JP2001000865A - Catalyst for producing ethylene oxide and method for producing ethylene oxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a catalyst for producing ethylene oxide having both high selectivity and excellent activity. SOLUTION: Ethylene characterized in that at least one kind of alkali metal and at least one kind of Group 4 element are supported as a pretreatment on a porous carrier, and then silver and at least one kind of alkali metal are supported. For producing ethylene oxide by oxidizing water and a method for producing ethylene oxide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an improved silver catalyst for producing ethylene oxide by subjecting ethylene to gas phase catalytic oxidation with molecular oxygen, and to a method for producing ethylene oxide. Ethylene oxide is used for the production of nonionic surfactants by addition polymerization of active hydrogen compounds, and is also used to make ethylene glycol by adding water, which is used as a raw material for polyester and polyurethane polymers, antifreeze for engines, etc. .

[0002]

2. Description of the Related Art A silver catalyst is used for industrially producing ethylene oxide by subjecting ethylene to gas phase catalytic oxidation with molecular oxygen. In order to efficiently produce ethylene oxide, there is a strong demand for improvement of the catalyst, and there is a demand for a catalyst having higher selectivity and longer life. For this reason, various methods have been conventionally proposed, but a combination of silver as a main active ingredient and an alkali metal or the like as a reaction accelerator, optimization of a compounding ratio thereof, improvement of a carrier carrying these, and the like have been proposed. That is the main thing.

For example, in US Pat. Nos. 4,908,343 and 5,057,481, various salts having cesium as a cation as a reaction accelerator and an oxyanion of a Group 3 to 7 element as an anion are supported. The catalyst is also U
SP 5, 102, 848 discloses an oxyanion of an element having a cation of lithium, sodium, potassium, rubidium, cesium, or the like, and having an atomic number of 21 to 74 selected from sulfate ion, fluoride ion, and group 3 to 6 groups. Catalysts supporting various salts having three components as anions have been disclosed. Further, US Pat. No. 5,703,001 discloses that rhenium-free promoting amounts of alkali metals and
It is stated that selectivity and lifetime are improved by a catalyst containing a Group 4 element added with a compound containing a Group 4 element cation. On the other hand, catalysts in which a carrier is pre-impregnated with an alkali metal have also been proposed (see JP-A-55-127144, JP-A-4-346835 and JP-A-8-244777).

[0004]

As described above, various proposals have been made regarding the use of Group 4 as a reaction accelerator, etc., and even when an alkali metal is used, for a catalyst for producing ethylene oxide. I have. However, the level has not yet reached a sufficiently satisfactory level, and efforts are being made to improve catalyst performance. An object of the present invention is to provide a catalyst for producing ethylene oxide which has higher selectivity and excellent activity as compared with conventional catalysts.

[0005]

According to the present invention, at least one of an alkali metal and at least one of a Group 4 element is supported on a porous carrier as a pretreatment, and then silver and at least one of an alkali metal are supported. The present invention relates to a catalyst for producing ethylene oxide by oxidizing ethylene, and a method for producing ethylene oxide.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the catalyst of the present invention will be described in detail. (Porous carrier) The catalyst of the present invention is a catalyst in which silver is supported on a porous carrier as a main component of the catalyst. Examples of the porous carrier include porous refractories such as alumina, silicon carbide, titania, zirconia, and magnesia.
Those which are alumina are particularly preferred. The porous carrier may contain a silica component with an upper limit of usually about 10%.

In the present invention, the physical properties of the porous carrier may greatly affect its catalytic activity, and the surface area of the porous carrier is usually 0.1 to 10 m ² / g, preferably 0.6 to ⁵ m ^{2. 2} / g, more preferably 0.8 to ² m ² /
g is desirable. Further, from the viewpoint of maintaining the surface area and facilitating the impregnation operation of the catalyst component, the water absorption of the carrier is preferably 20 to 50%, more preferably 25%.
~ 45% is desirable.

(Preparation of catalyst) The catalyst of the present invention is prepared by supporting an alkali metal and a Group 4 element on a porous carrier, and then supporting silver and an alkali metal.
Of the two stages of the supporting treatment, the first step of supporting the alkali metal and the Group 4 element on the porous carrier is referred to as a “pretreatment step”. This will be defined as "this processing step".

(Pretreatment step) The metals supported on the porous carrier in the pretreatment step are an alkali metal and a Group 4 element. The alkali metal may be, for example, any of lithium, sodium, potassium, rubidium, cesium and the like, but cesium is preferred. These are used alone or in combination of two or more. The Group 4 element may be, for example, any of titanium, zirconium and hafnium, but titanium is preferred. These can be used alone or in combination of two or more.

The amount of the alkali metal carried is preferably 50 to 2000 ppm, more preferably 100 to 1000 ppm, based on the total weight of the catalyst. The supported amount of the group 4 element is
Preferably 10 to 2000 ppm, more preferably 10
１０００1000 ppm. The kind of the alkali metal compound used in the pretreatment step is not particularly limited, and examples thereof include a nitrate, a hydroxide, a halide, a carbonate, a bicarbonate, an oxalate, and a carboxylate. The type of the Group 4 element compound is not particularly limited, and examples thereof include oxychloride, oxynitrate, oxycarbonate, halide, sulfate, nitrate, and halogenated quaternary ammonium salt.

In the pretreatment step, the solvent of the solution used for supporting the alkali metal compound and the group 4 element compound on the carrier may be any solvent which is soluble in the alkali metal compound and the group 4 element compound used. Water, a low-boiling organic solvent, a mixture of water and a low-boiling organic solvent, and the like can be used. As a method for impregnation, a method in which a porous carrier is immersed in a solution containing an alkali metal compound and a solution containing a Group 4 element compound, or a solution containing an alkali metal compound in a porous carrier and a Group 4 element compound A method of spraying a solution containing In this treatment, the treatment with the solution containing the alkali metal compound and the treatment with the solution containing the group 4 element compound may be performed separately, or the solution containing the alkali metal compound and the group 4 element compound may be used separately. And a solution containing both.

In the pretreatment step, as a method for supporting an alkali metal and a Group 4 element, a conventionally known method can be adopted. For example, a solution containing an alkali metal on a porous carrier and a solution containing a Group 4 element on a porous carrier are used. , And then carried out by a drying treatment. As the drying process,
After the impregnating treatment, separation of the porous carrier, the excess alkali metal compound and the group 4 element compound-containing solution, and then drying under reduced pressure or drying by heat treatment may be mentioned. The heat treatment is preferably performed at 100 to 300 ° C., more preferably 13 to 300 ° C.
A method using air, an inert gas such as nitrogen, or superheated steam at 0 to 270 ° C. is preferable. Particularly preferred is a method utilizing superheated steam.

(Main Processing Step) The main processing step of the present invention is as follows.
This is a process in which silver and an alkali metal are supported on a porous carrier that supports an alkali metal and a Group 4 element in the pretreatment step. The alkali metal used in this treatment step may be any of lithium, sodium, potassium, rubidium, cesium and the like as in the pretreatment. These can be carried by one type or two or more types.

The supported amount of silver is preferably 5 to 30% by weight, more preferably 8 to 20% by weight, based on the total weight of the catalyst. The supported silver is usually present on the support in the form of metallic silver. The amount of the alkali metal carried is preferably 10 to 10000 ppm, more preferably 50 to 5000 ppm, based on the total weight of the catalyst. When the alkali metal is cesium, 200 to 2000 ppm is particularly preferable. The total amount of the alkali metal contained in the catalyst of the present invention,
It is the sum of the amount carried in the pretreatment step and the amount carried in the main treatment step.

In the present processing step, examples of the silver compound advantageously used for supporting silver on a carrier include silver oxide, silver nitrate, silver carbonate, and various silver carboxylate such as silver acetate and silver oxalate. For example, it forms a complex soluble with an amine compound in a solvent and decomposes at a temperature of 500 ° C. or lower, preferably 300 ° C. or lower, more preferably 260 ° C. or lower to deposit silver. Of these, silver oxalate is particularly preferred. As the amine compound as a complexing agent, a compound that can solubilize the silver compound in a solvent is used. Such amine compounds include, for example, pyridine,
Ammonia and amines having 1 to 6 carbons. Among them, ammonia, pyridine, monoamines such as butylamine, alkanolamines such as ethanolamine, and polyamines such as ethylenediamine and 1,3-propanediamine are preferable. Particularly, the use of ethylenediamine and / or 1,3-propanediamine, particularly the mixed use thereof, is optimal.

The kind of the alkali metal compound used in this treatment step is not particularly limited, and examples thereof include nitrates, hydroxides, halides, carbonates, bicarbonates, oxalates and carboxylate salts. . In the present treatment step, a method for supporting the silver compound and the alkali metal compound can be a conventionally known method, for example, impregnated with a solution containing the silver compound and the alkali metal compound on the pre-treated porous carrier, Then, by carrying out a heat treatment, it can be supported.

As a method for impregnating a silver compound, it is most practical to use the silver compound in the form of an aqueous solution with an amine compound, but it can also be used as an aqueous solution to which an alcohol or the like is added. Finally, the silver concentration in the impregnating solution is determined so that 5 to 30% by weight of silver is supported as a catalyst component.
After the impregnation, if necessary, pressure reduction, heating, spraying, and the like can also be performed. The amine compound is added in an amount necessary to complex the silver compound (usually two amino groups correspond to one silver atom). In this case, it is preferable to add the amine compound in excess of the required amount by 5 to 30% from the viewpoint of reactivity.

The alkali metal compound may be dissolved in an aqueous solution of a silver compound and supported on a carrier simultaneously with silver. The heat treatment after the impregnation is performed by measuring the temperature and time required for silver to precipitate on the carrier. It is most preferable to select the conditions under which silver precipitates on the carrier as uniformly as possible and in the form of fine particles. Generally, the heat treatment is not preferable because the higher the temperature and the longer the time, the more the aggregation of the precipitated silver particles is promoted. Preferred heat treatment is 130 ° C to 300 ° C.
The use of heated air (or an inert gas such as nitrogen) or superheated steam at a temperature of 5 ° C. can be carried out in a short time of 5 to 30 minutes, which is also desirable from the viewpoint of shortening the time for the catalyst preparation step. It is particularly preferable to use superheated steam in that the distribution of silver on the carrier is uniform and the catalytic performance is improved.

(Reaction Method) The reaction for converting ethylene to ethylene oxide using the catalyst of the present invention can be carried out by a conventional operation. The reaction pressure is usually 0.1 to 3.6 MPa (0 to
35 kg / cm ² G), and the reaction temperature is usually 180 to
The temperature is 350 ° C, preferably 200 to 300 ° C. The composition of the reaction raw material gas is generally 1 to 40% by volume of ethylene,
A mixed gas containing 1 to 20% by volume of molecular oxygen is used, and generally a diluent, for example, an inert gas such as methane or nitrogen can be present at a fixed ratio, for example, 1 to 70% by volume. Air or industrial oxygen is usually used as the molecular oxygen-containing gas. Furthermore, by adding a halogenated hydrocarbon, for example, about 0.1 to 50 ppm as a reaction modifier to the reaction raw material gas, formation of hot spots in the catalyst can be prevented, and the performance of the catalyst, in particular, the catalyst selectivity is greatly reduced. Can be improved.

[0020]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Example 1 (1) Pretreatment Step An α-alumina carrier (surface area: 1.04 m ² /
g, a water absorption of 32.3%, an average pore diameter of 1.4 μm, silica of 3%, and a ring of 8 mm × 3 mm × 8 mm) 30 g were immersed in 50 ml of an aqueous solution in which 0.043 g of cesium carbonate (Cs ₂ CO ₃ ) was dissolved. , Drain the excess liquid and then
The carrier was heated with superheated steam at 50 ° C. for 15 minutes at a flow rate of 2 m / sec to prepare a carrier impregnated with cesium. Then
Ammonium fluorotitanate ((NH ₄ ) ₂ TiF ₆ )
9.7 ml of an aqueous solution in which 0.007 g was dissolved was impregnated with 30 g of an α-alumina carrier impregnated with cesium while heating at 40 ° C. under reduced pressure in an evaporator. This impregnated carrier was heated with superheated steam at 200 ° C. for 15 minutes at a flow rate of 2 m / sec to prepare a carrier impregnated with cesium and titanium.

(2) Preparation of silver oxalate 228 g of silver nitrate (AgNO ₃ ) and potassium oxalate (K
After dissolving each in 1 liter of water _{2 C 2 O 4 · H 2} O) 135g, gradually mixed while heating to 60 ° C. in an aqueous solution to give a white precipitate of silver oxalate. After filtration, the precipitate was washed with distilled water to remove potassium in the precipitate.

(3) Preparation of Silver Amine Complex Solution A part (6.95 g) of the silver oxalate (Ag ₂ C ₂ O ₄ , water content 17.09%) obtained in (2) was subjected to 2.05 g of ethylenediamine. , Propanediamine and 0.56 g of water and 2.65 g of water were gradually dissolved to prepare a silver amine complex solution. 0.72 ml of water is added to this silver amine complex solution, and 0.6 ml of a mixed aqueous solution containing 1.14 wt% of cesium chloride (CsCl) and 1.98 wt% of cesium nitrate (CsNO ₃ ) is further stirred. Was added.

(4) The present treatment step The silver amine complex solution containing cesium was added to 30 g of the α-alumina carrier impregnated with cesium and titanium prepared in (1) in an evaporator under reduced pressure while heating at 40 ° C. Impregnation. This impregnated carrier is heated with superheated steam at 200 ° C. for 1 hour.
Heating was performed for 5 minutes at a flow rate of 2 m / sec to obtain a catalyst. The supported amounts of silver (Ag), cesium (Cs) and titanium (Ti) in the catalyst were 12%, 595 ppm, 5
It was 0 ppm.

(5) Production of ethylene oxide The catalyst prepared by the above method is crushed to 6 to 10 mesh,
3 ml thereof was filled into a SUS reaction tube having an inner diameter of 7.5 mm, and a reaction gas (ethylene 30%, oxygen 8.5%, vinyl chloride 1.5ppm, carbon dioxide 6.0%, remaining nitrogen)
With a GHSV of 4300 h ^-1 and a pressure of 0.8 MPa (7 kg
/ Cm ² G) to carry out the reaction. Start reaction 1
Table 1 shows the reaction temperature T40 (° C.) when the oxygen conversion becomes 40% and the selectivity S40 (%) of ethylene based on ethylene when the oxygen conversion becomes 40% after a lapse of one week.

Example 2 A catalyst was prepared and reacted in the same manner as in Example 1 except that the concentration of the solution was changed so that the amount of titanium carried was 100 ppm. Table 1 shows the reaction results. Example 3 The amount of cesium supported in this treatment step was 553 ppm
A catalyst was prepared and reacted in the same manner as in Example 2 except that the concentration of the solution was changed so that the concentration was 753 ppm. Table 1 shows the reaction results.

Example 4 A catalyst was prepared and reacted in the same manner as in Example 3 except that the concentration of the solution was changed so that the amount of titanium carried was 200 ppm. Table 1 shows the reaction results. Example 5 Instead of ammonium fluorotitanate, ammonium fluorozirconate ((NH ₄ ) ₂ ZrF ₆ ) was used.
A catalyst was prepared and reacted in the same manner as in Example 1 except that the concentration of the solution was changed so that the amount of zirconium (Zr) carried was 100 ppm. Table 1 shows the reaction results.

The change density of the solution such that the supported rate is 100ppm oxychloride hafnium octahydrate in place of Example 6 ammonium fluoride titanate (HfOCl ₂ · 8H ₂ O) with, hafnium (Hf) A catalyst was prepared and reacted in the same manner as in Example 1 except that the reaction was performed. Table 1 shows the reaction results.

Comparative Example 1 Example 1 except that titanium was not supported on the carrier in the pretreatment step.
A catalyst was prepared and reacted in the same manner as described above. Table 1 shows the reaction results. Comparative Example 2 In the pretreatment step, titanium was not supported on the carrier, and in this treatment step, a 4.7% by weight aqueous solution of ammonium fluoride titanate of 0.6% was used.
A catalyst was prepared in the same manner as in Example 1 except that the solution was further impregnated with a cesium-containing silver amine complex solution so that the supported amount of titanium became 100 ppm, and the added solution was impregnated with a cesium-impregnated carrier. The reaction was performed. Table 1 shows the reaction results. Comparative Example 3 In a pretreatment step, titanium was not supported on a carrier, and in this treatment step, a 4.7% by weight aqueous solution of ammonium fluoride titanate of 0.6% was used.
A catalyst was prepared in the same manner as in Example 3, except that the solution was further impregnated with a cesium-containing silver amine complex solution so that the supported amount of titanium became 100 ppm, and the added solution was impregnated with a cesium-impregnated carrier. The reaction was performed. Table 1 shows the reaction results.

[0030]

[Table 1]

[0031]

According to the present invention, a catalyst in which at least one alkali metal and at least one Group 4 element are supported on a porous carrier, and then silver and at least one alkali metal are supported on the porous carrier. By using, ethylene oxide can be produced with a high selectivity under mild conditions as compared with conventional catalysts.

[Procedure amendment]

[Submission date] August 31, 1999 (1999.8.3)
1)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 8

[Correction method] Change

[Correction contents]

 ──────────────────────────────────────────────────続 き Continuing on the front page F term (reference) 4G069 AA03 AA08 AA15 BA01A BA02B BA27A BB08B BB12B BB16B BC01A BC03B BC06A BC06B BC32A BC32B BC50A BC50B BC52B BD12B BD15B BE14A CB08 EA06 EA18 EC02XEBEC02 EC02FB02

Claims (12)

[Claims] 1. A porous carrier comprising, as a pretreatment, at least one kind of alkali metal and at least one kind of Group 4 element, and then carrying at least one kind of silver and at least one kind of alkali metal. Catalyst for producing ethylene oxide by oxidizing ethylene. 2. The catalyst according to claim 1, wherein the alkali metal supported on the porous carrier as pretreatment is cesium. 3. The catalyst according to claim 1, wherein the Group 4 element is titanium. 4. An alkali metal loaded on a porous carrier as a pretreatment in an amount of 50 to 2000 ppm based on the total weight of the catalyst,
Further, the Group 4 element is 10 to 2000 ppm.
The catalyst according to any one of claims 1 to 3. 5. A pretreatment wherein silver to be carried on a porous carrier carrying at least one kind of alkali metal and at least one kind of Group 4 element is 5 to 30% by weight based on the total weight of the catalyst. The catalyst according to any one of claims 1 to 4, wherein the catalyst is 10 to 10000 ppm. 6. A porous carrier having a surface area of 0.6 to ⁵ m ² /
The catalyst according to any one of claims 1 to 5, which is g. 7. The catalyst according to claim 1, wherein the main component of the porous carrier is α-alumina. 8. The pretreatment is characterized in that the porous carrier is impregnated with a solution containing an alkali metal compound and a solution containing a Group 4 element compound, and then dried and supported. The catalyst according to any one of the above. 9. The catalyst according to claim 8, wherein superheated steam is used in the drying treatment of the pretreatment. 10. A porous carrier supporting at least one kind of alkali metal and at least one kind of Group 4 element as a pretreatment, a silver compound, at least one kind of alkali metal compound, and an amine compound as a complexing agent. The catalyst according to any one of claims 1 to 9, wherein the catalyst is impregnated with a solution containing, and then heat-treated to support silver and an alkali metal. 11. The catalyst according to claim 10, wherein superheated steam is used in the heat treatment for supporting silver and the alkali metal. 12. A process for producing ethylene oxide, comprising subjecting ethylene to gas-phase catalytic oxidation with molecular oxygen in the presence of the catalyst according to any one of claims 1 to 11.