Construction method and application of specific ruthenium crystal face induced by modulating TiO2 crystal phase through laser

Abstract

The invention discloses a construction method and application of a hydrogenation catalyst for inducing a specific crystal face of ruthenium by modulating a TiO2 crystal phase through laser, and belongs to the fields of hydrogenation catalyst preparation, biomass high-value utilization and renewable energy sources. The preparation method of the catalyst comprises the following steps: irradiating titanium dioxide by using laser with different intensities to convert the crystal phase of the titanium dioxide, and constructing the TiO2 supported ruthenium catalyst (Ru / TiO2) by taking the titanium dioxide (TiO2) treated by the laser as a carrier through a wet reduction method. According to the invention, TiO2 crystal phase transformation is regulated and controlled by laser, and the dominant crystal face of an active hydrogenation catalytic site is induced to be exposed by utilizing a crystal face induction effect, so that the catalytic activity of the hydrogenation catalyst is improved; meanwhile, the heterostructure of the mixed phase in TiO2 enhances the electron conduction performance, optimizes the electronic environment of Ru active sites, and improves the stability of the catalyst. The catalyst has the advantages of simple preparation method, high catalytic activity and strong stability, and can realize the function of catalytic hydrogen transfer hydrogenation of levulinic acid and ester compounds thereof. The catalytic system has a wide application prospect in the aspect of preparing high-added-value products from biomass-based platform compounds.

Description

Technical Field

[0001] This invention belongs to the technical fields of hydrogenation catalyst preparation, high-value utilization of biomass and renewable energy, specifically relating to a method and application for constructing a hydrogenation catalyst by inducing specific crystal faces of ruthenium through laser modulation of TiO2 crystal phase. Background Technology

[0002] With the rapid depletion of fossil resources and the increasing severity of environmental pollution, developing clean, low-carbon, and novel renewable resources has become an important way to ensure energy security and alleviate environmental pressure. Lignocellulosic biomass is a renewable carbon-neutral resource. Through biological and chemical methods, it can be converted into high-value-added chemicals and biofuels, effectively alleviating the fossil resource crisis and improving the environment. Lignocellulosic biomass is mainly composed of cellulose, hemicellulose, and lignin, and can be converted into glucose, xylose, furans, levulinic acid / esters, and aromatic compounds through chemical catalysis. Gamma-valerol (GVL) is a promising and widely used C5 platform molecule. It is chemically stable and has low toxicity. It can be used directly as a precursor for transportation fuels, green solvents, food additives, and fine chemicals. It can also be used as an organic synthesis intermediate in the production of polymers, olefins, and other value-added chemicals (such as 2-methyltetrahydrofuran, 1,4-pentanediol, and polyurethane).

[0003] The efficient preparation of GVL in alcohol solvents via catalytic transfer hydrogenation (CTH) is a typical method utilizing levulinic acid and its esters. This technology avoids the safety hazards of high-pressure hydrogen and the corrosion problems caused by formic acid. Currently, various heterogeneous metal catalysts such as Cu, Ni, Ru, Pt, and Pd are widely used in the hydrogenation reaction for GVL preparation via EL. Among them, Ru-based catalysts have attracted much attention due to their excellent catalytic performance. For example, Gao et al. (Journal of Catalysis, 2020, 389:60-70) reported the use of Ru / CeO2 catalysts with three CeO2 supports (nanoring rods, cubic nanoparticles, and octahedrons) for EL hydrogenation to GVL. The results showed that Ru / CeO2 nanorods had excellent catalytic performance, with a GVL yield of 99.4%. Although this catalyst achieved a high GVL yield, it still suffers from problems such as insufficient stability and easy agglomeration of Ru metal.

[0004] Therefore, it is of great significance to develop catalysts with high catalytic activity, simple preparation process and strong stability to achieve selective catalytic hydrogen transfer hydrogenation of carbon-oxygen double bonds. Summary of the Invention

[0005] Objective of the invention: To provide a method and application for constructing a hydrogenation catalyst for ruthenium with specific crystal faces induced by laser modulation of TiO2 crystal phase. This catalyst has advantages such as high catalytic activity, strong stability, simple preparation process, and mild conditions, and is suitable for large-scale production.

[0006] Technical solution: To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:

[0007] A method for preparing a ruthenium catalyst supported on titanium dioxide by laser treatment involves first treating TiO2 with a laser to achieve a phase transformation, then dispersing it in an appropriate amount of solvent, adding ruthenium metal salt and NaBH4 and continuing to stir and mix, then filtering, drying, and grinding the mixture to obtain the ruthenium catalyst supported on titanium dioxide.

[0008] Specifically, the steps include the following:

[0009] 1) Weigh TiO2 and TiC, mix them thoroughly, and then perform laser treatment on them. The laser current used is 0.1-10 A, and the treatment time is 0.5-200 s.

[0010] 2) Add the laser-treated TiO2 from step 1) to water and stir thoroughly to obtain a dispersion;

[0011] 3) Weigh a certain mass of ruthenium metal salt, dissolve it in water and sonicate it. After sonication, add it dropwise to the dispersion in step 2) and continue stirring for 0.01-12 h.

[0012] 4) Weigh a certain mass of NaBH4, dissolve it in water, and add the dissolved NaBH4 aqueous solution dropwise to the mixture in step 3) for reduction, and continue stirring for 2-12 h;

[0013] 5) The mixed liquid obtained in step 4) is filtered and dried to obtain Ru / TiO2 catalyst supported on titanium dioxide.

[0014] In step 1), the mass ratio of TiO2 and TiC is 0.01 to 10:1, preferably 8 to 12:1, and more preferably 9:1.

[0015] The laser current used is 0.1-10 A, preferably 2-8 A, more preferably 4 A-6 A; more preferably, the laser current used is 4 A or 6 A, and the processing time is 0.5-200 s, preferably 1-10 s, more preferably 3 s;

[0016] The TiO2 is anatase titanium dioxide.

[0017] In step 3), the mass ratio of TiO2 to ruthenium metal salt RuCl3·3H2O is 0.01-10, and the mass ratio of NaBH4 to ruthenium metal salt RuCl3·3H2O is 0.01-5.

[0018] Preferably, the mass ratio of TiO2 to ruthenium metal salt RuCl3·3H2O is (2-7):1.

[0019] In step 5), the drying temperature is 10-200 ℃ and the time is 2-36 h.

[0020] The titanium dioxide-supported ruthenium hydrogenation catalyst prepared by the above method.

[0021] During laser treatment, the anatase phase transforms into the rutile phase. After laser treatment, Ru and TiO2 have a stronger interaction. The average size of Ru nanoparticles in the prepared catalyst is 3.28-3.33 nm.

[0022] The Ru loading of the titanium dioxide-supported ruthenium hydrogenation catalyst is 2-8. Preferably, the Ru loading is 5-8, and more preferably, the Ru loading is 5.89. 5.89Ru / TiO2(4A) has the smallest average Ru nanoparticle size (3.28 nm).

[0023] The application of the titanium dioxide-supported ruthenium hydrogenation catalyst in the catalytic hydrogenation of levulinic acid and its ester compounds.

[0024] The catalyst, levulinic acid and its esters, and solvent are mixed and reacted under inert gas protection.

[0025] The above-mentioned titanium dioxide-supported ruthenium hydrogenation catalyst was added to a reaction tube with levulinic acid and its esters as substrates and solvent to form a reaction system.

[0026] The solvent is selected from one or more of methanol, ethanol, isopropanol, sec-butanol, and 3-pentanol; preferably isopropanol, sec-butanol, and 3-pentanol.

[0027] In the reaction system, the substrate mass is 0.01-10 mmol, preferably 0.1-5 mmol, more preferably 1 mmol; the mass ratio of catalyst to substrate is 0.1-10.0:1, preferably 0.1-5:1, more preferably 0.4:1.

[0028] The reaction is carried out at 20-200 °C under inert gas protection for 0.01-20 h. After the reaction is completed, the product is obtained through separation and purification, thus realizing catalytic transfer hydrogenation.

[0029] The preferred reaction temperature is 120-180 ℃, and the preferred reaction time is 8-15 h. More preferably, the preferred reaction temperature is 150 ℃ and the preferred reaction time is 12 h.

[0030] Anatase titanium dioxide and TiC were thoroughly mixed and ground to obtain a mixture, which was then treated with an 808nm laser for 3s at a current intensity of 4A to obtain a laser-treated titanium dioxide carrier TiO2 (4A); the preferred mass ratio of titanium dioxide to TiC was 9:1.

[0031] TiO2(4A) was dispersed in water by stirring. An aqueous solution of RuCl3·3H2O was added dropwise to the TiO2(4A) dispersion and stirred for 2 h. Then, an aqueous solution of NaBH4 was added dropwise to initiate a reduction reaction. After the reaction was complete, the mixture was filtered and dried to obtain a Ru-supported Ru / TiO2(4A) catalyst. Preferably, the mass ratio of TiO2 to ruthenium metal salt RuCl3·3H2O was (2-7):1, yielding Ru / TiO2(4A) catalysts with different Ru loadings. A preferred loading was 5.89 Ru / TiO2(4A).

[0032] 60 mg of 5.89Ru / TiO2(4A) catalyst and 1 mmol of ethyl levulinate were added to a solvent, and the reaction was carried out at 150 °C for 12 h with continuous stirring during the reaction to prepare γ-valerolactone. The solvent was preferably isopropanol, sec-butanol and 3-pentanol.

[0033] Beneficial effects:

[0034] Compared with existing technologies, the present invention has the following advantages:

[0035] (1) The present invention uses a simple and easy-to-operate impregnation method to prepare a catalyst Ru / TiO2 supported on a titanium dioxide support after laser treatment. The preparation process is simple and easy to scale up.

[0036] (2) The prepared Ru / TiO2 catalyst has high thermal and chemical stability and can maintain its activity under high temperature and corrosive environment, and the catalyst has good stability.

[0037] (3) The catalyst prepared in this invention has a high product yield and high reactant conversion rate in the selective hydrogenation of carbon-oxygen double bonds. Under optimal conditions, the yield of GVL reaches 95% and the conversion rate of EL reaches 96%. Attached Figure Description

[0038] Figure 1 The X-ray diffraction patterns of the catalysts prepared in this application are shown in Figure (a), which shows the TiO2 support, and Figure (b) shows the catalyst after loading with metal Ru.

[0039] Figure 2 The images shown are transmission electron microscope (TEM) images of the catalysts prepared in this application. In these images, (a) and (e) are Ru / TiO2 (Anatanse), (b) and (f) are Ru / TiO2 (4A), (c) and (g) are Ru / TiO2 (6A), and (a) and (e) are Ru / TiO2 (Rutile).

[0040] Figure 3 The following figures illustrate the effect of the catalyst prepared in this application on the transfer hydrogenation of ethyl levulinate to prepare γ-valerol: Figure (a) shows different Ru loadings, Figure (b) shows different reaction temperatures, Figure (c) shows different reaction times, and Figure (d) shows different catalyst amounts.

[0041] Figure 4 A diagram illustrating the recycling of the catalyst prepared in this application. Detailed Implementation

[0042] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to specific examples. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0043] Example 1: Preparation of Ru / TiO2 catalyst with ruthenium supported on laser-treated titanium dioxide.

[0044] The specific preparation process is as follows:

[0045] Anatase titanium dioxide (0.9 g) and TiC (0.1 g) were mixed to obtain a mixture. The mixture was then thoroughly ground to ensure homogeneity. Next, the sample was spread on a glass plate and treated with an 808 nm laser for 3 s at current intensities of 4 A and 6 A. The resulting samples were then ball-milled in a planetary ball mill. Through the above steps, a series of titanium dioxide supports treated with different laser currents were prepared at different current intensities, named TiO2 (4 A) and TiO2 (6 A), corresponding to current intensities of 4 A and 6 A, respectively.

[0046] 0.9 g of TiO2 (Anatanse), TiO2 (4A), TiO2 (6A), and TiO2 (Rutile) were placed in round-bottom flasks, and 20 mL of deionized water was added and stirred for 20 min to disperse them. Then, 0.2587 g of RuCl3·3H2O was weighed, dissolved in 5 mL of deionized water by ultrasonication, and added dropwise to the TiO2 dispersion and stirred for 2 h. Then, 0.0675 g of NaBH4 was weighed, dissolved in 5 mL of deionized water, and added dropwise to the mixture for reduction and stirred for 5 h. After filtration, the sample was placed in a vacuum oven and dried for 1 day at 80 ℃. Finally, the dried sample was ground into powder to prepare the catalysts Ru / TiO2 (Anatanse), Ru / TiO2 (4A), Ru / TiO2 (6A), and Ru / TiO2 (Rutile) supported on titanium dioxide.

[0047] The effects of different Ru / TiO2 catalysts will be discussed below.

[0048] Depend on Figure 1 It can be seen that the XRD characteristic diffraction peaks of the prepared Ru / TiO2 catalyst do not show obvious diffraction peaks of elemental Ru and its oxides. According to the corresponding standard card comparison, the main XRD diffraction peaks of the catalyst are Anatanse and Rutile phases of the TiO2 support.

[0049] Depend on Figure 2 It can be seen that the prepared catalyst has good metal dispersion, and high-resolution TEM further confirmed the loading of Ru metal. Among them, 5.89Ru / TiO2 (4A) has the smallest average Ru nanoparticle size (3.28 nm), which may be due to the stronger interaction between Ru and TiO2 after laser treatment. The HRTEM images of the samples also show that the lattice fringe spacing of the laser-treated TiO2 is 0.35 and 0.17 nm, which belong to the (101) and (211) crystal planes of the anatase and rutile phases, respectively, while TiO2(Anatanse) only has the anatase phase and TiO2(Rutile) only has the rutile phase. This result indicates that the anatase phase transforms into the rutile phase during laser treatment.

[0050] Example 2: Catalyst used in the preparation of γ-valerol from ethyl levulinate

[0051] The specific preparation process is as follows:

[0052]

[0053] A certain amount of Ru / TiO2 catalyst, 1 mmol of ethyl levulinate, and 5 mL of isopropanol were added sequentially to a 35 mL thick-walled pressure-resistant tube. Air was purged from the tube using a nitrogen gas stream. The tube was then sealed and placed in an oil bath set to the reaction temperature, with continuous stirring during the reaction. After the reaction was complete and cooled to room temperature, the products were analyzed using gas chromatography. The conversion rate of ethyl levulinate and the yield of γ-valerolactone were calculated using the area normalization method.

[0054] (1) Comparison of catalyst performance

[0055] Table 1. Catalytic performance of catalysts prepared under different conditions

[0056] Entry Catalysts GVL yield (%) EL Conv. (%) GVL selectivity (%) 1 <![CDATA[TiO2(Anatanse)]]> Trace 5 - 2 <![CDATA[TiO2(4A)]]> Trace 3 - 3 <![CDATA[TiO2(6A)]]> Trace 2 - 4 <![CDATA[Ru / TiO2(Anatanse)]]> 66 71 93.0 5 <![CDATA[Ru / TiO2(4A)]]> 95 96 99.0 6 <![CDATA[Ru / TiO2(6A)]]> 89 98 90.8 7 <![CDATA[Ru / TiO2(Rutile)]]> 36 54 66.7

[0057] Reaction conditions: EL 1.0 mmol, catalyst 60 mg, 2-PrOH 5 mL, 150℃, 12 h, N2.

[0058] As shown in Table 1, compared with catalysts prepared under other conditions, the Ru / TiO2(4A) catalyst exhibits higher catalytic activity in the in-situ selective hydrogenation of ethyl levulinate to prepare γ-valerolactone. The conversion rate of ethyl levulinate is 96%, and the yield of γ-valerolactone is 95%. Therefore, we chose the Ru / TiO2(4A) catalyst as an example for the following tests.

[0059] (2) Different Ru loading, reaction temperature, reaction time and catalyst amount

[0060] Preparation of catalysts with different Ru loading: 0.9 g TiO2(4A) was placed in a round-bottom flask, 20 mL of deionized water was added and stirred for 20 min. Then, different masses of RuCl3·3H2O were weighed, dissolved in 5 mL of deionized water by ultrasonication, and added dropwise to the TiO2 dispersion and stirred for 2 h. Then, NaBH4 was weighed, dissolved in 5 mL of deionized water, and added dropwise to the mixture for reduction. After stirring for 5 h, the sample was filtered and dried in a vacuum oven at 80 ℃ for 1 day. Finally, the dried sample was ground into powder to obtain Ru / TiO2(4A) catalysts with different Ru loading.

[0061] Among them, the different masses of RuCl3·3H2O were 0.1294 g, 0.2587 g, and 0.3881 g, respectively, and the corresponding amounts of NaBH4 were 0.0338 g, 0.0675 g, and 0.1013 g, respectively, to prepare three Ru / TiO2(4A) catalysts with different Ru loadings: 2.45Ru / TiO2(4A), 5.89Ru / TiO2(4A), and 7.34Ru / TiO2(4A).

[0062] Catalytic reaction process description: A certain amount of xRu / TiO2(4A) catalyst, 1 mmol of ethyl levulinate, and 5 mL of isopropanol were added sequentially to a 35 mL thick-walled pressure-resistant tube. Air was purged from the tube using a nitrogen gas stream. The tube was then sealed and placed in an oil bath set to the reaction temperature. Stirring was maintained throughout the reaction. After the reaction was complete and cooled to room temperature, the products were analyzed using gas chromatography.

[0063] Depend on Figure 3 It can be seen that when the reaction temperature reaches 150 °C and the reaction time is 12 h, the conversion rate of ethyl levulinate reaches 96% and the yield of γ-valerolactone reaches 95%. However, when the reaction temperature is further increased to 160 °C and the reaction time is further extended, the yield of γ-valerolactone and the conversion rate of ethyl levulinate both decrease.

[0064] (3) Studies on different hydrogen donors and substrates

[0065] The amount of 5.89Ru / TiO2(4A) catalyst was controlled at 60 mg, the reaction time was 12 h, and 5 mL of methanol, ethanol, sec-butanol, 3-pentanol, and isopropanol were used as hydrogen donor solvents, respectively. 1 mmol of ethyl levulinate was added, and the reaction temperature was controlled at 150 °C. γ-valerolactone was prepared under the above conditions, and the conversion rate of ethyl levulinate and the yield of γ-valerolactone were calculated. The results are shown in Table 2.

[0066] The catalyst dosage was controlled at 60 mg, the reaction time at 12 h, and 5 mL of isopropanol was used as the hydrogen donor solvent. 1 mmol of methyl levulinate and butyl levulinate were added, respectively, and the reaction temperature was controlled at 150 °C. γ-valerolactone was prepared under these conditions, and the conversion rates of methyl / butyl levulinate and the yield of γ-valerolactone were calculated. The results are shown in Table 2.

[0067] Table 2. Reaction performance tests of different hydrogen-donating solvents and different levulinates in this reaction system.

[0068] Entry Substrate Alcohol GVL yield (%) EL Conv. (%) GVL Selectivity (%) 1 EL MeOH 15.0 36.0 41.2 2 EL EtOH 13.4 34.7 38.6 3 EL 2-BuOH 99.0 100 99.0 4 EL 3-Pentanol 99.0 100 99.0 5 LA 2-PrOH 93.0 95.0 97.9 6 ML 2-PrOH 99.0 100 99.0 7 AL 2-PrOH Trace 9.6 -

[0069] Reaction conditions: Substrate 1.0 mmol, catalyst 60 mg, solvent 5mL, 150 ℃, 12 h, N2.

[0070] As shown in Table 2, when sec-butanol and 3-pentanol are used as hydrogen donor solvents, the conversion rate of ethyl levulinate reaches over 95% and the yield of γ-valerolactone reaches over 90% at a reaction temperature of 150 °C.

[0071] (4) Evaluation of catalyst recycling performance

[0072] The Ru / TiO2(4A) catalyst was used at a dosage of 60 mg, the reaction temperature was controlled at 150 °C, and the reaction time was 12 h. The catalyst was then reused 1-5 times under the above reaction conditions to prepare γ-valerolactone. The conversion rate of ethyl levulinate and the yield of γ-valerolactone were then calculated, yielding the following results: Figure 4 The test results are shown.

[0073] Depend on Figure 4 It can be seen that as the number of times the catalyst is reused increases, the conversion rate of EL remains almost unchanged, indicating that the Ru / TiO2(4A) catalyst exhibits high activity and stability after repeated use.

[0074] The above embodiments systematically studied the effects of preparation conditions on catalytic performance, including key parameters such as reaction temperature, reaction time, and catalyst dosage for different Ru loadings. The optimal reaction system for the hydrogenation of ethyl levulinate to γ-valerolactone was obtained, with Ru / TiO2 (4A) as the optimal catalyst. Under the conditions of a reaction temperature of 150 °C, a catalyst dosage of 60 mg, and a reaction time of 12 h, a γ-valerolactone yield of 95% and an ethyl levulinate conversion rate of 96% were achieved. This catalytic system exhibits mild reaction conditions, avoiding the high temperature and high pressure requirements of traditional processes. Both the raw materials and products are derived from biomass platform compounds, achieving a fully green and renewable conversion. Furthermore, the system demonstrates stable performance after multiple cycles and is easy to recover. Therefore, this technical solution has a significant positive impact on the research of the hydrogenation of ethyl levulinate to γ-valerolactone.

[0075] Finally, it should be noted that the above description of the disclosed embodiments enables those skilled in the art to implement 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 novelty disclosed herein.

Claims

1. A method for preparing a ruthenium catalyst supported on a titanium dioxide support by laser treatment, characterized in that, First, TiO2 is treated with laser to achieve phase transformation, then dispersed in an appropriate amount of solvent, and ruthenium metal salt and NaBH4 are added and stirred and mixed. The mixture is then filtered, dried and ground to obtain a titanium dioxide-supported ruthenium catalyst.

2. The method for preparing laser-treated titanium dioxide-supported ruthenium catalyst according to claim 1, characterized in that: The laser current is 0.1-10A.

3. The method for preparing a laser-treated titanium dioxide-supported ruthenium catalyst according to claim 1, characterized in that: The mass ratio of TiO2 to ruthenium metal salt is 0.01-10.

4. The titanium dioxide-supported ruthenium hydrogenation catalyst prepared by the preparation method according to any one of claims 1 to 3.

5. The application of the titanium dioxide-supported ruthenium hydrogenation catalyst according to claim 4 in the catalytic hydrogenation of levulinic acid and its ester compounds.

6. The application according to claim 5, characterized in that: The catalyst, levulinic acid and its esters, and solvent are mixed and reacted under inert gas protection.

7. The application according to claim 6, characterized in that: The solvent is selected from one or more of methanol, ethanol, isopropanol, sec-butanol, and 3-pentanol.

8. The application according to claim 6, characterized in that: The reaction temperature is 20-200 ℃, and the reaction time is 0.01-20 h.

9. The application according to claim 6, characterized in that: The catalyst dosage is 10-100 mg catalyst per 1 mmol substrate.

10. The application according to claim 6, characterized in that: The mass ratio of the catalyst to levulinic acid and its esters is 0.1-3.0:1.

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