JP2003010693A - Catalyst for manufacturing hydrogen peroxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a catalyst used for directly manufacturing hydrogen peroxide from hydrogen and oxygen and having excellent activity and selectivity, and to provide a method for manufacturing hydrogen peroxide using the catalyst. SOLUTION: The catalyst is constituted by supporting a platinum group metal on a meso-pore molecular sieve and the ratio of the platinum group metal is 1-30 mass % with respect to the sum total of the platinum group metal and the meso-pore molecular sieve. Hydrogen peroxide is directly manufactured from oxygen and hydrogen by the catalyst.

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. More specifically, the present invention relates to a platinum metal catalyst using mesopore molecular sieve as a carrier 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 and requires many steps such as reduction, oxidation of the anthraquinone medium, extraction of the produced hydrogen peroxide, purification and concentration, which makes the process complicated. I have a problem. 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 and JP-A-4-23.
8802, JP-A-4-285003, JP-A-5-17106, JP-A-5-43206, JP-A-9-301705 and the like, platinum group metal is activated carbon, amorphous silica, zeolite. , Rare earth oxides,
A method in which various carriers such as titania are supported and used has been proposed.

However, according to these methods, it was necessary to carry out the reaction under a high pressure condition in order to obtain a high concentration of hydrogen peroxide. However, the use of high-pressure conditions is industrially disadvantageous, is not preferable in terms of safety in terms of reaction between hydrogen and oxygen, and has a problem that hydrogen selectivity in hydrogen peroxide production is not sufficient.

[0005]

The object of the present invention is to:
It is to provide a catalyst for the production of hydrogen peroxide directly from oxygen and hydrogen, which gives high hydrogen peroxide concentration and hydrogen selectivity under relatively low pressure. Another object of the present invention is to provide a method for efficiently producing hydrogen peroxide using this catalyst.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies in order to achieve the above object. As a result, a catalyst in which a white metal metal is supported on a mesopore silica molecular sieve is supported in a high concentration. They have found that the catalyst is highly dispersed and has excellent sintering resistance, and that this catalyst is a very excellent catalyst for directly producing hydrogen peroxide from hydrogen and oxygen, and thus reached the present invention.

That is, the present invention is as follows. (1) A catalyst in which a platinum group metal is supported on a mesopore molecular sieve, wherein the proportion of the platinum group metal is 1 to 30% by mass based on the total amount of the platinum group metal and the mesopore molecular sieve. And a catalyst for producing hydrogen peroxide directly from hydrogen. (2) The catalyst for producing hydrogen peroxide according to (1), wherein the mesopore molecular sieve is an organic-inorganic hybrid silica mesopore molecular sieve. (3) The catalyst for producing hydrogen peroxide according to (1), wherein the platinum group metal is palladium. (4) A method for producing hydrogen peroxide, which comprises reacting in the presence of a catalyst for producing hydrogen peroxide described in (1) when producing hydrogen peroxide directly from hydrogen and oxygen.

The present invention will be described in detail below. The mesopore molecular sieve of the present invention means a mesopore region, particularly a diameter of 1.
It is a metal oxide porous body having monodisperse pores of 5 to 10 nm. Examples of the element that constitutes the metal oxide include silicon, aluminum, iron, titanium, niobium, tantalum, hafnium, zirconium, tin, and rare earth elements. Examples of the metal oxide include various metallosilicates containing silicon as a main component in addition to the above-mentioned metal oxides. Examples of various metallosilicates containing silicon as a main component include, for example, aluminum, gallium, 4, 5 or 6 group transition metal elements such as titanium, vanadium and chromium.
Examples thereof include metallosilicates such as 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
~ 100.

As the mesopore molecular sieve, organic-inorganic hybrid silica mesopore molecular sieve is preferable. The organic-inorganic hybrid silica mesopore molecular sieve has an organic component bonded to silicon that forms the skeleton with respect to silicon.
It is an organic-inorganic hybrid mesopore molecular sieve having ˜60 equivalent%. These organic components are hydrocarbon groups,
An alkyl group, an allyl group and an aralkyl group are preferred. 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 1 to 60 with respect to the silicon atom in the catalyst.
Equivalent%, preferably 5 to 50 equivalent%. In addition to silicon, the skeleton of these organic-inorganic hybrid silica mesopore molecular sieves may contain other metal oxides such as aluminum, titanium, niobium, zirconium, and boron. 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, preferably 10 to 100.
Is. The organic-inorganic hybrid mesopore molecular sieve can be produced by a known method described in JP-A-10-72212.

In the present invention, a preferable catalyst is a catalyst in which a platinum group metal is supported on a mesopore molecular sieve in the form of nanoparticles (specifically, a metal particle size is 1 to 5 nm), and the platinum group metal element is , Ruthenium, rhodium, palladium, iridium, platinum and the like, and those containing palladium as a main component are more preferable. These may be used alone or in combination of two or more. The ratio of the platinum group metal is 1 to 30% by mass, preferably 2 to 20% by mass, and most preferably 2 to 10% by mass, based on the total amount of the platinum group metal and the mesopore molecular sieve.

As a method for supporting these platinum group metals, soluble salts of these elements, for example, chlorides, acetates, ammine complexes, etc., or acetylacetonate, etc. are added to organic solvents such as ion-exchanged water, methanol, acetone, etc. It is dissolved and supported by an impregnation method or an ion exchange method. Then, the carrier supporting the metal component is sufficiently dried. Dry 5
Vacuum drying is preferably performed at 0 to 150 ° C. After drying, the catalyst of the present invention is manufactured by reduction treatment at 100 to 300 ° C. under hydrogen or a mixed gas atmosphere of hydrogen and nitrogen. The reduction treatment may be performed using a reducing agent such as formalin and hydrazine in an aqueous solution.

Although the catalyst of the present invention contains a high concentration of metal components, the platinum group metal is highly dispersed and has excellent sintering resistance, and is extremely effective for the reaction in the presence of hydrogen. Is. The mesopore molecular sieve of the present invention can be shaped and used. When shaping, it is preferable to add a metal oxide or its precursor as a binder.
As the metal oxide or its precursor added as a binder, silicon oxide, aluminum oxide, zirconium oxide or their precursors such as silica sol, alumina sol and zirconia sol are preferable, and silica sol is most preferable.

As a shaping method, there are an extrusion method, a method of coating a monolith structure and the like. The binder such as silica and alumina used for shaping is usually 5 to 90% by mass, preferably 10 to 80% by mass based on the mesopore molecular sieve. The platinum group metal can be supported before or after shaping. The catalyst of the present invention is suitable as a catalyst for producing hydrogen peroxide directly 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 with an organic solvent which forms a homogeneous phase with water, 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, hydrochloric acid or the like, or an organic acid such as formic acid, acetic acid, propionic acid, trifluoroacetic acid and the like to keep 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. Reaction pressure is usually from atmospheric pressure to 20MP
a, preferably atmospheric pressure to 5 MPa.

The amount of the catalyst used in the reaction is 0.1 to 100 per liter of the reaction medium as a platinum group metal.
About 0 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 sodium bromate, sodium bromide, potassium bromide, ammonium chloride, etc. are added. Is preferred. The addition amount is usually 0.001 mmol to 0.1 mol with respect to 1 liter of the reaction medium. 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.

[0016]

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

[0017]

Example 1 Tetraethoxysilane (124 g) was added to a mixed solution of n-dodecylamine (30 g), ethanol (240 g) and water (300 g), and aluminum isopropoxide (8.1 g) was gradually added thereto, and the mixture was stirred until a white precipitate was observed. , Let stand overnight. The white precipitate is filtered and collected,
After drying, 52 g of white powder was obtained. 20g of this dry powder
Is calcined in air at 300 ° C. for 2 hours and then at 550 ° C. for 3 hours to remove the template alkylamine,
A silica / 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 was added to a solution dissolved in 100 g of purified water) and evaporated to dryness. Then vacuum dry at 150 ° C for 2 hours (~ 1mm
Hg). Then, after reduction treatment at 300 ° C. for 3 hours in a hydrogen atmosphere, the product 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 3.0 nm, and it was dispersed in the nanoparticles.

[0019]

Example 2 83.2 g of tetraethoxysilane and 36.6 g of methyltriethoxysilane were added to 30 g of dodecylamine.
Was added to a mixed solution of 240 g of ethanol and 300 g of water, and the mixture was stirred until a white precipitate was observed, and further left 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 extract n-dodecylamine. Dry the extract,
14 g of methyl group-containing mesopore molecular sieves having 33 mol% of silicon atoms having methyl groups were obtained. The specific surface area of this mesopore molecular sieve is 900 m ² / g and the pore size is 1.
It was 9 nm.

10 g of the obtained mesopore molecular sieve was added to 50 g of a solution of hydrochloric acid-acidified ethanol-water (ethanol content 25% by mass, concentrated hydrochloric acid 10% by mass) and palladium chloride 0.877.
g was added and dissolved. This was heated, evaporated to dryness, and treated in the same manner as in Example 1 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.

[0021]

Example 3 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 supported in the same manner as in Example 2 to obtain a palladium-supported mesopore catalyst. The palladium content of this catalyst was 4.9% by mass, the specific surface area was 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.

[0022]

Example 4 The palladium-supported mesopore catalyst prepared in Example 1 was used as a catalyst for directly producing hydrogen peroxide from hydrogen and oxygen. The reaction was carried out in a 300 ml autoclave (Teflon (registered trademark) lining) with sulfuric acid 0.05 mol / L,
Purified water 20 containing 0.006 mol / L of sodium bromide
ml and a catalyst (7.2 mg) were added, and the atmosphere was replaced with hydrogen and then replaced with hydrogen.
Nitrogen was introduced at 0.5 MPa, oxygen was introduced at 0.36 MPa, hydrogen was introduced at 0.03 MPa, and the mixture was set in a water cooling bath at 10 ° C. and reacted under stirring. Hydrogen was added every hour corresponding to a reduced pressure. The hydrogen peroxide concentration in the aqueous solution after the reaction for 3 hours was 0.4% by mass. The hydrogen selectivity was 75%.

[0023]

Example 5 Palladium-supported methyl group-containing silica / alumina mesopore molecular sieve 10.8 m prepared in Example 2
A hydrogen peroxide production reaction was carried out in the same manner as in Example 4 except that g was used as a catalyst. As a result, the hydrogen peroxide concentration after the reaction for 3 hours was 0.54% by mass, and the hydrogen selectivity was 80.
%, The hydrogen peroxide concentration after the reaction for 6 hours was 1.3% by mass.

[0024]

Example 6 A hydrogen peroxide production reaction was carried out in the same manner as in Example 4 except that 10.8 mg of the silica-titania mesopore molecular sieve supporting palladium prepared in Example 3 was used as a catalyst. As a result, the concentration of hydrogen peroxide after the reaction for 3 hours was 0.41% by mass.

[0025]

Comparative Example 1 Commercially available silica carrier (N-602 manufactured by JGC Kagaku)
A) was crushed and sieved, and a 45 μm pass was used to prepare a catalyst supporting palladium in the same manner as in Example 2. The amount of palladium supported on this catalyst was 5% by mass, and the average particle diameter of palladium was 14 nm. Using this catalyst, a hydrogen peroxide production reaction was carried out in the same manner as in Example 4.
As a result, the hydrogen peroxide concentration after reacting for 3 hours was 0.3% by mass, and the hydrogen peroxide concentration after reacting for 6 hours was 0.62% by mass.

[0026]

Example 7 A sintering promotion test was conducted in which the catalyst prepared in Example 1 and the catalyst prepared in Comparative Example 1 were heat-treated in a hydrogen stream at 500 ° C. for 5 hours. As a result, no increase in the palladium particle size of the catalyst of Example 1 was observed. On the other hand, in the catalyst of Comparative Example 1, an increase in particle size was observed from 14 nm to 20 nm. As a result, the catalyst of the present invention has an extremely high dispersion despite the high concentration loading, and
It was found to have sintering resistance.

[0027]

INDUSTRIAL APPLICABILITY The catalyst of the present invention is highly dispersed and excellent in stability, even though the white metal metal as an active ingredient is supported at a high concentration, and hydrogen peroxide and hydrogen peroxide directly It exhibits high hydrogen peroxide production performance at a relatively low pressure when producing.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Sai Nakajima             2950-25 Kawashima-cho, Asahi-ku, Yokohama-shi, Kanagawa F-term (reference) 4G069 AA03 BA07A BA07B BC16A                       BC16B BC22A BC38A BC50A                       BC50B BC51A BC52A BC55A                       BC56A BC66A BC69A BC70A                       BC71A BC72A BC72B BC74A                       BC75A BD05A BD05B CB81                       EC04Y EC14Y FC08 ZA35A                       ZA35B ZA37A ZA37B ZA38A                       ZA43A ZA43B ZF05A ZF05B

Claims (4)

[Claims] 1. A catalyst in which a platinum group metal is supported on a mesopore molecular sieve, wherein the proportion of the platinum group metal is 1 to 30% by mass based on the total amount of the platinum group metal and the mesopore molecular sieve. A catalyst for producing hydrogen peroxide directly from oxygen and hydrogen. 2. The catalyst for producing hydrogen peroxide according to claim 1, wherein the mesopore molecular sieve is an organic-inorganic hybrid silica mesopore molecular sieve. 3. The catalyst for producing hydrogen peroxide according to claim 1, wherein the platinum group metal is palladium. 4. A method for producing hydrogen peroxide, which comprises reacting in the presence of a catalyst for producing hydrogen peroxide according to claim 1 when directly producing hydrogen peroxide from hydrogen and oxygen.