Preparation and application of catalyst for catalytically converting alpha-angelica lactone into beta-angelica lactone

Abstract

The invention provides a preparation method of a biomass platform molecule angelica lactone isomerization catalyst. The catalyst comprises one of the following solid metal oxides and one of potassium assistants: eight metal oxides (m-zirconium oxide, t-zirconium oxide, c-zirconium oxide, aluminum oxide, magnesium oxide, barium oxide, lanthanum oxide and neodymium oxide) and seven potassium sources (potassium nitrate, potassium carbonate, potassium acetate, potassium hydroxide, potassium chloride, potassium oxalate and potassium oxide). By designing the preparation method of the metal oxide, the high-specific-surface-area pure-crystalline-phase metal oxide is obtained; by introducing the potassium aid, the surface alkalinity of the catalyst is effectively regulated and controlled, so that the alpha-angelica lactone is simply and efficiently isomerized into the beta-angelica lactone. The catalyst provided by the invention has the characteristics of high activity, high selectivity, high stability and easy recovery, and provides a feasible technical approach for biomass platform molecule angelica lactone isomerization.

Description

Technical Field

[0001] The present invention belongs to the technical field of biomass platform molecule isomerization catalysts, and particularly relates to the preparation and application of a catalyst for catalytically converting α-angelica lactone into β-angelica lactone. Background Art

[0002] In the process of high-value utilization and energy conversion of biomass, non-conjugated butenolide (i.e., angelica lactone) intermediate products are often involved. As one of the biomass platform molecules, angelica lactone can be catalytically converted from readily available furfural or levulinate esters in large quantities, with a maximum yield of about ~80%. At the same time, as an unsaturated carbonyl compound, angelica lactone exhibits excellent catalytic activity and is widely used as an important intermediate in multiple fields, showing significant application potential and broad industrialization prospects.

[0003] Angelica lactone, also known as non-conjugated butenolide, has the molecular formula C5H6O2. According to the different positions of the C=C double bond in the furan ring, there are three isomers: namely, α-angelica lactone, β-angelica lactone, and γ-angelica lactone. Due to the structural differences, their chemical properties, reaction activities, and application fields are also significantly different. Existing research and reports mainly involve α- and β-angelica lactones. Among them, α-angelica lactone widely exists in plants such as grapes, soybeans, and licorice. Due to its sweet, coconut, and vanilla flavors, it is often used as a spice and food additive. In addition, α-angelica lactone can also be catalytically converted into high-value-added chemicals such as valerolactone, or used as a monomer in fields such as ultraviolet light-induced, cationic, and ring-opening polymerization.

[0004] β-angelica lactone can undergo a condensation reaction through deprotonation and form long-chain alkane biofuels through hydrodeoxygenation treatment. At the same time, due to its unique chiral symmetry, it also has important application value in the pharmaceutical field, such as the synthesis of antibiotic intermediates. However, in the current preparation methods of β-angelica lactone, the main product is α-angelica lactone, or a mixture of α- and β-angelica lactones, and it is difficult to obtain β-angelica lactone with a high yield. For example, H-ZSM-5 / SiO2 can catalytically convert levulinic acid into a mixture of angelica lactones (β-angelica lactone only contains 33%). Although some studies have proposed that using α-phenylthio-levulinic acid as a raw material, through reduction, esterification, cyclization, oxidation, and elimination reactions, pure β-angelica lactone can be obtained, its yield is only about ~67%. Moreover, the preparation process of this method is complex, requires strict control of reaction conditions, and is accompanied by the generation of a large number of by-products, making the subsequent purification process cumbersome, increasing the experimental difficulty, and reducing the effective yield. Therefore, it is necessary to design a new catalyst and improve the reaction path to improve its yield, efficiency, and process operability, and ensure its feasibility and cost-effectiveness in industrial production.

[0005] Metal oxides play a crucial role in the field of catalysis. Due to their unique chemical and physical properties, they are widely used in various catalytic reactions. At the same time, metal oxides can be precisely regulated due to their high specific surface area, thermal stability, mechanical strength, and adjustable acidity and basicity, enabling them to achieve high activity and high stability. The potassium-modified high-specific-surface-area pure crystalline phase metal oxide catalyst described in the present invention is applied to the heterogeneous catalysis of α-angelica lactone conversion to β-angelica lactone. For the first time, under mild reaction conditions, the isomerization of angelica lactone is achieved simply and efficiently. The reaction temperature is 60 - 120 °C, the conversion rate of α-angelica lactone > 80%, and the yield of β-angelica lactone > 80%. It solves the problems such as complex processes and by-products, providing a new approach for the preparation of β-angelica lactone. Summary of the Invention

[0006] In order to solve the problems and challenges existing in the preparation process of β-angelica lactone, the present invention aims to provide a preparation and application of a catalyst for catalyzing the isomerization of the biomass platform molecule angelica lactone. The catalyst provided by the present invention exhibits excellent performance in the isomerization reaction of angelica lactone, can efficiently carry out this conversion reaction under relatively mild conditions, with a conversion rate reaching 83% and a selectivity for β-angelica lactone reaching 100%. This preparation method significantly reduces the requirements for reaction equipment and reaction conditions. Compared with traditional preparation methods, it greatly reduces the energy consumption during the reaction process, improves the safety and economy of operation, and thus has good application prospects.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A catalyst for catalyzing the isomerization of the biomass platform molecule angelica lactone, which catalyst comprises a solid metal oxide and a potassium promoter.

[0009] The solid metal oxide is one of monoclinic zirconia (m-ZrO₂), tetragonal zirconia (t-ZrO₂), commercial zirconia (c-ZrO₂), alumina, magnesia, barium oxide, lanthanum oxide, neodymium oxide.

[0010] The potassium promoter is one of potassium nitrate, potassium carbonate, potassium acetate, potassium hydroxide, potassium chloride, potassium oxalate, potassium oxide.

[0011] The mass percentage of the potassium promoter and the solid metal oxide is 5 - 30 wt%.

[0012] The preparation method of the catalyst for catalyzing the isomerization of the biomass platform molecule angelica lactone comprises the following steps:

[0013] Preparation method one of metal oxides:

[0014] (1) By using the mechanochemical method, at room temperature, (NH4)2CO3 and ZrOCl2·8H2O are ground to a colloidal state in a ratio of 1 - 5:1 (molar ratio); transferred to a 50 ml reaction kettle, kept at a constant temperature of 80 - 200 °C for 12 - 24

[0015] h, after cooling to room temperature, washed with deionized water until there is no chloride ion, and dried in an oven at 80 - 140 °C to obtain the metal oxide precursor;

[0016] (2) The metal oxide precursor obtained in step (1) is calcined at 400 - 800 °C for 2 - 10 h to obtain m-ZrO2

[0017] (monoclinic).

[0018] Method for preparing metal oxide two:

[0019] (1) By using the mechanochemical method, at room temperature, NaOH and ZrOCl2·8H2O are ground to a colloidal state in a ratio of 1 - 5:1 (molar ratio); transferred to a 50 ml reaction kettle, kept at a constant temperature of 80 - 200 °C for 12 - 24 h, after cooling to room temperature, washed with deionized water until there is no chloride ion, and dried in an oven at 80 - 140 °C to obtain the metal oxide precursor;

[0020] (2) The metal oxide precursor obtained in step (1) is calcined at 400 - 800 °C for 2 - 10 h to obtain t-ZrO2

[0021] (tetragonal).

[0022] Method for preparing metal oxide three:

[0023] (1) By using the soft template method, first prepare a 10 g / L polyvinylpyrrolidone aqueous solution (PVP solution), take out two portions (20 ml each), and add them to M x Cl y solution (other metal chlorides, 0.1 mol / L, 50 ml)

[0024] and Na2CO3 (0.1 mol / L, 50 ml) solution and stir vigorously for 0.5 h;

[0025] (2) Add the sodium dodecyl sulfate aqueous solution (0.05 mol / L, 20 ml) to the above Na2CO3 solution and stir for 0.5 - 2 h, then quickly pour the M x Cl y mixed solution obtained in (1) into the above Na2CO3 mixed solution and stir for 0.5 - 2 h;

[0026] (3) The precipitate obtained in (2) is washed with deionized water and dried in an oven at 80 - 140 °C to obtain the metal oxide precursor;

[0027] (4) Calcinate the metal oxide precursor obtained in step (3) at 400 - 800 °C for 2 - 10 h to obtain M x O y .

[0028] Preparation method of potassium - modified metal oxide:

[0029] (1) Using the impregnation method, at room temperature, dissolve the potassium promoter in deionized water; then, add the solid metal oxide precursor in proportion, stir and impregnate for 12 - 24 h, with a rotation speed of 200 - 500 r / min, and then slowly evaporate to dryness in a constant - temperature water bath at 50 - 80 °C

[0030] and dry in an oven at 80 - 140 °C

[0031] (2) Calcinate the sample obtained in step (1) at 400 - 800 °C for 2 - 10 h to obtain the catalyst

[0032] Apply the catalyst prepared by the above - mentioned method to the isomerization of biomass platform molecule angelica lactone

[0033] The specific steps are as follows: Under the conditions of normal - pressure open - reaction, add α - angelica lactone and the catalyst to a round - bottom flask, the reaction temperature is 60 - 140 °C, the reaction time is 0.5 - 12 h, the stirring speed is 500 - 800 r / min, and the mass ratio of the catalyst to the α - angelica lactone raw material is 0.1

[0034] The beneficial effects of the present invention are as follows:

[0035] (1) High - specific - surface - area basic catalyst: The catalyst used in the present invention is a potassium - modified pure - crystalline - phase metal oxide catalyst with a high specific surface area (20 - 120 m 2 / g) obtained by using the mechanochemical method or the soft - template method to prepare the metal oxide precursor and using the impregnation method for potassium - promoter modification through one - step calcination

[0036] (1) High selectivity and high yield: The catalyst of the present invention shows high selectivity in the isomerization reaction of biomass platform molecule angelica lactone. Especially for potassium - modified t - ZrO2, the selectivity of β - angelica lactone can reach 100%, and the yield reaches 83%, overcoming the problem of low yield of β - angelica lactone in the traditional preparation method

[0037] (2) Process simplification: The preparation process of the potassium - promoter - modified metal oxide in the present invention is simple, avoiding complex preparation processes. At the same time, the reaction device for the isomerization of biomass platform molecule angelica lactone is simple, and the reaction conditions are mild, effectively simplifying the production process and reducing the production cost

[0038] (3) Environmental friendliness: The catalyst used in the present invention not only has a green and environmentally friendly preparation process, but also no harmful by-products are generated during the reaction process, meeting the requirements of sustainable development.

[0039] (4) High stability and low energy consumption: The catalyst used in the present invention can rapidly achieve the efficient isomerization of the biomass platform molecule angelica lactone under low temperature and solvent-free conditions. After 5 cycles of testing, the catalytic activity shows no obvious change. Description of the Drawings

[0040] Figure 1 XRD diagrams of the catalysts for Comparative Examples 1-3.

[0041] Figure 2 CO2-TPD diagrams of the catalysts for Examples 1-3.

[0042] Figure 3 Stability test diagram of the isomerization catalyst 2 of the biomass platform molecule angelica lactone at 120 °C. Detailed Description of the Invention

[0043] To make the content of the present invention easier to understand, the technical solutions of the present invention will be further described below in conjunction with specific embodiments. However, the present invention is not limited thereto.

[0044] Example 1

[0045] The catalyst for the isomerization of the biomass platform molecule angelica lactone described in this example was prepared from the following raw materials:

[0046] (NH4)2CO3: 3.8417 g;

[0047] ZrOCl2·8H2O: 6.4439 g;

[0048] KNO3: 0.0386 g; The mass fraction of KNO3 in the total (m-ZrO2+KNO3) is 15%

[0049] (1) At room temperature, 3.8417 g of (NH4)2CO3 and 6.4439 g of ZrOCl2·8H2O were ground to a gel-like state in a ratio of 2:1; transferred to a 50 ml reaction kettle, kept at a constant temperature of 160 °C for 20 h, and after cooling to room temperature, washed with deionized water until there was no chloride ion, and dried in an oven at 100 °C to obtain a metal oxide precursor;

[0050] (2) At room temperature, 0.0386 g of KNO3 was dissolved in 657 μl of deionized water; then it was added dropwise to a beaker containing 0.2195 g of the sample in (1), stirred and impregnated for 24 h at a rotation speed of 200 r / min, then slowly evaporated to dryness in a water bath at 50 °C, and dried in an oven at 100 °C.

[0051] (3) Calcinate the sample obtained in step (2) at 500 °C for 4 h to obtain the catalyst K / m-ZrO2.

[0052] Example 2

[0053] The catalyst for isomerization of the biomass platform molecule angelica lactone described in this example is prepared from the following raw materials:

[0054] NaOH: 3.1995 g;

[0055] ZrOCl2·8H2O: 6.4444 g;

[0056] KNO3: 0.0386 g; the mass fraction of the KNO3 in the total (t-ZrO2+KNO3) is 15%;

[0057] (1) At room temperature, grind 3.1995 g of NaOH and 6.4444 g of ZrOCl2·8H2O in a ratio of 4:1 to a gel-like state; transfer to a 50 ml reaction kettle, keep it at a constant temperature of 100 °C for 20 h, wait until it cools to room temperature, wash with deionized water until there is no chloride ion, and dry in a drying oven at 100 °C to obtain the metal oxide precursor.

[0058] (2) At room temperature, dissolve 0.0386 g of KNO3 in 657 μl of deionized water; then dropwise add it to a beaker containing 0.2195 g of the sample in (1), stir and impregnate for 24 h at a rotation speed of 200 r / min, then slowly evaporate to dryness in a constant temperature water bath at 50 °C, and dry in a drying oven at 100 °C.

[0059] (3) Calcinate the sample obtained in step (2) at 500 °C for 4 h to obtain the catalyst K / t-ZrO2.

[0060] Example 3

[0061] The catalyst for isomerization of the biomass platform molecule angelica lactone described in this example is prepared from the following raw materials:

[0062] c-ZrO2: 0.2195 g;

[0063] KNO3: 0.0386 g; the mass fraction of the KNO3 in the total (c-ZrO2+KNO3) is 15%;

[0064] (1) At room temperature, dissolve 0.0386 g of KNO3 in 657 μl of deionized water; then dropwise add it to a beaker containing 0.2195 g of the sample in (1), stir and impregnate for 24 h at a rotation speed of 200 r / min, then slowly evaporate to dryness in a constant temperature water bath at 50 °C, and dry in a drying oven at 100 °C.

[0065] (2) The sample obtained in step (1) is calcined at 500 °C for 4 h to obtain the catalyst K / c-ZrO2.

[0066] Example 4

[0067] The catalyst for the isomerization of the biomass platform molecule angelica lactone described in this example is prepared from the following raw materials:

[0068] PVP: 2.0014 g;

[0069] SDS: 0.2884 g;

[0070] MgCl2: 0.4761 g;

[0071] Na2CO3: 0.5299 g;

[0072] KNO3: 0.0386 g; the mass fraction of the KNO3 in the total (MgO + KNO3) is 15%;

[0073] (1) Dissolve 2.0014 g of polyvinylpyrrolidone (PVP) in 200 ml of deionized water, take out two portions (20 ml each), and add them to the MgCl2 solution (0.4761 g of MgCl2, 50 ml of deionized water) and Na2CO3

[0074] (0.5299 g of Na2CO3, 50 ml of deionized water) solution and stir vigorously for 0.5 h;

[0075] (2) Dissolve 0.2884 g of sodium dodecyl sulfate (SDS) in 20 ml of aqueous solution, add it to the above Na2CO3 solution and stir for 0.5 h, then quickly pour the MgCl2 mixed solution obtained in (1) into the above Na2CO3 mixed solution and stir for 1 h;

[0076] (3) Wash the precipitate obtained in (2) with deionized water and dry it in a drying oven at 100 °C to obtain the metal oxide precursor; it is calcined at 500 °C for 4 h to obtain MgO.

[0077] (4) At room temperature, dissolve 0.0386 g of KNO3 in 657 μl of deionized water; then dropwise add it to a beaker containing 0.2195 g of the sample in (3), stir and impregnate for 24 h, the rotation speed is 200 r / min, then slowly evaporate to dryness in a 50 °C constant temperature water bath and dry it in a drying oven at 100 °C.

[0078] (5) The sample obtained in step (4) is calcined at 500 °C for 4 h to obtain the catalyst K / MgO.

[0079] Example 5

[0080] In this example, the catalyst for the isomerization of the biomass platform molecule angelica lactone is prepared from the following raw materials:

[0081] PVP: 2.0018 g;

[0082] SDS: 0.2886 g;

[0083] LaCl3: 0.5612 g;

[0084] Na2CO3: 0.5995 g;

[0085] KNO3, 0.0388 g; the mass fraction of the KNO3 in the total (La2O3 + KNO3) is 15%;

[0086] (1) Dissolve 2.0018 g of polyvinylpyrrolidone (PVP) in 200 ml of deionized water, take out two portions (20 ml each), and add them to the LaCl3 solution (0.5612 g of LaCl3, 33 ml of deionized water) and Na2CO3

[0087] (0.5995 g of Na2CO3, 50 ml of deionized water) solution and stir vigorously for 0.5 h;

[0088] (2) Dissolve 0.2886 g of sodium dodecyl sulfate (SDS) in 20 ml of aqueous solution, add it to the above Na2CO3 solution and stir for 0.5 h, then quickly pour the LaCl3 mixed solution obtained in (1) into the above Na2CO3 mixed solution and stir for 1 h;

[0089] (3) Wash the precipitate obtained in (2) with deionized water and dry it in an oven at 100 °C to obtain the metal oxide precursor; it is calcined at 700 °C for 1 h to obtain La2O3.

[0090] (4) At room temperature, dissolve 0.0388 g of KNO3 in 657 μl of deionized water; then dropwise add it to a beaker containing 0.2195 g of the sample in (3), stir and impregnate for 24 h, with a rotation speed of 200 r / min, then slowly evaporate to dryness in a 50 °C constant temperature water bath and dry it in an oven at 100 °C.

[0091] (5) Calcinate the sample obtained in step (4) at 500 °C for 4 h to obtain the catalyst K / La2O3.

[0092] Example 6

[0093] In this example, the catalyst for the isomerization of the biomass platform molecule angelica lactone is prepared from the following raw materials:

[0094] PVP: 2.0017 g;

[0095] SDS: 0.2884 g;

[0096] NdCl3·6H2O: 1.1956 g;

[0097] Na2CO3: 0.5300 g;

[0098] KNO3: 0.0389 g; The mass fraction of KNO3 in the total (Nd2O3 + KNO3) is 15%;

[0099] (1) Dissolve 2.0017 g of polyvinylpyrrolidone (PVP) in 200 ml of deionized water. Take out two portions (20 ml each) and add them to the NdCl3·6H2O solution (1.1956 g of NdCl3·6H2O, 33 ml of deionized water) and the Na2CO3 (0.5300 g of Na2CO3, 50 ml of deionized water) solution respectively, and stir vigorously for 0.5 h;

[0100] (2) Dissolve 0.2884 g of sodium dodecyl sulfate (SDS) in 20 ml of aqueous solution, add it to the above Na2CO3 solution and stir for 0.5 h. Then quickly pour the NdCl3·6H2O mixed solution obtained in (1) into the above Na2CO3 mixed solution and stir for 1 h;

[0101] (3) Wash the precipitate obtained in (2) with deionized water and dry it in an oven at 100 °C to obtain the metal oxide precursor; calcine it at 700 °C for 1 h to obtain Nd2O3.

[0102] (4) At room temperature, dissolve 0.0389 g of KNO3 in 657 μl of deionized water; then dropwise add it to a beaker containing 0.2197 g of the sample obtained in (3), stir and impregnate for 24 h at a rotation speed of 200 r / min, then slowly evaporate to dryness in a 50 °C constant temperature water bath and dry it in an oven at 100 °C.

[0103] (5) Calcinate the sample obtained in step (4) at 500 °C for 4 h to obtain the catalyst K / Nd2O3.

[0104] Comparative Example 1

[0105] The preparation method of the catalyst used for the isomerization of the biomass platform molecule angelica lactone in this comparative example is as follows:

[0106] (NH4)2CO3: 3.8417 g;

[0107] ZrOCl2·8H2O: 6.4439 g;

[0108] (1) At room temperature, 3.8417 g of (NH4)2CO3 and 6.4439 g of ZrOCl2·8H2O were ground to a gel-like state in a ratio of 2:1; transferred to a 50 ml autoclave, kept at a constant temperature of 160 °C for 20 h, cooled to room temperature, washed with deionized water until no chloride ions remained, and dried in an oven at 100 °C to obtain a metal oxide precursor;

[0109] (2) The metal oxide precursor obtained in step (1) was calcined at 500 °C for 4 h to obtain m-ZrO2 (monoclinic) Comparative Example 2

[0110] The preparation method of the catalyst for the isomerization of the biomass platform molecule angelica lactone described in this comparative example is as follows:

[0111] NaOH: 3.1995 g;

[0112] ZrOCl2·8H2O: 6.4444 g;

[0113] (1) At room temperature, 3.1995 g of NaOH and 6.4444 g of ZrOCl2·8H2O were ground to a gel-like state in a ratio of 4:1; transferred to a 50 ml autoclave, kept at a constant temperature of 100 °C for 20 h, cooled to room temperature, washed with deionized water until no chloride ions remained, and dried in an oven at 100 °C to obtain a metal oxide precursor;

[0114] (2) The metal oxide precursor obtained in step (1) was calcined at 500 °C for 4 h to obtain t-ZrO2 (tetragonal) Comparative Example 3

[0115] The catalyst for the isomerization of the biomass platform molecule angelica lactone described in this comparative example was directly purchased as a commercial drug ZrO2(IV), and the sample was labeled as c-ZrO2.

[0116] Comparative Example 4

[0117] The catalyst for the isomerization of the biomass platform molecule angelica lactone described in this comparative example was prepared from the following raw materials:

[0118] PVP: 2.0014 g;

[0119] SDS: 0.2884 g;

[0120] MgCl2: 0.4761 g;

[0121] Na2CO3: 0.5299 g;

[0122] (1) Dissolve 2.0014 g of polyvinylpyrrolidone (PVP) in 200 ml of deionized water. Take out two portions (20 ml each) and add them to the MgCl2 solution (0.4761 g of MgCl2, 50 ml of deionized water) and Na2CO3

[0123] (0.5299 g of Na2CO3, 50 ml of deionized water) solution and stir vigorously for 0.5 h;

[0124] (2) Dissolve 0.2884 g of sodium dodecyl sulfate (SDS) in 20 ml of aqueous solution, add it to the above Na2CO3 solution and stir for 0.5 h. Then quickly pour the MgCl2 mixed solution obtained in (1) into the above Na2CO3 mixed solution and stir for 1 h;

[0125] (3) Wash the precipitate obtained in (2) with deionized water and dry it in an oven at 100 °C to obtain the metal oxide precursor; calcine it at 500 °C for 4 h to obtain MgO.

[0126] Comparative Example 5

[0127] The catalyst used for the isomerization of the biomass platform molecule angelica lactone in this comparative example is prepared from the following raw materials:

[0128] PVP: 2.0018 g;

[0129] SDS: 0.2886 g;

[0130] LaCl3: 0.5612 g;

[0131] Na2CO3: 0.5995 g;

[0132] (1) Dissolve 2.0018 g of polyvinylpyrrolidone (PVP) in 200 ml of deionized water. Take out two portions (20 ml each) and add them to the LaCl3 solution (0.5612 g of LaCl3, 33 ml of deionized water) and Na2CO3

[0133] (0.5995 g of Na2CO3, 50 ml of deionized water) solution and stir vigorously for 0.5 h;

[0134] (2) Dissolve 0.2886 g of sodium dodecyl sulfate (SDS) in 20 ml of aqueous solution, add it to the above Na2CO3 solution and stir for 0.5 h. Then quickly pour the LaCl3 mixed solution obtained in (1) into the above Na2CO3 mixed solution and stir for 1 h;

[0135] (3) Wash the precipitate obtained in (2) with deionized water and dry it in an oven at 100 °C to obtain the metal oxide precursor; calcine it at 700 °C for 1 h to obtain La2O3.

[0136] Comparative Example 6

[0137] The catalyst for the isomerization of the biomass platform molecule angelica lactone described in this example is prepared from the following raw materials:

[0138] PVP: 2.0017 g;

[0139] SDS: 0.2884 g;

[0140] NdCl3·6H2O: 1.1956 g;

[0141] Na2CO3: 0.5300 g;

[0142] (1) Dissolve 2.0017 g of polyvinylpyrrolidone (PVP) in 200 ml of deionized water, take out two portions (20 ml each), and add them to the NdCl3·6H2O solution (1.1956 g of NdCl3·6H2O, 33 ml of deionized water) and the Na2CO3 (0.5300 g of Na2CO3, 50 ml of deionized water) solution respectively, and stir vigorously for 0.5 h;

[0143] (2) Dissolve 0.2884 g of sodium dodecyl sulfate (SDS) in 20 ml of aqueous solution, add it to the above Na2CO3 solution and stir for 0.5 h, then quickly pour the NdCl3·6H2O mixed solution obtained in (1) into the above Na2CO3 mixed solution and stir for 1 h;

[0144] (3) Wash the precipitate obtained in (2) with deionized water and dry it in an oven at 100 °C to obtain the metal oxide precursor; calcine it at 700 °C for 1 h to obtain Nd2O3.

[0145] Performance evaluation of the above catalyst: Weigh 1.0 g of α-angelica lactone in a round-bottom flask, control the reaction temperature at 100 °C, the catalyst dosage at 0.1 g, the stirring speed at 500 r / min, and the reaction time at 5 h. The product is analyzed by GC-MS, and the results are calculated using the area normalization method. The conversion rate of α-angelica lactone and the yield of β-angelica lactone are shown in Table 1.

[0146] Table 1 Conversion rate of α-angelica lactone and yield of β-angelica lactone

[0147]

[0148] The results show that: in the present invention, metal oxides ZrO2 with different crystal forms and other metal oxides are used as catalyst matrices, and potassium promoters are selected to modify them by the wet impregnation method, so as to realize the efficient isomerization reaction of α-angelica lactone, and thus highly selectively obtain β-angelica lactone. The preparation method of this catalyst is simple, has a wide application range, and the yield is significantly improved compared with the existing methods, having good industrial application prospects.

[0149] Although the present invention has been described in detail through specific embodiments, those of ordinary skill in the art should understand that any changes in form and details made on this basis without exceeding the scope of protection of the claims belong to the scope of protection of the present invention.

Claims

1. A catalyst for catalytically converting α-angelica lactone into β-angelica lactone, characterized in that, The catalyst comprises a solid metal oxide and a potassium promoter; the solid metal oxide includes any one of m-zirconia, t-zirconia, c-zirconia, alumina, magnesia, barium oxide, lanthanum oxide, and neodymium oxide.

2. The catalyst according to claim 1, wherein The potassium promoter includes any one of potassium nitrate, potassium carbonate, potassium acetate, potassium hydroxide, potassium chloride, potassium oxalate, and potassium oxide.

3. The catalyst according to claim 1, characterized in that: The mass percentage of the potassium promoter and the solid metal oxide is 5-30 wt%.

4. A method for preparing the catalyst according to claim 1, characterized in that, It includes the following steps: (1) Prepare the solid metal oxide, which includes any one of m-zirconia, t-zirconia, c-zirconia, alumina, magnesia, barium oxide, lanthanum oxide, and neodymium oxide; (2) Modify the metal oxide with the potassium promoter.

5. The preparation method according to claim 4, wherein The preparation method of the m-zirconia in step (1) includes the following steps: (1) Using the mechanochemical method, at room temperature, grind (NH4)2CO3 and ZrOCl2·8H2O in a molar ratio of 1-5:1 until it becomes colloidal; transfer it to a 50 ml reaction kettle, keep it at a constant temperature of 80-200 °C for 12-24 h, wait until it cools to room temperature, wash it with deionized water until there is no chloride ion, and dry it in an oven at 80-140 °C to obtain the metal oxide precursor; (2) Calcinate the metal oxide precursor obtained in step (1) at 400-800 °C for 2-10 h to obtain monoclinic m-ZrO2.

6. The preparation method according to claim 4, characterized in that, The preparation method of the t-zirconia in step (1) includes the following steps: (1) Using the mechanochemical method, at room temperature, grind NaOH and ZrOCl2·8H2O in a molar ratio of 1-5:1 until it becomes colloidal; transfer it to a 50 ml reaction kettle, keep it at a constant temperature of 80-200 °C for 12-24 h, wait until it cools to room temperature, wash it with deionized water until there is no chloride ion, and dry it in an oven at 80-140 °C to obtain the metal oxide precursor; (2) Calcinate the metal oxide precursor obtained in step (1) at 400-800 °C for 2-10 h to obtain tetragonal t-ZrO2.

7. The preparation method according to claim 4, characterized in that The preparation method of the solid metal oxides such as alumina, magnesia, barium oxide, lanthanum oxide, and neodymium oxide in step (1) includes the following steps: (1) Using the soft template method, first prepare a 10 g / L aqueous solution of polyvinylpyrrolidone, take out two portions, each portion being 20 ml, and add them separately to 0.1 mol / L, 50 ml of M x Cl y solution and stir vigorously in 0.1 mol / L, 50 ml of Na2CO3 solution for 0.5 h; M is any one of metallic aluminum, magnesium, barium, lanthanum, and neodymium; (2) Add 20 ml of 0.05 mol / L sodium dodecyl sulfate aqueous solution to the above Na2CO3 solution and stir for 0.5 - 2 h. Then, quickly pour the M x Cl y mixed solution into the above Na2CO3 mixed solution and stir for 0.5 - 2 h; (3) Wash the precipitate obtained in (2) with deionized water and dry it in an oven at 80-140 °C to obtain the metal oxide precursor; (4) Calcinate the metal oxide precursor obtained in step (3) at 400 - 800 °C for 2 - 10 h to obtain M x O y .

8. The preparation method according to claim 4, characterized in that, The modification of the metal oxide with the potassium promoter in step (2) specifically includes the following steps: (1) Using the impregnation method, at room temperature, dissolve the potassium promoter in deionized water; then, add the solid metal oxide precursor in proportion, stir and impregnate for 12-24 h, with a rotation speed of 200-500 r / min, then slowly evaporate to dryness in a constant temperature water bath at 50-80 °C, and dry it in an oven at 80-140 °C; (2) Calcinate the sample obtained in step (1) at 400-800 °C for 2-10 h to obtain the catalyst.

9. Use of the catalyst according to any one of claims 1-3 in the catalytic conversion of α-angelica lactone to β-angelica lactone, characterized in that, Under the conditions of normal pressure and open reaction, add the catalyst and α-angelica lactone to a round-bottom flask, and the reaction temperature and time are 60-140 °C and 0.5-12 h; the ratio of the catalyst and α-angelica lactone is 0.05-0.15 mg / ml; the catalytic reaction is carried out under solvent-free conditions.

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