Preparation method and application of phosphorus species modified nickel-molybdenum catalyst

Abstract

The invention relates to an efficient phosphorus species modified NiMo catalyst for preparing methyl propionate through selective hydrogenation of methyl acrylate and a preparation method of the efficient phosphorus species modified NiMo catalyst. Through strong interaction between phosphorus species and Ni and Mo components in the catalyst, the active Ni and Mo components have high dispersibility in the catalyst, and compared with a modified catalyst prepared by a traditional impregnation method, the loading amount of Ni and Mo can be obviously reduced to 1 / 3 of the original loading amount, and the same activity can still be maintained. The phosphorus species modified NiMo catalyst is used for a reaction for preparing methyl propionate through selective hydrogenation of methyl acrylate in a fixed bed, the selectivity of the product methyl propionate can reach 100%, the yield of the product is 99% or above, and the catalyst is good in stability and has good industrial application value.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalytic synthesis of organic compounds, and relates to a preparation method of a phosphorus species modified nickel-molybdenum catalyst and its application in the reaction of selective hydrogenation of methyl acrylate to methyl propionate. Background Art

[0002] In the green technology of coal-based synthesis of methyl methacrylate (MMA), the hydrogenation of methyl acrylate (MA) to methyl propionate (MP) is a key and cost-effective step, providing a sustainable alternative route for traditional MMA production technologies. Traditional hydrocyanic acid production technologies have many drawbacks, including toxicity and high energy consumption. Therefore, the development of this route helps to reduce the energy consumption of MMA production and replace toxic raw materials, and operate under environmentally friendly conditions, meeting the goals of green and sustainable development.

[0003] MMA is a key monomer for synthesizing polymethyl methacrylate (PMMA). With the rapid development of industrialization and urbanization in China, its demand is increasing. The excellent transparency, durability and lightness of PMMA make it widely used in various industries, including advertising, electronics, automotive and construction. To support these industries and maintain China's economic growth, the overall production must continue to increase. It is worth noting that by 2030, the global integrated market is expected to reach $47.3 billion, and China will play a key role in this expansion. Methyl propionate is a basic raw material for the coal-based synthesis of MMA green technology. Therefore, the hydrogenation of methyl acrylate to methyl propionate is very necessary. Currently, nickel-based catalysts are often used in the hydrogenation reaction of carbon-carbon double bonds due to their high catalytic activity and affordability, but such nickel-based catalysts still have problems such as easy deactivation, difficult selectivity control and operational stability, and their structure and performance still need to be continuously improved.

[0004] Patent CN111905745A discloses a nickel-based catalyst for the hydrogenation of methyl acrylate, with W, Co, Fe, Cu or Zn as promoters and the main active component being Ni. Under the action of this catalyst, methyl acrylate can be effectively converted into methyl propionate, and the yield of methyl acrylate can reach more than 99%. However, the nickel loading of this catalyst is as high as 20 wt.%, making the overall production cost of the catalyst relatively high. Patent CN117531538A proposes an ionic liquid modified nickel-based catalytic system for the hydrogenation of methyl acrylate. Through ionic liquid modification, the catalytic activity is improved, and the yield of methyl propionate can reach more than 99%. However, the synthesis cost of the ionic liquid used is high and there are problems in industrial application scale-up. In addition, the nickel loading is also relatively high (up to 10 wt.%), and the preparation cost of the catalyst is also high.

[0005] The present invention utilizes the strong interaction between phosphorus species and Ni and Mo in the catalyst to disperse them well on the surface of the support, thereby improving the catalytic efficiency of the active components. When applied to the reaction of hydrogenating methyl acrylate to prepare methyl propionate, it exhibits high activity and stability at a low loading amount, thus significantly reducing the production cost of the catalyst. Summary of the Invention

[0006] The purpose of the present invention is to provide a phosphorus species modified nickel-molybdenum catalyst. This method uses a phosphorus source as a modifier to have a strong interaction with the active components Ni and Mo, improving their dispersion on the surface of the support, thereby reducing the loading amount of the active components and the catalyst preparation cost. The preparation method is simple and controllable, and is suitable for industrial applications.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] A phosphorus species modified nickel-molybdenum catalyst and its use for the selective hydrogenation of methyl acrylate to methyl propionate, the steps include:

[0009] (1) Dissolve the required Ni and Mo precursors in deionized water and stir evenly, then continue to add the phosphorus source and stir for 20 min at 40 - 60 °C to prepare an impregnation solution;

[0010] (2) Uniformly drop the above impregnation solution onto the γ-Al 2 O 3 support. After dropping, ensure that the support is just in a wet state, and then age it for 24 h;

[0011] (3) After aging, place the sample in an oven at 120 °C and dry it for 12 h, then calcine it at 450 - 650 °C for 3 h to obtain the catalyst sample;

[0012] (4) Load the obtained catalyst into a fixed-bed reactor, use a plunger pump to add methyl acrylate into the reactor, and control the ratio of H 2 to methyl acrylate through a mass flowmeter, so that methyl acrylate is hydrogenated on the catalyst to generate methyl propionate.

[0013] Preferably, the Ni precursor used in step (1) is NiCl 2 , NiNO 3 or Ni(CH 3 COO) 2 ; the Mo precursor is phosphomolybdic acid or (NH 4 ) 2 MoO 4 ; the phosphorus source is (NH 4 ) 3 PO 4 , (NH 4 ) 2 HPO4 , (NH 4 )H 2 PO 4 or H 3 PO 4 One or both of them.

[0014] Preferably, in step (2), the catalyst aging is carried out under ultrasonic or microwave conditions, and the aging temperature is controlled at 30 - 50 °C.

[0015] Preferably, in step (3), the catalyst calcination adopts the programmed temperature control Joule heat gradient calcination method, first maintaining at 200 - 300 °C for 1 - 2 h, and then raising the temperature to 450 - 650 °C for calcination for 3 h.

[0016] Preferably, in step (4), the reduction pretreatment temperature of the catalyst is 500 - 550 °C, the hydrogenation reaction temperature is 80 - 100 °C, the pressure is 0.6 - 1.0 MPa, and the space velocity is 0.8 - 1.2 h -1 , H 2 and the molar ratio of methyl acrylate is 3 - 5.

[0017] The beneficial effects of the present invention are as follows:

[0018] 1. The catalyst preparation method is simple, and the loading amount of the active component is significantly reduced.

[0019] 2. The catalytic efficiency is improved, the hydrogenation reaction conditions are mild, and the catalytic stability is good.

[0020] 3. The product is easy to separate after the reaction. Description of the Drawings

[0021] None Detailed Embodiments

[0022] Catalyst Preparation Examples

[0023] This example relates to a phosphorus species modified nickel - molybdenum catalyst and its preparation method, as shown in the following table:

[0024]

[0025]

[0026] Taking the phosphorus species modified nickel - molybdenum catalyst as Cat - 3 as an example, the preparation method is as follows:

[0027] First, dry the active γ - alumina support at 120 °C for 24 h, and then calcine it at 550 °C for 4 h. Take 14.8645 g of Ni(NO 3 ) 2 ·6H 2 O and 5.5207 g of (NH4 ) 2 MoO 4 ·4H 2 O and 6.3281 g are dissolved in an appropriate amount of deionized water, then 6.3281 g of phosphoric acid is added, and the mixture is stirred at 40 °C for 20 min to prepare an impregnation solution. Then, 100 g of the treated γ-alumina support is weighed, and the impregnation solution is evenly dropped onto the support to make it in a wet state, and aged at 40 °C for 24 h under ultrasonic treatment. After aging, it is dried at 120 °C for 12 h, and finally, the programmed temperature-controlled Joule heat gradient calcination method is used. First, it is maintained at 300 °C for 2 h, and then the temperature is raised to 550 °C and calcined for 3 h.

[0028] Catalyst evaluation example

[0029] This example relates to the application of a phosphorus species-modified nickel molybdenum catalyst in the selective hydrogenation of methyl acrylate to methyl propionate, as shown in the following table:

[0030] Catalyst Reaction temperature / °C Reaction pressure / MPa <![CDATA[H 2 / methyl acrylate ratio]]> <![CDATA[Air speed / h -1 > Yield / % Selectivity / % Cat-1 60 0.6 5 0.8 66.5 100 Cat-2 100 0.8 3 1.2 83.6 100 Cat-3 80 1.0 4 1.0 99.7 100 Cat-4 100 0.8 3 0.8 75.3 100 Cat-5 100 1.0 5 1.2 96.4 100 Cat-6 80 0.6 4 1.0 91.2 100

[0031] Taking the above phosphorus species-modified nickel molybdenum catalyst applied to the hydrogenation of methyl acrylate to methyl propionate as Cat-3 as an example, the following evaluation method is adopted:

[0032] 4 g of the Cat-3 catalyst is placed in a fixed-bed reactor and pre-reduced at 500 °C with 10% H 2 for 4 h first, and then purged with N 2 to remove the remaining H 2 in the reaction tube. Then, methyl acrylate is introduced into the fixed-bed reactor by a plunger pump, and the molar ratio of H 2 to methyl acrylate is controlled to be 4 by a mass flowmeter, ensuring that the liquid hourly space velocity is 1.0, and the reaction temperature and pressure are controlled to be 80 °C and 1.0 MPa respectively. After the reaction is stable, samples are taken for analysis.

[0033] The phosphorus species-modified nickel molybdenum catalyst of the present invention exhibits high catalytic performance under mild conditions, and no inactivation phenomenon is observed in the stability evaluation experiment, showing good stability. This type of catalyst is simple to prepare, has high catalytic hydrogenation activity, and has good industrial application prospects.

Claims

1. A phosphorus species modified nickel-molybdenum catalyst and its use in selective hydrogenation of methyl acrylate to produce methyl propionate, characterized in that: The loading amount of active components Ni and Mo is 0.5-5wt.%, and the loading amount of phosphorus species is 1-4wt.%. The preparation method of the catalyst and the catalyst for selective hydrogenation of methyl acrylate to produce methyl propionate include the following steps: (1) Dissolve the required Ni and Mo precursors in deionized water and stir evenly, then continue to add the phosphorus source, stir at 40-60°C for 20 minutes to prepare an impregnation solution; (2) The impregnation solution is evenly added to the γ-Al2O3 support, and the support is ensured to be just wetted after the addition, and then aged for 24 hours; (3) After aging, the sample was dried at 120°C for 12 hours, and then calcined at 450-650°C for 3 hours to obtain a catalyst sample; (4) The obtained catalyst is loaded into a fixed bed reactor, methyl acrylate is added into the reactor by a plunger pump, and the ratio of H2 to methyl acrylate is controlled by a mass flow meter, so that methyl acrylate is hydrogenated on the catalyst to generate methyl propionate.

2. The preparation method according to claim 1, characterized in that: The Ni precursor used in step (1) is NiCl2, NiNO3 or Ni(CH3COO)2; the Mo precursor is phosphomolybdic acid or (NH4)2MoO4; and the phosphorus source is one or two of (NH4)3PO4, (NH4)2HPO4, (NH4)H2PO4 or H3PO4.

3. The preparation method according to claim 1, characterized in that: In step (2), the catalyst is aged under ultrasonic or microwave conditions, and the aging temperature is controlled at 30-50°C.

4. The preparation method according to claim 1, characterized in that: In step (3), the catalyst is calcined by a programmed temperature-controlled Joule thermal gradient calcination method, firstly maintained at 300° C. for 1-2 hours, and then heated to 450-650° C. for calcination for 3 hours.

5. The use of the phosphorus species modified NiMo catalyst according to claim 1 in the selective hydrogenation of methyl acrylate to methyl propionate, characterized in that: In step (4), the catalyst reduction pretreatment temperature is 500-550°C, the hydrogenation reaction temperature is 80-100°C, the pressure is 0.6-1.0 MPa, and the space velocity is 0.8-1.2 h -1 , the molar ratio of H2 and methyl acrylate is 3-5.

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