Method for preparing hydrocarbon fuel through catalytic hydrogenation of papermaking dilute black liquor

Abstract

The invention discloses a method for preparing hydrocarbon fuel through catalytic hydrogenation of papermaking dilute black liquor, which comprises the following steps: S1, treating the papermaking dilute black liquor with acid to obtain organic matter precipitate, mixing the organic precipitate with phenol and a Ru / MCM-41 catalyst, adding the mixture into a high-temperature and high-pressure reaction kettle, and reacting to obtain bio-oil, namely a hydrocarbon fuel precursor; and S2, dissolving the bio-oil obtained in the step S1 into an n-hexane solvent, filling H2 into a reaction kettle, and carrying out a hydrodeoxygenation reaction at a high temperature under the action of a Ru / MCM-41 catalyst to obtain the hydrocarbon fuel with main products of dodecane, 2, 6, 10-trimethyltetradecane and 2, 6-dimethoxyphenol. According to the method, the yield (99.7%) of converting organic matters of the black liquor into the bio-oil is improved, and in hydrodeoxygenation upgrading of the bio-oil, the physical properties of the obtained hydrocarbon fuel are only second to those of RP-3 type aviation fuel, and the hydrocarbon fuel can be used as an aviation fuel additive.

Description

Technical Field

[0001] The invention belongs to the technical field of biomass chemicals, and in particular relates to a method for preparing hydrocarbon fuel by catalytic hydrogenation of dilute papermaking black liquor. Background Art

[0002] In recent years, with the increasing scarcity of non-renewable fossil energy and the increasing demand for energy in industrialization in various countries, the development of sustainable biomass clean energy is the current trend. Black liquor is a byproduct produced during the pulping and cooking process of biomass. It is the main source of pollution in the papermaking industry and also a special biomass resource. 30% of black liquor is inorganic matter, mainly including NaOH, Na2CO3, Na2S, silicate inorganic matter, etc. The rest is mostly organic biomass, mainly lignin and its derivatives produced by degradation, cellulose and hemicellulose degradation products, including organic acids and carbohydrates. Lignin is a renewable substance that naturally contains a large number of aromatic ring structures and is a potential raw material for the preparation of aromatic fuels. At present, the use of traditional alkali recovery technology to treat black liquor has problems such as high evaporation energy consumption, inefficient heat utilization, and environmental pollution, and also leads to the loss of potential value-added substances in black liquor. Therefore, converting black liquor components into hydrocarbon-rich liquid fuels is crucial to improving the properties of black liquor fuel, clean production, saving pulping costs, and high-value conversion and utilization.

[0003] At present, there are a lot of studies on the conversion of black liquor and its components into liquid fuels, mainly including pyrolysis, liquefaction and other technologies. For example, Jia et al. proposed the preparation of bio-oil by catalytic pyrolysis of black liquor and waste plastics. Although the addition of waste plastics and black liquor to co-pyrolysis significantly increased the hydrocarbon content in the liquid fuel, a large amount of waste plastics was consumed, and the calorific value of the plastic itself was high. André Heeres et al. used catalytic pyrolysis technology to convert black liquor into bioaromatics, but the content was low, and the subsequent separation and purification of aromatics would consume a lot of economic costs. Peng et al. studied the production of phenol by pyrolyzing alkali lignin and black liquor solids (BLS) in a fixed bed reactor at 350-550°C. The study found that the high-temperature pyrolysis process of BLS promoted the cleavage of the methoxyl group of lignin, and the liquid yield was as high as 27wt% at 450°C. In summary, it is feasible to convert black liquor into aromatics or bio-oil by pyrolysis technology, but there are problems such as low yield of pyrolysis liquid and easy coking of black liquor. At the same time, the rich water content of the prepared bio-oil limits its use. Currently, there are few literatures on the extraction of bio-oil from black liquor. Most of the literature focuses on the extraction of a certain type of substance from black liquor. Black liquor and bio-oil have similar components. et al. studied the recovery of short-chain organic acids from black liquor by ultrafiltration and liquid-liquid extraction. Jean-Pierre Magnin et al. used ionic liquids to extract polyphenols, polysaccharides and lactic acid from black liquor. Hee Sun Kwon used tri-n-octylphosphine oxide as an extractant to recover acetic acid from black liquor. However, most current studies focus on extracting certain substances from black liquor for high-value utilization, while ignoring the systematic utilization of black liquor. Ong et al. converted black liquor into bio-crude oil through hydrothermal liquefaction technology and upgraded it to produce a mixture of gasoline and diesel. The study found that the productivity of the process was 78.7 kt / y fuel. Léa Vilcocq et al. first proposed a catalytic process for chemical value-added of kraft black liquor. They used CuO / TiO2 catalyst to oxidize black liquor. The study found that a small amount of lignin depolymerization products were phenolic compounds mainly composed of vanillin, and mainly formed aliphatic compounds mainly composed of formic acid, succinic acid and malonic acid, which shows that the presence of the catalyst is conducive to the formation of phenolic and aliphatic compounds. Ojelade et al. extracted hydroxy acids from black liquor and catalytically converted them into ketones with high carbon chain lengths, which is conducive to subsequent upgrading and quality improvement. In summary, it is feasible to catalytically liquefy black liquor, but the products after black liquor liquefaction have problems such as high water content and difficulty in product separation, which limits the improvement of black liquor fuel properties.

[0004] CN 109825359B discloses a method for preparing bio-based lubricating oil from papermaking black liquor, which mainly uses ethanol to extract dilute black liquor to obtain supernatant, and the supernatant is subjected to acidification to extract suspension, high-temperature liquefaction of suspension, extraction and other steps to obtain bio-based lubricating oil (the lubricating oil yield is 1.3wt% of the mass of papermaking black liquor). However, the lubricating oil extraction steps are complicated and the extraction rate is low. In addition, it only focuses on the extraction of lubricating oil, and does not mention the problems of easy coking during the liquefaction of black liquor, poor quality of bio-oil and low conversion rate. CN115466627B discloses a method for alcoholysis and hydrogenation of lignin from papermaking black liquor. This method mainly treats lignin instead of considering the organic components in the black liquor as a whole. The treatment process is complicated. In addition, lignin itself will condense and coke during the alcoholysis of lignin, thereby affecting the yield and quality of bio-oil. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing hydrocarbon fuel by catalytic hydrogenation of dilute black liquor of papermaking, so as to improve the yield of organic matter in black liquor converted into bio-oil, further perform hydrogenation and deoxygenation to improve the quality of bio-oil, and obtain hydrocarbon fuel with good physical properties.

[0006] To achieve the above object, the present invention adopts the following technical solution:

[0007] The present invention provides a method for preparing hydrocarbon fuel by catalytic hydrogenation of papermaking dilute black liquor, comprising the following steps:

[0008] S1. Treating papermaking dilute black liquor with acid to obtain an organic precipitate, mixing the organic precipitate with phenol and Ru / MCM-41 catalyst, and adding the mixture to a high temperature and high pressure reactor for reaction, removing phenol from the liquid product by vacuum distillation to obtain bio-oil, i.e., a hydrocarbon fuel precursor;

[0009] S2. The bio-oil obtained in step S1 is dissolved in n-hexane solvent, H2 is charged into a reactor, and a Ru / MCM-41 catalyst is added. Under the action of the catalyst, a hydrodeoxygenation reaction is carried out at a high temperature to obtain a hydrocarbon fuel whose main products are dodecane, 2,6,10-trimethyltetradecane and 2,6-dimethoxyphenol.

[0010] Furthermore, the reaction in step S1 is carried out at 180° C. for 6 hours.

[0011] Furthermore, the mass ratio of the organic precipitate, phenol, and Ru / MCM-41 catalyst in step S1 is 10:500:1.

[0012] Furthermore, step S2 is to carry out a hydrodeoxygenation reaction at 200° C. for 6 hours.

[0013] Furthermore, step S2 is to charge 1.5 MPa of H2 into the reactor.

[0014] Furthermore, the mass ratio of the bio-oil to the Ru / MCM-41 catalyst in step S2 is 10:1.

[0015] Furthermore, the preparation method of the Ru / MCM-41 catalyst includes: adding ruthenium acetate and deionized water to the MCM-41 molecular sieve, vacuum impregnating for 12 hours and then drying the water, drying at 105°C and then grinding, crushing and screening, placing in a muffle furnace and calcining at 550°C for 2 hours, and then reducing with a 10% H2 / Ar mixed gas at 450°C for 10 hours to obtain the Ru / MCM-41 catalyst.

[0016] Furthermore, the mass of the metal ion ruthenium in the Ru / MCM-41 catalyst accounts for 1% of the mass of the MCM-41 molecular sieve.

[0017] In addition, the present invention also provides the use of the hydrocarbon fuel prepared by the above method as an aviation fuel additive.

[0018] The present invention has the following beneficial effects:

[0019] (1) The present invention utilizes Ru / MCM-41 catalyst to catalyze the depolymerization of organic matter in black liquor by phenol solvent to prepare bio-oil (hydrocarbon fuel precursor) at low temperature and high efficiency. Compared with the ethanol solvent used in the prior art, the present invention has the advantages of low preparation temperature (180°C), high bio-oil yield (99.7%), and good product performance (C3-C 25It accounts for 67.57% and has a calorific value of 29.86MJ / kg).

[0020] (2) The hydrocarbon fuel obtained by the present invention contains 2.0% chain alkanes, 20.7% monocyclic alkanes, 3.2% dicyclic alkanes, 25.5% total cycloalkanes, 27.5% total saturated hydrocarbons, 24.5% total monocyclic aromatic hydrocarbons, 42.1% total dicyclic aromatic hydrocarbons, and 72.5% total aromatic hydrocarbons, with a high aromatic hydrocarbon content; the density of the hydrocarbon fuel is 0.71 g / ml, the pH value is 6.58, and the lower calorific value is 43.56 MJ / kg. Its physical properties are second only to those of RP-3 aviation fuel, and it can be used as an aviation fuel additive. The method realizes the conversion of papermaking waste into aviation fuel, which is conducive to solving the pollution problem of waste.

[0021] (3) The bio-oil prepared by depolymerizing the organic components of black liquor with phenol in the present invention does not contain water and has a high calorific value and can be directly used as a fuel. The fuel prepared by dissolving the bio-oil in n-hexane and then performing hydrodeoxygenation can be used as an additive for civilian diesel or a precursor for aviation fuel. It also avoids the problem of high water content in hydrocarbon fuels, which is beneficial to subsequent utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a SEM image analyzing the morphology of the Ru / MCM-41 catalyst.

[0023] Figure 2 It is the FT-IR graph, analyzing the functional group properties of Ru / MCM-41 catalyst.

[0024] Figure 3 It is a BET diagram, analyzing the pore structure of Ru / MCM-41 catalyst.

[0025] Figure 4 This is an exploration of the catalytic process of black liquor organic matter (BLOM) depolymerization (reaction conditions: 0.02g catalyst, 0.2g BLOM, 10g solvent for 6h). (a) The effect of catalyst type on BLOM depolymerization; (b) The effect of reaction solvent percentage on BLOM depolymerization; c) The effect of reaction temperature on BLOM depolymerization.

[0026] Figure 5 It is a mass spectrometry method to determine the hydrocarbon composition in hydrocarbon fuels; (a) saturated hydrocarbons, (b) monocyclic aromatic hydrocarbons, and (c) polycyclic aromatic hydrocarbons. DETAILED DESCRIPTION

[0027] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments, but these embodiments should not be construed as limiting the present invention.

[0028] Example 1

[0029] A method for preparing hydrocarbon fuel by catalytic hydrogenation of papermaking dilute black liquor, comprising the following steps:

[0030] (1) 100 g of papermaking black liquor (mass concentration of 12.21%) was taken, and the papermaking black liquor was treated with sulfuric acid with a mass concentration of 15% to obtain 8.58 g of organic precipitate. 0.2 g of the organic precipitate was mixed with 10 g of phenol and 0.02 g of Ru / MCM-41 catalyst and added into a high temperature and high pressure reactor. The mixture was reacted at 180° C. for 6 h. The phenol in the liquid product was removed by vacuum distillation to obtain a bio-oil with a conversion rate of 99.7%, i.e., a hydrocarbon fuel precursor, which was 36.65% higher than that using ethanol solvent. DOM test showed that the hydrocarbon fuel contained 67.57% of C3~C 25 Fuel precursor, its calorific value is 29.86MJ / kg.

[0031] (2) 0.2 g of the bio-oil obtained in step (1) was dissolved in 100 mL of n-hexane solvent, 1.5 MPa of H2 was charged into a reactor (Laibei ABC500), 0.02 g of Ru / MCM-41 catalyst was added, and under the action of the catalyst, the reaction was carried out at 200° C. for 6 h to carry out a hydrodeoxygenation reaction, and a hydrocarbon fuel whose main products were dodecane, 2,6,10-trimethyltetradecane and 2,6-dimethoxyphenol was obtained. GCMS analysis showed that the relative content of aromatics in the fuel was 72.5%, the density of the hydrocarbon fuel was 0.71 g / ml, the pH value was 6.58, and the lower heating value was 43.56 MJ / kg. The physical properties of the fuel showed that it was second only to aviation fuel and could be used as an aviation fuel additive.

[0032] The preparation method of the Ru / MCM-41 catalyst used in this embodiment is as follows:

[0033] The Ru / MCM-41 catalyst was prepared by vacuum impregnation method: 0.5 g of MCM-41 molecular sieve was taken into a 250 mL beaker, and then ruthenium acetate (the mass of metal ion ruthenium accounted for 1% of the mass of MCM-41 molecular sieve) and deionized water were added and mixed. After vacuum impregnation for 12 hours, the sample was dried to remove moisture, dried at 105°C, ground, crushed and sieved, placed in a muffle furnace and calcined at 550°C for 2 hours, and then reduced with 10% H2 / Ar mixed gas at 450°C for 10 hours to obtain 1% Ru / MCM-41 catalyst.

[0034] The present invention selects Ru / MCM-41 as a catalyst to catalyze the liquefaction of black liquor organic matter to prepare bio-oil. The MCM-41 molecular sieve loaded with Ru can catalyze the hydrogenation and cracking of raw materials and has a high efficiency in removing heteroatoms. The catalyst loaded with Ru has better sulfur resistance than the catalyst loaded with Pt, Pd or Pd-Pt. Sulfur elements are introduced during the kraft pulping process, so metal Ru is more suitable for the catalytic liquefaction of black liquor. The mesoporous MCM-41 molecular sieve as a carrier has a high specific surface area, is conducive to the circulation of small molecules, and is not easy to coke.

[0035] The optimal process exploration process of the present invention:

[0036] (1) Through the research of the present invention, the optimal 1%Ru / MCM-41 catalyst is obtained, as follows:

[0037] The Ru / MCM-41 catalyst was prepared by vacuum impregnation method: 0.5 g of MCM-41 molecular sieve was taken into a 250 mL beaker, and then a certain amount of ruthenium acetate (the mass of metal ion ruthenium accounted for 1%, 3%, 5%, 7%, and 9% of the mass of MCM-41 molecular sieve) and deionized water were added and mixed in a certain proportion. After vacuum impregnation for 12 hours, the sample was dried to remove moisture, dried at 105°C, ground, crushed, and sieved, placed in a muffle furnace and calcined at 550°C for 2 hours, and then reduced with 10% H2 / Ar mixed gas at 450°C for 10 hours to obtain Ru / MCM-41 catalysts with different loading amounts.

[0038] Table 1 Physicochemical properties of Ru / MCM-41 catalysts with different loadings

[0039]

[0040] The N2 adsorption / desorption isotherms and pore size distribution of Ru are shown in Figure 2. Figure 3 (a) and Figure 3 (b) The N2 adsorption / desorption isotherms of MCM-41 before and after metal loading maintain the same trend, which indicates that the loading of metal Ru does not change the overall structure of the MCM-41 carrier. As shown in Table 1 above, the loading of Ru and its concentration have a significant effect on the surface area and pore volume of MCM-41. The BET surface area and pore volume of MCM-41 are 1040m 2 / g and 0.88cm 3 / g. With the increase of Ru loading, the BET surface area and mesopore volume increased from 1040m 2 / g and 0.88cm 3 / g reduced to 717m 2 / g and 0.36cm 3 / g (1%Ru / MCM-41). As the Ru loading increases from 1% to 9%, the BET surface area increases from 717m 2 / g(1%Ru / MCM-41) decreased to 623m 2 / g (9%Ru / MCM-41), which is because the surface area of ​​the catalyst is reduced due to the increase in its metal loading. FT-IR is used to study the functional group characteristics of the catalyst. Figure 2 As shown in the figure, due to the Si-O-Si asymmetric stretching, Si-O-Si symmetric stretching and Si-O-Si bending vibration, the catalyst samples all have a peak at 1084 cm -1 and 800cm -1 The characteristic peak of MCM-41 was obtained near 3419 cm -1 The stretching vibration of the OH bond is also observed at a wave number of about 1087 cm -1 and 798cm -1 The asymmetric and symmetric stretching vibration peaks of MOM (M represents Si or Al) are shown at 963 cm -1 A small peak appears at , which is caused by the functionalized Si-OH groups.

[0041] (2) Through the research of the present invention, the optimal process for depolymerization of organic matter in black liquor is obtained, which is as follows:

[0042] In order to explore the effect of catalyst on the depolymerization products of black liquor organic matter, the catalytic liquefaction was carried out in the systems of no catalyst / ethanol, MCM-41 / ethanol, Ru / MCM-41 / ethanol, no catalyst / phenol, MCM-41 / phenol, and 1% Ru / MCM-41 / phenol. The bio-oil yield was 98.7% when phenol was used as solvent without catalyst, and 55.35% when ethanol was used as solvent. The bio-oil yield increased significantly by 43.35% (e.g. Figure 4 a), indicating that phenol solvent has a significant effect on the depolymerization of black liquor. Using the same catalyst (MCM-41), the yield of bio-oil depolymerized by phenol is high (60.95% for ethanol and 99.1% for phenol), so more liquid fuel is produced. Using the same catalyst (1% Ru / MCM-41), the yield of bio-oil depolymerized by phenol is 36.65% higher than that of ethanol (63.05% for ethanol and 99.7% for phenol), so more liquid fuel is produced. The ethanol solvent has strong dispersibility for organic matter, and the pressure of ethanol as solvent reaction is higher under the same reaction conditions (5.78Mpa for ethanol and 0.76Mpa for phenol). In addition, the chemical bonds of condensed lignin in black liquor are difficult to break in the ethanol phase, so it is easy to coke in the reaction process. On the contrary, phenol can depolymerize condensed lignin, avoiding the condensation and coking of lignin in the reaction process, so the yield of bio-oil is high.

[0043] In order to improve the yield of bio-oil, the present invention studies the effects of solvent ratio and reaction temperature on the depolymerization of organic matter in black liquor. Figure 4 As shown. Figure 4 b It can be seen that when there is no phenol (100% ethanol), the conversion rate of bio-oil is 55.35%, when the phenol: ethanol ratio is 1:1, the conversion rate of bio-oil is 65.64%, and when the reaction solvent is completely phenol, the conversion rate of bio-oil is 99.7%. Therefore, it can be known that the conversion rate of black liquor bio-oil increases with the increase of phenol proportion. This is because the use of phenol as a solvent has the advantages of low pressure of the reaction system, preventing lignin condensation, and cross-linking with carbohydrates. Therefore, lignin and carbohydrate condensation and coking are avoided during the reaction process. The present invention also studies the effect of reaction temperature on bio-oil yield. When the reaction temperature is 150°C, the conversion rate of bio-oil is 90.78%, when the reaction temperature is 180°C, the conversion rate of bio-oil is 99.7%, and when the reaction temperature is further increased to 210°C and 240°C, the conversion rates of bio-oil are 99.5% and 99.56% respectively. Figure 4 c), at this time, the bio-oil conversion rate is not affected by temperature. If the temperature is further increased to 270°C, the conversion of bio-oil is 91%. The reason for the low conversion rate at this time is that there is a competitive reaction of depolymerization and condensation of wood fiber in the liquefaction process. The excessively high reaction temperature causes the organic matter to depolymerize violently, and it is easy to deposit on the surface of the catalyst to form coke, especially the carbohydrates in the organic matter. Further, by comparing the GPC of the products after the reaction with ethanol and phenol as solvents, it is found that the curve of the GPC of the depolymerization product using phenol is more curved, indicating that the molecular weight of the organic matter depolymerization product of phenol is smaller, which is conducive to further refining and thus improving the quality of bio-oil. Compared with other solvents, dehydration and polymerization reactions occur during the depolymerization of lignin to form more stable lignin dimers and trimers connected by CC bonds. These polymers are distributed in the liquefaction system and cannot be further degraded to form residues. The advantage of phenol depolymerization of organic matter is more obvious.

[0044] (3) Bio-oil hydrodeoxygenation and quality improvement

[0045] Black liquor bio-oil contains abundant oxygen-containing functional groups, and the quality of black liquor bio-oil fuel can be improved by hydrogenation and deoxygenation. Figure 5 a- Figure 5 c), as can be seen from the figure, in hydrocarbon fuels, chain alkanes account for 2.0%, monocyclic alkanes account for 20.7%, dicyclic alkanes account for 3.2%, total cycloalkanes account for 25.5%, total saturated hydrocarbons account for 27.5%, total monocyclic aromatic hydrocarbons account for 24.5%, total dicyclic aromatic hydrocarbons account for 42.1%, and the total aromatic content is 72.5%, with a high aromatic content. Black liquor is mainly composed of lignin and its derivatives, which form monophenol and diphenol in the process of phenol depolymerization, and are more likely to form aromatic hydrocarbons after hydrogenation and deoxygenation, so the aromatic hydrocarbon content is high. Further analysis of the components in hydrocarbon fuels by GCMS ( Figure 5 d), the main components of hydrocarbon fuels are phenol, 2-(methylthio)-, dodecane, tetradecane, 2,6,10-trimethyl-, phenol, 2,6-dimethoxy-, 1-hexadecanol, 2-methyl-, octadecane, 3-ethyl-5-(2-ethylbutyl)-, 2,4-di-tert-butylphenol, 4,4'-ethylenediphenol, 4,4'-ethylenediphenol, 4,4'-ethylenediphenol, 4,4'-ethylenediphenol, 4,4'-ethylenediphenol.

[0046] Table 2 Comparison of hydrocarbon fuels and typical RP-3 liquid fuels

[0047]

[0048] The color of hydrocarbon fuel is light blue, which is similar to the color of civilian gasoline and diesel, indicating that the chromophore groups in the fuel component are reduced after hydrodeoxygenation. The physical properties of hydrocarbon fuel are analyzed according to the national standard aviation fuel detection method and compared with RP-3 (Table 2). The density of hydrocarbon fuel is 0.71g / ml, which is at the lower limit of the density of traditional bio-oil, and the pH value is 6.58. Compared with RP-3, the hydrocarbon fuel prepared by the present invention basically meets its characteristics, except that the prepared fuel is obtained in the normal hexane phase, so it does not contain water, but because it is not completely deoxygenated, its calorific value is 43.56MJ / kg, so its calorific value is slightly lower than RP-3 (47.13MJ / kg), and it can be used as an aviation fuel additive.

Claims

1. A method for preparing hydrocarbon fuel by catalytic hydrogenation of papermaking dilute black liquor, characterized in that: The following steps are involved: S1. Treating papermaking dilute black liquor with acid to obtain an organic precipitate, mixing the organic precipitate with phenol and Ru / MCM-41 catalyst, and adding the mixture to a high temperature and high pressure reactor for reaction, removing phenol from the liquid product by vacuum distillation to obtain bio-oil, i.e., a hydrocarbon fuel precursor; S2. The bio-oil obtained in step S1 is dissolved in n-hexane solvent, H2 is charged into a reactor, and a Ru / MCM-41 catalyst is added. Under the action of the catalyst, a hydrodeoxygenation reaction is carried out at a high temperature to obtain a hydrocarbon fuel whose main products are dodecane, 2,6,10-trimethyltetradecane and 2,6-dimethoxyphenol.

2. The method for preparing hydrocarbon fuel by catalytic hydrogenation of papermaking weak black liquor according to claim 1, characterized in that: The reaction in step S1 is carried out at 180° C. for 6 h.

3. The method for preparing hydrocarbon fuel by catalytic hydrogenation of papermaking weak black liquor according to claim 1, characterized in that: The mass ratio of the organic precipitate, phenol, and Ru / MCM-41 catalyst in step S1 is 10:500:

1.

4. The method for preparing hydrocarbon fuel by catalytic hydrogenation of papermaking weak black liquor according to claim 1, characterized in that: Step S2 is to carry out a hydrodeoxygenation reaction at 200° C. for 6 hours.

5. The method for preparing hydrocarbon fuel by catalytic hydrogenation of papermaking weak black liquor according to claim 1, characterized in that: Step S2 is to charge 1.5 MPa of H2 into the reactor.

6. The method for preparing hydrocarbon fuel by catalytic hydrogenation of papermaking weak black liquor according to claim 1, characterized in that: The mass ratio of the bio-oil to the Ru / MCM-41 catalyst in step S2 is 10:

1.

7. The method for preparing hydrocarbon fuel by catalytic hydrogenation of papermaking weak black liquor according to claim 1, characterized in that: The preparation method of the Ru / MCM-41 catalyst comprises: adding ruthenium acetate and deionized water to the MCM-41 molecular sieve, vacuum impregnating for 12 hours and then drying the water, drying at 105° C. and then grinding, crushing and screening, placing in a muffle furnace and calcining at 550° C. for 2 hours, and then reducing with 10% H2 / Ar mixed gas at 450° C. for 10 hours to obtain the Ru / MCM-41 catalyst.

8. The method for preparing hydrocarbon fuel by catalytic hydrogenation of papermaking weak black liquor according to claim 7, characterized in that: The mass of metal ion ruthenium in the Ru / MCM-41 catalyst accounts for 1% of the mass of the MCM-41 molecular sieve.

9. Use of the hydrocarbon fuel prepared by the method for preparing hydrocarbon fuel by catalytic hydrogenation of papermaking dilute black liquor as claimed in claim 1 as an aviation fuel additive.

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