Catalyst for preparing allyl acetate through acetylation of propylene and preparation method of catalyst

Abstract

The invention relates to a catalyst for preparing allyl acetate through acetylation of propylene and a preparation method of the catalyst. The catalyst comprises a carrier, active components and an auxiliary agent, the average pore size of the carrier is 20-100 nm, the active components are bimetallic palladium Pd and antimony Sb, and the auxiliary agent is potassium acetate. The invention mainly solves the problems of low conversion rate, low selectivity, short service life and the like of the catalyst used in the current acryl acetylation reaction. Compared with the prior art, the catalyst provided by the invention has the advantages of high conversion rate and high selectivity on the acetylation reaction of the propylene, and solves the problem of poor stability of the existing catalyst.

Description

Technical Field

[0001] The invention relates to a preparation technology of allyl acetate, in particular to a catalyst for preparing allyl acetate by acetylation of propylene and a preparation method thereof. Background Art

[0002] Allyl acetate is a widely used organic compound, mainly used as a solvent, adhesive, and organic synthesis intermediate. At the same time, allyl acetate, as an important chemical raw material, can be used to prepare allyl alcohol and epichlorohydrin.

[0003] The main technology of producing allyl acetate at present is acetoxylation, i.e., using propylene, oxygen and acetic acid as raw materials, and carrying out gas phase reaction in a fixed bed reactor. The early disclosed patent EP1112775B1 adopts acetoxylation to prepare the catalyst of allyl acetate, and palladium metal active component and alkali (earth) metal auxiliary agent are loaded on silicon oxide carrier. However, the activity of this catalyst is low, and the space-time yield of allyl acetate is mostly no more than 60g / h / L catalyst, and the reaction temperature is higher, causing the selectivity of by-product carbon dioxide to be higher, and the allyl acetate selectivity has only 87%.

[0004] Many scholars have studied the active components of acetyl oxidation catalysts and the role of co-catalysts. For example, Zhao Zhenxing et al. proposed in "Mechanism and Kinetics of Gas-Phase Oxygen Acetylation of Ethylene" that molecular oxygen is the oxygen source involved in acetylation, and Pd can convert physically adsorbed acetic acid into chemically adsorbed acetic acid, thereby combining with molecular oxygen to form allyl acetate. Shu Qingyu et al. pointed out in "Gas-Phase Oxygen Acetylation Reaction on Pd-Sn-K / SiO2 Catalyst" that KOAc can improve the activation of CH bonds.

[0005] In order to improve catalyst activity and selectivity, in addition to the main catalyst metal palladium and alkaline (earth) metal activation aid, other co-catalyst metals need to be added. Currently disclosed co-catalysts have gold, copper, lead, ruthenium, rhenium, tin (EP0361484, CN106582871B, CN1131199C, CN103121954B). And in these catalysts, when copper is used as co-catalyst, there is higher catalytic activity and selectivity (USP 5,011,980), and US3,917,676 discloses a kind of preparation method with SiO2, Al2O3 or SiO2 and Al2O3 composition as carrier, loaded with Pd, Cu and potassium acetate catalyst.

[0006] However, in the disclosed catalysts for preparing allyl acetate by acetylation, in order to achieve higher catalytic activity and selectivity, in addition to adding a promoter to the catalyst, most of them still need to add a certain amount of water to the feed composition of propylene, acetic acid and oxygen to maintain the activity and life of the catalyst (USP 3,925,452, USP 5,011980, USP 4,647,690, CN106582856B). The addition of water not only limits the yield of allyl acetate but also increases the energy consumption of separation and purification of allyl acetate. Moreover, the maximum space-time yield of allyl acetate in the disclosed patents CN1101729C and CN101657259B is about 500g / L / h, and the activity of the catalyst decays rapidly. For example, CN1101729C discloses a supported catalyst of main catalyst metal palladium / co-catalyst metal tin / alkali (earth) metal compound, the space-time yield of allyl acetate decays rapidly, the activity decreases by 10% after 120 hours of reaction, and the selectivity of allyl acetate is less than 95%.

[0007] Therefore, the existing technology needs to be further improved and optimized in order to obtain higher catalytic activity, selectivity and stability and improve the overall performance of industrial production. Summary of the invention

[0008] The purpose of the present invention is to provide a catalyst for preparing allyl acetate by acetylation of propylene and a preparation method thereof in order to overcome the defects of the prior art. The catalyst involved in the present invention has improved carriers and promoter metals, and has high catalyst activity, high selectivity and good stability.

[0009] The purpose of the present invention can be achieved by the following technical solutions:

[0010] One of the present inventions provides a catalyst for preparing allyl acetate by acetylation of propylene. The catalyst comprises a carrier, an active component and an auxiliary agent. The active component is bimetallic palladium Pd and antimony Sb, and the auxiliary agent is potassium acetate.

[0011] Furthermore, the average pore size of the carrier is between 20 nm and 100 nm.

[0012] Furthermore, the carrier is TiO2, and the crystal orientation of the TiO2 is one or more of anatase phase and rutile phase.

[0013] Furthermore, the carrier is one or more of Al2O3 and SiO2.

[0014] Furthermore, the precursor of metal Pd is PdCl2, and the precursor of metal Sb is SbCl3.

[0015] Furthermore, the mass fraction of metal Pd in ​​the catalyst is 0.2%-2%, and the mass fraction of metal Sb is 0.2%-2%.

[0016] Furthermore, the mass fraction of potassium acetate in the catalyst is 1%-20%.

[0017] The second aspect of the present invention provides a method for preparing the above catalyst, and the steps for preparing the catalyst are as follows:

[0018] (1) dissolving the precursors of the active components PdCl2 and SbCl3 in hydrochloric acid;

[0019] (2) immersing the above-mentioned support in the precursor solution in (1) to obtain a catalyst precursor 1;

[0020] (3) adding an alkaline solution to the catalyst precursor 1 to obtain an aged catalyst precursor 2;

[0021] (4) adding a reducing agent to the precursor 2 to obtain a metallic Pd and Sb catalyst precursor 3;

[0022] (5) washing the catalyst precursor 3 to remove chloride ions, and then drying to obtain the catalyst precursor 4;

[0023] (6) Impregnating the catalyst precursor 4 with potassium acetate as an auxiliary agent, and drying again to obtain the above-mentioned finished catalyst product.

[0024] Compared with the prior art, the technical key of the present invention is that the average pore size of the carrier is between 20nm and 100nm, and the carrier has a small specific surface area and a large average pore size, which is conducive to the formation of an eggshell structure of active metal palladium Pd and antimony Sb on the carrier surface. The active components are bimetallic palladium Pd and antimony Sb, which have higher activity, selectivity and stability than bimetallic palladium Pd and copper Cu. Due to the adoption of the above technical solution, the activity, selectivity and stability of the propylene acetylation catalyst are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 HRTEM image of the Pd-Sb-CH3COOK / α-Al2O3 catalyst described in Example 1;

[0026] Figure 2 These are the stability test results of the Pd-Sb-CH3COOK / α-Al2O3 catalyst described in Example 1. DETAILED DESCRIPTION

[0027] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] Example 1

[0029] Provided is a method for preparing a catalyst for preparing allyl acetate by acetylation of propylene and a catalyst performance evaluation, specifically:

[0030] (1) Catalyst preparation

[0031] Step 1: Weigh 16.675 g PdCl2 and 9.375 g SbCl3 respectively and dissolve them in deionized water, add 50 mL 37.5% hydrochloric acid to form a clear precursor solution, and then impregnate the precursor solution into 1280 g α-Al2O3 carrier to obtain catalyst precursor 1;

[0032] Step 2: Prepare 1000 mL of solution with 42 g of KOH, add it to catalyst precursor 1, mix well, let stand at room temperature for 12 h, and dry in an oven at 110° C. for 1 h to obtain catalyst precursor 2;

[0033] Step 3: Add 21.5 mL of 85% hydrazine hydrate reducing agent to the precursor 2 to obtain the supported metal state Pd and Sb catalyst precursor 3;

[0034] The catalyst precursor 3 was washed to remove chloride ions, and the washing liquid was tested with a 0.1 mol / L silver nitrate solution until no white precipitate was produced, and then placed in an oven at 110° C. to dry for 2 h to obtain a catalyst precursor 4;

[0035] Step 4: 100g of potassium acetate as an auxiliary agent is prepared into a solution and impregnated into the catalyst precursor 4, and the Pd-Sb-CH3COOK / α-Al2O3 catalyst product is obtained after drying. The catalyst HRTEM image is as follows: Figure 1 shown.

[0036] (2) Catalyst performance evaluation

[0037] The catalyst was evaluated in a fixed bed reactor, and the evaluation parameters were: the catalyst loading was 500 mL; the pressure of the reaction system was 0.1-1 MPa, the reaction temperature was 100-170°C, and the gas volume space velocity was 1000-6000 h -1 , Reaction raw material composition (calculated in molar percentage) propylene: oxygen: acetic acid = (60-80%): (5-10%): (10-20%); The space-time yield and selectivity after the reaction is run for 120 hours are calculated as follows:

[0038] Space-time yield (STY) = mass of allyl acetate produced by reaction / (catalyst volume*reaction time) g / (L*h)

[0039] Selectivity (S) = number of moles of allyl acetate produced by the reaction / number of moles of propylene consumed by the reaction * 100%

[0040] In Example 1, select:

[0041] Reactor: fixed bed reactor;

[0042] Catalyst loading: 500mL;

[0043] Reaction system pressure: 0.5MPa;

[0044] Reaction system temperature: 150°C;

[0045] Reaction space velocity: 3000h -1 ;

[0046] Reaction time: 120h;

[0047] Reaction raw material composition (calculated by mole percentage): 72% propylene, 20% acetic acid, 8% oxygen;

[0048] The catalyst activity and selectivity were analyzed by online chromatography. The analysis results after 120 h of reaction are listed in Table 1.

[0049] The stability test results of Pd-Sb-CH3COOK / α-Al2O3 catalyst are shown in Figure 2 shown.

[0050] Embodiment 2-10

[0051] Except for the changes in the content of the carrier, the palladium-containing compound and the antimony-containing compound, and the content of potassium acetate, the other steps are the same as those in Example 1.

[0052] Comparative Example 1

[0053] The catalyst was prepared by the method of patent CN 101157030A. 400 mL of aqueous solution containing chloropalladic acid (H2PdCl4) equivalent to 1.5 g Pd and chloroauric acid (HAuCl4) equivalent to 0.15 g Au was prepared, 30 mL of 5 g / L PVP solution was added to the above solution, stirred for 1 hour, 200 mL of 6.0 g / L NaBH4 aqueous solution was added dropwise, and PVP-protected metal colloid was obtained after reduction. The metal colloid was loaded onto a 1 L silica carrier, dried at 110 ° C for 4 hours, cooled to room temperature, impregnated with an equal volume of a water bath containing 15 g KOAc, taken out and dried at 110 ° C, and finally the finished catalyst was obtained.

[0054] Comparative Example 2

[0055] The catalyst was prepared by the method of patent CN 103878022A. 1200 mL of an aqueous solution containing chloropalladic acid and copper chloride was used as an impregnation solution, wherein the palladium content in the solution was 2.75 g / L and the copper content was 0.625 g / L, and 1100 mL of a spherical silica carrier with a diameter of 4 to 6 mm was impregnated to obtain catalyst precursor 1; 27.5 g of sodium silicate nonahydrate was prepared into 100 mL of an aqueous solution and added to catalyst precursor 1, mixed evenly, allowed to stand for 24 hours, and then dried at 80°C for 8 hours to obtain catalyst precursor 2; a polyethylene-containing 100 mL of an aqueous solution of polyvinyl pyrrolidone (weight-average molecular weight of 360,000), wherein the content of polyvinyl pyrrolidone is 100 g / L, is used to impregnate catalyst precursor 2 to obtain catalyst precursor 3; catalyst precursor 3 is reduced in a hydrogen atmosphere at a hydrogen flow rate of 0.2 mL / min, a pressure of 0.5 MPa, and a reduction temperature of 200°C to obtain catalyst precursor 4; and potassium acetate aqueous solution is impregnated to make the potassium acetate content of 50 g / L, and the finished catalyst is obtained by drying.

[0056] The preparation conditions of the catalyst and the evaluation results after 120 hours of reaction are shown in Table 1. Table 2 shows the average pore sizes of different carriers.

[0057] Table 1 Preparation conditions of catalyst and evaluation results after 120h reaction

[0058]

[0059]

[0060] Table 2 Average pore size of different carriers

[0061] project Carrier Average pore size / nm Example 1 <![CDATA[α-Al2O3]]> 20.91 Example 2 <![CDATA[TiO2 - Anatase]]> 20.32 Example 3 <![CDATA[TiO2 - Rutile - A]]> 21.16 Example 4 <![CDATA[SiO2]]> 28.56 Embodiment 5-10 <![CDATA[TiO2 - Rutile - A]]> 21.16 Embodiment 11 <![CDATA[TiO2 - Rutile - B]]> 30.95 Example 12 <![CDATA[TiO2 - Rutile - C]]> 50.51 Example 13 <![CDATA[TiO2 - Rutile - D]]> 120.77

[0062] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A catalyst for preparing allyl acetate by acetylation of propylene, characterized in that: The catalyst comprises a carrier, an active component and an auxiliary agent. The average pore size of the carrier is between 20 nm and 100 nm. The active component is bimetallic palladium Pd and antimony Sb. The auxiliary agent is potassium acetate.

2. The catalyst for preparing allyl acetate by acetylation of propylene according to claim 1, characterized in that: The carrier is TiO2, and the crystal orientation of the TiO2 is one or more of anatase phase or rutile phase.

3. The catalyst for preparing allyl acetate by acetylation of propylene according to claim 1, characterized in that: The carrier is one or more of Al2O3 or SiO2.

4. The catalyst for preparing allyl acetate by acetylation of propylene according to claim 1, characterized in that: The mass fraction of metal Pd in ​​the catalyst is 0.2%-2%.

5. The catalyst for preparing allyl acetate by acetylation of propylene according to claim 1, characterized in that: The mass fraction of metal Sb in the catalyst is 0.2%-2%.

6. The catalyst for preparing allyl acetate by acetylation of propylene according to claim 1, characterized in that: The mass fraction of potassium acetate in the catalyst is 1%-20%.

7. A method for preparing a catalyst for preparing allyl acetate by acetylation of propylene as claimed in any one of claims 1 to 6, characterized in that: The following steps are involved: (1) Dissolving the precursors of the active components, PdCl2 and SbCl3, in hydrochloric acid; (2) immersing the support in the precursor solution in (1) to obtain a catalyst precursor 1; (3) adding an alkaline solution to the catalyst precursor 1 to obtain an aged catalyst precursor 2; (4) adding a reducing agent to the precursor 2 to obtain a metallic Pd and Sb catalyst precursor 3; (5) washing the catalyst precursor 3 to remove chloride ions, and then drying to obtain the catalyst precursor 4; (6) Impregnating the catalyst precursor 4 with the auxiliary agent potassium acetate, and drying it again to obtain the finished catalyst for preparing allyl acetate by acetylation of propylene.

8. The method for preparing a catalyst for preparing allyl acetate by acetylation of propylene according to claim 7, characterized in that: The precursor of the metal Pd is PdCl2, and the precursor of the metal Sb is SbCl3.

9. A method for synthesizing allyl acetate, comprising taking propylene, acetic acid and oxygen as raw materials and reacting them in the presence of the catalyst according to any one of claims 1 to 8 to obtain allyl acetate.

10. The method for synthesizing allyl acetate according to claim 9, characterized in that: The pressure of the reaction system is 0.1-1MPa, the reaction temperature is 100-170℃, and the gas volume space velocity is 1000-6000h -1 The molar ratio of the reaction raw materials is propylene (60-80%): oxygen (5-10%): acetic acid (10-20%).

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