WO2016078286A1 - Selective hydrogenation catalyst for alkadiene, preparation method therefor, and uses thereof - Google Patents

Abstract

A selective hydrogenation catalyst for alkadiene. A carrier of the catalyst is a carboxyl-functionalized step hole FZIF-8, an active component is palladium, and the content of the active component ranges from 0.1% to 10% on the basis of the total weight of the carrier of the catalyst. A method for preparing the catalyst comprises: mixing and crystallizing raw materials, and conducting extraction and drying to obtain an FZIF-8 carrier, and making palladium immerse the carrier, so as to obtain the catalyst. Uses of the catalyst in a selective hydrogenation reaction for alkadiene are also provided. A step hole structure is formed in the carrier of the catalyst, so that carboxyl groups have accessibility, and the active components and the carboxyl groups can mutually interact; the carboxyl groups are contained in the carrier of the catalyst, and can anchor the active components, so that high dispersion of the active components is achieved, agglomeration and drain of the active components during the reaction are prevented, and the catalyst has high activity.

Description

Diolefin selective hydrogenation catalyst and preparation method and application thereof Technical field

The invention relates to a diolefin selective hydrogenation catalyst, a preparation method and application thereof, and belongs to the technical field of catalyst preparation.

Background technique

The 21st century is a new era of clean and economically developed environment. Research and development of environmentally friendly clean fuels is one of the most important research topics in green chemistry.

In order to protect the atmosphere, increasingly stringent environmental regulations require gasoline to become an environmentally friendly petroleum product. The volume content of olefins in FCC gasoline is generally as high as 40%-60%. A small amount of diolefins are often present in olefins. Although their contents are small, these diolefins are easily polymerized to form colloid during the hydrogenation and upgrading of FCC gasoline, which blocks the catalyst pores and affects the catalyst life. Therefore, one of the keys to gasoline cleaning is to reduce the diolefins in the FCC gasoline and minimize the loss of octane.

Currently, the most economically viable process for the removal of diolefins is selective hydrogenation. Most of the selective hydrogenation catalysts use Pd as the main active component. The active components of the conventional catalyst are easily agglomerated and lost during the reaction, resulting in low conversion rate of the hydrogenation catalyst, and the diolefin is easily hydrogenated to form an alkane, resulting in low selectivity of the hydrogenation catalyst, resulting in the formation of a large amount of alkanes, causing A serious loss of octane number. In order to solve these problems, the researchers have developed a series of selective hydrogenation catalysts for diolefins in order to increase the hydrogenation selectivity of the catalyst while improving its hydrogenation selectivity, but the effect is not satisfactory.

Summary of the invention

In order to solve the above technical problems, an object of the present invention is to provide a diolefin selective hydrogenation catalyst which is excellent in both conversion and selectivity.

It is also an object of the present invention to provide a process for the preparation of the above-described diolefin selective hydrogenation catalyst.

In order to achieve the above object, the present invention firstly provides a diolefin selective hydrogenation catalyst, wherein the catalyst carrier is a carboxyl functionalized stepped pore FZIF-8, and the active component is palladium;

The active component palladium is present in an amount of from 0.1 to 10%, preferably 0.3%, based on the total weight of the catalyst support.

The diene selective hydrogenation catalyst provided by the invention can be used for anchoring the metal active component by introducing a carboxyl group on the carrier, thereby realizing high dispersion of the active component on the catalyst carrier, and effectively improving the active component of the catalyst. The problem of agglomeration and loss in the catalytic reaction increases the hydrogenation conversion rate of the catalyst; at the same time, the strong interaction between the carboxyl group and the active component changes the electron density of the active component and greatly improves the hydrogenation selectivity of the catalyst.

The invention also provides a preparation method of the above diene selective hydrogenation catalyst, which comprises the following steps:

Add sodium hydroxide, cationic surfactant, ligand to water, stir until completely dissolved, add zinc source, stir evenly to obtain a mixture, the weight ratio of mixed raw materials is sodium hydroxide: cationic surfactant: water: ligand: Zinc source = (15-45): (5-20): 250: (2-8): (1-6);

The mixture is crystallized, and then the crystallized product is extracted and dried to obtain a FZIF-8 carrier;

The FZIF-8 carrier is added to an impregnation solution in which Pd ²⁺ is dissolved, and palladium is impregnated, and then dried and reduced to prepare the diene selective hydrogenation catalyst.

In the above preparation method, preferably, the cationic surfactant used is a quaternary ammonium salt surfactant having a carbon chain length of C ₆ - C ₂₀ such as cetyltrimethylammonium bromide, CTAB. Cationic surfactants, especially CTAB, not only function as a templating agent in the synthesis system of the diene selective hydrogenation catalyst provided by the present invention, but also lead to the formation of a stepped pore structure and can be protected during the synthesis of the carrier. The carboxyl group does not coordinate with the metal ion forming the backbone structure of the support. The presence of the stepped pores provides accessibility to the carboxyl group and the active component is capable of interacting with the carboxyl group.

In the above production method, preferably, the ligand used is 2-methyl-1H-imidazole-4,5-dicarboxylic acid.

In the above preparation method, preferably, the zinc source used is one or a mixture of two or more of Zn(NO ₃ ) ₂ ·6H ₂ O, Zn(CH ₃ COO) ₂ .2H ₂ O, ZnCl ₂ .

In the above production method, preferably, the crystallization time is 12 to 48 hours, the crystallization temperature is 80 to 180 ° C, and the drying is 80 to 100 ° C for 2 to 8 hours.

In the above production method, preferably, the extract used for the extraction is one or a mixture of two or more of ethanol, propanol, acetone, and the like.

In the above production method, preferably, the immersion liquid used is one of a solution of palladium acetate, palladium nitrate, palladium chloride, palladium bisacetonitrile, palladium acetylacetonate. The solution may be an aqueous solution or an acetonitrile solution.

In the above production method, preferably, the reduction temperature is from 80 to 200 ° C, and the weight percentage of the active component to the carrier is from 0.1% to 10%. This condition is to define the ratio of the amount of Pd in the FZIF-8 carrier to the impregnation solution, and the ratio means that the active component is 0.1 to 10% by mass of the carrier.

The invention also provides the use of the above diene selective hydrogenation catalyst in the selective hydrogenation of diolefins.

The diolefin selective hydrogenation catalyst provided by the invention has the following advantages:

1. The catalyst carrier has a stepped pore structure, so that the carboxyl group is accessible, and the active component can interact with the carboxyl group;

2. The catalyst carrier contains a carboxyl group, which can anchor the active component, achieve high dispersion of the active component, and prevent agglomeration and loss of the active component during the reaction, and the catalyst activity is high;

3. The active component of the catalyst strongly interacts with the carboxyl group, which increases the electron density of the active component, greatly improves the selectivity reduction of the active component of the small particle due to the electron-deficient effect, and the comprehensive performance of the catalyst is good;

4. The catalyst can be applied to the hydro-upgrading of FCC gasoline, removing the diene in the oil, the reaction condition is moderate, the reaction temperature is low, the pressure is low, and the selective hydrogenation effect of the product is good.

DRAWINGS

1 is an XRD spectrum of a carrier in Example 1, Example 2, Comparative Example 1, and Comparative Example 2;

2A-2E are palladium particle size distribution diagrams of the catalysts of Example 1, Example 2, Comparative Example 1, Comparative Example 2, and Comparative Example 3, respectively;

3 is a result of evaluation of a catalyst in Example 1, Example 2, Comparative Example 1, Comparative Example 2, and Comparative Example 3 in a selective hydrogenation reaction of a diene.

detailed description

The detailed description of the technical features, the advantages and the advantages of the present invention will be understood by the following detailed description of the invention.

Example 1

This example provides a diene selective hydrogenation catalyst having a palladium content of 0.3 wt% based on the weight of the catalyst support, which is referred to as catalyst A.

The catalyst was prepared by the following steps:

Dissolve 3.6 g of CTAB, 3.0 g of NaOH in 50 ml of deionized water, stir until completely dissolved, add 1.3 g of 2-methyl-1H-imidazole-4,5-dicarboxylic acid, and add 1.2 g of Zn after dissolution. NO ₃ ) ₂ · 6H ₂ O, a mixed reaction solution is obtained;

The reaction solution was poured into a 100 ml polytetrafluoroethylene reactor, crystallized at 140 ° C for 24 hours, and then naturally cooled to room temperature after completion of the reaction. The solid product was separated by suction filtration, washed with deionized water, and extracted with anhydrous ethanol. The product was separated by centrifugation and dried at 100 ° C for 12 hours to prepare a catalyst carrier FZIF-8. The XRD spectrum thereof is shown in Fig. 1;

2.0 g of FZIF-8 was immersed in an acetonitrile solution in which 0.015 g of palladium chloride was dissolved, and stirred at normal temperature for 24 hours, and then dried at 100 ° C to remove the solvent. The dried sample was tablet-formed, crushed, and sieved for 20-40. The intended sample was reduced with high purity hydrogen at 150 ° C for 5 hours to prepare a catalyst Pd/FZIF-8, Catalyst A. The palladium particle size distribution is shown in Figure 2A.

Example 2

This example provides a diene selective hydrogenation catalyst having a palladium content of 0.3 wt% based on the weight of the catalyst support, which is referred to as catalyst B. The palladium particle size distribution is shown in Figure 2B.

The preparation method was the same as in Example 1, except that the amount of CTAB was changed to 2.6 g.

Comparative example 1

This comparative example provides a diolefin selective hydrogenation catalyst having a palladium content of 0.3 wt% based on the weight of the catalyst support, which is referred to as catalyst C. The palladium particle size distribution is shown in Figure 2C.

The catalyst was prepared by the following steps:

8.32 g of Zn(NO ₃ ) ₂ ·4H ₂ O, 1.76 g was dissolved in 100 ml of N,N-dimethylformamide, and then the reaction liquid was poured into a polytetrafluoroethylene reactor and crystallized at 100 ° C. hour;

After the crystallization reaction is completed, it is naturally cooled to room temperature, and the solid product is separated by suction filtration, and washed with deionized water to prepare a catalyst carrier MOF-5, and the XRD spectrum thereof is shown in FIG. 1;

The catalyst was prepared in the same manner as in Example 1, except that the FZIF-8 in the carrier was changed to the conventional MOF-5.

Comparative example 2

This comparative example provides a diolefin selective hydrogenation catalyst having a palladium content of 0.3 wt% based on the weight of the catalyst support, which is referred to as catalyst D. The palladium particle size distribution is shown in Figure 2D.

The catalyst was prepared by the following steps:

1.05 g of ZnCl ₂ and 0.3 g of 2-methylimidazole were dissolved in 90 ml of N,N-dimethylformamide, and the reaction solution was poured into a 100 ml polytetrafluoroethylene reactor and crystallized at 140 ° C for 24 hours. ;

After the crystallization reaction is completed, it is naturally cooled to room temperature, and the solid product is separated by suction filtration, and washed with deionized water to prepare a catalyst carrier ZIF-8, and the XRD spectrum thereof is shown in FIG. 1;

The catalyst was prepared in the same manner as in Example 1, except that the FZIF-8 in the carrier was changed to the conventional ZIF-8.

Comparative example 3

This comparative example provides a diolefin selective hydrogenation catalyst having a palladium content of 0.3 wt% based on the weight of the catalyst support, which is referred to as catalyst E. The palladium particle size distribution is shown in Figure 2E.

The catalyst was prepared by the following steps:

Preparing a 2 mol/L aluminum isopropoxide solution, hydrolyzing and stirring at 85 ° C for 1 hour;

Adding HNO ₃ to the obtained slurry to form a gel, and the sol was refluxed at 95 ° C for 12 hours;

Then, the sol is dried at 40 ° C for 48 hours; then the red dried sol is calcined in a muffle furnace at 600 ° C for 4 hours to prepare a catalyst carrier γ-Al ₂ O ₃ ;

The catalyst was prepared in the same manner as in Example 1, except that FZIF-8 in the carrier was changed to γ-Al ₂ O ₃ .

The active component data of the catalysts of Examples 1-2 and Comparative Examples 1-3 are shown in Table 1.

Table 1 Characterization data of active components of each catalyst

catalyst	Palladium content (%)	Palladium particle average size (nm)	Palladium particle dispersion (%)
				A	0.3	3.5	85
B	0.3	4	82
				C	0.3	16.5	20
D	0.3	13	twenty four
				E	0.3	15	twenty two

Activity evaluation of diolefin selective hydrogenation catalyst

The catalysts prepared in Examples 1, 2 and Comparative Examples 1-3 were subjected to evaluation of catalytic activity of diene selective hydrogenation.

The diene selective hydrogenation reaction evaluation is carried out on a high pressure continuous flow fixed bed micro-reactor, and the specific steps are as follows: the catalyst is diluted with quartz sand of equal particle size and charged into the reaction tube, and the reaction condition is: 1.0-4.0 MPa. 40-120 ° C, airspeed 8-20 h ^-1 , hydrogen to oil ratio (volume) 2-6, the reaction was stable for 24-72 h, and then sampled for analysis.

Model gasoline contains 85% (mass fraction) n-heptane, 5% isoprene, 10% isoamylene (2-methyl-2-butene: 90%, 2-methyl-1-butene: 10 %).

The diene conversion (X) and the monoolefin selectivity (S) were used as evaluation indexes, and the calculation formula was as follows:

Where X is the diene conversion and S is the monoolefin selectivity.

The specific evaluation results of the respective catalysts are shown in Fig. 3.

It can be seen from Fig. 3 that although the other conditions are the same, the catalyst Pd/FZIF-8 exhibits a higher ratio than the use of the catalysts Pd/ZIF-8, Pd/MOF-5 and Pd/Al ₂ O ₃ . Olefin conversion and monoolefin selectivity. The higher the dispersion of supported palladium particles and the smaller the particle size, the higher the conversion of isoprene, so the highest dispersion of Pd/FZIF-8 has the highest conversion of diene, and Pd/FZIF-8 has the most Excellent monoolefin selectivity, because the palladium particles have a strong interaction with the carboxyl groups in Pd/FZIF-8, resulting in an increase in the electron density of the palladium particles, which can avoid the single due to the electron-deficient effect of the small-sized palladium particles. The problem of olefin selectivity reduction.

Although the dispersion of palladium nanoparticles in Pd/MOF-5 is not high, due to the unsaturated metal coordination sites with Lewis acid activity in MOF-5, the metal coordination sites can promote the further hydrogenation of isoprene to form heterogeneous Pentane, so the conversion of diolefin can reach 95% on the Pd/MOF-5 catalyst, but the selectivity of monoolefin is only 70%. Pd / ZIF-8, and Pd / Al diene ₂ O ₃ conversion rate and selectivity of monoolefin not high, due to the Pd / ZIF-8, and Pd / Al nanoparticles of Pd ₂ O ₃ resulted in no agglomeration Sufficient catalytic activity sites are used for the selective hydrogenation of isoprene and the further hydrogenation of isoamylene to isopentane.

The above experimental results show that the diene selective hydrogenation catalyst provided by the invention anchors the active component through the carboxyl group, the palladium particle dispersion of the catalyst is high, and the strong interaction of the palladium particles with the carboxyl group changes the electron density of the palladium particle. At the same time, the conversion of diolefins and the selectivity of monoolefins are improved, and the hydrogenation reaction performance of the catalyst is greatly improved.

Claims (10)

1. a diolefin selective hydrogenation catalyst, wherein the carrier of the catalyst is a carboxyl functionalized stepped pore FZIF-8, and the active component is palladium;

   The active component palladium is present in an amount of from 0.1 to 10% based on the total weight of the catalyst support.
2. A method of preparing a diolefin selective hydrogenation catalyst according to claim 1, comprising the steps of:

   Add sodium hydroxide, cationic surfactant, ligand to water, stir until completely dissolved, add zinc source, stir evenly to obtain a mixture, the weight ratio of mixed raw materials is sodium hydroxide: cationic surfactant: water: ligand: Zinc source = (15-45): (5-20): 250: (2-8): (1-6);

   The mixture is crystallized, and then the crystallized product is extracted and dried to obtain a FZIF-8 carrier;

   The FZIF-8 carrier is added to an impregnation solution in which Pd ²⁺ is dissolved, and palladium is impregnated, and then dried and reduced to prepare the diene selective hydrogenation catalyst.
3. The production method according to claim 2, wherein the cationic surfactant is a quaternary ammonium salt surfactant having a carbon chain length of C ₆ - C ₂₀ .
4. The production method according to claim 2, wherein the ligand is 2-methyl-1H-imidazole-4,5-dicarboxylic acid.
5. The production method according to claim 2, wherein the zinc source is one or more of Zn(NO ₃ ) ₂ ·6H ₂ O, Zn(CH ₃ COO) ₂ ·2H ₂ O, and ZnCl ₂ mixture.
6. The production method according to claim 2, wherein the crystallization is carried out for 12 to 48 hours, the crystallization temperature is 80 to 180 ° C, and the drying is performed at 80 to 100 ° C for 2 to 8 hours.
7. The production method according to claim 2, wherein the extraction liquid used in the extraction is one or a mixture of two or more of ethanol, propanol and acetone.
8. The production method according to claim 2, wherein the immersion liquid is one of a solution of palladium acetate, palladium nitrate, palladium chloride, palladium acetonacetate or palladium acetylacetonate.
9. The production method according to claim 2, wherein the reduction temperature is from 80 to 200 ° C, and the weight percentage of the active component to the carrier is from 0.1% to 10%.
10. Use of the diolefin selective hydrogenation catalyst of claim 1 in the selective hydrogenation of diolefins.

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