Preparation method of cellulose carbon modified Zr / beta catalyst and application of cellulose carbon modified Zr / beta catalyst in catalytic direct conversion of xylose into gamma-valerolactone

Abstract

The present application relates to a kind of preparation method of cellulose carbon modified Zr / β catalyst and its application in the direct conversion of xylose into γ-valerolactone, belong to biomass energy chemical technology field.The present application uses zirconium salt as zirconium source, cellulose (CEL) as carbon modifier, and impregnation and calcination method is used to prepare cellulose carbon modified Zr / β catalyst (Zr-based catalyst with β zeolite-cellulose as carrier);The catalyst has larger specific surface area, pore volume and pore size;Zr active site is more evenly distributed, and stability is greatly improved;It also has the characteristics of ensuring the acid strength of dehydration, MVP reduction and ring-opening reaction, and appropriate proportion of Lewsi and acid site etc.In cosolvent system, with xylose as substrate, the cellulose carbon modified Zr / β catalyst is used to directly catalyze the conversion of xylose into γ-valerolactone, and the yield of γ-valerolactone can be as high as 54.3%.

Description

Technical Field

[0001] This invention relates to a method for directly preparing γ-valerolactone from xylose, belonging to the field of biomass energy chemical technology. Background Technology

[0002] Converting waste lignocellulosic biomass into biofuels and high-value chemicals helps achieve efficient resource utilization. Hemicellulose, an important component of lignocellulosic biomass, can be hydrolyzed to obtain monosaccharides, which serve as crucial intermediates for further conversion into high-value chemicals, thus enabling the efficient utilization of lignocellulosic biomass.

[0003] Xylose is a common monosaccharide found in hemicellulose hydrolysates. Catalyzing the directed conversion of xylose presents significant challenges. For example, the formation of xylitol and furfural typically involves single reaction steps such as hydrogenation or dehydration, while the one-pot synthesis of furfuryl alcohol, levulinic acid, alkyl levulinic acid esters, and γ-valerol relies on a cascade reaction, requiring catalysts with multiple unique active sites to drive the cascade process.

[0004] Under the action of an acid catalyst, xylose undergoes a dehydration reaction to produce furfural, which is then reduced to furfuryl alcohol via hydrogenation, followed by further etherification to obtain furfuryl ether. Next, in an alcoholic medium, furfuryl ether undergoes dehydration and isomerization reactions under the action of an acid catalyst to produce a mixture of levulinic acid and alkyl levulinic acid esters. Finally, these compounds are converted to γ-valerol via hydrogenation and lactone formation. This one-pot selective conversion of xylose into the aforementioned multiple biomass derivatives is an ideal way to reduce overall investment and operating costs. Therefore, designing a multifunctional catalyst capable of driving cascade reactions and generating multiple ideal biomass derivatives is crucial. To achieve this conversion reaction, a bifunctional catalyst is needed, i.e., the catalyst must possess both acidic and MPV reduction capabilities. In the reaction medium, a suitable alcohol solvent must be used as a hydrogen donor to achieve carbonyl reduction. The advantage of this transfer hydrogenation reaction is that it avoids the use of high-pressure hydrogen and expensive noble metal catalysts, thus reducing reaction costs. In this regard, catalysts containing Lewis acid sites have been successfully applied to the MPV carboxyl reduction reaction. On the other hand, the dehydration reaction of xylose and the conversion of furfuryl alcohol to levulinic acid and isopropyl furfuryl ether to isopropyl levulinate are mainly caused by... Driven by acid site action. By precisely controlling the acidity and reducing properties of the catalyst, it is hoped that a one-pot process can efficiently convert xylose into a variety of high-value chemicals.

[0005] In studies on the catalytic conversion of xylose to γ-valerolactone, Melero et al. were the first to report a one-pot direct conversion of xylose to γ-valerolactone on Zr-Al-Beta zeolite. However, to ensure the effective alternation of the MPV reduction reaction and the acid-catalyzed reaction steps, the Lewis acid sites and... The ratio of acid sites. By controlling the degree of dealumination of the catalyst, Melero et al. optimized the catalyst structure and finally obtained a γ-valerolactone yield of 34% under reaction conditions of 190°C and 10 hours. Similarly, Li et al. also used the method of dealuminating SCM-1 zeolite and loading it with active metal Zr, and by optimizing the degree of dealumination to obtain the optimal L / B value, they achieved a γ-valerolactone yield of 36.4% under reaction conditions of 170°C and 48 hours. Although some progress has been made in the study of catalytic xylose to γ-valerolactone conversion, the reported catalyst modification strategies often involve complex preparation processes such as dealumination, which to some extent limits their practical application in γ-valerolactone production. At present, in the study of catalytic xylose to γ-valerolactone preparation, there are still problems such as low γ-valerolactone yield, high reaction temperature, and long reaction time. Therefore, simplifying the catalyst preparation process and improving the γ-valerolactone yield and reaction efficiency have become the key points of current research. Summary of the Invention

[0006] To address the problems of complex catalyst preparation processes, long catalytic conversion times, and low product yields in existing technologies for the direct conversion of xylose to γ-valerol, this invention proposes a method for directly preparing γ-valerol from xylose. Using zirconium salt as the zirconium source and cellulose (CEL) as the carbon modifier, a cellulose carbon-modified Zr / β catalyst (a Zr-based catalyst supported on β-zeolite-cellulose) is prepared by impregnation and calcination. This catalyst offers advantages such as simple preparation method, high reactivity, high γ-valerol yield, and strong stability, making it highly valuable for practical applications. In a co-solvent system, using xylose as the substrate, this cellulose carbon-modified Zr / β catalyst directly catalyzes the conversion of xylose to γ-valerol, achieving a γ-valerol yield as high as 54.3%.

[0007] A method for preparing a cellulose carbon-modified Zr / β catalyst, the specific steps of which are as follows:

[0008] 1) Dissolve the zirconium salt in deionized water to obtain a zirconium salt solution;

[0009] 2) Add Hβ-25 zeolite and cellulose to zirconium salt solution, stir and react at room temperature for 0.5-1.5 h, then place at 110-130℃ and stir until the water is completely evaporated to obtain catalyst precursor;

[0010] 3) The catalyst precursor was placed in a nitrogen environment and heated at a constant rate to 500-600℃ and calcined at a constant temperature for 2.5-3.5h to obtain the cellulose carbon-modified Zr / β catalyst.

[0011] Preferably, the zirconium ion concentration in the zirconium salt solution in step 1) is 0.35–0.45 mol / L.

[0012] Preferably, in step 2), Hβ-25 zeolite accounts for 70-90% of the total mass of Hβ-25 zeolite and cellulose, which is 100%.

[0013] The active metal zirconium accounts for 20–40 wt% of the catalyst by mass percentage.

[0014] The specific steps for applying the cellulose carbon-modified Zr / β catalyst in the direct conversion of xylose to γ-valerol are as follows:

[0015] (1) Xylose, a hemicellulose derivative, was added to a cosolvent to prepare a reaction substrate solution;

[0016] (2) The cellulose carbon-modified Zr / β catalyst was added to the reaction substrate solution and catalyzed in an anaerobic environment to obtain γ-valerol.

[0017] The cosolvent in step (1) consists of organic solvent A and isopropanol, where organic solvent A is 1,4-dioxane.

[0018] Preferably, in step (1), the volume ratio of organic solvent A to isopropanol is 1:9 to 3:7.

[0019] The concentration of the reaction substrate solution in step (1) is 0.05–0.07 mol / L.

[0020] In step (2), the mass ratio of the cellulose carbon-modified Zr / β catalyst to xylose in the reaction substrate solution is 1:1 to 3:1.

[0021] The temperature of the catalytic reaction in step (2) is 170-190℃ and the time is 12-36h.

[0022] The beneficial effects of this invention are:

[0023] (1) This invention uses zirconium salt as the zirconium source and cellulose (CEL) as the carbon modifier to prepare a cellulose carbon-modified Zr / β catalyst (a Zr-based catalyst supported on β-zeolite-cellulose) by impregnation and calcination. The catalyst has a large specific surface area, pore volume, and pore size; uniform distribution of Zr active sites and significantly improved stability; and it also has the acid strength to ensure dehydration, MVP reduction, and ring-opening reactions, as well as a suitable ratio of Lewsi and... Characteristics such as acid sites;

[0024] (2) In the co-solvent system, the present invention uses xylose as substrate and utilizes the cellulose carbon-modified Zr / β catalyst to directly catalyze the conversion of xylose into γ-valerolactone, and the yield of γ-valerolactone can be as high as 54.3%. Attached Figure Description

[0025] Figure 1 This is a TEM image of catalyst A in Example 1;

[0026] Figure 2 Here is the XRD pattern of catalyst A in Example 1;

[0027] Figure 3 The image shows the NH3-TPD of catalyst A in Example 1.

[0028] Figure 4 The image shows the Py-FTIR spectrum of catalyst A in Example 1. Detailed Implementation

[0029] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the content described.

[0030] Example 1: A method for preparing a cellulose carbon-modified Zr / β catalyst, the specific steps of which are as follows:

[0031] 1) Dissolve Zr(NO3)4·5H2O in deionized water to obtain a zirconium salt solution; the zirconium ion concentration in the zirconium salt solution is 0.4 mol / L;

[0032] 2) Add Hβ-25 zeolite and cellulose to zirconium salt solution, stir and react at room temperature for 1 hour, then place at 120℃ and stir until the water is completely evaporated to obtain catalyst precursor; the mass ratio of Hβ-25 zeolite to cellulose is 8:2; by mass percentage, the active metal zirconium accounts for 30% in the catalyst.

[0033] 3) The catalyst precursor was placed in a nitrogen environment and heated at a constant rate to 550℃ and calcined at a constant temperature for 3h to obtain the cellulose carbon modified Zr / β catalyst, denoted as catalyst A;

[0034] The BET characterization data of catalyst A in this embodiment are shown in Table 1.

[0035] Table 1. BET characterization data of catalyst A

[0036]

[0037] As shown in Table 1, catalyst A has a large specific surface area (316.9 m²). 2 ·g –1 ), pore volume (0.244 cm³) 3 ·g–1 With its large volume and pore size (2.76 nm), it has high accessibility. The large empty volume and pore size can promote the diffusion and transport of reactants and products, thereby promoting the formation of γ-valerol.

[0038] The TEM characterization image of catalyst A in this embodiment is shown below. Figure 1 ,from Figure 1 It can be seen that lattice fringes corresponding to ZrO2 exist on the surface of catalyst A; the XRD characterization pattern of catalyst A in this embodiment is shown in [reference needed]. Figure 2 ,from Figure 2 It can be seen that catalyst A exhibits characteristic diffraction peaks of the ZrO2 crystal form; TEM and XRD characterization show that catalyst A, prepared by a simple impregnation and calcination step, has active metallic zirconium uniformly dispersed in the form of ZrO2 on the catalyst support.

[0039] The NH3-TPD characterization diagram of catalyst A in this embodiment is shown below. Figure 3 ,from Figure 3 It can be seen that catalyst A has high catalytic acidity and is suitable for catalyzing the relatively long reaction pathway of xylose cascade to prepare γ-valerol.

[0040] The Py-FTIR characterization diagram of catalyst A in this embodiment is shown below. Figure 4 ,from Figure 4 It can be seen that catalyst A has sufficient amount of The acidic sites facilitate the dehydration of xylose to furfural in the cascade reaction, and the ring-opening of furfuryl alcohol and furfuryl ether to prepare levulinic acid and levulinic acid ester. At the same time, the presence of sufficient Lewis acidic sites enables the MVP reduction reaction, thereby promoting the formation of γ-valerol.

[0041] Example 2: A method for preparing a cellulose carbon-modified Zr / β catalyst, the specific steps of which are as follows:

[0042] 1) Dissolve ZrCl4, ZrOCl2·8H2O or Zr(NO3)4·5H2O in deionized water to obtain a zirconium salt solution;

[0043] 2) Hβ-25 zeolite and cellulose were added to a zirconium salt solution and stirred at room temperature for 0.8 h. Then, the mixture was stirred at 120 °C until all the water was evaporated to obtain the catalyst precursor. The mass ratio of Hβ-25 zeolite to cellulose was 9:1. The zirconium content in the catalyst precursor was 25% by mass percentage.

[0044] 3) The catalyst precursor was placed in an argon atmosphere and heated at a constant rate to 500℃ and calcined at a constant temperature for 3.5h to obtain the cellulose carbon modified Zr / β catalyst, denoted as catalyst B;

[0045] In this embodiment, catalyst B has sufficient quantity The acidic sites facilitate the dehydration of xylose to furfural in the cascade reaction, and the ring-opening of furfuryl alcohol and furfuryl ether to prepare levulinic acid and levulinic acid ester. At the same time, the presence of sufficient Lewis acidic sites enables the MVP reduction reaction, thereby promoting the formation of γ-valerol.

[0046] Example 3: A method for preparing a cellulose carbon-modified Zr / β catalyst, the specific steps of which are as follows:

[0047] 1) Dissolve ZrCl4, ZrOCl2·8H2O or Zr(NO3)4·5H2O in deionized water to obtain a zirconium salt solution;

[0048] 2) Hβ-25 zeolite and cellulose were added to a zirconium salt solution and stirred at room temperature for 1.5 h. Then, the mixture was stirred at 130 °C until all the water was evaporated to obtain the catalyst precursor. The mass ratio of Hβ-25 zeolite to cellulose was 7:3. The zirconium content in the catalyst precursor was 38% by mass percentage.

[0049] 3) The catalyst precursor was placed in a vacuum and heated at a constant rate to 600℃ and calcined at a constant temperature for 2.5h to obtain the cellulose carbon modified Zr / β catalyst, denoted as catalyst C;

[0050] In this embodiment, catalyst C has sufficient quantity The acidic sites facilitate the dehydration of xylose to furfural in the cascade reaction, and the ring-opening of furfuryl alcohol and furfuryl ether to prepare levulinic acid and levulinic acid ester. At the same time, the presence of sufficient Lewis acidic sites enables the MVP reduction reaction, thereby promoting the formation of γ-valerol.

[0051] Example 4: A method for the direct conversion of xylose to γ-valerol using a cellulose carbon-modified Zr / β catalyst (catalyst A in Example 1), the specific steps of which are as follows:

[0052] (1) Xylose, a hemicellulose derivative, was added to a co-solvent to prepare a reaction substrate solution; wherein the co-solvent consisted of 1,4-dioxane and isopropanol, with a volume ratio of 1:9 between 1,4-dioxane and isopropanol; and the concentration of the reaction substrate solution was 0.06 mol / L.

[0053] (2) The cellulose carbon-modified Zr / β catalyst (catalyst A) was added to the reaction substrate solution, and the reaction was carried out under nitrogen atmosphere and temperature of 180℃ for 12h to obtain γ-valerolactone; wherein the mass ratio of cellulose carbon-modified Zr / β catalyst (catalyst A) to xylose in the reaction substrate solution was 2:1;

[0054] According to gas chromatography, the yield of γ-valerol in this embodiment was 27.0%.

[0055] Example 5: A method for the direct conversion of xylose to γ-valerol using a cellulose carbon-modified Zr / β catalyst (catalyst A from Example 1), the specific steps of which are as follows:

[0056] (1) Xylose, a hemicellulose derivative, was added to a co-solvent to prepare a reaction substrate solution; wherein the co-solvent consisted of 1,4-dioxane and isopropanol, with a volume ratio of 2:8 between 1,4-dioxane and isopropanol; and the concentration of the reaction substrate solution was 0.06 mol / L.

[0057] (2) The cellulose carbon-modified Zr / β catalyst (catalyst A) was added to the reaction substrate solution, and the reaction was carried out under nitrogen atmosphere and temperature of 180℃ for 12h to obtain γ-valerolactone; wherein the mass ratio of cellulose carbon-modified Zr / β catalyst (catalyst A) to xylose in the reaction substrate solution was 2:1;

[0058] According to gas chromatography, the yield of γ-valerol in this embodiment was 31.8%.

[0059] Example 6: A method for the direct conversion of xylose to γ-valerol using a cellulose carbon-modified Zr / β catalyst (catalyst B from Example 2), the specific steps of which are as follows:

[0060] (1) Xylose, a hemicellulose derivative, was added to a co-solvent to prepare a reaction substrate solution; wherein the co-solvent consisted of 1,4-dioxane and isopropanol, with a volume ratio of 3:7 between 1,4-dioxane and isopropanol; and the concentration of the reaction substrate solution was 0.06 mol / L.

[0061] (2) The cellulose carbon-modified Zr / β catalyst (catalyst B) was added to the reaction substrate solution, and the reaction was carried out under nitrogen atmosphere and temperature of 180℃ for 12h to obtain γ-valerolactone; wherein the mass ratio of cellulose carbon-modified Zr / β catalyst (catalyst B) to xylose in the reaction substrate solution was 2:1.

[0062] According to gas chromatography, the yield of γ-valerol in this embodiment was 37.5%.

[0063] Example 7: A method for the direct conversion of xylose to γ-valerol using a cellulose carbon-modified Zr / β catalyst (catalyst B from Example 2), the specific steps of which are as follows:

[0064] (1) Xylose, a hemicellulose derivative, was added to a co-solvent to prepare a reaction substrate solution; wherein the co-solvent consisted of 1,4-dioxane and isopropanol, with a volume ratio of 3:7 between 1,4-dioxane and isopropanol; and the concentration of the reaction substrate solution was 0.06 mol / L.

[0065] (2) The cellulose carbon-modified Zr / β catalyst (catalyst B) was added to the reaction substrate solution, and the reaction was carried out under nitrogen atmosphere and temperature of 180℃ for 16h to obtain γ-valerolactone; wherein the mass ratio of cellulose carbon-modified Zr / β catalyst (catalyst B) to xylose in the reaction substrate solution was 2:1;

[0066] According to gas chromatography, the yield of γ-valerol in this embodiment was 43.5%.

[0067] Example 8: A method for the direct conversion of xylose to γ-valerol using a cellulose carbon-modified Zr / β catalyst (catalyst C from Example 3), the specific steps of which are as follows:

[0068] (1) Xylose, a hemicellulose derivative, was added to a co-solvent to prepare a reaction substrate solution; wherein the co-solvent consisted of 1,4-dioxane and isopropanol, with a volume ratio of 3:7 between 1,4-dioxane and isopropanol; and the concentration of the reaction substrate solution was 0.06 mol / L.

[0069] (2) The cellulose carbon-modified Zr / β catalyst (catalyst C) was added to the reaction substrate solution, and the reaction was carried out under nitrogen atmosphere and temperature of 180℃ for 24h to obtain γ-valerolactone; wherein the mass ratio of cellulose carbon-modified Zr / β catalyst (catalyst C) to xylose in the reaction substrate solution was 2:1;

[0070] Gas chromatography analysis showed that the yield of γ-valerol in this embodiment was 51.5%.

[0071] Example 9: A method for the direct conversion of xylose to γ-valerol using a cellulose carbon-modified Zr / β catalyst (catalyst C from Example 3), the specific steps of which are as follows:

[0072] (1) Xylose, a hemicellulose derivative, was added to a co-solvent to prepare a reaction substrate solution; wherein the co-solvent consisted of 1,4-dioxane and isopropanol, with a volume ratio of 3:7 between 1,4-dioxane and isopropanol; and the concentration of the reaction substrate solution was 0.06 mol / L.

[0073] (2) The cellulose carbon-modified Zr / β catalyst (catalyst C) was added to the reaction substrate solution, and the reaction was carried out under nitrogen atmosphere and temperature of 180℃ for 36 h to obtain γ-valerolactone; wherein the mass ratio of cellulose carbon-modified Zr / β catalyst (catalyst C) to xylose in the reaction substrate solution was 2:1;

[0074] According to gas chromatography, the yield of γ-valerol in this example was 54.3%.

Claims

1. The application of cellulose carbon-modified Zr / β catalyst in the direct conversion of xylose to γ-valerol, characterized in that, The specific steps are as follows: (1) Xylose, a hemicellulose derivative, is added to a co-solvent to prepare a reaction substrate solution; the co-solvent consists of organic solvent A and isopropanol, organic solvent A is 1,4-dioxane, and the volume ratio of organic solvent A to isopropanol is 1:9~3:7; the concentration of the reaction substrate solution is 0.05~0.07mol / L; (2) Add the cellulose carbon-modified Zr / β catalyst to the reaction substrate solution and catalyze the reaction in an anaerobic environment to obtain γ-valerolactone; the temperature of the catalytic reaction is 170~190℃ and the time is 12~36h; The specific steps for preparing the cellulose carbon-modified Zr / β catalyst are as follows: 1) Dissolve the zirconium salt in deionized water to obtain a zirconium salt solution; 2) Add Hβ-25 zeolite and cellulose to a zirconium salt solution and stir at room temperature for 0.5-1.5 h. Then, stir at 110-130℃ until all water is evaporated to obtain the catalyst precursor. Based on the total mass of Hβ-25 zeolite and cellulose being 100%, Hβ-25 zeolite accounts for 70-90%. 3) The catalyst precursor was placed in a nitrogen environment and heated at a constant rate to 500~600℃ and calcined at a constant temperature for 2.5~3.5h to obtain cellulose carbon modified Zr / β catalyst; the active metal zirconium in the catalyst accounted for 20~40wt% by mass percentage.

2. The application according to claim 1, characterized in that: Step 1) The zirconium ion concentration in the zirconium salt solution is 0.35~0.45 mol / L.

3. The application according to claim 1, characterized in that: In step (2), the mass ratio of the cellulose carbon-modified Zr / β catalyst to xylose in the reaction substrate solution is 1:1 to 3:1.

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