Bicatalytic center catalyst, preparation method and application thereof, and preparation method of diol

Abstract

The present invention relates to the technical field of catalytic chemistry, and particularly relates to a dual-catalytic center catalyst, a preparation method and application thereof, and a preparation method of diol. The catalyst includes: a porous support, C3N4 supported on the porous support, a hydrogenation metal, and an aldol retro-condensation catalytic metal; the hydrogenation metal and the aldol retro-condensation catalytic metal form clusters with C3N4. The hydrogenation metal and the aldol retro-condensation catalytic metal are coordinated with N sites and supported on the porous support, and form clusters with C3N4, effectively stabilizing the metal active sites. This catalyst is used for preparing diol from polyhydroxy compounds, with very high substrate conversion rate and product diol selectivity, and high cycle stability of the catalyst. The catalyst does not show inactivation after being recycled four times.

Description

Technical Field

[0001] The present invention relates to the technical field of catalytic chemistry, and particularly relates to a dual-catalytic center catalyst, a preparation method and application thereof, and a preparation method of diol. Background Art

[0002] Among numerous bulk chemicals, ethylene glycol is an important basic chemical raw material for producing polyester materials (PET, PEF), antifreeze, and coolant. At present, the industrial production route of ethylene glycol in China mainly uses petroleum or natural gas as raw materials. This route has disadvantages such as dependence on fossil fuels, high energy consumption, and high carbon dioxide emissions. Using sugar-based biomass as the starting material can avoid these disadvantages. Sugar-based biomass is widely present in nature, with rich and easily available sources. The catalytic conversion of sugar-based biomass to ethylene glycol has the following advantages: 1. Good atom economy; 2. Easily available raw materials; 3. Renewable resources; 4. Low carbon dioxide emissions. Currently, the technology for catalytic conversion of sugar-based biomass to ethylene glycol is not yet mature. Therefore, developing new catalysts and new processes can promote the industrialization process of this technology, and thus generate huge environmental and economic benefits.

[0003] CN105523890A discloses a method for preparing diol from sugar. Directly using glucose as the raw material, under the action of tungstate and an alloy hydrogenation catalyst, hydrolysis and hydrogenation are carried out to prepare diol. This method requires an alloy as a co-catalyst, with a large amount of metal used. And an additional tungstate needs to be added as a co-catalyst in the reaction system, and it will be lost with the solvent. CN102190562A, CN101735014A, and CN102731258A mainly use WC2 and Ni nanoparticles as catalytic active components to convert glucose into ethylene glycol, and the highest yield of diol is 60%. CN103420796A uses a composite catalyst composed of noble metal Ru / C and tungstic acid, and the yield of ethylene glycol is 52 - 57%.

[0004] In summary, the existing technologies mainly have problems such as low yield of the product diol or poor cycle stability of the catalyst, which bring great problems to industrial practical applications. Summary of the Invention

[0005] The purpose of the present invention is to overcome the problems such as poor cycle stability of the catalyst for preparing diol from sugar existing in the prior art, and to provide a dual-catalytic center catalyst, which is used for preparing diol from polyhydroxy compounds and has the advantages of low loss rate of active components and excellent cycle stability.

[0006] To achieve the above purpose, in the first aspect of the present invention, a dual-catalytic center catalyst is provided, which includes: a porous support and C3N4, a hydrogenation metal, and an aldolase reverse catalytic metal supported on the porous support; the hydrogenation metal and the aldolase reverse catalytic metal form clusters with C3N4.

[0007] The second aspect of the present invention provides a method for preparing the catalyst of the present invention, the method comprising:

[0008] (1) Dissolving an inverse aldol catalytic metal source, a hydrogenation metal source and a C3N4 precursor in a solvent, and loading the inverse aldol catalytic metal source, the hydrogenation metal source and the C3N4 precursor onto a porous support;

[0009] (2) Calcining the product obtained in step (1) under an inert gas atmosphere.

[0010] The third aspect of the present invention provides an application of the catalyst of the present invention in the preparation of diols from polyhydroxy compounds.

[0011] The fourth aspect of the present invention provides a method for preparing a diol, comprising hydrolyzing and hydrogenating a polyhydroxy compound in the presence of a catalyst and hydrogen to prepare a diol; the catalyst comprises the catalyst of the present invention.

[0012] In the prior art, the porous structure of activated carbon is beneficial to the diffusion of biomass macromolecules, but is not conducive to preventing the loss of metal active sites. For the catalyst of the present invention, the hydrogenation metal and the inverse aldol catalytic metal are coordinated with N sites and loaded on a porous support, and form clusters with C3N4, effectively stabilizing the metal active sites.

[0013] In the preparation method of the present invention, after the inverse aldol catalytic metal source, the hydrogenation metal source and the C3N4 precursor are dissolved in a solvent and pre-coordinated, they are loaded onto a porous support, so that the hydrogenation metal and the inverse aldol catalytic metal are coordinated with N sites and loaded on the porous support, and form clusters with C3N4.

[0014] The catalyst of the present invention is used for the preparation of diols from polyhydroxy compounds, and both the substrate conversion rate and the product diol selectivity are very high. Moreover, the hydrogenation metal and the inverse aldol catalytic metal form clusters with C3N4. Due to the coordination effect between the metal and the N sites, the loss of the hydrogenation metal and the inverse aldol catalytic metal during the reaction is greatly reduced, effectively stabilizing the metal active sites, increasing the cyclic stability of the catalyst, and no inactivation of the catalyst is observed after four cycles of use. Description of the Drawings

[0015] Figure 1 It is a scanning electron microscope (SEM) image of the NiW-C3N4 / AC catalyst in Example 1;

[0016] Figure 2 It is an X-ray photoelectron spectroscopy (XPS) image of the Ni element contained in the catalyst obtained in Example 1;

[0017] Figure 3 It is an X-ray photoelectron spectroscopy (XPS) image of the W element contained in the catalyst obtained in Example 1;

[0018] Figure 4 XRD pattern of the catalyst obtained in Example 1;

[0019] Figure 5 HAADF image, EDS image and particle size distribution image of the catalyst obtained in Example 1;

[0020] Figure 6 Cluster size statistical chart of the catalyst obtained in Example 1. Detailed implementation manners

[0021] The endpoints and any values within the ranges disclosed herein are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoints of each range, between the endpoints of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0022] In a first aspect of the present invention, a dual-catalytic center catalyst is provided, and the catalyst includes:

[0023] A porous support and C3N4, a hydrogenation metal, and an aldol retro-condensation metal supported on the porous support; the hydrogenation metal and the aldol retro-condensation metal form clusters with C3N4. In the catalyst of the present invention, the hydrogenation metal and the aldol retro-condensation metal are coordinated with N sites and supported on the porous support, and form clusters with C3N4, effectively stabilizing the metal active sites.

[0024] According to a preferred embodiment of the present invention, the particle size range of the clusters is 5 - 100 nm, more preferably 5 - 30 nm.

[0025] According to a preferred embodiment of the present invention, the hydrogenation metal and the aldol retro-condensation metal are supported on the support in the form of metal single sites.

[0026] According to a preferred embodiment of the present invention, the size of the porous support is 0.01 - 1 mm, preferably 0.1 - 0.5 mm.

[0027] According to a preferred embodiment of the present invention, the specific surface area of the porous support is 200 - 2000 m 2 g -1 .

[0028] In the present invention, the mass content of the hydrogenation metal in the catalyst can be selected within a relatively wide range. According to a preferred embodiment of the present invention, based on the total mass of the catalyst, the content of the hydrogenation metal is 1% - 50%, preferably 6% - 30%.

[0029] In the present invention, in the catalyst, the mass content range of the retro-aldol catalytic metal is relatively wide. According to a preferred embodiment of the present invention, based on the total mass of the catalyst, the content of the retro-aldol catalytic metal is 0.1%-50%, preferably 10%-30%.

[0030] In the present invention, in the catalyst, the mass content range of the porous support is relatively wide. According to a preferred embodiment of the present invention, based on the total mass of the catalyst, the content of the porous support is 25-96.9%, preferably 40-84%.

[0031] In the present invention, in the catalyst, the mass content range of C3N4 is relatively wide. According to a preferred embodiment of the present invention, based on the total mass of the catalyst, the content of C3N4 is 2-50%, preferably 10-30%.

[0032] According to a preferred embodiment of the present invention, the mass ratio of the retro-aldol catalytic metal to the hydrogenation metal is 0.5-6, preferably 0.8-2.5.

[0033] In the present invention, the types of the porous support that can be selected are relatively wide, and conventional porous supports in the art can all be used in the present invention. According to a preferred embodiment of the present invention, the porous support is a carbon-based porous support, preferably selected from at least one of graphene, graphdiyne, activated carbon fibers, activated carbon, and carbon nanotubes, and more preferably activated carbon.

[0034] In the present invention, there is no particular limitation on the type of the hydrogenation metal, and conventional hydrogenation metals in the art can all be used in the present invention. According to a preferred embodiment of the present invention, the hydrogenation metal is selected from at least one of Ni, Fe, and Cu.

[0035] In the present invention, there is no particular limitation on the type of the retro-aldol catalytic metal, and conventional retro-aldol catalytic metals in the art can all be used in the present invention. According to a preferred embodiment of the present invention, the retro-aldol catalytic metal is selected from at least one of W, Mo, and Ce.

[0036] In the present invention, as long as the catalyst has the characteristics described in the present invention, the object of the present invention can be achieved, and there is no particular requirement for the preparation method of the catalyst. For the present invention, a second aspect of the present invention provides a preparation method of the catalyst described in the present invention, and the method includes:

[0037] (1) Dissolve the retro-aldol catalytic metal source, the hydrogenation metal source, and the C3N4 precursor in a solvent, and then contact with the porous support for loading;

[0038] (2) Calcinate the product obtained in step (1) under an inert gas atmosphere. In the present invention, after the retro-aldol catalytic metal source, the hydrogenation metal source and the C3N4 precursor are dissolved in a solvent and pre-coordinated, they are loaded onto a porous support, so that the hydrogenation metal and the retro-aldol catalytic metal are coordinated with the N sites and loaded onto the porous support, and form clusters with C3N4.

[0039] According to a preferred embodiment of the present invention, step (1) includes:

[0040] i) Dissolve the retro-aldol catalytic metal source and the C3N4 precursor in a solvent to obtain a first solution; dissolve the hydrogenation metal source and the C3N4 precursor in a solvent to obtain a second solution;

[0041] ii) Impregnate and dry the first solution, the second solution and the porous support respectively.

[0042] According to a preferred embodiment of the present invention, the impregnation method is equal-volume impregnation. According to the preparation method of the present invention, by using simple impregnation, the obtained catalyst does not need to be reduced by hydrogen and can be directly calcined for use as a catalyst. The method of the present invention is simple, the raw materials are cheap, suitable for large-scale industrial production, and has achieved good technical effects.

[0043] According to a preferred embodiment of the present invention, the impregnation process adopts the method of multiple equal-volume impregnations. After each impregnation, a drying treatment is carried out, and the number of impregnations is adjusted according to the concentration of the impregnation solution and the impregnation target.

[0044] According to a preferred embodiment of the present invention, the conditions for drying include: the temperature is 50-120 °C and the time is 5-15 hours.

[0045] The present invention does not make requirements on the number of impregnations, which is determined according to actual needs.

[0046] In the present invention, the retro-aldol catalytic metal source, the hydrogenation metal source and the C3N4 precursor are dissolved in a solvent and pre-coordinated, and the dissolution rate can also be accelerated by means such as ultrasonic waves and stirring.

[0047] In the present invention, there are no special limitations on the calcination conditions, and the conventional calcination methods in the art can be used in the present invention. According to a preferred embodiment of the present invention, the calcination conditions include: the calcination temperature is 300-600 °C and the calcination time is 0.5-12 hours.

[0048] In the present invention, the mass ratio range of the hydrogenation metal source to the C3N4 precursor is relatively wide. According to a preferred embodiment of the present invention, the mass ratio of the hydrogenation metal source to the C3N4 precursor is (0.5-10):1, preferably (1-3):1.

[0049] In the present invention, the mass ratio of the retro-aldol catalytic metal source to the C3N4 precursor can be selected within a relatively wide range. According to a preferred embodiment of the present invention, the mass ratio of the retro-aldol catalytic metal source to the C3N4 precursor is (0.5 - 10):1, preferably (1 - 3):1.

[0050] According to a preferred embodiment of the present invention, the product obtained in step (1) is pretreated before calcination. The pretreatment conditions include: treating at 30 - 100 °C for 0.25 - 24 hours, preferably at 35 - 90 °C for 0.5 - 18 hours, and more preferably at 50 - 85 °C for 6 - 12 hours, in an inert gas or air atmosphere.

[0051] In the present invention, there is no particular limitation on the type of the C3N4 precursor. Conventional C3N4 precursors in the art can be used in the present invention. According to a preferred embodiment of the present invention, the C3N4 precursor is selected from at least one of urea, dicyandiamide, melamine, and guanidine hydrochloride, preferably at least two of urea, dicyandiamide, melamine, and guanidine hydrochloride.

[0052] According to a preferred embodiment of the present invention, the C3N4 precursor is selected from a mixture of melamine and guanidine hydrochloride. More preferably, the mass ratio of melamine to guanidine hydrochloride is 0.5 - 2:1, such as 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.2:1, 1.5:1, 1.8:1, 2:1.

[0053] In the present invention, there is no particular limitation on the type of the hydrogenation metal source. Conventional hydrogenation metal sources in the art can be used in the present invention. According to a preferred embodiment of the present invention, the hydrogenation metal source is selected from at least one of soluble salts of hydrogenation metals, preferably hydrogenation metal acetates, hydrogenation metal nitrates, hydrogenation metal chlorides, and hydrogenation metal sulfates.

[0054] According to a preferred embodiment of the present invention, the hydrogenation metal source is at least one of nickel acetate, nickel nitrate, nickel chloride, and nickel sulfate.

[0055] In the present invention, there is no particular limitation on the type of the retro-aldol catalytic metal source. Conventional retro-aldol catalytic metal sources in the art can be used in the present invention. According to a preferred embodiment of the present invention, the retro-aldol catalytic metal source is selected from at least one of soluble salts of retro-aldol catalytic metals, soluble acids of retro-aldol catalytic metals, and oxides of retro-aldol catalytic metals.

[0056] According to a preferred embodiment of the present invention, the retro-aldol catalytic metal source is at least one of tungstic acid, ammonium metatungstate, and tungsten oxide.

[0057] In the present invention, there is no particular limitation on the type of solvent, and conventional solvents in the art can be used in the present invention. The solvent is selected from at least one of water, methanol, ethanol, and ethyl acetate, and is preferably water and / or methanol.

[0058] According to a preferred embodiment of the present invention, the solvent of the first solution is methanol, and the solvent of the second solution is water.

[0059] The third aspect of the present invention provides an application of the catalyst described in the present invention in the preparation of diols from polyhydroxy compounds. The catalyst described in the present invention is particularly suitable for the preparation of diols from polyhydroxy compounds; the polyhydroxy compounds are selected from at least one of starch, hemicellulose, sucrose, glucose, fructose, furfural, and fructan. The catalyst described in the present invention is used for the preparation of diols from polyhydroxy compounds, and both the substrate conversion rate and the product diol selectivity are very high, and the catalyst has high cycle stability.

[0060] The fourth aspect of the present invention provides a method for preparing diols. In the presence of a catalyst and hydrogen, a polyhydroxy compound is hydrolyzed and hydrogenated to prepare diols; the catalyst includes the catalyst described in the present invention.

[0061] According to a preferred embodiment of the present invention, the mass ratio of the polyhydroxy compound to the catalyst is 10 - 0.1, preferably 5 - 0.5.

[0062] According to a preferred embodiment of the present invention, the mass ratio of water to the polyhydroxy compound is 30 - 300:1.

[0063] According to a preferred embodiment of the present invention, the initial filling hydrogen pressure is 0.5 - 10 MPa, preferably 1 - 6 MPa.

[0064] According to a preferred embodiment of the present invention, the hydrolysis and hydrogenation conditions include: the reaction temperature is 150 - 300 °C, preferably 200 - 245 °C; the reaction time is 0.5 - 12 h, preferably 0.5 - 4 h.

[0065] In the present invention, the reaction product diols (such as ethylene glycol, propylene glycol, butylene glycol) are qualitatively analyzed by gas chromatography - mass spectrometry (GC - MS), and the yields of the product diols (such as ethylene glycol, propylene glycol, butylene glycol) and the conversion rate of the reaction substrate glucose are analyzed by gas chromatography (GC). The gas chromatography - mass spectrometer is Agilent 7890A of Agilent Technologies, USA, the chromatographic column is HP - 5 non - polar capillary column (30 m, 0.53 mm), the gas chromatograph is Agilent 7890B, the detector is a flame ionization detector (FID), and the chromatographic column is SE - 54 capillary column (30 m, 0.53 mm).

[0066] In the present invention, the valence state of the metal loaded on the catalyst is characterized by X - ray photoelectron spectroscopy.

[0067] In the present invention, the single-site state of the metal is characterized by aberration-corrected electron microscopy.

[0068] In the present invention, the loss amount of the metal after the reaction is characterized by inductively coupled plasma optical emission spectrometry (ICP).

[0069] The calculation formula for the metal loss rate of the catalyst is:

[0070] Metal loss % of the catalyst = (metal content in the solution after the reaction) / (metal content in the initial reaction catalyst) × 100%.

[0071] The calculation formula for the glucose conversion rate is:

[0072] Glucose conversion % = (moles of glucose participating in the reaction) / (moles of glucose in the initial reaction substrate) × 100%.

[0073] The calculation formula for the yield of the product diol (ethylene glycol, propylene glycol, butylene glycol) is:

[0074] Yield % of the product diol = (number of carbon atoms corresponding to the moles of diol produced in the reaction) / (number of carbon atoms corresponding to the moles of glucose in the initial reaction substrate) × 100%.

[0075] Selectivity % of the product diol = (number of carbon atoms corresponding to the moles of diol produced in the reaction) / (moles of glucose participating in the reaction) × 100%.

[0076] Test method for cluster size: Based on the obtained electron microscopy images, the Nanomeasurer particle size analysis software is used to statistically analyze the cluster size.

[0077] To facilitate the understanding of the present invention, the following examples are listed, but the examples are only used to help understand the present invention and should not be regarded as specific limitations on the present invention.

[0078] In the following examples, the activated carbon has a size of 0.25 - 1 mm and a specific surface area of 1682 m 2 g -1 .

[0079] Example 1

[0080] (1) 0.102 g of ammonium metatungstate and 0.1 g of dicyandiamide were heated and dissolved in 3 mL of deionized water, and ultrasonicated for half an hour to prepare solution A. 0.107 g of nickel acetate tetrahydrate and 0.1 g of dicyandiamide were heated and dissolved in 3 mL of deionized water, and ultrasonicated for half an hour to prepare solution B. The impregnation process was carried out by multiple equal-volume impregnation. The impregnation steps were as follows: One portion of solution A or B was added to 1 g of activated carbon (AC), shaken until evenly mixed, and placed in an 80 °C drying oven for 10 h. This impregnation step was repeated 8 times, adding a total of 2 portions of solution A (solution A was impregnated 2 times) and 6 portions of solution B (solution B was impregnated 6 times). The obtained product was pretreated in a nitrogen atmosphere at 70 °C for 9 hours.

[0081] (2) The obtained sample was heated to 550 °C in a nitrogen atmosphere and calcined for 2 h to obtain Ni 15 W 15 -C3N4 / AC catalyst.

[0082] The SEM electron micrograph of the catalyst is as shown in Figure 1 Figure [X], and the active sites exist inside the pores of the activated carbon, and only a few can be observed on the surface;

[0083] The XPS spectrum of the catalyst is as shown in Figure 2 , Figure 3 Figure [X], indicating that Ni and W elements are mainly coordinated with carbon nitride in ionic form and supported on the activated carbon;

[0084] The XRD spectrum of the catalyst is as shown in Figure 4 Figure [X], indicating that Ni and W elements do not exist in the form of nanoparticles on the support;

[0085] The transmission electron microscope of the catalyst is as shown in Figure 5 Figure [X], indicating that the distribution of W, Ni, and N sites on the activated carbon in the sample is consistent; The cluster size statistics of the catalyst are as shown in Figure 6 Figure [X], and the size of the NiW-C3N4 clusters ranges from 11 - 23 nm. The catalyst composition and cluster size range are shown in Table 1.

[0086] Example 2

[0087] According to the method of Example 1, the difference is that in step (1), the impregnation steps are as follows: One portion of solution A or B was added to 1 g of activated carbon, shaken until evenly mixed, and placed in an 80 °C drying oven for 10 h. This impregnation step was repeated 6 times, adding a total of 2 portions of solution A and 4 portions of solution B; The other conditions were the same as those in Example 1 to obtain Ni 10 W 15 -C3N4 / AC catalyst. The catalyst composition is shown in Table 1.

[0088] Example 3

[0089] According to the method of Example 2, the difference is that in step (1), the solvent for dissolving ammonium metatungstate is methanol. Specifically, 0.102 g of ammonium metatungstate and 0.1 g of dicyandiamide are heated and dissolved in 3 mL of methanol, and ultrasonic treatment is performed for half an hour to prepare solution A. 0.107 g of nickel acetate tetrahydrate and 0.1 g of dicyandiamide are heated and dissolved in 3 mL of deionized water, and ultrasonic treatment is performed for half an hour to prepare solution B; other conditions are the same as those in Example 2 to obtain Ni 10 W 15 -C3N4 / AC catalyst. The catalyst composition is shown in Table 1.

[0090] Example 4

[0091] According to the method of Example 1, the difference is that in step (1), the impregnation step is as follows: one portion of solution A or B is added to 1 g of activated carbon, shaken until evenly mixed, and placed in an 80 °C drying oven for 10 h; this impregnation step is repeated 2 times, with a total of 0.33 portions of solution A and 1 portion of solution B added; other conditions are the same as those in Example 1 to obtain Ni 2.5 W 2.5 -C3N4 / AC catalyst. The catalyst composition is shown in Table 1.

[0092] Example 5

[0093] According to the method of Example 1, the difference is that in step (1), methanol is used as the solvent instead of deionized water; other conditions are the same as those in Example 1 to obtain Ni 15 W 15 -C3N4 / AC catalyst. The catalyst composition is shown in Table 1.

[0094] Example 6

[0095] According to the method of Example 1, the difference is that in step (1), ethanol is used as the solvent instead of deionized water; other conditions are the same as those in Example 1 to obtain Ni 15 W 15 -C3N4 / AC catalyst. The catalyst composition is shown in Table 1.

[0096] Example 7

[0097] According to the method of Example 1, the difference is that in step (1), ethyl acetate is used as the solvent instead of deionized water; other conditions are the same as those in Example 1 to obtain Ni 15 W 15 -C3N4 / AC catalyst. The catalyst composition is shown in Table 1.

[0098] Example 8

[0099] According to the method of Example 1, the difference is that in step (1), melamine and guanidine hydrochloride (with a mass ratio of 1:1) are used to replace dicyandiamide, and the total amount of C3N4 source remains unchanged to prepare solutions A and B; other conditions are the same as those in Example 1. The catalyst composition is shown in Table 1.

[0100] Example 9

[0101] (1) 0.103 g of ammonium molybdate and 0.1 g of dicyandiamide are heated and dissolved in 3 mL of deionized water, and ultrasonicated for half an hour to prepare solution A. 0.135 g of copper chloride dihydrate and 0.1 g of dicyandiamide are heated and dissolved in 3 mL of deionized water, and ultrasonicated for half an hour to prepare solution B; the impregnation process adopts the method of multiple equal-volume impregnations; the impregnation steps are as follows: one portion of solution A or B is added to 1 g of activated carbon (AC), shaken until evenly mixed, and placed in an 80°C drying oven for 10 h; this impregnation step is repeated 6 times, with a total of 2 portions of solution A and 4 portions of solution B added;

[0102] (2) The obtained sample is heated to 550°C in a nitrogen atmosphere and calcined for 2 h to obtain the Cu 20 Mo 10 -C3N4 / AC catalyst. The catalyst composition is shown in Table 1.

[0103] Comparative Example 1

[0104] 0.102 g of ammonium metatungstate is heated and dissolved in 3 mL of deionized water, and ultrasonicated for half an hour to prepare solution A. 0.107 g of nickel acetate tetrahydrate is heated and dissolved in 3 mL of deionized water, and ultrasonicated for half an hour to prepare solution B. The impregnation process adopts the method of multiple equal-volume impregnations. The standard steps are as follows: one portion of solution A or B is added to 1 g of activated carbon, shaken until evenly mixed, and placed in an 80°C drying oven for 10 h. This step is repeated 8 times throughout the process, with a total of 2 portions of solution A and 6 portions of solution B added. The obtained sample is heated to 600°C in a nitrogen atmosphere, calcined for 4 h, and then reduced at 450°C in a hydrogen environment for 2 h to obtain the Ni 15 W 15 / AC catalyst. The catalyst composition is shown in Table 1.

[0105] Comparative Example 2

[0106] Ni 15 W 15The Ni 15 W 15 / AC-C3N4 catalyst was prepared by the incipient wetness impregnation method: 0.102 g of ammonium metatungstate was heated and dissolved in 3 mL of deionized water, and ultrasonicated for half an hour to prepare solution A. 0.107 g of nickel acetate was heated and dissolved in 3 mL of deionized water, and ultrasonicated for half an hour to prepare solution B. The impregnation process adopted the method of multiple incipient wetness impregnations. The standard procedure was to add one portion of solution A or B to the activated carbon loaded with C3N4 (where the activated carbon was 1 g and C3N4 was 0.6 g), shake until evenly mixed, and place it in an 80 °C drying oven for 10 h. This step was repeated 8 times in total, adding 2 portions of solution A and 6 portions of solution B. The obtained sample was heated to 600 °C in a nitrogen atmosphere, calcined for 4 h, and then reduced at 450 °C in a hydrogen environment for 2 h to obtain the Ni 15 W 15 / AC-C3N4 catalyst. The catalyst composition is shown in Table 1. 15 W 15 / AC-C3N4 catalyst.

[0107] Examples 10 - 18

[0108] The reaction for catalytic conversion of glucose to ethylene glycol was carried out in a closed reaction kettle. 0.075 g of the catalyst from Examples 1 - 9 above, 0.25 g of glucose, and 25 mL of deionized water were added to a high-pressure reaction kettle with stirring. Hydrogen was introduced and replaced three times, and then hydrogen was filled to 4 MPa and sealed. The heating jacket was heated to 245 °C, and magnetic stirring was used. The reaction was carried out at 245 °C for 1 h. The products in the reaction solution were quantitatively analyzed by gas chromatography, and the raw materials in the reaction solution were quantitatively analyzed by liquid chromatography. The conversion rate of glucose and the yield of diol were calculated according to the aforementioned formula, as shown in Table 2. The selectivity of diol was calculated according to the aforementioned formula, as shown in Table 3.

[0109] Comparative Examples 3 - 4

[0110] The difference from Examples 10 - 18 was that the catalyst used in Comparative Example 3 was the Ni 15 W 15 / AC catalyst prepared in Comparative Example 1; the catalyst used in Comparative Example 4 was the Ni 15 W 15 / AC-C3N4 catalyst prepared in Comparative Example 2. 15 W 15 / AC catalyst; the catalyst used in Comparative Example 4 was the Ni 15 W 15 / AC-C3N4 catalyst. 15 W 15 / AC-C3N4 catalyst.

[0111] Table 1

[0112]

[0113]

[0114] Table 2

[0115] Catalyst source Glucose conversion rate (%) Yield of diol (%) Example 10 Example 1 >99 80.0 Example 11 Example 2 >99 74.8 Example 12 Example 3 >99 78.6 Example 13 Example 4 >99 61.0 Example 14 Example 5 >99 77.3 Example 15 Example 6 >99 75.1 Example 16 Example 7 >99 70.8 Example 17 Example 8 >99 82.2 Example 18 Example 9 >99 73.7 Comparative Example 3 Comparative Example 1 >99 55.3 Comparative Example 4 Comparative Example 2 >99 56.7

[0116] Table 3

[0117] Ethylene glycol selectivity (%) 1,2 - propylene glycol selectivity (%) 1,2 - butanediol selectivity (%) Example 10 41.8 16.9 21.3 Example 11 37.7 15.5 21.6 Example 12 40.9 16.2 21.5 Example 13 35.2 11.5 14.3 Comparative Example 1 43.2 5.0 7.1 Comparative Example 2 42.0 6.5 8.2

[0118] The metal content in the reaction solutions obtained in Examples 10 - 18 and Comparative Examples 3 - 4 was quantitatively analyzed by ICP, and the results are shown in Table 4.

[0119] Table 4

[0120]

[0121]

[0122] As shown in Table 4, the dual - catalytic - center catalyst of the present invention has the advantages of low loss rate of active components and excellent cycle stability.

[0123] Example 19

[0124] The catalyst prepared in Example 1 was washed and then dried and put into the next reaction, and the reaction was cycled 4 times in total. The results are shown in Table 5. 0.075 g of Ni 15 W 15 -C3N4 / AC catalyst, 0.25 g of furfural, and 25 mL of deionized water were added to a high - pressure reaction kettle with stirring. The air was displaced three times with hydrogen, and then hydrogen was filled to 4 MPa and sealed. The heating jacket was heated to the preset temperature, and magnetic stirring was used for stirring. The reaction solution was analyzed by gas phase. The reaction was carried out at 245 °C for 1 h. The products in the reaction solution were quantitatively analyzed by gas chromatography, and the raw materials in the reaction solution were quantitatively analyzed by liquid chromatography.

[0125] Table 5

[0126]

[0127]

[0128] As shown in Table 5, the dual - catalytic - center catalyst of the present invention has high catalyst stability, and no catalyst deactivation was observed after being recycled four times.

[0129] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A dual-catalytic center catalyst, characterized in that, The catalyst comprises: a porous support and C3N4, a hydrogenation metal, and an aldolase reverse catalytic metal supported on the porous support; the hydrogenation metal and the aldolase reverse catalytic metal form clusters with C3N4; the hydrogenation metal is selected from at least one of Ni, Fe, and Cu; the aldolase reverse catalytic metal is selected from at least one of W, Mo, and Ce.

2. The catalyst according to claim 1, wherein the particle size range of the clusters is 5-100 nm; and / or the hydrogenation metal and the aldolase reverse catalytic metal are supported on the porous support in the form of metal single sites; and / or the size of the porous support is 0.01-1 mm; and / or The specific surface area of the porous carrier is 200 - 2000 m 2 g -1 .

3. The catalyst according to claim 1 or 2, wherein the particle size range of the clusters is 5-30 nm; and / or the size of the porous support is 0.1-0.5 mm.

4. The catalyst according to claim 1 or 2, wherein based on the total mass of the catalyst, the content of the hydrogenation metal is 1%-50%; the content of the aldolase reverse catalytic metal is 0.1%-50%; the content of the porous support is 25-96.9%; the content of C3N4 is 2-50%; the mass ratio of the aldolase reverse catalytic metal to the hydrogenation metal is 0.5-6.

5. The catalyst according to claim 4, wherein based on the total mass of the catalyst, the content of the hydrogenation metal is 6%-30%; and / or the content of the aldolase reverse catalytic metal is 10%-30%; and / or the content of the porous support is 40-84%; and / or the content of C3N4 is 10-30%; and / or the mass ratio of the aldolase reverse catalytic metal to the hydrogenation metal is 0.8-2.

5.

6. The catalyst according to claim 1 or 2, wherein The porous support is selected from carbon-based porous supports.

7. The catalyst according to claim 1 or 2, wherein, The porous support is selected from at least one of graphene, graphdiyne, activated carbon fibers, activated carbon, and carbon nanotubes.

8. The catalyst according to claim 1 or 2, wherein, The porous support is activated carbon.

9. The preparation method of the catalyst according to any one of claims 1-8, characterized in that, The method comprises: (1) Dissolving an aldolase reverse catalytic metal source, a hydrogenation metal source, and a C3N4 precursor in a solvent, and then contacting with a porous support for loading; (2) Calcining the product obtained in step (1) in an inert gas atmosphere.

10. The preparation method according to claim 9, wherein the solvent is selected from at least one of water, methanol, ethanol, and ethyl acetate; and / or step (1) comprises i) Dissolving the aldolase reverse catalytic metal source and the C3N4 precursor in a solvent to obtain a first solution; dissolving the hydrogenation metal source and the C3N4 precursor in a solvent to obtain a second solution; ii) Impregnating and drying the first solution and the second solution with the porous support respectively; and / or the calcination conditions include: the calcination temperature is 300-600 °C, and the calcination time is 0.5-12 hours.

11. The preparation method according to claim 10, wherein the solvent is water and / or methanol; and / or the solvent of the first solution is methanol, and the solvent of the second solution is water; and / or the impregnation method is equal-volume impregnation.

12. The preparation method according to claim 9 or 10, wherein the mass ratio of the hydrogenation metal source to the C3N4 precursor is 0.5-10:1; the mass ratio of the aldolase reverse catalytic metal source to the C3N4 precursor is 0.5-10:1; The product obtained in step (1) is pretreated before roasting. The pretreatment conditions include: treating at 30-100 °C for 0.25-24 hours in an inert gas or air atmosphere.

13. The preparation method according to claim 9 or 10, wherein the mass ratio of the hydrogenation metal source to the C3N4 precursor is 1-3:1; and / or the mass ratio of the retro-aldol catalytic metal source to the C3N4 precursor is 1-3:

1.

14. The preparation method according to claim 9 or 10, wherein the C3N4 precursor is selected from at least one of urea, dicyandiamide, melamine, and guanidine hydrochloride; the hydrogenation metal source is selected from at least one of soluble salts of hydrogenation metals; the retro-aldol catalytic metal source is selected from at least one of soluble salts of retro-aldol catalytic metals, soluble acids of retro-aldol catalytic metals, and oxides of retro-aldol catalytic metals.

15. The preparation method according to claim 9 or 10, wherein the C3N4 precursor is at least two of urea, dicyandiamide, melamine, and guanidine hydrochloride; and / or the hydrogenation metal source is at least one of hydrogenation metal acetates, hydrogenation metal nitrates, hydrogenation metal chlorides, and hydrogenation metal sulfates.

16. Use of the catalyst according to any one of claims 1-8 in the preparation of diols from polyhydroxy compounds.

17. A method for preparing a diol, characterized in that, In the presence of a catalyst and hydrogen, the polyhydroxy compound is hydrolyzed and hydrogenated to prepare a diol; the catalyst includes the catalyst according to any one of claims 1-8.

18. The preparation method according to claim 17, wherein the mass ratio of the polyhydroxy compound to the catalyst is 10-0.1; and / or the mass ratio of water to the polyhydroxy compound is 30-300:1; and / or the initial filling hydrogen pressure is 0.5-10 MPa; and / or the hydrolysis and hydrogenation conditions include: the reaction temperature is 150-300 °C; the reaction time is 0.5-12 h; and / or the polyhydroxy compound is selected from at least one of starch, hemicellulose, sucrose, glucose, fructose, furfural, and fructan.

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