A method for preparing hydrocarbon fuel from low concentration of furfural in aqueous phase

Abstract

The application provides a method for preparing hydrocarbon fuel from low-concentration furfural water phase, and belongs to the field of high-value utilization of biomass and preparation of aviation fuel. The method directly uses low-concentration furfural water phase as a starting raw material, reduces the number of front-end separation units, shortens the process flow, and improves the added value of industrial by-products. The hydroxyl aldehyde condensation activity of furfural in the water phase under an alkaline environment is utilized, the feeding sequence and rate are controlled to make the reaction substrates uniformly contact and the local alkali concentration stable and controllable, and the condensation reaction is ensured to continuously and stably proceed. The amount of the alkali catalyst is controlled to provide sufficient catalytic active centers to ensure that the double condensation reaction fully proceeds, side reactions are inhibited, and the selectivity of the target product is improved. The reaction temperature is controlled to meet the reaction kinetics, and the yield and purity of the double condensation product are improved. Finally, the obtained double condensation product is subjected to catalytic hydrogenation and deoxidation, and hydrocarbon fuel which meets the performance standard and is suitable for aviation can be efficiently obtained.

Description

Technical Field

[0001] This invention belongs to the field of high-value utilization of biomass and aviation fuel preparation, specifically relating to a method for preparing hydrocarbon fuels from a low-concentration furfural aqueous phase. Background Technology

[0002] Furfural is produced by acid-catalyzed hydrolysis of lignocellulose. It is a key intermediate connecting biomass resources and high-end fuel chemicals. It can be converted into high-density cycloalkane fuels through aldol condensation and hydrodeoxygenation reactions, and has the potential to replace traditional petroleum-based aviation kerosene.

[0003] Existing technologies for preparing high-density aviation fuel from furfural all use high-purity furfural as raw material. However, to obtain furfural with a purity greater than 99.5%, a complex furfural separation unit must be installed beforehand. This not only significantly increases production costs but also wastes industrial low-concentration furfural-containing aqueous phase resources. If the industrial low-concentration furfural aqueous phase is directly used for the condensation reaction, the high water content and impurities in the system will lead to a decrease in reaction rate, an increase in side reactions, and difficulties in product separation, making it difficult to achieve efficient conversion and stable production. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing hydrocarbon fuels using a low-concentration furfural aqueous phase. The method provided by this invention can directly and efficiently convert a low-concentration furfural aqueous phase into a cycloalkane-type high-density fuel without requiring high-purity refining of furfural, thereby shortening the process flow and reducing production costs.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing hydrocarbon fuels from low-concentration furfural in an aqueous phase, comprising the following steps: (1) A low-concentration furfural aqueous solution is mixed with a cyclic ketone to obtain a mixed solution, and then an aqueous solution of an alkaline catalyst is added to the mixed solution to carry out a double condensation reaction to obtain bis(2-furanmethylene)cycloalkanone; the concentration of furfural in the low-concentration furfural aqueous solution is 8~10wt%; the concentration of the aqueous solution of the alkaline catalyst is 0.3~1.0mol / L; the volume ratio of the aqueous solution of the alkaline catalyst to the aqueous solution of furfural is 0.3~0.7:1; the addition rate of the aqueous solution of the alkaline catalyst is 0.5~5mL / min; the temperature of the double condensation reaction is 20~50℃; (2) The bis(2-furanmethylene)cycloalkanone obtained in step (1) is subjected to catalytic hydrogenation and deoxygenation to obtain hydrocarbon fuel.

[0006] Preferably, the alkaline catalyst in the aqueous solution of the alkaline catalyst in step (1) is one or more of sodium hydroxide, potassium hydroxide, sodium carbonate and organic base.

[0007] Preferably, the concentration of the alkaline catalyst aqueous solution in step (1) is 0.4~0.8 mol / L; the volume ratio of the alkaline catalyst aqueous solution to the furfural aqueous solution is 0.4~0.6:1.

[0008] Preferably, the temperature of the double condensation reaction in step (1) is 35~40℃.

[0009] Preferably, the time for the double condensation reaction in step (1) is 2 to 6 hours.

[0010] Preferably, the cyclic ketone in step (1) is cyclopentanone or cyclohexanone.

[0011] Preferably, in step (1), the molar ratio of furfural to cyclic ketone in the low-concentration furfural aqueous solution is (1.5~2.5):1.

[0012] Preferably, the catalyst for the catalytic hydrogenation deoxygenation reaction in step (2) is Pt / NbOPO4; the mass ratio of the bis(2-furanmethylene)cycloalkanone to the catalyst is (10~20):1.

[0013] Preferably, the temperature of the catalytic hydrogenation deoxygenation reaction in step (2) is 240~290℃ and the reaction time is 4~8h.

[0014] Preferably, the initial hydrogen pressure of the catalytic hydrodeoxygenation reaction in step (2) is 3~5 MPa.

[0015] This invention provides a method for preparing hydrocarbon fuels from a low-concentration furfural aqueous phase, comprising the following steps: (1) mixing a low-concentration furfural aqueous solution with a cyclic ketone to obtain a mixed solution, and then adding an aqueous solution of an alkaline catalyst to the mixed solution to carry out a double condensation reaction to obtain bis(2-furanmethylene)cycloalkanone; the concentration of furfural in the low-concentration furfural aqueous solution is 8~10wt%; the concentration of the aqueous solution of the alkaline catalyst is 0.3~1.0mol / L; the volume ratio of the aqueous solution of the alkaline catalyst to the aqueous solution of furfural is 0.3~0.7:1; the addition rate of the aqueous solution of the alkaline catalyst is 0.5~5mL / min; the temperature of the double condensation reaction is 20~50℃; (2) subjecting the bis(2-furanmethylene)cycloalkanone obtained in step (1) to a catalytic hydrogenation deoxygenation reaction to obtain hydrocarbon fuels. This invention directly uses a low-concentration furfural aqueous phase as the starting material, reducing the number of front-end separation units and shortening the process flow. It offers advantages such as reduced overall energy consumption, reduced equipment investment, and increased added value of industrial by-products. Utilizing the aldol condensation activity of furfural in the aqueous phase under alkaline conditions, the feeding sequence and rate are controlled to ensure uniform contact of the reaction substrate and stable, controllable local alkali concentration, guaranteeing the continuous and stable condensation reaction. Controlling the amount of alkali catalyst provides sufficient catalytic active centers to ensure the complete initiation of the double condensation reaction, suppressing side reactions and improving the selectivity of the target product. Controlling the reaction temperature satisfies reaction kinetics, improving the yield and purity of the double condensation product. Finally, the obtained double condensation product is subjected to catalytic hydrodeoxygenation to efficiently obtain hydrocarbon fuels with performance meeting standards and suitable for aviation use. The results of the examples show that the preparation method provided by this invention can prepare hydrocarbon fuels with densities reaching 0.820~0.845 g / cm³. 3 With a volumetric calorific value of not less than 35.8 MJ / L and a freezing point as low as -50℃, it possesses excellent characteristics of high density, high volumetric calorific value, and low freezing point, meeting the requirements for the use of high-density aviation fuel. Attached Figure Description

[0016] Figure 1 This is a process flow diagram of industrial furfural production and high-value utilization of by-products in an embodiment of the present invention. Detailed Implementation

[0017] This invention provides a method for preparing hydrocarbon fuels from low-concentration furfural in an aqueous phase, comprising the following steps: (1) A low-concentration furfural aqueous solution is mixed with a cyclic ketone to obtain a mixed solution, and then an aqueous solution of an alkaline catalyst is added to the mixed solution to carry out a double condensation reaction to obtain bis(2-furanmethylene)cycloalkanone; the concentration of furfural in the low-concentration furfural aqueous solution is 8~10wt%; the concentration of the aqueous solution of the alkaline catalyst is 0.3~1.0mol / L; the volume ratio of the aqueous solution of the alkaline catalyst to the aqueous solution of furfural is 0.3~0.7:1; the addition rate of the aqueous solution of the alkaline catalyst is 0.5~5mL / min; the temperature of the double condensation reaction is 20~50℃; (2) The bis(2-furanmethylene)cycloalkanone obtained in step (1) is subjected to catalytic hydrogenation and deoxygenation to obtain hydrocarbon fuel.

[0018] In this invention, a low-concentration furfural aqueous solution is mixed with a cyclic ketone to obtain a mixed solution, and then an aqueous solution of an alkaline catalyst is added to the mixed solution to carry out a double condensation reaction to obtain bis(2-furanmethylene)cycloalkanone.

[0019] In this invention, the mass fraction of the low-concentration furfural aqueous solution is 8-10 wt%, preferably 8-9.2 wt%. This concentration range matches the actual composition of the aqueous phase after condensation and phase separation in the industrial furfural production process, ensuring direct utilization of raw materials while also taking into account high reaction efficiency and convenient subsequent separation.

[0020] In one embodiment of the present invention, the low-concentration furfural aqueous solution can be the furfural aqueous solution at the top layer of the separator in an industrial furfural production unit. In embodiments of the present invention, such as... Figure 1 As shown, the biomass raw material, after pretreatment, enters an acid catalytic reactor. Under the action of steam, it undergoes acid catalytic hydrolysis to obtain hydrolysis products and bottom residue. The hydrolysis products enter a steam stripping tower for stripping under the action of steam to obtain stripping products and bottom aqueous phase. The stripping products enter a condenser for condensation and then enter a phase separator for settling and separation. The upper layer is separated to obtain a low-concentration furfural-containing aqueous phase; the lower layer is a crude aldehyde phase, which is purified into crude aldehyde and then enters a vacuum distillation tower for vacuum distillation to obtain the light component, which is high-purity furfural, while the heavy component is discharged from the bottom of the tower. The low-concentration furfural-containing aqueous phase, i.e., the low-concentration furfural aqueous solution, can be used as the raw material of this invention.

[0021] In this invention, the cyclic ketone is preferably cyclopentanone or cyclohexanone. In this invention, when the cyclic ketone is cyclopentanone, a C10-C15 fuel mainly composed of dialkylcyclopentane is ultimately generated; when the cyclic ketone is cyclohexanone, a C11-C16 fuel mainly composed of dialkylcyclohexane is ultimately generated.

[0022] In this invention, the preferred molar ratio of furfural to cyclic ketone in the low-concentration furfural aqueous solution is (1.5~2.5):1, more preferably 2:1. By controlling the amount of each component, this invention facilitates the smooth progress of the double condensation reaction.

[0023] The present invention does not have any special limitations on the mixing method of the low-concentration furfural aqueous solution and the cyclic ketone; any conventional mixing method that can achieve uniform mixing is acceptable.

[0024] After obtaining the mixture, the present invention preferably further includes measuring the pH value of the mixture. By measuring the initial pH value and adjusting the amount of alkaline catalyst added, the present invention can maintain a stable weakly alkaline environment in the reaction system, thereby improving the efficiency of the double condensation reaction and reducing the occurrence of side reactions.

[0025] In this invention, the alkaline catalyst in the aqueous solution is preferably one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, and organic bases, more preferably sodium hydroxide. The use of an aqueous solution of the alkaline catalyst in this invention facilitates two-phase mixing and mass transfer. By controlling the presence of the alkaline catalyst in the form of an aqueous solution, the reaction rate and local concentration can be controlled, ensuring that the bicondensation and reaction proceed fully.

[0026] In this invention, the concentration of the alkaline catalyst aqueous solution is 0.3~1.0 mol / L; as one embodiment of this invention, the concentration of the alkaline catalyst aqueous solution can be 0.4~0.8 mol / L, 0.4~0.6 mol / L, or 0.5 mol / L. In this invention, the volume ratio of the alkaline catalyst aqueous solution to the furfural aqueous solution is 0.3~0.7:1. As one embodiment of this invention, the volume ratio of the alkaline catalyst aqueous solution to the furfural aqueous solution can be 0.4~0.6:1, 0.4~0.55:1, or 0.5:1. This invention, by controlling the concentration and amount of the alkaline catalyst, provides sufficient catalytic active centers to ensure the complete occurrence of the double condensation reaction, suppresses the formation of side reactions, and improves the selectivity of the target product.

[0027] In this invention, the addition rate of the alkaline catalyst aqueous solution is 0.5~5 mL / min. As one embodiment of this invention, the alkaline catalyst aqueous solution can be added dropwise to the mixture. By controlling the order of addition and the addition rate of the alkaline catalyst aqueous solution, this invention ensures uniform contact between the alkaline catalyst and the reaction substrate, resulting in a stable and controllable local alkaline concentration. This avoids local overheating or excessively high alkaline concentration caused by adding the alkaline solution all at once, thereby effectively suppressing side reactions and ensuring the continuous and stable progress of the double condensation reaction.

[0028] In one embodiment of the present invention, the sodium hydroxide aqueous solution can be added to the mixture under stirring conditions after the reactor temperature has been raised to the double condensation reaction temperature. The present invention does not have special requirements for the specific stirring method; any stirring method well known to those skilled in the art can be used. In another embodiment of the present invention, magnetic stirring is preferred.

[0029] After sodium hydroxide is added to the mixture, the pH value of the mixture is preferably controlled at pH 8-10. By controlling the pH value of the mixture, the present invention can maintain a stable weakly alkaline environment in the reaction system, thereby improving the efficiency of the double condensation reaction and reducing the occurrence of side reactions.

[0030] In this invention, the preferred temperature for the double condensation reaction is 35-40°C. By controlling the temperature of the double condensation reaction, this invention ensures the full kinetics of the reaction and improves the yield and purity of the double condensation product.

[0031] In this invention, the time for the double condensation reaction is 2-6 hours. As one embodiment of this invention, the time for the double condensation reaction can be 3-5 hours, or even 4 hours. By controlling the temperature of the double condensation reaction, this invention ensures that furfural and cyclic ketones undergo a complete double condensation reaction, thereby improving the yield and selectivity of bis(2-furanmethylene)cycloalkanone formation.

[0032] In an embodiment of the present invention, the double condensation reaction is carried out in a three-necked flask, the flask being connected to a condenser and the outlet being sealed with a rubber stopper, and simultaneously connected to a constant pressure funnel containing an aqueous solution of sodium hydroxide.

[0033] After the bicondensation reaction is completed, the product obtained by the bicondensation reaction is preferably subjected to cooling, filtration, washing, drying, recrystallization and baking in sequence to obtain bis(2-furanmethylene)cycloalkanone.

[0034] The present invention does not have any special requirements for the specific operation of the cooling. Any cooling method known to those skilled in the art can be used to cool bis(2-furanmethylene)cycloalkanone to room temperature.

[0035] In an embodiment of the present invention, the filtration is performed by filtering through a 0.45µm microporous membrane in a Buchner funnel.

[0036] In one embodiment of the present invention, the detergent used for washing can be deionized water; the present invention does not have special requirements on the number of washing cycles, as long as the pH of the filtrate is maintained at 7.

[0037] The present invention does not have any special requirements for the specific drying method; any drying method known to those skilled in the art can be used to remove residual water.

[0038] In this invention, the reagent used for recrystallization is preferably ethanol; the recrystallization temperature is preferably 60°C.

[0039] In an embodiment of the present invention, the drying temperature is 80°C and the drying time is 8 hours.

[0040] The present invention does not have special requirements on the number of washing cycles, as long as the pH of the filtrate is maintained at 7.

[0041] After obtaining bis(2-furanmethylene)cycloalkanone, the present invention performs a catalytic hydrogenation deoxygenation reaction on the bis(2-furanmethylene)cycloalkanone to obtain hydrocarbon fuel.

[0042] In this invention, the catalyst for the catalytic hydrodeoxygenation reaction is preferably Pt / NbOPO4.

[0043] The specific surface area of ​​the Pt / NbOPO4 catalyst described in this invention is preferably 100-150 m². 2 / g.

[0044] In this invention, the Pt loading of the Pt / NbOPO4 catalyst is preferably 1 wt%; the average Pt particle size is preferably 2-3 nm.

[0045] In an embodiment of the present invention, the preparation method of the Pt / NbOPO4 catalyst is as follows: Nb2O5 and NH4H2PO4 were mixed in a molar ratio of 1:1 and then ground. After grinding, the mixture was calcined at 500°C in air for 4 hours to obtain NbOPO4 support. The NbOPO4 support was impregnated in H2PtCl6 solution, then dried at 110℃ for 12 h, and finally calcined at 400℃ for 3 h to obtain the Pt / NbOPO4 catalyst.

[0046] In this invention, the catalyst for the catalytic hydrodeoxygenation reaction is preferably subjected to reduction treatment before use; the atmosphere for the reduction treatment is preferably a 10% H2-Ar mixture; the heating rate for the reduction treatment is preferably 5℃ / min; the temperature for the reduction reaction is preferably 300℃; and the duration of the reduction reaction is preferably 4h. After the reduction reaction is completed, the reduced catalyst is preferably transferred to a glove box for storage. This invention, by reducing the catalyst for the catalytic hydrodeoxygenation reaction, can effectively reduce the active metal components on the catalyst surface to a zero-valent active state, improve the dispersion of metal active sites and intrinsic catalytic activity, enhance the catalytic ability for the hydrogenation and deoxygenation of bis(2-furanmethylene)cycloalkanones, and effectively improve the feed conversion rate and the selectivity of the target cycloalkane product; at the same time, the inert atmosphere reduction and the air-isolated storage in the glove box can avoid catalyst oxidation and deactivation, surface impurity adsorption, maintain the stability of the catalyst structure and the long-term effectiveness of catalytic performance, and ensure the stable and efficient conduction of the hydrodeoxygenation reaction.

[0047] In this invention, the preferred mass ratio of the bis(2-furanomethylene)cycloalkanone to the Pt / NbOPO4 catalyst is (10~20):1. As one embodiment of this invention, the mass ratio of the bis(2-furanomethylene)cycloalkanone to the Pt / NbOPO4 catalyst can be 10:1. By controlling the ratio of the two components, this invention ensures that the catalyst provides sufficient active sites, allowing the bis(2-furanomethylene)cycloalkanone to fully undergo the hydrodeoxygenation reaction.

[0048] In one embodiment of the present invention, the temperature of the catalytic hydrodeoxygenation reaction can be 240~290℃ or 280~290℃; the reaction time of the catalytic hydrodeoxygenation reaction can be 4~8h or 6~8h. The present invention provides suitable activation conditions for the catalytic hydrodeoxygenation reaction by controlling the temperature and time, ensuring that bis(2-furanmethylene)cycloalkanone undergoes sufficient hydrodeoxygenation conversion, thereby improving the feed conversion rate and the yield of the target cycloalkane product.

[0049] As one embodiment of the present invention, the catalytic hydrodeoxygenation reaction may include: mixing bis(2-furanmethylene)cycloalkanone, cyclohexane and a Pt / NbOPO4 catalyst that has undergone reduction pretreatment, introducing hydrogen gas and heating to carry out the reaction, to obtain hydrocarbon fuel.

[0050] This invention does not impose any special limitations on the mixing method of bis(2-furanmethylene)cycloalkanone, cyclohexane and the pre-treated Pt / NbOPO4 catalyst; any conventional mixing method that can achieve uniform mixing is acceptable.

[0051] In an embodiment of the present invention, when the mass ratio of bis(2-furanmethylene)cycloalkanone to Pt / NbOPO4 catalyst is (10~20):1, the amount of cyclohexane added is 20 mL. By controlling the amount of cyclohexane added, the present invention facilitates the formation of a homogeneous and stable liquid-phase reaction system, enhances the contact mass transfer between the material and the active sites of the catalyst, and promotes the smooth progress of the hydrodeoxygenation reaction.

[0052] In this invention, the initial hydrogen pressure for the catalytic hydrodeoxygenation reaction is preferably 3-5 MPa. As one embodiment of this invention, the initial hydrogen pressure for the catalytic hydrodeoxygenation reaction can also be 4 MPa. By controlling the initial hydrogen pressure of the catalytic hydrodeoxygenation reaction, this invention can provide a sufficient hydrogen source atmosphere for the hydrogenation saturation and deoxygenation reactions, effectively promoting furan ring opening saturation and removal of oxygen-containing groups, thereby improving the feedstock conversion rate and the selectivity of the target cycloalkane product.

[0053] This invention does not impose any particular limitation on the reaction apparatus for the catalytic hydrodeoxygenation reaction; conventional reaction apparatus can be used. As one embodiment of this invention, the reaction apparatus can be a batch-type stainless steel high-pressure reactor.

[0054] In one embodiment of the present invention, after the catalytic hydrodeoxygenation reaction is completed, the resulting product can be sequentially cooled, depressurized, and the liquid product separated to obtain hydrocarbon fuel. The present invention does not impose any special limitations on the specific operations of cooling, depressurizing, and separating the liquid product; conventional methods for cooling, depressurizing, and separating the liquid product can be used.

[0055] In an embodiment of the present invention, the process flow for preparing hydrocarbon fuels from low-concentration furfural aqueous phase is as follows: Figure 1 As shown, a low-concentration furfural-containing aqueous phase is introduced into the double condensation reaction unit and mixed with cyclopentanone or cyclohexanone in an aqueous solution with an alkaline catalyst to undergo a double condensation reaction, generating bis(2-furanmethylene)cycloalkanone. After separation and purification, the double condensation product enters the hydrodeoxygenation reaction unit, where it undergoes a catalytic hydrodeoxygenation reaction in the presence of a Pt / NbOPO4 catalyst and hydrogen, ultimately preparing C10~C15 fuel or C11~C16 fuel.

[0056] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0057] Example 1 A method for preparing hydrocarbon fuels from low-concentration furfural in aqueous phase: (1) Take the top layer of furfural aqueous solution from the industrial furfural production separator as raw material. Mix 9.2 wt% furfural aqueous solution with cyclopentanone at a molar ratio of furfural to cyclopentanone of 2:1 to obtain a mixed solution. The pH of the mixed solution is tested to be 4.5. Transfer the above mixed solution to a three-necked flask, connect a condenser to the flask and seal the outlet with a rubber stopper. At the same time, connect a constant pressure funnel containing 0.5 mol / L sodium hydroxide aqueous solution, wherein the volume ratio of sodium hydroxide aqueous solution to furfural aqueous solution is 0.5:1. Add sodium hydroxide aqueous solution at a dropping rate of 2 mL / min under stirring conditions using magnetic stirring. While stirring, the pH of the system was controlled at 8.5 after the addition was completed, and the reaction was carried out at 35℃ for 4 hours. After the reaction was completed, the mixture was cooled to room temperature, and the reaction system was poured into a Buchner funnel and filtered through a 0.45µm microporous membrane. Then, deionized water was added to wash the filter cake until the pH of the filtrate was 7. The obtained filter residue was dried, dissolved in ethanol at 60℃, filtered, and recrystallized. The obtained product was transferred to an oven and dried at 80℃ for 8 hours to obtain the bicondensed product 2,5-bis(2-furanmethylene)cyclopentanone. The separation yield of the bicondensed product 2,5-bis(2-furanmethylene)cyclopentanone was determined to be 92.3%, and the purity was 98.1%.

[0058] (2) Take 1g of 2,5-bis(2-furanmethylene)cyclopentanone, 0.1g of Pt / NbOPO4 catalyst, and 20mL of cyclohexane and add them to a batch stainless steel high-pressure reactor. Purge with hydrogen to an initial hydrogen pressure of 4MPa and react at 280℃ for 6h. After the reaction, cool and depressurize, and separate the liquid product. Gas chromatography analysis showed that the furfural conversion rate was >90%, the carbon yield of the target product was 78.5%, and the cycloalkane selectivity was >85%. The obtained fuel was mainly composed of 1,3-dipentylcyclopentane with a density of 0.82~0.83g / cm³. 3 Its volumetric calorific value is approximately 35.8 MJ / L, and its freezing point is approximately -27.7℃ to -31.5℃.

[0059] Example 2 A method for preparing hydrocarbon fuels from low-concentration furfural in an aqueous phase comprises the following steps: (1) Take the top layer of furfural aqueous solution from the industrial furfural production separator as raw material, and mix 9.2 wt% furfural aqueous solution with cyclohexanone at a molar ratio of 2:1 to obtain a mixed solution. The pH of the mixed solution is tested to be 4.5. Transfer the above mixed solution to a three-necked flask, connect a condenser to the flask, and seal the outlet with a rubber stopper. At the same time, connect a constant pressure funnel containing 0.5 mol / L sodium hydroxide aqueous solution, wherein the volume ratio of sodium hydroxide aqueous solution to furfural aqueous solution is 0.5:1. Add sodium hydroxide aqueous solution at a dropping rate of 2 mL / min under stirring conditions using magnetic stirring. After stirring and dropwise addition, the pH of the system was controlled at 8.5, and the reaction was carried out at 40℃ for 4 hours. After the reaction was completed, the mixture was cooled to room temperature, and the reaction system was poured into a Buchner funnel and filtered through a 0.45µm microporous membrane. Deionized water was then added to wash the filter cake until the pH of the filtrate was 7. The resulting filter residue was dried, dissolved in ethanol at 60℃, filtered, and recrystallized. The resulting product was transferred to an oven and dried at 80℃ for 8 hours to obtain the bicondensed product 2,6-bis(2-furanomethylene)cyclohexanone. The separation yield of the bicondensed product 2,6-bis(2-furanomethylene)cyclohexanone was determined to be 90.8%, and the purity was 97.6%.

[0060] (2) Take 1g of 2,6-bis(2-furanmethylene)cyclohexanone, 0.1g of Pt / NbOPO4 catalyst, and 20mL of cyclohexane and add them to a batch stainless steel high-pressure reactor. Purge with hydrogen to an initial hydrogen pressure of 4MPa and react at 290℃ for 6h. After the reaction, cool and depressurize, and separate the liquid product. Gas chromatography analysis showed that the furfural conversion rate was >92%, the carbon yield of the target product was 80.2%, and the cycloalkane selectivity was >87%. The obtained fuel was mainly composed of 1,3-dipentylcyclohexane with a density of 0.835~0.845g / cm³. 3Its volumetric calorific value is approximately 35.9~36.2 MJ / L, and its freezing point is below -50℃ to -31.5℃.

[0061] Comparative Example 1 A method for preparing hydrocarbon fuels from low-concentration furfural in an aqueous phase comprises the following steps: (1) Take the top layer of furfural aqueous solution from the industrial furfural production separator as raw material, and mix 9.2 wt% furfural aqueous solution with cyclopentanone at a molar ratio of 2:1 to obtain a mixed solution. The pH of the mixed solution is tested to be 4.5. Transfer the above mixed solution to a three-necked flask, connect a condenser to the flask, and seal the outlet with a rubber stopper. At the same time, connect a constant pressure funnel containing 0.2 mol / L sodium hydroxide aqueous solution, wherein the volume ratio of sodium hydroxide aqueous solution to furfural aqueous solution is 0.5:1. Add sodium hydroxide aqueous solution at a dropping rate of 2 mL / min under stirring conditions using magnetic stirring. After stirring and dropwise addition, the pH of the system was controlled at 8.5, and the reaction was carried out at 35℃ for 4 hours. After the reaction was completed, the mixture was cooled to room temperature, and the reaction system was poured into a Buchner funnel and filtered through a 0.45µm microporous membrane. Deionized water was then added to wash the filter cake until the pH of the filtrate was 7. The resulting filter residue was dried, dissolved in ethanol at 60℃, filtered, and recrystallized. The resulting product was transferred to an oven and dried at 80℃ for 8 hours to obtain the bicondensate 2,5-bis(2-furanomethylene)cyclopentanone. The separation yield of the bicondensate 2,5-bis(2-furanomethylene)cyclopentanone was determined to be 87.5%, and the purity was 96.6%.

[0062] (2) Take 1g of 2,5-bis(2-furanmethylene)cyclopentanone, 0.1g of Pt / NbOPO4 catalyst, and 20mL of cyclohexane and add them to a batch stainless steel high-pressure reactor. Purge with hydrogen to an initial hydrogen pressure of 4MPa and react at 280℃ for 6h. After the reaction is complete, cool and depressurize, and separate the liquid product. Gas chromatography analysis showed that the furfural conversion rate was 82.7%, the carbon yield of the target product was 66.8%, and the cycloalkane selectivity was 80.3%.

[0063] Comparative Example 2 A method for preparing hydrocarbon fuels from low-concentration furfural in an aqueous phase comprises the following steps: (1) Take the top layer of furfural aqueous solution from the industrial furfural production separator as raw material, mix 9.2 wt% furfural aqueous solution with cyclopentanone at a molar ratio of 2:1 to obtain a mixed solution, and test the pH of the mixed solution to be 4.5; transfer the above mixed solution to a three-necked flask, connect a condenser to the flask and seal the outlet with a rubber stopper, and connect a constant pressure funnel containing 0.5 mol / L sodium hydroxide aqueous solution, wherein the volume ratio of sodium hydroxide aqueous solution to furfural aqueous solution is 1:1; use magnetic stirring to add sodium hydroxide aqueous solution at a dropping rate of 2 mL / min under stirring conditions, while stirring. After the addition was complete, the pH of the system was controlled at 8-10, and the reaction was carried out at 35℃ for 4 hours. After the reaction was completed, the mixture was cooled to room temperature, and the reaction system was poured into a Buchner funnel and filtered through a 0.45µm microporous membrane. Then, deionized water was added to wash the filter cake until the pH of the filtrate was 7. The resulting filter residue was dried, dissolved in ethanol at 60℃, filtered, and recrystallized. The resulting product was transferred to an oven and dried at 80℃ for 8 hours to obtain the bicondensed product 2,5-bis(2-furanmethylene)cyclopentanone. The separation yield of the bicondensed product 2,5-bis(2-furanmethylene)cyclopentanone was determined to be 79.8%, and the purity was 94.5%.

[0064] (2) Take 1g of 2,5-bis(2-furanmethylene)cyclopentanone, 0.1g of Pt / NbOPO4 catalyst, and 20mL of cyclohexane and add them to a batch stainless steel high-pressure reactor. Purge with hydrogen to an initial hydrogen pressure of 4MPa and react at 280℃ for 6h. After the reaction is complete, cool and depressurize, and separate the liquid product. Gas chromatography analysis showed that the furfural conversion rate was 83.8%, the carbon yield of the target product was 70.2%, and the cycloalkane selectivity was 82.8%.

[0065] Comparative Example 3 A method for preparing hydrocarbon fuels from low-concentration furfural in an aqueous phase comprises the following steps: (1) Take the top layer of furfural aqueous solution from the industrial furfural production separator as raw material, and mix 9.2 wt% furfural aqueous solution with cyclopentanone at a molar ratio of 2:1 to obtain a mixed solution. The pH of the mixed solution is tested to be 4.5. Transfer the above mixed solution to a three-necked flask, connect a condenser to the flask, and seal the outlet with a rubber stopper. At the same time, connect a constant pressure funnel containing 0.3 mol / L sodium hydroxide aqueous solution, wherein the volume ratio of sodium hydroxide aqueous solution to furfural aqueous solution is 0.5:1. Add sodium hydroxide aqueous solution at a dropping rate of 2 mL / min under stirring conditions using magnetic stirring. After stirring and dropwise addition, the pH of the system was controlled at 8.5, and the reaction was carried out at 60℃ for 4 hours. After the reaction was completed, the mixture was cooled to room temperature, and the reaction system was poured into a Buchner funnel and filtered through a 0.45µm microporous membrane. Deionized water was then added to wash the filter cake until the pH of the filtrate was 7. The resulting filter residue was dried, dissolved in ethanol at 60℃, filtered, and recrystallized. The product was transferred to an oven and dried at 80℃ for 8 hours to obtain the bicondensate 2,5-bis(2-furanomethylene)cyclopentanone. The separation yield of the bicondensate 2,5-bis(2-furanomethylene)cyclopentanone was determined to be 88.6%, and the purity was 95.6%.

[0066] (2) Take 1g of 2,5-bis(2-furanmethylene)cyclopentanone, 0.1g of Pt / NbOPO4 catalyst, and 20mL of cyclohexane and add them to a batch stainless steel high-pressure reactor. Purge with hydrogen to an initial hydrogen pressure of 4MPa and react at 280℃ for 6h. After the reaction is complete, cool and depressurize, and separate the liquid product. Gas chromatography analysis showed that the furfural conversion rate was 86.6%, the carbon yield of the target product was 72.4%, and the cycloalkane selectivity was 80.5%.

[0067] Comparative Example 4 A method for preparing hydrocarbon fuels from low-concentration furfural in an aqueous phase comprises the following steps: (1) Take the top layer of furfural aqueous solution from the industrial furfural production separator as raw material, and mix 9.2 wt% furfural aqueous solution with cyclohexanone at a molar ratio of 2:1 to obtain a mixed solution. The pH of the mixed solution is tested to be 4.5. Transfer the above mixed solution to a three-necked flask, connect a condenser to the flask, and seal the outlet with a rubber stopper. At the same time, connect a constant pressure funnel containing 0.2 mol / L sodium hydroxide aqueous solution, wherein the volume ratio of sodium hydroxide aqueous solution to furfural aqueous solution is 0.5:1. Add sodium hydroxide aqueous solution at a dropping rate of 2 mL / min under stirring conditions using magnetic stirring. After stirring and dropwise addition, the pH of the system was controlled at 8.5, and the reaction was carried out at 40℃ for 4 hours. After the reaction was completed, the mixture was cooled to room temperature, and the reaction system was poured into a Buchner funnel and filtered through a 0.45µm microporous membrane. Deionized water was then added to wash the filter cake until the pH of the filtrate was 7. The resulting filter residue was dried, dissolved in ethanol at 60℃, filtered, and recrystallized. The product was transferred to an oven and dried at 80℃ for 8 hours to obtain the bicondensed product 2,6-bis(2-furanomethylene)cyclohexanone. The separation yield of the bicondensed product 2,6-bis(2-furanomethylene)cyclohexanone was determined to be 83.4%, and the purity was 94.5%.

[0068] (2) Take 1g of 2,6-bis(2-furanmethylene)cyclohexanone, 0.1g of Pt / NbOPO4 catalyst, and 20mL of cyclohexane and add them to a batch stainless steel high-pressure reactor. Purge with hydrogen to an initial hydrogen pressure of 4MPa and react at 290℃ for 6h. After the reaction is completed, cool and depressurize, and separate the liquid product. Gas chromatography analysis showed that the furfural conversion rate was 89.3%, the carbon yield of the target product was 77.5%, and the cycloalkane selectivity was 83.7%.

[0069] Comparative Example 5 A method for preparing hydrocarbon fuels from low-concentration furfural in an aqueous phase comprises the following steps: (1) Take the top layer of furfural aqueous solution from the industrial furfural production separator as raw material, mix 9.2 wt% furfural aqueous solution with cyclohexanone at a molar ratio of 2:1 to obtain a mixed solution, and test the pH of the mixed solution to be 4.5; transfer the above mixed solution to a three-necked flask, connect a condenser to the flask and seal the outlet with a rubber stopper, and connect a constant pressure funnel containing 0.5 mol / L sodium hydroxide aqueous solution, wherein the volume ratio of sodium hydroxide aqueous solution to furfural aqueous solution is 1:1; use magnetic stirring to add sodium hydroxide aqueous solution at a dropping rate of 2 mL / min under stirring conditions, while stirring. After the addition was complete, the pH of the system was controlled at 8.5, and the reaction was carried out at 40℃ for 4 hours. After the reaction was completed, the mixture was cooled to room temperature, and the reaction system was poured into a Buchner funnel and filtered through a 0.45µm microporous membrane. Then, deionized water was added to wash the filter cake until the pH of the filtrate was 7. The resulting filter residue was dried, dissolved in ethanol at 60℃, filtered, and recrystallized. The product was transferred to an oven and dried at 80℃ for 8 hours to obtain the bicondensed product 2,6-bis(2-furanomethylene)cyclohexanone. The separation yield of the bicondensed product 2,6-bis(2-furanomethylene)cyclohexanone was determined to be 86.1%, and the purity was 92.7%.

[0070] (2) Take 1g of 2,6-bis(2-furanmethylene)cyclohexanone, 0.1g of Pt / NbOPO4 catalyst, and 20mL of cyclohexane and add them to a batch stainless steel high-pressure reactor. Purge with hydrogen to an initial hydrogen pressure of 4MPa and react at 290℃ for 6h. After the reaction is completed, cool and depressurize, and separate the liquid product. Gas chromatography analysis showed that the furfural conversion rate was 85.6%, the carbon yield of the target product was 69.5%, and the cycloalkane selectivity was 81.4%.

[0071] Comparative Example 6 A method for preparing hydrocarbon fuels from low-concentration furfural in an aqueous phase comprises the following steps: (1) Take the top layer of furfural aqueous solution from the industrial furfural production separator as raw material, and mix 9.2 wt% furfural aqueous solution with cyclohexanone at a molar ratio of 2:1 to obtain a mixed solution. The pH of the mixed solution is tested to be 4.5. Transfer the above mixed solution to a three-necked flask, connect a condenser to the flask, and seal the outlet with a rubber stopper. At the same time, connect a constant pressure funnel containing 0.5 mol / L sodium hydroxide aqueous solution, wherein the volume ratio of sodium hydroxide aqueous solution to furfural aqueous solution is 0.5:1. Add sodium hydroxide aqueous solution at a dropping rate of 2 mL / min under stirring conditions using magnetic stirring. After stirring and dropwise addition, the pH of the system was controlled at 8.5, and the reaction was carried out at 60℃ for 4 hours. After the reaction was completed, the mixture was cooled to room temperature, and the reaction system was poured into a Buchner funnel and filtered through a 0.45µm microporous membrane. Deionized water was then added to wash the filter cake until the pH of the filtrate was 7. The resulting filter residue was dried, dissolved in ethanol at 60℃, filtered, and recrystallized. The product was transferred to an oven and dried at 80℃ for 8 hours to obtain the bicondensed product 2,6-bis(2-furanomethylene)cyclohexanone. The separation yield of the bicondensed product 2,6-bis(2-furanomethylene)cyclohexanone was determined to be 88.2%, and the purity was 93.3%.

[0072] (2) Take 1g of 2,6-bis(2-furanmethylene)cyclohexanone, 0.1g of Pt / NbOPO4 catalyst, and 20mL of cyclohexane and add them to a batch stainless steel high-pressure reactor. Purge with hydrogen to an initial hydrogen pressure of 4MPa and react at 290℃ for 6h. After the reaction is completed, cool and depressurize, and separate the liquid product. Gas chromatography analysis showed that the furfural conversion rate was 87.9%, the carbon yield of the target product was 70.3%, and the cycloalkane selectivity was 83.7%.

[0073] As can be seen from the above examples and comparative examples, the method provided by the present invention can prepare bis(2-furanmethylene)cycloalkanone with a yield of >90% and a purity of >97%, and the prepared hydrocarbon fuel has a carbon yield of >78% and a cycloalkane selectivity of >85%. The process is simple and the production cost is low.

[0074] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing hydrocarbon fuels using a low-concentration furfural aqueous phase, characterized in that, Includes the following steps: (1) A low-concentration furfural aqueous solution is mixed with a cyclic ketone to obtain a mixed solution, and then an aqueous solution of an alkaline catalyst is added to the mixed solution to carry out a double condensation reaction to obtain bis(2-furanmethylene)cycloalkanone; the concentration of furfural in the low-concentration furfural aqueous solution is 8~10wt%; the concentration of the aqueous solution of the alkaline catalyst is 0.3~1.0mol / L; the volume ratio of the aqueous solution of the alkaline catalyst to the aqueous solution of furfural is 0.3~0.7:1; the addition rate of the aqueous solution of the alkaline catalyst is 0.5~5mL / min; the temperature of the double condensation reaction is 20~50℃; (2) The bis(2-furanmethylene)cycloalkanone obtained in step (1) is subjected to catalytic hydrogenation and deoxygenation to obtain hydrocarbon fuel.

2. The method according to claim 1, characterized in that, In step (1), the alkaline catalyst in the aqueous solution is one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, and organic bases.

3. The method according to claim 1 or 2, characterized in that, In step (1), the concentration of the alkaline catalyst aqueous solution is 0.4~0.8 mol / L; the volume ratio of the alkaline catalyst aqueous solution to the furfural aqueous solution is 0.4~0.6:

1.

4. The method according to claim 1, characterized in that, The temperature of the double condensation reaction in step (1) is 35~40℃.

5. The method according to claim 1 or 4, characterized in that, The time for the double condensation reaction in step (1) is 2 to 6 hours.

6. The method according to claim 1, characterized in that, In step (1), the cyclic ketone is cyclopentanone or cyclohexanone.

7. The method according to claim 1, characterized in that, In step (1), the molar ratio of furfural to cyclic ketone in the low-concentration furfural aqueous solution is (1.5~2.5):

1.

8. The method according to claim 1, characterized in that, The catalyst for the catalytic hydrogenation and deoxygenation reaction in step (2) is Pt / NbOPO4; the mass ratio of the bis(2-furanmethylene)cycloalkanone to the catalyst is (10~20):

1.

9. The method according to claim 1, characterized in that, The temperature of the catalytic hydrogenation deoxygenation reaction in step (2) is 240~290℃, and the reaction time is 4~8h.

10. The method according to claim 1 or 9, characterized in that, The initial hydrogen pressure of the catalytic hydrodeoxygenation reaction in step (2) is 3~5 MPa.

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