CN102008969B - Hydrogen type montmorillonite-supported ruthenium catalyst as well as preparation method and application method thereof - Google Patents

Abstract

The invention belongs to the technical field of catalyst preparation, in particular to a hydrogen-type montmorillonite-supported ruthenium catalyst, a preparation method and an application method. It is composed of active component RuCl ₃ and carrier activated clay, wherein the load of active component RuCl ₃ is 0.5%~10% by mass; wherein the carrier activated clay is montmorillonite with layered structure treated with acid earth. The method includes the following steps: (1) sodium exchange, (2) preparation of hydrogen-pillared montmorillonite; (3) preparation of activated clay-supported Ru catalyst; (4) activation. It can be used for the catalytic hydrogenation reaction of diaminodiphenylmethane. The invention uses cheap activated clay as a carrier, reduces the cost of the catalyst, improves the recycling rate of precious metals, and reduces the consumption of the catalyst.

Description

Hydrogen-type montmorillonite supported ruthenium catalyst, preparation method and application method

technical field

The invention belongs to the technical field of catalyst preparation, and relates to a supported Ru catalyst, a preparation method and an application method.

Background technique

4,4'-diamino-dicyclohexylmethane (PACM for short) is an intermediate for the synthesis of methylene dicyclohexyl diisocyanate (PICM for short), generally prepared from 4,4'-diaminodiphenylmethane ( MDA) liquid-phase catalytic hydrogenation preparation. PICM is a non-yellowing aliphatic isocyanate, mainly used in PU elastomers, coatings, leather, etc., and its products are superior to HDI in terms of performance. Its preparation is usually carried out in the following steps: first, diamine is prepared by condensation of aniline and formaldehyde, that is, diaminodiphenylmethane (MDA for short), and then hydrogenated into diaminodicyclohexyl in the presence of a catalyst. methane (PACM). Finally, it becomes PICM through phosgenation like the preparation of other aliphatic isocyanates. Its reaction equation is as follows:

① Preparation of 4,4’-MDA

；

;

② Hydrogenation of 4,4’-MDA (preparation of PACM)

；

;

③ Preparation of PICM by reaction of PACM and phosgene

；

;

.

It can be seen that the synthesis of PACM is a key step in this route. At present, the recognized hydrogenation method is to hydrogenate MDA and hydrogen under the metal catalyst composed of ruthenium and rhodium. The use of the mixed metal catalyst can be pre-selected from 5% to 50% (mass fraction), mainly 14% to 28%. The ratio of trans-trans isomers, this is because MDA produces three isomers when hydrogenated, namely trans-trans, trans-cis, cis-cis, its structural formula is as follows:

(anti-cis)

(anti-anti)

(cis-cis) .

The composition of isomers determines the properties and uses of it and its subsequent products, and it is difficult to obtain PACM with a single or specific isomer composition by means of separation. Therefore, PACM products in industry are all kinds of stereoisomer mixtures and are customarily used The anti-trans isomer content defines the specifications and uses of PACM. The anti-trans isomer content is less than 20%, which is called PACM-20, which is mainly used for the preparation of aliphatic polyurethane. PACM-50 is mainly used to prepare polyamide resin.

Low trans-trans PACM is obtained by hydrogenating MDA with ruthenium as a catalyst, and then extracting excess trans-trans isomers from the reaction product. PICM produced by PACM-20 is a stable liquid diisocyanate at room temperature . In contrast, the corresponding PICM produced from PACM-50, which has a trans-trans isomer content of nearly 50%, is solid at room temperature. Therefore, for the production of isocyanate and its further application in polyurethane, PACM-20 is better than PACM-50 in the synthesis of PICM.

Whitman found in his research report that Ru catalysts have unique selectivity in the preparation of PACM stereoisomer mixtures, and that Ru catalysts can effectively promote aromatic nitrogen compounds to the corresponding cyclohexyl aliphatic amines at relatively low temperatures The high yield of one-step hydrogenation reaction, so ruthenium has been applied in the reaction of this system very early.

Catalysts prepared by impregnation and evaporation are usually supported by metals on inert carriers, and suitable inert carriers include charcoal, calcium carbonate, rare earth oxides, aluminum oxide, diatomaceous earth, titanium dioxide, silicon dioxide, and the like. However, these studies did not involve the preparation and application of catalysts containing montmorillonite supports.

As an effective solid acid catalyst, montmorillonite catalysts have been widely used in organic reactions. So far, such catalysts have been successfully used in substitution reactions, addition reactions, oxidation reactions, and rearrangement reactions.

With the continuous improvement of montmorillonite modification technology, activated clay has more and more uses. In addition to the traditional decolorization field, activated clay has broad application prospects in the fields of preparing solid acid catalysts and alkaline bentonite. For example, the publication number is The Chinese patent of CN200510101332.X discloses alkaline calcium-based bentonite and its preparation method. The preparation and application of water-resistant solid acid SO42--TiO2-Clay catalyst is reported on pages 1111-1116 of the sixth issue of "Acta Inorganic Chemistry" in 2007. They are all modified with activated clay as raw material, and the effect of modification is directly related to the amount of hydrogen ions that can be exchanged between the layers of activated clay.

Contents of the invention

The technical problem to be solved in the present invention is to provide a catalyst and preparation method for catalytic hydrogenation of MDA under the premise of not using the precious metal rhodium Rh. .

The present invention is achieved through the following technical solutions:

The described hydrogen-type montmorillonite supported ruthenium catalyst of the present invention is composed of active component _RuCl and carrier activated clay, wherein the loading of active component _RuCl is 0.5% to 10% by mass; preferably 5% ~10%, wherein the carrier activated clay is montmorillonite with layered structure treated with acid.

The preparation method of above-mentioned hydrogen type montmorillonite supported ruthenium catalyst , carries out according to the following steps:

(1) Sodium exchange:

Mix Ca-based montmorillonite sieved to 200 mesh with distilled water, stir until slurry, then add NaCl crystals equivalent to 0.1-1 times the dry weight of soil by weight, heat and stir at 60°C for 2 hours, and the sodiumization reaction is completed Afterwards, centrifugally filter, wash the precipitate with deionized water until there is no chloride ion, and dry at 80°C to obtain Na-based montmorillonite;

(2) Preparation of hydrogen pillared montmorillonite:

Soak the above-mentioned Na-based montmorillonite in a solution with a volume fraction of 10-30% H ₂ SO ₄ , react at a constant temperature for 2-7 hours, the reaction temperature is 50-100°C, and the mass ratio of sulfuric acid to Na-based montmorillonite is 2 ~5:1; filter the activated soil slurry, wash the filter cake with distilled water until the pH value is 4~5, dry it at 105°C, grind it, pass through 200 meshes, and obtain the carrier activated clay;

(3) Preparation of activated clay-supported Ru catalyst:

Determine the total amount of _RuCl3 required according to the ruthenium load of 5 to 10% by mass, and dissolve it in distilled water to form a solution. Add carrier activated clay to the solution by excessive impregnation, and keep stirring until the color becomes lighter. ; Use NaOH to adjust the pH to be neutral; wash with distilled water, suction filter, wash away NaCl to neutrality, and dry;

(4) Activation: Weigh the above-mentioned ruthenium catalyst according to the ratio required for the catalytic hydrogenation reaction, and reduce it with H ₂ at 250-500°C for 1-5 hours; the supported Ru catalyst is prepared.

The application method of the supported Ru catalyst prepared above , its steps are as follows:

Add the supported Ru catalyst and MDA dissolved in tetrahydrofuran (THF) into the autoclave, the amount of the catalyst is 4wt% of the reaction system, the temperature rises to 120°C, and the reaction pressure is controlled under 1200r/min stirring to 5.5MPa~ 8 MPa, react for 1 to 20 hours, control the reaction process by controlling the amount of hydrogen absorbed; when the reaction is over, turn off the heating, pass in cooling water, when the temperature of the reaction kettle is lower than 45 ℃, stop stirring, release the pressure, and discharge; then The remaining catalyst was washed out, and the reaction product was obtained by vacuum filtration.

The invention uses cheap activated clay as a carrier, reduces the cost of the catalyst, improves the recycling rate of precious metals, and reduces the consumption of the catalyst.

Detailed ways

Example 1:

Preparation of Catalyst 1

Add Ca-type montmorillonite with a particle size of 200 mesh (purchased from Zhejiang Fenghong New Material Co., Ltd.), add distilled water at a solid-to-liquid ratio of 1:10, and stir until slurry; add NaCl equivalent to 6% of the mass of montmorillonite Crystals were heated and stirred at 60°C for 2 hours, centrifuged, and the precipitate was washed with deionized water until there was no Cl ^- , dried and ground at 80°C, and passed through 200 mesh to obtain Na-type montmorillonite;

Weigh Na-type montmorillonite, soak it in a solution with a volume fraction of 10%H ₂ SO ₄ , press m (montmorillonite) at 100°C: V(10%H ₂ SO ₄ )=l(g): 30 (ml), stirred and reacted for 6 hours, filtered the activated soil slurry, washed the filter cake with distilled water until the pH value was 4~5, dried at 105°C, ground, and passed through 200 meshes to obtain activated clay.

Add 1.9g of activated clay to a beaker containing 10g of deionized water, and stir for 5min. Take 0.2703g of ruthenium chloride (RuCl ₃ ) and dissolve it in deionized water, and disperse the solution evenly on the activated clay under the condition of stirring. Use NaOH solution to adjust the pH value to be neutral, then repeatedly wash with deionized water, and filter until no ^Cl- exists in the filtrate. The prepared catalyst was dried in air at 200°C for 4 hours and reduced in the presence of hydrogen at 250°C for 2 hours. A 5% Ru/attapulgite catalyst 1 was prepared.

Example 2:

Preparation of Catalyst 2

With embodiment 1. The difference is that the dried samples were reduced with _H2 at 500 °C for 2 h. The desired supported 5%Ru/attapulgite catalyst 2 was prepared.

Example 3:

Preparation of Catalyst 3

Add distilled water to the Ca-type montmorillonite with a particle size of 200 mesh at a solid-to-liquid ratio of 1:10, and stir until it becomes a slurry; add NaCl crystals equivalent to 6% of the mass of the montmorillonite, heat and stir at 60°C for 2 hours, and centrifuge. Wash the precipitate with deionized water until there is no Cl ^- , dry and grind at 80°C, and pass through 200 mesh to obtain Na-type montmorillonite;

Weigh Na-type montmorillonite, soak it in a solution with a volume fraction of 30%H ₂ SO ₄ , press m (montmorillonite) at 100°C: V(30%H ₂ SO ₄ )=l(g): 30 (ml), stirred and reacted for 6 hours, filtered the activated soil slurry, washed the filter cake with distilled water until the pH value was 4~5, dried at 105°C, ground, and passed through 200 meshes to obtain activated clay.

Add 1.9g of activated clay to a beaker containing 10g of deionized water, and stir for 5min. Take 0.2703g of ruthenium chloride (RuCl ₃ ) and dissolve it in deionized water, and disperse the solution evenly on the activated clay under the condition of stirring. Use NaOH solution to adjust the pH value to be neutral, then repeatedly wash with deionized water, and filter until no ^Cl- exists in the filtrate. The prepared catalyst was dried in air at 200°C for 4 hours and reduced in the presence of hydrogen at 250°C for 2 hours. A 5% Ru/activated clay catalyst was prepared.

Example 4:

Preparation of Catalyst 4

With embodiment 3. The difference is that the dried samples were reduced with _H2 at 500 °C for 2 h. The desired supported 5%Ru/attapulgite catalyst 4 was obtained.

The application method of embodiment 5 loaded Ru catalysts:

Add 5 g of 4,4′-diaminodiphenylmethane into a stirred stainless steel autoclave, add additives, 0.2 g of the above-mentioned 5% Ru/activated clay catalyst. Seal the kettle, check for leaks, turn on the stirring, keep the rotation speed at 1200r/min, replace the air in the reactor with _H2 three times, heat the reactor to 120°C under the hydrogen pressure of 5.0MPa, and then feed hydrogen to 8.0MPa to maintain the reaction state. Pressure is required until the reaction is complete. The reaction solution was taken out, the catalyst was removed by filtration, the filtrate was analyzed by gas chromatography, and the yield of the target product was calculated by the internal standard method. The results of the gas chromatographic analysis of the reaction products in the above examples are listed in Table 1.

The data in Table 1 shows that after a certain period of acidification treatment, the reaction yield increases with the increase of acid concentration, which may be because low-concentration sulfuric acid is beneficial to maintain the layered structure of montmorillonite, and high-concentration sulfuric acid makes The structural destruction of montmorillonite is beneficial to the loading of reagents, thereby improving the activity of the reaction;

Catalyst activity decreases during high temperature activation, which may be due to the loss of active centers on the catalyst surface due to high calcination temperature, resulting in a decrease in catalytic activity.

Claims (1)

1. Hydrogen montmorillonite load ruthenium catalyst is characterized in that wherein the load capacity of active component Ru is 5% ~ 10% in mass,

Prepare according to following step:

(1) sodium exchange:

To be sized to 200 purpose Ca base montmorillonites and mix, be stirred to pulpous state, and add again and be equivalent to the NaCl crystal of 0.1 ~ 1 times of native dry weight consumption by weight with distilled water; At 60 ℃ of heated and stirred 2h; After natridization reaction finishes, centrifugal filtration, with deionized water washing sediment to there not being chlorion; 80 ℃ of oven dry obtain the Na base montmorillonite;

(2) preparation of hydrogen pillared montmorillonite:

It is 10 ~ 30%H that above-mentioned Na base montmorillonite is soaked in volume fraction ₂SO ₄In the solution, isothermal reaction 2 ~ 7 hours, reaction temperature is 50 ~ 100 ℃, the mass ratio of sulfuric acid and sodium-based montmorillonite is 2 ~ 5:1; Soil paste after the activation is filtered, and it is to grind after 4 ~ 5,105 ℃ of oven dry that filter cake uses distilled water to be washed till the pH value, crosses 200 orders, promptly gets the carrier atlapulgite;

(3) active clay loaded Ru Preparation of catalysts:

According to the load capacity of ruthenium is 5～10% to confirm required RuCl in mass ₃Total amount, and be dissolved in wiring solution-forming in the distilled water, adopt excessive infusion process in solution, to add the carrier atlapulgite, constantly be stirred to color and shoal; Use NaOH to transfer pH to be neutrality; Extremely neutral with distilled water washing, suction filtration, flush away NaCl, drying;

(4) activation:, use H at 250 ~ 500 ℃ in the required above-mentioned ruthenium catalyst of ratio weighing of catalytic hydrogenation reaction ₂Reduction 1 ~ 5h; Make load Ru catalyst.