KR100467769B1 - Method of preparing gammma-alumina catalyst for high temperature desulfurization - Google Patents

Abstract

The present invention relates to a method for producing gamma alumina for high temperature desulfurization, and in particular, to a method for preparing electrodeposited gamma alumina catalyst which is stable at high temperature and has excellent desulfurization effect. For this purpose, a) an aqueous aluminum salt solution, an aqueous molybdenum metal salt solution, And adding an aqueous metal salt solution selected from the group consisting of nickel and tungsten to prepare a mixed slurry; b) adjusting the pH to 8.5 to 9.5 by adding urea and ammonia water to the mixed slurry; c) preparing a slurry of electrodeposited gamma alumina by electrodepositing the pH-adjusted mixed slurry at a temperature of 70 ° C. or higher; d) washing the slurry of electrodeposited gamma alumina with water, filtering and drying the slurry; e) It provides a method for producing a high temperature desulfurization gamma alumina catalyst comprising the step of heat-treating the dried electrodeposited gamma alumina at a temperature of 850 to 1050 ℃.

The gamma alumina catalyst for high temperature desulfurization produced by the production method of the present invention is thermally excellent when used as a catalyst for high temperature steam reforming reaction, flue gas treatment, or high temperature desulfurization, thereby ensuring stability, thereby extending the life of the catalyst. In addition, the cost required to replace the catalyst can be expected to reduce the effect.

Description

METHODS OF PREPARING GAMMMA-ALUMINA CATALYST FOR HIGH TEMPERATURE DESULFURIZATION

[Industrial use]

The present invention relates to a method for producing gamma alumina for high temperature desulfurization, and more particularly, to a method for producing an electrodeposited gamma alumina catalyst having excellent desulfurization effect while being stable at high temperatures.

[Prior art]

Gamma alumina catalysts used for desulfurization are thermally unstable at high temperatures. Conventionally, in order to use such a desulfurization gamma alumina catalyst at high temperature, a method of adding metal ions to gamma alumina was used. This method is an impregnation method in which a water-soluble salt is dissolved in water to prepare an aqueous solution, and the aqueous solution is impregnated with gamma alumina to add ions.

In addition, in preparing a catalyst carrier containing an oxide such as silica in Japanese Patent Laid-Open No. 7-31878, the raw materials are mixed in advance to prepare a solution, and then sprayed and adsorbed onto the surface of the catalyst to prepare a catalyst carrier. How to do is known.

In addition, Japanese Laid-Open Patent Publication No. 9-164334 contains molybdenum in an amount of 5 to 20% by weight in terms of an oxide on a carrier of an inorganic oxide, followed by drying and calcining, followed by addition of other materials such as nickel and the like. A method of firing at a temperature is known.

However, these methods are still insufficient for use as a catalyst for desulfurization at high temperatures. The reason is that as gamma alumina diffuses oxygen ions by an incomplete spinel structure at a high temperature, rearrangement of atoms occurs and the specific surface area is drastically reduced, thereby degrading the characteristics and activity of the catalyst. As a result, the reaction in the desulfurization catalyst reaction is delayed and the efficiency is reduced. As a result, sulfur conversion rate is drastically reduced, sulfur production is lowered, and the process is lowered, resulting in operational problems. Therefore, there is a problem in that the catalyst of the desulfurization process should be frequently replaced with a new catalyst.

In view of the problems of the prior art, it is an object of the present invention to provide a method for producing a high temperature desulfurization gamma alumina catalyst.

Another object of the present invention is to provide a method for producing a high temperature desulfurization gamma alumina catalyst having excellent high temperature stability by electrodeposition precipitation and more excellent desulfurization performance.

Figure 1 shows a flow chart of the production process of the high temperature desulfurization gamma alumina catalyst of the present invention.

Figure 2 is a graph showing the amount of molybdenum deposited (mol%) according to the electrodeposition pH conditions of the present invention.

3 is a graph showing the relationship between electrodeposition reaction temperature and reaction termination time of the present invention.

Figure 4 is a graph showing the weight change (wt%) according to the heat treatment temperature of the present invention.

5 is a graph showing the specific surface area (m 2 / g) according to the heat treatment temperature of the present invention.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a method for producing a high temperature desulfurization gamma alumina catalyst,

a) to gamma alumina

Iii) an aqueous aluminum salt solution,

Ii) an aqueous molybdenum metal salt solution, and

Iii) a metal salt selected from the group consisting of nickel and tungsten

Aqueous solution

Adding to prepare a mixed slurry;

b) pH of 8.5 to 9.5 by adding urea and ammonia water to the mixed slurry.

Adjusting to;

c) electrodeposition reaction of the pH-adjusted mixed slurry at a temperature of 70 ℃ or more

Preparing a slurry of electrodeposited gamma alumina;

d) washing the slurry of electrodeposited gamma alumina with water, filtering and drying the slurry;

e) heat treatment of the dried electrodeposited gamma alumina at a temperature of 850 to 1050 ℃.

Steps to

It provides a method for producing a high temperature desulfurization gamma alumina catalyst comprising a.

Hereinafter, the present invention will be described in detail.

[Action]

Unlike the conventional methods, the present invention effectively adds metal ions of molybdenum and nickel or tungsten to gamma alumina so that the metal ions are evenly distributed. In particular, molybdenum ions, nickel and / or tungsten ions are simultaneously added to gamma alumina using water-soluble salts to electrodeposit on the surface of gamma alumina.

To this end, when molybdenum ions, nickel ions, and / or tungsten ions are added to gamma alumina, the present invention prepares an aqueous solution of the respective metal salts, and then mixes uniformly to be equal to the concentration ratio of the aqueous aluminum salt solution. Gamma alumina is mixed to prepare a mixed slurry. Urea and ammonia water having the same concentrations were added to the mixed slurry to adjust the pH to 8.5 to 9.5, followed by electrodeposition by maintaining the reaction temperature at 70 ° C. or higher. The electrodeposited gamma alumina is washed with water, filtered and dried, and heat treated at a temperature of 850 to 1050 ° C. to produce gamma alumina that is stable at high temperatures.

In general, when molybdenum, nickel, tungsten, and aluminum salt aqueous solution is reacted with gamma alumina and a mixed slurry in a state of high basicity, hydroxides are formed and separated without uniformly adhering to the surface of gamma alumina. There is a tendency to not get an additive effect. In addition, if the reaction conditions are not suitable, precipitation does not form, making it impossible to electrodeposit the desired molybdenum, nickel and tungsten ions. In addition, when added to gamma alumina by the conventional impregnation method, the variation in concentration is severe, rather it shows a phenomenon of inhibiting the high temperature stability of gamma alumina.

In consideration of the above matters, the present invention first adjusts the amount of molybdenum, nickel and tungsten to be included in gamma alumina to be the same as the concentration and amount of the aluminum salt solution, and prepares a mixed slurry by mixing gamma alumina. The respective aqueous aluminum solution, molybdenum aqueous solution, aqueous nickel solution, and tungsten aqueous solution are not limited, but each is preferably a sulfate or hydrochloride solution based on salts that can be prepared as an aqueous solution. In the preparation step of the mixed slurry, a uniform adsorption state is maintained on the surface of gamma alumina on the mixed slurry so that aluminum ions, molybdenum ions, nickel, or tungsten ions are mutually chemically reacted.

Next, urea and ammonia are added to the mixed slurry to adjust the pH to 8.5 to 9.5 so that the mixed slurry is basic, followed by electrodeposition reaction by maintaining the temperature of the mixed slurry as a reactant at 70 ° C or higher. In the electrodeposition reaction, pH and reaction temperature are very important factors, and the amount of metal to be electrodeposited is limited according to pH conditions. At pH below 8.5, aluminum ions, molybdenum, nickel, and tungsten ions are dissolved in the aqueous solution. It is difficult for electrodeposition reaction. On the other hand, when the pH is more than 9.5, the aluminum ions become amphoteric ions, making the electrodeposition reaction itself difficult. In addition, in the electrodeposition reaction, the reaction temperature is slow when the reaction temperature is less than 70 ℃, the reaction time takes at least 3 hours, it is possible to perform the rapid electrodeposition reaction within 2 hours at 70 ℃ or more.

Next, after the electrodeposition reaction, the prepared electrodeposited gamma alumina slurry may be washed with water, filtered, and dried, followed by heat treatment at 850 to 1050 ° C., thereby preparing a gamma alumina catalyst having excellent high temperature stability to which molybdenum, nickel, and tungsten are added. If the heat treatment temperature is less than 850 ℃ may cause some undecomposed state and inhibit the catalytic activity, it is difficult to produce a normal gamma alumina, the catalytic activity may be inhibited at a temperature above 1050 ℃.

In the metal content of gamma alumina of the present invention, the content of molybdenum is preferably 5 to 10 mol%, and the content of nickel or tungsten 1 or 2 is preferably 2 to 5 mol%. This is related to high temperature stability.

The method of the present invention is to prepare a gamma alumina catalyst having excellent high temperature stability by addition of molybdenum, nickel and tungsten, and a series of manufacturing steps are shown in the flowchart of FIG.

The present invention will be described in more detail with reference to the following examples. However, an Example is for illustrating this invention and is not limited only to these.

EXAMPLE

Example 1

(Base condition)

In order to derive the basicity condition in the electrodeposition reaction of the present invention, the concentration of the molybdenum sulfate aqueous solution was prepared so that 8 mol% molybdenum was added to gamma alumina, and an aqueous aluminum sulfate solution was prepared by adjusting the concentration of the molybdenum sulfate aqueous solution. Together with gamma alumina, a mixed slurry was prepared.

Urea and ammonia water of the same concentration and amount were added to the mixed slurry to adjust the pH of the mixed slurry at 8.0, 8.5, 9.0, 9.5, and 10.0, respectively, and then an electrodeposition reaction was performed at a reaction temperature of 70 deg.

After washing and filtration, the content of molybdenum from each electrodeposited alumina was analyzed by an ICP (Inductively coupled plasma) analyzer, and the results are shown in FIG. 2.

In Figure 2, when the pH condition is different under the condition that the reaction temperature is constantly reacted at 70 ℃, it appeared that the state of the electrodeposition reaction is different, in particular the difference in the amount of electrodeposition occurred.

Indeed, in the present embodiment, 8 mol% of molybdenum was added, but the actual yield was less than that. The yield was 80% or less at pH 8 and 10, but more than 90% electrodeposition occurred at pH 8.5, 9.0, and 9.5.

Example 2

(Reaction temperature condition)

In order to derive reaction temperature conditions in the electrodeposition reaction of the present invention, electrodeposition gamma alumina was prepared in the same manner as in Example 1, but the pH was fixed at 9, and the reaction temperature was maintained at 10 ° C. to 60 to 90 ° C. at intervals of 10 ° C. Each was carried out. At this time, the reaction termination time according to each reaction temperature was measured by redox potential (ORP), and the results are shown in FIG. 3.

In Figure 3, the reaction termination time is directly connected to the reaction rate, it can be seen that the reaction termination time is shorter as the reaction time is faster, in particular, it can be seen that the reaction termination time is sharply reduced as the temperature rises.

In fact, it was found that the reaction was terminated within 2 hours above 70 ° C., whereas it took 3 hours above 60 ° C.

Example 3

(Heat treatment condition)

Electrodeposited gamma alumina was prepared in the same manner as in Example 1, except that the conditions of the electrodeposition reaction were adjusted to pH 8.5 of the mixed slurry and the reaction temperature of 80 ° C.

In order to derive heat treatment conditions of the electrodeposited gamma alumina, a gamma alumina catalyst for high temperature desulfurization was prepared by performing heat treatment at 100 ° C. intervals for 2 hours to 750 to 1150 ° C., respectively.

Each catalyst prepared was tested by thermogravimetric method and the results are shown in FIG. 4. In FIG. 4, the change in thermogravimetry depending on the temperature means that there is an undecomposed reactant at the time of heat treatment, which is judged to be inhibited to serve as a catalyst with complete gamma alumina, and the heat treatment at a temperature of 850 ° C. or higher Selected.

In addition, the specific surface area of each prepared catalyst was measured by the BET method, and the results are shown in FIG. 5. In FIG. 5, the specific surface area increases as the temperature increases at a temperature of 750 ° C. or higher, and a rapid decrease occurs at 1150 ° C. or higher. In consideration of the specific surface area directly affecting the activity of the catalyst, the upper limit of the heat treatment temperature was selected as 1050 ° C.

Example 4

(Molybdenum content)

An aqueous solution of molybdenum sulfate is added to gamma alumina so as to change the molybdenum content to 4 to 11 mol% as shown in Table 1 below, and an aqueous nickel sulfate solution and a tungsten sulfate solution are added to fix the content of nickel and tungsten at 3 mol%. After adding the same ratio to prepare a mixed slurry, the electrodeposition gamma alumina was prepared in the same manner as in Example 1 except that the pH was adjusted to 9.0 and the electrodeposition reaction at a reaction temperature of 80 ℃ for 2 hours.

The electrodeposited gamma alumina was washed with water, filtered, and dried, followed by heat treatment at a temperature of 900 ° C. for 2 hours to prepare a gamma alumina catalyst.

50 g of each gamma alumina catalyst prepared for the desulfurization performance test was installed in a tube furnace, mixed with hydrogen sulfide (H ₂ S) gas and sulfur dioxide (SO ₂ ) at a molar ratio of 2: 1, and then exhaust gas. The component of was analyzed by gas chromatography to calculate the desulfurization conversion rate, and the results are shown in Table 1 below.

TABLE 1

Molybdenum addition amount (mol%) 4 5 6 7 8 9 10 11 Desulfurization Conversion Rate (%) 85 91 93 95 98 98 95 87

From the above results, the desulfurization conversion rate of molybdenum content was found to be 85% at 4 mol%, 11 mol% to 87%, and did not maintain a proper desulfurization conversion rate of 90% or more. Therefore, in order to maintain a desulfurization conversion rate of 90% or more, it is preferable that 5 to 10 mol% molybdenum is included in gamma alumina.

Example 5

(Nickel, tungsten content)

In order to determine the stability by the content of nickel and tungsten, an aqueous molybdenum sulfate solution was added to the electrodeposited gamma alumina so that molybdenum was fixed at 8 mol%, and nickel sulfate was changed so that the content of nickel and tungsten was changed as shown in Table 2 below. An aqueous solution and an aqueous tungsten sulfate solution were added, and an aluminum sulfate aqueous solution was prepared in the same manner as in Example 4 except that the aqueous solution of molybdenum sulfate, nickel sulfate, and tungsten sulfate solution was added in the same amount. It was.

Each of the prepared gamma alumina catalysts was subjected to a thermal stability test at 1,200 ° C., and then the specific surface area thereof was measured, and the results are shown in Table 2 below.

TABLE 2

Nickel content (mol%) Tungsten Content (%) Specific surface area (㎡ / g) One 0 10.5 One One 20.3 0 2 20.1 2 2 24.5 2 3 25.5 3 3 18.6

As can be seen from the above results, the specific surface area according to the high temperature stability test when added with varying the ratio of nickel and tungsten shows that the sum of the content of nickel and tungsten (mol%) is maintained at 20 molm / g or more at 2mol% or more. In addition, it can be seen that the sum of the contents of nickel and tungsten is rather reduced at 6 mol% or more.

Therefore, in order to maintain high temperature stability in the present invention, it is preferable to add 2 to 5 mol% of one or two kinds of nickel and tungsten.

The gamma alumina catalyst for high temperature desulfurization produced by the production method of the present invention is thermally excellent when used as a catalyst for high temperature steam reforming reaction, flue gas treatment, or high temperature desulfurization, thereby ensuring stability, thereby extending the life of the catalyst. In addition, the cost required to replace the catalyst can be expected to reduce the effect.

Claims (3)

In the method for producing a high temperature desulfurization gamma alumina catalyst, a) to gamma alumina Iii) aluminum salt aqueous solution; Ii) aqueous molybdenum metal salt solution; And Iii) a metal salt selected from the group consisting of nickel and tungsten Aqueous solution Adding to prepare a mixed slurry; b) pH of 8.5 to 9.5 by adding urea and ammonia water to the mixed slurry. Adjusting to; c) electrodeposition reaction of the pH-adjusted mixed slurry at a temperature of 70 ℃ or more Preparing a slurry of electrodeposited gamma alumina; d) washing the slurry of electrodeposited gamma alumina with water, filtering and drying the slurry; e) heat treatment of the dried electrodeposited gamma alumina at a temperature of 850 to 1050 ℃. Steps to Method for producing a high temperature desulfurization gamma alumina catalyst comprising a. The method of claim 1, The gamma alumina heat-treated in step e) is a molybdenum content of 5 to 10 mol%, one or two nickel or tungsten content of 2 to 5 mol% method for producing a gamma alumina catalyst for high temperature desulfurization. The method of claim 1, A method of producing a gamma alumina catalyst for high temperature desulfurization, wherein the concentration of the aqueous solution of aluminum salt of step a) is the sum of the concentrations of ii) aqueous molybdenum metal salt and iii) at least one metal salt solution selected from the group consisting of nickel and tungsten.