CS251793B2 - Method of silver catalysts' efficiency improvement - Google Patents

Abstract

Bei diesem Verfahren wird der zu behandelnde Silberträgerkatalysator mit einer Lösung aus Cäsiumhydroxid, einem Cäsiumalkoholat eines niedrigen aliphatischen gesättigten Alkohols oder einer Mischung davon als Cäsiumverbindung und aus einem niedrigen aliphatischen gesättigten Alkohol und 0 bis 20 Gew.-% Wasser als Lösungsmittel bei einer Temperatur von 60 bis 200°C imprägniert, wobei auf den in Behandlung stehenden Silberträgerkatalysator 1 bis 1000 mg Cäsium pro Kilogramm Katalysator aufgebracht werden. Diese Silberträgerkatalysatoren werden insbesondere für die Herstellung von Ethylenoxid durch Umsetzung von Ethylen mit Sauerstoff oder Luft eingesetzt.

Description

The present invention relates to a method for improving the efficiency of silver supported catalysts for producing ethylene oxide by reacting ethylene with oxygen or air.

Nooic silver catalysts are used to produce ethylene oxide by oxidizing ethylene with oxygen or air. A general description of this direct ethylene oxidation is found, for example, in Kirk-Othmer: Encyclopedia of Chemicai Technology, Vol. 9, pp. 432-471, edited by John Wiley, London-New York, 1980. Typically, only a fraction of the ethylene used is reacted to produce ethylene oxide and essentially carbon dioxide and water as undesirable by-products.

The efficiency of the supported silver catalyst is determined in essence by its activity and selectivity. The selectivity is the molar percentage of ethylene reacted that has reacted to ethylene oxide. The activity is characterized by the concentration of ethylene oxide at the point of exit from the reactor under otherwise varying conditions (such as pressure, temperature, gas quantity and catalyst quantity). The higher the concentration of ethylecsxil, the higher the activity, or in other words, the lower the temperature required to achieve: certain concentrations of ethylene oxide, the higher the activity. In particular, the increased selectivity of catalysts is of particular economic importance in the face of rising raw material prices and increasing resource scarcity.

In recent years, two methods have been described in principle in the literature by means of which silver catalysts can be obtained on a support with increased efficacy. One way is to develop new catalysts. Thus, for example, U.S. Pat. No. 3,962,136 discloses a silver co-catalyst which is obtained by applying to the alumina at the same time a silver promoter of 0.000 to 0.022 grams of potassium, rubidium and / or cesium naphthalene. 1 kg of catalyst, for example in the case of cesium 53 to 360 mg cesium per kg catalyst. Another method for producing silver catalysts on a carrier with improved efficiency consists in that selectivity is improved, in particular, by means of an after-treatment of the finished catalyst. Such processes are known from U.S. Pat. Nos. 4,051,068. 4,123,385, _4,177,169, 4,033,903, _4,186,106, 4,125,480, _4,278,562 and 4,335,014.

In these processes, the treated catalyst is impregnated with a solution consisting of at least one cesium and / or rubidium compound and a solvent from the group of lower aliphatic ethers of saturated alcohols and water, thereby applying about 1 to 1000 mg of cesium and / or rubidium per kg of catalyst. as promoter to the support material (silver supported catalyst) and then the excess impregnating solution (solvent) is separated from the impregnated catalyst. A more recent process of this type is described in U.S. Pat. No. 4,478,948. The treatment (impregnation) of the catalyst with cesium and / or rubidium compounds contained in the solution (impregnating solution) is carried out to deposit 1 to 1000 mg of cesium or / a rubidium per kg at elevated temperature (hot impregnation). ·

With respect to cesium compounds and rubidium compounds which are used in known production methods and in known methods for treating silver catalysts to cooil, all publications mentioned above indicate that the type of cesium · or rubidium used does not play a role in the desired selectivity improvement. ; it is only a matter of applying a certain amount of cesium and / or rubidium, i.e. about 1 to 100 mg per kg, to the material which serves as the carrier.

Possible cesium and rubidium compounds include various inorganic and organic salts as well as hydroxides and oxides. Where these compounds are reported to be particularly suitable or preferred, this is clearly to be understood as purely practical considerations such as cost, availability and solvent solubility in order to produce the impregnating solution. ,

Surprisingly, it has now been found that a particularly good improvement in the effectiveness of the supported silver catalysts is achieved when a solution consisting of cesium hydroxide, cesium alkoxide derived from a lower aliphatic saturated alcohol or a mixture thereof as a cesium compound and a lower cesium compound is used as the impregnation solution; More saturated alcohol and 0 to 5% by weight of water as solvent, and if the post-treatment (impregnation) is carried out at elevated temperature. Of the many cesium compounds and rubidium compounds mentioned in the prior art, it was not to be expected that with the selected cesium compounds, ie cesium hydroxide and cesium alkoxide, seletites, this is particularly the case when the cesium compounds combine with hot impregnation, although in both the production and aftertreatment of silver catalysts to cesium and rubidium compounds, and in particular also the anion, in any case the trititection is a condition for the desired increase in selectivity.

a comparatively higher use of these carrier-related speeial techniques indicates that it is not a

Process according to the invention for improving the efficiency of silver supported catalysts for producing ethylene oxide by reacting ethylene with oxygen or air, impregnating the catalyst with a solution consisting of at least one cesium compound and a solvent to deposit 1 to 1000 mg cesium per kg catalyst. from lower alifaickkých saturated 'alcohols and a ^ ⁱ ^ Mpre ^g NACE ^p rov ^and di- ^p s temperature of from ⁶⁰ to ²⁰⁰ ° C and the excess ^NO Nu impregnating soln ^ is separated from the impregnated catalyst, characterized in IE uses of an impregnating solution consisting of cesium hydroxide, cesium methoxide, cesium ethoxide, cesium propoxide, cesium isopropoxide or a mixture of cesium hydroxide and one of these cesium alkoxides and cesium compound, methanol, ethanol, propanol or itopropyl alcohol and ai 5% strength water percent with relationship! impregnating solution). .

In the process according to the invention, the cesium cesium hydroxide compound is cesium hydroxide. Thus, the impregnating solution containing cesium methoxide, cesium ethoxide, cesium propoxide or the impregnating solution consists of methanol, ethanol, propanol and 5% by weight of water.

If they are to be used in the impregnating solution. According to the invention, cesium hydroxide and / or cesium oxides are present as cesium compounds, then cesium compounds which are present as cesium hydroxide and / or cesium oxide in the solvent used according to the invention are suitable for the preparation of the impregnation solution. Such cesium compounds are cesium hydroxide, cesium oxide, cesium oxide and cesium metal, with cesium hydroxide and cesium oxide being particularly preferred. These cesium compounds are soluble in the alcohols; water in said quantity can be used to accelerate solubility. Suitably, the alcohol used as the solvent agrees with the alcohol serving as the alcoholic sloika in the cesium aoxide,, the cesium hydroxide may be cesium-free cesium hydroxide (CsOH) or cesium hydroxide containing crystalline water (CsOH). xH 10, x = the number of water liquors (^). Cesium hydroxide is generally omitted as CsOH. H ^ O.

When ^{p p} u ^ Ostu climb by impregnation temperature ^P bends on ^{d 60 d 200} ° C above ^h o ^{n e} of from 80 to 150 ° C. By impregnating the treated silver catalyst on the support of the invention, 1 to 1000 mg of cesium per kg of catalyst, preferably 50 and 500 mg of cesium per kg of catalyst, are to be applied to the catalyst.

The preparation of the impregnating solution, the impregnation of the silver catalyst on the carrier and the separation of the excess impregnating solution from the impregnated catalyst are known per se and are described in detail in the above publications.

In the impregnation solution, the concentration of cesium compound can vary over a wide range. It is only important that the impregnation according to the invention precipitates the above-mentioned amount of cesium, i.e. 1 to 1000 mg, preferably 50 to 500 mg of cesium per kg of catalyst, onto the treated silver catalyst. Preferred impregnating solutions consist

(a) from H, H, ethanol, propanol or isopropyl alcohol.

(b) from 0 to 15% by weight of water; and

c) from 0.005 to 0.2% by weight of cesium, preferably 0.01 to 0.1% by weight of cesium, in the form of the cesium compounds used (percentages by weight based on the impregnating solution; 0.005 to 0.2% by weight and 0.01% by weight). up to 0.1% by weight of cesium corresponds, for example, to 0.006 to 0.24% by weight or 0.012 to 0.12% by weight of CsOH.

The amount of impregnating solution is generally selected so that a volume excess is present based on the impregnated silver catalyst on the support. As a rule, 0.5 to 3 times, preferably 1 to 2 times, the volume of impregnating liquid, based on the volume of impregnated catalyst, is used.

Of course, the impregnation time, i.e. the time the catalyst remains in contact with the ipregulation liquid, must be selected such that the required amount of cesium (cesium compound) is applied to the catalyst (carrier). This time depends primarily on the concentration of cesium (cesium compound) in the impregnation solution and on the catalyst support material which is impregnated and is generally 1 to 15 hours, preferably 3 to 10 hours.

According to an advantageous method, the impregnation according to the invention is carried out by pouring the catalyst in the vessel (autoclave) with an impregnating solution, then heating the catalyst and the impregnating liquid, optionally with stirring, to said temperature and maintaining this temperature for 1-15 hours, preferably up to 10 hours (contact time).

According to another expedient method, the so-called flooding, the impregnation is carried out on a catalyst which is arranged as a fixed bed in one or more tubes. This method is particularly recommended for large-scale plants in which there is already a catalyst to be treated in the reactor tubes. Flooding can be carried out one or more times (with a separate or newly prepared impregnating solution) continuously or discontinuously. In continuous impregnation, the impregnating solution is passed through the pump in the circuit while maintaining the required contact time. Also in the case of flooding, it is expedient to reach the impregnation temperature and adjust it so that the catalyst and the impregnating liquid are heated to this temperature (it is understood that increased impregnation temperatures according to the invention result in increased pressures corresponding to the vapor pressures used). impregnating liquids).

After impregnation, the excess impregnating liquid is separated from the catalyst by casting, filtering, centrifuging or simply flooding the impregnating liquid in the event of flooding.

Although the catalyst thus obtained, due to the presence of alcohol and optionally water, still more or less moist catalyst loses its moisture when heated for a particular application, it is nevertheless generally advisable to include drying the catalyst after treatment according to the invention. This drying is generally carried out at a temperature of from 20 to 150 ° C, preferably at 50 to 120 ° C. The evaporation of the solvent can optionally be accelerated, for example, by means of hot inert gases such as air, nitrogen and / or carbon dioxide. This temperature generally depends on the boiling point of the impregnating solution solvent. According to a preferred method, the drying is carried out in the presence of an inert gas and at a temperature of 50 to 120 ° C.

After carrying out the process of the invention, a finished catalyst with improved efficiency is obtained.

The process according to the invention is independent of the kind of supported silver catalyst. Any silver supported catalyst suitable for the direct oxidation of ethylene to ethylene oxide by oxygen or air is suitable for the process of the invention. These silver catalysts generally consist of silver in an amount of 3 to 20% by weight, preferably 7 to 14% by weight, and optionally promoters such as potassium, sodium, lithium, cesium and / or rubidium in an amount of 0.002 to 0.08 %, preferably from 0.003 to 0.05% by weight, on a porous support material which is thermally stable (the percentages by weight are based on the total weight of the catalyst; these percentages correspond to 20 to 800 mg per kg and 30 to 500 mg per kg, respectively). 1 kg). Silver is known to be metal on the inner and outer surfaces of the carrier material.

The morphology of the silver deposited on the carrier material can vary within wide limits. It generally has the shape of hemispherical particles with a diameter of from 0.01 to 10 gums. Examples of carriers include alumina of various structures, magnesium oxide, silicon dioxide, pumice, silica, silicon carbide, clays (alumina, corundum, zeelites, metal oxides, etc.). have a very uniform pore diameters. the carrier maateiály usually chharattzizují speeifickým surface area (m / g) Lepoglava of ^b Jem ^to R ^{s (cm 3 /} g) and the ambiance ^p rum ^of REM ^to R ^{s (/} im). Generally mmjí shape Grans ^{j í,} Bulíček rings or the like.

As mentioned above, any silver catalyst on the salt which is suitable for direct oxidation of ethylene to ethyl oxide can be provided as starting material for the process of the present invention. This may be, for example, fresh silver catalyst on salt (with or without promoter content), freshly prepared and heat-treated (stabiizable) silver catalyst on bearer, silver catalyst on salt activated by promoters such as potassium, sodium, sodium. In all these cases, the treatment according to the invention results in an improvement in efficiency. The heat treatment is known to be the heating of the catalyst to an elevated temperature until it reaches a state of < Desc / Clms Page number 13 > Usage is understood to be the fact that the catalyst has already been used for the reaction of ethylene to ethyl ester with oxygen or air, and its ingestion can vary over a wide range, ranging from a few hours to several years. the catalyst may lose its activity or may have substantially its original activity ost.

In the process according to the invention, it is advantageous to use spent silver catalysts on the catalysts whose efficiency has decreased and which therefore flow to the so-called aged or tired catalysts. Spent catalysts may contain said promoters or may be free of promoters. They can also be regenerated once or several times (reactivases) according to one of the known methods, for example according to the method described in U.S. Pat. No. 4,051,068. The process according to the invention is particularly advantageous in the case of regenerated silver catalysts on a siccum.

The process according to the invention increases the activity and sewage of the silver catalyst on the soap. It is therefore possible to reduce the reaction temperature of the catalysts treated according to the invention, whereby the same or even increased conversion is achieved. This is of particular importance since the formation of undesirable by-products such as carbon dioxide, formaldehyde and acetaldehyde is strongly suppressed at a lower reaction temperature. Due to the large amount of ethylene oxide produced in the oxidation process from ethylene, an increase in yield of even a few percent or even a deseeisy percent yields a significant ecornornic effect.

The invention is illustrated in more detail by the following examples (examples for the process of the invention and comparative examples).

The experiments were carried out in an experimental reactor in the form of a vertical reaction tube of chrome vanadium steel having a light of 30 mm and a height of 300 mm. The jacketed reaction tube is heated by hot oleate flowing through the jacket. The reaction tube is filled up to 200 mm with alpha-AlgOg pellets; this chamber serves to preheat the incoming gas. The catalyst to be examined is placed on an inert charge. The plush used enters the reaction tube through the bottom (under atmospheric vacuum) and leaves the reaction tube at the head of the reaction tube.

The gas mixture used consists of:

% ^C A% wastage

CH.

% ubjemuv%

C0 ₂ % by volume

% less vinyl chloride

0.000 2% ubiquitous (inhibitor)

Ryychust relative to the decrease in time and amount is:

400 · gas volumes h. reducing catalyst parts

The murmur of the copper that composes the heat transfer varies from that of the oaks, and even the constant conversion of 7% of the ethylene content is reduced.

The gas exiting the top of the reactor is analyzed by gas chromatography, and the results of the analysis are determined by conversion (activity) and selectivity.

. and

The following silver catalysts are used in the examples:

Catalyst I:

It is a freshly prepared silver catalyst on a carrier, which consists of 10% by weight of silver on aluminum oxide with a crystal modification alpha (specific coating).

0.3 m per 1 g), 0.003% cesium (i.e. 30 g cesium per kg catalyst), whereby silver and cesium in the form of cesium nitrate are simultaneously precipitated onto the bulk material (prucenta ^ ο ^ ο ^ η! Se). refers to a silver catalyst per carrier).

Catalyst II:

This catalyst corresponds to Catalyst I, but is stable. S ^ <^ 1 ^ ^ I11 sition (heat treatment) was ptovádí by způsubem, freshly prepared silver catalyst ^with or οos Udrc ^p u CBU ¹⁰ Todina ^T epl.c ^{E 220 i} ^ ^o C ^ u suučso line ^ ⁰ ynč with a network consisting of 95% air and 5 οoSárοích% mc érních ethylene.

Catalyst III:

This catalytic catalyst is a silver catalyst for uterine permeation of a motor consisting of 11% by weight of silver on an oxide of crystalline crystalline alpha (specific coating).

0.4 m per g), which was used by 3 hands for the technical extraction of the ethylcycloxide by the oxidation of ethylene.

Catalyst IV: - ‘

This catalyst is indicative of Catalyst III, with the fact that it has been regenerated in the pustas described in Example 18 of the U.S. Pat. No. 4,051,068, i.e., it was impregnated with a solution consisting of a solution of methanol and methanol, for 3 years. % wtcCncsto5c CsOH. RO (i.e., 0.061% of cesium) and was also used in the oak for 2 years for the technical extraction of ethyl ketyl oxide.

Examples y 1 to 19

In these examples, catalysts I to IV were tested using the described experimental reactor under the conditions indicated.

Examples 1 to 19 below illustrate the conditions of the following comparative experiments as well as the test results are summarized in the table (examples which do not illustrate the method of the invention are indicated as examples). .

Example 1 (comparative example)

Catalyst I was tested without further treatment.

Examples 2 to 5 (comparative examples)

478 948

Catalyst I was modified according to U.S. Pat.

and then tested using cesium nitrate, cesium sulfate, cesium acetate and cesium oxalate as the cesium compounds. .

1,466 g of cesium nitrate are dissolved in 50 g of distilled water and then this solution is made up to methanol with a total of 1000 g of solution. Analogous solutions are prepared using 1.361 g of cesium sulfate, 1.444 g of honest acetate and 1.331 g of honestate. Thus, the four impregnating solutions consist of meehannl, 5% by weight of water and 0.147% by weight of cesium nitrate, 0.136% by weight of cesium sulfate, 0.144% by weight of cesium acetate, or 0.133% by weight of cesium, respectively. 1, in the impregnating solution, the poisoningol is present to such an extent that the total weight of the components of the impregnating solution is 100% by weight (this applies analogously to all other examples).

g of catalyst I in a tube of a ^ S ^ l (^ C ^ H ^ Ti.] ^ of steel 250 ml poured in each case ^{40 g of} the impregnating mite oids ^ was warmed to 15 ⁰ C and after DOC L ⁰ hours The solution is maintained at this temperature (hot impregnation with cesium nitrate, cesium sulfate, cesium acetate and cesium sulfate as cesium compounds) After cooling, the excess impregnation solution is separated by decantation and the wet catalyst is always ¹²⁰ ° C for 1 hour. ^{1 kg} čtaí-yz-Oru in ^{ZDY 450} m ^g, oven dried at a temperature of cesium.

The catalyst I thus tested is tested.

He said a 6

Catalyst I is treated according to the present invention using cesium hydroxide as the cesium compound.

then it is tested, whereupon

1.263 g cesium hydroxide (CsOH. 1₂The reaction mixture was dissolved in 50 g of water, and methanol was added to the solution. so as to obtain 1000 g of solution. The impregnating solution therefore consists of methanol, 5% water and 0.126% of mono -ootic CsOH. · H₂0.1 ° C corresponds to 0.100% of the dark-cesium cesium. In a manner analogous to that of Examples 2 to 5, g of catalyst I is added to a 250 ml tube of 40 ml of impregnating solution in a 250 ml steel tube.^bsa^h warms up to¹⁵⁰ ° C¹⁰ hours on this tepioté.^Po ochla The excess impregnating solution is separated by decantation and the wet catalyst is dried for a period of time¹ hours^y in su ^ rn^{1 p}ři tt^plot^{l 12}Low: 14 ° C. ^ pregnancy on^{1 kg} read the application

450 mg cesium.

The catalyst I modified according to the invention is tested.

Example 7 (comparative example)

Catalyst II is tested without further treatment.

Examples 8 to 10 (comparative examples)

Catalyst II was modified according to U.S. Pat. No. 4,478,948 and then tested using cesium formate, cesium carbonate and cesium bicarbonate as the cesium compounds.

0.937 g of cesium formate was dissolved in 10 g of an estilated salt, and this solution was then treated with iopind · methanone to give a total amount of 1000 g of solution. The analytical solutions were prepared at the same time as 0.858 g of cesium carbonate and 1.016 g of cesium carbonate. The three impregnating solutions also consist of methanol, 1% by weight of ammonium nitrate and 0.094% by weight of cesium formate, 0.086% by weight of cesium carbonate, respectively. 0.102% by weight of cesium bicarbonate; in each case 0.070% of the mono-rotary cesium.

In a 250 ml stainless steel autoclave (II), 40 g of the impregnating solution is poured over a g of catalyst II, heated to 130 DEG C. and maintained at that temperature for 10 hours (hot impregnation with cesium formate, cesium carbonate) as cesium compounds). After cooling, the excess impregnating solution was decanted off and the wet catalyst was dried in an oven at 120 ° C for 1 hour. With these impregnations, 300 mg of cesium is applied per kg of catalyst.

The catalyst II thus tested is tested.

Example 11

The catalyst was treated according to the invention and then tested using cesium iodide as the cesium compound.

A solution of 0.863 g of cesium methoxide in 999.137 g of methanol is prepared. Thus, the impregnation solution consists of methanol and 0.086% of the cmoho-methoxide, i.e., 0.070% of the 10-molar amount of cesium. In an analogous manner to Examples 8-10, 50 g of catalyst II in a 250 ml stainless steel tube are poured over 40 g of impregnating solution, the contents of the sealed tube are heated to 130 [deg.] C. and then maintained at that temperature for 10 hours. After cooling, the excess impregnating solution was decanted off and the wet catalyst was dried in an oven at 120 ° C for 1 hour. 300 mg of cesium is deposited on this 1 kg catalyst.

. Catalyst II treated with the process of the invention is tested.

Example 1 to 12 * 19

The use of catalysts III and IV is analogous to that of catalysts I and II. The cesium compounds used to prepare the impregnation solution, the impregnation temperatures used and the amount of cesium in mg cesium per kg of catalyst applied to the catalyst are shown in the following table.

As the test results in the following table show, those supported silver catalysts which were hot impregnated with cesium hydroxide and cesium alkoxides as cesium compounds in the present invention surprisingly have better activity and selectivity than those cesium silver catalysts that were impregnated with cesium. but with other compounds that have been designed according to the invention.

Table Example (SP = Comparative Examples) cesium compound for preparation of impregnation solution impregnation temperature (° C) applied amount of cesium (mg / kg) adjustment result (effect) temperature for 7% C ₂ H conversion.

(° C) of the invention ielektivita konvvezi at 7% C 2 H ₄ (%) (catalyst

AND)

1 SP - - - 208 75.0 2 SP CsNOg 150 450 200 78.2 - 3 SP CS2SO4 150 450 198 78.0 4 SP ch ₃ coocs 150 450 199 78.1 5 SP (COO) ₂ Cs ₂ 150 450 200 77.9 6 CsOH-O 150 450 195 80.5 (catalyst II) 7 SP - - - 206 75.1 8 SP HCOOCs 130 300 197 78.1 9 SP ^Cs 2 ^{CO 3} 130 300 193 78.2 10 SP CsHCOj 130 300 194 78.2 11 CH / OCs 130 300 191 80.6 (catalyst III) 12 SP - - - 240 68.6 13 SP C3H5O3Cs (lactate) 80 100 ALIGN! 228 77.8 14 CSOH.H2O 80 100 ALIGN! 222 78.8

Table continuation:

example cesium compound temperature at applied the result of the treatment according to the invention (SP = compares- for preparation impregnation m (eiekt) (example) impregnation (° C) cesia temperature for 7% ieeeecivitj at solution (mg / kg) konveezi CgH. 7% konveezi C ₂ H (° C) (%)

(Catalyst IV)

15 SP - - 16 SP CsCl 110 17 SP CsNOg 180 18 c ₂ h ₅ ocs 110 19 Dec iso-C ₂ H 2 OC 5 180

- 233 73.1 70 230 77.5 60, 229 77.8 70 220 78.8 60 221 78.9

E T E Y N E E U

Claims (1)

A process for improving the efficiency of silver supported catalysts for producing ethylene oxide by reacting ethylene with air or air, e.g. wherein te the catalyst to Depositing 1 1 000 mg of cesium per 1 kg of the catalyst is impregnated with a solution consisting of at least one compound of cesium and solvent from the group of lower aliaaiicýých saturated alcohols and VOD ^y impregnation with ^p rovádí ^p s te ^p ture on ^{d 60 d} of ²⁰⁰ ° C and ^d byte ^No. Nu im ^p re ^{g of} NaCN soln ^ o ^k is separated from the impregnated catalyst vyznaačjící in that use is made of the impregnating solution consisting of a hydroxide, cesium methoxide, cesium ethoxide, cesium propoxide, cesium iisprspsxiěu % cesium or a mixture of cesium hydroxide and one of these cesium alkoxides as the cesium compound and from methanol, ethanol, propanol or i-propyl alcohol and up to 5% by weight of water as solvent.