A catalyst with selectively supported ruthenium on its outer surface, its preparation method and application

Abstract

This invention belongs to the field of biomass catalysis technology and discloses a catalyst with selectively supported ruthenium on its outer surface, its preparation method, and its application. Specifically: (1) Tetrapropylammonium hydroxide is dissolved in deionized water, aluminum isopropoxide is added, then niobium ethoxy is added dropwise, and stirring is continued; finally, tetraethyl silicate is added dropwise, and stirring is carried out to form a gel; the gel is subjected to hydrothermal reaction, the dried product is calcined in air and then ground to obtain the support NbAlS; (2) A metal precursor solution is prepared using tris(2,2'-bipyridine)ruthenium chloride complex, the support NbAlS is added to the precursor solution, stirred at room temperature, vacuum dried and then ground and placed in a tube furnace for calcination to obtain the catalyst Ru-NbAlS-2. This invention solves the problems of low selectivity of existing catalysts for lignin pyrolysis products and easy deep hydrogenation of aromatic rings.

Description

Technical Field

[0001] This invention relates to the field of biomass catalysis technology, and more specifically to a catalyst with selectively supported active noble metal ruthenium on its outer surface, a method for preparing the catalyst, and the application of the catalyst in the hydrogenation cracking of lignin model compounds such as benzylphenyl ether to prepare high-value-added aromatic compounds. Background Technology

[0002] With the depletion of fossil fuels and the escalation of environmental problems, biomass, as a renewable resource, has significant potential in replacing fossil fuels to produce high-value-added chemicals. Lignin, one of the main components of biomass, has a complex structure, and its efficient and targeted conversion into aromatic compounds is a current research challenge.

[0003] Existing methods for lignin degradation mainly include pyrolysis, microwave-assisted degradation, and acid-base catalytic degradation, but they have many shortcomings: pyrolysis and microwave degradation have high energy consumption, complex products, and low selectivity for aromatic compounds; acid-base catalytic degradation requires high temperature and high pressure conditions and uses corrosive reagents, which pollute the environment.

[0004] Therefore, it is of great significance to develop a highly selective lignin hydrocracking catalyst under mild conditions. Summary of the Invention

[0005] In view of this, the present invention provides a catalyst with selectively supported ruthenium on its outer surface, its preparation method and application.

[0006] The purpose of this invention is to provide a catalyst with selectively supported ruthenium on its outer surface and its preparation method, solving the problems of low selectivity and easy deep hydrogenation of aromatic rings in existing catalysts for lignin pyrolysis products. Simultaneously, this invention provides the application of this catalyst in the hydrocracking of lignin model compounds, achieving highly selective preparation of high-value aromatic compounds such as benzene, phenol, and toluene.

[0007] One objective of this invention is to provide a method for preparing a catalyst with selectively supported ruthenium on its outer surface, the specific steps of which are as follows:

[0008] (1) Preparation of niobium-doped molecular sieve support NbAlS: Tetrapropylammonium hydroxide was dissolved in deionized water and magnetically stirred until completely dissolved. Aluminum isopropoxide was added and stirred until dissolved. Then, niobium ethoxy was added dropwise and stirred continuously. Finally, tetraethyl silicate was added dropwise and stirred continuously to form a gel. The gel was transferred to a hydrothermal reactor and centrifuged after hydrothermal reaction at 5000 r / min for 5 min. The gel was washed three times with deionized water and vacuum dried at 80 °C. The dried product was placed in a high-temperature furnace, calcined in air, and then ground to obtain the support NbAlS.

[0009] (2) Preparation of ruthenium catalyst with selective external surface support: Using tris(2,2'-bipyridine)ruthenium chloride complex as a precursor, a metal precursor solution was prepared by dissolving it in deionized water. The support NbAlS was added to the precursor solution, stirred at room temperature for a certain time, dried under vacuum at 120°C, and then ground into powder. The powder was placed in a quartz boat and calcined in a tube furnace to obtain the catalyst Ru-NbAlS-2 with selective external surface support of ruthenium.

[0010] Preferably, the volume ratio of tetrapropylammonium hydroxide to deionized water is 1 mL:2 mL; the concentration of aluminum isopropoxide in deionized water is 11.032 mg / mL; the concentration of niobium ethoxylate in deionized water is 136 μL / mL; and the volume ratio of tetraethyl silicate to deionized water is 4.47 mL:10 mL.

[0011] Preferably, the stirring and dissolving process is carried out for 2 hours, the continued stirring is carried out for 2 hours, and the continuous stirring is carried out for 24 hours.

[0012] Preferably, the hydrothermal reaction is aging and crystallization at 170°C for 72 hours, and the air calcination is air calcination at 550°C for 6 hours.

[0013] Preferably, the concentration of tris(2,2'-bipyridine)ruthenium chloride complex in the metal precursor solution is 3.70 mmol / L, and the ruthenium loading on the NbAlS support is 5%; the stirring at room temperature is 6 h.

[0014] Preferably, the specific operation of the tubular furnace calcination is as follows: calcination at 250°C for 3 hours under a nitrogen atmosphere, with a nitrogen flow rate of 50 mL / min and a heating rate of 2°C / min; then switching to a hydrogen atmosphere and reduction at 450°C for 3 hours, with a hydrogen flow rate of 50 mL / min and a heating rate of 2°C / min.

[0015] A second objective of this invention is to provide a catalyst with selectively supported ruthenium on its outer surface obtained by the above preparation method.

[0016] A third objective of this invention is to provide an application of a catalyst with selectively supported ruthenium on its external surface in the hydrogenolysis of biomass to prepare high-value-added aromatic compounds. Specifically, biomass and the catalyst are added to methanol, a reaction vessel is installed and its airtightness is checked, hydrogen gas is introduced to purge air from the vessel, and the hydrogenation reaction is carried out at a reaction temperature of 130°C and a hydrogen pressure of 1.5 MPa. After the reaction, the reaction vessel is cooled to room temperature, the product is removed, and filtered using a 0.46 μm nylon syringe filter. The product composition is analyzed using an Agilent 7890b gas chromatograph, and the product yield and conversion rate are calculated.

[0017] Preferably, the biomass includes, but is not limited to, benzylphenyl ether, diphenyl ether, and phenoxyethylbenzene.

[0018] Preferably, the ratio of the amount of biomass to the amount of catalyst is 1 mmol: 20 mg, and the ratio of the amount of biomass to the amount of methanol is 1 mmol: 15 mL.

[0019] As can be seen from the above technical solution, compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0020] 1. This invention uses a macromolecular ruthenium complex as a precursor to achieve selective loading of ruthenium on the outer surface of the NbAlS support, thus preventing ruthenium from entering the pores of the support.

[0021] 2. The ruthenium active sites loaded on the outer surface can reduce the mass transfer resistance of reactants and intermediates. After the products are generated, they quickly detach from the catalyst surface, effectively inhibiting the deep hydrogenation of aromatic rings and significantly improving the selectivity of high-value aromatic compounds such as toluene and phenol.

[0022] 3. The catalyst preparation process of the present invention is simple, the reaction conditions are mild, no high temperature and high pressure or corrosive reagents are required, it is green and environmentally friendly, and it is suitable for industrial promotion.

[0023] 4. The novel catalyst exhibits a much higher selectivity for aromatic compounds than the ruthenium-uniformly supported catalyst. For example, under optimal reaction conditions, the conversion rate of benzylphenyl ether can reach 99.99%, and the yields of toluene and phenol can reach 23% and 50%, respectively. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0025] Figure 1 The images show transmission electron microscopy (TEM) images of the 5% Ru-NbAlS-2 catalyst. Figure a is a HADDF image of a cross-section of the catalyst particles, and Figure b is a TEM-EDS image of a cross-section of the catalyst particles. It can be seen that the ruthenium particles are uniformly distributed on the outer surface of the support without agglomeration.

[0026] Figure 2 The images show transmission electron microscopy (TEM) images of the 5% Ru-NbAlS-1 catalyst. Figure a is a HADDF image of a cross-section of the catalyst particles, and Figure b is a TEM-EDS image of a cross-section of the catalyst particles. It can be seen that the ruthenium particles are uniformly distributed on the support without agglomeration.

[0027] Figure 3 The figures show the nitrogen adsorption-desorption isotherms of the support and catalyst, indicating that the support retains its mesoporous structure after ruthenium loading.

[0028] Figure 4 The diagram shows the pore size distribution of the support and catalyst, indicating that the support retains its mesoporous structure after ruthenium loading.

[0029] Figure 5 The gas chromatogram of the hydrogen pyrolysis product of benzylphenyl ether in Example 3 shows that toluene and phenol are the main products.

[0030] Figure 6 The gas chromatogram of the hydrogen pyrolysis products of benzylphenyl ether in Comparative Example 2 shows that toluene and phenol are the main products.

[0031] Figure 7 The gas chromatogram of the hydrogenation cracking products of diphenyl ether ether in Example 4 shows that acetophenone and phenol are the main products.

[0032] Figure 8 The gas chromatogram of the hydrogenation cracking products of diphenyl ether 3 in Comparative Example 3 shows that acetophenone and phenol are the main products.

[0033] Figure 9 The gas chromatogram of the hydrogen pyrolysis products of phenoxyethylbenzene in Example 5 shows that benzene and phenol are the main products.

[0034] Figure 10 The gas chromatogram of the hydrogen pyrolysis products of phenoxyethylbenzene in Comparative Example 4 shows that benzene and phenol are the main products. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] Example 1: Preparation of Niobium-Doped Molecular Sieves Support NbAlS

[0037] Take 10 mL of deionized water in a beaker, add 5 mL of tetrapropylammonium hydroxide, and stir to dissolve. Add 110.32 mg of aluminum isopropoxide and stir for 2 h until completely dissolved. Add 136 μL of niobium ethoxylate dropwise and stir for 2 h. Add 4.47 mL of tetraethyl silicate dropwise and stir for 24 h to form a gel. Transfer the gel to a hydrothermal reactor and age at 170 °C for 72 h to crystallize. Centrifuge at 5000 r / min for 5 min, wash three times with deionized water, and vacuum dry at 80 °C. Calcinate in air at 550 °C for 6 h, and grind to obtain the support NbAlS.

[0038] Example 2: Preparation of Ru-NbAlS-2 catalyst selectively supported on the outer surface

[0039] 41.5 mg of tris(2,2'-bipyridine)ruthenium chloride complex was dissolved in 15 mL of deionized water to prepare an aqueous solution as the precursor solution. 100 mg of the supported NbAlS was added to the precursor solution, and the mixture was stirred at room temperature for 6 h. After vacuum drying at 120 °C, the mixture was ground and placed in a tube furnace for calcination at 250 °C for 3 h under a nitrogen atmosphere (nitrogen flow rate 50 mL / min, heating rate 2 °C / min); followed by reduction at 450 °C for 3 h under a hydrogen atmosphere (hydrogen flow rate 50 mL / min, heating rate 2 °C / min). A Ru-NbAlS-2 catalyst with a 5% ruthenium loading was thus prepared.

[0040] Comparative Example 1: Preparation of conventional uniformly supported ruthenium catalyst Ru-NbAlS-1

[0041] 10.80 mg of ruthenium trichloride was dissolved in 15 mL of deionized water to prepare an aqueous solution as a precursor solution. 100 mg of the NbAlS support (Example 1) was added to the precursor solution and stirred at room temperature for 6 h. After vacuum drying at 120 °C, the solution was ground and placed in a tube furnace: calcined at 250 °C for 3 h under a nitrogen atmosphere (nitrogen flow rate 50 mL / min, heating rate 2 °C / min); then reduced at 250 °C for 3 h under a hydrogen atmosphere (hydrogen flow rate 50 mL / min, heating rate 2 °C / min). A conventional uniformly supported ruthenium catalyst was obtained, and a comparative catalyst of Ru-NbAlS-1 with a ruthenium loading of 5% was also prepared.

[0042] Example 3: Application of catalyst in the hydrogenation cracking of benzylphenyl ether

[0043] 1 mmol of benzylphenyl ether, 20 mg of 5% Ru-NbAlS-2 catalyst, and 15 mL of methanol were added to a reaction vessel. Hydrogen gas was introduced to purge air, and the reaction was carried out at 130 °C, 1.5 MPa, and for 3 h. After the reaction, the mixture was cooled, filtered, and the products were analyzed by gas chromatography. The results showed that the conversion rate of benzylphenyl ether was 99.99%, the yield of toluene was 23%, and the yield of phenol was 50%.

[0044] Comparative Example 2: Hydrocracking reaction using Ru-NbAlS-1 catalyst

[0045] The reaction conditions were the same as in Example 3, but the catalyst was replaced with Ru-NbAlS-1. The results showed that the products mainly consisted of cyclohexanol, cyclohexanone, and other cycloalkanes, while the total yield of toluene and phenol was less than 10%.

[0046] Example 4: Application of catalysts in the hydrocracking of diphenyl ether

[0047] 1 mmol of diphenyl ether, 20 mg of 5% Ru-NbAlS-2 catalyst, and 15 mL of methanol were added to a reaction vessel. Hydrogen gas was introduced to purge air, and the reaction was carried out at 170 °C, 1.5 MPa, and for 1 h. After the reaction was complete, the mixture was cooled, filtered, and the products were analyzed by gas chromatography. The results showed that the conversion rate of diphenyl ether was 99.99%, the yield of benzene was 20%, and the yield of phenol was 14%.

[0048] Comparative Example 3: Hydrocracking reaction using Ru-NbAlS-1 catalyst

[0049] The reaction conditions were the same as in Example 4, but the catalyst was replaced with Ru-NbAlS-1. The results showed that the products mainly consisted of cyclohexanol, cyclohexanone, and other cycloalkanes, with the total yield of benzene and phenol less than 10%.

[0050] Example 5: Application of catalyst in the hydrogenation cracking of phenoxyethylbenzene

[0051] 1 mmol of phenoxyethylbenzene, 20 mg of 5% Ru-NbAlS-2 catalyst, and 15 mL of methanol were added to a reaction vessel. Hydrogen gas was introduced to purge air, and the reaction was carried out at 150 °C, 1.5 MPa, and for 3 h. After the reaction was complete, the mixture was cooled, filtered, and the products were analyzed by gas chromatography. The results showed that the conversion rate of phenoxyethylbenzene was 99.99%, the yield of phenol was 30%, and the yield of acetophenone was 22%.

[0052] Comparative Example 4: Hydrocracking reaction using Ru-NbAlS-1 catalyst

[0053] The reaction conditions were the same as in Example 5, but the catalyst was replaced with Ru-NbAlS-1. The results showed that the products mainly consisted of cyclohexanol, cyclohexanone, and other cycloalkanes, while the total yield of phenol and acetophenone was less than 10%.

[0054] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. The application of a catalyst with selectively supported ruthenium on its outer surface in the preparation of high-value-added aromatic compounds by biomass hydrogenolysis, characterized in that, The catalyst is prepared by the following method: (1) Preparation of niobium-doped molecular sieve support NbAlS: Tetrapropylammonium hydroxide was dissolved in deionized water, aluminum isopropoxide was added and stirred to dissolve; then niobium ethoxy was added dropwise and stirred continuously; finally, tetraethyl silicate was added dropwise and stirred continuously to form a gel; the gel was hydrothermally reacted, centrifuged, washed, and vacuum dried, and the dried product was calcined in air and then ground to obtain support NbAlS; (2) Preparation of ruthenium catalyst with selective external surface support: The tris(2,2'-bipyridine)ruthenium chloride complex was dissolved in deionized water to prepare a metal precursor solution. The support NbAlS was added to the precursor solution, stirred at room temperature for a certain time, dried under vacuum and ground into powder. The powder was placed in a tube furnace for calcination to obtain the catalyst Ru-NbAlS-2 with selective external surface support. The concentration of the tris(2,2'-bipyridine)ruthenium chloride complex in the metal precursor solution was 3.70 mmol / L, and the ruthenium loading on the NbAlS support was 5%. The specific operation of the tubular furnace calcination is as follows: calcination at 250°C for 3 hours under a nitrogen atmosphere, with a nitrogen flow rate of 50 mL / min and a heating rate of 2°C / min; then switching to a hydrogen atmosphere and reduction at 450°C for 3 hours, with a hydrogen flow rate of 50 mL / min and a heating rate of 2°C / min. The biomass includes one or more of benzylphenyl ether, diphenyl ether, and phenoxyethylbenzene.

2. The application of the catalyst with selectively supported ruthenium on its outer surface according to claim 1 in the preparation of high-value-added aromatic compounds by biomass hydrogenolysis, characterized in that, The volume ratio of tetrapropylammonium hydroxide to deionized water is 1 mL:2 mL; the concentration of aluminum isopropoxide in deionized water is 11.032 mg / mL; the concentration of niobium ethoxylate in deionized water is 136 μL / mL; and the volume ratio of tetraethyl silicate to deionized water is 4.47 mL:10 mL.

3. The application of the catalyst with selectively supported ruthenium on its outer surface according to claim 1 in the preparation of high-value-added aromatic compounds by biomass hydrogenolysis, characterized in that, The stirring and dissolving process takes 2 hours, the continued stirring takes 2 hours, and the continuous stirring takes 24 hours.

4. The application of the catalyst with selectively supported ruthenium on its outer surface according to claim 1 in the preparation of high-value-added aromatic compounds by biomass hydrogenolysis, characterized in that, The hydrothermal reaction is aging and crystallization at 170℃ for 72 hours, and the air calcination is calcination at 550℃ for 6 hours.

5. The application of the catalyst with selectively supported ruthenium on its outer surface according to claim 1 in the preparation of high-value-added aromatic compounds by biomass hydrogenolysis, characterized in that, This includes adding biomass and the catalyst to methanol and carrying out a hydrocracking reaction in a hydrogen atmosphere at 130°C and 1.5 MPa.

6. The application of the catalyst with selectively supported ruthenium on its outer surface according to claim 5 in the preparation of high-value-added aromatic compounds by biomass hydrogenolysis, characterized in that, The ratio of biomass to catalyst is 1 mmol: 20 mg, and the ratio of biomass to methanol is 1 mmol: 15 mL.

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