KR20050050389A - Method for preparing adsorbents for removing acid gases and method for removing acid gases with the adsorbent prepared by the same - Google Patents

Abstract

The present invention relates to a method for preparing an acid gas removal adsorbent and a method for removing an acid gas, specifically preparing a zinc oxide, supporting a metal precursor in zinc oxide, and then heat treating the layered double hydroxide under hydrothermal conditions. The present invention relates to a method for preparing an adsorbent and a method for removing an acidic gas, comprising the steps of preparing an adsorbent in a containing form and preparing an adsorbent in a form containing a complex oxide by calcining the adsorbent at high temperature.

The adsorbent prepared by the method for preparing an acidic gas adsorbent according to the present invention exhibits an improved adsorption rate and adsorption capacity compared to an adsorbent prepared by zinc oxide, including a layered double hydroxide or complex oxide form, resulting in petrochemical processes. It can be effectively used for the removal of acidic gas compounds and the like contained in the waste gas of the acidic gas and the semiconductor process.

Description

METHODS FOR PREPARING ADSORBENTS FOR REMOVING ACID GASES AND METHOD FOR REMOVING ACID GASES WITH THE ADSORBENT PREPARED BY THE SAME}

The present invention relates to a method for preparing an acid gas removal adsorbent and a method for removing acid gas using the adsorbent prepared by the method.

Acid gas is a generic term for sulfur oxides (SO _x ) such as hydrogen chloride, hydrogen sulfide, chlorine, sulfur dioxide, and nitrogen oxides (NO _x ) such as nitrogen monoxide. It is a substance that must be removed, such as causing corrosion. These acid gases are contained in petrochemical fractions, are discharged from petrochemical plants, and are also discharged from semiconductor manufacturing processes such as etching processes.

As a method for removing a conventional acid gas can be considered divided into a wet method and a dry method.

First, as a wet method, there is a scrubber method using a caustic soda solution, and there is also a method of neutralizing and removing a material containing an acidic gas component through a base solution such as amines and hydroxides (Domestic Application No. 2001). -0053250, US Pat. No. 4,234,388). However, since the wet method releases a large amount of wastewater, it is difficult to post-treat the wastewater, and the apparatus required for this is complicated and large-scaled, and there is a problem that these apparatuses and their management are expensive. In addition, there have been management problems such as the risk of leakage in the pipe for discharging the waste water.

Accordingly, a dry method in which no waste water is generated is preferred, and the dry method is a method of purifying the harmful gas by passing the harmful gas through a packed column packed with an adsorbent, depending on the type of harmful component containing the acidic gas. The ingredients will be different.

Such adsorbents include zinc oxide (US Pat. No. 6,432,374), zinc oxide / calcium oxide (US Pat. No. 3,935,295), zinc oxide / aluminum oxide / alkali compound (Domestic Patent No. 0326123) and alumina containing an alkali metal (US Pat. Oxides, nickel, and the like Metals such as cobalt and iron or metal hydrides (US Pat. No. 5,928,500), strontium hydroxide / iron oxide (Domestic Patent No. 0318352), zinc hydroxide and metal chloride compounds (Domestic Patent Publication No. 2000-0050484) are used. For example, the acid gas can be removed by adsorption through an acid-base reaction. However, these adsorbents have a disadvantage of low adsorption capacity or green oil (alumina adsorbent) and low adsorption rate (zinc oxide / calcium oxide).

In addition, attempts have been made to remove sulfur oxides (SO _x ) gases such as sulfurous acid gas using layered double hydroxides, but the operation temperature is very high, such as 400 to 900 ° C. The need for the addition of metal-containing oxo-anions, etc., was impractical and the gas being removed was limited to sulfur oxides.

Conventional adsorbents have been mainly produced by physical mixing and shaping of raw materials, which leads to limitations in obtaining uniform mixing between adsorbent components, resulting in unsatisfactory performance. In particular, when the particle size of each component is large, the physical properties between the components are expressed separately, so the performance of the adsorbent is very low.

An object of the present invention is to solve the above problems, to provide a method for producing an adsorbent with improved adsorption performance and adsorption capacity, and thereby an adsorbent and an acid gas removal method using the same.

In order to achieve the above object, the present invention provides a method for producing an acid gas removal adsorbent, and an acid gas removal method using the adsorbent and the adsorbent prepared thereby.

Hereinafter, the present invention will be described in detail.

The present invention provides a method for preparing an adsorbent for removing acid gas.

Specifically, preparing a zinc oxide (step 1),

Supporting a solution consisting of a metal precursor in a mixture of zinc oxide and a binder (step 2),

It provides a method for producing an acidic gas removal adsorbent comprising the step (step 3) of preparing an adsorbent containing a layered double hydroxide by heat treatment under hydrothermal conditions after supporting.

In another aspect, the present invention further comprises the step of producing an adsorbent in the form of a composite oxide by calcining the adsorbent in the form containing the layered double hydroxide of step 3 under high temperature in an air atmosphere.

In step 1, zinc oxide is prepared.

Zinc oxide is a main component of the acid gas removal adsorbent and reacts with acid gas to produce harmless zinc salts and oxygen or water. In the present invention, in order to improve the adsorption rate and the adsorption capacity, zinc oxide uses a uniform and small particle size. Specifically, zinc oxide of less than 500 nm is used, and preferably zinc oxide of 100 nm or less is used. When the particle size of zinc oxide is 500 nm or more, the diffusion of molecules to be adsorbed is very slow, resulting in a very low adsorption and removal rate.

As a method of reducing the particle size of zinc oxide, either a physical method or a chemical method can be used. For example, oxidation using zinc peroxide decomposition {Chemistry letter, p606-607, 2001} and oxidation in step 2 below A mixture of zinc, a binder and a layered double hydroxide or a mixed oxide may be a physical method using ball milling, such as centrifugal ball milling and planetary ball milling.

In step 2, the metal precursor solution is supported on zinc oxide.

Specifically, the zinc oxide of step 1 is mixed well with a binder to form a uniform mixture, and then the metal precursor is dissolved in a solvent and then added dropwise to the zinc oxide and binder mixture to be supported. Solvents such as water and alcohol can be used when preparing the zinc oxide and binder mixtures. In addition, the metal precursor liquid may be added to the zinc oxide and binder mixture, and conversely, the zinc oxide and binder mixture may be added to the metal precursor solution and mixed.

As the metal precursor, one or more selected from the group consisting of magnesium, calcium, and aluminum compounds may be used, wherein the magnesium compound, the calcium compound, and the aluminum compound may be nitrate, chloride, acetate, sulfate. Any type of salt may be used as long as it can be used by dissolving in a solvent.

The solvent may be any solvent as long as it can dissolve salts such as water and alcohol to some extent. However, due to cost and ease of use, water is mainly used as a solvent.

At this time, the composition ratio of zinc oxide: binder: metal precursor is preferably 30 to 80%: 10 to 50%: 10 to 50% as the weight ratio. If the ratio of zinc oxide is less than the above range, the adsorption capacity to remove the acidic gas is reduced. If the ratio exceeds the above range, the adsorption capacity is advantageous but the manufacturing cost is high and the strength of the granulated particles is low. There is a disadvantage that it is not practical to be fragile when applied. In addition, when the ratio of the metal precursor exceeds the above range, green oil by aluminum may be produced. When the ratio is below the above range, it is difficult to expect an effect due to the addition of the metal precursor.

In step 3, an adsorbent in the form of a layered double hydroxide is prepared by heat treatment.

At this time, the adsorbent in the form containing the layered double hydroxide, is obtained by heat-treating the material prepared in step 2 under hydrothermal conditions, the heat treatment is preferably carried out for 20 to 300 ℃ for 0.1 to 168 hours. If the temperature or time is too high or too long, the layered double hydroxide structure is changed to another structure during hydrothermal reaction, and thus the adsorption performance is reduced.

In addition, in step 4, the adsorbent in the form containing the layered double hydroxide is calcined at high temperature to prepare an adsorbent in the form containing the complex oxide.

At this time, the firing conditions are carried out at 100 to 800 ℃ for 0.1 to 72 hours. If the temperature or time is too high or too long, the zinc oxide agglomerates and crystals grow during the firing, so that the adsorption performance is reduced.

The binder is for bonding zinc oxide particles, zinc oxide and layered double hydroxides or mixed oxides, and includes clay, silica sol, water glass, bentonite, boehmite, and shoe. All conventionally used binders such as pseudoboehmite can be used. However, binders with high acidity are not suitable because they can cause side reactions by acid catalysis.

The adsorbent prepared by the above production method includes a layered double hydroxide or a composite oxide in addition to zinc oxide, which has an advantage that the adsorption process can be effectively and quickly occurred due to the basic and adsorbent properties of the layered double hydroxide or the composite oxide. .

In order to substantially apply the adsorbent prepared by the above method, the shape and size may be adjusted in various ways. For example, the adsorbent may be adjusted by pellets, tablets, granules, spheres, extrudates, and the like. .

The present invention also provides a method for removing acidic gas using the adsorbent of the present invention.

Specifically, the acidic gas is contacted with the adsorbent of the present invention to remove the acidic gas. At this time, the adsorption temperature is irrelevant if the temperature is more than 0 ℃, preferably 10 to 500 ℃, more preferably 20 to 400 ℃, the adsorption pressure is irrelevant in any range, the adsorption method is carried out both continuous reaction or batch reaction can do.

The acid gas substances to be adsorbed are acid gases such as hydrogen chloride (HCl), hydrogen sulfide (H ₂ S), chlorine, sulfur dioxide and nitrogen monoxide (NO), organic chlorides or organic sulfides. In particular, hydrogen chloride and hydrogen sulfide are adsorbed more effectively by the adsorption method of the present invention.

An example of a purification apparatus for performing the method of removing the generated acidic gas is as shown in FIG.

Hazardous gases containing acidic gases are discharged from the hazardous gas discharge process, and these are very toxic and are discharged into the atmosphere through the filling tower 30 filled with the adsorbent. The filling tower 30 is connected by the harmful gas discharge process 10 and the harmful gas discharge pipe 20 for discharging the acid gas, the blower 40 is installed at the distal end of the harmful gas discharge pipe 20 The blower may not be installed if the pressure of the noxious gas discharge process is above atmospheric pressure. Therefore, the harmful gas containing the acidic gas discharged from the harmful gas discharge process 10 is the filling tower 30 along the harmful gas discharge pipe 20 by the suction force of the blower 40 or the pressure of the harmful gas discharge process. ), Where the acid gas in the noxious gas is removed by the adsorbent.

This adsorption method can be used to remove acidic gas compounds derived from petrochemical processes and crude oil, including acidic gas compounds and similar materials. The processes that need to remove acid gas compounds include the catalytic reforming reaction of naphtha used to produce benzene, toluene, xylene, etc. . In addition, this adsorption method can be used for the adsorption treatment of the waste gas discharged from the semiconductor process such as etching process, epi process, etc., and it quickly adsorbs in case of leakage of acid gas used in the semiconductor manufacturing process and discharges only harmless gas to damage the environment and human life. It can prevent giving.

Hereinafter, the present invention will be described in detail by way of examples.

However, the following examples are merely to illustrate the present invention is not limited to the contents of the present invention.

Example 1 Preparation of Adsorbent of the Present Invention

(Step 1) Preparation of Zinc Oxide

Zinc hydroxide was added dropwise to 1000 ml of zinc nitrate (Zn (NO ₃ ) ₂ 6H ₂ O) 0.1 M aqueous solution, and 1000 ml of 0.1 M aqueous solution of sodium hydroxide was added dropwise to obtain 500 ml of hydrogen peroxide. After maintaining for 2 hours at dry using a rotary evaporator. After drying, heat treatment was performed at 300 ° C. for 2 hours to obtain zinc oxide powder.

The obtained zinc oxide powder was confirmed from the X-ray diffraction pattern, and the half width showed that the crystal size was very small. As shown in FIG. 2, it was confirmed that the particle size was about 20 to 50 nm through a scanning electron microscope.

(Step 2) Supporting the Metal Precursor

7.93 g of magnesium nitrate was dissolved in 20 g of distilled water, 7.3 g of calcium nitrate was dissolved in 20 g of distilled water, 7.8 g of aluminum nitrate was dissolved in 20 g of distilled water, and the above three kinds of nitrate solutions were mixed. 5 g of zinc oxide prepared in Step 1 and 2.5 g of clay were added and mixed with 50 g of distilled water, and the nitrate solution was slowly added dropwise while stirring. At this time, the composition is based on the oxide weight ZnO: Clay: MgO: CaO: Al ₂ O ₃ = 5.0: 2.5: 1.25: 1.73: 1.07.

1.6 g of sodium carbonate was dissolved in 10 g of distilled water and slowly added to the mixture prepared above. The mixture thus prepared was stirred and a 2.0 M NaOH aqueous solution was added dropwise to have a pH of 10.

(Step 3) Formation of layered double hydroxide

The resulting mixture was well blocked and held at 70 ° C. for 8 hours to form a layered double hydroxide. The structure of the layered double hydroxide produced was confirmed from the X-ray diffraction pattern. From the X-ray diffraction pattern of FIG. 3, it was found that a layered double hydroxide structure was formed in addition to zinc oxide, and the half-width value showed that the particle size was very small and well dispersed.

(Step 4) High Temperature Firing

In order to convert the layered double hydroxide into a composite oxide, it was calcined under an air atmosphere at 500 ° C. for 4 hours. At this time, it can be seen that the X-ray diffraction peak of the layered double hydroxide disappears and an amorphous composite oxide was formed (FIG. 4). It was found that even after firing, crystal growth or agglomeration of zinc oxide did not occur (FIG. 4).

The adsorbent was processed to form a cylindrical pellet, having a height of 5 mm and a diameter of the bottom 3 mm.

Example 2 Preparation of Adsorbent of the Present Invention

In Example 1, the adsorbent was prepared by excluding the high temperature firing step of step 4.

Example 3 Preparation of Adsorbent of the Present Invention

An adsorbent was prepared in a similar manner as in Example 1, but the composition was ZnO: Clay: MgO: Al ₂ O ₃ = 5.0: 2.5: 2.5: 1.05.

Example 4 Preparation of Adsorbent of the Present Invention

An adsorbent was prepared in a similar manner to Example 1, but the composition was ZnO: Clay: CaO: Al ₂ O ₃ = 5.0: 2.5: 2.5: 0.76.

Example 5 Preparation of Adsorbent of the Present Invention

An adsorbent was prepared in a similar manner as in Example 1, but activated clay was used as a binder instead of clay.

Comparative Example 1

Adsorbents were prepared similarly to Example 1, but commercially available zinc oxide was used, and electron micrographs showed that the particle size of zinc oxide was relatively large and nonuniform (around 500 nm).

Magnesium oxide, calcium oxide, and aluminum oxide used commercially available oxides instead of being prepared from solutions.

Comparative Example 2

Adsorbents were prepared similarly to Example 2, but commercially available zinc oxide was used, and the electron micrographs showed that the particle size of zinc oxide was relatively large and uneven (about 500 nm).

The layered double hydroxide was prepared in a separate reactor instead of being prepared from a solution, and physically mixed with zinc oxide.

Comparative Example 3

An adsorbent was prepared in the same manner as in Example 3, but commercially available zinc oxide was used as in Comparative Example 1.

<Comparative Example 4>

Adsorbents were prepared similarly to Example 4, but only zinc oxide and a binder were used, and no magnesium, calcium, or aluminum compounds were used.

Experimental Example 1 Adsorption Experiment Using Adsorbent of the Present Invention

(1) adsorption experiment of acid gas

Adsorption experiments were performed using the adsorbents prepared in Examples 1 to 5 and Comparative Examples 1 to 4.

3 g of the adsorbent was charged into a fixed bed reactor made of quartz, dehydrated by holding at 200 ° C. for 2 hours, and then maintained at a constant temperature of 40 to 300 ° C., followed by flowing dry hydrogen chloride gas at a rate of 20 cc / min. Dose was measured. The amount of acid gas adsorbed with adsorption temperature and adsorption time was measured by weight gain and chemical analysis. The results are shown in Table 1 below.

(2) sulfur adsorption experiment

The removal capacity of hydrogen sulfide was confirmed using the adsorbents prepared in Example 1 and Comparative Example 1. As the adsorption gas, 10% hydrogen sulfide diluted in nitrogen was flowed at a flow rate of 80 cc / min, the adsorption temperature was 200 ° C., and the adsorption results are summarized in Table 1.

As shown in Table 1, it can be seen that the adsorbents of Examples 1 to 5 of the present invention are improved in the adsorption rate and adsorption capacity compared to the adsorbents of Comparative Examples 1 to 4. In particular, the more uniform and smaller the size of the zinc oxide was able to obtain an excellent effect, it can be seen that the adsorption rate and adsorption capacity is improved by the effect of the layered double hydroxide or composite oxide of the present invention compared to Comparative Example 4.

In addition, as a result of the adsorption experiment of sulfur using the adsorbents of Example 1 and Comparative Example 1, it can be seen that after 2 and 10 hours of adsorption, 18 and 30% of sulfur is adsorbed, respectively. It can be seen that high.

As described above, the adsorbent prepared by the method for producing an acidic gas adsorbent according to the present invention has a form of layered double hydroxide or complex oxide, which shows an improved adsorption rate and adsorption capacity compared to an adsorbent prepared by zinc oxide. It can be effectively used for the removal of acidic gas generated in by-products and the like and acidic gas compounds contained in the waste of semiconductor process.

1 is a view showing a schematic configuration diagram of a purification apparatus for performing the acid gas removal method using the adsorbent of the present invention,

Figure 2 is a photograph of the observation of the zinc oxide prepared in Example 1 of the present invention with an electron microscope.

3 is an X-ray diffraction pattern of the zinc oxide and layered double hydroxide mixture prepared in Example 1 of the present invention.

4 is an X-ray diffraction pattern after calcining the zinc oxide and layered double hydroxide mixture prepared in Example 1 of the present invention.

<Description of the symbols for the main parts of the drawings>

10: harmful gas discharge process, 20: harmful gas discharge pipe,

30: filling tower, 40: blower

Claims (8)

Preparing zinc oxide (step 1), Supporting a solution of a metal precursor in zinc oxide (step 2), A process for producing an acidic gas removal adsorbent, comprising the step (step 3) of preparing an adsorbent containing a layered double hydroxide by heat treatment under hydrothermal conditions after loading. The method of claim 1, further comprising the step of calcining the layered double hydroxide at high temperature to produce an adsorbent in the form of a composite oxide. The method of claim 1 wherein the particle size of the zinc oxide is less than 500 nm. The method of claim 1, wherein the composition ratio of the zinc oxide: binder: metal precursor of step 2 is 30 to 80%: 10 to 50%: 10 to 50% by weight. The method of claim 1, wherein the metal precursor is at least one selected from the group consisting of magnesium compounds, calcium compounds and aluminum compounds. An adsorbent comprising a substance in the form of a layered double hydroxide or a complex oxide prepared by the method of claim 1. An acid gas adsorption and removal method characterized in that the acid gas is contacted with the adsorbent of claim 6 to remove the acid gas. The method of claim 7, wherein the acid gas adsorption method is carried out at 10 ~ 500 ℃.