A core-shell structured catalyst, a preparation method and use thereof

Abstract

A core-shell structured catalyst comprising: a metal nanoparticle, a non-acidic, spherically shaped inner core, and an acid, spherically shaped outer shell, wherein the metal nanoparticle is supported on the spherically shaped inner core. Also disclosed is a method for preparing the core-shell structured catalyst and use thereof for the hydrodeoxygenation of guaiacol to produce an oxygen-free, polycyclic, high-density fuel precursor.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of catalysts, and particularly relates to a core-shell structure catalyst, a preparation method thereof, and an application thereof to high-density fuel synthesis. BACKGROUND

[0002] Biomass high-density fuel is a liquid hydrocarbon fuel with the characteristics of high density (usually > 0.8 g / mL) synthesized from biomass. These fuels are mostly based on compounds with ring structures and potential C-C coupling functions. Unlike conventional biofuels, these biomass high-density fuels usually have cyclic carbon skeleton structures, increasing the ring strain, i.e., the fuel combustion can release more energy, giving the loading device more range and load. In order to obtain fuel molecules with cyclic skeleton structures, the selection of raw materials tends to choose substances with cyclic structures, such as pinene, cyclohexene, norbornene, phenol, guaiacol, anisole, cyclohexanone, cyclopentanone, cyclopentanol, cyclohexanol, cyclopentene, etc., or precursors that can synthesize these cyclic substances through one or more steps, such as 5-hydroxyfurfural, furfuryl alcohol, methylfurfural, 2,5-hexanedione, etc.; in the synthesis method, C-C coupling is a common method for increasing the ring of biomass high-density fuel molecular structure, usually including alkylation, aldol condensation, oligomerization, Diels-Alder reaction, etc. Through the selection of these specific raw materials and key methods, double-ring to five-ring annular alkanes or even more complex high-density fuels can be synthesized (Design and synthesis. John Wiley & Sons, 2020.).

[0003] Guaiacol, as a lignin derivative, is a typical raw material for the synthesis of high-density fuels from biomass. There are reports on the conversion of guaiacol and other components to prepare high-density fuels; such as guaiacol and cyclic alcohol compounds to prepare bicycloalkanes through two steps of alkylation-hydrodeoxygenation (Chem. Eng. Sci. 207 (2019): 441-447; Chem. Eng. Sci. 158 (2017): 64-69.), or dicyclohexylmethane and perhydrofluorene (Chem. Eng. Sci. 173 (2017): 91-97); guaiacol and furan to synthesize alkyl-substituted cyclohexane (Fuel Process. Tech. 163 (2017): 45-50.). Although the literature (Chem. Commun. 46 (2010): 412-414) reported that cyclohexane could be obtained by hydrodeoxygenation with guaiacol as a single raw material, there was no report on the synthesis of polycyclic high-density fuels with guaiacol as a single raw material; and in the conversion of guaiacol, the PhO-Me bond needs to be broken at high temperature and strong acid, which is a relatively harsh condition (Mol. Catal. 441 (2017): 28-34). At present, all the reports on the synthesis of high-density fuels from biomass are through C-C coupling to synthesize high-density fuel precursors, and then to synthesize high-density fuels from these precursors; the intermediates are transferred, and different catalysts are used in each stage, which increases the complexity of preparation; especially in the process of hydrodeoxygenation of high-density fuel precursors, because the temperature is relatively high, the consumption of catalyst is large, which often causes the sintering of reduced nanoparticles. There is no report on the one-step synthesis of high-density fuel precursors from guaiacol as a single raw material.

[0004] Core-shell structured nanomaterials are widely used in the field of catalysis. A large number of patents and doctoral theses have reported core-shell structures, such as patents CN118179588A and CN118002194A, which disclose a porous inner core loaded with metal and a porous outer shell without metal, but the inner core is not hollow, increasing the mass transfer resistance. Patents CN118186478A, CN118117088A, CN118079916A, and CN110064399A disclose a core-shell structure material with metal or metal oxide as the core and metal oxide as the shell. The metal or metal oxide core only has the core surface that plays a catalytic role, and the utilization rate is relatively low. This structure is not suitable for macromolecular reactions. Patent CN117983289A discloses a core-shell structure HMOR@AlPO4-11 composite molecular sieve catalyst with HMOR molecular sieve as the core and AlPO4-11 molecular sieve as the shell, but does not report the effect of introducing metal, and the core is not hollow, and resistance still exists. Patents CN106910907B, CN105749908B, CN105749908A, CN116371407A, CN106910907A, and literature (Hebei University, 2023. DOI:10.27103 / d.cnki.ghebu.2023.002557.) report a "yolk-eggshell" structure core-shell catalyst that can reduce the mass transfer resistance between the shell and the core. However, the utilization rate of the core is limited to the surface of the core or the core is not hollow, and the mass transfer resistance still exists, which is not suitable for macromolecular reactions. Therefore, hollow core structure has become a research hotspot. CN110316740A, CN112808282B, CN116328757A, CN116328757A, CN115920976A, CN118079958A, CN110316740A, CN104475124A, CN103752328B, and literature (Jilin University, 2022. DOI:10.27162 / d.cnki.gjlin.2021.000702.), literature (Zhejiang University of Technology, 2022. DOI:10.27786 / d.cnki.gzjlg.2021.000172.) report hollow core-shell structure catalysts, but none of them play the role of reducing metal in the structure. CN115254171B and CN114260013B introduce reducing metal into the core or shell layer of the core-shell structure, but there is no catalyst with an acidic outer shell structure.

[0005] In summary, there is no hollow non-acidic porous inner core and strong acidic porous outer shell structure catalyst in the currently reported core-shell structure catalysts; and these catalysts are not used in the preparation of high-density fuel precursors from biomass. In addition, the preparation methods of hollow structure catalysts reported in the literature mostly use hard template method, with carbon sphere as the center template, or with silica or aluminum oxide as the template for strong alkali or strong acid treatment to remove, etc. (Chem. Soc. Rev., 2020, 49, 2937; Chinese J. Catal. 36 (2015): 683-691; Sci. Technol. Adv. Mat. 15.4 (2014): 043502) increase the complexity of catalyst preparation.

[0006] To solve the above problems, the present application is proposed. SUMMARY

[0007] The present application first prepares a non-acidic spherical shell inner core and an acidic spherical shell outer shell loaded with metal nanoparticles, and the inner core shell wall and the outer shell shell wall have pores. The catalyst is used to directly prepare high-density fuel precursors from guaiacol as a single raw material in one pot, and the obtained high-density fuel precursors do not contain oxygen; the high-density fuel precursors are directly hydrogenated to obtain high-density fuel, which is easy to realize under mild conditions.

[0008] The technical scheme of the present application is as follows:

[0009] The first aspect of the present application discloses a core-shell structure catalyst, which comprises: metal nanoparticles, a non-acidic spherical shell inner core and an acidic spherical shell outer shell, wherein the metal nanoparticles are loaded on the spherical shell inner core. The inner core shell wall has a hollow cavity, and the inner core and the outer shell can be regular spherical shell or irregular spherical shell, such as ellipsoidal shell, flat spherical shell or other irregular spherical shell.

[0010] Preferably, the inner core shell wall has pores with a pore size of 0.5 nm-30 nm, the average diameter of the hollow cavity in the inner core shell wall is 5-200 nm, and the thickness of the inner core shell wall is 5-100 nm; the outer shell shell wall also has pores, and the pore size gradually decreases from 5 nm-100 nm to 0.5 nm-30 nm from the outside to the inside, and the thickness of the outer shell shell wall is 5-500 nm. The pores on the inner core shell wall and the pores on the outer shell shell wall are interconnected.

[0011] Preferably, the core is one or several of silicon dioxide, titanium dioxide, zirconium dioxide, cerium dioxide, magnesium oxide, calcium oxide, zinc oxide or pure silicon molecular sieve, the metal nanoparticles are one or more than one, the ratio of the metal nanoparticles to the core is 5wt% to 50wt% (the numerator is the mass of the metal nanoparticles, and the denominator is the core not containing the metal nanoparticles); the shell is one or more molecular sieves, one or more metal oxides, or a composite of one or more metal oxides and silicon dioxide, or a composite of one or more molecular sieves and silicon dioxide.

[0012] Preferably, the core-shell structure catalyst comprises: Ni / SiO2@NbWOx, Ni / SiO2@Al-MCM-41, Au / Silicalite-1@WO3, Ni / TiO2@Al-SBA-15, RuNiCu / ZrO2@Al-SBA-16, NiFe / MgO@Ti-MCM-41, Ni / SBA-15@HY, Ni / SiO2@Hβ, Ir / SBA-16@HZSM-5, NiCo / SiO2@Al2O3, Pt / MCM-48@Nb2O5, RuNiCu / ZrO2@SiO2-Al2O3, NiFe / MgO@CsTPA, Pt / ZnO@HfTPA / MCM-41, RuNi / CeO2@SiO2-Nb2O5, RhFe / MCM-41@MOF-808-2.5SO4, PtCu / MCM-22@HfTPA, RuMo / SiO2@SnTPA, RuNiCu / SiO2@ZrTPA, NiCoMo / Si-CeOx@SO4 2- / ZrO2, NiZn / Ce-MgO x @ITQ, NiIr / Ce-MgO x @KIT-6, Au / Silicalite-1@Mordenite, Ni / SiO2@MMT-K10, Ni / TiO2@HPW / MCM-41. The above expression mode a / b@c, wherein a / b before @ represents that the metal nanoparticles a are loaded on the core b; c after @ represents the shell, and c represents the shell component; the above expression mode a / b@c / d, wherein a / b before @ represents that the metal nanoparticles a are loaded on the core b; c / d after @ represents the composite of the shell components c and d.

[0013] The second aspect of the present application discloses a preparation method of the core-shell structure catalyst, comprising the following steps:

[0014] (1) adding a first surfactant to an aqueous solution containing ammonia and ethanol, adding an emulsifier, and converting the mixture into an emulsion by ultrasonic; heating, adding a core precursor, a metal precursor and ethanol under stirring; transferring into a closed container for hydrothermal crystallization for a period of time, and solid-liquid separation to obtain a solid powder;

[0015] (2) adding the solid powder obtained in step (1) and a second surfactant into alcohol and mixing uniformly, then adding a shell precursor and continuing to mix uniformly; then adding water and continuing to mix to obtain a sol; gelling the obtained sol at a certain temperature for a period of time, then heating and drying for a period of time, and calcining to obtain the core-shell structure catalyst precursor; or,

[0016] adding a certain amount of a third surfactant into water and dissolving, then adding the solid powder obtained in step (1) and mixing uniformly, then adding a shell precursor and continuing to mix; adjusting the pH value of the solution to 10-11, then transferring into a closed container for hydrothermal crystallization at a certain temperature for a period of time, then solid-liquid separation and calcining to obtain the core-shell structure catalyst precursor;

[0017] (3) reducing the core-shell structure catalyst precursor obtained in step (2) in a hydrogen atmosphere at a certain temperature for a period of time to obtain the core-shell structure catalyst.

[0018] Preferably, the first surfactant, the second surfactant and the third surfactant are independently: a polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123), a polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymer (F127), a polyvinylpyrrolidone (PVP), a polyethylene oxide (PEO), an oleylamine polyoxyethylene ether (PEG), a polypropylene oxide amide (PPG), a sorbitan monooleate polyoxyethylene ether (Tween 80), a sorbitan monooleate (Span 80), a dodecylphenol polyoxyethylene ether (OP-10), an isooctylphenyl polyoxyethylene ether (TX-100), an octadecyl alcohol polyoxyethylene ether (Brij 76), a fatty alcohol polyoxyethylene ether (AEO-9), a polyethylene glycol octylphenyl ether (Triton X-100), a coconut fatty acid monoethanolamide (CMEA), a C12-14 alkyl glucoside (APG), a fatty alcohol polyoxyethylene 3 / 7 / 9 ether (AEO-3 / 7 / 9), a nonylphenol polyoxyethylene ether (TX-4.5 / 6.5 / 10 / 15 / 20 / 40), Genapol UD-080, Genapol UD-080, triethanolamine monostearate (Emulsifier 4H), dodecyltrimethylammonium chloride (DTAC), dodecyltrimethylammonium bromide (DTAB), hexadecyltrimethylammonium chloride (CTAC), hexadecyltrimethylammonium bromide (CTAB), tetrabutylammonium hydroxide (TBAOH), tetrapropylammonium hydroxide (TPAOH), dodecyldimethylbenzylammonium chloride (DDAC), dodecyldimethylbenzylammonium bromide (DDAB), behenyltrimethylammonium methylsulfate (BTMS), alkylpyridines, alkylmorpholines, alkylimidazolines, alkylazepines, lauryl amidopropylamine oxide (AMP), cocamidopropyl betaine (DEHYTON K), dodecylpropyl betaine (BS-12), dodecyldimethylamine oxide (OA-12), cocamidopropyl dimethyl betaine (CAB-35), cocamidopropyl hydroxysultaine (CHS-35), cocylimidazoline (CAMA-30), peregal O-9 (AEO-9), sodium dodecyl sulfate (SDS), secondary alkyl sulfates (Teep01), fatty alcohol sulfates (FAS), fatty alcohol ethoxysulfates (AES), alpha-sulfated fatty acid disodium salt (DSFA), dodecylphosphonate (MAP-85), dodecylphosphonate potassium salt (MAP-K), dodecylphosphonate triethanolamine (MAP-A), sodium tetrapolypropylene benzene sulfonate (ABS), sodium alkyl benzene sulfonate (LAS), sodium dodecyl benzene sulfonate (SDBS), primary alkyl sulfonates (AS), secondary alkyl sulfonates (SAS), alpha-olefin sulfonates (AOS), alpha-sulfo fatty acid methyl ester (MES), fatty acid sulfoalkyl ester (1gepon A), fatty acid sulfoalkyl amide (1gepon T), sodium diisooctyl sulfosuccinate (Aerosol OT), alkyl glyceryl ether sulfonate (AGS), sodium dibutyl naphthalene sulfonate (penetrant BX), sodium p-methoxy fatty amido benzene sulfonate (detergent LS), sodium methylene bis naphthalene sulfonate (NNO), fatty acid methyl ester sulfonate (MES), fatty acid sodium (SOAP), Lamepon A, sodium carboxymethylcellulose (SCMC), sodium fatty acyl sarcosinate (DX107) at a concentration of 0.1% (w / v) to 10% (w / v).

[0019] Preferably, the emulsifier in step (1) is a liquid alkane; the core precursor is one or more of 1,2-bis(triethoxysilyl)ethane, tetrabutyl titanate, tetraethyl silicate, titanium oxalate, zirconium chloride, cerium nitrate, zinc oxalate, magnesium chloride, and calcium chloride; the ultrasonic power is greater than 20 kHz; the stirring rate is greater than 1000 rpm; the hydrothermal crystallization temperature is 100-200℃, and the time is 24h-120h; the metal precursor is a salt of a metal with hydrogenation activity, such as nitrate, sulfate, hydrochloride, organic acid salt, or acetylacetonated metal, etc.; the hydrogen flow rate during the reduction of the core-shell structure catalyst precursor in step (3) in the atmosphere furnace is less than 200 SCCM; the hydrogen pressure in the fixed bed is not greater than 4 MPa, or at atmospheric pressure, the temperature is 350℃-600℃, and the time is 1-6h.

[0020] Preferably, the alcohol used in step (2) is 1-propanol or 2-propanol; the gelation temperature is 45-180℃, and the time is 1-12 days; the drying temperature is 90℃-120℃, and the time is 10-24h; the calcination temperature is 350℃-800℃, and the time is more than 2h.

[0021] Preferably, in step (2), the hydrothermal crystallization temperature is 100-200℃ and the time is 24-120h; the calcination temperature is 350℃-800℃ and the time is more than 2h.

[0022] The core-shell structured catalyst described in the third aspect of this invention is used for the one-pot hydrodeoxygenation of guaiacol as a single feedstock to prepare an oxygen-free polycyclic high-density fuel precursor.

[0023] The beneficial effects of this invention are:

[0024] 1. This invention is the first to prepare a core-shell structured catalyst, in which the pores on the core shell wall and the pores on the outer shell wall are interconnected, such as... Figure 1 and Figure 2 As shown, this increases the permeability of the pores. Used in catalytic reactions, this reduces mass transfer resistance and improves mass transfer efficiency. The catalyst of this invention solves the problems of high mass transfer resistance in the solid core, poor permeability between the core and shell, and high mass transfer resistance in macromolecule synthesis found in existing technologies.

[0025] 2. The core-shell catalyst of this invention has a non-acidic core loaded with metal nanoparticles capable of catalytic hydrogenation; the outer shell is enhanced with molecular sieves or strongly acidic metal oxides, resulting in a strongly acidic outer shell. When used in catalytic reactions, it effectively solves the problem of requiring strong acidity to break the PhO-Me bond, thereby effectively reducing the reaction temperature.

[0026] 3. The core-shell structure catalyst of the present application is used for catalyzing the catalytic reaction of guaiacol as a single raw material to prepare high-density fuel precursors in one pot, and the conversion rate of guaiacol is 100%; the yield of the fuel precursors is not less than 90%, and can be as high as 99%; guaiacol is basically converted into dimers and trimers, and the mass ratio of the trimers can reach or be close to 90%, such as 88%.

[0027] 4. The preparation method of the core-shell structure catalyst of the present application uses the microemulsion method and prepares the hollow spherical shell inner core through the centrifugation step and the subsequent high-temperature calcination step; at the same time, the surfactant acting as a template is removed through the calcination step to form the interconnected pores on the shell wall of the inner core and the shell wall of the outer shell, thereby solving the problems of the existing technology, such as the large mass transfer resistance of the solid inner core, the poor permeability between the core-shell layers, and the large mass transfer resistance of the macromolecular synthesis. In the preparation method of the present application, the metal precursor is directly introduced in the preparation of the inner core, and the metal is introduced in the inner core and the outer shell after the coating of the outer shell, which constitutes the protection and limitation of the metal precursor, prevents the sintering of the metal nanoparticles, and improves the dispersibility of the metal nanoparticles and the service life of the catalyst. In the preparation method of the present application, the inner core and the shell layer are orderly synthesized at a lower temperature through the combination of the emulsion method and the sol-gel method, or the combination of the emulsion method and the hydrothermal crystallization method, and the catalyst is prepared through calcination and reduction of H2, thereby simplifying the preparation process of the catalyst; the preparation process conditions are mild, and the method is simple and easy to implement.

[0028] 5. The core-shell structure catalyst of the present application is used for the catalytic reaction of guaiacol to prepare high-density fuel precursors, and the guaiacol is directly used as a single raw material to obtain the oxygen-free polycyclic high-density fuel precursors through one-pot series hydrogenation and deoxidation and polymerization, and the fuel precursors are saturated through hydrogenation to obtain high-density fuels, which are easy to implement under mild conditions. In the preparation process of the fuel precursors of the present application, the intermediate is avoided to be obtained and separated and transferred, and the synthesis process is simplified. Therefore, the core-shell structure catalyst of the present application is used for the catalytic reaction of guaiacol to prepare high-density fuel precursors, and the guaiacol is directly used as a single raw material to synthesize polycyclic high-density fuels, which fills the blank of the direct synthesis of polycyclic high-density fuels from phenolic compounds as a single raw material, and improves the catalytic efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 It is a schematic diagram of the core-shell structure catalyst of the present application.

[0030] Figure 2 It is a TEM diagram of the core-shell structure catalyst obtained in Example 1.

[0031] Figure 3 It is a process schematic diagram of the core-shell structure catalyst of the present application for the synthesis of polycyclic high-density fuel precursors from guaiacol as a single raw material.

[0032] Figure 4 GC-MS chart of the main product obtained by hydrodeoxygenation and polymerization of guaiacol.

[0033] Figure 5 Figure 4 Molecular structure corresponding to the polycyclic high-density fuel precursor in DETAILED DESCRIPTION

[0034] The technical solutions of the present application are described in detail below in combination with specific examples. The raw materials used in the examples are all commercial products unless otherwise specified; the processes used are all conventional processes in the art unless otherwise specified.

[0035] Example 1: Preparation of a core-shell structure catalyst.

[0036] (1) The inner core was prepared by a microemulsion method: 2.0 g of CTAB was dissolved in a mixed solution of 350 mL of water, 35 mL of ethanol, and 20 mL of concentrated ammonia (25 wt%), followed by the addition of 5 mL of decane; the mixture was converted into an emulsion by ultrasonication at 40 kHz for 20 min; the temperature was raised to 100°C, and 2.5 mL of 1,2-bis(triethoxysilyl)ethane, 0.10 g of nickel acetylacetonate, and 7.5 mL of ethanol were added under stirring at 1100 rpm; after continuous stirring for 2 h, the mixture was transferred into a reaction kettle with a polytetrafluoroethylene inner liner for hydrothermal crystallization under autogenous pressure for 24 h; the solid was collected by centrifugation, washed with water three times, and dried in a 100°C drying oven for 12 h to obtain a solid powder;

[0037] (2) The core-shell structure catalyst precursor was prepared by a sol-gel method, including the following steps: 1 g of the solid powder obtained in step (1) and 1 g of the surfactant P123 were added to 10 g of anhydrous 1-propanol and mixed uniformly under stirring at 2000 rpm, followed by the addition of 3 mmol of niobium chloride and 3 mmol of tungsten chloride and continued stirring and mixing until uniform; then, 30 mmol of water was added and continued stirring and mixing to obtain a sol; the obtained sol was gelled in a petri dish at 50°C for 2 days, and then dried in a 100°C dryer for 12 h; then, the core-shell structure catalyst precursor with an outer shell of NbWOxwas obtained by calcination in a muffle furnace at 500°C for 5 hours;

[0038] (3) The core-shell structure catalyst precursor obtained in step (2) was reduced in a 450°C atmosphere furnace under a hydrogen atmosphere of 150 SCCM for 4 h to obtain a core-shell structure catalyst, which was Ni / SiO2@NbWOx.

[0039] Figure 2 TEM chart of the obtained core-shell structure catalyst. As can be seen from Figure 2 The obtained core-shell structure catalyst has an irregular spherical inner core and an irregular spherical outer shell, and there are pores on the inner core shell wall and the outer shell wall.​

[0040] Example 2: Using the Ni / SiO2@NbWOx core-shell structure catalyst obtained in Example 1 for catalytic reaction of preparing high-density fuel precursors from guaiacol as a single raw material.

[0041] The core-shell structure catalyst obtained in Example 1 is used in the hydrodeoxygenation reaction of guaiacol in a batch high-pressure reactor or a fixed bed reactor to prepare oxygen-free polycyclic high-density fuel precursors in one step. The process schematic diagram is shown in Figure 3 The specific steps are as follows:

[0042] 25 g of guaiacol and 3 g of the core-shell structure catalyst Ni / SiO2@NbWOx obtained in Example 1 are added into a high-pressure reactor, the air is replaced with nitrogen for three times, 4 MPa of hydrogen is injected, mechanical stirring is performed at 600 rpm, and the reaction is performed at 250℃ for 15 h; after the reaction is completed, the catalyst is separated when the temperature drops to room temperature. The analysis results are as follows: the conversion rate of guaiacol is 100%, the yield of fuel precursors is 98%, the mass ratio of dimers is 41%, and the mass ratio of trimers is 59%. The GC-MS diagram of the main product is shown in Figure 4 and Figure 5 .

[0043] Example 3: Preparation of a core-shell structure catalyst.

[0044] (1) The same as step (1) of Example 1.

[0045] (2) The core-shell structure catalyst precursor is prepared by a hydrothermal crystallization method, including the following steps: 1.8 g of CTAB is dissolved in 70 mL of water, heated and stirred to form a transparent solution, and left to stand for 10 min; 1 g of the powder of step (1), 0.2 g of aluminum nitrate, and 5.7 g of sodium silicate are sequentially added under continuous stirring to make them uniformly mixed, and the stirring is continued for 2 h; the pH of the solution is adjusted to about 10.50 with a 2 mol / L sulfuric acid solution, and the stirring is continued for 0.5 h to form a uniform phase, and then the pH is adjusted again to about 10.50; then it is moved into a sealed stainless steel reactor with a polytetrafluoroethylene liner, and hydrothermal crystallization is performed at 120℃ for 72 h; after the hydrothermal crystallization is completed, the product is filtered, washed with water, dried at 80℃, and calcined at 550℃ for 10 h to obtain a core-shell structure catalyst precursor with an outer shell of Al-MCM-41.

[0046] (3) The same as step (3) of Example 1, and the core-shell structure catalyst obtained is Ni / SiO2@Al-MCM-41.

[0047] Example 4: Using the Ni / SiO2@Al-MCM-41 core-shell structure catalyst obtained in Example 3 for catalytic reaction of preparing high-density fuel precursors from guaiacol as a single raw material.

[0048] The core-shell structured catalyst obtained in Example 1 was used in the hydrodeoxygenation reaction of guaiacol to produce oxygen-free polycyclic high-density fuel precursors in one step in a batch high-pressure reactor or a fixed-bed reactor. The process schematic is shown in Figure 3 The specific steps are as follows:

[0049] 25 g of guaiacol and 5 g of the core-shell structured catalyst Ni / SiO2@Al-MCM-41 obtained in Example 3 were added to a high-pressure reactor, the air was replaced with nitrogen three times, 4 MPa of hydrogen was injected, mechanical stirring was performed at 600 rpm, and the reaction was performed at 250°C for 15 h. After the reaction, the catalyst was separated when the temperature dropped to room temperature. The analysis results were as follows: the conversion rate of guaiacol was 100%, the yield of fuel precursors was 96%, the mass fraction of dimers was 45%, and the mass fraction of trimers was 55%.

[0050] The results of using other core-shell structured catalysts of the application to catalyze the preparation of fuel precursors from guaiacol under different conditions are shown in Table 1. The preparation methods of the other core-shell structured catalysts are the same as those in Example 1 or Example 3.

[0051] Table 1 Preparation of fuel precursors from guaiacol

[0052]

[0053] As can be seen from Table 1, guaiacol can be used to produce fuel precursors in Ni / SiO2@NbWOx, Ni / SiO2@Al-MCM-41, Au / Silicalite-1@WO3, Ni / TiO2@Al-SBA-15, RuNiCu / ZrO2@Al-SBA-16, NiFe / MgO@Ti-MCM-41, Ni / SBA-15@HY, Ni / SiO2@Hβ, Ir / SBA-16@HZSM-5, NiCo / SiO2@Al2O3, Pt / MCM-48@Nb2O5, RuNiCu / ZrO2@SiO2-Al2O3, NiFe / MgO@CsTPA, Pt / ZnO@HfTPA / MCM-41, RuNi / CeO2@SiO2-Nb2O5, RhFe / MCM-41@MOF-808-2.5SO4, PtCu / MCM-22@HfTPA, RuMo / SiO2@SnTPA, RuNiCu / SiO2@ZrTPA, NiCoMo / Si-CeOx@SO4 2- / ZrO2, NiZn / Ce-MgO x @ITQ, NiIr / Ce-MgO xThe raw material conversion rate is 100%, the yield of fuel precursor is not less than 90%, and the mass ratio of the trimer can reach 88% under the catalysis of KIT-6, Au / Silicalite-1, Mordenite, Ni / SiO2, MMT-K10, Ni / TiO2, HPW / MCM-41, etc. at a temperature range of 180-300 ℃ and a hydrogen pressure of 3-6 MPa.

[0054] Finally, it should be noted that: the above examples are used to illustrate the technical solutions of the present application, but not to limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. The use of a core-shell structured catalyst for the hydrodeoxygenation of guaiacol to prepare an oxygen-free polycyclic high-density fuel precursor, characterized in that, The core-shell structured catalyst comprises: metal nanoparticles, a non-acidic spherical core, and an acidic spherical outer shell, wherein the metal nanoparticles are loaded on the spherical core; the core shell wall has pores with a pore size of 0.5 nm-30 nm, the average diameter of the hollow cavity within the core shell wall is 5-200 nm, and the thickness of the core shell wall is 5-100 nm; the outer shell wall also has pores, with the pore size gradually decreasing from 5 nm-100 nm to 0.5 nm-30 nm from the outside to the inside, and the thickness of the outer shell wall is 5-500 nm; the core is silicon dioxide, and the metal nanoparticles account for 5 wt% to 50 wt% of the core; the core-shell structured catalyst is: Ni / SiO2@NbWO x One or more of Ni / SiO2@Al-MCM-41, Ni / SiO2@Hβ, NiCo / SiO2@Al2O3, or Ni / SiO2@MMT-K10.

2. The use according to claim 1, characterized in that, The preparation method of the core-shell structured catalyst includes the following steps: (1) Add the first surfactant to an aqueous solution containing ammonia and ethanol, add an emulsifier, and use ultrasound to convert the mixture into an emulsion; The temperature is increased, and a core precursor, a metal precursor, and ethanol are added under stirring; the mixture is then transferred to a sealed container for hydrothermal crystallization for a period of time, followed by solid-liquid separation to obtain a solid powder. The emulsifier is a liquid alkane. (2) Add the solid powder and the second surfactant obtained in step (1) to the alcohol and mix evenly, then add the shell precursor and continue mixing evenly; then add water and continue mixing to obtain a sol; gel the obtained sol at a certain temperature for a period of time, then heat and dry for a period of time, and calcine to obtain the core-shell structured catalyst precursor; or, A certain amount of the third surfactant was added to the water to dissolve, and the solid powder obtained in step (1) was added and mixed evenly. Then the shell precursor was added and the mixture was continued to be mixed. The pH value of the solution was adjusted to 10-11, and then it was transferred to a sealed container and hydrothermally crystallized at a certain temperature for a period of time. After solid-liquid separation, it was calcined to obtain the core-shell structure catalyst precursor. (3) The core-shell structure catalyst precursor obtained in step (2) is reduced in a hydrogen atmosphere at a certain temperature for a period of time to obtain the core-shell structure catalyst.

3. The use according to claim 2, characterized in that, The first, second, and third surfactants are each independently one or more of the following: polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymer, polyvinylpyrrolidone, octadecyl alcohol polyoxyethylene ether, dodecyl trimethylammonium chloride, dodecyl trimethylammonium bromide, hexadecyl trimethylammonium chloride, hexadecyl trimethylammonium bromide, tetrabutylammonium hydroxide, tetrapropylammonium hydroxide, dodecyl dimethyl benzyl ammonium chloride, or dodecyl dimethyl benzyl ammonium bromide, with a surfactant concentration of 0.1% w / v to 10% w / v.

4. The use according to claim 2, characterized in that, Step (1) The core precursor is one or both of 1,2-bis(triethoxysilyl)ethane or tetraethyl silicate; the ultrasonic power is greater than 20 kHz; the stirring rate is greater than 1000 rpm; the hydrothermal crystallization temperature is 100-200℃ and the time is 24h-120h; Step (3) The hydrogen flow rate during the reduction of the core-shell structure catalyst precursor in the atmosphere furnace is less than 200 SCCM; the hydrogen pressure in the fixed bed is not greater than 4 MPa, the temperature is 350℃-600℃, and the time is 1-6h.

5. The use according to claim 2, characterized in that, The alcohol used in step (2) is 1-propanol or 2-propanol; the gelation temperature is 45-180℃ and the time is 1-12 days; the drying temperature is 90℃-120℃ and the time is 10-24 h; the calcination temperature is 350℃-800℃ and the time is more than 2 h.

6. The use according to claim 2, characterized in that, Step (2) Hydrothermal crystallization temperature 100-200℃, time 24-120h.

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