A preparation method of a glycerol hydrogenolysis catalyst

Abstract

The present invention discloses a method for preparing a glycerol hydrogenolysis catalyst, belonging to the field of glycerol hydrogenolysis. The method uses ammonium metatungstate as a tungsten source, further improves the acidic sites and oxygen vacancy content on the surface of a WO3 carrier by metal doping, and synthesizes hollow mesoporous carrier spheres using mesoporous hollow silica spheres as a hard template. Active metals copper and nickel are loaded by atomic layer deposition to obtain a glycerol hydrogenolysis catalyst. The catalyst has small metal particles, high dispersion, excellent catalytic activity, and is rich in oxygen vacancies and acidic sites, which facilitate active metal anchoring and mass transfer, effectively improving reaction activity.

Description

Technical Field

[0001] The invention belongs to the technical field of glycerol hydrogenolysis, and particularly relates to a method for preparing a glycerol hydrogenolysis catalyst. Background Art

[0002] As biodiesel technology becomes increasingly mature, it is being vigorously developed worldwide, resulting in an increasing content of its by-product glycerol. In this process, approximately 0.1 kg of glycerol is produced for every kg of fatty acid methyl ester produced, leading to an oversupply of glycerol on the world market.

[0003] The production of 1,3-propylene glycol (1,3-PD) from glycerol not only alleviates glycerol oversupply, but is also a key commercial product widely used in the food, cosmetics, and pharmaceutical industries. The synthesis of polytrimethylene terephthalate (PTT) holds the greatest potential, accounting for 80% of total consumption. This polyester can be used to produce PTT fibers for applications in clothing, carpets, and other industries. However, the catalyst activity for the hydrogenolysis of 1,3-PD from glycerol in existing technologies needs to be improved, and the catalyst's low selectivity for 1,3-PD results in a high number of byproducts, increasing the cost of separation and purification.

[0004] The Chinese invention patent document with publication number CN111036206A discloses a glycerol hydrogenolysis catalyst and its preparation method, in which dual active components are loaded onto an alumina carrier by impregnation. The active components are precious metals such as platinum and rhodium, which are expensive. At the same time, the loading by impregnation results in a low dispersion of the active metals and a small exposed active specific surface area, which is not conducive to the reaction.

[0005] A Chinese invention patent document with publication number CN102728380A discloses a catalyst for preparing 1,3-propylene glycol by hydrogenolysis of glycerol. The catalyst uses mesoporous tungsten oxide as a carrier and platinum or other precious metals as active components. The carrier has a small specific surface area and is insufficient to disperse the active metal. In the reaction to prepare 1,3-propylene glycol, the conversion rate of glycerol is less than 25%. Summary of the Invention

[0006] The present invention aims to provide a method for preparing a glycerol hydrogenolysis catalyst. By designing a tungsten oxide carrier with a hollow mesoporous structure, introducing oxygen vacancies and acidic sites, and using atomic layer deposition technology to load bimetallic active components, the activity of the catalyst is significantly improved. The prepared glycerol hydrogenolysis catalyst has a higher glycerol conversion rate and 1,3-propylene glycol selectivity, low preparation cost, and broad application prospects.

[0007] In order to solve the above problems, the present invention provides the following technical solutions:

[0008] (1) Dissolve bicarbonate and cationic surfactant in an alcohol solvent, add an organic silicon source, stir at a constant temperature of 30-50°C, and centrifuge to obtain hollow mesoporous silica spheres;

[0009] (2) dissolving the metal precursor and the tungsten source in a mixed solution of alcohol and deionized water in a volume ratio of 1:1 to 3, adding the hollow mesoporous silica spheres obtained in step (1), and stirring at room temperature to obtain a SiO2 solid coated with the tungsten source and the metal precursor;

[0010] (3) calcining the SiO2 solid coated with the tungsten source and the metal precursor to obtain MO2WO3@SiO2;

[0011] (4) Add MO2WO3@SiO2 to the alkaline solution, stir, separate the solid and liquid, and dry the solid to obtain MO2WO3 hollow mesoporous spheres.

[0012] (5) Using MO2WO3 hollow mesoporous spheres as carriers, β-diketone copper complex and nickelocene as copper and nickel sources, respectively, and ozone as oxygen source, atomic layer deposition equipment was used to deposit nickel oxide and copper oxide layers on the surface of MO2WO3 hollow mesoporous spheres. The product was then calcined and reduced in hydrogen to obtain a glycerol hydrogenolysis catalyst.

[0013] Preferably, in step (1), the alcohol solvent is one of methanol, ethanol, and propanol; the bicarbonate is sodium bicarbonate or ammonium bicarbonate; the cationic surfactant is one of octadecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide, and hexadecyldimethylammonium chloride; the organosilicon source is ethyl orthosilicate or methyl orthosilicate; the volume mass ratio of the alcohol solvent, bicarbonate, cationic surfactant, and organosilicon source is 5-10 mL:0.5-1 g:0.1-0.5 g:1-3 mL, and the constant temperature stirring time is 12-24 h.

[0014] Preferably, in step (2), the metal precursor is one of cerium nitrate, ammonium molybdate, and zirconium nitrate; the tungsten source is ammonium metatungstate or ammonium paratungstate; the molar ratio of the metal precursor to the tungsten source is 0.05:0.5-1; and the mass ratio of the tungsten source to the hollow mesoporous silica spheres is 1:0.5-2.

[0015] Preferably, in step (3), the calcination temperature is 400-600° C. and the calcination time is 1-3 h.

[0016] Preferably, in step (4), the alkaline solution is potassium hydroxide or sodium hydroxide solution; the molar ratio of MO2WO3@SiO2 to the alkaline solution is 1:2-4; and the stirring time is 6-12 h.

[0017] Preferably, in step (5), the molar ratio of copper to nickel in the copper source and nickel source is 1:1 to 5; the atomic layer deposition temperature is 180 to 250°C, and the deposition cycle is 5 to 20 cycles; the hydrogen flow rate of the hydrogen calcination reduction is 80 to 120 ml / min, the calcination reduction temperature is 400 to 550°C, and the time is 1 to 3 hours.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) The technical solution provided by the present invention is to prepare hollow tungsten oxide balls as catalyst carriers by adopting a hard template method. Tungsten oxide not only contains Bronsted acid sites. When used for glycerol hydrogenolysis, glycerol dehydrates under the action of Bronsted acid sites to form 3-hydroxypropenol intermediates, and then hydrogenates under the action of active metals to form 1,3-propylene glycol. In addition, during the catalyst preparation process, the tungsten oxide is partially reduced to form oxygen vacancies. The oxygen vacancies in the tungsten oxide promote the adsorption of hydrogen, which is beneficial to the activation of hydrogen. At the same time, the oxygen vacancies can be used to anchor the active components, enhance the interaction between the active metal and the carrier, and thus will not migrate during the reaction, maintain a high dispersion, and be beneficial to the reaction. At the same time, the present invention dopes different metals such as cerium, molybdenum or zirconium in the process of preparing the catalyst carrier, introduces the second metal into the crystal lattice, helps the formation of oxygen vacancies, promotes the formation of more strong acid sites, and further improves the catalytic efficiency.

[0020] (2) The present invention uses atomic layer deposition to load active metals, which can accurately realize the construction of catalytic species on the support surface. Compared with the traditional method of preparing catalysts by impregnation, the metal particles obtained by atomic layer deposition are smaller and more dispersed, which significantly improves the catalytic activity.

[0021] (3) The technical solution provided by the present invention not only has a high specific surface area (252m 2 / g), helps disperse the active components and enhances catalytic activity. Furthermore, reactants can enter the hollow spheres through the pores, increasing the reaction contact area while creating a microenvironment. The pore structure accelerates mass transfer and improves reaction efficiency. Glycerol conversion reaches 68.5%, and selectivity for 1,3-propylene glycol is 58.3%. Compared with existing technologies, this catalyst significantly improves both conversion and selectivity, and produces fewer byproducts, reducing separation and purification costs.

[0022] (4) The technical solution provided by the present invention uses copper-nickel bimetallic as an active component, and the two have a synergistic effect; copper is more conducive to hydrogen dissociation and overflow to the carrier, and nickel effectively adsorbs reactants and transfers products. Compared with the existing technology that uses platinum as an active component to catalyze the hydrogenolysis of glycerol to prepare 1,3-propylene glycol, it has the advantages of low cost, high activity and high selectivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention will be further described below with reference to the accompanying drawings and examples:

[0024] Figure 1 This is the X-ray diffraction (XRD) pattern of the catalyst prepared in Example 1;

[0025] Figure 2 This is a transmission electron microscope (TEM) image of the catalyst prepared in Example 1;

[0026] Figure 3 This is a transmission electron microscope (TEM) image of the catalyst prepared in Comparative Example 1;

[0027] Figure 4 This is a transmission electron microscope (TEM) image of the catalyst prepared in Comparative Example 2;

[0028] Figure 5 NiCuCeO2WO prepared in Example 1 x Catalyst, NiCuWO prepared in Comparative Example 3 x Comparative NH3-TPD spectra of catalysts. DETAILED DESCRIPTION

[0029] To make the purpose, technical solution and effects of the present invention clearer, the technical solution of the present invention will be described in detail below. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in this field without making any creative work are within the scope of protection of the present invention. The atomic layer deposition equipment used in the embodiments of the present invention is an MNT f-150-212 thermal atomic layer deposition equipment. Example 1

[0030] (1) Add 0.5 g of ammonium bicarbonate and 0.3 g of hexadecyltrimethylammonium bromide to 5 mL of ethanol and stir until dissolved. Add 2 ml of ethyl orthosilicate and stir at 40 °C for 18 h. Centrifuge to obtain hollow mesoporous silica spheres.

[0031] (2) Cerium nitrate and ammonium metatungstate were dissolved in a solution of ethanol and deionized water in a volume ratio of 1:1, with the molar ratio of cerium nitrate to ammonium metatungstate being 0.05:0.8. Hollow mesoporous silica spheres were added, with the mass ratio of ammonium metatungstate to hollow mesoporous silica spheres being 1:1. The mixture was stirred at room temperature for 3 h to obtain ammonium metatungstate and cerium nitrate@SiO2.

[0032] (3) Transfer ammonium metatungstate and cerium nitrate@SiO2 into a muffle furnace, heat to 500℃ and keep constant for 2h, and calcine to obtain CeO2WO3@SiO2;

[0033] (4) CeO2WO3@SiO2 was added to a sodium hydroxide solution and stirred to remove the ordered mesoporous silica. The molar ratio of CeO2WO3@SiO2 to sodium hydroxide was 1:2. The mixture was stirred for 9 h, and the solid-liquid separation and drying were performed to obtain CeO2WO3 hollow mesoporous spheres.

[0034] (5) CeO2WO3 hollow mesoporous spheres were used as carriers, β-diketone copper complex and nickelocene were used as copper and nickel sources, respectively, and ozone was used as oxygen source. Atomic layer deposition equipment was used to deposit nickel oxide and copper oxide layers on the surface of the hollow mesoporous spheres. The molar ratio of copper to nickel was 1:3, the deposition temperature was 220℃, and the deposition cycle was 15 cycles. The obtained sample was placed in a tube furnace, hydrogen was introduced at a flow rate of 120ml / min, and the temperature was raised to 500℃ for reduction for 2h to obtain NiCuCeO2WO x The nickel loading of the catalyst was 2.25%. Example 2

[0035] (1) Add 1 g of sodium bicarbonate and 0.5 g of octadecyltrimethylammonium chloride to 10 mL of methanol and stir until dissolved. Add 3 ml of methyl orthosilicate and stir at 30 °C for 12 h. Centrifuge to obtain hollow mesoporous silica spheres.

[0036] (2) Dissolve zirconium nitrate and ammonium paratungstate in a solution of ethanol and deionized water in a volume ratio of 1:2, with a molar ratio of zirconium nitrate to ammonium paratungstate of 0.05:1, add hollow mesoporous silica spheres, with a mass ratio of ammonium paratungstate to hollow mesoporous silica spheres of 1:0.5, and continue stirring at room temperature for 5 hours to obtain ammonium paratungstate and zirconium nitrate@SiO2;

[0037] (3) Transfer ammonium paratungstate and zirconium nitrate @SiO2 into a muffle furnace, heat to 400℃ and keep constant for 3h, and calcine to obtain ZrO2WO3@SiO2;

[0038] (4) ZrO2WO3@SiO2 was added to potassium hydroxide solution and stirred to remove ordered mesoporous silica. The molar ratio of ZrO2WO3@SiO2 to sodium hydroxide was 1:3. The mixture was stirred for 6 h, solid-liquid separation was performed, and drying was performed to obtain ZrO2WO3 hollow mesoporous spheres.

[0039] (5) ZrO2WO3 hollow mesoporous spheres were used as carriers, β-diketone copper complex and nickelocene were used as copper and nickel sources, respectively, and ozone was used as oxygen source. Atomic layer deposition equipment was used to deposit nickel oxide and copper oxide layers on the surface of the hollow mesoporous spheres. The molar ratio of copper to nickel was 1:5, the deposition temperature was 250℃, and the deposition cycle was 5 cycles. The obtained sample was placed in a tube furnace, hydrogen was introduced at a flow rate of 100 ml / min, and the temperature was raised to 400℃ for reduction for 3 h to obtain NiCuZrO2WO x The nickel loading of the catalyst was 0.75%. Example 3

[0040] (1) Add 0.8 g of sodium bicarbonate and 0.1 g of hexadecyldimethylammonium chloride to 7 mL of propanol and stir until dissolved. Add 1 ml of ethyl orthosilicate and stir at 50 °C for 24 h. Centrifuge to obtain hollow mesoporous silica spheres.

[0041] (2) Dissolve ammonium molybdate and ammonium metatungstate in a solution of ethanol and deionized water in a volume ratio of 1:3, with a molar ratio of ammonium molybdate to ammonium metatungstate of 0.05:0.5, add hollow mesoporous silica spheres, with a mass ratio of ammonium metatungstate to hollow mesoporous silica spheres of 1:2, and continue stirring at room temperature for 6 hours to obtain ammonium metatungstate and ammonium molybdate@SiO2;

[0042] (3) Transfer ammonium metatungstate and ammonium molybdate@SiO2 into a muffle furnace, heat to 600℃ and keep constant for 1h, and calcine to obtain MoO2WO3@SiO2;

[0043] (4) MoO2WO3@SiO2 was added to a sodium hydroxide solution and stirred to remove the ordered mesoporous silica. The molar ratio of MoO2WO3@SiO2 to sodium hydroxide was 1:4. The solution was stirred for 12 h, and the solid-liquid separation and drying were performed to obtain MoO2WO3 hollow mesoporous spheres.

[0044] (5) MoO2WO3 hollow mesoporous spheres were used as carriers, β-diketone copper complex and nickelocene were used as copper and nickel sources, respectively, and ozone was used as oxygen source. Atomic layer deposition equipment was used to deposit nickel oxide and copper oxide layers on the surface of the hollow mesoporous spheres. The molar ratio of copper to nickel was 1:1, the deposition temperature was 180℃, and the deposition cycle was 20 cycles. The obtained sample was placed in a tube furnace, hydrogen was introduced at a flow rate of 80ml / min, and the temperature was raised to 550℃ for reduction for 1h to obtain NiCuMoO2WO x The catalyst has a nickel loading of 3%. Comparative Example 1

[0045] Step (2) Dissolve cerium nitrate and ammonium metatungstate in a solution of ethanol and deionized water in a volume ratio of 1:1, where the molar ratio of cerium nitrate to ammonium metatungstate is 0.05:0.8. Add hollow mesoporous silica spheres, where the mass ratio of ammonium metatungstate to hollow mesoporous silica spheres is 1:0.2, and continue stirring at room temperature for 3 hours to obtain ammonium metatungstate and cerium nitrate@SiO2. Other conditions are the same as those in Example 1. Comparative Example 2

[0046] Step (5) CeO2WO x Hollow mesoporous spheres were used as carriers, and nickel oxide and copper oxide were loaded by impregnation, with a nickel loading of 2.25%. Other conditions were the same as in Example 1. Other conditions were the same as in Example 1. Comparative Example 3

[0047] Step (2) dissolving ammonium metatungstate in a solution of ethanol and deionized water in a volume ratio of 1:1, adding hollow mesoporous silica spheres, wherein the mass ratio of ammonium metatungstate to hollow mesoporous silica spheres is 1:1, and continuing stirring at room temperature for 3 hours to obtain ammonium metatungstate@SiO2; other conditions are the same as those in Example 1.

[0048] Figure 1 The X-ray diffraction (XRD) pattern of the catalyst prepared in Example 1 is as follows: Figure 1 It can be seen that in addition to WO x The diffraction peaks do not show the diffraction peaks of CeO2, indicating that CeO2 enters the interior of WO3 in the form of a lattice, which helps the formation of oxygen vacancies, is more conducive to hydrogen dissociation and overflow, and promotes the formation of more Bronsted acid sites. At the same time, there are no diffraction peaks of copper and nickel, indicating that the active metal is loaded by atomic layer deposition, making it highly uniformly dispersed. x The catalyst is used in the glycerol hydrogenolysis reaction, with a glycerol conversion rate of up to 68.3%, of which the selectivity of 1,3-propylene glycol can reach 58.3%.

[0049] Figure 2 This is a transmission electron microscope (TEM) image of the catalyst prepared in Example 1. Figure 1 It can be seen that the catalyst presents a complete hollow sphere structure with uniform size and thickness, indicating that CeO2WO3 hollow mesoporous spheres were successfully synthesized using silica hollow mesoporous spheres as hard templates. This is mainly due to the control of the ratio of ammonium metatungstate to silica hollow mesoporous spheres (1:0.5~2) and the use of atomic layer deposition to load active metals.

[0050] Figure 3 This is a transmission electron microscope (TEM) image of the catalyst prepared in Comparative Example 1. During the preparation process, the mass ratio of ammonium metatungstate to hollow mesoporous silica spheres was greater than 1:0.5, and the obtained NiCuCeO2WO x The CeO2WO3 layer in the catalyst is too thick, which prevents the internal substances from contacting the reactants, reducing its utilization rate. Therefore, when it is applied to the glycerol hydrogenolysis reaction, the glycerol conversion rate is as low as 40.8%, of which the selectivity of 1,3-propylene glycol is only 41.5%.

[0051] Figure 4 This is the transmission electron microscope (TEM) image of the catalyst prepared in Comparative Example 2. Figure 4It can be seen that compared with Example 1, the catalyst surface thickness formed in Comparative Example 2 is not uniform. This is because the copper and nickel precursors are unevenly attached to the CeO2WO3 surface during the preparation of the catalyst by the impregnation method. After calcination and reduction, the copper and nickel loaded on the surface of some carrier CeO2WO3 are too thick, and the internal metal cannot contact the reactants, resulting in a decrease in catalytic activity; the other part of the CeO2WO3 surface is not loaded with copper and nickel, lacks active metals, and is not conducive to the catalytic activation of glycerol.

[0052] A chemical adsorption instrument was used to conduct an NH3 temperature-programmed desorption experiment (NH3-TPD) on the catalyst to determine the adsorption of NH3 by the catalyst. The greater the amount of ammonia adsorbed, the more acidic sites the sample has. First, the sample was placed in a U-shaped quartz tube, and the program was set to introduce carrier gas and hydrogen for reduction. After the reduction was completed, the hydrogen was turned off and purged with carrier gas, and then the ammonia was turned on for adsorption. After the adsorption was completed, the ammonia was turned off, and the temperature was programmed to record the signal.

[0053] Figure 5 NiCuCeO2WO prepared in Example 1 x Catalyst, NiCuWO prepared in Comparative Example 3 x Comparative NH3-TPD spectra of catalysts. Figure 5 It can be seen that with the increase of temperature, two signal peaks appear in the NH3-TPD spectra of the catalysts of Example 1 and Comparative Example 3, but the signal peak area of Example 1 is significantly larger than the signal peak area of the catalyst of Comparative Example 3, indicating that the former has a larger adsorption capacity of ammonia, and thus indicates that the catalyst of Example 1 contains more acidic sites. This is because the introduction of the second metal cerium into the lattice of tungsten trioxide contributes to the formation of oxygen vacancies, which is more conducive to hydrogen dissociation and overflow, forming more acidic sites, and thus improving the catalytic activity.

[0054] The catalysts prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were respectively applied to glycerol hydrogenolysis reactions, which are within the scope of the prior art. The results are listed in Table 1.

[0055]

Claims

1. A method for preparing a glycerol hydrogenolysis catalyst, characterized in that: The steps include: (1) Dissolve bicarbonate and cationic surfactant in an alcohol solvent, add an organic silicon source, stir at a constant temperature of 30-50°C, and centrifuge to obtain hollow mesoporous silica spheres; (2) dissolving the metal precursor and the tungsten source in a mixed solution of alcohol and deionized water in a volume ratio of 1:1 to 3, adding the hollow mesoporous silica spheres obtained in step (1), and stirring at room temperature for 3 to 6 hours to obtain a SiO2 solid coated with the tungsten source and the metal precursor; the mass ratio of the tungsten source to the hollow mesoporous silica spheres is 1:0.5 to 2; (3) calcining the SiO2 solid coated with the tungsten source and the metal precursor obtained in step (2) to obtain MO2WO3@SiO2; (4) Add MO2WO3@SiO2 to an alkaline solution, stir, separate, and dry the solid to obtain MO2WO3 hollow mesoporous spheres; (5) Using MO2WO3 hollow mesoporous spheres as carriers, β-diketone copper complex and nickelocene as copper and nickel sources, respectively, and ozone as oxygen source, atomic layer deposition equipment was used to deposit nickel oxide and copper oxide layers on the surface of MO2WO3 hollow mesoporous spheres. The product was then calcined and reduced in hydrogen to obtain a glycerol hydrogenolysis catalyst.

2. The method for preparing a glycerol hydrogenolysis catalyst according to claim 1, wherein In the step (1), the alcohol solvent is one of methanol, ethanol, and propanol; the bicarbonate is sodium bicarbonate or ammonium bicarbonate; the cationic surfactant is one of octadecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide, and hexadecyldimethylammonium chloride; the organosilicon source is ethyl orthosilicate or methyl orthosilicate; the volume mass ratio of the alcohol solvent, bicarbonate, cationic surfactant, and organosilicon source is 5-10 mL:0.5-1 g:0.1-0.5 g:1-3 mL, and the constant temperature stirring time is 12-24 h.

3. The preparation method of the glycerol hydrogenolysis catalyst according to claim 1, wherein In the step (2), the metal precursor is one of cerium nitrate, ammonium molybdate, and zirconium nitrate; the tungsten source is ammonium metatungstate or ammonium paratungstate; and the molar ratio of the metal precursor to the tungsten source is 0.05:0.5-1.

4. The method for preparing a glycerol hydrogenolysis catalyst according to claim 1, wherein In the step (3), the calcination temperature is 400-600° C. and the calcination time is 1-3 hours.

5. The method for preparing a glycerol hydrogenolysis catalyst according to claim 1, wherein In the step (4), the alkaline solution is potassium hydroxide or sodium hydroxide solution; the molar ratio of MO2WO3@SiO2 to the alkaline solution is 1:2-4; and the stirring time is 6-12 hours.

6. The method for preparing a glycerol hydrogenolysis catalyst according to claim 1, wherein In the step (5), the molar ratio of copper to nickel is 1:1 to 5; the atomic layer deposition temperature is 180 to 250°C, and the deposition cycle is 5 to 20 cycles; the hydrogen flow rate of the hydrogen calcination reduction is 80 to 120 mL / min, the calcination reduction temperature is 400 to 550°C, and the time is 1 to 3 hours.

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