KR20050051505A - Absorbent for removing moisture and methanol of formaldehyde having high degree of purity - Google Patents

Abstract

The present invention relates to an adsorbent for removing water and methanol as trace impurities present in high-purity formaldehyde. The present invention is based on 3A zeolite, wherein silica or silica sol is used as the main binder, and the adsorbent of the present invention. In case of using the conventional polyethylene glycol, there are many advantages such as the reduction of investment cost, manpower and operation cost due to the simplification of the process, as well as eliminating the post-treatment process (purification, storage) of the polyethylene glycol of the existing process.

Description

Absorbent for removing moisture and methanol of formaldehyde having high degree of purity}

The present invention relates to an adsorbent for removing water and methanol in formaldehyde, and more particularly, to an adsorbent for effectively removing a small amount of water and methanol generated in the process of preparing formaldehyde for producing acetal resin.

Formaldehyde is itself used as a disinfectant, preservative, etc., but is an important compound widely used in manufacturing thermosetting plastics together with phenol, urea and melamine. Formaldehyde is often produced through the dehydrogenation reaction under high temperature catalyst using methanol as a raw material under the addition of water in the production process, and thus is obtained in the form of water and methanol. The aqueous solution of formaldehyde is called 'formalin'.

If the water contained in the formaldehyde and unreacted methanol are not removed, condensation reaction is induced during process transfer to produce powder of impurities such as methyl formate to block the pipeline, or to manufacture a polymer of acetal resin as a final product. Since the melting point constant (MI) is not constant, it may cause deterioration of physical properties of the acetal resin and should be removed.

Conventional techniques for removing such impurities include a method of purifying by adding a polyalkylene oxide compound which is inert to formaldehyde and has a high affinity with water and methanol, as disclosed in Korean Patent Laid-Open Publication No. 1999-021572. However, since this method extracts polyalkylene oxide by supplying 30 times or more with respect to the total amount of water and formalin, it is possible to obtain high purity formaldehyde, but it has a problem in that the process is complicated and the required device must be enlarged. In addition, this method removes impurities by repeating the adsorption / desorption process using polyethylene glycol, but in this process, the cooling process to minus 10-20 ℃ for adsorption and the heating up to 200-230 ℃ for desorption Since the process is repeated 2-4 times, there is a problem such as wasting a lot of energy in the iterative process.

As a technique for solving the problems of the prior art, there is a method for removing impurities in formaldehyde with an adsorbent. For example, WO 02/48082 removes methanol impurities using Amberlite-15 to remove methanol in formaldehyde solution. However, this technique can effectively remove impurities in aqueous solution, but has a disadvantage in that it can be used only in aqueous solution because it has a disadvantage of shortening the life of organic Amberlite-15 ion exchange resin due to high temperature in the gas phase.

U.S. Patent 4,285,811 reported that K-A, Ba-A or mixed zeolites can effectively remove the water present in formaldehyde and report that the effect is increased through acid treatment. However, in case of KA type, the substitution degree of metal ion is more than 94%. However, if the substitution degree of K ion is 50% or more, it shows adsorption characteristic irrelevant to substitution degree. In the process of activation, high temperature heat treatment is required in the process of removing the moisture contained in the adsorbent by heating the adsorbent to a high temperature, but in the case of Ba-A, the structure of the zeolite was very weak to heat and thus could not be seen. (ZEOLITE MOLECULAR SIEVES, D. W. Breck, p. 495, 1974, John Wiley & Sons, inc)

In addition, in the case of acid treatment, part of the zeolite structure is destroyed, which causes the inhibition of adsorption capacity. In addition, when using a clay (clay) which is used a lot in the manufacture of zeolite molecular sieves, the strength is good, but formaldehyde is decomposed and cannot be used.

The present invention is to provide an adsorbent that can significantly reduce the energy consumed in the adsorption and desorption method using the existing polyethylene glycol by providing an adsorbent for removing water and methanol, which are impurities generated during the production of formaldehyde. . Another object of the present invention is to provide an adsorbent which is simple in the manufacturing process and can remove the water and methanol in the formaldehyde in which dust generation is minimized due to the decrease in strength with use. Still another object of the present invention is to provide an adsorbent for removing impurities in which decomposition of formaldehyde is prevented.

The adsorbent is characterized by having a 3A zeolite having a pore size of 3 mm 3, and having silica powder or silica sol as a binder for forming the 3A zeolite. Sodium silicate or potassium silicate may be used as an auxiliary binder to improve moldability.

The appropriate amount of silica powder or silica sol, which is the main binder, is 5-25% by weight (based on solid content in the case of silica sol), and the strength of the obtained adsorbent is insufficient when it is below this range. The adsorption effect of the obtained adsorbent becomes insufficient. When silica powder is used, an appropriate amount of water is added for molding.

The use of sodium silicate or carbosilicate as an auxiliary binder improves moldability, and its appropriate amount is 5-25% by weight. If it is less than this range, the moldability improvement effect will become inadequate, and if it exceeds this range, the adsorption effect of the adsorbent obtained will become inadequate. When the auxiliary binder is used, the total amount of binder used is suitably within 30% by weight. If it exceeds this range, the adsorption effect of the obtained adsorbent will be insufficient.

The adsorbent of the present invention is obtained by mixing 3A zeolite and the main binder with auxiliary binder, if necessary, followed by granulation, drying and calcining. Suitable drying temperatures are 50-100 ° C. If the drying temperature exceeds this range, the granules will crack. The suitable firing temperature is 700-850 ° C., and the strength of the obtained adsorbent is insufficient when it is less than this range, and when the range exceeds this range, the adsorption capacity of the obtained adsorbent is lowered. Suitable firing times are 10 to 40 minutes.

When 4A zeolite is used as a raw material or when sodium silicate is used as an auxiliary binder, it is necessary to convert 4A zeolite to 3A zeolite or to convert sodium silicate to potassium silicate, before granulation or granulation, and then replacing with potassium chloride solution. There is this.

An embodiment of the present invention is as follows.

<Example 1>

2 kg of 4A zeolite and 400 g of silica were mixed and granulated with addition of water. The granules were completely dried at 80 ° C. and then prebaked in 400 ° C. kiln. The calcined product was left to stand at room temperature for 18 hours using 0.2 mol potassium chloride solution, washed and dried, and activated at 750 ° C. kiln to prepare 3A zeolite molecular sieve.

<Example 2>

2 kg of 3A zeolite was mixed with 350 g of silica, and 100 g of 30% silica sol was added to prepare a granule foam having a diameter of about 2 mm. Then, a small amount of the powder mixed with 3 A zeolite and 350 g of silica was added in small portions. The granules were grown to 3-4 mm in diameter while the solutions were administered alternately. The subsequent process is the same as in Example 1.

<Example 3>

As in Example 2, the difference was 4A zeolite instead of 3A zeolite, and sodium silicate instead of carry silicate.

<Example 4>

2 kg of 3A zeolite powder and 350 g of silica were mixed, and granules obtained by granulation using water were completely dried at 80 ° C., and then immersed in a solution of commercial No. 3 sodium silicate solution diluted 2: 1 with water for 30 minutes. It was. Thereafter, the surface of the granules was washed with water and then soaked in saturated ammonium carbonate to gel sodium silicate. Thereafter, the mixture was left at room temperature for 18 hours using 0.2 mol potassium chloride solution as in Example 1, washed and dried, and activated at 750 ° C. kiln to prepare 3A zeolite molecular sieve.

Example 5

The adsorption performance of trace amounts of water and methanol contained in high-purity formaldehyde using the 3A zeolite molecular sieve prepared in the above example was measured and shown in Table 1 below. At this time, the column used was 80cm in length, 5cm in diameter and heated to a hot wire outside to fix the temperature at 105 ℃, the amount of adsorbent used was fixed at 920g. At this time, the flow rate of high purity formaldehyde was fixed at 5 kg / hr.

<Example 6>

In order to find a suitable binder for the removal of water and methanol in high-purity formaldehyde, the total binder amount was fixed to 20wt% using a zeolite substituted with 60% K, and the column and flow rate were the same as in Example 5. The results are shown in Table 2 below.

Comparative Example 1

The same procedure as in Example 1, except that the silica was prepared using a clay commonly used for molecular sieve granules.

 Table 1

Sample Name Moisture content before passing Methanol content before passing Moisture content after 30 minutes Methanol content after 30 minutes Example 1 480 ppm 230 ppm 0.01 ppm 0.01 ppm Example 2 480 ppm 230 ppm 0.22 ppm 0.05 ppm Example 3 480 ppm 230 ppm 0.25 ppm 0.05 ppm Example 4 480 ppm 230 ppm 0.02 ppm 0.01 ppm Comparative Example 1 480 ppm 230 ppm 1500 ppm 3500 ppm

Table 2

Binder Silica powder Silica sol Silicate Carry Sodium Silicate Clay No reaction Impurity Removal Rate Case 1 100% - - - - radish ~ 100% Case 2 0 100% 0 0 - radish ~ 100% Case 3 0 50% 50% 0 - radish ~ 100% Case 4 50% 20% 10% 10% - radish ~ 100% Case 5 30% 50% 20% - radish ~ 100% Case 6 20% 50% 20% 20% - radish ~ 100% Case 7 20% 40% 20% 20% 10% U ~ 70% Case 8 50% 20% 10% 10% U ~ 68% Case 9 30% 20% 30% 20% - radish ~ 100% Case 10 - - - - 100% U ~ 0% Case 11 50% 20% 0 0 30% U ~ 40%

In the case of using the adsorbent of the present invention, it is possible to reduce the investment cost, manpower and operation cost due to the simplification of the process, and to omit the post-treatment process (purification, storage) of the polyethylene glycol of the existing process. There is an advantage. In addition, the application of this adsorption process can be operated continuously by repeating the use and regeneration alternately in a two-bed operation, there is an advantage that can be used continuously for 2-3 years because the use of the adsorbent is semi-permanent.

Claims (4)

An adsorbent for removing water and methanol in high purity formaldehyde, characterized by using 3A zeolite as a main spindle and silica or silica sol as main binders. The adsorbent for removing water and methanol in high purity formaldehyde according to claim 1, wherein sodium silicate or potassium silicate is further used as an auxiliary binder. The adsorbent for removing water and methanol in high purity formaldehyde according to claim 1, wherein the binder content is 5-25% by weight. The adsorbent for removing water and methanol in high purity formaldehyde according to claim 1, wherein the 3A type zeolite has a degree of substitution of 50 to 90% of K ions.