CN110560158A - High-dispersion supported ionic liquid-palladium aluminum oxide catalyst and preparation method and application thereof - Google Patents

Abstract

The invention provides a high-dispersion supported ionic liquid-palladium alumina catalyst, a preparation method and application thereof, wherein the catalyst is prepared from the following materials: alumina carrier, ionic liquid and palladium compound; the high-dispersion supported ionic liquid-palladium alumina catalyst is prepared by reducing and stabilizing palladium ions by using hydroxyl or nitrile ionic liquid to obtain palladium nanoparticles with higher dispersion degree, and then loading the palladium nanoparticles into alumina; the high-dispersion supported ionic liquid-palladium alumina catalyst provided by the invention has the advantages of higher acetylene conversion rate, higher ethylene selectivity, better stability and the like when applied to acetylene selective hydrogenation reaction.

Description

A kind of highly dispersed loaded ionic liquid-palladium alumina catalyst and preparation method thereof and application

(1) Technical field

The invention relates to a high-dispersion loaded ionic liquid-palladium alumina catalyst, a preparation method thereof, and an application in acetylene selective hydrogenation reaction.

(2) Background technology

Ethylene is one of the most important chemical products in the world and is widely used in various fields such as synthetic plastics, rubber, fibers, medicine, pesticides and dyes. Industrial ethylene is mainly produced through the cracking of raw materials such as naphtha and diesel, but in the process of preparing ethylene gas, about 0.3%-3% of acetylene is often generated; these traces of acetylene will poison the Ziegler-Natta of the downstream polyethylene process The catalyst will not only reduce the activity and service life of the catalyst, but also seriously affect the product quality of the polyethylene process. Therefore, the removal of trace acetylene in raw gas has important industrial significance.

The method commonly used in industry to remove acetylene is selective hydrogenation, which has the advantages of no pollution, low energy consumption, and simple process, so it is widely used. However, although the palladium-based catalysts traditionally used in industry have better catalytic activity, they have poor ethylene selectivity, which will cause excessive hydrogenation to generate ethane or oligomerization to generate green oil, which will affect the performance of the catalyst. service life. Therefore, the ethylene selectivity of palladium-based catalysts in the acetylene hydrogenation reaction is crucial to the ethylene industry, so it is necessary to modify the catalyst to prevent ethylene from excessive hydrogenation to ethane, thereby further improving the ethylene selectivity .

Ionic liquids are a class of electrolytes that are in a liquid state at room temperature or low temperature, and have the advantages of low vapor pressure, non-flammability, low toxicity, excellent thermodynamics, and chemical stability; ionic liquids have special physical and chemical properties, which make ions The liquid itself can be used as a catalyst or as a solvent in catalytic reactions and has been widely used; at the same time, as a solvent, ionic liquid is also a good medium, which can be used to prepare nanoparticles of stable homogeneous catalysts. Therefore, ionic liquids can be used to prepare more stable and dispersed metal particles, and further prepare highly dispersed catalysts with smaller metal particle sizes.

Based on the above background, the present invention proposes the preparation of a highly dispersed and supported ionic liquid palladium-alumina catalyst to improve the selectivity of the palladium-based catalyst in the selective hydrogenation of acetylene.

(3) Contents of the invention

The object of the present invention is to provide a highly dispersed and loaded ionic liquid-palladium alumina catalyst and its preparation method, as well as its application in the selective hydrogenation reaction of acetylene. The preparation method of the invention has simple process, and the prepared catalyst can greatly improve the ethylene selectivity in the acetylene selective hydrogenation reaction.

Technical scheme of the present invention is as follows:

A highly dispersed and loaded ionic liquid-palladium alumina catalyst, consisting of the following materials: an alumina carrier, an ionic liquid, and a palladium compound;

The specific surface area of the alumina carrier is 60-420m ² /g;

The palladium compound is chloropalladium acid, palladium nitrate, palladium acetate, palladium acetylacetonate, dichlorodiammine palladium, ammonium tetrachloropalladate, sodium chloropalladate or tetraammine palladium nitrate, preferably palladium acetate;

The ionic liquid is an imidazole ionic liquid, the cations are imidazolium cations with hydroxyl or nitrile groups of different carbon chain lengths, and the anions are chloride, bromide, hexafluorophosphate, tetrafluoroborate or (three Fluoromethanesulfonyl)imide ions, specific examples: 1-hydroxyethyl-3-methylimidazolium tetrafluoroborate, 1-hydroxyethyl-3-methylimidazolium chloride, 1-nitrile propyl-3 - Methylimidazolium tetrafluoroborate or 1-cyanopropyl-3-methylimidazolium chloride, preferably 1-hydroxyethyl-3-methylimidazolium chloride; the ionic liquid can be used as a reduction agent for palladium nanoparticles agents, stabilizers and protectants;

In the catalyst, based on the mass of the carrier, the loading of the palladium compound as palladium is 0.01-0.5wt% (preferably 0.01-0.1wt%, more preferably 0.01-0.03wt%), and the loading of the ionic liquid is 10-40wt% % (preferably 10-30wt%, more preferably 30wt%).

A kind of preparation method of highly dispersed loaded ionic liquid-palladium alumina catalyst, described preparation method comprises the following steps:

(1) dissolving the palladium compound in a solvent to obtain a palladium impregnation solution;

In the palladium impregnation solution, the concentration of the palladium compound in terms of palladium is 0.001-0.01g/mL;

Described solvent is decided according to the kind of palladium compound, can be water, hydrochloric acid, ethanol, acetone etc., the present invention has no special requirement to this;

(2) adding the ionic liquid into a solvent to dissolve, then adding palladium impregnating solution, and stirring at 90° C. for 24 hours in a nitrogen atmosphere to obtain an ionic liquid-palladium nanoparticle mixed solution;

The solvent used to dissolve the ionic liquid here is the same as the solvent in the palladium impregnating solution;

(3) Immerse the alumina carrier in the ionic liquid-palladium nanoparticle mixture, disperse evenly, immerse at room temperature (20-30°C) for 9-12h, and then dry at 110-130°C for 9-12h to obtain the obtained Described highly dispersed loaded ionic liquid-palladium alumina catalyst;

In the present invention, after step (3) the aluminum oxide is immersed in the ionic liquid-palladium nanoparticle mixed solution and immersed for 9-12 hours, the system can be placed in a microwave reactor and microwaved at 100-140° C. for 20-80 minutes, and further Promote the dispersion of metal active components in the catalyst, and then put the sample into an oven at 110-130° C. to dry for 9-12 hours to obtain the final catalyst.

In the preparation method of the catalyst described in the present invention, the palladium compound and the ionic liquid can be considered to be fully loaded, and those skilled in the art can select the added amount of the palladium compound and the ionic liquid according to the required loading amount.

The highly dispersed and supported ionic liquid-palladium alumina catalyst of the invention can be applied to the hydrogenation reaction of acetylene. Specifically, the method of the application is:

Before the selective hydrogenation of acetylene, the catalyst needs to be reduced in an atmosphere of hydrogen, the reduction temperature is 130-230°C, and the time is 1-3h; then the reduced catalyst is used for selective hydrogenation of acetylene Reaction, the reaction conditions are: temperature 100-210°C (preferably 120-190°C), pressure 0.1-1MPa (preferably 0.1-0.3MPa, more preferably normal pressure), space velocity 1000-10000h ^-1 (preferably 4000-8000h ^-1 );

In the selective hydrogenation reaction of acetylene, the gas composition at the beginning of the reaction is (volume fraction): 0.33% C ₂ H ₂ , 0.66% H ₂ , 33.3% C ₂ H ₄ , and the balance N ₂ .

Compared with prior art, the beneficial effect of the present invention is:

(1) The highly dispersed loaded ionic liquid-palladium alumina catalyst of the present invention utilizes hydroxyl or nitrile ionic liquids to reduce and stabilize palladium ions into palladium nanoparticles with higher dispersion, and then this palladium nanoparticle load in alumina. On the other hand, palladium particles with smaller particle size and higher degree of dispersion can not only obtain higher reactivity in acetylene hydrogenation reaction, but also greatly improve the selectivity of acetylene reaction.

(2) The preparation method of the highly dispersed and loaded ionic liquid-palladium alumina catalyst of the present invention has a simple process.

(3) The preparation method of the highly dispersed supported ionic liquid-palladium alumina catalyst of the present invention introduces a microwave treatment step, which can further promote the dispersion of palladium nanoparticles, thereby further improving the ethylene selectivity in the reaction.

(4) The highly dispersed and supported ionic liquid-palladium alumina catalyst of the present invention has the advantages of higher acetylene conversion rate, higher ethylene selectivity, better stability and the like in the selective hydrogenation reaction of acetylene.

(4) Specific implementation methods

The present invention will be further described below through specific examples, but the protection scope of the present invention is not limited thereto.

Example 1-5

Weigh a certain amount of _PdCl2 and dissolve it in concentrated hydrochloric acid, transfer it to a volumetric flask, add a certain amount of deionized water to the corresponding scale, and prepare a chloropalladium acid solution with a mass concentration of palladium of 0.001 g/mL. According to the loads and proportions listed in Table 2, the metered chloropalladium acid solution and the ionic liquid were mixed. After obtaining the stable palladium-ionic liquid impregnation solution, pipette quantitative palladium-ionic liquid mixed solution in a watch glass, and add a certain amount of deionized water, after stirring evenly, the aluminum oxide carrier (specific surface area is 360m ² /g) into the impregnating solution, and ultrasonically disperse it evenly. The wet alumina was impregnated at room temperature for 12 hours, and dried at 110° C. for 12 hours to prepare a highly dispersed supported ionic liquid-palladium alumina catalyst.

In Example 4, the comparison of the texture properties of the alumina carrier before and after loading ionic liquid and Pd is shown in Table 1:

Table 1 Comparison of texture properties of supports before and after loading ionic liquid and Pd

The data in Table 1 shows that too much ionic liquid forms a layer of ionic liquid film on the inner surface of the carrier, resulting in a decrease in specific surface area and pore volume. And the prepared catalyst is highly dispersed, and the palladium particle size is about 2-5nm.

Example 6

Referring to the operation of Example 5, the only difference is that the carrier is replaced by alumina with a specific surface area of 60 m ² /g, and a high-dispersion supported ionic liquid-palladium alumina catalyst with better performance is obtained.

Example 7

Referring to the operation of Example 5, the only difference is that the carrier is replaced by alumina with a specific surface area of 420m ² /g, and a high-dispersion supported ionic liquid-palladium alumina catalyst with better performance is obtained.

Example 8

The highly dispersed supported ionic liquid-palladium alumina catalyst prepared in Example 2 was reacted in a microwave reactor at 100° C. for 80 minutes to obtain a finished catalyst.

Example 9

The highly dispersed supported ionic liquid-palladium alumina catalyst prepared in Example 5 was reacted in a microwave reactor at 120° C. for 60 minutes to obtain a finished catalyst.

Prepared catalyst carries out catalyst performance evaluation according to the following method:

Put 0.32g of the catalyst in a small quartz tube reactor, place the quartz tube in a temperature-controllable heating mantle, and place the catalyst in a pure _H2 atmosphere at 180°C for 1 hour before performing selective hydrogenation of acetylene. , the reducing gas flow rate was 10mL/min; after the reduction was completed, the reaction was carried out at the temperature shown in Table 2. The composition of the reaction gas is (volume fraction): 0.33% acetylene, 33.% ethylene, 0.66% hydrogen and the remainder nitrogen, and the flow rate of the reaction gas is 50 mL/min. In addition, the reaction pressure is normal pressure. The outlet of the reaction gas was connected to gas chromatography for on-line detection, and the evaluation results of the catalyst are shown in Table 2 below.

Table 2 Evaluation results of selective hydrogenation of acetylene over highly dispersed supported ionic liquid-palladium alumina catalyst

Examples 10-15

With reference to the preparation method of the catalyst of Examples 1-5, see Table 3 for the ionic liquid, load and proportion, select 1-hydroxyethyl-3-methylimidazole chloride salt and 1-nitrile propyl-3-methylimidazole These two ionic liquids of chloride salt are used to prepare highly dispersed loaded ionic liquid-palladium alumina catalyst.

The evaluation method of the catalytic performance of the catalyst is the same as above, the reaction temperature is changed to 110-140° C., and the evaluation results of the catalyst are shown in Table 3 below.

Table 3 Evaluation results of selective hydrogenation of acetylene over highly dispersed supported ionic liquid-palladium alumina catalyst

Example Loading capacity/wt% Types of Ionic Liquids (IL) Reaction temperature/℃ Acetylene conversion rate/% Ethylene selectivity/% Example 10 Pd=0.1, IL=30 1-Hydroxyethyl-3-methylimidazolium chloride 130 99.2 88.4 Example 11 Pd=0.1, IL=30 1-Hydroxyethyl-3-methylimidazolium chloride 140 ≥99.7 88.8 Example 12 Pd=0.1, IL=30 1-Nitropropyl-3-methylimidazolium chloride salt 110 86.3 80.5 Example 13 Pd=0.1, IL=30 1-Nitropropyl-3-methylimidazolium chloride salt 120 ≥99.5 83.9 Example 14 Pd=0.1, IL=30 1-Nitropropyl-3-methylimidazolium chloride salt 130 ≥99.7 85.1 Example 15 Pd=0.1, IL=30 1-Nitropropyl-3-methylimidazolium chloride salt 140 ≥99.8 84.4

Comparative example 1-2

With reference to the catalyst preparation method of Examples 1-5, the ionic liquid, loading capacity and proportioning ratio are as shown above, select 1-hydroxyethyl-3-methylimidazolium chloride salt ionic liquid to prepare highly dispersed loaded ionic liquid-palladium alumina catalyst.

The palladium-alumina catalyst was prepared by a simple impregnation method and the catalyst performance was compared with the highly dispersed supported ionic liquid-palladium alumina catalyst. The catalytic performance evaluation method of the catalyst was the same as above, and the reaction temperature was 120°C. The evaluation results are shown below.

Claims (7)

1. A high-dispersion supported ionic liquid-palladium alumina catalyst is characterized by comprising the following materials: alumina carrier, ionic liquid and palladium compound;

The palladium compound is chloropalladic acid, palladium nitrate, palladium acetate, palladium acetylacetonate, dichlorodiammine palladium, ammonium tetrachloropalladate, sodium chloropalladate or tetraamminepalladium nitrate;

The ionic liquid is imidazole ionic liquid, the cation of the ionic liquid is imidazole cation with hydroxyl or nitrile group, and the anion of the ionic liquid is chloride ion, bromide ion, hexafluorophosphate radical, tetrafluoroborate radical or (trifluoromethanesulfonyl) imide ion;

in the catalyst, the loading amount of the palladium compound in terms of palladium is 0.01-0.5 wt% and the loading amount of the ionic liquid is 10-40 wt% based on the mass of the carrier.

2. The highly dispersed supported ionic liquid-palladium alumina catalyst of claim 1 wherein the ionic liquid is: 1-hydroxyethyl-3-methylimidazolium tetrafluoroborate, 1-hydroxyethyl-3-methylimidazolium chloride, 1-cyanopropyl-3-methylimidazolium tetrafluoroborate or 1-cyanopropyl-3-methylimidazolium chloride.

3. The method for preparing the highly dispersed supported ionic liquid-palladium alumina catalyst according to claim 1, wherein the method comprises the steps of:

(1) dissolving a palladium compound in a solvent to prepare a palladium impregnation solution;

(2) Adding the ionic liquid into a solvent for dissolving, then adding a palladium impregnation solution, and stirring for 24 hours at 90 ℃ in a nitrogen atmosphere to obtain an ionic liquid-palladium nanoparticle mixed solution;

(3) Immersing an alumina carrier in the ionic liquid-palladium nanoparticle mixed solution, uniformly dispersing, immersing for 9-12h at room temperature, and then drying for 9-12h at 110-130 ℃ to obtain the high-dispersion supported ionic liquid-palladium alumina catalyst.

4. The method according to claim 3, wherein in the step (1), the concentration of the palladium compound in the palladium-impregnated solution is 0.001 to 0.01g/mL in terms of palladium.

5. The preparation method of claim 3, wherein the alumina in the step (3) is immersed in the ionic liquid-palladium nanoparticle mixed solution and is soaked for 9-12h, the system is placed in a microwave reactor, the microwave is carried out for 20-80 min at 100-140 ℃, and then the sample is placed in an oven at 110-130 ℃ and is dried for 9-12h to obtain the final catalyst.

6. The use of the highly dispersed supported ionic liquid-palladium alumina catalyst of claim 1 in acetylene hydrogenation reactions.

7. The application of claim 6, wherein the method of applying is:

Before the selective hydrogenation reaction of acetylene, the catalyst is placed in the atmosphere of hydrogen for reduction at the temperature of 130-230 ℃ for 1-3 h; and then the reduced catalyst is used for acetylene selective hydrogenation reaction, and the reaction conditions are as follows: the temperature is 100-210 ℃, the pressure is 0.1-1MPa, and the space velocity is 1000-10000h^-1；

In the acetylene selective hydrogenation reaction, the initial reaction gas composition is as follows: 0.33% C₂H₂、0.66％H₂、33.3％C₂H₄the balance N₂。