A higher alcohol for preparing aviation fuel and its preparation method and application

Abstract

The present invention discloses a higher alcohol for preparing aviation fuel and a preparation method and application thereof, and specifically relates to the technical field of organic synthesis. The preparation method of the higher alcohol for preparing aviation fuel disclosed in the present invention adopts a multi-stage programmed temperature method to perform ethanol water phase coupling to generate C8-C 16 The reaction of higher alcohols, and by adjusting the temperature of each insulation stage in the heating program, the number of insulation stages and other parameters, so that the different intermediates generated in the reaction process can continue to couple under the most suitable temperature conditions for their own continued reaction, and finally form C8-C 16 Therefore, the preparation method of the higher alcohol for preparing aviation fuel provided by the present invention can rapidly convert ethanol while suppressing the occurrence of side reactions, thereby improving the C8-C 16 Yield of higher alcohols.

Description

Technical Field

[0001] The invention relates to the technical field of organic synthesis, and in particular to a higher alcohol for preparing aviation fuel, and a preparation method and application thereof. Background Art

[0002] Aviation fuel refers to the fuel used to power aircraft, and its main components are straight / branched alkanes, cycloalkanes and aromatics with carbon numbers ranging from 8 to 16.

[0003] In the existing process of preparing aviation fuel, transition metal and base catalysts are often used to catalyze the coupling of ethanol in water to form C8-C 16 Higher normal / isomeric alcohols can be selectively generated by reducing higher normal / isomeric alcohols to produce C8-C 16 Straight / branched alkanes are the main components for preparing aviation fuel. Ethanol is coupled in the water phase to form C8-C 16 Higher-grade n- / isomerized alcohols are an important process in the preparation of aviation fuels. Their coupling mode follows the principle of Guerbet reaction and can be divided into three parts: (1) alcohol dehydrogenation catalyzed by metal catalysts; (2) aldol condensation catalyzed by base catalysts; and (3) metal catalysts hydrogenate the aldol condensation products to generate long-chain alcohols.

[0004] Although the process of preparing aviation fuel from ethanol has been studied, the existing process is still inefficient in preparing aviation fuel. This is because the C8-C 16 In the process of higher alcohols, there are a series of alcohol intermediates with different carbon atoms, and as the carbon chain grows, alcohol dehydrogenation requires higher energy. Therefore, when ethanol is coupled at low temperature, not only is the conversion rate of ethanol slow, but also intermediates such as butanol are difficult to dehydrogenate and further couple; however, high temperature is not conducive to the ethanol coupling reaction, because when reacting at high temperature, ethanol is more likely to undergo reforming side reactions. Although the conversion rate of ethanol is increased at high temperature, and the conversion rate of ethanol is increased in the same reaction time, the target product C8-C 16 Therefore, the yield of the target product will be reduced, which means that C8-C 16 The selectivity of the reaction of higher alcohols is reduced. Specifically, in the prior art, ethanol coupling is used to prepare C8-C 16 When the conversion rate of ethanol is high, C8-C 16 The highest yield of higher alcohols can only reach about 30%, that is, the selectivity of the target reaction is poor; 16Under the premise that the yield of higher alcohols can reach 30% and the conversion rate of ethanol is also low (selectivity of target reaction = yield of target product ÷ conversion rate of reactants), the selectivity of the target reaction is improved, but the efficiency of the preparation method is reduced.

[0005] The prior art discloses a gradient temperature-controlled continuous condensation method for preparing polyarylene sulfide resin, wherein the reactants are mixed and continuously sent to reactors connected in series for reaction, and the materials are ensured to have sufficient residence time in different reactors; by setting each reactor to be constant at a different temperature or temperature range, the temperature gradient control of the condensation reaction is achieved, and the different progress of the polymerization reaction is adapted to produce a polyarylene sulfide resin with a concentrated and stable molecular weight. However, in the gradient temperature-controlled continuous condensation method provided by the prior art, the temperature gradient of the reaction is set according to different intermediate products in the synthesis process of the polyarylene sulfide resin, and at the same time, due to the generation of C8-C 16 The process of preparing higher alcohols involves many intermediate reactions and complex products. Therefore, the C8-C 16 It is difficult to use the existing technology to improve the conversion rate of ethanol in the ethanol-water coupling reaction and the generation of C8-C 16 Selectivity of the target reaction of higher alcohols. Summary of the invention

[0006] In order to solve the problem that the high conversion rate of ethanol and the generation of C8-C 16 In order to solve the problem of high selectivity of the reaction of higher alcohols, the present invention provides a method for preparing higher alcohols for preparing aviation fuel, which adopts a multi-stage heating procedure based on the ethanol water phase coupling reaction, and controls the temperature, the number of heating steps and other parameters of each heating stage in the heating procedure, so as to suppress the occurrence of side reactions while making ethanol rapidly converted, thereby improving the generation of C8-C 16 Selectivity of this reaction for higher alcohols.

[0007] Another object of the present invention is to provide a higher alcohol for preparing aviation fuel.

[0008] Another object of the present invention is to provide an aviation fuel.

[0009] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0010] A method for preparing higher alcohols for preparing aviation fuel comprises the following steps:

[0011] An ethanol aqueous solution, a metal catalyst and a homogeneous base are mixed, and a multi-stage programmed temperature method is used to carry out an ethanol-water phase coupling reaction to obtain a higher alcohol having a carbon number of 8 to 16 for preparing aviation fuel;

[0012] The temperature program in the multi-stage programmed temperature method includes n insulation stages, wherein the insulation temperature of the first stage is 120-180°C, and the insulation temperature of the nth stage is 250-280°C. In the (n-2) insulation stages between the first stage and the nth stage, the insulation temperature gradually increases with the increase of the stage number, and is not lower than the insulation temperature of the first stage, nor higher than the insulation temperature of the nth stage;

[0013] The total insulation time of all insulation stages in the heating program is t, wherein the insulation time of each stage is t / n, and the total insulation time t is higher than 6h.

[0014] In a specific embodiment of the present invention, the ethanol aqueous solution may be an aqueous solution with an ethanol content of 50 wt%, and the mass ratio of the reactants may be metal catalyst: homogeneous base: ethanol aqueous solution = 0.16:0.17:2.

[0015] In the process of ethanol-water coupling to form higher alcohols for the preparation of aviation fuel, since the coupling mode of ethanol follows the Guerbet reaction principle, metal catalysts and base catalysts are needed to catalyze the dehydrogenation or hydrogenation and aldol condensation processes respectively. Therefore, the present invention adds two catalysts, a metal catalyst and a homogeneous base, to the reaction system, wherein the homogeneous base is a base dissolved in the aqueous phase. In a specific embodiment of the present invention, the homogeneous base can be sodium hydroxide, and the metal catalyst can be 5% Pd / C selected from Macklin, or a nitrogen-doped carbon-coated nickel catalyst, a NiSn / C core-shell composite nanocatalyst, and a sulfur-doped carbon-coated nickel catalyst from patents 202110256353.8, 202110217123.0, and 202111585174.5, respectively.

[0016] The multi-stage programmed temperature method is used to carry out the ethanol-water phase coupling reaction in order to adapt to the characteristics that small molecule ethanol is suitable for low temperature reaction, while longer chain molecules such as butanol require higher temperature to react due to the increase in carbon chain length. This is also the reason why the present invention limits the insulation temperature of the (n-2) insulation stages between the first stage and the nth stage to between the first stage and the nth stage and gradually increases. In the process of ethanol coupling to form higher alcohols for the preparation of aviation fuel, the final product C8-C 16Higher alcohols are not directly obtained by coupling several molecules of ethanol, but are obtained by coupling intermediate products such as butanol and hexanol, which are produced by coupling ethanol. The reason why the temperature required for the coupling reaction increases with the increase of the carbon chain length of the reactants is that the longer the carbon chain length, the higher the activation energy required for the reactants to participate in the reaction. It should be noted that the specific insulation temperature of the (n-2) insulation stages between the first stage and the nth stage has little effect on the conversion rate of the reactants, the yield of the target product, and the selectivity of the target reaction.

[0017] The insulation temperature of the first stage of the temperature program in the multi-stage temperature program method is limited to 120-180°C because the main reactions occurring in the first insulation stage are the coupling of two molecules of ethanol to form butanol, and the coupling of one molecule of butanol and one molecule of ethanol to form hexanol. The reaction temperature is limited to 120-180°C to adapt to the activation energy required by these two main reactions. If the reaction temperature of the first stage is lower than 120°C, ethanol and butanol cannot absorb enough heat energy from the reaction system to become activated molecules, and thus it is difficult for the coupling reaction to occur; however, the reaction temperature of the first stage should not be higher than 180°C, because there is also a side reaction in the reaction system where ethanol is reformed to form products such as carbon dioxide and water. When the reaction temperature is too high, the coupling reaction of ethanol and butanol will no longer dominate the reaction system, and the reforming reaction of ethanol will become the main reaction in the system, and the reforming reaction is not conducive to the formation of intermediates, and thus is not conducive to the formation of C8-C 16 Therefore, although the conversion rate of ethanol increases at high temperatures, the C8-C 16 The yield of higher alcohols decreased, which means that ethanol was coupled to form C8-C 16 The selectivity of this reaction decreases with higher alcohols.

[0018] It should be noted that in actual industrial production, in order to ensure production efficiency, the reaction is often not allowed to proceed to the maximum limit, that is, when the reaction reaches equilibrium, so the conversion rate of the reactant ethanol refers to the conversion rate of ethanol after the reaction is completed, but in the present invention, the end of the reaction is not necessarily when the reaction reaches equilibrium. Therefore, in the reaction system of the present invention, the higher the conversion rate of ethanol, the higher the conversion rate of ethanol, and if the conversion rate of ethanol decreases, the conversion rate will also decrease accordingly.

[0019] The reason why the holding temperature of the nth stage of the multi-stage temperature program is limited to 250-280°C is similar. In the nth holding stage, the main reaction in the system is the coupling of the intermediates to form C8-C 16The carbon chain of the intermediate product is longer than that of ethanol, so the activation energy required for the reaction is greater and the temperature of the system needs to be higher. When the insulation temperature of the nth stage is lower than 250℃, the intermediate product couples to generate C8-C 16 The reaction selectivity of higher alcohols is low, which makes the C8-C 16 The yield of higher alcohols decreased. When the holding temperature was higher than 280°C, the decomposition reaction of the intermediate products in the side reaction gradually began to dominate, generating C8-C 16 The selectivity of the target reaction of higher alcohols will also decrease.

[0020] The total holding time t of all holding stages in the heating program is limited to more than 6 h because the total holding time is too short to form C8-C 16 This reaction of higher alcohols cannot be fully carried out, the conversion rate of ethanol is insufficient, and the product C8-C 16 The yield of higher alcohols is also low, which means that ethanol produces C8-C 16 The selectivity of the reaction of higher alcohols is not high; at the same time, the insulation time of each insulation stage is limited to t / n in order to ensure that the reaction time of each insulation stage is sufficient when the total insulation time is sufficient.

[0021] Preferably, the insulation temperature of the first stage in the temperature rising program is 160-180°C.

[0022] When the insulation temperature of the first stage is within the temperature range of 160-180°C, the higher the temperature, the faster the conversion rate of ethanol. At the same time, since the reaction is carried out at a lower temperature, the catalytic activity of the catalyst for the ethanol reforming reaction is lower. When ethanol reacts on the catalyst, it can be effectively dehydrogenated into ethanol but will not be further decomposed, thereby ensuring the effective conversion of ethanol.

[0023] Preferably, the insulation temperature of the nth stage in the temperature rising program is 250-265°C.

[0024] When the insulation temperature of the nth stage is lower than this temperature range, the intermediate products such as butanol and hexanol generated by ethanol coupling are not easily catalytically dehydrogenated to form high-carbon aldehydes, that is, the intermediate products are difficult to undergo further coupling; and when the insulation temperature of the nth stage is higher than this temperature range, the reforming reaction of the catalyst on higher alcohols will be intensified, resulting in the decomposition of high-carbon aldehydes, thereby reducing the yield of high-carbon products and the target reaction selectivity.

[0025] Preferably, the order n of the temperature rising program is 2-5.

[0026] When the order n of the temperature program is 2, the ethanol water phase coupling reaction carried out using the multi-stage temperature program has a higher ethanol conversion rate and C8-C 16The yields of higher alcohols have been greatly improved; the insulation order n of the heating program continues to increase, and the temperature of the reaction system can better match the temperature required for the coupling reaction of different intermediates. 16 The yield of higher alcohols is improved; at the same time, the increase in the number of insulation steps means that there are more "buffer insulation steps" between the first and nth insulation stages, and within a certain temperature range, ethanol that has not completely reacted in the initial insulation stage can continue to be converted into intermediate products such as butanol and hexanol in the "buffer insulation step", and the reaction rate is accelerated. Therefore, within this certain temperature range, the insulation step increases, and the conversion rate of the reactant ethanol is also higher. However, when n continues to increase to more than 5, the degree of improvement in the conversion rate of the reactant and the yield of the product is not obvious. Therefore, considering comprehensively, the preferred number of heating program steps is 2 to 5.

[0027] More preferably, the order n of the temperature rising program is 2-3.

[0028] Preferably, the rate of programmed temperature increase between different insulation stages in the temperature increase program is 0.5-10° C. / min.

[0029] When the heating rate of the reaction system is too high, the proportion of ethanol reforming reaction in all reactions in the system increases. This is because the reaction of ethanol coupling to form intermediate products, that is, the target reaction, accounts for a higher proportion of all reactions within a certain temperature range. A too high heating rate means that the system temperature stays in this temperature range for a short time, so ethanol is prone to reforming reaction. Even if the conversion rate of ethanol is increased, the generation of C8-C 16 The selectivity of the reaction of higher alcohols is also reduced; and the heating rate of the programmed temperature is too low, which means that the temperature of the reaction system stays in a lower temperature range for a longer time, and the conversion rate of ethanol slows down accordingly.

[0030] More preferably, the rate of programmed temperature increase between different insulation stages in the temperature increase program is 2.5-7.5° C. / min.

[0031] Most preferably, the heating rate of the programmed temperature in the temperature program is 5°C / min.

[0032] Preferably, the total insulation time t of all insulation stages in the heating program is 10 to 15 hours.

[0033] When the total holding time t of all holding stages in the heating program is higher than 10 h, ethanol coupling to form C8-C 16 The overall reaction of higher alcohols has almost reached equilibrium, and the conversion rate of reactants and the yield of products are higher; when t is higher than 15h, the overall reaction has reached equilibrium, and almost all of the ethanol in the system has been converted, so the degree of improvement in the conversion rate of reactants and the yield of products is not obvious.

[0034] More preferably, the total insulation time t of all insulation stages in the heating program is 12 h.

[0035] The present invention also protects a higher alcohol for preparing aviation fuel, which is prepared by the above-mentioned preparation method of the higher alcohol for preparing aviation fuel.

[0036] The present invention also protects the above aviation fuel, which is prepared from the above higher alcohol for preparing aviation fuel.

[0037] In a specific embodiment of the present invention, when the above-mentioned higher alcohol is used to prepare aviation fuel, it needs to be hydrodeoxygenated to obtain C8-C 18 Higher alkane aviation fuel components.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] The preparation method of higher alcohol for preparing aviation fuel provided by the present invention adopts a multi-stage heating method to carry out ethanol water phase coupling to generate C8-C 16 The reaction of higher alcohols solves the problem of not being able to balance the high conversion rate of ethanol and the generation of C8-C 16 The problem of high selectivity of the reaction of higher alcohols. The preparation method provided by the present invention is used to prepare C8-C 16 The conversion rate of higher alcohols and ethanol is basically above 80%. 16 The yield of higher alcohols is also substantially higher than 60%, that is, the selectivity of the target reaction is above 75%. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 Schematic diagram of the heating program in Example 1 of the present invention.

[0041] Figure 2 C8-C in Example 1, Comparative Example 1 and Comparative Example 2 of the present invention 16 Higher alcohols and the final C8-C 16 Schematic diagram of the yield of alkanes. DETAILED DESCRIPTION

[0042] The present invention is further described below in conjunction with specific embodiments, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the raw materials and reagents used in the embodiments of the present invention are conventionally purchased raw materials and reagents.

[0043] Example 1

[0044] A method for preparing higher alcohols for preparing aviation fuel comprises the following steps:

[0045] 5% Pd / C provided by Macklin was used as a metal catalyst, and an ethanol aqueous solution, a metal catalyst and sodium hydroxide were mixed, wherein the mass ratio of the reactants was metal catalyst: homogeneous base: ethanol aqueous solution = 0.16:0.17:2; a multi-stage programmed temperature method was used to carry out the ethanol aqueous phase coupling reaction, wherein the programmed temperature rate in the temperature program was 5°C / min, the number of insulation stages was 2, wherein the insulation temperature of the first stage was 180°C, the insulation temperature of the second stage was 250°C, each insulation stage was incubated for 6 hours, that is, the total insulation time of all insulation stages was 12 hours. The product obtained after the reaction was completed was a liquid phase, and the product was confirmed to be C4-C after gas chromatography. 16 Higher alcohols are obtained by distilling away alcohol products with carbon numbers less than 8 to obtain C8-C 16 Higher alcohols.

[0046] Example 2

[0047] A method for preparing a higher alcohol for preparing aviation fuel, which is different from Example 1 in that:

[0048] The first stage of the heating program had a holding temperature of 120°C, and the second stage had a holding temperature of 250°C. The product obtained after the reaction was completed was a liquid phase, and the product was confirmed to be C4-C by gas chromatography. 16 Higher alcohols are obtained by distilling away alcohol products with carbon numbers less than 8 to obtain C8-C 16 Higher alcohols.

[0049] Example 3

[0050] A method for preparing a higher alcohol for preparing aviation fuel, which is different from Example 1 in that:

[0051] The first stage of the heating program has a holding temperature of 180°C, and the second stage has a holding temperature of 280°C. The product obtained after the reaction is liquid, and the product is confirmed to be C4-C by gas chromatography. 16 Higher alcohols are obtained by distilling away alcohol products with carbon numbers less than 8 to obtain C8-C 16 Higher alcohols.

[0052] Example 4

[0053] A method for preparing a higher alcohol for preparing aviation fuel, which is different from Example 1 in that:

[0054] There are 3 insulation stages in the heating program. The insulation temperatures of each insulation stage are 180, 215, and 250°C, respectively. Each insulation stage is kept for 4 hours, that is, the total insulation time of all insulation stages is 12 hours. The product obtained after the reaction is completed is liquid. After gas chromatography, it is confirmed that the product is C4-C 16 Higher alcohols are obtained by distilling away alcohol products with carbon numbers less than 8 to obtain C8-C 16 Higher alcohols.

[0055] Example 5

[0056] A method for preparing a higher alcohol for preparing aviation fuel, which is different from Example 1 in that:

[0057] There are 5 insulation stages in the heating program. The insulation temperatures of each insulation stage are 180, 198, 216, 234, and 250°C, respectively. Each insulation stage is kept for 2.4 hours, that is, the total insulation time of all insulation stages is 12 hours. The product obtained after the reaction is completed is liquid, and the product is confirmed to be C4-C by gas chromatography. 16 Higher alcohols are obtained by distilling away alcohol products with carbon numbers less than 8 to obtain C8-C 16 Higher alcohols.

[0058] Example 6

[0059] A method for preparing a higher alcohol for preparing aviation fuel, which is different from Example 1 in that:

[0060] There are 6 insulation stages in the heating program, and the insulation temperature of each insulation stage is 180℃.

[0061] 194℃, 208℃, 222℃, 236℃, 250℃, each insulation stage is kept for 2h, that is, the total insulation time of all insulation stages is 12h. The product obtained after the reaction is completed is liquid phase, and the product is confirmed to be C4-C by gas chromatography. 16 Higher alcohols are obtained by distilling away alcohol products with carbon numbers less than 8 to obtain C8-C 16 Higher alcohols.

[0062] Example 7

[0063] A method for preparing a higher alcohol for preparing aviation fuel, which is different from Example 1 in that:

[0064] Each insulation stage was kept for 3 hours, that is, the total insulation time of all insulation stages was 6 hours. The product obtained after the reaction was completed was liquid, and after gas chromatography, it was confirmed that the product was C4-C 16 Higher alcohols are obtained by distilling away alcohol products with carbon numbers less than 8 to obtain C8-C 16 Higher alcohols.

[0065] Example 8

[0066] A method for preparing a higher alcohol for preparing aviation fuel, which is different from Example 1 in that:

[0067] Each insulation stage was kept for 5 hours, that is, the total insulation time of all insulation stages was 10 hours. The product obtained after the reaction was completed was liquid, and after gas chromatography, it was confirmed that the product was C4-C 16 Higher alcohols are obtained by distilling away alcohol products with carbon numbers less than 8 to obtain C8-C 16 Higher alcohols.

[0068] Example 9

[0069] A method for preparing a higher alcohol for preparing aviation fuel, which is different from Example 1 in that:

[0070] Each insulation stage was kept for 7.5 hours, that is, the total insulation time of all insulation stages was 15 hours. The product obtained after the reaction was completed was liquid, and after gas chromatography, it was confirmed that the product was C4-C 16 Higher alcohols are obtained by distilling away alcohol products with carbon numbers less than 8 to obtain C8-C 16 Higher alcohols.

[0071] Example 10

[0072] A method for preparing a higher alcohol for preparing aviation fuel, which is different from Example 1 in that:

[0073] Each insulation stage is kept for 12 hours, that is, the total insulation time of all insulation stages is 24 hours. The product obtained after the reaction is completed is liquid, and after gas chromatography, it is confirmed that the product is C4-C 16 Higher alcohols are obtained by distilling away alcohol products with carbon numbers less than 8 to obtain C8-C 16 Higher alcohols.

[0074] Embodiment 11

[0075] A method for preparing a higher alcohol for preparing aviation fuel, which is different from Example 1 in that:

[0076] The rate of temperature increase in the temperature program was 0.5°C / min. The product obtained after the reaction was completed was a liquid phase, and the product was confirmed to be C4-C 16 Higher alcohols are obtained by distilling away alcohol products with carbon numbers less than 8 to obtain C8-C 16 Higher alcohols.

[0077] Example 12

[0078] A method for preparing a higher alcohol for preparing aviation fuel, which is different from Example 1 in that:

[0079] The rate of temperature increase in the temperature program was 10°C / min. The product obtained after the reaction was completed was a liquid phase, and the product was confirmed to be C4-C by gas chromatography. 16 Higher alcohols are obtained by distilling away alcohol products with carbon numbers less than 8 to obtain C8-C 16 Higher alcohols.

[0080] Embodiment 13

[0081] A method for preparing a higher alcohol for preparing aviation fuel, which is different from Example 1 in that:

[0082] The rate of temperature increase in the temperature program was 2.5°C / min. The product obtained after the reaction was completed was a liquid phase, and the product was confirmed to be C4-C by gas chromatography. 16 Higher alcohols are obtained by distilling away alcohol products with carbon numbers less than 8 to obtain C8-C 16 Higher alcohols.

[0083] Embodiment 14

[0084] A method for preparing a higher alcohol for preparing aviation fuel, which is different from Example 1 in that:

[0085] The rate of temperature increase in the temperature program was 7.5°C / min. The product obtained after the reaction was completed was a liquid phase, and the product was confirmed to be C4-C by gas chromatography. 16 Higher alcohols are obtained by distilling away alcohol products with carbon numbers less than 8 to obtain C8-C 16 Higher alcohols.

[0086] Embodiment 15

[0087] A method for preparing a higher alcohol for preparing aviation fuel, which is different from Example 1 in that:

[0088] The rate of temperature increase in the temperature program was 12°C / min. The product obtained after the reaction was completed was a liquid phase, and the product was confirmed to be C4-C by gas chromatography. 16 Higher alcohols are obtained by distilling away alcohol products with carbon numbers less than 8 to obtain C8-C 16 Higher alcohols.

[0089] Example 16

[0090] A method for preparing a higher alcohol for preparing aviation fuel, which is different from Example 1 in that:

[0091] The nitrogen-doped carbon-coated nickel catalyst provided by Chinese Patent 202110256353.8 was used as the metal catalyst. The product obtained after the reaction was completed was a liquid phase, and after gas chromatography, it was confirmed that the product was C4-C 16 Higher alcohols are obtained by distilling away alcohol products with carbon numbers less than 8 to obtain C8-C 16 Higher alcohols.

[0092] Comparative Example 1

[0093] A method for preparing a higher alcohol for preparing aviation fuel, which is different from Example 1 in that:

[0094] The ethanol-water coupling reaction was carried out by direct heating, the reaction temperature was 180°C, and the reaction system was kept warm for 12 hours. The product obtained after the reaction was completed was liquid, and the product was confirmed to be C4-C 16 Higher alcohols are obtained by distilling away alcohol products with carbon numbers less than 8 to obtain C8-C 16 Higher alcohols.

[0095] Comparative Example 2

[0096] A method for preparing a higher alcohol for preparing aviation fuel, which is different from Example 1 in that:

[0097] The ethanol-water coupling reaction was carried out by direct heating, the reaction temperature was 250°C, and the reaction system was kept warm for 12 hours. The product obtained after the reaction was completed was a liquid phase, and the product was confirmed to be C4-C by gas chromatography. 16 Higher alcohols are obtained by distilling away alcohol products with carbon numbers less than 8 to obtain C8-C 16 Higher alcohols.

[0098] Comparative Example 3

[0099] A method for preparing a higher alcohol for preparing aviation fuel, which is different from Example 1 in that:

[0100] The second stage holding temperature was 300°C. The product obtained after the reaction was completed was a liquid phase, and the product was confirmed to be C4-C 16 Higher alcohols are obtained by distilling away alcohol products with carbon numbers less than 8 to obtain C8-C 16 Higher alcohols.

[0101] Comparative Example 4

[0102] A method for preparing a higher alcohol for preparing aviation fuel, which is different from Example 1 in that:

[0103] The first stage was kept at 90°C. The product obtained after the reaction was liquid, and the product was confirmed to be C4-C16 Higher alcohols are obtained by distilling away alcohol products with carbon numbers less than 8 to obtain C8-C 16 Higher alcohols.

[0104] Comparative Example 5

[0105] A method for preparing a higher alcohol for preparing aviation fuel, which is different from Example 1 in that:

[0106] Each insulation stage was kept for 2 hours, that is, the total insulation time of all insulation stages was 4 hours. The product obtained after the reaction was completed was liquid, and after gas chromatography, it was confirmed that the product was C4-C 16 Higher alcohols are obtained by distilling away alcohol products with carbon numbers less than 8 to obtain C8-C 16 Higher alcohols.

[0107] Comparative Example 6

[0108] A method for preparing a higher alcohol for preparing aviation fuel, wherein the method is different from Example 16 in that:

[0109] The ethanol-water coupling reaction was carried out by direct heating, the reaction temperature was 230°C, and the reaction system was kept warm for 12 hours. The product obtained after the reaction was completed was a liquid phase, and the product was confirmed to be C4-C by gas chromatography. 16 Higher alcohols are obtained by distilling away alcohol products with carbon numbers less than 8 to obtain C8-C 16 Higher alcohols.

[0110] Performance Testing

[0111] Ethanol conversion and C8-C 16 Higher alcohol yield test: The liquid product obtained by the reaction is distilled to remove the alcohol product with a carbon number less than 8 to obtain C8-C 16 Higher alcohols are detected and analyzed by gas chromatography.

[0112] The performance test data is shown in Tables 1 and 2 below:

[0113] Table 1. Summary of main experimental parameters of examples and comparative examples

[0114]

[0115]

[0116] Table 2. Summary of experimental data of embodiments and comparative examples

[0117]

[0118]

[0119] From the data of Examples 1 to 3 in Tables 1 to 2, it can be seen that when the temperature of the first stage in the heating program is 180°C and the temperature of the second stage is 250°C, the conversion rate of the product ethanol and the C8-C 16 The yield of higher alcohols has a balanced high value; when the first stage insulation temperature is not within the preferred range of 160-180°C of the present invention, the conversion rate of ethanol is lower, and when the nth stage insulation temperature is not within the preferred range of 250-265°C of the present invention, the C8-C 16 The yield of higher alcohols is lower, which means that the selectivity of the target reaction is lower.

[0120] From the data of Examples 1 and 4 to 6 in Tables 1 to 2, it can be seen that when the insulation stage number n in the temperature rising program increases, the conversion rate of the product and the yield of the higher alcohols are improved to a certain extent, but the degree of improvement is not high. In the process of increasing the insulation stage number from the 2nd stage to the 6th stage, the conversion rate of the C8-C 16 The yield of higher alcohols is increased by no more than 3%. Taking all factors into consideration, the present invention preferably uses n of 2 to 5 as the heat preservation stage of the temperature increase program in the present invention.

[0121] From the data of Examples 1 and 7 to 10 in Tables 1 to 2, it can be seen that the appropriate extension of the holding time can promote the conversion of ethanol and the generated butanol and hexanol to a certain extent, thereby increasing the C8-C 16 The yield of higher alcohols and the selectivity of the target reaction were significantly decreased, but when the total holding time exceeded 12 h, the C8-C 16 Although the yield of higher alcohols has increased, it is not obvious. Therefore, in practical applications, a total insulation time of 10 to 15 hours is more appropriate, and 12 hours is the most suitable.

[0122] From the data of Examples 1 and 11 to 15 in Tables 1 to 2, it can be seen that a relatively low heating rate can ensure the stability of the heating process of the instrument and the smooth progress of the reaction. However, when the heating rate is too fast, the reaction solution will "fly" after the temperature reaches the rated temperature, thereby aggravating the reforming reaction, and ultimately causing ethanol to be decomposed in the initial stage instead of being converted into butanol and hexanol. Although the conversion rate of ethanol is increased, the C8-C 16 The yield of higher alcohols is reduced, and C8-C 16 The reaction selectivity of higher alcohols is also reduced.

[0123] In Comparative Example 1, the reaction temperature was too low, and the ethanol conversion rate was only 67.4%, and finally only a relatively low C8-C 16 Yield of higher alcohols.

[0124] In Comparative Example 2, the reaction temperature was too high. Although a high conversion rate of 86% was achieved, the side reaction ethanol reforming was more serious. Therefore, the C8-C16 The yield of higher alcohols was only 39.4%.

[0125] Comparative Examples 3 and 4 are comparative examples in which the first-stage insulation temperature is too high and the second-stage insulation temperature is too low, respectively. It can be seen that too low a reaction temperature cannot effectively catalyze the dehydrogenation of ethanol. A large amount of incompletely reacted ethanol will be reformed under the higher temperature reaction conditions in the next stage, thereby reducing the selectivity of the reaction to produce higher alcohols. Too high a reaction temperature will also cause the generated higher alcohols to undergo severe reforming reactions on the catalyst.

[0126] In Comparative Example 5, the insulation time of each insulation stage in the heating program is too short, so that ethanol cannot be effectively converted in the initial stage of the reaction, and reforming is easily caused in the further high-temperature reaction stage. The effect is more similar to that of ethanol directly reacting at high temperature for a short time.

[0127] Comparative Example 6 is actually the technical solution disclosed in Chinese Patent No. 202110256353.8. It can be seen from the data of Comparative Example 6 that although Chinese Patent No. 202110256353.8 discloses that C prepared by the preparation method of Comparative Example 6 4+ The yield of higher alcohols can reach up to 52.24% and C 4+ The selectivity of the reaction of higher alcohols is about 80%, but the specific determination of C8-C 16 The yield of higher alcohols can be seen in the prior art. 16 The yield of higher alcohols is low, which means that when the temperature is not programmed, the system produces C8-C 16 The target reaction selectivity of higher alcohols is low. From the data obtained from the preparation method provided in Example 16, after the reaction is carried out by programmed temperature rise, C8-C 16 The yield of higher alcohols was increased by nearly 3 times, indicating that programmed temperature can effectively promote the conversion of ethanol to C8-C 16 Selective conversion of higher alcohols.

[0128] Figure 1 Schematic diagram of the heating program in Example 1 of the present invention.

[0129] Figure 2 C8-C in Example 1, Comparative Example 1 and Comparative Example 2 of the present invention 16 Higher alcohols and the final C8-C 16 Schematic diagram of the yield of alkanes. Figure 2 It can be seen that the method for preparing a higher alcohol for preparing aviation fuel provided in Example 1 of the present invention is used to prepare C8-C 16 Higher alcohols can obtain higher yields, which means that the target reaction (i.e., ethanol to C8-C 16The reaction of higher alcohols) has higher selectivity, so in the use of C8-C 16 Higher alcohols generate C8-C 16 The yield is also higher for higher alkanes.

[0130] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A method for preparing higher alcohols for preparing aviation fuel, characterized in that: The specific steps include: An ethanol aqueous solution, a metal catalyst and a homogeneous base are mixed, and a multi-stage programmed temperature method is used to carry out an ethanol-water phase coupling reaction to obtain a higher alcohol having a carbon number of 8 to 16 for preparing aviation fuel; The temperature rise program in the multi-stage programmed temperature rise method includes n insulation stages, wherein the insulation temperature of the first stage is 120-180°C, the insulation temperature of the nth stage is 250-280°C, and in the n-2 insulation stages between the first stage and the nth stage, the insulation temperature gradually increases with the increase of the stage number, and is not lower than the insulation temperature of the first stage and not higher than the insulation temperature of the nth stage; the stage number n of the temperature rise program is 2-5; The total insulation time of all insulation stages in the heating program is t, wherein the insulation time of each stage is t / n, and the total insulation time t is greater than 6h; The metal catalyst is 5% Pd / C; the homogeneous base is sodium hydroxide.

2. The method for preparing higher alcohols for preparing aviation fuel according to claim 1, characterized in that: The first stage of the temperature increase procedure has a temperature of 160-180°C.

3. The method for preparing higher alcohols for preparing aviation fuel according to claim 1, characterized in that: The insulation temperature of the nth stage in the temperature rising program is 250-265°C.

4. The method for preparing higher alcohols for preparing aviation fuel according to claim 1, characterized in that: The order n of the temperature rising program is 2-3.

5. The method for preparing higher alcohols for preparing aviation fuel according to claim 1, characterized in that: The rate of program heating between different insulation stages in the heating program is 0.5-10°C / min.

6. The method for preparing higher alcohols for preparing aviation fuel according to claim 5, characterized in that: The rate of program heating between different insulation stages in the heating program is 2.5-7.5°C / min.

7. The method for preparing higher alcohols for preparing aviation fuel according to claim 1, characterized in that: The total insulation time t of all insulation stages in the heating program is 10 to 15 hours.

Images