KR101616195B1 - Direct synthesis of hydrogen peroxide using Pd/silica-alumina catalysts having core/shell structure - Google Patents

Abstract

The present invention relates to a palladium / silica-alumina catalyst having a core / shell structure and a method for producing hydrogen peroxide directly using the same, and more particularly, to a process for producing hydrogen peroxide using a core / shell structure palladium / silica- To a method for producing hydrogen peroxide directly from hydrogen and oxygen.

Description

Technical Field [0001] The present invention relates to a direct synthesis method of hydrogen peroxide using a palladium / silica-alumina catalyst having a core / shell structure,

The present invention relates to a process for the direct production of hydrogen peroxide using a palladium / silica-alumina catalyst having a core / shell structure and more particularly to a process for producing hydrogen peroxide using a core / shell structure palladium / silica- And a method for producing hydrogen peroxide directly from oxygen.

Hydrogen peroxide is used as a bleaching agent for pulp and fiber, disinfectant disinfectant, semiconductor cleaning liquid, oxidizer for water treatment process, and environmentally friendly oxidizer for chemical reaction (propylene oxide synthesis). As of 2009, 2.2 million tons of hydrogen peroxide are produced annually, and demand for hydrogen peroxide is expected to rise along with an increase in demand for propylene oxide.

At present, hydrogen peroxide is produced by successive oxidation and hydrogenation processes starting from anthraquinone-based compounds, as known from Korean Patent Publication Nos. 1999-0027774 and 2001-0076225, wherein a large amount of organic solvent There is a problem that it is used as waste and is generated as waste. In addition, there is also a problem that the production of hydrogen peroxide requires a lot of energy consumption through a multistage continuous process and purification and concentration process after production.

Direct production processes for the synthesis of hydrogen peroxide by directly reacting hydrogen and oxygen have been attracting attention. This direct production process has been studied as an alternative process of commercial process because water is produced as a reaction by-product and use of organic solvent is low. In addition, the direct production process can be manufactured and supplied where hydrogen peroxide is needed because of its simple structure, which greatly reduces the risk of explosion when storing and transporting hydrogen peroxide.

Therefore, researches on catalysts and reaction systems for direct production of hydrogen peroxide are underway. However, most catalyst systems for direct production of hydrogen peroxide are metal catalysts, and it is common to add an acid to the solvent. The role of acid (H ⁺ ion) has been reported in various roles, among which the role of inhibiting the decomposition of synthesized hydrogen peroxide and increasing the selectivity of hydrogen peroxide has been reported. However, the use of an acid can lead to the elution of the active metal of the catalyst or to the corrosion of the reactor. In addition, it is preferable that the amount of acid to be added is little or no in the purification of soil using hydrogen peroxide, bleaching process of cloth or cloth. Therefore, it is necessary to use no acid added to the solvent, or to reduce the amount used.

In addition, various catalysts using palladium as a catalyst for directly producing hydrogen peroxide from hydrogen and oxygen have been developed. However, in the case of using a catalyst carrier in the direct production of hydrogen peroxide, it has been reported that the amount of acid used in the solvent is reduced by changing the acid property of the carrier, but the case of using a nanocatalyst that has not yet used a carrier has been reported It is not.

In particular, research has not been conducted to suppress the elution of the catalyst and the corrosion of the reactor by reducing the amount of the acid added to the solvent by utilizing the acid sites of the palladium / silica-alumina catalyst of the core / shell structure.

Korean Patent Publication No. 1999-0027774 Korean Patent Publication No. 2001-0076225

In order to solve the above problems,

The present invention aims to use a core / shell structure palladium / silica-alumina catalyst which is a nano catalyst in the process of directly producing hydrogen peroxide from hydrogen and oxygen.

Further, the present invention aims at reducing the amount of acid used in the direct production method of hydrogen peroxide and increasing the production amount of hydrogen peroxide because the palladium / silica-alumina catalyst of the core / shell structure has acid sites.

In order to achieve the above object,

The present invention provides a method for the direct production of hydrogen peroxide, characterized in that hydrogen peroxide is directly produced from hydrogen and oxygen using a palladium / silica-alumina catalyst having a core / shell structure.

The palladium / silica-alumina catalyst of the core / shell structure of the present invention has an acid site and can be used in a method of directly producing hydrogen peroxide from hydrogen and oxygen, thereby reducing the amount of acid used in direct production of hydrogen peroxide, It is possible to increase the amount of production.

1 is a TEM photograph of a palladium / silica-alumina catalyst with a core / shell structure.
Figure 2 is a TEM photograph of a palladium / silica catalyst with a core / shell structure.
3 is a graph showing the ammonia desorption amount of a palladium / silica-alumina catalyst having a core / shell structure and a palladium / silica catalyst having a core / shell structure.
Figure 4 is a FT-IR graph of pyridine adsorbed on a palladium / silica-catalyzed palladium / silica-alumina catalyst of core / shell structure and core / shell structure.
FIG. 5 is a graph showing hydrogen peroxide production according to the phosphoric acid content of the palladium / silica-alumina catalyst of the core / shell structure and the palladium / silica catalyst of the core / shell structure.

Hereinafter, the present invention will be described in more detail.

Hydrogen peroxide is produced by successive oxidation and hydrogenation processes starting from anthraquinone type compounds. In this case, a large amount of organic solvent is used and it is generated as waste. In addition, there is also a problem that the production of hydrogen peroxide requires a lot of energy consumption through a multistage continuous process and purification and concentration process after production.

Direct production processes for the synthesis of hydrogen peroxide by directly reacting hydrogen and oxygen have been attracting attention. Since this direct production process is a reaction by-product, water is produced and the use of organic solvents is low. have.

Accordingly, the present invention provides a direct production method of hydrogen peroxide which is characterized in that hydrogen peroxide is directly produced from hydrogen and oxygen using a palladium / silica-alumina catalyst having a core / shell structure.

The palladium / silica-alumina catalyst of the core / shell structure used in the direct production method of hydrogen peroxide of the present invention has a size of 10 to 500 nm and palladium nanoparticles of 1 to 30 nm in size exist as a core in the silica- Palladium / silica-alumina catalyst in an amount of 0.1 to 20% by weight based on the total weight of the catalyst. When the palladium nanoparticles are contained in the above content range, the catalyst can be preferably performed in the direct production of hydrogen peroxide.

Also, the shell of the catalyst is a porous shell made of silica-alumina, and the shell is mixed with silicon and aluminum in a molar ratio of 10 to 300: 1, more preferably 20 to 80: 1 . Since the silica-alumina shell is porous, the material can be transferred through the pores to the core of palladium nanoparticles.

In the present invention, a method of directly producing hydrogen peroxide from hydrogen and oxygen is a method of directly producing hydrogen peroxide by supplying hydrogen and oxygen as reactants to a reactor including a palladium / silica-alumina catalyst of the core / shell structure and an alcohol solvent have. In addition, it is preferable that the reactor is further reacted by additionally supplying nitrogen as a reactant.

More specifically, the direct production method of hydrogen peroxide of the present invention allows an alcohol solvent to be used as a reaction medium so that the direct production method of hydrogen peroxide can proceed to a liquid phase. The alcohol solvent may be selected from those suitable for the use of hydrogen peroxide, preferably methanol, ethanol or a mixed solution of alcohol and water, more preferably a mixed solution of ethanol and water.

The reaction is carried out in a high-temperature autoclave, and a reaction temperature of 10 to 30 ° C is maintained through a heating device surrounding the outer wall of the reactor and a thermometer and a cooling device installed in the reactor to directly produce hydrogen peroxide .

The reactants, hydrogen and oxygen, are injected into the reactor in the form of a gas. In order to improve the solubility with respect to the solvent, it is preferable to directly supply the hydrogen and oxygen to the solvent using a dip tube. The hydrogen gas and the oxygen gas are preferably flowed at a flow rate of 1 to 4 mL / min and 10 to 40 mL / min, respectively, and more preferably at a flow rate of 1.5 to 2.5 mL / min and 15 to 25 mL / min, respectively. Due to the flow rates of the hydrogen gas and oxygen gas, consequently, hydrogen and oxygen are maintained at a molar ratio of 1: 5 to 15 and are injected into the reactor.

The hydrogen gas and the oxygen gas are supplied to the reactor at the above-mentioned flow rate, and the total reaction pressure is regulated using a BPR (Back Pressure Regulator). The reaction pressure is measured through a pressure gauge connected to the reactor. In the direct production method of hydrogen peroxide, the reaction pressure is maintained at 1 to 40 atm, preferably at atmospheric pressure.

In the direct production method of hydrogen peroxide of the present invention, it is more preferable to further include a halogen compound in the alcohol solvent. In the case of a catalyst containing palladium, when a halogen compound is added, a part of the halogen compound is adsorbed on palladium. It is known that the active site adsorbed by the halogen compound is more adsorbed to the active site where water is generated than the active site where hydrogen peroxide is generated. Therefore, when a small amount of a halogen compound is added, the selectivity of hydrogen peroxide is increased and the production amount of hydrogen peroxide can be increased.

The halogen compound may be a compound containing at least one member selected from the group consisting of bromine (Br), chlorine (Cl) and iodine (I) ions, Compound.

When the halogen compound is further used, it is used in a concentration of more than 0 to 0.1M, preferably in a concentration of more than 0 and 5 mM or less.

Further, in the direct production method of hydrogen peroxide of the present invention, more preferably, the alcohol solvent may further include an acid.

The acid is sulfuric acid (H ₂ SO _4), hydrochloric acid (HCl), phosphoric acid (H ₃ PO ₄₎ and nitric acid is at least one member selected from the group consisting of (HNO _3), preferably phosphoric acid (H ₃ PO ₄₎ the use.

When the acid is further used, it is used in a concentration of more than 0 and 1M, preferably in a concentration of more than 0 and 0.03M or less.

By including an acid, it is possible to inhibit the decomposition of hydrogen peroxide synthesized and to increase the selectivity of hydrogen peroxide. However, there is a problem that the active metal of the catalyst is eluted due to the use of an acid, or corrosion of the reactor is caused.

However, the palladium / silica-alumina catalyst of the core / shell structure used in the direct production method of hydrogen peroxide of the present invention has an acid point, and can replace the role of an acid, and therefore the amount of acid used in the direct production method of hydrogen peroxide Can be reduced, and the production amount of hydrogen peroxide can be increased.

More specifically, the silica-alumina shell of the palladium / silica-alumina catalyst of the core / shell structure has acid sites. This is because, when silicon-aluminum is mixed, there are three types of structural defects in the silica-alumina due to the different bonding methods of aluminum and silicon atoms. First, aluminum ions substituted in the silicon cation sites of the tetrahedral coordination structure; second, aluminum cations in the modified tetrahedral structure; and third, silicon cations in the modified tetrahedral structure. Among them, Bronsted acidity and Lewis acidity appear in defects produced by aluminum cations having a tetrahedral coordination structure.

Consequently, the acid sites of the palladium / silica-alumina catalyst of the core / shell structure used in the present invention may depend on the molar ratio of silicon to aluminum, since the types of acid sites change depending on the combination of silicon and aluminum.

Therefore, in the present invention, it is preferable to mix silicon and aluminum in a molar ratio of 10 to 300: 1, more preferably 20 to 80: 1 in a molar ratio.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail based on examples. However, the embodiments of the present invention described below are merely examples, and the scope of the present invention is not limited to these embodiments. The scope of the present invention is indicated in the claims, and moreover, includes all changes within the meaning and range of equivalency of the claims.

Example  1. Preparation of palladium / silica-alumina catalyst (Pd @ SA) with core / shell structure

16 mL of a solution obtained by dissolving 0.068 mmol of ascorbic acid, 0.189 mmol of PVP and 5 mmol of potassium bromide (KBr) in tertiary ultrapure water was prepared and stirred at 80 ° C for 10 minutes using a magnetic rod. 6 mL of disodium tetrachloropalladate (Na ₂ PdCl ₄ ) solution (64 mM) was added thereto, and the mixture was stirred at the same temperature for 3 hours with a magnetic stirrer to proceed the reaction.

After the reaction, the reaction solution and acetone were mixed at a ratio of 1:10, the nanoparticles produced through a centrifuge (3500 rpm, 10 minutes) were recovered, and washed several times with tertiary ultrapure water to obtain palladium Cube particles were prepared.

The prepared palladium nanoparticles were redispersed in 200 mL of ethanol, and then 18 mL of water and 24 mL of ammonia water were added. After stirring for 3 hours, a silica precursor, TEOS, and an alumina precursor, Di-sec-butoxyaluminoxy-triethoxysilane, were synthesized with a molar ratio of Si: Al of 20: 1.

After stirring for 24 hours using a magnetic rod, the nanoparticles produced through the centrifugal separator were collected. The recovered nanoparticles were washed several times with tertiary ultrapure water and then heat-treated at 500 ° C. for 6 hours to prepare palladium (silica-alumina core / shell) Pd @ SA (FIG.

Comparative Example  1. Preparation of palladium / silica catalyst (Pd @ S) with core / shell structure

Pd @ S was produced in the same manner as in Example 1 except that the alumina precursor was not used but only the silica precursor was used (FIG. 2).

The physical properties of the Pd @ SA catalyst prepared in Example 1 and the Pd @ S catalyst prepared in Comparative Example 1 were measured using an inductively coupled plasma spectrometer (ICP-OES), and the specific surface area Respectively. The measurement results are shown in Table 1 below.

division Pd wt%
(ICP-OES) Si / Al ratio
(ICP-OES) Specific surface area
(m ² / g) Example 1 (Pd @ SA) 2.98 19.9 305.8 Comparative Example 1 (Pd @ S) 2.89 - 335.1

Experimental Example  1. Ammonia desorption experiment of Pd @ SA catalyst

0.03 g of the Pd @ SA catalyst prepared in Example 1 was pretreated at 400 ° C. for 2 hours in a helium atmosphere (50 mL / min). Thereafter, ammonia was adsorbed at 50 DEG C for 30 minutes in an ammonia atmosphere (50 mL / min). Helium was flowed at 150 ° C for 2 hours to remove physically adsorbed ammonia. Thereafter, the temperature was raised to 500 deg. C at a rate of 5 deg. C / min at 50 deg. C to determine the desorption amount of ammonia.

As a result, it was found that the Pd @ SA catalyst prepared in Example 1 had an acid site and that the Pd @ S catalyst prepared in Comparative Example 1 had no acid sites (FIG. 3).

Experimental Example  2. Pyridine adsorption experiment of Pd @ SA and Pd @ S catalyst

Pressure was applied to the Pd @ SA catalyst prepared in Example 1 and 0.06 g of the Pd @ S catalyst prepared in Comparative Example 1 to form a thin film, and the thin film was injected into the IR-Cell. Pretreatment was carried out at 300 캜 for 2 hours in a vacuum condition, followed by cooling to 150 캜.

Thereafter, pyridine was vaporized and adsorbed on each of the above samples for 30 minutes, and analysis was carried out at a temperature of 150 ° C. Vacuum was applied until the physical adsorption of the pyridine disappeared and the analytical value of 100 times was used.

As a result, it was confirmed that the Pd @ S catalyst prepared in Example 1 had a Bronsted acid point and a Lewis acid point, and that the Pd @ S catalyst prepared in Comparative Example 1 had no acid point 4).

Experimental Example  3. Measurement of hydrogen peroxide production by phosphoric acid concentration

1. Pd @ SA catalyst

A double jacket reactor was charged with a reaction solvent (120 mL of ultrapure water; 30 mL of ethanol; and 0.9 mM KBr). 50 mg of the Pd @ SA catalyst prepared in Example 1 was added to the double jacket reactor and the reaction was carried out for 3 hours.

The reaction temperature was maintained at 20 ° C and the pressure was maintained at 1 atm. The reaction gas (H ₂ / O ₂ = 1/10) was flowed constantly at 22 mL / min. After the reaction, the amount of produced hydrogen peroxide was measured.

In addition, by proceeding in the same manner as above except that phosphoric acid was added to the reaction solvent and the concentration of phosphoric acid was 0.01M, 0.02M and 0.03M, the amount of hydrogen peroxide production according to the concentration of phosphoric acid (0.01, 0.02 and 0.03M) Respectively.

2. Pd @ S catalyst

Except that the Pd @ S catalyst prepared in Comparative Example 1 was used instead of the Pd @ SA catalyst prepared in Example 1 above.

In addition, by proceeding in the same manner as above except that phosphoric acid was added to the reaction solvent and the concentration of phosphoric acid was 0.01M, 0.02M and 0.03M, the amount of hydrogen peroxide production according to the concentration of phosphoric acid (0.01, 0.02 and 0.03M) Respectively.

After each reaction, the generated hydrogen peroxide was collected and the concentration of hydrogen peroxide was measured by the following equation (1) using the iodometric titration method, and the amount of hydrogen peroxide production was calculated by the following equation (2).

[Equation 1]

&Quot; (2) "

As a result, the Pd @ S catalyst prepared in Comparative Example 1 had a maximum concentration of 0.02M of hydrogen peroxide. However, the Pd @Sa catalyst prepared in Example 1 exhibited the highest yield of hydrogen peroxide Was observed at 0.01M. In addition, the Pd @ SA catalyst prepared in Example 1 showed an increase in the amount of hydrogen peroxide produced as the concentration of phosphoric acid decreased (FIG. 5).

From the above results, it is possible to directly produce hydrogen peroxide using a Pd @ SA catalyst having a core / shell structure. Since the Pd @ SA catalyst has an acid site, it is confirmed that the amount of hydrogen peroxide does not decrease even when the acid concentration is decreased .

Therefore, the present invention can directly produce hydrogen peroxide using a Pd @ SA catalyst having a core / shell structure.

In addition, since the Pd @ SA catalyst of the core / shell structure of the present invention has an acid site, when hydrogen peroxide is directly produced using the catalyst, degradation of synthesized hydrogen peroxide can be suppressed, and addition of hydrogen peroxide It is possible to prevent the elution of the active metal of the catalyst and the corrosion of the reactor. Further, there is an effect that the production amount of hydrogen peroxide can be increased.

Claims (12)

By directly producing hydrogen peroxide from hydrogen and oxygen using a palladium / silica-alumina catalyst with a core / shell structure,
Wherein the silica-alumina shell of the palladium / silica-alumina catalyst is prepared by mixing silicon and aluminum in a molar ratio of 10 to 300: 1, having a porosity and having a B -sted acid point or Lewis acid point, Way The method of claim 1, wherein the palladium of the palladium / silica-alumina catalyst is nanoparticles of 1 to 30 nm in size. delete The method according to claim 2, wherein the palladium nanoparticles are contained in an amount of 0.1 to 20 wt% based on the total weight of the palladium / silica-alumina catalyst. The method according to claim 1, wherein the palladium / silica-alumina catalyst has a size of 10 to 500 nm. The direct production method of hydrogen peroxide according to claim 1, wherein the direct production of hydrogen peroxide is carried out by supplying hydrogen and oxygen as reactants to a reactor including a core / shell structure palladium / silica-alumina catalyst and an alcohol solvent, Way. The method of claim 6, wherein the reactor is further fed with nitrogen. 7. The method of claim 6, wherein the alcohol solvent further comprises a halogen compound. 7. The method of claim 6, wherein the alcohol solvent further comprises an acid. [Claim 11] The method according to claim 9, wherein the acid is at least one selected from the group consisting of sulfuric acid, hydrochloric acid, phosphoric acid and nitric acid. [7] The method of claim 6, wherein the hydrogen peroxide is directly produced by reacting at a temperature of 1 to 40 atm and at a temperature of 10 to 30 [deg.] C. 7. The method of claim 6, wherein the supplied hydrogen and oxygen are supplied at a molar ratio of 1: 5-15.

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