Preparation of nickel-aluminum oxide catalyst and application of nickel-aluminum oxide catalyst in preparation of furfuryl alcohol through furfural hydrogenation

Abstract

The invention relates to the chemical field of efficient catalytic conversion of biomass platform compounds into high-added-value chemicals, and particularly provides a preparation method of a flower-shaped nickel aluminum oxide and application of the flower-shaped nickel aluminum oxide in preparation of furfuryl alcohol through catalytic transfer hydrogenation of furfural. The preparation method mainly comprises the following steps: dissolving 0.01 mol of aluminum nitrate, 0.02 mol of nickel nitrate and 0.084 mol of urea in 60 ml of deionized water, stirring at room temperature for 1 h to form a clear solution, transferring the clear solution into a lining of a hydrothermal kettle, aging at 140 DEG C for 7 h, naturally cooling to room temperature, and repeatedly washing with deionized water until the pH value of supernate is 7; and dispersing the separated green muddy precipitate in 200ml of methanol, stirring at room temperature for 2 hours, filtering and washing, and drying at 60 DEG C for 24 hours. And grinding the obtained hydrotalcite precursor into powder, putting the powder into a quartz boat, and carrying out high-temperature calcination for 2 hours in argon flow of 60 ml / min at the temperature of 500 DEG C to finally obtain the grey green solid catalyst. The metal oxide prepared by the invention has the characteristics of uniform components, rich acid-base sites and the like as a catalyst, and has the characteristics of simple preparation method, no need of reduction, environment friendliness and the like when being applied to industrial production. Therefore, when the catalyst is applied to a reaction for preparing furfuryl alcohol through furfural transfer hydrogenation, efficient conversion of furfural can be realized, the conversion rate can reach 100%, and the selectivity is 92.1%.

Description

Technical Field

[0001] The invention belongs to the field of catalyst preparation, and specifically designs a preparation method of a flower-shaped nickel-aluminum bimetallic oxide and an application of the same in a furfural transfer hydrogenation reaction. Background Art

[0002] The catalytic conversion of biomass into fuels and chemicals can mediate the dependence on fossil fuels and increase the utilization of waste resources. Therefore, among non-fossil carbon energy sources, the utilization of biomass is considered to be a very promising option and a good implementation of the carbon neutrality initiative. Furfural is usually a product of biomass (such as wood fiber, straw, etc.), and its main structure is aldehyde group and furan ring. Through catalytic hydrogenation, it can generate a variety of high value-added products, making it have certain application value.

[0003] Furfuryl alcohol is one of the most value-added downstream compounds prepared by direct selective hydrogenation of furfural. It is an important organic raw material and is widely used in synthetic fiber, rubber, pesticide and other industries. Transition metals, especially precious metals such as Ru and Pd, have high activity in the selective hydrogenation of furfural to produce furfuryl alcohol. However, its production cost is high, and the active ingredients are lost under harsh reaction conditions, which makes it impossible to apply it to industrial production. Non-precious metals such as Ni and Cu also have high catalytic activity in the system of furfural hydrogenation to produce furfuryl alcohol, but its single product is difficult to control, and in the direct hydrogenation system with hydrogen as the hydrogen source, high pressure and the reduced state of the metal inevitably increase the difficulty of operation and the cost of the device. Therefore, under relatively mild reaction conditions, the use of solvents and metal oxides for transfer hydrogenation becomes a more competitive option.

[0004] In the field of catalytic transfer hydrogenation, common catalysts include metal catalysts, acidic zeolites, hydroxides and metal oxides. Formic acid or alcohols are used as hydrogen sources instead of high-pressure and explosive hydrogen. 2 The mode of hydrogenation, catalytic transfer hydrogenation is more economical, safe and environmentally friendly, but this type of catalyst has disadvantages such as low reactivity and low yield. Therefore, a nickel-aluminum hydrotalcite precursor is prepared by a simple hydrothermal method, and a high-load nickel-aluminum metal oxide is obtained by calcination under a nitrogen atmosphere. The catalyst has abundant acidic and basic sites and has a single activity for furfuryl alcohol. This type of cheap, non-toxic and highly selective catalyst is applied to the industrial production of furfural selective hydrogenation, and has a very obvious catalytic effect on the hydrogenation selectivity of furfural-rich biomass. Summary of the invention

[0005] The purpose of the invention is to provide a method for preparing flower-shaped nickel-aluminum metal oxide by a hydrothermal method and its application in catalytic transfer hydrogenation of furfural. The metal oxide has unique structural advantages as a catalyst and has excellent selectivity for the reaction of furfural to furfuryl alcohol.

[0006] The method for preparing the metal oxide of the present invention is as follows:

[0007] (1): Preparation of metal precursor solution: add 0.01-0.05 mol / L nickel salt, 0.01-0.05 mol / L aluminum salt, and 0.05-0.1 mol / L alkali source into 60 ml of deionized water, wherein the anion of the metal nickel salt is any one of nitrate, phosphate, chlorate, and sulfate, the anion of the metal aluminum salt is any one of nitrate, phosphate, chlorate, and sulfate, and the alkali source is any one of urea, sodium hydroxide, sodium carbonate, ammonium carbonate, and ammonia water.

[0008] (2): The solution in (1) was stirred at room temperature for 0.5 h to 4 h until it became a uniform transparent solution, and then transferred to a polytetrafluoroethylene hydrothermal autoclave lining. After aging, it was naturally cooled to room temperature and repeatedly rinsed with deionized water until the pH of the supernatant was 7.

[0009] (3): The sample obtained in (2) was dispersed in 200 ml of methanol, stirred evenly at room temperature, filtered and separated, and the obtained muddy precipitate was dried at 60°C for 6h to 24h.

[0010] (4): The solid obtained in (3) is ground into powder, placed in a quartz boat, and calcined at 400°C to 600°C in an argon flow or air at a heating rate of 2°C / min to 10°C / min for 2h to 4h to finally obtain a gray-green target catalyst.

[0011] Preferably, in step (1), the ratio of nickel ions to aluminum ions is controlled within the range of 3:1 to 1:4, and the loading amount of nickel oxide = {nickel oxide / (nickel oxide+aluminum oxide)}*100%.

[0012] Preferably, in step (2), the aging time of the metal precursor solution is 5 h to 12 h, and the aging temperature is controlled at 100° C. to 180° C.

[0013] Preferably, the stirring time of the methanol solution in step (3) is 2 h to 24 h.

[0014] Preferably, the calcination conditions in step (4) are: heating to 400°C to 600°C at a rate of 2°C / min to 10°C / min and maintaining for 2h to 4h.

[0015] The metal oxide prepared by the above method is used to catalyze the selective hydrogenation reaction of furfural.

[0016] The conditions for the catalytic furfural selective hydrogenation reaction are as follows: weigh 10 mg to 60 mg of the catalyst and put it in a 10 ml high pressure reactor, add 0.5 mmol of furfural and 3 ml of solvent, fill with nitrogen to 0.5 MPa to 3 MPa, set the stirring speed to 500 rpm to 1000 rpm, heat to 100° C. to 180° C. and start timing the reaction for 1 h to 5 h. After the reaction is completed, quickly put it in an ice water bath to cool it down, and separate the solid catalyst for sampling and analysis after the reactor is depressurized.

[0017] After the catalytic reaction, the catalyst was separated, rinsed three times with deionized water and ethanol alternately, and dried at 40°C for 12 h for subsequent cyclic reactions.

[0018] Beneficial effects:

[0019] (1) The present invention adopts the traditional hydrothermal method to prepare the intermetallic compound with uniform dispersion, high specific surface area and abundant acid and base sites. The method is green and economical, simple and feasible to operate, has low energy consumption, and omits the reduction process step, and is suitable for industrial mass production.

[0020] (2) Compared with the traditional method of using hydrogen for hydrogenation, catalytic transfer hydrogenation is more economical, safer and environmentally friendly, and effectively solves the key problem of the catalyst selectively hydrogenating the C=O functional group while preserving the C=C double bond to prepare furfuryl alcohol. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is the NH of the catalyst used in Example 1 3- TPD diagram, CO 2- TPD diagram.

[0022] Figure 2 is a SEM image of the catalyst used in Example 1.

[0023] Figure 3 This is a cycle performance diagram of the catalyst used in Example 1 in the hydrogenation of furfural to furfuryl alcohol. Specific implementation examples

[0024] Example 1: Ni 2 The preparation method of Al-LDH catalyst is as follows:

[0025] (1): Dissolve 0.01 mol aluminum nitrate, 0.02 mol nickel nitrate, and 0.084 mol urea in 60 ml deionized water, stir at room temperature for 1 hour until a clear solution is obtained, and then transfer to the inner lining of a hydrothermal kettle. Aging at 140°C for 7 hours, naturally cooling to room temperature, and repeatedly rinsing with deionized water until the pH of the supernatant is 7.

[0026] (2): The green mud precipitate obtained by separation was dispersed in 200 ml of methanol, stirred at room temperature for 2 h, then filtered and washed, and dried in an oven at 60°C for 24 h.

[0027] (3): The obtained hydrotalcite precursor was ground into powder and placed in a quartz boat. The temperature was raised to 500°C at a heating rate of 2°C / min in a 60 ml / min argon flow and calcined for 2 h to finally obtain a gray-green solid catalyst.

[0028] Catalyst structure characterization

[0029] Figure 1 NH for preparing the catalyst in Example 1 3- TPD diagram and CO 2- TPD Diagram. NH 3 -TPD is performed by measuring the NH 3 The chemical desorption intensity and desorption amount can be used to determine the acid strength and surface acidity of the catalyst. Figure 1 It can be seen from a that the catalyst has desorption peaks at 100-200 and 450-600 °C, corresponding to the weak acid site and strong acid site of the catalyst. 2- TPD proves that the catalyst has abundant basic sites, among which the desorption peaks at 50-200℃, 200-400℃, and 500-600℃ correspond to the weak basic site, medium strong basic site, and strong basic site of the catalyst, respectively. Figure 1 This indicates that the catalyst prepared by the present invention has abundant acid and base sites.

[0030] Figure 2 This is a SEM image of the catalyst prepared in Example 1. As can be seen from the figure, flower-like nickel-aluminum hydrotalcite was synthesized by hydrothermal method, and the flower-like hydrotalcite has an array-like structure, a large specific surface area, and good dispersion.

[0031] Catalyst activity test

[0032] Reaction operation: The catalytic transfer hydrogenation reaction was carried out in a 10ml stainless steel autoclave with a magnetic stirrer. 20mg of catalyst, 60mg of furfural, 3ml of isopropanol (solvent and hydrogen source) were added to the autoclave, 1.4Mpa of argon was filled in, and then the reactor was sealed. The stirring speed was set to 1000rpm, and the temperature was raised to 160℃ and the reaction was carried out for 3h. After the reaction was completed, it was quickly placed in an ice water bath for cooling. After the pressure in the reactor was released, the liquid was separated and sampled for analysis. The reaction activity of the catalyst was qualitatively and quantitatively determined by gas chromatography, and the furfural conversion rate was calculated to be 100%, and the furfuryl alcohol selectivity was 92.1%.

[0033] Catalyst cycle performance test

[0034] Example 1 After the reaction, the system was centrifuged to separate the catalyst, and the recovered catalyst was rinsed three times with deionized water and ethanol alternately, dried at 40° C. for 12 h, and then put into the next reaction.

[0035] Figure 3 The figure is a cycle performance diagram of the catalyst prepared in Example 1 in the hydrogenation of furfural to furfuryl alcohol. The results show that after the catalyst prepared in Example 1 was reused five times in the hydrogenation of furfural to furfuryl alcohol reaction, the catalytic activity hardly decreased, showing good repeatability.

Claims

1. A method for preparing a flower-shaped nickel-aluminum metal oxide for preparing furfuryl alcohol by transfer hydrogenation of furfural, the specific steps of which are as follows: S1: Add 0.01-0.05 mol / L nickel salt, 0.01-0.05 mol / L aluminum salt, and 0.05-0.1 mol / L alkali source into 60 ml of deionized water, wherein the anion of the metal nickel salt is any one of nitrate, phosphate, chlorate, and sulfate, the anion of the metal aluminum salt is any one of nitrate, phosphate, chlorate, and sulfate, and the alkali source is any one of urea, sodium hydroxide, sodium carbonate, ammonium carbonate, and ammonia water. S2: Stir the solution in S1 at room temperature for 0.5h~4h to form a uniform transparent solution, transfer it to the inner lining of a polytetrafluoroethylene hydrothermal autoclave, and age it at 100℃~200℃ for 5h~10h. Cool naturally to room temperature, and rinse repeatedly with deionized water until the pH of the supernatant is 7. Disperse the obtained sample in 200ml of methanol, stir at room temperature for 1h~12h, filter and separate, and dry the obtained muddy precipitate at 60℃ for 6h~24h. Grind the obtained solid into powder, place it in a quartz boat, and heat it to 400℃~600℃ in a 60ml / min argon flow or air at a heating rate of 2℃ / min~10℃ / min for calcination for 2h~4h to finally obtain a gray-green solid catalyst.

2. The nickel-aluminum bimetallic oxide catalyst prepared according to claim 1 is applied to the process of preparing furfuryl alcohol by transfer hydrogenation of furfural, characterized in that: Weigh 10mg to 60mg of any catalyst prepared in claim 1 and put it in a 10ml high-pressure reactor, add 0.5mmol furfural and 3ml solvent, fill with hydrogen or nitrogen to 0.5MPa to 3MPa, set the stirring speed to 500rmp to 1000rmp, heat to 100℃ to 180℃ and start timing reaction for 1h to 5h. After the reaction is completed, quickly cool it in an ice water bath, release the pressure in the reactor, separate the solid and liquid for sampling and analysis. After the catalyst after the catalytic reaction is separated, rinse it with deionized water and ethanol alternately three times, dry it at 40℃ for 12h, and use it for subsequent cyclic reactions. S1: The solvent in the furfural hydrogenation reaction in claim 2 is any one of isopropanol, methanol, ethanol, cyclohexane, and N,N-dimethylformamide.

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