阅读说明：本技术 一种用于碳酸氢盐加氢制甲酸的镍基催化剂及其制备方法 (Nickel-based catalyst for preparing formic acid by hydrogenating bicarbonate and preparation method thereof ) 是由 王加升 靳浩华 文晨曦 吴桐 李涵希 包明 于 2019-09-24 设计创作，主要内容包括：一种用于碳酸氢盐加氢制甲酸的镍基催化剂及其制备方法,属于纳米催化及能源环境交叉领域。该方法首先将阳离子表面活性剂、助表面活性剂、油相加入氨水中,再加入硝酸镍水溶液、硝酸锌水溶液,滴入正硅酸四乙酯、异丙醇,得到反应液。然后,将反应液超声、离心后,将得到的固相洗涤、干燥。再将干燥后的样品放置于管式炉内进行煅烧,得到镍锌金属氧化物/二氧化硅。最后,通入H<Sub>2</Sub>与N<Sub>2</Sub>的混合气体对样品中的高价镍进行还原,最终得到产物Ni-ZnO/SiO<Sub>2</Sub>催化剂。本发明制备工艺简单,制得的复合材料作为非均相催化剂,活性高,对于催化碳酸氢盐加氢还原制甲酸具有较高的活性与稳定性。(A nickel-based catalyst for preparing formic acid by hydrogenating bicarbonate and a preparation method thereof belong to the cross field of nano catalysis and energy environment. The method comprises the steps of adding a cationic surfactant, a cosurfactant and an oil phase into ammonia water, adding a nickel nitrate aqueous solution and a zinc nitrate aqueous solution, and dripping tetraethyl orthosilicate and isopropanol into the mixture to obtain a reaction solution. Then, the reaction solution was subjected to ultrasonic treatment and centrifugation, and the obtained solid phase was washed and dried. And then placing the dried sample in a tubular furnace for calcining to obtain the nickel-zinc metal oxide/silicon dioxide. Finally, H is introduced 2 And N 2 the mixed gas reduces the high-valence nickel in the sample to finally obtain the product Ni-ZnO/SiO 2 A catalyst. The preparation process is simple, and the prepared composite material is used as a heterogeneous catalystThe catalyst has high activity and high stability for catalyzing hydrogen carbonate hydrogenation reduction to prepare formic acid.)

1. A preparation method of a nickel-based catalyst for preparing formic acid by hydrogenating bicarbonate is characterized by comprising the following steps:

(1) Adding a cationic surfactant, a cosurfactant and cyclohexane into analytically pure ammonia water, stirring at 25-35 ℃ until the mixture is clear, adding a nickel nitrate aqueous solution with the concentration of 0.1-1 mol/L and a zinc nitrate aqueous solution with the concentration of 0.1-1 mol/L, heating to 35-45 ℃, stirring for 30-50 min, dropwise adding tetraethyl orthosilicate, and continuing to react for 2-4 h; finally, adding isopropanol to react for 10-30 min to obtain reaction liquid;

The molar ratio of the cationic surfactant to the cosurfactant to the cyclohexane is 1: 4-7: 13-18; the molar ratio of the cationic surfactant to ammonia water to nickel nitrate to zinc nitrate to tetraethyl orthosilicate is 10: 15-30: 0.080-0.80: 3-6: 130-260.

(2) Transferring the reaction liquid obtained in the step (1) to an ultrasonic instrument for ultrasonic treatment at room temperature, centrifuging, then pouring off the liquid phase after centrifugal separation, washing the obtained solid phase with isopropanol, and drying at 70-150 ℃ for 6-15 h;

(3) After the dried sample obtained in the step (2) is cooled to room temperature, grinding the sample into powder; calcining in a tubular furnace at 500-600 ℃, and keeping for 4-6 h to obtain NiO-ZnO/SiO₂；

(4) Cooling the sample obtained in the step (3) to room temperature, and introducing H into the tube furnace₂And N₂The mixed gas of (2) reduces the high-valence nickel in the sample; heating to 500-600 ℃, and keeping for 2-5 h; the sample obtained after reduction is the corresponding Ni-ZnO/SiO₂A catalyst.

2. the method for preparing the nickel-based catalyst for preparing the formic acid by hydrogenating the bicarbonate according to the claim 1, wherein the cationic surfactant in the step (1) is cetyl trimethyl ammonium bromide, cetyl trimethyl ammonium chloride; the cosurfactant comprises n-propanol, n-butanol, n-pentanol, n-hexanol and cyclohexanol.

3. The preparation method of the nickel-based catalyst for preparing formic acid through bicarbonate hydrogenation according to claim 1, wherein the ultrasonic treatment time in the step (2) is 10-30 min.

4. The method for preparing the nickel-based catalyst used for preparing the formic acid by hydrogenating the bicarbonate according to claim 1, wherein the centrifugal rotation speed in the step (2) is 8000-10000 rpm, and the centrifugal time is 10-20 min.

5. The method for preparing the nickel-based catalyst used for preparing the formic acid by hydrogenating the bicarbonate according to claim 1, wherein the temperature rise rate in the step (3) and the temperature rise rate in the step (4) are both 2-6 ℃/min.

6. The preparation method of the nickel-based catalyst for preparing formic acid through hydrogen carbonate hydrogenation according to claim 1, wherein the velocity of the mixed gas introduced in the step (4) is 20-60 mL/min.

7. The method according to claim 1, wherein the mixed gas introduced in step (4) comprises 5% H₂And 95% N₂。

Technical Field

The invention belongs to the cross field of nano catalysis and energy environment, and relates to Ni-ZnO/SiO₂Composite material and preparation thereof for catalyzing hydrogen carbonate hydrogenation to prepare formic acid

Background

Since the use of large amounts of fossil fuels leads to an increase in the carbon dioxide content in the atmosphere, causing severe greenhouse effect, causing global temperature rise, glaciers melting, and sea level rise, the conversion and utilization of carbon dioxide is imminent. Due to the characteristic of low chemical activity of carbon dioxide, higher energy is required to be provided by direct utilization, and the economic benefit is lower. After the carbon dioxide reacts with alkali to be converted into bicarbonate, the chemical activity is obviously improved.

Gonz lez et al (Applied Catalysis B: Environmental,2018,224:368.) supported nickel on carbon as a catalyst, and hydrogenated with sodium bicarbonate water as a carbon source, and the yield of formic acid was only 1.2% at normal temperature and pressure, but no by-product was generated during the reaction. Wang et al (Green Chemistry,2017,19:716.) have shown good results in the hydrogenation reduction of bicarbonates by improving the preparation method of Raney nickel to increase the specific surface area of metallic nickel and thus the catalyst effect. The yield of formic acid can reach 86.6% at most under the conditions of 200 ℃ and 6MPa by using sodium bicarbonate as a carbon source; when the carbon source was replaced with potassium bicarbonate, the yield of formic acid reached 92.1% and substantially no by-products were formed. However, raney nickel has the disadvantages of being easily oxidized and difficult to store.

based on the above, the invention aims to synthesize a nickel-based catalyst with silicon dioxide as a carrier and zinc oxide as a modifier. Because of the electron transmission function between the nickel and the zinc oxide, the two components have a synergistic effect, and the activity and the stability of the catalyst can be obviously improved.

Disclosure of Invention

The invention provides a composite material Ni-ZnO/SiO₂Wherein the silicon dioxide carrier is spherical and has a particle size of 20-100 nm(ii) a The active component nickel-zinc oxide is highly dispersed in the silicon dioxide spheres, and the particle size is 1.0-3.0 nm. The content of the active component is 1 wt% -10 wt%. The material is used as a heterogeneous catalyst and has higher activity and stability for catalyzing the preparation of formic acid by the hydrogenation of bicarbonate.

In order to prepare the catalyst, the technical scheme adopted by the invention is as follows:

A process for preparing the Ni-base catalyst used for preparing formic acid by hydrogenating hydrocarbonate is disclosed, which is Ni-ZnO/SiO₂The preparation method of the composite material comprises the following steps:

(1) Adding a cationic surfactant, a cosurfactant and cyclohexane into analytically pure ammonia water, stirring at 25-35 ℃ until the mixture is clear, adding a nickel nitrate aqueous solution with the concentration of 0.1-1 mol/L and a zinc nitrate aqueous solution with the concentration of 0.1-1 mol/L, heating to 35-45 ℃, stirring for 30-50 min, dropwise adding tetraethyl orthosilicate, and continuing to react for 2-4 h; and finally adding isopropanol to react for 10-30 min to obtain reaction liquid.

The molar ratio of the cationic surfactant to the cosurfactant to the cyclohexane is 1: 4-7: 13-18. The ammonia water is analytically pure, the concentration of the ammonia water is 25% -28%, and the molar ratio of the cationic surfactant to the ammonia water to the nickel nitrate to the zinc nitrate to the tetraethyl orthosilicate is 10: 15-30: 0.080-0.80: 3-6: 130-260.

The cationic surfactant is cetyl trimethyl ammonium bromide and cetyl trimethyl ammonium chloride; the cosurfactant comprises n-propanol, n-butanol, n-pentanol, n-hexanol and cyclohexanol (C3-C6 short carbon chain alcohol).

The stirring speed is 500-600 rpm.

(2) And (2) at room temperature, transferring the reaction liquid obtained in the step (1) into an ultrasonic instrument, performing ultrasonic treatment for 10-30 min, transferring the reaction liquid into a centrifugal tube, performing centrifugal separation for 10-20 min at the rotating speed of 8000-10000 rpm, pouring to remove a liquid phase after the centrifugal separation, washing an obtained solid phase with isopropanol, and drying at 70-150 ℃ for 6-15 h.

(3) after the dried sample obtained in the step (2) is cooled to room temperature, the sample is cooledGrinding into powder. Calcining in a tubular furnace at 500-600 ℃, and keeping for 4-6 h to obtain NiO-ZnO/SiO₂。

(4) Cooling the sample obtained in the step (3) to room temperature, and introducing 5% H into the tube furnace₂And 95% N₂The mixed gas of (2) reduces the high-valence nickel in the sample. Heating to 500-600 ℃, and keeping for 2-5 h. The sample obtained after reduction is the corresponding Ni-ZnO/SiO₂a catalyst.

The heating rate in the step (3) and the step (4) is 2-6 ℃/min; and (4) introducing the mixed gas in the step (4) at a rate of 20-60 mL/min.

The invention has the beneficial effects that:

(1) The Ni-ZnO/SiO of the invention₂The catalyst has high activity in the process of catalyzing the reduction of bicarbonate, and can obtain higher yield of formic acid of 97 percent; the selectivity of the catalyst to formic acid is 100%, and no by-product is generated in the reaction process.

(2) The Ni-ZnO/SiO of the invention₂As the catalyst for preparing formic acid by hydrogenating bicarbonate, the preparation process is simple and the conditions are mild. The synthesized catalyst has high stability and can be stored in the environment for a long time.

Drawings

FIG. 1 shows 1.2 wt% Ni-ZnO/SiO of the catalyst prepared in example 1₂A TEM image of the material;

FIG. 2 shows 5.4 wt% Ni-ZnO/SiO of the catalyst prepared in example 2₂A TEM image of the material;

FIG. 3 shows 9.0 wt% Ni-ZnO/SiO of the catalyst prepared in example 5₂A TEM image of the material;

FIG. 4 shows 5.4 wt% Ni-ZnO/SiO of the catalyst prepared in example 2₂HRTEM image of (A);

FIG. 5 shows 5.4 wt% Ni-ZnO/SiO of the catalyst prepared in example 2₂The active component under the HRTEM of (1);

FIG. 6 shows 5.4 wt% Ni-ZnO/SiO of the catalyst prepared in example 2₂The histogram of the catalyst particle diameter (a) and the size distribution of the active component (b) of (a).

Detailed Description

The present invention will be described in further detail with reference to embodiments, but it should be understood that the present invention is not limited to the embodiments.