JP2003024794A - Catalyst for producing hydrogen peroxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a catalyst excellent in activity and selectivity for synthesizing hydrogen peroxide directly from hydrogen and oxygen and a method for producing hydrogen peroxide using the catalyst. SOLUTION: The catalyst for synthesizing hydrogen peroxide directly from oxygen and hydrogen comprising at least one element selected from platinum group elements, rare earth elements, titanium, niobium, nickel, molybdenum, and tungsten and the method for producing hydrogen peroxide using the catalyst are provided.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a catalyst used for producing hydrogen peroxide directly from hydrogen and oxygen and a method for producing hydrogen peroxide using this catalyst.

[0002]

2. Description of the Related Art Hydrogen peroxide is a clean oxidant.
It is used for the oxidation of various organic and inorganic substances. Currently, hydrogen peroxide is industrially produced by the anthraquinone method. However, this method requires a large amount of a relatively expensive reaction medium, requires many steps such as reduction, oxidation of the anthraquinone medium, extraction of the produced hydrogen peroxide, purification, and concentration, which complicates the process. have. Furthermore, loss of anthraquinone is also a problem.

In order to solve these problems, conventionally, a method of producing hydrogen peroxide from hydrogen and oxygen in an aqueous medium in the presence of a noble metal catalyst has been proposed. It has been shown to generate. For example,
JP-A-63-156005, JP-A-4-2388
02, JP-A-4-285003, JP-A-5
In JP-17106, JP-A-5-43206, JP-A-9-301705, etc., a platinum group metal is used by being supported on various carriers such as activated carbon, amorphous silica, zeolite, rare earth oxides and titania. JP-A-6-305715 and JP-A-7-33410 propose a method using a platinum group metal catalyst modified with tin, lead, zinc, gallium, bismuth or the like.

However, in order to obtain a high concentration of hydrogen peroxide, it was necessary to carry out the reaction under high pressure conditions. The use of high-pressure conditions is industrially disadvantageous, and is unfavorable in terms of safety from the viewpoint of reaction between hydrogen and oxygen. Further, there is a problem that hydrogen selectivity in producing hydrogen peroxide is not sufficient.

[0005]

The object of the present invention is to:
Provided is a catalyst which gives a high hydrogen peroxide concentration and hydrogen selectivity under relatively low pressure when producing hydrogen peroxide directly from oxygen and hydrogen, and an efficient method for producing hydrogen peroxide using this catalyst. That is.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies in order to achieve the above object, and as a result, at least one selected from platinum group metals and rare earths, titanium, niobium, nickel, molybdenum and tungsten. The inventors have found that a catalyst composed of one element is an excellent catalyst for directly synthesizing hydrogen peroxide from oxygen and hydrogen, and arrived at the present invention. That is, the present invention is as follows. (1) Used for producing hydrogen peroxide directly from oxygen and hydrogen, characterized by comprising a platinum group metal and at least one element selected from rare earths, titanium, niobium, nickel, molybdenum and tungsten catalyst. (2) The hydrogen peroxide according to (1), wherein the platinum group metal is supported on a carrier together with at least one element selected from rare earths, titanium, niobium, nickel, molybdenum and tungsten. The catalyst used to do this. (3) The catalyst used for producing hydrogen peroxide according to (1) or (2), wherein the platinum group metal is palladium. (4) The catalyst used for producing hydrogen peroxide according to (2) or (3), wherein the carrier is a mesopore molecular sieve. (5) A method for producing hydrogen peroxide, which comprises reacting in the presence of the catalyst according to any one of (1) to (4) when synthesizing hydrogen peroxide directly from hydrogen and oxygen.

The present invention will be described in detail below. The catalyst of the present invention comprises hydrogen and oxygen by being composed of a platinum group metal and at least one element selected from rare earths, titanium, niobium, nickel, molybdenum and tungsten (hereinafter referred to as a modifying component). It exhibits an excellent catalytic function when hydrogen peroxide is directly produced from. The catalyst of the present invention exhibits an excellent effect only with the platinum group metal and the modifying component, but it is preferably used by being supported on a carrier.

As the platinum group metal constituting the catalyst component,
Examples thereof include ruthenium, rhodium, radium, iridium and platinum. These may be used alone or in combination of two or more. In particular, those mainly containing palladium are preferable. When the platinum group metal is used by being supported on the carrier, the proportion of the platinum group metal is preferably 0.1 to 20% by mass, more preferably 0.2 to 10% by mass, based on the total amount of the platinum group metal and the carrier. , Most preferably 0.5 to
It is 5% by mass.

The ratio of the modifying component element used in the catalyst of the present invention to the platinum group metal is preferably 0.01 to 10 atomic ratio, more preferably 0.05 to 2 atomic ratio. The method for preparing the catalyst of the present invention is such that when the catalyst is not supported on the carrier,
For example, the pH is adjusted by adding carbonate or the like to a mixed aqueous solution of a soluble salt of a platinum group metal element and a soluble salt of an element used as a modifying component to prepare a coprecipitation slurry. Next, a catalyst in the form of a slurry is prepared by reduction in liquid using hydrogen or a reduction method using a reducing agent such as formalin and hydrazine.

When the catalyst is supported on the carrier, there is a method of supporting the modifying component on the carrier simultaneously with or separately from the platinum group component. In order to support the platinum group metal on the catalyst, a soluble salt of the platinum group metal element is deionized water, methanol,
It is dissolved in an organic solvent such as acetone, supported on a carrier by an impregnation method or an ion exchange method, and the carrier supporting the platinum group metal component is sufficiently dried. Vacuum drying is preferably performed at 50 to 150 ° C. Then, reduction treatment is performed at 100 to 300 ° C. under hydrogen or a mixed gas atmosphere of hydrogen and nitrogen. A reducing agent such as formalin or hydrazine in an aqueous solution can be used for the reduction treatment. In order to prepare a catalyst composed of a modifying component and a platinum group metal, a soluble salt of the element used as the modifying component is dissolved in water, alcohol, acetone, etc., and the platinum group component is simultaneously or separately applied to the carrier by an impregnation method or the like. Carry it. After loading, the catalyst is usually produced by the reduction treatment as described above.

Examples of soluble salts of platinum group elements include, for example,
Examples thereof include chlorides, acetates, ammine complexes, and acetylacetonates. Examples of the soluble salt of the modifying component element include rare earth chlorides, nitrates, nickel chloride, nickel nitrate, titanium oxalate, niobium oxalate, molybdic acid, tungstic acid and its salts, niobium and titanium peroxides, and alkoxides. And so on. As the carrier used, silica, silica-alumina, alumina, titania, zirconia, hafnia, Y
Type, beta type, MFI type, MCM-22 and other zeolites, rare earth oxides, mesopore molecular sieves, activated carbon and other porous carriers. In particular, a mesopore molecular sieve is preferable.

The mesopore molecular sieve is a metal oxide porous body having a mesopore region, in particular, monodisperse pores having a diameter of 1.5 to 10 nm. As the elements constituting the metal oxide, silicon, aluminum, iron, titanium, niobium,
Examples thereof include tantalum, hafnium, zirconium, tin and rare earths. Examples of the metal oxide include various metallosilicates containing silicon as a main component, in addition to the above metal oxides. As various metallosilicates containing silicon as a main component, for example, aluminum, gallium,
Examples include transition metal elements of Groups 4, 5 or 6 such as metallosilicates of titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, zirconium, niobium, molybdenum and tungsten. The ratio of these metal oxides to silicon in the mesopore molecular sieve is such that when the metal is represented by M, the silicon / M atomic ratio is 5 or more, and preferably 10 to 100.

Methods for synthesizing these mesopore molecular sieves include US Pat. Nos. 5,098,684 and 5,510.
No. 2643, No. 5108725, and Japanese Patent Publication No. 5-503499, and the like is synthesized by hydrothermal synthesis using a quaternary ammonium salt or phosphonium salt having a long-chain alkyl group as a template. A method is disclosed. Organic-inorganic hybrid silica belonging to mesopore molecular sieves Mesopore molecular sieves are likewise used as carriers. The organic-inorganic hybrid silica mesopore molecular sieve is an organic-inorganic hybrid mesopore molecular sieve having an organic component bonded to silicon forming a skeleton in an amount of 1 to 60% by weight based on silicon. These organic components are hydrocarbon groups, preferably alkyl groups, allyl groups and aralkyl groups. A methyl group as the alkyl group, a phenyl group as the allyl group, and a methylphenyl group as the aralkyl group are particularly preferable. The organic component is contained in an amount of 1 to 60 equivalent%, preferably 5 to 50 equivalent% based on the silicon atom in the catalyst.

In addition to silicon, the skeleton of these organic-inorganic hybrid silica mesopore molecular sieves can contain other metal oxides as the above-mentioned metallosilicates. The ratio of these other metal oxides to silicon in the mesopore molecular sieve is such that when the other metal is represented by M, the silicon / M atomic ratio is 5 or more, and preferably 10 to 100.
Organic-inorganic hybrid mesopore molecular sieves are disclosed in
It can be produced by a known method described in, for example, 0-72212.

The catalyst of the present invention is suitable as a catalyst for directly synthesizing hydrogen peroxide from hydrogen and oxygen. As a condition for directly producing hydrogen peroxide from hydrogen and oxygen, it is preferable in terms of safety that the partial pressure of oxygen to hydrogen is in the range of 50/1 to 1/50, and the reaction is carried out outside the explosion range as much as possible. An oxygen-containing gas such as air can be used instead of oxygen. The reaction medium used for the production of hydrogen peroxide is usually an aqueous medium, but it is also possible to use a mixture of water and an organic solvent forming a homogeneous phase, for example, alcohol, acetone, acetonitrile and the like. The pH of the reaction medium is preferably kept neutral to acidic. Usually, it is preferable to add a mineral acid such as sulfuric acid, phosphoric acid or hydrochloric acid or an organic acid such as formic acid, acetic acid, propionic acid or trifluoroacetic acid to maintain the acidity. The acid concentration is preferably about 0.001 to 0.5 N. The reaction temperature is usually 0 to 70 ° C., preferably 5
~ 50 ° C is used. The reaction pressure is usually from atmospheric pressure to 2
It is 0 MPa, preferably atmospheric pressure to 5 MPa.

The amount of the catalyst used in the reaction is 0.1 to 1 per liter of the reaction medium as the platinum group metal component.
About 000 mg is used. Further, as a co-catalyst, a halogen compound such as sodium chloride, ammonium chloride, sodium bromate, sodium bromide, potassium bromide, ammonium bromide, sodium iodide, potassium iodide, ammonium iodide, etc., preferably bromic acid Preference is given to adding sodium, sodium bromide, potassium bromide or ammonium chloride. The addition amount is usually 0.001 mmol to 0.1 mo with respect to 1 liter of the reaction medium.
It is l. The reaction can be performed in a batch system or a continuous system. It is also possible to adopt a method of supplying a gas phase and a liquid phase in a fixed bed method using a shaped catalyst.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below with reference to Examples, but the present invention is not limited to these Examples. In the present invention, the pore size of the catalyst is measured by the nitrogen adsorption method. The content of the metal component is measured by a fluorescent X-ray analysis method (Rig-3000 RIX-3000 model). The amount of hydrogen peroxide in the reaction solution is determined by the iodometry method.

[0018]

Example 1 124 g of tetraethoxysilane was added to a mixed solution of 30 g of n-dodecylamine and 240 g of ethanol-300 g of water. Then, 8.1 g of aluminum isopropoxide was gradually added, and the mixture was stirred until a white precipitate was observed, and the mixture was allowed to stand overnight. The white precipitate was collected by filtration and dried to obtain 52 g of white powder. This dry powder 2
0 g was calcined in air at 300 ° C. for 2 hours and then at 550 ° C. for 3 hours to remove n-dodecylamine to remove silica.
An alumina mesopore molecular sieve was obtained. This product had a specific surface area of 1100 m ² / g and a pore size of 3.4 nm.

13.5 g of the obtained mesopore molecular sieve
2.5 g of palladium chloride was added to a hydrochloric acid aqueous solution (concentrated hydrochloric acid 10
g to 100 g of purified water), evaporated to dryness and vacuum dried at 150 ° C. for 2 hours (vacuum degree ˜1 mm
Hg)). Then, reduction treatment was carried out at 300 ° C. for 3 hours in a hydrogen atmosphere, and the resultant was thoroughly washed with purified water and dried to obtain a palladium-supported mesopore catalyst. The palladium content of this catalyst was 9.8% by mass, the specific surface area was 700 m ² / g, and the pore size was 3.3 nm. The average particle diameter of palladium determined by the Schiller's formula from the half-width of the Pd diffraction peak of X-ray diffraction was 2.8 nm, and the palladium was dispersed in the nanoparticles. Then
1 g of this palladium-supported catalyst was impregnated with a solution of 31 mg of sodium tungstate dihydrate in 10 ml of water, evaporated to dryness and dried. After that, under hydrogen atmosphere 30
Reduction treatment was performed at 0 ° C. for 3 hours to obtain a tungsten-modified palladium catalyst. From the fluorescent X-ray analysis, the atomic ratio of W / Pd is 0.
It was 102.

[0020]

Example 2 A niobium-modified palladium catalyst was obtained in the same manner as in Example 1 except that 29.9 mg of niobium pentaethoxide was dissolved in 10 ml of ethanol instead of the sodium tungstate aqueous solution. . N
The b / Pd atomic ratio was 0.098.

[0021]

Example 3 Instead of the sodium tungstate aqueous solution, 21 mg of titanium tetraethoxide was added to ethanol 1
A titanium-modified palladium catalyst was obtained in the same manner as in Example 1 except that 0 ml was used. Ti /
The Pd atomic ratio was 0.099.

[0022]

Example 4 In place of the aqueous sodium tungstate solution, 40.5 mg of ytterbium nitrate tetrahydrate was added to purified water 1
The ytterbium-modified palladium catalyst was obtained in the same manner as in Example 1 except that the solution dissolved in 0 ml was used. The Yb / Pd atomic ratio was 0.10.

[0023]

Example 5 83.2 g of tetraethoxysilane and 36.6 g of methyltriethoxysilane were added to 30 g of dodecylamine.
Of ethanol (240 g) -water (300 g) was added, and the mixture was stirred until a white precipitate was observed, and the mixture was allowed to stand overnight. The white precipitate was collected by filtration and dried to obtain 54 g of white powder. 20 g of this dry powder was extracted twice with 1 liter of ethanol containing 2 ml of concentrated hydrochloric acid at 60 ° C. to remove n-dodecylamine by extraction, and dried to obtain 33 mol% of silicon having a methyl group based on the total silicon. 14 g of methyl group-containing mesopore molecular sieves were obtained. The specific surface area of the obtained mesopore molecular sieve was 900 m ² / g, and the pore size was 1.9 nm.

10 g of the obtained mesopore molecular sieve was added to hydrochloric acid-acidic ethanol-water (ethanol content 25%, concentrated hydrochloric acid 1
0.877 g of palladium chloride was added to 50 g of the solution (0 mass%), dissolved, heated, and evaporated to dryness. The same treatment as in Example 1 was carried out to obtain a palladium-supported methyl group hybrid silica / alumina mesopore molecular sieve catalyst. The palladium content of this catalyst was 4.9% by mass, and the average particle diameter of palladium was less than 2.0 nm.

This palladium-supported catalyst was prepared in the same manner as in Example 1 except that a solution prepared by dissolving 20 mg of sodium tungstate in 10 ml of purified water was used to obtain a tungsten-modified palladium catalyst. W / Pd of this thing
The atomic ratio was 0.13.

[0026]

Example 6 A silica / titania mesopore molecular sieve was obtained in the same manner as in Example 1 except that 4.53 g of tetraethoxy titanium was dissolved in 5 g of propanol instead of aluminum isopropoxide. This had a specific surface area of 980 m ² / g, a pore size of 3.2 nm, and a silica / titania atomic ratio of 32. Using the obtained mesopore molecular sieve, palladium was loaded in the same manner as in Example 2 to obtain a palladium-loaded mesopore catalyst. The catalyst had a palladium content of 4.9% by mass and a specific surface area of 800 m ^2.
/ G, and the pore size was 2.8 nm. The average particle diameter of palladium determined by the Schiller's formula from the half-width of the Pd diffraction peak of X-ray diffraction was 2.6 nm, and it was dispersed in the nanoparticles.

1 g of this Pd-supported catalyst was treated with sodium tungstate in the same manner as in Example 5 to obtain a tungsten-modified palladium catalyst. The W / Pd atomic ratio of this product was 0.12.

[0028]

Example 7 The tungsten-modified palladium-supported mesopore catalyst prepared in Example 1 was used as a catalyst for directly synthesizing hydrogen peroxide from hydrogen and oxygen. The reaction was carried out using a 300 ml autoclave (Teflon (registered trademark)).
20 ml of purified water containing 0.05 mol / L of sulfuric acid and 0.006 mol / L of sodium bromide and 10 mg of a catalyst were added to the inner liner), and after substitution with nitrogen, substitution with hydrogen was carried out, and after substitution for 1 hour at room temperature, substitution with nitrogen was performed again. 0.5MP for Chisso
a, oxygen of 0.36 MPa and hydrogen of 0.03 MPa were introduced, and the mixture was set in a water cooling bath at 10 ° C. and reacted under stirring.
The reaction was performed by adding hydrogen corresponding to the reduced pressure every hour. After the reaction for 3 hours, the hydrogen peroxide concentration in the aqueous solution was 0.
At 55% by weight, the hydrogen selectivity was 75%. The hydrogen peroxide concentration after reacting for 6 hours was 1.6% by mass.

[0029]

Example 8 A hydrogen peroxide synthesis reaction was carried out in the same manner as in Example 7 except that 10 mg of the niobium-modified palladium-supported catalyst prepared in Example 2 was used as a catalyst. as a result,
The hydrogen peroxide concentration in the reaction for 3 hours was 0.58% by mass.

[0030]

Example 9 A hydrogen peroxide synthesis reaction was carried out in the same manner as in Example 7 except that 10 mg of the titanium-modified palladium-supported catalyst prepared in Example 3 was used as a catalyst. as a result,
The concentration of hydrogen peroxide in the reaction for 3 hours was 0.45% by mass.

[0031]

Example 10 A hydrogen peroxide synthesis reaction was carried out in the same manner as in Example 7 except that 10 mg of the ytterbium-modified palladium-supported catalyst prepared in Example 4 was used as a catalyst. As a result, the hydrogen peroxide concentration in the reaction for 3 hours was 0.48% by mass.

[0032]

Example 11 Tungsten-modified palladium-supported methyl group-containing mesopore molecular sieve catalyst 10 prepared in Example 5
Same as Example 7 except that mg was used as the catalyst, except that 2 g of ethanol was added to improve the dispersibility of the catalyst,
A synthetic reaction of aqueous hydrogen peroxide was performed. As a result, the concentration of hydrogen peroxide in the reaction for 3 hours was 0.9% by mass, and after the reaction for 6 hours was 2% by mass.

[0033]

Example 12 Example 7 except that 10 mg of the tungsten-modified palladium-supported catalyst prepared in Example 6 was used as the catalyst.
In the same manner as above, a synthetic reaction of water hydrogen peroxide was performed. As a result, the hydrogen peroxide concentration in the reaction for 3 hours was 0.5% by mass.

[0034]

Comparative Example 1 Using the palladium-supported catalyst (unmodified) prepared in Example 1, a hydrogen peroxide synthesis reaction was carried out in the same manner as in Example 7. As a result, the hydrogen peroxide concentration was 0.36% by mass.

[0035]

INDUSTRIAL APPLICABILITY When the catalyst of the present invention is used for producing hydrogen peroxide directly from hydrogen and oxygen, the reaction can be carried out at a relatively low pressure and a high concentration of hydrogen peroxide can be obtained.
Exhibits excellent hydrogen selectivity.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Sai Nakamura             2950-25 Kawashima-cho, Asahi-ku, Yokohama-shi, Kanagawa F-term (reference) 4G069 AA03 BC07A BC22A BC31A                       BC35A BC38A BC44B BC50A                       BC50B BC51A BC54A BC55A                       BC55B BC56A BC58A BC59A                       BC60A BC60B BC62A BC66A                       BC67A BC68A BC69A BC70A                       BC71A BC72A BC72B BC74A                       BC75A CB81 EC05Y EC13Y                       EC14Y ZA35A ZA35B ZA37A                       ZA37B ZA38A ZA43A ZA43B                       ZF05A ZF05B

Claims (5)

[Claims] 1. A method for producing hydrogen peroxide directly from oxygen and hydrogen, which comprises a platinum group metal and at least one element selected from rare earths, titanium, niobium, nickel, molybdenum and tungsten. Catalyst used for. 2. The platinum group metal is rare earth, titanium, niobium,
The catalyst used for producing hydrogen peroxide according to claim 1, which is supported on a carrier together with at least one element selected from nickel, molybdenum and tungsten. 3. The catalyst used for producing hydrogen peroxide according to claim 1, wherein the platinum group metal is palladium. 4. The catalyst used for producing hydrogen peroxide according to claim 2 or 3, wherein the carrier is a mesopore molecular sieve. 5. A method for producing hydrogen peroxide, which comprises reacting in the presence of the catalyst according to any one of claims 1 to 4 when directly producing hydrogen peroxide from hydrogen and oxygen.