阅读说明：本技术 一种高分散NiSn/MgAlO催化剂及其制备方法和应用 (High-dispersion NiSn/MgAlO catalyst and preparation method and application thereof ) 是由 王铁军 吴小平 蔡学颖 仇松柏 张浅 孟庆伟 皮云红 于 2021-07-22 设计创作，主要内容包括：本发明公开了一种高分散NiSn/MgAlO催化剂及其制备方法和应用,所述方法包括如下步骤：S1.将可溶性镍盐、可溶性镁盐、可溶性铝盐加入到去离子水中,搅拌形成均质溶液；可溶性镍盐、可溶性镁盐与可溶性铝盐的摩尔比为(10～30)：(40～60)：(15～25)；S2.配置碱性溶液,将S1所述均质溶液与所述碱性溶液通过共沉淀法制备得到镍基三元水滑石；S3.将锡酸盐和镍基三元水滑石加入到去离子水中,搅拌后抽滤、干燥得到NiSn水滑石；所述锡酸盐和镍基三元水滑石中Sn：Ni摩尔比1：(10～30)；S4.将NiSn水滑石置于还原气氛中500～700℃煅烧0.5～4h得到高分散NiSn/MgAlO催化剂。本发明所述高分散NiSn/MgAlO催化剂用于水相小分子醇碳碳偶联制备高级醇时具有较高的有机相收率和C4+高级醇收率,具有广泛的应用前景。(The invention discloses a high-dispersion NiSn/MgAlO catalyst and a preparation method and application thereof, wherein the method comprises the following steps: s1, adding soluble nickel salt, soluble magnesium salt and soluble aluminum salt into deionized water, and stirring to form a homogeneous solution; the molar ratio of the soluble nickel salt to the soluble magnesium salt to the soluble aluminum salt is (10-30): (40-60): (15-25); s2, preparing an alkaline solution, and preparing the nickel-based ternary hydrotalcite from the homogeneous solution of S1 and the alkaline solution by a coprecipitation method; s3, adding stannate and nickel-based ternary hydrotalcite into deionized water, stirring, performing suction filtration, and drying to obtain NiSn hydrotalcite; sn in the stannate and nickel-based ternary hydrotalcite: molar ratio of Ni 1: (10-30); s4, placing NiSn hydrotalcite in a reducing atmosphere and calcining at 500-700 ℃ for 0.5-4 h to obtain the high-dispersion NiSn/MgAlO catalyst. The high-dispersion NiSn/MgAlO catalyst has higher organic phase yield and C4+ higher alcohol yield when being used for preparing higher alcohol by aqueous phase micromolecule alcohol carbon coupling, and has wide application prospect.)

1. A preparation method of a high-dispersion NiSn/MgAlO catalyst is characterized by comprising the following steps:

s1, adding soluble nickel salt, soluble magnesium salt and soluble aluminum salt into deionized water, and stirring to form a homogeneous solution; the molar ratio of the soluble nickel salt to the soluble magnesium salt to the soluble aluminum salt is (10-30): (40-60): (15-25);

s2, preparing an alkaline solution, and preparing the nickel-based ternary hydrotalcite from the homogeneous solution of S1 and the alkaline solution by a coprecipitation method;

s3, adding stannate and nickel-based ternary hydrotalcite into deionized water, stirring, performing suction filtration, and drying to obtain NiSn hydrotalcite; sn in the stannate and nickel-based ternary hydrotalcite: molar ratio of Ni 1: (10-30);

s4, placing NiSn hydrotalcite in a reducing atmosphere and calcining at 500-700 ℃ for 0.5-4 h to obtain the high-dispersion NiSn/MgAlO catalyst.

2. The method of claim 1, wherein in step S1, the ratio of Ni in the soluble nickel salt and the soluble magnesium salt is: mg molar ratio is 1: (2-3).

3. The method for preparing the highly dispersed NiSn/MgAlO catalyst according to claim 1, wherein in step S3, the ratio of Sn: the molar ratio of Ni is 1: (15-25).

4. The method for preparing the highly dispersed NiSn/MgAlO catalyst according to claim 1, wherein in step S4, the calcination temperature is 525 to 600 ℃ and the calcination time is 1 to 3 hours.

5. The method of claim 1, wherein the soluble nickel salt is selected from the group consisting of Ni (NO)₃)₂、NiSO₄、NiCl₂One or more of (a).

6. The method of claim 1, wherein the soluble magnesium salt is selected from the group consisting of Mg (NO)₃)₂、MgSO₄、MgCl₂One or more of (a).

7. The method of claim 1, wherein the soluble aluminum salt is selected from the group consisting of Al (NO)₃)₃、Al₂(SO₄)₃、AlCl₃One or more of (a).

8. A high-dispersion NiSn/MgAlO catalyst is characterized by being prepared by the method of any one of claims 1 to 7.

9. The use of the highly dispersed NiSn/MgAlO catalyst of claim 8 in the synthesis of higher alcohols from aqueous small molecule alcohols.

10. The use according to claim 9, wherein the small molecule alcohol is ethanol and the higher alcohol is an alcohol having 4 to 16 carbon atoms.

Technical Field

The invention relates to the technical field of catalysts, and particularly relates to a high-dispersion NiSn/MgAlO catalyst and a preparation method and application thereof.

Background

Biomass energy, which is a renewable energy source, is a good alternative to fossil fuels, mainly by converting carbon dioxide and water through biological photosynthesis, but if energy efficiency is low and it is uneconomical to obtain through direct combustion, the subject of developing and utilizing biofuels is receiving increasing attention and attention.

The development of biomass liquid fuel at present mainly focuses on ethanol produced by sugar-containing crops through fermentation. Bioethanol is widely used as a renewable clean biofuel and has been used as a gasoline additive in the united states, china and some european countries, but has disadvantages of water solubility, corrosiveness, and low energy density. This clearly limits their use and application rates in high performance high energy fuels. These problems associated with ethanol are effectively mitigated by the use of butanol or other C4+ higher alcohols, which are water immiscible, non-corrosive, higher energy density, etc., and more closely approach the octane number of gasoline. According to the characteristic of the higher alcohol, the proportion of the higher alcohol in the fuel can be properly increased, the problem of shortage of fossil fuel is effectively relieved, and the higher alcohol is a well-recognized gasoline substitute.

The carbon-carbon coupling of the micromolecule alcohol can realize the carbon chain growth to prepare the higher alcohol, mainly through a Guerbet reaction path, alcohol dehydrogenation, aldol condensation and hydrogenation are mainly carried out in the process, and the finally obtained product is mostly branched higher alcohol. The first and third steps of the reaction require the participation of a dehydrogenation/hydrogenation active center, and the second step of aldol condensation reaction is associated with an acid-base active center. Therefore, a highly efficient carbon-carbon coupling reaction catalyst should have both suitable dehydrogenation/hydrogenation and acid-base active sites. It is inferred that the catalyst system is constructed by using transition zone metal elements having d orbital electrons or empty d orbitals according to the type of the catalyst required, so at present, organometallic, Ru, Rh, Pa, 0s, Ir, Pt and other transition noble metal catalyst systems are mostly used, but there are problems that separation and recovery are difficult or the application cost of noble metal catalyst is high.

Nickel is a transition metal element relatively abundant in the earth's crust and one of the best noble metal substitute materials. The Chinese invention patent CN10240712A discloses a Ni/MgAlO catalyst for hydrogenation of levulinic acid by using hydrotalcite-like compound as a carrier, but because of strong metallicity of metal Ni, the Ni/MgAlO catalyst is easy to cause serious methanation in the dehydrogenation process of aqueous-phase small-molecular alcohol and is not beneficial to the generation of higher alcohol.

Disclosure of Invention

The invention aims to overcome the problem that the yield of C4+ higher alcohol is low (21.2%) when the existing nickel-based catalyst is used for synthesizing higher alcohol by using aqueous-phase small-molecular alcohol, and provides a preparation method of a high-dispersion NiSn/MgAlO catalyst.

It is another object of the present invention to provide a highly dispersed NiSn/MgAlO catalyst.

It is a further object of the present invention to provide the use of the above highly dispersed NiSn/MgAlO catalyst.

The above object of the present invention is achieved by the following technical solutions:

a preparation method of a high-dispersion NiSn/MgAlO catalyst comprises the following steps:

s1, adding soluble nickel salt, soluble magnesium salt and soluble aluminum salt into deionized water, and stirring to form a homogeneous solution; the molar ratio of the soluble nickel salt to the soluble magnesium salt to the soluble aluminum salt is (10-30): (40-60): (15-25);

s2, preparing an alkaline solution, and preparing the nickel-based ternary hydrotalcite from the homogeneous solution of S1 and the alkaline solution by a coprecipitation method;

s3, adding stannate and nickel-based ternary hydrotalcite into deionized water, stirring, performing suction filtration, and drying to obtain NiSn hydrotalcite; sn in the stannate and nickel-based ternary hydrotalcite: molar ratio of Ni 1: (10-30);

s4, placing NiSn hydrotalcite in a reducing atmosphere and calcining at 500-700 ℃ for 0.5-4 h to obtain the high-dispersion NiSn/MgAlO catalyst.

According to the invention, the specific amount of the metal auxiliary Sn is introduced to adjust the electronic environment and the space structure of the active metal Ni, so that the metallicity of Ni is reduced, the occurrence of side reaction is effectively prevented, and the yield of a target object is increased. Meanwhile, the existence of Sn can inhibit metal sintering and promote coke substances to diffuse from the metal surface to the carrier, and can also enable active metal Ni to be distributed more uniformly on the carrier surface to form small Sn atom clusters, thereby improving the catalytic activity and stability of Ni.

In addition, the calcination temperature and time have a large influence on the catalyst performance. During the calcination dehydration process of the nickel-containing hydrotalcite precursor, Ni (Mg) O solid solution is formed due to the strong interaction of Ni and Mg. When the calcination temperature is too low and the calcination time is too short in the hydrogen atmosphere, only a small amount of Ni is contained²⁺Can be reduced from Ni (mg) O solid solution to elemental Ni (active sites for dehydrogenation and hydrogenation), resulting in poor catalytic reaction performance. Excessive Ni when the calcination temperature is too high and the calcination time is too long²⁺The simple substance Ni can be reduced into simple substance Ni, the simple substance Ni not only has the performance of dehydrogenation and hydrogenation, but also has the capability of breaking carbon-carbon bonds, excessive simple substance Ni can cause the serious degree of ethanol cracking, and a large amount of micromolecular gas byproducts are generated, thereby reducing the yield of C4+ higher alcohol when the water-phase micromolecular alcohol is used for synthesizing the higher alcohol.

In the invention, the Ni content in the soluble nickel salt and the soluble magnesium salt is as follows: the Mg molar ratio affects the regularity of the hydrotalcite produced. Preferably, in step S1, the ratio of Ni: mg molar ratio is 1: (2-3). More preferably 1: 3.

the alkaline solution is a mixed solution of sodium hydroxide and sodium carbonate, and the molar ratio of the sodium hydroxide to the sodium carbonate in the mixed solution is 2: 1.

in the invention, the introduced dosage of the metal auxiliary Sn can influence the morphology characteristics of the catalyst, and the catalyst is further used for the catalytic activity of synthesizing higher alcohol by using water-phase small molecular alcohol. Too high amount of Sn will result in too much covering of active sites of simple substance Ni, resulting in low catalytic reaction performance, low ethanol conversion rate, and too low amount of Ni will not reduce metallicity, and generate a large amount of small molecule gas by-products.

Preferably, in step S3, the ratio of Sn: the molar ratio of Ni is 1: (15-25). More preferably 1: 20.

preferably, in the step S4, the calcination temperature is 525 to 600 ℃ and the calcination time is 1 to 3 hours.

More preferably, in step S4, the calcination temperature is 550 ℃ and the calcination time is 1.5 h.

The stannate of the invention is selected from Na₂SnO₃、K₂SnO₃One or two of them.

The soluble nickel salt of the present invention is selected from Ni (NO)₃)₂、NiSO₄、NiCl₂One or more of (a).

The soluble magnesium salt of the invention is selected from Mg (NO)₃)₂、MgSO₄、MgCl₂One or more of (a).

The soluble aluminium salt of the present invention is selected from Al (NO)₃)₃、Al₂(SO₄)₃、AlCl₃One or more of (a).

A high-dispersion NiSn/MgAlO catalyst is prepared by the method.

The invention also protects the application of the high-dispersion NiSn/MgAlO catalyst in synthesizing higher alcohol by using small molecular alcohol.

Preferably, the small molecular alcohol is ethanol, and the higher alcohol is alcohol with 4-16 carbon atoms. Wherein the alcohol having 4 to 16 carbon atoms may be n-butanol, 2-ethyl-1-butanol, n-hexanol, 2-ethyl-1-hexanol, n-octanol, 2-ethyloctanol, n-decanol, isomeric C10+ alcohols, or the like. The high-dispersion NiSn/MgAlO catalyst has high selectivity when used for catalyzing ethanol to synthesize higher alcohol with 4-16 carbon atoms.

The invention also provides a step of synthesizing the higher alcohol by catalyzing ethanol by the high-dispersion NiSn/MgAlO catalyst, which comprises the following steps:

mixing a high-dispersion NiSn/MgAlO catalyst, NaOH, ethanol and water, and reacting for 10-14 h at 200-300 ℃, wherein the NiSn/MgAlO catalyst: NaOH: ethanol: the mass ratio of water is 1:1:20: 20.

Compared with the prior art, the invention has the beneficial effects that:

the invention takes layered hydrotalcite as a carrier, introduces a metal additive Sn by an anion exchange method, and controls the calcination temperature and the calcination time to prepare the high-dispersion NiSn/MgAlO catalyst. The high-dispersion NiSn/MgAlO catalyst has a proper amount of high-dispersion active phase and more acid-base bifunctional sites, and has higher organic phase product yield and C4+ higher alcohol yield when being used for synthesizing higher alcohol from aqueous phase small molecular alcohol.

Drawings

FIG. 1 is an XRD diffraction pattern of a highly dispersed NiSn/MgAlO catalyst prepared in example 1 of the present invention and a Ni/MgAlO catalyst prepared in comparative example 1;

FIG. 2 is an SEM image of a highly dispersed NiSn/MgAlO catalyst prepared in example 1 of the present invention;

FIG. 3 is an SEM photograph of a Ni/MgAlO catalyst prepared in comparative example 1 of the present invention;

FIG. 4 is a TEM image of a highly dispersed NiSn/MgAlO catalyst prepared in example 1 of the present invention;

FIG. 5 is a HRTEM image of a highly dispersed NiSn/MgAlO catalyst prepared in example 1 of the present invention;

FIG. 6 is a TEM image of a Ni/MgAlO catalyst prepared in comparative example 1 of the present invention;

FIG. 7 is a HRTEM image of a Ni/MgAlO catalyst prepared in comparative example 1 of the present invention.

Detailed Description

In order to more clearly and completely describe the technical scheme of the invention, the invention is further described in detail by the specific embodiments, and it should be understood that the specific embodiments described herein are only used for explaining the invention, and are not used for limiting the invention, and various changes can be made within the scope defined by the claims of the invention.

Example 1

A preparation method of a high-dispersion NiSn/MgAlO catalyst comprises the following steps:

s1, mixing Ni (NO)₃)₂·6H₂O、Mg(NO₃)₂·6H₂O and Al (NO)₃)₃·9H₂Adding O into deionized water, and stirring to form a homogeneous solution;

s2, preparing NaOH and Na₂CO₃The molar ratio is 2: 1, obtaining a mixed solution by coprecipitation of the homogeneous solution of S1 and the alkaline solution, stirring at 80 ℃, and performing suction filtration and drying to obtain a Ni-LDHs carrier;

s3, mixing Na₂SnO₃·3H₂Adding O and Ni-LDHs carriers into deionized water, stirring to form a mixed solution, stirring at 80 ℃, carrying out suction filtration and drying to obtain NiSn-LDHs powder, wherein the mass ratio of Ni, Sn, Mg and Al elements is 20:1:60: 20;

s4, putting NiSn-LDHs powder in H₂Calcining for 1.5h at 550 ℃ in the atmosphere to obtain the high-dispersion NiSn/MgAlO catalyst.

Example 2

This example is a second example of the present invention, and differs from example 1 in that the ratio of the amounts of the Ni, Sn, Mg, and Al elements in this example is 15:1:45: 15.

Example 3

This example is a third example of the present invention, and differs from example 1 in that the ratio of the amounts of the Ni, Sn, Mg, and Al elements in this example is 25:1:75: 25.

Example 4

This example is a fourth example of the present invention, and is different from example 1 in that the ratio of the amounts of the Ni, Sn, Mg, and Al elements in this example is 10:1:60: 20.

Example 5

This example is a fifth example of the present invention, and differs from example 1 in that the ratio of the amounts of the Ni, Sn, Mg, and Al elements in this example is 30:1:60: 20.

Example 6

This example is a sixth example of the present invention, and differs from example 1 in that the ratio of the amounts of the Ni, Sn, Mg, and Al elements in this example is 20:1:40: 20.

Example 7

This example is a seventh example of the present invention, and differs from example 1 in that the calcination temperature is 525 ℃ and the calcination time is 3 hours.

Example 8

This example is an eighth example of the present invention, and differs from example 1 in that the calcination temperature is 600 ℃ and the calcination time is 1 hour.

Example 9

This example is a ninth example of the present invention, and differs from example 1 in that the calcination temperature is 500 ℃ and the calcination time is 4 hours.

Example 10

This example is a tenth example of the present invention, and differs from example 1 in that the calcination temperature is 700 ℃ and the calcination time is 0.5 h.

Comparative example 1

The comparative example provides a preparation method of a Ni/MgAlO catalyst, which comprises the following steps:

mixing Ni (NO)₃)₂·6H₂O，Mg(NO₃)₂·6H₂O and Al (NO)₃)₃·9H₂Adding O into deionized water, and stirring to form a homogeneous solution; preparing alkaline solution (NaOH/Na)₂CO₃) Mixing the above homogeneous solution with the mixed solution by coprecipitation, stirring at 80 deg.C, vacuum filtering, and drying to obtain Ni-LDHs powder containing Ni, Mg and AlThe ratio of the amount of the substance of the elements is 1:3: 1; mixing Ni-LDHs powder in H₂Reducing for 1h at 550 ℃ under the atmosphere to obtain the Ni/MgAlO catalyst.

This comparative example differs from example 1 in that the metal assistant Sn is not introduced.

Comparative example 2

The present comparative example provides a method for preparing a highly dispersed NiSn/MgAlO catalyst, which is different from example 1 in that the calcination temperature is 450 ℃.

Comparative example 3

This comparative example provides a method for preparing a highly dispersed NiSn/MgAlO catalyst, which is different from example 1 in that the calcination temperature is 750 ℃.

Characterization of the test

Adding the catalysts described in examples 1-10 and comparative examples 1-3 into a 50mL steel high-pressure slurry reactor, and carrying out a carbon-carbon coupling reaction of ethanol under the concerted catalysis of homogeneous alkali to synthesize higher alcohol, wherein the catalyst: NaOH: ethanol: the mass ratio of water is 1:1:20:20, the reaction temperature is 250 ℃, the initial pressure is 0.1MPa, the reaction time is 12 hours, after the reaction is finished, the catalyst is cooled to the room temperature, the gas phase is collected by using the gas bag, the liquid phase product in the reaction kettle is taken out, the liquid phase and the solid phase of the catalyst are obtained after centrifugation and filtration, and the liquid phase can spontaneously delaminate after standing to obtain two parts of an oil phase and a water phase. The gas phase products were analyzed qualitatively and quantitatively mainly by gas chromatography, while the oil phase main product was C4+ higher alcohol. The analytical results are shown in Table 1.

TABLE 1

From the above table 1 and the examples 1 to 10, it can be seen that the high-dispersion NiSn/MgAlO catalyst provided by the invention has higher organic phase product yield and C4+ higher alcohol yield when used for preparing higher alcohol through carbon-carbon coupling of ethanol, wherein the catalyst has the best catalytic performance when calcined at 550 ℃ for 1.5 hours in a hydrogen atmosphere at a ratio of Ni to Sn to Mg to Al of 20:1:60:20, and the ethanol conversion rate and the C4+ higher alcohol yield reach higher levels.

In the comparative example 1, as the electronic environment and the space structure of the active metal Ni are adjusted without adding the metal additive Sn, the metal property of Ni is reduced, the catalytic activity of the obtained catalyst for catalyzing ethanol to prepare higher alcohol is lower, and the yield of organic phase products and the yield of C4+ higher alcohol are lower.

Comparative example 2 since the calcination temperature was less than 500 ℃, the support was changed from the oxide structure to the hydroxide structure in the aqueous phase and in the high-temperature, high-pressure, and strong alkali environment, causing the agglomeration of the active metal, and further causing the reduction of the catalytic activity.

Comparative example 3 the support goes from oxide structure to spinel (MgAl) due to calcination temperature higher than 700 ℃₂O₄) The structure is changed, the specific surface area of the spinel is much smaller than that of the hydrotalcite, resulting in a decrease in catalytic performance.

FIG. 1 is an XRD diffraction pattern of a highly dispersed NiSn/MgAlO catalyst prepared in example 1 of the present invention and an Ni/MgAlO catalyst prepared in comparative example 1. As is clear from the figure, when the auxiliary metal Sn is doped, the signal intensity of the characteristic peak of the metal Ni becomes weak, and MgNiO₂The peak shape becomes strong. The XRD diffraction pattern of the high-dispersion NiSn/MgAlO catalyst in the embodiments 2-10 is similar to that of the embodiment 1.

FIG. 2 is an SEM photograph of a highly dispersed NiSn/MgAlO catalyst prepared in example 1 of the present invention, and FIG. 3 is an SEM photograph of a Ni/MgAlO catalyst prepared in comparative example 1 of the present invention. As can be seen from fig. 2 and 3, the structure of the hydrotalcite is not changed on the whole, and the hydrotalcite presents a needle shape and a petal shape, but it can be seen that the supporting assistant metal Sn can change the morphological characteristics of the catalyst to a certain extent, so that the catalyst is dispersed more uniformly and regularly. SEM images of the highly dispersed NiSn/MgAlO catalysts of examples 2-10 are similar to those of example 1.

FIG. 4 is a TEM image of a highly dispersed NiSn/MgAlO catalyst prepared in example 1 of the present invention; FIG. 5 is a HRTEM image of a highly dispersed NiSn/MgAlO catalyst prepared in example 1 of the present invention; FIG. 6 is a TEM image of a Ni/MgAlO catalyst prepared in comparative example 1 in the practice of the present invention; FIG. 7 is an HRTEM image of a Ni/MgAlO catalyst prepared in comparative example 1, which is an example of the present invention. As can be seen from fig. 4, 5, 6, and 7, the particle size of the catalytically active phase metal Ni becomes smaller with Sn loading, and the degree of dispersion becomes more uniform. When the Ni/MgAlO catalyst without the metal auxiliary Sn is used, the breaking effect of the carbon-carbon bond of the catalyst is more obvious by analyzing from the product, the main reaction Guerbet reaction is weakened by the side reactions such as carbon-carbon bond cracking, water gas shift, steam reforming and the like, the obtained product is mainly gaseous micromolecule products, and the amount of the generated higher alcohol is greatly reduced. The metal dispersity of the catalyst prepared by adding the metal auxiliary agent Sn is greatly improved, and the NiSn/MgAlO catalyst prepared by calcining at 550 ℃ has the optimal catalyst activity when the molar ratio of Ni to Sn to Mg to Al is 20:1:60: 20. Examples 2-10 TEM and HRTEM images of highly dispersed NiSn/MgAlO catalysts are similar to FIGS. 4 and 5, respectively.

It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.