A method for producing a bio-oil

Abstract

The application discloses a kind of biological oil preparation methods.The method includes the following steps: (1) after being pulverized, lignocellulosic biomass is mixed with internal hollow zeolite molecular sieve loaded with metal and sent into reactor, and pyrolysis is carried out in inert gas atmosphere;(2) gas obtained in step (1) is condensed.The catalyst used in the method, metal species is loaded inside hollow zeolite molecular sieve, not only has the potential of directional deoxidization to promote the generation of hydrocarbons to prepare high-quality biological oil, but also can inhibit catalyst deactivation to prolong the service life of catalyst;At the same time, the process of the method is simple, the yield of biological oil obtained is high, the selectivity of hydrocarbon compounds is high and the content of oxide is low, which provides an efficient conversion path for the preparation of lignocellulosic biomass to hydrocarbon-rich biological oil.

Description

Technical Field

[0001] This invention relates to the field of biofuel production technology, and in particular to a method for preparing biofuel. Background Technology

[0002] The dwindling oil resources have led to energy shortages and soaring oil prices, drawing increasing attention to alternatives to petroleum fuels. Biomass, a renewable resource abundant globally, has garnered significant attention due to its potential to replace petroleum fuels. It can be converted into liquid fuels through rapid pyrolysis technology. Specifically, this involves a reaction at a high heating rate (10–200 °C / s), medium temperature (400–600 °C), and short residence time (<5 s), accompanied by rapid cooling of the pyrolysis steam. The resulting liquid product is commonly referred to as pyrolysis oil or bio-oil. However, bio-oil has an extremely complex composition, typically containing hundreds of oxygenated compounds. Compared to fossil fuels, it suffers from lower calorific value, higher acidity, and poorer stability, preventing its practical application in existing petrochemical infrastructure. Therefore, it is necessary to improve the quality of bio-oil to enable it to compete with fossil fuels and serve as a green fuel in the future. Developing suitable conversion technologies is crucial for the clean and efficient utilization of biomass. Among various biomass conversion technologies, catalytic rapid pyrolysis is considered a very promising energy conversion technology. A suitable and efficient catalyst is very effective in regulating the degree of rapid catalytic pyrolysis and the distribution of products.

[0003] To date, scholars both domestically and internationally have developed and explored various catalysts for the catalytic pyrolysis of lignocellulose to produce high-quality bio-oils in numerous studies, mainly including zeolite molecular sieves, metal oxides, and mesoporous catalysts. Zeolite molecular sieves are a research topic of great interest, as they significantly improve the selectivity of hydrocarbon compounds, with ZSM-5 molecular sieves being the most prominent example. However, the narrow micropores of ZSM-5 hinder the diffusion of reactants and products, easily leading to carbon buildup and deactivation within the catalyst pores. This results in a short lifespan during the aromatization of catalytic pyrolysis gases, limiting its large-scale application. Using nanoscale and porous ZSM-5 zeolite molecular sieves can effectively shorten the micropores, thereby improving the yield of the desired product, but the drawbacks of easy carbon buildup and low conversion rates still exist. Furthermore, combining active species such as metals with zeolite molecular sieves to prepare bifunctional catalysts can further enhance catalyst activity and promote the formation of the target product. Currently, species such as gallium, nickel, zinc, iron, and cobalt have been shown to promote hydrogen transfer reactions, decarbonylation reactions, and / or olefin aromatization reactions.

[0004] In recent years, hollow materials have emerged, possessing not only unique intracavitary microenvironments and confinement effects but also significantly enhancing mass transfer. Hollow zeolite molecular sieves can optimize the pore properties of catalysts and the synergistic effect of active sites, exhibiting excellent diffusion and catalytic performance. For example, patents CN110090661A and CN111530493A utilize surface-loaded metal hollow molecular sieves for the conversion of alkanes to aromatics, achieving advantages such as high conversion rates and good aromatic selectivity. Furthermore, patent CN113368891A applies surface-loaded metal hollow molecular sieves reduced with hydrogen to the hydrogenation of polycyclic aromatic hydrocarbons to prepare high-density aviation fuel. Benefiting from the high specific surface area and mesoporous pore volume of hollow ZSM-5 molecular sieves, diffusion of macromolecules and intermediates is promoted, and good metal dispersion is also achieved. Summary of the Invention

[0005] The inventors discovered that in the prior art, when using hollow molecular sieves with surface-loaded metal as catalysts to prepare aromatics, the metal located on the outer surface of the hollow molecular sieve has the disadvantage of slow loss under harsh high-temperature reaction conditions.

[0006] To at least partially address the technical problems existing in the prior art, the inventors made this invention, providing a method for preparing bio-oil through specific embodiments. This includes the following steps:

[0007] (1) The pulverized lignocellulosic biomass is mixed with a hollow molecular sieve loaded with metal inside and then fed into a reactor for thermal pyrolysis in an inert gas atmosphere.

[0008] (2) Condense the gas obtained in step (1).

[0009] The beneficial effects of the above-described technical solutions provided in the embodiments of the present invention include at least the following:

[0010] The bio-oil preparation method provided in this invention involves mixing pulverized lignocellulosic biomass with a hollow molecular sieve internally loaded with metal, and then feeding the mixture into a reactor for thermal pyrolysis in an inert gas atmosphere. The resulting gas is then condensed to obtain bio-oil. The metal species loaded inside the hollow zeolite molecular sieve not only possess the potential for directional deoxygenation to promote hydrocarbon generation and prepare high-quality bio-oil, but also inhibit catalyst deactivation and extend catalyst lifespan. Furthermore, this method features a simple process flow, high bio-oil yield, high selectivity for hydrocarbon compounds, and low oxide content, which helps reduce the use of hydrogen in subsequent bio-oil refining and upgrading, providing an efficient conversion pathway for the preparation of hydrocarbon-rich bio-oil from lignocellulosic biomass.

[0011] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description, claims, and drawings.

[0012] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0013] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0014] Figure 1 This is a flowchart of the bio-oil preparation method in Example 1 of the present invention;

[0015] Figure 2 This is a flowchart of the method for preparing hollow molecular sieves with internally loaded metal in Embodiment 3 of the present invention;

[0016] Figure 3 This is a comparison of the selectivity of the bio-oil products obtained by the zeolite molecular sieve prepared in Example 4 of the present invention through catalytic pyrolysis of lignocellulose with that of conventional zeolite molecular sieves and non-catalytic cracking.

[0017] Figure 4 This is a comparison chart showing the selectivity of the bio-oil products obtained by catalytic pyrolysis of lignocellulose using the zeolite molecular sieve prepared in Example 5 of the present invention with that obtained by conventional zeolite molecular sieves and non-catalytic cracking.

[0018] Figure 5 This is a comparison of the selectivity of the bio-oil products obtained by the zeolite molecular sieve prepared in Example 6 of the present invention through catalytic pyrolysis of lignocellulose with that of conventional zeolite molecular sieves and non-catalytic cracking.

[0019] Figure 6 Comparative diagrams showing the selectivity of bio-oil products obtained by catalytic pyrolysis of lignocellulose using zeolite molecular sieves prepared in Example 6, Comparative Example 1, and Comparative Example 2 of the present invention.

[0020] Figure 7 This is a comparison chart showing the selectivity of the bio-oil products obtained by catalytic pyrolysis of lignocellulose using the zeolite molecular sieve prepared in Example 7 of the present invention with that obtained by conventional zeolite molecular sieves and non-catalytic cracking.

[0021] Figure 8 This is a comparison chart showing the selectivity of the bio-oil products obtained by catalytic pyrolysis of lignocellulose using the zeolite molecular sieve prepared in Example 8 of the present invention with that obtained by conventional zeolite molecular sieves and non-catalytic cracking. Detailed Implementation

[0022] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0023] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0024] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0025] In the description of this invention, it should be noted that the terms "comprising", "including", "having", "containing", etc., are all open-ended terms, meaning that they include but are not limited to.

[0026] To address the problem in existing technologies where the metal on the outer surface of hollow molecular sieves loaded with surface metal is easily lost under harsh high-temperature reaction conditions when using them as catalysts to prepare aromatics, this invention provides a method for preparing bio-oil using hollow molecular sieves loaded with internal metal as catalysts. This method features a simple process, high bio-oil yield, high selectivity for hydrocarbon compounds, and low oxide content.

[0027] Example 1

[0028] Example 1 of this invention provides a method for preparing bio-oil, the process of which is as follows: Figure 1 As shown, it includes the following steps:

[0029] Step S11: The pulverized lignocellulosic biomass is mixed with a hollow molecular sieve loaded with metal and then fed into a reactor for thermal pyrolysis in an inert gas atmosphere.

[0030] Specifically, lignocellulosic biomass can be natural biomass, that is, agricultural and forestry waste that has not been converted or altered, including one or more types of straw or sawdust.

[0031] In some embodiments, the mass ratio of lignocellulosic biomass to hollow molecular sieves internally loaded with metal is 1:0.5 to 1:10; more preferably, the mass ratio of lignocellulosic biomass to hollow molecular sieves internally loaded with metal is 1:0.5 to 1:2.

[0032] The inert gas contains less than 3% hydrogen and less than 3% oxygen. The inert gas includes at least one of helium, nitrogen and argon; alternatively, other inert gases may also be included.

[0033] Furthermore, the mixed lignocellulosic biomass and the hollow molecular sieve loaded with internal metals undergo rapid thermal pyrolysis in an inert gas atmosphere under normal pressure and at a temperature of 450–600°C.

[0034] The pyrolysis unit, i.e. the reaction bed, can be a fixed bed reactor, a moving bed reactor, or a suspended bed reactor, etc.

[0035] The catalyst used for the thermal pyrolysis reaction, namely a hollow molecular sieve with internally loaded metal, is characterized in detail and its preparation process is described in Examples 2 and 3 below.

[0036] Step S12: Condense the obtained gas.

[0037] The liquid product obtained by condensing the gas obtained in step S11 is hydrocarbon-rich bio-oil.

[0038] The bio-oil preparation method provided in Example 1 of this invention involves mixing pulverized lignocellulosic biomass with a hollow molecular sieve internally loaded with metal, and then feeding the mixture into a reactor for thermal pyrolysis in an inert gas atmosphere. The resulting gas is then condensed to obtain bio-oil. The metal species loaded inside the hollow zeolite molecular sieve not only possess the potential for directional deoxygenation to promote hydrocarbon generation and prepare high-quality bio-oil, but also inhibit catalyst deactivation and extend catalyst lifespan. Furthermore, this method features a simple process flow, high bio-oil yield, high selectivity for hydrocarbon compounds, and low oxide content, which helps reduce the use of hydrogen in subsequent bio-oil refining and upgrading, providing an efficient conversion pathway for the preparation of hydrocarbon-rich bio-oil from lignocellulosic biomass.

[0039] Example 2

[0040] Embodiment 2 of the present invention provides a hollow molecular sieve with internally loaded metal, wherein the metal species are encapsulated in the internal cavity of the hollow molecular sieve, and is used as a catalyst for the thermal cracking of biomass to produce bio-oil.

[0041] Hollow molecular sieves can be MFI, BEA, MEL or FAU type zeolite hollow molecular sieves; preferably, they are MFI type zeolite hollow molecular sieves.

[0042] The cavity volume of the hollow molecular sieve accounts for 60-70% of the total volume of the hollow molecular sieve; the silicon-to-aluminum molar ratio of the hollow molecular sieve is 25-100. Preferably, the cavity volume of the hollow molecular sieve accounts for 64-69% of the total volume of the hollow molecular sieve; the silicon-to-aluminum molar ratio of the hollow molecular sieve is 40-60.

[0043] The mass ratio of the metal loaded on the hollow molecular sieve to the hollow molecular sieve is 0.5:99.5 to 10:90; preferably, the mass ratio of the metal loaded on the hollow molecular sieve to the hollow molecular sieve is 1:99 to 5:95.

[0044] The metal supported on the hollow molecular sieve is at least one selected from alkali metals, alkaline earth metals, transition metals, and post-transition metals. Preferably, the metal supported on the hollow molecular sieve is a post-transition metal; more preferably, the metal is at least one selected from iron, cobalt, nickel, zinc, and gallium.

[0045] In some embodiments, the hollow molecular sieve can be a molecular sieve with three-dimensional intersecting channels, and the pore size can be [missing information]. Even better, the aperture size of the three-dimensional intersecting channel is

[0046] The hollow molecular sieve used in Example 1 of this invention is specifically any of the hollow molecular sieves in Example 2 above.

[0047] Example 3

[0048] Embodiment 3 of the present invention provides a method for preparing a hollow molecular sieve with an internally loaded metal, specifically, the method for preparing the hollow molecular sieve in Embodiment 2 above, the process of which is as follows: Figure 2 As shown, it includes the following steps:

[0049] Step S21: The hollow molecular sieve with surface-loaded metal is mixed with a quaternary ammonium alkali solution and then heated to react.

[0050] Specifically, the surface-loaded metal molecular sieve is mixed with a quaternary ammonium alkali solution and heated to 100–200°C for 27–96 hours; preferably, the surface-loaded metal hollow molecular sieve is mixed with a quaternary ammonium alkali solution and heated to 150–180°C for 48–72 hours.

[0051] The aforementioned hollow molecular sieves with surface-loaded metal can be prepared by the following method:

[0052] A hollow molecular sieve with a metal salt solution is mixed and impregnated to obtain a hollow molecular sieve with a metal surface.

[0053] Specifically, the metal salt is an inorganic metal salt or a metal complex salt; further, the metal salt is at least one of nitrate, chloride, and sulfate.

[0054] Metal salt solutions can be mixed and impregnated with hollow molecular sieves using methods such as equal-volume impregnation or wet impregnation.

[0055] Step S22: After the reaction, the hollow molecular sieve is separated, dried and calcined to obtain a hollow molecular sieve with internally loaded metal.

[0056] The following Examples 4-8 illustrate the specific applications of the bio-oil preparation method.

[0057] All raw materials used in the embodiments of this invention are commercially available products of analytical purity.

[0058] The yield was calculated as the ratio of the actual weight of the zeolite molecular sieve obtained after dissolution-recrystallization to the theoretical weight (after complete recrystallization). The cavity volume as a percentage of the total molecular sieve volume was calculated as the ratio of the mesopore volume to the total pore volume. The non-catalytic and ZSM-5 pyrolysis reaction conditions in each example were consistent with those for metal-supported hollow ZSM-5 molecular sieves. The comparative examples were consistent with the pyrolysis reaction conditions of the examples.

[0059] Example 4

[0060] ZSM-5 molecular sieves with surface-loaded iron were obtained by impregnating them with an aqueous solution of ferric nitrate (the molar ratio of silicon to aluminum in the ZSM-5 molecular sieve was 60, and the mass ratio of metal to molecular sieve was 1:99). The ZSM-5 molecular sieves with surface-loaded iron were then mixed with tetramethylammonium hydroxide and reacted at 150°C for 48 hours to obtain hollow ZSM-5 molecular sieves with internally loaded iron species, with a yield of 84.6%. The cavity volume of the obtained hollow ZSM-5 molecular sieves with internally loaded iron species accounted for 66% of the total volume of the molecular sieve.

[0061] The iron-containing internally supported hollow ZSM-5 zeolite molecular sieve prepared above was used as a catalyst and mixed with pulverized poplar wood chips at a 1:1 mass ratio. The mixture was then placed in the heating zone of a fixed-bed reactor for pyrolysis at 450℃ under a nitrogen atmosphere. After the reaction, the condensed liquid product was collected as hydrocarbon-rich bio-oil.

[0062] See Figure 3 As shown, the hydrocarbon selectivity was 37.21% by area, the phenol selectivity was 39.4% by area, and the oxygen-containing compound selectivity was 22.3% by area. The hydrocarbon selectivity of the iron-supported hollow ZSM-5 zeolite molecular sieve in Example 4 was 37.21% and 26.59% higher by area than that of non-catalytic pyrolysis and the parent ZSM-5 zeolite molecular sieve (conventional ZSM-5 zeolite molecular sieve) in Example 4, respectively.

[0063] Example 5

[0064] ZSM-5 zeolite molecular sieves with cobalt-loaded surfaces were obtained by impregnating them with a cobalt chloride aqueous solution (the molar ratio of silicon to aluminum in the ZSM-5 molecular sieve was 50, and the mass ratio of metal to molecular sieve was 3:97). The cobalt-loaded ZSM-5 molecular sieves were then mixed with tetrapropylammonium hydroxide and reacted at 155 °C for 54 hours to obtain hollow ZSM-5 zeolite molecular sieves with internally loaded cobalt species, with a yield of 85.7%. The cavity volume of the obtained hollow ZSM-5 zeolite molecular sieves with internally loaded cobalt species accounted for 69% of the total volume of the molecular sieve.

[0065] The cobalt-supported hollow ZSM-5 zeolite molecular sieve prepared above was used as a catalyst and mixed with pulverized willow wood chips at a mass ratio of 1:0.5. The mixture was then placed in the heating zone of a moving bed reactor for pyrolysis at 500°C under a helium atmosphere. After the reaction, the condensed liquid product was collected, which is the hydrocarbon-rich bio-oil.

[0066] See Figure 4 As shown, the hydrocarbon selectivity is 38.33% by area, the phenol selectivity is 38.85% by area, and the oxygen-containing compound selectivity is 22.82% by area. The hydrocarbon selectivity of the cobalt-supported hollow ZSM-5 zeolite molecular sieve catalyst in Example 5 is 38.33% and 26.43% higher by area, respectively, than that of non-catalytic pyrolysis and the parent ZSM-5 zeolite molecular sieve (conventional ZSM-5 zeolite molecular sieve) in Example 5.

[0067] Example 6

[0068] ZSM-5 zeolite molecular sieves with nickel loading were obtained by impregnating them with an aqueous nickel sulfate solution (the molar ratio of silicon to aluminum in the ZSM-5 molecular sieve was 50, and the mass ratio of metal to molecular sieve was 3:97). The surface-loaded nickel ZSM-5 molecular sieves were then mixed with tetramethylammonium hydroxide and reacted at 160°C for 60 hours to obtain hollow ZSM-5 zeolite molecular sieves with internally loaded nickel species, with a yield of 84.2%. The cavity volume of the obtained hollow ZSM-5 zeolite molecular sieves with internally loaded nickel species accounted for 69% of the total volume of the molecular sieve.

[0069] The nickel species internally supported hollow ZSM-5 zeolite molecular sieve prepared above was used as a catalyst and mixed with crushed corn stalks at a mass ratio of 1:0.5. The mixture was then placed in the heating zone of a suspended bed reactor for pyrolysis at a temperature of 550℃ under a nitrogen atmosphere. After the reaction, the condensed liquid product was collected as hydrocarbon-rich bio-oil.

[0070] See Figure 5As shown, the hydrocarbon selectivity was 41.56% by area, the phenol selectivity was 39.73% by area, and the oxygen-containing compound selectivity was 18.71% by area. The hydrocarbon selectivity of the nickel-species-supported hollow ZSM-5 zeolite molecular sieve catalyst in Example 6 was 38.14% and 30.66% higher by area than that of non-catalytic pyrolysis and the parent ZSM-5 zeolite molecular sieve (conventional ZSM-5 zeolite molecular sieve) in Example 6, respectively.

[0071] Comparative Example 1 of Example 6

[0072] ZSM-5 molecular sieve (with a silicon-to-aluminum molar ratio of 50) was reacted in tetramethylammonium hydroxide solution at 160°C for 60 hours to obtain hollow ZSM-5 zeolite molecular sieve. Hollow ZSM-5 zeolite molecular sieve was then impregnated with nickel sulfate aqueous solution (metal to molecular sieve mass ratio of 3:97) to obtain hollow ZSM-5 zeolite molecular sieve with nickel species loaded on the surface, with a yield of 83.9% and a cavity volume accounting for 63% of the total volume of the molecular sieve.

[0073] The catalyst, with nickel species supported on the surface of hollow ZSM-5 zeolite molecular sieve prepared above, was mixed with pulverized corn stalks at a mass ratio of 1:0.5 and placed in the heating zone of a suspended bed reactor for pyrolysis at a temperature of 550℃ under a nitrogen atmosphere. After the reaction, the condensed liquid product was collected as hydrocarbon-rich bio-oil.

[0074] See Figure 6 As shown, the hydrocarbon selectivity was 35.95% of the area, the phenol selectivity was 38.12% of the area, and the oxygen-containing compound selectivity was 25.93% of the area. The hydrocarbon selectivity of the catalyst with nickel species supported on the surface of the hollow ZSM-5 zeolite molecular sieve in Comparative Example 1 was 5.61% lower than that in Example 6.

[0075] Comparative Example 2 of Example 6

[0076] ZSM-5 zeolite molecular sieves with nickel loading were obtained by impregnating them with an aqueous nickel sulfate solution (the molar ratio of silicon to aluminum in the ZSM-5 molecular sieve was 50, and the mass ratio of metal to molecular sieve was 3:97). The ZSM-5 molecular sieves with nickel loading were then mixed with tetramethylammonium hydroxide and reacted at 160°C for 24 hours to obtain hollow ZSM-5 zeolite molecular sieves with nickel species loaded internally, with a yield of 85.4% and a cavity volume accounting for 52% of the total volume of the molecular sieve.

[0077] The nickel species internally supported hollow ZSM-5 zeolite molecular sieve prepared above was used as a catalyst and mixed with crushed corn stalks at a mass ratio of 1:0.5. The mixture was then placed in the heating zone of a suspended bed reactor for pyrolysis at a temperature of 550℃ under a nitrogen atmosphere. After the reaction, the condensed liquid product was collected as hydrocarbon-rich bio-oil.

[0078] See Figure 6 As shown, the hydrocarbon selectivity was 30.53% by area, the phenol selectivity was 42.54% by area, and the oxygen-containing compound selectivity was 26.27% by area. The hydrocarbon selectivity of the nickel species-supported hollow ZSM-5 zeolite molecular sieve catalyst prepared by Comparative Example 2 with a shorter treatment time (24 hours) was 11.03% lower by area than that of Example 6.

[0079] Example 7:

[0080] ZSM-5 zeolite molecular sieves with zinc-loaded surfaces were obtained by impregnating them with zinc chloride aqueous solution (the molar ratio of silicon to aluminum in ZSM-5 molecular sieves was 40, and the mass ratio of metal to molecular sieves was 5:95). The ZSM-5 molecular sieves with zinc-loaded surfaces were then mixed with tetrabutylammonium hydroxide at a ratio of 1:15 g / mL and reacted at 160 °C for 72 hours to obtain hollow ZSM-5 zeolite molecular sieves with zinc-loaded interiors, with a yield of 85.1% and a cavity volume accounting for 64% of the total volume of the molecular sieve.

[0081] The zinc species internally supported hollow ZSM-5 zeolite molecular sieve prepared above was used as a catalyst and mixed with crushed rice straw at a mass ratio of 1:2. The mixture was then placed in the heating zone of a suspended bed reactor for pyrolysis at a temperature of 550℃ under an argon atmosphere. After the reaction, the condensed liquid product was collected as hydrocarbon-rich bio-oil.

[0082] See Figure 7 As shown, the hydrocarbon selectivity was 33.01% by area, the phenol selectivity was 40.04% by area, and the oxygen-containing compound selectivity was 26.95% by area. The hydrocarbon selectivity of the zinc-supported hollow ZSM-5 zeolite molecular sieve catalyst in Example 7 was 29.59% and 22.11% higher by area than that of non-catalytic pyrolysis and the parent ZSM-5 zeolite molecular sieve (conventional ZSM-5 zeolite molecular sieve) in Example 7, respectively.

[0083] Example 8:

[0084] ZSM-5 zeolite molecular sieves with gallium loaded on the surface were obtained by impregnating them with an aqueous gallium nitrate solution (the molar ratio of silicon to aluminum in the ZSM-5 molecular sieve was 40, and the mass ratio of metal to molecular sieve was 5:95). The ZSM-5 molecular sieves with gallium loaded on the surface were mixed with tetrapropylammonium hydroxide and reacted at 180°C for 72 hours to obtain hollow ZSM-5 zeolite molecular sieves with gallium species loaded inside, with a yield of 84.3% and a cavity volume accounting for 67% of the total volume of the molecular sieve.

[0085] The gallium species-supported hollow ZSM-5 zeolite molecular sieve prepared above was used as a catalyst and mixed with pulverized elm wood chips at a mass ratio of 1:0.5. The mixture was then placed in the heating zone of a suspended bed reactor for pyrolysis at a temperature of 600℃ under a nitrogen atmosphere. After the reaction, the condensed liquid product was collected as hydrocarbon-rich bio-oil.

[0086] See Figure 8 As shown, the hydrocarbon selectivity was 44.03% by area, the phenol selectivity was 37.11% by area, and the oxygen-containing compound selectivity was 17.59% by area. The hydrocarbon selectivity of the gallium-supported hollow ZSM-11 zeolite molecular sieve catalyst in Example 8 was 43.01% and 32.27% higher by area than that of non-catalytic pyrolysis and the parent ZSM-5 zeolite molecular sieve (conventional ZSM-5 zeolite molecular sieve) in Example 8, respectively.

[0087] It should be understood that the specific order or hierarchy of steps in the disclosed process is an example of an exemplary method. Based on design preferences, it should be understood that the specific order or hierarchy of steps in the process may be rearranged without departing from the scope of this disclosure. The appended method claims provide elements of various steps in an exemplary order and are not intended to limit the scope to the specific order or hierarchy described.

[0088] In the detailed description above, various features are combined together in a single embodiment to simplify this disclosure. This approach to disclosure should not be construed as reflecting an intention that embodiments of the claimed subject matter require more features than are explicitly stated in each claim. Rather, as reflected in the appended claims, the invention is presented with fewer features than all of the features in a single disclosed embodiment. Therefore, the appended claims are hereby explicitly incorporated into the detailed description, with each claim representing a separate preferred embodiment of the invention.

[0089] The foregoing description includes examples of one or more embodiments. It is certainly impossible to describe all possible combinations of components or methods in order to describe the above embodiments, but those skilled in the art will recognize that further combinations and arrangements of the various embodiments are possible. Therefore, the embodiments described herein are intended to cover all such changes, modifications, and variations that fall within the scope of the appended claims. Furthermore, the term "comprising" as used in the specification or claims is interpreted in a manner similar to the term "including," as interpreted when used as a conjunction in the claims. Additionally, the use of any term "or" in the specification of the claims is intended to mean "non-exclusive or."

Claims

1. A method for preparing bio-oil, characterized in that, Includes the following steps: (1) The pulverized lignocellulosic biomass is mixed with a hollow molecular sieve loaded with metal and then fed into a reactor for thermal pyrolysis in an inert gas atmosphere. The cavity volume of the hollow molecular sieve accounts for 60-70% of the total volume of the hollow molecular sieve. The silicon-aluminum molar ratio of the hollow molecular sieve is 25-100. The mass ratio of the metal loaded in the hollow molecular sieve to the hollow molecular sieve is 0.5:99.5-10:

90. The metal is at least one of iron, cobalt, nickel, zinc and gallium. The hollow molecular sieve is a molecular sieve with three-dimensional cross channels and a pore size of 5-7.5 Å. The hollow molecular sieve is prepared by the following steps: the hollow molecular sieve loaded with metal on the surface is mixed with a quaternary ammonium alkali solution and then heated to react. The hollow molecular sieve after reaction is separated, dried and calcined to obtain the hollow molecular sieve loaded with metal inside. (2) Condense the gas obtained in step (1).

2. The method as described in claim 1, characterized in that, The mass ratio of the lignocellulose biomass to the hollow molecular sieve with internally loaded metal is 1:0.5 to 1:

10.

3. The method as described in claim 2, characterized in that, The weight ratio of the lignocellulose biomass to the hollow molecular sieve with internally loaded metal is 1:0.5~1:2; The thermal decomposition specifically includes: Thermal decomposition was carried out under reaction conditions of 450~600℃.

4. The method as described in claim 1, characterized in that, The hollow molecular sieve has a cavity volume that accounts for 64-69% of the total volume of the hollow molecular sieve; The silicon-aluminum molar ratio of the hollow molecular sieve is 40-60.

5. The method as described in claim 1, characterized in that, The mass ratio of the metal loaded in the hollow molecular sieve to the hollow molecular sieve is 1:99 to 5:

95.

6. The method as described in claim 1, characterized in that, The hollow molecular sieve with surface-loaded metal is prepared by the following steps: mixing and impregnating a metal salt solution with a hollow molecular sieve to obtain a hollow molecular sieve with surface-loaded metal, wherein the metal salt is an inorganic metal salt or a metal complex salt. The process of mixing the hollow molecular sieve with surface-loaded metal with a quaternary ammonium alkali solution and then heating it for reaction specifically includes: Hollow molecular sieves with surface-loaded metal are mixed with quaternary ammonium alkali solution and heated to 100-200℃ for 27-96 hours.

7. The method as described in claim 6, characterized in that, The metal salt is at least one of nitrate, chloride, and sulfate; The process of mixing the hollow molecular sieve with surface-loaded metal with a quaternary ammonium alkali solution and then heating it for reaction specifically includes: Hollow molecular sieves with surface-loaded metal are mixed with quaternary ammonium alkali solution and heated to 150-180℃ for 48-72 hours.

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