The method of obtaining catalysts with improved catalytic properties

 

This invention relates to the field of catalysts. The described method of applying one or more catalytically active metal on the carrier, and the above-mentioned method includes selecting the media and drawing on the media of one or more catalytically active metals, and the application is carried out by immersing the carrier in the solution for impregnation, the activity of hydrogen ions in this solution for impregnation reduced. In addition, the invention relates to catalysts obtained by this method. In the examples, the silver and the promoter is applied to the carrier of aluminum oxide in the presence of hydroxide of tetraethylammonium. Effect: these catalysts suitable for use in obtaining ethylene oxide. 2 N. and 7 C.p. f-crystals, 2 tab.

The scope of the invention

This invention relates to a method for producing catalysts with improved catalytic properties, in particular with improved initial activity, the initial selectivity and/or characteristic of the activity and/or selectivity over time.

The background to the invention

There are many ways of drawing media catalytically active m the distribution of the catalytically active metal components on the media using the solution for impregnation, containing compound catalyst precursor and organic timeslot, or mercaptoethanol acid. In U.S. patent No. 4005049, issued January 25, 1977, discloses the receipt of the catalyst based on the silver/transition metal, which is useful in oxidation reactions. In international publication WO 96/23585, published on August 8, 1996, indicated that increasing the amount of alkali metal promoter in a solution of silver leads to improved properties.

In the examples of U.S. patent No. 4212772, issued July 15, 1980, and U.S. patent No. 4994587, issued February 19, 1991, both of which are catalysts for the epoxidation of ethylene, it is noted that in the solution of silver, which was used for impregnation of the catalyst carrier, using a weakly basic, primary amines, such as Isopropylamine, secondary butyl amine, monoethanolamine and Ethylenediamine. Their goal is to link a silver complex. In the literature also warns against some ways. In U.S. patent No. 4908343, issued March 13, 1990, warned that the silver solution had a high acidity or basicity, as a solution of a strong acid or base will be any leaching leached impurities from the media, becoming part of Surestore in oxidation reactions.

In U.S. patent No. 4361500, issued November 30, 1982, describes a method for catalyst on the carrier containing at least one metal (which may be silver) by reductive deposition of metal(minerals) on the carrier with a solution containing ions or compounds of the metal(minerals), and then restore the vehicle, characterized in that the metal(s) is applied to the carrier in the presence of at least one Quaternary ammonium compounds, the anion of which is a hydroxyl group, or the residue of an organic or mineral acid, this recovery is carried out by hydrogenation at a temperature not exceeding 300With, and do not hold the stage of calcination.

Unexpectedly it was found that the deposition of metal and catalytic properties can be significantly improved by reducing the activity of hydrogen ions in a solution for impregnation.

Brief description of the invention

In accordance with one method embodiment of the invention, provided is a method of obtaining a catalyst suitable for the epoxidation of olefins in the gas phase, comprising the stage of:

- select inorganic carrier;

- drawing on the nose the RA for impregnation, the activity of the hydrogen ions which are reduced at least 5 times.

In particular, the activity of hydrogen ions in the solution used for impregnation reduce adding Foundation.

Preferably, the activity of hydrogen ions in the solution used for impregnation reduced the five - thousand times. In the aquatic environment, these figures correspond to the increase of pH at a value of 0.5 and 0.5-3, respectively.

Description of preferred embodiments

It was found that the decrease of activity of hydrogen ions in the solution used for impregnation used for drawing on the media catalytically active metals, provides catalysts which have improved catalytic properties, such as activity, selectivity, and characteristics of the activity and/or selectivity over time. I believe that the method improves the properties of most of the catalysts in which the metal is applied to the carrier using a solution for impregnation.

The catalysts are usually obtained by applying to the medium a catalytically effective amount of one or more catalytically active metals to produce the catalyst precursor. Usually this carrier is impregnated with a metal or compound(s), cook used here “catalytically effective amount” means that amount of metal that will provide measurable catalytic effect.

The impregnated carrier, or the precursor of the catalyst is dried in the presence of the atmosphere, which also restores the catalytic metal. Known in the art drying methods include steam drying, drying in an atmosphere having a controlled oxygen concentration, drying in a reducing atmosphere, drying in air and stepwise drying using an appropriate linear or stepwise the temperature curve.

In the method of the invention the improvement in the properties of the catalyst may occur when the coating metal is carried out at the contact of the carrier with a solution for impregnation, the activity of hydrogen ions which are reduced. “The activity of hydrogen ions”, as used here, represents the activity of hydrogen ions, as measured by the potential of the hydrogen ion-selective electrode. As used here, the solution with “low” activity of hydrogen ions refers to the solution, the activity of hydrogen ions which is changed by adding the base so that the activity of hydrogen ions this modified solution seanne to change the solution, you can choose from any of the base or connection with the PKblower than the initial solution for impregnation. Especially, it is desirable to choose a Foundation that does not change the composition of the solution used for impregnation; that is, that does not change the desired metal concentration in the solution used for impregnation and supported on a carrier. Do not change the concentration of metals in the solution used for impregnation of an organic base, examples of which include hydroxides of tetraalkylammonium and 1,8-bis(dimethylamino)naphthalene. If the change in the concentration of metals in solution for impregnation is not important, you can use the metal hydroxides.

If the solution for impregnation is at least partially water, the indication changes in the activity of the hydrogen ions can be determined by using pH meter, with the understanding that the resulting measurement is not the true pH of the aqueous definition. “Measured pH” as used here, will mean a similar pH non-aqueous system using a standard pH probe. Effective even small changes in the measured pH in the transition from the initial solution used for impregnation of the solution with the addition of the base, and improvement in the catalytic properties continue with the increase does not adversely affect the operation of the catalyst; however, it was observed that adding large amounts of hydroxides cause formation of a precipitate in the solution for impregnation, which leads to manufacturing difficulties. In the case when the addition of the base is too small, the activity of hydrogen ions will not be affected.

As described, this method is effective to improve at least one of the catalytic properties of the catalyst, in which the coating or impregnation of the carrier of the catalytically active metal is used the solution for impregnation. “Improvement of catalytic properties”, as used here, means that the properties of the catalyst are improved compared with a catalyst obtained by using the same solution used for impregnation, the activity of the hydrogen ions which have not been reduced. The catalytic properties of the mean activity of the catalyst, the selectivity characteristic of the activity and/or selectivity over time, performance (resistance to being out of control), conversion and speed.

Further improvements in properties can be achieved at lower concentrations inisheer particles on the surface of the carrier, before the stage of application. Typically, the carriers are inorganic is a, or their combinations, such as media based on aluminum oxide-silicon dioxide. Ionithermie particles, usually located on the native inorganic type include sodium, potassium, aluminates, soluble silicate, calcium, magnesium, silicate, cesium, lithium, and combinations thereof. Reducing the concentration of undesirable inisheer particles can be accomplished in any way: (i) that is effective to transfer inisheer particles in the ionic state and the removal of these particles, or (ii), which translates Ionithermie particles in the insoluble state, or (iii), which translates Ionithermie particle in a stationary state; however, the use of aggressive media such as acids or bases, is undesirable because these environments tend to dissolve the medium to extract too much of the substance of mass and generate acidic or basic sites in the pores.

Effective ways to reduce concentrations include washing media; ion exchange, evaporation, deposition, or the binding of impurities in the industry; carry out reaction for translation inisheer particles on the surface in the insoluble state; and a combination thereof. Examples of solutions for washing and ion exchange include water rakamonie, ammonium acetate, lithium carbonate, barium acetate, strontium acetate, crown ether, methanol, ethanol, dimethylformamide and mixtures thereof. You can handle the completed carrier, or can be processed to be used to obtain carrier substances before manufacture of the carrier. When the processing of materials for the media prior to the manufacture of media even greater improvement is observed when re-processing the surface of the media. After removal of an ionisable particles of the medium do not necessarily dry. When the removal process is carried out by washing with an aqueous solution, it is recommended drying.

Using the example method will be described in more detail for a catalyst suitable for the production of epoxides in the gas phase, known as the catalyst for the epoxidation.

First of all choose the carrier. In the case of the epoxidation catalyst carrier is typically an inorganic substance, such as a carrier based on alumina, such as-aluminum oxide.

In the case of media containing-aluminum oxide, is preferred as the specific surface of which is defined by the method of B. E. T., ranges from 0.03 to 10 m2/g predpochtitel is the principal method of water absorption, is from 0.1 to 0.75 ml/g volume. Method B. E. T. the determination of the specific surface detail Brunauer, S., Emmett, P. Y., and Teller, E., J. Am. Chem. Soc., 60, 309-16 (1938).

Some types of media that contains-aluminium oxide is especially preferred. These carriers from-aluminium oxide have relatively uniform pore diameters and are more fully characterized by the fact that have a B. E. T. surface area from 0.1 to 3 m2/g, preferably from 0.1 to 2 m2/g and a water volume of pores of from 0.10 to about 0,55 ml/year In the number of producers of these media is part of Norton Chemical Process Products Corporation and United Catalysts, Inc. (UCI).

The media usually impregnate compound(s), complex(themselves) and/or salt(salts) of the metal dissolved in a suitable solvent sufficient to cause the desired application to the media. When an excess of the solution for impregnation the impregnated carrier is subsequently separated from the solution prior to recovery of the applied compound of the metal to the metal state.

In the method of the invention the activity of hydrogen ions in the solution used for impregnation of reduce before beginning the process of application or impregnation. The usual solution for impregnation in the beginning is doval is especially desirable to choose the base, which does not change the composition of the solution used for impregnation, such as organic bases; however, if the change in the concentration of metals in solution for impregnation does not matter, you can use the base metals. Examples of strong bases include hydroxide of alkylamine, such as the hydroxide of tetraethylammonium, a metal hydroxide such as lithium hydroxide and cesium hydroxide. You can also use combinations of bases. To maintain the desired composition of the impregnating solution and download metal prefer organic base, such as hydroxide of tetraethylammonium. These desirable limits add reasons usually lead to change “measured pH”, which varies in the range of from about 0.5 to about 3, with the understanding that this “measured pH” is not true pH, because the system for water treatment is not.

When an excess of the solution for impregnation the impregnated carrier is subsequently separated from the solution prior to recovery of the deposited metal link. In addition, the carrier either prior to, or simultaneously, or after the application of the catalytically active metal can also be applied promoters, components, effective to provide Ulich components.

When using just described the stage of reduction of the concentration inisheer particle concentration inisheer particles on the carrier surface, reduce stage before coating or impregnation. Ionithermie particles on the media from-aluminium oxide, for example, typically include sodium, potassium, aluminates, soluble silicates, calcium, magnesium, silicates and combinations thereof. It was found that silicates and some other anions are particularly undesirable Ionithermie particles in the epoxidation catalyst. The rate of solubilization of the silicates may be determined by the method of inductively coupled plasma (ICP), and the number of silicon particles on the surface can be determined by x-ray photoelectron spectroscopy (RFS); however, because sodium is soluble in the same solvents, in which the soluble silicates, the rate of solubilization of the sodium becomes more simple way to check for the removal inisheer particles. Another detection method is to measure the conductivity of the solution to be processed.

The concentration of undesirable inisheer particles can be reduced in any way that is efficient for translation inisheer particles in ion soumah particles in a stationary state. Means, effective to reduce the concentration of undesirable inisheer particles on the surface include washing, ion exchange, evaporation, precipitation, binding impurities in the complex struggle with impurities and their combination. Cleaning media on the basis of aluminum oxide can be effectively and reasonably with the cost to perform by washing or ion exchange. You can use any solution that is able to reduce the concentration of unwanted present inisheer particles, in particular anionic inisheer particles and, in particular, inisheer silicates. After that, the carrier optionally dried; however, if the removal method is the washing, drying is recommended.

The carrier is impregnated with metal ions or compound(s), complex(mi) and/or salt(salt) dissolved in a suitable solvent sufficient to cause the desired application to the media. If the applied substance is silver, conventional deposition is from 1 to 40 wt.%, preferably from 1 to 30 wt.% silver based on the weight of the entire catalyst. Then the impregnated carrier is separated from the solution and deposited compound of the metal(minerals) reduced to metallic silver the motors catalysts for epoxidation is usually chosen from sulfur, phosphorus, boron, fluorine, metals of group IA to group VIII, and rare earth metals and combinations thereof. The promoting substance, as a rule, is a compound(I) and/or salt(salt) promoter, dissolved in a suitable solvent.

For oxide catalysts for the epoxidation of olefins metals of group IA usually chosen from potassium, rubidium, cesium, lithium, sodium, and combinations thereof; preferred are potassium and/or cesium and/or rubidium. Even more preferred is a combination of cesium and at least one additional metal of group IA, such as cesium and potassium, cesium and rubidium, or cesium, and lithium. The metals of group IIA usually chosen from magnesium, calcium, strontium, barium and combinations thereof, transition metals of group VIII are usually chosen from cobalt, iron, Nickel, ruthenium, rhodium, palladium, and combinations thereof, and rare earth metals are usually chosen from lanthanum, cerium, neodymium, samarium, gadolinium, dysprosium, erbium, ytterbium and mixtures thereof. Non-limiting examples of other promoters include perrenate, sulfate, molybdate, tungstate, chromate, phosphate, borate, sulfate anion, fluoride anion, the oxy-anions of groups IIIB through VIB, the oxy-anions of an element selected from groups III VIIB, salts of alkaline metal from the groups IA is usually in the range from 10 o'clock per million up to 1500 hours per million, expressed as metal, by weight of the total catalyst, and the metal of group VIIb less than 3,600 hours per million, expressed as metal, by weight of the total catalyst.

Other methods of embodiments of the invention provide catalysts obtained just described ways.

You just described the final epoxidation catalysts used to produce in the gas phase epoxides, in particular of ethylene oxide. The usual method of epoxidation involves loading of the catalysts in the reactor. Designed for the conversion of raw materials, as a rule, a mixture of ethylene, oxygen, carbon dioxide, nitrogen and ethyl chloride, is passed over the catalyst bed at elevated pressure and temperature. The catalyst converts raw materials into the output stream of a product containing ethylene oxide. To improve the characteristics of the conversion of the catalyst to feedstock can also add oxides of nitrogen (NOx).

The following examples illustrate the invention.

EXAMPLES

Media

In table.I see the media used for examples.

using a Micromeritics Autopore 9210 9200 or (contact angle 130, the surface tension of mercury 0,473 N/m).

Methods of washing but the La 300 g of boiling deionized water for 15 minutes Then the media was removed and placed in 300 g of fresh boiling water for another 15 minutes This procedure was repeated once more, a total of three dives; at this point the medium was separated from water and dried in a ventilated oven at 150C for 18 hours then dried carrier used for the preparation of the catalyst of ways, the main provisions of which are set out in the following examples.

The solution for impregnation

The raw material solution containing a silver-amine-oxalate was prepared by the following method:

415 g of chemically pure sodium hydroxide dissolved in 2340 ml of deionized water and brought the temperature up to 50;

1699 g of silver nitrate high purity “Spectropure” was dissolved in 2100 ml of deionized water and brought the temperature up to 50C.

To the silver nitrate solution slowly, with stirring, was added a solution of sodium hydroxide, maintaining the temperature of the solution at 50C. the Mixture was stirred 15 min, then the temperature was lowered to 40S. Of sludge formed during mixing, removed the water and measured the conductivity of water containing sodium ions and nitrate ions. The silver solution was again added is repeated until until the conductivity of the withdrawn water was not less than 90 MKMHOm/see then added to 1500 ml of fresh deionized water.

Added 630 g of dihydrate of oxalic acid of high purity by increments of approximately 100, the Temperature was maintained at 40C, and the pH was maintained above 7.8.

From this mixture were removed water, having a containing silver suspension of high concentration. Cooled slurry of silver oxalate 30C.

Added 699 g of 92 wt.% Ethylenediamine (8% deionized water), keeping the temperature not exceeding 30C. the resulting solution contained approximately 27-33 wt.% silver.

To this solution was added a sufficient amount of 45 wt.% water s and water, having a final catalyst containing a 14.5 wt.% silver and the desired loading of cesium (see examples).

Methods of measuring pH

Measure the pH of a solution of silver was performed using a pH meter model Metrohm 744, using combined electrode model 6.0220.100 and platinum resistance thermometer model 6.1110.100 for temperature compensation. The meter was calibrated commercially available buffer solutions before each uptae as the impregnation of the catalyst, filtered in a glass chemical glass of 100 ml in 2-micron filter attached to a plastic syringe. In the solution, stir on a magnetic stirrer, lowered the pH probe and recorded after 3 minutes of evidence as the equilibrium pH. The probe was cleaned before each measurement deionized water and checked the calibration. Special attention was paid to prevent the accumulation of precipitation gl on the membrane of the electrode. This accumulation was removed by soaking the probe in a solution of ammonium hydroxide, as recommended by the manufacturer.

Evaporation

This method is used to remove unwanted ions from the surface of the carrier by any means, which lead to the movement of these ions in the gas phase. In some cases, this may be a simple heating to the desired temperature. In the case of alkali metal ions ordinary temperatures at which formed the basis of alpha-aluminum oxide, are sufficient to remove most, but not all, of the quantity of alkali metal ions. Typically, ions of metals it is necessary to add a chemical agent to produce a volatile sample. One common method is the introduction of compounds b US 2069060/. For example, in the case of sodium get Na2IN4formed /Kirk-Othmer Index, vol.4, R. 77 (1stEdition)/. Can be used by other reagents.

Another well-known agent is a fluoride of iron, which leads to the production of volatile fluorine compounds with many metals. The boiling point of the metal fluoride is much lower than the corresponding chlorides, and this property is used for cleaning metals, mixtures of metals for many years. The most famous example of the use of fluoride has been very successful during the evaporation of rare earth metals for the separation of uranium from other rare earths present in the ore /"Advanced Inorganic Chemistry", Cotton & Wilkinson, Eds. $th Edition, copyright 1980, John Wiley & Sons,. p.1030/. Fluorides are also effective for the evaporation of silicon compounds with the formation of low-boiling SiF4. It finds its application in the synthesis of alpha-alumina with a very low silicon content and can be performed at relatively low temperatures /"Alumina as a Ceramic Material, Walter H. Glitzen, Ed., copyright 1970, Alumina Ceramic society, p.25/.

Often combine methods of heating and the action of a chemical agent to increase the rate of removal of undesirable substances. This is often done in the synthesis of the respective materials of the basics. Examples of phenomena is undesirable ions on the surface by a chemical reaction with the formation of insoluble compounds. The basis for this method is well-known procedure for the deposition of ions from solutions. The list of methods of deposition and chemical agents used for the deposition of cations can be found in books on General chemistry or analytical chemistry in the sections on qualitative analysis. In this case, the use of cations, which do not lead to deterioration of the properties of the catalysts is suitable.

Non-limiting examples include lithium, barium, calcium, strontium, magnesium, transition metal ions, ions of rare earth elements. Especially used are lithium ions, which can be administered in various forms such as hydroxide, nitrate, bicarbonate, carbonate, chloride, fluoride, and so on). Lithium forms an insoluble silicate Li2SiO3and lithium itself is relatively harmless on the surface of the catalyst of silver.

Complexation (sequestration)

This method focuses on the immobilization of unwanted ions on the surface, rendering them immobile (unable to move). Dictionary Webster's New Collegiate Dictionary, copyright 1980 by G.&C. Merriam Co. describes the sequestration as “the holding (as metal ion) by including appropriate coordination included is described. Examples of capture cations include the use of molecular sieves, crown ethers, aluminosilicates, clays, granulated clay or other rich oxygen symmetric environment.

Example 1a (comparative - main case of the medium And washing)

The catalyst precursor obtained from the carrier And subjecting the first media washing. After washing approximately 30 g of the washed carrier And placed in a vacuum when to 3.33 kPa for 1 min at ambient temperature. Then introduced approximately 50 g of the solution for impregnation to immerse him in the media and kept in vacuum at to 3.33 kPa for 3 minutes Indicator on cesium amounted to 450 h in million/g of the final catalyst. Thereafter, the vacuum was removed and removed from the catalyst precursor excess solution impregnation by centrifugation at 500 rpm for two minutes. Then, the catalyst precursor was dried with shaking at 240C for 4 min in a stream of air flowing with a speed of 11.3 m3/PM

Example 2A (comparative - main case of the media And no washing)

The carrier was impregnated as described in example 1A; however, this media is not subjected to washing. Figure cesium amounted to 400 h in the example 1A. Figure cesium amounted to 500 million hours/year of the final catalyst. In addition to the main solution for impregnation was added 35% aqueous hydroxide of tetraethylammonium (TAAG) to rate 117,8 micromoles of HE-/ml Hell, to reduce the activity of hydrogen ions to “measured pH” in 13,7.

Example 4

The catalyst was obtained in the same manner as in example 1. Figure cesium amounted to 720 hours per million/g of the final catalyst. In addition, TAAG dissolved in water and added to the main solution for impregnation to 117,8 micromoles of HE-/ml Hell of a solution to reduce the activity of hydrogen ions to “measured pH” in 13.2 and NH4ReO4dissolved in water and added in the raw material solution to provide 1.5 micromoles of Re/g of the final catalyst.

Example 5

500 g medium And subjected to washing, then plunged in 1500 ml of boiling 5 wt.% water TAAG 15 minutes After that, the medium was separated from the solution and washed successively with boiling water in accordance with the wash procedure of the media. Then the media used for preparation of the catalyst according to the procedure described in example 2 with the “measured pH” 13,6. Figure cesium amounted to 400 million hours/year of the final catalyst.

3and LiOH was added to the raw material solution for impregnation, reducing the activity of hydrogen ions to “measured pH” 12,5.

Example 7

The media And subjected to washing and impregnation as described in example 1. Figure cesium amounted to 450 million hours/year of the final catalyst. In addition, LiOH dissolved in water and added in the raw material solution for impregnation in order to reduce the activity of hydrogen ions to “measured pH” 13,2.

Example 8A (comparative)

The carrier And the catalyst was impregnated as described in example 6, however, the carrier is not subjected to washing. Figure cesium amounted to 400 million hours/year of the final catalyst.

Example 9 (comparative)

Prepared in a solution of silver as described in example 6. “Measured pH of this solution was 13.2. To the solution was slowly barbotirovany CO2up until “measured pH” was not 12,0. This solution was used for preparation of the catalyst as described in example 1.

Example 10

The catalyst was obtained in the same manner as in example 1. Figure cesium amounted to 650 million hours/year of the final catalyst. In addition, LiOH dissolved in water and added in the raw material solution for impregnation, Civili in the raw material solution to provide 1.5 micromoles of Re/g of the final catalyst.

Example 11 (comparative - main case of the media, lavage)

The media used for preparation of the catalyst as described in example 1. Figure cesium amounted to 450 million hours/year of the final catalyst.

Example 12A (comparative - main case of the media, no washing)

The carrier was impregnated as described in example 1, however, this media is not subjected to washing. Figure cesium amounted to 500 million hours/year of the final catalyst.

Example 13

The media used for preparation of the catalyst as described in example 1. Figure cesium amounted to 550 million hours/year of the final catalyst. In addition, LiOH dissolved in water and added in the raw material solution for impregnation in order to reduce the activity of hydrogen ions to “measured pH” 13,2.

Example 14

The catalyst prepared as described in example 13, however, the carrier is not subjected to the washing procedure. Figure cesium amounted to 500 million hours/year of the final catalyst.

The catalysts of examples 1A-14 used to obtain ethylene oxide from ethylene and oxygen. In the U-shaped stainless steel tube with an inner diameter of 6.35 mm downloaded from 3 to 5 g of the crushed catalyst. This U-shaped tube pahrudinovna catalyst and the velocity of the incoming gas was adjusted so in order to achieve the hourly volume rate of gas 6800 ml of gas per 1 ml of catalyst per hour. Input gas pressure was 14500 kPa.

The gas mixture passed through the catalyst bed (in single mode) during the full experimental run (including running), consisted of 25% ethylene, to 7.0% oxygen, 5% carbon dioxide, 63% of nitrogen and from about 2.0 to 6.0. 'clock million on ethyl chloride.

The initial temperature of the reactor (heat medium) was 180C. the Temperature was linearly increased at a rate of 10With in an hour from 180With up to 225With, and then adjusted in such a way as to achieve a constant level of ethylene oxide 1.5% vol. in the output gas stream. Data on the operation at this level of conversion was usually obtained when the catalyst was in the thread in General, at least 1-2 days. Due to small differences in the composition of the raw gas, the velocity of the gas stream and calibration of analytical instruments used to determine the compositions of gaseous raw materials and product, a certain selectivity and activity of this catalyst may vary slightly from one experimental run to another.

Identified the>what you can see significant improvements in the properties of the catalyst are observed when the activity of hydrogen ions in solution for applying reduced. This effect is not specific to the particular media that is shown in the example where two different media are improved with increasing “measured pH” solution for impregnation. It also remains in effect for significantly modified carrier as in example 5, where the media were extracted And strongly basic solution. Moreover, it is shown that the converse is true when the solution is “forced” to return to a more acidic pH, as can be seen from example 9a. In these examples, it is shown that a more acidic pH (increase in the activity of hydrogen ions), the unfavourable performance of the final catalyst, but this loss can be eliminated by restoring the pH of the system. An even greater improvement observed in the washing medium before application to the carrier of the catalytic metal. In addition, it is obvious that the phenomenon of the pH effect is not limited to a particular composition of the catalyst, which is best illustrated in examples 4 and 10, where the solution for impregnation add an additive that improves the selectivity, such as rhenium.

this application is carried out using the solution for impregnation, in which adding the Foundation of the measured pH value of the solution is at least 12,5.

2. The method according to p. 1, characterized in that the measured value of the pH of the solution used for impregnation is in the range from 12.5 to 13.7.

3. The method according to any of paragraphs. 1 and 2, characterized in that use, the medium with reduced concentration inisheer particles on its surface.

4. The method according to p. 3, characterized in that the concentration of one or more inisheer particles on the carrier surface to reduce method, effective for transfer inisheer particles in the ionic state and particle removal, or transfer inisheer particles in the insoluble state, or translation inisheer particles in the stationary state.

5. The method according to p. 4, in which the said method selected from washing, ion exchange, evaporation, precipitation, complexation, and combinations thereof.

6. The method according to any of paragraphs. 1 to 5, comprising, in addition, the application of one or more compounds of one or more promoters selected from sulfur, phosphorus, boron, fluorine, metals from groups group IA is chosen from potassium, rubidium, cesium, lithium, sodium, and combinations thereof, the metal of group IIA, if present, are selected from magnesium, calcium, strontium, barium and combinations thereof, the metal from group VIIb, if any, represents the rhenium and a metal from group VIII, if present, is chosen from cobalt, iron, Nickel, ruthenium, rhodium, palladium, and combinations thereof.

8. Method for the catalytic epoxidation of alkene oxygen-containing gas, in which the use of the catalyst obtained by the method of any of paragraphs. 1-7.

9. The method according to p. 8, in which the oxygen-containing gas add at least one of the oxides of nitrogen.

 

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