A method for preparing perhydrofluorene based on biomass-based catalyst

Abstract

The present invention relates to a green catalytic method for preparing perhydrofluorene by hydrodeoxygenation cyclization reaction of o-hydroxydiphenylmethane, specifically, a clean aqueous phase catalyst obtained by in-situ reduction of ruthenium acetate by sodium lignin sulfonate in an aqueous solution, a method for catalyzing o-hydroxydiphenylmethane to prepare perhydrofluorene by hydrodeoxygenation cyclization reaction under aqueous phase conditions, and belongs to the field of biomass high-value catalytic conversion. The present invention uses sodium lignin sulfonate, a derivative product of black liquor produced as a by-product of the papermaking industry, as a raw material, utilizes its skeleton structure and functional group characteristics, coordinates and stabilizes metallic ruthenium with acetate in aqueous solution, and performs in-situ reduction, obtains a clean aqueous phase dispersed metallic ruthenium catalyst without other auxiliary reagents, and is directly used for the hydrodeoxygenation cyclization reaction of o-hydroxydiphenylmethane, and can prepare perhydrofluorene gently and efficiently. After the reaction, the aqueous phase dispersed metallic ruthenium catalyst is simply self-separated from the organic phase product by standing, and the recovered catalyst can be directly recycled and has good stability. The invention has both the effectiveness of reaction and the simplicity of separation, and the catalytic system and catalytic process are environmentally friendly, and is a green catalytic process for preparing perhydrofluorene.

Description

Technical Field

[0001] The invention relates to a green catalytic method for preparing perhydrofluorene through the hydrodeoxygenation cyclization reaction of o-hydroxydiphenylmethane, specifically, a water-phase catalytic system prepared by reducing a stable Ru salt with sodium lignin sulfonate is used to catalyze the water-phase hydrodeoxygenation cyclization reaction of o-hydroxydiphenylmethane to prepare perhydrofluorene, and belongs to the field of biomass high-value catalytic conversion. Background Art

[0002] In the context of "dual carbon", the use of renewable biomass resources to develop and construct high-density jet fuel molecules with multi-ring saturated hydrocarbon structural characteristics is a very promising direction for the expansion of fuel sources and a method for high-value biomass. Phenolic compounds and benzyl compounds in the catalytic cracking products of lignin can be alkylated to form o-hydroxydiphenylmethane, and o-hydroxydiphenylmethane can undergo intramolecular cyclization under metal-catalyzed hydrogen atmosphere reaction conditions to obtain perhydrofluorene products [Chem Eng Sci. 2017; 158: 64-69]. This tricyclic saturated hydrocarbon compound is an important liquid organic hydrogen carrier [Int J Hydrog Energy. 2023; 76 (5): 29651-29662], and is also a very potential biomass high energy density fuel additive [Chem Eng Sci. 2017; 173: 91-97]. Therefore, the development of efficient, mild, and environmentally friendly catalytic reaction methods to prepare perhydrofluorene products with high selectivity will be of great significance for the development of renewable energy and the high-value transformation of lignin resources.

[0003] In the prior art, there are few reports on the catalytic hydrodeoxygenation of o-hydroxydiphenylmethane to prepare perhydrofluorene. Someone once used sulfided CoOMoO3 / γ-Al2O3 as a catalyst and hexadecane as a solvent to catalyze the hydrogenation reaction of o-hydroxydiphenylmethane, a model compound obtained by catalytic liquefaction of lignin. At 300-330°C and 1000psig H2 pressure, (benzene + cyclohexane), toluene, benzylcyclohexane, diphenylmethane and phenol were mainly obtained. In addition, a small amount of o-cresol, alkylated phenol and isomers of o-hydroxydiphenylmethane were also obtained in the product, but no perhydrofluorene product was obtained [Ind Eng Chem Prod Res Dev. 1985; 24(4): 635-641]. CN105732291A discloses the use of metal and acid catalyst composite catalysis to replace diphenylmethane and prepare perhydrofluorene through hydrodeoxygenation cyclization. Under the conditions of 3-8MPa hydrogen pressure and 120-250°C, diphenylmethane derivatives can achieve 100% conversion to generate two saturated hydrocarbon derivatives, dicyclohexylmethane and perhydrofluorene. Increasing the proportion of metal catalyst in the composite catalyst can improve the selectivity of perhydrofluorene. Taking o-hydroxydiphenylmethane as the substrate, using palladium carbon-zeolite dual catalyst, under 6MPa hydrogen pressure and 180°C for 10h, the product is still mainly dicyclohexylmethane; while using palladium carbon or nickel-based catalyst alone, 96% perhydrofluorene can be obtained [Chem Eng Sci.2017;173:91-97]. Using 5wt% Pd / C as a catalyst and water as a reaction medium to catalyze the hydrogenation of o-hydroxydiphenylmethane, an 85% hydrocarbon yield can be obtained under the conditions of 6MPa hydrogen pressure and 180℃ for 10h, of which the perhydrofluorene product accounts for 75.2%, and the upper organic product can be separated from the water phase after the reaction [ACS Sustain Chem Eng. 2021; 9(20): 7112-7119]. Using Ru / C to catalyze the in-situ hydrodeoxygenation reaction of phenol and benzyl alcohol alkylation products, 100% conversion of o-hydroxydiphenylmethane can be achieved under the conditions of 6MPa H2 and 180℃ for 10h, and the perhydrofluorene selectivity can reach 96% [Fuel. 2024; 360: 130570].

[0004] In summary, the prior art uses commercial Pd / C and Ru / C to catalyze the hydrodeoxygenation reaction of o-hydroxydiphenylmethane, which can prepare perhydrofluorene products with a higher yield, but the reaction conditions are relatively harsh. The present invention provides a method for efficiently preparing perhydrogen products by catalyzing the hydrodeoxygenation cyclization reaction of o-hydroxydiphenylmethane under mild water-phase catalytic system conditions. After the reaction is completed, the product phase and the water-phase catalyst are self-separated, and the catalyst can be easily recovered and has good recycling performance. The water-phase catalyst used in the present invention only uses cheap and renewable sodium lignin sulfonate as a reducing stabilizer for the metal Ru salt, and no other reagents are required. The preparation method is simple, gentle and clean, and provides a new green method for preparing perhydrofluorene by hydrodeoxygenation cyclization of o-hydroxydiphenylmethane. So far, the method for preparing perhydrofluorene by catalyzing the hydrodeoxygenation cyclization reaction of o-hydroxydiphenylmethane using a water-phase catalyst prepared by reducing and stabilizing transition metals of lignin derivatives has not been reported in domestic and foreign literature. Summary of the invention

[0005] The present invention utilizes the natural macromolecular skeleton structure and functional group characteristics of sodium lignin sulfonate, a waste biomass resource, to carry out complex stabilization and in-situ reduction of ruthenium acetate in an aqueous solution to construct an aqueous phase catalytic system, and efficiently catalyzes the hydrodeoxygenation cyclization of o-hydroxydiphenylmethane to prepare perhydrofluorene under mild conditions, and the catalyst has good separation and reuse performance.

[0006] The purpose of the present invention is to turn waste into treasure, and use the cheap and easily available industrial by-product sodium lignin sulfonate as a raw material to prepare a stable and efficient aqueous metal Ru catalyst, thereby providing a mild and environmentally friendly new catalytic method for the hydrodeoxygenation and cyclization of o-hydroxydiphenylmethane to prepare a potential biomass fuel additive product, perhydrofluorene.

[0007] The technical solution of the present invention is:

[0008] Add the raw material o-hydroxydiphenylmethane into a stainless steel autoclave lined with polytetrafluoroethylene, and adjust the molar ratio of o-hydroxydiphenylmethane to ruthenium acetate in the catalyst to n. (邻羟基二苯甲烷) / n (醋酸钌) =100-200, add the prepared aqueous catalyst, add solvent water to a ratio of 6 mL water per mmol of o-hydroxydiphenylmethane, seal the kettle and replace the air with hydrogen, and react for 3-5 hours under a hydrogen pressure of 1.0-2.0 MPa and 70-90° C. with stirring. After the reaction is completed, the mixture is allowed to stand for stratification, and the separated upper organic phase is quantitatively analyzed by gas chromatography. The lower aqueous catalyst can be directly reused after separation and recovery.

[0009] The aqueous phase catalyst described in the above technical solution is a metal Ru catalyst that is stable by reduction of sodium lignin sulfonate, and the preparation method is as follows:

[0010] According to the formula of 1.17~1.67×10 per gram of sodium lignin sulfonate -3 The ruthenium acetate dissolved in ultrapure water was added dropwise into the sodium lignin sulfonate aqueous solution, and ultrapure water was added to the sodium lignin sulfonate concentration of 10 g / L. The mixed solution was stirred at 60 ° C for 3 h and cooled to room temperature to obtain a metal Ru catalyst that was stable for the aqueous phase reduction of sodium lignin sulfonate.

[0011] Compared with the prior art, the method for preparing perhydrofluorene by hydrodeoxygenation cyclization of o-hydroxydiphenylmethane catalyzed by a metal Ru catalyst with stable water phase reduction of sodium lignin sulfonate provided by the present invention has the following characteristics:

[0012] (1) The preparation method of perhydrofluorene provided by the present invention is carried out in an aqueous phase under mild conditions, and no organic dispersion medium is required during the reaction process, and no extraction agent is required after the reaction, and the product phase can be directly separated from the catalyst system. The preparation process is mild, efficient, clean and pollution-free.

[0013] (2) The preparation of the catalyst in the method provided by the present invention is also carried out in the water phase, and no other reagents are required except sodium lignin sulfonate and ruthenium acetate. The water phase catalyst system is easy to separate from the product and has stable recycling performance.

[0014] (3) The reaction substrate o-hydroxydiphenylmethane and the catalyst of the present invention are both made of renewable lignin resources, which is a new green method for turning waste into treasure and preparing perhydrofluorene, a biomass-based fuel additive product, in a gentle and efficient manner.

[0015] “Dual carbon” goals and industry development trends. DETAILED DESCRIPTION

[0016] The following examples are used to further illustrate the present invention, but are not intended to limit the present invention.

[0017] [Example 1] Preparation of Ru catalyst A stabilized by sodium lignin sulfonate reduction

[0018] 60 mg of vacuum-dried sodium lignin sulfonate was added to 2 mL of ultrapure water and stirred at room temperature until fully dissolved. 0.08 mmol of ruthenium acetate was added to 2 mL of ultrapure water and ultrasonicated until completely dissolved, and then added dropwise to the sodium lignin sulfonate aqueous solution. 2 mL of ultrapure water was added to the resulting mixture, and the mixture was reacted at 60°C for 3 h under magnetic stirring at 400 rpm and then cooled to room temperature.

[0019] [Example 2] Preparation of Ru catalyst B stabilized by sodium lignin sulfonate reduction

[0020] 60 mg of vacuum-dried sodium lignin sulfonate was added to 2 mL of ultrapure water and stirred at room temperature until fully dissolved. 0.07 mmol of ruthenium acetate was added to 2 mL of ultrapure water and ultrasonicated until completely dissolved, and then added dropwise to the sodium lignin sulfonate aqueous solution. 2 mL of ultrapure water was added to the resulting mixture, and the mixture was reacted at 60°C for 3 h under magnetic stirring at 400 rpm and then cooled to room temperature.

[0021] [Example 3] Preparation of Ru catalyst C stabilized by sodium lignin sulfonate reduction

[0022] 60 mg of vacuum-dried sodium lignin sulfonate was added to 2 mL of ultrapure water and stirred at room temperature until fully dissolved. 0.10 mmol of ruthenium acetate was added to 2 mL of ultrapure water and ultrasonicated until completely dissolved, and then added dropwise to the sodium lignin sulfonate aqueous solution. 2 mL of ultrapure water was added to the resulting mixture, and the mixture was reacted at 60°C for 3 h under magnetic stirring at 400 rpm and then cooled to room temperature.

[0023] [Example 4]

[0024] 0.6 mL of the sodium lignin sulfonate reduction-stabilized Ru catalyst A prepared in Example 1, 1 mmol of o-hydroxydiphenylmethane and 5.4 mL of ultrapure water were added to a stainless steel autoclave with a polytetrafluoroethylene liner, and after replacing the air with hydrogen, the reaction was stirred at 80° C. for 4 h under an initial H2 pressure of 1.5 MPa. After the reaction was completed, the self-separated upper organic phase was quantitatively analyzed by gas chromatography, and the results are shown in Table 1.

[0025] [Example 5]

[0026] 0.6 mL of the sodium lignin sulfonate reduction-stabilized Ru catalyst B prepared in Example 2, 1 mmol of o-hydroxydiphenylmethane and 5.4 mL of ultrapure water were added to a stainless steel autoclave with a polytetrafluoroethylene liner, and after replacing the air with hydrogen, the reaction was stirred at 80° C. for 4 h under an initial H2 pressure of 1.5 MPa. After the reaction was completed, the self-separated upper organic phase was quantitatively analyzed by gas chromatography, and the results are shown in Table 1.

[0027] [Example 6]

[0028] 0.6 mL of the sodium lignin sulfonate reduction-stabilized Ru catalyst C prepared in Example 3, 1 mmol of o-hydroxydiphenylmethane and 5.4 mL of ultrapure water were added to a stainless steel autoclave with a polytetrafluoroethylene liner, and after replacing the air with hydrogen, the reaction was stirred at 80° C. for 4 h under an initial H2 pressure of 1.5 MPa. After the reaction was completed, the self-separated upper organic phase was quantitatively analyzed by gas chromatography, and the results are shown in Table 1.

[0029] [Example 7]

[0030] 0.75 mL of the sodium lignin sulfonate reduction-stabilized Ru catalyst A prepared in Example 1, 1 mmol of o-hydroxydiphenylmethane and 5.25 mL of ultrapure water were added to a stainless steel autoclave with a polytetrafluoroethylene liner, and after replacing the air with hydrogen, the reaction was stirred at 80° C. for 5 h under an initial H2 pressure of 1.5 MPa. After the reaction was completed, the self-separated upper organic phase was quantitatively analyzed by gas chromatography, and the results are shown in Table 1.

[0031] [Example 8]

[0032] 0.50 mL of the sodium lignin sulfonate reduction-stabilized Ru catalyst A prepared in Example 1, 1 mmol of o-hydroxydiphenylmethane and 5.50 mL of ultrapure water were added to a stainless steel autoclave with a polytetrafluoroethylene liner, and after replacing the air with hydrogen, the reaction was stirred at 80° C. for 5 h under an initial H2 pressure of 1.5 MPa. After the reaction was completed, the self-separated upper organic phase was quantitatively analyzed by gas chromatography, and the results are shown in Table 1.

[0033] [Example 9]

[0034] 0.38 mL of the sodium lignin sulfonate reduction-stabilized Ru catalyst A prepared in Example 1, 1 mmol of o-hydroxydiphenylmethane and 5.62 mL of ultrapure water were added to a stainless steel autoclave with a polytetrafluoroethylene liner, and after replacing the air with hydrogen, the reaction was stirred at 80° C. for 5 h under an initial H2 pressure of 1.5 MPa. After the reaction was completed, the self-separated upper organic phase was quantitatively analyzed by gas chromatography, and the results are shown in Table 1.

[0035] [Example 10]

[0036] 0.38 mL of the sodium lignin sulfonate reduction-stabilized Ru catalyst A prepared in Example 1, 1 mmol of o-hydroxydiphenylmethane and 5.62 mL of ultrapure water were added to a stainless steel autoclave with a polytetrafluoroethylene liner, and after replacing the air with hydrogen, the reaction was stirred at 80° C. for 4 h under an initial H2 pressure of 1.5 MPa. After the reaction was completed, the self-separated upper organic phase was quantitatively analyzed by gas chromatography, and the results are shown in Table 1.

[0037] [Example 11]

[0038] 0.38 mL of the sodium lignin sulfonate reduction-stabilized Ru catalyst A prepared in Example 1, 1 mmol of o-hydroxydiphenylmethane and 5.62 mL of ultrapure water were added to a stainless steel autoclave with a polytetrafluoroethylene liner, and after replacing the air with hydrogen, the reaction was stirred at 80° C. for 3 h under an initial H2 pressure of 1.5 MPa. After the reaction was completed, the self-separated upper organic phase was quantitatively analyzed by gas chromatography, and the results are shown in Table 1.

[0039] [Example 12]

[0040] 0.38 mL of the sodium lignin sulfonate reduction-stabilized Ru catalyst A prepared in Example 1, 1 mmol of o-hydroxydiphenylmethane and 5.62 mL of ultrapure water were added to a stainless steel autoclave with a polytetrafluoroethylene liner, and after replacing the air with hydrogen, the reaction was stirred at 90° C. for 4 h under an initial H2 pressure of 1.5 MPa. After the reaction was completed, the self-separated upper organic phase was quantitatively analyzed by gas chromatography, and the results are shown in Table 1.

[0041] [Example 13]

[0042] 0.38 mL of the sodium lignin sulfonate reduction-stabilized Ru catalyst A prepared in Example 1, 1 mmol of o-hydroxydiphenylmethane and 5.62 mL of ultrapure water were added to a stainless steel autoclave with a polytetrafluoroethylene liner, and after replacing the air with hydrogen, the reaction was stirred at 70° C. for 4 h under an initial H2 pressure of 1.5 MPa. After the reaction was completed, the self-separated upper organic phase was quantitatively analyzed by gas chromatography, and the results are shown in Table 1.

[0043] [Example 14]

[0044] 0.38 mL of the sodium lignin sulfonate reduction-stabilized Ru catalyst A prepared in Example 1, 1 mmol of o-hydroxydiphenylmethane and 5.62 mL of ultrapure water were added to a stainless steel autoclave with a polytetrafluoroethylene liner, and after replacing the air with hydrogen, the reaction was stirred at 80° C. for 4 h under an initial H2 pressure of 2.0 MPa. After the reaction was completed, the self-separated upper organic phase was quantitatively analyzed by gas chromatography, and the results are shown in Table 1.

[0045] [Example 15]

[0046] 0.38 mL of the sodium lignin sulfonate reduction-stabilized Ru catalyst A prepared in Example 1, 1 mmol of o-hydroxydiphenylmethane and 5.62 mL of ultrapure water were added to a stainless steel autoclave with a polytetrafluoroethylene liner, and after replacing the air with hydrogen, the reaction was stirred at 80° C. for 4 h under an initial H2 pressure of 1.0 MPa. After the reaction was completed, the self-separated upper organic phase was quantitatively analyzed by gas chromatography, and the results are shown in Table 1.

[0047] [Examples 16-19] Cyclic performance of Ru catalyst A catalyzed by sodium lignin sulfonate reduction to prepare full hydrogen products

[0048] After the reaction of Example 4 was completed, the upper organic product phase was removed by simple liquid separation, 1 mmol of o-hydroxydiphenylmethane was added to the catalyst phase of the lower layer, and the air was replaced with hydrogen. Then, 1.5 MPa of hydrogen was charged, and the reaction was stirred at 80° C. for 4 h under an initial H2 pressure of 1.5 MPa. After the reaction was completed, the separated upper organic phase was quantitatively analyzed by gas chromatography, and the above operation was repeated. The results of the four-time cycle are shown in Table 2.

[0049] Table 1 Performance of sodium lignin sulfonate reduced Ru catalyst for the preparation of perhydrofluorene

[0050]

[0051] Table 2 Recycling performance of Ru catalyst A catalyzed by sodium lignin sulfonate reduction to prepare perhydrofluorene

[0052]

[0053] [Comparative Example 1]

[0054] 60 mg of vacuum-dried sodium lignin sulfonate and 0.10 mmol of sodium chloropalladate were added to 6 mL of ultrapure water and fully dissolved. The mixture was reacted at 80° C. for 3 h under magnetic stirring at 400 rpm and then cooled to room temperature to obtain an aqueous phase Pd catalyst stabilized by sodium lignin sulfonate.

[0055] 0.6 mL of the sodium lignin sulfonate reduction-stabilized Pd catalyst prepared above, 1 mmol of o-hydroxydiphenylmethane and 5.4 mL of ultrapure water were added to a stainless steel autoclave with a polytetrafluoroethylene liner, and after replacing the air with hydrogen, the reaction was stirred at 80°C for 4 h under an initial H2 pressure of 1.5 MPa. After the reaction was completed, the self-separated upper organic phase was quantitatively analyzed by gas chromatography, and the results are shown in Table 3.

[0056] [Comparative Example 2]

[0057] 60 mg of vacuum-dried sodium lignin sulfonate and 0.10 mmol of hydrated rhodium trichloride were added to 6 mL of ultrapure water and fully dissolved, and reacted at 80° C. for 3 h under magnetic stirring at 400 rpm and then cooled to room temperature to obtain a sodium lignin sulfonate-stabilized aqueous Rh catalyst.

[0058] 0.6 mL of the sodium lignin sulfonate reduction-stabilized Rh catalyst prepared above, 1 mmol of o-hydroxydiphenylmethane and 5.4 mL of ultrapure water were added to a stainless steel autoclave with a polytetrafluoroethylene liner, and after replacing the air with hydrogen, the reaction was stirred at 80°C for 4 h under an initial H2 pressure of 1.5 MPa. After the reaction was completed, the self-separated upper organic phase was quantitatively analyzed by gas chromatography, and the results are shown in Table 3.

[0059] [Comparative Example 3]

[0060] 60 mg of vacuum-dried sodium lignin sulfonate and 0.10 mmol of silver nitrate were added to 6 mL of ultrapure water and fully dissolved, reacted at 80° C. for 3 h under magnetic stirring at 400 rpm, and then cooled to room temperature to obtain an aqueous phase Ag catalyst stabilized by sodium lignin sulfonate.

[0061] 0.6 mL of the sodium lignin sulfonate reduction-stabilized Ag catalyst prepared above, 1 mmol of o-hydroxydiphenylmethane and 5.4 mL of ultrapure water were added to a stainless steel autoclave with a polytetrafluoroethylene liner, and the air was replaced with hydrogen. The reaction was stirred at 80°C for 4 h under an initial H2 pressure of 1.5 MPa. After the reaction was completed, the self-separated upper organic phase was quantitatively analyzed by gas chromatography, and the results are shown in Table 3.

[0062] [Comparative Example 4]

[0063] 60 mg of vacuum-dried sodium lignin sulfonate and 0.10 mmol of chloroplatinic acid hexahydrate were added to 6 mL of ultrapure water and fully dissolved. The mixture was reacted at 80° C. for 3 h under magnetic stirring at 400 rpm and then cooled to room temperature to obtain an aqueous phase Pt catalyst stabilized by sodium lignin sulfonate.

[0064] 0.6 mL of the sodium lignin sulfonate reduction-stabilized Pt catalyst prepared above, 1 mmol of o-hydroxydiphenylmethane and 5.4 mL of ultrapure water were added to a stainless steel autoclave with a polytetrafluoroethylene liner, and the air was replaced with hydrogen. The reaction was stirred at 80°C for 4 h under an initial H2 pressure of 1.5 MPa. After the reaction was completed, the self-separated upper organic phase was quantitatively analyzed by gas chromatography, and the results are shown in Table 3.

[0065] Table 3 Comparison of catalyst performance in preparing perhydrofluorene

[0066]

[0067] [Comparative Example 5]

[0068] 60 mg of vacuum-dried sodium lignin sulfonate and 0.10 mmol of hydrated ruthenium trichloride were added to 6 mL of ultrapure water and fully dissolved. The mixture was reacted at 80° C. for 3 h under magnetic stirring at 400 rpm and then cooled to room temperature to obtain a sodium lignin sulfonate-stabilized aqueous Ru comparison catalyst.

[0069] 0.6 mL of the above-prepared sodium lignin sulfonate reduction-stabilized Ru comparative catalyst, 1 mmol of o-hydroxydiphenylmethane and 5.4 mL of ultrapure water were added to a stainless steel autoclave with a polytetrafluoroethylene liner, and after replacing the air with hydrogen, the reaction was stirred at 80°C for 4 h under an initial H2 pressure of 1.5 MPa. After the reaction was completed, the self-separated upper organic phase was quantitatively analyzed by gas chromatography, and the results are shown in Table 3.

Claims

1. A method for preparing perhydrofluorene by aqueous phase hydrodeoxygenation cyclization of o-hydroxydiphenylmethane, characterized in that: Sodium lignin sulfonate is used as both a reducing agent and a stabilizer, and ruthenium acetate is used as a metal precursor. No other chemical reagents and organic solvents need to be added. A water-phase dispersed metal Ru catalyst is prepared in an aqueous solution to directly catalyze the hydrodeoxygenation cyclization reaction of o-hydroxydiphenylmethane to prepare perhydrofluorene. The specific preparation method of the water-phase dispersed metal Ru catalyst is as follows: 1.17-1.67×10 -3 The ruthenium acetate dissolved in ultrapure water was added dropwise into the sodium lignin sulfonate aqueous solution, and ultrapure water was added to the sodium lignin sulfonate concentration of 10 g / L. The mixed solution was stirred and reacted at 60°C for 3 h.

2. A method for preparing perhydrofluorene by aqueous phase hydrodeoxygenation cyclization of o-hydroxydiphenylmethane according to claim 1, characterized in that The catalytic reaction process is as follows: The raw material o-hydroxydiphenylmethane and the aqueous phase dispersed metal Ru catalyst are mixed in an amount of n (邻羟基二苯甲烷) / n (醋酸钌) =100-200 ratio is added into a stainless steel autoclave, and ultrapure water is added to 6 mL of water per mmol of o-hydroxydiphenylmethane. Under a H2 pressure of 1.0-2.0 MPa, the reaction is stirred at 70-90°C for 3-5 hours. After the reaction is completed, the reaction is allowed to stand and self-separate to obtain an upper organic product phase mainly composed of perhydrofluorene. The catalyst in the lower aqueous phase is recovered and directly recycled.

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