Method and catalyst for preparing ultra-low freezing point aviation fuel component

Abstract

The present invention discloses a method for preparing ultra-low freezing point aviation fuel components. This method uses ketones derived from biomass platform compounds such as acetone and methyl pivalate as raw materials, uses N,N-dimethylformamide (DMF) as solvent, and performs Claisen condensation under the catalysis of potassium tert-butoxide to prepare a long carbon chain oxygen-containing precursor with a branched structure. This precursor is then hydrodeoxygenated over a metal-solid acid bifunctional catalyst to produce a hydrocarbon fuel with a low freezing point. The preparation method disclosed in the present invention has a low reaction temperature, is simple to operate, and has high selectivity and yield. The freezing points of the prepared aviation fuel components are all less than 60°C, and some components have freezing points below 100°C.

Description

Technical Field

[0001] The present invention relates to the field of biomass liquid ultra-low freezing point fuel, and in particular to a technology for preparing ultra-low freezing point aviation fuel components from a biomass-derived platform compound. Background Art

[0002] Modern aircraft have increasingly stringent requirements for performance indicators such as payload, speed, range, and altitude, placing higher demands on the fuels they use. For example, to meet the low-temperature operating environment of aircraft at high altitudes, fuels must have excellent low-temperature flow properties, meaning a low freezing point and viscosity.

[0003] Currently, the platform compounds primarily use specific hydrocarbons derived from fossil feedstocks, such as cyclopentadiene, as platform compounds. Through polymerization, hydrogenation, isomerization, separation, and purification, high-performance aviation fuels with high density and low freezing points are produced. For example, JP-10, a fuel synthesized from cyclopentadiene, boasts a freezing point as low as -79°C.

[0004] However, the yield of the C5 portion, especially cyclopentadiene, in products obtained from traditional fossil raw material routes is extremely low (10-20 g / ton coal tar or 14 kg / ton naphtha), resulting in limited JP-10 fuel production and high prices.

[0005] Biomass can be converted to produce a variety of platform compounds, such as furfural, levulinic acid, 5-HMF, acetone, cyclopentanone, glutaraldehyde, methylfuran, etc.

[0006] Under existing technological conditions, the carbon chain structures of these platform compounds are mostly straight-chain or cyclic-chain. After coupling reactions such as aldol condensation, hydroxyalkylation and DA, the prepared long-carbon-chain aviation fuel precursors have a low degree of branching, which often leads to a relatively high freezing point of the final hydrocarbon components, making it difficult to achieve the goal of improving low-temperature fluidity and broadening the range of fuel use. Summary of the Invention

[0007] The purpose of the invention is to address the deficiencies in the prior art and provide a method for preparing an ultra-low freezing point aviation fuel component and a catalyst for preparing the ultra-low freezing point aviation fuel component, which has a relatively low freezing point of a hydrocarbon component, improves low-temperature fluidity, and broadens the range of fuel use.

[0008] The present invention aims to provide a method for preparing an ultra-low freezing point aviation fuel component using a biomass platform compound as a raw material.

[0009] In order to solve the above technical problems, the technical method adopted by the present invention is as follows: The present invention discloses a method for preparing an ultra-low freezing point aviation fuel component, comprising the following steps:

[0010] S1. Claisen condensation reaction was carried out using ketone and ester as raw materials and N,N-dimethylformamide (DMF) as solvent under the catalysis of potassium tert-butoxide.

[0011] S2. Under stirring conditions at room temperature, the solution in step S1 is neutralized, and then filtered and washed with pure water to obtain an isoalkane precursor having a low freezing point property;

[0012] S3. The precursor is hydrodeoxygenated under the action of a metal-solid acid hydrodeoxygenation catalyst to convert it into an alkane aviation fuel component with a branched structure.

[0013] Furthermore, in the step S1, in the Claisen condensation reaction, the molar ratio of the ketone compound to the ester is 1:1 to 2;

[0014] The condensation reaction time is 5 to 10 hours, and the condensation reaction temperature is 25° C. to 50° C.

[0015] Furthermore, in step S2, the solution in step S1 is neutralized to a weak acidic state using hydrochloric acid.

[0016] Furthermore, the ketone includes a straight-chain or branched-chain ketone compound; the ester is a compound with a chemical formula of C6H 12 Methyl pivalate of O2.

[0017] Further, the ketone includes methyl isopropyl ketone C5H 10 O, 2-butanone C4H8O, 2-pentanone C5H 10 O、Pinacolone C6H 12 O, methyl isobutyl ketone C6H 12 O, 2-hexanone C6H 12 O, 5-methyl-2-hexanone C7H 14 O, 2-heptanone C7H 14 O.

[0018] Furthermore, the metal-solid acid hydrodeoxygenation catalyst is a supported bifunctional catalyst, the metal includes nickel, platinum, palladium, and ruthenium, and the solid acid includes HZSM-5, H-β, USY, and Nb2O5.

[0019] Furthermore, the catalyst is 5wt% Pd / USY.

[0020] Furthermore, in step S3, the temperature of the hydrodeoxygenation reaction is between 200 and 400° C., and the hydrogen pressure is between 3 and 6 MPa.

[0021] The present invention also discloses a catalyst for preparing ultra-low freezing point aviation fuel components, which is a supported bifunctional catalyst. The metals include nickel, platinum, palladium, and ruthenium, and the solid acids include HZSM-5, H-β, USY, Nb2O5, etc.

[0022] Furthermore, the catalyst is 5wt% Pd / USY.

[0023] Beneficial effects:

[0024] Compared to existing technologies, this invention offers a new approach to producing high-performance aviation fuel. This preparation method offers mild reaction conditions, high yields, and the potential to reduce production costs. Using α-H-containing ketone compounds derived from biomass as raw materials, the method uses methyl pivalate in a Claisen condensation reaction. Branched hydrocarbon fuel molecules are produced through carbon chain extension and hydrodeoxygenation, enabling the targeted production of ultra-low freezing point aviation fuel components.

[0025] Compared with the existing technology, the method of the present invention is simple, the conditions are easy to control, the selectivity is high, and the post-processing steps are fewer. The freezing points of the obtained aviation fuel components are all less than -60°C, which is lower than the -40°C required by the existing No. 3 jet fuel standard. The freezing points of some components are lower than -100°C. DETAILED DESCRIPTION

[0026] The technical solutions of the present invention are further described below in conjunction with the embodiments. The following embodiments are illustrative rather than restrictive, and the protection scope of the present invention cannot be limited by the following embodiments.

[0027] Example 1

[0028] 6 ml of ethanol, 1.732 g of methyl pivalate, and 0.797 g of methyl isobutyl ketone (C6H12O) were added to a flask equipped with a magnetic rod, and potassium tert-butoxide was added as a catalyst. The reaction was stirred at 80°C for 7 hours. After the reaction, the reaction solution was neutralized with hydrochloric acid to a slightly acidic state, filtered, and the filtrate was washed three times with water and dried by rotary evaporation for 30 minutes. The oil phase was collected for testing and analysis, and the conversion rate of methyl isobutyl ketone was 86%, and the yield of bio-aviation fuel precursor was 2.17%.

[0029] Examples 2 to 5

[0030] Similar to Example 1, different solvents (or no solvent), methyl pivalate, and methyl isobutyl ketone were added to a flask equipped with a magnetron, and a precursor preparation reaction was carried out using potassium tert-butoxide as a catalyst. The reaction conditions and reaction results are shown in Table 1.

[0031] Table 1 Selectivity and yield of precursors in different solvents

[0032]

[0033] Conditions: ketone (8mmol), ester (15mmol), t-BuOK (2.2g); T=80°C, t=10h.

[0034] As can be seen from Table 1, the magnetron can achieve high selectivity and yield in the polar aprotic solvent DMF. However, the yield is low because methyl pivalate undergoes hydrolysis or alcoholysis in the polar protic solvent water.

[0035] Examples 6 to 10

[0036] DMF solvent, methyl pivalate, and methyl isobutyl ketone were added to a flask equipped with a magnetic particle, and a precursor preparation reaction was carried out using potassium tert-butoxide as a catalyst. The specific implementation method was similar to that of Example 1. The reaction results under different temperature conditions are shown in Table 2.

[0037] Table 2 Selectivity and yield of precursors at different temperatures

[0038]

[0039]

[0040] Conditions: ketone (8mmol), ester (15mmol), t-BuOK (2.2g); DMF 6ml, t=10h.

[0041] As can be seen from Table 2, the reaction temperature required for this preparation route is relatively low, methyl isobutyl ketone can be completely converted at room temperature, and the yield of the aviation fuel precursor reaches 94.9%.

[0042] Examples 11 to 22

[0043] Examples 11 to 22 investigated the selectivity and yield of the precursors under different mass ratios, as shown in Table 3.

[0044] Table 3 Selectivity and yield of precursors at different mass ratios

[0045]

[0046] Conditions: DMF 6ml; T=RT, t-BuOK=2.2g, t=10h

[0047] As can be seen in Table 3, when methyl pivalate is in excess, the conversion of methyl isobutyl ketone (MIBK) increases, and the precursor yield also increases. However, when the ketoester equivalent ratio is 1:1.7, the yield remains almost unchanged. When methyl isobutyl ketone (MIBK) is in excess, the conversion increases and the selectivity decreases, presumably due to the self-condensation of the ketone to form the C12 bio-aviation fuel precursor.

[0048] Examples 23 to 32

[0049] The effects of different reaction times on the Claisen condensation reaction are shown in Table 4.

[0050] Table 4 Selectivity and yield of precursors at different reaction times

[0051]

[0052] Conditions: ketone (8mmol), ester (14mmol), t-BuOK (2.2g), DMF 6ml.

[0053] As can be seen from Table 4, the precursor yield increases with the extension of reaction time. The yield reaches the maximum after 7 hours of reaction.

[0054] Examples 33 to 41

[0055] In Examples 33 to 40, the reaction characteristics of preparing bio-aviation fuel precursors by condensing different ketones with methyl pivalate were investigated, as shown in Table 5.

[0056] Table 5 Yields of bio-aviation fuel precursors prepared by condensation of different ketones with methyl pivalate

[0057]

[0058] Reaction conditions: ketone (8 mmol), methyl pivalate (14 mmol), t-BuOK (2.2 g), DMF 6 ml.

[0059] As can be seen from Table 5, the raw material conversion rate, product selectivity and yield of this preparation method are relatively high, so this condensation method has certain universality for the preparation of aviation fuel precursors.

[0060] Example 41

[0061] Methyl isobutyl ketone and methyl pivalate were added to an autoclave for condensation to prepare 0.2 g of a precursor and 0.1 g of a 5 wt% Pt / HZSM-5 catalyst. Hydrodeoxygenation was carried out by stirring at 200° C. and a hydrogen pressure of 6.0 MPa using cyclohexane as a solvent. After 6 hours of reaction, the yield of the target product reached 13.39%.

[0062] During the hydrodeoxygenation process, the backbone carbon chain will rearrange under the action of the catalyst to form carbon chain isomer products. The freezing points of these hydrodeoxygenation products obtained by the hydrodeoxygenation reaction are very low, as shown in the following formula.

[0063]

[0064] Examples 42 to 50

[0065] The operation method is the same as that of Example 41, but the catalyst, reaction temperature or hydrogen pressure are changed. The hydrodeoxygenation reaction characteristics of the precursor prepared by condensation of methyl isobutyl ketone and methyl pivalate are shown in Table 6.

[0066] Table 6 Hydrodeoxygenation reaction of precursors prepared by condensation of methyl isobutyl ketone and methyl pivalate under different conditions

[0067]

[0068] Reaction conditions: 0.2 g of precursor, 0.1 g of catalyst, 6 hours of reaction time, 30 mL of cyclohexane

[0069] As can be seen from Table 6, the precursor prepared by condensation of methyl isobutyl ketone and methyl pivalate under the action of solid acid-supported noble metal bifunctional catalyst can be efficiently converted into hydrocarbon fuel molecules. The catalytic effect varies greatly depending on the metal-supported molecular sieve.

[0070] Examples 51 to 57

[0071] Different precursors, a 5 wt% Pd / USY catalyst, and cyclohexane solvent were added to an autoclave, and hydrodeoxygenation reactions were carried out at 200°C and a hydrogen pressure of 6.0 MPa for 6 hours. The freezing points and total yields of the hydrodeoxygenation products are shown in Table 7.

[0072] Table 7 Hydrodeoxygenation reaction characteristics of different precursors

[0073]

[0074] Reaction conditions: 1.0 g of precursor, 0.2 g of 5 wt% Pt / HZSM-5 catalyst, reaction temperature 280° C., hydrogen pressure 4.0 MPa, reaction time 10 hours, and 30 mL of cyclohexane.

[0075] * The number marked is the freezing point of the substance.

[0076] The reaction results in Table 7 demonstrate that the synthesized precursor can be efficiently hydrodeoxygenated to hydrocarbons using a 5wt% Pd / USY catalyst. The freezing points of the hydrodeoxygenated products obtained are significantly lower than the -40°C requirement for No. 3 jet fuel, with some products reaching below -100°C. These products are excellent low-freezing-point additive components, beneficial for improving the low-temperature flow properties of jet fuel.

[0077] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the foregoing embodiments. The foregoing embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing an ultra-low freezing point aviation fuel component, characterized in that: The method comprises the following steps: S1. Using ketone and ester as raw materials, and N,N-dimethylformamide (DMF) as solvent, a Claisen condensation reaction is carried out under the catalysis of potassium tert-butoxide; the ketone includes a straight-chain or branched-chain ketone compound; the ester is a compound with a chemical formula of C6H 12 Methyl pivalate of O2; S2. Under stirring conditions at room temperature, the solution in step S1 is neutralized, and then filtered and washed with pure water to obtain an isoalkane precursor having a low freezing point property; S3. The precursor is hydrodeoxygenated under the action of a metal - solid acid hydrodeoxygenation catalyst to form an alkane aviation fuel component having a branched structure; In the step S1, in the Claisen condensation reaction, the molar ratio of the ketone compound to the ester is 1:1-2; The condensation reaction time is 5 to 10 hours, and the condensation reaction temperature is 25°C to 50°C; The ketone includes methyl isopropyl ketone C5H 10 O, 2-butanone C4H8O, 2-pentanone C5H 10 O、Pinacolone C6H 12 O, methyl isobutyl ketone C6H 12 O, 2-hexanone C6H 12 O, 5-methyl-2-hexanone C7H 14 O or 2-heptanone C7H 14 One or more of O; The metal-solid acid hydrodeoxygenation catalyst is a supported bifunctional catalyst, wherein the metal comprises one or more of nickel, platinum, palladium or ruthenium, and the solid acid comprises one or more of HZSM-5, H-β, USY or Nb2O5.

2. The method for preparing an ultra-low freezing point aviation fuel component according to claim 1, characterized in that: In step S2, the solution in step S1 is neutralized to a weak acidic state using hydrochloric acid.

3. The method for preparing an ultra-low freezing point aviation fuel component according to claim 1, characterized in that: The catalyst is 5 wt% Pd / USY.

4. The method for preparing an ultra-low freezing point aviation fuel component according to claim 1, characterized in that: In step S3, the temperature of the hydrodeoxygenation reaction is between 200 and 400° C., and the hydrogen pressure is between 3 and 6 MPa.

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