Epoxidation catalyst and process

Epoxidation catalyst and process for using it

Full description

Background of the invention

The invention relates to silver-containing catalysts suitable for the epoxidation of olefins free of allylic hydrogen, in particular ethylene, and to the use of catalysts in the preparation of ethylene oxide. Catalysts are prepared using a unique alpha alumina based carrier.

Catalysts for the production of ethylene oxide from ethylene and molecular oxygen are generally silver-supported catalysts. These catalysts are typically enhanced with alkali metals. The use of small amounts of potassium, rubidium, and cesium, useful alkali metals, as promoters in silver-supported catalysts has been noted in US Patent No. 3,962,136, issued on June 8, 1976, and US Patent No. 4,010,115, issued on March 1, 1977. The use of other auxiliary enhancers such as rhenium or rhenium with sulphur, molybdenum, tungsten and chromium is disclosed in U.S. Patent No. 05 47661 issued on August 23, 1988 and No. 4808738 issued on February 28, 1989. U.S. Patent No. 4,908,343 issued on March 13, 1990 discloses a silver-enriched catalyst containing a mixture of a cesium salt and one or more alkaline earth metal salts.

US Patent 4,897,498, issued on January 30, 1990, discloses the use of supported, alkali metal-enhanced, silver-based catalysts in epoxidation of olefins processes free of allylic hydrogens.

Alumina-based catalyst carrier materials have previously been described in a number of patents, such as US Patent No. 5,100,859 issued on March 1, 1992, No. 5,055,442 issued on October 8, 1991, No. 5037794 issued on August 6, 1991, and No. 4874739 issued on August 17. October 1989. These materials contain alumina

It has wide potential applications in the catalytic field and is especially useful when the alumina base is alpha alumina and in this application corrosion resistance is a desirable property.

US Patent 5,063,195, issued in November 1991, discloses catalysts for the production of ethylene oxide, based on a carrier made of trihydrated alumina, boehmite (also hydrated alumina), fluoride, and excipients.

General description of the invention

This invention relates to a suitable catalyst for the epoxidation of olefins free of allylic hydrogen, in particular ethylene, with oxygen in the vapor phase. This catalyst includes a catalytically active amount of silver and an enhanced amount of an alkali metal supported on a carrier material whose base is alpha alumina. Alumina with a crush strength of at least 2.3 kg and a stable packing density of at least 48. Kg/L, which includes two components, alpha alumina, the first and the second, with the first component, alpha alumina, in the form of particles with an average crystalline size of 0.4 to 4 micrometers, giving from 95% to 40% of the total weight of alpha alumina in the material. The carrier and the second alpha alumina component are generated at the reaction site by a colloidal solution-gel process from a hydrolyzed source of alpha alumina, which is optionally seeded and gives the rest of the alpha alumina in the carrier material.

Catalysts with this unique alumina carrier have been found to have improved selectivities and/or activities over catalysts with conventional alumina carriers. These catalysts also have improved selective stability and/or stability of activity.

Detailed description of the invention

We describe in detail below the carrier, the catalyst prepared with the carrier and the use of the catalyst. carrier

The catalyst carrier material of the present invention is a new alpha alumina based catalyst carrier material with a crush strength (as measured by the Compton Tensile Tester, Model 50-OP) of at least 2.3 kg and a stable packing density, (as measured by the Compton Tensile Tester, Model 50-OP).

Measurement of 87-4699-ASTM D, modified using a cylinder with an inner diameter of 9.52 cm and a length of 45.7 cm), at least 0.48 kg/L, preferably at least 0.56 kg/L, more preferably at least 0 61 kg/L, which includes two alpha alumina components, the first and the second, with the first alpha alumina component in the form of particles with an average crystalline size of 0.4 to 4 micrometers, given from 95% to 40%, preferably from 95% to 65% of the total weight of alpha alumina in the carrier material and the second alpha alumina component generated at the reaction site By means of a colloidal solution-gel process from a hydrolyzed source of alpha alumina, which is optionally seeded and the rest of the alpha alumina is given in the carrier material.

As used herein, the term “sol-gel process” refers to a process involving heating a colloidal alumina sol and/or alumina gel (i.e., hydrated alumina) to a temperature that converts at least a portion of the colloidal solution and/or alumina gel to alumina with a ruby (natural aluminum oxide) crystalline structure (i.e. a closely packed hexagonal structure). Generally used for this transformation are temperatures of at least 400°C, preferably above 1100°C, and preferably more than 1100°C to 1500°C.

The catalyst carrier is prepared by the process from the protecting element 12 hereinafter mentioned.

The catalyst carrier may be formulated with a number of alpha alumina components selected to contribute to the desired physical properties, including porosity, pore size, crush strength, etc. A combination of two different alpha alumina components is often preferred, with a first component having larger particles mixed with A second ingredient has smaller particles, in weight ratios of 90:10 to 10:90. The first ingredient typically comprises 10% to 90%, preferably 40% to 80%, by weight of the first alpha alumina component, and the second ingredient typically comprises 10% to 90%, preferably 20% to 60%, by weight of the first component Alpha alumina first. The goal is to obtain a surface area in the final roasted carrier from 0.4 to 5 m2/g. As used here, “surface area” is used to refer to the BET surface area measured using nitrogen or krypton as the adsorbed gas. The surface area of the final carrier material is somewhat less than that of free alumina particles. Thus, a suitable mixture may include, for example;

There are two types of alpha alumina particles, the first has a surface area of 0.9 to 1.4, preferably 1 m2/g, an average particle size of 2 to 4, preferably 3 to 3.4 micrometers, and an average crystalline size of 1.6 to 2. 2 µm; The second has a surface area of 3 to 5 m2/g, an average particle size of 4 to 8 µm, and an average crystallite size of 0.4 to 0.8 µm.

It is preferable that the hydrated precursor for alpha alumina be based on a monohydrate such as boehmite, but we also get good results if the source includes a mixture of boehmite with aluminum trihdrate such as gibbsite or bayerite. When using this mixture, it is often preferable to use a weight ratio of monohydrate (boehmite) to trihydrate from 10:1 to 3:1, and preferably more than 8:1 to 4:1. When an alpha alunrina source contains aluntina trihydrate, it typically contains 10% to 35% by weight alumina trihydrate, based on the total weight of alpha alumina in the carrier. Although other alumina trihydrates can be used, the commonly used alumina trihydrate is gibbsite with an average particle size of 4 to 20 micrometers.

In a preferred embodiment the hydrolyzed source of alpha alumina is seeded. The seed used may be any material effective in producing nucleation sites at the source in order to lower the transition temperature at which alumina is transformed into alpha alumina. Seeds that achieve this goal generally have the same crystal lattice as alpha alumina itself, and lattice dimensions that do not differ greatly from those of alpha alumina. It is clear that the most suitable seed is alpha alumina itself, and that particles of less than a micrometer in size from alpha alumina are the best seed. In a granulated embodiment, the alpha alumina seed has an average particle size of less than 0.1 µm, comprising 0.2% to 5% by weight based on the total weight of alumina, measured as alpha alumina, usually carrying the catalyst. However, it is possible to use other colors such as alpha ferric oxide, chromium oxide, and certain complex titanium oxides.

The alpha alumina formed from the seeded source when the extruded mixture is burned generally has a much finer crystal size than the alpha alumina particles with which the seeded source is mixed unless, during burning, it is kept at a high temperature for an extended period of time. When produced, the seeded colloidal-gel material has a sub-micrometer crystal structure, but at temperatures above 1400°C for extended periods of time, crystal growth begins and the size difference may become less pronounced.

The final roasted carrier material should preferably have a porosity of at least 50% and preferably more than 60% to 75%, a crushing strength of at least 2.3 kg, and a stable packing density of at least 0.5 kg per liter, preferably at least 0.6 kg per litre. Liter. The surface area of the roasted carrier material is preferred

The final range is from 0.4 to 5 m2/gram, preferably more than 0.6 to 1.2 m2/gram.

It is often preferable to add titania to the mixture to be extruded in an amount representing from 0.05% to 1%, preferably from 0.05% to 0.5%, more preferably from 0.08% to 0.4%, and preferably from 0.08. % to 0.25%, of the weight of the burning carrier material. Certain forms of alumina and titania may also be contained as impurities. These forms of titania are not included in the quantities specified above. Titania can be added as dioxide, as titanate, or as a source of titania. In the following description, it is understood that all of the above choices are included in the term "titania". It is thought that titania may act as a form of crystal growth inhibitor in alpha alumina formed as a result of seed source transformation. Therefore, it may be expected that other materials will be used as alternatives to titania, such as zirconia or magnesia. It is believed that complex solid state interactions between alumina/bond, impurities and titania added to the carrier can occur and result in increased resistance and density of the carrier.

Titania is preferably in powder form with a relatively high surface area, meaning at least 8 and preferably from 8 to 300 m2/g. In practical application, the preferred titania has neither crystallization nor anatase structure. While not being bound by any theory, it is believed that the rutile structure of titania does not generally exhibit the advantages obtainable with the amorphous and anatase structures of titania because they typically have a much smaller surface area. Commercial titania tinctures can also give good results.

The alumina components of the carrier are then typically mixed with a combustion and/or binding agent and water, formed into specific shapes and roasted.

A combustion agent is a substance added to the mixture such that upon roasting, it is completely removed from the carrier, leaving uniform porosity in the carrier. These materials are carbonaceous materials such as coke, carbon powders, graphite, powdered plastics such as polyethylene, polystyrene and polycarbonate, rosin, cellulose and cellulose-based materials, sawdust and other plant materials, such as ground walnut shells. For example, pecan shells, bean shells, walnuts, and hazelnuts. Carbon-based combustion agents can also be used as binding agents. Combustion agents are available in an amount and size distribution to give a final carrier with a water pore volume (water absorption) of 0.2 to 0.6 mL/g, thanks to 0.3 to 0.5 mL/g. Combustion agents typically comprise 5% to 40% by weight, depending on the weight of alpha alumina in the carrier. Preferred combustion agents are materials derived from cellulose, such as ground walnut shells.

The term “binding agent” as used herein refers to an agent that holds together the various components of the carrier material after they have been formed into their final form, such as extrusion or pelleting. Binding agents allow the formed materials to be dried and baked without disintegration. These binding agents are generally “sticky” organic materials such as polyvinyl alchohols or cellulosic materials. Correlation factors may also be used as emergence aids; In certain cases, peptizing acids may be used instead of binding agents.

While it may appear that the alpha alumina formed from the seed source acts somewhat as a binder for the fabric of the material to hold the remaining alpha alumina particles together, it is usually preferable to add a ceramic binder to the mixture to add resistance to the burned carrier. Ceramic binder is typically present in an amount of 1% to 3% by weight based on the total weight of alumina components, embodied in alpha alumina. Conventional ceramic binders can be used after firing and typically include components (embodied in oxides) such as silica, alumina, alkali metal oxides, alkaline earth metal oxides, iron oxide and titanium oxide.

The first two substances are the dominant components. In a preferred embodiment, the ceramic bond comprises the following components, embodied as oxides, in the following approximate amounts: 60% by weight silica, 29% by weight alumina, 3% by weight calcium oxide, 2% by weight magnesia, 4% by weight of alkali metal oxides, and less than 1% by weight of ferric oxide and titania.

After mixing the components of the carrier material together, for example by grinding, the mixed material is extruded into pellets of specific shape, for example, cylinders, rings, trilobites, quaternions, etc. It is permissible to use “extrusion aids” such as Vaseline petroleum jelly and materials Lubricate other organs to facilitate extrusion. The sprout is dried to remove water that turns into steam during roasting and to destroy the sprout. After drying to a low water content, meaning less than 2%, the extrudate is roasted under conditions sufficient to remove combustion agents, extrusion aids and binding agents and to coalesce the alpha alumina particles into a solid, porous mass. Roasting typically takes place in an oxidizing atmosphere, for example oxygen gas or preferably air, and at a maximum temperature greater than 1300 Celsius, preferably ranging from 1350 to 1500 Celsius. Times at maximum temperatures typically range from 0.1 to 10, preferably from half an hour to 5 hours.

Roasted carriers and catalysts made from them typically have pore volumes (water) ranging from 0.2 to 0.6, preferably from 0.3 to 0.5 mL/g, and surface areas ranging from 0.15 to 3, preferably from 0.3 to 2 m2/g.

The carrier preparation should preferably have a low soda content of less than 0.06% by weight. In practical application, it is very difficult to obtain a sodium-free preparation, and soda contents of 0.02 to 0.06% by weight are usually considered acceptable.

The carrier materials described above are very suitable for the preparation of ethylene oxide catalysts with high starting selectivities. Catalyst

The catalysts of the present invention ignite on a catalytically effective amount of silver and an enhanced amount of alkali metal(s) deposited on the carrier material as described above. It is permissible to inform

The presence of other enhancers in enhanced quantities, such as rare earths oxides, magnesium, rhenium, and rhenium co-promoters selected from sulfur, chromium, molybdenum, tungsten, and mixtures thereof.

In general, the catalysts of the present invention are prepared by impregnation of refractory porous supports comprising alpha alumina with silver ions or compound(s), complex(s) and/or salt(s) dissolved in a suitable solvent sufficient to cause Silver deposits on the support in an amount of 1 to 40, preferably 1 to 30 per ounce by weight, based on the weight of the total catalyst. The impregnated support then separates from the solution and the precipitated silver compound is reduced to metallic silver. Also deposited on the support, either before, with or after the deposition of the silver, are suitable ions or compound(s) and/or salt(s) of an alkali metal dissolved in a suitable solvent. Also deposited appropriately on the carrier material at the same time as the silver and/or alkali metal compound(s), complex(s) and/or enhanced salt(s) dissolved in a suitable solvent.

The catalysts of the present invention are prepared by a technique in which the alkali metal enhancer as well as any additional enhancers in the form of salts and/or soluble compounds are deposited on the catalyst and/or support before, simultaneously with, or after the deposition of the silver and each other. The preferred method is to deposit silver and alkali metal simultaneously on the support, meaning in a single imbibition step, although it is believed that single or simultaneous deposition of alkali metal before and/or after silver deposition will also produce suitable catalysts.

Enhanced quantities of alkali metal or mixtures of alkali metal are deposited on a porous support using a suitable solution. Although alkali metals exist in a pure metallic state, they are not suitable for use in this form and are used as ions or as alkali metal compounds dissolved in a suitable solvent for the purpose of imbibition. The carrier is impregnated with a solution of ions, salt(s) and/or compound(s) of an alkali metal reinforcement before, during or after the impregnation of the ions, salt(s), complex(s) and/or compound(s) of silver. An alkali metal enhancer may also be deposited on the carrier material after reduction to metallic silver has occurred. The amount of alkali metal booster used will depend on many variables, such as surface area, pore structure, surface chemical properties of the carrier used, silver content

In the catalyst and special ions used in combination with the alkali metal cation, optional co-enhancers. The amount of alkali metal enhancer deposited on the support or present on the catalyst is generally between 10 and 3000, preferably between 15 and 0 0 0 2 and more preferably between 20 and 1500 ppm by weight of the total catalyst. It is best for the quantity to range between 50 and 1000 ppm by weight of the total catalyst.

For convenience of formula, the amount of alkali metal deposited on the support or present on the catalyst is expressed in metal. Without wishing to limit the scope of the invention, the alkali metal compounds are believed to be oxide compounds. In particular, it is believed that alkali metal compounds are likely to take the form of mixed surface oxides, double surface oxides, or complex surface oxides with the aluminum of the support and/or silver of the catalyst, possibly in combination with species present in or formed from the reaction mixture, e.g. Chlorides, carbonates, or remaining types of imbibition solution(s).

In a preferred embodiment, at least a major portion (greater than 50% by weight) of the alkali metals is selected from the group consisting of potassium, rubidium, cesium, and mixtures thereof.

A preferred alkali metal reinforcer is cesium. A particularly preferred alkali metal booster is cesium plus at least one additional alkali metal. It is preferable to choose the additional alkali metal from sodium, lithium, and mixtures thereof, with preference to lithium.

It should be understood that the amounts of alkali metal enhancers on catalysts are not necessarily the total amounts of these metals present in the catalyst. Instead, they are the amounts of alkali metal enhancers that have been added to the catalyst by impregnation with a suitable solution of alkali metal ions, salts and/or compounds and/or complexes. These quantities do not include quantities of alkali metals that are trapped in the support, such as by roasting, or that cannot be extracted in a suitable solvent such as water, lower alkanol, amine, or mixtures thereof, which do not provide an enhancing effect. It should also be understood that a source of the alkali metal booster ions, salts and/or compounds used to enhance the catalyst may be the carrier material. This means that the carrier may contain extractable amounts of an alkali metal that can be extracted with a suitable solvent, such as water or alcohol.

lower alkanol, thus preparing a solution to drink from which ions, salts and/or alkali metal compounds can be deposited or re-deposited on the support.

The catalyst may also contain modest amounts of chloride for the purpose of improving the starting process of the catalyst. When chloride is added to the catalyst, the carrier may be impregnated with a solution of ions, salt(s) and/or chloride intermediate(s) before, during or after imbibition of the ions, salt(s), complex(s) and/or occurs. Silver compound(s) and before, during or after imbibition of ions or salt(s), complex(s) and/or compound(s) of the enhancer. The chloride intermediate may also be deposited on the carrier material after reduction to metallic silver has occurred. Suitable chloride-containing salts used in the preparation of imbibition solutions include enhanced chlorides such as lithium chloride, sodium chloride, potassium chloride, rubidium chloride, cesium chloride, and ammonium chloride. Ammonium chloride is a preferred salt for use in the preparation of imbibition solutions containing chloride. Other compounds that dissolve into the chloride ion upon catalyst treatment are also suitable. Imbibition solutions containing chloride usually contain at least a small amount of water to improve the solubility of the salt or chloride-containing compound. Other auxiliary enhancers and enhancers may be used in combination with alkali metal and silver enhancers.

Non-exclusive examples of other enhancers include rhenium, sulfate, molybdate, tungstate, and chromate (see US Patent No. 4,766,105); sulfate anion, fluordie anion, oxyanions of an element selected from groups (3b) to (6b) (see US Patent No. 5,102,848); 1) oxidized anions of an element selected from groups (3) to (7b) and 2) alkali metal salts with anions of halides, and oxyanions selected from Groups (3a) to (7a) and (3b) to (7b) (see US Patent No. 4,908,343).

The resulting impregnated carrier is heated to reduce silver to metallic silver. It is convenient to heat them to a temperature in the range of 50 to 600 C, during a period sufficient for the reduction of the silver salt, compound or complex to take place to metallic silver and to form a layer of fine fine silver, which bonds with the surface of the carrier material, on the interior and the surface of the pores. Air, or other oxidizing gas, reducing gas; Inert gas or mixtures thereof may be passed over the carrier material during the heating step.

A method for preparing a silver-containing catalyst can be found in US Patent No. 3,702,259. Other methods for preparing silver-containing catalysts that additionally contain higher alkali metal enhancers can be found in U.S. Patents No. 4,010,115, No. 4,356,342, No. 3,962,136, and 4012425. Methods for preparing silver-containing catalysts that contain higher alkali metal enhancers may be found. and rhenium in U.S. Pat. No. 4,761,394, and methods for preparing silver-containing catalysts containing higher alkali metal enhancers, rhenium, and rhenium co-enhancers may be found in U.S. Pat. No. 4766105. Methods for preparing silver-containing catalysts with a variety of different enhancers can be found in US Patents 4,908,343 and 5,057,481.

The concentration of silver (expressed as metal) in a solution containing ms silver will range from 1 g/L up to the solubility limit when a single impregnation unit is used. The alkali metal concentration (expressed as metal) will range from 1 x 10-3 g/L to 12 g/L and preferably from 10 x 10-3 g/L to 12 g/L when using a single impregnation step. The concentrations chosen above depend on the pore size of the catalyst, the final amount desired in the final catalyst and whether the impregnation is single or

several .

It has been observed that, regardless of the form in which the silver is present in the solution before precipitation on the carrier, the term "reduction to metallic silver" is used, while at the same time often decomposition by heating occurs. We refer to the use of the term & reduction, due to the transformation of the Ag+ ion into a metallic Ag atom. The reduction tenses may generally vary from

About half a minute to about 8 hours, depending on conditions.

the operation

In a commercial process, ethylene and oxygen are converted to ethylene oxide in an ethylene oxide reactor that includes a large fixed tube heat exchanger containing thousands of tubes filled with catalysts. A coolant is used on the cap side of the reactor to remove the heat of the reaction. Coolant temperatures are often used as a function of catalyst activity, with higher coolant temperatures corresponding to lower catalyst activities.

In the reaction of ethylene with oxygen to produce ethylene oxide, ethylene is typically present in at least double the amount (on a molar basis) than oxygen, but the amount of ethylene used is generally much higher. It is therefore convenient to calculate the conversion according to the molecular percentage of oxygen that was consumed in the reaction to form ethylene oxide and any oxygenated byproducts. The conversion of oxygen depends on the reaction temperature, and the reaction temperature is a measure of the activity of the catalyst used. The T40 value indicates the temperature when 40% oxygen is converted in the reactor, and the T value is expressed in degrees Celsius. This temperature for any given catalyst is higher when the oxygen conversion is higher. In addition, the temperature strongly depends on the catalyst used and the reaction conditions. Selectivity (to ethylene oxide) refers to the molecular amount of ethylene oxide in the reaction product compared to the total molecular amount of converted ethylene. In this standard, the selectivity is indicated as S40, meaning that the selectivity is at 40% oxygen conversion.

The conditions for performing this oxidation reaction in the presence of silver catalysts according to the present invention generally comprise those described in the prior art. This applies, for example, to appropriate temperatures, pressures, retention times, diluents such as nitrogen, carbon dioxide, steam, argon, methane or other saturated hydrocarbons, provided that moderating agents are present to control the catalytic reaction, For example, 1,2-dichloroethane, vinyl chloride, ethyl chloride or chlorinated polyphenyl compounds, if recycling processes are desired or successive conversions are applied in different reactors To increase ethylene oxide productions,

And any other special conditions that can be chosen in the processes of preparing ethylene oxide. Generally, pressures in the range of atmospheric pressure to 3500 kPa are used. However, higher pressures are not ruled out. Molecular oxygen used as reactants can be obtained from conventional sources. A suitable oxygen charge may consist of substantially or relatively pure oxygen, a concentrated oxygen stream comprising oxygen in the main quantity with smaller amounts of one or more diluents, such as nitrogen and argon, or another stream containing oxygen, such as air. . Therefore, it is established that the use of current silver catalysts in ethylene oxide reactions is not limited to using special conditions within the conditions known to be effective. By way of illustration only, the following table shows the range of conditions often used in common commercial ethylene oxide reactor units that are also suitable for the present process.

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* Units of volume of gas at a typical temperature and pressure passing over one unit volume of catalyst packed per hour.

In a preferred application of silver catalysts according to the invention, ethylene oxide is produced when a gas containing oxygen comes into contact with ethylene in the presence of the present catalysts at a temperature in the range of 5180 to 330 C, preferably from 200 to 325 C.

While the catalysts of the present invention are preferably used to convert ethylene to ethylene oxide, they can also be used to epoxidize olefins.

Others free of allylic hydrogens, such as generally described in US Patent No. 4,897,498. Examples of these olefins are butadiene, tertiary butyl ethylene, vinyl furan, methyl vinyl ketone, N-vinyl pyirolidone, etc. The currently preferred olefin for use in the practical application of this process is butadiene because of its ease of acquisition, relatively low cost, and wide range of potential uses for the epoxide reaction product. US Patent No. 5,081,096, issued on January 14, 1992, discloses a supported catalyst, with a silver base, reinforced with an alkali metal, used from the epoxidation of butadiene by treating the primary catalyst, after impregnation with a silver compound, with a gas containing hydrogen at a temperature Do not exceed 350 Celsius. The same can be done with catalysts according to the present invention.

The invention will be depicted in the following embodiments. Pictorial embodiments of carrier preparation Carrier material (A):

Mix the ceramic components with a retardant (walnut shell flour) and boric acid for about one minute. Water and the seed component are then added, and water is added in the amount necessary to make the mixture germinable and is generally about 30% of the weight of the total solids present. Mix the mixture for two to four minutes and then add, as an eruption aid, 5% by weight petroleum jelly (Vaseline brand name) based on the weight of the ceramic components. The mixture is then mixed for an additional two to four minutes before being extruded into cylinders and dried to less than 2% unconsolidated water. This is fired in a tube furnace with a maximum temperature of 1500°C for approximately four days.

hours. The carrier is described with respect to its preparation in Table 2 and with respect to its physical properties

In Table 3.

Carrier material (B):

The carrier substance (B) is prepared in a similar way to the carrier substance (A), except for the addition of titania to the carrier preparation. The carrier is described with respect to its preparation in Table 2 and with respect to its physical properties in Table 3. Carrier material (c):

Carrier material (C) is prepared in a similar manner to carrier material (A), except that the carrier material does not contain an alpha alumina component generated from the colloidal solution-gel process, and a seed component, meaning Alpha Alumina No. 5, is not added to the carrier preparation. The carrier is described with respect to its preparation in Table 2 and with respect to its physical properties in Table 3. Carrier material (D):

The carrier substance (D) is prepared in a similar manner to the carrier substance (A), except that the carrier substance does not contain an alpha almnina component generated from the colloidal solution-gel process, and a seed component, meaning Alpha Alumina No. 5, is not added to the carrier preparation. The carrier is described with respect to its preparation in Table 2 and with respect to its physical properties in Table 3.

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(1) Refers to ceramic components and the specific percentages are based on 100% ceramic components. (2) &amp;Alpha Alumina No. 1&amp; is alpha alumina with an average particle size of 3 to 3.4 micrometers, a BET surface area of 0.9 to 1.4 m2/g, a crystal size of 1.6 to 2.2 micrometers, and a soda content of 0. ,02% to 0.06%.

(3) &amp;Alpha Alumina No. 2&amp; is alpha alumina with an average particle size of 4 to 8 micrometers, a surface area of 3 to 5 m2/g, a crystal size of 0.4 to 0.8 micrometers, and a soda content of 0.1 to 0.3%. %.

(4) &amp;Alpha Alumina No. 3&amp; is alpha alumina with an average particle size of 3.6 to 4.2 micrometers, a BET surface area of 0.8 to 1 m2/g, a crystal size of 3 to 4 micrometers, and a soda content of 0.05%. .

(5) &amp;Alpha Alumina No. 4&amp; is alpha alumina with an average particle size of 2.5 to 3.5 µm, a BET surface area of 3 to 4 m2/g, a crystal size of 3 to 4 µm and a soda content of 0.1%.

(6) &amp;Alpha Alumina No. 5&amp; is alpha alumina used as seed for sources of gibbsite and boehmite for alpha alumina. Its average particle size is less than 0.1 micrometer.

(7) Gibbsite has an average particle size of 4 to 20 micrometers. (8) Boehmite disperses as a colloidal solution.

(9) The ceramic bond for the carrier materials (A) and (B) contains components, called oxides, in the following approximate amounts: 60% by weight silica, 29% by weight alumina, 3% by weight calcium oxide, 2% By weight magnesia, 4% by weight alkali metal oxides and less than 1% by weight each of ferric oxide and titania.

(10) Percentages are based on the total weight of the ceramic components.

(11) The ceramic bond for the carrier material (C) contains the components, called oxides, in the following approximate amounts: 67% by weight silica, 30% by weight alumina, about 1% by weight

Weight each of ferric oxide and titania, and a small amount of alkali metal and alkaline earth oxides. (12) The ceramic binder used for the carrier material (D) is calcium silicate. (13) Percentages are based on the total weight of solids.

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(1) Water Absorption is a measurement of the increase in weight of the carrier material after it is immersed in water and weighed.

(2) “Packing Density” is the stable packing density as measured by a modified ASTM D-4699-87 device using a cylinder with an inner diameter of 88 mm and a length of 45.7 cm, or its equivalent.

(3) Crush Strength measured on Compton Tensile Tester, Model 50-OP.

(4) Surface Area is the surface area of BET measured using nitrogen or krypton as the usual adsorbent.

Catalyst preparation

The following representative embodiment describes preparatory techniques for making catalysts of the present invention (catalysts (a), (b), (c), (d) and (e)) and comparative catalysts (comparator catalysts (f) and (g)) and a technique for measuring the properties of these Catalysts.

Part A: Preparation of a stock silver oxalate/ethylene-diamine solution for use in preparing a catalyst:

(1) Dissolve 415 grams of reagent grade sodium hydroxide in 2340 milliliters of deionized water. Set the temperature to 50°C.

(2) Dissolve 1699 grams of silver nitrate (high purity) in 2100 milliliters of deionized water. Set the temperature to 50°C.

(3) Slowly add the sodium hydroxide solution to the silver nitrate solution while stirring while maintaining the temperature at 50 Celsius and stir for 15 minutes after the addition is complete, then reduce the temperature to 40 Celsius.

(4) Insert a filter stick and withdraw as much water as possible from the precipitate formed in step (3) to remove sodium and nitrate ions. The conductivity of the removed water is measured and added again as much fresh deionized water as possible versus what was removed by the filter sticks. Stir for 15 minutes at 40°C. This process is repeated until the conductivity of the removed water is less than 90 µΩ/cm. Then add 1500 ml of deionized water again.

(5) Add 630 grams of high-purity oxalic acid dihydrate to approximately 100 grams of additional materials. Keep the temperature at 40°C and stir the mixture well. Add the last portion of oxalic acid dihydrate slowly and monitor the pH to ensure it does not drop below 7.8.

(6) Remove as much water as possible from the mixture using clean filter sticks in order to form a slurry containing highly concentrated silver. Cool the silver oxalate slurry to 30°C.

(7) Add 399 grams of ethylenediamine (92% by weight) and deionized water (8% by weight). The temperature is not allowed to exceed 30°C during addition.

The above procedure produces a solution containing approximately 27-33% by weight silver which provides the “stock solution” used in the preparation of catalysts (a), (b), (c), (d) and (e)

The two compared stimuli (f) and (g) are below.

Part (b): Preparation of impregnation solutions for catalyst (a):

A solution of 161.8 grams of silver stock with a specific gravity of 1.543 is diluted with 2.4 grams of water and 13.5 grams of monoethanolamine. Dissolve 0.0350 grams of NH4F

In 2 milliliters of water and add to the silver solution. C5OH (50% solution in water) is added in an amount of 367 1.0 grams to 0.6 grams of the above diluted silver solution and the resulting mixture is used to impregnate the carrier material. For catalyst (b):

A solution of 175.4 grams of silver stock with a specific gravity of 1.53 is diluted with 3.6 grams of water. Dissolve 0.387 grams of NHF in 2 cm3 of water and add it to the silver solution. C5OH (50% solution in water) is added in an amount of 0.1536 grams to 60 ha of the above diluted silver solution and the resulting mixture is used to impregnate the carrier material. For catalyst (c):

A 165.3 g solution of silver stock with a specific gravity of 1.55 is diluted with 13.9 g of monoethanolamine. Dissolve 0.0426 g of NHF in 2.5 g of water and add to

Silver solution. C5OH (50% solution in water) is added in an amount of 0.1406 g to 60 g of the above diluted silver solution and the resulting mixture is used to impregnate the carrier. For catalyst (d):

A solution of 161.2 g of silver stock with a specific gravity of 1.555 is diluted with 17.8 g of water. Dissolve 0.0868 g of NH4 (ReO4) in 2 cm3 water/EDA mixture (50/50 by weight) and add to the silver solution. C5OH (50% solution in water) is added in an amount of 0.1743 g to 60 mm of the above diluted silver solution and the resulting mixture is used to impregnate the carrier.

For the comparative stimulus (e):

A solution of 129.7 g of silver stock containing 29.7% silver is diluted with 14 g of water and 6.3 g of monoethanolamine. Dissolve 0.0285 g of NH4F in 2

Milliliters of water and added to the silver solution. Add C5OH (50% solution in water) in an amount of 0.582. gm to 50 gm of the above diluted silver solution and the resulting mixture is used to impregnate the carrier material. For catalyst (f):

A solution of 168.1 g of silver stock with a specific gravity of 1.546 is diluted with 10.9 g of water. 1442 melts. g of (NH4)ReO4, 0.0704 g of Li2SO4.H2O, 0.303 g

About 2 milliliters of ethylenediamine/water (50/50 by weight) are added to the silver solution. Add C5OH (50% solution in water) in an amount of 1985,. gm to 50 gm of the above diluted silver solution and the resulting mixture is used for impregnation of the carrier material. For the comparative stimulus (g):

A 101 g solution of silver stock with a specific gravity of 1.558 is diluted with 12.9 g of water. Dissolve 0.0766 g of NH4 (ReO4), 0.074 g of Li2SO4.H2O, and 0.1616 g of LiNO3 in about 2 g of ethylenediamine/water (50/50 by weight) and add to the silver solution. Add C5OH (50% solution in water) in an amount of 111. gm to 50 gm of the above diluted silver solution and the resulting mixture is used to impregnate the carrier material. Part (c) Carrier Impregnation and Catalyst Treatment (a):

Apply approximately 30 g of carrier A (described above in Tables 2 and 3) under 25 mm suction for 3 minutes at room temperature. Approximately 50 to 60 grams of a similar impregnating solution (as described in Part (b) above under the heading "For Catalyst A") is then added to immerse the carrier, and the suction is maintained at 25 mm for an additional 3 minutes. At the end of this time, the Aspiration, and excess impregnation solution is removed from the carrier by centrifugation for several minutes at 500 rpm. If the impregnation solution is prepared without monoethanolamine, then the impregnated carrier is treated by continuous shaking in an air stream

850 liters/hour flowing over a cross-sectional area of approximately 19.4-32.3 cm at 240-270 C for 3-6 minutes. If monoethanolamine is present in large quantities

In the impregnation solution, the impregnated carrier is then treated by continuous shaking in an air stream of 850 liters/hour at 250 to 270 C for 4-8 minutes. The processed catalyst is then ready for testing.

The properties of the catalyst (A) are shown in Table 4 below. Catalyst B:

Catalyst (B) is prepared in the same way as Catalyst (A), except that the carrier material (B) for the catalyst is used instead of the carrier material (A) for the catalyst, and the impregnation solution used is the one described in Part (B) above under the heading “For Catalyst (B)” . The properties of catalyst (B) are shown in Table 4 below.

Catalyst (C):

Catalyst (C) is prepared using a double impregnation technique. In this technique, 120 grams of carrier (B) of the catalyst are impregnated with 240 grams of silver stock solution having a specific gravity of 1.555. The impregnated carrier is dried/roasted to decompose the silver salts into metallic silver. The pore volume of water is determined after the first imbibition and is used to calculate impurity concentrations. The second impregnation is carried out with the impregnation solution described in Part (b) above under the heading “For catalyst (c)”. The catalyst is treated in a similar manner as described above. The properties of catalyst (c) are shown in Table 4 below.

Catalyst (d):

Apply approximately 0.3 grams of carrier (A) (described above in Tables 2 and 3) under 25 mm suction for 3 minutes at room temperature. Then 50 to 60 grams of a similar impregnating solution (as described in Part (b) above under the heading “For Catalyst (D)”) is quickly added to immerse the carrier, and the suction is maintained at 25 mm for an additional 3 minutes. At the end of this time, it is released. Aspiration, and excess impregnation solution is removed from the carrier by centrifugation for 2 minutes at 500 rpm. If the impregnation solution is prepared without monoethanolamine, then the impregnated carrier is treated by continuous shaking in an air stream of 850 l/h flowing over a cross-sectional area of approximately 19.4-32.3 cm at 240-270°C for 3-6 minutes. . If monoethanolamine is present in large quantities

In the impregnation solution, the impregnated carrier is then treated by continuous shaking in an air stream of 850 liters/hour at 250 to 270 C for 4-8 minutes. The processed catalyst is then ready for testing.

The properties of catalyst (D) are shown in Table 4 below. Comparative stimulus (e):

The comparative catalyst (E) is prepared in the same manner as catalyst (A), except that the carrier material (C) for the catalyst is used instead of the carrier material (A) for the catalyst and the impregnation solution (A) used is the one described in Part (B) above under the heading &amp;For the catalyst Comparison)&amp;. The properties of the compared catalyst (e) are shown in Table 4 below.

Catalyst (f):

Catalyst (F) is prepared in the same manner as Catalyst (D), except that carrier (B) for the catalyst is used instead of carrier (A) for the catalyst, and the impregnation solution used is the one described in Part (B) under the heading "For Catalyst (F)". The properties of the catalyst (f) are shown in Table 4 below.

Comparative catalyst (g):

The comparative catalyst (G) is prepared in the same manner as catalyst (D), except that the carrier material (D) for the catalyst is used instead of the carrier material (A) for the catalyst and the impregnation solution (A) used is the one described in Part (B) above under the heading &amp;For the catalyst Comparator (g)''. The properties of the compared catalyst (g) are shown in Table 4 below.

<img file="SA686B1_D0004.tif" />

The actual silver content of the catalyst can be determined by any number of typical, published procedures. The actual level of cesium on the catalyst can be determined by using a solution

Cesium hydroxide stock, which has been labeled with a radioactive isotope of cesium in the catalyst preparation. The cesium content of the catalyst can then be determined by measuring the radiation of the catalyst. Alternatively, the cesium content of the catalyst can be determined by elution of the catalyst with boiling deionized water. In this extraction process, cesium, as well as other alkali metals, is measured by extraction from the catalyst. Boiling 10 grams of the total catalyst in 20 milliliters of water for 5 minutes, and repeating the above two additional times, combining the above extracted materials and determining the amount of alkali metal present in comparison with the alkali metal solutions. Typical reference alkali metals using a NRI absorption spectrometer (using a Varian Techtron Model 1200 or equivalent).

Part D: Testing of a typical microscopic reactor catalyst

Conditions/Procedure

A- For stimuli (a), (b), (c) and the comparative stimulus (e):

One to three grams of the purified catalyst are packed from 841,. - 0.595 mm (20-30 eyes)

In a U-shaped stainless steel tube with a diameter of 6.4 mm. The U-tube is immersed in a molten metal bath (hot medium) and the ends are connected to a gas flow system. The weight of the catalyst used and the inlet gas flow rate are adjusted to achieve a vacuum gas velocity per hour of 6800. The outlet gas pressure is 1550 kPa.

The gas mixture passing through the bottom of the catalyst (in a single pass) during the total test cycle (including this start) consists of 25% ethylene, 7% oxygen, 5% oxygen, carbon dioxide, 1.25 to 5 ppm. One million ethyl chloride, and the remainder is nitrogen/argon.

The starting procedure includes jumping the temperature from 180°C to 230°C in the following manner: one hour at 180°C, one hour at 190°C, one hour at 200°C, one hour at 210°C, one hour at 220°C, 2 hours at 220°C, Two hours at 225°C, two hours at 230°C, then the temperature is adjusted to give 1.5% ethylene oxide at the reactor outlet. At these conditions, catalyst selectivity (S1.5) and catalyst activity (T1.5) are measured.

In order to obtain a logical comparison of the performance of the tested stimulus at different times, the simultaneity of the stimuli (a), (b), (c) and the comparison stimulus (e) are tested with a typical reference stimulus which has S1.5 = 81.7% and T1.5. = 235 Celsius.

The catalysts (A), (B), (C) and the comparative catalyst (E) prepared above are tested using the procedure described above and the results are shown from Table 5 below. B- For the catalyst (D):

Stimulus (d) is tested in a manner similar to that described for stimuli (a), (b), (c) and the comparative stimulus (e) above, except that the initiation procedure is as follows. The initial reactor temperature (hot medium) is 225°C. After 3 hours under a flow of nitrogen at this initial temperature, the temperature increases to 235 C for one hour, then to 245 C for one hour. The temperature is then adjusted to give 1.5% ethylene oxide at the reactor outlet. The results are given in Table 5 below.

<img file="SA686B1_D0005.tif" />

As you can see in Table 5, the initial selectivity of catalysts (a), (b), (c) and (d) is better than the initial selectivity of the compared catalyst (e). It can also be seen that the initial activities of catalysts (a), (b) and ( C) improves on the comparative stimulus (E). C- For the stimulus (f) and the comparative stimulus (g):

3 to 5 grams of purified stimulator (14-20 doses) are packed in a stainless steel U-shaped tube with a diameter of 0.25 inches. The U-tube is immersed in a molten metal bath (heat medium) and the ends are connected to a gas flow system. The weight of the catalyst used and the inlet gas flow rate are adjusted to achieve a vacuum gas velocity at 0 0 33 hours. The outlet gas pressure is 210 psi.

The gas mixture passing through the bottom of the catalyst (in a single pass operation) during the total test cycle (including start-up) consists of 30% ethylene, 8.5% oxygen; 5% dioxide

Carbon dioxide, 1.5 to 5 ppm ethyl chloride, the rest is nitrogen/argo.

Before contact with reactant gases, catalysts are typically pretreated with nitrogen gas at 225°C for three hours for all fresh catalysts and for 24 hours or longer for older, but untested, catalysts.

The reactor's initial temperature (average temperature) is 225°C. After one hour at this initial temperature, the temperature increases to 235°C, then to 245°C for one hour. The temperature is then adjusted to achieve a constant oxygen conversion (T40) of 40%. The mediator level varies for 4-24 hours at each level to determine the optimal mediator level. We usually obtain it at T40 and S40 when the catalyst has been in current for a total of about 24 hours. This is shown in Table 6. Due to slight variations in feed gas composition, gas flow rates, and calibration of analytical instruments used to determine feed and product gas compositions, the selectivity and measured activity of a given catalyst may vary slightly from

One test cycle to another.

To allow a reasonable comparison of the performance of the tested stimuli at different times, all stimuli described in this pictorial embodiment are tested concurrently with a typical reference stimulus which is

S40 = 81% and T40 = 230 Celsius.

The catalyst (F) and comparative catalyst (G) prepared above are tested using the above procedure and the results are given in Table 6 below.

<img file="SA686B1_D0006.tif" />

As we can see in Table 6, the initial selectivity and initial activity of the catalyst (f) are better than the initial selectivity and initial activity of the compared catalyst (g).