Condensation reaction method of mixed bio-oil aldehyde ketone compound and aviation fuel precursor

Abstract

The invention belongs to the technical field of biomass energy conversion, and particularly discloses a condensation reaction method of a mixed bio-oil aldehyde ketone compound and an aviation fuel precursor. The condensation reaction method comprises the following steps: 1) a first condensation stage: in the presence of an acid-base bifunctional catalyst, carrying out condensation reaction on a mixed reactant containing cyclopentanone, valeraldehyde, furfural and 2-pentanone at 30-90 DEG C; 2) a separation step: separating the mixture after the reaction in the step 1) to obtain a fraction rich in the first condensation product and a fraction rich in unreacted reactants; and 3) a second condensation stage: in the presence of an acid-base bifunctional catalyst, carrying out a condensation reaction on the fraction rich in unreacted reactants obtained in the step 2) at 90-130 DEG C to obtain a second condensation product. According to the method, a complex reaction network is selectively regulated and controlled by coupling a hierarchical reaction and physical separation, so that the oriented synthesis of the aviation fuel precursor is realized.

Description

Technical Field

[0001] This invention belongs to the field of biomass energy conversion technology, specifically, it relates to a condensation reaction method for mixed bio-oil aldehyde-ketone compounds and an aviation fuel precursor. Background Technology

[0002] Bio-oil is the main product obtained from the rapid pyrolysis and liquefaction of biomass. It has a complex composition, rich in various oxygen-containing compounds such as aldehydes, ketones, and phenols. Among these, aldehydes and ketones, such as cyclopentanone, pentanal, furfural, and 2-pentanone, can form longer-chain oxygen-containing intermediates through aldol condensation. After further hydrogenation and deoxygenation, the hydrocarbon products from these intermediates meet the specifications for aviation fuel in terms of carbon number distribution (mainly C8-C16) and key physical properties (such as freezing point, flash point, and calorific value), and are therefore considered high-value-added aviation fuel precursors. The efficient and selective preparation of these precursors is a core step in the targeted conversion of bio-oil into green aviation fuel.

[0003] However, in actual bio-oil refining processes, the aforementioned aldehyde and ketone components often exist in mixtures, posing a significant challenge to directional condensation. The substantial differences in intrinsic reactivity of the reactants lead to uncontrolled reaction selectivity. In mixed systems, the reactivity of different aldehyde and ketone components varies significantly. For example, furfural, due to the strong electron-withdrawing effect of its furan ring, exhibits much higher reactivity as an electrophile (carbonyl group) than ketones such as cyclopentanone and 2-pentanone. Pentanone, as a straight-chain aldehyde, also has higher reactivity than ketones. When they coexist, the highly reactive furfural and pentanone preferentially and rapidly react with each other or self-polymerize, not only consuming large quantities of these key components but also generating complex and difficult-to-control byproducts. Meanwhile, less reactive chain ketones such as 2-pentanone may remain in large quantities due to "failed competition," resulting in insufficient utilization of raw materials and low selectivity for the target product.

[0004] Current research on the condensation of mixed aldehydes and ketones focuses primarily on developing novel, highly efficient catalysts. While these can improve the overall conversion rate to some extent, they fail to fundamentally address the bottleneck issues arising from the aforementioned differences in activity. For example, using catalysts with strongly basic sites may exacerbate the reactions of all components, leading to further increases in product complexity. While shape-selective catalysts can screen some macromolecules, they cannot precisely guide specific reaction pathways. Therefore, there is an urgent need in this field for an innovative process capable of achieving highly efficient condensation of mixed aldehyde and ketone components in bio-oils, aiming to improve the overall conversion rate of feedstocks while simultaneously enabling precise control of product distribution and effectively simplifying the separation process. Summary of the Invention

[0005] In view of the above, the purpose of this invention is to provide a condensation reaction method for mixed bio-oil aldehyde-ketone compounds and an aviation fuel precursor. The method solves the technical problems of poor reaction selectivity and insufficient utilization of raw materials in the mixed bio-oil aldehyde-ketone system caused by differences in reactivity and overlapping boiling points through staged condensation.

[0006] A first aspect of the present invention provides a method for the condensation reaction of mixed bio-oil aldehyde-ketone compounds, the method comprising:

[0007] 1) First condensation stage: In the presence of an acid-base bifunctional catalyst, a mixture of reactants containing cyclopentanone, pentanal, furfural and 2-pentanone is subjected to a condensation reaction at 30-90℃.

[0008] 2) Separation step: Separate the mixture after the reaction in step 1) to obtain a fraction rich in the first condensation product and a fraction rich in unreacted reactants;

[0009] 3) Second condensation stage: In the presence of an acid-base bifunctional catalyst, the fraction rich in unreacted reactants obtained in step 2) is subjected to a condensation reaction at 90-130℃ to obtain the second condensation product.

[0010] A second aspect of the present invention provides an aviation fuel precursor prepared by the above-described condensation reaction method of mixed bio-oil aldehyde-ketone compounds.

[0011] Compared with the prior art, the present invention has the following beneficial effects:

[0012] 1. The condensation reaction method of the present invention selectively controls a complex reaction network by coupling stepwise reactions and physical separation to achieve the directional synthesis of high-value chemical aviation fuel precursors.

[0013] 2. The condensation reaction method of the present invention can improve the total conversion rate of raw materials, the selectivity of target products, and simplify the separation of products.

[0014] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0015] Figure 1 This is a reaction pathway diagram involving the first condensation stage of the present invention;

[0016] Figure 2 This is a reaction pathway diagram involving the second condensation stage of the present invention. Detailed Implementation

[0017] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0018] According to a first aspect of the present invention, the present invention provides a method for the condensation reaction of mixed bio-oil aldehyde-ketone compounds, the condensation reaction method comprising:

[0019] 1) First condensation stage: In the presence of an acid-base bifunctional catalyst, a mixture of reactants containing cyclopentanone, pentanal, furfural and 2-pentanone is subjected to a condensation reaction at 30-90℃.

[0020] 2) Separation step: Separate the mixture after the reaction in step 1) to obtain a fraction rich in the first condensation product and a fraction rich in unreacted reactants;

[0021] 3) Second condensation stage: In the presence of an acid-base bifunctional catalyst, the fraction rich in unreacted reactants obtained in step 2) is subjected to a condensation reaction at 90-130℃ to obtain the second condensation product.

[0022] In this invention, the acid-base bifunctional catalyst can be selected from magnesium-aluminum layered bimetallic oxides, magnesium-aluminum-zirconium layered bimetallic oxides, and magnesium-zirconium composite metal oxides.

[0023] Among them, magnesium-aluminum layered bimetallic oxides and magnesium-aluminum-zirconium layered bimetallic oxides can be prepared by the hydrotalcite precursor method, that is, the corresponding hydrotalcite precursor is first prepared, and then the metal oxides are obtained by calcination.

[0024] Specifically, the preparation method of magnesium-aluminum layered bimetallic oxide may include: weighing magnesium salt and aluminum salt (such as magnesium nitrate and aluminum nitrate) according to the Mg / Al molar ratio of (1-4):(1-4) to prepare a mixed salt solution; under vigorous stirring, adding the mixed salt solution and an alkaline precipitant (one or more alkaline precipitant solutions of sodium carbonate, potassium carbonate, sodium hydroxide, potassium hydroxide or ammonia water) dropwise into a four-necked flask, controlling the pH value at 10 for co-precipitation; after precipitation, aging the resulting slurry at 60-90℃ for 6-24 hours; filtering and washing until the filtrate is neutral, and drying to obtain a layered bimetallic hydroxide precursor; finally, calcining the dried precursor at 400-600℃ for 3-7 hours to obtain the magnesium-aluminum layered bimetallic oxide.

[0025] The preparation method of magnesium aluminum zirconium layered bimetallic oxide may include: weighing magnesium salt, aluminum salt and zirconium salt (such as magnesium nitrate, aluminum nitrate, zirconium oxynitrate) according to the molar ratio of Mg / Al / Zr of (1-4):(1-4):(0.1-1) to prepare a mixed salt solution; under vigorous stirring, adding the mixed salt solution and an alkaline precipitant (one or more alkaline precipitant solutions of sodium carbonate, potassium carbonate, sodium hydroxide, potassium hydroxide or ammonia water) dropwise into a four-necked flask, controlling the pH value at 10 for co-precipitation; after precipitation, aging the resulting slurry at 60-90℃ for 6-24 hours; filtering and washing until the filtrate is neutral, and drying to obtain a layered bimetallic hydroxide precursor; finally, calcining the dried precursor at 400-600℃ for 3-7 hours to obtain the magnesium aluminum zirconium layered bimetallic oxide.

[0026] The preparation method of magnesium-zirconium composite metal oxide may include: weighing magnesium salt and zirconium salt (such as magnesium nitrate, zirconium oxynitrate) according to the molar ratio of Mg / Zr of (1-4):(1-4) to prepare a mixed salt solution; under vigorous stirring, adding the mixed salt solution and an alkaline precipitant (one or more alkaline precipitant solutions of sodium carbonate, potassium carbonate, sodium hydroxide, potassium hydroxide or ammonia water) dropwise into a four-necked flask, controlling the pH value at 10 for co-precipitation; after precipitation, aging the resulting slurry at 60-90℃ for 6-24 hours; filtering and washing until the filtrate is neutral, and drying to obtain a bimetallic hydroxide precursor; finally, calcining the dried precursor at 400-600℃ for 3-7 hours to obtain the magnesium-zirconium composite metal oxide.

[0027] Preferably, the acid-base bifunctional catalyst is a magnesium aluminum zirconium layered bimetallic oxide (MgAlZr-LDO). This catalyst has good acid-base properties and a stable layered structure, resulting in better activity and selectivity, and is also beneficial for catalyst recovery and reuse.

[0028] In the 30-90℃ temperature range of step 1), highly active cyclopentanone, pentanal, and furfural can be selectively activated and react, while less active 2-pentanone remains essentially inert.

[0029] In a preferred embodiment, in step 1), the reaction temperature is 50-90℃ and the reaction time is 1-24 hours.

[0030] According to the present invention, in step 2), the separation method can be atmospheric distillation, vacuum distillation or rectification.

[0031] It should be noted that the catalyst needs to be recovered before separation, which involves rapidly cooling the reaction mixture and filtering to recover the catalyst (which can be recycled). The filtrate is then separated, for example, by removing light components through rotary evaporation or by direct distillation, controlling the distillation range to collect the first condensation product with a higher boiling point and the unreacted reactant fraction with a lower boiling point.

[0032] In this invention, the first condensation product mainly includes one or more of the cross-condensation products of cyclopentanone-pentanal, cyclopentanone-furfural, and pentanal-furfural. The unreacted reactants mainly include 2-pentanone and a small amount of cyclopentanone. The first condensation product typically has a high boiling point and is easily separated from the unreacted reactants with lower boiling points.

[0033] At a temperature range of 90-130°C in step 3), the unreacted and less active 2-pentanone from step 1) is fully activated and can undergo self-condensation or cross-condensation with the remaining cyclopentanone.

[0034] In a preferred embodiment, in step 3), the reaction temperature is 100-130℃ and the reaction time is 2-24 hours.

[0035] In this invention, the second condensation product mainly includes the self-condensation of 2-pentanone or the cross-condensation product with residual cyclopentanone.

[0036] According to a second aspect of the present invention, the present invention provides an aviation fuel precursor prepared by the above-described condensation reaction method of mixed bio-oil aldehyde-ketone compounds.

[0037] The aviation fuel precursor prepared by this invention mainly comprises aldehyde-ketone condensation compounds with carbon numbers in the range of C10-C15. Its molecular structure is characterized by branched and cyclic structures, and it has suitable thermal stability and controllable oxygen content.

[0038] The substances and parameters not limited in this invention can be selected according to existing technology, which is a conventional technical means in this field.

[0039] The present invention will be further described below with reference to embodiments. However, the invention is not limited to these embodiments.

[0040] The catalysts used in the various embodiments and comparative examples were prepared using the following method:

[0041] The preparation method of magnesium-aluminum layered bimetallic oxide includes: weighing magnesium nitrate and aluminum nitrate at a Mg / Al molar ratio of 3:1 and preparing a mixed salt solution; adding the mixed salt solution and an alkaline precipitant (a mixed solution of sodium carbonate and sodium hydroxide) dropwise into a reactor under vigorous stirring, controlling the pH value at 10 for co-precipitation; after precipitation, aging the resulting slurry at 80°C for 12 hours; filtering and washing until the filtrate is neutral, and drying to obtain a magnesium-aluminum layered bimetallic hydroxide precursor; finally, calcining the dried precursor at 500°C for 5 hours to obtain the magnesium-aluminum layered bimetallic oxide.

[0042] The preparation method of magnesium aluminum zirconium layered bimetallic oxide includes: weighing magnesium nitrate, aluminum nitrate, and zirconium oxynitrate according to the Mg / Al / Zr molar ratio of 3:0.9:0.1 to prepare a mixed salt solution; under vigorous stirring, adding the mixed salt solution and an alkaline precipitant (a mixed solution of sodium carbonate and sodium hydroxide) dropwise into a reactor in a parallel stream, controlling the pH value at 10 for co-precipitation; after precipitation, aging the resulting slurry at 80°C for 12 hours; filtering and washing until the filtrate is neutral, and drying to obtain a magnesium aluminum zirconium layered bimetallic hydroxide precursor; finally, calcining the dried precursor at 500°C for 5 hours to obtain the magnesium aluminum zirconium layered bimetallic oxide.

[0043] The preparation method of magnesium-zirconium composite metal oxide includes: weighing magnesium nitrate and zirconium oxynitrate at a Mg / Zr molar ratio of 3:1 and preparing a mixed salt solution; adding the mixed salt solution and an alkaline precipitant (a mixed solution of sodium carbonate and sodium hydroxide) to a reactor in a co-current flow under vigorous stirring, controlling the pH value at 10 for co-precipitation; after precipitation, aging the resulting slurry at 80°C for 12 hours; filtering and washing until the filtrate is neutral, and drying to obtain a magnesium-zirconium bimetallic hydroxide precursor; finally, calcining the dried precursor at 500°C for 5 hours to obtain the magnesium-zirconium composite metal oxide.

[0044] Example 1

[0045] A condensation reaction method for mixed bio-oil aldehyde-ketone compounds, the condensation reaction method comprising:

[0046] First condensation stage: Cyclopentanone (20 mmol), pentanal (20 mmol), furfural (20 mmol), 2-pentanone (20 mmol) and 0.35 g of the above magnesium aluminum zirconium layered bimetallic oxide catalyst were added to a 25 mL thick-walled pressure-resistant reaction tube, and the reaction was stirred at 90 °C for 24 hours.

[0047] Intermediate Separation and Product Analysis: After the reaction was completed, the mixture was cooled in an ice-water bath and centrifuged to separate the catalyst. Gas chromatography-mass spectrometry (GC-MS) analysis of the liquid products showed that furfural conversion was 100%, pentanal conversion was 100%, cyclopentanone conversion was 83.4%, while 2-pentanone conversion was only 0.1%. The first fraction, rich in C10-C15 condensation products, was obtained by vacuum distillation. The specific reaction is as follows... Figure 1 As shown in Table 1, the reaction results are as follows.

[0048] Second condensation stage: The unreacted fraction obtained by separation (mainly containing 2-pentanone and cyclopentanone) is added back into the reaction tube, and 0.27g of the above-mentioned magnesium aluminum zirconium layered bimetallic oxide catalyst is added. The reaction is carried out at 130°C for 20 hours.

[0049] Final product analysis: GC-MS analysis showed that the final total conversion of 2-pentanone reached 95%, mainly producing the self-condensation product of 2-pentanone and the cross-condensation product with cyclopentanone. The specific reaction is as follows... Figure 2 As shown in Table 1, the reaction results are as follows.

[0050] Example 2

[0051] Referring to Example 1, the difference from Example 1 is that the catalyst used in the first condensation stage and the second condensation stage is the above-mentioned magnesium-aluminum layered bimetallic oxide catalyst. The reaction results are shown in Table 1.

[0052] Example 3

[0053] Referring to Example 1, the difference from Example 1 is that the catalyst used in the first condensation stage and the second condensation stage is the above-mentioned magnesium-zirconium composite metal oxide catalyst. The reaction results are shown in Table 1.

[0054] Example 4

[0055] Referring to Example 1, the difference from Example 1 is that the reaction temperature of the first condensation stage is 60°C. The reaction results are shown in Table 1.

[0056] Example 5

[0057] Referring to Example 1, the difference from Example 1 is that the reaction temperature for both the first condensation stage and the second condensation stage is 90°C. The reaction results are shown in Table 1.

[0058] Example 6

[0059] Referring to Example 1, the difference from Example 1 is that the reaction temperature of the second condensation stage is 110°C. The reaction results are shown in Table 1.

[0060] Comparative Example 1

[0061] Referring to Example 1, the difference from Example 1 is that the reaction temperature for both the first condensation stage and the second condensation stage is 60°C. The reaction results are shown in Table 1.

[0062] Comparative Example 2

[0063] Referring to Example 1, the difference from Example 1 is that the reaction temperature for both the first and second condensation stages is 130°C. Due to the temperature sensitivity of furfural, a large amount of furfural undergoes self-polymerization during the first condensation stage, resulting in a carbon yield of only 14.1% in the first stage. The specific reaction results are shown in Table 1.

[0064] Comparative Example 3

[0065] Referring to Example 1, the difference is that no intermediate separation step is set between the first condensation stage and the second condensation stage. When the reaction temperature reaches 130°C, the color of the product becomes darker with the extension of the reaction time. Analysis of the final reaction solution shows that the carbon yield of the product is 18.6%, indicating that prolonged reaction at high temperature will trigger serious side reactions, such as excessive condensation, polymerization, and even carbonization, resulting in the loss of a large number of carbon atoms from the target product chain. The specific reaction results are shown in Table 1.

[0066] Comparative Example 4

[0067] Referring to Example 1, the difference from Example 1 is that no intermediate separation step was set, and the reaction was not carried out in stages; the reaction was directly carried out at 90°C with stirring for 44 hours. The reaction results are shown in Table 1.

[0068] Comparative Example 5

[0069] Referring to Comparative Example 4, the difference is that the reaction was directly stirred at 110℃ for 44 hours. The reaction results are shown in Table 1.

[0070] Comparative Example 6

[0071] Compared with Comparative Example 4, the difference is that the reaction was directly stirred at 130°C for 44 hours.

[0072] GC-MS analysis of the products showed that the conversion rates of furfural, pentanal, and cyclopentanone were close to 100%, but a large number of furfural self-polymerization and deep condensation byproducts were detected in the products, resulting in an extremely complex product distribution. The conversion rate of 2-pentanone was only 1.3%. The carbon yield of the final product was 34.8%. The entire product mixture was dark in color and highly viscous, making subsequent separation extremely difficult. Specific reaction results are shown in Table 1.

[0073] Table 1

[0074]

[0075]

[0076] Note: The conversion rate of each reactant in the second stage is the conversion rate of the reactant remaining after the reaction in the first stage in the second stage; “” indicates that the reactant does not exist in the second stage.

[0077] This invention utilizes a staged condensation method to achieve efficient conversion of both highly reactive components (furfural and pentanal) and less reactive components (2-pentanone) under their respective optimal conditions. As shown in Table 1, in Example 1, the final total conversion rate of 2-pentanone was increased to 95.1%, and the carbon yield of the final product was 89.7%. In contrast, the conversion rates of 2-pentanone in Comparative Examples 1-6 were significantly lower (e.g., Comparative Example 1 was only 0.1%). This set of comparative data clearly demonstrates that this invention not only achieves near-complete conversion of all aldehyde and ketone components but also more efficiently converts raw material carbon into high-value aviation fuel precursors, avoiding the loss of carbon atoms due to ineffective side reactions.

[0078] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A method for the condensation reaction of mixed bio-oil aldehydes and ketones, characterized in that, The condensation reaction method includes: 1) First condensation stage: In the presence of an acid-base bifunctional catalyst, a mixture of reactants containing cyclopentanone, pentanal, furfural and 2-pentanone is subjected to a condensation reaction at 30-90℃. 2) Separation step: Separate the mixture after the reaction in step 1) to obtain a fraction rich in the first condensation product and a fraction rich in unreacted reactants; 3) Second condensation stage: In the presence of an acid-base bifunctional catalyst, the fraction rich in unreacted reactants obtained in step 2) is subjected to a condensation reaction at 90-130℃ to obtain the second condensation product.

2. The condensation reaction method for mixed bio-oil aldehyde-ketone compounds according to claim 1, wherein, The acid-base bifunctional catalyst is selected from magnesium-aluminum layered bimetallic oxides, magnesium-aluminum-zirconium layered bimetallic oxides, and magnesium-zirconium composite metal oxides.

3. The condensation reaction method for mixed bio-oil aldehyde-ketone compounds according to claim 2, wherein, The acid-base bifunctional catalyst is a magnesium aluminum zirconium layered bimetallic oxide.

4. The condensation reaction method for mixed bio-oil aldehyde-ketone compounds according to claim 1, wherein, In step 1), the reaction temperature is 50-90℃ and the reaction time is 1-24 hours.

5. The condensation reaction method for mixed bio-oil aldehyde-ketone compounds according to claim 1, wherein, In step 2), the separation method is atmospheric distillation, vacuum distillation, or rectification.

6. The condensation reaction method for mixed bio-oil aldehyde-ketone compounds according to claim 1, wherein, The first condensation product includes one or more of the following: cyclopentanone-pentanal, cyclopentanone-furfural, and pentanal-furfural cross-condensation products.

7. The condensation reaction method for mixed bio-oil aldehyde-ketone compounds according to claim 1, wherein, In step 3), the reaction temperature is 100-130℃ and the reaction time is 2-24 hours.

8. The condensation reaction method for mixed bio-oil aldehyde-ketone compounds according to claim 1, wherein, The second condensation product includes a self-condensation of 2-pentanone or a cross-condensation product with residual cyclopentanone.

9. An aviation fuel precursor prepared by the condensation reaction method of the mixed bio-oil aldehyde-ketone compound according to any one of claims 1-8.

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