron or iron nitrate in the form of metal powder are used, and as the organic ligand, terephthalic acid or benzene tricarboxylic acid is more preferable, and iron terephthalate or iron benzene tricar as a porous organic-inorganic hybrid. Cyxlate is prepared.

In addition, if the reaction temperature is too low, less than 100 ℃ is not effective because the reaction rate is slow, if the reaction temperature is too high exceeding 250 ℃, it is easy to obtain a material without pores and the reaction rate is too fast and impurities are easily incorporated. In addition, the internal pressure of the reactor is increased, which makes the construction of the reactor uneconomical. The reactor pressure is practically unlimited but it is simple to synthesize at the autogeneous pressure of the reactants at the reaction temperature. In addition, an inert gas such as nitrogen or helium may be added to carry out the reaction at a high pressure. In the case of irradiating microwaves with the reaction heat source, any microwave having a frequency of about 300 MHz to 300 GHz can be used to heat the reactant, but it is simple and efficient to use microwaves of frequency 2.45 GHz and 0.915 GHz, which are widely used industrially. . The microwave irradiation method has a shorter reaction time compared to the electric heating method, the particle size of the prepared porous organic-inorganic hybrids is relatively small, and the specific surface area is high, so that the characteristics of the moisture adsorbent are better.

In addition, in order to use for humidification or dehumidification as an adsorbent, adsorption and desorption characteristics are more important than initial 10 minutes, preferably within 5 minutes. That is, even if the adsorption amount is large, if the speed is too low, it may not be suitable for use in the use of humidification and dehumidification. However, in the case of the adsorbent prepared by the method of irradiating microwaves in the adsorbent according to the present invention, the adsorption rate is very high, and the desorption rate is also excellent, and thus has more suitable properties for use in such applications. That is, after drying for 10 to 30 minutes at 60 ~ 80 ℃ 5 minutes under the relative humidity 60 ~ 80% conditions, the water adsorption amount is 0.35 ~ 0.45g / g per weight of the adsorbent is very high initial adsorption rate.

In the above production method, the reaction can be carried out in a batch as well as in a continuous manner. Batch reactors are suitable for producing small amounts of organic-inorganic hybrids with low output per hour, while continuous reactors are expensive and are suitable for mass production. In the case of a batch type, the reaction time is suitably about 1 minute to 8 hours, and when the reaction time is too long, impurities are easily mixed and particles are grown, making it difficult to make nanoparticles. If the reaction time is too short, the reaction conversion rate is low. The reaction time is more preferably 1 minute to 1 hour. The residence time of the continuous reactor is preferably about 1 minute to 1 hour. Too long residence time results in low productivity and large particles, while too short residence time results in low reaction conversion. The residence time is more preferably 1 to 20 minutes. During the batch reaction, the reactants may be agitated and the agitation speed may be 100-1000 rpm, but it may be performed without agitation. Without stirring, it is simple and easy to apply in the reactor configuration or operation.

Because microwave reactions occur at a very high rate, it is recommended to irradiate the microwaves in a pre-processed state to increase the uniformity or the solubility of the reactants as well as to generate some crystal nuclei. If the reaction by microwave is started immediately in the absence of pretreatment, the reaction may be slow, impurities may be mixed, or the uniformity of particle size may be low, but the process may be simplified. The pretreatment can be carried out by ultrasonication of the reactants or by vigorous stirring. The pretreatment temperature is preferably between room temperature and reaction temperature. If the temperature is too low, the pretreatment effect is weak and if it is too high, impurities are easily generated. There is a drawback to the complexity of the installation. Pretreatment time is suitable for 1 minute or more and less than 5 hours, 1 minute or more for ultrasonic, 5 minutes or more for stirring. When the pretreatment step is performed by stirring, it is preferable to stir the metal material and the organic material at 50 to 2000 rpm for 5 to 600 minutes in the presence of a solvent, and when performing the ultrasonic irradiation, the ultrasonic wave at 15000 Hz to 30 MHz is 1 to 600 minutes. It is more preferable to carry out by irradiation. If the pretreatment time is too short, the pretreatment effect is weak and if the pretreatment is performed for too long, the pretreatment efficiency is also lowered. Pretreatment using ultrasonics is more effective in the pretreatment time and in the homogeneity of the reactants.

Hereinafter, the present invention is described in more detail in the following non-limiting examples.

Example 1 Preparation of Porous Organic-Inorganic Hybrids (Fe-BTCA) by Microwave Irradiation

To the Teflon reactor were added 1 mmol of metal iron, 60 ml of 1M HNO ₃ , 40 ml of 5M HF (aqueous solution) and 7 mmol of 1,3,5-benzenetricarboxylic acid (BTCA), followed by distilled water, and the final molar ratio of the reactant was Fe: HF: NHO ₃ : BTCA: H ₂ O = 1: 2: 0.6: 0.7; 278. The reaction was stirred at 500 rpm at room temperature for 20 minutes to ensure a uniform reaction. The Teflon reactor containing the pretreated reactant was mounted in a microwave reactor (CEM Co., Model Mars-5) and irradiated with microwave (2.54 kW) to raise the temperature to 200 ° C., and then maintained at 200 ° C. for 2 minutes to perform a crystallization reaction. After cooling to room temperature, centrifugation, washing (distilled water) and drying to obtain a porous organic-inorganic hybrid (Cr-BTCA). X-ray diffraction pattern of the obtained porous organic-inorganic hybrid was as shown in Figure 1, the elemental analysis showed a molar ratio of Fe: C: F = 1: 6.5: 0.32, nitrogen adsorption experiment results of 2,050 ㎡ / g Yield with BET surface area and pore volume of 1.0 ml / g formed 86% porous particles (FIG. 2).

The results showed that the crystal structure of the Bulletin of Korean Chemical Society vol. 26, p. 880 (2005) is similar to that of Cr-MIL-100.

Example  2: porous organic-inorganic hybrid by electric heating (Fe- BTCA Manufacturing

A porous organic-inorganic hybrid was prepared in the same manner as in Example 1, but instead of irradiating microwaves with a heat source, an organic-inorganic hybrid was prepared by heating for 144 hours using an electric heating method using a conventional convection oven. XRD analysis showed that the crystal structure of the prepared organic-inorganic hybrid was different, but the diffraction pattern was obtained at the same position as Example 1, and the nitrogen adsorption experiment showed that the BET surface area and 0.9 ml / g were 1,820 m 2 / g. Pore volume of.

Comparative Example 1 Zeolite Water Absorbent

Zeolite Y (Aldrich, Si / Al = 5.6, specific surface area = 827 m ² / g, pore volume = 0.35 ml / g) used as a commercial moisture adsorbent was prepared.

Comparative Example 2: Preparation of porous organic-inorganic hybrid (Fe-BTCA) by a single acid

A porous organic-inorganic hybrid was prepared in the same manner as in Example 1, but a hybrid was prepared using a single acid without nitric acid. 1 mmol of metal iron, 40 ml of 5M HF (aqueous solution) and 7 mmol of 1,3,5-benzenetricarboxylic acid (BTCA) were added to the Teflon reactor, and distilled water was added thereto. The final molar ratio of the reactants was Fe: HF: BTCA: H ₂ O = 1: 2: 0.6; 278. Microwave irradiation temperature of the organic-inorganic hybrid was carried out at 200 ℃, reaction time 1 hour. The obtained porous organic-inorganic hybrid had a yield of 82%, and the X-ray diffraction pattern of the porous organic-inorganic hybrid was similar to that of Example 1, but the overall peak intensity was low and the results of nitrogen adsorption experiments were 1,590 m 2 / g. BET surface area and pore volume of 0.7 ml / g.

Test Example 1: Water adsorption test

The adsorbents obtained in Examples 1 and 2 were vacuum dried at 70 ° C. for 30 minutes, and then adsorption experiments of water were carried out by gravimetric method (FIG. 3). Even at a relative humidity of 68%, the amount of water adsorption per weight of the adsorbent was 0.67 g / g in Example 1 and 0.59 g / g in Example 2.

Compared with zeolite Y used as a commercial moisture adsorbent of Comparative Example 1, the zeolite Y was vacuum-dried at 200 ° C. for 30 minutes, and the same water adsorption experiment was carried out. The water adsorption amount was 0.35 g / g (FIG. 3). ). That is, although the adsorbent of the example was set to 70 ℃ desorption temperature, the adsorbent according to the present invention showed a water adsorption amount of 1.6 times or more.

In addition, the adsorbent of Example 1 prepared using microwave showed an adsorption amount of 0.4g / g after the initial 5 minutes, 0.56g / g after 10 minutes, while the adsorbent of Comparative Example 1 0.25g / after 5 minutes g, 10 minutes after the adsorption amount of 0.28g / g shows that the adsorbent according to Example 1 of the present invention is very high initial adsorption rate.

Test Example 2: Water Desorption Test

The adsorbent prepared in Example 1 and sodium zeolite Y (NaY) were kept in the upper layer of the desiccator containing saturated aqueous ammonium chloride solution for 3 days to sufficiently adsorb moisture, and then desorption amount was analyzed by gravimetric analysis. Desorption condition was measured by the weight loss of the adsorbent while flowing nitrogen 300ml / min. At this time, the desorption temperature was 70 ° C. in the adsorbent of Example 1, and sodium zeolite Y (NaY) in Comparative Example 1 was 200 ° C.

Figure 4 is a graph showing the weight loss results over time with the total weight of the adsorbent adsorbed water to 100%. If the weight loss rate is no longer reduced, it means that all of the removable moisture is desorbed. Example 1 shows a weight loss of about 40% by weight after 10 minutes, and in the case of Comparative Example 1 showed a weight loss of 25% by weight. In the case of Example 1, the adsorptive moisture adsorption amount per weight of the adsorbent is 40/60 = 0.67 g / g, and in the case of Comparative Example 1, the adsorptive moisture adsorption amount per weight of the adsorbent is 25/75 = 0.33 g / g. It can be seen that the absolute moisture adsorption amount is two times or more as compared with the adsorbent of Comparative Example 1. In addition, the desorption rate within the initial 5 minutes was also higher in the adsorbent of Example 1 compared to the adsorbent of Comparative Example 1.

From the above results, it can be seen that the adsorbent according to the present invention has a property of easily desorbing moisture at a temperature of 100 ° C. and having a high water adsorption amount per unit weight. You can expect to see excellent performance.

As described above, the iron-containing porous organic-inorganic hybrid prepared according to the present invention has a high adsorption amount of water and excellent desorption amount characteristics at a low temperature of less than 100 ℃ can be used in dehumidifiers, humidifiers, air conditioners using this as an adsorbent. In particular, the desorption temperature is very low, there is an advantage that the operating cost of these equipment can be greatly reduced.

Claims (9)

1) preparing a reactant mixture by mixing iron or iron salt as an iron precursor, terephthalic acid or benzenetricarboxylic acid as an organic ligand, and a mixed acid of hydrofluoric acid and nitric acid as a solvent and a reaction accelerator; And 2) heating the reactant mixture by electric heating or microwave irradiation; Prepared by a manufacturing method comprising a having a surface area of more than 1,700 m ² / g less than 10000 m ² / g and a pore volume of more than 0.8 mL / g less than 10 mL / g, using iron terephthalate or iron benzene tricarbonate Moisture adsorbent. delete delete The method of claim 1, The iron-containing porous organic-inorganic hybrid is a moisture adsorbent, characterized in that the moisture adsorption amount is 0.4 ~ 0.7g / g per weight of the porous inorganic hybrid after drying for 10 to 30 minutes at 60 ~ 80 ℃ relative humidity 60 ~ 80% . The method of claim 1, The temperature of heating the reactant mixture is a moisture adsorbent, characterized in that 100 ~ 250 ℃. delete The method of claim 5, The heating method is a moisture adsorbent, characterized in that the microwave irradiation. The method of claim 5, The production reactor is a water adsorbent, characterized in that using a batch reactor. The method of claim 5, After the step 1) is stirred for 50 minutes to 600 minutes at 50 ~ 2000 rpm, or further comprises a pre-treatment step of forming a crystal nucleus by irradiating 15000 Hz ~ 30 MHz ultrasound for 1 ~ 600 minutes absorbent.

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