57 results about "Silver catalyst" patented technology

The present application belongs to the field of silver catalysts, and relates to a silver catalyst for ethylene oxidation to produce ethylene oxide, and a preparation method and application thereof. The silver catalyst comprises an alumina carrier, silver supported thereon, nano manganese dioxide and an additive. The content of the silver is 2-39 wt% based on the total weight of the silver catalyst; the content of the nano manganese dioxide is 0.001-0.5 wt%. The silver catalyst is obtained by impregnating the alumina carrier in a silver ammonia solution, solid-liquid separation and calcination. The silver ammonia solution comprises a chelating agent, and the content of the chelating agent is 0.01-20.0 wt%. The porous alumina carrier is impregnated in the silver ammonia solution containing the chelating agent and the nano manganese dioxide, and the silver catalyst prepared therefrom has high reactivity, and is particularly suitable for the reaction of ethylene oxidation to produce ethylene oxide.

The invention belongs to the technical field of electrocatalytic carbon dioxide reduction catalysts, and discloses a silver-based catalyst suitable for fluctuating carbon dioxide electrolysis and a preparation method of the silver-based catalyst. The preparation method comprises the following steps: uniformly and continuously dropwise adding a potassium hydroxide solution into a silver nitrate solution to prepare a silver oxide catalyst, and further applying a constant reduction current to the silver oxide catalyst in the presence of carbon dioxide gas for in-situ reduction to prepare the quintuple twin crystal silver-based catalyst. The preparation method disclosed by the invention combines precipitation titration and in-situ electroreduction methods, and has the characteristics of simplicity in operation, greenness, high efficiency and suitability for mass production; meanwhile, the catalyst can maintain high selectivity to carbon monoxide products in an extremely wide potential window range of 3V when being used in an electro-catalysis carbon dioxide conversion reaction, and is very suitable for being directly matched and coupled with fluctuating renewable energy sources.

The invention relates to a copper-indium-silver catalyst, a preparation method thereof and a method for preparing synthesis gas with an adjustable ratio of carbon monoxide to hydrogen through electrocatalysis of carbon dioxide. The preparation method comprises the following steps: dispersing a multi-walled carbon nanotube in water to obtain a dispersion liquid A; dispersing copper nitrate trihydrate, indium nitrate hydrate and silver nitrate in water to obtain dispersion liquid B; mixing the dispersion liquid A and the dispersion liquid B to obtain dispersion liquid C; adding alkali into the dispersion liquid C to obtain a mixed solution D; and filtering and drying the mixed solution to obtain the copper-indium-silver electrocatalyst. The invention also provides the copper-indium-silver catalyst prepared by the method and a method for preparing synthesis gas with an adjustable ratio of carbon monoxide to hydrogen by electrocatalysis of carbon dioxide. According to the copper-indium-silver electrocatalyst provided by the invention, an electron-rich Cu site is formed by utilizing the synergistic effect of three metals, CO2 adsorption and CO desorption are promoted, and HER is inhibited, so that CO2RR and HER are balanced, and the selectivity of carbon monoxide synthesis gas is effectively improved.

This invention relates to a method for preparing a highly efficient silver single-atom bactericidal material. The invention utilizes an oxide as a carrier, modifies the oxide surface with phenolic compounds, anchors silver ions with phenolic hydroxyl groups to achieve uniform dispersion, and finally reduces the silver ions to silver single atoms via hydrogen reduction, ultimately obtaining a single-atom silver catalyst supported on the oxide carrier surface. This invention uses inexpensive, mass-producible commercial oxides as carriers, and through two simple steps—phenolic compound modification and hydrogen reduction—obtains a highly efficient single-atom silver bactericidal material with a low loading. The preparation steps are simple, the synthesis time is short, no large-scale equipment is required, it is easy to promote and apply, and it has a wide range of applications, suitable for bactericidal use on both solid surfaces and inside liquids.

The invention relates to the field of early warning regulation and control methods suitable for the process of producing a silver catalyst for catalyzing ethylene epoxidation, and relates to a regulation and control method and system suitable for the process of producing a silver catalyst for catalyzing ethylene epoxidation. Comprising the following steps: (1) acquiring normal working condition historical data of impregnation liquid in an impregnation section of the silver catalyst for ethylene epoxidation; (2) performing normalization preprocessing on the historical data of the normal working condition, setting upper and lower alarm thresholds according to data distribution, and obtaining a conventional data change trend; (3) monitoring real-time sampling data of the impregnation liquid on line, judging whether the real-time sampling data conforms to a conventional data change trend or not, and sending out an alarm signal if the real-time sampling data does not conform to the conventional data change trend; and (4) receiving the alarm signal, and carrying out regulation and control processing operation. According to the regulation and control method, the solution containing the precious metal salt can be fully utilized, and the production cost is reduced to the maximum extent.

The invention belongs to the technical field of catalysts, and discloses a silver catalyst and a preparation method and application thereof, and the preparation method comprises the following steps: a, preparing a silver-containing impregnation liquid; b, the alpha-aluminum oxide carrier is loaded into a rotor of a supergravity rotating packed bed, the loading amount of the alpha-aluminum oxide carrier is 200-500 g / L, the rotating speed of the rotor is 600-1500 r / min, the silver-containing impregnation liquid is sprayed to the inner edge of the rotor and fully makes contact with the alpha-aluminum oxide carrier in the rotor in the radial direction for impregnation, the alpha-aluminum oxide carrier is circularly impregnated with the silver-containing impregnation liquid, and the silver-containing impregnation liquid and the alpha-aluminum oxide carrier in the rotor are fully impregnated; the circulation flow of the silver-containing impregnation liquid is 0.5-1.0 L / min, and the circulation impregnation time is 5-30 min; and c, activating the impregnated alpha-alumina carrier to obtain the silver catalyst. The silver catalyst provided by the invention has obviously improved activity and stability.

The application discloses a carbon-loaded silver catalyst and a preparation method and application thereof. Silver nitrate and carbon are impregnated at room temperature, and then the obtained precursor is ground into powder at room temperature, and the carbon-loaded silver catalyst is obtained after calcination. The carbon-loaded silver catalyst can be applied to electrocatalytic reduction of carbon dioxide to carbon monoxide. The application mainly adjusts the calcination temperature in the preparation process to adjust the interaction between silver and carbon. The formation of the carbon-loaded silver with a carbon semi-coating structure not only strengthens the electron transfer in the reaction process, but also strengthens the adsorption and stability of an intermediate COO ‑ . In addition, the enhancement of the interaction between silver and carbon limits the reconstruction of silver in the reaction process, and realizes stability at a high current. The application in the reduction of carbon dioxide to carbon monoxide shows excellent performance in the reduction of carbon dioxide to carbon monoxide.

The invention belongs to the technical field of catalysts, and discloses an alpha-alumina carrier and a preparation method thereof, a silver catalyst for ethylene epoxidation and an ethylene oxidation method, the preparation method comprises the following steps: preparing a solid mixture; the solid mixture is put into a rotor to be evenly mixed, the rotating speed R1 of the rotor ranges from 100 r / min to 300 r / min, and the alternating interval of forward rotation and reverse rotation of the rotor ranges from 2 s to 10 s; s3, the rotating speed R2 of the rotor is adjusted to be 200-500 r / min, the alternating interval between forward rotation and reverse rotation of the rotor is 2-10 s, and the binder makes full contact with the solid mixture in the rotor in a spraying mode; s4, the rotating speed R3 of the rotor is adjusted to be 800-1500 r / min, the alternating interval between forward rotation and reverse rotation of the rotor is 2-10 s, the solid mixture added with the binder forms paste, and extrusion molding is conducted; and S5, drying the molded body, and roasting at high temperature to obtain the alpha-alumina carrier. The pore permeability of the carrier is improved, and the selectivity and stability of the silver catalyst are improved.

The application belongs to the field of catalysts, and relates to an alpha-alumina carrier and a preparation method thereof, a silver catalyst for ethylene epoxidation, and an ethylene oxidation method. The preparation method of the alpha-alumina carrier comprises the following steps: preparing a solid mixture with the following components: trihydro-alpha-Al2O3, pseudo-monohydrate Al2O3, a pore-forming agent, a combustible lubricating material, a fluoride mineralizer, and an alkaline earth metal compound; wherein the pore-forming agent is a non-spherical organic polymer particle; mixing the solid mixture, a binder, and optional water, kneading, and extruding into a shaped body; drying and calcining the shaped body to obtain the alpha-alumina carrier. The application uses different forms of non-spherical organic polymer particles as the pore-forming agent, which has no residue during the calcination of the carrier, and can form a specific pore shape, improve the connectivity between the pores of the carrier, reduce the tortuosity, and improve the permeability, which can significantly improve the activity and selectivity of the catalyst.

This invention belongs to the field of silver catalysts, and relates to an α-alumina support, its preparation method, and silver catalysts and their applications. The preparation method of the α-alumina support includes the following steps: at least one of α-Al₂O₃ and α-Al₂O₃ trihydrate is mixed uniformly with pseudo-Al₂O₃ to obtain a solid mixture; this mixture is then wet-milled with deionized water in a ball mill to obtain a slurry; the resulting slurry is spray-granulated to obtain solid microsphere powder; the solid microsphere powder is mixed uniformly with a binder, flow aid, lubricant, and pore-forming agent to obtain pressed granules; the pressed granules are dry-pressed to obtain a molded body, which is then calcined to obtain the α-alumina support. The support obtained by this invention has a more controllable shape, and when used for the oxidation of ethylene to ethylene oxide, its selectivity and stability are significantly improved while maintaining activity.

The present application relates to a kind of initiator of preparation triangular nano silver base ethylene oxide catalyst and its application, it is related to the technical field of ethylene oxide catalyst preparation, the initiator includes the following components by weight percentage: water 5~20wt%, polyvinylpyrrolidone 0.1~20wt%, normal alkane alcohol 65~85wt% and ethanol 1~20wt%;Wherein, the normal alkane alcohol is at least one in C3~C6 normal alkane alcohol.The present application is by using the initiator of this specific composition as the mother liquor system of silver base ethylene oxide catalyst impregnation liquid, the morphology control is applied to silver base ethylene oxide catalyst, after silver is uniformly dispersed in carrier, morphology is controlled synthesis, and triangular nano silver morphology silver base ethylene oxide catalyst is prepared, the preparation of controllable morphology controllable nano silver catalyst is realized, the contact area of nano silver with reactant is increased, to improve the performance of triangular nano silver base ethylene oxide catalyst.

The invention relates to the technical field of electrocatalytic reduction, and discloses a method for electrocatalytic reduction of CO2 by using a silver catalyst with a low coordination structure, and the method comprises the following steps: (1) preparing silver powder to obtain an Ag NPs electrode, and preparing an AgO electrode by using the Ag NPs electrode as a working electrode and adopting a cyclic voltammetry method; and (2) carrying out electrochemical reduction modification by taking the AgO electrode as a cathode electrode, and finishing the modification when the voltage is stable, so as to prepare the silver catalyst with a low-coordination structure. And (3) carrying out electrocatalytic reduction on CO2 by taking the silver catalyst with a low coordination structure as a cathode electrode. Through electrochemical in-situ modification, a low-coordination structure is introduced under the condition that the morphology structure and the valence of the silver catalyst are not changed, the catalytic activity and the catalytic stability are greatly improved, operation is easy and convenient, and large-scale industrial application is facilitated.

The invention belongs to the field of silver catalysts, and relates to a composite alpha-alumina carrier, a preparation method thereof, a silver catalyst and application. The composite alpha-alumina carrier comprises an alpha-alumina carrier and a titanium-containing porous alumina film coating the alpha-alumina carrier, the porosity of pores contained in the titanium-containing porous alumina film is not less than 15%, the content of titanium is 0.05-5.0 wt%, and on the basis of the total weight of the composite alpha-alumina carrier, the porosity of the pores contained in the titanium-containing porous alumina film is not less than 15%. The content of the titanium-containing porous aluminum oxide film is 0.05 to 10.0 weight percent. The preparation method comprises the following steps: adding a proper amount of a pore-forming agent, a mineralizing agent and a titanate coupling agent into an aluminum-containing solution, carrying out ultrasonic oscillation, dipping and drying an alumina carrier in the aluminum-containing solution, and carrying out high-temperature heating so that the pore-forming agent is heated and decomposed to generate gas, thereby forming a layer of titanium-containing porous film on the surface of the alumina carrier. Finally, the silver catalyst prepared from the carrier has higher reaction activity and selectivity.

The present invention belongs to the field of catalysts, and relates to a silver catalyst for the production of ethylene oxide by ethylene epoxidation, characterized in that the silver catalyst comprises a porous inert carrier, metallic silver, a high-valence transition metal element, and a co-auxiliary element, and the high-valence transition metal element is closely associated with the metallic silver in the form of a compound, wherein based on the total weight of the silver catalyst, the silver content, calculated as elemental silver, is 10-40 wt%, the high-valence transition metal element is a molybdenum element and / or a tungsten element, and the content of the high-valence transition metal element in the catalyst is such that the weight ratio of the molybdenum element, the tungsten element, and the silver element satisfies the following relationship: MMo is 0-0.0021, MW is 0-0.0053, and F1 is 0.0015-0.0053, wherein MMo and MW are the weight ratio of the molybdenum element to the silver element in the catalyst and the weight ratio of the tungsten element to the silver element in the catalyst respectively, and F1=MW+2.52MMo, wherein the silver catalyst has a tungsten element retention rate and / or a molybdenum element retention rate of not less than 70%, preferably not less than 80%, and more preferably not less than 85% after being subjected to a water‑leaching treatment. In the present invention, by controlling the content of the high-valence transition metal element, the silver catalyst has the characteristics of rapidly reaching a high-selectivity state during the initial stage of operation.

The application belongs to the field of catalysts and relates to a method for preparing ethylene oxide by ethylene epoxidation. The method comprises the following steps: mixing a silver catalyst, ethylene, oxygen, a stabilizing gas and a chloride in a reactor to perform an ethylene epoxidation reaction; after the operation of the reactor, the concentration of the chloride is controlled to be stabilized at 2-5 ppm; when the concentration of ethylene oxide at the outlet of the reactor reaches 0.5-3.0 mol%, the concentration of the chloride is reduced to 0.1-2 ppm; the silver catalyst comprises an alpha-alumina carrier and an active component silver supported on the alpha-alumina carrier; the alpha-alumina carrier contains manganese elements, and the content of the manganese elements is 0.001-2.0 wt.% based on the weight of the alpha-alumina carrier.

This invention discloses a silver-catalyzed method for synthesizing benzo[d]isothiazol-3(2H)-one via sulfur-nitrogen atom exchange, belonging to the field of organic synthesis technology. The method uses benzodisulfonic acid ketone compounds and azide compounds as raw materials, and, under the action of a silver catalyst, inorganic base, and organophosphorus compounds, with acetonitrile as the solvent, undergoes a heated reaction followed by separation and purification to obtain the target product. This invention achieves molecular skeleton editing of benzodisulfonic acid ketone through S-N atom exchange. The reaction conditions are mild, require no inert gas protection, are simple to operate, exhibit good functional group tolerance, and achieve high yields. It can be applied to the later-stage transformation of active molecules and drug molecules, providing a new route for the efficient synthesis of benzo[d]isothiazol-3(2H)-one compounds.

The application belongs to the field of silver catalysts, and relates to a composite alpha-alumina carrier for a silver catalyst for ethylene oxidation to produce ethylene oxide, a preparation method of the composite alpha-alumina carrier, the silver catalyst and application. The composite alpha-alumina carrier comprises an alpha-alumina carrier and a porous alumina film containing zirconium coated outside the alpha-alumina carrier. The preparation method of the composite alpha-alumina carrier comprises the following steps: (1) dissolving an aluminum-containing compound, a pore-forming agent and a zirconium-containing compound in water, and preparing a solution after stirring; the pore-forming agent is urea, hexanediamine, sucrose or starch; (2) immersing the alpha-Al2O3 carrier in the solution obtained in step (1), and performing drying and calcination after leaching, to obtain the composite alpha-alumina carrier coated with a porous alumina film containing zirconium on the outer surface. The silver catalyst prepared from the alpha-alumina carrier of the application shows good reactivity and selectivity in the process of ethylene oxidation to produce ethylene oxide.

This invention belongs to the field of catalyst preparation technology, and discloses a low-silver-content ethylene oxide catalyst with a silver-rich surface, its preparation method, and its application. The method employs an economical and industrially applicable low-silver-content high-efficiency catalyst preparation system, innovatively using a "nebulized spray fluorine impregnation-calcination" process. By precisely controlling the penetration depth of fluorine on the alumina support surface through atomized solution, the calcined support forms a gradient structure of "surface lamellar alumina - internal dense alumina," providing support for the preparation of the surface-rich silver catalyst. Utilizing the high specific surface area and adsorption activity of the surface lamellar structure of the support, combined with the low adsorption of the internal dense structure, silver is preferentially enriched on the support surface during impregnation, forming a "surface-rich silver - internal-silver-poor" distribution state. This overcomes the technical bottleneck of low internal silver utilization caused by the uniform distribution of silver in traditional catalysts.

The invention belongs to the technical field of organic matter degradation, and discloses application of a nano-silver catalyst in organic dye catalytic degradation. According to the invention, methylene blue, methyl orange, p-nitroaniline and p-nitrophenol are taken as examples for experiments, and the four dyes start to degrade after reacting for a period of time. In the four dyes, the catalytic effect of methylene blue is worst, and the degradation degree within 20 minutes after the nano-silver catalyst synthesized by biotransformation of the blue-like bacteria FL15 is added can reach the degradation degree of reaction for 6 hours when the catalyst is not added; the effect of catalyzing the degradation of methyl orange is the best, and the degradation rate can reach 95% or above within 10 min; the degradation rate of paranitroaniline and paranitrophenol can reach 95% or above within 20 min. Therefore, the activity of the AgNPs mediated and synthesized by the endophytic fungi FL15 is relatively strong.

The application discloses an alpha-alumina carrier and a preparation method of the alpha-alumina carrier and a silver catalyst. The preparation method of the alpha-alumina carrier comprises the following steps: (1) preparing "non-flaky" alpha-Al2O3 seeds; (2) mixing the seeds obtained in the step (1), hydrated alumina, an additive and an F-containing inorganic salt according to the mass ratio of (1.5-3):100:(0.1-0.3):(1-3); (3) adding a binder with a mass concentration of 25%-45% and an extrusion aid, continuously mixing and forming into particles according to the mass ratio of the mixture in the step (2):the binder:the extrusion aid=100:(25-45):(8-12), and drying and calcining to obtain the alpha-alumina carrier. The alpha-alumina carrier prepared by the application has the advantages of "non-flaky" and "flaky" micro-morphologies, the silver catalyst prepared by the alpha-alumina carrier has the performance advantages of the catalysts prepared by the two kinds of micro-morphology carriers, and the silver catalyst has good stability.

The invention belongs to the field of catalysts, and relates to a method for activating a silver catalyst as well as the catalyst and application thereof. Comprising the following steps: (1) fully contacting an alpha-alumina carrier with a silver-containing impregnation liquid, and leaching to remove redundant impregnation liquid to obtain a silver catalyst precursor; and (2) the silver catalyst precursor obtained in the step (1) is subjected to infrared radiation activation treatment, and the conditions of the infrared radiation activation treatment are as follows: the air velocity is 0-5000h <-1 >, the irradiation temperature is 100-500 DEG C, and the irradiation time is 1-50min. The activation method disclosed by the invention is advanced in process, safe, environment-friendly and simple to operate, the active components and the cocatalyst of the silver catalyst are uniformly distributed, and the prepared catalyst shows more excellent activity and selectivity in olefin epoxidation reaction.

The invention belongs to the technical field of catalysts, and discloses a silver catalyst and a preparation method and application thereof, and the mass content difference of silver inside and outside silver catalyst particles of the silver catalyst is 0.02%-7.00%, preferably 0.02%-6.50%. The carrier particles are uniform in external and internal morphology, transparent in pore channels and uniform in strength, and active center silver particles outside and inside the silver catalyst particles are uniformly dispersed; therefore, the prepared silver catalyst has good catalytic performance.

This invention relates to the field of catalysts, specifically to an alumina support and a silver catalyst, their preparation method, and applications. The alumina support has a sheet-like three-dimensional configuration, with each alumina sheet possessing both hexagonal and quadrilateral facets. The ratio S of the average size of the hexagonal facets to the average size of the quadrilateral facets is 5–20. The size of each hexagonal facet is the length of its longest diagonal, and the size of each quadrilateral facet is the length of its shortest side. The catalyst prepared using the support provided by this invention significantly improves the selectivity of the ethylene epoxidation reaction and has broad application prospects. Furthermore, the ratio S of the average size of the hexagonal facets to the average size of the quadrilateral facets in the alumina sheet is substantially proportional to the selectivity of the silver catalyst in the ethylene epoxidation reaction, which has a positive effect on the study of the silver catalyst support and the ethylene epoxidation reaction.

The present application relates to a kind of silver catalytic oxidation preparation sulfoxide method, first preparation is supported silver catalyst, under the action of this silver catalyst, catalytic hydrogen peroxide oxidation sulfide preparation sulfoxide.The silver catalyst prepared by this method has high stability and can be recycled multiple times.It catalyzes the oxidation of sulfide to obtain sulfoxide with high efficiency.Silver catalytic oxidation of sulfoxide reaction process has the advantages of high efficiency and high selectivity, and the catalyst is easy to recover, and is friendly to the environment.The product is easy to separate, and has good industrial application prospect.

The invention belongs to the field of catalysts, and relates to a silver catalyst for producing ethylene oxide through ethylene epoxidation, which is characterized in that the silver catalyst contains a porous inert carrier, metal silver, a high-valence transition metal element and a co-assistant element, and the high-valence transition metal element is tightly combined with the metal silver in the form of a compound; wherein on the basis of the total weight of the silver catalyst, the content of silver in terms of silver element is 10-40 wt%, the high-valence transition metal element is a molybdenum element and / or a tungsten element, and the weight ratio of the molybdenum element to the tungsten element to the silver element meets the following relation: MMo is 0-0.0021, MW is 0-0.0053, and F1 is 0.0015-0.0053; wherein MMo and MW are respectively a weight ratio of a molybdenum element to a silver element and a weight ratio of a tungsten element to the silver element in the catalyst, and F1 = MW + 2.52 MMo; wherein after the silver catalyst is subjected to water dissolution treatment, the tungsten element retention rate and / or the molybdenum element retention rate of the silver catalyst are / is not lower than 70%, preferably not lower than 80%, and more preferably not lower than 85%. By controlling the content of high-valence transition metal elements, the silver catalyst has the characteristic of quickly reaching a high-selectivity state at the initial stage of use.

The application discloses a kind of manganese dioxide supported monatomic silver catalyst and preparation method of positive electrode film, comprising the following steps: S1.the potassium permanganate of a certain mass, manganese sulfate monohydrate and silver nitrate are mixed with deionized water respectively to prepare solution with different concentrations;S2.manganese sulfate monohydrate solution is added to potassium permanganate solution and is magnetically stirred, in the process of stirring, add conductive carbon black, after uniform mixing, obtain mixed solution A;S3.continuously keep the magnetic stirring speed of S2, and drop silver nitrate solution to mixed solution A to obtain mixed solution B;S4.mixed solution B is transferred to reaction kettle and is hydrothermally reacted, after reaction, the substance is centrifuged, and precipitate is obtained, after drying and grinding, catalyst MnO2 / C-Ag is obtained, i.e.manganese dioxide supported monatomic silver catalyst.The application can realize that silver monatomic atom is uniformly dispersed on the surface of manganese dioxide, silver monatomic atom and carrier interact strongly, and preparation process is simple, and cost is low.

The application belongs to the field of silver catalysts, and particularly relates to a carrier for preparing a silver catalyst, a preparation method of the carrier, the silver catalyst, a preparation method and application of the silver catalyst. The carrier comprises an alpha-Al2O3 carrier, hollow-configuration zirconium oxide and tungsten oxide loaded on the surface of the alpha-Al2O3 carrier; and the content of each component relative to the alpha-Al2O3 carrier is as follows: 0.02-4.00 wt% of the hollow-configuration zirconium oxide and 0.002-0.500 wt% of the tungsten oxide. The application makes the alpha-Al2O3 carrier rough by acid etching on the surface of the alpha-Al2O3 carrier, sequentially carries out ordered loading of the hollow-configuration zirconium oxide and the tungsten oxide, and then carries out high-temperature calcination and solidification, so that the silver catalyst prepared therefrom has high selectivity and reaction activity, and is particularly suitable for the reaction of ethylene oxidation for producing ethylene oxide.

This invention discloses an adamantylphosphine ligand with a cinchona alkaloid skeleton, a silver catalyst containing such ligand, and its applications. The ligand has a structure as shown in formula (I) or its tautomers, enantiomers, and diastereomers: In formula (I), R 1 is ethyl or vinyl; the substituent R 2 The novel catalyst, composed of a cinchona alkaloid skeleton adamantylphosphine ligand and a silver salt, can efficiently catalyze the asymmetric [3+2] cycloaddition reaction of aromatic aldehydes and isocyanatoacetic acid esters, obtaining the corresponding chiral oxazoline intermediates with high stereoselectivity and high yield. This technology can be applied to the asymmetric synthesis of florfenicol intermediates and chloramphenicol intermediates, and has the advantages of a short synthetic route, high yield, and good stereoselectivity, thus providing good economic and social benefits.

The invention belongs to the field of silver catalysts, and relates to a silver impregnation liquid for olefin epoxidation, a preparation method of the silver catalyst for olefin epoxidation, the silver catalyst prepared by the method, and applications of the silver impregnation liquid and the silver catalyst in olefin epoxidation. The silver impregnation liquid comprises the following components: 1) a silver amine complex; 2) steeping liquor stabilizer; 3) water; 4) an optional auxiliary agent; wherein the steeping liquor stabilizer is a small molecular organic matter which has electron withdrawing capability and contains carboxyl, ester group or anhydride functional group, and the content of the steeping liquor stabilizer is 0.01-20wt% on the basis of the total weight of the steeping liquor. The stability of the silver impregnation liquid is improved, suspended zero-valent silver nanoparticles in the impregnation liquid can be greatly reduced, the size distribution condition of activated catalyst silver particles is improved, and then the selectivity and stability of the catalyst are improved.