Copper-manganese-silicon composite oxide catalyst and preparation method and application thereof

Abstract

The invention relates to the technical field of fine chemical engineering, in particular to a composite oxide catalyst as well as a preparation method and application thereof. The invention relates to a copper-manganese-silicon composite oxide catalyst for co-production of heliotropin and piperonic acid compounds through oxidative decarboxylation of 2, 4-methylenedioxy phenylethanolic acid compounds, a preparation method thereof and a co-production method. The chemical formula of the catalyst is CuO (x)-MnO2 (y)-SiO2 (1-x-y), wherein based on the total mole of the metal elements, the mole ratio of the copper element is x, the mole ratio of the manganese element is y, the mole ratio of the silicon element is 1-x-y, x is larger than or equal to 0.1 and smaller than or equal to 0.6, and y is larger than or equal to 0.05 and smaller than or equal to 0.4. The Cu-Mn-Si ternary composite oxide catalyst has the advantages that the Cu-Mn-Si ternary composite oxide catalyst provided by the invention shows high catalytic activity on an oxidative decarboxylation reaction of 3, 4-methylenedioxy phenylethanolic acid through a synergistic effect among the components, and the high total selectivity reaches 95% or above. Active components of CuO and MnO2 are effectively dispersed by the silicon dioxide carrier, sintering is prevented, the thermal stability of the catalyst is remarkably improved, and the service life of the catalyst is remarkably prolonged.

Description

Technical Field

[0001] This invention relates to the field of fine chemical technology, specifically to a composite oxide catalyst and its preparation method and application, particularly to a copper-manganese-silicon composite oxide catalyst for the oxidative decarboxylation of 3,4-methylenedioxyphenylethanolic acid compounds to co-produce piperaldehyde and piperic acid compounds, its preparation method, and the co-production method. Background Technology

[0002] Piperanal (3,4-methylenedioxybenzaldehyde) is an important fragrance and organic synthesis intermediate, widely used in perfumes, food flavorings, and pharmaceutical synthesis. Its industrial synthesis mainly involves processes using safrole or catechol as raw materials. While the traditional nitric acid oxidation-decarboxylation method is relatively mature, it presents environmental and safety challenges due to the use of highly corrosive and hazardous concentrated nitric acid, the generation of nitrogen oxide-containing waste gas, and difficult-to-treat nitration byproducts, which does not align with the trend towards green chemistry.

[0003] In recent years, catalytic oxidative decarboxylation processes using oxygen or air as green oxidants have attracted widespread attention. This route uses 3,4-methylenedioxyphenylethanolic acid as a raw material, directly decarboxylating it to piperine under the action of a catalyst. However, this reaction pathway inevitably involves partial over-oxidation to generate the byproduct piperic acid (3,4-methylenedioxybenzoic acid). Existing technologies mostly focus on suppressing side reactions and improving the selectivity of piperine, often treating the generated piperic acid as waste, resulting in resource waste. Piperic acid itself is an important intermediate in the synthesis of various drugs such as ciloxacin and oxoryl acid, and has high economic value.

[0004] Therefore, developing a highly efficient and stable catalyst that can catalyze the oxidative decarboxylation of 3,4-methylenedioxyphenylethanolic acid, and enabling the co-production and controllable adjustment of piperaldehyde and piperic acid by regulating reaction conditions, while simultaneously achieving high-value utilization of by-products, is of great significance for improving the economic and environmental benefits of this process. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a copper-manganese-silicon composite oxide catalyst for the oxidative decarboxylation of 3,4-methylenedioxyphenylethanolic acid compounds and the co-production of piperaldehyde and piperic acid compounds, its preparation method, and the co-production method. The Cu-Mn-Si ternary composite oxide catalyst provided by this invention exhibits high catalytic activity and a high overall selectivity of over 95% in the oxidative decarboxylation reaction of 3,4-methylenedioxyphenylethanolic acid through the synergistic effect between its components. The silica support effectively disperses the CuO and MnO2 active components, preventing sintering and significantly improving the thermal stability and service life of the catalyst.

[0006] This invention is achieved through the following technical solution: a copper-manganese-silicon composite oxide catalyst is provided, the chemical formula of which is CuO. （x） -MnO 2（y） -SiO 2（1-x-y） ; Among them, in terms of the total molar amount of metal elements, the molar percentage of copper is x, the molar percentage of manganese is y, and the molar percentage of silicon is 1-xy, where 0.1≤x≤0.6 and 0.05≤y≤0.4.

[0007] Furthermore, the catalyst was prepared by means of copper precursor salt, manganese precursor salt, silicon precursor salt and inorganic base.

[0008] Furthermore, the copper precursor salt includes one or more of copper nitrate, copper acetate, copper chloride, and copper sulfate; And / or, the manganese precursor salt includes one or more of manganese nitrate, manganese acetate, and manganese chloride; And / or, the silicon precursor salt includes one or more of silica sol, sodium silicate, tetraethyl orthosilicate, and methyl orthosilicate.

[0009] Preferably, the inorganic base is selected from one of sodium hydroxide, sodium carbonate, potassium hydroxide, potassium carbonate, sodium methoxide, and sodium ethoxide.

[0010] Furthermore, after the catalyst is deactivated, it is regenerated by calcination at 500~650℃ in an oxygen atmosphere for 2~5 hours, and the regenerated catalyst can be recycled.

[0011] A method for preparing the above-mentioned copper-manganese-silicon composite oxide catalyst is also provided. The method uses copper precursor salt and manganese precursor salt as active component precursors and silicon precursor salt as support, and obtains the catalyst through impregnation, drying, calcination and activation.

[0012] Finally, a method for preparing piperine and piperic acid compounds is provided. This method uses 3,4-methylenedioxyphenylethanolic acid compounds as raw materials and uses the copper-manganese-silicon composite oxide catalyst described in any one of claims 1-5 to carry out an oxidative decarboxylation reaction in an oxygen-rich atmosphere and an inorganic base environment to obtain piperine and piperic acid compounds.

[0013] Furthermore, the oxygen-enriched condition is oxygen or an oxygen-rich mixed gas, wherein the oxygen content in the mixed gas is not less than 0.5%, and the specific synthesis route is as follows: ; In the formula, structural formula (I) is a 3,4-methylenedioxyphenylethanol acid compound; structural formula (II) is a piperaldehyde compound; structural formula (III) is a piperic acid compound; R1, R2, and R3 are low molecular weight alkyl groups or hydrogen groups with 4 or fewer carbon atoms.

[0014] Furthermore, the oxidative decarboxylation reaction is carried out under the conditions of the inorganic base, at a reaction temperature of 40~95℃, and for a reaction time of 0.5~5h.

[0015] Further, after the oxidative decarboxylation reaction is completed, the mixture is cooled to room temperature and filtered to remove the catalyst. Then, the pH of the reaction filtrate is adjusted to 1-2 using an inorganic acid or its diluted solution. The reaction filtrate is then extracted with an extractant. After extraction, the product of structural formula (II) is distilled off using a conventional negative pressure distillation method. Based on the presence of compounds of structural formula (III) in the distillation vessel residue, 2 to 4 times the amount of ethanol was added to the distillation vessel residue and boiled, and then cooled to below 0°C to crystallize out the compounds of structural formula (III). And / or, the extractant is selected from one or more of methyl isobutyl ketone, ethyl acetate, toluene, xylene, and ethers.

[0016] Beneficial effects The Cu-Mn-Si ternary composite oxide catalyst provided by this invention exhibits high catalytic activity and a high overall selectivity (over 95%) in the oxidative decarboxylation reaction of 3,4-methylenedioxyphenylethanolic acid through the synergistic effect between its components. The silica support effectively disperses the CuO and MnO2 active components, preventing sintering and significantly improving the catalyst's thermal stability and lifespan. Using water and air as the main reaction medium and oxidant avoids the safety and environmental risks of the traditional nitric acid process, resulting in less waste and conforming to green chemistry principles. Simultaneously, it converts the original byproduct, piperic acid, into a high-value co-product, improving the overall economic efficiency of the process.

[0017] By adjusting parameters such as reaction temperature and time, the yield ratio of piperine to piperic acid can be controlled within a certain range, increasing production flexibility and adapting to changes in market demand. The catalyst exhibits good stability, can be reused multiple times in batch reactions, and can be efficiently regenerated through simple calcination after deactivation. It can also achieve long-term continuous operation in fixed-bed reactors, significantly reducing catalyst usage costs and demonstrating promising prospects for industrial application. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the oxidative decarboxylation reaction route used in the embodiments of the present invention; Figure 2 The catalyst CuO in the examples (0.3) -MnO 2(0.15) -SiO 2(0.55)A schematic diagram of the overall selectivity change curve after multiple applications and regeneration.

[0019] In the diagram, 1-Air pump; 2-Condenser A; 3-Reaction vessel; 4-Precision filter I; 5-Neutralization vessel; 6-Packed extraction tower; 7-Distillation tower A; 8-Condenser B; 9-Distillation tower B; 10-Condenser C; 11-Recrystallization vessel A; 12-Precision filter II; 13-Recrystallization vessel B. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0021] Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or as recommended by the manufacturer. Unless otherwise stated, all percentages, ratios, proportions, or parts are by weight.

[0022] Unless otherwise specified, the reagents and raw materials used in the embodiments and comparative examples of this invention are commercially available.

[0023] 1. Raw materials 3,4-Methylenedioxyphenylethanolic acid and its derivatives: prepared in the laboratory, using piperine rings and other raw materials, reacted with glyoxylic acid under concentrated sulfuric acid catalysis, and purified by conventional methods, with a purity ≥99.0%.

[0024] Chemicals used in catalyst preparation: The silicon source was purchased from Guangzhou Lingwei Technology Group Co., Ltd., using HOMSOL® brand silica sol, neutral LZ series, with a solid content of 30% and a particle size of 8-16nm; The solid silica is SP15 nano-sized silica with a particle size of 15±5nm; The nano-copper oxide has an average particle size of 40nm, was purchased from Qinghe County Chaotai Metal Materials Co., Ltd., and has a purity of ≥99.5%. The ultrafine manganese dioxide was purchased from Qinghe County Chaotai Metal Materials Co., Ltd., with the grade ML-MnO2-N500 and a purity ≥99.0%.

[0025] 2. Detection Method Piperaldehyde purity: The detection conditions for gas chromatography area normalization are as follows: Column: 50% phenylmethyl polysiloxane capillary column, 30m × 0.32mm × 0.25μm (or other similar equivalent column); Detector: flame ionization detector; Column oven temperature: 150℃ for 15min, then increased to 230℃ at 20℃ / min and held for 11min; Detector temperature: 250℃; Injector temperature: 230℃; Carrier gas (nitrogen) flow rate: 1mL / min; Fuel gas (hydrogen) flow rate: 30mL / min.

[0026] Reaction solution and piperic acid content: The detection conditions for high performance liquid chromatography with external standard method are as follows: detector: ultraviolet detector; column: C18, 150 mm × 3.9 mm; mobile phase: methanol-acetic acid aqueous solution; flow rate: 0.8 mL / min; column temperature: 30 ℃; wavelength: 277 nm; injection volume: 10 μL.

[0027] Catalyst Examples A method for preparing a copper-manganese-silicon composite oxide catalyst involves taking 75.02 g (0.4 mol) of copper nitrate and 35.79 g (0.2 mol) of manganese nitrate (50% aqueous solution), adding 200 ml of water, and adding 80.11 g of silica sol while stirring. The stirring continues, maintaining a temperature of 20-30℃. A 10% sodium hydroxide solution is added dropwise to adjust the pH to 8-9 over approximately 30 min. The reaction is continued with stirring for 2 h, followed by aging for 10 h. The mixture is then filtered, and the filter cake is transferred to a muffle furnace and calcined at 550℃ for 5 h in air. After cooling to room temperature, a black catalyst, denoted as CuO, is obtained. （0.4） -MnO 2（0.2） -SiO 2（0.4） .

[0028] CuO was prepared using the same method. （0.4） SiO 2（0.6） MnO 2（0.2） -SiO 2（0.8） CuO （0.3） -MnO 2（0.3） -SiO 2（0.4） CuO （0.2） -MnO 2（0.4） -SiO 2（0.4） CuO （0.5） -MnO 2（0.1） -SiO 2（0.4） and CuO （0.4） -MnO 2（0.2） CuO （0.30） -MnO 2（0.15） -SiO 2（0.55） CuO （0.2） -MnO 2（0.1） -SiO 2（0.7） CuO（0.5） -MnO 2（0.25） -SiO 2（0.25） CuO （0.6） -MnO 2（0.3） -SiO 2（0.1） .

[0029] Catalyst Comparative Example Using a physical blending method, 31.82 g (0.4 mol) of nano-copper oxide, 17.39 g (0.2 mol) of ultrafine manganese dioxide, and 24.03 g (0.4 mol) of nano-silica were mixed evenly in a mixer, and the mixture was denoted as M / CuO. （0.4） -MnO 2（0.2） -SiO 2（0.4） .

[0030] Application Examples A method for preparing piperine and piperic acid compounds by co-production is as follows: 50g of 3,4-methylenedioxyphenylethanolic acid is added to a three-necked flask, along with 200g of water. The mixture is magnetically stirred, and a certain amount of 30% sodium hydroxide is slowly added to adjust the pH to 10.5-11.0. Stirring continues until the raw material is completely dissolved. 2.5g of catalyst is added, and air is continuously introduced from the bottom of the three-necked flask at a rate of 60L / min using an air pump. The exhaust gas is discharged through a reflux condenser. The mixture is heated to 55℃ in a water bath to initiate the reaction. Samples are taken every 30 minutes for testing. The reaction is stopped when the residual amount of raw material is less than 0.1%. The mixture is then stirred and cooled, and the reaction time is recorded. The selectivity of piperine and piperic acid is calculated.

[0031]

[0032] Where w is the weight of the reaction solution after deducting the weight of the added catalyst; a is the detected value of the raw material in the reaction solution; b is the detected value of piperaldehyde in the reaction solution; and c is the detected value of piperic acid in the reaction solution.

[0033] A method for preparing piperine and piperic acid compounds, such as... Figure 1As shown, 3,4-methylenedioxyphenylethanolic acid, deionized water, and an inorganic base are weighed and added to reactor 3. The stirring device is started, and the stirring speed is controlled to ensure complete dissolution of the materials, forming a homogeneous alkaline aqueous solution. A specified amount of copper-manganese-silicon composite oxide catalyst is added to the above solution. Air pump 1 is started, and air is continuously and stably introduced into the bottom of the reactor at a set flow rate through a gas distributor. The reactor jacket heating is turned on to control and maintain the temperature of the reaction system at a predetermined value. Volatile substances generated during the reaction are fully condensed by condenser A2 and returned to the reaction system, while non-condensable tail gas is discharged. The conversion rate of raw materials and the distribution of products are monitored by periodic sampling and analysis. When the residual amount of raw materials is lower than the set threshold, the reaction endpoint is determined. After the reaction is completed, heating and aeration are stopped, and the cooling system is started to cool the reaction mixture to room temperature or the set temperature. Subsequently, the reaction slurry is pumped or pressurized into precision filter I4 for solid-liquid separation. The filter cake is collected and stored for later use. It can be sent to a regeneration furnace for calcination and regeneration at 500-650℃ in an aerobic atmosphere for 2-5 hours before being recycled. The collected filtrate was transferred to neutralization vessel 5. While stirring, an inorganic acid solution was slowly and gradually added to the vessel, with the pH value monitored in real time until it stabilized within the range of 1-2. This operation converts the water-soluble sodium salt into free piperine and piperic acid.

[0034] The acidified aqueous phase is pumped to the designated inlet of packed extraction column 6. Simultaneously, the selected extractant is pumped in from the other end of the column, forming a countercurrent contact with the aqueous phase. The flow rates of the two phases are adjusted to achieve sufficient mass transfer within the packed column, allowing the target product to be efficiently transferred to the organic phase. After operation stabilizes, the product-rich organic phase is collected from the top of the column, and the raffinate aqueous phase is discharged from the bottom. After the raffinate aqueous phase is tested and confirmed to meet the target product content standard, it is then subjected to subsequent wastewater treatment or reused. The extractant is fed into distillation column A7. The vacuum system is activated to maintain the pressure inside the column at a slightly negative pressure. By controlling the heating of the column bottom, most of the extractant evaporates and is condensed and recovered by condenser B8. The recovered extractant can be returned to packed extraction column 6 as fresh extractant for recycling. The concentrate, after removing a large amount of solvent, mainly consists of piperaldehyde and piperic acid, is transferred to distillation column B9. Precision fractionation is performed under a higher vacuum. By precisely adjusting the heating power of the reboiler and the reflux ratio at the top of the column, the light components and residual solvent are first distilled off and collected as the fore-distillate. Subsequently, the main distillate is collected, and its condensate (after passing through condenser C10) is the high-purity piperonal product, with a purity of not less than 99.0% as tested.

[0035] Transfer the residue from distillation column B9 to recrystallization vessel A11. Add 2-4 times (by weight) of ethanol to the vessel and heat to boiling with stirring to completely dissolve the residue. Stop heating and start programmed temperature control cooling to slowly cool the solution at a low rate. When the temperature drops to near the crystallization point, a small amount of piperic acid seed crystals can be added to induce crystallization. Continue cooling to around 0°C and maintain this temperature for aging for a period of time. Pump the resulting crystal slurry into precision filter II12 for solid-liquid separation to obtain wet piperic acid (crude product). Put the obtained wet product into recrystallization vessel B13, add an appropriate amount of fresh ethanol, and heat again to dissolve. Then perform programmed temperature cooling crystallization and filtration. After vacuum drying, white needle-like high-purity piperic acid crystals are obtained with a purity of not less than 98.0%. The recrystallization mother liquor can be concentrated to recover some ethanol and piperic acid and reused to improve the overall yield.

[0036] In summary, this process uses 3,4-methylenedioxyphenylethanolic acid as raw material and, under alkaline conditions and with the aid of a copper-manganese-silicon composite oxide catalyst, utilizes air for catalytic oxidation and decarboxylation to co-produce piperaldehyde and piperic acid. It provides an efficient, clean, and economical technical route for the co-production of piperaldehyde and piperic acid, and has broad prospects for industrial application.

[0037] The results of experiments conducted using different catalysts are summarized below:

[0038] A comparison of Examples 1-12 shows that the three-element composite catalyst has a greater advantage in terms of overall selectivity. Increasing the proportion of Mn oxides in the catalyst can improve the selectivity of piperic acid and, to some extent, increase the reaction efficiency. The reaction rate and the selectivity of piperic acid are directly proportional to the proportion of active metal oxides in the catalyst; the higher the proportion, the faster the reaction rate and the higher the selectivity of piperic acid, but the overall selectivity decreases. For example, CuO... （0.4） -MnO 2（0.2） -SiO 2（0.4） Taking the catalyst as an example, the reaction time was extended by 2 hours, 4 hours, and 6 hours, and samples were taken for testing. The selectivity of piperaldehyde and piperic acid at different reaction times was calculated, and the results are summarized below:

[0039] In summary, the comparison shows that the selectivity of piperic acid increases with the extension of reaction time, but the overall selectivity steadily decreases, indicating that certain byproducts occur during the conversion of piperaldehyde to piperic acid.

[0040] The catalyst lifespan was investigated using CuO. （0.30） -MnO 2（0.15） -SiO 2（0.55） and CuO （0.4）-MnO 2（0.2） -SiO 2（0.4） Two catalysts were applied directly without any treatment, and their performance changes were observed. The experimental results are summarized below:

[0041] Summary: Catalyst CuO （0.30） -MnO 2（0.15） -SiO 2（0.55） It has a relatively stronger resistance to toxicity and still has a total selectivity of over 85% after being applied 4 times. However, the reaction time is significantly longer. To ensure production efficiency, roasting and regeneration can be carried out.

[0042] The obviously deactivated catalyst was placed in a muffle furnace for calcination in air at a temperature of 550°C for 4 hours. After calcination, the catalyst was reused, and its performance changes were observed. The results are summarized below:

[0043] Summary: CuO （0.30） -MnO 2（0.15） -SiO 2（0.55） The activity recovery is relatively better because the proportion of metal oxides in this catalyst is relatively small, resulting in better dispersion of the active components, while CuO... （0.30） -MnO 2（0.15） -SiO 2（0.55） Observation of the metal oxides using transmission electron microscopy revealed that the particle size of the metal oxides was significantly larger.

[0044] We continue our investigation of the catalyst CuO （0.30） -MnO 2（0.15） -SiO 2（0.55） The method was repeated, with roasting and regeneration performed every three uses, for a total of 10 cycles. The results are summarized below:

[0045] In summary, the catalyst maintained a high level of activity even after being used 10 times consecutively.

[0046] Comparative application examples: Using self-made 2-hydroxy-2-(7-methyl-1,3-benzodioxane-5-yl)acetic acid, 2-hydroxy-2-(4-methyl-1,3-benzodioxane-5-yl)acetic acid, and 2-hydroxy-2-(6-methyl-1,3-benzodioxane-5-yl)acetic acid as raw materials, and CuO was used as the raw material. （0.30） -MnO 2（0.15） -SiO 2（0.55） The catalyst was used in the reaction, and oxidative decarboxylation was carried out under the same reaction conditions. The results are summarized below:

[0047] In summary, the catalyst prepared in this patent also showed good reaction results in the oxidative decarboxylation reaction of 3,4-methylenedioxyphenylethanolic acid.

[0048] Post-processing example: After mixing a portion of the reaction filtrate, the pH was adjusted to 1 with a 36-38% hydrochloric acid solution. The analysis revealed a piperine content of 14.43% and a piperic acid content of 1.88%. 1000g of this neutralized solution was extracted four times with 150g of methyl isobutyl ketone, yielding a total of 496.52g of oil phase and 947.01g of aqueous phase, resulting in a loss of 6.47g. The piperine and piperic acid contents in the aqueous phase after extraction were 0.079% and 0.054%, respectively, with extraction rates of 99.48% and 97.26%, respectively. The extracted oil phase was transferred to a rotary evaporator, and the extractant was distilled off and reused under slight negative pressure. The residue from the rotary evaporation was then... The product was transferred to a distillation column. The distillation column was a packed column with an inner diameter of approximately 24 mm, and the packing material was φ3-5 mm stainless steel high-efficiency packing with an effective packing height of 35 cm. Under vacuum conditions of -0.98 MPa, the temperature of the bottom of the distillation vessel was adjusted to 40-45℃, and the reflux ratio was 3:1. 23.19 g of the fore-distillate was obtained. Detection by gas chromatography using the area normalization method showed that the content of piperaldehyde was 93.45%, and the other substances were methyl isobutyl ketone and by-product light impurities. 115.46 g of piperaldehyde product was obtained, with a product purity of 99.3%. The distillation yield of piperaldehyde was 80.43%, with the main loss occurring in the fore-distillate. The fore-distillate can be reused to improve the distillation yield.

[0049] After the distillation vessel residue was cooled to about 50°C, 60g of ethanol was added, and the mixture was heated to boiling with stirring to completely dissolve the residue. The mixture was then slowly cooled with stirring at a rate of 0.2°C / min. When the temperature reached 31°C, 0.1g of seed crystals was added, and the mixture was stirred and cooled further until it reached a minimum of 0°C. After aging at this temperature for 2 hours, the mixture was filtered. The wet product was light red needle-like crystals. The filter cake was placed in a vacuum drying oven and dried under vacuum at 50°C for 5 hours. The dried product was light red needle-like crystals, yielding 16.21g of dried product with a purity of 94.48%. After recrystallization with 30g of ethanol, the dried product was white needle-like crystals, and the weight of the piperic acid product was 14.62g with a purity of 98.78%. The high-purity piperic acid separation yield was 79.98%. The yield can be improved to some extent by reusing the recrystallization mother liquor.

[0050] In summary, the copper-manganese composite metal oxide catalyst exhibits higher reaction efficiency compared to single metal oxides, indicating that copper-manganese oxides possess a certain synergistic catalytic effect. Manganese oxides have relatively stronger oxidizing properties; the higher the proportion of manganese oxides in the catalyst, the higher the selectivity for piperic acid. The selectivity of piperaldehyde and piperic acid can be adjusted by regulating the ratio of copper oxides to manganese oxides in the composite catalyst, thus broadening the catalyst's applicability. Furthermore, due to the introduction of silica as a support, the catalyst prepared by precipitation allows copper, manganese, and silicon to form a more complex pore structure compared to direct physical mixing, resulting in higher reaction efficiency and a longer catalyst lifespan.

[0051] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A copper-manganese-silicon composite oxide catalyst, characterized in that, The chemical formula of the catalyst is CuO. （x） -MnO 2（y） -SiO 2（1-x-y） ; Among them, in terms of the total molar amount of metal elements, the molar percentage of copper is x, the molar percentage of manganese is y, and the molar percentage of silicon is 1-xy, where 0.1≤x≤0.6 and 0.05≤y≤0.

4.

2. The copper-manganese-silicon composite oxide catalyst according to claim 1, characterized in that, The catalyst was prepared by using copper precursor salt, manganese precursor salt, silicon precursor salt, and inorganic base.

3. The copper-manganese-silicon composite oxide catalyst according to claim 2, characterized in that, The copper precursor salt includes one or more of copper nitrate, copper acetate, copper chloride, and copper sulfate; And / or, the manganese precursor salt includes one or more of manganese nitrate, manganese acetate, and manganese chloride; And / or, the silicon precursor salt includes one or more of silica sol, sodium silicate, tetraethyl orthosilicate, and methyl orthosilicate.

4. The copper-manganese-silicon composite oxide catalyst according to claim 2, characterized in that, The inorganic base is selected from one of sodium hydroxide, sodium carbonate, potassium hydroxide, potassium carbonate, sodium methoxide, and sodium ethoxide.

5. The copper-manganese-silicon composite oxide catalyst according to claim 1, characterized in that, After the catalyst is deactivated, it is regenerated by calcination at 500~650℃ in an oxygen atmosphere for 2~5 hours. The regenerated catalyst can be recycled.

6. A method for preparing a copper-manganese-silicon composite oxide catalyst according to any one of claims 2-5, characterized in that, This method uses copper and manganese precursor salts as active precursors and silicon precursor salt as a carrier, and obtains the product through impregnation, drying, calcination and activation.

7. A method for preparing piperine and piperic acid compounds, characterized in that, This method uses 3,4-methylenedioxyphenylethanolic acid compounds as raw materials and employs the copper-manganese-silicon composite oxide catalyst described in any one of claims 1-5 to carry out an oxidative decarboxylation reaction in an oxygen-rich atmosphere and an inorganic base environment to obtain piperine and piperic acid compounds.

8. The method for preparing piperine and piperic acid compounds according to claim 7, characterized in that, The oxygen-enriched condition refers to oxygen or an oxygen-rich mixed gas, wherein the oxygen content in the mixed gas is not less than 0.5%. The specific synthesis route is as follows: ； In the formula, structural formula (I) is a 3,4-methylenedioxyphenylethanol acid compound; structural formula (II) is a piperaldehyde compound; structural formula (III) is a piperic acid compound; R1, R2, and R3 are low molecular weight alkyl groups or hydrogen groups with 4 or fewer carbon atoms.

9. The method for preparing piperine and piperic acid compounds according to claim 7, characterized in that, The oxidative decarboxylation reaction is carried out under the conditions of the inorganic base, at a reaction temperature of 40~95℃, and for a reaction time of 0.5~5h.

10. The method for preparing piperine and piperic acid compounds according to claim 9, characterized in that, After the oxidative decarboxylation reaction is completed, the mixture is cooled to room temperature and then filtered to remove the catalyst. The pH of the reaction filtrate is then adjusted to 1-2 using an inorganic acid or its diluted solution. The reaction filtrate is then extracted with an extractant. After extraction, the product of structural formula (II) is distilled off using a conventional negative pressure distillation method. Based on the presence of compounds of structural formula (III) in the distillation vessel residue, 2 to 4 times the amount of ethanol was added to the distillation vessel residue and boiled, and then cooled to below 0°C to crystallize out the compounds of structural formula (III). And / or, the extractant is selected from one or more of methyl isobutyl ketone, ethyl acetate, toluene, xylene, and ethers.

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