KR20130082267A - Metal aqueous solution, supported catalyst for cnt, and a method for preparing thereof - Google Patents

Abstract

The present invention relates to an aqueous metal solution, a supported catalyst, and a method for preparing the same, and does not precipitate for a long time, and is a uniform and stable aqueous metal solution and a metal supported amount, which is produced therefrom, has a high and uniform metal loading, and is free of cracks and hard metals that may occur during firing. There is an effect of providing an aqueous solution, a supported catalyst, and a production method thereof.

Description

Metal Aqueous Solution, Supported Catalysts and Methods for Making the Same {Metal Aqueous Solution, Supported Catalyst for CNT, and a Method for Preparing Thereof}

The present invention relates to an aqueous metal solution, a supported catalyst, and a method for preparing the same, and more particularly, does not precipitate for a long time, and is a uniform and stable aqueous metal solution and a metal supporting amount prepared therefrom, which may have a high and uniform metal loading, and cracks that may occur during firing. It relates to a supported catalyst that is free of solids and a process for producing the same.

Carbon nanotubes (hereinafter referred to as 'CNT') are understood to mean cylindrical carbon tubes having a diameter of 3 to 150 nm, specifically 3 to 100 nm and a length several times the diameter, that is, 100 times or more. These tubes consist of a layer of aligned carbon atoms and have different types of cores. Such carbon nanotubes are also called carbon fibrils or hollow carbon fibers, for example. Because of the size and specific properties of these carbon nanotubes, the carbon nanotubes described herein are of industrial importance in the manufacture of composites. There is a further possibility inherent in electronic uses, energy uses and further uses.

The carbon nanotubes are generally manufactured by arc discharge, laser ablation, chemical vapor deposition, or the like. However, the arc discharge method and the laser evaporation method are difficult to mass-produce, and an excessive production cost of an arc or a cost of purchasing a laser device is a problem.

In addition, in the case of the above-mentioned chemical vapor deposition method, there is a problem that the synthesis rate is very slow and the CNT particles to be synthesized are too small in the case of a method using a gas phase dispersion catalyst. There is a limit to the mass production of CNTs.

The catalyst may be a supported catalyst, a co-precipitation catalyst, etc., in which the catalytically active component has an oxide form, a partially or fully reduced form, or a hydroxide form, and which can be commonly used for preparing CNTs. It is preferable to use a double supported catalyst, which, when used, has a higher bulk density of the catalyst itself than the coprecipitation catalyst, and unlike the coprecipitation catalyst, there is less fineness of less than 10 microns, which prevents attrition that may occur during fluidization. This is because the possibility of fine powder generation can be reduced, and the mechanical strength of the catalyst itself is also excellent, which can stabilize the reactor operation.

In addition, as a method of preparing a supported catalyst, a technique of preparing a catalyst by mixing a metal solution with a support and then coating-drying (impregnating) has been proposed, but in this case, the prepared catalyst has a disadvantage of having a limit of catalyst loading. . In addition, the heterogeneous distribution of the active ingredient and the catalyst ingredient plays an important role in the CNT growth yield and the CNT diameter distribution, but there is no technique to control this.

Therefore, the situation is required to study a uniform and stable metal aqueous solution to increase the catalyst loading.

In order to solve the problems of the prior art as described above, the present invention is not precipitated for a long time, the uniform and stable metal aqueous solution prepared from it, the metal loading amount is high and uniform, there is no cracks and solid metal aqueous solution, which can occur during firing, It is an object to provide a catalyst and a method for producing the same.

In order to achieve the above object, the present invention comprises water, a precursor of the catalyst component, a precursor of the active component and a multicarboxylic acid (multicarboxylic acid), the multicarboxylic acid in the molar ratio of the multicarboxylic acid and the active component It provides a metal aqueous solution, characterized in that the product of the number of carboxylic acid groups of 0.5 to 1.9.

The present invention also provides a supported catalyst prepared using the above-described aqueous metal solution and a CNT prepared using these supported catalysts.

In addition, the present invention is a method for producing a metal aqueous solution,

a) preparing an aqueous solution of a precursor of the active ingredient;

b) mixing the multicarboxylic acid into the aqueous solution of the precursor of the active ingredient; And

c) mixing the precursor of the catalyst component with the precursor of the active ingredient and the aqueous solution of multicarboxylic acid.

Furthermore, the present invention is a method for producing a supported catalyst,

a) preparing an aqueous solution of a precursor of the active ingredient;

b) mixing the multicarboxylic acid into the aqueous solution of the precursor of the active ingredient;

c) preparing a metal aqueous solution by mixing the precursor of the active ingredient and the precursor of the catalyst component with the aqueous solution of multicarboxylic acid; And

d) injecting a support into the aqueous metal solution.

Hereinafter, the present invention will be described in detail.

The aqueous metal solution of the present invention comprises water, a precursor of a catalyst component, a precursor of an active component, and a multicarboxylic acid, but the number of carboxylic acid groups of the multicarboxylic acid in the molar ratio of the multicarboxylic acid and the active component. Multiplying by 0.5 to 1.9 as one technical feature.

Specifically, the catalyst component used in the present invention may be at least one selected from Fe, Co, and Ni, and it is preferable to use Fe as described in the following examples. The catalyst component precursor may be one or more selected from Fe, Co, and Ni, specifically, Co (NO ₃ ) ₂ · 6H ₂ O, Fe (NO ₃ ) ₂ · 6H ₂ O, Fe (NO ₃ ) _2. Nitrides such as 9H ₂ O or Ni (NO ₃ ) ₂ .6H ₂ O can be used.

In addition, the active ingredient used in the present invention is preferably Mo. Examples of the Mo precursor include, but are not limited to, nitrides such as (NH ₄ ) ₆ Mo ₇ O ₂₄ .4H ₂ O, and the like.

The catalyst component and the active component are preferably added at a weight ratio of 1 to 15: 10 to 30, based on 100 weights of the support, in terms of CNT production activity.

Moreover, it is preferable that the multicarboxylic acid used by this invention is 1 or more types chosen from the group which consists of dicarboxylic acid, tricarboxylic acid, and tetracarboxylic acid. As described above, it is preferable that the product of the molar ratio of the multicarboxylic acid and the active component multiplied by the number of carboxylic acid groups of the multicarboxylic acid is 0.5 to 1.9. If it is less than the lower limit, precipitation occurs in the aqueous metal solution. If exceeded, the acidity becomes high, which causes OO-anion in which MoO ^- forms clusters, which causes heterogeneous distribution of Fe and Mo in the preparation of catalysts, and also causes cracks due to excessive organic acid decomposition during firing. It is not preferable because it lowers catalyst stability.

This is also shown in the following examples, specifically, in the case of Examples 1 to 3 where the value of the molar ratio of the multicarboxylic acid and the active component multiplied by the number of carboxylic acid groups of the multicarboxylic acid satisfies the range of 0.5 to 1.9. As can be seen from the lower yield of CNT production compared to Comparative Example 3 having a calculated value of less than 0.5, or Comparative Example 4 having a calculated value of more than 1.9, the calculated value satisfies the range of 0.5 to 1.9.

The concentration of the homogeneous aqueous solution obtained in this way is 0.4 g / ml or less, specifically 0.3 g / ml, which is efficient when considering the reactivity.

In the present invention, a supported catalyst can also be provided using such an aqueous metal solution. The supported catalyst is a supported catalyst used for CNT synthesis, and in the present invention, CNTs can be provided using these supported catalysts.

On the other hand, look at with respect to the specific manufacturing method of the aqueous metal solution is as follows:

That is, it is preferable to prepare a precursor aqueous solution of the active ingredient, mix the multicarboxylic acid with the precursor aqueous solution of the active ingredient, and then mix the precursor of the active ingredient and the precursor of the catalyst component with the aqueous solution of multicarboxylic acid. Do.

This is a case where a Fe precursor (iron nitrate) is added as a catalyst component in water and then a Mo precursor (Ammonium Molybdate) is added as an active ingredient. For example, Fe 3+ cation and MoO- anion are present in water. ,

At room temperature, these Fe ³⁺ and MoO ^- because it forms a dark orange precipitate such as Fe (MoO) ₃ ↓ by the reaction ^of-the Fe ^{3 +} and 3MoO.

In order to suppress such precipitation, but using a multicarboxylic acid, as shown in the following examples, the catalyst component in water, the multi-carboxylic acid is added, and finally the active ingredient in Comparative Example 1, Alternatively, in the case of Comparative Example 2 in which the active ingredient was added to water, then the catalyst ingredient was added, and finally the multicarboxylic acid was added, it was confirmed that precipitation still occurred.

That is, only Examples 1 to 3 in which the active ingredient was added to water, followed by the multicarboxylic acid, and finally the catalyst ingredient were added, were observed in a clear solution state without precipitation being observed.

Therefore, it is another technical feature of the present invention to add multicarboxylic acid to the active component in the state where the catalyst component is not added.

In addition, the amount of the multicarboxylic acid and the active ingredient is preferably added so that the value obtained by multiplying the molar ratio of the multicarboxylic acid and the active ingredient by the number of carboxylic acid groups of the multicarboxylic acid is 0.5 to 1.9, which is less than the lower limit. This is because precipitation occurs in the aqueous metal solution, and if the upper limit is exceeded, cracking is caused during the calcination process, thereby lowering the catalyst stability.

Therefore, the process for preparing the supported catalyst in the present invention is preferably carried out in the following order:

a) preparing an aqueous solution of a precursor of the active ingredient;

b) mixing the multicarboxylic acid into the aqueous solution of the precursor of the active ingredient;

c) preparing a metal aqueous solution by mixing the precursor of the active ingredient and the precursor of the catalyst component with the aqueous solution of multicarboxylic acid; And

d) adding a support to the aqueous metal solution.

Supports used in the present invention are commercially available alumina, magnesium oxide, and silica. , And it is preferable to use alumina as described in the following examples.

In this case, the mixing ratio of the aqueous metal solution to the support is determined by the mass ratio of the sum of the catalyst component and the active component to the support, and the mass ratio is preferably in the range of 0.1 to 0.35.

The mixture obtained is then rapidly vacuum dried and then calcined to impregnate and coat the catalyst component on the support surface to obtain a supported catalyst. At this time, the rapid vacuum drying step is preferably a rotary evaporation under 45 to 80 ℃, the rapid vacuum drying time is preferably in the range of 30 minutes to 3 hours.

The supported catalyst may be a spherical type having an average particle diameter in the range of 30 to 150 μm and a surface particle size of 10 to 50 nm.

In addition, the firing conditions are preferably carried out for 30 minutes to 5 hours at 650 to 800 ℃.

In particular, in the present invention, it is more preferable to ripen within 20 minutes through rotation or stirring at 45 to 80 ℃ before the rapid vacuum drying.

As described above, according to the present invention, there is provided a stable and stable metal solution which is not precipitated for a long time, and has a uniform and stable metal support, and has a high metal loading amount, uniformity and no cracks that may occur during firing, and a supported catalyst and a method of preparing the same. Can provide.

1 is a photograph showing an SEM image of CNTs using the catalyst of Example 1 of the present invention (x100).

Hereinafter, preferred embodiments of the present invention will be described in order to facilitate understanding of the present invention, but the present invention is not limited thereto.

 [Example]

Example  1 < CNT  Preparation of Catalyst-Calculated Equation 0.6>

A. Metal Aqueous Solution

0.14 mmol of citric acid was added to Flask A in which 0.104 mmol of (NH ₄ ) ₆ Mo ₇ O ₂₄ .4H ₂ O was dissolved in 3 ml of water. 0.89 mmol of Fe (NO ₃ ) ₂ .9H ₂ O was added to prepare.

The prepared aqueous metal solution was observed as a clear solution without precipitation even after 48 hours. Furthermore, when left for 30 days or more, it was confirmed that the transparent solution was maintained.

In addition, since 7 mol of Mo per 1 mol of (NH ₄ ) ₆ Mo ₇ O ₂₄ 4H ₂ O exists, the mole number of the active ingredient Mo is 0.73 mmol (molar ratio of the multicarboxylic acid and the active ingredient) x multicarboxylic acid It was confirmed that it was 0.57 by the calculated value of 0.14 / 0.73x3 of the number of the carboxylic acid groups of.

B. Support Preparation

In addition, Flask B containing 4.9 mmol of Al ₂ O ₃ (D50v = 80 micron, D50n = 55 micron, pore volume: 0.64 cm ³ / g, surface area: 237 m ² / g, manufactured by Saint Gobain) was prepared.

C. Preparation of Supported Catalysts from Aqueous Metal Solution and Support

The flask A was added to Flask B to sufficiently support the catalytically active metal precursor in Al ₂ O ₃ , and then aged by stirring for 5 minutes in a 60 ° C. thermostat. It is dried for 30 minutes under vacuum drying while maintaining the temperature. The dried catalyst was calcined at 700 ° C. for 3 hours to prepare a homogeneous supported catalyst.

Example  2 < CNT  Preparation of Catalysts-Formula 1.0

The same process as in Example 1 was repeated except that 0.24 mmol of citric acid in Example 1 was added.

The prepared aqueous metal solution was observed as a clear solution without precipitation even after 48 hours, and maintained a clear solution even when left for more than 30 days.

Moreover, it was confirmed that it was 0.98 as a result of calculating the number of carboxylic acid groups of (molar ratio of multicarboxylic acid and an active component) x multicarboxylic acid.

Example  3 < CNT  Preparation of Catalysts-Formula 1.5

The same process as in Example 1 was repeated except that 0.53 mmol of oxalic acid was substituted for citric acid in Example 1.

At this time, the prepared aqueous metal solution was observed as a clear solution without precipitation even after 48 hours, and (calculated molar ratio of multicarboxylic acid and active ingredient) x the number of carboxylic acid groups of the multicarboxylic acid was found to be 1.45. there was.

Example  4 < CNT  Preparation of Catalysts-Formula 0.7>

The same process as in Example 1 was repeated except that 0.24 mmol of tartaric acid was substituted for citric acid in Example 1.

At this time, the prepared aqueous metal solution was observed as a clear solution without precipitation even after 48 hours, and (calculated molar ratio of multicarboxylic acid and active ingredient) x the number of carboxylic acid groups of the multicarboxylic acid was found to be 0.66. there was.

Comparative example  1 < CNT  Preparation of catalysts-formula calculated below 0.5>

The same process as in Example 1 was repeated except that the citric acid in Example 1 was removed.

At this time, the prepared aqueous metal solution precipitated and a clear solution was obtained after vigorous stirring for 30 hours, but reprecipitation occurred when the stirring was stopped and left to stand. (Molar ratio of multicarboxylic acid and active component) As a result of calculating the number of carboxylic acid groups of x multicarboxylic acid, it was confirmed that it was zero.

Comparative example  2 < CNT  Preparation of catalysts-formula calculated below 0.5>

The same process as in Example 1 was repeated except that 0.048 mmol of citric acid in Example 1 was added.

At this time, the prepared aqueous metal solution precipitated, but after 6 hours of strong stirring, a clear solution was obtained. However, when the solution was left after stirring, reprecipitation gradually occurred after 8 hours. (Molar ratio of multicarboxylic acid and active component) As a result of calculating the number of carboxylic acid groups of x multicarboxylic acid, it was confirmed that it was 0.2.

Comparative example  3 < CNT  Preparation of Catalysts-Equation 2.0 or higher>

The same process as in Example 1 was repeated except that 0.48 mmol of citric acid in Example 1 was added.

At this time, the prepared aqueous metal solution formed a transparent solution in which precipitation did not occur. Moreover, it was confirmed that it was 2.0 as a result of calculating the number of carboxylic acid groups of (molar ratio of multicarboxylic acid and an active component) x multicarboxylic acid.

However, after the preparation of the catalyst it was confirmed that the CNT growth yield falls.

Comparative example  4 < CNT  Preparation of Catalysts-Aqueous Metal Solution Substitution 1 >

In Example A. Aqueous metal solution preparation step in Example 2, The same process as in Example 2 was repeated except that the order was added in the order of Fe, CA, and MoO.

At this time, the prepared aqueous metal solution was precipitated, and the precipitate disappeared through strong stirring for about 36 hours, but when the stirring was stopped, reprecipitation could be observed, and also (molar ratio of multicarboxylic acid and active ingredient). As a result of calculating the number of carboxylic acid groups of the x multicarboxylic acid, it was confirmed that it was 0.98.

Comparative example  5 < CNT  Preparation of Catalysts-Aqueous Metal Solution Substitution 2 >

In Example A. Aqueous metal solution preparation step in Example 2, the same process as in Example 2 was repeated except that the order was changed in the order of MoO, Fe, CA.

At this time, the prepared aqueous metal solution was precipitated, and the precipitate disappeared through strong stirring for about 36 hours, but it was also observed that reprecipitation occurred when the stirring was stopped.

On the other hand, it was confirmed that it was 0.98 as a result of calculating the number of carboxylic acid groups of (molar ratio of multicarboxylic acid and an active component) x multicarboxylic acid.

CNT Manufacturing example

Carbon nanotube synthesis was tested in a laboratory scale fixed bed reactor using the catalyst for synthesizing CNTs prepared in Examples 1 to 4.

The prepared CNT synthesis catalyst was mounted in the middle of a vertical quartz tube having an inner diameter of 20 mm and a height of 550 mm, and then heated up to 700 ° C. at a volume mixing ratio of nitrogen and hydrogen at 50: 3, and then maintained. A volume mixing ratio of hydrogen and ethylene gas was synthesized for 1 hour while flowing from top to bottom at 50: 3: 10 to synthesize a predetermined amount of carbon nanotubes.

Synthesized carbon nanotubes were obtained at room temperature, and their contents were measured using an electronic balance. In this case, the reaction yield was calculated based on the weight of the catalyst for synthesizing CNT and the weight increase after the reaction.

CNT yield (%) = (total weight after reaction (g)-weight of catalyst used (g)) / weight of catalyst used (g) x 100

The CNTs collected in the CNT recovery unit after the 1 hour reaction showed a CNT yield of 363% compared to the catalyst input in Example 1, and the average outer diameter of the obtained CNTs was 20 nm. The results of Examples 2 to 4 are summarized together in Table 1 below. In addition, SEM images of CNTs are shown in FIG. 1 using the catalyst of Example 1 of the present invention. As shown in Figure 1, it was confirmed that the spherical type of CNT is produced.

Comparative Manufacturing Example  One

Except for using the catalyst of Comparative Examples 1 to 5 instead of the catalyst of Example 1 was carried out in the same manner as in Example 1.

CNT collected in the CNT recovery unit after the 1 hour reaction showed a yield of 248% compared to the catalyst input in the case of Comparative Example 1, and the average outer diameter of the obtained CNT was 20 nm. The results of Comparative Examples 2 to 5 are also summarized in Table 1 below.

division Example Comparative example One 2 3 4 One 2 3 4 5 Mixed order MoO-> CA-> Fe MoO-> CA-> Fe MoO-> CA-> Fe MoO-> CA-> Fe MoO-> CA-> Fe MoO-> CA-> Fe MoO-> CA-> Fe Fe-> CA-> Mo MoO-> Fe-> CA CA type Citric acid Citric acid Oxalic acid Tartaric acid Citric acid Citric acid Citric acid Citric acid Citric acid Fe / Mo /
Al ₂ O ₃ 14/11/75 CA mmol 0.14 0.24 0.53 0.24 - 0.048 0.48 0.24 0.24 CA / Mo [A] 0.20 0.33 0.74 0.33 - 0.07 0.65 0.33 0.33 COOH number of CA [B] 3 3 2 2 3 3 3 3 3 [A] * [B] 0.57 0.98 1.45 0.66 0.0 0.2 2.0 0.98 0.98 Dissolution (hr) 0 0 0 0 30 6 0 36 36 Reprecipitation (hr) NA NA NA NA Sedimentation 8 NA Sedimentation Sedimentation Weight change after heat treatment (%) 75 74 75 77 78 77 69 - - CNT yield (%) 363 380 313 320 248 280 224 - -

As shown in the table, in Examples 1 to 4 according to the present invention it was confirmed that the reprecipitation does not occur for a long time compared to Comparative Examples 1 to 5 and has an improved CNT yield.

Claims (13)

It comprises water, precursors of the catalytic component, precursors of the active component and multicarboxylic acid,
A metal aqueous solution, wherein a value obtained by multiplying the molar ratio of the multicarboxylic acid and the active component by the number of carboxylic acid groups of the multicarboxylic acid is 0.5 to 1.9.
The method of claim 1,
The aqueous metal solution is an aqueous metal solution, characterized in that the metal aqueous solution used for the production of the supported catalyst for CNT synthesis.
The method of claim 1,
The catalyst component is an aqueous metal solution, characterized in that at least one selected from Fe, Co and Ni.
The method of claim 1,
The active ingredient is an aqueous metal solution, characterized in that Mo.
The method of claim 1,
The multicarboxylic acid is at least one member selected from the group consisting of dicarboxylic acid, tricarboxylic acid and tetracarboxylic acid.
The method of claim 1,
The catalyst component and the active component is an aqueous metal solution, characterized in that the weight ratio of 1 to 15: 10 to 30 based on the weight of the support 100.
Supported catalyst prepared using the aqueous metal solution of any one of claims 1 to 6.
8. The method of claim 7,
The supported catalyst is a supported catalyst, which is used for CNT synthesis.
CNT prepared using the supported catalyst of claim 7.
a) preparing an aqueous solution of a precursor of the active ingredient;
b) mixing the multicarboxylic acid into the aqueous solution of the precursor of the active ingredient; And
c) mixing the precursor of the catalyst component with the precursor of the active ingredient and the aqueous solution of multicarboxylic acid.
The method of claim 10,
The metal aqueous solution is a method of producing an aqueous metal solution, wherein a value obtained by multiplying the molar ratio of the multicarboxylic acid and the active component by the number of carboxylic acid groups of the multicarboxylic acid is 0.5 to 1.9.
a) preparing an aqueous solution of a precursor of the active ingredient;
b) mixing the multicarboxylic acid into the aqueous solution of the precursor of the active ingredient;
c) preparing a metal aqueous solution by mixing the precursor of the active ingredient and the precursor of the catalyst component with the aqueous solution of multicarboxylic acid; And
and d) injecting a support into the aqueous metal solution.
13. The method of claim 12,
The support is alumina, magnesium oxide, and silica Method for producing a supported catalyst, characterized in that selected from.

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