KR20010091269A - Preparing method of an absorbent for formaldehyde - Google Patents

Abstract

PURPOSE: A method for manufacturing an adsorbent for selectively adsorbing formaldehyde from flue gas bearing gaseous formaldehyde is provided to effectively meet with international environmental regulations. CONSTITUTION: The adsorbent is manufactured by (i) blending 70-95wt.% of activated white clay, 5-25wt.% of stone powder, 0-5wt.% of activated carbon; (ii) preparing a solution comprising 5-10wt.% of ammonium acetate, 0.1-0.5wt.% of acetylacetone, 0.1wt.% of acetic acid; (iii) mixing above solid material with prepared solution in a ratio of 6:4; (iv) press-forming above mixture into pellet; and then (v) drying the pellet to be moisture content of 10 to 30wt.%.

Description

Preparation method of formaldehyde adsorbent {Preparing method of an absorbent for formaldehyde}

The present invention provides a dry adsorbent which selectively forms and removes formaldehyde chemically and physically in an exhaust gas containing formaldehyde by adding activated carbon and a small amount of reactants thereon as an active material and an acidic or neutral substance such as activated clay and stone powder. It is about a method.

Even if we do not mention the damages of various air pollutants caused by high industrialization to our living environment, we are well aware of it. In 1992, the United Nations Conference on Environment and Development (UNCED) in Rio adopted Agenda 21 and began linking trade with the environment. At present, the company's management may face serious difficulties if there is a lack of environmentally friendly elements such as the production process of various products and disposal after use. In view of this trend, formaldehyde gas is generated in the production process of the product, so serious concerns are expected for air pollution as well as the health of workers. Formaldehyde gas is generated from various industrial activities such as synthetic resin manufacturing industry such as phenol resin, dye industry, textile industry, leather industry, plywood manufacturing industry and formalin manufacturing. This gas produces a colorless irritating odor and is a flammable gas that can explode. The effects on the human body are strong irritation to the eyes, bronchus and mucous membranes when exposed to the skin, and accompanied by anorexia and chest compressions when inhaled. In case of prolonged inhalation, there is a risk of carcinogenesis. Formaldehyde gas, a harmful gas that has a harmful effect on humans, is strongly regulated to less than 20 ppm in all emission facilities under the Korean Air Environment Conservation Act. In addition, formaldehyde gas is a noxious odor gas that must be removed in terms of industrial safety and health due to the fact that field workers are directly exposed to the gas at the generating company.

Looking at the chemical properties of formaldehyde, the molecular weight is 30, the melting point is -92 ℃, boiling point is -21 ℃ and the chemical formula is as shown in (1). Formaldehyde is gaseous at room temperature, and anhydrides are easy to polymerize, so that three molecules are polymerized to trioxane (2). Commercially, it is used in 37 aqueous solution called formalin. When it is used for synthesis, it is made of solid polymer of paraformaldehyde (3).

As in the chemical structure of formaldehyde, a substance having a double bond of carbon and oxygen is called a carbonyl compound, and various kinds of aldehydes, ketones, carboxylic acids, and amides exist. The double bonds of carbon and oxygen that these materials have in common are important functional groups of chemical reactions. Since carbon is more electrically positive than oxygen, it can easily react with a material having an electrically negative element. Using these properties, some reactions that can be applied to chemisorbing of formaldehyde are shown below.

4NH ₄ Cl + 6CH ₂ O → C ₆ H ₁₂ N ₄ + 6H ₂ O + 4HCl

NaHSO ₃ + CH ₂ O → HOCH ₂ SO ₃ Na

(HOCHRCH ₂ ) ₂ NH + CH ₂ O → (HOCHRCH ₂ ) ₂ NCH ₂ OH

Among the above reactions, the reactions that can be introduced to formaldehyde removal must first be harmless to the reactants and products, and must be able to react with gaseous formaldehyde even in the presence of a little moisture to satisfy dry adsorption conditions. Must satisfy

At present, the method of removing formaldehyde gas is only a general technology for removing harmful gases, and a method of selectively removing formaldehyde gas has not been developed. Generally, gaseous pollutants that are currently used include absorption, adsorption, combustion oxidation, and condensation. The most widely used absorption method is a non-regenerated wet process, in which oxidizing agents such as O ₃ , KMnO ₄ , NaCl, and ClO ₂ , which are highly oxidizing, are added to an absorption solvent to absorb and decompose gaseous substances. Since the treatment performance is largely dependent on the equipment of the absorption tower, it is difficult to introduce a new process without changing the entire apparatus, and additional wastewater treatment facilities are needed due to the corrosion of the equipment due to the addition of oxidants and the generation of wastewater by the absorbent liquid. Secondary environmental pollution is generated, such as by-products of the reaction that produce wastes with environmental pollution problems. In addition, there is a combustion oxidation method, a condensation method, etc., but there are weak problems such as low economic efficiency and low removal efficiency. Existing adsorption method has a limitation in the removal efficiency because it only depends on the physical adsorption using the pores of the adsorbent such as activated carbon, zeolite, clay. However, the present invention has the characteristic of completely removing the harmful odor gas in parallel with physical-chemical adsorption.

The main removal methods of formaldehyde are absorption and adsorption methods. The disadvantages of absorption methods include excessive equipment cost, secondary pollutant generation, wastewater treatment and sludge treatment, and the adsorption method uses physical properties of the adsorbent. There is a problem that the removal efficiency is low because it depends on the physical adsorption. The present invention is easy to install the device by supplementing and improving the disadvantages of the absorption method and the adsorption method by completely removing the formaldehyde gas in parallel with physical-chemical adsorption to collect the formaldehyde gas sent to the adsorption tower filled with the adsorbent adsorption. The equipment cost is low and the adsorbents used are low cost and do not cause waste water and secondary pollution. In addition, the formaldehyde adsorbent after the adsorption is landfilled in a non-regenerated manner, and activated clay and stone dust, which are the main raw materials of the adsorbent, are incidentally stabilized in soil and have the effect of adsorbing heavy metals in the soil.

The present invention is a method for producing a dry adsorbent that can effectively remove formaldehyde gas.

The formaldehyde adsorbent preparation method of the present invention will be described in detail as follows. 70 to 95wt of activated clay, 5 to 25wt of stone powder, and 0 to 5wt of activated carbon were mixed in the solid raw material ratio, and acetylacetone aqueous solution (5 to 10wt of ammonium acetate, 0.1 to 0.5wt of acetylacetone, 0.1wt of acetic acid) was prepared. After mixing the raw materials and the aqueous solution in a ratio of 6: 4, the mixture is extruded to prepare pellet adsorbents, and the moisture is dried to 10 to 30 wt% with respect to the total adsorbent weight ratio.

Activated clay and stone powder used in this formaldehyde adsorbent are low in price and easy to purchase, and have good moldability and can improve porosity and specific surface area depending on the treatment method, so that formaldehyde gas can be removed more easily. have. In addition, activated clay maintains weakly acidic conditions so that the reaction between formaldehyde and acetylacetone can be active, and stone powder not only enhances the formability and strength of the adsorbent, but also helps stabilize the soil during the landfill treatment of the used adsorbent.

Activated carbon is divided into granular and powdered activated carbon. It has a large specific surface area, excellent deodorizing performance of organic substances and neutral compounds, and is widely used to remove heavy metals during wastewater treatment. In the present invention, in order to maximize the formaldehyde adsorption capacity, the powder activated carbon was used at low cost and fast adsorption rate.

Acetyl acetone aqueous solution that directly acts to remove formaldehyde is applied to the adsorbent by using the characteristic that formaldehyde and acetylacetone react in the presence of ammonium salt in weakly acidic conditions and serves to remove formaldehyde by chemisorption.

The chemical reaction formula used is as follows.

The 3,5-diacetyl-1,4-dihydrotizinine produced in this reaction is recovered or discarded.

Formaldehyde gas removal process using the adsorbent of the present invention is a method of adsorbing and removing formaldehyde by flowing the formaldehyde-containing gas into the adsorption tower filled with the adsorbent is simpler than the conventional treatment process, and the equipment cost is low and effective It has the characteristic of removing formaldehyde.

Prior to the embodiment, to determine the degree of adsorption of formaldehyde on each solid raw material, adsorption and removal experiments of formaldehyde were carried out using only activated clay, stone powder and activated carbon. As a result, the concentration of outlet gas was detected at 10ppm, which took about 10 minutes for activated clay and stone powder and 25 minutes for activated carbon, respectively.

Example 1.

Using activated clay as the main raw material, stone powder and activated carbon were mixed in the raw material composition ratio as shown in Table 1, and an aqueous solution of ammonium acetate, acetylacetone, and acetic acid was mixed in the raw material concentration composition ratio of Table 1 to 2/3 of the solid raw material. After the addition, the formaldehyde adsorbent, which was extruded and molded into pellets, was dried at a water content of 30.

400 g of the adsorbent was packed in a column (Φ40, L700mm), and the inlet formaldehyde gas concentration was 2,000 ppm (diluent gas: N ₂ ), a flow rate of 500 cc / min.

The adsorption capacity of formaldehyde is represented by the adsorption duration until 10 ppm of formaldehyde is detected in the outlet gas.

Table 1 shows the raw material ratio of the formaldehyde adsorbent prepared in this example and the adsorption capacity of the formaldehyde adsorbent.

As shown in Table 1, it can be seen that the adsorption capacity of the adsorbent increases as the ratio of activated clay increases. This is because the acidic reaction conditions are stabilized by the increase of the activated clay ratio, and the removal reaction of formaldehyde occurs more actively.

Formaldehyde Adsorption Capacity According to Raw Material Composition of Example 1 Experimental Example Raw material costs () Water content () Formaldehyde 10ppm Detection Time (hr) Solid Raw Material Costs (60) Acetyl Acetone Solution Raw Material Cost (40) Activated clay Stone powder Activated carbon Ammonium Acetate Acetylacetone Acetic acid One 70 25 5 7.5 0.3 0.1 30 27 2 80 15 5 7.5 0.3 0.1 30 31 3 90 5 5 7.5 0.3 0.1 30 34

Example 2

Table 2 shows the results of adsorbing and removing formaldehyde by adjusting the raw material ratio of the acetylacetone aqueous solution to the solid raw material ratio as in the third experiment of Example 1.

In Table 2, it can be seen that the adsorption capacity of the adsorbent increases as the ratio of ammonium acetate and acetylacetone in the acetylacetone aqueous solution increases. This is because the adsorbent can chemisorb with higher amounts of formaldehyde due to an increase in the concentration of reactants that can react with formaldehyde in the adsorbent.

Formaldehyde Adsorption Capacity According to Raw Material Composition of Example 2 Experimental Example Raw material costs () Water content () Formaldehyde 10ppm Detection Time (hr) Solid Raw Material Costs (60) Acetyl Acetone Solution Raw Material Cost (40) Activated clay Stone powder Activated carbon Ammonium Acetate Acetylacetone Acetic acid One 90 5 5 5.0 0.2 0.1 30 29 2 90 5 5 7.5 0.3 0.1 30 34 3 90 5 5 10.0 0.5 0.1 30 41

Example 3.

Table 3 shows the results of adsorbing and removing formaldehyde by drying the adsorbent prepared at the same raw material composition as the third experiment of Example 2 at 70 ° C. to adjust the water content to the total weight.

As shown in the experimental results, the adsorption capacity was the best when the water content of the adsorbent was maintained at about 10-15 wt. Excessive moisture in the adsorbent decreases the specific surface area of the adsorbent, which lowers the probability of contact with the adsorbent material, resulting in poor adsorption capacity. When too much moisture is present, ammonium acetate is ionized by decreasing the amount of hydrogen ions that maintain acidic conditions. Since the probability of the presence of ammonium cations decreases, the reaction between formaldehyde and acetylacetone does not occur actively, resulting in poor adsorption capacity.

Formaldehyde Adsorption Capacity According to Water Content of Example 3 Experimental Example Raw material costs () Water content () Formaldehyde 10ppm Detection Time (hr) Solid Raw Material Costs (60) Acetyl Acetone Aqueous Solution Raw Material Cost (40) Activated clay Stone powder Activated carbon Ammonium acetate Acetylacetone Acetic acid One 90 5 5 7.5 0.3 0.1 35 25 2 90 5 5 7.5 0.3 0.1 30 34 3 90 5 5 7.5 0.3 0.1 25 45 4 90 5 5 7.5 0.3 0.1 15 52 5 90 5 5 7.5 0.3 0.1 10 50 6 90 5 5 7.5 0.3 0.1 5 41

Example 4.

Under the same conditions as in Example 3, the weight ratio of activated clay was increased to 95 without adding activated carbon in the solid raw material, and then the adsorption removal experiment was performed and the results are shown in Table 4.

When the activated carbon is not added as shown in Table 4, the physical adsorption effect is lower than that in Table 3, but the total adsorption time of the adsorbent is not significantly changed. This is due to the fact that formaldehyde gas has a polar structure favoring chemisorption rather than physical adsorption.

Formaldehyde Adsorption Capacity According to Solid Raw Material Ratio of Example 4 Experimental Example Raw material costs () Water content () Formaldehyde 10ppm Detection Time (hr) Solid Raw Material Costs (60) Acetyl Acetone Aqueous Solution Raw Material Cost (40) Activated clay Stone powder Activated carbon Ammonium Acetate Acetylacetone Acetic acid One 95 5 0 7.5 0.3 0.1 35 21 2 95 5 0 7.5 0.3 0.1 30 31 2 95 5 0 7.5 0.3 0.1 25 41 2 95 5 0 7.5 0.3 0.1 15 48 3 95 5 0 7.5 0.3 0.1 10 46 4 95 5 0 7.5 0.3 0.1 5 37

Formaldehyde gas removal process using the adsorbent of the present invention is simple compared to the conventional removal method, the sludge or waste water does not occur, only formaldehyde gas can be selectively removed and has the advantage of having high efficiency. In addition, when the landfill treatment is performed after using the adsorbent, soil stabilization and heavy metal adsorption effects can be expected, which helps to reinforce the ground and early stabilize the landfill.

Claims (2)

In the method for producing a formaldehyde adsorbent, 70 to 95 wt% of activated clay, 5 to 25 wt% of stone powder, and 0 to 5 wt% of activated carbon are mixed, and an aqueous acetylacetone solution (5 to 10 wt% of ammonium acetate and 0.1 to acetylacetone concentration) is added. 0.5 wt, acetic acid concentration 0.1 wt) to prepare a mixture of the solid raw material and the aqueous solution in the ratio of 6: 4, and then the mixture is extruded to prepare a pellet-type adsorbent (10 ~ 1) by weight of the total adsorbent weight ratio Method for producing a formaldehyde adsorbent dried to 30wt. The method according to claim 1, wherein 75 to 90 wt of activated clay and 5 to 25 wt of stone powder are mixed in a solid raw material ratio, and an aqueous acetylacetone solution (5 to 10 wt of ammonium acetate, 0.1 to 0.5 wt of acetylacetone, 0.1 wt of acetic acid) is added. Prepared and mixed with a solid material and an aqueous solution in a ratio of 6: 4, and then the mixture is extruded to prepare a pellet-type adsorbent and to prepare a dry formaldehyde adsorbent so that the water is 10 to 30wt relative to the total weight of the adsorbent Way.