Cyclic regeneration method of catalyst for preparing 3, 3-dialkoxy propyl compound

Abstract

The invention discloses a cyclic regeneration method of a catalyst for preparing a 3, 3-dialkoxy propyl compound, which comprises the following steps: reacting an allyl compound with nitrite under the action of the catalyst, adding a reducing agent into the reaction system after the reaction is finished, filtering, and continuously rectifying the filtrate to obtain the 3, 3-dialkoxy propyl compound. The filter residues are oxidized by an oxidizing agent under the action of acid to generate a catalyst, and the catalyst is a bivalent palladium catalyst or a mixture of the bivalent palladium catalyst and a bivalent copper catalyst. An oxidizing agent and a reducing agent are added into a reaction system, so that the conversion of deactivation and reactivation of the catalyst is realized, coordination ions of the catalyst are provided by acid, and the cyclic regeneration of the catalyst is realized under the action of the oxidizing agent.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis technology, specifically to a method for recycling and regenerating catalysts used in the preparation of 3,3-dialkoxypropyl compounds. Background Technology

[0002] 3,3-Dialkoxypropyl compounds are important C3 synthons, including but not limited to methyl 3,3-dimethoxypropionate, ethyl 3,3-diethoxypropionate, 3,3-dimethoxypropionitrile, and 3,3-diethoxypropionitrile. They have wide applications in industry: in the pharmaceutical industry, they are the mainstream raw materials for synthesizing pyrimidine compounds such as cytosine and uracil; in the pesticide industry, they are often used to prepare pyrazole ring compounds; in the fragrance industry, they can be used as a potential raw material for preparing coumarins; in addition, they can also be used in the resin industry for the synthesis of resins, coatings, coating agents, adhesives, and flexible plastics.

[0003] Given the above, the importance of a green and low-cost industrial production method for 3,3-dialkoxypropyl compounds is self-evident. Chinese patent document CN102633680A discloses a series of methods for preparing 3,3-dialkoxypropyl compounds by reacting allyl compounds with oxygen under the catalysis of Pd(II) compounds. While this method offers advantages such as low raw material costs, high reaction selectivity, and high yield, it suffers from the following technical drawbacks: moisture in the system easily leads to hydrolysis of the catalyst and product, significantly shortening the catalyst's lifespan; free chloride ions in the reaction system are corrosive to the reaction equipment, greatly increasing equipment maintenance costs and safety risks; oxygen concentration is difficult to control precisely, posing significant safety hazards; and frequent side reactions occur during the liquid-phase reaction, resulting in reduced selectivity of the target product. Therefore, this process cannot meet the requirements of green chemistry and is difficult to achieve large-scale continuous clean production.

[0004] To overcome the above-mentioned defects, Chinese patent document CN112457215A discloses a process for preparing 3,3-dialkoxypropyl compounds using methyl nitrite and allyl compounds as raw materials via a "gas-phase method" to replace the "oxygen process". The aforementioned "gas-phase method" produces target products such as methyl 3,3-dimethoxypropionate or 3,3-dimethoxypropionitrile through the reaction of reactant gases containing raw materials in a fixed catalyst bed, offering advantages such as continuous operation, automation, and safety. However, this process has the following drawbacks: First, due to substrate activity limitations, the single-pass conversion rate of the raw materials is typically less than 20%, significantly increasing the difficulty of subsequent separation; second, because the substrates methyl acrylate or acrylonitrile are chemically unstable and prone to polymerization, the resulting polymers can deposit and cover the active sites of the catalyst, leading to catalyst deactivation and severely restricting the industrial application of this process.

[0005] To address the inherent problem of substrate polymerization, a technical scheme for preparing 3,3-dialkoxypropyl compounds via a "liquid-phase method" was reported in references 1-3 (The Chemical Society of Japan, 1994, 7, 667-673; Res. Chem. Intermed, 1998, 24, 2, 213-225; Petrotech, 1992, 15, 6, 564-568). However, this technical scheme still faces challenges, as the Pd(II) catalyst cannot be recycled through simple separation. The formation of high-boiling substances during the reaction and the gradual conversion of the Pd(II) catalyst into other inactive Pd compounds during catalysis prevent the direct recycling of the Pd(II) catalyst through simple separation. Furthermore, the high cost of Pd catalysts limits the industrial viability of this technical scheme.

[0006] While references 1-3 disclose a process for preparing 3,3-dialkoxypropionate from nitrite and methyl acrylate, and propose a reduction method to recover Pd(II) catalyst to obtain Pd black, the recovered Pd black lacks catalytic activity and cannot be directly used in subsequent reactions. This leaves the technical problem of catalyst recycling unresolved. Therefore, converting Pd black into Pd(II) catalyst at low cost is the core technical point for achieving catalyst recycling.

[0007] Currently, the mainstream methods for recovering Pd black into Pd(II) compounds include those disclosed in patents such as CN201610763052.3 and CN201110108313.5, which involve dissolving in aqua regia, concentrating to remove nitrates, and drying to prepare Pd(II) compounds, or reacting palladium black with HCl-peroxide to prepare Pd(II) compounds; and the method reported in reference 4 (J. Chem. Soc, 1949, 3135-3141) which uses Pd black and nitrite chloride as raw materials to prepare Pd(II) compounds. Although the above-mentioned existing technologies can realize the conversion of Pd black into Pd(II) catalysts, they have technical problems such as high equipment requirements, cumbersome process steps, difficult separation, and high cost.

[0008] Therefore, there is an urgent need to find a method for recycling and regenerating the catalyst used in the preparation of 3,3-dialkoxypropyl compounds. Summary of the Invention

[0009] To address the aforementioned technical problems, this invention provides a method for the recycling and regeneration of catalysts used in the preparation of 3,3-dialkoxypropyl compounds. This method involves adding a reducing agent to the reaction system to recover the main components of the catalyst. The recovered catalyst components are then oxidized under acidic conditions using an oxidizing agent to transform back into the catalyst.

[0010] A method for recycling and regenerating a catalyst used in the preparation of 3,3-dialkoxypropyl compounds includes the following steps: Allyl compounds are reacted with nitrite esters in the presence of a catalyst. After the reaction is complete, a reducing agent is added to the reaction system, and the mixture is filtered. The filtrate is then further distilled to obtain 3,3-dialkoxypropyl compounds. The filter residue is oxidized by an oxidizing agent in the presence of acid to generate a catalyst.

[0011] The catalyst is a divalent palladium catalyst, or a mixture of a divalent palladium catalyst and a divalent copper catalyst.

[0012] The divalent palladium catalyst and divalent copper catalyst can be prepared in the reaction system using low-valent palladium and copper compounds under acidic conditions.

[0013] The low-valent compound can be selected from at least one of elemental palladium, elemental copper, and monovalent copper compounds. These low-valent compounds, together with acids as ligands, can generate divalent palladium and divalent copper catalysts in situ under the oxidation of nitrite esters.

[0014] In this invention, the main components of the catalyst can be recovered by adding a reducing agent to the reaction system; the recovered main components of the catalyst are then converted into a catalyst by an oxidizing agent under acidic conditions.

[0015] The catalyst of this invention is a divalent palladium catalyst, or a mixture of a divalent palladium catalyst and a divalent copper catalyst. When a mixed catalyst is used, the divalent palladium catalyst is the main catalyst, and the divalent copper catalyst is the co-catalyst, the latter accelerating the reaction process.

[0016] Preferably, the oxidant is at least one selected from oxygen, ozone, hydrogen peroxide, chlorine, divalent copper, nitrite, nitric acid, aqua regia, nitrosyl chloride, nitryl chloride, persulfate, hypohalite, halide, and perhalite.

[0017] Preferably, when the catalyst is a mixture of divalent palladium and divalent copper catalysts, the reaction system is reduced and then filtered to obtain palladium-containing filter residue; the filtrate is further desolvated to precipitate copper-containing precipitate, which is then filtered to obtain copper-containing filter residue. The palladium-containing filter residue and the copper-containing filter residue are then oxidized by an oxidant under acidic conditions to generate divalent palladium and divalent copper catalysts.

[0018] More preferably, the palladium-containing filter residue and the copper-containing filter residue can be oxidized separately or together to obtain a divalent palladium catalyst and a divalent copper catalyst, or a mixture thereof.

[0019] More preferably, when the solvent used in the oxidation step is the same as the solvent used to prepare the 3,3-dialkoxypropyl compound, in order to simplify the reaction steps, palladium-containing filter residue, copper-containing filter residue, and acid as a ligand can be directly added to the reaction system for reaction.

[0020] Preferably, the acid is an organic acid or an inorganic acid, or its anhydride or acyl chloride.

[0021] In this invention, the acid can be sulfuric acid, hydrochloric acid, nitric acid, nitrous acid, phosphoric acid, sulfur trioxide (SO3), hydrogen chloride (HCl), dinitrogen pentoxide (N2O5), dinitrogen trioxide (N2O3), phosphorus pentoxide (P2O5), sulfonyl chloride, nitryl chloride, nitrosyl chloride, phosphorus oxychloride, C1-C4 organic acids, and their corresponding anhydrides or acyl chlorides. In this invention, the acid used for catalyst regeneration can be selected based on the acid anion added to the catalyst.

[0022] Preferably, the divalent palladium catalyst and the divalent copper catalyst are compounds formed by divalent palladium ions or divalent copper ions and acid radical ions, respectively, or complexes formed by the compounds and ligands.

[0023] Preferably, the ligand can be a cyano ligand, such as acetonitrile or benzonitrile; an amine-containing ligand, such as ammonia, ethylenediamine, pyridine, bipyridine, or isoquinoline; or a phosphorus ligand, such as 1,1'-diphenylphosphine, triphenylphosphine, di-tert-butylphosphine chloride, tricyclohexylphosphine, or diphenylphosphine phenyl ether.

[0024] In this invention, both the divalent palladium catalyst and the divalent copper catalyst can be compounds formed by divalent palladium ions or divalent copper ions and acid radical ions, such as palladium chloride, palladium sulfate, palladium nitrate, palladium acetate, copper chloride, ketone nitrate, copper acetate, and ketone sulfate. They can also be complexes formed by the compound and ligands, such as PdCl2(pph3)2, PdCl2(CH3CN)2, and PdCl2(NH2CH2CH2NH2)2.

[0025] More preferably, when the divalent palladium catalyst and divalent copper catalyst are complexes, corresponding ligand compounds need to be added during or after the oxidation of the filter residue.

[0026] More preferably, the filter residue can also be regenerated into a catalyst through a gas-solid phase reaction.

[0027] Preferably, the reducing agent is at least one selected from hydrogen, formic acid, borohydride, lithium aluminum hydride, hydrazine hydrate, C1-C4 alcohols, C1-C4 aldehydes, and allyl compounds.

[0028] Preferably, the molar ratio of the catalyst to the reducing agent is 1:0.25~100.

[0029] Preferably, the molar ratio of the catalyst to the oxidant is 1:0.25~100.

[0030] Preferably, the temperature for reacting with the reducing agent is 20~150℃, and the temperature for reacting with the oxidizing agent is 20~150℃.

[0031] Preferably, the structure of the allyl compound is as follows: R1 is selected from cyano, carboxyl, C2-C5 ester, C1-C5 amide, and C6-C9 aryl.

[0032] Preferably, the structure of the nitrite is as follows: R2 is selected from C1 to C4 alkyl groups.

[0033] Preferably, the molar ratio of the allyl compound to the nitrite is 1:1 to 20.

[0034] Preferably, the reaction temperature of the allyl compound with the nitrite is 20~150 °C.

[0035] More preferably, the reducing agent is an allyl compound, and the oxidizing agent is a nitrite.

[0036] In this invention, the reducing agent and oxidizing agent can be selected from the reaction raw materials allyl compound and nitrite ester, respectively. There is no need to introduce new compounds into the reaction system, and the regenerated catalyst can be recycled indefinitely. This improves the atom economy of the reaction while reducing the consumption of catalyst, thereby achieving the green preparation of 3,3-dialkoxypropyl compound.

[0037] The molar ratio of the catalyst to the allyl compound is 1:50~5000.

[0038] The solvent for the reaction of the allyl compound with the nitrite is at least one of the following: C1-C4 alcohols, C2-C6 nitriles, C2-C6 ethers, C3-C8 ketones, C2-C6 esters, C1-C6 haloalkanes, benzene, alkyl and / or halogen-substituted benzenes, C4-C8 alkanes, or cycloalkanes.

[0039] Preferably, the solvent for the reaction of the filter residue with the oxidant is at least one of water, C1-C4 alcohols, C2-C6 nitriles, C2-C6 ethers, C3-C8 ketones, C2-C6 esters, C1-C6 haloalkanes, benzene, alkyl and / or halogen-substituted benzene, C4-C8 alkanes, or cycloalkanes.

[0040] The C1 to C4 alcohols mentioned above can be methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol, ethylene glycol, 1,2-propanediol, 1,3-propanediol, glycerol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, and 1,2,4-butanetriol. The aforementioned C2~C6 nitrile can be acetonitrile, 1-propionitrile, 2-propionitrile, 1-butyronitrile, 2-methylpropionitrile, cyclopropylformonitrile, 1,4-butadionitrile, 1-pentanitrile, 2-methylbutyronitrile, 3-methylbutyronitrile, 2,2-dimethylpropionitrile, cyclopropylacetonitrile, 1,5-adiponitrile, 1-hexanenitrile, 2-methylpentanitrile, 3-methylpentanitrile, 4-methylpentanitrile, 2,2-dimethylbutyronitrile, 2,3-dimethylbutyronitrile, 2-ethylbutyronitrile, 3-ethylbutyronitrile, cyclobutylformonitrile, cyclopropylacetonitrile, 3,3-dimethylbutyronitrile, 1,6-adiponitrile, and 2-methylglutaronitrile; The C2 to C8 ethers mentioned above can be dimethyl ether, formaldehyde dimethyl acetal, formaldehyde diethanol, methyl ethyl ether, diethyl ether, acetaldehyde dimethyl acetal, acetaldehyde diethanol, methyl propyl ether, methyl n-butyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, 1,3-propanediol dimethyl ether, 1,2-propanediol dimethyl ether, 1,3-propanediol diethyl ether, 1,2-propanediol diethyl ether, 1,4-dioxane, 1,3-dioxane, propyl ether, isopropyl ether, butyl ether, isobutyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, 3-methyltetrahydrofuran, 2,5-dimethylfuran, cyclopentyl methyl ether, cyclopentyl ethyl ether, tetrahydropyran; The C3 to C8 ketones mentioned above can be acetone, butanone, 2-pentanone, 3-pentanone, 2,4-pentanedione, 3-methyl-2-butanone, 2-hexanone, 3-hexanone, 2-methyl-3-pentanone, 4-methyl-2-pentanone, 2-heptanone, 3-heptanone, 4-heptanone, 2,4-dimethyl-3-pentanone, 2-octanone, 5-methyl-3-heptanone, cyclopentanone, cyclohexanone, methylcyclohexanone, and cycloheptanone. The aforementioned C1-C6 haloalkanes can be chloromethane, dichloromethane, chloroform, carbon tetrachloride, chloroethane, 1,2-dichloroethane, 1,1-dichloroethane, 1,1-trichloroethane, 1,1,2-trichloroethane, 1,1,1,2-tetrachloroethane, 1,1,2,2-tetrachloroethane, pentachloroethane, hexachloroethane, chloropropane, 2-chloropropane, 1,2-dichloropropane, 1,3-dichloropropane, 1,2,3-dichloropropane, chlorobutane, 2-chlorobutane, 1-chloro-2-methylpropane, 2-chloro-2-methylpropane, 1,4-dichlorobutane, chloropentane, dichloropentane, 1,5-dichloropentane, mixed chloropentanes, and chlorohexane; The C2~C6 esters mentioned above can be methyl formate, ethyl formate, propyl formate, isopropyl formate, butyl formate, isobutyl formate, methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, isobutyl acetate, methyl propionate, ethyl propionate, propyl propionate, isobutyl propionate, methyl butyrate, and ethyl butyrate. The benzene or alkyl and / or halogen-substituted benzene mentioned above can be benzene, toluene, 1,2-dimethylbenzene, 1,3-dimethylbenzene, 1,4-dimethylbenzene, ethylbenzene, 1,2,3-trimethylbenzene, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene, propylbenzene, isopropylbenzene, chlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, 2,3-dichlorotoluene, 2,4-dichlorotoluene, 2,5-dichlorotoluene, 2,6-dichlorotoluene, fluorobenzene, 1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, 2,3-difluorotoluene, 2,4-difluorotoluene, 2,5-difluorotoluene, 2,6-difluorotoluene; The C4-C8 alkanes or cycloalkanes mentioned above can be butane, n-pentane, 2-methylbutane, hexane, 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane, 2,3-dimethylbutane, cyclobutane, heptane, a mixture of heptane isomers, octane, cyclopentane, cyclohexane, methylcyclopentane, methylcyclohexane, ethylhexane, octane, cycloheptane, and cyclooctane. More preferably, the solvent used for the reaction of the allyl compound with the nitrite, and the solvent used for the reaction of the filter residue with the oxidant, are both C1-C4 alcohols, or a mixture of C1-C4 alcohols and other solvents.

[0041] Preferably, the molar ratio of the raw material allyl compound to the solvent is 1:2 to 20.

[0042] Compared with the prior art, the advantages of the present invention are as follows: In the preparation of 3,3-dialkoxypropyl compounds, this invention achieves the recovery of the main components of the catalyst by adding a reducing agent to the reaction system. The recovered catalyst components are then oxidized back to the catalyst under acidic conditions by an oxidant. Simultaneously, the reducing agent and oxidant can be selected from the reactants, allyl compounds and nitrites, respectively, eliminating the need to introduce new compounds into the reaction system. The regenerated catalyst can be recycled indefinitely, improving the atom economy of the reaction while reducing catalyst consumption, thus achieving the green preparation of 3,3-dialkoxypropyl compounds. Attached Figure Description

[0043] Figure 1 This is a flowchart of a method for recycling and regenerating a catalyst used in the preparation of 3,3-dialkoxypropyl compounds according to the present invention.

[0044] Figure 2 The gas chromatogram of methyl 3,3-dimethoxypropionate prepared in Example 1.

[0045] Figure 3 The 1H NMR spectrum of methyl 3,3-dimethoxypropionate prepared in Example 1.

[0046] Figure 4 The gas chromatogram of ethyl 3,3-diethoxypropionate prepared in Example 5.

[0047] Figure 5 The 1H NMR spectrum of ethyl 3,3-diethoxypropionate prepared in Example 5.

[0048] Figure 6 The gas chromatogram of 3,3-dimethoxypropionitrile prepared in Example 7.

[0049] Figure 7 The 1H NMR spectrum of 3,3-dimethoxypropionitrile prepared in Example 7.

[0050] Figure 8 The gas chromatogram of 3,3-diethoxypropionitrile prepared in Example 8.

[0051] Figure 9 The 1H NMR spectrum of 3,3-diethoxypropionitrile prepared in Example 8.

[0052] Figure 10 The gas chromatogram of 3,3-dimethoxypropionic acid prepared in Example 11.

[0053] Figure 11 The 1H NMR spectrum of 3,3-dimethoxypropionic acid prepared in Example 11.

[0054] Figure 12The gas chromatogram of phenylacetaldehyde dimethyl acetal prepared in Example 13 is shown.

[0055] Figure 13 The 1H NMR spectrum of phenylacetaldehyde dimethyl acetal prepared in Example 13. Detailed Implementation

[0056] The present invention will be further described in detail below with reference to the embodiments, but the implementation of the present invention is not limited to the following embodiments.

[0057] All raw materials used in this invention are commercially available.

[0058] Example 1: Synthesis of methyl 3,3-dimethoxypropionate The specific process is as follows: Figure 1 As shown.

[0059] Methyl acrylate (5 mol, 430.40 g), PdCl2 (5 mmol, 0.89 g), and methanol (25 mol, 800.00 g) were added to a reaction vessel and heated to 50 °C. Methyl nitrite gas was introduced at a rate of 500 mL / min. During the process, the gas phase was monitored to ensure the methyl acrylate reaction was complete. After 10 h of reaction, the reaction temperature was maintained, and hydrogen gas (250 mmol, 5.60 L) was introduced into the reaction system for reduction reaction for 4 h. The residue was filtered, and the filtrate was further distilled to obtain methyl 3,3-dimethoxypropionate (705.24 g, yield 95.20%). The gas chromatogram and 1H NMR spectrum are shown below. Figure 2 and Figure 3 As shown, the filter residue was oxidized by methyl nitrite (50 mmol, 3.05 g) in a methanol solution of HCl (50 mmol, 1.82 g) to generate PdCl2 (0.88 g, recovery rate 99.8%).

[0060] The catalyst was repeatedly applied 10 times, and the results are shown in Table 1: Table 1: Conversion and yield of the recovered PdCl2 catalyst after 10 reuses in Example 1 Example 2: Synthesis of methyl 3,3-dimethoxypropionate The specific process is as follows: Figure 1 As shown.

[0061] Methyl acrylate (5 mol, 430.40 g), PdCl2 (5 mmol, 0.89 g), and methanol (25 mol, 800.00 g) were added to a reaction vessel and heated to 50 °C. Methyl nitrite gas was introduced at a rate of 500 mL / min. During the process, the gas phase was monitored until 20% of the methyl acrylate remained unreacted. After the reaction was completed for 7 h, the temperature was increased to 120 °C and the reaction was continued for 4 h. The residue was filtered, and the filtrate was further distilled to obtain methyl 3,3-dimethoxypropionate (564.19 g, yield 76.16%). The residue was oxidized by introducing oxygen (50 mmol, 1.12 L) in the presence of dioxane solution (HCl, 50 mmol, 1.82 g) to generate PdCl2 (0.88 g, recovery rate 99.6%).

[0062] The catalyst was repeatedly applied 10 times, and the results are shown in Table 2: Table 2: Conversion and yield of the recovered PdCl2 catalyst after 10 reuses in Example 2 Example 3: Synthesis of methyl 3,3-dimethoxypropionate The specific process is as follows: Figure 1 As shown.

[0063] Methyl acrylate (5 mol, 430.40 g), PdSO4 (5 mmol, 1.01 g), and methanol (25 mol, 800.00 g) were added to a reaction vessel and heated to 50 °C. Methyl nitrite gas was introduced at a rate of 600 mL / min. During the process, the gas phase was monitored to ensure the methyl acrylate reaction was complete. After 10 h of reaction, the temperature was raised to 100 °C, and formic acid (100 mmol, 4.60 g) was added to the reaction system. The reaction was continued for 4 h, and the residue was filtered. The filtrate was further distilled to obtain methyl 3,3-dimethoxypropionate (594.12 g, yield 80.20%). The residue was oxidized by adding NaClO (50 mmol, 3.72 g) in the presence of an aqueous solution of H2SO4 (100 mmol, 9.80 g) to generate PdSO4 (1.01 g, recovery 99.7%).

[0064] Example 4: Synthesis of methyl 3,3-dimethoxypropionate The specific process is as follows: Figure 1 As shown.

[0065] Methyl acrylate (5 mol, 430.40 g), PdCl2 (5 mmol, 0.89 g), CuCl2 (30 mol, 4.03 g), and methanol (25 mol, 800.00 g) were added to a reaction vessel and heated to 50 °C. Methyl nitrite gas was introduced at a rate of 800 mL / min. During the process, the gas phase was monitored to ensure the methyl acrylate reaction was complete. After 6 h of reaction, the temperature was lowered to 20 °C, and hydrogen gas (250 mmol, 5.60 L) was introduced into the reaction system for reduction for 4 h. The filtrate was further distilled to obtain methyl 3,3-dimethoxypropionate (702.42 g, yield 94.82%) and copper-containing filter residue. The palladium-containing filter residue was oxidized by adding NaClO3 (2.5 mmol, 0.27 g) in the presence of an aqueous solution of HCl (20 mmol, 0.73 g) to generate PdCl2 (1.01 g, recovery 99.9%). The copper-containing filter residue was oxidized by methyl nitrite (30 mmol, 1.10 g) in a methanol solution of HCl (30 mmol, 1.83 g) to produce CuCl2 (3.99 g, recovery rate 99.0%).

[0066] The catalyst was repeatedly applied 10 times, and the results are shown in Table 3: Table 3: Conversion rate and yield of PdCl2 and CuCl2 recovered in Example 4 after 10 cycles Example 5: Synthesis of ethyl 3,3-diethoxypropionate The specific process is as follows: Figure 1 As shown.

[0067] Pd and CuCl are regenerated in situ with elemental Pd, CuCl, and HCl to obtain PdCl2 and CuCl2.

[0068] Ethyl acrylate (5 mol, 500.60 g), Pd powder (5 mmol, 0.53 g), CuCl (20 mmol, 1.98 g), HCl (30 mmol, 1.10 g), and ethanol (25 mol, 1151.75 g) were added to a reaction vessel and heated to 60 °C. Ethyl nitrite was introduced at a rate of 600 mL / min. During the reaction, the ethyl acrylate was monitored in the gas phase until 20% of the ethyl acrylate remained. After 7 h of reaction, the temperature was raised to 80 °C for a reduction reaction for 4 h. The residue containing palladium was obtained by filtration. The filtrate was further distilled to obtain ethyl 3,3-diethoxypropionate (713.63 g, yield 75.02%). Its gas chromatogram and 1H NMR spectrum are shown below. Figure 4 and Figure 5(as shown) and copper-containing filter residue were combined, and then HCl (30 mmol, 1.10 g), ethanol (25 mol, 1151.75 g), and ethyl acrylate (5 mol, 500.60 g) were added and ethyl nitrite was circulated at 600 mL / min for the reaction.

[0069] The catalyst was repeatedly applied 10 times, and the results are shown in Table 4: Table 4: Conversion rate and yield of the filter residue recovered in Example 5 after applying the above scheme 10 times. Example 6: Synthesis of n-Butyl 3,3-dibutoxypropionate The specific process is as follows: Figure 1 As shown.

[0070] In a reaction vessel, n-butyl acrylate (5 mol, 640.85 g), Pd(NO3)2 (10 mmol, 2.30 g), and n-butanol (30 mol, 2223.60 g) were added and heated to 80 °C. Nitrite (15 mol, 1546.80 g) was added dropwise. During the process, the gas phase was monitored to ensure the n-butyl acrylate reaction was complete. After 10 h of reaction, the reaction temperature was maintained, and sodium borohydride (10 mmol, 0.38 g) was added to the reaction system. The reaction was continued for 2 h, filtered, and the filtrate was further distilled to obtain 3,3-di-n-butoxypropionic acid n-butyl ester (1286.98 g, yield 93.80%). The filter residue was oxidized by n-butyl nitrite (50 mmol, 6.41 g) in a 97% aqueous solution of HNO3 (500 mmol, 32.48 g) to generate Pd(NO3)2 (2.29 g). g, recovery rate 99.5%.

[0071] Example 7: Synthesis of 3,3-dimethoxypropionitrile The specific process is as follows: Figure 1 As shown.

[0072] Acrylonitrile (5 mol, 265.30 g), Pd(CHCOO)₂ (5 mmol, 1.12 g), Cu(CH₃COO)₂ (30 mmol, 5.45 g), and methanol (25 mol, 800.00 g) were added to a reaction vessel and heated to 60 °C. Methyl nitrite was introduced at a rate of 500 mL / min, with gas phase monitoring throughout the process. The reaction lasted for 8 h. 20% of the acrylonitrile remained unreacted. After the reaction was complete, the temperature was increased to 80 °C for reduction reaction for 4 h. The residue containing palladium was obtained by filtration. The filtrate was further distilled to obtain 3,3-dimethoxypropionitrile (533.74 g, yield 92.72%). Its gas chromatogram and 1H NMR spectrum are shown below. Figure 6 and Figure 7The palladium-containing filter residue and the copper-containing filter residue were combined and oxidized with methyl nitrite (70 mmol, 4.27 g) in a methanol dioxane solution containing acetic acid (100 mmol, 6.01 g) to produce Pd(CH3COO)2 (1.12 g, 99.8% recovery) and Cu(CH3COO)2 (5.39 g, 99.0% recovery).

[0073] The catalyst was repeatedly applied 10 times, and the results are shown in Table 5: Table 5: Conversion rate and yield of Pd(CH3COO)2 and Cu(CH3COO)2 recovered in Example 7 after 10 cycles. Example 8: Synthesis of 3,3-diethoxypropionitrile The specific process is as follows: Figure 1 As shown.

[0074] Acrylonitrile (5 mol, 265.30 g), PdCl2 (20 mmol, 3.55 g), CuCl2 (50 mmol, 6.72 g), and ethanol (20 mol, 921.40 g) were added to a reaction vessel and heated to 78 °C. Ethyl nitrite was introduced at a rate of 600 mL / min, and the reaction of acrylonitrile was monitored in the gas phase until completion. After 6 h of reaction, the temperature was increased to 100 °C, and hydrogen gas (100 mmol, 2.24 L) was introduced into the reaction system for 4 h. The mixture was filtered to obtain palladium-containing residue. Further distillation of the filtrate yielded 3,3-diethoxypropionitrile (669.94 g, 93.58% yield) and copper-containing residue. The palladium-containing residue was oxidized by ethyl nitrite (80 mmol, 3.75 g) in an ethanol solution containing HCl (80 mmol, 2.92 g) to produce PdCl2 (3.54 g). g, recovery rate 99.8%, its gas chromatogram and nuclear magnetic resonance hydrogen spectrum are as follows: Figure 8 and Figure 9 (As shown). The copper-containing filter residue was oxidized by ethyl nitrite (50 mmol, 3.75 g) in an ethanol solution of HCl (100 mmol, 3.65 g) to produce CuCl2 (6.62 g, recovery rate 98.5%).

[0075] Example 9: Synthesis of 3,3-diethoxypropionitrile The specific process is as follows: Figure 1 As shown.

[0076] Acrylonitrile (5 mol, 265.30 g), PdCl2(CH3CN)2 (10 mmol, 2.59 g), and ethanol (20 mol, 921.40 g) were added to a reaction vessel and heated to 78 °C. Ethyl nitrite was introduced at a rate of 600 mL / min. During the process, the acrylonitrile reaction was monitored in the gas phase until it was completely completed. After the reaction was completed for 8 h, the temperature was raised to 100 °C, and hydrogen gas (100 mmol, 2.24 L) was introduced into the reaction system for 4 h. The residue was filtered, and the filtrate was further distilled to obtain 3,3-diethoxypropionitrile (669.94 g, yield 93.58%). The palladium-containing residue was oxidized by ethyl nitrite (80 mmol, 3.75 g) in an ethanol solution containing HCl (80 mmol, 2.92 g) to generate PdCl2. 10 mL of acetonitrile was added to react and PdCl2(CH3CN)2 (2.58 g, recovery 99.7%) was obtained.

[0077] Example 10: Synthesis of 3,3-dipropoxypropionitrile The specific process is as follows: Figure 1 As shown.

[0078] Acrylonitrile (5 mol, 265.30 g), PdCl2 (20 mmol, 3.55 g), and n-propanol (25 mol, 1502.5 g) were added to a reaction vessel and heated to 90 °C. Propyl nitrite (12.5 mol, 1113.66 g) was added dropwise. During the process, the acrylonitrile reaction was monitored in the gas phase until completion. After 14 h of reaction, the temperature was increased to 100 °C and the reaction was continued for 4 h. The residue was filtered, and the filtrate was further distilled to obtain 3,3-dipropoxypropionitrile (759.01 g, yield 88.68%). The residue was oxidized by propyl nitrite (80 mmol, 7.13 g) in a n-propanol solution with HCl (80 mmol, 2.92 g) to generate PdCl2 (3.53 g, recovery 99.5%).

[0079] Example 11: Synthesis of 3,3-dimethoxypropionic acid The specific process is as follows: Figure 1 As shown.

[0080] Acrylic acid (5 mol, 360.32 g), PdCl2 (50 mmol, 8.87 g), CuCl2 (50 mmol, 6.72 g), and methanol (20 mol, 640.00 g) were added to a reaction vessel and heated to 150 °C. Methyl nitrite was introduced at a rate of 500 mL / min. During the process, the reaction of acrylic acid was monitored by gas chromatography until it was completely reacted. After 8 h of reaction, the temperature was lowered to 20 °C, and sodium borohydride (100 mmol, 3.78 g) was added to the reaction system. The reaction was carried out for 2 h. The residue containing palladium was obtained by filtration. The filtrate was further distilled to obtain 3,3-dimethoxypropionic acid (626.12 g, yield 93.36%). Its gas chromatogram and 1H NMR spectrum are shown below. Figure 10 and Figure 11 (as shown) and copper-containing filter residue. The palladium-containing filter residue and copper-containing filter residue were combined and oxidized with methyl nitrite (100 mmol, 6.10 g) in the presence of ethyl acetate solution containing HCl (200 mmol, 7.30 g) to produce PdCl2 (8.84 g, 99.7% recovery) and CuCl2 (6.65 g, 99.0% recovery).

[0081] Example 12: Synthesis of 3,3-dimethoxypropionamide The specific process is as follows: Figure 1 As shown.

[0082] Acrylamide (5 mol, 355.50 g), Pd(NO3)2 (5 mmol, 1.15 g), Cu(NO3)2 (30 mol, 5.63 g), and methanol (25 mol, 800.00 g) were added to a reaction vessel and heated to 50 °C. Methyl nitrite was introduced at a rate of 500 mL / min. During the process, the acrylamide reaction was monitored in the gas phase until it was complete. After the reaction was completed for 12 h, the temperature was raised to 80 °C, and hydrogen gas (200 mmol, 4.48 L) was introduced into the reaction system. The reaction was continued for 8 h. The residue was filtered, and the filtrate was further distilled to obtain 3,3-dimethoxypropionamide (550.24 g, yield 82.65%). The palladium-containing residue was oxidized by adding HNO3 (50 mmol, 3.15 g) aqueous solution to generate Pd(NO3)2 (1.14 g, recovery 99.5%). The copper-containing filter residue was oxidized by an aqueous solution of HNO3 (60 mmol, 6.30 g) to produce Cu(NO3)2 (5.52 g, recovery rate 98.3%).

[0083] Example 13: Synthesis of phenylacetaldehyde dimethyl acetal The specific process is as follows: Figure 1 As shown.

[0084] Styrene (5 mol, 520.75 g), Pd(CH3COO)2 (10 mmol, 2.25 g), and methanol (25 mol, 800.00 g) were added to a reaction vessel and heated to 40 °C. Methyl nitrite was introduced at a rate of 800 mL / min. During the process, the gas phase was monitored to ensure the styrene reaction was complete. After 5 h of reaction, the temperature was maintained, and formaldehyde (300 mmol, 9.01 g) was added to the reaction system. The reaction was continued for 2 h, and the residue was filtered. The filtrate was further distilled to obtain phenylacetaldehyde dimethyl acetal (802.84 g, yield 96.60%). Its gas chromatogram and 1H NMR spectrum are shown below. Figure 12 and Figure 13 As shown), the filter residue was oxidized by passing ozone (50 mmol, 1.12 L) through a toluene solution of CH3COOH (20 mmol, 0.73 g) to produce Pd(CH3COO)2 (2.24 g, recovery rate 99.8%).

[0085] The catalyst was repeatedly applied 10 times, and the results are shown in Table 6: Table 6: Conversion rate and yield of Pd(CH3COO)2 recovered in Example 13 after 10 reuses Example 14: Synthesis of phenylacetaldehyde dimethyl acetal The specific process is as follows: Figure 1 As shown.

[0086] Styrene (5 mol, 520.75 g), PdCl2(pph3)2 (2.5 mmol, 1.75 g), and methanol (25 mol, 800.00 g) were added to a reactor and heated to 50 °C. Methyl nitrite was introduced at a rate of 800 mL / min. During the process, the gas phase was monitored to ensure the styrene reaction was complete. After 8 h of reaction, the temperature was maintained, and lithium aluminum hydride (20 mmol, 0.76 g) was added to the reaction system. The reaction was continued for 2 h, and the residue was filtered. The filtrate was further distilled to obtain phenylacetaldehyde dimethyl acetal (774.34 g, yield 93.17%). The residue was oxidized by chlorine gas (50 mmol, 1.12 L) in the presence of HCl (20 mmol, 0.73 g) and dichloromethane solution to generate PdCl2. Triphenylphosphine (25 mmol, 6.55 g) was then added, and the reaction was stirred at room temperature for 2 h. h, yielded PdCl2(pph3)2 (1.74 g, recovery rate 99.8%).

[0087] The above description is merely 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 method for recycling and regenerating a catalyst used in the preparation of 3,3-dialkoxypropyl compounds, characterized in that, Includes the following steps: An allyl compound was reacted with a nitrite ester in the presence of a catalyst. After the reaction was complete, a reducing agent was added to the reaction system, followed by filtration. The filtrate was then distilled to obtain a 3,3-dialkoxypropyl compound. The filter residue was oxidized by an oxidizing agent under acidic conditions to generate a catalyst. The catalyst is a divalent palladium catalyst, or a mixture of a divalent palladium catalyst and a divalent copper catalyst.

2. The method for recycling and regenerating the catalyst used in the preparation of the 3,3-dialkoxypropyl compound according to claim 1, characterized in that, The reducing agent is at least one of hydrogen, formic acid, borohydride, lithium aluminum hydride, hydrazine hydrate, C1-C4 alcohols, C1-C4 aldehydes, and allyl compounds.

3. The method for recycling and regenerating the catalyst used in the preparation of the 3,3-dialkoxypropyl compound according to claim 1, characterized in that, The oxidant is at least one of oxygen, ozone, hydrogen peroxide, chlorine, divalent copper, nitrite, nitric acid, aqua regia, nitrosyl chloride, nitryl chloride, persulfate, hypohalite, halide, and perhalite.

4. The method for recycling and regenerating the catalyst used in the preparation of the 3,3-dialkoxypropyl compound according to claim 1, characterized in that, The acid is an organic acid or an inorganic acid, or its anhydride or acyl chloride.

5. The method for recycling and regenerating the catalyst used in the preparation of the 3,3-dialkoxypropyl compound according to claim 1, characterized in that, The divalent palladium catalyst and the divalent copper catalyst are compounds formed by divalent palladium ions or divalent copper ions and acid radical ions, respectively, or complexes formed by the compounds and ligands.

6. The method for recycling and regenerating the catalyst used in the preparation of the 3,3-dialkoxypropyl compound according to claim 1, characterized in that, The molar ratio of the catalyst to the reducing agent is 1:0.25~100.

7. The method for recycling and regenerating the catalyst used in the preparation of the 3,3-dialkoxypropyl compound according to claim 1, characterized in that, The molar ratio of the catalyst to the oxidant is 1:0.25~100.

8. The method for recycling and regenerating the catalyst used in the preparation of the 3,3-dialkoxypropyl compound according to claim 1, characterized in that, The reaction temperature with the reducing agent is 20~150 ℃, and the reaction temperature with the oxidizing agent is 20~150 ℃.

9. The method for recycling and regenerating the catalyst used in the preparation of the 3,3-dialkoxypropyl compound according to claim 1, characterized in that, The structure of the allyl compound is shown below: ， R1 is selected from cyano, carboxyl, C2-C5 ester, C1-C5 amide, and C6-C9 aryl.

10. The method for recycling and regenerating the catalyst used in the preparation of the 3,3-dialkoxypropyl compound according to claim 1, characterized in that, The structure of the nitrite is shown below: , R2 is selected from C1 to C4 alkyl groups.

11. The method for recycling and regenerating the catalyst used in the preparation of the 3,3-dialkoxypropyl compound according to claim 1, characterized in that, The molar ratio of the allyl compound to the nitrite is 1:1 to 20.

12. The method for recycling and regenerating the catalyst used in the preparation of the 3,3-dialkoxypropyl compound according to claim 1, characterized in that, The reaction temperature of the allyl compound with the nitrite is 20~150 °C.

13. The method for recycling and regenerating the catalyst used in the preparation of the 3,3-dialkoxypropyl compound according to claim 1, characterized in that, The molar ratio of the catalyst to the allyl compound is 1:50~5000.

14. The method for recycling and regenerating the catalyst used in the preparation of the 3,3-dialkoxypropyl compound according to claim 1, characterized in that, The solvent for the reaction of the allyl compound with the nitrite is at least one of the following: C1-C4 alcohols, C2-C6 nitriles, C2-C6 ethers, C3-C8 ketones, C2-C6 esters, C1-C6 haloalkanes, benzene, alkyl and / or halogen-substituted benzenes, C4-C8 alkanes, or cycloalkanes.

15. The method for recycling and regenerating the catalyst used in the preparation of the 3,3-dialkoxypropyl compound according to claim 1, characterized in that, The solvent for the reaction of the filter residue with the oxidant is at least one of water, C1-C4 alcohols, C2-C6 nitriles, C2-C6 ethers, C3-C8 ketones, C2-C6 esters, C1-C6 haloalkanes, benzene, alkyl and / or halogen-substituted benzene, C4-C8 alkanes or cycloalkanes.

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