CN114832844B - Catalyst for preparing cycloalkanes by selective hydrodeoxygenation of phenolic compounds and preparation method thereof - Google Patents

Abstract

A catalyst for preparing cycloalkane by selective hydrodeoxygenation of phenolic compound is prepared from the central radial nano Si-Al oxide Si _xAl_y -O as carrier and Ni ₂ P active phase on said carrier. The catalyst adopts cheap Ni ₂ P as an active phase, and the catalyst synthesis method is simple, and has the advantages of low catalyst preparation cost, short preparation time, high hydrogenation activity, good naphthene selectivity and the like; the method for preparing cycloalkane by selective hydrogenation of the phenolic compound has the advantages of short hydrodeoxygenation reaction time and high hydrogenation activity, and realizes the excellent effect of preparing cycloalkane by efficient hydrodeoxygenation of the phenolic compound through perfect combination of catalytic activity, selectivity and mass transfer.

Description

A catalyst for preparing cycloalkanes by selective hydrodeoxygenation of phenolic compounds and its preparation method

Technical Field

The invention belongs to the technical field of catalysis, and particularly relates to a catalyst for preparing cycloalkane by selective hydrodeoxygenation of phenolic compounds and a preparation method thereof.

Background technique

With the increasing shortage of energy and pollution, the search for sustainable green energy has become the current primary issue. Lignin is the second largest biomass resource in nature besides cellulose, and it is also the only clean non-petroleum resource in nature that can provide renewable aromatic compounds. The biomass oil obtained by pyrolysis of lignin contains more benzene ring structural units, which is a cheap and clean resource that can be converted into high-energy aromatics and cycloalkanes, and is one of the most promising petroleum supplementary energy sources. At present, lignin has been successfully depolymerized into crude biomass oil through various advanced conversion technologies such as pyrolysis and liquefaction. However, crude biomass oil has a high oxygen content and contains oxygen-containing compounds such as phenols, ketones, aldehydes, furans, alcohols, ethers and esters, which leads to its low combustion calorific value, poor stability and oil solubility, and strong corrosiveness, and its practical application is greatly limited. Therefore, it is of great significance to improve the quality of crude biomass oil to achieve its high-grade utilization.

Hydrodeoxygenation (HDO) is an effective way to convert oxygenated derivatives in inferior crude biomass oil into clean oxygen-free cycloalkanes. There are two main pathways for the hydrodeoxygenation of typical biomass oil model compounds: (1) direct deoxygenation (DDO), where the deoxygenation products are aromatics; and (2) hydrodeoxygenation-deoxygenation (HYD), where the deoxygenation products are cycloalkanes (Figure 1). The cycloalkanes obtained by the HYD reaction pathway have high calorific value and low freezing point. They are not only an important component of transportation fuels such as gasoline, diesel and aviation kerosene, but also an important chemical raw material with high product added value. Therefore, the selection of HDO for the preparation of cycloalkanes from crude biomass oil has attracted much attention.

Among the oxygen-containing compounds in crude biomass oil, phenolic compounds have the highest content. Because the oxygen in the phenolic hydroxyl group of these phenolic oxygen-containing compounds is directly connected to the benzene ring, the oxygen-containing functional group is relatively stable, and the activation energy required to break such C-O bonds is relatively high. Therefore, HDO is difficult, the reaction conditions are harsh, and the reaction time is long. At present, there are many articles and patents reporting methods for preparing hydrocarbon fuels using oxygen-containing organic compounds HDO. However, in the existing hydrodeoxygenation catalytic technology, precious metal catalysts have high reaction activity, but the catalyst stability is poor, the cost is high, and the industrial application is limited. Non-precious metal metal sulfide catalysts need to introduce sulfides to maintain their activity, and sulfides will cause product contamination. Table 1 summarizes the performance of different catalysts for meta-cresol HDO reported in the literature. It can be seen from the table that different catalysts for meta-cresol HDO generally have long reaction times (>240min) and low raw material conversion rates of some catalysts. In order to achieve high methylcyclohexane selectivity, harsh reaction conditions such as high temperature or high pressure are required. Therefore, it is particularly important to develop an efficient HDO catalyst, shorten the reaction time, and realize the selective hydrogenation of phenolic compounds to produce high-value-added cycloalkanes.

Table 1 Summary of the performance of different catalysts for HDO of m-cresol reported in the literature

Previous studies have shown that the hydrogenation activity of phenolic compounds can be improved by regulating the morphology of Pt nanocrystals. For example, the hydrogenation activity of Pt concave cubes with high index faces is 6.3 times and 1.3 times higher than that of Pt cubes and octahedrons, respectively. Similarly, the specific surface area, pore structure, morphology and crystal faces of the carrier also have a significant effect on the catalytic activity of the catalyst. As a HDO catalyst carrier, (1) it must have a large enough specific surface area to facilitate the dispersion of hydrogenation active components; (2) it must have a suitable pore volume and pore structure to facilitate mass transfer of reactants and products; and (3) it must provide suitable acidic sites or defect sites to improve the activity of the catalyst. However, so far, there are few reports on the effects of special pore structure carriers on the HDO preparation of cycloalkanes from phenolic compounds.

Summary of the invention

The first object of the present invention is to provide a catalyst for the selective hydrodeoxygenation of phenolic compounds to prepare cycloalkanes, which overcomes the problems of high cost of precious metal catalysts and long reaction time of non-precious metal catalysts when using HDO catalysts in the prior art to prepare cycloalkanes from phenolic oxygenated compounds, and realizes efficient hydrodeoxygenation of phenolic oxygenated compounds to prepare cycloalkanes.

The second object of the present invention is to provide a method for preparing the above-mentioned catalyst for preparing cycloalkane by selective hydrodeoxygenation of phenolic compounds.

The third object of the present invention is to provide a method for preparing cycloalkanes by selective hydrodeoxygenation of the above phenolic compounds.

The present invention is achieved through the following technical solutions:

1. A catalyst for preparing cycloalkanes by selective hydrodeoxygenation of phenolic compounds. The catalyst is composed of a center-radial nano-silicon aluminum oxide _{SixAly -} O carrier and a _Ni2P active phase on the carrier.

2. A preparation method for preparing a cycloalkane catalyst by selective hydrodeoxygenation of the above-mentioned phenolic compounds, wherein tetraethyl orthosilicate is used as a silicon source, aluminum nitrate is used as an aluminum source, hexadecyl ammonium bromide is used as a surfactant, sodium o-hydroxybenzoate is used as a structure directing agent, and triethanolamine is used as a chelating agent. The pH of the solution is controlled by ethanolamine to adjust the hydrolysis rate, thereby synthesizing a silicon-aluminum composite oxide carrier _{SixAly -} O, and then loading a nickel source and a phosphorus source to obtain a _Ni2P / _{SixAly -} O catalyst by reduction.

Furthermore, the x:y=5-20:1.

Further, the specific steps are as follows:

(1) 1.4 mmol of triethanolamine and 3.7 mmol of sodium o-hydroxybenzoate were dissolved in 75 mL of water, and then cetyl ammonium bromide was added, with the molar ratio of cetyl ammonium bromide to sodium o-hydroxybenzoate being 0.2-0.6:1, and ultrasonically stirred at 80°C for 30 min;

(2) adding 12 mL of silicon source and stirring ultrasonically for 60 min, then adding aluminum source, adjusting the pH value of the solution to 9 with ethanolamine, continuing ultrasonic stirring for 15 min, placing in an oven at 80° C. for 2 to 3 h, cooling to room temperature, filtering, washing, and drying, and placing the obtained white powder in a muffle furnace and calcining at 550° C. for 6 h to obtain a Si _{x Aly} -O composite oxide carrier; the silicon source is tetraethyl orthosilicate, the aluminum source is NaAlO ₂ , and the Si/Al molar ratio is 5 to 20:1;

(3) adding a nickel source, a phosphorus source and the _{SixAly -} O composite oxide support obtained in (2) into water, stirring continuously for 2 hours, standing at room temperature for 12 hours, and then placing in a 90°C forced air drying oven for 12 hours to obtain a catalyst precursor, and then subjecting the catalyst to programmed temperature reduction to obtain a _Ni2P / _{SixAly -} O catalyst; the Ni concentration is 0.1-0.5 mol/L, the Ni/P molar ratio is 1:2, and the mass ratio of Ni to the _{SixAly -} O composite oxide support is 1:9.

Furthermore, the nickel source is any one of nickel chloride, nickel nitrate and nickel acetate.

Furthermore, the phosphorus source is any one of ammonium hypophosphite and sodium hypophosphite.

Furthermore, the washing in step (2) is performed by washing with ethanol and water alternately for 3 to 6 times, and the drying is performed by vacuum drying at 50 to 100° C. for 8 to 24 hours.

Furthermore, the temperature-programmed reduction method in step (3) is specifically to place the catalyst precursor in a tubular furnace, and in a 150 mL/min hydrogen atmosphere, heat the temperature from room temperature to 400°C at a heating rate of 3°C/min and maintain for 2 h, then cool to 50°C, switch to air treatment for 1 h, and then cool to room temperature to obtain the _Ni2P / _{SixAly -} O catalyst.

3. A method for preparing cycloalkanes by selective hydrodeoxygenation of phenolic compounds, using a mixture of straight-chain alkanes and naphthalene as solvent and phenolic compounds as raw materials, at a reaction temperature of 200-275°C, a hydrogen partial pressure of 2-4 MPa, a reaction time of 0.5-2 hours, stopping the reaction, and taking the supernatant to analyze the product composition by gas chromatography. The mass percentage of the phenolic compounds in the reaction system is 5-10%, and the mass ratio of the _Ni2P / _{SixAly -} O catalyst to phenol is 0.002-0.008:1.

Furthermore, the phenolic compound is one of phenol, o-cresol, m-cresol and p-cresol, and the mixture of straight-chain alkanes and naphthalene is a mixed solvent of stable n-dodecane and any one of decahydronaphthalene and tetrahydronaphthalene, wherein the mass percentage of n-dodecane is 80%.

The positive effects of adopting the above technical solutions:

(1) The catalyst of the present invention uses cheap Ni ₂ P as an active phase, and the catalyst synthesis method is simple, and has the advantages of low catalyst preparation cost, short preparation time, high hydrogenation activity, and good cycloalkane selectivity;

(2) The method for selective hydrogenation of phenolic compounds to cycloalkanes provided by the present invention has the advantage of short HDO reaction time, mainly because: (a) by means of micelles formed by surfactant hexadecyl ammonium bromide in aqueous solution, a special pore structure that expands straight from the center to the outside is formed, and a large pore volume that cannot be achieved by other conventional methods is obtained, while the catalyst has a large pore size (13.2nm); this greatly improves the mass transfer rate of reactants to the active sites on the catalyst surface; (b) the addition of ethanolamine can further control the hydrolysis rate of tetraethyl orthosilicate by adjusting the pH value of the solution, thereby ensuring that the obtained carrier has a radial pore structure with a regular and uniform size (~200nm), which promotes the mass transfer rate of reactants. Therefore, the reaction time of the obtained _Ni2P / _{SixAly -} O catalyst for hydrogenation of phenols to cycloalkanes is greatly shortened.

(3) The method for selectively hydrogenating phenolic compounds to produce cycloalkanes provided by the present invention has high hydrogenation activity, mainly because: (a) the special straight pore structure of the _Ni2P / _{SixAly -} O catalyst that expands from the center to the outside is conducive to the full utilization of the active sites inside the catalyst, and the large specific surface area is conducive to the high dispersion of the active phase, thereby improving the activity of the catalyst; (b) in the process of hydrolyzing tetraethyl orthosilicate to form oxides, the silicon source and the aluminum source can be in close and sufficient contact, thereby forming a uniform Si-O-Al structured _SixAly - _O composite oxide carrier, which regulates the acidity of the catalyst and improves the reaction activity of the catalyst C-OH group hydrogenation dehydration to produce cyclohexane; (c) Al added during the preparation of the carrier can be uniformly embedded in the silica bulk phase, so that, compared with the carrier without Al added, the specific surface area is further increased, which is conducive to the high dispersion of the active phase and improves the HDO activity of the catalyst.

(4) In the method for preparing cycloalkanes by selective hydrogenation of phenolic compounds provided by the present invention, when silicon dioxide is used as a _Ni2P catalyst carrier, the HDO activity of the catalyst is poor; when alumina is used as a _Ni2P catalyst carrier, due to the strong interaction between Al and P, inactive aluminum phosphate is formed due to the strong interaction between Al and P, and the HDO activity of the catalyst is very low; therefore, the _{SixAly -} O composite oxide carrier prepared by the present invention not only overcomes the problem of poor HDO activity when silicon dioxide is used as a carrier, and the problem of low HDO activity when alumina is used as a carrier due to the strong interaction between Al and P, but also improves the hydrogenation activity of the catalyst and the selectivity of the target product cycloalkanes;

(5) Through the perfect combination of catalytic activity, selectivity and mass transfer, the excellent effect of efficient HDO of phenolic compounds to cycloalkanes is achieved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a chemical reaction equation for preparing cycloalkanes by hydrodeoxygenation;

FIG2 is an XRD pattern of Ni ₂ P/Si ₅ Al ₁ -O catalyst;

FIG3 is a TEM (a) of Ni ₂ P/Si ₁₀ Al ₁ -O catalyst and a comparison of supported activity (b);

FIG4 shows the effect of reaction time on the HDO performance of Ni ₂ P/Si ₂₀ Al ₁ -O catalyst;

FIG5 shows the effect of reaction temperature on the HDO performance of Ni ₂ P/Si ₂₀ Al ₁ -O catalyst;

FIG6 shows the effect of reaction pressure on the HDO performance of Ni ₂ P/Si ₂₀ Al ₁ -O catalyst;

Detailed ways

The technical solution of the present invention is further described below in conjunction with specific embodiments, but it should not be construed as limiting the present invention:

Example 1

This example illustrates the preparation, XRD and FTIR of Ni ₂ P/Si ₅ Al ₁ -O catalyst.

(1) Preparation of Si ₅ Al ₁ -O composite oxide support:

(a) Weigh 1.4 mmol of triethanolamine, 3.7 mmol of sodium o-hydroxybenzoate and 0.8 mmol of hexadecyl ammonium bromide, dissolve in 75 mL of water, and stir ultrasonically at 80°C for 30 min.

(b) Add 12 mL of tetraethyl orthosilicate to the solution obtained in (a) and stir ultrasonically for 60 min, then add a certain amount of NaAlO ₂ (Si/Al molar ratio is 5:1), adjust the pH value of the solution to 9 with ethanolamine, continue to stir ultrasonically for 15 min, and place in an oven at 80°C for 2 h. After cooling to room temperature, filter, wash with ethanol and water alternately for 3 times, and vacuum dry at 80°C for 12 hours. The obtained white powder is placed in a muffle furnace and calcined at 550°C for 6 h to obtain a Si ₅ Al ₁ -O composite oxide support.

(2) Preparation of Ni ₂ P/Si ₅ Al ₁ -O catalyst:

(a) The Si ₅ Al ₁ -O composite oxide support, nickel chloride and ammonium hypophosphite obtained in (1) above were dissolved in water. The Ni concentration in the water was 0.1 mol/L, the Ni/P molar ratio was 1:2, and the mass ratio of Ni to the Si ₅ Al ₁ -O composite oxide support was 1:9. The mixture was stirred for 2 h, allowed to stand at room temperature for 12 h, and then placed in a 90°C forced air drying oven for 12 h to obtain a catalyst precursor.

(b) The catalyst precursor obtained in (a) above was placed in a tubular furnace, and heated from room temperature to 400°C at a heating rate of 3°C/min in a 150 mL/min hydrogen atmosphere and maintained for 2 h. After being cooled to 50°C, the temperature was switched to air treatment for 1 h, and then cooled to room temperature to obtain a Ni ₂ P/Si ₅ Al ₁ -O catalyst.

The Ni ₂ P/Si ₅ Al ₁ -O catalyst obtained in this example is characterized by XRD and FTIR:

The Ni ₂ P/Si ₅ Al ₁ -O catalyst obtained in (2) was characterized by XRD, and the active phase in the catalyst was analyzed. The results showed (see Figure 2) that an amorphous characteristic peak appeared near 2θ=23°, which was a characteristic peak of Si ₅ Al ₁ -O composite oxide. The characteristic peaks at 2θ=40.8°, 44.6°, 47.3° and 54.2° were attributed to the Ni ₂ P phase, which were Ni ₂ P (111), (201), (210) and (300) crystal planes (PDF#03-0953), respectively, indicating that the active phase in the Ni ₂ P/Si ₅ Al ₁ -O catalyst existed in the form of Ni ₂ P nanoparticles. No diffraction peaks of other Ni phases were found in the spectrum, indicating that there were only single Ni ₂ P nanoparticles in the catalyst without other impurities.

The Ni ₂ P/Si ₅ Al ₁ -O catalyst obtained in (2) was characterized by FTIR. In the FTIR spectrum, the stretching vibration peak of Si-O-Si appeared at 1050-1300 cm ^-1 , the bending vibration peak of Si-O-Si appeared at 471 cm ^-1 , and the characteristic peak of Si-O-Al appeared at 806 cm ^-1 , indicating that silicon and aluminum in the catalyst formed a composite oxide. During the synthesis process, the reaction in aqueous solution was carried out in three steps. In the first step, ethyl orthosilicate was hydrolyzed to form a hydroxylated product (silicic acid) and the corresponding alcohol (Equation 1), while sodium aluminate produced sodium tetrahydroxyaluminate, which can be further converted into aluminum hydroxide (Equation 2).

Si(OC ₂ H ₅ ) ₄ +4H ₂ O＝Si(OH) ₄ +4C ₂ H ₅ OH (1)

NaAlO ₂ + 2H ₂ O = NaAl(OH) ₄ = Al(OH) ₃ + NaOH (2)

The second step is the condensation reaction between silicic acid, aluminum hydroxide (Equation 3) and orthosilicic acid:

In the third step, the formed polymers continue to polymerize to form Si ₅ Al ₁ -O composite oxides:

Therefore, adding an aluminum source before hydrolysis of tetraethyl orthosilicate can embed Al into the framework of _SiO2 , thereby forming a uniform Si-O-Al structured _SixAly - _O composite oxide support.

During the carrier synthesis process, it is extremely important to adjust the pH of the solution with ethanolamine, because the pH control can control the hydrolysis rate of tetraethyl orthosilicate and sodium aluminate, promote the formation of Si-O-Al structure, and control the particle size of the carrier (see TEM characterization).

Example 2

This example illustrates the preparation of Ni ₂ P/Si ₁₀ Al ₁ -O catalyst and its TEM characterization and supported activity comparison.

(1) Preparation of Si ₁₀ Al ₁ -O composite oxide support:

(a) Weigh 1.4 mmol of triethanolamine, 3.7 mmol of sodium o-hydroxybenzoate and 1.0 mmol of hexadecyl ammonium bromide, dissolve in 75 mL of water, and stir ultrasonically at 80°C for 30 min.

(b) Add 12 mL of tetraethyl orthosilicate to the solution obtained in (a) and stir ultrasonically for 60 min, then add a certain amount of NaAlO ₂ (Si/Al molar ratio is 10:1), adjust the pH value of the solution to 9 with ethanolamine, continue to stir ultrasonically for 15 min, and place in an oven at 80°C for 3 h. After cooling to room temperature, filter, wash with ethanol and water alternately 5 times, and vacuum dry at 80°C for 12 hours. The obtained white powder is placed in a muffle furnace and calcined at 550°C for 6 h to obtain a Si ₁₀ Al ₁ -O composite oxide support.

(2) Preparation of Ni ₂ P/Si ₁₀ Al ₁ -O catalyst:

(a) The Si ₁₀ Al ₁ -O composite oxide support obtained in (1) above, nickel acetate and ammonium hypophosphite were dissolved in water. The Ni concentration in the water was 0.1 mol/L, the Ni/P molar ratio was 1:2, and the mass ratio of Ni to the Si ₁₀ Al ₁ -O composite oxide support was 1:9. The mixture was stirred for 2 h, allowed to stand at room temperature for 12 h, and then placed in a 90°C forced air drying oven for 12 h to obtain a catalyst precursor.

(b) The catalyst precursor obtained in (a) above was placed in a tubular furnace, and heated from room temperature to 400°C at a heating rate of 3°C/min in a 150 mL/min hydrogen atmosphere and maintained for 2 h. After being cooled to 50°C, the temperature was switched to air treatment for 1 h and cooled to room temperature to obtain a Ni ₂ P/Si ₁₀ Al ₁ -O catalyst.

TEM characterization of the Ni ₂ P/Si ₁₀ Al ₁ -O catalyst obtained in this example:

The Ni ₂ P/Si ₁₀ Al ₁ -O catalyst obtained in (2) was characterized by TEM. The results are shown in FIG3 . The active phase Ni ₂ P in the catalyst is uniformly dispersed without obvious aggregation. By adjusting the pH of the solution and controlling the hydrolysis rate of tetraethyl orthosilicate, Ni ₂ P/Si ₁₀ Al ₁ -O catalyst particles with a particle size of about 200 nm were obtained. The Ni ₂ P/Si ₁₀ Al ₁ -O catalyst has a straight-through pore structure that expands from the center to the outside (see FIG3 (a)). The pores of the traditional catalyst carrier are partially blocked by the loaded active components, and the utilization rate of the internal active sites and the mass transfer rate are low. The special structure carrier prepared by the present invention is conducive to fully utilizing the catalytic active sites, and the reaction raw materials can quickly reach the active sites on the catalyst surface, and can promote the reaction products to quickly leave the catalyst surface (see FIG3 (b)). This is the key to the high phenol hydrogenation activity of the catalyst and the conversion of its phenolic compounds into cycloalkanes in a short time.

Example 3

This example illustrates the preparation and BET characterization of Ni ₂ P/Si ₂₀ Al ₁ -O catalyst.

(1) Preparation of Si ₂₀ Al ₁ -O composite oxide support:

(a) Weigh 1.4 mmol of triethanolamine, 3.7 mmol of sodium o-hydroxybenzoate and 1.8 mmol of hexadecyl ammonium bromide, dissolve in 75 mL of water, and stir ultrasonically at 80°C for 30 min.

(b) Add 12 mL of tetraethyl orthosilicate to the solution obtained in (a) and stir ultrasonically for 60 min, then add a certain amount of NaAlO ₂ (Si/Al molar ratio is 10:1), adjust the pH value of the solution to 9 with ethanolamine, continue to stir ultrasonically for 15 min, and place in an oven at 80°C for 2 h. After cooling to room temperature, filter, wash with ethanol and water alternately for 3 times, and vacuum dry at 80°C for 24 hours. The obtained white powder is placed in a muffle furnace and calcined at 550°C for 6 h to obtain a Si ₂₀ Al ₁ -O composite oxide support.

(2) Preparation of Ni ₂ P/Si ₃₀ Al ₁ -O catalyst:

(a) The Si ₂₀ Al ₁ -O composite oxide support, nickel nitrate and sodium hypophosphite obtained in (1) above were dissolved in water, wherein the concentration of Ni in the water was 0.5 mol/L, the molar ratio of Ni/P was 1:2, and the mass ratio of Ni to the Si ₂₀ Al ₁ -O composite oxide support was 1:9. The mixture was stirred for 2 h, allowed to stand at room temperature for 12 h, and then placed in a 90°C forced air drying oven for 12 h to obtain a catalyst precursor.

(b) The catalyst precursor obtained in (a) above was placed in a tubular furnace, and heated from room temperature to 400°C at a heating rate of 3°C/min in a 150 mL/min hydrogen atmosphere and maintained for 2 h. After being cooled to 50°C, the temperature was switched to air for 1 h, and then cooled to room temperature to obtain a Ni ₂ P/Si ₂₀ Al ₁ -O catalyst.

BET characterization of the Si ₂₀ Al ₁ -O composite oxide support and Ni ₂ P/Si ₃₀ Al ₁ -O catalyst obtained in this example:

For the convenience of comparison, the BET data of SiO ₂ (conventional method), Al ₂ O ₃ (conventional method), SiO ₂ (no Al added in the present invention) (i.e. prepared by the method of the present invention but without adding Al), Si ₃₀ Al ₁ -O (two-step method) (i.e. first preparing SiO ₂ according to the method of the present invention and then introducing Al), Si ₂₀ Al ₁ -O (present invention) carriers and corresponding catalysts are listed in Table 2.

Table 2 Structural properties of carriers and catalysts

As can be seen from Table 2, the specific surface area of the Si ₂₀ Al ₁ -O (the present invention) carrier is as high as 604 m ² /g, and the pore volume and pore diameter are 1.90 cm ³ /g and 13.2 nm respectively, which not only has a large specific surface area, but also has a huge pore volume and a large pore diameter. Compared with the Ni ₂ P / SiO ₂ (the present invention does not add Al) catalyst, the specific surface area of the Ni ₂ P / Si ₃₀ Al ₁ -O (the present invention) catalyst is greatly improved, and the pore volume loss after loading nickel phosphide is very small. The Si ₃₀ Al ₁ -O (two-step method) carrier has a specific surface area of 355 m ² /g and a pore volume of only 1.54 cm ³ /g. Compared with the SiO ₂ (the present invention does not add Al) carrier, the specific surface area is reduced instead, and the pore volume loss after loading nickel phosphide is huge. The way of introducing Al has a great influence on the structure of the carrier. Although the same amount of Al is added, the method of the present invention adds Al to greatly increase the specific surface area, while the "two-step method" of adding Al greatly reduces the specific surface area. This is because the bonding modes of Al and Si in the carriers obtained by the two methods are completely different, which shows that the way of adding Al is also a key factor affecting the catalyst structure.

Compared with the corresponding SiO ₂ (ordinary method) and Al ₂ O ₃ (ordinary method), the specific surface area and pore volume of the Si ₂₀ Al ₁ -O (present invention) carrier are increased by at least one time, indicating that the method can obtain a carrier with a high specific surface area. Compared with SiO ₂ (unmodified according to the present invention), the specific surface area of the Si ₂₀ Al ₁ -O (present invention) carrier is increased, indicating that Al modification is conducive to the high dispersion of the active phase.

In summary, the method for preparing Si ₂₀ Al ₁ -O proposed in the present invention has obvious advantages. The large specific surface area is conducive to the high dispersion of the active phase, thereby improving the activity of the catalyst. The specific surface area and pore volume of the Ni ₂ P/Si ₂₀ Al ₁ -O catalyst obtained after loading Ni ₂ P are also significantly larger than those of catalysts loaded by other carriers.

Example 4

This example illustrates the preparation of Ni ₂ P/Si ₂₀ Al ₁ -O catalyst and the effect of NaAlO ₂ modification on the catalytic hydrogenation performance of m-cresol.

(1) Preparation of Si ₂₀ Al ₁ -O composite oxide support:

(a) Weigh 1.4 mmol of triethanolamine, 3.7 mmol of sodium o-hydroxybenzoate and 1.7 mmol of hexadecyl ammonium bromide, dissolve in 75 mL of water, and stir ultrasonically at 80°C for 30 min.

(b) Add 12 mL of tetraethyl orthosilicate to the solution obtained in (a) and stir ultrasonically for 60 min, then add a certain amount of NaAlO ₂ (Si/Al molar ratio is 20:1), adjust the pH value of the solution to 9 with ethanolamine, continue to stir ultrasonically for 15 min, and place in an oven at 80°C for 2 h. After cooling to room temperature, filter, wash with ethanol and water alternately 6 times, and vacuum dry at 50°C for 24 hours. The obtained white powder is placed in a muffle furnace and calcined at 550°C for 6 h to obtain a Si ₂₀ Al ₁ -O composite oxide support.

(2) Preparation of Ni ₂ P/Si ₂₀ Al ₁ -O catalyst:

(a) The Si ₂₀ Al ₁ -O composite oxide support obtained in (1) above, nickel chloride and ammonium hypophosphite were dissolved in water. The concentration of Ni in the water was 0.5 mol/L, the molar ratio of Ni/P was 1:2, and the mass ratio of Ni to the Si ₂₀ Al ₁ -O composite oxide support was 1:9. The mixture was stirred for 2 h, allowed to stand at room temperature for 12 h, and then placed in a 90°C forced air drying oven for 12 h to obtain a catalyst precursor.

(b) The catalyst precursor obtained in (a) above was placed in a tubular furnace, and heated from room temperature to 400°C at a heating rate of 3°C/min in a 150 mL/min hydrogen atmosphere and maintained for 2 h. After being cooled to 50°C, the temperature was switched to air for 1 h, and then cooled to room temperature to obtain a Ni ₂ P/Si ₂₀ Al ₁ -O catalyst.

For comparison, SiO ₂ obtained by the method of the present invention without adding Al was used as a carrier, and a catalyst was prepared by the same method, which was recorded as Ni ₂ P/SiO ₂ - catalyst without adding Al of the present invention.

The Ni ₂ P/Si ₂₀ Al ₁ -O catalyst is used for the reaction of preparing methylcyclohexane by hydrodeoxygenation of m-cresol:

Ni ₂ P/Si ₂₀ Al ₁ -O catalyst was used in the experiment of selective hydrodeoxygenation of m-cresol to prepare methylcyclohexane. A mixture of decahydronaphthalene and n-dodecane was used as solvent, wherein the mass fraction of n-dodecane was 80%, and a reaction solution system with a mass fraction of phenol of 5% was prepared. Ni ₂ P/Si ₂₀ Al ₁ -O catalyst was added, wherein the mass ratio of catalyst to phenol solution was 0.002:1, the reactor was sealed, nitrogen was tested for leaks, and hydrogen was replaced three times, and then hydrogen was introduced. At 250℃ and 3MPa, the reaction was stirred for 1 hour, and the reaction was stopped; the reactor was cooled to room temperature, hydrogen was discharged, the reaction mixture was poured out, and the supernatant was taken to analyze the product composition by gas chromatography. The experimental results show that the conversion rate of m-cresol over Ni ₂ P/Si ₂₀ Al ₁ -O catalyst is >99.9%, and the selectivity of methylcyclohexane is 99.9%. Under the same conditions, the m-cresol conversion rate of the Ni ₂ P/SiO ₂ - catalyst without Al addition of the present invention is only 64.7%, and the selectivity of methylcyclohexane is 91.0%, indicating that the effect of adding Al is obvious. In order to analyze the reason, the Ni ₂ P/Si ₂₀ Al ₁ -O catalyst and the Ni ₂ P/SiO ₂ - catalyst without Al addition of the present invention are characterized by H ₃ -TPD, and it is found that the Ni ₂ P/Si ₂₀ Al ₁ -O catalyst has a certain weak acidity, while the Ni ₂ P/SiO ₂ - catalyst without Al addition of the present invention has no acidity. Therefore, the reason why the Ni ₂ P/Si ₂₀ Al ₁ -O catalyst has high hydrodeoxygenation performance is that in addition to its special pore structure with straight through center expanding outward and large specific surface area, it can form a uniform Si-O-Al structure carrier, thereby regulating the acidity of the Ni ₂ P/Si _{x Aly} -O catalyst and improving the catalyst C-OH group hydrogenation dehydration to generate cyclohexane reaction activity (see Figure 1).

Example 5

This example illustrates the preparation of Ni ₂ P/Si ₂₀ Al ₁ -O catalyst and the catalytic hydrogenation experiment of m-cresol.

(1) Preparation of Si ₂₀ Al ₁ -O composite oxide support:

(a) Weigh 1.4 mmol of triethanolamine, 3.7 mmol of sodium o-hydroxybenzoate and 1.7 mmol of hexadecyl ammonium bromide, dissolve in 75 mL of water, and stir ultrasonically at 80°C for 30 min.

(b) Add 12 mL of tetraethyl orthosilicate to the solution obtained in (a) and stir ultrasonically for 60 min, then add a certain amount of NaAlO ₂ (Si/Al molar ratio is 20:1), adjust the pH value of the solution to 9 with ethanolamine, continue to stir ultrasonically for 15 min, and place in an oven at 80°C for 2 h. After cooling to room temperature, filter, wash with ethanol and water alternately 6 times, and vacuum dry at 50°C for 24 hours. The obtained white powder is placed in a muffle furnace and calcined at 550°C for 6 h to obtain a Si ₂₀ Al ₁ -O composite oxide support.

(2) Preparation of Ni ₂ P/Si ₂₀ Al ₁ -O catalyst:

(a) The Si ₂₀ Al ₁ -O composite oxide support obtained in (1) above, nickel chloride and ammonium hypophosphite were dissolved in water. The concentration of Ni in the water was 0.5 mol/L, the molar ratio of Ni/P was 1:2, and the mass ratio of Ni to the Si ₂₀ Al ₁ -O composite oxide support was 1:9. The mixture was stirred for 2 h, allowed to stand at room temperature for 12 h, and then placed in a 90°C forced air drying oven for 12 h to obtain a catalyst precursor.

(b) The catalyst precursor obtained in (a) above was placed in a tubular furnace, and heated from room temperature to 400°C at a heating rate of 3°C/min in a 150 mL/min hydrogen atmosphere and maintained for 2 h. After being cooled to 50°C, the temperature was switched to air for 1 h, and then cooled to room temperature to obtain a Ni ₂ P/Si ₂₀ Al ₁ -O catalyst.

The Ni ₂ P/Si ₂₀ Al ₁ -O catalyst is used for the hydrogenation of m-cresol to prepare methylcyclohexane:

Ni ₂ P/Si ₂₀ Al ₁ -O catalyst was used in the experiment of selective hydrogenation of m-cresol to prepare methylcyclohexane. A mixture of decahydronaphthalene and n-dodecane was used as solvent, wherein the mass fraction of n-dodecane was 80%, and a reaction solution system with a mass fraction of phenol of 5% was prepared. Ni ₂ P/Si ₂₀ Al ₁ -O catalyst was added, wherein the mass ratio of catalyst to phenol solution was 0.002:1, the reactor was sealed, nitrogen was checked for leaks, and hydrogen was replaced three times, and then hydrogen was introduced. At 250°C and 3MPa, the reaction was stirred for a certain hour, and the reaction was stopped; the reactor was cooled to room temperature, hydrogen was discharged, the reaction mixture was poured out, and the supernatant was taken to analyze the product composition by gas chromatography. The experimental results are shown in Figure 4. When the reaction time was 30min, the conversion rate of m-cresol was 77.5%, and the selectivity of methylcyclohexane was 95.2%. When the reaction time was extended to 60min, the conversion rate of m-cresol was >99.9%, and the selectivity of methylcyclohexane was 99.9%.

Example 6

This example illustrates the preparation of Ni ₂ P/Si ₅ Al ₁ -O catalyst and the catalytic hydrogenation experiment of m-cresol.

(1) Preparation of Si ₅ Al ₁ -O composite oxide support:

(a) Weigh 1.4 mmol of triethanolamine, 3.7 mmol of sodium o-hydroxybenzoate and 0.9 mmol of hexadecyl ammonium bromide, dissolve in 75 mL of water, and stir ultrasonically at 80°C for 30 min.

(b) Add 12 mL of tetraethyl orthosilicate to the solution obtained in (a) and stir ultrasonically for 60 min, then add a certain amount of NaAlO ₂ (Si/Al molar ratio is 5:1), adjust the pH value of the solution to 9 with ethanolamine, continue to stir ultrasonically for 15 min, and place in an oven at 80°C for 2 h. After cooling to room temperature, filter, wash alternately with ethanol and water for 6 times, and vacuum dry at 100°C for 18 hours. The obtained white powder is placed in a muffle furnace and calcined at 550°C for 6 h to obtain a Si ₅ Al ₁ -O composite oxide support.

(2) Preparation of Ni ₂ P/Si ₅ Al ₁ -O catalyst:

(a) The Si ₁₀ Al ₁ -O composite oxide support, nickel nitrate and sodium hypophosphite obtained in (1) above were dissolved in water. The Ni concentration in the water was 0.5 mol/L, the Ni/P molar ratio was 1:2, and the mass ratio of Ni to the Si ₅ Al ₁ -O composite oxide support was 1:9. The mixture was stirred for 2 h, allowed to stand at room temperature for 12 h, and then placed in a 90°C forced air drying oven for 12 h to obtain a catalyst precursor.

(b) The catalyst precursor obtained in (a) above was placed in a tubular furnace, and heated from room temperature to 400°C at a heating rate of 3°C/min in a 150 mL/min hydrogen atmosphere and maintained for 2 h. After being cooled to 50°C, the temperature was switched to air for 1 h and then cooled to room temperature to obtain a Ni ₂ P/Si ₅ Al ₁ -O catalyst.

The Ni ₂ P/Si ₅ Al ₁ -O catalyst is used for the hydrogenation of m-cresol to prepare methylcyclohexane:

Ni ₂ P/Si ₅ Al ₁ -O catalyst was used in the experiment of selective hydrogenation of m-cresol to prepare methylcyclohexane. A mixture of decahydronaphthalene and n-dodecane was used as solvent, wherein the mass fraction of n-dodecane was 80%, and a reaction solution system with a mass fraction of p-cresol of 2% was prepared. Ni ₂ P/Si ₅ Al ₁ -O catalyst was added, wherein the mass ratio of catalyst to phenol solution was 0.008:1, the reactor was sealed, nitrogen was checked for leaks, and hydrogen was replaced three times, and then hydrogen was introduced. At 200-275°C and 3MPa, the reaction was stirred for 60 minutes, and the reaction was stopped; the reactor was cooled to room temperature, hydrogen was discharged, the reaction mixture was poured out, and the supernatant was taken to analyze the product composition by gas chromatography. The experimental results are shown in Figure 5. When the reaction temperature was 200°C, the conversion rate of m-cresol was 68.0%, and the selectivity of methylcyclohexane was 90.7%. When the reaction temperature was increased to 250°C, the conversion rate of m-cresol was >99.9%, and the selectivity of methylcyclohexane was 99.9%.

Example 7

This example illustrates the preparation of Ni ₂ P/Si ₁₀ Al ₁ -O catalyst and the catalytic hydrogenation experiment of m-cresol.

(1) Preparation of Si ₁₀ Al ₁ -O composite oxide support:

(a) Weigh 1.4 mmol of triethanolamine, 3.7 mmol of sodium o-hydroxybenzoate and 0.9 mmol of hexadecyl ammonium bromide, dissolve in 75 mL of water, and stir ultrasonically at 80°C for 30 min.

(b) Add 12 mL of tetraethyl orthosilicate to the solution obtained in (a) and stir ultrasonically for 60 min, then add a certain amount of NaAlO ₂ (Si/Al molar ratio is 10:1), adjust the pH value of the solution to 9 with ethanolamine, continue to stir ultrasonically for 15 min, and place in an oven at 80°C for 2 h. After cooling to room temperature, filter, wash alternately with ethanol and water for 6 times, and vacuum dry at 80°C for 24 hours. The obtained white powder is placed in a muffle furnace and calcined at 550°C for 6 h to obtain a Si ₁₀ Al ₁ -O composite oxide support.

(2) Preparation of Ni ₂ P/Si ₁₀ Al ₁ -O catalyst:

(a) The Si ₁₀ Al ₁ -O composite oxide support, nickel acetate and ammonium hypophosphite obtained in (1) above were dissolved in water. The Ni concentration in the water was 0.5 mol/L, the Ni/P molar ratio was 1:2, and the mass ratio of Ni to the Si ₁₀ Al ₁ -O composite oxide support was 1:9. The mixture was stirred for 2 h, allowed to stand at room temperature for 12 h, and then placed in a 90°C forced air drying oven for 12 h to obtain a catalyst precursor.

(b) The catalyst precursor obtained in (a) above was placed in a tubular furnace, and heated from room temperature to 400°C at a heating rate of 3°C/min in a 150 mL/min hydrogen atmosphere and maintained for 2 h. After being cooled to 50°C, the temperature was switched to air for 1 h, and then cooled to room temperature to obtain a Ni ₂ P/Si ₁₀ Al ₁ -O catalyst.

The Ni ₂ P/Si ₁₀ Al ₁ -O catalyst is used for the hydrogenation of m-cresol to prepare methylcyclohexane:

Ni ₂ P/Si ₁₀ Al ₁ -O catalyst was used in the experiment of selective hydrogenation of m-cresol to prepare methylcyclohexane. A mixture of decahydronaphthalene and n-dodecane was used as solvent, wherein the mass fraction of n-dodecane was 80%, and a reaction solution system with a mass fraction of m-cresol of 3% was prepared. Ni ₂ P/Si ₁₀ Al ₁ -O catalyst was added, wherein the mass ratio of catalyst to phenol solution was 0.005:1, the reactor was sealed, nitrogen was tested for leaks, and hydrogen was replaced three times, and then hydrogen was introduced. At 250°C and 2-4MPa, the reaction was stirred for 60min, and the reaction was stopped; the reactor was cooled to room temperature, hydrogen was discharged, the reaction mixture was poured out, and the supernatant was taken to analyze the product composition by gas chromatography. The experimental results are shown in Figure 6. When the reaction pressure was 2MPa, the conversion rate of m-cresol was 78.0%, and the selectivity of methylcyclohexane was 94.7%. When the reaction pressure was increased to 3MPa, the conversion rate of m-cresol was >99.9%, and the selectivity of methylcyclohexane was 99.9%.

Example 8

This example illustrates the preparation of Ni ₂ P/Si ₂₀ Al ₁ -O catalyst and catalytic experiments of different phenolic compounds.

(1) Preparation of Si ₂₀ Al ₁ -O composite oxide support:

(a) Weigh 1.4 mmol of triethanolamine, 3.7 mmol of sodium o-hydroxybenzoate and 0.9 mmol of hexadecyl ammonium bromide, dissolve in 75 mL of water, and stir ultrasonically at 80°C for 30 min.

(b) Add 12 mL of tetraethyl orthosilicate to the solution obtained in (a) and stir ultrasonically for 60 min, then add a certain amount of NaAlO ₂ (Si/Al molar ratio is 10:1), adjust the pH value of the solution to 9 with ethanolamine, continue to stir ultrasonically for 15 min, and place in an oven at 80°C for 2 h. After cooling to room temperature, filter, wash with ethanol and water alternately for 3 times, and vacuum dry at 80°C for 24 hours. The obtained white powder is placed in a muffle furnace and calcined at 550°C for 6 h to obtain a Si ₂₀ Al ₁ -O composite oxide support.

(2) Preparation of Ni ₂ P/Si ₂₀ Al ₁ -O catalyst:

(a) The Si ₂₀ Al ₁ -O composite oxide support, nickel acetate and ammonium hypophosphite obtained in (1) above were dissolved in water. The Ni concentration in the water was 0.5 mol/L, the Ni/P molar ratio was 1:2, and the mass ratio of Ni to the Si ₂₀ Al ₁ -O composite oxide support was 1:9. The mixture was stirred for 2 h, allowed to stand at room temperature for 12 h, and then placed in a 90°C forced air drying oven for 12 h to obtain a catalyst precursor.

(b) The catalyst precursor obtained in (a) above was placed in a tubular furnace, and heated from room temperature to 400°C at a heating rate of 3°C/min in a 150 mL/min hydrogen atmosphere and maintained for 2 h. After being cooled to 50°C, the temperature was switched to air for 1 h, and then cooled to room temperature to obtain a Ni ₂ P/Si ₂₀ Al ₁ -O catalyst.

The Ni ₂ P/Si ₂₀ Al ₁ -O catalyst is used for the hydrogenation of different phenolic compounds to prepare methylcyclohexane:

Ni ₂ P/Si ₂₀ Al ₁ -O catalyst was used for the selective hydrogenation of phenol, o-cresol and p-cresol to prepare methylcyclohexane. A mixture of decahydronaphthalene and n-dodecane was used as solvent, in which the mass fraction of n-dodecane was 80%, and reaction solution systems with a mass fraction of phenol, o-cresol and p-cresol were prepared respectively. Ni ₂ P/Si ₂₀ Al ₁ -O catalyst was added to the three systems respectively, in which the mass ratio of catalyst to phenolic compound was 0.008:1. The reactor was sealed, nitrogen was used for leak detection, and hydrogen was replaced three times. Hydrogen was introduced, and the reaction was stirred at 250℃ and 3MPa for 90min, and the reaction was stopped; the reactor was cooled to room temperature, hydrogen was discharged, the reaction mixture was poured out, and the supernatant was taken to analyze the product composition by gas chromatography. The results showed that the conversion rates of phenol and p-cresol reached 99.9%, and the selectivity of methylcyclohexane also reached 99.9%. The conversion rate of o-cresol was 96.4%, and the selectivity of methylcyclohexane was 98.0%.

Claims (8)

1. A catalyst for preparing cycloalkane by selective hydrodeoxygenation of phenolic compounds is characterized in that: the catalyst is composed of a carrier of nano silicon aluminum oxide Si _xAl_y -O with radial center and an active phase of Ni ₂ P on the carrier; the preparation method of the catalyst comprises the steps of taking tetraethyl orthosilicate as a silicon source, aluminum nitrate as an aluminum source, cetyl ammonium bromide as a surfactant, taking sodium benzoate O-hydroxy as a structure directing agent, taking triethanolamine as a chelating agent, controlling the pH value of a solution to be 9 through the ethanolamine, regulating and controlling the hydrolysis speed, synthesizing a silicon-aluminum composite oxide carrier Si _xAl_y -O, loading a nickel source and a phosphorus source, and obtaining a Ni ₂P/Si_xAl_y -O catalyst through reduction; and x is y=5-20:1.

2. The process for preparing a cycloalkane catalyst according to claim 1, wherein the process comprises the steps of: the method comprises the following specific steps:

(1) Dissolving 1.4 mmol triethanolamine and 3.7 mmol sodium benzoate o-hydroxy in 75mL water, adding cetyl ammonium bromide, stirring at 80deg.C under ultrasonic condition at a molar ratio of cetyl ammonium bromide to sodium benzoate o-hydroxy of 0.2-0.6:1 for 30 min;

(2) Adding 12mL silicon source, ultrasonically stirring 60 min, adding aluminum source, regulating the pH value of the solution to 9 with ethanolamine, continuing to ultrasonically stir 15 min, placing the solution in an 80 ℃ oven for constant temperature 2-3 h, cooling to room temperature, filtering, washing, drying, and placing the obtained white powder in a muffle furnace for roasting 6 h at 550 ℃ to obtain the Si _xAl_y -O composite oxide carrier; the silicon source is tetraethyl orthosilicate, the aluminum source is Al (NO ₃) ₃, si/Al molar ratio is 5-20:1;

(3) Adding a nickel source, a phosphorus source and a Si _xAl_y -O composite oxide carrier into water, continuously stirring for 2h, standing for 12 h at room temperature, then placing in a 90 ℃ blast drying oven for 12 h to obtain a catalyst precursor, and obtaining a Ni ₂P/Si_xAl_y -O catalyst by a temperature programming reduction method; the concentration of Ni is 0.1-0.5 mol/L, the molar ratio of Ni to P is 1:2, and the mass ratio of Ni to Si _xAl_y -O composite oxide carrier is 1:9; the temperature programming reduction method specifically comprises the steps of placing a catalyst precursor into a tube furnace, heating to 400 ℃ from room temperature at a heating rate of 3 ℃/min in a hydrogen atmosphere of 150 mL/min, keeping the temperature at 2h, cooling to 50 ℃, switching air to treat for 1h, and cooling to the room temperature to obtain the Ni ₂P/Si_xAl_y -O catalyst.

3. The process for preparing a cycloalkane catalyst according to claim 2, wherein the process comprises the steps of: the nickel source is any one of nickel chloride, nickel nitrate and nickel acetate.

4. The process for preparing a cycloalkane catalyst according to claim 2, wherein the process comprises the steps of: the phosphorus source is any one of ammonium hypophosphite and sodium hypophosphite.

5. The process for preparing a cycloalkane catalyst according to claim 2, wherein the process comprises the steps of: the washing in the step (2) is to alternately wash 3-6 times by ethanol and water, and the drying is to be carried out for 8-24 hours at 50-100 ℃.

6. Use of the catalyst according to claim 1 or the catalyst prepared according to any one of claims 2 to 5 in the preparation of cycloalkanes by selective hydrodeoxygenation of phenolic compounds.

7. The use according to claim 6, characterized in that: taking a mixture of linear alkane and naphthalene as a solvent, taking a phenolic compound as a raw material, stopping the reaction at a reaction temperature of 200-275 ℃ and a hydrogen partial pressure of 2-4 MPa for 0.5-2 hours, and taking a supernatant liquid to analyze the product composition by using gas chromatography; the phenolic compound is phenol, the mass percentage of the phenol in the reaction system is 5-10%, and the mass ratio of the Ni ₂P/Si_xAl_y -O catalyst to the phenol is 0.002-0.008:1.

8. The use according to claim 7, characterized in that: the phenolic compound is one of phenol, o-cresol, m-cresol and p-cresol; the straight-chain alkane solvent is a mixed solvent of n-dodecane with stable property, decalin and tetrahydronaphthalene, wherein the mass percentage of the n-dodecane is 80%.