CN112206798A - Silver catalyst for preparing ethylene oxide by ethylene oxidation and preparation method and application thereof - Google Patents

Silver catalyst for preparing ethylene oxide by ethylene oxidation and preparation method and application thereof Download PDF

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CN112206798A
CN112206798A CN202011184083.6A CN202011184083A CN112206798A CN 112206798 A CN112206798 A CN 112206798A CN 202011184083 A CN202011184083 A CN 202011184083A CN 112206798 A CN112206798 A CN 112206798A
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silver
ethylene
catalyst
silver catalyst
preparing
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CN112206798B (en
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卓润生
刘新生
王洪飞
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Runhe Catalytic Materials Zhejiang Co Ltd
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
    • B01J27/20—Carbon compounds
    • B01J27/22—Carbides
    • B01J27/224—Silicon carbide
    • B01J27/228—Silicon carbide with phosphorus, arsenic, antimony or bismuth
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
    • B01J21/02—Boron or aluminium; Oxides or hydroxides thereof
    • B01J21/04—Alumina
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/48—Silver or gold
    • B01J23/50—Silver
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
    • B01J35/61—Surface area
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/0201—Impregnation
    • B01J37/0205—Impregnation in several steps
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/08—Heat treatment
    • B01J37/082—Decomposition and pyrolysis
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D301/00—Preparation of oxiranes
    • C07D301/02—Synthesis of the oxirane ring
    • C07D301/03—Synthesis of the oxirane ring by oxidation of unsaturated compounds, or of mixtures of unsaturated and saturated compounds
    • C07D301/04—Synthesis of the oxirane ring by oxidation of unsaturated compounds, or of mixtures of unsaturated and saturated compounds with air or molecular oxygen
    • C07D301/08—Synthesis of the oxirane ring by oxidation of unsaturated compounds, or of mixtures of unsaturated and saturated compounds with air or molecular oxygen in the gaseous phase
    • C07D301/10—Synthesis of the oxirane ring by oxidation of unsaturated compounds, or of mixtures of unsaturated and saturated compounds with air or molecular oxygen in the gaseous phase with catalysts containing silver or gold
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D303/00—Compounds containing three-membered rings having one oxygen atom as the only ring hetero atom
    • C07D303/02—Compounds containing oxirane rings
    • C07D303/04—Compounds containing oxirane rings containing only hydrogen and carbon atoms in addition to the ring oxygen atoms
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    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/50—Improvements relating to the production of bulk chemicals
    • Y02P20/52—Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts

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Abstract

A silver catalyst for preparing ethylene oxide by ethylene oxidation and a preparation method and application thereof belong to the technical field of petrochemical industry, and the silver catalyst comprises 10-20% of silver, 0.001-1% of IA group element, 0.1-10% of IIA group element, 0.1-10% of VIIA group element, 0.01-1% of rare earth element, 0.1-1% of high-valence metal modified element and 0.1-5% of nonmetal modified element on a composite carrier formed by alpha-silicon carbide and alpha-alumina by mass percentage based on the total dry mass of the silver catalyst; the silver catalyst has a porosity of 45-75%, a specific surface area of 0.1-2 square meters/g and a pore volume of 0.4-1.0 ml/g. The silver catalyst has good conduction, diffusion and reaction performances, uniform distribution of metal active components, and high selectivity, activity and stability in the oxidation reaction process.

Description

Silver catalyst for preparing ethylene oxide by ethylene oxidation and preparation method and application thereof
Technical Field
The invention relates to a silver catalyst and a preparation method thereof, in particular to a silver catalyst for producing ethylene oxide by oxidizing ethylene and a preparation method thereof, and also relates to application of the silver catalyst in producing ethylene oxide by oxidizing ethylene, belonging to the technical field of petrochemical industry.
Background
The gas phase oxidation of olefins produces many useful organic compounds, of which ethylene epoxidation to ethylene oxide is important. Ethylene oxide is an important organic chemical product of ethylene industrial derivatives, second only to polyethylene and polyvinyl chloride, and is mainly used for producing ethylene glycol except for part of nonionic surfactants, amino alcohols and glycol ethers, and the latter is a main raw material for producing polyester resins and is also used as an antifreeze agent in large quantities. Almost all ethylene oxide is now integrated with ethylene glycol production, with most or all of the ethylene oxide being used to produce ethylene glycol and only a small proportion being used to produce other chemical products.
Ethylene oxide is produced by two processes, the chlorohydrin process and the direct oxidation process. The chlorohydrin process is firstly industrialized by united states co-carbon corporation (UCC) in 1925, low-concentration ethylene can be used as a raw material, the unit consumption of ethylene is low, equipment is simple, the operation is easy to control, and sometimes propylene oxide can be co-produced. But the production cost is high, equipment corrosion is caused, and the environment is seriously polluted, and the direct oxidation method is gradually replaced from the 20 th century to the 50 th century.
The direct oxidation process was also successfully developed by united states co-carbon in 1938. Due to the current limitations of the state of the art, the construction of large industrial plants was not started until the 50 s. In 1953, a production device for preparing ethylene oxide by a direct air oxidation method is built by American scientific design company (SD company) with the annual production of 2.7 ten thousand tons. In 1958 Shell chemical development (Shell) in the United states first built a 2-million/a ethylene oxide production plant using oxygen as oxidant.
Ethylene oxide produced using the technology of the three companies mentioned above now accounts for about 92% of the total ethylene oxide production worldwide. Other companies possessing ethylene oxide production technology include Japanese catalyst chemistry (e.g., CN1007702B, CN1008513B), Snan Progetti in Italy, Huels in Germany, and the like.
As the air separation devices are more and more built and the scale is larger and larger, the sources of oxygen are more and more, and the price tends to be low. Thus, in recent decades, most plants for the production of ethylene oxide have been constructed using pure oxygen direct oxidation technology, such as CN 103896884A.
Some ethylene oxide plants originally using air as an oxidant also have been changed to direct oxidation technology using pure oxygen. The pure oxygen direct oxidation technology has the advantages that the discharged gas contains less ethylene than the air method, the ethylene consumption rate is lower than the air method, and the equipment and the pipeline are also lower than the air method. The oxygen method is also adopted in most of the Chinese direct oxidation methods. However, the prior art (CN1762584A) of air oxidation using a monolithic catalyst has been continuously reported.
Ethylene can be catalyzed by a silver catalyst to directly generate ethylene oxide in one step, as described in Chinese patents CN1010565B, CN1068319C, CN1187817A and CN 1210524A. Under the action of silver catalyst, ethylene is oxidized to produce ethylene oxide mainly, and side reaction to produce carbon dioxide and water occurs simultaneously, wherein activity, selectivity and stability are the main performance indexes of the silver catalyst, such as CN102414187A and CN 102558099A.
The silver catalyst with high activity, high selectivity and good stability is used in the process of producing ethylene oxide by oxidizing ethylene, so that the economic benefit can be greatly improved. Therefore, silver catalysts with high activity, high selectivity and good stability are the main direction in the research of catalysts for ethylene oxidation to produce ethylene oxide (CN 1101388C).
The performance of the silver catalyst is not only important in relation to the composition of the catalyst and the preparation method, but also particularly important in relation to the performance of the carrier used for the catalyst and the preparation method. Therefore, there are a lot of technical application cases in the prior art, such as CN1008514B and CN1009829B, which use halogens such as fluorine and chlorine to improve the performance of the catalyst; CN1126750C also adopts sulfur element to modify; CN105233824A is modified by using nonmetal elements such as sulfur and phosphorus.
The prior art of improvement in the preparation process and method has also been reported, for example, CN1071596C is changed into a multi-stage calcination catalyst, CN102133545A low-temperature-high-temperature calcination treatment catalyst; CN1310703C was modified with a hydrothermal treatment catalyst.
CN1175928C and CN1175932C were modified by treating the carrier with an alkali solution, CN104707665A was modified by acid treatment, and CN103357440A was modified by acid-base combination treatment. CN102247845A adopts ionizing radiation to activate the catalyst; CN110639518A also adopts a modification method of ultraviolet irradiation to improve the dispersion degree of silver on the catalyst.
The silver catalyst consists of an active component, a cocatalyst and a carrier, and can be firmly combined with the carrier, uniformly distributed, proper in particle size and small in silver particle sintering tendency by a large amount of prior art improvements, such as CN1022891C, CN1044416A and CN 1130257C. The use of metallic silver, which is different from natural isotopic abundance, is also disclosed in prior art CN 110586089A.
In the prior art, a large number of methods for loading active component silver and various auxiliary agents on a carrier are disclosed, and an impregnation method is mainly adopted, namely, an alumina carrier is immersed in a solution prepared from silver salt, organic amine and various auxiliary agents, the solution is removed, and then the impregnated carrier is heated and reduced to activate, as described in CN 1168644A; CN87102701 and CN110605116A adopt a complexing method to load silver; CN1140341C and CN1386580A adopt a chemical plating method to load silver; CN100441300C also adopts a microorganism reduction loading method.
The silver catalyst has been improved most recently by modification with an auxiliary, with emphasis on improving the selectivity of the catalyst. Alkali metals are the most commonly used adjuvants, such as CN1009059B, etc.; the prior art using alkaline earth metal assistants has also been reported publicly, such as CN1093774C, CN1102929C, CN103357439A, and the like.
Further, modification methods of rare earth element compounds (CN1126597C, CN1400048A), rhenium elements (CN1226187A, CN101850243A), gallium elements (CN107413342A), manganese elements (CN104220160A), cobalt elements (CN106607035A), titanium elements (CN1134382C), nickel elements (CN1136976C), tungsten and molybdenum elements (CN1257487A, CN103212415A), niobium and tantalum element modifications (CN1219892C), zirconium and boron element modifications (CN108283943A), and the like have been reported.
A great deal of related modification techniques are also reported in foreign patents, for example, US4376718 describes that an auxiliary agent bed layer is added at the upper section of a reactor, and the auxiliary agent is selected from compounds of potassium, matters, gorgeous and barium, so that the stability of the catalyst bed layer is improved; the silver catalyst prepared by US4305844 and EP0017725 contains 0.01-0.25% of barium and alkali metal additive; strontium and barium are used in the silver catalyst manufacturing process of US4350616, with a selectivity of 84.0%.
US4812437, EP0247414 deposit silver and at least one of sodium, potassium, flail on a carrier containing silicon-aluminum oxide, with a selectivity up to 81.2%; when the catalysts are prepared, the alkaline earth metal is firstly deposited before the silver and alkali metal auxiliary agent are deposited, and the initial activity of the catalysts is higher.
US4400308 discloses the use of carriers with specific surface of 0.4 to 0.5m2The preparation method of the silver catalyst comprises the steps that the particle size of the loaded silver is 0.3-0.4 micron, 0.001-0.03% of alkali metal cesium and 0.05-0.5% of alkaline earth metal barium are used, and the selectivity of the prepared silver catalyst can reach 81.5% at most; SU1685510 uses a specific surface area of less than 1m2The alumina carrier is treated with silver salt amino complex, alkali metal salt and alkaline earth metal compound, and then treated with alkali metal salt and surfactant after drying, and the alkaline earth metal salt is calcium nitrate and barium nitrate.
DD289413A and DD288067 disclose the application of an acidic solution of silver organo-acid, excess lactic acid, alkaline earth metal and alkali metal to a specific surface of less than 0.3m2A method on a g support, the alkaline earth metal used being barium, which results in an improved selectivity of the catalyst; DE3310752, US4760042 and US4841080 deposit silver on the specific surface 0.3-0.8 m2Activating the carrier, depositing alkali metal, and alkaline earth metal assistant to obtain Ag catalyst with selectivity up to 79.7%.
The modification of the auxiliary agents can bring certain benefits to the improvement of the comprehensive performance of the catalyst, for example, the addition of potassium salt improves the selectivity of the catalyst; the barium salt is added to improve the anti-sintering capability of the catalyst, which is beneficial to improving the thermal stability of the catalyst, prolonging the service life of the catalyst and improving the catalytic activity, but the selectivity is reduced.
In more than a decade, the addition of cesium salts of alkali metals (e.g. CN1008075B) has been highly appreciated, and has significantly improved the selectivity of the catalyst, from 76% to over 82%, as described in CN1017780B and the like.
There are also many reports of modifying supports with tin salts, CN86104390A, CN1361105A, JP4363139, EP0255975 and EP0299569 all using Sn as an additive to modify alumina supports. However, the experimental results of JP4363139 show that the addition of Sn salt only increases the selectivity of the catalyst by 0.8, but significantly reduces the activity, and increases the reaction temperature by 7 ℃ in contrast to the catalyst without the addition of an additive.
There are many reports on the modification of the carrier, such as chinese patent CN102139212A using hydrotalcite as the carrier to make the silver on the catalyst highly dispersed; CN104437666A uses SBA-15 mesoporous carrier doped with aluminum; CN104437663A used mullite in the carrier; CN108283942A is mixed with mesoporous molecular sieve in the carrier; CN102527430A uses titanium silicon molecular sieve in the carrier; CN103566980A discloses the introduction of elemental silicon or silicon containing compounds to improve the support.
The prior art of CN1171672C, CN100408169C and the like adopts porous alpha-A12O3As a carrier; CN103357437A and CN103769233A adopt alumina of various different phase types as carriers; CN108686712A is prepared by doping mesoporous and macroporous alumina into the carrier.
Chinese patents CN1009437B, CN1034678A, CN1232349C and CN1232350C disclose that the specific surface area of the mixture is 0.2 to 2m2The catalyst comprises an alumina carrier with a pore volume of about 0.5ml/g, wherein more than 25% of pores with the diameter of more than 30 microns are used for ethylene epoxidation reaction, and the selectivity of 83-84% can be achieved; in addition, the prior art successively discloses a large number of similar contentsImproved methods, such as CN1009437B, CN1034678A, CN1142154C, CN1162416C, CN1171672C, CN1361105A, CN1426835A, CN1428936A, etc.
In the process of modifying the carrier, the modification of the pore structure is particularly interesting, such as CN100553763C, CN100408168C, CN1112239C, CN1142154C, CN 1642637A. Pore formers are also widely used in the prior art, as described in CN109201027A, CN111437888A, and the like.
Despite the numerous reports in the published patent literature on the improvement of alumina supports and the use of modification aids, there remains a need in the art for silver catalysts and methods for their preparation that are continuously improved in activity, selectivity, and stability to continuously reduce the cost of ethylene epoxidation. Therefore, there is a need for improved research.
Disclosure of Invention
In the epoxidation of ethylene, a reduction in temperature is more advantageous for the main reaction, since the activation energy for the reaction to ethylene oxide and carbon dioxide is 63 and 84kJ/mol, respectively. Therefore, the epoxidation of ethylene requires a catalyst having good reactivity, which makes it possible to lower the reaction temperature.
Secondly, the catalyst has good selectivity, which means that the side reaction is weakened, the heat released by the side reaction is reduced, the reaction temperature is easy to control, and the yield of the product ethylene oxide can be improved.
Secondly, the service life of the catalyst is long, and the content of silver in the silver catalyst is generally between 10 and 20 percent, so that the selling price of the silver catalyst is quite high, and the service life of the catalyst is prolonged, which is equivalent to cost reduction.
Finally, the alpha-A1 is used in consideration of the pore structure, specific surface area, thermal conductivity, heat resistance and strength of the catalyst2O3Suitable specific surface area and pore structure are highly desirable for the carrier as the main component, which, on the one hand, provides sufficient space for the ethylene epoxidation reaction to diffuse out the reaction heat energy, and, on the other hand, facilitates the timely desorption of the reaction product ethylene oxide to avoid deep oxidation to carbon dioxide as a by-product.
In the prior art, the preparation method of the silver catalyst comprises two processes of preparing a porous carrier (such as alumina) and loading an active component and an auxiliary agent on the carrier. It is known that in order to increase the catalyst activity, it is necessary to provide a high specific surface area of the silver particles, thereby requiring a sufficiently large specific surface area of the support. However, the large specific surface makes it difficult to remove the heat of reaction, and the side reaction is accelerated, and the selectivity is lowered.
In the process of preparing ethylene oxide by ethylene oxidation, if side reactions are carried out quickly, the released heat cannot be transferred out of the system in time, the reaction temperature is rapidly increased, a temperature runaway phenomenon is generated, the catalyst is deactivated by sintering, even an explosion accident is caused, and the reason is one of important reasons why the direct oxidation method cannot be carried out on a large-scale industrial production late.
In order to improve the selectivity of the catalyst, an ideal pore structure which is adaptive to the surface is required, good heat transfer and mass transfer conditions are formed, and the occurrence of side reactions is reduced. Because the reaction is carried out under the condition close to diffusion control, finding the carrier with the best matching of the pore structure and the specific surface and improving the diffusion and heat conduction properties become one of important research contents for developing high-selectivity silver catalysts.
In the process of preparing ethylene oxide by oxidizing ethylene, the activity of the silver catalyst refers to the reaction temperature required when the ethylene oxide production process reaches a certain reaction load, and the lower the reaction temperature is, the higher the activity of the catalyst is. Selectivity refers to the ratio of the moles of ethylene converted to ethylene oxide in the reaction to the total moles of ethylene reacted. Stability is expressed as the rate of decline of activity and selectivity, with the smaller the rate of decline the better the stability of the catalyst. Meanwhile, the uniformity of the reaction temperature can be influenced due to the good and bad heat-conducting property, and the selectivity can be even improved by 2 percent.
The silver catalyst for preparing ethylene oxide by oxidizing ethylene has been required to continuously improve the performance in these aspects, but the oxidation mechanism of ethylene on the silver catalyst has not been clarified so far, and is limited by the factor influence on the development of catalytic materials, and the work on research and improvement is greatly influenced.
It is speculated from theoretical analysis that the selectivity of the synthesized ethylene oxide may exceed 85.7%. There have been some reports of studies claiming initial selectivities in excess of 86%, such as CN 101426573A. Therefore, silver catalysts have many points where improvement in the properties can be and is desired in terms of diffusion of raw materials and reaction products, heat conduction, mechanical strength, and suppression of side reactions.
Commonly used carrier alpha-alumina for silver catalyst and containing small amount of SiO2Of alpha-alumina, etc., their specific surface area is generally less than 1m2In terms of a/g, porosity of around 50% and mean pore diameter of around 4.4 μm or more, these supports being characterized in order to meet the requirements of a strongly exothermic oxidation reaction. In addition, their thermal conductivity and heat resistance are also required to meet the requirements of the reaction process more, and stabilization of the support structure and properties affects stabilization of the catalytic performance of the catalyst.
The invention aims to meet the needs in the actual reaction process, overcome the defects in the prior art, provide an improved silver catalyst for preparing ethylene oxide by oxidizing ethylene for further improving the performance of the silver catalyst for preparing ethylene oxide by oxidizing ethylene,
the composite carrier formed by alpha-silicon carbide and alpha-alumina contains 10-20 wt% of silver, 0.001-1 wt% of IA group element, 0.1-10 wt% of IIA group element, 0.1-10 wt% of VIIA group element, 0.01-1 wt% of rare earth element, 0.1-1 wt% of high-valence metal modified element and 0.1-5 wt% of nonmetal modified element, wherein the mass ratio of the alpha-silicon carbide to the alpha-alumina is 1: 5-90.
The invention provides a silver catalyst for preparing ethylene oxide by oxidizing ethylene, wherein the IA group element is preferably strontium, and the IIA group element is preferably magnesium and barium; said elements of group VIIA are preferably fluorine and chlorine; the rare earth elements are praseodymium and cerium; the high valence metal modified element is tin and titanium; the nonmetal modifying elements are phosphorus and boron.
The invention provides a silver catalyst for preparing ethylene oxide by ethylene oxidation, and more preferably the silver catalyst comprises 16-18 wt% of silver, 0.001-0.1 wt% of strontium, 0.1-5 wt% of magnesium, 0.1-5 wt% of fluorine, 0.01-0.5 wt% of rare earth, 0.1-0.5 wt% of tin, 0.1-0.5 wt% of phosphorus and 0.1-0.5 wt% of boron, wherein the total mass of the silver catalyst on a dry basis is taken as a reference.
The thermal conductivity is not only relevant to the derivation of reaction heat, but also has an important effect on the homogenization of the bed temperature of the reactor. The improvement of selectivity to limit the exothermic quantity of side reaction and the use of carrier with good heat-conducting property can make the hot point in the bed layer of reactor be not obvious, so that it is very important for prolonging service life of catalyst and safety production.
In the past, a bonding method was used for preparing the catalyst, i.e., three components were bonded together with a binder, and then dried and thermally decomposed to prepare catalyst particles having catalytic activity. The disadvantages of this preparation method are the uneven distribution of the active components, the easy exfoliation of the silver powder, the poor strength, the inability to withstand high space velocities and the short lifetime.
Impregnation methods have been commonly employed, in which the support is immersed in a solution of water-soluble organic silver, such as a silver-organic ammonium complex, and a promoter, followed by washing, drying and thermal decomposition. The preparation method ensures that the active component silver can obtain high dispersion, silver crystal grains are uniformly distributed on the outer surface and the hole wall of the carrier, the combination with the carrier is firmer, and the high airspeed can be borne. The prepared catalyst mostly adopts a hollow cylinder, and the silver content is generally controlled within the range of 10-20%.
The invention also provides a preparation method of the silver catalyst for preparing ethylene oxide by oxidizing ethylene, which comprises the following preparation steps:
step 1), mixing an aluminum hydroxide precursor of high-pore-volume aluminum oxide, alpha-silicon carbide powder, microcrystalline cellulose, a carbon-containing material, aluminum hydroxychloride, a fluorine compound, a magnesium compound and a rare earth compound according to required mass, adding a solution of a cesium compound, a tin compound, a phosphorus compound and a boron compound into an acid solution, uniformly mixing, adding the mixture into the powder of the composition, kneading and peptizing, and preparing a precursor blank of a hollow cylindrical composite carrier by molding;
step 2), drying the precursor blank, and calcining at 1450-1560 ℃ for 0.1-6 hours to prepare a composite carrier;
step 3), weighing the silver compound, the ethylenediamine and the ethanolamine according to the required mass, wherein the ratio of the total molar weight of the ethylenediamine and the ethanolamine to the molar weight of the silver compound is 1:3
Preparing a silver solution from an ethylenediamine and ethanolamine silver compound, impregnating the composite carrier under the vacuum condition of 0.001-0.08 MPa in a step-by-step impregnation roasting mode for 2-5 times, drying in vacuum, and roasting at 200-700 ℃ in an inert atmosphere.
The step-by-step (multiple) dipping and roasting mode is that the steps of dipping and then drying, roasting, dipping and then drying and roasting are sequentially carried out.
The pore volume of the alumina obtained by calcining and dehydrating the aluminum hydroxide precursor of the high-pore-volume alumina is 0.7-1.1 ml/g.
The silver catalyst for preparing ethylene oxide by ethylene oxidation has the porosity of 45-75%, the specific surface area of 0.1-2 square meters per gram and the pore volume of 0.4-1.0 milliliter per gram, wherein the pores with the pore diameter of 5-30 micrometers account for 80-95%, and the pores with the pore diameter of more than or equal to 30 micrometers account for 5-20%.
The silver catalyst for preparing ethylene oxide by ethylene oxidation is characterized in that the molded and roasted hollow cylindrical catalyst has the shape of 7.0-9.0 mm in length, the inner diameter of 1.0-2.0 mm, the outer diameter of 7.0-9.0 mm, the bulk density of 0.5-0.9 g/ml and the side crushing strength of 40-80N/g. Molding processes are well known to those skilled in the art, and molding apparatus are readily available in commercially available forms.
The invention provides a preparation method of a silver catalyst for preparing ethylene oxide by oxidizing ethylene, wherein in the process of preparing a precursor blank, combined powder is ground and sieved by a sieve of 40-200 meshes; screening methods are well known to those skilled in the art and screening devices are readily available in commercial quantities.
The invention provides a preparation method of a silver catalyst for preparing ethylene oxide by ethylene oxidation, wherein a dissolving solution used in the preparation process of a mixed solution containing a cesium compound, a tin compound, a phosphorus compound and a boron compound is one or more of nitric acid, oxalic acid and acetic acid, and the acids can be conveniently obtained in a commercially available mode.
The invention provides a method for preparing a silver catalyst for preparing ethylene oxide by oxidizing ethylene.A precursor of aluminum hydroxide of high-pore-volume aluminum oxide is dry rubber powder obtained by neutralizing, gelatinizing, washing and drying a sodium aluminate solution and an aluminum sulfate solution; the preparation condition is that alkaline aluminum salt solution and acidic aluminum salt solution are added and mixed under the condition of pH7.5-10.5, and the pore volume of the carrier prepared after roasting and activation can reach 0.7-2.3 ml/g; preferably, sodium metaaluminate and aluminum sulfate are added and mixed under the condition of pH8.5-9.5, and the pore volume of the carrier prepared after roasting and activation can reach 0.9-1.4 ml/g; the alkaline aluminum salt, acidic aluminum salt, sodium metaaluminate and aluminum sulfate can be conveniently obtained by a commercial mode.
According to the preparation method of the silver catalyst for preparing ethylene oxide by ethylene oxidation, provided by the invention, alpha-silicon carbide powder is one of common grinding materials; the bastnaesite powder is a common rare earth extraction raw material, and the fluorine compound and the rare earth compound are common reagents and chemical raw materials and can be conveniently obtained in a commercial mode.
According to the preparation method of the silver catalyst for preparing ethylene oxide by ethylene oxidation, the addition amount of microcrystalline cellulose with the average particle size of 0.8-1.2 micrometers is 1-10 wt% of the total dry-basis mass of the silver catalyst composition, the microcrystalline cellulose is one of common food additives, and different from common cellulose, the microcrystalline cellulose has small and regular fiber size and can be conveniently obtained in a commercially available mode.
According to the preparation method of the silver catalyst for preparing ethylene oxide by oxidizing ethylene, the addition amount of the carbon-containing material is 10-30 wt% of the total dry-basis mass of the silver catalyst composition.
According to the preparation method of the silver catalyst for preparing ethylene oxide by oxidizing ethylene, provided by the invention, the carbon-containing material is selected from one or more of petroleum coke, carbon powder, graphite, polyethylene, polypropylene and rosin, and the carbon-containing material can be conveniently obtained in a commercially available mode.
The invention provides a preparation method of a silver catalyst for preparing ethylene oxide by oxidizing ethylene, which is characterized in that the addition amount of aluminum hydroxychloride is 5-30 wt% of the total dry-based mass of a catalyst composition calculated by alumina; aluminum hydroxychloride is one of the commonly used building material binders and is conveniently available in a commercially available manner.
In the preparation method of the silver catalyst for preparing ethylene oxide by oxidizing ethylene, the tin compound is stannous chloride and/or stannic chloride; the magnesium compound is one or more of magnesium chloride, magnesium nitrate and magnesium oxide; the cesium compound is one or more of cesium chloride, cesium nitrate, cesium acetate and cesium oxide; the non-metal modified element boron is derived from boric acid; the nonmetal modified element phosphorus is from a phosphorus compound and is selected from one or more of phosphoric acid and ammonium phosphate; and the ethylene diamine and the ethanolamine are all conveniently available in a commercially available manner.
The invention also provides a method for preparing ethylene oxide by ethylene oxidation, wherein the ethylene oxide is prepared at the temperature of 170-290 ℃, the pressure of 1-3 MPa and the space velocity of 4500-13000 NL/Kgcat-1Then, ethylene is oxidized to produce ethylene oxide. Preferably at 200-250 deg.C, 1.8-2.2 MPa pressure and 5000-8000 Kgcat-1Then, ethylene is oxidized to produce ethylene oxide. The chemical operations involved in the present invention are conventional in the art and are well known and routinely practiced by those of ordinary skill in the art.
The beneficial technical effects of the invention are as follows: the silver catalyst provided by the invention has good diffusion performance and conductivity, and the active components are distributed more uniformly and are not easy to aggregate. When applied in the technical process of preparing the ethylene oxide by oxidizing the ethylene, the catalyst has good catalytic reaction performance, higher activity, selectivity and stability. The yield of the ethylene oxide is high, the reaction raw materials can be saved, and the reaction byproducts are reduced, so that the cost is saved. The silver catalyst provided by the present invention is particularly useful in the commercial production of ethylene oxide by the epoxidation of ethylene, and other features and advantages of the invention will be described in more detail in the detailed description which follows.
Detailed Description
The following examples are intended to further illustrate the contents and effects of the present invention, and are illustrative of the embodiments of the present invention, but not intended to limit the broad interpretation thereof.
The silver catalyst of the invention is suitable for the production process of ethylene oxide by ethylene oxidation. In the examples, the content of the elements in the catalyst was determined by X-ray fluorescence and the chlorine content by electrode method; the specific surface area, pore volume and distribution of the catalyst are measured by combining a nitrogen adsorption method and a mercury porosimetry method; the composition analysis of the raw materials and the reaction products is completed by adopting a gas chromatograph, and the mechanical strength of the catalyst is measured by adopting a pressure tester.
Other analytical tests can be found in the relevant analytical methods in (national Standard of methods for testing Petroleum and Petroleum products, published in 1989 by Chinese standards Press) and in (analytical methods for petrochemical engineering (RIPP test), published in 1990 by scientific Press).
Example 1
And continuously dropwise adding a sodium aluminate solution into a 1-liter stirring tank, neutralizing and gelatinizing by using the mass fraction of the alumina as 10% and an aluminum sulfate solution by using the mass fraction of the alumina as 10%, and washing and drying the colloid under the condition that the flow is controlled to ensure that the pH value of the colloid is 8.5-9.5 to obtain the high-pore-volume alumina aluminum hydroxide precursor dry gel powder.
Taking 1000 g of high-pore-volume aluminum hydroxide dry glue powder obtained by the preparation steps, 150 g of alpha-silicon carbide powder, 150 g of microcrystalline cellulose with the average particle size of 0.8-1.2 microns, 200 g of petroleum coke, 20 g of magnesium nitrate, 17 g of ammonium fluoride and raw material powder, screening by a 200-mesh sieve, kneading with 1000 g of aluminum hydroxychloride solution, adding a predetermined amount of cesium nitrate, stannous chloride, boric acid and phosphoric acid solution into the nitric acid solution, uniformly mixing, adding the mixture into the composition powder, kneading and peptizing, and preparing a precursor blank of the hollow cylindrical composite carrier by molding; and calcining the precursor blank at 1460 ℃ for 4 hours after drying to prepare the composite carrier.
Weighing silver compound, ethylenediamine and ethanolamine with required mass, wherein the total molar weight of the ethylenediamine and the ethanolamine and the molar weight of the silver compound are 1:3, preparing the ethylenediamine and the ethanolamine silver compound into silver solution, impregnating the silver solution on the composite carrier under the vacuum condition of 0.05MPa in a step-by-step impregnation roasting mode for 2 times, drying the silver solution under the vacuum condition, and roasting the silver solution at 500 ℃ under the inert atmosphere.
The hollow cylindrical catalyst obtained in example 1 had an outer shape of 7.2mm, an inner diameter of 1.5mm, an outer diameter of 7.5mm, a bulk density of 0.63 g/ml, and a side crushing strength of 65N/pellet;
example 1 the silver catalyst contained 17 wt% silver, 0.05 wt% strontium, 0.5 wt% magnesium, 0.65 wt% fluorine, 0.05 wt% cerium, 0.25 wt% tin, 0.15 wt% phosphorus, 0.15 wt% boron on a dry basis total mass basis.
The silver catalyst in the embodiment 1 has the water absorption rate of 55%, the specific surface area of 0.91 square meter/g and the pore volume of 0.52 ml/g, wherein 89% of pores with the pore diameter of 5-30 micrometers and 11% of pores with the pore diameter of more than or equal to 30 micrometers.
Comparative example 1
An α -alumina carrier was prepared by the same method as in example 1 using commercially available aluminum hydroxide powder, graphite powder, ammonium fluoride, magnesium chloride, cesium nitrate, and stannous chloride, and a silver impregnation solution was prepared by the same method, but silver of the same content was loaded only by one impregnation step, and after drying, the catalyst of comparative example 1 having the same external dimensions as in example 1 was obtained by one calcination.
Comparative example 1 the catalyst had a bulk density of 0.62 g/ml, a side crush strength of 61N/pellet, 17 wt% silver, 0.06 wt% strontium, 0.45 wt% magnesium, 0.63 wt% fluorine, 0.23 wt% tin, based on the total mass of the catalyst on a dry basis.
The catalyst of comparative example 1 has a water absorption of 51%, a specific surface area of 1.38 square meters per gram and a pore volume of 0.51 ml/gram, wherein 85% of pores with a pore diameter of 5-30 micrometers and 15% of pores with a pore diameter of more than or equal to 30 micrometers are present.
Comparative example 2
The same procedure as in comparative example 1 was followed except that a predetermined amount of cellulose was added to the aluminum hydroxide powder to obtain a catalyst of comparative example 2 having an external shape having a bulk density of 0.62 g/ml, a side crushing strength of 55N/pellet, 17 wt% of silver, 0.03 wt% of strontium, 0.6 wt% of magnesium, 0.71 wt% of fluorine, and 0.22 wt% of tin, based on the total mass of the catalyst on a dry basis, as in example 1.
The catalyst of comparative example 2 has a water absorption of 56%, a specific surface area of 1.97 m/g and a pore volume of 0.55 ml/g, wherein 75% of pores with a pore diameter of 5-30 μm and 25% of pores with a pore diameter of not less than 30 μm.
Comparative example 3
The same procedure as in comparative example 1 was followed except that a predetermined amount of cerium nitrate was added to the nitric acid solution to obtain the catalyst of comparative example 3. The bulk density of the catalyst was 0.64 g/ml, the side crush strength was 59N/pellet, and the catalyst had 17 wt% silver, 0.05 wt% strontium, 0.55 wt% magnesium, 0.63 wt% fluorine, 0.04 wt% cerium and 0.28 wt% tin, based on the total mass of the catalyst on a dry basis, as in example 1.
The catalyst of comparative example 3 has a water absorption of 50%, a specific surface area of 1.29 square meters per gram and a pore volume of 0.54 ml/gram, wherein 87% of pores with a pore diameter of 5-30 micrometers and 13% of pores with a pore diameter of more than or equal to 30 micrometers are present.
Comparative example 4
The same procedure as in comparative example 1 was followed except that a predetermined amount of phosphoric acid was added to the nitric acid solution to obtain the catalyst of comparative example 4. The external dimension of the catalyst is the same as that of the catalyst 1, the bulk density is 0.67 g/ml, the side crushing strength is 62N/grain, and the catalyst comprises 17 wt% of silver, 0.06 wt% of strontium, 0.4 wt% of magnesium, 0.67 wt% of fluorine, 0.14 wt% of phosphorus and 0.26 wt% of tin based on the total mass of the catalyst on a dry basis.
The catalyst of comparative example 4 has a water absorption of 51%, a specific surface area of 1.31 m/g and a pore volume of 0.52 ml/g, wherein 89% of pores with a pore diameter of 5-30 μm and 11% of pores with a pore diameter of not less than 30 μm.
Comparative example 5
The same procedure as in comparative example 1 was followed except that a predetermined amount of boric acid was added to the nitric acid solution to obtain the catalyst of comparative example 5. The external dimension of the catalyst is the same as that of the catalyst 1, the bulk density is 0.65 g/ml, the side crushing strength is 61N/grain, and the catalyst comprises 17 wt% of silver, 0.04 wt% of strontium, 0.5 wt% of magnesium, 0.55 wt% of fluorine, 0.15 wt% of boron and 0.27 wt% of tin based on the total mass of the catalyst on a dry basis.
The catalyst of comparative example 5 has a water absorption of 52%, a specific surface area of 1.23 square meters per gram and a pore volume of 0.50 ml/gram, wherein 87% of pores with a pore diameter of 5-30 micrometers and 13% of pores with a pore diameter of more than or equal to 30 micrometers.
Example 2
Taking 1000 g of the high-pore-volume aluminum hydroxide dry glue powder prepared in the embodiment 1, 250 g of alpha-silicon carbide powder, 200 g of microcrystalline cellulose with the average size of 0.8-1.2 microns, 250 g of carbon powder and raw material powder, sieving by a 200-mesh sieve, and kneading with 1000 g of aluminum hydroxychloride solution, 16 g of ammonium fluoride, 25 g of magnesium nitrate and a predetermined amount of lanthanum nitrate.
Adding a predetermined amount of cesium nitrate, stannous chloride, boric acid and ammonium phosphate solution into a nitric acid solution, uniformly mixing, adding the mixture into the composition powder, kneading and peptizing, and preparing a precursor blank of the hollow cylindrical composite carrier by molding; and calcining the precursor blank at 1450 ℃ for 5 hours after drying to prepare the composite carrier.
The silver solution was prepared according to the same procedure as in example 1, and was vacuum-dried in a stepwise immersion roasting manner 2 times, followed by roasting at 520 ℃ under an inert atmosphere.
Example 2 the catalyst had the same physical dimensions as example 1, a bulk density of 0.65 g/ml, a side crush strength of 66N/pellet, 17 wt% silver, 0.06 wt% strontium, 0.6 wt% magnesium, 0.63 wt% fluorine, 0.06 wt% lanthanum, 0.25 wt% tin, 0.14 wt% phosphorus, 0.12 wt% boron, all on a dry basis.
The catalyst of the embodiment 2 has the water absorption rate of 54 percent, the specific surface area of 0.91 square meter/g and the pore volume of 0.51 milliliter/g, wherein the pores with the pore diameter of 5-30 micrometers account for 88 percent, and the pores with the pore diameter of more than or equal to 30 micrometers account for 12 percent.
Example 3
Taking 1000 g of the high-pore-volume aluminum hydroxide dry glue powder prepared in the embodiment 1, sieving 200 g of alpha-silicon carbide powder, 100 g of microcrystalline cellulose with the average size of 0.8-1.2 microns, 250 g of graphite powder and raw material powder by a 200-mesh sieve, and kneading with 800 g of aluminum hydroxychloride solution, 18 g of ammonium fluoride, a predetermined amount of cerium-rich mischmetal and magnesium chloride.
Adding a predetermined amount of cesium nitrate, stannous chloride, boric acid and phosphoric acid solution into a nitric acid solution, uniformly mixing, adding the mixture into the composition powder, kneading and peptizing, and preparing a precursor blank of the hollow cylindrical composite carrier by molding; and drying the precursor blank, and calcining the precursor blank at 1470 ℃ for 3 hours to prepare the composite carrier.
The same procedure as in example 1 was followed to prepare a silver solution, which was then vacuum-dried in 3 stepwise immersion-roasting modes and roasted at 450 ℃ in an inert atmosphere.
Example 3 the catalyst had the same physical dimensions as example 1, a bulk density of 0.64 g/ml, a side crush strength of 63N/pellet, 17 wt% silver, 0.07 wt% strontium, 0.5 wt% magnesium, 0.65 wt% fluorine, 0.05 wt% cerium, 0.01 wt% lanthanum, 0.29 wt% tin, 0.13 wt% phosphorus, 0.14 wt% boron, all on a dry basis.
Example 3 catalyst Water absorption 53% and specific surface area 0.91 m2The pore volume is 0.52 ml/g, wherein 84 percent of pores with the pore diameter of 5-30 microns and 16 percent of pores with the pore diameter of more than or equal to 30 microns.
Example 4
The same procedure as in example 1 was followed, but impregnation-drying-calcination was carried out in one step, to obtain the catalyst of example 4, which was used to embody the effects of the preparation method of the present invention.
Example 4 the catalyst had the same physical dimensions as example 1, a bulk density of 0.62 g/ml, a side crush strength of 62N/pellet, 17 wt% silver, 0.05 wt% strontium, 0.45 wt% magnesium, 0.56 wt% fluorine, 0.07 wt% cerium, 0.26 wt% tin, 0.15 wt% phosphorus, 0.16 wt% boron, all on a dry basis.
The catalyst of the embodiment 4 has the water absorption of 51 percent, the specific surface area of 0.90 square meter/g and the pore volume of 0.50 ml/g, wherein the pores with the pore diameter of 5-30 microns account for 85 percent, and the pores with the pore diameter of more than or equal to 30 microns account for 15 percent.
Example 5
In example 5, various silver catalysts of the present invention will be tested for activity and selectivity using a laboratory microreactor evaluation apparatus.
The stainless steel reaction tube of the microreactor is placed in a heating jacket, the filling volume of the catalyst is 5ml, and the upper part and the lower part of the reactor are filled with inert fillers, so that a catalyst bed layer is positioned in a constant-temperature area of the heating jacket.
TABLE 1 reaction gas composition
Item Ethylene Dichloroethane Oxygen gas Carbon dioxide Nitrogen gas
Composition/mol% 25～30 1～5ppm 7～8 1～3 60～67
TABLE 2 micro-inversion assay results
Figure BDA0002750976150000191
The composition of the raw material gas with activity and selectivity adopted by the invention is shown in table 1, the bed temperature of the reaction tube after the same reaction time period and the average selectivity of the reaction tube after the same reaction time period are taken, and the evaluation result is shown in table 2.
As can be seen from Table 2, the reaction temperatures of the silver catalysts of examples l to 4 provided by the present invention were lower than those of the catalysts of comparative examples 1 to 5, indicating that the silver catalysts of the present invention have higher activity than the catalysts of the comparative examples.
In table 2, the silver catalysts of examples 1 to 4 have higher selectivity than the catalysts of comparative examples 1 to 5, so the silver catalysts of the present invention have better catalytic reaction performance, higher conversion activity and better selectivity of ethylene oxide product, and the stability of the catalysts of examples 1 to 4 of the present invention is also shown as the result of the long-term reaction accumulation.
It should be noted that the above-mentioned embodiments are only for illustrating the technical solution of the present invention and not for limiting, although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions may be made to the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention.

Claims (10)

1. A silver catalyst for preparing ethylene oxide by ethylene oxidation is characterized in that a composite carrier formed by alpha-silicon carbide and alpha-alumina contains 10-20 wt% of silver, 0.001-1 wt% of IA group elements, 0.1-10 wt% of IIA group elements, 0.1-10 wt% of VIIA group elements, 0.01-1 wt% of rare earth elements, 0.1-1 wt% of high-valence metal modified elements and 0.1-5 wt% of nonmetal modified elements, wherein the total mass of the silver catalyst on a dry basis is taken as a reference; the mass ratio of the alpha-silicon carbide to the alpha-aluminum oxide is 1: 5-90;
the silver catalyst has the porosity of 45-75%, the specific surface area of 0.1-2 square meters/g and the pore volume of 0.4-1.0 ml/g, wherein the pores with the pore diameter of 5-30 microns account for 80-95%, and the pores with the pore diameter of more than or equal to 30 microns account for 5-20%.
2. The silver catalyst for ethylene oxidation to ethylene oxide according to claim 1, wherein the silver catalyst comprises 16 to 18 wt% of silver, 0.001 to 0.1 wt% of strontium, 0.1 to 5 wt% of magnesium, 0.1 to 5 wt% of fluorine, 0.01 to 0.5 wt% of rare earth elements, 0.1 to 0.5 wt% of tin, 0.1 to 0.5 wt% of phosphorus, and 0.1 to 0.5 wt% of boron, based on the total dry mass of the silver catalyst.
3. A method for preparing a silver catalyst for preparing ethylene oxide by oxidizing ethylene is characterized by comprising the following preparation steps:
step 1), mixing an aluminum hydroxide precursor of high-pore-volume aluminum oxide, alpha-silicon carbide powder, microcrystalline cellulose, a carbon-containing material, aluminum hydroxychloride, a fluorine compound, a magnesium compound and a rare earth compound to obtain composition powder, adding a mixed solution containing a cesium compound, a tin compound, a phosphorus compound and a boron compound into an acid solution, uniformly mixing, adding the mixture into the composition powder, kneading and peptizing, and preparing a precursor blank of a hollow cylindrical composite carrier by molding;
step 2), drying the precursor blank, and calcining at 1450-1560 ℃ for 0.1-6 hours to prepare a composite carrier;
and 3), weighing a silver compound, ethylenediamine and ethanolamine, wherein the molar weight ratio of the total molar weight of the ethylenediamine and the ethanolamine to the silver compound is 1:3, preparing the ethylenediamine, the ethanolamine and the silver compound into a silver solution, impregnating the silver solution on the composite carrier in a step-by-step impregnation roasting mode for 2-5 times under the vacuum condition of 0.001-0.08 MPa, drying in vacuum, and roasting at 200-700 ℃ in an inert atmosphere.
4. The preparation method of the silver catalyst for preparing the ethylene oxide by oxidizing the ethylene as claimed in claim 3, wherein in the process of preparing the precursor blank, the combined powder is firstly ground and sieved by a sieve of 40-200 meshes.
5. The method of claim 3, wherein the solution of the mixture of cesium compound, tin compound, phosphorus compound and boron compound is one or more of nitric acid, oxalic acid and acetic acid.
6. The method for preparing the silver catalyst for preparing the ethylene oxide by oxidizing the ethylene as claimed in claim 3, wherein the average grain diameter of the microcrystalline cellulose is 0.8-1.2 microns, and the addition amount of the microcrystalline cellulose is 1-10 wt% of the total dry-basis mass of the silver catalyst.
7. The method for preparing a silver catalyst for preparing ethylene oxide by oxidizing ethylene according to claim 3, wherein the carbonaceous material is added in an amount of 10 to 30 wt% based on the total mass of the silver catalyst on a dry basis.
8. The method for preparing the silver catalyst for preparing the ethylene oxide by oxidizing the ethylene as claimed in claim 7, wherein the carbonaceous material is one or a mixture of petroleum coke, carbon powder, graphite, polyethylene, polypropylene and rosin.
9. The process for preparing a silver catalyst for ethylene oxidation to ethylene oxide according to claim 3, wherein the aluminum hydroxychloride is added in an amount of 5 to 30 wt% based on the total mass of the silver catalyst on a dry basis in terms of alumina.
10. The use of the silver catalyst of claim 1 in a process for the preparation of ethylene oxide by oxidation of ethylene, wherein the catalytic conditions of the silver catalyst in the process for the preparation of ethylene oxide by oxidation of ethylene are as follows: 170-290 ℃, 1-3 MPa of pressure and 4500-13000 NL/Kgcat-1。
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