Method and system for preparing aromatic fuel by biomass two-stage catalytic coupling middle-section alcohol supply

Abstract

The invention provides a method and a system for preparing aromatic fuel through biomass two-stage catalytic coupling middle-section alcohol supply. Biomass can be efficiently converted into key aromatic components in gasoline, diesel oil and aviation fuel. The invention provides a method for preparing aromatic fuel by biomass two-stage catalytic coupling middle-section alcohol supply, and the method comprises the following steps: a pyrolysis step: carrying out rapid pyrolysis on a biomass raw material in a pyrolysis reactor to generate biomass pyrolysis volatile components; a middle-stage alcohol supply step: introducing an alcohol hydrogen supply source into the reaction system, and fully mixing the alcohol hydrogen supply source with upstream pyrolysis volatile components to form mixed gas; and a two-stage catalysis step: carrying out a catalytic upgrading reaction on the mixed gas through a two-stage catalysis system, and condensing the obtained product to obtain the aromatic fuel and pyrolysis tail gas. By introducing an alcohol hydrogen supply source and designing a two-stage catalytic system, the integrated system efficiently realizes conversion from biomass to high-quality aromatic fuel, and can improve the quality of a liquid-phase product.

Description

Technical Field

[0001] The invention relates to the technical field of high-value utilization of biomass, and in particular to a method and system for preparing aromatic fuel by using biomass two-stage catalytic coupling and middle-stage alcohol supply. Background Art

[0002] In global energy consumption, the rapid development of renewable energy has optimized the energy structure and promoted the world's move towards low carbonization. Biomass energy provides an effective way to reduce dependence on fossil fuels because it can be directly converted into carbon-containing liquid fuels. This not only helps to reduce dependence on traditional energy, but also significantly reduces greenhouse gas emissions and helps build a clean, safe and sustainable energy system.

[0003] Among the many biomass energy conversion technologies, pyrolysis technology has attracted attention due to its high conversion efficiency and feasibility of industrial production. It can convert biomass into liquid fuel with high energy density and easy storage and transportation. However, the bio-oil produced by pyrolysis has problems such as high water content, low calorific value, high oxygen content, strong acidity and corrosiveness, poor stability and high viscosity, which makes it difficult to directly replace gasoline, diesel and aviation fuel.

[0004] In order to improve the quality of bio-oil, the industry usually uses technologies such as catalytic cracking and hydroprocessing for upgrading and modification. However, due to the high oxygen content of bio-oil, it is easy to cause component condensation and catalyst deactivation during the upgrading process. In addition, the energy loss and increased equipment cost during the upgrading process also affect the economic efficiency. At present, online upgrading of volatiles produced by biomass pyrolysis is a common method to improve the quality of bio-oil. In the online upgrading mode, the process conditions of pyrolysis and upgrading can be adjusted independently to ensure that the catalyst operates under optimal conditions to efficiently generate the target product. In addition, in order to solve the characteristics of biomass raw materials being poor in hydrogen and rich in oxygen, studies have shown that the introduction of external hydrogen sources such as hydrogen and plastics during pyrolysis and upgrading can increase the effective hydrogen-carbon ratio of the reaction system and increase the yield of the target product. Although hydrogenation and pressurization can further improve the quality of bio-oil, it has high requirements for equipment, increases costs, and limits large-scale production. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a method and system for preparing aromatic fuels by coupling biomass two-stage catalysis with mid-stage alcohol supply. The present invention introduces an alcohol hydrogen source and designs a two-stage catalytic system. The integrated system efficiently realizes the conversion of biomass into high-quality aromatic fuels, thereby improving the quality of liquid products.

[0006] On the one hand, the present invention provides a method for preparing aromatic fuel by coupling biomass two-stage catalysis with alcohol supply in the middle stage, comprising the following steps:

[0007] Pyrolysis step: the biomass raw material is rapidly pyrolyzed in a pyrolysis reactor to generate biomass pyrolysis volatiles;

[0008] Mid-stage alcohol supply step: introducing an alcohol hydrogen supply source into the reaction system and fully mixing it with the upstream pyrolysis volatiles to form a mixed gas;

[0009] Two-stage catalytic step: The mixed gas undergoes a catalytic upgrading reaction through a two-stage catalytic system, and the resulting products are subsequently condensed to obtain aromatic fuel and pyrolysis tail gas.

[0010] According to the technical scheme, firstly, the present invention pyrolyzes biomass to form pyrolysis volatiles, thereby realizing efficient conversion of biomass into hydrocarbon liquid fuels, and then supplies an alcohol hydrogen source to the system through a mid-stage alcohol supply step, thereby improving the effective hydrogen-carbon ratio of the reaction system, and then the mixed gas of the biomass pyrolysis volatiles and alcohols is deeply deoxygenated through a series of dehydration, decarboxylation and decarbonylation reactions in a two-stage catalytic step, and then high-quality aromatic liquid fuels and pyrolysis tail gas are obtained through condensation.

[0011] Compared with other hydrogen sources (such as hydrogen and plastics), alcohol hydrogen sources have relatively low requirements for reaction equipment, and the catalytic quality improvement reaction process does not require pressurization and depolymerization energy consumption. In other words, the reaction system of the two-stage catalytic step using alcohol as the hydrogen source does not need to be closed, showing more outstanding economy and safety.

[0012] In the two-stage catalytic step, a two-stage catalytic system consisting of a first-stage catalyst and a second-stage catalyst with different functions is adopted. The first-stage catalyst pre-deoxygenates the biomass pyrolysis volatiles by promoting decarboxylation, ketonization and demethoxylation reactions to generate hydrocarbon precursors. The second-stage catalyst deeply deoxygenates the hydrocarbon precursors through multiple reactions such as dehydration, decarbonylation, oligomerization and aromatization, and converts them into high-quality aromatic fuels.

[0013] As a preferred technical solution, the reaction temperature of the double-stage catalytic step is 400-550°C.

[0014] According to the technical solution, the catalytic upgrading reaction is carried out in the range of 400-550°C, which can effectively promote the cracking of macromolecular oxygen-containing compounds, resulting in more heavy phenols being further converted into light phenols through dehydration and demethoxylation reactions, thereby reducing the steric hindrance of their entry into the catalyst pores, making it easier for them to reach the catalyst acid sites, further improving the rate and reaction limit of the online upgrading reaction, thereby improving the yield and quality of aromatic fuels.

[0015] As a preferred technical solution, in the middle alcohol supply step, the alcohol hydrogen source is a small molecule monohydric alcohol, including but not limited to methanol and ethanol.

[0016] According to this technical solution, small molecule monohydric alcohols such as methanol and ethanol can effectively increase the effective hydrogen-carbon ratio of the reaction system, thereby increasing the yield of the target product, inhibiting the polymerization of monocyclic aromatic hydrocarbons, thereby inhibiting carbon deposit formation and extending the catalyst life.

[0017] As a preferred technical solution, in the two-stage catalytic step, a two-stage catalytic system consisting of a first-stage catalyst and a second-stage catalyst with different functions is adopted. The first-stage catalyst includes metal oxide catalysts (such as Al2O3, CaO, MgO, Fe2O3, NiO, ZnO, ZrO2, etc.), natural mineral catalysts (attapulgite, talc, hydroxyapatite, montmorillonite and bentonite, etc.), etc., which pre-deoxygenate the biomass pyrolysis volatiles by promoting decarboxylation, ketonization and demethoxylation reactions to generate hydrocarbon precursors; the second-stage catalyst mainly includes zeolite molecular sieve catalysts (such as HY, Hβ and HZSM-5, etc.), metal-modified molecular sieve catalysts (loaded metals include iron, cobalt, nickel, molybdenum, zinc and other metals), etc., which deeply deoxygenate the hydrocarbon precursors through various reactions such as dehydration, decarbonylation, oligomerization and aromatization, and convert them into high-quality aromatic fuels. Compared with a single catalyst, the dual-stage catalytic system further optimizes the product distribution, especially increases the total content of aromatics in the product, and continuously enhances the inhibitory effect on phenols in the product.

[0018] As a preferred technical solution, in the middle alcohol supply step, under the condition of a given mass space velocity, the feed rate ratio of the alcohol hydrogen supply source to the biomass raw material is 0.5-2.

[0019] According to the technical solution, the co-conversion of biomass pyrolysis volatiles and alcohol hydrogen sources can significantly improve the distribution of aromatic products in liquid products and effectively alleviate the deactivation of catalysts, and this improvement effect is further enhanced within a certain range as the alcohol supply ratio increases. However, excessive alcohol supply will exceed the processing capacity of the catalyst, resulting in a decrease in aromatic yield. Controlling the feed rate ratio of alcohol hydrogen source to biomass raw material to between 0.5-2 can take into account both the aromatic yield and the catalytic efficiency of the catalyst.

[0020] As a preferred technical solution, this method of producing aromatic fuels by coupling the biomass two-stage catalytic middle stage with alcohol also includes a tail gas utilization step: a part of the pyrolysis tail gas obtained in the two-stage catalytic step is recycled back to the pyrolysis reactor as a pyrolysis carrier gas, and the other part is used for combustion to provide heat and electricity for the system, or is used for reforming to produce hydrogen, methanol and / or dimethyl ether and other chemicals.

[0021] According to this technical solution, the alcohol consumption of the system is further reduced and the economy of the system is improved.

[0022] Another aspect of the present invention provides a system for preparing aromatic fuel by coupling biomass two-stage catalysis with alcohol supply in the middle stage, the system comprising:

[0023] Pyrolysis unit: pyrolyze the biomass raw materials in the pyrolysis reactor to generate biomass pyrolysis volatiles;

[0024] Mid-stage alcohol supply unit: introduces the alcohol hydrogen source into the reaction system and fully mixes it with the upstream biomass pyrolysis volatiles to form a mixed gas;

[0025] Two-stage catalytic unit: The mixed gas undergoes a catalytic upgrading reaction through a two-stage catalytic system, and the upgraded pyrolysis volatiles are finally condensed to obtain high-quality aromatic fuel and pyrolysis tail gas;

[0026] Tail gas utilization unit: Part of the pyrolysis tail gas is filtered, dehydrated and pressurized by a circulating fan before being circulated to the pyrolysis reactor for use as a pyrolysis carrier gas. The other part is burned to provide heat and electricity for the system, or converted into hydrogen through technologies such as catalytic reforming, or generated into synthesis gas through gas modulation technologies such as steam reforming and partial oxidation, which is used to prepare chemicals such as methanol and dimethyl ether. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic flow chart of the method for producing aromatic fuel by biomass two-stage catalytic coupling and mid-stage alcohol supply provided in Example 1 of the present invention.

[0028] Figure 2 is the pore size distribution of hydroxyapatite (HAP) in Example 1 of the present invention.

[0029] Figure 3 is the pore size distribution of HZSM-5 in Example 1 of the present invention.

[0030] Figure 4 1 is the XRD spectrum of hydroxyapatite (HAP) and HZSM-5 in Example 1 of the present invention.

[0031] Figure 5 This is the SEM spectrum of hydroxyapatite (HAP) in Example 1 of the present invention.

[0032] Figure 6 This is the SEM spectrum of HZSM-5 in Example 1 of the present invention.

[0033] Figure 7 1 is the XRD spectrum of the HZSM-5 catalyst before and after metal loading in Example 1 of the present invention.

[0034] Figure 8 This is a schematic diagram of the structure of the system for producing aromatic fuels using biomass two-stage catalytic coupling and mid-stage alcohol supply provided in Example 2 of the present invention.

[0035] Reference numerals:

[0036] 1-pyrolysis unit; 11-drying device; 12-feeding device; 13-pyrolysis reactor; 14-gas-solid separation device; 15-coke combustion device; 2-middle alcohol supply unit; 3-two-stage catalytic unit; 31-first fixed bed reactor; 32-second fixed bed reactor; 4-tail gas utilization unit; 41-tail gas circulation device; 42-catalytic reforming device; 43-combustion reactor. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] Example 1

[0039] Based on the experimental results of Example 1, the effect of the method of producing aromatic fuel by biomass two-stage catalytic coupling and mid-stage alcohol supply of the present invention is described.

[0040] Figure 1 The method for preparing aromatic fuel by coupling the biomass two-stage catalysis and providing alcohol in the middle stage provided in this embodiment comprises the following steps:

[0041] Pyrolysis step S1: the biomass raw material is pyrolyzed in a pyrolysis reactor to generate biomass pyrolysis volatiles;

[0042] Mid-stage alcohol supply step S2: introducing an alcohol hydrogen supply source into the reaction system and fully mixing it with the upstream pyrolysis volatiles to form a mixed gas;

[0043] Two-stage catalytic step S3: the mixed gas is subjected to a catalytic upgrading reaction in a two-stage catalytic system, and the obtained products are condensed to obtain aromatic fuel and pyrolysis tail gas;

[0044] Tail gas utilization step S4: A portion of the pyrolysis tail gas is circulated back to the pyrolysis reactor as a pyrolysis carrier gas, and the other portion is used for combustion to provide heat and electricity for the system, or is used for reforming to produce hydrogen, methanol, dimethyl ether and other chemicals.

[0045] In this embodiment, the biomass raw material is first cracked into pyrolysis volatiles in a pyrolysis reactor through a pyrolysis step S1; methanol is then supplied to the system through a mid-stage alcohol supply step S2 to increase the effective hydrogen-carbon ratio of the reaction system; the mixed gas of the biomass pyrolysis volatiles and alcohols is then deeply deoxygenated through a series of dehydration, decarboxylation and decarbonylation reactions in a two-stage catalytic step S3, thereby obtaining high-quality aromatic fuel. Among them, a two-stage catalytic system consisting of a first-stage catalyst and a second-stage catalyst with different functions is adopted in the two-stage catalytic step S3. The first-stage catalyst mainly pre-deoxygenates the biomass pyrolysis volatiles through decarboxylation, ketonization and demethoxylation reactions to generate hydrocarbon precursors. The second-stage catalyst mainly deoxygenates the hydrocarbon precursors through multiple reactions such as dehydration, decarbonylation, oligomerization and aromatization, and converts them into high-quality aromatic fuels.

[0046] In addition, preferably, a biomass pretreatment step is further included before the pyrolysis step S1, in which the biomass is dried in advance to prevent residual moisture from affecting the deoxygenation reaction of the biomass.

[0047] Preferably, in the two-stage catalytic step S3, the first-stage catalyst includes metal oxide catalysts (Al2O3, CaO, MgO, Fe2O3, NiO, ZnO, ZrO2, etc.), natural mineral catalysts (attapulgite, talc, hydroxyapatite, montmorillonite and bentonite, etc.), etc.; the second-stage catalyst mainly includes zeolite molecular sieve catalysts (such as HY, Hβ and HZSM-5, etc.), metal-modified molecular sieve catalysts (loaded metals include iron, cobalt, nickel, molybdenum, zinc and other metals), etc.

[0048] Among them, preferably, the biomass in this embodiment can be woody biomass and / or herbaceous biomass, for example, one or more of poplar, pine, rice husk, and straw.

[0049] In the following, the catalyst and product of the method for preparing aromatic fuel from biomass by two-stage catalytic coupling and mid-stage alcohol supply provided in this embodiment are characterized by experiments. For the convenience of the experiment, the following test adopts the method of drying and pretreating the raw materials before passing them into the pyrolysis reactor for reaction.

[0050]

Material preparation

[0051] Poplar wood powder is taken as biomass raw material, and after drying, the biomass is placed in a pyrolysis reactor, and a pyrolysis reaction is carried out through a pyrolysis step S1 under normal pressure and inert atmosphere conditions, and the pyrolysis temperature is 550°C. The obtained biomass pyrolysis volatiles enter the middle alcohol supply step S2 after gas-solid separation and are fully mixed with the alcohol hydrogen supply source, and the mixed gas then enters the two-stage catalytic step S3, the required catalyst is placed in the upgrading tube in advance before the instrument is heated, and quartz wool is placed at both ends of the upgrading tube for fixing, the catalytic upgrading temperature is 500°C, the alcohol hydrogen supply source used is methanol, the feeding rate ratio of methanol to biomass is 1.5, the ratio of hydroxyapatite (HAP) to HZSM-5 is 2:4, and the metal loading modification of the rear section HZSM-5 in the two-stage catalytic system is carried out by impregnation method, and the loaded metals are iron, cobalt, nickel, molybdenum, and zinc, and all metal loadings are set to 2wt.%, and the mass ratio of the catalyst to the biomass raw material is 1:1.

[0052]

Catalyst Characterization

[0053] The BET results and TEM results show that hydroxyapatite (HAP) is a mesoporous catalyst with both acid and base functions, which can provide alkaline and acidic sites for the partial deoxygenation of macromolecular oxygen-containing compounds. The details are shown in Table 1.

[0054] The XRD spectrum results show that the pore size distribution of hydroxyapatite (HAP) is relatively wide, mainly concentrated in the mesopore range of 3-15nm, so that large molecular oxygen-containing compounds of different sizes can enter the pores. In addition, the V-type isotherm with an H3-type hysteresis loop also shows that HAP has an uneven mesoporous structure. The pore size of HZSM-5 is mainly distributed in the micropore range of 0-2nm and has a type I isotherm, which is a typical feature of microporous materials. In general, the average pore size of hydroxyapatite (HAP) is much larger than that of HZSM-5, so hydroxyapatite (HAP) and HZSM-5 constitute a mesoporous-microporous dual-stage catalytic system. Specifically, Figure 2 , Figure 3 , Figure 4 shown.

[0055] Figure 2 The pore size distribution of hydroxyapatite (HAP) in Example 1 of the present invention is shown in the figure, which is the nitrogen adsorption-desorption curve of hydroxyapatite at a temperature of 77 K. In the main figure, the horizontal axis represents the diameter of the pore, and the vertical axis represents the rate of change of the pore volume in a certain pore section with the change of the pore diameter; in the sub-figure, the horizontal axis P / P0 represents the relative pressure, and the vertical axis represents the adsorption amount.

[0056] Figure 3The pore size distribution of HZSM-5 in Example 1 of the present invention is shown in the figure, which is the nitrogen adsorption-desorption curve of HZSM-5 at 77 K. In the main figure, the horizontal axis represents the diameter of the pore, and the vertical axis represents the rate of change of the pore volume in a certain pore section with the change of the pore diameter; in the sub-figure, the horizontal axis represents the relative pressure, and the vertical axis represents the adsorption amount.

[0057] Figure 4 The XRD patterns of hydroxyapatite (HAP) and HZSM-5 in Example 1 of the present invention are shown in FIG. 1 , where the abscissa 2θ represents twice the incident angle of the x-ray, and the ordinate represents the intensity of the diffraction peak at different diffraction angles.

[0058] The SEM image results show that at the same magnification, the morphology of HAP presents a loose and smooth rod-shaped particle structure with pores. HZSM-5 presents a hexagonal morphology and is a typical MFI zeolite. Figure 5 , Figure 6 shown.

[0059] XRD spectrum results show that all metal-modified HZSM-5 show MFI-type zeolite structural characteristic diffraction peaks similar to the original catalyst, and no additional diffraction peaks are observed, indicating that at a metal loading of 2wt.%, the metal is highly dispersed in the catalyst pores and does not change the catalyst skeleton structure. By comparison, it was found that the diffraction peak intensity of Fe and Mo-modified HZSM-5 at 7-9° was reduced, which may be due to the formation of amorphous metal oxides on the outer surface of HZSM-5. Specifically, Figure 7 shown.

[0060] Table 1 Acid-base sites and pore structure parameters of HAP and HZSM-5

[0061]

[0062]

Analysis of pyrolysis oil products

[0063] The liquid product was passed into a gas chromatograph-mass spectrometer (GC / MS) for detection. The distribution of liquid products of HAP-HIZSM-5 two-stage catalytic coupling mid-stage alcohol supply is shown in Table 2. Compared with the mid-stage alcohol supply experiment on HZSM-5, the distribution of liquid products was further optimized after coupling the two-stage catalysis. The total content of aromatics in the liquid product increased from 91.02% to 95.57%, and the inhibitory effect of the system on phenols continued to increase, and the relative content of phenols decreased from 8.98% to 4.43%. Specifically, the relative content of monocyclic aromatic hydrocarbons increased from 56.30% to 61.91%, while polycyclic aromatic hydrocarbons decreased slightly from 34.72% to 33.66%. It is worth noting that in the HZSM-5 catalytic system, high-value alkylphenols in phenolic products accounted for only 15.81%, but when the two-stage catalysis was introduced, the selectivity for alkylphenols in phenolic products was significantly increased to 100%.

[0064] Table 3 shows the relative contents of each component of the liquid product of the alcohol supply in the middle stage of the metal-modified two-stage catalytic coupling and the yield of aromatics. Compared with the unmodified catalytic system, the metal-modified two-stage catalysis did not change the type of liquid product, but affected the relative content of each product. Among the modified metals, Zn showed better catalytic performance. The modification of Zn further promoted the conversion of aromatics, achieved the highest total aromatics content, and effectively reduced the content of oxygenated phenols. Specifically, the total content of aromatics increased from 95.57% to 97.41%, while phenols decreased from 4.43% to 2.59%, and the relative content of C6-C9 monocyclic aromatic hydrocarbons (MAHs) in aromatics also increased from 61.91% to 65.27%, and the relative content of polycyclic aromatic hydrocarbons (PAHs) decreased slightly from 33.66% to 32.14%. Although the modification of Fe and Mo promoted the increase of the relative content of monocyclic aromatic hydrocarbons (MAHs), it limited the deoxygenation capacity of the catalytic system, resulting in an increase in the relative content of oxygenated phenols. The effect of Ni modification on the liquid product was almost the same as that of the unmodified one, in which the content of monocyclic aromatic hydrocarbons (MAHs) decreased slightly. It was further found that other metal modifications except Ni reduced the content of polycyclic aromatic hydrocarbons (PAHs) and increased the content of monocyclic aromatic hydrocarbons (MAHs). The above results show that the two-stage catalytic system modified by Zn further optimized the composition of bio-oil, while Fe and Mo modification seemed to have the opposite effect. The aromatization reaction of methanol in the alcohol system promoted the formation of aromatics. From the perspective of aromatics yield, HAP-2% ZHZSM-5 modified by Zn is the only two-stage catalytic system significantly higher than HAP-HZSM-5. In addition to hydrocarbons, the content of the only oxygenated phenol in the liquid product dropped to 2.59%, which has the potential to be used directly as a liquid fuel component or additive.

[0065] In the present embodiment, under an inert atmosphere at normal pressure, methanol is used as a hydrogen source, and a two-stage catalytic system is designed to achieve efficient conversion of biomass to high-quality aromatic fuels. The method has a short process, a simple process, and a high energy conversion efficiency, and has significant economic advantages. In addition, in the present embodiment, in the two-stage catalytic step S3, a natural mineral catalyst is first used to pre-treat the pyrolysis volatiles, and the initial deoxygenation of the pyrolysis volatiles is achieved mainly by decarboxylation, ketonization, and demethoxylation reactions, which effectively reduces the acidity of the liquid product and reduces the potential corrosion to the equipment. Secondly, a molecular sieve catalyst is used to deeply deoxygenate the volatiles through various reactions such as dehydration, decarbonylation, oligomerization, and aromatization, and convert them into high-quality aromatic fuels. The two-stage catalytic system constructed by the present invention and the mid-stage alcohol supply method show good gas deoxygenation performance and high aromatic mass yield, further optimizing product quality.

[0066] Table 2 Relative contents of various components and aromatics yields of the liquid product from the alcohol supply in the middle stage of the two-stage catalytic coupling

[0067]

[0068] Table 3 Relative contents of various components and aromatics yields of liquid products from metal-modified two-stage catalytic coupling in the middle alcohol supply stage

[0069]

[0070] Preferably, under the hydroxyapatite (HAP) catalyst and modified Zn / HZSM-5 catalyst system, the conversion of carboxylic acids and phenols can be more effectively promoted to obtain aromatics with higher mass yield and selectivity, wherein the mass yield of monocyclic aromatic hydrocarbons is 13.20%, the selectivity is 65.27%, the mass yield of polycyclic aromatic hydrocarbons is 3.29%, the selectivity is 32.14%, the mass yield of total aromatic hydrocarbons is 16.49%, and the energy conversion rate of hydrocarbon products is calculated to be 31.2%.

[0071] Example 2

[0072] In an embodiment of the present invention, a system for producing liquid fuel by online upgrading of biomass by dual-stage catalytic coupling is provided. Figure 8 It is a simplified structural diagram of a system for online upgrading of biomass to produce liquid fuel by two-stage catalytic coupling in an embodiment of the present invention.

[0073] like Figure 8 As shown, the system for preparing aromatic fuel by coupling biomass two-stage catalysis with middle-stage alcohol supply provided in this embodiment includes: a pyrolysis unit 1, a middle-stage alcohol supply unit 2, a two-stage catalytic unit 3 and a tail gas utilization unit 4. The details are as follows:

[0074] First, in the pyrolysis unit 1, the biomass raw material is dried in the drying device 11, and then continuously fed into the pyrolysis reactor 13 through the feeding device 12 for pyrolysis to obtain a gas-solid mixture. The pyrolysis reactor 13 is generally a fluidized bed reactor; the gas-solid mixture is separated by the gas-solid separation device 14 to obtain coke, bed material and biomass pyrolysis volatiles; the separated coke and bed material are fed into the coke combustion device 15 for combustion; the solid material after combustion is circulated back to the pyrolysis reactor 13 to provide heat for the pyrolysis reaction.

[0075] Then, the mixed gas of the pyrolysis volatile matter and methanol is mixed in the middle alcohol supply unit 2 to obtain a mixed gas and input into the two-stage catalytic unit 3.

[0076] The two-stage catalytic unit 3 is equipped with two groups of fixed bed reactors with interchangeable functions. The first fixed bed reactor 31 and the second fixed bed reactor 32 are connected in parallel. Each fixed bed reactor has the dual functions of upgrading / regeneration. Through the dynamic switching of the relevant operating valves, the pyrolysis volatile matter and the alcohol hydrogen supply source can be continuously introduced into the upgrading furnace to ensure the continuity of the catalytic upgrading reaction. The pyrolysis volatile matter and methanol are first mixed in the pipeline of the middle section alcohol supply unit 2 to obtain a mixed gas and input it into the first fixed bed reactor 31 or the second fixed bed reactor 32; after the reaction, the catalyst is taken out from the first fixed bed reactor 31 or the second fixed bed reactor 32, and the carbon deposits attached to the surface are burned by a high-temperature device in the first fixed bed reactor 31 or the second fixed bed reactor 32 for storage and standby, so as to realize the reuse of the catalyst in the two-stage catalytic unit 3, thereby realizing the continuous production of the system.

[0077] In the tail gas utilization unit 4, part of the pyrolysis tail gas is filtered, dehydrated and pressurized in the tail gas circulation device 41 and then returned to the pyrolysis unit 1 as a pyrolysis carrier gas. The remaining part of the pyrolysis tail gas is used to prepare hydrogen, methanol, dimethyl ether and other chemicals through the catalytic reforming device 42, and is burned through the combustion reactor 43 to provide heat for various components of the system and drive the steam turbine to generate electricity.

[0078] This embodiment uses Aspen Plus software to simulate the process of the system, and the process includes a pyrolysis unit, a two-stage catalytic unit and a tail gas utilization unit. The biomass raw material of the pyrolysis unit is set to poplar, the feed rate is set to 100kg / h, the energy input is 1896MJ / h, and the pyrolysis temperature is set to 550°C. In order to meet the fluidization operation requirements, the pyrolysis carrier gas is realized by the internal gas circulation of the system, and the pyrolysis cycle carrier gas flow rate is set to 148.5kg / h. In the two-stage catalytic unit, methanol is used as a hydrogen source, the feed amount is 150kg / h, the energy input is 2996.24MJ / h, and the catalytic system adopts a two-stage catalytic combination of hydroxyapatite (HAP) and Zn / HZSM-5, and the catalytic reaction temperature is set to 500°C. In the tail gas utilization unit, part of the pyrolysis tail gas is used for system circulation, and the other part is used for combustion to generate heat and drive the steam turbine to generate electricity. The simulation results show that the system's aromatics yield is 15.18wt.%, the energy output is 1554.7MJ / h, the output electricity is 428.34MJ / h, and the calculated energy conversion rate of aromatic fuel is 31.78%. If the electricity output is taken into account, the energy efficiency of the entire system reaches 40.53%.

[0079] In this embodiment, the present invention applies a two-stage catalytic system composed of a natural mineral catalyst and a metal-modified molecular sieve catalyst, and by introducing methanol as a hydrogen source in the system, the efficient integration of biomass pyrolysis and online catalytic upgrading to produce aromatic fuels is achieved. This system effectively reduces small molecular oxygen-containing compounds such as acids and ketones in the liquid phase product by deep deoxygenation of biomass pyrolysis volatiles, and significantly reduces the oxygen content of bio-oil. In addition, the catalytic system of the system promotes aromatization and isomerization reactions, improves the yield of monocyclic aromatic hydrocarbons (C6-C9) in bio-oil, and thus obtains high-quality biomass liquid fuel with aromatic hydrocarbons as the main component. Through the recycling of tail gas, this system further enhances its economy and environmental performance, not only reduces the consumption of alcohol raw materials, but also effectively improves the overall energy efficiency of the system.

[0080] So far, the technical solution of the present invention has been described in conjunction with the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to the above specific embodiments. Those skilled in the art can make equivalent changes or substitutions to the relevant technical features without departing from the principles of the present invention, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

Claims

1. A method for preparing aromatic fuel by coupling biomass with two-stage catalysis and middle-stage alcohol supply, characterized in that: The following steps are involved: Pyrolysis step: the biomass raw material is pyrolyzed in a pyrolysis reactor to generate biomass pyrolysis volatiles; The middle alcohol supply step is to mix the alcohol hydrogen supply source with the biomass pyrolysis volatile matter to obtain a mixed gas; Two-stage catalytic step: the mixed gas obtained in the middle alcohol supply step is subjected to a catalytic upgrading reaction through a two-stage catalytic system, and the products obtained from the catalytic upgrading reaction are condensed to obtain aromatic fuel and pyrolysis tail gas.

2. The method for preparing aromatic fuel by biomass two-stage catalytic coupling and middle-stage alcohol supply according to claim 1 is characterized in that: The reaction temperature of the double-stage catalytic step is 400-550°C.

3. The method for preparing aromatic fuel by biomass two-stage catalytic coupling and middle-stage alcohol supply according to claim 1 or 2, characterized in that: In the two-stage catalytic step, the alcohol hydrogen source is a small molecule monohydric alcohol.

4. The method for preparing aromatic fuel by biomass two-stage catalytic coupling and middle-stage alcohol supply according to claim 1 or 2, characterized in that: The two-stage catalytic system includes a first-stage catalyst and a second-stage catalyst. In the two-stage catalytic step, the first-stage catalyst is used to pre-deoxygenate the biomass pyrolysis volatiles to generate hydrocarbon precursors; and the second-stage catalyst is used to deeply deoxygenate the hydrocarbon precursors to convert them into aromatic fuels.

5. The method for preparing aromatic fuel by biomass two-stage catalytic coupling and middle-stage alcohol supply according to claim 1 or 2, characterized in that: Under the condition of a given mass space velocity, in the dual-stage catalytic step, the feed rate ratio of the alcohol hydrogen source to the biomass pyrolysis volatile matter is 0.5-2.

6. The method for preparing aromatic fuel by biomass two-stage catalytic coupling and middle-stage alcohol supply according to claim 1 or 2, characterized in that: The method also includes a tail gas utilization step: a portion of the pyrolysis tail gas produced in the two-stage catalytic step is recycled back to the pyrolysis reactor as a pyrolysis carrier gas, and the other portion is used for combustion to provide heat and electricity for the system, or is used for reforming to produce hydrogen, methanol and / or dimethyl ether.

7. A system for producing aromatic fuel by coupling biomass two-stage catalysis with alcohol supply in the middle stage, characterized in that: The following units are included: The pyrolysis unit (1) comprises a drying device (11), a feeding device (12), a pyrolysis reactor (13), a gas-solid separation device (14) and a coke combustion device (15). The biomass raw material is first dried in the drying device (11), and then continuously fed into the pyrolysis reactor (13) through the feeding device (12) for pyrolysis to obtain a gas-solid mixture. The gas-solid mixture is separated by the gas-solid separation device (14) to obtain coke, bed material and biomass pyrolysis volatile matter. Middle-stage alcohol supply unit (2): the alcohol hydrogen supply source and the biomass pyrolysis volatile matter are fully mixed in the middle-stage alcohol supply unit (2) to form a mixed gas, which is then transported to the two-stage catalytic unit (3); The two-stage catalytic unit (3) comprises a first fixed bed reactor (21) and a second fixed bed reactor (22), the two fixed bed reactors are connected in parallel and have dual functions of biomass catalytic upgrading and catalyst regeneration. The mixed gas obtained by the middle alcohol supply unit (2) enters any one of the fixed bed reactors for catalytic upgrading reaction, while the catalyst regeneration reaction is carried out in the other fixed bed reactor. The two fixed bed reactors are rotated regularly, and the reaction products obtained by catalytic upgrading are condensed to obtain aromatic fuel and pyrolysis tail gas. The tail gas utilization unit (4) comprises a tail gas circulation device (41), a catalytic reforming device (42) and a combustion reactor (43). Part of the pyrolysis tail gas obtained by the two-stage catalytic unit (3) is filtered, dehydrated and pressurized in the tail gas circulation device (41) and then returned to the pyrolysis unit (1). The remaining part of the pyrolysis tail gas is used to prepare hydrogen, methanol and / or dimethyl ether through the catalytic reforming device (42), or is used for combustion through the combustion reactor (43) to provide heat for various components of the system.

8. The system for preparing aromatic fuel by using biomass two-stage catalytic coupling and middle-stage alcohol supply according to claim 7 is characterized in that: The coke and bed material separated by the gas-solid separation device (14) are sent to the coke combustion device (15) and the solid material after combustion is circulated back to the pyrolysis reactor (13).

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