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Method for preparing hydrotalcite supported silver catalyst and application thereof

A silver catalyst, hydrotalcite technology, applied in chemical instruments and methods, oxidative preparation of carbonyl compounds, catalysts for physical/chemical processes, etc., can solve the problem that the conversion rate or selectivity is not particularly satisfactory, and the catalyst is expensive to synthesize cost. The synthesis process is widely used, a large number of by-products, etc., to achieve the effect of convenient industrial production, high yield, and high conversion rate of reactants

Inactive Publication Date: 2011-08-03
BEIJING UNIV OF CHEM TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The traditional preparation methods of styrene oxide include haloalcohol method or peracid method. These traditional methods not only have many steps, but also produce a large number of by-products, causing serious environmental pollution. The preparation of fine chemicals by clean catalytic process is the future of fine chemicals Main route of production. Directly from H 2 o 2 Epoxidation of styrene as oxidant is a better way to achieve green catalysis
With hydrogen peroxide as the oxidant, the current catalysts are mainly concentrated on some titanium-containing heteroatom molecular sieve catalysts, such as TS-1, Ti / SiO 2 , Ti-MCM-41, but the expensive synthesis cost and complex synthesis process of the above catalysts limited its wide application. After that, many catalysts using hydrogen peroxide as oxidant to catalyze the epoxidation of styrene were developed and reported successively, but Neither conversion nor selectivity gave particularly satisfactory results

Method used

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  • Method for preparing hydrotalcite supported silver catalyst and application thereof
  • Method for preparing hydrotalcite supported silver catalyst and application thereof

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0021] A: Weigh 61.54g Mg(NO 3 ) 2 ·6H 2 O and 45.02g Al(NO 3 ) 3 9H 2 O was dissolved in deionized water to make 300mL mixed salt solution; then weighed 23.04g NaOH and 25.44g NaOH 2 CO 3 Dissolve in deionized water to make 300mL mixed alkali solution; add the above two mixed solutions into the total back-mixed liquid membrane reactor at the same time, adjust the slit width between the reactor rotor and stator to 0.02mm, the working voltage to 100V, and the rotor speed 4000rpm, add the obtained mixed slurry into the crystallization kettle and stir, keep the temperature of the mixed slurry in the kettle at 95-105°C for reflux crystallization for 6 hours, and obtain the magnesium-aluminum hydrotalcite precursor slurry; the magnesium-aluminum hydrotalcite precursor The slurry was centrifuged and washed to a pH of 7.5, and dried at 90°C for 24 hours to obtain magnesium-aluminum hydrotalcite, whose chemical formula is [Mg 2 Al(OH) 6 ] + (CO 32- ) 0.5 10H 2 O.

[0022]...

Embodiment 2

[0026] A: with embodiment 1;

[0027] B: At 0°C, measure 10ml of 7.88g / L silver nitrate solution, add 1.0g of magnesium-aluminum hydrotalcite, and then add 10ml of deionized water, respectively add the above substances into a 50ml flat-bottomed flask, stir magnetically at 0°C and Keep at constant temperature for 60 minutes; add 10ml of ascorbic acid solution with a concentration of 17.5g / L and a temperature of 0°C into the above solution, stir at a constant temperature of 0°C and keep for 1h, after the reaction, the slurry is centrifuged and washed 3 times until there is no chloride ion, and dried at 70°C , Take it out after 10h and put it in a vacuum desiccator for storage.

[0028] The hydrotalcite-supported silver catalyst prepared above is catalyzed to oxidize styrene to generate phenyloxirane. The reaction conditions are: reaction temperature 82° C., reaction pressure normal pressure, acetonitrile as solvent, solvent consumption 5ml / 10mmol styrene, every Add 0.086 g of t...

Embodiment 3

[0031] A: with embodiment 1;

[0032] B: At 0°C, measure 2ml of 7.88g / L silver nitrate solution, add 1.0g of magnesium-aluminum hydrotalcite, then add 10ml of deionized water, add the above substances into a 50ml flat-bottomed flask, stir magnetically at 0°C and Keep at a constant temperature for 50 minutes; add 10ml of sodium citrate solution with a concentration of 17.5g / L and a temperature of 0°C into the above solution, stir at a constant temperature of 0°C for 1 hour, and centrifuge and wash the slurry 3 times until there is no chloride ion after the reaction. It was dried at ℃, taken out after 10 hours, and stored in a vacuum desiccator.

[0033] The hydrotalcite-supported silver catalyst prepared above is catalyzed to oxidize styrene to generate phenyloxirane. The reaction conditions are: reaction temperature 82° C., reaction pressure normal pressure, acetonitrile as solvent, solvent consumption 5ml / 10mmol styrene, every Add 0.086 g of the catalyst obtained in step B t...

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Abstract

The invention discloses a method for preparing a supported silver catalyst with low load and high activity by using hydrotalcite as a carrier in the technical field of catalyst preparation. The hydrotalcite is used as the carrier, and silver atoms with catalytic activity are highly dispersed and tightly anchored on the high-energy crystal face of the hydrotalcite by using uniform hydroxyl dot matrix and different crystal face orientation of the hydrotalcite so that more active silver particles are exposed. The invention provides the method for preparing the supported silver catalyst, and the method has the advantages of simple equipment and process, high yield, convenience in industrialized production, low prepared silver granularity and good reproducibility. When the catalyst is applied in synthesis of styrene oxide by catalytic oxidation of styrene, the conversion rate of reactants is high, and the selectivity of a product is high.

Description

technical field [0001] The invention belongs to the technical field of catalyst preparation, and in particular relates to a highly active loaded silver catalyst with hydrotalcite as a carrier and a preparation method thereof. Background technique [0002] Hydrotalcites (LDHs), also known as double hydroxyl complex metal hydroxides, are anionic clays with a general chemical formula [M II 1-x m III x (OH) 2 ] x+ (A n- ) x / n ·yH 2 O, where M II and M III They are divalent and trivalent metal cations respectively, located on the main laminate; A n- is an interlayer anion; x is M III / (M II +M III ) molar ratio; y is the number of interlayer water molecules. LDHs have a layered structure, tunability of layer elements and exchangeability of anions between layers. This special chemical and structural property not only makes it have ion exchange properties, but also has a wide range of applications in many fields such as catalysis, adsorption, ion exchange, electrical...

Claims

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Application Information

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IPC IPC(8): B01J23/66C07D303/04C07D301/12C07C47/54C07C47/228C07C45/28
Inventor 徐赛龙王晓彤梁忠强卫敏张法智
Owner BEIJING UNIV OF CHEM TECH
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