Silver catalyst to obtain ethylene oxide, method of its preparation and a method of producing ethylene oxide

 

(57) Abstract:

The invention relates to the field of silver catalysts for production of ethylene oxide and to methods of its preparation. The catalyst contains media comprising as a main component is aluminum oxide, and silicon oxide and a metal or compound of at least one element selected from elements of groups Ib and IIb of the periodic system of elements, such as, for example, silver oxide and precipitated silver as the active ingredient. This carrier is obtained by mixing at least-aluminum oxide, silicon compound, an organic binder and a compound of at least one element selected from elements of groups Ib and IIb of the periodic system of elements, followed by firing the mixture at a temperature in the range 1000-1800°C. the obtained carrier precipitated silver in the amount of 1-30 wt.%. The catalyst may contain alkali metal in an amount of 0.01-100 MK mol/m surface area of a specified catalyst. The catalyst allows to obtain ethylene oxide with high selectivity for a long time. 3 S. and 11 C.p. f-crystals, 1 table.

The invention relates to a catalyst for obtaining the ACS is refers to the silver catalyst, which has advantages in catalytic activity, selectivity and durability, and allows to obtain ethylene oxide with higher selectivity for a longer time to method thereof and method of producing ethylene oxide using this silver catalyst.

The production of ethylene oxide by catalytic vapor-phase oxidation of ethylene gas containing molecular oxygen, in the presence of a silver catalyst, is widely used on an industrial scale. As for the silver catalyst, which should be used for the catalytic vapor-phase oxidation, were filed patent applications on numerous inventions, covering the media for such a catalyst, methods of applying a catalyst on such media and the promoters of the reaction.

For example, the patent application US-5077256 expounds the idea of using media, which is formed by applying a coating layer of amorphous silicon oxide on a carrier of alumina. Japanese patent application A-02-363139 expounds the idea of using media that is produced by adding to-alumina compounds of one whom the on periods and groups IlIa - VIIa and Illb - Vb of the periodic system of elements (such as, for example, titanium, tin, hafnium) firing of these stacked on top of other layers.

Although the proposed up to the present time silver catalysts already have a high level of selectivity, it was considered desirable to give greater selectivity of these silver catalysts, since the scale of the receipt of the ethylene oxide so great that even the increase in selectivity of only 1% can lead to significant savings of ethylene as raw material, and, therefore, to provide significant economic benefits. Under the existing circumstances, the development of a silver catalyst having the best catalytic efficiency, remains an ongoing challenge for researchers in this field of technology.

However, the silver catalysts, which are described in the aforementioned patent publications, have insufficient selectivity and unsatisfactory from the point of view of life.

Thus, the objective of this invention to provide a silver catalyst has excellent catalytic capabilities and allows to obtain ethylene oxide with high selectivity over a silver catalyst.

This problem is solved by using a silver catalyst to obtain ethylene oxide, which is formed by deposition of silver on the carrier, the main component of which is aluminum oxide including silicon oxide and a metal or compound of at least one element selected from the class consisting of elements of groups Ib and IIb of the periodic system of elements.

In addition, the problem is solved using the method of preparation of a catalyst to obtain ethylene oxide, which comprises mixing at least-aluminum oxide, silicon compound, an organic binder and a compound of at least one element selected from elements of groups Ib and IIb of the Periodic system of elements, the subsequent firing the obtained mixture at a temperature in the range of 1000 - 1800oC obtaining in this way the media, and the subsequent application of at least silver on this media.

Further, this task is solved by the method of producing ethylene oxide, which includes providing a vapor-phase oxidation of ethylene gas containing molecular oxygen, in the presence of the above catalyst to obtain ethylene oxide.

The authors set is in the media, consisting mainly of aluminum oxide, to enter the silicon oxide and a metal or compound of at least one element selected from the class consisting of elements of groups Ib and IIb of the Periodic system of elements (typical is the silver oxide). Based on this, the authors have successfully carried out this invention.

Thus, the catalyst to obtain ethylene oxide according to this invention has improved characteristics in terms of activity, selectivity and durability and allows to obtain ethylene oxide with high selectivity for a long time.

The carrier used in this invention, form the introduction of the aluminum oxide, which is the main component, metal or compounds of at least one element selected from the class consisting of elements of groups Ib and IIb of the periodic system of elements.

The bearer of this structure is obtained by mixing particles of aluminum oxide, silicon compound, an organic binder and a metal or compound of at least one element selected from elements of groups Ib and IIb of the periodic system of elements; optionally forming from the mixture of particles of a given size and shape, then ü according to this invention, containing the aluminum oxide as its main component, usually consists of 65 - to 99.5 wt.%, Preferably 90 to 99 wt. percent aluminum oxide, 0 to 30 wt.%, preferably 0 to 10 wt.%, amorphous aluminum oxide, 0 to 5 wt.%, preferably 0.01 to 4 wt.% (as oxide) of alkali and 0 to 5 wt.%, preferably 0.01 to 3 wt.%, oxide of the transition metal.

As for the particle diameter of the carrier, consisting mainly of aluminum oxide, the initial particle size of the aluminum oxide is 0.01 - 100 μm, preferably 0.1 to 20 μm, more preferably 0.5 to 10 μm, and particularly preferably 1 to 5 microns in diameter. The size of the secondary particles of aluminum oxide should be 0.1 - 1000 μm, preferably 1 to 500 μm, more preferably 10 to 200 μm, and particularly preferably 30 to 100 microns in diameter.

A silver catalyst according to this invention is characterized by a carrier, which is formed in such a way that in the media, consisting mainly of aluminum oxide, introducing a silicon oxide and a metal or compound of at least one element selected from elements of groups Ib and IIb of the periodic system of elements.

In this invention, this carrier will be called "finished and it finally processed media concentrated nitric acid can be monitored using x-ray fluorescence analysis most of the compounds of silver was recorded in the media. Thus, we can assume that this is finally processed the carrier has a structure in which at least part of the surface of the aluminum oxide layer is formed of silicon oxide, and silver oxide occluded in the layer of silicon oxide.

As the metals or compounds of elements of groups Ib and IIb of the periodic system of elements include such metals as copper, silver, gold and zinc, or their compounds, for example oxides. Among the above-mentioned metals and compounds most preferred for use are silver oxide, and zinc. The best choice is silver oxide.

The content of silicon oxide is typically in the range of 0.01 - 15 wt.%, preferably 0.1 to 10 wt.%, and more preferably 1 to 5 wt.% in relation to the total number of media. The content of the metal or compound of at least one element selected from the class consisting of elements of groups Ib and IIb of the periodic system of elements is typically in the range 0.001 to 15 wt.%, preferably 0,01 -10 wt.%, and more preferably 0.1 to 5 wt.% based on the metal.

To obtain the above-mentioned final obrasocial can be easily obtained by mixing at least an aluminum oxide and an organic binder with a silicon compound as the source of silicon oxide and a metal or compound of at least one element, selected from elements of groups Ib and/or IIb of the periodic system of elements, followed by firing the mixture at a temperature in the range of 1000 - 1800oC, preferably 1400-1700oC.

As typical examples of the above-mentioned silicon compounds include compounds with covalent bonds, such as silicon oxide, silicon nitride, silicon carbide, silane sulfate and silica; silicates such as sodium silicate, ammonium silicate, sodium aluminosilicate, aluminosilicate ammonium, sodium and ammonium salts of phosphorus-silicic acid; compound with silicon-containing compounds such as feldspar and clay; and mixtures containing silicon oxide.

As typical examples of the organic binder can lead methylcellulose, ethylcellulose, hydroxyethyl cellulose, carboxymethyl cellulose, corn starch and alkali metal salts of these compounds.

As typical examples of the compounds of elements of groups Ib and IIb of the periodic system of elements can result in such metals as copper, silver, gold and zinc, preferably silver, and zinc, as well as oxides, organic acid salts and inorganic salts of such metals. Among others, the above compound salt (for example, such as acetates), inorganic salts (such as silver chloride), etc., is Shown, which is particularly desirable is the use of silver oxide.

It is only necessary that the amount of coupling at least one element selected from elements of groups Ib and IIb of the periodic system of elements, which should be used was such that the content of the metal compound (oxide) could fall into the above interval relative to the number of finished media. And the amount of silicon compound should be such that the content of silicon oxide could fall into the above interval relative to the number of finished media.

It is necessary that the purity of the powder of aluminum oxide, which should be used for educational media, the main component of which is aluminum oxide, was not less than 90%, preferably at least 95%, more preferably at least 99%, and particularly preferably not less than 99.5% pure. The size of the primary particles of aluminum oxide is 0.01 - 10 μm, preferably 0.1 to 3 microns in diameter. Suitable size of secondary particles of aluminum oxide is 1 to 100 μm, predoc main component, may include aluminum oxide, especially amorphous aluminum oxide, silicon oxide, aluminium silicate, mullite, and zeolite (which will be referred to under the collective name of "amorphous oxides of aluminum"); oxides of alkali metals and oxides of alkaline earth metals such as potassium oxide, sodium oxide and cesium oxide (which will be referred to under the collective name of "alkali"); and oxides of transition metals, such as iron oxide and titanium oxide, in addition to the above-alumina.

It is necessary that the above-mentioned finished carrier had a specific surface area by BET method in the range of 0.03 - 10 m2/g, preferably 0.1 to 5 m2/g and more preferably of 0.5 - 2 m2/, If the specific surface area is excessively small, usually due to the fact that the media is excessively sintered, he will not be able to achieve sufficient absorption coefficient of water, and will not be able to effectively carry catalytic component. On the contrary, if the specific surface area is excessively large, the media will have excessive pores of small diameter, and the formed ethylene oxide is involved in accelerated sequential reaction.

Water absorption ratio of Dalgety excessively low, the media will not be able to effectively carry catalytic component. On the contrary, if the absorption coefficient of water is excessively high, the media will not reach sufficient for practical purposes tensile crushing.

The average diameter of the pores should be in the range of 0.1 - 5 μm, preferably 0.2 to 3 μm, more preferably of 0.3 - 0.9 μm. If the average pore diameter is excessively small, the resulting gas will stagnate, and the resulting ethylene oxide is involved in accelerated sequential reaction.

For the finished carrier is not particularly significant form of its particles. This form can be, for example, in the form of spheres, tablets or rings. The media should have an average diameter in the range of 0.1 - 30 mm, preferably 1 to 15 mm

The catalyst according to this invention to obtain ethylene oxide is usually formed by plotting finished media promoter reactions and what they use as a secondary promoter reactions in addition to silver. As typical examples of the promoter reactions can lead to alkali metals, particularly potassium, rubidium, cesium and mixtures thereof. Among the other aforementioned metals, the most suitable for use is clinic funds to accelerate the reaction, which should be applied. They need only enough to obtain ethylene oxide. For example, a suitable interval silver content is 1-30 wt. %, preferably 5-20 wt.% relative to the weight of catalyst to obtain ethylene oxide. The amount of alkali metal, which must be applied, may lie in the range from 0.01 to 100 µmol/m2, preferably 0.1 to 50 µmol/m2, more preferably 0.5 to 20 µmol/m2and particularly preferably 1 to 10 µmol/m2.

The catalyst according to this invention to obtain ethylene oxide can be made according to the traditional method of producing ethylene oxide using the aforementioned finished carrier as the carrier for catalyst.

For example, a carrier to obtain ethylene oxide receive, as described in JP-A-62-114654, soaking the above prepared carrier with an aqueous solution prepared by dissolving in water of silver salts, such as, for example, silver nitrate, silver carbonate, silver oxalate, silver acetate, propionate, silver, silver lactate, silver citrate and/or needcan silver, and a complexing agent, such as, for example, m is abucay dried carrier in air at a temperature in the range of 50 - 400oC, preferably 90 -300oC, which leads to the deposition of metallic silver in the form of fine particles on the inner and outer surfaces of the carrier. The reaction promoter and other components can be dissolved in an aqueous solution of silver-amine complex before the comprehensive carrier is impregnated with this aqueous solution, and the resulting solution can be used during impregnation or deposited after the deposition of the silver.

Obtaining ethylene oxide by vapor-phase oxidation of ethylene in the presence of a catalyst to obtain ethylene oxide according to this invention can be carried out following the standard procedure, using as catalyst for the oxidation catalyst to obtain ethylene oxide according to this invention.

In the production on an industrial scale is used, for example, the reaction temperature in the range 150 - 300oC, preferably 180 to 280oC, the reaction pressure (gauge) in the range of 0.2 - 4 MPa (2 to 40 kg/cm2), preferably 1 to 3 MPa (10 to 30 kg/cm2), and space velocity in the range of 1000 - 30000 h-1(N. W.), preferably 3000 to 8000 h-1(N. y.). The supply gas, which must pass through catalysate as nitrogen, argon, steam and lower hydrocarbons such as methane and ethane, and about 0.1 - 10 million hours (ppm) (by volume) halides, such as ethylene dichloride and ethyl chloride as an inhibitor of the reaction.

As typical examples containing molecular oxygen gas, which should be used in this invention include air, oxygen enriched air.

The degree of conversion and selectivity, which are mentioned in the following examples and control experiments, represent the values calculated in accordance with the following formulas.

The degree of conversion (%) = [(Number of moles of ethylene consumed in the reaction)/(Number of moles of ethylene contained in the feed gas)] x 100

Selectivity (%) = [(Number of moles of ethylene converted to ethylene oxide)/(Number of moles of ethylene absorbed in the reaction)] × 100

Next, this invention will be described more specifically with reference to examples. The symbol"% " used here means "wt.%" .

Example 1.

Finally the processed media was prepared by thorough mixing 900 g powder-alumina (diameter of primary particles of 1.5 μm and the diameter of the secondary particles of 45 m is hydroxyethyl cellulose, 50 g of carboxymethyl cellulose, 50 g of corn starch and 100 g ANZUBURID with 100 g water added to them, by extrusion molding the mixture, cutting the extruded mixture into tablets (10 mm in diameter and 10 mm in length), drying of these tablets and firing the dried pellets at 1500oC within 2 hours.

The catalyst (A) to obtain ethylene oxide was obtained by soaking 300 g ready carrier (specific surface area of 1.0 m2/g according to BET, the coefficient of water absorption of 34% and an average pore diameter of 0.8 μm) solution of complex, composed of 57.3 g of silver oxalate, and 38.6 ml of monoethanolamine, 41,4 ml of water and 0.18 g of cesium nitrate, heat treatment of the impregnated carrier, drying, hot carrier at 120oC for 1 hour and heat treatment of the dried carrier in a stream of air at 300oC for 0.25 hour.

Example 2

Finally the processed media, and then the catalyst (C) to obtain ethylene oxide were obtained according to the procedure of example 1 while changing the number of silver oxide with 10 g to 30 g

Example 3

Finally the processed media, and then the catalyst (C) to obtain ethylene oxide were obtained according to the procedure prinia processed media and then the catalyst (D) to obtain ethylene oxide were obtained according to the procedure of example 1, using 20 g of silver powder (released Wako Junyaku Co., Ltd.) instead of 10 g of silver oxide.

Example 5

Finally the processed media, and then the catalyst (E) to obtain ethylene oxide were obtained according to the procedure of example 1, using 20 g of silver acetate (released Wako Junyaku Co., Ltd.) instead of 10 g of silver oxide.

Example 6

Finally the processed media, and then the catalyst (F) to obtain ethylene oxide were obtained according to the procedure of example 1, using 20 g of silver chloride (released Wako Junyaku Co., Ltd.) instead of 10 g of silver oxide.

Example 7

Finally the processed media, and then the catalyst (G) to obtain ethylene oxide were obtained according to the procedure of example 1, using 20 g of silver nitrate (released Wako Junyaku Co., Ltd.) instead of 10 g of silver oxide.

Example 8

Finally the processed media, and then the catalyst (N) to obtain ethylene oxide were obtained according to the procedure of example 1, using 20 g of copper oxide (99.5% of the issued Wako Junyaku Co., Ltd.) instead of 10 g of silver oxide.

obtained according to the procedure of example 1 using 100 g of colloidal gold (Au content 20%) instead of 10 g of silver oxide.

Example 10

Finally the processed media, and then the catalyst (J) to obtain ethylene oxide were obtained according to the procedure of example 1, using 20 g of zinc oxide (released Wako Junyaku Co., Ltd.) instead of 10 g of silver oxide.

Example 11

Finally the processed media, and then the catalyst (K) to obtain ethylene oxide were obtained according to the procedure of example 1, using 20 g of powdered zinc (released Wako Junyaku Co., Ltd.) instead of 10 g of silver oxide.

Example 12

Finally the processed media, and then the catalyst (L) to obtain ethylene oxide were obtained according to the procedure of example 1, using 20 g of zinc chloride (released Wako Junyaku Co., Ltd.) instead of 10 g of silver oxide.

Example 13

Finally the processed media, and then the catalyst (M) to obtain ethylene oxide were obtained according to the procedure of example 1, using 20 g of zinc nitrate (released Wako Junyako Co., Ltd.) instead of 10 g of silver oxide.

Example 14

Finally the processed media, and then the catalyst (N) to obtain ethylene oxide were obtained according to the procedure of example 1, using 20 g of zinc sulfate (released the media, and then the catalyst (A) to obtain ethylene oxide were obtained according to the procedure of example 1, without the use of silver oxide.

Example 15

Each of the catalysts (A)-(O) was crushed, and was selected fraction 600-850 mesh. A portion of the grains of 1.2 g was loaded in the reaction tube of stainless steel with an inner diameter of 3 mm and a length of 600 mm In the thus prepared reaction tube was carried out vapor-phase oxidation of ethylene under the following conditions. To the reaction system were determined selectivity and the reaction temperature in the catalyst bed when the degree of conversion of ethylene 10%.

The temperature of the heating medium: 230oC

The volumetric rate (N. W.): 5500 h-1< / BR>
The reaction pressure (gauge): 2 MPa (20 kg/cm2)

The composition of the feed gas: 21% of ethylene, 7.8% of oxygen, 5.7% carbon dioxide, 2 million hours (ppm) ethylene dichloride; the rest is methane, nitrogen, argon and ethane.

The results are shown in the table.

1. Silver catalyst to obtain ethylene oxide, which is formed by deposition of silver on a carrier, characterized in that the carrier includes alumina as a main component, comprising oxnov groups Ib and IIb of the Periodic system of elements.

2. The catalyst p. 1, in which the content of silicon oxide is in the range from 0.01 to 15 wt.% with respect to the weight of the finished media.

3. The catalyst p. 1, in which the contents of the specified metal or compound oxide of the specified element is in the range 0.001 to 15 wt.% with respect to the weight of the finished media.

4. The catalyst according to any one of paragraphs.1 to 3, in which the specified element is silver or zinc.

5. The catalyst according to any one of paragraphs.1 to 4, in which the amount of silver deposited in the catalyst is in the range from 1 to 30 wt.% with respect to the weight of the finished catalyst.

6. The catalyst p. 5, which additionally contains an alkaline metal deposited in the amount of between 0.01 - 100 μmol/m2surface area of a specified catalyst.

7. The catalyst according to any one of paragraphs.1 - 6, wherein said carrier has a specific surface area by BET method in the range of 0.03 - 10 m2/g, coefficient of water absorption in the range of 10 - 70% and an average particle diameter in the range of 0.1 - 5 μm.

8. The method of preparation of a catalyst to obtain ethylene oxide, including the application of silver on a carrier, characterized in that Khujand is of at least one element, selected from elements of groups Ib and IIb of the Periodic system of elements, the subsequent firing the obtained mixture at a temperature in the range of 1000 - 1800oWith obtaining such by the media, and the subsequent application of at least silver to the specified device.

9. The method according to p. 8, wherein said oxide of aluminum is a granular substance, the primary particles which have a diameter in the range of 0.01 - 100 μm.

10. The method according to p. 9, in which the content of silicon oxide is in the range from 0.01 to 15 wt.% relative to the weight of the finished image, and the contents of the specified metal or compounds of at least one element selected from the class consisting of elements of groups Ib and IIb of the periodic system of elements is in the range of 0.001 to 15 wt.%.

11. The method according to any of paragraphs.8 to 10, in which the solution or suspension of the compounds of silver is applied to the specified device so that the quantity of precipitated silver was in the range of 1 to 30 wt.% with respect to the weight of the finished catalyst.

12. The method according to p. 11, which further cause alkaline metal in the amount of between 0.01 - 100 μmol/m2surface area of a specified catalyst.

P> 14. Method for the production of ethylene oxide which comprises vapor-phase oxidation of ethylene gas containing molecular oxygen, in the presence of a silver catalyst, which is formed by deposition of silver on a carrier, characterized in that the carrier includes alumina as a main component, comprising silicon oxide and a metal or compound of at least one element selected from the class consisting of elements of groups Ib and IIb of the periodic system of elements.

 

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