Rare earth metal lanthanum modified carbon-coated nickel catalyst and preparation method and application thereof

Abstract

The invention discloses a rare earth metal lanthanum modified carbon-coated nickel catalyst as well as a preparation method and application thereof, and belongs to the technical field of catalysts. The preparation method of the rare earth metal lanthanum modified carbon-coated nickel catalyst comprises the following steps: carrying out a heating reaction on a homogeneous solution containing soluble nickel salt and citric acid, after the reaction is finished, filtering, collecting a precipitate, and then washing, drying and roasting for the first time to obtain a Ni-coated C catalyst; suspending the Ni-coated C catalyst in an aqueous solution containing soluble lanthanum salt, carrying out ultrasonic treatment, and drying to obtain a precursor; the precursor is subjected to secondary roasting, and the rare earth metal lanthanum modified carbon-coated nickel catalyst is obtained. The catalyst provided by the invention can enhance the interaction between the metal and the carrier, thereby reducing carbon deposition and improving the activity and stability of the catalyst.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, and specifically relates to a rare earth metal lanthanum modified carbon-coated nickel catalyst, its preparation method, and its application. Background Technology

[0002] Higher alcohols play a vital role in the chemical, pharmaceutical, fragrance, and food industries. In surfactant preparation, higher alcohols, as core raw materials for amphiphilic substances, are frequently used to produce surfactants such as detergents and dispersants, finding wide application in daily chemical products and industrial cleaning. Furthermore, in polymer modification, higher alcohols can be used to produce plasticizers. Molecular modification can be achieved by weakening intermolecular forces and crystallinity, increasing molecular mobility, thereby improving the plasticity and flexibility of plastic products.

[0003] Currently, research on higher alcohols in the field of biofuels is gradually increasing. Compared with traditional low-carbon alcohol fuels, higher alcohols have higher energy output efficiency and better combustion performance. They have good miscibility with diesel and can be used directly in the engine. Higher alcohols are green and environmentally friendly fuel additives that can replace the consumption of fossil fuels and effectively reduce the emission of harmful gases such as sulfur oxides and nitrogen oxides.

[0004] The synthesis of higher alcohols is currently a research focus. Among these, the Guerbet aldol condensation reaction, a key carbon chain growth reaction, involves three main steps: First, dehydrogenation occurs, where alcohol molecules lose two hydrogen atoms under a metal catalyst to form an aldehyde intermediate. Second, aldol condensation occurs, where these aldehyde intermediates undergo condensation under a basic catalyst to form new carbon-carbon bonds and lose a water molecule. Third, hydrogenation occurs, where the condensation product is reduced by hydrogen on a metal catalyst to finally generate a long-chain alcohol. Because both dehydrogenation and hydrogenation require metal catalysts, and most metal catalysts possess both functions, in practical applications, the Guerbet reaction catalytic system typically employs a bifunctional dehydrogenation / hydrogenation catalyst in conjunction with a basic catalyst. Therefore, most current catalytic systems utilize organometallic compounds and transition noble metals such as Ru, Rh, Pa, Os, Ir, and Pt. However, challenges remain regarding separation and recovery, as well as the high cost of noble metal catalysis.

[0005] Nickel is a relatively abundant transition metal element in the Earth's crust and is one of the best alternatives to precious metals. For example, patent CN117138788A discloses a carbon-coated nickel Ni@C catalyst for catalyzing the CO methanation reaction. It has a high CH bond breaking ability, which promotes the formation of nickel carbides, leading to carbon deposition. However, when the reaction temperature is too high, the carbon layer may degrade or detach, exposing nickel particles and causing sintering. This can lead to the methanation of small molecule alcohols, which is detrimental to the Guerbet carbon-carbon condensation reaction. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a rare-earth metal lanthanum-modified carbon-coated nickel catalyst, its preparation method, and its application. The primary objective of this invention is to overcome the problem of low C4+ higher alcohol yield (25.0%) when using existing carbon-coated nickel-based catalysts for the aqueous synthesis of higher alcohols from small molecules, and to provide a method for preparing a lanthanum-coated carbon-coated nickel catalyst.

[0007] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for preparing a rare earth metal lanthanum-modified carbon-coated nickel catalyst, comprising the following steps: heating a homogeneous solution containing soluble nickel salt and citric acid to react, filtering after the reaction is completed, collecting the precipitate, and then washing, drying and first calcining to obtain a Ni@C catalyst; The Ni@C catalyst was suspended in an aqueous solution containing a soluble lanthanum salt, ultrasonically treated, and then dried to obtain the precursor. The precursor was subjected to secondary calcination to obtain the rare earth metal lanthanum-modified carbon-coated nickel catalyst.

[0008] Furthermore, the molar ratio of the soluble nickel salt to citric acid is 1:2; the molar ratio of the soluble nickel salt to the soluble lanthanum salt is (5-25):1.

[0009] Furthermore, the soluble nickel salt is nickel nitrate, and the soluble lanthanum salt is lanthanum nitrate.

[0010] Furthermore, the heating reaction is carried out at a temperature of 100°C for 12 hours.

[0011] Furthermore, the first calcination is carried out at 550°C for 2 hours under an inert atmosphere.

[0012] Furthermore, the secondary calcination is carried out at 550°C for 2 hours under an inert atmosphere.

[0013] Secondly, the present invention provides a rare earth metal lanthanum-modified carbon-coated nickel catalyst prepared by the aforementioned preparation method.

[0014] This invention introduces a Ni-based catalyst modified with a specific rare-earth metal, lanthanum. Due to the abundance of oxygen vacancies and the redox effects of lanthanum ions, the surface oxygen mobility is enhanced, accelerating the carbon oxidation reaction. This reduces coke formation and increases the proportion of easily oxidizable amorphous carbon, thus reducing carbon deposition through a carbon shell. Furthermore, the La-modified Ni-based catalyst increases the number of active sites, promotes the interaction between the material and the Ni-based catalyst, and adjusts the surface pH of the catalyst, improving hydrocarbon adsorption and reactivity. This enhances the catalyst's resistance to carbon deposition and its cycling performance, promotes hydrogenation and dehydrogenation processes, and guides the reactants to form more higher carbon alcohols.

[0015] Thirdly, the present invention provides an application of the rare earth metal lanthanum modified carbon-coated nickel catalyst in the preparation of higher alcohols.

[0016] Fourthly, this invention provides a method for preparing higher alcohols, comprising the following steps: placing the rare earth metal lanthanum-modified carbon-coated nickel catalyst, sodium hydroxide, ethanol, and water in a reaction vessel, mixing and checking for leaks, replacing the air in the reaction vessel with high-purity hydrogen, and stirring the reaction to prepare the higher alcohol. After the reaction, the substrate spontaneously separates into oil and water phases, which are then separated by centrifugation and analyzed by gas chromatography.

[0017] Further, the mass ratio of the rare earth metal lanthanum-modified carbon-coated nickel catalyst, sodium hydroxide, ethanol, and water is 1:1:20:20; and / or, The stirring reaction was carried out at a temperature of 180-210℃, an initial pressure of 0.1MPa, and a stirring speed of 1500 rpm.

[0018] The rare-earth metal lanthanum-modified carbon-coated nickel catalyst of this invention, when used for the carbon-carbon coupling of aqueous small-molecule alcohols to prepare higher alcohols, effectively promotes the adsorption and desorption of reactant molecules, improves the catalyst's resistance to carbon deposition and cycling performance, and increases reaction efficiency. It exhibits high organic phase yield and C4+ higher alcohol yield, and has broad application prospects.

[0019] Compared with the prior art, the present invention has the following advantages and technical effects: The rare-earth metal lanthanum-modified carbon-coated nickel catalyst provided by this invention can enhance the interaction between the metal and the support, thereby reducing carbon deposition and improving the catalyst's activity and stability. The lanthanum promoter not only enhances the redox capability of the Ni-based catalyst and provides more active sites, but also regulates the surface pH of the catalyst while reducing the interaction between nickel particles, thus improving the catalyst's resistance to carbon deposition and its cycling performance.

[0020] The rare earth metal lanthanum modified carbon-coated nickel catalyst provided by this invention is a heterogeneous catalyst, which is easy to separate, recover and reuse in the preparation of higher alcohols. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 The images show the XRD patterns of Ni@C-La prepared in Example 1 and Ni@C prepared in Comparative Example 1. Detailed Implementation

[0023] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0024] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0025] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0026] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0027] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0028] The room temperature in this invention refers to 25±2℃.

[0029] Unless otherwise specified, all materials used in this invention are commercially available products.

[0030] In this embodiment of the invention, the inert gas is nitrogen.

[0031] Example 1: A method for preparing a rare earth metal lanthanum-modified carbon-coated nickel catalyst. S1. Dissolve soluble nickel salt (nickel nitrate) and citric acid (the molar ratio of soluble nickel salt to citric acid is 1:2) in distilled water and stir to form a homogeneous solution, wherein the concentration of soluble nickel salt is 0.5 mol / L; S2. The homogeneous solution obtained in S1 was transferred to a stainless steel autoclave lined with polytetrafluoroethylene and heated at 100°C for 12 h to achieve precipitation. The solid was then collected using a Buchner funnel, washed 12 times with deionized water and ethanol, and dried (80°C, 18 h) to obtain a dark brown solid. S3. The dark brown solid prepared in S2 was placed under an inert atmosphere and calcined at 550°C for 2 hours to obtain the Ni@C catalyst; S4. The Ni@C catalyst prepared in S3 was suspended in 40 mL of distilled water containing 0.033 mol / L soluble lanthanum salt (lanthanum nitrate). After ultrasonic treatment for 60 min, it was dried (80 °C, 120 h) to obtain the precursor. The molar ratio of soluble nickel salt to soluble lanthanum salt was 15:1. S5. The precursor prepared in S4 was placed in an inert atmosphere and calcined at 550°C for 2 hours to obtain a rare earth metal lanthanum-modified carbon-coated nickel catalyst, denoted as Ni@C-La.

[0032] Example 2: A method for preparing a rare earth metal lanthanum-modified carbon-coated nickel catalyst. Same as Example 1, except that in S4 the molar ratio of soluble nickel salt to soluble lanthanum salt is 25:1.

[0033] Example 3: A method for preparing a rare earth metal lanthanum-modified carbon-coated nickel catalyst. Same as Example 1, except that in S4 the molar ratio of soluble nickel salt to soluble lanthanum salt is 20:1.

[0034] Comparative Example 1: A method for preparing a carbon-coated nickel-based catalyst S1. Dissolve soluble nickel salt (nickel nitrate) and citric acid (the molar ratio of soluble nickel salt to citric acid is 1:2) in distilled water and stir to form a homogeneous solution, wherein the concentration of soluble nickel salt is 0.5 mol / L; S2. The homogeneous solution obtained in S1 was transferred to a stainless steel autoclave lined with polytetrafluoroethylene and heated at 100°C for 12 h to achieve precipitation. The solid was then collected using a Buchner funnel, washed 12 times with deionized water and ethanol, and dried (80°C, 18 h) to obtain a dark brown solid. S3. The dark brown solid prepared in S2 was placed under an inert atmosphere and calcined at 550°C for 2 hours to obtain the Ni@C catalyst.

[0035] Comparative Example 2 Same as Example 1, except that in S4 the molar ratio of soluble nickel salt and soluble lanthanum salt is 10:1.

[0036] Comparative Example 3 Same as Example 1, except that in S4 the molar ratio of soluble nickel salt to soluble lanthanum salt is 5:1.

[0037] Application Examples 1-3 The rare-earth metal lanthanum-modified carbon-coated nickel catalyst prepared in Examples 1-3 was used in conjunction with a homogeneous base to catalyze the carbon-carbon coupling reaction of ethanol to produce higher alcohols. Specifically, 0.5 g of the catalyst prepared in Examples 1-3 was added to a 70 mL high-pressure reactor, followed by 0.5 g of NaOH, 10 g of ethanol, and 10 g of water. After leak testing, the air in the reactor was replaced with high-purity hydrogen. The reaction was then carried out continuously for 8 hours at a reaction temperature of 190 °C, an initial pressure of 0.1 MPa, and a stirring speed of 1500 rpm. After the reaction, the reaction system was cooled to room temperature, and the gas phase was collected using a gas bag. The liquid phase product was then removed from the reactor. The liquid and solid phase catalysts were separated by centrifugation and filtration. After standing, the liquid phase naturally separated into an oil phase and an aqueous phase. The gas phase products, aqueous phase and oil phase were all qualitatively and quantitatively analyzed by gas chromatography. The results showed that the main product of the oil phase was C4+ higher alcohols. The analysis showed that C4+ higher alcohols are mainly composed of alcohols with 4 to 16 carbon atoms. The analytical results are shown in Table 1 below.

[0038] Application Example 4 The rare-earth metal lanthanum-modified carbon-coated nickel catalyst prepared in Example 1 was used to co-catalyze the carbon-carbon coupling reaction of ethanol to produce higher alcohols with a homogeneous base. The specific procedure was as follows: 0.5 g of the catalyst prepared in Example 1 was added to a 70 mL high-pressure reactor, followed by 0.5 g of NaOH, 10 g of ethanol, and 10 g of water. After leak testing, the air in the reactor was replaced with high-purity hydrogen. The reaction was then carried out continuously for 8 hours at a reaction temperature of 180 °C, an initial pressure of 0.1 MPa, and a stirring speed of 1500 rpm. After the reaction was completed, the reaction system was allowed to cool to room temperature. The gas phase was collected using a gas bag, and the liquid phase product was removed from the reactor. The liquid and solid phase catalysts were separated by centrifugation and filtration. After standing, the liquid phase naturally separated into oil and water phases. The gas phase products, aqueous phase and oil phase were all qualitatively and quantitatively analyzed by gas chromatography. The results showed that the main product of the oil phase was C4+ higher alcohols. The analysis showed that C4+ higher alcohols are mainly composed of alcohols with 4 to 16 carbon atoms. The analytical results are shown in Table 1 below.

[0039] Application Example 5 The rare-earth metal lanthanum-modified carbon-coated nickel catalyst prepared in Example 1 was used to co-catalyze the carbon-carbon coupling reaction of ethanol to produce higher alcohols with a homogeneous base. Specifically, 0.5 g of the catalyst prepared in Example 1 was added to a 70 mL high-pressure reactor, followed by 0.5 g of NaOH, 10 g of ethanol, and 10 g of water. After leak testing, the air in the reactor was replaced with high-purity hydrogen. The reaction was then carried out continuously for 8 hours at a reaction temperature of 200 °C, an initial pressure of 0.1 MPa, and a stirring speed of 1500 rpm. After the reaction, the reaction system was allowed to cool to room temperature. The gas phase was collected using a gas bag, and the liquid product in the reactor was removed. The liquid and solid catalyst phases were separated by centrifugation and filtration. After standing, the liquid phase naturally separated into an oil phase and an aqueous phase. The gas phase products, aqueous phase and oil phase were all qualitatively and quantitatively analyzed by gas chromatography. The results showed that the main product of the oil phase was C4+ higher alcohols. The analysis showed that C4+ higher alcohols are mainly composed of alcohols with 4 to 16 carbon atoms. The analytical results are shown in Table 1 below.

[0040] Application Example 6 The rare-earth metal lanthanum-modified carbon-coated nickel catalyst prepared in Example 1 was used to co-catalyze the carbon-carbon coupling reaction of ethanol to produce higher alcohols with a homogeneous base. The specific procedure was as follows: 0.5 g of the catalyst prepared in Example 1 was added to a 70 mL high-pressure reactor, followed by 0.5 g of NaOH, 10 g of ethanol, and 10 g of water. After leak testing, the air in the reactor was replaced with high-purity hydrogen. The reaction was then carried out continuously for 8 hours at a reaction temperature of 210 °C, an initial pressure of 0.1 MPa, and a stirring speed of 1500 rpm. After the reaction was completed, the reaction system was allowed to cool to room temperature. The gas phase was collected using a gas bag, and the liquid phase product was removed from the reactor. The liquid and solid phase catalysts were separated by centrifugation and filtration. After standing, the liquid phase naturally separated into oil and water phases. The gas phase products, aqueous phase and oil phase were all qualitatively and quantitatively analyzed by gas chromatography. The results showed that the main product of the oil phase was C4+ higher alcohols. The analysis showed that C4+ higher alcohols are mainly composed of alcohols with 4 to 16 carbon atoms. The analytical results are shown in Table 1 below.

[0041] Comparative Application Examples 1-3 The catalysts prepared in Comparative Examples 1-3 were used in conjunction with a homogeneous base to catalyze the carbon-carbon coupling reaction of ethanol to produce higher alcohols. The specific procedure was as follows: 0.5 g of the catalysts prepared in Comparative Examples 1-3 were added to separate 70 mL high-pressure reactors, followed by 0.5 g of NaOH, 10 g of ethanol, and 10 g of water. After leak testing, the air in the reactor was replaced with high-purity hydrogen. The reaction was then carried out continuously for 8 hours at a reaction temperature of 190 °C, an initial pressure of 0.1 MPa, and a stirring speed of 1500 rpm. After the reaction was completed, the reaction system was cooled to room temperature, and the gas phase was collected using a gas bag. The liquid product in the reactor was then removed. The liquid and solid catalyst phases were separated by centrifugation and filtration. Upon settling, the liquid phase naturally separated into an oil phase and an aqueous phase. The gas phase products, aqueous phase and oil phase were all qualitatively and quantitatively analyzed by gas chromatography. The results showed that the main product of the oil phase was C4+ higher alcohols. The analysis showed that C4+ higher alcohols are mainly composed of alcohols with 4 to 16 carbon atoms. The analytical results are shown in Table 1 below.

[0042] Table 1 As shown in Table 1, the catalysts prepared in Examples 1-3 by changing the ratio of soluble nickel salt to soluble lanthanum salt, when used in the carbon-carbon coupling reaction of ethanol to prepare higher alcohols, exhibited relatively high catalytic performance, ethanol conversion rate, organic phase product yield, selectivity of liquid phase product C4+ higher alcohols, and yield of C4+ higher alcohols. Among them, the catalyst prepared in Example 1 showed the best catalytic performance. The catalysts prepared in Comparative Examples 2 and 3, due to the excessive addition of soluble lanthanum salt, may have caused lanthanum metal and its oxides to deposit on the pore gates of active nickel metal, potentially leading to pore blockage and a smaller specific surface area, thus resulting in poorer catalytic performance. In Comparative Example 1, the lack of rare earth metal lanthanum doping during catalyst preparation prevented the dispersion of the active component nickel, reducing the number of active sites and resulting in lower yields of C4+ higher alcohols, ethanol conversion rate, and organic phase yield.

[0043] Furthermore, this invention also confirms that within a certain temperature range (180-210℃), the rare earth metal lanthanum modified carbon-coated nickel catalyst prepared by this invention can efficiently catalyze the formation of higher alcohols from ethanol via carbon-carbon coupling reaction.

[0044] Figure 1 XRD patterns of Ni@C-La prepared in Example 1 and Ni@C prepared in Comparative Example 1. (The text abruptly ends here.) Figure 1 It can be seen that the introduction of rare earth metal La significantly reduces the crystallinity of Ni, making the nickel grains in Ni@C smaller or more amorphous, which is beneficial to increasing the number of catalytic active sites, thereby optimizing the structure of the catalyst and enhancing its activity and stability in the ethanol coupling reaction.

[0045] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a rare earth metal lanthanum-modified carbon-coated nickel catalyst, characterized in that, Includes the following steps: A homogeneous solution containing soluble nickel salt and citric acid was heated to react. After the reaction was completed, the mixture was filtered, the precipitate was collected, and then washed, dried, and calcined for the first time to obtain the Ni@C catalyst. The Ni@C catalyst was suspended in an aqueous solution containing a soluble lanthanum salt, ultrasonically treated, and then dried to obtain the precursor. The precursor was subjected to secondary calcination to obtain the rare earth metal lanthanum-modified carbon-coated nickel catalyst.

2. The preparation method according to claim 1, characterized in that, The molar ratio of the soluble nickel salt to citric acid is 1:2; the molar ratio of the soluble nickel salt to the soluble lanthanum salt is (5-25):

1.

3. The preparation method according to claim 1, characterized in that, The soluble nickel salt is nickel nitrate, and the soluble lanthanum salt is lanthanum nitrate.

4. The preparation method according to claim 1, characterized in that, The heating reaction was carried out at a temperature of 100°C for 12 hours.

5. The preparation method according to claim 1, characterized in that, The first calcination was carried out at 550°C for 2 hours under an inert atmosphere.

6. The preparation method according to claim 1, characterized in that, The secondary calcination is carried out at 550°C for 2 hours under an inert atmosphere.

7. A rare earth metal lanthanum-modified carbon-coated nickel catalyst prepared by the preparation method according to any one of claims 1-6.

8. The application of the rare earth metal lanthanum modified carbon-coated nickel catalyst according to claim 7 in the preparation of higher alcohols.

9. A method for preparing higher alcohols, characterized in that, The process includes the following steps: placing the rare earth metal lanthanum modified carbon-coated nickel catalyst of claim 7, sodium hydroxide, ethanol and water in a reaction vessel, mixing and checking for leaks, replacing the air in the reaction vessel with high-purity hydrogen, and stirring the reaction to prepare the higher alcohol.

10. The preparation method according to claim 9, characterized in that, The mass ratio of the rare earth metal lanthanum modified carbon-coated nickel catalyst, sodium hydroxide, ethanol, and water is 1:1:20:20; and / or, The stirring reaction was carried out at a temperature of 180-210℃, an initial pressure of 0.1MPa, and a stirring speed of 1500rpm.

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