A method for synthesizing polycyclic alkanes from phenols derived from lignin via a one-pot two-step process

Abstract

The present invention discloses a method for synthesizing polycyclic alkanes from phenols derived from lignin via a one-pot two-step process. 1) In the first step of the reaction, the phenolic compound derived from lignin is first converted into a ketone compound under the action of a hydrogenation catalyst, and then the ketone compound rapidly undergoes aldol condensation under the action of a solid acid to generate a jet fuel precursor; 2) In the second step of the reaction, the product of the first step is not separated, but the reaction conditions are directly strengthened. The jet fuel precursor is directly subjected to complete hydrodeoxygenation to generate polycyclic alkanes under the action of the hydrogenation catalyst and the solid acid in the first step; the phenolic compound derived from lignin is synthesized into polycyclic jet fuel by changing the reaction conditions in a single reaction vessel. Compared with traditional chain-like jet fuel, it has a higher density and a higher calorific value and can be used as a substitute for traditional aviation fuel. The catalyst and raw materials used in the present invention are abundant in source, low in price, and easy to separate; the entire production process is simple to operate.

Description

Technical Field

[0001] A method for synthesizing polycycloalkanes from lignin-derived phenolic compounds via a one-pot, two-step process. The method involves two steps in one pot: the first step involves hydrogenating the lignin-derived phenolic compounds to form ketone compounds, followed by aldol condensation of the ketone compounds under the action of a solid acid, which simultaneously saturates the carbon-carbon double bonds; the second step involves a complete hydrodeoxygenation reaction. Background Art

[0002] Biomass energy offers advantages such as abundant reserves, renewable nature, and CO₂ neutrality. Therefore, utilizing biomass resources to produce aviation fuel components or chemicals to partially replace traditional refining fuels or chemicals would not only reduce my country's dependence on foreign oil but also align with current green development concepts. Lignin is the second largest biomass resource in nature after cellulose and the only clean, non-petroleum resource that can provide renewable aromatic compounds. Biomass oil derived from lignin pyrolysis contains a high concentration of benzene ring structural units, making it an inexpensive, clean resource that can be converted into high-energy aromatics and cycloalkanes, making it one of the most promising energy sources to supplement petroleum.

[0003] Cyclohexanone and its derivatives are important biomass platform compounds. They can be obtained by hydrogenating lignin-derived phenols ([CN103724174B]; Sheng, X.; Wang, C.; Wang, W. Organic Process Research & Development 2021, 25(11), 2425-2431; Xu, GY; Guo, JH; Zhang, Y.; Fu, Y.; Chen, JZ; Ma, LL; Guo, QX Chemcatchem 2015, 7(16), 2485-2492.). Cyclohexanone and its derivatives can undergo aldol condensation and then be hydrodeoxygenated to obtain polycycloalkanes. However, this process involves multiple reaction processes, many separation steps, and high energy consumption. Therefore, compared with the step-by-step synthesis strategy, it is more attractive to directly convert lignin-derived phenols into polycycloalkanes through a single-pot cascade reaction. Summary of the Invention

[0004] The present invention utilizes an easily separable solid acid catalyst and a hydrogenation catalyst to convert lignin-derived phenols into oxygenated jet fuel precursors under mild conditions. Subsequently, the catalyst and solvent used in the previous step are continuously utilized to obtain liquid fuel in high yield through a two-step process by simply increasing the temperature and reaction pressure. The catalyst of the present invention has the characteristics of being solvent-free, easy to separate, having a simple operation process, low energy consumption, and low cost, thereby providing a new route for synthesizing high-density polycyclic jet fuel from lignin-derived phenolic compounds.

[0005] The present invention is achieved through the following technical solutions:

[0006] The reaction process is achieved through a one-pot two-step reaction process.

[0007] In the first step of the reaction, lignin-derived phenolic compounds are first selectively hydrogenated to ketones in a hydrogen atmosphere under the action of a hydrogenation catalyst. Subsequently, the ketones rapidly undergo aldol condensation under the action of a solid acid catalyst to form jet fuel precursors, which are unsaturated organic compounds containing multiple carbon atoms.

[0008] The reaction is carried out in a batch reactor, the molar ratio of lignin-derived phenols to the active components in the hydrogenation catalyst is 1:0.0002-0.005, the mass ratio of the amount of the solid acid catalyst to the reaction substrate is between 0.2 and 1, the reaction temperature is between 80 and 120°C, the reaction time is between 2 and 12 hours, and the reaction pressure is between 0.5 MPa and 2 MPa.

[0009] The second step continues with the catalyst and solvent from the first step. After step 1, the hydrogen pressure is increased to 3-5 MPa without opening the reactor, and the temperature is raised to 180-240°C. The reaction time is 4-12 hours. The jet fuel precursor is completely hydrodeoxygenated to form polycycloalkanes using the hydrogenation catalyst and solid acid from the first step.

[0010] Furthermore, in the above technical solution, the above two-step reaction is carried out in a hydrogen atmosphere.

[0011] Furthermore, in the above technical solution, the hydrogenation catalyst described in the first step is a supported catalyst A / X, comprising a metal active site A supported on a support and a support X. Support X is at least one of SiO2, TiO2, CeO2, Al2O3, MgAl-HT, MgO, and LiAl-HT; and the supported metal is one or more of Pt, Pd, Ru, Ir, Rh, Ni, Fe, and Cu, wherein the catalyst loading is between 0.1 wt% and 15 wt%.

[0012] Furthermore, in the above technical solution, the solid acid catalyst in the first step is Nafion-212, Amberlyst-15, Amberlyst-36, TiP2, CeP2, AlP2, ZrP 0.5, ZrP1, ZrP2, ZrP3 at least one; wherein the solid acid Nafion-212, Amberlyst-15, Amberlyst-36 are purchased commercially, and the other solid acids are prepared by co-precipitation method. TiP2, CeP2, AlP2, etc. are prepared by mixing and stirring the metal precursor nitrate solution and the ammonium dihydrogen phosphate solution at a certain molar ratio at 50 ° C, and then adding concentrated ammonia water dropwise to adjust the pH value to 8-10, stirring continuously for 4-8 hours, filtering and washing, drying at 80 ° C overnight, and calcining at 350-650 ° C for 5-8 hours. Zirconium phosphate (ZrP x ) By preparing basic zirconium oxide solution and ammonium dihydrogen phosphate solution in different molar ratios, then adding the ammonium dihydrogen phosphate solution dropwise into the basic zirconium oxide solution, stirring for 4 hours after the addition, filtering and washing until neutral, and then drying at 120°C overnight and calcining at 400°C for 4 hours.

[0013] Through the above steps, we successfully synthesized high-density aviation fuel with a multi-ring structure.

[0014] The structure of the product polycycloalkane is:

[0015]

[0016] This application presents a method combining an inexpensive and readily available solid acid catalyst with a precious metal hydrogenation catalyst to achieve the desired tandem process. This process can be divided into two steps. Under unchanged catalyst and solvent conditions, the first step involves hydrogenation of phenolic compounds and subsequent aldol condensation to produce an oxygenated jet fuel precursor. The second step, by enhancing the reaction conditions, achieves complete hydrodeoxygenation of the oxygenated jet fuel precursor, ultimately yielding polycycloalkanes. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The mass spectrum of the product of Example 64 is shown;

[0018] Figure 2 The mass spectrum of the product of Example 67 is shown;

[0019] Figure 3 The mass spectrum of the product of Example 68 is shown;

[0020] Figure 4 The mass spectrum of the product of Example 69 is shown;

[0021] Figure 5 This is the mass spectrum of the product distribution of the raw material phenol in the first step of the reaction of Example 64;

[0022] Figure 6 This is the mass spectrum of the target product of the raw material phenol in the first step reaction process of Example 64. DETAILED DESCRIPTION

[0023] The present invention will be described below with reference to specific embodiments, but the protection scope of the present invention is not limited to these embodiments.

[0024] Sources of the catalysts in the following examples: The hydrogenation catalyst described in the first step is a supported catalyst A / X, comprising a metal active site A supported on a support and a support X. Support X is at least one of SiO2, TiO2, CeO2, Al2O3, MgAl-HT, MgO, and LiAl-HT; the supported metal is one or more of Pt, Pd, Ru, Ir, Rh, Ni, Fe, and Cu, with the catalyst loading ranging from 0.1% to 15%.

[0025] Solid acid catalysts are Nafion-212, Amberlyst-15, Amberlyst-36, TiP2, CeP2, AlP2, ZrP 0.5 , ZrP1, ZrP2, ZrP3 at least one; wherein the solid acid Nafion-212, Amberlyst-15, Amberlyst-36 are purchased commercially, and the other solid acids are prepared by co-precipitation method. TiP2, CeP2, AlP2, etc. are prepared by mixing and stirring the metal precursor nitrate solution and the ammonium dihydrogen phosphate solution at a certain molar ratio at 50 ° C, and then adding concentrated ammonia water dropwise to adjust the pH value to 8-10, stirring continuously for 4-8 hours, filtering and washing, drying at 80 ° C overnight, and calcining at 350-650 ° C for 5-8 hours. Zirconium phosphate (ZrP x ) By preparing basic zirconium oxide solution and ammonium dihydrogen phosphate solution in different molar ratios, then adding the ammonium dihydrogen phosphate solution dropwise into the basic zirconium oxide solution, stirring for 4 hours after the addition, filtering and washing until neutral, and then drying at 120°C overnight and calcining at 400°C for 4 hours.

[0026] Example 1:

[0027] The following reaction formula is the reaction route of the present invention, using the reaction conditions in Example 2.

[0028]

[0029] Examples 2 to 10:

[0030] 1) In the first step, 0.4 g of phenol (or other phenols) and a certain amount of catalyst were added to a reactor, and 40 ml of cyclohexane was added as a solvent. The reaction was carried out at a certain temperature and pressure for a period of time. The detailed reaction results are shown in Table 1.

[0031] Table 1 Reaction conditions and results of hydrogenation and aldol condensation of phenol and its derivatives.

[0032]

[0033] As can be seen from Table 1, the conversion activity of different lignin-derived phenols is related to their structure. Phenol is easily hydrogenated and undergoes aldol condensation reactions. The conversion activity of para-substituted alkylphenols is similar to that of phenol, followed by meta-substituted alkylphenols and ortho-substituted alkylphenols. At the same time, the substituent type also affects the conversion activity of phenol derivatives.

[0034] 2) The effects of different combinations of catalysts on the first step reaction.

[0035] 0.4 g of phenol and a catalyst (including a hydrogenation catalyst and a solid acid) were added to a 100 ml batch reactor and 40 ml of cyclohexane was added as a solvent, and the reaction was carried out under certain conditions; the detailed reaction results are shown in Table 2.

[0036] Table 2 Reaction results of phenol using different catalyst combinations in the first step reaction.

[0037]

[0038] Table 2 shows that phenol exhibits varying conversion activities under different catalyst combinations. Catalytic performance influences the hydrogenation of phenol to ketones and their subsequent conversion to aldol condensation products. Overall, noble metals exhibit excellent hydrogenation performance, but different noble metals exhibit varying selective hydrogenation effects on phenol. Some noble metal catalysts exhibit over-hydrogenation, which can affect subsequent aldol condensation reactions. Furthermore, different solid acids exhibit varying aldol condensation abilities. Strong aldol condensation abilities of solid acids can also inhibit over-hydrogenation of cyclohexanone to alcohols to a certain extent. Metal loading also significantly influences the catalytic selective hydrogenation of phenol.

[0039] 3) Effect of reaction conditions on the selective hydrogenation of phenol and aldol condensation reaction.

[0040] 0.4 g of phenol and 40 ml of cyclohexane were added to a 100 ml batch reactor, and a certain amount of combined catalyst was added. The reaction was carried out under different conditions for a period of time; the results are shown in Table 3.

[0041] Table 3 Reaction results of phenol under different reaction conditions

[0042]

[0043] As can be seen in Table 3, reaction conditions have a certain impact on product distribution. Metal hydrogenation catalysts primarily act on the hydrogenation of phenol to form ketones or alcohols. Too little hydrogenation catalyst dosage results in incomplete phenol reaction, while too much catalyst dosage reduces ketone selectivity. Temperature and pressure also have similar effects on the hydrogenation process. Solid acid catalysts primarily act on the aldol condensation of ketones. However, excessive acid levels can lead to a decrease in carbon balance, potentially causing the hydrogenation of alcohols to alkanes. After optimizing reaction conditions, we were able to recover 89% of the oxygenated jet fuel precursor, which was directly hydrodeoxygenated to alkanes in the second step.

[0044] 4) A one-pot two-step synthesis of polycyclic alkanes from phenols derived from lignin

[0045] In the first step, 0.4 g of the substrate of Example 2-10 and 1 wt% Pd / MgAl-HT catalyst and ZrP2 catalyst in the amounts shown in Table 4 were added to a reactor, and 40 ml of cyclohexane was added as a solvent. The reaction was carried out at a hydrogen pressure of 100 psi and a temperature of 120° C. for 12 hours.

[0046] Complete hydrogenation and deoxygenation of different oxygen-containing jet fuel precursors.

[0047] After the first step of the reaction was completed, the temperature was cooled to room temperature, and then hydrogen was introduced to 4 MPa and the temperature was raised for reaction. The reaction conditions are shown in Table 4. The raw materials of Examples 64-72 correspond to the target products of the substrates of Examples 2-10 in Step 1 after 12 hours of the first step reaction. These target products were directly hydrodeoxygenated in the second step to obtain the corresponding bicycloalkane fuels.

[0048] The above two-step reactions are both carried out in a hydrogen atmosphere.

[0049] Table 4 Bicycloalkanes synthesized from different lignin-derived phenols in a one-pot two-step process

[0050]

[0051] As can be seen from Table 4, after the cascade reaction, we can directly obtain polycycloalkanes in one pot. The process is simple and does not require separation, which is beneficial to chemical production.

Claims

1. A method for synthesizing polycycloalkanes from phenols derived from lignin via a one-pot two-step process, characterized in that: 1) In the first step of the reaction, lignin-derived phenolic compounds are first selectively hydrogenated to ketones in a hydrogen atmosphere over a hydrogenation catalyst. Subsequently, the ketones rapidly undergo aldol condensation over a solid acid catalyst to form high-carbon unsaturated organic compounds, which are the precursors of jet fuel. 2) In the second step, instead of separating the products from the first step, the reaction conditions are directly strengthened, increasing the hydrogen pressure to 3 MPa-5 MPa, the temperature to 180-240°C, and the reaction time to 4-12 hours. The jet fuel precursor is directly and completely hydrodeoxygenated to form polycycloalkanes by the action of the hydrogenation catalyst and solid acid in the first step. In step 1), the lignin-derived phenolic compound is phenol, o-cresol, m-cresol, p-cresol, p-ethylphenol, p-propylphenol, guaiacol, methylguaiacol, and o-diphenol; In steps 1 and 2), the hydrogenation catalyst is at least one of Pd / MgAl-HT and Pd / LiAl; wherein the metal active component loading of the catalyst is between 0.1 wt% and 15 wt%; In steps 1 and 2), the solid acid catalyst is TiP2, ZrP 0.5 , at least one of ZrP1, ZrP2, and ZrP3.

2. The method according to claim 1, wherein: The molar ratio of lignin-derived phenols to the active components on the hydrogenation catalyst carrier is 1:0.0002-0.005, and the mass ratio of the amount of the solid acid catalyst to the reaction substrate is between 0.2-1.

3. The method according to claim 1, wherein: In step 1), the hydrogenation and aldol condensation reactions are carried out in a batch reactor at a reaction temperature between 80 and 180° C., a reaction time between 2 and 12 h, and a reaction pressure between 0.5 MPa and 2 MPa. A hydrogenation catalyst and a solid acid need to be added simultaneously during the reaction process.

4. The method according to claim 1, wherein: In step 2), hydrodeoxygenation is carried out on the basis of step 1. After step 1, the reaction pressure is directly increased to 3 MPa-5 MPa without opening the kettle, and the temperature is raised to 180-240°C. The reaction time is 4 h-12 h.

5. The method according to claim 1, wherein: The structure of the product polycycloalkane is 、 、 、 、 、 、 .

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