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GB2101495A - Process for the removal of potassium from used ethylene oxide catalysts - Google Patents

Process for the removal of potassium from used ethylene oxide catalysts Download PDF

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Publication number
GB2101495A
GB2101495A GB08218914A GB8218914A GB2101495A GB 2101495 A GB2101495 A GB 2101495A GB 08218914 A GB08218914 A GB 08218914A GB 8218914 A GB8218914 A GB 8218914A GB 2101495 A GB2101495 A GB 2101495A
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United Kingdom
Prior art keywords
catalyst
alkali metal
solvent
reactor
containing impurities
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Application number
GB08218914A
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GB2101495B (en
Inventor
Paul Joseph Busse
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NORTHERN PETRO CHEM CO
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NORTHERN PETRO CHEM CO
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    • CCHEMISTRY; METALLURGY
    • C07ORGANIC CHEMISTRY
    • C07DHETEROCYCLIC COMPOUNDS
    • C07D301/00Preparation of oxiranes
    • C07D301/02Synthesis of the oxirane ring
    • C07D301/03Synthesis of the oxirane ring by oxidation of unsaturated compounds, or of mixtures of unsaturated and saturated compounds
    • C07D301/04Synthesis of the oxirane ring by oxidation of unsaturated compounds, or of mixtures of unsaturated and saturated compounds with air or molecular oxygen
    • C07D301/08Synthesis of the oxirane ring by oxidation of unsaturated compounds, or of mixtures of unsaturated and saturated compounds with air or molecular oxygen in the gaseous phase
    • C07D301/10Synthesis of the oxirane ring by oxidation of unsaturated compounds, or of mixtures of unsaturated and saturated compounds with air or molecular oxygen in the gaseous phase with catalysts containing silver or gold
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01JCHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/90Regeneration or reactivation
    • B01J23/96Regeneration or reactivation of catalysts comprising metals, oxides or hydroxides of the noble metals
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02PCLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00Technologies relating to chemical industry
    • Y02P20/50Improvements relating to the production of bulk chemicals
    • Y02P20/52Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02PCLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00Technologies relating to chemical industry
    • Y02P20/50Improvements relating to the production of bulk chemicals
    • Y02P20/584Recycling of catalysts

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Catalysts (AREA)
  • Epoxy Compounds (AREA)
  • Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)

Abstract

An in-reactor method for removing alkali metal-containing impurities from supported silver catalysts which have been used for the direct oxidation of ethylene oxide comprises: a) contacting the catalyst in the reactor with a nonaqueous solvent for from 0.1 to 10 hours; b) removing the used solvent and the alkali metal-containing impurities contained therein; c) causing fresh solvent to flow through the reactor for sufficient time to reduce the alkali metal concentration in the effluent to 50 parts per million or less; d) draining the solvent from the catalyst; and e) drying the catalyst. The washed catalyst may be impregnated with a C3 and/or Rb component.

Description

SPECIFICATION Process for the removal of potassium from used ethylene oxide catalysts This invention relates to an in-reactor method for removing alkali metal-containing impurities from supported silver catalysts which have been used for the direct oxidation of ethylene oxide.
Supported silver-based catalysts have been used industrially for many years for the oxidation of ethylene to ethylene oxide with oxygen or air. Most of the ethylene which is reacted is converted into ethylene oxide on the silver-impregnated catalyst support material and the remainder of the ethylene is converted amost exclusively to carbon dioxide and water. The aim is to react as much ethylene as possible, i.e. high productivity, such that the greater amount of the ethylene is converted to ethylene oxide, i.e. high selectivity.
It is known that the selectivity of these silver catalysts tends to decrease after the catalysts have been used for a number of years. We have found that one reason for the decrease in selectivity is the build-up of alkali metal-containing impurities on the catalysts. The decrease in selectivity results in less favourable economy of operation. It becomes advantageous to reactivate or regenerate the catalysts since an increase in selectivity of as little as one percentage point (selectivity equals 100 times the amount of ethylene converted to ethylene oxide divided by the total amount of ethylene consumed) can and will result in the savings of many thousands of dollars in a commercial operation.
There are several known methods for reactivating or regenerating silver catalysts. U.S Patent Nos.
4,051,068, 4,123,385, 4,125,480 and 4,177,169 disclose four such methods for regenerating silver catalysts.
An essential part of the process of U.S. Patent No. 4,125,480 is a washing step wherein the used catalyst is washed with one to ten times its volume of water or a mixture of water and an organic solvent before additional promoters are deposited on the catalyst. Treatment with water or watercontaining solutions can be detrimental to catalyst performance. In addition, exposure of the reactors to aqueous solutions can result in corrosion of the reactor and the formation of iron oxides which can be detrimental to the ethylene oxide manufacturing process.
U.S. Patent No. 4,186,106 discloses a process to improve the activity of supported silver catalysts which comprises washing the catalyst with an inert organic liquid and then applying cesium, rubidium, or a mixture thereof to the catalyst. The use of such non-aqueous solvents may provide adequate cleaning of the catalyst and eliminate the problems involved with exposure of the catalyst and/or reactor to an aqueous environment.
The aforementioned U.S. Patent No. 4,186,106 discloses both batch and continuous methods for washing the silver.catalyst with the inert organic liquid specified therein. The batch method merely comprises allowing the catalyst to stand in the liquid for a period of time and then removing the liquid.
In the continuous method, the liquid is pumped througn a glass tube containing the catalyst for a period of time and then the catalyst is drained. The continuous method described therein does not provide sufficient contact between the alkali metal-containing impurities in the catalyst and the washing liquid.
The batch method is more expensive because it requires much more solvent and takes more time. Also the amount of alkali metal-containing impurities which can be removed using the batch method is limited because a certain amount of contaminated solvent is always left behind in the catalyst. The method of the present invention at least substantially eliminates all of the above disadvantages.
According to the present invention there is provided an in-reactor method for removing alkali metal-containing impurities from supported silver catalysts which have been used for the direct oxidation of ethylene oxide which comprises: a) contacting the catalyst in the reactor with a non-aqueous solvent for from 0.1 hours to 10 hours; b) removing the used solvent and the alkali metal-containing impurities contained therein; c) causing fresh solvent to flow through the reactor for sufficient time to reduce the alkali metal concentration in the effluent to 50 parts per million or less; d) draining the solvent from the catalyst; and e) drying the catalyst.
Preferably, the time period should be from 5 to 10 hours to achieve the desired results. The catalyst is then drained and dried. This method can be used as the first step in a process for reacting or regenerating such silver catalysts wherein the second step comprises contacting the catalyst with cesium, rubidium, and/or mixtures thereof.
The process of the present invention combines the best aspects of batch and continuous processes for washing used supported silver catalysts. We have found that the presence of alkali metalcontaining impurities in the used silver based catalysts discussed herein is one of the major causes of the decrease in their selectivity over a long period of use. The invention described herein removes most of the alkali metal-containing impurities and thus assists in increasing the selectivity of the used catalyst.
A typical ethylene oxide reactor is comprised of a number of tubes containing a supported silver catalyst. U.S. Patent No. 4,066,575 describes a process for making such a catalyst. Our process is intended to be used in place in the reactor and thus a non-aqueous solvent is placed in the reactor tubes so as to contact the used catalyst. The solvent is allowed to stand for a period of from 0.1 hours to 10 hours (preferably at least 2 hours, since that time should normally be sufficient) to allow it to dissolve the alkali metal-containing impurities. Next, the used solvent is removed by draining it away or, preferably, by causing the fresh solvent to flow into and through the reactor and thereby push the used solvent out. It can be purified for reuse or discarded.
If the catalyst was not treated further with a solvent or if it was merely repeatedly treated according to the known batch process, there would be much of the solvent left within the pores of the catalyst and there would also be a significant amount of the alkali metal-containing impurities remaining in the pores, both dissolved in the residual solvent and remaining undissolved. When the catalyst is dried, this contaminated solvent will leave behind these impurities. In order to remove this residual solvent and as much of the remaining alkali metal-containing impurities as is possible, fresh solvent is caused to flow through the tubes for sufficient time to reduce the alkali metal concentration in the effluent to 50 parts per million or less. This is necessary to achieve substantial improvement in the performance of the catalyst.It is highly preferred that the concentration be lowered to 10 parts per million or less to achieve the greatest possible improvement in catalyst performance. Then the solvent is shut off and the catalyst is drained. Finally, the catalyst is dried by any convenient method such as blowing an inert gas like nitrogen over the catalyst at a slightly elevated temperature until it is dry. If it is desired to regenerate the catalyst immediately following the washing step, the drying portion of this process can be dispensed with.
The non-aqueous solvent should be an inert organic liquid. It is highly preferred that the composition disclosed in our copending application No. filed concurrently herewith, be used as the non-aqueous solvent in the present invention. Thus, the non-aqueous solvent should be comprised of an inert organic liquid and from 0.1% to 10%, by weight, of a solubilizing agent. The inert organic liquid can be an aliphatic, alicyclic, or aromatic hydrocarbon, ether, alcohol, or ketone. It may also be an aliphatic or aromatic ester, amine, aldehyde or nitrile. The solubilizing agent can be an aliphatic or aromatic acid or amine, or a crown ether. The preferred inert organic liquid is methanol and the preferred solubilizing agents are acetic acid, salicyclic acid, lactic acid, propionic acid, and ethylenediamine.If the catalyst is to be regenerated as described below, amines should not be used because the selectivity is adversely affected. Amines can be used if only the washing step is to be used. The reason for this is unknown.
The catalyst can be regenerated according to the processes disclosed in U.S. Patent Nos.
4,051,068, 4,123,385, 4,125,480 and 4,177,169 discussed above. It is preferred that from 1 to 1000 parts per million of cesium, rubidium, or mixtures thereof be deposited upon the catalyst.
The process of the present invention is easier, cheaper and more practical than the batch process disclosed in U.S. Patent No. 4,186,106 discussed above and provides more complete washing than the continuous method described therein. As discussed before, causing fresh solvent to flow through the already treated catalyst allows much greater cleaning and alkali metal-containing impurity removal than the batch method. Our method also uses less solvent than the batch method and requires less time.
Finally, our method provides longer and more complete contact between the solvent and the catalyst than the continuous method disclosed in U.S. Patent No.4,186,106.
The present invention will be further illustrated with reference to the following non-limitative examples.
EXAMPLES For these examples, a used silver catalyst containing an average of 346 ppm of potassium was washed with 3% acetic acid in methanol. The catalyst was loaded in a 1 in. (2.54 cm) tube to a total catalyst length of 24 ft. (7.3 m). The tube was equipped with a valve at the bottom for flow moderation.
The catalyst in the tube was completely covered with the acetic acid-methanol solution (2.5 liters) and allowed to stand to dissolve the potassium-containing impurities for the time indicated in Table 1. After the digestion period flow was initiated with fresh solvent at the top of the tube in the range of 1 5-25 milliliters per minute and continued for sufficient time to reduce the potassium level in the outlet stream to less than 10 ppm. The approximate flow time, final outlet concentration, and solvent usage, as well as the average potassium concentration on the catalyst, are shown in Table 1.
The catalysts were then dried by flowing nitrogen at the rate of 3 liters per minute through the tube for a period of 1 2-1 8 hours. The catalysts were treated with a solution of cesium acetate in methanol to give the cesium concentration on the catalyst indicated in Table 2 (the untreated sample was not regenerated). The catalysts were then dried and used to make ethylene oxide with a process stream consisting of 18% ethylene, 7% oxygen, 5% carbon dioxide, and balance nitrogen with 1,2dichloroethane added as inhibitor in the range of 30-250 ppm. A sample of catalyst which was not washed in accordance with the above procedure was also evaluated.
TABLE 1 Final K Avg. K Volume Digestion Flow Outlet Conc. of Solv.
Time Time Conc. on Cat. Added Sample (Hours) (Hours) (ppm) (ppm) (liters) 1 4.75 6 3 7.6 6 (3% HOAc/MeOH) 2 9 8.5 3 8.6 7.5 (3% HOAc/MeOH) 2.5 (MeOH) (postwash) TABLE 2 AEO Selectivity Temp. Cesium Potassium Sample % % "F Conc. Conc.
Untreated 1.5 62 510 0 346 1 1.5 66.2 490 231 7.6 2 1.5 65.6 500 185 8.6 It can be seen that the selectivities of the two catalyst samples which were washed are much higher than the selectivity of the untreated catalyst sample at the same productivity (AEO).

Claims (12)

1. An in-reactor method for removing alkali metal-containing impurities from supported silver catalysts which have been used for the direct oxidation of ethylene oxide which comprises: a) contacting the catalyst in the reactor with a nonaqueous solvent for from 0.1 hours to 10 hours b) removing the used solvent and the alkali metal-containing impurities contained therein; c) causing fresh solvent to flow through the reactor for sufficient time to reduce the alkali metal concentration in the effluent to 50 parts per million or less; d) draining the solvent from the catalyst; and e) drying the catalyst.
2. A method as claimed in claim 1, wherein the nonaqueous solvent is comprised of an inert organic liquid and from 0.1% or 10%, by weight, of a solubilizing agent.
3. A method as claimed in claim 2 wherein the inert organic liquid is selected from aliphatic, alicyclic, and aromatic hydrocarbons, esters, alcohols, and ketones, and aliphatic and aromatic esters, amines, amides, aldehydes, and nitriles, and the solubilizing agent is selected from aliphatic and aromatic acids and amines, and crown ethers.
4. A method as claimed in claim 1,2 or 3 wherein step c) is carried out until the alkali metal concentration is reduced to 10 parts per million or less.
5. An in-reactor method for removing alkali metal-containing impurities from supported silver catalysts which have been used for the direct oxidation of ethylene oxide, as claimed in any preceding claim, substantially as hereinbefore described and exemplified.
6. An in-reactor method for regenerating supported silver catalysts which have been used for the direct oxidation of ethylene to ethylene oxide and contain alkali metal-containing impurities which comprises: a) contacting the catalyst in the reactor with a nonaqueous solvent for from 0.1 hours to 10 hours; b) removing the used solvent and the alkali metal-containing impurities contained therein; c) causing fresh solvent to flow through the reactor for sufficient time to reduce the alkali metal concentration in the effluent to 50 parts per million or less; d) draining the solvent from the catalyst; e) contacting the catalyst with 1 to 1000 parts per 1 million parts of catalyst of cesium, rubidium, or mixtures thereof; f) draining the catalyst; and g) drying the catalyst.
7. A method as claimed in claim 6 wherein the nonaqueous solvent is comprised of an inert organic liquid and from 0.1 to 10%, by weight, of a solubilizing agent.
8. A method as claimed in claim 7 wherein the inert organic liquid is selected from aliphatic, alicyclic, and aromatic hydrocarbons, esters, alcohols, and ketones, and aliphatic and aromatic esters, amines, amides, aldehydes, and nitrides; and the solubilizing agent is selected from aliphatic and aromatic acids, and crown ethers.
9. A method as claimed in claim 6, 7 or 8, wherein step c) is carried out until the alkali metal concentration is reduced to 10 parts per million or less.
10. An in-reactor method for regenerating supported silver catalysts which have been used for the direct oxidation of ethylene to ethylene oxide and contain alkali metal-containing impurities, as claimed in claim 6, 7, 8 or 9 substantially as hereinbefore described and exemplified.
11. A method for regenerating supported silver catalysts which have been used for the direct oxidation of ethylene to ethylene oxide and contain alkali metal-containing impurities as claimed in any one of claims 6 to 10, including the additional step of contacting the catalyst with 1 to 1000 parts per 1 million parts of catalyst of cesium, rubidium, or mixtures thereof.
12. A method as claimed in claim 11, substantially as hereinbefore described and exemplified.
GB08218914A 1981-07-17 1982-06-30 Process for the removal of potassium from used ethylene oxide catalysts Expired GB2101495B (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US28420881A 1981-07-17 1981-07-17

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GB2101495A true GB2101495A (en) 1983-01-19
GB2101495B GB2101495B (en) 1985-01-09

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GB08218914A Expired GB2101495B (en) 1981-07-17 1982-06-30 Process for the removal of potassium from used ethylene oxide catalysts

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JP (1) JPS5824349A (en)
AU (1) AU8600482A (en)
DE (1) DE3226896A1 (en)
ES (1) ES514036A0 (en)
FR (1) FR2509630B1 (en)
GB (1) GB2101495B (en)
IT (1) IT1157219B (en)
SE (1) SE8203955L (en)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4391735A (en) * 1981-07-17 1983-07-05 Internorth, Inc. Cleaning and regenerating ethylene oxide catalysts
JPS6174545U (en) * 1984-10-23 1986-05-20
JPH0118599Y2 (en) * 1985-02-06 1989-05-31
GB9605175D0 (en) * 1996-03-12 1996-05-15 Entertainment Uk Ltd Improvements in or relating to securing apparatus

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2351661A1 (en) * 1973-10-15 1975-04-24 Huels Chemische Werke Ag Recovery of silver oxide and catalyst carrier - from spent silver catalysts used for mfr. of ethylene oxide
DE2636680C3 (en) * 1976-08-14 1979-04-05 Hoechst Ag, 6000 Frankfurt Process for improving the effectiveness of supported silver catalysts
DE2649359C3 (en) * 1976-10-29 1979-07-26 Hoechst Ag, 6000 Frankfurt Process for improving the effectiveness of used supported silver catalysts
DE2740480B2 (en) * 1977-09-08 1979-07-05 Hoechst Ag, 6000 Frankfurt Process for improving the effectiveness of supported silver catalysts
GB1591308A (en) * 1977-10-25 1981-06-17 Ici Ltd Regeneration of silver catalysts for the production of olefine oxides
GB2014133B (en) * 1978-02-10 1982-09-22 Ici Ltd Production of alkylene oxides using a silver catalyst
DE2938245A1 (en) * 1979-09-21 1981-04-09 Hoechst Ag, 6000 Frankfurt METHOD FOR IMPROVING THE EFFECTIVENESS OF SILVER CARRIER CATALYSTS
US4391735A (en) * 1981-07-17 1983-07-05 Internorth, Inc. Cleaning and regenerating ethylene oxide catalysts

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Publication number Publication date
AU8600482A (en) 1983-01-20
IT1157219B (en) 1987-02-11
FR2509630B1 (en) 1986-12-19
ES8308320A1 (en) 1983-08-16
GB2101495B (en) 1985-01-09
SE8203955L (en) 1983-01-18
ES514036A0 (en) 1983-08-16
DE3226896A1 (en) 1983-03-03
JPS5824349A (en) 1983-02-14
SE8203955D0 (en) 1982-06-24
IT8248818A0 (en) 1982-07-15
FR2509630A1 (en) 1983-01-21

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