JPS5946229B2 - Method for producing ethylene oxide - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing ethylene oxide by catalytic gas phase oxidation of ethylene with molecular oxygen, and particularly to a catalyst used in the process.

Catalysts used industrially to produce ethylene oxide by catalytic gas phase oxidation of ethylene with molecular oxygen are required to have high activity and selectivity as well as long catalyst life. Ru. Generally, a catalyst is used in which silver is supported on a suitable carrier by methods such as electrolysis, coating, and impregnation. In some known methods, catalysts consisting solely of silver are used, but in many cases various compounds, etc. are used as reaction promoters.
For example, catalysts containing compounds of alkali and alkaline earth elements, such as barium lactate, lithium carbonate, iron hydroxide, nickel hydroxide, and various compounds of group Ⅰ elements, are used. Many reports have been published regarding catalysts containing these reaction promoters. For example, special public relations
The specification of Japanese Patent Publication No. 4605 describes a catalyst consisting of silver and a sulfate of an alkali metal, the specification of Japanese Patent Publication No. 41-1095 describes a catalyst consisting of a compound of silver and an alkaline earth metal, and the specification of Japanese Patent Publication No. 44-3807 discloses a catalyst consisting of a compound of silver and an alkaline earth metal. The publication describes the use of catalysts consisting of a compound of silver and aluminum and a compound of boron.

However, it cannot be said that these known catalysts exhibit satisfactory properties in terms of ethylene conversion rate, selectivity to ethylene oxide, and catalyst life.

In particular, not all catalysts containing reaction promoters exhibit good selectivity (ie, the ability to selectively convert ethylene to ethylene oxide). Moreover, a catalyst containing a reaction accelerator has not yet been found to have a sufficient sustainability of the effect of addition. In addition to these, preparation of silver or silver compounds, addition of reaction accelerators, selection of carriers, loading of catalysts on carriers, reaction conditions, and treatment conditions for the purpose of obtaining catalysts for producing ethylene oxide suitable for industrial use. Many attempts and proposals have been made regarding this.

However, all of them have many problems to be solved and have not yet reached the level of practical use. An object of the present invention is to improve the above-mentioned problems with the known catalysts for producing ethylene oxide, and to provide a catalyst that is highly active and highly selective, and has a long life.

The present inventors have formulated a metal selected from thallium or its compounds as a reaction accelerator in a specific proportion, and precipitated it together with silver on an inorganic support having a specific specific surface area. It has been found that a catalyst in which the atomic ratio of each of the elements added as a reaction accelerator to silver is in a specific range with respect to the specific surface area of the catalyst has been found to meet this objective of the present invention.

The present invention provides a catalyst to be used when producing ethylene oxide by catalytic gas phase oxidation of ethylene with molecular oxygen.
On an inorganic support with a specific surface area of 0.1 to 37 TI/9, thallium (Tl) is added at a gram atomic ratio of e = 0.0003 to 0.01 to silver (Ag) a = 1 gram atom [however,
e/S=0,001-0.05 (S is the specific surface area of the carrier 7
This is a method for producing ethylene oxide, characterized in that it uses a catalyst comprising silver and silver supported on it.

Further, the oxygen content in the catalyst is determined by the amount of oxygen in the metal oxide or composite metal oxide formed during catalyst production. In other words, the catalyst of the present invention deposits thallium elements including silver on an inorganic support having a specific specific surface area, and has a specific atomic ratio of the thallium element to silver. , the atomic ratio of thallium (e) or the specific surface area of the support (S) is a critical ratio e/
S=0.001-0.

05, preferably within the range of 0.005 to 0.03, its excellent properties are exhibited.

As is clear from the comparative examples described below, amounts and ratios that deviate from the range defined by the present invention do not improve the selectivity at all. In particular, the ratio of the atomic ratio of thallium to silver in the additive metal to the specific surface area of the carrier, that is, the ratio of the amount of precipitated metal to the specific surface area of the carrier, is critical as shown in the Examples and Comparative Examples below, and is important for the activity. , is dominant in improving selectivity. Furthermore, the long-term sustainability of the effect is also dramatically improved. When the catalyst of the present invention is used, the detailed catalytic reaction mechanism is unknown, or the activity, selectivity, and life of the catalyst are improved compared to a catalyst in which only silver is supported on an inorganic support. In a catalyst in which silver or a silver compound is supported on an inorganic support having a specific surface area by supporting an appropriate amount of thallium element or its compound in a specific ratio, a metal element or compound added as a reaction accelerator in addition to silver and silver. It is thought that the atomic ratio of the added metal to silver and the ratio of the specific surface area of the carrier each worked synergistically to exhibit excellent performance.

The inorganic carrier used in the present invention is selected from porous inorganic carriers known in this field.

For example, it is preferable to use spherical or amorphous particles having physical properties such as a specific surface area of 0.1 to 3 TI/9, an apparent porosity of 20 to 60 (f), and a particle size of 1/8 to 5/16 inch. . Examples of suitable supports include the support sold under the trade name Alundunl by Norton, porous aggregates of molten alumina, silicon carbide and zirconia, or relatively high concentrations of Supports containing α-alumina are preferred. In the present invention, the catalyst contains 2 to 30% by weight of silver as silver metal, preferably 5 to 15% by weight of silver.

Amounts greater than this amount are not economically effective. ``Silver or silver compounds that can be used to obtain such silver metal include so-called zero-valent silver such as reduced silver and electrolytic silver, silver carbonate and silver oxide, silver nitrate, silver lactate, It is preferable to use other water-soluble silver salts such as organic water-soluble silver salts.

Thallium, which is a metallic element other than silver, used in the present invention can be used as various organic compounds or organic compounds, such as oxides, hydroxides, nitrates, etc. of each element.
It is preferable to use carbonates, sulfates, chlorides, acetates, oxalates, lactates, tartrates, etc., or water-soluble salts. It is also preferable to use a solution of an organic solvent or the like that can be burned out even by firing at a relatively low temperature. There may be various embodiments of the method for producing the catalyst according to the method of the present invention.

For example, for each metal element other than silver, an inorganic compound and/or an organic compound that can be deposited on the surface of the carrier by drying and firing is prepared using an aqueous solution or a liquid medium that can be burned out. In the impregnation method, a carrier material is immersed in the solution, the solution is drained, and the silver catalyst is obtained by drying and firing. In the coating method, the silver catalyst of the present invention is prepared by adding a carrier material to the slurry, stirring well, drying, and baking.

To explain more specifically, in the case of the impregnation method, an aqueous solution of thallium hydroxide is added to an aqueous silver lactate solution obtained by reacting silver oxide and lactic acid, then an α-alumina carrier is immersed as a carrier, and the liquid is drained. After drying, dry at 150-250℃ for 2 to 30 minutes.
By heating for 12 hours, a catalyst containing 2 to 30% by weight of silver, preferably 5 to 15% by weight, is obtained.

In addition, in the case of the coating method, an aqueous solution of thallium hydroxide is added to paste-like silver oxide, stirred well, an α-alumina carrier is added, the surface is coated, and after drying,
The catalyst is obtained by heating at 5'C for 2 to 12 hours. A supported catalyst produced by an impregnation method or a coating method is preferably further heated and treated with air, nitrogen, urinated hydrogen gas, etc. before use.

The reaction conditions for producing ethylene oxide from ethylene using the catalyst of the present invention include a temperature of 180 to 350°C, preferably 200 to 250°C, 2 to 40 kg/CTi
tl preferably 10-30 kg/CTd pressure, 3,0
00~10,000hr-1, preferably 5,000~
A space velocity of 8,500 hr-1 is preferred.

The composition of the raw material gas passed over the catalyst is ethylene 0.5
~30% by volume, 3-10% by volume of oxygen, 5-3% by volume of carbon dioxide
It is preferable that the remaining nitrogen is an inert gas such as a lower hydrocarbon (for example, methane, ethane, etc.), and 0.1 to 10 pI1n of a halogen compound such as ethylene dichloride or diphenyl chloride is added as a reaction inhibitor. It is even more preferable that it be included.

Air, pure oxygen and enriched air are advantageously used as the molecular oxygen source used in the present invention.

EXAMPLES The present invention will be explained in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples unless it goes against the spirit of the invention.

Note that the rate of change and selectivity in the main text, Examples, and Comparative Examples were calculated using the following formula. Example Silver oxide 1
209 and 4001) 6 ml of a 5.0% thallium sulfate aqueous solution was added to the silver lactate aqueous solution obtained by reacting the lactic acid aqueous solution 2609.
Add and stir well while heating to 90-100°C.

The resulting solution has a specific surface area of 0.3 d/9 and a porosity of 40 to 6.
00I), spherical α-alumina carrier 11 with a particle size of 4 to 6 mm
was soaked and concentrated to dryness.

Further, this was fired at a temperature of 150 to 200'C for 3 hours. The catalyst thus obtained had an inner diameter of 18.5 m11.
The mixture was filled into a stainless steel reaction tube with a tube length of 5 m, and heated to 250° C. under air circulation to completely decompose the organic matter. In this catalyst, the metal elements precipitated on the carrier, their amounts relative to the 19 precipitated silver atoms, and the ratio of their sum to the specific surface area of the catalyst were as shown in Table 1. Next, ethylene 1
A raw material mixed gas consisting of 5% by volume, 6% by volume of oxygen, 7% by volume of carbon dioxide, the remaining 72% by volume of inert gas such as nitrogen, methane, argon, etc., and 1 volume of ethylene dichloride was introduced into the reaction tube, and the reaction pressure was increased. The reaction was carried out at a temperature of 20k9/CTIL29, a space velocity of 6000 hr-1, and a reaction temperature of 215°C.

As a result, the results shown in Table 1 were obtained after 240 hours. Comparative Example 1 The same operation as in Example 1 was performed except that the amount of thallium sulfate was changed as shown in Table 1 to obtain a catalyst as shown in Table 1.

Using this catalyst, a reaction was carried out under the same conditions as in Example 1 except that the reaction temperature was different, and the results shown in Table 1 were obtained. Comparative Examples 2 to 5 The same operations as in Example 1 were carried out to obtain catalysts whose M/S values as shown in Table 1 were outside the range of the present invention.

Using this catalyst, a reaction was carried out under the same conditions as in Example 1 except that the reaction temperature was different, and the results shown in Table 1 were obtained. Examples 2 to 6 By the same method as in Example 1, reactions were carried out under the conditions shown in Table 1 using various elements to be deposited on the catalyst and the atomic ratio to silver, and the results were as shown in Table 1. I got good results.

Example 7 In the same manner as in Example 1, a reaction was carried out under the conditions shown in Table 2 using a catalyst whose atomic ratio to the elements to be deposited on the catalyst and silver was shown in Table 2. The results shown in Table 2 were obtained.

Comparative Examples 6 to 7 Using the same method as in Example 1, the elements to be deposited on the catalyst, the atomic ratio to silver, and the amount of supported silver were the same as in Example 1, but the specific surface area of the support was changed in Table 2. When the reaction was carried out under the conditions shown, the results shown in Table 2 were obtained.

Claims (1)

[Claims] 1. When producing ethylene oxide by catalytic gas phase oxidation of ethylene with molecular oxygen, as a catalyst used, on an inorganic carrier having a specific surface area of 0.1 to 3 m^2/g, Silver (Ag
) For a=1 gram atom, thallium (Tl) is e=0
．． 0003~0.01 [However, e/S=0.001~
0.05 (S represents the specific surface area m^2/g of the carrier)]
A method for producing ethylene oxide, characterized by using a catalyst comprising silver and supported on it.