KR20000040938A - Production process of high-purity gamma alumina from kaolinite - Google Patents

Abstract

PURPOSE: A high-purity gamma alumina is provided which is cost-effective and preferable in terms of recycling resources using local kaolinte. CONSTITUTION: A production process of the gamma kaolinite contains the following steps of: (1) a first step wherein the kaolinte is treated with heat at 800-900°C, the sample powder is extracted and reacted in a sulfuric acid at 60-80°C to produce an aqueous aluminum sulfate solution and then impurities are filtered and eliminated; (2) a second step wherein a hydrous aluminum sulfate crystal is precipitated from the aqueous aluminum sulfate solution using an ethyl alcohol and filtered; and (3) a third step wherein the hydrous aluminum sulfate crystal is dried and treated with heat at 900-1000°C to produce the gamma alumina. The second step is repeated more than 2 times.

Description

Method for producing high purity gamma alumina from kaolinite

The present invention relates to a method for producing gamma alumina used for a catalyst carrier from kaolinite with high purity. More specifically, after dissolving kaolinite in sulfuric acid, aluminum hydroxide is precipitated with ethyl alcohol and pyrolysis treatment produces gamma alumina. It is about how to.

Gamma alumina is one of the most widely used materials for catalyst carriers. It is widely used because its specific surface area is large and its surface activity is superior to that of other materials, thus allowing efficient catalytic reactions due to many reaction sites. As an important characteristic of the carrier, a high-purity material is required, and the reaction yield may be lowered due to the progress of the side reaction or the selectivity of the reaction during chemical reaction. In this case, a catalytically active component is added to gamma alumina and used as a catalyst for various chemical reactions.

In the prior art, gibbsite is prepared by bayer process in bauxite, and the prepared gibbsite is prepared immediately by gamma alumina, or dissolved in acid or alkali and neutralized with alkaline solution to prepare gamma alumina. There is a problem in the complexity of the gamma alumina manufacturing process and a large amount of impurities contained in the alumina.

In general, gamma alumina for carriers is currently industrially manufactured by metal dehydration, neutralization, and the like, and these preparation methods mostly use expensive gibbsite as a starting material. These production methods are very expensive due to the use of low soda type gibbsite or pure reagents in view of the basic requirements of carriers requiring high purity gamma alumina. In addition, there is a problem in producing high purity gamma alumina in the process.

Thus, the present inventors have been researched and experimented repeatedly to produce high purity gamma alumina with more economical efficiency and based on the results, the present invention obtains an aqueous aluminum sulfate solution using kaolinite and sulfuric acid, It is an object of the present invention to provide a method for producing a higher purity gamma alumina at a low cost by depositing crystals using ethyl alcohol to produce aluminum sulfate and performing heat treatment.

Figure 1 (a) is a flow chart of a process for producing gamma alumina by a conventional method,

(b) is a flowchart of the process of manufacturing gamma alumina by the method of this invention.

In the present invention for achieving the above object, in the method for producing gamma alumina, after the kaolinite heat treatment at 800-900 ℃ extract sample reaction at 60-80 ℃ with sulfuric acid solution to produce an aluminum sulfate aqueous solution, Filtering out impurities; Precipitating and filtering aluminum sulfate salt from the obtained aluminum sulfate using ethyl alcohol; It relates to a method for producing high purity gamma alumina from kaolinite, including; and drying the prepared aluminum sulfate to heat treatment at 900-1000 ° C. to obtain gamma alumina.

Hereinafter, the present invention will be described in detail.

In the present invention, the kaolinite is heat-treated at 800-900 ° C, and then the sample powder is extracted and reacted at 60-80 ° C with sulfuric acid solution to prepare aluminum sulfate, and impurities are filtered out.

The kaolinite may be conventional. Representative examples thereof include kaolinite having a composition as shown in Table 1 below, but the present invention is not limited thereto.

division SiO ₂ Al ₂ O ₃ Fe ₂ O ₃ CaO Na ₂ O Ignition loss (ig.loss) Kaolinite (% by weight) 42-47 35-39 0.5-.2 0.3-0.9 0.01-0.7 8.3-15.3

The kaolinite is usually decomposed at around 600 ° C and the activation of the holosite as the main component around 800 ° C. In addition, above 800 ° C, activated alumina causes phase transition and reacts with silica in the vicinity of 900 ° C to form spinel. When spinel is formed, impurities are chemically bonded and only aluminum ions can be easily extracted by sulfuric acid. Thus, in the present invention, it is preferable to heat the kaolinite at 800-900 ° C.

In the extraction reaction of the heat-treated sample powder with sulfuric acid solution, the extraction amount increases as the temperature of the reaction solution increases, but it tends to decrease rather than 80 ° C. This is because dissociation with H ⁺ and SO ₄ ^-2 in aqueous sulfuric acid solution increases, but due to the strong oxidation of sulfuric acid due to the generation of generator oxygen, Al ⁺³ ions are self-immobilized by Al ₂ O ₃ so that the solubility decreases. Moreover, when it is less than 60 degreeC, reaction occurs too slowly and it exists in the tendency for extraction yield to fall. Therefore, in the present invention, it is preferable to advance the extraction reaction temperature at 60-80 ℃.

The reaction ratio of the heat-treated sample powder and the sulfuric acid solution is preferably as much sulfuric acid solution as the sample powder can be sufficiently dissolved.

Impurities in the extracted aluminum sulfate aqueous solution can be removed through a conventional filtration method.

In the present invention, the aluminum sulfate salt crystal is precipitated from the obtained aluminum sulfate and filtered using ethyl alcohol.

Ethyl alcohol is added to the filtered aqueous solution of aluminum sulfate to precipitate aluminum sulfate crystals as precipitates. Aluminum sulfate salt is insoluble in ethyl alcohol, but other impurities are soluble so that impurities can be removed by crystallization. do. In particular, iron sulfate is easily soluble in ethyl alcohol, so it is easy to remove. Therefore, high purity aluminum sulfate crystals can be produced.

The ethyl alcohol is preferably added as long as the aluminum sulfate can be sufficiently precipitated with aluminum hydrosulfate salt crystals.

In addition, in the present invention, the dried aluminum sulfate is heat-treated at 900-1000 ° C. to produce high purity gamma alumina.

In order to produce gamma alumina by thermal decomposition of the prepared aluminum sulfate salt, the crystal structure is changed according to temperature conditions. Below 850 ° C., undecomposed fire of aluminum sulfate is present, and when it exceeds 1100 ° C., phase transition occurs to alpha alumina, and thus it cannot be used as a catalyst carrier. Although these conditions are theoretically shown, the experimental results suggest that the most suitable gamma alumina can be produced under the conditions of 900 ° C to 1000 ° C. It is preferable to carry out at 1000 degreeC.

In order to compare the method of the present invention as described above with the conventional method, a gamma alumina manufacturing process according to the conventional method is shown in FIG. 1 (a), and a gamma alumina manufacturing process according to the present invention is shown in FIG.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Example 1

In the present embodiment, in order to derive the heat treatment conditions of kaolinite, 200 g of kaolinite was heat-treated at 600 ° C to 1000 ° C at 100 ° C intervals, and the extraction reaction was performed at 700 ° C with sulfuric acid 1M solution. Table 2 shows.

division Comparative Example 1 Inventive Example 1 Inventive Example 2 Comparative Example 2 Heat treatment temperature (℃) 700 800 900 1000 Yield vs. Theoretical Extraction (%) 75.8 96.4 97.6 40.1

In Table 2, the yield compared to the theoretical extract amount was considerably low as 75.8% at the kaolinite heat treatment temperature of 700 ° C, and very low as 40.1% at 1000 ° C. can see. Since the yield of 95% or more is shown at 800-900 degreeC which is the temperature conditions of the invention example 1-2, in this invention, it is preferable to carry out the heat processing conditions of this kaolinite at 800-900 degreeC.

Example 2

In the present embodiment, in order to derive the reaction temperature of the aqueous solution during the aluminum ion extraction reaction, 18 g of the sample heat-treated with kaolinite at 800 ° C. was placed in 600 ml of 1 M sulfuric acid solution, and the temperature conditions were varied from 50 ° C. to 90 ° C. for 10 hours. The extraction reaction test results are shown in Table 3 in terms of yields in terms of theoretical extraction.

division Comparative Example 3 Inventive Example 3 Inventive Example 4 Inventive Example 5 Comparative Example 4 Extraction reaction temperature (℃) 50 60 70 80 90 Yield% of theoretical extract 81.8 93.4 96.4 98.8 85

In Table 3, the extraction reaction temperature of Comparative Example 3 shows a yield of 81.8% at 50 ° C and an 85% yield at 90 ° C. Although the extraction reaction temperature is high and the yield is low, the dissociation of H ⁺ and SO ₄ ^-2 in sulfuric acid solution increases, but the strong oxidation of sulfuric acid due to the generation of generator oxygen causes Al ⁺³ ions to self-immobilize Al ₂ O ₃ . This is because the solubility is lowered. However, in Example 3-6 of the present invention, the yield is higher than 93%. Therefore, it is preferable to set the extraction reaction temperature between 60 and 80 ° C. to obtain a reasonable high yield in the process.

Example 3

In the present invention, in order to remove impurities contained in the aqueous solution of aluminum sulfate, crystals are removed by using ethyl alcohol to remove impurities. After the impurities are repeatedly precipitated with impurities before and after removing impurities, the impurities are analyzed and analyzed by ICP ( Inductively Coupled Plasma) analysis results are shown in Table 4 below.

Unit: μg / ml (PPM) ingredient Si Na K Ca Mg Fe Extracted Aluminum Sulfate Solution 1.2 20.1 2.56 3.5 1.5 5.6 1st crystallization 0.32 7.3 0.59 0.72 0.28 1.3 Second Crystallization 0.1 4.6 0.21 0.11 0.01 0.02

In Table 4, it can be seen that a large amount of impurities can be removed by crystallization of impurities with ethyl alcohol in the extracted aluminum sulfate solution. Also, more impurities could be removed during the second crystallization than during the first crystallization. It is possible to remove impurities below 10PPM only by the first crystallization.

In the present invention, it can be presented as the production conditions of the present invention for producing aluminum sulfate salt by crystallization more than once with ethyl alcohol.

Example 4

In this example, the aluminum hydrosulfate salt prepared in Example 3 was dried at 60 ° C. for 3 hours.

In order to derive the heat treatment condition of the dried sample in the electric heating furnace, the holding time was fixed at a heating time of 10 ℃ per minute at 100 ℃ intervals from 800 ℃ to 1100 ℃, and the heat treatment time was then heat treated. The results of analyzing the crystal phases are shown in Table 5 below.

division Comparative Example 5 Inventive Example 6 Inventive Example 7 Comparative Example 6 Heat treatment temperature (℃) 800 900 1000 1100 Crystal phase Anhydrous Aluminum Sulfate [Al ₂ (SO ₄ ) ₃ ] Gamma Alumina (γ-Al ₂ O ₃ ) Gamma Alumina (γ-Al ₂ O ₃ ) Theta Alumina + Alpha Alumina (θ-Al ₂ O ₃ + α-Al ₂ O ₃ )

As can be seen in Table 5, the crystal phase shown according to the heat treatment temperature in Comparative Example 5 and Comparative Example 6 can be seen as undecomposed into anhydrous aluminum sulfate at 800 ℃ and the temperature is high at 1100 ℃ gamma alumina phase transition It is a mixed phase of alpha and theta alumina. Therefore, undecomposed aluminum sulfate and alpha alumina are difficult to expect a role as a catalyst.

On the contrary, in Inventive Example 6-7, a typical gamma alumina crystal phase is shown and a large specific surface area can be seen as preferable, so that aluminum sulfate is preferably heat-treated at 900-1000 ° C.

As described above, according to the present invention, by preparing gamma alumina using kaolinite, gamma alumina can be manufactured with high purity, and a cost reduction effect in processing can be expected, and domestic kaolinite is used. Therefore, it can be said to be desirable in terms of resource utilization.

Claims (2)

In the method for producing gamma alumina, Heat-treating kaolinite at 800-900 ° C., extracting the sample powder at 60-80 ° C. with sulfuric acid solution to prepare an aluminum sulfate solution, and then filtering and removing impurities; Precipitating and filtering aluminum sulfate salt from the obtained aluminum sulfate using ethyl alcohol; And Method of producing a high purity gamma alumina from kaolinite comprising the step of obtaining the gamma alumina by drying the prepared aluminum sulfate sulfate and heat treatment at 900-1000 ℃ The method of claim 1, Method for producing high purity gamma alumina from kaolinite, characterized in that the step of precipitating aluminum sulfate salt crystals using ethyl alcohol two or more times