Preparation method of bio-based aviation fuel precursor

Abstract

The invention discloses a preparation method of a bio-based aviation fuel precursor, and belongs to the technical field of biomass conversion. According to the technical scheme, biological isomeric fatty alcohol obtained through an ethanol coupling process is dehydrogenated in a fixed bed reactor to obtain biological isomeric fatty aldehyde, the biological isomeric fatty aldehyde, biological low-carbon ketone and alkali are added into the reactor for a reaction, and a target product is obtained after the reaction is finished. According to the technical scheme provided by the invention, the raw materials are all from biomass, the ethanol is obtained by fermenting the biomass, the isomeric fatty alcohol can be obtained by performing water-phase coupling on the ethanol, the low-carbon ketone can be synthesized by performing gas-phase reaction on the ethanol, and the whole process is carbon-negative; the synthesized product contains one or more ethyl groups, and is a fuel precursor with high energy density, high octane number and low freezing point; meanwhile, the method is short in reaction time, high in yield, high in raw material utilization rate and applicable to industrial production; the used catalyst can be recycled and reused, and the separation in the technical process is simple.

Description

Technical Field

[0001] The invention belongs to the technical field of biomass conversion, and in particular relates to a method for preparing a bio-based aviation fuel precursor. Background Art

[0002] Biomass energy comes from plants, animals, and microorganisms, and is a renewable energy source. Compared with limited fossil fuels, the renewability of biomass energy has advantages in sustainable energy. Among them, ethanol obtained by fermentation process is an important bio-based platform molecule that can be converted into a variety of important organic chemicals. Using ethanol directly as fuel has disadvantages such as low energy density, insufficient calorific value, and corrosion of the engine.

[0003] In recent years, the use of bio-based ethanol to grow carbon chains to obtain high carbon number fuels has attracted the attention of many scholars at home and abroad. Among them, the ethanol water phase coupling process is a relatively important carbon chain growth process. In the ethanol water phase coupling process, ethanol undergoes dehydrogenation, aldol condensation and hydrogenation to achieve carbon chain growth. The ultimate conversion product of this process is isomeric fatty alcohols mainly composed of 2-ethylbutanol and 2-ethylhexanol. Because isomeric fatty alcohols have large steric hindrance and only one α-H molecular structure, it is difficult to continue carbon chain growth.

[0004] Compared with aliphatic primary aldehydes, molecules such as acetone, butanone and 2-pentanone have α-H on both the left and right carbonyl carbons, and the α-H activity is slightly weaker. Their ability to undergo aldol condensation is slightly weaker, and they are ideal molecules for cross-coupling or bridging with isomeric aliphatic aldehydes. At present, the main production source of acetone is as a by-product in the production process of phenol, and its production is affected by the phenol market.

[0005] At the end of the last century, some scholars discovered that ethanol can produce acetone in a gas phase reaction, and the product also contains some butanone and 2-pentanone. Since ethanol can be obtained through biomass fermentation, the research on using ethanol to synthesize acetone has attracted the attention of many scholars.

[0006] Aviation fuel (hydrocarbon C8-C 16 ) requires the fuel to have suitable energy density, high calorific value, low temperature fluidity and good stability. The isomeric fatty alcohols synthesized by the ethanol coupling process contain branched structures and have the potential to synthesize aviation fuels, but the energy density of the main products 2-ethylbutanol and 2-ethylhexanol is still low. Isomeric fatty alcohols can be dehydrogenated in a continuous flow fixed bed reactor to obtain aldehydes of corresponding structures. The use of acetone, butanone, 2-pentanone and other molecules obtained from the ethanol gas phase reaction and isomeric fatty aldehydes for cross-coupling or bridging can achieve carbon chain growth. The final product is a liquid fuel with a special structure containing one or more ethyl groups, high energy density, high octane number and low freezing point. Summary of the invention

[0007] The purpose of the present invention is to overcome the difficulty in growing the carbon chain of ethanol coupling and to provide a method for preparing a bio-based aviation fuel precursor. The preparation method is carried out under normal pressure and can obtain isomerized liquid fuel with high yield in a short time.

[0008] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0009] S1. Dehydrogenating bio-isomerized fatty alcohols to bio-isomerized fatty aldehydes in a continuous flow fixed bed tubular reactor;

[0010] S2. Add the bio-isomerized fatty aldehyde, bio-low carbon ketone and base prepared in step S1 into a reaction vessel, heat to (25-110)°C, stir and react for (2-12) hours, and obtain the target product after the reaction is completed;

[0011] The molar ratio of the bio-isomerized fatty aldehyde, the bio-low-carbon ketone and potassium hydroxide is 5:5:2 or 5:5:1 or 10:10:1 or 15:15:1 or 20:20:1.

[0012] Furthermore, in the method for preparing the bio-based aviation fuel precursor of the present invention, the bio-isomerized fatty alcohol described in S1 is one of 2-ethylbutanol and 2-ethylhexanol, and the corresponding dehydrogenation products are 2-ethylbutanal and 2-ethylhexanal, respectively.

[0013] Furthermore, in the method for preparing the bio-based aviation fuel precursor of the present invention, the biological low-carbon ketone in S2 is one of acetone, butanone or 2-pentanone.

[0014] Furthermore, in the method for preparing the bio-based aviation fuel precursor of the present invention, the base in S2 is one of potassium hydroxide, sodium hydroxide or barium hydroxide.

[0015] Furthermore, in the method for preparing the bio-based aviation fuel precursor of the present invention, the molecular molar ratio of the bio-isomerized fatty aldehyde to the bio-low-carbon ketone in S2 is (0.5-3):1.

[0016] Furthermore, in the method for preparing the bio-based aviation fuel precursor of the present invention, the molecular molar ratio of the bio-isomerized fatty aldehyde, bio-low carbon ketone and potassium hydroxide in S2 is 5:5:2 or 5:5:1 or 10:10:1 or 15:15:1 or 20:20:1.

[0017] Furthermore, in the method for preparing the bio-based aviation fuel precursor of the present invention, the reaction temperature in S2 is 70°C.

[0018] Furthermore, in the method for preparing the bio-based aviation fuel precursor of the present invention, the reaction time in S2 is 4 hours.

[0019] The beneficial effects of the present invention are:

[0020] (1) The technical solution provided by the present invention replaces traditional fossil resources, uses biomass-synthesized isomeric fatty alcohols to dehydrogenate isomeric fatty aldehydes, and then synthesizes long-chain, high-octane isomeric liquid fuels with low-carbon ketones. The raw materials are renewable, and the synthesis process is carbon negative.

[0021] (2) The yield and raw material utilization rate of the present invention are high, and the carbon number distribution of the product can be adjusted by changing the reaction conditions, so the operability is strong.

[0022] (3) The reaction time of the present invention is short, the economic benefit is high, and it can be used for industrial production.

[0023] (4) The catalyst used in the present invention can be recycled and reused, and the separation process is simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a GC graph of the product after the reaction of 2-ethylbutanol and acetone in step 2) of Example 1 of the present invention;

[0025] Figure 2 This is a GC graph of the product after the reaction of 2-ethylhexanol and acetone in step 2) of Example 2 of the present invention;

[0026] Figure 3 This is a GC graph of the product after the reaction of 2-ethylbutanol and butanone in step 2) of Example 3 of the present invention;

[0027] Figure 4 This is a GC chart of the product after the reaction of 2-ethylbutanol and 2-pentanone in step 2) of Example 4 of the present invention;

[0028] Figure 5 This is the MS analysis chart of the product 5-ethyl-3-ene-2-heptanone prepared in Example 1;

[0029] Figure 6 This is the MS analysis chart of the product 3,9-diethyl-4,7-diene-6-undecanone prepared in Example 1;

[0030] Figure 7 This is the MS analysis chart of the product 5-ethyl-3-ene-2-nonanone prepared in Example 2;

[0031] Figure 8 This is the MS analysis chart of the product 5,11-diethyl-6,9-diene-8-pentadecanone prepared in Example 2;

[0032] Fig. 9 This is the MS analysis chart of the product 6-ethyl-4-ene-3-octanone prepared in Example 3;

[0033] Fig.10 This is the MS analysis chart of the product 3,9-diethyl-5-methyl-4,7-diene-6-undecanone prepared in Example 3;

[0034] Fig.11 This is the MS analysis chart of the product 7-ethyl-5-ene-4-nonanone prepared in Example 4. DETAILED DESCRIPTION

[0035] The present invention is further described below in conjunction with the accompanying drawings and specific examples, which do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0036] Unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0037] The chemical reaction formulas involved in Examples 1-19 are as follows:

[0038]

[0039] Where: R 1 -CH3 or -CH2CH2CH3

[0040]

[0041] Where: R 1 is -CH3 or -CH2CH2CH3, R 2 It is -CH3 or -CH2CH3 or -CH2CH2CH3.

[0042] Example 1

[0043] Step 1) 1.0 g of commercial nano zinc oxide catalyst and 2.0 g of quartz sand (40-60 mesh) were mixed and loaded into a continuous flow fixed bed tubular reactor (stainless steel material, inner diameter 10 mm, length 350 mm), and dehydrogenation reaction was carried out to prepare 2-ethylbutyraldehyde under the conditions of 30 mL / min nitrogen atmosphere, 370° C., normal pressure, and 2-ethylbutanol feed flow rate of 0.005 mL / min. The product was collected and the product and yield were determined by GC-MS analysis; the 2-ethylbutanol reaction conversion rate and 2-ethylbutyraldehyde selectivity are shown in Table 1 below;

[0044] Step 2) 3.3 g of 2-ethylbutyraldehyde prepared in step 1) of Example 1 was added to a 25 mL round-bottom flask reactor with 1.8 g of acetone and 0.18 g of potassium hydroxide (the molar ratio of 2-ethylbutyraldehyde, potassium hydroxide and acetone was 10:10:1), and reacted at 70 ° C for 4 h. After the reaction, a solution containing the target product was obtained. The product and yield were determined by GC-MS analysis. The GC chart is shown in Figure 1The reaction conversion rate and product selectivity are shown in Table 2. MS analysis shows that product 1 is 5-ethyl-3-ene-2-heptanone, with the structural formula

[0045] As shown in Formula 1; and product 2 is 3,9-diethyl-4,7-diene-6-undecanone, the structural formula of which is shown in Formula 2.

[0046]

[0047] Example 2

[0048] Step 1) 1.0 g of commercial nano zinc oxide catalyst and 2.0 g of quartz sand (40-60 mesh) were mixed and loaded into a continuous flow fixed bed tubular reactor (stainless steel material, inner diameter 10 mm, length 350 mm), and dehydrogenation reaction was carried out under the conditions of 30 mL / min nitrogen atmosphere, 370° C., normal pressure, and 2-ethylhexanol feed flow rate of 0.005 mL / min to prepare 2-ethylhexyl aldehyde, and the product was collected and analyzed by GC-MS to determine the product and yield; the 2-ethylhexanol reaction conversion rate and 2-ethylhexyl aldehyde selectivity are shown in Table 1 below

[0049] Step 2) 3.5 g of 2-ethylhexanal prepared in step 1) of Example 2 was added to a 25 mL round-bottom flask reactor with 1.5 g of acetone and 0.17 g of potassium hydroxide (the molar ratio of 2-ethylhexanal, potassium hydroxide and acetone was 10:10:1), and reacted at 70 ° C for 4 h. After the reaction, a solution containing the target product was obtained. The product and yield were determined by GC-MS analysis. The GC chart is shown in Figure 2 The reaction conversion rate and product selectivity are shown in Table 2. MS analysis shows that product 1 is 5-ethyl-3-ene-2-nonanone, with a structural formula shown in Formula 3; and product 2 is 5,11-diethyl-6,9-diene-8-pentadecanone, with a structural formula shown in Formula 4.

[0050]

[0051] Table 1

[0052]

[0053] Table 2

[0054]

[0055] Example 3

[0056] The other reaction parameters and materials of this embodiment are the same as those of embodiment 1, except that an equimolar amount of butanone is used instead of acetone in step 2); the GC chart of the product after the reaction of 2-ethylbutanol and butanone in step 2) is shown in FIG. Figure 3The reaction conversion rate and product selectivity are shown in Table 3. MS analysis shows that product 1 is 6-ethyl-4-ene-3-octanone, with the structural formula shown in u; product 2 is 3,9-diethyl-5-methyl-4,7-diene-6-undecanone, with the structural formula shown in formula 6.

[0057]

[0058] Example 4

[0059] The other reaction parameters and materials of this embodiment are the same as those of embodiment 1, except that an equimolar amount of 2-pentanone is used instead of acetone in step 2); the GC chart of the product after the reaction of 2-ethylbutanol and 2-pentanone in step 2) is shown in FIG. Figure 4 The reaction conversion rate and product selectivity are shown in Table 3. MS analysis shows that the product is 7-ethyl-5-ene-4-nonanone; the structural formula is shown in Formula 7.

[0060]

[0061] Table 3

[0062]

[0063]

[0064] Example 5

[0065] The other reaction parameters and materials of this embodiment are the same as those of embodiment 1, except that an equimolar amount of sodium hydroxide is used instead of potassium hydroxide in step 2); the reaction conversion rate and product selectivity are shown in Table 4 below.

[0066] Example 6

[0067] The other reaction parameters and materials of this embodiment are the same as those of embodiment 1, except that an equimolar amount of barium hydroxide is used instead of potassium hydroxide in step 2); the reaction conversion rate and product selectivity are shown in Table 4 below.

[0068] Table 4

[0069]

[0070] Example 7

[0071] The other reaction parameters and materials of this embodiment are the same as those of embodiment 1, except that the molar ratio of 2-ethylbutyraldehyde to acetone in step 2) is 0.5:1; the reaction conversion rate and product selectivity are shown in Table 5 below.

[0072] Example 8

[0073] The other reaction parameters and materials of this embodiment are the same as those of Example 1, except that the molar ratio of 2-ethylbutyraldehyde to acetone in step 2) is 2:1; the reaction conversion rate and product selectivity are shown in Table 5 below.

[0074] Example 9

[0075] The other reaction parameters and materials of this embodiment are the same as those of embodiment 1, except that the molar ratio of 2-ethylbutyraldehyde to acetone in step 2) is 3:1; the reaction conversion rate and product selectivity are shown in Table 5 below.

[0076] Table 5

[0077]

[0078] Example 10

[0079] The other reaction parameters and materials of this embodiment are the same as those of Example 1, except that the molar ratio of 2-ethylbutyraldehyde, potassium hydroxide and acetone in step 2) is 5:5:2; the reaction conversion rate and product selectivity are shown in Table 6 below.

[0080] Embodiment 11

[0081] The other reaction parameters and materials of this embodiment are the same as those of Example 1, except that in step 2), the molar ratio of 2-ethylbutyraldehyde, potassium hydroxide and acetone is 5:5:1; the reaction conversion rate and product selectivity are shown in Table 6 below.

[0082] Example 12

[0083] The other reaction parameters and materials of this embodiment are the same as those of Example 1, except that the molar ratio of 2-ethylbutyraldehyde, potassium hydroxide and acetone in step 2) is 15:15:1; the reaction conversion rate and product selectivity are shown in Table 6 below.

[0084] Embodiment 13

[0085] The other reaction parameters and materials of this embodiment are the same as those of Example 1, except that the molar ratio of 2-ethylbutyraldehyde, potassium hydroxide and acetone in step 2) is 20:20:1; the reaction conversion rate and product selectivity are shown in Table 6 below.

[0086] Table 6

[0087]

[0088]

[0089] Embodiment 14

[0090] The other reaction parameters and materials of this embodiment are the same as those of embodiment 1, except that the reaction temperature in step 2) is 50°C; the reaction conversion rate and product selectivity are shown in Table 7 below.

[0091] Embodiment 15

[0092] The other reaction parameters and materials of this embodiment are the same as those of embodiment 1, except that the reaction temperature in step 2) is 90°C; the reaction conversion rate and product selectivity are shown in Table 7 below.

[0093] Example 16

[0094] The other reaction parameters and materials of this embodiment are the same as those of embodiment 1, except that the reaction temperature in step 2) is 110°C; the reaction conversion rate and product selectivity are shown in Table 7 below.

[0095] Table 7

[0096]

[0097]

[0098] Embodiment 17

[0099] The other reaction parameters and materials of this embodiment are the same as those of embodiment 1, except that the reaction time in step 2) is 2 h; the reaction conversion rate and product selectivity are shown in Table 8 below.

[0100] Embodiment 18

[0101] The other reaction parameters and materials of this embodiment are the same as those of embodiment 1, except that the reaction time in step 2) is 8 h; the reaction conversion rate and product selectivity are shown in Table 8 below.

[0102] Embodiment 19

[0103] The other reaction parameters and materials of this embodiment are the same as those of embodiment 1, except that the reaction time in step 2) is 12 h; the reaction conversion rate and product selectivity are shown in Table 8 below.

[0104] Table 8

[0105]

[0106]

[0107] Comparative Example 1

[0108] The difference from Example 1 is that potassium phosphate is used as the base in this comparative example, and the conditions and reagents in the remaining steps are consistent with those in Example 1. The reaction conversion rate and product selectivity of this comparative example are shown in Table 9 below.

[0109] Comparative Example 2

[0110] The difference from Example 1 is that potassium carbonate is used as the base in this comparative example, and the conditions and reagents in the remaining steps are consistent with those in Example 1. The reaction conversion rate and product selectivity of this comparative example are shown in Table 9 below.

[0111] Table 9

[0112]

[0113] Comparative Example 3

[0114] The difference from Example 1 is that the molar ratio of 2-ethylbutyraldehyde, potassium hydroxide and acetone in this comparative example is 1:1:2, and the conditions and reagents of the remaining steps are consistent with those of Example 1. The reaction conversion rate and product selectivity of this comparative example are shown in Table 10 below.

[0115] Comparative Example 4

[0116] The difference from Example 1 is that the molar ratio of 2-ethylbutyraldehyde, potassium hydroxide and acetone in this comparative example is 25:25:1, and the conditions and reagents of the remaining steps are consistent with those of Example 1. The reaction conversion rate and product selectivity of this comparative example are shown in Table 10 below.

[0117] Table 10

[0118]

[0119] As can be seen from Example 1, 2-ethylbutanol and 2-ethylhexanol can be dehydrogenated to the corresponding aldehydes with high yields using commercial nano zinc oxide in a continuous flow fixed bed. Examples 1 to 4 show the characteristic products obtained by reacting different bio-isomerized fatty aldehydes with different bio-low-carbon ketones. Examples 5 to 19 explore the effects of different base types, aldehyde / ketone molar ratio, base dosage, temperature and time on the reaction. Among them, potassium hydroxide is used as the base, the molar ratio of 2-ethylbutyraldehyde, potassium hydroxide and acetone is 10:10:1, 70°C, and the reaction conditions of 4h are the best.

[0120] Although the bases in Comparative Examples 1 and 2 can have a higher selectivity for the target product, the conversion rate is very low due to its weak alkalinity. It can be seen from Comparative Examples 3 and 4 that the amount of base needs to be within the range. Adding an excess of base (the aldehyde / ketone / base molar ratio is 1:1:2) can make the raw materials react completely, but a large amount of highly condensed products will be generated, resulting in low selectivity for the target product; adding a small amount of base (the aldehyde / ketone / base molar ratio is 25:25:1) has a higher selectivity for the target product, but the conversion rate is low. If reaction conditions exceeding the preferred range are used, the yield of the target product will decrease.

[0121] The above embodiments describe the implementation methods of the present invention in detail. The present invention is not limited to the above embodiments, and those skilled in the art can make various changes without departing from the purpose of the present invention. The above embodiments are only preferred implementation methods of the present invention, and do not limit the scope of rights of the present invention. Any equivalent structural changes made using the contents of the present invention specification are included in the scope of rights of the present invention.

Claims

1. A method for preparing a bio-based aviation fuel precursor, characterized in that: The steps are as follows: S1. dehydrogenating bio-isomerized fatty alcohols into bio-isomerized fatty aldehydes in a continuous flow fixed bed tubular reactor; S2. Add the bio-isomerized fatty aldehyde, bio-low carbon ketone and base prepared in step S1 into a reaction vessel, heat to (25-110) °C, stir and react for (2-12) h, and after the reaction is completed, obtain the target product; The molar ratio of the bio-isomerized fatty aldehyde, the bio-low-carbon ketone and potassium hydroxide is 5:5:2 or 5:5:1 or 10:10:1 or 15:15:1 or 20:20:

1.

2. The method for preparing a bio-based aviation fuel precursor according to claim 1, characterized in that: S1 The bio-isomerized fatty alcohol is one of 2-ethylbutanol and 2-ethylhexanol.

3. The method for preparing a bio-based aviation fuel precursor according to claim 1, characterized in that: S1 The bioisomerized fatty aldehyde is one of 2-ethylbutyraldehyde and 2-ethylhexanal.

4. The method for preparing a bio-based aviation fuel precursor according to claim 1, characterized in that: S2 The biological low-carbon ketone is one of acetone, butanone and 2-pentanone.

5. The method for preparing a bio-based aviation fuel precursor according to claim 1, characterized in that: The alkali S2 is one of potassium hydroxide, sodium hydroxide and barium hydroxide.

6. The method for preparing a bio-based aviation fuel precursor according to claim 1, characterized in that: The molar ratio of S2 bio-isomerized fatty aldehyde, bio-low carbon ketone and potassium hydroxide is 5:5:2 or 5:5:1 or 10:10:1 or 15:15:1 or 20:20:

1.

7. The method for preparing a bio-based aviation fuel precursor according to claim 1, characterized in that: The reaction temperature in S2 is 70°C.

8. The method for preparing a bio-based aviation fuel precursor according to claim 1, characterized in that: The reaction time in S2 is 4 h.

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