Catalyst for the preparation of higher unsaturated aldehydes by aldol condensation and preparation and use thereof

Abstract

The application discloses a catalyst for preparing high-level unsaturated aldehyde through hydroxy aldehyde condensation reaction and a preparation method thereof. Specifically relates to a method for preparing propylene aldehyde through hydroxy aldehyde condensation reaction of a mixed solution of formaldehyde and acetaldehyde, in which, a basic metal is loaded on a modified CeO2 carrier; the reaction is carried out in a fixed bed under normal pressure; the catalyst provided by the application is cheap, and the preparation method is simple, efficient, and has the characteristics of high conversion rate of acetaldehyde in the reaction process, the highest conversion rate can reach 95%, and the selectivity of propylene aldehyde can reach 70%.

Description

Technical Field

[0001] This invention relates to a catalyst for the preparation of higher unsaturated aldehydes via aldol condensation and a method thereof; specifically, it relates to a method for preparing acrolein via aldol condensation using an alkali metal supported on a modified CeO2 support. Background Technology

[0002] Acrolein, an important chemical raw material, can be synthesized from methyl acetaldehyde via a gas-phase aldol condensation catalytic reaction. Acrolein is mainly used in the synthesis of methionine, acrylic acid, and their ester compounds. In recent years, with the maturation of the development and application technology of the novel polyester material polypropylene terephthalate (PTT), the demand for acrolein, as an important raw material for synthesizing the PTT monomer 1,3-propanediol, has further increased.

[0003] Aldol condensation refers to the nucleophilic addition of compounds containing α-H, such as aldehydes, ketones, carboxylic acids, and esters, to carbonyl compounds under the action of a catalyst to yield β-hydroxy aldehydes or acids, or further dehydration to yield α,β-unsaturated aldehydes, ketones, or acid esters. If both aldehydes involved in the aldol condensation contain α-H, they can undergo cross-condensation reactions with each other or their own self-condensation reactions. These reactions can form new C-C bonds to lengthen the carbon chain. Catalysts for gas-phase aldol condensation reactions can be alkali metal or alkaline earth metal hydroxides, oxides, soluble salts, etc., supported on an inert support. For example, the catalyst in Chinese patent CN01809710.3 uses inert alumina and silica as supports to support alkali metal compounds; US patent US2288306 uses alkali metals and alkali metal phosphates, with clay and alumina as supports, to develop the earliest catalyst for the condensation of formaldehyde and acetaldehyde to acrolein. This process was one of the industrial production processes for acrolein at that time. Furthermore, Chinese patent CN00128456.8 uses an aqueous sodium hydroxide solution as a catalyst for the aldol condensation reaction of aldehydes and / or ketones with fewer than 15 carbon atoms. However, because the catalyst is an alkaline solution, product separation is relatively difficult. US patent US2451485 uses the propylene method to prepare acrolein, but the raw materials for the propylene method are largely derived from petrochemicals. With the depletion of petroleum resources, propylene prices remain high, leading to a significant increase in production costs. Developing new alternative processes is of significant practical importance. The gas-phase aldol condensation of low-carbon aldehydes from natural gas and coal chemical sources to prepare acrolein will inevitably see further development. Summary of the Invention

[0004] The present invention aims to provide a solid catalyst and its preparation method for preparing higher unsaturated aldehydes via aldol condensation of low-carbon aldehydes. The catalyst is characterized by using an alkali metal as the active center, and by modifying the CeO2 support to obtain suitable active sites. Compared with alkali catalysts, it can reduce the occurrence of side reactions, and the catalyst is prepared using a simple method that results in low cost, good stability, and high efficiency.

[0005] A catalyst for the preparation of higher unsaturated aldehydes in aldol condensation reactions and a method thereof, specifically:

[0006] The active component of the catalyst is one or more of the alkaline metal oxides NbO, MgO, Cs2O, and K2O; the modified metal of the support CeO2 is one or more of Al, Zr, Ti, P, V, and Fe; the reaction evaluation is carried out in a fixed-bed reactor, and the reaction raw materials are a mixed solution of formaldehyde, acetaldehyde, and methanol prepared in a certain molar ratio, or a mixed solution of formaldehyde, acetaldehyde, methanol, and water prepared in a certain molar ratio;

[0007] The modified metal precursor of the CeO2 carrier is one or more of Al(NO3)3·9H2O, AlPO4, (CH3COO)(OH)2Al, ZrO(NO3)2·xH2O, Zr(SO4)2·4H2O, Zr(NO3)4·5H2O, tetrabutyl titanate, tetrabutyl titanate, n-propyl titanate, tetraethyl titanate, NH4VO3, and (NH4)2HPO4; the content of the modified metal relative to CeO2 (based on metal oxides) is 0.1wt%-7wt%, preferably 0.3wt%-5wt%, more preferably 0.5wt%-3wt%;

[0008] The active component of the catalyst is one or more of the basic metal oxides NbO, MgO, Cs2O, and K2O; the content of the metal oxide relative to the support is 0.5wt%-15wt%, preferably 1wt%-10wt%, and more preferably 2wt%-6wt%.

[0009] The CeO2 carrier modification method is either co-precipitation or hydrothermal synthesis.

[0010] The coprecipitation method involves dissolving a certain amount of modified metal precursor in water, precipitating it using excess ammonia at pH 9-12, filtering and separating the precipitate, drying it, and calcining it in air at 450-700℃ for 3-10 hours to obtain the metal-modified CeO2 support.

[0011] The hydrothermal synthesis method involves dissolving hexadecyltrimethylammonium bromide in water and heating and stirring until complete dissolution, preparing a solution of 0.01-0.05 g / ml. A certain amount of the modified metal precursor is weighed and dissolved in this solution. Excess ammonia water with pH=9-12 is added dropwise to the above system. This mixture is placed in a synthesis reactor and crystallized at 80-150℃ for 1-3 days, followed by filtration, washing, and drying. Finally, it is calcined in air at 450-700℃ for 3-10 hours to obtain the metal-modified CeO2 support.

[0012] The active component of the catalyst is loaded onto a modified CeO2 support by impregnation. Specifically, a certain amount of precursor salt of the active component is weighed and dissolved in water, such as nitrate, bicarbonate, carbonate, or sulfate. The modified CeO2 support is then added to the solution, stirred for 1-6 hours, dried, and finally calcined at 450-700°C in air for 3-10 hours to obtain the catalyst for preparing higher unsaturated aldehydes.

[0013] The activity of the catalyst was evaluated using a fixed-bed reactor. The middle section of the bed was filled with the catalyst prepared in the above process (the shaped catalyst was selected from 40-60 mesh), and the upper and lower sections were filled with quartz sand. The raw material was a mixed solution of formaldehyde, acetaldehyde, and methanol (where n... 甲醛 :n 乙醛 =1-6:1) or its aqueous mixture (where m 甲醛 :m 乙醛 :m 水 =1-6:1:1.5-9); reaction temperature is 240-400℃, carrier gas is an oxygen-free inert atmosphere, LHSV of the reaction process is 0.1-5h. -1 The final product is a mixed solution with acrolein as the main product.

[0014] The reactions involved in this invention can be represented by the following reaction equations:

[0015]

[0016] Beneficial technical effects of the present invention

[0017] 1. my country has abundant rare earth resources. The CeO2 support selected in this invention is inexpensive and abundant. Through a simple preparation method, a catalyst with suitable active centers is prepared, which gives the catalyst high reactivity.

[0018] 2. In view of my country's energy structure of "abundant coal, scarce oil and gas", the preparation of acrolein using low-carbon aldehydes from natural gas chemical and coal chemical sources as raw materials can reduce the dependence on fossil resources of traditional methods, while avoiding cumbersome processes, and has great application value.

[0019] The catalyst provided by this invention has the characteristics of low cost, simple and efficient preparation method, high conversion rate of acetaldehyde during the reaction process, with a maximum conversion rate of up to 95%, and a selectivity of 70% for acrolein. Detailed Implementation

[0020] The preferred embodiments of the present invention will be described in detail below so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more explicit definition of the scope of protection of the present invention.

[0021] Example 1

[0022] 0.1104 g of aluminum nitrate nonahydrate was dissolved in 10 ml of deionized water and denoted as solution a. 5 g of cerium oxide was added to solution a and stirred for 2 h. Then, 30 g of ammonia solution with pH = 10 was added and stirred at room temperature for 3 h. After a precipitate was formed, the precipitate was filtered to remove excess solution. The filtered precipitate was dried and calcined at 500 °C for 6 h in air. The final modified support was 0.3 wt% Al-CeO2 and denoted as C-1.

[0023] 1.8526 g of niobium oxalate was weighed and dissolved in 10 ml of deionized water, and this solution was denoted as solution b. Solution b was added to C-1 for impregnation, stirred at room temperature for 2 h, dried, and then calcined at 500 °C for 4 h in air atmosphere. The final catalyst was 15 wt% NbO / 0.3 wt% Al-CeO2, and this was denoted as Cat-1.

[0024] The obtained catalyst Cat-1 was compressed into tablets to 40-60 mesh and then loaded into a stainless steel tube fixed-bed reactor (fixed bed inner diameter 8 mm). The reaction temperature was 240℃, and the LHSV was 4 h. -1 The raw materials are a mixed solution of formaldehyde, acetaldehyde and methanol (where n 甲醛 :n 乙醛 =2:1). Gas chromatography online monitoring; final analysis showed an acetaldehyde conversion rate of 90% and an acrolein selectivity of 68%.

[0025] Example 2

[0026] 0.1196 g of aluminum phosphate was dissolved in 10 ml of deionized water and denoted as solution a. 5 g of cerium oxide was added to solution a and stirred for 2 h. Then, 30 g of ammonia solution with pH = 9 was added and stirred at room temperature for 3 h to form a precipitate. The precipitate was then filtered to remove excess solution. The filtered precipitate was dried and calcined at 600 °C for 5 h in air. The final modified support was 1% Al-CeO2 and denoted as C-2.

[0027] Weigh 0.3986 g of basic magnesium carbonate and dissolve it in 10 ml of deionized water, denoted as solution b; add solution b to C-2 for impregnation, stir at room temperature for 2 h and dry, and then calcine at 500 °C for 3 h in air atmosphere; the final catalyst obtained is 4% MgO / 1% Al-CeO2, denoted as Cat-2.

[0028] The obtained catalyst Cat-2 was compressed into tablets to 40-60 mesh and then loaded into a stainless steel tube fixed-bed reactor (fixed bed inner diameter 8 mm). The reaction temperature was 300℃, and the LHSV was 3h. -1 The raw materials are a mixed solution of formaldehyde, acetaldehyde, methanol and water (where m 甲醛 :m 乙醛 :m 水 =1.36:1:2.02); gas chromatography online monitoring; final analysis showed that the acetaldehyde conversion rate was 95% and the acrolein selectivity was 70%.

[0029] Example 3

[0030] 0.5887 g of aluminum hypoacetate was dissolved in 10 ml of deionized water and denoted as solution a. 5 g of cerium oxide was added to solution a and stirred for 2 h. Then, 30 g of ammonia solution with pH = 11 was added and stirred for 3 h at room temperature. After a precipitate was formed, the precipitate was filtered to remove excess solution. The filtered precipitate was dried and calcined at 700 °C for 7 h in air. The final modified support was 5% Al-CeO2 and denoted as C-3.

[0031] Weigh 0.0681 g of cesium acetate and dissolve it in 10 ml of deionized water, denoted as solution b; add solution b to C-3 for impregnation, stir at room temperature for 2 h and dry, and then calcine at 600 °C for 6 h in air atmosphere; the final catalyst obtained is 1% Cs2O / 5% Al-CeO2, denoted as Cat-3.

[0032] The obtained Cat-3 catalyst was compressed into tablets to 40-60 mesh and then loaded into a stainless steel tube fixed-bed reactor (fixed bed inner diameter 8 mm). The reaction temperature was 320℃, and the LHSV was 5 h. -1 The raw materials are a mixed solution of formaldehyde, acetaldehyde and methanol (where n 甲醛 :n 乙醛 =1:1). Gas chromatography online monitoring; final analysis showed an acetaldehyde conversion rate of 92% and an acrolein selectivity of 69%.

[0033] Example 4

[0034] 0.0469 g of zirconium oxynitrate was dissolved in 10 ml of deionized water and denoted as solution a. 5 g of cerium oxide was added to solution a and stirred for 2 h. Then, 30 g of ammonia solution with pH = 12 was added and stirred at room temperature for 3 h. After a precipitate was formed, the precipitate was filtered to remove excess solution. The filtered precipitate was dried and calcined at 700 °C for 7 h in air. The final modified support was 0.5% Zr-CeO2 and denoted as C-4.

[0035] Weigh 0.3668 g of potassium carbonate and dissolve it in 10 ml of deionized water, denoted as solution b; add solution b to C-4 for impregnation, stir at room temperature for 2 h and dry, then calcine at 600 °C for 6 h in air atmosphere; the final catalyst obtained is 5% K2O / 0.5% Zr-CeO2, denoted as Cat-4.

[0036] The obtained Cat-4 catalyst was compressed into tablets to 40-60 mesh and then loaded into a stainless steel tube fixed-bed reactor (fixed bed inner diameter 8 mm). The reaction temperature was 400℃, and the LHSV was 3 h. -1 The raw materials are a mixed solution of formaldehyde, acetaldehyde and methanol (where n 甲醛 :n 乙醛 =4:1). Gas chromatography online monitoring; final analysis showed an acetaldehyde conversion rate of 89% and an acrolein selectivity of 67%.

[0037] Example 5

[0038] 0.1442 g of zirconium sulfate tetrahydrate was dissolved in 10 ml of deionized water and denoted as solution a. 5 g of cerium oxide was added to solution a and stirred for 2 h. Then, 30 g of ammonia solution with pH = 10 was added and stirred for 3 h at room temperature to form a precipitate. The precipitate was then filtered to remove excess solution. The filtered precipitate was dried and calcined at 450 °C for 4 h in air. The final modified support was 1% Zr-CeO2 and denoted as C-5.

[0039] 1.8623 g of magnesium acetate tetrahydrate was dissolved in 10 ml of deionized water and denoted as solution b. Solution b was added to C-5 for impregnation, stirred at room temperature for 2 h and dried, and then calcined at 600 °C for 6 h in air atmosphere. The final catalyst was 7% MgO / 1% Zr-CeO2 and denoted as Cat-5.

[0040] The obtained Cat-5 catalyst was pressed into tablets to 40-60 mesh and then loaded into a stainless steel tube fixed-bed reactor (fixed bed inner diameter 8 mm). The reaction temperature was 500℃, and the LHSV was 2h. -1 The raw materials are a mixed solution of formaldehyde, acetaldehyde, methanol and water (where m 甲醛 :m 乙醛 :m 水=6:1:9); gas chromatography online monitoring; final analysis showed that the acetaldehyde conversion rate was 91% and the acrolein selectivity was 69%.

[0041] Example 6

[0042] 0.8710 g of zirconium nitrate pentahydrate was dissolved in 10 ml of deionized water and denoted as solution a. 5 g of cerium oxide was added to solution a and stirred for 2 h. Then, 30 g of ammonia solution with pH = 11 was added and stirred at room temperature for 3 h to form a precipitate. The precipitate was then filtered to remove excess solution. The filtered precipitate was dried and calcined at 650 °C for 4 h in air. The final modified support was 5% Zr-CeO2 and denoted as C-6.

[0043] 0.0289 g of cesium carbonate was dissolved in 10 ml of deionized water and denoted as solution b. Solution b was added to C-6 for impregnation, stirred at room temperature for 2 h, dried, and then calcined at 600 °C for 6 h in air atmosphere. The final catalyst was 0.5% Cs2O / 5% Zr-CeO2 and denoted as Cat-6.

[0044] The obtained Cat-6 catalyst was compressed into tablets to 40-60 mesh and then loaded into a stainless steel tube fixed-bed reactor (fixed bed inner diameter 8 mm). The reaction temperature was 340℃, and the LHSV was 4 h. -1 The raw materials are a mixed solution of formaldehyde, acetaldehyde, methanol and water (where m 甲醛 :m 乙醛 :m 水 =1:1:1.5 (methanol content 8 vol%); gas chromatography online monitoring; final analysis showed that the acetaldehyde conversion rate was 87% and the acrolein selectivity was 65%.

[0045] Example 7

[0046] 0.0474 g of tetrabutyl titanate was dissolved in 10 ml of deionized water and denoted as solution a. 5 g of cerium oxide was added to solution a and stirred for 2 h. Then, 30 g of ammonia solution with pH = 11 was added and stirred at room temperature for 3 h. After a precipitate was formed, the precipitate was filtered to remove excess solution. The filtered precipitate was dried and calcined at 500 °C for 3 h in air. The final modified support was 0.2% Ti-CeO2 and denoted as C-7.

[0047] Weigh 1.0842 g of potassium citrate and dissolve it in 10 ml of deionized water, denoted as solution b. Add solution b to C-7 for impregnation, stir at room temperature for 2 h, dry, and then calcine at 700 °C for 10 h in air atmosphere. The final catalyst obtained is 10% K2O / 0.2% Ti-CeO2, denoted as Cat-7.

[0048] The obtained Cat-7 catalyst was compressed into tablets to 40-60 mesh and then loaded into a stainless steel tube fixed-bed reactor (fixed bed inner diameter 8 mm). The reaction temperature was 280℃, and the LHSV was 1 h. -1 The raw materials are a mixed solution of formaldehyde, acetaldehyde and methanol (where n 甲醛 :n 乙醛 =6:1). Gas chromatography online monitoring; final analysis showed an acetaldehyde conversion rate of 90% and an acrolein selectivity of 66%.

[0049] Example 8

[0050] 0.5 g of hexadecyltrimethylammonium bromide was weighed and dissolved in 10 ml of deionized water. The solution was heated and stirred until dissolved, forming a solution with a concentration of 0.05 g / ml. Then, 0.0237 g of tetrabutyl titanate was added to this solution and stirred until completely dissolved. This solution was denoted as solution a. 5 g of cerium oxide was weighed and added to solution a. After stirring for 2 hours, 30 g of ammonia solution with pH = 12 was added. The solution was placed in a synthesis reactor and crystallized at 90 °C for 2 days. The solution was then filtered, washed, and dried. Finally, it was calcined at 550 °C for 6 hours in air. The resulting modified support was 0.1% Ti-CeO2, denoted as C-8.

[0051] 1.7919 g of magnesium sulfate was dissolved in 10 ml of deionized water and denoted as solution b. Solution b was added to C-8 for impregnation, stirred at room temperature for 2 h and dried, and then calcined at 700 °C for 5 h in air atmosphere. The final catalyst was 12% MgO / 0.1% Ti-CeO2 and denoted as Cat-8.

[0052] The obtained Cat-8 catalyst was compressed into tablets to 40-60 mesh and then loaded into a stainless steel tube fixed-bed reactor (fixed bed inner diameter 8 mm). The reaction temperature was 320℃, and the LHSV was 3h. -1 The raw materials are a mixed solution of formaldehyde, acetaldehyde, methanol and water (where m 甲醛 :m 乙醛 :m 水 =2:1:3); gas chromatography online monitoring; final analysis showed that the acetaldehyde conversion rate was 88% and the acrolein selectivity was 69%.

[0053] Example 9

[0054] 0.5932 g of tetrapropyl titanate was dissolved in 10 ml of deionized water and denoted as solution a. 5 g of cerium oxide was added to solution a and stirred for 2 h. Then, 30 g of ammonia solution with pH = 11 was added and stirred at room temperature for 3 h to form a precipitate. The precipitate was then filtered to remove excess solution. The filtered precipitate was dried and calcined at 500 °C for 6 h in air. The final modified support was 3% Ti-CeO2 and denoted as C-9.

[0055] Weigh 0.1284 g of cesium sulfate and dissolve it in 10 ml of deionized water, denoted as solution b; add solution b to C-9 for impregnation, stir at room temperature for 2 h and dry, then calcine at 500 °C for 4 h in air atmosphere; the final catalyst obtained is 2% Cs2O / 0.2% Ti-CeO2, denoted as Cat-9.

[0056] The obtained Cat-9 catalyst was compressed into tablets of 40-60 mesh and then loaded into a stainless steel tube fixed-bed reactor (fixed bed inner diameter 8 mm). The reaction temperature was 360℃, and the LHSV was 2.5 h⁻¹. -1 The raw materials are a mixed solution of formaldehyde, acetaldehyde and methanol (where n 甲醛 :n 乙醛 =3:1). Gas chromatography online monitoring; final analysis showed an acetaldehyde conversion rate of 85% and an acrolein selectivity of 63%.

[0057] Example 10

[0058] 0.1270 g of tetraethyl titanate was dissolved in 10 ml of deionized water and denoted as solution a. 5 g of cerium oxide was added to solution a and stirred for 2 h. Then, 30 g of ammonia solution with pH = 9 was added and stirred at room temperature for 3 h to form a precipitate. The precipitate was then filtered to remove excess solution. The filtered precipitate was dried and calcined at 600 °C for 3 h in air. The final modified support was 0.8% Ti-CeO2 and denoted as C-10.

[0059] Weigh 1.2502 g of potassium acetate and dissolve it in 10 ml of deionized water, denoted as solution b. Add solution b to C-10 for impregnation, stir at room temperature for 2 h, dry, and then calcine at 500 °C for 4 h in air atmosphere. The final catalyst obtained is 12% Cs2O / 0.8% Ti-CeO2, denoted as Cat-10.

[0060] The obtained catalyst Cat-10 was pressed into tablets to 40-60 mesh and then loaded into a stainless steel tube fixed-bed reactor (fixed bed inner diameter 8 mm). The reaction temperature was 340℃, and the LHSV was 5 h. -1 The raw materials are a mixed solution of formaldehyde, acetaldehyde and methanol (where n 甲醛 :n 乙醛 =2:1). Gas chromatography online monitoring; final analysis showed an acetaldehyde conversion rate of 89% and an acrolein selectivity of 67%.

[0061] Example 11

[0062] 0.1 g of hexadecyltrimethylammonium bromide was weighed and dissolved in 10 ml of deionized water. The solution was heated and stirred until dissolved, forming a solution with a concentration of 0.01 g / ml. Then, 0.1930 g of ammonium metavanadate was added to this solution and stirred until completely dissolved. This solution was denoted as solution a. 5 g of cerium oxide was weighed and added to solution a. After stirring for 2 hours, 30 g of ammonia solution with pH = 9 was added. The solution was placed in a synthesis reactor and crystallized at 80 °C for 3 days. The solution was then filtered, washed, and dried. Finally, it was calcined at 650 °C for 4 hours in air. The resulting modified support was 3% V-CeO2, denoted as C-11.

[0063] Weigh 0.0133 g of potassium bicarbonate and dissolve it in 10 ml of deionized water, denoted as solution b; add solution b to C-11 for impregnation, stir at room temperature for 2 h and dry, and then calcine at 500 °C for 4 h in air atmosphere; the final catalyst obtained is 0.5% K2O / 3% V-CeO2, denoted as Cat-11.

[0064] The obtained Cat-11 catalyst was compressed into tablets of 40-60 mesh and then loaded into a stainless steel tube fixed-bed reactor (fixed bed inner diameter 8 mm). The reaction temperature was 450℃, and the LHSV was 0.5 h⁻¹. -1 The raw materials are a mixed solution of formaldehyde, acetaldehyde and methanol (where n 甲醛 :n 乙醛 =5:1). Gas chromatography online monitoring; final analysis showed an acetaldehyde conversion rate of 86% and an acrolein selectivity of 62%.

[0065] Example 12

[0066] 0.6512 g of diammonium hydrogen phosphate was dissolved in 10 ml of deionized water and denoted as solution a. 5 g of cerium oxide was added to solution a and stirred for 2 h. Then, 30 g of ammonia solution with pH = 12 was added and stirred at room temperature for 3 h to form a precipitate. The precipitate was then filtered to remove excess solution. The filtered precipitate was dried and calcined at 650 °C for 3 h in air. The final modified support was 7% P-CeO2 and denoted as C-12.

[0067] Weigh 0.2987 g of magnesium sulfate and dissolve it in 10 ml of deionized water, denoted as solution b; add solution b to C-12 for impregnation, stir at room temperature for 2 h and dry, and then calcine at 500 °C for 5 h in air atmosphere; the final catalyst obtained is 2% MgO / 7% P-CeO2, denoted as Cat-12.

[0068] The obtained Cat-12 catalyst was compressed into tablets of 40-60 mesh and then loaded into a stainless steel tube fixed-bed reactor (fixed bed inner diameter 8 mm). The reaction temperature was 500℃, and the LHSV was 0.1 h⁻¹. -1 The raw materials are a mixed solution of formaldehyde, acetaldehyde and methanol (where n 甲醛:n 乙醛 =2:1). Gas chromatography online monitoring; final analysis showed an acetaldehyde conversion rate of 88% and an acrolein selectivity of 69%.

[0069] Comparative Example 1

[0070] 1.8526 g of niobium oxalate was dissolved in 10 ml of deionized water and denoted as solution a. 5 g of cerium oxide was added to solution a for impregnation. After stirring at room temperature for 2 h, the solution was dried and then calcined at 500 °C for 4 h in air. The final catalyst was 15% NbO / CeO2 and denoted as Cat-13.

[0071] The obtained catalyst Cat-13 was compressed into tablets to 40-60 mesh and then loaded into a stainless steel tube fixed-bed reactor (fixed bed inner diameter 8 mm). The reaction temperature was 240℃, and the LHSV was 4 h. -1 The raw materials are a mixed solution of formaldehyde, acetaldehyde and methanol (where n 甲醛 :n 乙醛 =2:1). Gas chromatography online monitoring; final analysis showed an acetaldehyde conversion rate of 65% and an acrolein selectivity of 42%.

[0072] Comparative Example 2

[0073] 0.3668 g of potassium carbonate was dissolved in 10 ml of deionized water and denoted as solution a. 5 g of cerium oxide was added to solution a for impregnation. After stirring at room temperature for 2 h, the solution was dried and then calcined at 600 °C for 6 h in air. The final catalyst was 5% K2O / CeO2 and denoted as Cat-14.

[0074] The obtained catalyst, Cat-14, was compressed into tablets to a mesh size of 40-60 and then loaded into a stainless steel tube fixed-bed reactor (8 mm inner diameter). The reaction temperature was 400℃, and the LHSV was 0.1 h⁻¹. -1 The raw materials are a mixed solution of formaldehyde, acetaldehyde and methanol (where n 甲醛 :n 乙醛 =2:1). Gas chromatography online monitoring; final analysis showed an acetaldehyde conversion rate of 73% and an acrolein selectivity of 50%.

[0075] Comparative Example 3

[0076] 1.7919 g of magnesium sulfate was dissolved in 10 ml of deionized water and denoted as solution a. 5 g of cerium oxide was added to solution a for impregnation. After stirring at room temperature for 2 h, the solution was dried and then calcined at 700 °C for 5 h in air. The final catalyst was 12% MgO / CeO2 and denoted as Cat-15.

[0077] The obtained catalyst Cat-15 was compressed into tablets to 40-60 mesh and then loaded into a stainless steel tube fixed-bed reactor (fixed bed inner diameter 8 mm). The reaction temperature was 320℃, and the LHSV was 3h. -1 The raw materials are a mixed solution of formaldehyde, acetaldehyde, methanol and water (where m 甲醛 :m 乙醛 :m 水 =1.36:1:2.33 (methanol content 8 vol%); gas chromatography online monitoring; final analysis showed that the acetaldehyde conversion rate was 79% and the acrolein selectivity was 56%.

[0078] Comparative Example 4

[0079] 0.1284 g of cesium sulfate was dissolved in 10 ml of deionized water and denoted as solution a. 5 g of cerium oxide was added to solution a for impregnation. After stirring at room temperature for 2 h, the solution was dried and then calcined at 500 °C for 4 h in air. The final catalyst was 2% Cs₂O / CeO₂ and denoted as Cat-16.

[0080] The obtained Cat-16 catalyst was compressed into tablets of 40-60 mesh and then loaded into a stainless steel tube fixed-bed reactor (fixed bed inner diameter 8 mm). The reaction temperature was 360℃, and the LHSV was 2.5 h⁻¹. -1 The raw materials are a mixed solution of formaldehyde, acetaldehyde and methanol (where n 甲醛 :n 乙醛 =2:1 (methanol content 8 vol%). Gas chromatography online monitoring was performed; final analysis showed an acetaldehyde conversion rate of 76% and an acrolein selectivity of 59%.

[0081] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

[0082] Comparisons between Comparative Example 1 and Example 1, Comparative Example 2 and Example 4, Comparative Example 3 and Example 8, and Comparative Example 4 and Example 9 revealed that, under the same active components and evaluation conditions, the unmodified CeO2 support exhibited lower acetaldehyde conversion and acrolein selectivity, and its stability was also worse. This may be because the modified metal M forms a MO-Ce structure with the CeO2 support. On one hand, this makes the catalyst more stable, avoiding severe carbon buildup and catalyst poisoning from numerous acidic sites while simultaneously reducing product selectivity. On the other hand, the modification of the metal allows the support to form more medium-to-strong acidic sites, and the impregnation with basic active metals gives the catalyst suitable acid-base active sites, which is more conducive to acetaldehyde conversion and acrolein selectivity.

Claims

1. The application of a catalyst in the catalytic aldol condensation reaction to prepare higher unsaturated aldehydes, characterized in that: The catalyst is a supported catalyst, and the active component is one or more of the basic metal oxides NbO, MgO, Cs2O, and K2O; the support is metal-modified CeO2; the modified metal is one or more of Al, Zr, Ti, P, and V; the content of the modified metal relative to CeO2 based on the metal oxide is 0.1 wt% - 7 wt%, and the content of the basic metal oxide relative to the support is 0.5 wt% - 15 wt%.

2. The application of the catalyst according to claim 1 in the catalytic aldol condensation reaction to prepare higher unsaturated aldehydes, characterized in that: The content of modified metal relative to CeO2 (calculated as metal oxide) is 0.3 wt%-5 wt%, and the content of alkali metal oxide relative to the support is 1 wt%-10 wt%.

3. The application of the catalyst according to claim 1 in the catalytic aldol condensation reaction to prepare higher unsaturated aldehydes, characterized in that: The content of modified metal relative to CeO2 (calculated as metal oxide) is 0.5 wt% - 3 wt%; the content of alkali metal oxide relative to the support is 2 wt% - 6 wt%.

4. The application of the catalyst according to claim 1 in the catalytic aldol condensation reaction to prepare higher unsaturated aldehydes, characterized in that: The catalyst is prepared by impregnating the active component of the catalyst onto a modified CeO2 support. The modification method of the support CeO2 is co-precipitation or hydrothermal synthesis; the modified metal precursor of the support CeO2 is one or more of Al(NO3)3·9H2O, AlPO4, (CH3COO)(OH)2Al, ZrO(NO3)2, Zr(SO4)2·4H2O, Zr(NO3)4·5H2O, tetrabutyl titanate, tetrabutyl titanate, n-propyl titanate, tetraethyl titanate, NH4VO3, and (NH4)2HPO4.

5. The application of the catalyst according to claim 4, characterized in that: The coprecipitation method for CeO2 carrier modification is as follows: the modified metal precursor is weighed and dissolved in water, and precipitation is carried out using excess ammonia water with pH=9-12. The precipitate is filtered and separated, then dried, and calcined at 450-700 ℃ in air atmosphere for 3-10 h to obtain the metal-modified CeO2 carrier. The hydrothermal synthesis method is as follows: hexadecyltrimethylammonium bromide is dissolved in water to prepare a solution of 0.01-0.05 g / mL. A certain amount of modified metal precursor is weighed and dissolved in the hexadecyltrimethylammonium bromide solution. Excess ammonia water with pH=9-12 is added dropwise to the above system. This mixture is placed in a synthesis vessel and crystallized at 80-150 ℃ for 1-3 days. Then, it is filtered, washed, and dried. Finally, it is calcined in air at 450-700 ℃ for 3-10 h to obtain the metal-modified CeO2 support.

6. The application of the catalyst according to claim 4, characterized in that: The impregnation method involves weighing and dissolving the precursor salt of the active component in water; the precursor salt is C. 10 H5NbO 20 One or more of the following are used: (MgCO3)4·Mg(OH)2·5H2O, MgSO4, Mg(CH3COO)2·4H2O, Cs(CH3COO), Cs2CO3, Cs2SO4, K(CH3COO), C6H5K3O7, K2CO3, KHCO3, KNO3, and K2SO4; the modified CeO2 support is added to the above solution, stirred for 1-6 h, dried, and finally calcined at 450-700 ℃ in air for 3-10 h to obtain a catalyst for the preparation of higher unsaturated aldehydes.

7. The application according to claim 1, characterized in that: The reaction is carried out in a fixed-bed reactor, and the reaction raw materials are a mixed solution of formaldehyde, acetaldehyde, and methanol, or a mixed solution of formaldehyde, acetaldehyde, methanol, and water. A fixed-bed reactor was used, with the catalyst prepared in the above process filled in the middle section of the bed (40-60 mesh), and the upper and lower sections filled with quartz sand; the raw materials were formaldehyde and nitrogen. 甲醛 :n 乙醛 A mixed solution of acetaldehyde and methanol with a ratio of 1-6:1 or m 甲醛 :m 乙醛 :m 水 Aqueous mixed solutions with a ratio of 1:6:1:1.5-9 were used; the reaction was carried out at 240-400 °C under normal pressure, with an oxygen-free inert atmosphere as the carrier gas, consisting of one or more of N2, Ar, and He; the LHSV of the reaction process was 0.1-5 h. -1 ; to obtain acrolein.

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