DD160187A5 - PROCESS FOR THE PRODUCTION OF ETHYLENE OXIDE - Google Patents

Abstract

The present invention relates to a process for producing ethylene oxide using silver-bearing catalysts. The object of the invention is to provide an improved process which achieves a synergistic effect on the ethylene oxide selectivity and improves the efficiency of the process. According to the invention, a novel silver cross-linking catalyst is used with a combination of (a) zesium and (b) at least one other alkali metal selected from the group consisting of lithium, sodium, potassium and rubidium. This combination comprises (a) and (b) in such proportions with respect to the amount of silver therein that is sufficient to increase the efficiency of production of ethylene oxide to a level greater than the efficiencies associated with general working conditions are obtained with the aid of the known catalysts containing either only the relevant amount of (a) or only the relevant amount of (b).

Description

Berlin, 31.3 * 1981

Excretion accumulation from 58 985/18

Process for the production of ethylene oxide Use η c | se] ebie ^ t de r_ invention

The present invention relates to a process for the production of ethylene oxide using novel silver catalysts »

Characteristic of the known technical solutions

The production of ethylene oxide by the reaction of oxygen or oxygen-containing gases with ethylene in the presence of a silver catalyst is an old and well-developed process. For example, U.S. Patent No. 2,040,782, issued May 12, 1936, describes the preparation of ethylene oxide by the reaction of Oxygen with Ethylene in the Presence of Silver Catalysts Containing a Class of Metal Activators "In the unaltered revision of US Pat. No. 20,370 of May 18, 1937, Leferte _{f describes} that the formation of olefin oxides can be effected by reducing the olefins be brought ^ to unite directly with molecular oxygen in the presence of a silver catalyst _o From that point on has the earlier technology efforts focused on. · the efficiency of the catalyst. at the factory. ·. to improve cation of ethylene oxide «,

In the characterization dor present invention, the terms "conversion", "selectivity" and "yield" as used such as from 7 * Oanuar 1959 in the column 3 in the line 24 in dsr US-PS 3,420,784 -. 35 including

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jl

This definition of "selectivity" is consistent with that described in US Pat. No. 2,766,261 at column 6 in lines 5-22 and US Pat. No. 3,144,916 at lines 58-61 »The definitions of" yield "and" conversion "have different meanings in this field of technology and are not to be used according to the definition, for example in the above-mentioned US Pat. No. 2,766,261 * The terms" efficiency "and" Selectivity ", as used in the present description and in the points of the invention claim, are considered as synonymous»

Significant changes have been made to the silver catalysts used in the production of ethylene oxide since their initial stage of development. As reported in the art, the silver particles were first applied to support materials, with little attention being paid to support properties such as the effective Surface,. pore volume and chemical inertness. "Further developments in this field of technology have resulted in specific technologies relating to the supports or support materials containing the silver, with greater efficiencies for the reaction of the ethylene oxygen to produce ethylene oxide were obtained * -Heutzutage correspond DIE .. .. · 'most' Tragersubstanzen for the silver catalysts homogeneous, consisting of single solid particles materi-, lien that can be introduced into the interior of a reactor. 'wherein the Possibility exists; that. the reaction gases and the gaseous products of the reaction penetrate into these homogeneous solid particles and around them

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Can herumbevvegen particles to pass therethrough through the reactor and recovered to become _e The shape of the vehicle is a variable factor, and the selected particular shape for the reactor used for the required gas flow and the effective surface characteristic, "This is features for optimizing the reaction, taking into account other factors as well *

The carrier materials that have been used are typically derived from inorganic materials, generally having a mineral character. In most instances, the preferred carrier substance is alpha alumina _# as described in the patent literature; See, for example, U.S. Patent Nos. 2,294,383, 3,172,893, 3,332,887, 3,423,328, and 3,563,914.

The silver applied to these supports is typically in the form of small particles. The patent literature shows that the size of the silver is a factor in the effectiveness. of the catalyst, and in most cases, the fine particle silver is recovered using standard techniques in the art; see in * - for example, the., US-PS 2,554,459,. 2 83.1 87O ₅ 3 '423. , 328 ', which specify that silver particles having a particle size of 150 to 400 α are used; U.S. Patent 3,702,259 describes a production process for obtaining silver particles having a diameter smaller than 1 ura, and US Pat No. 3,758,418 describes silver particles with a diameter smaller than 1000 %,

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The application of silver to the support can be achieved by a number of techniques, but the two most commonly used techniques involve, in one case, impregnating the support with a silver solution followed by heat treatment of the impregnated support coating the carrier with the silver by the deposition of silver or by preformation of silver into a slurry such g that the silver particles are brought to the carrier to deposit for the purpose of deposition of the silver on the carrier · »material and in the other case, and thereby adhere to the carrier surface when the carrier substance or carrier material is heated »in order to remove the existing liquids. These different processes are described in more detail in various patents, such as US Pat. Nos. _2,773,844 , 3,207,700, 3,501,407 and 3,664,970 (see GB ~ PS 754 593) and also 3 172 893,

The active surface * provided by the support has been of considerable interest in the development of silver catalysts. Descriptions of the effective surface area of the catalysts can be found in the following patents: US Pat. No. 2,766,261 (described herein) an effective surface of 0 ^, 002

  - '2 ·' '· -

to 10.m / g is suitable),. U.S. Patent No. 3,172,893 (here;

a porosity of 35 to 65 % and a pore diameter of 80 to 200 jusn described), · US-PS 3,725,307 (it is

an effective surface area of less than 1 m / g and an average pore diameter of 10 to 15: pm); US-PS 3,664,970 (here a carrier substance with a minimum porosity of about 30% is used, wherein

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at least 90 % of the pores have diameters ranging from 1 to 30 / jm and the average of these diameters ranges from 4 to 10 ρ) and U.S. Patent No. 3 563 914 (this is a catalyst support having an effective surface area less than 1 m / g, a volume of 0 * 23 ml / g and a particle size between 0.074 and 0.30 mm) «

In the earliest developments of the silver catalysts for the production of ethylene oxide, it has been determined that a number of metals, if present in combination with the silver, could act as activators of the silver catalyst. "These materials are not catalysts in themselves, but contribute to improving the percentage or amount of ethylene oxide recovered. "One of the problems in determining whether these metals appear as activators or not is the nature of the reaction itself. The reaction between the oxygen and the ethylene Formation of ethylene oxide is a highly exothermic reaction. "Even more exothermic than the reaction, however, is the combustion of ethylene or ethylene oxide into throat dioxide. These transformations occur simultaneously, and the critical factor in determining the effectiveness of the overall process is the measure of control for these two competing reactions. Inevitably, a material that enhances the production of ^: ethylene oxide could also be considered as such be that inhibits complete combustion of the ethylene to ethylene oxide to carbon "dioxide _Ä Thus, there is a problem in the way in the definition, whether the material is considered as an activator, in fact an inhibitor of Verbrermungs-

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reaction "It is well known that there are materials" which, when added to the reaction, contribute to the formation of a smaller amount of carbon dioxide. Such materials are referred to as inhibitors. "There are also materials which when added to the catalysts, contribute to a greater amount of ethylene oxide. * Such materials are referred to as promoters * Whether the latter materials are in fact inhibitors or activators, j seems to be a negligible issue * What is significant is that is the statement that the result of the reaction is advantageous for the recovery of the ethylene oxide. For this reason, when it comes to the determination or characterization of a catalytic process for the production of ethylene oxide, there is a significant factor involved in that process or contributes to the qualification of that procedure, »in selectivity of the process for the production of ethylene oxide _e This refers to the selectivity according to the definition given above «

The use of alkali metals as activators for the silver catalyst-driven production of ethylene oxide is extremely well known in the art * U.S. Patent 2,177,361 issued Oct. 1939 mentions the use of Al kai in the et al in silver, ·; to find catalysts. U.S. Patent 2,238,471 discloses that lithium is very useful as an activator, but that potassium and cesium are considered undesirable. The examples of that patent use substantially 10 mass% of potassium hydroxide or cesium hydroxide with respect to the silver oxide from which in the preparation of the catalyst

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sators. Later, US Pat. No. 2,404,438 states that sodium and lithium are effective activators for this reaction. Essentially the same statements can be found in US Pat. No. 2,424,084. US Pat. No. 2,424,086 contains generalizations about alkali metals as activators and specifically specifying the sodium for these purposes. "In US Pat. No. 2,671,764, the patentees considered that the alkali metals in the form of their sulfates are effective as activators for such silver catalysts * In particular, the patentees found that US Pat. No. 2,765,203 describes the pretreatment of a carrier substance with a dilute solution of a chlorine-containing compound and has led to the conclusion that such chlorine compounds are used Special references to suitable anorganic chlorine compounds include Natriu chloride, lithium chloride and potassium chlorate «. This patent specified that represents the proportion of inorganic chlorine "containing compound _f which is applied to the catalyst support, 0.0001 to 0.2 mass ~, o on the basis of mass. U.S. Patent No. 2,615,900. (Sears) describes the use of metal halides in the treatment of the supported catalyst and specifies that such halides; Alkali metals. ¹ , such as lithium, sodium, potassium and cesium. The metal halide is present in the range of 0.01 to 50 mass% based on the mass of metallic silver. The patent specifies also that Genischo of the individual metal halides, which are generally classified in the patent, can advantageously be used to

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Thus, a particular catalyst treated with a metal halide would develop a short term high initial efficiency, whereas other metal halides would have a longer term moderate efficacy This patent takes the position that the metal halides present in the catalyst in question serve * to prevent the combustion of ethylene to carbon dioxide. Therefore, these materials are used as passivating agents for the catalyst or catalyst US Pat. No. 2,709,173 describes the use of a silver catalyst for the production of ethylene oxide, wherein simultaneously with the introduction of the silver catalyst into the solid support any alkali metal halides, such as lithium, sodium, potassium and rubidium compounds of chlorine, bromine and oxy, may be provided to increase the total production of ethylene oxide *. The patent specifies small proportions "less than about 0.5 mass%" desirable "" In particular, the patent emphasizes "proportions of alkali metal halide within the range of: about 0.0001 to about I O _1% by mass" for the bevorzugtesten * Das'Patent notes '' that _t "although the preferred catalyst composition contains a particular activator, this is not always necessary because, during the preparation of the catalyst, the alkali metal halide may be converted to some extent into the corresponding alkali metal oxide which acts as an activator. Dio U.S. Patent 2,766,261 seems to suggest the statements U.S. Patent 2,238

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to take cautious note, namely cesium and potassium in silver catalysts as disadvantageous and undesirable; However, US Pat. No. 2,769,016 states that sodium, potassium, and lithium are to be considered as activators when used in silver catalysts. This latter patent also recommends the pretreatment of the catalyst. Carrier with Dilute Solutions of Sodium Chloride, Lithium Chloride or Potassium Chlorate * U.S. Patent 2,799,687 (Gould u ₍ a ») states that the addition of the metal halides is within the scope of Sears' U.S. Patent

This is particularly true in the case of the alkali metal halides, especially the chloride and fluoride of sodium and potassium. "The patentees recommend that the inorganic halide component of the catalyst be within the range of 0, 01-5 Mäsce-%, preferably within the range of 0.01 to 0.1 mass'% "oxidative catalytic silver component" on the basis of the mass of d _e h _e, is maintained the over-run in elemental silver silver salt. U.S. Patent 3,144,415 mentions a variety of metals as activators, and one of them is the cesium

No. 3,258,433 states that sodium is an effective activator. US Pat. No. 3,563,913 recommends the use of 'alkali metals' - for example, lithium compounds, as activators. PiQ preferred amount of anion activating material is reported to be about 0.03 to 0.5 mass% of metal oxide based on the mass of the carrier. U.S. Patent 3,585,217 states that it is known of the alkali metal chlorides ., "counteract the formation of carbon dioxide" and these "chlorides" are included in the catalyst

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US Pat. No. 3,125,538 discloses a silver support catalyst having a simultaneously applied alkali metal selected from the group consisting of potassium, rubidium and cesium in a specified gram atomic ratio relative to the silver. The mass of silver preferably corresponds to 2 to 5 mass%. Yes, the catalyst "The patentees characterize this catalyst as particularly suitable for the reaction of nitrogen (II) oxide with propylene." US Pat. Nos. 3,962,135 and 4,012,425 describe the identical catalyst as suitable for the production of ethylene oxide U.S. Patent 3,962,136 discloses the simultaneous application of alkali metals with the silver to the support, with the alkali metals in their final form being present on the support as an oxide, the oxides consisting of cesium, rubidium, or mixtures thereof in optional combination with one smaller proportion of an oxide of potassium «The proportions

~ 5 of such oxides amount to about 4.0 χ 10 * mass% / kg to about 8.0 χ "" "mass% / kg of the total catalyst." U.S. Patent No. 4,010,115, issued March 1, 1977, differs however, by using as the oxide of the alkali metal the oxide of the potassium with optional combination with a smaller proportion of an oxide of rubidium or cesium. The patent application with the German patent no. 317 349 of 21 December 1972 as source for the US Pat -PS 3 962 136 and. 4 010 115 and others contains some.e · interesting information that it. deserve to be mentioned ".

Example 2, which contains some comparative experiments, describes the preparation of a catalyst containing 310 ppm in concurrently added potassium. It was found in this context that

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However, we have found that the proportion of potassium in the catalyst within the range * as described in US Patent No. 4,010,115 ₄ for the Production of ethylene oxide, although there is nothing in the patent in question to support this view *

British Pat. No. 821,439 based on British Patent 1,489,335 describes that a catalyst equivalent to that disclosed in U.S. Patents 3,962,136, 4,012,425 and 4,010,115 (Nielsen et al.) Can be prepared _s by the method modified by which the alkali metal of the carrier substance is fed "in the Belgian patent and British equivalent of a porous refractory support having a specified effective surface is first impregnated with an alkali metal in order to apply this to the carrier material in specified amounts ( both the proportions and the nature of the porous support are those values equivalent to those in the above-mentioned US-PS (Nielsen and others) are illustrated) _p the carrier material is then dried to bind the alkali metal, and then the silver is fed to the carrier »This procedure corresponds to sequential application of the alkaline calsa activator. and the silver catalyst, and yet the same type of catalyst was actually obtained by the simultaneous application of the alkali metal salt ur.d of silver. This was shown by comparing the data in the examples of the Belgian PS with the data in those mentioned above US-PS by Nielsen and others prove »the critical

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The element in the method of applying the alkali metal to the support seems dubious in view of the manner of description and description in US Pat. Nos. 4,033,903 and 4,125,480, which teach that a silver-containing catalyst used is for subsequent addition of an element It is obvious that such a treatment will regenerate the ability of the catalyst to improve the selectivity towards the ethylene oxide. Another patent which indicates that a subsequent addition of alkali metal , such as cesium, gives results equivalent to either a previous addition or a simultaneous addition, US Pat. No. 4,066,575.

U.S. Patent No. 3,962,136 and the related patents were taken from the US patent application with the IFD _e No * 216 ISS from 7 * Oanuar 1972 now abandoned _e, U.S. Patent 3,962,136 describes that "the highest selectivity with potassium-modified catalysts is typically less under otherwise comparable state conditions than with rubidium "or zäsiummodifizierten catalysts recoverable" (see column _2, lines 38 - = 42), U.S. Patent application lfde No. _E 216 188 includes a drawing relative the - efficacy of rubidium * cesium and potassium to improve the selectivity of the ethylene oxide represents "when these elements are used in a Siiberkatalysator * the drawing shows that the curve which results in the addition of the Zäsiums'wiedergibt, the greatest degree represents improve the selectivity C, while curve B, which represents the addition of rubidium, takes an intermediate and the potassium z represented by curve A. ugabe

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is superior, in a change of 11 * April 1975 in the US Patent Application Serial _e no. 480896 of 19, Duni 1974, which is considered as the source of the application of US Patent No. 4,010, the applicant assumes in that the invention and the points of the claim of the invention do not contain any "synergistic effects with the use of the mixtures" of the alkali metals. The same statement can be found in the modification of April 11, 1975 in the US patent application Ser. No. "471 398 of 20 May 1974, which is to be regarded as the (') source for the application of US Pat. No. 4,012,425 »

DE-OS 2,640,540 describes in its examples a silver catalyst for the production of ethylene oxide containing sodium and either rubidium, potassium or cesium. "Table 1 of this specification contains the alkali content of all catalysts as obtained in the examples of which contain many sodium, potassium, and cesium. "A footnote to the table states that the presence of potassium in all the catalysts studied (except one that did not have cesium) was attributable to the impurities in the support ." The concentration of such impurities "was less specified for the usefulness in the context of the invention _o the description does not state ,, in that the cesium can with the potassium and / or sodium .trium be combined advantageously _r illustrate still in: '.. ·. information on the efficiency of any 'synergistic interaction of cesium with sodium or with potassium impurities in the catalysts'

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The description of the OP Patent Application Serial "No. 95 213/75 relates to a method for the production of ethylene oxide using a catalyst composition of silver» barium, potassium and cesium in specified Ätomverhältnissen "Table 1 of this description summarizes the efficiencies that be achieved with the various catalyst compositions of Examples »No synergism with cesium and potassium was demonstrated any" one of the cesium-potassium-barium mixtures of Examples "indeed, a comparison of some examples from table 1 seems to be the lack of a Zäsium- to illustrate potassium synergism, it is shown that the efficiency achieved with a cesium-potassium mixture is smaller than the efficiency "achieved with the same amount of cesium in the absence of potassium ,,

For example, the two examples 3 and 7 relate to catalysts having an identical atomic ratio between cesium and silver (0.05 atoms / 100 atoms Ag), but with different potassium contents. The atomic ratio of the potassium in Example 3 is equal to 0.times.100 atoms K / 100 atoms AgV and the corresponding ratio in Example 7 is 0.05. The efficiency achieved in Example 3 was 75.4 % and that in Example 7 was 75.9 %. _o Thus the larger potassium content resulted in Example 7 to a decrease in the efficiency of the catalyst * In. Similarly, Examples 1 and 4 relate to catalysts having an identical atomic ratio between ~. see the cesium and silver, with the catalyst in Example 1 having an amount of potassium an order of magnitude greater than the catalyst in Example. 4 "Nevertheless, the reported efficiencies for both catalytic converters

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substantially the same, 76.7 % and 76.6 % for Examples 1 and 4, respectively *

US Pat. No. 4,039,551 describes a catalyst for the production of ethylene oxide. This catalyst contains silver, tin, antimony, thallium, potassium, cesium and oxygen in specified atomic ratios. Mixtures of cesium and potassium are not described as desirable combinations indeed For example, Table 1 of the '' patent describes a silver-cesium-potassium combination, which is considered to be a "control" example, not in accordance with the invention described, and wherein a selectivity of 73.0 % is achieved is a value which is smaller than the selectivities in appreciably, which are found in the 45 examples in tables 2 and 3 * in addition, the efficiencies in tables 2 and 3 for the various catalysts can not be used to order to demonstrate the existence of any synergistic combination between cesium and potassium among the numerous combinations of elements It is also noteworthy that the aforesaid US-PS 4 039 551 claims priority over "a Japanese patent application of OaHr-G 1973 and, subsequent to this application, the same applicant : .. · .. OP patent application -Ii.t: .der. 'Mr, 25 703/77 filed in the V. a catalyst for the production of ethylene oxide from. wird.β described the same metallic elements as described in US Patent with the exception of cesium and potassium The latter described in the examples of Japanese Patent Application. Efficiencies are similar to those in dom US Patent * The Influence of Cesium

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and potassium in the catalyst composition as described in the US patent is therefore likely to be significant.

The BE "PS 854 904 describes silver catalysts with various mixtures of sodium and cesium", GB GB patent application GB 2 002 252 A describes in Table 2 support silver catalysts with various mixtures of cesium and thallium * some of which additionally potassium or antimony US Pat. No. 4,007,135 describes generally (in column 2 _t lines 25 ~ 30) silver catalysts for the production of alkylene oxide containing silver. Together with an accelerating amount of at least one activator selected from the group lithium, potassium _f sodium , Rubidium, cesium, copper, gold, magnesium, zinc, cadmium, strontium, calcium, niobium, tantalum, molybdenum, tungsten, chromium, vanadium and barium. The European Patent Publication No. ₁₁ 0003 642 describes in table silver-containing Catalysts containing mixtures of potassium and cesium, and a catalyst having a sodium and cesium content. The above publications contain no evidence for a synergistic interaction of cesium with other alkali metals _β

BE ~ PS 867 045 describes carrier silver catalysts. , Esinem lithium content, which can, as an effective conceives, Menge.nah-, Part _F and a substantially lower proportion of an alkali metal selected from the group _f j cesium rubidium, and / or potassium "Table .1 of the patent describes three catalysts, all contain cesium, sodium, potassium and lithium, the lithium concentration being at least an order of magnitude greater than the concentrate

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tion cesium or potassium "Referring to Table 1, the catalysts Ll, L2 and L3 markedly different concentrations of cesium, potassium and sodium on, in Table 2 is shown, however, that these catalysts have substantially similar selectivities," it There is no evidence for a synergistic interaction of cesium with either potassium or sodium in the described silver catalysts.

The BE-PS 857 185 describes supporting silver catalysts for the production of ethylene oxide with a specified amount of potassium and at least one other alkali metal selected from the group Rubidium and Zäsiuiru Table 1 describes the composition of 14 potassium-containing catalysts, of which two potassium in a combination containing cesium (catalyst G and H) ₉ It can be seen that the selectivities of catalysts G and H are identical at a pressure of 1.03 bar, but slightly different at the higher pressure of 16.55 bar, From the data no silver "i <alium" cesium "synergism can be inferred"

The object of the invention is to provide a process for the production of ethylene oxide using, a; ^ Catalyst having a synergistic effect as Ethylenoxidselektivität and a selectivity that is greater than that according to the prior art anticipated or described "'"

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Explanation., The essence of the invention

The invention has for its object to provide a process for the production of ethylene oxide, in which the silver catalysts used at least two alkali metals (excluding francium), one of which alkali metal corresponds to the cesium and apply each of the alkali metals in such a proportion is that the combination thereof with respect to the proportion of silver in the catalyst gives a synergistic effect on the ethylene yield *

The catalyst employed according to the present invention consists of a silver bearing catalyst. The catalyst contains a combination of (a) cesium and (b) at least one other alkali metal selected from the group consisting of lithium, sodium, potassium and Rubidium, wherein (a) and (b) are present in such proportions with respect to the amount of silver therein as to increase the efficiency of production of ethylene oxide to a level greater than the efficiencies achieved in the context of general working conditions can be obtained with the aid of the catalysts in question, which correspond to the catalyst according to the invention, except that one catalyst contains the increasing amount of (a) and the other catalyst contains the amount of (b) in question to contain both (a) and (b). Catalyst during use in the production of ethylene oxide, a grain, bination of cesium and one or more other alkali metals (excluding francium) in a quantity, whereby a synergistic effect according to the further

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The method of the present invention defines such synergism as a function of the silver content of the catalyst. Thus, for any given amount of silver in the catalyst, the present invention provides the corresponding correlation between the alkali metal and the silver, thereby providing specific synergism Combinations of cesium and one or more other alkali metals can be selected which allow efficiencies to be achieved in the production of ethylene oxide * which exceed the higher efficiency that can be achieved with such a proportion of silver when combined with the amount of either cesium or the other alkali metals present in such a mixture ».

As described in more detail below, the binary Al are kaliinetallkombinationen cesium-lithium, ~ sodium, cesium-potassium and cesium-rubidium _£ contributing Cesium in combination with silver at a particular catalyst carrier and at an appropriate catalyst preparation to a synergistic result, defined " However, the new catalysts are not limited to binary combinations of the alkali metal. Other alkali metals may advantageously each of the aforementioned synergists. After all, binary combinations are added for the purpose., we rdo η ,. increase or decrease the work temperature of the catalyst, improve initial catalyst efficiency during start-up, and / or outperform the catalytic converter's aging properties over longer working hours. In some cases, the addition of a third or even a fourth Alkali metal to an otherwise synergistic

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see binary combination cause a further increase in the efficiency of the catalyst »

The mathematical relationships from which the synergistic binary alkali metal combinations of the present invention are derived are set forth below and exemplified by a cesium-potassium combination. Binary combinations of cesium with any other alkali metals according to the present invention will be readily understood by an analogous reference Method wherein said specific alkali metal of interest for potassium is substituted in the method described below *.

The relationship between cesium ^ potassium and silver to achieve a synergistic result, as defined herein, is characterized by a mathematical equation or mathematical model »where efficiency is expressed as a function of silver in mass ~ / o, of cesium in mass ~% and the potassium in mass / o is related to each other. "These elements are deposited on the support of the catalyst Thus, synergism with mixtures of cesium and potassium can be obtained at any concentration of silver in the finished catalyst *

The 'general' form of the mathematical equation, referred to as the "efficiency model", defines the effect. grad (or selectivity) as a function of mass / o of silver, cesium and potassium, depositing these elements on the support of the catalyst as follows:

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Efficiency in % = b _Q '+ O ₁ (BG). + B ₂ (BCs) + O ₃

+ b ₄ (BG) ² + b ₅ (BCs) ² + b ₆ (BK) ²

+ b _? (BG) χ BCs) + bg (BG χ BK) + b _g (BCs x BK).

where b _{o <} b ^ b ^, b ^, b ^ _t b ^, b ^, b _yi b _Q and b _{g are} the relevant coefficients for each member of the efficiency model and are made up of a series of constants for a particular catalyst support substance and a special method for the preparation of kaiaIysato in accordance with an intended series of experiments as described below, "The value of some of these coefficients may be zero"

BG = (mass% Ag - mass% Ag);

where mass'-5o Ag = average value of mass ~ ya Ag using in the intended series of experiments «

BCs = (MaGse% Cs - mass% Cs);

where mass% Cs' = average mass of 5'6 Cs using in the intended ROINE of experiments «

BK '= _ (Hasse-% K - mass- ^ K);''''''''

where mass / o K = average value of mass% K using in the intended series of experiments »

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The proposed set of experiments is the be ~ quemsten manner in the arrangement of a composite structure with three independent variables as described by D * L _e Davies in the thesis "The design and analysis of industrial experiments", Hafner Publishing Company, I960, pages 532 - 535, planned »For this purpose, the three independent variables correspond to the mass% of silver, cesium or» potassium «. The ranges of the respective variables are selected in such a way that the selectivity and activity of all catalysts in the intended series of experiments It is therefore desirable first to perform some preliminary experiments to find out the particular area in order to determine the appropriate ranges of cesium and potassium for this purpose »corresponds to zero mass% of cesium and / or potassium a comfortable lower limit for use in the context of the composite structure "The upper concentration limit of cesium and potassium can be readily determined by a series of experiments with catalysts containing successively larger amounts of either cesium or potassium." This is done as follows: An initial catalyst is prepared (using a method of preparation, if desired, as described further below in the Examples) containing a small amount (on the order of about 0.001 Ma.sse <~%). either cesium or potassium with a constant amount of, say, 7 mass% silver contains. Dig selectivity of this catalyst is then determined for the recovery of ethylene oxide under the desired test conditions. This experiment is then repeated with a catalyst that's the double

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Thus, experiments are repeated in a series of experiments, each successive experiment using a catalyst having twice the alkali metal content of the catalyst of the previous experiment until the measured selectivity of the last catalyst tested smaller than that of the starting catalyst. The upper limit of the cesium or potassium concentration is defined in this way for the composite structure,

The iterative process described above can be advantageously changed to more quickly determine the upper limit of the concentration in the case where it is observed that a double increase in the alkali metal content of the catalyst does not produce a significant change in the selectivity of the catalyst. In particular, such a case is very likely to occur, for example, in the case of catalysts with lithium or sodium (depending on the particular carrier and the manufacturing process used), as opposed to other alkali metal catalysts in which, in the sense of In general, the efficiency is more sensitive to an increasing concentration of alkali metal. "Accordingly, in the event that the efficiency of the catalyst is substantially unaffected. , changes blabt ', when .the Alkal.xnietallgehalt, the catalyst ^ has been doubled in the above-described iteration to use a 1Ofache increase in alkali metal content · until the measured efficiency of the final catalyst! thy than that of the starting catalyst is * After that, it may be ervürecht _s recent iteration step Verwendung- less alkaline '

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metal concentration, such as using a 3 or 5-fold increase in the alkali metal content, to more accurately determine the upper limit of the alkali metal concentration for the composite structure. "

The range of silver concentration in the composite embodiment may typically be 6-16 mass / ö, with an average value of silver (mass-So Ag) of 11 mass%. "Similarly, the ranges of cesium and Potassium concentrations typically 0.0 to 0.02 mass% _e For rubidium, the concentration range is also typically 0.0 to 0.02 wet%, while for lithium and sodium the ranges are characteristically 0.0 to 0 , 1 mass%. For some excipients, the upper concentration limit of cesium and / or potassium may be 5 to 10 times greater * This is particularly likely to apply to excipients containing exchangeable cations

Table 11-5 on page 533 of the DaviGs paper mentioned above describes a three variable composition based on the units of - 'C, -l _f . 0, +1 and + * £., Where -1 is a "low level" of the variable concerned. _r.ep lawn-.V. advantage; + 1 a "high level" - expresses such a variable; 0 represents the average value of the variables; "X denotes a value which is slightly lower than the value represented by"1; and where + zA denotes a level that is slightly higher than the value + 1 * The special choice of - j? c and + od is not critical «,

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However, Table 11,6 on page 534 of the Davies publication suggests values for -ei and + ^ which are particularly useful for a composite construction according to the present invention *

The proposed series of experiments is thus typically composed of 16 to 20 experiments, testing catalysts with different concentrations of silver, cesium, and potassium. "For example, a preferred composite construction in which the mass% of silver 7, 0 to 15.0, the mass% of cesium is 0.0 to 0.02 and the mass% of potassium is 0.0 to Ο, ΌΙ, as follows:

-zo silver _hasse ~ / o cesium mass ^ potassium

9 0.005 0,002 13 0.005 0,002 9 0 * 015 0,002 13 0,015 0,002 9 0.005 0 _f 008 13 0.005 0,008 9 0,015 0,008 13 0.0915 0,008 11  Ό, οιο 0.005 11 : ... ο, οιο '. 0.005 '' ·· 'ο * οίο · • "/ 0,005 15 ' 0,010 0.005 11 0.0 .O _S OO5 11 0,020 0.005 ii 0,010 0.0 11 0, Oio 0,010

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The catalysts of the foreseen series of experiments are tested by means well known in the art for measuring their selectivity and activity * A convenient measure of the activity, d _# h _#, for the degree of conversion of the reactant into a product each Time unit, is the temperature required to either obtain a fixed ethylene oxide production or to obtain a selected value of ethylene conversion (or oxygen turnover) in moles _e ~ / b. Thus, a mathematical equation for the catalyst temperature (temperature model ) are developed in a manner similar to the efficiency model, that is, for each catalyst two behaviors (selectivity and temperature) are obtained which are related to the three controlled variables (mass% of silver, cesium and potassium) The relationship between the respective behavior and the controlled V ariablen is obtained in the manner 'by these data with the equations or mathematical models by the method of least squares as described in Chapter 8 of the book "Statistical Methods in Research and Production" by _e 0 .L "Davies and P _a L * Goldsmith, Longman Group, Ltd. ", London, 4 * Edition, 1976." In practice, the mathematical models are fit to such data routinely by means of a digital computer according to the. Description in the ^..: book "Applied Regression Analysis" N, R _5, Draper and H ₀ Smith, Oohn Wiley and Sons, Inc ",, 1966" The models resulting thereby (the IVirkungsgradmodell and the temperature model) describing the relationship between. Behaviors and the controlled variables *

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It is well known in the art that the number of experiments required to establish mathematical relationships among many variables depends on the reproducibility of the data. Thus, in a compound setup with approximately 16 experiments, it may occasionally be necessary to to repeat the entire series of the intended experiments or part of these experiments to the relationship between the}. Determine efficiency and mass / o of silver, cesium and potassium precisely to achieve an acceptable level of statistical confidence * In practice, it has been found that for a given set of about 16 experiments, the mass% of silver ranging from about 7 to about 15, a full repetition of the intended experiments is usually sufficient to establish this relationship, assuming that the standard deviation of a single experimental test result is not greater than about 0.7 % efficiency units * during the course For example, data from both the preliminary experiments mentioned above for finding the corresponding regions and all the additional ones can be taken from experimentation, data that does not correspond to the intended series of experiments that are useful for the development of the model described above experimenting tellen. Data, the. in . ·. , respect up the particular catalyst carrier and the manufacturer · position process of interest, are at your disposal, considered desirably together with those data were derived on the basis of the composite was building _o The equations are adapted in this way the data "As a result, can under practical

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Conditions Data from about 30 to 60 experiments for the development of efficiency and temperature models. be available"

The general form of the mathematical equation, referred to below as the "temperature model" defines the temperature as a function of mass / o of silver, cesium and potassium deposited on the support of the catalyst. The notation is as follows:

Temperature in C ⁰ = a + a.fBG) + a ₂ (8CS) + a ₃ (BK)

+ a ₄ (BG) ² + a ₅ (BCs) ² + a _ß (BK) ² + a _? (BCs χ BG) + a _g (BG χ BK) + a _g (BCs χ BK)

where a _Qi a ^, a ₂ , a ^ _t a ₄ ^: _f a _gl a _& ; a _y , a _Q and a _g correspond to the respective coefficients for each member in the temperature model and are made up of a series of constants specific to a particular catalyst support and a particular method of catalyst preparation in accordance with a designated series of experiments according to the present invention The values of some of these coefficients may be equal to "zero", BG ₁ BCs and BK correspond to the defi nitions _e : ':::.

The most convenient use of the efficiency and temperature models for defining the range of synergism for any selected mass of silver in the catalyst is to graph the efficiency and temperature behaviors, generally understood to be level maps

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are, as the description in Chapter 11 of the above-mentioned book "The execution and analysis of industry" experiments "can be seen." Thus, Figures 1 and 2 contain the level diagrams of the efficiency and the temperature for a selected carrier and a catalyst production process 7 and The level diagrams were derived from a series of experiments in which the mass was ~% of silver, 5.33 to 15.05, the mass of cesium 0.00 to 0.0.19 and the mass% of potassium is 0.00 to 0.021. Table 1 below provides a summary of the experimental data available for the selected catalyst support and catalyst preparation method from which the level traces were derived. The experiments were performed in two different experimental transducers according to the standard procedure described below under the heading "Catalyst Comparisons". , Experiments used two similar but slightly different substrates. Table 1 represents the experimental data on a common basis, o% h. The data were adjusted to account for the observed differences between the transposers and those used Compensate catalyst supports »

'. Table Ir experiment hurry data. - -. , : ... .. · ''. ''.',.

Mass% Mass%% Temperature Efficiency Silver Cesium Potassium (C) (%) 11.14 '0.00477 0.00158 256 _s 0': 73.9 10.53 .0.00897. 0.0 · 256.4 77.5 11.14 0.00479 0.0 256.0 72.9

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Mass ~% silver  Mass% cesium Mass ~%. potassium Temperature ( ⁰ C) Efficiency (%) 11 VOl 0.00941 0.00312 256.0 77.4 11.21 0.00240 0.00080 258.0 70.7 10.92 0.01865 0.0 282.2 74.3 11.04 0.00941 0.0 257.2 76.3 11.04 0.00941 0.0 255.0 76.3 11.09 0.01421 0.00412 270.7 75.7 1Q41 0.0 0.0 263.0 68.5 10.41 0.0 0.0 265.0 68.4 11.16 0.01909 0.00633 292.6 72.0 10.94 0.01403 0.0 267.0 76.7 10.70 0.01128 0.00379 262.0 77.5 9.08 0.01900 0.00315 293.0 71.8  9.31 0.00968 0.00645 269.9 76.6 13.17 0.00617 0.00102 254.9 74.2 9.10 0.00323 0.00214 260.0 72.7 13.14 0 _f 00915 0.00513 259.1 77.5 11.11 0.00950 0.00315 259.6 77.6 11.31 0.01205 0.0 260 _f 3 77.4 11.05 0.00236 0.00078 260 _f 4 70.1 12.72 0.00311 0.00207 255.8 71.6 16.05 0.00941 0.00313 263.0 77.7 5.88 0.00924 0.00305 269.1 76.8 ii> 04 ' 0,01421 ·. 0.00157 , 268 _ff 9 ·. · / V-. .-76j7 · ·; ...: 10.89 0.00462 0.00450 256.4 ' 75.4 10,80 0.0 0.00613 250.5 69.9 8.93 0.00630 0 _f 00105 260.4 74.4 15.51 0.01288 0.0 266.4 77.2 6.03 0.01341 0.0 280 _t 3 73.7 13.11. 0.00897. 0.00810 266.2 77.1 16.00 0.00888 0.00800 264.3 77.8

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silver cesium Mass% potassium temperature ( ⁰ C) efficiency 10.93 0.0 0.01230 263.4 73.3 12.95 0.01562 0.00459 277.1 76.0 13.12 0.01313 0.00386 263.1 77.0 12.85 0.00150 0.0 264.4 68.2 13.12 0.01047 0.00297 257.3 78.3 > 13.26 0.01784 0.00540 282.3 74.5 12,91 0.01384 0.00407 269.4 77.0 12,91 0.01384 0.00407 269.3 77.2 12,91 0.01038 ^ 0.00295 257.0 78.3 12,91 0.01038 0.00295 257.2 78.6 13,00 0.00150 0.02100 299.0 67.0 13,00 0.01038 0.01500 290 _t 7 72.2 6 _? 83 0.00150 O ₁ 01470 288.6 73.7 7.14 0.01056 0.01220 289.2 72.3 7 _t 06 0.00594 0.01010 280.4 75.2 8.00 0.00727 0.00192 263.3 75.7 8.00 0.01153 0.00330 274.4 76.9 8.15 0.01171 0.00339 272.7 77.6 8 _s 30 0.00749 0.00199 262.2 76.5 3.03 0.00150 0.0 268.0 69.0 7.00 0.01056 0.0 264.0 75.5 7.00 O _S O1O56 0.00400 271.0. 76.2

The specific efficiency and temperature models derived from the above data according to the above-mentioned least squares method can be stated as follows:.

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Efficiency in % ~

77.19 + 0.196 (BG) + 133.4 (BCs) +120.5 (BK) ~ 63787.0 (BCs) ² ~ 47229.0 (BK) ² + 52.1 (BG χ BCs) ~ 60823, 0 (BCs χ BK) and

Temperature in -C. = 259.44 ~ 1279 (BG) + 1555.8 (BCs)

+ 794 * 1 (BK) + 0.3456 (BG) ² + 168544.0

(BCs) ¹ + 145856 _f 0 (BK) ² + 132807.0 (BCs X BK)

where: BG

BC's BK

(Mass% Ag (mass% Cs (mass% K

11.0) 0.01)

0.003)

Figures 1 and 2 show level diagrams with constant efficiency and at a constant temperature in the potassium / zein concentration range. _E The darker lines represent selectivity levels with selectivity values for each line »The lighter, broken lines represent temperature level lines with temperatures indicated in ⁰ C ₀ The efficiency and the temperature for points between the designated level lines can be interpolated. The maximum selectivity achievable for each combination of cesium and potassium is a function of the cesium concentration by the curve of the designation Sei.,. This curve represents the maximum synergism that can be achieved for any given cesium value. The synergism curve (denoted "A" in Figures 1 and 2) separates the range of synergism as defined here

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and the ranges of additive and antagonistic effects _e Additive effects appear when the efficiency obtained with a combination of cesium and potassium corresponds to a weighted average of the efficiencies to be achieved under general conditions with the respective catalysts being the same as the catalyst. containing said combination other than containing both potassium and cesium, one containing the amount of cesium in question and the other catalyst containing the amount of potassium in question. Antagonistic effects occur when the level of effectiveness of a mixture of , Cesium and potassium is less than the efficiencies obtained with corresponding catalysts containing the relevant amount of cesium and the relevant amount of potassium individually as described above. The area between the ordinate, the abscissa and the Synergismuskurve (curve "A") defines the area of synergism in accordance with the present invention _β, the area on the right side of the Synergismuskurve "A" represents the range of additive and antagonistic effects according to ¹ the above description, and thus defines mixtures which are not in accordance with the present invention, the preferred combinations between the cesium and potassium are the j enigen For any given level of line image, the SeIekt ivitä th. according to the. - · \ ... · Be, curve or near the same cause "Generally, however, preferred mixtures are those wherein cesium and potassium in a mass ratio of about 100: 1 to 1: 100 depending on the particular catalyst support. © rsubstanz and the selected Herstellungsverfähren exist _e case of mixtures of cesium and

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Lithium or cesium and sodium are the preferred mixtures most often those having the alkali metals in a mass ratio of about 1000: 1 to 1: 1000.

Referring to Figure 1, a catalyst having, for example, 0.003 mass% Cs and 0% H% K has an efficiency of about 73 % . The addition of about 0.008 mass% K to this catalyst leads to an increase in efficiency to about 76.0 % _s with the maximum selectivity at this cesium concentration (d * h # meaning the value on the side). " curve), further additions of potassium to about 0.016 mass ~% K (d _e h is ₀ meant the value on the curve "A") would efficiencies equal give those to or greater than those that the amount bodice given to cesium alone (0.003 mass -%) are obtained (d <> h _oil no alkali metal except the cesium is present); Potassium additions via O ₄ OLS mass ~% K also lead to efficiencies lower than those mass% cesium are 0 ^ 003 to obtain alone d _e h _e, we are in the range of either the additive effects or antagonistic effects, Nevertheless, such an amount of potassium _s causes the such antagonistic effects, even a catalyst having a very desirable selectivity deliver .and activity for a given mode of operation ;, · '''' · '. ·' · ''. · ^

The range of synergism varies with the silver content of the catalyst as described by the efficiency model. Figure 2 illustrates the range of synergism for a silver content of 13% by mass "The Sei .. curve and the synergistic curve (curve" A ") of Figure 2

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correspond aer hereinbefore defined with reference to Figure 1 * A comparison of Figures 1 and 2 shows that the _e efficiency level similar lines extend, but are shifted with respect to the Zäsium- and potassium axes. For example, the efficiency level envelope for efficiency equal to 76 % in Figure 1 covers an area smaller than the area bounded by the corresponding level line in Figure 2. * Further, the maximum selectivity is 7 mass / o silver is obtained, d * h _e the maximum along. , Sel _M line, slightly above 75 % (Figure 1), while the corresponding maximum for 13% by mass silver is slightly above 77 ^ 8 % (Figure 2),

The efficiency model and temperature model that have been developed are specific for a particular method of catalyst preparation, for a particular catalyst substrate sub- stance, as well as for a particular binary alkali metal combination, changes either in the catalyst production process or in the vehicle or in the process With respect to the particular binary combination, the coefficients of the models can change and therefore the shape of the level lines derived therefrom. Thus, the curves "A" and "S ^" may consist of straight lines or curves and intersect one or both axes (namely, the cesium axis and that of the other alkali metal in the binary combination). " For example, cut in Figures 1 and 2, the curves "A" and Se! .. 'both' axes and the Zäsiumachse at an angle greater than 90 _p at a different carrier, a different method of catalyst preparation or a different binary alkali metal combination

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with cesium, however, the resulting curves "A"

and Sei., the cesium axis is smaller than _o max at an angle

The coefficients for the model and resulting level line images can be readily determined for each of the changes noted above using the intended set of experiments, as described above. _E

The concentration of silver in the final catalyst may vary between 2% and 20% by weight, the preferred range being about 6% to about 16% by mass of silver.

However, from an economic point of view, lower syllable concentrations are preferable. However, the optimum silver concentration for any particular catalyst will depend on both the economic factors and the performance characteristics, such as the catalyst's efficiency, the catalyst's rate of aging, and the reaction temperature.

A variety of methods can be used to prepare catalysts containing the combinations of cesium with another alkali metal or with several other alkali metals (except the germanium) according to the present invention. The preferred method is as follows:

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(1) A porous catalyst carrier substance is impregnated with a solution consisting of a solvent or a solubilizing agent, a silver salt in an amount sufficient to deposit the desired silver mass on the carrier, and salts (a) of Cesium and (b) at least one other alkali metal selected from the group consisting of lithium, sodium, potassium and rubidium, in an amount sufficient to provide the relevant proportions of (a) and (b) on the carrier to bring deposition, such that the efficiency of the finished catalyst for the production of ethylene oxide is increased to a value ^ overlying the efficiencies that are obtained under general conditions with the respective catalysts which are the same as said catalyst? except that it of a catalyst this quantity instead of containing both (a) and (b) at ,,

(a) and the other catalyst the amount in question

(b) contains? and subsequently (2) the impregnated support is treated such that at least one fraction of the silver salt is converted to silver metal and the precipitation of silver (a) or (b) on the top of the support occurs4 Deposition of the silver and the alkali all happens in general by elevated temperatures of the carrier substance bsi. Purpose © of evaporation © of liquid · ..V. innörha3..b the Trägersubstans and the deposition of the silver and "the Alkalirastal3.es tien on inner and outer surfaces of the Trägersubstahz * Alternatively, a Übep · train from Silbsr and alkali metals on the carrier. einar from ODSR emulsion slurry are formed ,, in which the elements to be deposited are located, followed by

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heating of the vehicle as indicated above description _β · The impregnation of the carrier is generally the preferred technique for silver deposition because this silver is utilized more effectively than in the coating "or" coating process "The latter are not generally Able to cause significant silver deposition on the inner surfaces of the substrate * In addition, coated catalysts are more sensitive to silver losses due to mechanical wear «

The order of impregnation or deposition with respect to the surfaces of the carrier with silver and alkali metals is optional. Thus, impregnation and deposition of silver and alkali metals may be carried out simultaneously or sequentially, d. h ", the alkali metals can be before, during or after the silver addition to the carrier substance for the separation reach _e The alkali metals may together or sequentially deposited" For example, may be deposited cesium first, followed by the simultaneous or sequential deposition of silver and other alkali metals ( the other alkali metal), or such another alkali metal (such other alkali metals) may be deposited first, followed by the simultaneous or sequential deposition of the silver v. and cesium * '''.'. ,

The impregnation of the catalyst support substance is carried out using one or more solutions of silver and alkali metal compounds in accordance with the well known methods for simultaneous or concurrent reaction.

2 3

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made subsequent depositions. In case of simultaneous. Deposition is followed by impregnation to heat or impregnate the impregnated support to reduce the silver compound to silver metal and to deposit the alkali metals onto the catalyst surfaces. In the case of subsequent deposition, the support is initially co-precipitated Silver or alkali metal impregnated (depending on the order used) and then heated or chemically treated, as described above. This is followed by a second impregnation section and a corresponding heating or chemical treatment to arrive at the finished catalyst containing silver and alkali metals.

The silver "solution used to impregnate the carrier material comprises a silver salt or a silver compound in a solvent or a complexing / solubilizing agent, as is the case with the Silver solutions that are known in this field of the art _e The particular silver salt used If is not critical and may, for example, silver nitrate, silver ~ (I) ~ oxide or Silberkarboxylaten * such as silver acetate, 'SIlberoxolat ".Silberzitrat, silver phthalate _f silver lactate, and Silberpropionat' Silbe.rbutyrat, as well as of salts of higher fatty acids selected * ... .. · ... ·· ..:.

A wide variety of solvents or complexing / solubilizing agents can be used to solubilize the silver in the impregnation medium to the desired concentration. Among the solvents known in the art and suitable for use in the art

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suitable for this purpose are: lactic acid (U.S. Patents 2,477,435 (Aries) and 3,501,417 (DeMaio)); Ammonia (US-PS

2 463 228 (West and others)); Alcohols such as ethylene glycol (US Pat. No. 2,825,701 (Endler et al.) And US Pat

3 563 914 (Wa £ tim @ i $ a); as well as amines and aqueous mixtures

Amines (U.S. Patent 2,459,896 (Schwarz), 3,563,914 (Wattimena), 3,702,259 (Nielsen) and 4,097,114 (Cavitt)).

Suitable alkali metal salts include all those salts which are soluble in the particular solvent or solubilizing agent used. Accordingly, inorganic and organic salts of the alkali metals may be used, such as nitrates, halides, hydroxides, sulfates and carboxylates., When co-precipitated with the silver is the verwendete- alkali metal salt, preferably such salt, the _t does not respond in aet solution with the silver salt to prevent premature SiIberpräzipitation from the salt to avoid "So alkali metal halides, for example, preferably not verwendetί in lactic acid solution because they react with the contained silver ions"

Following impregnation of the catalyst support with silver and alkali metal salts, the impregnated inert particles are stripped of any residuals of unabsorbed solution or slurry. This is conveniently effected by removal of the excess impregnation medium or, alternatively, by the treatment. Use of separation techniques, such as by filtration or centrifugation * The impregnated support is then generally heat treated (for example, by roasting) to decompose the silver metal salt into metallic silver

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Such reduction may be carried out at a temperature of from about 100 ° C to 900 ° C, preferably from 200 ^° C to 700 ° C, for a time sufficient to provide substantially all of the silver salt to convert into silver metal. In general, the higher the temperature, the shorter the reduction time required. * For example, at a temperature of 400 ^° C. to 900 ^° C., the reduction can be carried out in about 1 to 5 minutes. "Although a wide range of periods of heating in the art has been proposed to thermally treat the impregnated carrier (for example, US Pat. No. 3,553,914 suggests heating below 300 seconds, with drying but no roasting being effected to reduce the catalyst; US ~ PS 3702259 describes a heating from 2 to 8 hours at a temperature of 100 ⁰ C to 375 ⁰ C to reduce the silver salt in the catalyst; and U.S. Patent No. 3 962 136. brings ^x / 2. up to 8 hours for the same temperature range in proposal), it is only of importance that the time period for the reduction with the temperature is in such a correlation that essentially a complete Reduction of the silver salt to the metallic silver is effected "For this purpose a continuous or stepwise heating program can be used". '·. ... ', ·:, ·

The heat treatment is preferably carried out in air, but a nitrogen "or carbon dioxide atmosphere may also be used ^ The used for such heat treatment industrial plant can machon use of a static or flowing atmosphere of such gases to

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to reach the reduction »

The particle size of silver metal deposited on the support constitutes a function of the method used to prepare the catalyst. Thus, the particular choice of solvent and / or complexing agent, silver salt, heat treatment conditions, and catalyst support may vary the size of the resulting silver particles äffizieren. For excipients of general interest for the production of ethylene oxide, a distribution of silver particle sizes in the range of 0.05 to 2.0 is typically obtained. However, the role of the particle size of the silver catalyst on the effectiveness of the catalyst in the production of ethylene oxide is not clearly understood , In view of the Tätsache that is of the silver particles is known to migrate on the surface of the catalyst when this see at a Katalytic reaction is used, with significant changes oer size and shape of the silver particles revealed the Silberteilchengröße can not be a significant Factor to be considered when acting on a catalytic conversion *

The catalyst support utilized in the practice of the present invention may be selected from known porous refractory materials which are substantially inert to ethylene, ethylene oxide, and other reactants and products under reaction conditions

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Materials are generally referred to as "macroporous" and consist of porous materials with effective

seed surfaces smaller than 10 m / g (square meter per gram of vehicle) and preferably smaller than

2 1 m / g _# The effective surface is measured by the well-known B "-E" .- T _# method as described by Brunauer, S *, Emmet, P, and Teller, E in D _# Am "Chem * Soc *, Volume 6O ₄ pages 309 to 316 (1938) * The materials are further characterized by pore volumes in the range of about 0.15 to 0.8 cm / g, preferably in the range of about 0.2 to 0, 6 cm / g "the pore volumes can be measured by the known mercury porosimetry or water absorption techniques" Mean pore diameters for the above-described carriers range from about 0.01 to 100 pm _g corresponding to a preferred range of about 0.5 to 50

The support preferably may not contain ions which are exchangeable with the alkali metals introduced into the catalyst, either in the preparation or use of the catalyst, so as not to interfere with the amount of alkali metal resulting in the desired synergism If the carrier contains such ions, they must be removed by standard chemical methods, such as dissolution. In addition, if the carrier substance is. includes a Mengenariteil of alkali metal, OCE is transferable to the "silver _t whereby the synergistic combination is disturbed to treat the carrier, then in such a way to remove such excess alkali metal or der.Mengenanteil an.dem alkali metal, which in the Catalyst introduced must be smaller

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than the synergistic amount, whereby there is the possibility that> the alkali metal transferred produces the desired synergistic amounts. «

The chemical composition of the carrier substance is not exactly critical. The carrier substances may consist of, for example, alpha-alumina, silicon carbide, silica, zirconia, magnesia and various clays. In general, materials based on alpha-alumina are preferred alpha alumina may have a very high purity, d _p h ≦ 98 mass% alpha alumina, with the remaining components being SiIiZiUm- (IV) -OXXd, alkali metal oxides (for example, sodium monoxide), and trace amounts of other metals. and non-metal impurities * or the materials may be of low purity, about 80% by weight alpha alumina, with balance being achieved by a mixture of silica, various alkali oxides, alkaline earth oxides, iron oxide and other metal and non-metal oxides Carrier substances with the lower purity are herge in the way sets _s to be inert "in the context of preparation of the catalyst and under reaction conditions A wide variety of such carriers is commercially available" The carriers may be in the form of pellets, strranggepreßten particles, spheres, rings and the like, "available * The size of the carrier substances can vary from 'about''/ 16 inches to VZ inches »The size of the vehicle is chosen so. In general, it has been found that in fixed bed converter applications, sizes in the range of YB inches to 3/8 inches in the typical tube converter at

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which is used under commercial working conditions »

Her position of Eth yl ene oxide

The new silver catalysts are particularly useful in the production of ethylene oxide by the vapor phase oxidation of ethylene with molecular oxygen. The reaction conditions for carrying out the oxidation reaction are well known and have been extensively described in the context of the earlier processes. This refers to the reaction conditions. such as temperature, pressure, residence time, concentration of reactants, diluents (for example, nitrogen, methane, and COp), retarders (e.g., ethylene dichloride), and the like. * In addition, the desirability of the recycle of unconsumed feedstock may in the circulation or use of a continuous flow system or the use of successive reactions to enhance ethylene turnover by the use of series reactors are readily ascertained by those versed in the art Selection of the mode of the ¹ work 8-drain it is mostly determined by the.support of the technical procedure,.

In the most general! the process is carried out in an oer manner · ,, that a feedstock, which is composed of ethylene and oxygen, is continuously fed to a reactor containing the catalyst catalyst at a temperature of about .2GO C to 300 C and a pressure of Atmosphere up to about 30 atmospheres depending on

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The residence times in large-scale material reactors generally have orders of magnitude of about 1 to 5 seconds. The oxygen may be passed to the reaction in an oxygen-containing stream, such as air stream or commercial oxygen stream resulting ethylene oxide is separated and recovered from the reaction products using known methods,

Working Example

The catalysts listed in the tables below were all evaluated for comparison purposes under standard test "For this autoclave aer type" Magne Drive "back-mixed and ground," were disposed of agitation, as in Figure 2 of the paper by 0 _e M * Berty "fabric converters for catalytic vapor phase studies The chemical reactor was operated at 1.0 mol% of ethylene oxide in the exit gas under the following standard conditions of entry: in Chemical Engineering Progress, Vol. 70 _E No. 5, pages 78-84.

component

Oxygen Ethylene Ethane

Carbon dioxide nitrogen

Ethylene chloride in ppm

6.0

8, o '· ": 0.50 6 * 5

for producing the weight of the gases

7.5

Equal-

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The pressure was held constant at 19 _t 3 at (275 psig) and the total exit to 0.640 m / h (22.6 SCFHj where SCFH is cubic feet per hour at standard and standard pressures, namely at 0 C and 1 atmosphere) Concentration of the exiting ethylene oxide was maintained at 1.0 % ! the temperature of the reaction (in C) and the catalyst efficiency are obtained as the behaviors that describe the performance of the catalysts *

A typical test procedure for testing a catalyst consists of the following steps:

1.80 cm of the catalyst are placed in a backflow autoclave. The volume of the catalyst is measured in a 25.4 mm (1 inch) inner diameter cylinder after the cylinder has been knocked several times to remove the catalyst completely to get into the measuring cylinder. The mass of the catalyst is determined and logged "

2 «The autoclave with backmixing is heated in an embroidery station of 0.5G6 m / h (20 SCFH), with the fan operating at 1500 rpm» almost to the reaction temperature. The nitrogen flow is then suppressed and the feedstock described above introduced into the material reactor «. The total exit amount of gas is regulated to 22.40 SCFH (0.640 m / h). The temperature is adjusted in the next few hours so that the concentration of ethylene oxide in the exiting gas comes to about 1.0 % _β

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The concentration of the exiting oxide is monitored over the next 4 to 6 days to assure that the catalyst has reached its maximum steady state performance. The temperature is periodically adjusted to provide an outgoing oxide in an amount of 1% "The selectivity of the catalyst over the ethylene oxide and the temperature is thus obtained.

The standard deviation of a single test result, with a record of the catalyst efficiency according to the method described above, is equal to 0.7 % efficiency units *.

Tables 2 to 6 indicate below test results in a summary again, which were silver catalysts without the addition of additives and with silver catalysts with cesium in conjunction with an alkali metal or more alkali metals selected from lithium, sodium, potassium and rubidium, received _P Tests were carried out using a large number of catalyst support substances and different production processes. Catalysts produced on the same preparation process on a similar support substance are identified in the tables by a common number.

Table .2: Results ·

Experi «mass ~% mass% mass ~% EFF in % Temperature ment Ag. Cs K ++) ... in C

IA '. 11,14-. 0.00379 0.0000 71.7 256 IB 11.14 0.00477 0 _t 00158 73.9 256

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Experiment Ag £ mass ~% Cs Mass% K EFF in % Temperature in ^B C IC 10.89 0.00461 0.00450 75.4 256 ID 10.41 0.0000 0.0000 68.4 265 IE 10,80 0.0000 0.00513 69.9 261 IF 10.93 0.0000 0.0123 73.3 264 IG 10,90 0.0000 0.0210 66.6 299 IH 11.04 0.00941 0.0000 75.6 256 11 11.06 0.00941 0.00313 76.9 258 ID 10.92 0.0186 0.0000 73.1 283 IK 11.16 .0191 0.00633 72.0 293 IL 8.04 _t 0,004 0,008 75.0 269.3 IN THE 7.84 - 0.0078 75.0 263.8 IN 8.28 0.0041 - 73.8 258.3 10 S ₄ 07 - 67.3 260.0 IP 14.97 - - 65.7 252.9 IQ 15.19 0.00405 - 72.6 252.0 IR 14,80 0.0079 75.5 255.5 IS 15,10 0,004 0.0031 77.9 256.6 2A 17.4 0,000 0.093 73.5 278 2 B 16.6 O, 0044 0.088 74.7 279 2C 16.5 0.0085 0,089 74.2 - 278 2D 17.3 0,000 0,000. 68-67 +) "284-299 2E 17.0 O, 0044 0.0016 70.8 276 2F ' ^; .15 / 7. 0.0044 0.059. .74,1 "280.;,: 2G 16.5 0.0092 .0,0028 72.2 275 ' 2 H 16.5 , 0.0092 0,038 73 _f 2. 287

+) Due to the rapid inactivation of this catalyst, the initial and / or final performance are given «

+ ·:) "EFF" corresponds to the abbreviation for the efficiency according to the previous definition »

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The experiments IB and IC demonstrate the synergism obtained with silver catalysts containing mixtures of cesium and potassium according to the present invention relative to the catalyst IA "with cesium" containing silver und'Zäsium substantially the same concentration, but no potassium. "As used herein, the term" only with cesium "refers to a catalyst in which the cesium is the only alkali" metal which has been deposited on the carrier. "The terms" potassium only "," only " with lithium "and" only with sodium "are defined accordingly for the catalysts in question» Thus, the efficiency with the combination of the alkali metals in the experiment IB was about 2 % higher than that achieved with the corresponding catalyst "only with cesium" efficiency of the experiment IA _e The further addition of potassium in an amount of 0 _e 00158 mass% (Example IB) up to a proportion of 0.004 5 mass ~% (Experiment IC) _f wherein Ag and Cs were held substantially constant, resulted in an even greater improvement of the efficiency relative to IA, there These were about 3.7% _e The catalyst according to the experiment ID contained no Cesium or potassium and gave a relatively low efficiency of 68.4% ,. Experiments IE, IF and IG demonstrate that "potassium only" catalysts having essentially the same amount of silver as the catalysts "1B and iC ^ gave a selectivity no higher than 73, 3% was significantly below that which was with the catalysts IB and IC obtained with the mixtures of cesium and potassium "It is also to be noted that, in addition to a higher efficiency, the catalysts (IB and IC) according to the present invention at lower Temperatures worked as the catalyst.

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catalysts (IE, IF and IG) "with potassium only", which results in higher activity of the catalysts (IB and IC). · Although the catalyst "only with cesium" (IA) worked at the same low temperature as catalysts IB and IC , he delivered a substantially lower efficiency «

The catalyst of Experiment IH was a "cesium only" catalyst with a cesium content almost twice as high as that of catalysts IA ₁ , IB, and IC. "Addition of 0.0031 moles of potassium to a catalyst of such composition caused an improvement the efficiency greater than 1 % _t as Example 1 can be taken «.

Experiments 10 and IK illustrate a non-synergic combination of cesium and potassium. Thus, the addition of potassium to the cesium-only catalyst 13 resulted in a silver content of about 11 mass% and a relatively high cesium concentration of 0.0186 mass Thus, it can be stated that the combination of potassium and cesium in the experiment IK did not lead to a synergistic result. Accordingly, such a cesium / potassium mixture is present as well of the present invention. Match ^ · '

Experiments IL through 10 demonstrate the synergism of the present invention for catalysts with one. Silver content of about 8 'mass% The efficiency of the catalyst IL with a synergistic combination of

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Cesium and potassium were 1 % higher than the catalyst "IM only with potassium" and more than 2 % higher than the catalyst "only with cesium" IN. The silver catalyst 10, which contained no cesium or potassium, achieved an efficiency of almost 9 % below that of the catalyst IL,

The experiments IP to IS demonstrate the synergism of the present invention for catalysts with a silver content of almost 15 mass%. The efficiency of the catalyst IS _8, which contained a synergistic mixture of cesium and potassium, was more than 5 % higher than the efficiency of the catalyst Catalyst IQ "only with cesium" containing the relevant amount of cesium in such a mixture, and about 2,5 % higher than the efficiency of the catalyst "only potassium" IR, which determines the relevant amount of potassium in such a mixture contained. The catalyst IP, which contained no additives, reached an efficiency of about 11 % below the efficiency of the catalyst IS «'

Experiments 2B and 2C demonstrate the efficiencies achieved with potassium / cesium blends for a catalyst with a silver content of about 17% by weight compared with the "only potassium" experiment of experiment 2A 0 ^ 0044 mass% cesium in Experiment 2B led to an improved efficiency of .74 ', 7 * / O ₄ compared to the "73 _i 5 ~ / ö" degree of activity "found in Experiment 2A The silver catalyst 2D ,, which had no alkali metal deposition on the carrier, is given in the table for comparison purposes.

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A comparison of experiments 2E and 2F shows that when the potassium concentration was increased from 0.0016% by mass to 0.069% by mass and the cesium concentration was kept constant, the efficiency was improved by more than 3 % . * A comparison of the experiments also illustrates this 2G and 2H _f that an increase in the potassium concentration while keeping the silver and cesium concentrations constant resulted in a 1% improvement in the efficiency, J.

Three catalysts having a silver content of 7 fiasse-% were prepared with the optimum Zäsiumkonzentration according to the determination on the basis of the efficiency model, as described above, _f obtained from a provided set of experiments, the catalysts (Experiments 3A, 3B and 3C) contained all about 7% by mass of silver and 0.00906% by mass of cesium without potassium. To demonstrate the mode of action of the efficiency model, three additional catalysts were prepared (Experiments 3D, 3E, and 3F), each containing approximately 7.0% by mass of silver, 0.00906% by mass of cesium, and 0.004% by mass of potassium the efficiency of the cesium / potassium catalysts relative to the cesium-only catalysts was predicted to be approximately 0.6 % efficiency units due to the efficiency model. " Again. Table 3 below. ^: '' · Can be seen, the actually observed · \. Difference in efficiency with '0,7' % was found to be a reflection of the agreement with the prediction from the efficiency model »The experiment 3G. provides the efficiency of a catalyst "only with potassium" with a silver and potassium content of the same concentration as in the catalysts of experiments 3D _r

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3Ε and 3F «How to demonstrate the synergism achieved with the cesium / potassium combination«

Table 3: Results

experiment

Efficiency in %

Temperature in C

Catalysts only with cesium: 7.0% by mass of silver

0.00905 mass% cesium

3A 75.4 263.9 3B 75.7 261.4 3C 75.4 266.1

Average 75.5 "-. 0.17 *)

Catalysts Cesium plus potassium: 7.0% by mass of silver

O, 00906 mass% cesium 0.004 mass-> o potassium

3D 3E F

76.0 76 _ff 76 ₁ 4 Average 76 ^ 2

271.4 271.5 270.9

i 0.21 +)

Catalyst only with potassium: 7.0% by mass of silver .... , 0.0040% by mass of potassium

+) These values correspond to the standard deviations

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Table 4 below illustrates the synergism achieved with a combination of cesium and lithium (Experiment 4C) relative to the corresponding catalyst only with cesium of Experiment 4A and to the corresponding catalyst with lithium only of Experiment 4B. Thus, the catalyst of Experiment 4C had an efficiency about 10 % higher than that of Catalyst 4B with only lithium and about 3.5 % higher than that of Catalyst 4A with only cesium,

Experiment 4D demonstrates that when the lithium concentration of catalyst 4C was increased by about 10 times, the resulting efficiency was reduced by more than 3 % . However, comparison of catalysts 4D and 4E shows that the efficiency achieved with catalyst 4D is It is to be noted at this point that the catalyst of experiment 4G was inactive only with cesium (corresponding to the cesium concentration of experiment 4E), i.e., the cesium concentration was increased from 0.0053 mass / o to 0.0300 mass% However, the combination of this concentration of cesium with 0.0300 mass% of lithium gave a very active catalyst (4E) _# Similarly, in the catalyst, 4F was only lithium (corresponding to the lithium concentration of the experiment 4E) - ε, άη relatively low efficiency of 65.4 %>' This is how it is observed in the catalytic converter 4E achieved synergism due to the sharp contrast of its efficiency relative to the poor results achieved with catalysts 4F and 4G

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Table 4: Results

Catalysts with synergistic combinations of silver, cesium and lithium

Experimental mass% mass% mass%% Temgerature silver cesium Lithium degree in % in C

4A 12.8 0.0052 0.0000 72.6 257 4B 13.1 0,000 0.0030 65.9 267 4C 12.8 0.0052 0.0030 76.0 257 4D 13.1 0.0053 0.0302 72.8 258 4E 13.0 0.0300 0.0300 78.6 258 4F 13 0,000 0.0300 65.4 268 4G 13.0 0.0300 0,000 inactive +) -

+) No measurable ethylene oxide was recovered »

Table 5 below demonstrates the synergism achieved with the catalyst of Experiment 5C relative to the corresponding catalyst of Experiment 5A only with cesium and to the corresponding catalyst of Experiment 5B with only sodium. Thus, catalyst 5C has a 6 % greater efficiency than the catalyst 5A * the experiment 5D shows only with cesium and a larger by 7 _r 2% efficiency than the catalyst 5B only sodium that the enlargement of the Natriumkon.zentration to that löfache relative to the concentration in the catalyst 5C ...; has the effect of lowering the catalytic converter efficiency «-

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- 57'- 58 985/18 Table 5: Results

Catalysts with synergistic combinations of silver _t cesium and sodium

Experimental mass% mass% Masee- ment% Wirkungs- temperature silver Cesium sodium degree in% in C

5A 12.8 0.005 • 0.000 72.5 257 5B 13.0 0,000 0,010 71.4 259 5C 13.0 O, 005 0,010 78.6 251 5D 12, 4 0.005 0,100 77.6 263

Table 6 below demonstrates the synergism achieved with a silver and cesium catalyst in combination with potassium, sodium and lithium according to Experiment 6A *

The presence of chloride ions in the catalyst concentrations of Experiments 6A, 6B and 60 indicates that at least a portion of the alkali metal salts utilized in the catalyst preparation processes were in the form of the chlorides. The efficiency achieved with the synergistic combination of Experiment 6A was approximately 1.2 % higher than the efficiency of the corresponding 6C catalyst with only cesium and approximately 9 % greater than the efficiency of the corresponding catalyst of Experiment 6B with the combination of potassium, sodium and lithium *.

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Table 6: Results

Catalysts with synergistic combinations of silver, cesium, potassium, sodium and lithium

Ex- Mass- Mass «Mass- Mass- Mass- Mass- We- Tempe-

p%% . %%%% kratrat ^ r

ri ~ silver cesium potassium Na- Li chi-grade in C

ment trium thium chloride in %

6A 13.1 0.0132 0.001 0.002 0.006 0.0137 78.4 +) 262 6B 13.0 0.000 0.001 0.002 0.006 0.0137 69.4 267 6C 13.1 0.0132 0.000 0.000 0.000 0.0035 77.2 265

+) The values for the efficiency represent the average value of two experiments.

The catalysts of the invention can be prepared using a variety of excipients and methods of preparation. Dor defined synergism can be obtained with combinations of cesium with other alkali metals is, for example, not to a particular type or a particular chemical composition of the catalyst carrier, a special order of deposition of the silver and the alkali metal or to a specific class of solvents or solvents used in the manufacturing process are limited «

Claims (2)

31.3.1981 Exemption application from AP B Ol D / 219 762 Q ζ Π 1 - 59 - 58 985/18. E r fi η d υ η Cj-Sa η sp ru ch A process for producing ethylene oxide, wherein ethylene and oxygen in the vapor phase at a temperature of about 200 ⁰ C to 300 ⁰ C with each other * in the presence of a supported catalyst made of silver to form ethylene oxide using a supported catalyst of silver, which consists of a Combination of (a) cesium and (b) at least one other alkali metal selected from the group consisting of lithium, sodium, potassium and rubidium, characterized in that in combination (a) and (b) there are amounts of the amount of silver contained therein is sufficient and sufficient to increase the effectiveness of the production of ethylene oxide to a value greater than the effectiveness achieved under general conditions with corresponding catalysts, using the same catalysts mentioned above, except that they not both (a) and (b) contain, but one of them either the corresponding amount (a) or the corresponding amount (b) .2 _e Method according to item 1, characterized in that the 'Catalyst silver in an amount of about 2 to; 20% by weight contains «· '· ._".', 3 * Method according to item 1, characterized in that the catalyst contains silver in an amount of about 5 to 15% by weight, 03/31/1981 Divisional application from AP B Ol 3/219 762 ~ 60 - 58 985/18 4 «Method according to item 1, characterized in that the alkali metal is sodium * 5 «method according to item 1, characterized in that the alkali metal is lithium, 6 * Process according to item 1, characterized in that the alkali metal is potassium »- ·, 7 «method according to item I _1, characterized in that the alkali metal is rubidium * 8 «Method according to item 6, characterized in that cesium and potassium are present in a weight ratio of approximately 100: 1 to 1: 100 * 9p method according to item 1, characterized in that the supported catalyst contains alpha-aluminum « 0 «method according to item 1, characterized in that the surface of the supported catalyst less than about 2
1 m per gram » lieno iOeiten drawings