阅读说明：本技术 一种用于异丁烯氧化制备甲基丙烯醛催化剂及制备和应用 (Catalyst for preparing methylacrolein by oxidizing isobutene, preparation and application thereof ) 是由 高爽 张毅 吕迎 于 2019-11-29 设计创作，主要内容包括：一种用于异丁烯氧化制备甲基丙烯醛催化剂的制备方法,采用钼、铋、钴、镍、铁、锰及碱性金属的前驱体溶液与载体1充分混合形成淤浆,再将得到的混合淤浆与载体2充分混合后经过焙烧得到一种核壳形貌催化剂,该形貌的催化剂解决了氧化过程中催化剂局部过热、活性组分Mo升华流失及深度氧化的技术问题,同时该形貌的催化剂具有良好的机械强度、较好的水热稳定性、对产物有较高选择性、具有良好的工业应用价值。(A preparation method for preparing a methylacrolein catalyst by oxidizing isobutene adopts the steps of fully mixing a precursor solution of molybdenum, bismuth, cobalt, nickel, iron, manganese and alkali metals with a carrier 1 to form slurry, fully mixing the obtained mixed slurry with a carrier 2, and roasting to obtain a core-shell-shaped catalyst.)

1. A preparation method of a catalyst for preparing methacrolein by oxidizing isobutene is characterized by comprising the following steps: precursor solutions of molybdenum, bismuth, cobalt, nickel, iron, manganese and alkaline metals are fully mixed with a carrier 1 to form slurry, and the obtained mixed slurry is fully mixed with a carrier 2 and then roasted to obtain the core-shell catalyst.

2. The method of claim 1, wherein: the molybdenum precursor is selected from ammonium molybdate, and the bismuth, cobalt, nickel, iron and manganese precursors are selected from nitrates of bismuth, cobalt, nickel, iron and manganese; the mass ratio of the precursors of molybdenum, bismuth, cobalt, nickel, iron and manganese is 1.0-3.0: 0.1-0.7: 0.8-2.0: 0.02-0.1: 0.1-0.5: 0.01-0.05; the alkaline metal element precursor is selected from more than two of potassium, sodium, rubidium and cesium; the mass ratio of the alkaline metal element precursor to the molybdenum precursor is 0.05-0.1: 1, and the mass ratio of more than two alkaline metal element precursors is 0.5-2.0: 0.5-2.0.

3. The method of claim 1, wherein: the carrier 1 is selected from one of alumina, zirconia and titania, and the particle size of the carrier 1 is 5-350 microns; the mass ratio of the precursors of molybdenum, bismuth, cobalt, nickel, iron, manganese and alkaline metal to the carrier 1 is 1: 5-100, preferably 1: 10-45.

4. The method according to claim 1 or 3, characterized in that: the carrier 2 is selected from one of silicon dioxide, graphite and carbon nano tubes, the shape of the carrier 2 is spherical, the mass ratio of the carrier 2 to the carrier 1 is 1: 5-60, and silicon dioxide is preferred.

5. The method of claim 1, wherein: precursor solutions of molybdenum, bismuth, cobalt, nickel, iron, manganese and alkaline metals are fully mixed with the carrier 1 to form slurry, and then the pH value of the slurry is adjusted to be neutral.

6. The method of claim 1, wherein: the neutral slurry obtained in claim 5 is fully stirred and uniformly mixed with a carrier, dehydrated and dried at 100-200 ℃, and then roasted at 400-600 ℃ for 3-6 hours.

7. A catalyst obtainable by the process of any one of claims 1 to 6.

8. Use of the catalyst of claim 7 in the oxidation of isobutylene to produce methacrolein.

Technical Field

The invention relates to a preparation method of a catalyst for preparing methacrolein by oxidizing isobutene, in particular to a core-shell morphology catalyst which is obtained by fully mixing precursor solution of molybdenum, bismuth, cobalt, nickel, iron, manganese and alkaline metal with a carrier 1 to form slurry, fully mixing the obtained mixed slurry with a carrier 2 and then roasting.

Background

Methacrolein (MAL) is an important intermediate for the synthesis of methacrylic acid (MAA) and Methyl Methacrylate (MMA), and is also an important intermediate for the synthesis of fine chemicals such as medicines and pesticides. The oxidation of isobutene to prepare MAL is a key step for preparing MAA and MMA (called isobutene oxidation method for short), the isobutene oxidation method for preparing MAA has better technical economy compared with the traditional ACH method, and the production process has the advantages of energy conservation, environmental protection and good economic benefit.

The current MMA industrial production mainly adopts methods such as acetone cyanohydrin method, isobutylene oxidation method and ethylene carbonylation method. The acetone cyanohydrin method comprises the steps of firstly, carrying out cyanidation reaction on hydrocyanic acid and acetone in the presence of a catalyst (alkali or an organic catalyst) to synthesize acetone cyanohydrin, and then carrying out amidation reaction and esterification reaction on the acetone cyanohydrin to obtain MMA; in the isobutene oxidation method, isobutene is used as a raw material and is selectively oxidized on a composite metal oxide to generate MAL, and then the MAL is subjected to one-step oxidation esterification with methanol and oxygen to generate MMA through a catalyst loaded with metal palladium (Pd).

The catalyst for preparing methacrolein by oxidizing isobutene at present is mainly a Mo-Bi-Fe-Co composite oxide catalyst, and the composite metal catalyst has two problems which are difficult to overcome, one is that the methacrolein prepared by oxidizing isobutene is an exothermic reaction, and the specific surface area of the traditional Mo-Bi-Fe-Co composite oxide catalyst is smaller than 3-20 m³The specific surface area of the catalyst is small, and the active component is too concentrated, so that the local overheating of the catalyst during reaction is easily caused, the active component Mo in the catalyst is sublimated and lost, and the activity and the selectivity of the catalyst are reduced.

Secondly, in the oxidation process of isobutene, hydrocarbon raw materials and more active reaction products are easy to be oxidized under reaction conditions, so that the control of deep oxidation and the improvement of the selectivity of the target product are always the most challenging technical problems.

Disclosure of Invention

The invention aims to provide a preparation method of a catalyst for preparing methacrolein by oxidizing isobutene, which comprises the steps of fully mixing precursor solution of molybdenum, bismuth, cobalt, nickel, iron, manganese and alkaline metal with a carrier 1 to form slurry, fully mixing the obtained mixed slurry with a carrier 2, and roasting to obtain the catalyst with the shape of a core-shell.

The catalyst has a large specific surface area, and molybdenum, bismuth, cobalt, nickel, iron, manganese and alkaline metal elements are uniformly dispersed in the shell layer of the catalyst.

In the oxidation process of isobutene, the morphology catalyst has a large specific surface area, and molybdenum, bismuth, cobalt, nickel, iron, manganese and alkali metal elements are well dispersed in a shell layer of the catalyst uniformly, so that the morphology catalyst has the best performance for controlling deep oxidation and improving the selectivity of a target product.

In order to solve the technical problems of local overheating of the catalyst, sublimation loss of an active component Mo and deep oxidation of the traditional Mo-Bi-Fe-Co composite oxide catalyst in the oxidation process of isobutene, the invention adopts the following technical scheme:

the molybdenum precursor is selected from ammonium molybdate, and the bismuth, cobalt, nickel, iron and manganese precursors are selected from bismuth, cobalt, nickel, iron and manganese nitrates; the mass ratio of the precursors of molybdenum, bismuth, cobalt, nickel, iron and manganese is 1.0-3.0: 0.1-0.7: 0.8-2.0: 0.02-0.1: 0.1-0.5: 0.01-0.05; the precursor of the alkaline metal element is selected from more than two of potassium, sodium, rubidium and cesium. The mass ratio of the precursors of potassium, sodium, rubidium and cesium to the precursor of molybdenum is 0.05-0.1: 1, and the mass ratio of the precursors of more than two alkaline metal elements is 0.5-2.0: 0.5-2.0.

The carrier 1 is selected from one of alumina, zirconia and titania, and the particle size of the carrier 1 is 5-150 microns. The mass ratio of the precursors of molybdenum, bismuth, cobalt, nickel, iron, manganese and alkaline metal to the carrier 1 is 1: 5-100.

The carrier 2 is selected from one of silicon dioxide, graphite and carbon nano tubes, and the shape of the carrier 2 is spherical. The mass ratio of the carrier 2 to the carrier 1 is 1: 5-60.

Fully mixing precursor solution of molybdenum, bismuth, cobalt, nickel, iron, manganese and alkaline metal with a carrier 1 to form slurry, and adjusting the pH value of the slurry to be 2-6.

And fully stirring and uniformly mixing the obtained neutral slurry and the carrier, dehydrating and drying at 100-200 ℃, and roasting at 400-600 ℃ for 3-6 hours.

Compared with the traditional Mo-Bi-Fe-Co composite oxide catalyst, the specific surface area of the core-shell morphology catalyst can reach 20-200 m³Large increase in/gThe specific surface area of the catalyst is reduced, the problem of local overheating during the reaction of the catalyst is solved, the sublimation loss of the active component Mo is well solved, the activity and the selectivity of the catalyst are stabilized, the metal clusters in the metal composite oxide are more uniformly distributed on the shell layer of the core-shell structure, the active sites are more fully exposed, and the deep oxidation of the product is effectively controlled, so that the activity and the selectivity of the catalyst are improved; in addition, the selectivity of the product can be obviously improved by adding the alkali metal.

The catalyst synthesized by the method is used for preparing the methacrolein by oxidizing isobutene and comprises the following steps: preheating isobutene, water vapor and air according to the ratio of 1: 1-2: 10-16, feeding the preheated isobutene, water vapor and air into a tubular fixed bed reactor filled with the catalyst to perform oxidation reaction to generate methacrolein, wherein the reaction temperature is 340-420 ℃, the reaction pressure is between normal pressure and 0.3MPa, and the feeding airspeed is 1000-8000 h^-1In the meantime.

Meanwhile, the catalyst has better catalyst activity and product selectivity in the process of preparing acrolein by propylene oxidation.

Detailed Description

The method for preparing the catalyst and the reaction performance in the reaction for preparing methacrolein by oxidizing isobutylene according to the present invention will be described with reference to the following specific examples, but the scope of the present invention is not limited to the examples.

Example 1

Dissolving 1.4g of ammonium molybdate into 8.0g of water to obtain a solution A;

dissolving 0.5g of bismuth nitrate, 0.3g of ferric nitrate, 1.6g of cobalt nitrate, 0.01g of nickel nitrate, 0.05g of cesium nitrate and 0.01g of potassium nitrate in 2.0g of a 10 wt% nitric acid aqueous solution to obtain a solution B;

40g of alumina and 50g of water were stirred uniformly at 45 ℃ to obtain solution C.

And simultaneously adding the solution B and the solution A into the obtained solution C, and uniformly stirring to obtain a solution D.

And uniformly stirring and mixing the solution D and 6g of spherical silicon dioxide to obtain a solution E.

Stirring and aging the solution E for 0.1-24 h, drying at 90-110 ℃ for 3-24 h, and drying at 180-300 ℃ for 3-6 h to obtain a solidCalcining the solid powder at 500 ℃ for 3.5h, and performing scanning electron microscope and BET specific surface area characterization analysis to obtain a powder with a specific surface area of 122m³A catalyst with a shape of a core-shell per gram.

Filling 1ml of core-shell catalyst into a tubular fixed bed layer, filling gaps in the bed layer with quartz sand, setting the temperature of the catalyst bed layer at 385 ℃, the pressure at 0.1MPa, the feeding ratio of isobutene, water vapor and air at 0.5-2.0: 5-15, and the feeding airspeed at 3600h^-1The conversion of isobutylene was 98.5%, and the selectivity of methacrolein was 91.8%.