Bimetal composite catalyst for catalytic deoxidation of fatty acid as well as preparation method and application of bimetal composite catalyst

Abstract

The invention discloses a bimetallic composite catalyst for catalytic deoxidation of fatty acid as well as a preparation method and application of the bimetallic composite catalyst. The catalyst comprises a carrier, Cu-Ce bimetal loaded on the carrier and an in-situ carbon layer uniformly attached to the surface of the bimetal element, the carrier is a biomass carbon material; the Cu-Ce bimetallic accounts for 1-8 wt% of the total mass of the composite catalyst. The preparation process of the catalyst comprises the following steps: dissolving soluble copper salt and soluble cerium salt in deionized water, adding the carrier in a stirring state, and then fully dipping in a sealed shade place to obtain a precursor; and drying the precursor, and carbonizing in a reducing atmosphere to obtain the product. The catalyst is used for fatty acid catalytic deoxidation of diesel-grade hydrocarbon-rich fuel, deep deoxidation of fatty acid can be achieved in a low-hydrogen or hydrogen-free state, the raw material conversion rate can reach 65%, the target product selectivity is 85% or above, and the activity retention rate is still maintained at about 90% after multiple cycles. And the problems of cost and safety caused by hydrogen supply and high-pressure reaction are fundamentally eliminated.

Description

Technical Field

[0001] This invention relates to a fatty acid deoxygenation catalyst, specifically to a bimetallic composite catalyst for fatty acid catalytic deoxygenation, its preparation method, and its application, belonging to the field of biofuel technology. Background Technology

[0002] Fatty acid catalytic deoxygenation is a core process for converting biomass oils into petroleum-based hydrocarbon fuels. Currently, the most straightforward reaction pathways are mainly hydrodeoxygenation and non-hydrodeoxygenation processes. Hydrodeoxygenation processes typically employ precious metal, cobalt-molybdenum, or nickel-based sulfide catalysts, operating under high temperature and high pressure hydrogen conditions to achieve deoxygenation through hydrogenation and cracking of fatty acid molecules. While this technology can achieve high conversion rates, hydrogen consumption accounts for 30-50% of the total production cost, and the high-pressure reactor significantly increases equipment investment and safety risks. Non-hydrodeoxygenation routes avoid hydrogen dependence, but are limited by catalyst material performance, especially transition metal oxides which are prone to sintering and deactivation during the reaction, and suffer from bottlenecks such as poor sulfur resistance, where even trace amounts of sulfur impurities can lead to permanent poisoning and failure.

[0003] Even more serious is that if the pore structure design of traditional catalyst supports (such as molecular sieves, alumina, and silicon carbide) is unreasonable, it can easily lead to increased resistance to the diffusion of fatty acid molecules, and the reaction often takes 4-6 hours to complete. Furthermore, diesel-grade hydrocarbon-rich fuels (C... 15 -C 18 The target product selectivity is low. Furthermore, under high-temperature operating conditions, the metal active sites rapidly deactivate due to sintering and agglomeration. In addition, the fatty acid deoxygenation process is accompanied by a strong tendency to coke, which covers the active sites and blocks the support pores, significantly reducing the catalyst's stability and lifespan, severely restricting the continuous production and economic efficiency of industrial plants. These shortcomings collectively make it difficult for existing technologies to balance activity, cost, and sustainability, hindering the large-scale industrialization of biofuels.

[0004] In summary, the main problems in the existing technology are as follows: 1. Highly active metals (such as precious metals) and cost-effectiveness are mutually exclusive; 2. Reaction kinetic efficiency is limited by mass transfer barriers and runaway side reactions; 3. The catalyst structure lacks a long-term stable mechanism in a high-temperature reducing environment. Therefore, the existing technology urgently needs a catalytic deoxygenation catalyst with high catalytic activity, long catalytic lifetime and low price to meet the industrialization requirements of fatty acid deoxygenation to prepare biomass fuel. Summary of the Invention

[0005] To address the problems existing in the prior art, the first objective of this invention is to provide a bimetallic composite catalyst for the catalytic deoxygenation of fatty acids. This catalyst, based on the active sites of a Cu-Ce bimetallic compound, utilizes the cell wall chambers of biomass carbon materials as a microchannel reactor. While significantly improving the catalyst's dispersibility, stability, and catalytic activity, it achieves deep deoxygenation of fatty acids, greatly enhancing their selectivity for isomerization and cyclization.

[0006] The second objective of this invention is to provide a method for preparing a bimetallic composite catalyst for fatty acid catalytic deoxygenation. This method employs a long impregnation period, allowing the Cu-Ce bimetallic system to deeply penetrate the hierarchical pores of the support. Then, under a reducing atmosphere, a two-stage carbonization process of low temperature and high temperature is used. This avoids the collapse of the support pores while achieving high dispersion and spatial confinement of the Cu-Ce bimetallic system, thereby effectively improving the structural stability and catalytic activity of the catalyst.

[0007] The third objective of this invention is to provide an application of a bimetallic composite catalyst for the catalytic deoxygenation of fatty acids, used in the preparation of diesel-grade hydrocarbon-rich fuels. Based on the characteristics of this catalyst, its application in the process of preparing diesel-grade hydrocarbon-rich fuels through catalytic deoxygenation of fatty acids achieves deep deoxygenation of fatty acids under low-hydrogen or hydrogen-free conditions. Tests have shown that, under a protective atmosphere, a fatty acid deoxygenation conversion rate of ≥65% can be achieved within 1-2 hours, resulting in diesel-grade hydrocarbon-rich fuels (C... 15 -C 18 The product selectivity is >85%, and the activity retention rate remains at around 90% after 10 cycles, fundamentally eliminating the cost and safety issues caused by hydrogen supply and high-pressure reaction.

[0008] To achieve the above technical objectives, the present invention provides a bimetallic composite catalyst for fatty acid catalytic deoxygenation, comprising a support, a Cu-Ce bimetal supported on the support, and an in-situ carbon layer uniformly attached to the surface of the bimetallic element; the support is a biomass carbon material; the Cu-Ce bimetal accounts for 1 to 8 wt% of the total mass of the composite catalyst.

[0009] In the catalyst provided by this invention, Cu and Ce coexist in a co-occurring or core-shell manner. At the interface between the two, there is a Cu–O–Ce ternary active structure. The oxygen vacancies in this structure serve as strong adsorption sites, which can capture oxygen atoms in fatty acid molecules and promote decarboxylation or dehydration reactions. This process does not depend on hydrogen and can achieve the deoxyisomerization of fatty acids without the need for hydrogenation.

[0010] As a preferred embodiment, the biomass carbon material is fruit shells and / or cake meal.

[0011] This invention uses biomass carbon materials as a carrier, which on the one hand realizes the resource utilization of biomass solid waste materials, and on the other hand utilizes the abundant cell wall cavities inside to form a microchannel reactor. This structure not only provides a physical confinement environment for Cu-Ce bimetals, inhibiting the migration and aggregation of metal particles, but also significantly shortens the diffusion path of reactants (fatty acids) to active sites (Cu-Ce bimetals), greatly improves the mass transfer rate, and thus enhances the kinetic efficiency of the deoxygenation reaction.

[0012] As a preferred embodiment, the molar ratio of Cu to Ce in the Cu-Ce bimetallic solution is 1:0.5~2. More preferably, the molar ratio of Cu to Ce is 1:0.8~1.2.

[0013] It is worth noting that in the Cu-Ce bimetallic system, Cu is the main carbonyl deoxygenation center, while Ce is the main carbonyl capture center. The bimetallic structure formed by the two in the above ratio range not only greatly improves the catalytic activity, but also significantly improves the structural stability and lifespan of the catalyst. After 10 catalytic cycles, it can still maintain about 90% of the catalytic activity.

[0014] As a preferred embodiment, the in-situ carbon layer is obtained from the pyrolysis of biomass carbon materials, and its thickness is 0.5~4 nm. The in-situ carbon layer obtained by the present invention is mainly a graphene-like structure, which not only facilitates electron migration during the catalytic reaction process, but also spatially confines the Cu-Ce bimetallic system, preventing its aggregation; in addition, this structure can accelerate product desorption and inhibit the formation of reaction byproducts, such as coke and small molecule alkanes, thereby improving carbon atom utilization and significantly reducing the probability of catalyst deactivation due to carbon deposition.

[0015] The present invention also provides a method for preparing a bimetallic composite catalyst for fatty acid catalytic deoxygenation, the process of which is as follows: soluble copper salt and soluble cerium salt are dissolved in deionized water, a support is added under stirring, and then the catalyst is fully impregnated in a sealed and cool place to obtain a precursor; the precursor is dried and then carbonized under a reducing atmosphere to obtain the final product.

[0016] The method provided by this invention has simple steps and mild conditions, which ensures the yield of catalysts while also taking into account the economy and scalability of the production process.

[0017] As a preferred embodiment, the soluble copper salt is at least one of copper chloride, copper nitrate, and copper acetate.

[0018] As a preferred embodiment, the soluble cerium salt is at least one of cerium chloride, cerium nitrate, and cerium acetate.

[0019] As a preferred embodiment, the thorough impregnation method is over-volume impregnation, the conditions of which are: the carrier is completely immersed in the solution at 15~25℃ under sealed conditions for more than 10 days. Biomass carbon materials contain a large amount of polysaccharides and a small amount of lipids and proteins, resulting in a low internal diffusion coefficient. Traditional short-time impregnation is insufficient to penetrate deep into the carrier. Therefore, thorough impregnation is necessary to achieve full-pore depth loading within the carrier, avoiding the active sites being limited to the outer surface.

[0020] As a preferred embodiment, the stirring speed is 100~300 r / min.

[0021] As a preferred embodiment, the drying conditions are: drying at 15~40°C to constant weight under an inert atmosphere.

[0022] As a preferred embodiment, the reducing atmosphere is a mixture of nitrogen and hydrogen in a volume ratio of 80~98:2~20.

[0023] As a preferred embodiment, the carbonization process is as follows: the precursor is placed in a muffle furnace, a reducing atmosphere is introduced to completely replace the air in the furnace, and then the temperature is increased from room temperature to 180-200°C at a rate of 3-5°C for 1-3 hours, followed by an increase from room temperature to 260-280°C at a rate of 10-15°C / min for 5-15 minutes, thus obtaining the precursor. The carbonization method used in this invention primarily focuses on the gentle removal of volatile components from the precursor at low temperatures, while at high temperatures it primarily focuses on inducing the rapid formation of in-situ graphene-like carbon layers. Furthermore, the high-temperature stage is selected within the critical temperature window for the local graphitization transformation of biomass carbon materials. Within this range, the carbon skeleton rearranges, and sp... 2 The hybrid structure develops rapidly, forming a continuous graphene-like layer with a thickness of 0.5–4 nm, a process that can be completed in just 5–15 minutes.

[0024] It is important to note that the above process must be carried out strictly in accordance with the carbonization conditions to avoid prolonged high temperature causing sintering of metal particles or collapse of the carrier pore structure. At the same time, it is necessary to ensure that the carbon layer spatially confines and encapsulates the Cu-Ce bimetal, suppressing agglomeration and enhancing electronic conductivity.

[0025] The present invention also provides a method for preparing a bimetallic composite catalyst for fatty acid catalytic deoxygenation, the process of which involves: using it for fatty acid catalytic deoxygenation to prepare diesel-grade hydrocarbon-rich fuel.

[0026] As a preferred embodiment, the process for preparing diesel-grade hydrocarbon-rich fuel by fatty acid catalytic deoxygenation is as follows: the catalyst addition amount is 3~10wt%, the reaction temperature is 400~420℃ under a protective atmosphere and normal pressure, and the reaction time is 1~2h.

[0027] Compared with the prior art, the beneficial technical effects of the technical solution provided by the present invention are as follows:

[0028] 1) The catalyst provided by this invention is based on the active sites of Cu-Ce bimetals and uses the cell wall chambers in biomass carbon materials as microchannel reactors. Under the premise of greatly improving the catalyst's dispersibility, stability and catalytic activity, it achieves deep deoxygenation of fatty acids and greatly improves their selectivity for isomerization and cyclization.

[0029] 2) The preparation method provided by the present invention adopts a long impregnation period, which allows the Cu-Ce bimetallic system to deeply penetrate into the multi-level pores of the support. Then, under a reducing atmosphere, a two-stage carbonization process of low temperature and high temperature is adopted. While avoiding the collapse of the support pores, the high dispersion and spatial confinement of Cu-Ce bimetallic are also achieved, thereby effectively improving the structural stability and catalytic activity of the catalyst.

[0030] 3) In the technical solution provided by this invention, based on the characteristics of the above-mentioned catalyst, when it is used in the process of fatty acid catalytic deoxygenation to prepare diesel-grade hydrocarbon-rich fuel, deep deoxygenation of fatty acids can be achieved under low-hydrogen or hydrogen-free conditions; tests have shown that under a protective atmosphere, a fatty acid deoxygenation conversion rate of ≥65% can be achieved within 1-2 hours, and diesel-grade hydrocarbon-rich fuel (C 15 -C 18 The product selectivity is >85%, and the activity retention rate remains at around 90% after 10 cycles, fundamentally eliminating the cost and safety issues caused by hydrogen supply and high-pressure reaction. Attached Figure Description

[0031] Figure 1 This is a TEM image of the catalyst obtained in Example 1 of the present invention;

[0032] in, Figure 1 (a) is a TEM image with a resolution of 50 nm. Figure 1 (b) is a TEM image with a resolution of 2 nm;

[0033] Figure 2 The image shows the NH3-TPD test result of the catalyst obtained in Example 1 of this invention.

[0034] Figure 3 This is a fine Cu 2p spectrum of the catalyst obtained in Example 1 of the present invention. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the present invention more apparent, exemplary embodiments according to the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are merely a part of the embodiments of the present invention, and not all of the embodiments of the present invention. It should be understood that the present invention is not limited to the exemplary embodiments described herein. Based on the embodiments of the present invention described herein, all other embodiments obtained by those skilled in the art without inventive effort should fall within the protection scope of the present invention.

[0036] Example 1

[0037] This embodiment provides a bimetallic composite catalyst for fatty acid catalytic deoxygenation. The specific preparation process is as follows: 0.01 mol cerium chloride and 0.01 mol copper chloride are dissolved in 0.2 L of deionized water at a stirring rate of 150 r / min. Then, 10 g of dried soybean meal is added and impregnated at 20 °C under sealed conditions for 15 days to obtain a precursor. After the precursor is removed, it is dried at 40 °C to constant weight under N2 atmosphere and then carbonized in a muffle furnace to obtain the final product.

[0038] The carbonization process is as follows: the precursor is placed in a muffle furnace, a reducing atmosphere is introduced to completely replace the air in the furnace, and then the temperature is raised from room temperature to 200°C at 5°C and held for 1 hour. Then the temperature is raised from room temperature to 280°C at 15°C / min and held for 10 minutes to obtain the precursor. The reducing atmosphere is a mixture of nitrogen and hydrogen with a flow ratio of 85:15.

[0039] The average thickness of the in-situ carbon layer on the catalyst surface obtained in this embodiment is 1.5 nm.

[0040] Example 2

[0041] This embodiment provides a bimetallic composite catalyst for fatty acid catalytic deoxygenation. The specific preparation process is as follows: 0.01 mol of cerium nitrate and 0.01 mol of copper nitrate are dissolved in 0.2 L of deionized water at a stirring rate of 100 r / min. Then, 10 g of camellia fruit shell is added and the mixture is impregnated at 30 °C under sealed conditions for 15 days to obtain a precursor. After the precursor is removed, it is dried at room temperature under N2 atmosphere to constant weight, and then carbonized in a muffle furnace to obtain the final product.

[0042] The carbonization process is as follows: the precursor is placed in a muffle furnace, a reducing atmosphere is introduced to completely replace the air in the furnace, and then the temperature is increased from room temperature to 180°C at 5°C for 2 hours, and then increased from room temperature to 260°C at 10°C / min for 5 minutes to obtain the product; the reducing atmosphere is a mixture of nitrogen and hydrogen with a flow ratio of 95:5.

[0043] The average thickness of the in-situ carbon layer on the catalyst surface obtained in this embodiment is 0.9 nm.

[0044] Example 3

[0045] This embodiment is exactly the same as Example 1, except that the amount of cerium chloride added is 0.01 mol and the amount of copper chloride added is 0.015 mol. The average thickness of the in-situ carbon layer on the catalyst surface obtained in this embodiment is 1.8 nm.

[0046] Comparative Example 1

[0047] This comparative example is exactly the same as Example 1, except that the carbonization process is as follows: the precursor is placed in a muffle furnace, a reducing atmosphere is introduced to completely replace the air in the furnace, and then the temperature is raised from room temperature to 200°C at 5°C and held for 1 hour, and then raised from room temperature to 350°C at 15°C / min and held for 10 minutes to obtain the product; the reducing atmosphere is a mixture of nitrogen and hydrogen with a flow ratio of 85:15.

[0048] The average thickness of the in-situ carbon layer on the catalyst surface obtained in this comparative example is 2.2 nm.

[0049] Comparative Example 2

[0050] This comparative example is exactly the same as Example 1, except that the amount of cerium chloride added is 0.01 mol and the amount of copper chloride added is 0.04 mol.

[0051] The average thickness of the in-situ carbon layer on the catalyst surface obtained in this embodiment is 1.4 nm.

[0052] This invention presents experiments on the catalytic hydrogenation of *Gnaphalium affine* oil to produce diesel-grade hydrocarbon-rich fuel, based on the above-described embodiments and comparative examples. The process is as follows: 100g of soybean saponin fatty acids are added to a continuous reactor, followed by 5g of catalyst, and the mixture is thoroughly mixed. The air inside the reactor is completely replaced with nitrogen, and then the reactor is heated to the reaction temperature for catalytic deoxygenation. After the reaction, the product is discharged, allowed to cool naturally to room temperature, and then filtered and dehydrated to obtain the final product. The conditions for the above catalytic deoxygenation reaction are: reaction temperature 400℃, nitrogen atmosphere, and atmospheric pressure. The experimental results are shown in Table 1.

[0053]

[0054] TEM analysis of the catalyst in Example 1 revealed that the catalyst support exhibited a sheet-like or rod-like structure with uniformly distributed Cu and Ce metals. The active metal sites were encapsulated by a carbon layer formed by the carbonization of the support, with a lattice spacing of approximately 0.25 nm, suggesting a graphitized carbon structure. This graphitized carbon layer structure effectively confines and encapsulates the active metal sites, while also preventing contact between the carbon deposits generated during the reaction and the active centers, thereby improving the catalyst's activity and stability. However, when the carbon layer thickness is too high, i.e., the calcination temperature is too high, as in Comparative Example 1, it can affect the contact between the catalytic active sites and the reactants, thus reducing the catalyst's performance.

[0055] Furthermore, NH3-TPD characterization revealed that the acidic sites on this catalyst are moderately strong acids. According to existing literature, moderately strong acids are precisely the active sites for catalyzing the deoxygenation (decarbonylation) of oils and fats. Combined with the Cu 2p fine spectrum, the Cu on this catalyst exists primarily as Cu. 2+ This species can effectively promote the breaking of carbon-oxygen bonds, but when the Cu component content is too high, as shown in Comparative Example 2, it may inhibit the adsorption or capture of C=O bonds by the Ce component, resulting in a reduction in the directional deoxygenation effect of the catalyst.

[0056] Furthermore, the catalyst obtained in Example 1 was used for cyclic testing. The cyclic testing process was exactly the same as that in Example 1. After 10 cycles, the fatty acid conversion rate was 62.86%, C 15 -C 18 With a selectivity of 83.2%, it can be seen that its catalytic activity is approximately 92%, still above 90%, demonstrating the excellent cycle stability of the catalyst provided by this invention.

Claims

1. A bimetallic composite catalyst for fatty acid catalytic deoxygenation, characterized in that: The catalyst comprises a support, a Cu-Ce bimetal supported on the support, and an in-situ carbon layer uniformly attached to the surface of the bimetal element; the support is a biomass carbon material; the Cu-Ce bimetal accounts for 1 to 8 wt% of the total mass of the composite catalyst.

2. The bimetallic composite catalyst for fatty acid catalytic deoxygenation according to claim 1, characterized in that: The biomass carbon material is fruit shells and / or cakes; in the Cu-Ce bimetal, the molar ratio of Cu to Ce is 1:0.5~2.

3. The bimetallic composite catalyst for fatty acid catalytic deoxygenation according to claim 1, characterized in that: The in-situ carbon layer is obtained by pyrolysis of biomass carbon materials and has a thickness of 0.5~4nm.

4. A method for preparing a bimetallic composite catalyst for fatty acid catalytic deoxygenation according to any one of claims 1 to 3, the process comprising: dissolving soluble copper salt and soluble cerium salt in deionized water, adding a support under stirring, and then fully impregnating the catalyst in a sealed, cool place to obtain a precursor; drying the precursor and then carbonizing it under a reducing atmosphere to obtain the final product.

5. The method for preparing a bimetallic composite catalyst for fatty acid catalytic deoxygenation according to claim 4, wherein the soluble copper salt is at least one of copper chloride, copper nitrate and copper acetate; and the soluble cerium salt is at least one of cerium chloride, cerium nitrate and cerium acetate.

6. The preparation method of a bimetallic composite catalyst for fatty acid catalytic deoxygenation according to claim 4, wherein the process is as follows: the full impregnation method is over-volume impregnation, and the conditions are: the support is completely impregnated in the solution at 15~25℃ under sealed conditions for more than 10 days.

7. The preparation method of a bimetallic composite catalyst for fatty acid catalytic deoxygenation according to claim 4, wherein the stirring speed is 100~300 r / min; and the drying conditions are: drying to constant weight at 15~40℃ under an inert atmosphere.

8. The method for preparing a bimetallic composite catalyst for fatty acid catalytic deoxygenation according to claim 4, wherein the process comprises: the reducing atmosphere is a mixture of nitrogen and hydrogen, with a volume ratio of 80~98:2~20; the carbonization process comprises: placing the precursor in a muffle furnace, introducing a reducing atmosphere to completely replace the air in the furnace, then raising the temperature from room temperature to 180~200℃ at 3~5℃ for 1~3h, and then raising the temperature from room temperature to 260~280℃ at 10~15℃ / min for 5~15min, thereby obtaining the catalyst.

9. The application of the bimetallic composite catalyst for fatty acid catalytic deoxygenation according to any one of claims 1 to 3, wherein the process is: used for fatty acid catalytic deoxygenation to prepare diesel-grade hydrocarbon-rich fuel.

10. The application of the bimetallic composite catalyst for fatty acid catalytic deoxygenation according to claim 9, wherein the process is as follows: the process of preparing diesel-grade hydrocarbon-rich fuel by fatty acid catalytic deoxygenation is: the catalyst addition amount is 3~10wt%, the reaction temperature is 400~420℃ under a protective atmosphere and normal pressure, and the reaction time is 1~2h.

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