Synthetic method of dicarboxylic acid compound

Abstract

The invention provides a synthetic method of a dicarboxylic acid compound, which comprises the following steps: by taking a compound as shown in a formula (1) and / or a formula (2) as a raw material, reacting in the presence of a catalytic system, hydrogen and oxygen to prepare the dicarboxylic acid compound as shown in a formula (3), wherein the formula (1), the formula (2) and the formula (3) are shown in the specification; the catalytic system comprises a first catalyst and a second catalyst, the first catalyst comprises a carrier and an active component loaded on the carrier, the active component is a first metal or an alloy formed by the first metal and a second metal, the first metal is selected from one or more of palladium, platinum, rhodium and iridium, and the second metal is gold and / or tin; the second catalyst is a tungsten-containing compound. According to the synthetic method, the compound shown in the formula (1) and / or the formula (2) can be efficiently converted into the corresponding dicarboxylic acid compound, the reaction path is simple, the product yield is high, the method is more environmentally friendly, and the economical efficiency and sustainability of the process are good.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis technology, and specifically to a method for synthesizing dicarboxylic acid compounds. Background Technology

[0002] Dicarboxylic acid compounds are a class of widely used chemical products. For example, adipic acid plays an important role in chemical production (nylon 66, polyurethane, etc.), organic synthesis, pharmaceuticals, plasticizers, and lubricant manufacturing. The traditional industrial production process of adipic acid is as follows: Figure 1 As shown, the first step is the partial hydrogenation reaction of benzene to cyclohexene, which simultaneously produces the fully hydrogenated product cyclohexane; the second step is the hydration reaction of cyclohexene to cyclohexanol or the oxygen oxidation reaction of cyclohexane to KA oil (a mixture of cyclohexanol and cyclohexanone); the third step is the nitric acid oxidation reaction of KA oil to adipic acid. The above process has the following defects: (1) Low single-pass conversion rate: This problem exists in hydrogenation reaction, oxygen oxidation reaction and hydration reaction, especially oxygen oxidation reaction. In order to avoid the occurrence of over-oxidation reaction, the conversion rate of this step is generally limited to about 3% in industry. (2) High energy consumption for separation: This defect stems from the low reaction conversion rate on the one hand, and from the similar physical properties of the products and raw materials on the other hand. For example, the boiling points of benzene, cyclohexene and cyclohexane are 80.1℃, 85.6℃ and 80.7℃, respectively, and it is difficult to separate the three by general distillation methods. (3) Serious environmental pollution: The oxidation reaction of nitric acid releases an equivalent amount of nitrous oxide (N2O), whose single-molecule warming potential is 298 times that of carbon dioxide (IPCC, 2007), making it the third largest greenhouse gas produced by humankind.

[0003] Besides adipic acid, other typical dicarboxylic acid compounds include: pentadecanoic acid, which is mainly used to synthesize pentadecylone, cyclopentadecanolactone, and synthetic musk. Synthetic musk can replace natural musk in the formulation of various precious traditional Chinese medicines, and has antibacterial, anti-inflammatory, and blood-activating effects; sebacic acid, which can be used to synthesize nylon-based biodegradable materials for applications such as surgical sutures or tissue engineering scaffolds; and diethyl sebacic acid, prepared from sebacic acid as a substrate, can be used as a drug solvent or transdermal absorption enhancer; and 2-aminoadipic acid, which has two structures, D / L. Type I amino acids are important and can be used as tool compounds to study certain disease-related metabolic pathways, or as potential drug targets. They can also be used to synthesize compounds with special biological activities, providing a foundation for drug development. For example, maleic acid is an unsaturated dicarboxylic acid containing cis double bonds. As a pharmaceutical intermediate, it can be used to synthesize antimalarial drugs, antibiotics, etc. Maleate salts prepared from maleic acid (such as chlorpheniramine maleate) are common anti-allergy drugs. Its acidic salt formation improves the solubility of the drug in water.

[0004] In summary, it is clear that dicarboxylic acid compounds are a class of organic chemicals with important practical value. Developing new synthetic methods for dicarboxylic acid compounds to overcome the problems of low yield, high separation energy consumption, and serious pollution is of great urgency.

[0005] The above background information is provided only to aid in understanding the concept and technical solution of this application. It does not necessarily belong to the prior art of this application, nor does it necessarily provide technical guidance. In the absence of clear evidence that the above information was disclosed before the filing date of this application, the above background information should not be used to evaluate the novelty and inventiveness of this application. Summary of the Invention

[0006] The purpose of this invention is to provide a novel method for synthesizing dicarboxylic acid compounds, which has a short reaction process, high yield, and is more environmentally friendly.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The present invention provides a method for synthesizing dicarboxylic acid compounds, using compounds shown in formula (1) and / or formula (2) as raw materials, and reacting them in a catalytic system in the presence of hydrogen and oxygen to obtain dicarboxylic acid compounds shown in formula (3); Equation (1) is: Equation (2) is: Equation (3) is: ; wherein, R in equations (1), (2), and (3) 1 R 2 R 3 and R4 Each R is independently selected from a monovalent organic group, or any two or more of them are connected to each other to form a ring structure; n is an integer between 0 and 12, and when n is an integer greater than 1, each R 4 Same or different; The catalytic system includes a first catalyst and a second catalyst. The first catalyst includes a support and an active component loaded thereon. The active component is a first metal or an alloy formed by the first metal and a second metal. The first metal is selected from one or more of palladium, platinum, rhodium, and iridium. The second metal is gold and / or tin. The second catalyst is a tungsten-containing compound.

[0008] This invention employs a catalytic system comprising a first catalyst and a second catalyst, enabling the oxidation reaction of compounds shown in formula (1) and / or formula (2), thereby efficiently and selectively preparing dicarboxylic acid compounds as shown in formula (3). When only the first catalyst or the second catalyst is used, it is difficult to achieve the effective synthesis of the aforementioned dicarboxylic acid compounds. Furthermore, the epoxidation of olefins is a mature industrial process; for example, cyclohexene can be almost quantitatively converted to cyclohexane oxide under the action of a homogeneous molybdenum catalyst. Therefore, the synthesis of dicarboxylic acid compounds using the epoxide compound shown in formula (2) or the vicinal diol compound shown in formula (1) as raw materials has a good industrial application basis.

[0009] In some embodiments, the first catalyst comprises, based on a total mass of 100%, the first catalyst: Carrier 85%~99.99%; First metal: 0.01%~10%; Secondary metal content: 0-5%.

[0010] In some preferred embodiments, the first catalyst comprises, based on a total mass of 100%, the first catalyst: Carrier 98.5%~99.99%; First metal 0.01%~1%; Second metal 0~0.5%.

[0011] This invention, by employing a low-loading active component, can both control the formation rate of the peroxide intermediate (hydrogen peroxide) during the reaction process and effectively suppress further side reactions such as deep hydrogenation or spontaneous decomposition of the intermediate. Furthermore, introducing a second metal into the catalyst system can stabilize the peroxide intermediate by forming an alloy structure, thereby improving hydrogen efficiency to a certain extent.

[0012] In some embodiments, the support is selected from one or more of metal oxides and molecular sieves. Further, the metal oxide includes alumina, silicon oxide, titanium oxide, magnesium oxide, zirconium oxide, cerium oxide, and gallium oxide. The molecular sieve includes ZSM-5.

[0013] In some embodiments, the preparation method of the first catalyst includes: impregnating the support with a solution containing the active component, followed by drying and calcination.

[0014] In this invention, "a solution containing the active component" refers to any suitable solution that can be converted into the target active component through dissolution or reaction, and may be selected from, but is not limited to: 1) water or organic solutions containing soluble salts, such as nitrates, hydrochlorides, or acetates; 2) solutions prepared by dissolving the active component in a suitable acid (such as nitric acid, acetic acid, or hydrochloric acid). Furthermore, an acid (including but not limited to hydrochloric acid) may be added to the solution to adjust the pH of the system to acidic, preferably to a pH of 1-3.

[0015] In this invention, the term "impregnation" is a conventional technique in the art, including but not limited to equal-volume impregnation, excess solution impregnation, and spray impregnation. When using excess solution impregnation, solid-liquid separation (such as filtration, centrifugation, or evaporation) is usually required after impregnation.

[0016] In this invention, the drying temperature is preferably 30℃~100℃, more preferably 50℃~90℃; the calcination temperature is 300℃~600℃, more preferably 300℃~450℃, such as 300℃, 330℃, 350℃, 380℃, 400℃, 430℃, 450℃; the calcination time is 3h~8h, more preferably 5h~7h, such as 5.5h, 6h, 6.5h, 7h.

[0017] In some embodiments, the mass ratio of the raw material to the first catalyst is 1:(0.005~1), preferably 1:(0.1~0.6), such as 1:0.1, 1:0.15, 1:0.2, 1:0.25, 1:0.3, 1:0.35, 1:0.4, 1:0.45, 1:0.5, 1:0.55, 1:0.6.

[0018] In some embodiments, the tungsten-containing compound is selected from one or more of tungstic acid or its salts, metatungstates, heteropolytungstic acid or its salts. Further, the tungstic acid or its salts include tungstic acid, lithium tungstate, sodium tungstate, potassium tungstate, cesium tungstate, cadmium tungstate, calcium tungstate, nickel tungstate, bismuth tungstate, zinc tungstate, strontium tungstate, silver tungstate, copper tungstate, and ammonium tungstate. The metatungstate includes ammonium metatungstate. The heteropolytungstic acid or its salts include silicotungstic acid, phosphotungstic acid, selerotungstic acid, germanottungstic acid, arsostungstic acid, and salts formed by these acids with alkali metals, alkaline earth metals, or ammonium; preferably, the salts are sodium salts, potassium salts, calcium salts, or ammonium salts, such as: sodium tungstate, potassium tungstate, calcium tungstate, ammonium tungstate, sodium phosphotungstate, potassium phosphotungstate, calcium phosphotungstate, ammonium phosphotungstate, sodium selerotungstate, potassium selerotungstate, calcium selerotungstate, ammonium selerotungstate, sodium germanottungstate, potassium germanottungstate, calcium germanottungstate, ammonium germanottungstate, sodium arsostungstate, potassium arsostungstate, calcium arsostungstate, and ammonium arsostungstate.

[0019] In some embodiments, the mass ratio of the raw material to the second catalyst is 1:(0.01~1.5), preferably 1:(0.1~1.3), more preferably 1:(0.3~1.3), such as 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, 1:1.3.

[0020] In some embodiments, the catalytic system further includes an auxiliary agent selected from one or more protonic acids and strong base-weak acid salts. Further, the protonic acid includes hydrochloric acid, sulfuric acid, nitric acid, hydrobromic acid, p-toluenesulfonic acid, phosphoric acid, metaphosphoric acid, pyrophosphoric acid, phosphorous acid, hypophosphoric acid, silicic acid, polysilicic acid, orthogermic acid, metagermic acid, selenic acid, selenite, arsenic acid, arsenite, metaarsenic acid, and benzoarsine; the strong base-weak acid salt includes sodium orthosilicate.

[0021] This invention introduces an auxiliary agent to construct a binuclear or multinuclear catalytic active center with a second catalyst. This multinuclear active center can simultaneously act on peroxide intermediates generated in situ in the system, thereby achieving highly efficient and selective recognition and utilization of the oxidation intermediates, and thus promoting the oxidation of the substrate to the target product. When the second catalyst itself is heteropolytungstic acid, it can form a multinuclear cluster structure on its own, achieving selective recognition and utilization of peroxide intermediates without additional auxiliary agents, achieving the same or similar promoting effect.

[0022] In some embodiments, the mass ratio of the raw material to the auxiliary agent is 1:(0.01~0.5), preferably 1:(0.04~0.3), more preferably 1:(0.05~0.3), such as 1:0.05, 1:0.1, 1:0.15, 1:0.2, 1:0.25, 1:0.3.

[0023] In some embodiments, the mass ratio of the first catalyst, the second catalyst and the auxiliary agent in the catalytic system is 1:(1~20):(0~15), preferably 1:(1~5):(0~1), and more preferably 1:(2~5):(0.3~1).

[0024] In some embodiments, the reaction temperature is 80°C to 100°C, preferably 85°C to 95°C.

[0025] In some embodiments, the reaction is carried out in the presence of a solvent, which is water or a mixture of water and an organic solvent. The organic solvent is preferably a nitrile solvent, including but not limited to one or more of acetonitrile, propionitrile, butyronitrile, and benzonitrile. Further, when the solvent is a mixture of water and an organic solvent, the mass ratio of water to organic solvent is 1:(0.01~0.3), preferably 1:(0.05~0.3). Adding a certain amount of organic solvent can increase the solubility of hydrogen and also improve the miscibility between the raw materials and the peroxide intermediate generated in the reaction system, which is beneficial for improving reaction efficiency and product yield.

[0026] In this invention, the monovalent organic group is not particularly limited in principle and can be selected and used according to the types of compounds already available in the art. In some specific embodiments, the monovalent organic group includes hydrogen, straight-chain or branched or cyclic alkyl groups, aryl, benzyl, alkoxy, carboxyl, ester, nitro, halogen, and sulfonic acid groups. The straight-chain or branched alkyl group may have 1 to 6 carbon atoms, and non-limitingly includes methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, etc. The cyclic alkyl group may have 3 to 6 carbon atoms, and exemplary includes cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl. In specific embodiments, the aryl group may be phenyl, naphthyl, etc.; the alkoxy group may include methoxy, ethoxy, propoxy, etc.; the halogen may be fluorine, chlorine, bromine, iodine; the ester group may be -COOR, where R is a C1-C6 alkyl group; and the sulfonic acid group may be -SO3H or its salt form.

[0027] In this invention, the cyclic structure comprises a cyclic alkyl group and an aryl group. Preferably, the cyclic alkyl group has 3 to 10 carbon atoms, and for example includes cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl. The aryl group can be a monocyclic or polycyclic aryl group, and exemplary examples include phenyl, naphthyl, anthraceneyl, phenanthrene, and biphenyl. The aryl group may optionally be substituted with one or more substituents, which are independently selected from C1-C4 alkyl, halogen, nitro, cyano, hydroxyl, amino, carboxyl, or C1-C4 alkoxy groups.

[0028] In this invention, n is preferably an integer from 0 to 10, and more preferably an integer from 1 to 5, such as 1, 2, 3, 4 or 5.

[0029] In some embodiments, the synthesis method further includes a step of separating the obtained dicarboxylic acid compound from the reaction system. Specifically, this involves removing the first catalyst from the reaction system, concentrating the resulting mixture to remove some of the solvent, and then inducing crystallization by cooling to achieve the separation and purification of the target product. This synthetic route is simple to use, the concentration of the target dicarboxylic acid in the system after the reaction is high, and its solubility is sensitive to temperature changes. Cooling crystallization can efficiently achieve the separation and purification of the product. The mother liquor from crystallization can be reused in the next batch of reactions.

[0030] In this invention, the reaction can be either a batch reaction or a continuous reaction.

[0031] In some embodiments, when the reaction is a batch reaction, hydrogen, oxygen, and an inert gas are introduced into the reaction system, and the partial pressures of hydrogen and oxygen in the reaction system are controlled to be no less than 0.1 MPa, and the total pressure of the reaction system is 2 MPa to 10 MPa. Preferably, the partial pressure of hydrogen in the reaction system is controlled to be 0.1 MPa to 0.2 MPa, such as 0.1 MPa, 0.15 MPa, or 0.2 MPa. The partial pressure of oxygen in the reaction system is controlled to be 0.2 MPa to 0.5 MPa, such as 0.2 MPa, 0.25 MPa, 0.3 MPa, 0.35 MPa, 0.4 MPa, 0.45 MPa, or 0.5 MPa. The total pressure of the reaction system is controlled to be 3 MPa to 5.5 MPa, such as 3 MPa, 3.5 MPa, 4 MPa, 4.5 MPa, 5 MPa, or 5.5 MPa.

[0032] In this invention, the feeding method of hydrogen, oxygen, and inert gas is not specifically limited. In some specific embodiments, the hydrogen is fed in the form of a first premixed gas containing hydrogen and inert gas, wherein the volume percentage of hydrogen in the first premixed gas is 1% to 10%, preferably 2% to 5%; the oxygen is fed in the form of a second premixed gas containing oxygen and inert gas, wherein the volume percentage of oxygen in the second premixed gas is 20% to 30%. In other specific embodiments, the hydrogen, oxygen, and inert gas are premixed before being introduced into the reaction system. In still other specific embodiments, the hydrogen, oxygen, and inert gas are introduced into the reaction system independently.

[0033] In this invention, the type of inert gas is not specifically limited, and inert gases conventionally used in the art can be used. For example, the inert gas can be a single gas such as nitrogen or helium, or a mixture of multiple inert gases.

[0034] In some embodiments, when the reaction is a continuous reaction, the first catalyst is loaded into a continuous reactor, and the reaction liquid containing the raw materials, the second catalyst, the solvent, and optional additives, and a mixed gas containing hydrogen, oxygen, and an inert gas, either separately or pre-mixed, are continuously introduced into the continuous reactor. Preferably, the pressure of the reaction system is controlled at 0.1 MPa to 2 MPa, more preferably 0.1 MPa to 1 MPa, and even more preferably 0.3 MPa to 0.8 MPa, such as 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa, 0.7 MPa, or 0.8 MPa. The gas-liquid volume ratio of the feed flow rate of the mixed gas to the feed flow rate of the reaction liquid is (1500 to 6000):1, preferably (1500 to 2500):1, such as 1500:1, 1800:1, 2000:1, 2200:1, or 2500:1. The volume ratio of hydrogen to oxygen in the mixed gas is 1:(3~8), preferably 1:(4~6). The hydrogen accounts for 1%~3% of the volume fraction of the mixed gas. The liquid hourly space velocity (LHSV) of the reaction liquid relative to the first catalyst is 0.05 h⁻¹. -1 ~0.5h -1 Preferably 0.1h -1 ~0.2h -1 .

[0035] Compared to batch reactors, continuous reactors are more suitable for industrial production. By loading sufficient catalyst at once, the operation time between reactions in each reactor can be eliminated, improving production efficiency. In addition, continuous reactors, such as trickle beds, also have advantages such as high catalyst utilization, low loss, stable reaction process, flexible operation, simple structure, and low maintenance cost.

[0036] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art: The synthesis method described in this invention can efficiently convert the compounds shown in formula (1) and / or formula (2) into corresponding dicarboxylic acid compounds. The reaction pathway is simple and the product yield is high. This process uses a mixture of hydrogen and oxygen as the final oxidant, replacing traditional highly corrosive reagents such as nitric acid. The only byproduct is water, exhibiting outstanding green and environmentally friendly characteristics. In the catalyst system used, the first catalyst is easy to prepare, has excellent stability, and is suitable for industrial-scale application; the second catalyst is readily available and can be recycled from the mother liquor, further improving the economy and sustainability of the process. Attached Figure Description

[0037] Figure 1 A schematic diagram of the traditional industrial production process of adipic acid; Figure 2 The separated product (adipic acid) in the embodiments of the present invention 1H-NMR spectrum (400MHz, in d6-DMSO); Figure 3 The separated product (adipic acid) in the embodiments of the present invention 13 C-NMR spectrum (400MHz, in d6-DMSO); Figure 4 This is a schematic diagram of the process of continuous reaction using a continuous reactor in an embodiment of the present invention. Detailed Implementation

[0038] The present invention will be further described below with reference to embodiments. However, the present invention is not limited to the following embodiments. The implementation conditions used in the embodiments can be further adjusted according to different requirements of specific applications, and the implementation conditions not specified are conventional conditions in the industry. The technical features involved in the various embodiments of the present invention can be combined with each other as long as they do not conflict with each other.

[0039] In this invention, unless the context explicitly requires otherwise, the numerical range referred to as "numerical value A to numerical value B" refers to the range including the endpoints A and B. The numerical range referred to as "above" or "below" refers to the numerical range including the stated number. "Optional" or "optional" indicates that certain substances, components, execution steps, application conditions, etc., may or may not be used, and there is no limitation on the manner of use.

[0040] In this invention, unless the context explicitly requires otherwise, all numerical parameters modified by terms such as "about" (including but not limited to time, temperature, pressure, concentration, weight percentage, pH value, and size) should be understood to cover a reasonable range centered on the stated value, based on the fluctuation range of conventional experimental or production equipment. Specifically, this range typically includes ±10% of the stated value, and may be extended to ±20% of the stated value in certain embodiments or where conventional precision in the art allows. Such deviations should be understood as inherent fluctuations caused by differences in measuring instruments, operating methods, environmental conditions, or batch variations of materials, and the technical solutions within this range of fluctuations can achieve the core objectives and beneficial effects of this invention.

[0041] In this invention, unless the context explicitly requires otherwise, "filling with a first gas at a value of X MPa and filling with a second gas at a value of Y MPa" should be understood as follows: under specified conditions, a first gas is first filled into a specified space or system until the pressure in that space or system reaches X MPa, and then a second gas is filled into that space or system until the total pressure increases by Y MPa on top of the original X MPa; or, the term can also be understood as follows: under specified conditions, a second gas is first filled into a specified space or system until the pressure in that space or system is Y MPa, and then a first gas is filled into that space or system until the total pressure increases by X MPa on top of the original Y MPa. During the above filling process, the specific pressure characteristics (such as absolute pressure or relative pressure) and measurement conditions (such as temperature, reference standards, etc.) should be determined based on the conventional understanding of those skilled in the art, the explicit description of the relevant embodiments, or the general standards of the relevant technical field.

[0042] Unless otherwise specified, all raw materials used in the following examples and comparative examples are commercially available or prepared by conventional methods in the art.

[0043] Preparation of supported catalysts: 3.4 mg of palladium chloride was added to 20 mL of water, and the pH was adjusted to 2 with 30% hydrochloric acid. 5 g of nano-titanium dioxide was added in portions over approximately 10 minutes with rapid stirring. After the addition was complete, stirring continued for 12 hours. The aqueous solution was then heated to 70°C to evaporate the water, yielding a slurry. The slurry was placed in a vacuum drying oven and dried at 80°C for 20 hours to obtain the precursor. The precursor was thoroughly ground and then calcined at 350°C for 6 hours to obtain the catalyst, designated Pd₄ / TiO₂.

[0044] 3.4 mg of palladium chloride was added to 20 mL of water, and the pH was adjusted to 2 with 30% hydrochloric acid. 5 g of fumed silica powder was added in portions over approximately 10 minutes with rapid stirring. After the addition was complete, stirring continued for 12 hours. The aqueous solution was then heated to 70°C to evaporate the water, yielding a slurry. The slurry was placed in a vacuum drying oven and dried at 80°C for 20 hours to obtain the precursor. The precursor was thoroughly ground and then calcined at 350°C for 6 hours to obtain the catalyst, designated Pd₄ / SiO₂.

[0045] 3.4 mg of palladium chloride was added to 20 mL of water, and the pH was adjusted to 2 with 30% hydrochloric acid. 5 g of alumina powder was added in portions over approximately 10 minutes with rapid stirring. After the addition was complete, stirring continued for 12 hours. The aqueous solution was then heated to 70°C to evaporate the water, yielding a slurry. The slurry was placed in a vacuum drying oven and dried at 80°C for 20 hours to obtain the precursor. The precursor was thoroughly ground and then calcined at 350°C for 6 hours to obtain the catalyst, designated Pd4 / γ-Al2O3.

[0046] 3.4 mg of palladium chloride was added to 20 mL of water, and the pH was adjusted to 2 with 30% hydrochloric acid. 5 g of gallium oxide powder was added in portions over approximately 10 minutes with rapid stirring. After the addition was complete, stirring continued for 12 hours. The aqueous solution was then heated to 70°C to evaporate the water, yielding a slurry. The slurry was placed in a vacuum drying oven and dried at 80°C for 20 hours to obtain the precursor. The precursor was thoroughly ground and then calcined at 350°C for 6 hours to obtain the catalyst, designated Pd₄ / Ga₂O₃.

[0047] 3.4 mg of palladium chloride was added to 20 mL of water, and the pH was adjusted to 2 with 30% hydrochloric acid. 5 g of ZSM-5 molecular sieve was added in portions over approximately 10 minutes with rapid stirring. After the addition was complete, stirring continued for 12 hours. The aqueous solution was then heated to 70°C to evaporate the water, yielding a slurry. The slurry was placed in a vacuum drying oven and dried at 80°C for 20 hours to obtain the precursor. The precursor was thoroughly ground and then calcined at 350°C for 6 hours to obtain the catalyst, designated Pd4 / ZSM-5.

[0048] 1.7 mg of palladium chloride was added to 20 mL of water, and the pH was adjusted to 2 with 30% hydrochloric acid. 5 g of nano-titanium dioxide was added in portions over approximately 10 minutes with rapid stirring. After the addition was complete, stirring continued for 12 hours. The aqueous solution was then heated to 70°C to evaporate the water, yielding a slurry. The slurry was placed in a vacuum drying oven and dried at 80°C for 20 hours to obtain the precursor. The precursor was thoroughly ground and then calcined at 350°C for 6 hours to obtain the catalyst, designated Pd2 / TiO2.

[0049] 3.4 mg of palladium chloride was added to 20 mL of water, and the pH was adjusted to 2 with 30% hydrochloric acid. 5 g of nano-titanium dioxide was added in portions over approximately 10 minutes with rapid stirring. After the addition was complete, stirring continued for 12 hours. The aqueous solution was then heated to 70°C to evaporate the water, yielding a slurry. The slurry was placed in a vacuum drying oven and dried at 80°C for 20 hours to obtain the precursor. The precursor was thoroughly ground and then calcined at 450°C for 6 hours to obtain the catalyst, designated Pd4 / TiO2-450.

[0050] 3.4 mg of palladium chloride was added to 20 mL of water, and the pH was adjusted to 2 with 30% hydrochloric acid. 5 g of nano-titanium dioxide was added in portions over approximately 10 minutes with rapid stirring. After the addition was complete, stirring continued for 12 hours. The aqueous solution was then heated to 70°C to evaporate the water, yielding a slurry. The slurry was placed in a vacuum drying oven and dried at 80°C for 20 hours to obtain the precursor. The precursor was thoroughly ground and then calcined at 350°C for 5 hours to obtain the catalyst, designated Pd4 / TiO2-5.

[0051] 1.7 mg of palladium chloride and 0.5 mg of tetrachloroauric acid were added to 20 mL of water. The pH was adjusted to 2 with 30% hydrochloric acid. 5 g of nano-titanium dioxide was added in portions over approximately 10 minutes with rapid stirring. After the addition was complete, stirring continued for 12 hours. The aqueous solution was then heated to 70°C to evaporate the water, yielding a slurry. The slurry was placed in a vacuum drying oven and dried at 80°C for 20 hours to obtain the precursor. The precursor was thoroughly ground and then calcined at 350°C for 6 hours to obtain the catalyst, designated Pd₂Au / TiO₂.

[0052] 1.7 mg of palladium chloride and 0.6 mg of tin tetrachloride were added to 20 mL of water, and the pH was adjusted to 2 with 30% hydrochloric acid. 5 g of nano-titanium dioxide was added in portions over approximately 10 minutes with rapid stirring. After the addition was complete, stirring continued for 12 hours. The aqueous solution was then heated to 70°C to evaporate the water, yielding a slurry. The slurry was placed in a vacuum drying oven and dried at 80°C for 20 hours to obtain the precursor. The precursor was thoroughly ground and then calcined at 350°C for 6 hours to obtain the catalyst, designated Pd₂Sn / TiO₂.

[0053] 2.8 mg of platinum chloride was added to 20 mL of water, and the pH was adjusted to 2 with 30% hydrochloric acid. 5 g of nano-titanium dioxide was added in portions over approximately 10 minutes with rapid stirring. After the addition was complete, stirring continued for 12 hours. The aqueous solution was then heated to 70°C to evaporate the water, yielding a slurry. The slurry was placed in a vacuum drying oven and dried at 80°C for 20 hours to obtain the precursor. The precursor was thoroughly ground and then calcined at 350°C for 6 hours to obtain the catalyst, designated Pt4 / TiO2.

[0054] 4.1 mg of rhodium chloride was added to 20 mL of water, and the pH was adjusted to 2 with 30% hydrochloric acid. 5 g of nano-titanium dioxide was added in portions over approximately 10 minutes with rapid stirring. After the addition was complete, stirring continued for 12 hours. The aqueous solution was then heated to 70°C to evaporate the water, yielding a slurry. The slurry was placed in a vacuum drying oven and dried at 80°C for 20 hours to obtain the precursor. The precursor was thoroughly ground and then calcined at 350°C for 6 hours to obtain the catalyst, designated Rh4 / TiO2.

[0055] Example 1: 12 g of water, 0.07 g of sodium tungstate dihydrate, 0.01 g of phosphoric acid (85% mass concentration), 0.116 g of trans-1,2-cyclohexanediol, 30 mg of the aforementioned Pd4 / TiO2, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen (volume ratio) mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen (volume ratio) mixture and a 1.2 MPa 25% oxygen / 75% nitrogen (volume ratio) mixture were introduced. The reactor was placed in a heating furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the remaining hydrogen was analyzed by gas chromatography with a TCD detector, and the content of raw materials and adipic acid was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 1.

[0056] Example 2: 12 g of water, 0.07 g of sodium tungstate dihydrate, 0.01 g of phosphoric acid (85% mass concentration), 0.116 g of trans-1,2-cyclohexanediol, 30 mg of the aforementioned Pd4 / SiO2, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen (volume ratio) mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen (volume ratio) mixture and a 1.2 MPa 25% oxygen / 75% nitrogen (volume ratio) mixture were introduced. The reactor was placed in a heating furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the remaining hydrogen was analyzed by gas chromatography with a TCD detector, and the content of raw materials and adipic acid was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 1.

[0057] Example 3: 12 g of water, 0.07 g of sodium tungstate dihydrate, 0.01 g of phosphoric acid (85% mass concentration), 0.116 g of trans-1,2-cyclohexanediol, 30 mg of the aforementioned Pd4 / γ-Al2O3, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen (volume ratio) mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen (volume ratio) mixture and a 1.2 MPa 25% oxygen / 75% nitrogen (volume ratio) mixture were introduced. The reactor was placed in a heating furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the amount of hydrogen remaining was analyzed by gas chromatography with a TCD detector, and the content of raw materials and adipic acid was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 1.

[0058] Example 4: 12 g of water, 0.07 g of sodium tungstate dihydrate, 0.01 g of phosphoric acid (85% mass concentration), 0.116 g of trans-1,2-cyclohexanediol, 30 mg of the aforementioned Pd4 / Ga2O3, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen (volume ratio) mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen (volume ratio) mixture and a 1.2 MPa 25% oxygen / 75% nitrogen (volume ratio) mixture were introduced. The reactor was placed in a heating furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the remaining hydrogen was analyzed by gas chromatography with a TCD detector, and the content of raw materials and adipic acid was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 1.

[0059] Example 5: 12 g of water, 0.07 g of sodium tungstate dihydrate, 0.01 g of phosphoric acid (85% mass concentration), 0.116 g of trans-1,2-cyclohexanediol, 30 mg of the aforementioned Pd4 / ZSM-5, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen (volume ratio) mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen (volume ratio) mixture and a 1.2 MPa 25% oxygen / 75% nitrogen (volume ratio) mixture were introduced. The reactor was placed in a heating furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the amount of hydrogen remaining was analyzed by gas chromatography with a TCD detector, and the content of raw materials and adipic acid was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 1.

[0060] Example 6: 12 g of water, 0.07 g of sodium tungstate dihydrate, 0.01 g of phosphoric acid (85% mass concentration), 0.116 g of trans-1,2-cyclohexanediol, 30 mg of the aforementioned Pd2 / TiO2, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen (volume ratio) mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen (volume ratio) mixture and a 1.2 MPa 25% oxygen / 75% nitrogen (volume ratio) mixture were introduced. The reactor was placed in a heating furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the amount of hydrogen remaining was analyzed by gas chromatography with a TCD detector, and the content of raw materials and adipic acid was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 1.

[0061] Example 7: 12 g of water, 0.07 g of sodium tungstate dihydrate, 0.01 g of phosphoric acid (85% mass concentration), 0.116 g of trans-1,2-cyclohexanediol, 30 mg of the aforementioned Pd4 / TiO2-450, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen (volume ratio) mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen (volume ratio) mixture and a 1.2 MPa 25% oxygen / 75% nitrogen (volume ratio) mixture were introduced. The reactor was placed in a heating furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the amount of hydrogen remaining was analyzed by gas chromatography with a TCD detector, and the content of raw materials and adipic acid was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 1.

[0062] Example 8: 12 g of water, 0.07 g of sodium tungstate dihydrate, 0.01 g of phosphoric acid (85% mass concentration), 0.116 g of trans-1,2-cyclohexanediol, 30 mg of the aforementioned Pd4 / TiO2-5, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen (volume ratio) mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen (volume ratio) mixture and a 1.2 MPa 25% oxygen / 75% nitrogen (volume ratio) mixture were introduced. The reactor was placed in a heating furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the remaining hydrogen was analyzed by gas chromatography with a TCD detector, and the content of raw materials and adipic acid was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 1.

[0063] Example 9: 12 g of water, 0.07 g of sodium tungstate dihydrate, 0.01 g of phosphoric acid (85% mass concentration), 0.116 g of trans-1,2-cyclohexanediol, 30 mg of the aforementioned Pd2Au / TiO2, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen (volume ratio) mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen (volume ratio) mixture and a 1.2 MPa 25% oxygen / 75% nitrogen (volume ratio) mixture were introduced. The reactor was placed in a heating furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the amount of hydrogen remaining was analyzed by gas chromatography with a TCD detector, and the content of raw materials and adipic acid was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 1.

[0064] Example 10: 12 g of water, 0.07 g of sodium tungstate dihydrate, 0.01 g of phosphoric acid (85% mass concentration), 0.116 g of trans-1,2-cyclohexanediol, 30 mg of the aforementioned Pd2Sn / TiO2, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen (volume ratio) mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen (volume ratio) mixture and a 1.2 MPa 25% oxygen / 75% nitrogen (volume ratio) mixture were introduced. The reactor was placed in a heating furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the amount of hydrogen remaining was analyzed by gas chromatography with a TCD detector, and the content of raw materials and adipic acid was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 1.

[0065] Example 11: 12 g of water, 0.07 g of sodium tungstate dihydrate, 0.01 g of phosphoric acid (85% mass concentration), 0.116 g of trans-1,2-cyclohexanediol, 30 mg of the aforementioned Pt4 / TiO2, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen (volume ratio) mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen (volume ratio) mixture and a 1.2 MPa 25% oxygen / 75% nitrogen (volume ratio) mixture were introduced. The reactor was placed in a heating furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the remaining hydrogen was analyzed by gas chromatography with a TCD detector, and the content of raw materials and adipic acid was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 1.

[0066] Example 12: 12 g of water, 0.07 g of sodium tungstate dihydrate, 0.01 g of phosphoric acid (85% mass concentration), 0.116 g of trans-1,2-cyclohexanediol, 30 mg of the aforementioned Rh4 / TiO2, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen (volume ratio) mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen (volume ratio) mixture and a 1.2 MPa 25% oxygen / 75% nitrogen (volume ratio) mixture were introduced. The reactor was placed in a heating furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the amount of hydrogen remaining was analyzed by gas chromatography with a TCD detector, and the content of raw materials and adipic acid was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 1.

[0067] Table 1

[0068] As shown in Table 1, the catalyst system of the present invention can efficiently oxidize vicinal diols, represented by trans-1,2-cyclohexanediol, into dicarboxylic acid compounds, represented by adipic acid, with a selectivity of 99% for adipic acid.

[0069] The highest yield of the target product was achieved when using a catalyst system composed of Pd4 / TiO2 or Pd4 / Ga2O3 with sodium tungstate dihydrate and phosphoric acid; followed by a catalyst system composed of Pd4 / SiO2 with sodium tungstate dihydrate and phosphoric acid.

[0070] Example 13: 12 g of water, 0.07 g of sodium tungstate dihydrate, 0.01 g of phosphoric acid (85% mass concentration), 0.116 g of trans-1,2-cyclohexanediol, 5 mg of the aforementioned Pd4 / TiO2, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen (volume ratio) mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen (volume ratio) mixture and a 1.2 MPa 25% oxygen / 75% nitrogen (volume ratio) mixture were introduced. The reactor was placed in a heating furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the amount of hydrogen remaining was analyzed by gas chromatography with a TCD detector, and the content of raw materials and adipic acid was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 2.

[0071] Example 14: 12 g of water, 0.07 g of sodium tungstate dihydrate, 0.01 g of phosphoric acid (85% mass concentration), 0.116 g of trans-1,2-cyclohexanediol, 50 mg of the aforementioned Pd4 / TiO2, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen (volume ratio) mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen (volume ratio) mixture and a 1.2 MPa 25% oxygen / 75% nitrogen (volume ratio) mixture were introduced. The reactor was placed in a heating furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the remaining hydrogen was analyzed by gas chromatography with a TCD detector, and the content of raw materials and adipic acid was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 2.

[0072] Example 15: 12 g of water, 0.035 g of sodium tungstate dihydrate, 0.005 g of phosphoric acid (85% mass concentration), 0.116 g of trans-1,2-cyclohexanediol, 30 mg of the aforementioned Pd4 / TiO2, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen (volume ratio) mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen (volume ratio) mixture and a 1.2 MPa 25% oxygen / 75% nitrogen (volume ratio) mixture were introduced. The reactor was placed in a heating furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the amount of hydrogen remaining was analyzed by gas chromatography with a TCD detector, and the content of raw materials and adipic acid was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 2.

[0073] Example 16: 12 g of water, 0.14 g of sodium tungstate dihydrate, 0.02 g of phosphoric acid (85% mass concentration), 0.116 g of trans-1,2-cyclohexanediol, 30 mg of the aforementioned Pd4 / TiO2, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen (volume ratio) mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen (volume ratio) mixture and a 1.2 MPa 25% oxygen / 75% nitrogen (volume ratio) mixture were introduced. The reactor was placed in a heating furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the remaining hydrogen was analyzed by gas chromatography with a TCD detector, and the content of raw materials and adipic acid was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 2.

[0074] Example 17: 12 g of water, 0.07 g of sodium tungstate dihydrate, 0.005 g of phosphoric acid (85% mass concentration), 0.116 g of trans-1,2-cyclohexanediol, 30 mg of the aforementioned Pd4 / TiO2, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen (volume ratio) mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen (volume ratio) mixture and a 1.2 MPa 25% oxygen / 75% nitrogen (volume ratio) mixture were introduced. The reactor was placed in a heating furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the amount of hydrogen remaining was analyzed by gas chromatography with a TCD detector, and the content of raw materials and adipic acid was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 2.

[0075] Example 18: 12 g of water, 0.07 g of sodium tungstate dihydrate, 0.02 g of phosphoric acid (85% mass concentration), 0.116 g of trans-1,2-cyclohexanediol, 30 mg of the aforementioned Pd4 / TiO2, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen (volume ratio) mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen (volume ratio) mixture and a 1.2 MPa 25% oxygen / 75% nitrogen (volume ratio) mixture were introduced. The reactor was placed in a heating furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the remaining hydrogen was analyzed by gas chromatography with a TCD detector, and the content of raw materials and adipic acid was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 2.

[0076] Example 19: 12 g of water, 0.14 g of phosphotungstic acid, 0.116 g of trans-1,2-cyclohexanediol, 30 mg of the aforementioned Pd4 / TiO2, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen (volume ratio) mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen (volume ratio) mixture and a 1.2 MPa 25% oxygen / 75% nitrogen (volume ratio) mixture were introduced. The reactor was placed in a heating furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the amount of hydrogen remaining was analyzed by gas chromatography with a TCD detector, and the content of raw materials and adipic acid was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 2.

[0077] Example 20: 12 g of water, 0.07 g of potassium tungstate, 0.01 g of phosphoric acid (85% mass concentration), 0.116 g of trans-1,2-cyclohexanediol, 30 mg of the aforementioned Pd4 / TiO2, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen (volume ratio) mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen (volume ratio) mixture and a 1.2 MPa 25% oxygen / 75% nitrogen (volume ratio) mixture were introduced. The reactor was placed in a heating furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the amount of hydrogen remaining was analyzed by gas chromatography with a TCD detector, and the content of raw materials and adipic acid was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 2.

[0078] Example 21: 12 g of water, 0.05 g of tungstic acid, 0.01 g of phosphoric acid (85% mass concentration), 0.116 g of trans-1,2-cyclohexanediol, 30 mg of the aforementioned Pd4 / TiO2, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen (volume ratio) mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen (volume ratio) mixture and a 1.2 MPa 25% oxygen / 75% nitrogen (volume ratio) mixture were introduced. The reactor was placed in a heating furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the amount of hydrogen remaining was analyzed by gas chromatography with a TCD detector, and the content of raw materials and adipic acid was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 2.

[0079] Example 22: 12 g of water, 0.07 g of sodium tungstate dihydrate, 0.01 g of sulfuric acid (98% mass concentration), 0.116 g of trans-1,2-cyclohexanediol, 30 mg of the aforementioned Pd4 / TiO2, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen (volume ratio) mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen (volume ratio) mixture and a 1.2 MPa 25% oxygen / 75% nitrogen (volume ratio) mixture were introduced. The reactor was placed in a heating furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the remaining hydrogen was analyzed by gas chromatography with a TCD detector, and the content of raw materials and adipic acid was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 2.

[0080] Example 23: 12 g of water, 0.07 g of sodium tungstate dihydrate, 0.03 g of selenic acid (40% mass concentration), 0.116 g of trans-1,2-cyclohexanediol, 30 mg of the aforementioned Pd4 / TiO2, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen (volume ratio) mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen (volume ratio) mixture and a 1.2 MPa 25% oxygen / 75% nitrogen (volume ratio) mixture were introduced. The reactor was placed in a heating furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the amount of hydrogen remaining was analyzed by gas chromatography with a TCD detector, and the content of raw materials and adipic acid was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 2.

[0081] Example 24: 12 g of water, 0.07 g of sodium tungstate dihydrate, 0.012 g of arsenic acid, 0.116 g of trans-1,2-cyclohexanediol, 30 mg of the aforementioned Pd4 / TiO2, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen (volume ratio) mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen (volume ratio) mixture and a 1.2 MPa 25% oxygen / 75% nitrogen (volume ratio) mixture were introduced. The reactor was placed in a heating furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the remaining hydrogen was analyzed by gas chromatography with a TCD detector, and the content of raw materials and adipic acid was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 2.

[0082] Example 25: 12 g of water, 0.07 g of sodium tungstate dihydrate, 0.02 g of sodium orthosilicate (80% mass concentration), 0.116 g of trans-1,2-cyclohexanediol, and 30 mg of Pd4 / TiO2, along with a magnetic stir bar, were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen (volume ratio) mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen (volume ratio) mixture and a 1.2 MPa 25% oxygen / 75% nitrogen (volume ratio) mixture were introduced. The reactor was placed in a furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the remaining hydrogen was analyzed by gas chromatography with a TCD detector, and the content of raw materials and adipic acid was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 2.

[0083] Table 2

[0084] As shown in Table 2, the amount of heterogeneous catalyst, the type and amount of homogeneous catalyst in the catalytic system all have a certain impact on the hydrogen conversion rate and efficiency, as well as the yield of the target product.

[0085] Example 26: 12 g of water, 0.07 g of sodium tungstate dihydrate, 0.01 g of phosphoric acid (85% mass concentration), 0.058 g of trans-1,2-cyclohexanediol, 30 mg of the aforementioned Pd4 / TiO2, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen (volume ratio) mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen (volume ratio) mixture and a 1.2 MPa 25% oxygen / 75% nitrogen (volume ratio) mixture were introduced. The reactor was placed in a heating furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the amount of hydrogen remaining was analyzed by gas chromatography with a TCD detector, and the content of raw materials and adipic acid was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 3.

[0086] Example 27: 12 g of water, 0.07 g of sodium tungstate dihydrate, 0.01 g of phosphoric acid (85% mass concentration), 0.232 g of trans-1,2-cyclohexanediol, 30 mg of the aforementioned Pd4 / TiO2, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen (volume ratio) mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen (volume ratio) mixture and a 1.2 MPa 25% oxygen / 75% nitrogen (volume ratio) mixture were introduced. The reactor was placed in a heating furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the amount of hydrogen remaining was analyzed by gas chromatography with a TCD detector, and the content of raw materials and adipic acid was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 3.

[0087] Example 28: 12 g of water, 0.07 g of sodium tungstate dihydrate, 0.01 g of phosphoric acid (85% mass concentration), 0.116 g of trans-1,2-cyclohexanediol, 30 mg of the aforementioned Pd4 / TiO2, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen (volume ratio) mixture. Then, a 2.32 MPa 5% hydrogen / 95% nitrogen (volume ratio) mixture and a 0.96 MPa 25% oxygen / 75% nitrogen (volume ratio) mixture were introduced. The reactor was placed in a heating furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the remaining hydrogen was analyzed by gas chromatography with a TCD detector, and the content of raw materials and adipic acid was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 3.

[0088] Example 29: 12 g of water, 0.07 g of sodium tungstate dihydrate, 0.01 g of phosphoric acid (85% mass concentration), 0.116 g of trans-1,2-cyclohexanediol, 30 mg of the aforementioned Pd4 / TiO2, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen (volume ratio) mixture. Then, a 3.6 MPa 5% hydrogen / 95% nitrogen (volume ratio) mixture and a 1.5 MPa 25% oxygen / 75% nitrogen (volume ratio) mixture were introduced. The reactor was placed in a heating furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the amount of hydrogen remaining was analyzed by gas chromatography with a TCD detector, and the content of raw materials and adipic acid was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 3.

[0089] Example 30: 12 g of water, 0.07 g of sodium tungstate dihydrate, 0.01 g of phosphoric acid (85% mass concentration), 0.116 g of trans-1,2-cyclohexanediol, 30 mg of the aforementioned Pd4 / TiO2, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen (volume ratio) mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen (volume ratio) mixture and a 0.6 MPa 25% oxygen / 75% nitrogen (volume ratio) mixture were introduced. The reactor was placed in a heating furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the amount of hydrogen remaining was analyzed by gas chromatography with a TCD detector, and the content of raw materials and adipic acid was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 3.

[0090] Example 31: 12 g of water, 0.07 g of sodium tungstate dihydrate, 0.01 g of phosphoric acid (85% mass concentration), 0.116 g of trans-1,2-cyclohexanediol, 30 mg of the aforementioned Pd4 / TiO2, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen (volume ratio) mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen (volume ratio) mixture and a 1.8 MPa 25% oxygen / 75% nitrogen (volume ratio) mixture were introduced. The reactor was placed in a heating furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the amount of hydrogen remaining was analyzed by gas chromatography with a TCD detector, and the content of raw materials and adipic acid was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 3.

[0091] Example 32: 12 g of water, 0.07 g of sodium tungstate dihydrate, 0.01 g of phosphoric acid (85% mass concentration), 0.116 g of trans-1,2-cyclohexanediol, 30 mg of the aforementioned Pd4 / TiO2, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen (volume ratio) mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen (volume ratio) mixture and a 1.2 MPa 25% oxygen / 75% nitrogen (volume ratio) mixture were introduced. The reactor was placed in a heating furnace and heated to 80°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the amount of hydrogen remaining was analyzed by gas chromatography with a TCD detector, and the content of raw materials and adipic acid was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 3.

[0092] Example 33: 12 g of water, 0.07 g of sodium tungstate dihydrate, 0.01 g of phosphoric acid (85% mass concentration), 0.116 g of trans-1,2-cyclohexanediol, 30 mg of the aforementioned Pd4 / TiO2, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen (volume ratio) mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen (volume ratio) mixture and a 1.2 MPa 25% oxygen / 75% nitrogen (volume ratio) mixture were introduced. The reactor was placed in a heating furnace and heated to 100°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the amount of hydrogen remaining was analyzed by gas chromatography with a TCD detector, and the content of raw materials and adipic acid was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 3.

[0093] Example 34: 12 g of water, 0.07 g of sodium tungstate dihydrate, 0.01 g of phosphoric acid (85% mass concentration), 0.116 g of trans-1,2-cyclohexanediol, 30 mg of the aforementioned Pd4 / TiO2, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen (volume ratio) mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen (volume ratio) mixture and a 1.2 MPa 25% oxygen / 75% nitrogen (volume ratio) mixture were introduced. The reactor was placed in a heating furnace and heated to 90°C. The reaction was carried out for 10 hours with rapid stirring. After the reaction, the remaining hydrogen was analyzed by gas chromatography with a TCD detector, and the content of raw materials and adipic acid was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 3.

[0094] Example 35: 12 g of water, 0.07 g of sodium tungstate dihydrate, 0.01 g of phosphoric acid (85% mass concentration), 0.116 g of trans-1,2-cyclohexanediol, 30 mg of the aforementioned Pd4 / TiO2, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen (volume ratio) mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen (volume ratio) mixture and a 1.2 MPa 25% oxygen / 75% nitrogen (volume ratio) mixture were introduced. The reactor was placed in a heating furnace and heated to 90°C. The reaction was carried out for 20 h with rapid stirring. After the reaction, the amount of hydrogen remaining was analyzed by gas chromatography with a TCD detector, and the content of raw materials and adipic acid was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 3.

[0095] Example 36: 12 g water / 2 g acetonitrile, 0.07 g sodium tungstate dihydrate, 0.01 g phosphoric acid (85% mass concentration), 0.116 g trans-1,2-cyclohexanediol, 30 mg of the aforementioned Pd4 / TiO2, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen (volume ratio) mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen (volume ratio) mixture and a 1.2 MPa 25% oxygen / 75% nitrogen (volume ratio) mixture were introduced. The reactor was placed in a heating furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the remaining hydrogen was analyzed by gas chromatography with a TCD detector, and the content of raw materials and adipic acid was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 3.

[0096] Example 37: 12 g water / 3 g acetonitrile, 0.07 g sodium tungstate dihydrate, 0.01 g phosphoric acid (85% mass concentration), 0.116 g trans-1,2-cyclohexanediol, 30 mg of the aforementioned Pd4 / TiO2, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen (volume ratio) mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen (volume ratio) mixture and a 1.2 MPa 25% oxygen / 75% nitrogen (volume ratio) mixture were introduced. The reactor was placed in a heating furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the remaining hydrogen was analyzed by gas chromatography with a TCD detector, and the content of raw materials and adipic acid was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 3.

[0097] Example 38: 12 g water / 1 g benzonitrile, 0.07 g sodium tungstate dihydrate, 0.01 g phosphoric acid (85% mass concentration), 0.116 g trans-1,2-cyclohexanediol, 30 mg of the aforementioned Pd4 / TiO2, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen (volume ratio) mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen (volume ratio) mixture and a 1.2 MPa 25% oxygen / 75% nitrogen (volume ratio) mixture were introduced. The reactor was placed in a heating furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the remaining hydrogen was analyzed by gas chromatography with a TCD detector, and the content of raw materials and adipic acid was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 3.

[0098] Example 39: 12 g of water, 0.07 g of sodium tungstate dihydrate, 0.01 g of phosphoric acid (85% mass concentration), 1.16 g of trans-1,2-cyclohexanediol, 30 mg of the aforementioned Pd4 / TiO2, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed by installing the lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen (volume ratio) mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen (volume ratio) mixture and a 1.2 MPa 25% oxygen / 75% nitrogen (volume ratio) mixture were introduced. The reactor was placed in a heating furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring.

[0099] Afterward, the reaction solution was cooled to room temperature and the waste gas was released. Fresh mixed gas (i.e., 2.9 MPa 5% hydrogen / 95% nitrogen mixture and 1.2 MPa 25% oxygen / 75% nitrogen mixture) was then introduced, and the reaction was repeated three times.

[0100] After the reaction was completed, the amount of hydrogen remaining was analyzed by gas chromatography with a TCD detector, and the content of raw materials and adipic acid was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 3.

[0101] Table 3

[0102] Table 3 shows that as the amount of substrate in the reaction system increases, the selectivity of the target product remains at 99%, while the substrate conversion rate decreases. The amount of hydrogen and oxygen introduced into the reaction system has a certain impact on the conversion rate: a higher substrate conversion rate can be obtained when a 5% hydrogen / 95% nitrogen mixture is introduced at a pressure not lower than 2.9 MPa, and a 25% oxygen / 75% nitrogen mixture is introduced at a pressure not lower than 1.2 MPa. Furthermore, the reaction temperature should be controlled within a suitable range; excessively high temperatures can easily lead to side reactions, while excessively low temperatures result in incomplete reactions. The reaction time should not be too short to avoid incomplete reactions; for energy-saving purposes, it should not be too long either. The reaction solvent can be pure water or a mixture of water and nitrile solvents.

[0103] Comparative Example 1: 12 g of water, 0.07 g of sodium tungstate dihydrate, 0.01 g of phosphoric acid (85% mass concentration), 0.116 g of trans-1,2-cyclohexanediol, 0.38 g of 30% hydrogen peroxide, and a magnetic stir bar were added to a reaction tube. The reaction tube was placed in an oil bath and heated to 90°C. The reaction was carried out for 12 h with rapid stirring. After the reaction was completed, the amount of hydrogen peroxide remaining was analyzed by cerium sulfate titration. The content of raw materials and adipic acid was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard.

[0104] In this comparative example, the hydrogen peroxide conversion rate was 99%, the hydrogen peroxide efficiency was 54%, the substrate conversion rate was 69%, and the adipic acid selectivity was 86%.

[0105] Comparing Example 1 and Comparative Example 1, it is evident that while adding hydrogen peroxide directly to the reaction system yields adipic acid, the selectivity is only 86%, significantly lower than that of the embodiments of this invention. Low selectivity means that under the same reaction conditions, a higher proportion of reactants are converted into byproducts or other non-target compounds. This not only reduces the actual yield of the target product but also increases the difficulty and cost of subsequent separation and purification. Furthermore, the formation of byproducts may lead to catalyst deactivation, decreased reaction system stability, and adversely affect the overall product quality and process economy.

[0106] Example 40: This example is basically the same as Example 39, except that: After the reaction was complete, the reaction solution was heated to 70°C, and the Pd₄ / TiO₂ catalyst was removed by hot filtration. The filtrate was transferred to a round-bottom flask, and 8 g of solvent was removed by rotary evaporation. The reaction solution was then placed at 4°C overnight, and adipic acid was obtained by filtration. Its 1H and 1C spectra are shown below. Figure 2 , Figure 3 As shown, the separation yield was 31% and the purity was 99%.

[0107] Mother liquor reuse: Add the above-mentioned mother liquor obtained after adipic acid crystallization separation, 8 g of water, 0.42 g of trans-1,2-cyclohexanediol, 30 mg of the aforementioned Pd4 / TiO2, and a magnetic stir bar to a high-pressure reactor. Seal the reactor with the lid and retaining ring, and purge the gas three times using a 5% hydrogen / 95% nitrogen mixture. Then, purge with a 2.9 MPa 5% hydrogen / 95% nitrogen mixture and a 1.2 MPa 25% oxygen / 75% nitrogen mixture. Place the reactor in a heating furnace and heat to 90°C, reacting for 12 hours with rapid stirring. After cooling the reaction solution to room temperature, release the waste gas and purge with fresh mixed gas (i.e., a 2.9 MPa 5% hydrogen / 95% nitrogen mixture and a 1.2 MPa 25% oxygen / 75% nitrogen mixture), repeating the reaction three times. After the reaction was completed, the amount of hydrogen remaining was analyzed by gas chromatography with a TCD detector, and the content of raw materials and adipic acid was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard.

[0108] The process of separating adipic acid crystals and reusing the mother liquor was repeated three times, and the results are shown in Table 4.

[0109] Table 4

[0110] As shown in Table 4, reaction solutions containing unreacted raw materials can be directly reused.

[0111] Example 41: 12 g of water, 0.07 g of sodium tungstate dihydrate, 0.01 g of phosphoric acid (85% mass concentration), 0.116 g of cis-1,2-cyclohexanediol, 30 mg of the aforementioned Pd4 / TiO2, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen mixture and a 1.2 MPa 25% oxygen / 75% nitrogen mixture were introduced. The reactor was placed in a heating furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the amount of hydrogen remaining was analyzed by gas chromatography with a TCD detector, and the content of raw materials and adipic acid was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 5.

[0112] Example 42: 12 g of water, 0.07 g of sodium tungstate dihydrate, 0.01 g of phosphoric acid (85% mass concentration), 0.098 g of cyclohexene oxide, 30 mg of the aforementioned Pd4 / TiO2, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen mixture and a 1.2 MPa 25% oxygen / 75% nitrogen mixture were introduced. The reactor was placed in a heating furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the amount of hydrogen remaining was analyzed by gas chromatography with a TCD detector, and the content of raw materials and adipic acid was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 5.

[0113] Example 43: 12 g of water, 0.07 g of sodium tungstate dihydrate, 0.01 g of phosphoric acid (85% mass concentration), 0.144 g of cis-1,2-cyclooctanediol, 30 mg of the aforementioned Pd4 / TiO2, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen mixture and a 1.2 MPa 25% oxygen / 75% nitrogen mixture were introduced. The reactor was placed in a heating furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the amount of hydrogen remaining was analyzed by gas chromatography with a TCD detector, and the content of raw materials and octanoic acid was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 5.

[0114] Example 44: 12 g of water, 0.07 g of sodium tungstate dihydrate, 0.01 g of phosphoric acid (85% mass concentration), 0.144 g of trans-1,2-cyclooctanediol, 30 mg of the aforementioned Pd4 / TiO2, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen mixture and a 1.2 MPa 25% oxygen / 75% nitrogen mixture were introduced. The reactor was placed in a heating furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the amount of hydrogen remaining was analyzed by gas chromatography with a TCD detector, and the content of raw materials and octanoic acid was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 5.

[0115] Example 45: 12 g of water, 0.07 g of sodium tungstate dihydrate, 0.01 g of phosphoric acid (85% mass concentration), 0.126 g of 1,2-epoxycyclooctane, 30 mg of the above-mentioned Pd4 / TiO2, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen mixture and a 1.2 MPa 25% oxygen / 75% nitrogen mixture were introduced. The reactor was placed in a heating furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the amount of hydrogen remaining was analyzed by gas chromatography with a TCD detector, and the content of raw materials and octanoic acid was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 5.

[0116] Example 46: 12 g of water, 0.07 g of sodium tungstate dihydrate, 0.01 g of phosphoric acid (85% mass concentration), 0.158 g of 4-isopropyl-trans-1,2-cyclohexanediol, 30 mg of the aforementioned Pd4 / TiO2, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen mixture and a 1.2 MPa 25% oxygen / 75% nitrogen mixture were introduced. The reactor was placed in a heating furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the amount of hydrogen remaining was analyzed by gas chromatography with a TCD detector, and the content of raw materials and reaction products was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 5.

[0117] Example 47: 12 g of water, 0.07 g of sodium tungstate dihydrate, 0.01 g of phosphoric acid (85% mass concentration), 0.192 g of 4-phenyl-trans-1,2-cyclohexanediol, 30 mg of the aforementioned Pd4 / TiO2, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen mixture and a 1.2 MPa 25% oxygen / 75% nitrogen mixture were introduced. The reactor was placed in a heating furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the amount of hydrogen remaining was analyzed by gas chromatography with a TCD detector, and the content of raw materials and reaction products was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 5.

[0118] Example 48: 12 g of water, 0.07 g of sodium tungstate dihydrate, 0.01 g of phosphoric acid (85% mass concentration), 0.198 g of 4-cyclohexyl-trans-1,2-cyclohexanediol, 30 mg of Pd4 / TiO2, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen mixture and a 1.2 MPa 25% oxygen / 75% nitrogen mixture were introduced. The reactor was placed in a furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the amount of hydrogen remaining was analyzed by gas chromatography with a TCD detector, and the content of raw materials and reaction products was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 5.

[0119] Example 49: 12 g of water, 0.07 g of sodium tungstate dihydrate, 0.01 g of phosphoric acid (85% mass concentration), 0.131 g of 3-amino-trans-1,2-cyclohexanediol, 30 mg of the aforementioned Pd4 / TiO2, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen mixture and a 1.2 MPa 25% oxygen / 75% nitrogen mixture were introduced. The reactor was placed in a heating furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the amount of hydrogen remaining was analyzed by gas chromatography with a TCD detector, and the content of raw materials and reaction products was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 5.

[0120] Example 50: 12 g of water, 0.07 g of sodium tungstate dihydrate, 0.01 g of phosphoric acid (85% mass concentration), 0.158 g of 1-(3,4-dihydroxycyclohexyl) acetone, 30 mg of Pd4 / TiO2, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen mixture and a 1.2 MPa 25% oxygen / 75% nitrogen mixture were introduced. The reactor was placed in a furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the amount of hydrogen remaining was analyzed by gas chromatography with a TCD detector, and the content of raw materials and reaction products was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 5.

[0121] Example 51: 12 g of water, 0.07 g of sodium tungstate dihydrate, 0.01 g of phosphoric acid (85% mass concentration), 0.146 g of 4-methoxy-trans-1,2-cyclohexanediol, 30 mg of the aforementioned Pd4 / TiO2, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen mixture and a 1.2 MPa 25% oxygen / 75% nitrogen mixture were introduced. The reactor was placed in a heating furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the amount of hydrogen remaining was analyzed by gas chromatography with a TCD detector, and the content of raw materials and reaction products was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 5.

[0122] Example 52: 12 g of water, 0.07 g of sodium tungstate dihydrate, 0.01 g of phosphoric acid (85% mass concentration), 0.161 g of 4-nitro-trans-1,2-cyclohexanediol, 30 mg of the aforementioned Pd4 / TiO2, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen mixture and a 1.2 MPa 25% oxygen / 75% nitrogen mixture were introduced. The reactor was placed in a heating furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the amount of hydrogen remaining was analyzed by gas chromatography with a TCD detector, and the content of raw materials and reaction products was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 5.

[0123] Example 53: 12 g of water, 0.07 g of sodium tungstate dihydrate, 0.01 g of phosphoric acid (85% mass concentration), 0.2 g of 4,5-dicarboxy-trans-1,2-cyclohexanediol, 30 mg of the aforementioned Pd4 / TiO2, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen mixture and a 1.2 MPa 25% oxygen / 75% nitrogen mixture were introduced. The reactor was placed in a heating furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the amount of hydrogen remaining was analyzed by gas chromatography with a TCD detector, and the content of raw materials and reaction products was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 5.

[0124] Example 54: 12 g of water, 0.07 g of sodium tungstate dihydrate, 0.01 g of phosphoric acid (85% mass concentration), 0.172 g of 3,4,5,6-tetramethyl-trans-1,2-cyclohexanediol, 30 mg of the aforementioned Pd4 / TiO2, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen mixture and a 1.2 MPa 25% oxygen / 75% nitrogen mixture were introduced. The reactor was placed in a heating furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the amount of hydrogen remaining was analyzed by gas chromatography with a TCD detector, and the content of raw materials and reaction products was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 5.

[0125] Example 55: 12 g of water, 0.07 g of sodium tungstate dihydrate, 0.01 g of phosphoric acid (85% mass concentration), 0.212 g of trans-9,10-dihydroxy-9,10-dihydrophenanthrene, 30 mg of the aforementioned Pd4 / TiO2, and a magnetic stir bar were added to a high-pressure reactor. The reactor was sealed with a lid and retaining ring. The reactor was purged three times with a 5% hydrogen / 95% nitrogen mixture. Then, a 2.9 MPa 5% hydrogen / 95% nitrogen mixture and a 1.2 MPa 25% oxygen / 75% nitrogen mixture were introduced. The reactor was placed in a heating furnace and heated to 90°C. The reaction was carried out for 12 hours with rapid stirring. After the reaction, the amount of hydrogen remaining was analyzed by gas chromatography with a TCD detector, and the content of raw materials and reaction products was analyzed by nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 5.

[0126] Table 5

[0127] As shown in Table 5, the preparation method of the present invention has wide applicability; dicarboxylic acid compounds can be obtained using compounds of formula (1) or formula (2) as raw materials. Wherein, R 1 To R 4 Different functional groups result in different values ​​of n, which can have a certain impact on the yield of the product.

[0128] Example 56: The present invention also provides a method for preparing dicarboxylic acid compounds using a continuous reactor, comprising the following steps: Weigh 8 g of the Pd₂Au / TiO₂ and 12 g of SiO₂, mix them evenly, and then press, crush, and sieve to obtain catalyst particles with a particle size of 1 mm to 2 mm. Pack the catalyst particles into a stainless steel reaction tube with an inner diameter of 12 mm, with a total volume of 30 mL. Figure 4 (As shown).

[0129] The catalyst-containing reaction tube was heated to 90°C. A mixed gas with a composition of 2% hydrogen / 10% oxygen / 88% nitrogen (volume ratio) was continuously introduced at a certain flow rate and pressure. Simultaneously, a reaction solution with a composition of 20 wt% trans-1,2-cyclohexanediol, 1.4 wt% sodium tungstate dihydrate, and 0.2 wt% phosphoric acid (85% mass concentration) was continuously introduced at a certain flow rate. The reactant gas and reaction solution continued to flow through a condenser and a gas-liquid separator. After the reaction stabilized, they were collected separately. The residual hydrogen in the mixed gas was analyzed using gas chromatography with a TCD detector, and the content of raw materials and adipic acid in the reaction solution was analyzed using nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 6.

[0130] Table 6

[0131] As shown in Table 6, the preparation method described in this invention is applicable not only to batch reactors but also to continuous reactors.

[0132] Example 57: The present invention also provides a method for preparing dicarboxylic acid compounds using a continuous reactor, comprising the following steps: Weigh 8 g of the Pd2Au / TiO2 and 12 g of SiO2, mix them evenly, and then press, crush and sieve to obtain catalyst particles with a particle size of 1 mm to 2 mm. The catalyst particles are then loaded into a stainless steel reaction tube with an inner diameter of 12 mm, with a total volume of 30 mL.

[0133] The reaction tube containing the catalyst was heated to 90°C. A mixed gas consisting of 2% hydrogen, 10% oxygen, and 88% nitrogen (volume ratio) was continuously introduced at a flow rate of 160 mL / min while maintaining a pressure of 0.4 MPa. Simultaneously, a reaction solution consisting of 20 wt% trans-1,2-cyclohexanediol, 1.4 wt% sodium tungstate dihydrate, and 0.2 wt% phosphoric acid (85%) was continuously introduced at a flow rate of 0.07 mL / min. The reactant gas and reaction solution continued to flow through a condenser and a gas-liquid separator, and were collected at regular intervals. The residual hydrogen in the mixed gas was analyzed using gas chromatography with a TCD detector, and the content of raw materials and adipic acid in the reaction solution was analyzed using nuclear magnetic resonance. Benzoic acid was used as an internal standard. The results are shown in Table 7.

[0134] Table 7

[0135] As shown in Table 7, in the continuous reaction system of the present invention, the hydrogen conversion rate, substrate conversion rate and product selectivity remain basically stable as the sampling time increases, indicating that the catalyst activity has not significantly decreased and the reaction system has good operational stability and time reliability.

[0136] The present invention has been described in detail above, with the aim of enabling those skilled in the art to understand and implement the invention. However, this description should not be construed as limiting the scope of protection of the invention. All equivalent changes or modifications made in accordance with the spirit and essence of the invention should be included within the scope of protection of the invention.

Claims

1. A method for synthesizing a dicarboxylic acid compound, characterized in that: Using the compounds shown in formula (1) and / or formula (2) as raw materials, the dicarboxylic acid compounds shown in formula (3) are prepared by reacting them in a catalytic system in the presence of hydrogen and oxygen. Equation (1) is: Equation (2) is: Equation (3) is: ; wherein, R in equations (1), (2), and (3) 1 R 2 R 3 and R 4 Each R is independently selected from a monovalent organic group, or any two or more of them are connected to each other to form a ring structure; n is an integer between 0 and 12, and when n is an integer greater than 1, each R 4 Same or different; The catalytic system includes a first catalyst and a second catalyst. The first catalyst includes a support and an active component loaded thereon. The active component is a first metal or an alloy formed by the first metal and a second metal. The first metal is selected from one or more of palladium, platinum, rhodium, and iridium. The second metal is gold and / or tin. The second catalyst is a tungsten-containing compound.

2. The method for synthesizing dicarboxylic acid compounds according to claim 1, characterized in that: Based on the total mass of the first catalyst being 100%, the first catalyst comprises: Carrier 85%~99.99%; First metal: 0.01%~10%; Secondary metal content: 0-5%.

3. The method for synthesizing dicarboxylic acid compounds according to claim 1, characterized in that: The carrier is selected from one or more of metal oxides and molecular sieves; and / or, The tungsten-containing compound is selected from one or more of tungstic acid or its salts, metatungstate, heteropolytungstic acid or its salts.

4. The method for synthesizing dicarboxylic acid compounds according to claim 3, characterized in that: The metal oxides include aluminum oxide, silicon oxide, titanium oxide, magnesium oxide, zirconium oxide, cerium oxide, and gallium oxide; and / or, The tungstic acid or its salts include tungstic acid, lithium tungstate, sodium tungstate, potassium tungstate, cesium tungstate, cadmium tungstate, calcium tungstate, nickel tungstate, bismuth tungstate, zinc tungstate, strontium tungstate, silver tungstate, copper tungstate, and ammonium tungstate; and / or, The metatungstate includes ammonium metatungstate; and / or, The heteropolytungstic acid or its salts include silicotungstic acid, phosphotungstic acid, selenotungstic acid, germanantungstic acid, arsenictungstic acid, and salts formed by these acids with alkali metals, alkaline earth metals, or ammonium.

5. The method for synthesizing dicarboxylic acid compounds according to claim 1, characterized in that: The catalytic system also includes an auxiliary agent, which is selected from one or more protic acids and strong base-weak acid salts; The protic acids include hydrochloric acid, sulfuric acid, nitric acid, hydrobromic acid, p-toluenesulfonic acid, phosphoric acid, metaphosphoric acid, pyrophosphoric acid, phosphorous acid, hypophosphoric acid, silicic acid, polysilicic acid, orthogermic acid, metagermic acid, selenic acid, selenite, arsenic acid, arsenite, metaarsenic acid, and benzoarsine. The strong base-weak acid salt includes sodium orthosilicate.

6. The method for synthesizing dicarboxylic acid compounds according to claim 1, characterized in that: In the catalytic system, the mass ratio of the first catalyst, the second catalyst and the auxiliary agent is 1:(1~20):(0~15).

7. The method for synthesizing dicarboxylic acid compounds according to claim 1, characterized in that: The reaction temperature is 80℃~100℃.

8. The method for synthesizing dicarboxylic acid compounds according to claim 1, characterized in that: The reaction is carried out in the presence of a solvent, which is water or a mixture of water and a nitrile solvent.

9. The method for synthesizing dicarboxylic acid compounds according to claim 1, characterized in that: The monovalent organic group includes hydrogen, straight-chain or branched or cyclic alkyl, aryl, benzyl, alkoxy, carboxyl, ester, nitro, halogen, and sulfonic acid groups; and / or, The cyclic structure includes cyclic alkyl and aryl groups; and / or, The n is an integer from 1 to 5.

10. The method for synthesizing dicarboxylic acid compounds according to any one of claims 1 to 9, characterized in that: The reaction is either a batch reaction or a continuous reaction.

11. The method for synthesizing dicarboxylic acid compounds according to claim 10, characterized in that: When the reaction is a batch reaction, hydrogen, oxygen and inert gas are introduced into the reaction system, and the partial pressure of hydrogen and oxygen in the reaction system is controlled to be not less than 0.1 MPa, and the total pressure of the reaction system is 2 MPa to 10 MPa.

12. The method for synthesizing dicarboxylic acid compounds according to claim 10, characterized in that: When the reaction is a continuous reaction, the first catalyst is loaded into a continuous reactor, and the reaction liquid containing the raw material, the second catalyst, the solvent and optional auxiliary agent, and a mixed gas containing hydrogen, oxygen and inert gas are continuously introduced into the continuous reactor, either separately or in advance.

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