Method for catalytically converting fatty acid into olefin with equal carbon number by using Cu-based catalyst

Abstract

The invention discloses a method for catalytically converting fatty acid into olefin with equal carbon number by using a Cu-based catalyst, and belongs to the technical field of catalytic chemistry. In order to solve the problems of low selectivity, high catalyst cost or insufficient activity in preparation of isocarbon olefin from fatty acid in the prior art, the adopted method comprises the following steps: carrying out acid treatment on a porous zeolite carrier; then loading copper salt on the modified zeolite by an impregnation method, drying and calcining to obtain a catalyst precursor; and finally, activating the precursor in a hydrogen atmosphere. By utilizing the synergistic effect of Cu species in the catalyst and zeolite orifice acid sites, long-chain fatty acid can be promoted to generate olefin with equal carbon number, and meanwhile, the side reaction of carbon chain loss caused by alkane generation or cracking due to excessive hydrogenation is effectively avoided. The Cu-based catalyst prepared by the method is low in cost, has high activity and high selectivity for converting long-chain fatty acid into olefin with equal carbon number, and provides an effective way for high-value utilization of biological fatty acid.

Description

Technical Field

[0001] This invention belongs to the field of high-quality utilization technology of biomass energy, specifically relating to a method for preparing a porous zeolite-supported copper (Cu)-based catalyst and its application in the conversion of fatty acids into olefins with equal carbon number. Background Technology

[0002] Biomass, as an important renewable resource, can be readily converted into high-value chemicals for industrial applications using existing catalytic and chemical technologies. In recent years, researchers have conducted extensive research and technological development to enhance the high-value resource development and utilization of fatty acid biomass compounds. Selective catalytic hydrodeoxygenation is an effective pathway for the high-value conversion of biomass fatty acids, transforming them into saturated alkanes, isoalkanes, and alkenes. Among these, the highly selective conversion of biomass fatty acids into olefins with unchanged carbon numbers under hydrogen-containing conditions not only achieves carbon atom economy but also significantly increases the added value of biomass fatty acids. This is because olefins are important chemical intermediates, which can significantly broaden the application of biomass fatty acids in high-end downstream products, such as the synthesis of surfactants, high-grade lubricants, fragrances, and coatings.

[0003] For the conversion and utilization of biomass fatty acids, taking hexadecanoic acid conversion as an example, it is usually carried out on a metal (Pt, Pd, Ni) catalyst, through a hydrodeoxygenation process to generate saturated alkanes, such as pentadecane and hexadecane, with pentadecane often accounting for a larger proportion. This is because the energy required for the C-C bond breaking in biomass fatty acids (384.9 kJ / mol) is less than the energy required for the CO bond breaking (461.5 kJ / mol). To address this, researchers have achieved highly selective conversion of hexadecanoic acid to n-hexadecane (>90%) by preparing bimetallic catalysts (RuRe, CuW, and RuSn) or selecting carbon nanotube supports with fewer surface functional groups, while maintaining good carbon economy. Further research has shown that by using acidic zeolite molecular sieves (SAPO-11, ZSM-22) with unique pore structures as supports, and loading Pt or PtSn alloy catalysts with strong hydrogenation properties, it is possible to achieve hydrodeoxygenation-hydroisomerization of bio-fatty acids into isoalkanes with different carbon numbers. These studies have advanced the high-value utilization of bio-fatty acids.

[0004] However, compared to saturated long-chain alkanes, long-chain unsaturated alkenes have higher commercial value. Therefore, researchers are actively exploring ways to convert bio-fatty acids into more commercially viable unsaturated alkenes. In this regard, Chinese scholar Zhao Chen used silica as a support to load a PtSn catalyst (PtSn / SiO2) and, under a N2 atmosphere, achieved the decarbonylation and dehydrogenation of octadecanoic acid, converting it into unsaturated heptadecanes. Professor Fu Jie of Zhejiang University used MOFs to assemble Pt and Zn metals, followed by high-temperature calcination, to prepare a porous carbon-supported PtZn catalyst (PtZn / C). Milligram-level catalysts were packed in 1.5 mL stainless steel tubes (6 mm inner diameter), and long-chain fatty acids were decarbonylated and dehydrogenated through sand bath heating, converting them into long-chain olefins (heptadecanes) lacking one carbon atom. This research group further used MOFs to assemble metallic Co and calcined it at high temperatures to obtain Co. x Nitrogen catalysts are used for the decarbonylation and dehydrogenation of long-chain fatty acids. However, the high cost of the catalysts used in this catalytic pyrolysis method limits its large-scale industrial application. In addition, scientists have used homogeneous noble metal catalysts such as Pd, Rh, and Ru, and added additives such as acid anhydrides and triphenylphosphine to the reaction system to achieve the decarbonylation of fatty acids into long-chain unsaturated olefins with one less carbon atom. Although these catalytic systems can achieve high olefin yields, the use of additives such as acid anhydrides and triphenylphosphine makes the reaction system complex, which is not conducive to product separation and large-scale industrial production. Many reaction pathways tend to produce alkanes or undergo decarboxylation reactions, resulting in shorter carbon chains.

[0005] Therefore, achieving highly selective conversion of biomass fatty acids into olefins with an unchanged carbon number, while also considering the feasibility of large-scale production, is an extremely challenging task. Summary of the Invention

[0006] To address the problems in the prior art, this invention provides a method for preparing a Cu-based catalyst and its application in the conversion of long-chain fatty acids, such as hexadecanoic acid, into olefins with an equal number of carbon atoms. This invention uses porous zeolite materials as a support to load a metallic Cu catalyst, utilizing the Cu in the Cu-based catalyst... + / Cu 0 The synergistic catalytic effect of species and zeolite pore acid sites enables fatty acids such as hexadecanoic acid to undergo further dehydration to form olefins when generating hexadecyl alcohol, while avoiding further hydrogenation or cracking reactions, thus achieving high selectivity for olefins with the same number of carbons.

[0007] The purpose of this invention is to develop a low-cost catalyst with high activity and high selectivity for the conversion of fatty acids into olefins with an equal number of carbons.

[0008] The specific implementation steps of this invention are as follows: (1) Select porous zeolites with abundant pore structures as carriers, such as ZSM-5, Y, Beta, ZSM-22, ZSM-23, SAPO-11, and Mordenite (MOR), etc. The surface area of ​​the zeolite used is 180~500 m². 2 / g, with a total pore volume of 0.1~0.5 ml / g.

[0009] (2) Surface modification treatment was performed on the selected porous zeolite, and acid treatment was performed on the zeolite support in (1) above: a certain amount of zeolite sample was mixed with 1 mol / L ammonium fluoride solution, wherein the solid-liquid mass ratio was 1:15 ~ 1:25, and treated in an oil bath at 100 °C for 3-5 h. The filtered sample was then stirred in a dilute nitric acid solution with pH=3 at room temperature for 24 h. The sample was then filtered and washed until the pH was neutral. Finally, the filtered sample was dried at 100 °C overnight and calcined at 500-550 °C for 3 h to obtain the fluorine-treated zeolite sample.

[0010] (3) Dissolve the inorganic salt containing Cu in distilled water, add the resulting copper solution dropwise to the zeolite support treated in (2) above, let it stand at room temperature for more than 12 hours, dry it, and calcine it at 450 °C to obtain the catalyst precursor; wherein the loading of Cu is 2.0-11.0 wt.%.

[0011] (4) Catalyst activity evaluation: The catalyst prepared in step (3) was pressed into tablets, sieved, and 0.3 g of 20-40 mesh catalyst sample was mixed with 1.0 g of 20-40 mesh quartz sand. The mixture was then placed in the constant temperature zone of the fixed bed reactor. The catalyst was activated under H2 atmosphere as follows: First, the catalyst was heated from room temperature to 120 °C at 10 °C / min and held for 1 h, with an H2 flow rate of 60 mL / min; then the temperature was increased to 250-400 °C at 2 °C / min and held for 3 h, with an H2 flow rate of 60 mL / min. After cooling to the reaction temperature, a cyclohexane solution containing 1.0 wt.% fatty acids (such as hexadecanoic acid) was continuously fed by a plunger pump. The reaction pressure was controlled at 2.0 MPa, the reaction temperature at 240-280 °C, the H2 / feed liquid volume ratio at 500:1 (corresponding to an H2 flow rate of 30 mL / min), and the weight hourly space velocity at 9.4 h. -1 .

[0012] As a preferred option, the selected porous zeolite carrier is mainly a porous zeolite with a one-dimensional channel structure, such as SAPO-11 and MOR, but is not limited to these two types of zeolite.

[0013] Preferably, the Cu salt mentioned in step (3) of the present invention is copper nitrate, basic copper carbonate, or copper acetate; further, it is preferred that the Cu loading in the catalyst is 6.0-11.0 wt.%.

[0014] Furthermore, the fatty acid is CH3-(CH2). x -COOH, x=2~18. The resulting isocarbon olefins are a mixture of isocarbon olefins with different double bond positions.

[0015] Furthermore, the reactions used are not limited to hexadecanoic acid reaction solution, but also include cyclohexane solutions of fatty acids such as octadecanoic acid, dodecanoic acid, and octadecanoic acid.

[0016] This invention employs a one-dimensional porous zeolite-supported Cu catalyst. The pore structure of the zeolite provides a certain degree of confinement for Cu nanoparticles, and the hydroxyl groups on the zeolite surface interact strongly with the Cu particles. This results in the reduced catalyst having a certain Cu content on the surface of the Cu particles. + / Cu 0 The ratio of zeolite to fatty acid catalytic reactions enables highly efficient deoxygenation while selectively generating long-chain olefins without carbon loss. This is closely related to the suitable acidity of the zeolite support used, breaking through the traditional understanding of hydrogenation reactions. This is of great significance for the high-quality utilization of bio-fatty acids. Attached Figure Description

[0017] Figure 1 The results are from chromatographic analysis of the reaction solution in Example 3.

[0018] Figure 2 The results are from GC-MS analysis of the reaction solution in Example 3.

[0019] Figure 3 This is to analyze the GC-MS data obtained from the reaction solution of Example 3 and to determine the compounds with different residence times.

[0020] Figure 4 Cu 8.0 H2-TPR results for / MOR catalyst.

[0021] Figure 5 Cu 8.0 XPS analysis results of / MOR catalyst.

[0022] Figure 6 This represents the relationship between the catalytic performance of the Cu / MOR catalyst and the Cu loading.

[0023] Figure 7 Cu 8.0 The relationship between the catalytic performance of / MOR catalysts and reaction temperature.

[0024] Figure 8 The catalytic results are shown for Cu catalysts supported on different types of zeolites.

[0025] Figure 9 The results show the hydrogenation conversion of various fatty acids using a Cu / MOR catalyst. Detailed Implementation

[0026] To further understand the purpose, content and advantages of the present invention, the specific implementation schemes of the present invention are described in detail below, but should not be limited to the examples mentioned below, and should be freely combined according to the actual situation.

[0027] The carrier sample (such as MOR carrier, ZSM-5 carrier, Y carrier, ZSM-22 carrier, ZSM-23 carrier, Beta carrier, SAPO-11 carrier) was mixed with a 1 mol / L ammonium fluoride solution, with a solid-liquid mass ratio of 1:20. The mixture was treated in an oil bath at 100 °C for 4 h. The filtered sample was then stirred in a dilute nitric acid solution at pH 3 at room temperature for 24 h. The sample was then filtered and washed until the pH was neutral. Finally, the filtered sample was dried at 100 °C overnight and calcined at 525 °C for 3 h to obtain the treated zeolite sample, which was used in the following examples.

[0028] Example 1: Accurately weigh 1.0 g of the treated MOR support, then dissolve 0.0760 g of copper nitrate trihydrate (Cu(NO3)2·3H2O) in 1.2 mL of distilled water. After complete dissolution, add the solution dropwise to 1.0 g of MOR powder. After impregnation, let it stand at room temperature for 12 h, then dry it in a 100 ºC oven for 12 h. The calcined catalyst is then pressed into tablets, pulverized, and sieved. A 20-40 mesh catalyst is calcined in a muffle furnace at 450 ºC for 3 h (heating rate 3 ºC / min) and labeled as Cu. 2.0 / MOR catalyst, wherein the Cu loading is 2.0 wt.%.

[0029] Performance evaluation: Weigh 0.3 g of Cu 2.0 The MOR catalyst was packed into a fixed-bed reactor and activated under H2 atmosphere. The temperature was increased from room temperature to 120 °C at a rate of 10 °C / min and held for 1 h, then increased to 400 °C at a rate of 2 °C / min and held for 3 h. The H2 flow rate was 60 mL / min. After activation, the fixed-bed reactor temperature was lowered to the reaction temperature. A 1.0 wt.% cyclohexane hexadecanoic acid solution was then introduced into the fixed-bed reactor at a feed rate of 3.6 mL / h, an H2 flow rate of 30 mL / min, a reaction pressure of 2.0 MPa, and a weight hourly space velocity (WHSV) of 9.4 h⁻¹. -1The reaction was carried out at a temperature of 260 ºC. After the reaction stabilized, the liquid products were collected and the conversion rate of hexadecanoic acid and the olefin products were quantitatively analyzed by gas chromatography. The conversion rate of hexadecanoic acid was 50.2%, and the selectivity for hexadecene was 29.7%.

[0030] Example 2: Accurately weigh 1.0 g of the treated MOR support, then dissolve 0.1901 g of copper nitrate trihydrate (Cu(NO3)2·3H2O) in 1.2 mL of distilled water. After complete dissolution, add the solution dropwise to 1.0 g of MOR powder. After impregnation, let it stand at room temperature for 12 h, then dry it in a 100 ºC oven for 12 h. The calcined catalyst is then pressed into tablets, pulverized, and sieved. A 20-40 mesh catalyst is calcined in a muffle furnace at 450 ºC for 3 h (heating rate 3 ºC / min) and labeled as Cu. 5.0 / MOR catalyst, wherein the Cu loading is 5.0 wt.%.

[0031] Performance evaluation: Weigh 0.3 g of Cu 5.0 The MOR catalyst was packed into a fixed-bed reactor and activated under H2 atmosphere. The temperature was increased from room temperature to 120°C at a rate of 10°C / min and held for 1 h, then increased to 400°C at a rate of 2°C / min and held for 3 h. The H2 flow rate was 60 mL / min. After activation, the fixed-bed reactor temperature was lowered to the reaction temperature. A 1.0 wt.% cyclohexane hexadecanoic acid solution was then introduced into the fixed-bed reactor at a feed rate of 3.6 mL / h, an H2 flow rate of 30 mL / min, a reaction pressure of 2.0 MPa, and a weight hourly space velocity (WHSV) of 9.4 h⁻¹. -1 The reaction was carried out at a temperature of 260 ºC. After the reaction stabilized, the liquid products were collected and the conversion rate of hexadecanoic acid and the olefin products were quantitatively analyzed by gas chromatography. The conversion rate of hexadecanoic acid was 58.7%, and the selectivity for hexadecene was 41.1%.

[0032] Example 3: Accurately weigh 1.0 g of the treated MOR support, then dissolve 0.3041 g of copper nitrate trihydrate (Cu(NO3)2·3H2O) in 1.2 mL of distilled water. After complete dissolution, add the solution dropwise to 1.0 g of MOR powder. After impregnation, let it stand at room temperature for 12 h, then dry it in a 100 ºC oven for 12 h. The calcined catalyst is then pressed into tablets, pulverized, and sieved. A 20-40 mesh catalyst is calcined in a muffle furnace at 450 ºC for 3 h (heating rate 3 ºC / min) and labeled as Cu. 8.0 / MOR catalyst, wherein the Cu loading is 8.0 wt.%.

[0033] Performance evaluation: Weigh 0.3 g of Cu 8.0 The MOR catalyst was packed into a fixed-bed reactor and activated under H2 atmosphere. The temperature was increased from room temperature to 120°C at a rate of 10°C / min and held for 1 h, then increased to 400°C at a rate of 2°C / min and held for 3 h. The H2 flow rate was 60 mL / min. After activation, the fixed-bed reactor temperature was lowered to the reaction temperature. A 1.0 wt.% cyclohexane hexadecanoic acid solution was then introduced into the fixed-bed reactor at a feed rate of 3.6 mL / h, an H2 flow rate of 30 mL / min, a reaction pressure of 2.0 MPa, and a weight hourly space velocity (WHSV) of 9.4 h⁻¹. -1 The reaction was carried out at a temperature of 260 ºC. After the reaction stabilized, the liquid products were collected and the conversion rate of hexadecanoic acid and the olefin products were quantitatively analyzed by gas chromatography. The conversion rate of hexadecanoic acid was 95.1%, and the selectivity for hexadecene was 74.2%.

[0034] Figure 1 and Figure 2 The GC and GC-MS analyses of the reaction solution confirm the presence of a large amount of hexadecene in the products. The relevant products are marked in the gas chromatogram. According to... Figure 3 GC-MS analysis showed that the product with an elution time of 13.882 min was hexadecane, while the other product peaks between 13.5 and 14.2 min were all hexadecene. This is because isomerism occurred at the C=C double bond position, forming isomers of hexadecene.

[0035] Figure 4 Cu 8.0 H2-TPR results for / MOR catalyst; by Figure 4 It can be seen that in Cu 8.0 The reduction temperature of Cu species on the / MOR catalyst is mainly concentrated at 210 ºC.

[0036] Figure 5 Cu 8.0 XPS analysis results of the / MOR catalyst. (From...) Figure 5 It can be seen that in the reduction of Cu 8.0 Cu exists on the surface of / MOR + / Cu 0 To further distinguish the proportions of the two species, Auger spectroscopy analysis was performed on the Cu species on the catalyst to obtain Cu... + / Cu 0 The ratio was 0.76. In addition, a small amount of Cu was present on the catalyst surface. 2+ This is because the active Cu species on the catalyst surface are oxidized during the transfer process.

[0037] Example 4: Accurately weigh 1.0 g of the treated MOR support, then dissolve 0.4182 g of copper nitrate trihydrate (Cu(NO3)2·3H2O) in 1.2 mL of distilled water. After complete dissolution, add the solution dropwise to 1.0 g of MOR powder. After impregnation, let it stand at room temperature for 12 h, then dry it in a 100 ºC oven for 12 h. The calcined catalyst is then pressed into tablets, pulverized, and sieved. A 20-40 mesh catalyst is calcined in a muffle furnace at 450 ºC for 3 h (heating rate 3 ºC / min) and labeled as Cu. 11.0 / MOR catalyst, wherein the Cu loading is 11.0 wt.%.

[0038] Performance evaluation: Weigh 0.3 g of Cu 11.0 The MOR catalyst was packed into a fixed-bed reactor and activated under H2 atmosphere. The temperature was increased from room temperature to 120°C at a rate of 10°C / min and held for 1 h, then increased to 400°C at a rate of 2°C / min and held for 3 h. The H2 flow rate was 60 mL / min. After activation, the fixed-bed reactor temperature was lowered to the reaction temperature. A 1.0 wt.% cyclohexane hexadecanoic acid solution was then introduced into the fixed-bed reactor at a feed rate of 3.6 mL / h, an H2 flow rate of 30 mL / min, a reaction pressure of 2.0 MPa, and a weight hourly space velocity (WHSV) of 9.4 h⁻¹. -1 The reaction was carried out at a temperature of 260 ºC. After the reaction stabilized, the liquid products were collected and the conversion rate of hexadecanoic acid and the olefin products were quantitatively analyzed by gas chromatography. The conversion rate of hexadecanoic acid was 77.8%, and the selectivity for hexadecene was 57.1%.

[0039] Figure 6 To investigate the relationship between the catalytic performance of Cu / MOR catalysts and Cu loading: The effect of Cu loading on the hydrodeoxygenation catalytic performance of hexadecanoic acid on the MOR zeolite support was examined at 260 °C. As shown in the figure, Cu... 8.0 The / MOR catalyst exhibits the highest conversion rate of hexadecanoic acid and the highest selectivity for hexadecene, indicating that the 8.0 wt.% copper loading provides better catalytic activity.

[0040] Example 5: Cu prepared according to Example 3 8.0Using MOR as the research object, the effect of reaction temperature on catalytic performance was further investigated. 1.0 g of the treated MOR support was accurately weighed, and 0.3041 g of copper nitrate trihydrate (Cu(NO3)2·3H2O) was dissolved in 1.2 mL of distilled water. After complete dissolution, the solution was added dropwise to 1.0 g of MOR powder. After impregnation, the solution was allowed to stand at room temperature for 12 h, then dried in an oven at 100 ºC for 12 h. The calcined catalyst was then pressed into tablets, pulverized, and sieved. 20-40 mesh catalyst was calcined in a muffle furnace at 450 ºC for 3 h (heating rate 3 ºC / min) and labeled as Cu. 8.0 / MOR catalyst, wherein the Cu loading is 8.0 wt.%.

[0041] Performance evaluation: Weigh 0.3 g of Cu 8.0 The MOR catalyst was packed into a fixed-bed reactor and activated under H2 atmosphere. The temperature was increased from room temperature to 120°C at a rate of 10°C / min and held for 1 h, then increased to 400°C at a rate of 2°C / min and held for 3 h. The H2 flow rate was 60 mL / min. After activation, the fixed-bed reactor temperature was lowered to the reaction temperature. A 1.0 wt.% cyclohexane hexadecanoic acid solution was then introduced into the fixed-bed reactor at a feed rate of 3.6 mL / h, an H2 flow rate of 30 mL / min, a reaction pressure of 2.0 MPa, and a weight hourly space velocity (WHSV) of 9.4 h⁻¹. -1 The reaction temperature was 240-280 ºC. After the reaction stabilized, the liquid products were collected and the conversion rate of hexadecanoic acid and the olefin products were quantitatively analyzed by gas chromatography.

[0042] Cu 8.0 The relationship between the catalytic performance of MOR catalysts and reaction temperature is as follows: Figure 7 As shown, with increasing reaction temperature, the conversion rate of hexadecanoic acid continuously increases (from 240 to 280 °C, the conversion rates are 83.7%, 90.2%, 95.1%, 99.4%, and 100%), while the selectivity of hexadecene first increases and then decreases (from 240 to 280 °C, the selectivity of hexadecene is 66.4%, 67.2%, 74.2%, 64.1%, and 62.5%), with the highest selectivity at 240 °C, indicating that Cu... 8.0 The / MOR catalyst exhibits better catalytic activity at a reaction temperature of 260 °C.

[0043] Example 6: Accurately weigh 1.0 g of the treated ZSM-5 support, then dissolve 0.3041 g of copper nitrate trihydrate (Cu(NO3)2·3H2O) in 1.2 mL of distilled water. After complete dissolution, add the solution dropwise to the 1.0 g ZSM-5 support. After impregnation, let it stand at room temperature for 12 h, then dry it in a 100 ºC oven for 12 h. The calcined catalyst is then pressed into tablets, pulverized, and sieved. A 20-40 mesh catalyst is calcined in a muffle furnace at 450 ºC for 3 h (heating rate 3 ºC / min) and labeled as Cu. 8.0 / ZSM-5 catalyst, wherein the Cu loading is 8.0 wt.%.

[0044] Performance evaluation: Weigh 0.3 g of Cu 8.0 The ZSM-5 catalyst was packed into a fixed-bed reactor. Under an H2 atmosphere, the temperature was increased from room temperature to 120°C at a rate of 10°C / min and held for 1 h, then increased to 400°C at a rate of 2°C / min and held for 3 h. The H2 flow rate was 60 mL / min. After activation, the fixed-bed reactor temperature was lowered to the reaction temperature. A 1.0 wt.% solution of cyclohexane hexadecanoic acid was then introduced into the fixed-bed reactor at a feed rate of 3.6 mL / h, an H2 flow rate of 30 mL / min, a reaction pressure of 2.0 MPa, and a weight hourly space velocity (WHSV) of 9.4 h⁻¹. -1 The reaction was carried out at a temperature of 260 ºC. After the reaction stabilized, the liquid products were collected and the conversion rate of hexadecanoic acid and the olefin products were quantitatively analyzed by gas chromatography. The conversion rate of hexadecanoic acid was 100.0%, and the selectivity for hexadecene was 29.8%.

[0045] Example 7: Accurately weigh 1.0 g of the treated Y support, then dissolve 0.3041 g of copper nitrate trihydrate (Cu(NO3)2·3H2O) in 1.2 mL of distilled water. After complete dissolution, add the solution dropwise to 1.0 g of the Y support. After impregnation, let it stand at room temperature for 12 h, then dry it in a 100 ºC oven for 12 h. The calcined catalyst is then pressed into tablets, pulverized, and sieved. A 20-40 mesh catalyst is calcined in a muffle furnace at 450 ºC for 3 h (heating rate 3 ºC / min) and labeled as Cu. 8.0 / Y catalyst, wherein the Cu loading is 8.0 wt.%.

[0046] Performance evaluation: Weigh 0.3 g of Cu 8.0The / Y catalyst was packed into a fixed-bed reactor. Under an H2 atmosphere, the temperature was increased from room temperature to 120°C at a rate of 10°C / min and held for 1 h, then increased to 400°C at a rate of 2°C / min and held for 3 h. The H2 flow rate was 60 mL / min. After activation, the fixed-bed reactor temperature was lowered to the reaction temperature. A 1.0 wt.% solution of cyclohexane hexadecanoic acid was then introduced into the fixed-bed reactor at a feed rate of 3.6 mL / h, an H2 flow rate of 30 mL / min, a reaction pressure of 2.0 MPa, and a weight hourly space velocity (WHSV) of 9.4 h⁻¹. -1 The reaction was carried out at a temperature of 260 ºC. After the reaction stabilized, the liquid products were collected and the conversion rate of hexadecanoic acid and the olefin products were quantitatively analyzed by gas chromatography. The conversion rate of hexadecanoic acid was found to be 58.6%, and the selectivity for hexadecene was 8.9%.

[0047] Example 8: Accurately weigh 1.0 g of the treated ZSM-22 support, then dissolve 0.3041 g of copper nitrate trihydrate (Cu(NO3)2·3H2O) in 1.2 mL of distilled water. After complete dissolution, add the solution dropwise to the 1.0 g ZSM-22 support. After impregnation, let it stand at room temperature for 12 h, then dry it in a 100 ºC oven for 12 h. The calcined catalyst is then pressed into tablets, pulverized, and sieved. A 20-40 mesh catalyst is calcined in a muffle furnace at 450 ºC for 3 h (heating rate 3 ºC / min) and labeled as Cu. 8.0 / ZSM-22 catalyst, wherein the Cu loading is 8.0 wt.%.

[0048] Performance evaluation: Weigh 0.3 g of Cu 8.0 The ZSM-22 catalyst was packed into a fixed-bed reactor. Under an H2 atmosphere, the temperature was increased from room temperature to 120°C at a rate of 10°C / min and held for 1 h, then increased to 400°C at a rate of 2°C / min and held for 3 h. The H2 flow rate was 60 mL / min. After activation, the fixed-bed reactor temperature was lowered to the reaction temperature. A 1.0 wt.% solution of cyclohexane hexadecanoic acid was then introduced into the fixed-bed reactor at a feed rate of 3.6 mL / h, an H2 flow rate of 30 mL / min, a reaction pressure of 2.0 MPa, and a weight hourly space velocity (WHSV) of 9.4 h⁻¹. -1 The reaction was carried out at a temperature of 260 ºC. After the reaction stabilized, the liquid products were collected and the conversion rate of hexadecanoic acid and the olefin products were quantitatively analyzed by gas chromatography. The conversion rate of hexadecanoic acid was 91.6%, and the selectivity for hexadecene was 57.1%.

[0049] Example 9: Accurately weigh 1.0 g of the treated ZSM-23 support, then dissolve 0.3041 g of copper nitrate trihydrate (Cu(NO3)2·3H2O) in 1.2 mL of distilled water. After complete dissolution, add the solution dropwise to the 1.0 g ZSM-23 support. After impregnation, let it stand at room temperature for 12 h, then dry it in a 100 ºC oven for 12 h. The calcined catalyst is then pressed into tablets, pulverized, and sieved. A 20-40 mesh catalyst is calcined in a muffle furnace at 450 ºC for 3 h (heating rate 3 ºC / min) and labeled as Cu. 8.0 / ZSM-23 catalyst, wherein the Cu loading is 8.0 wt.%.

[0050] Performance evaluation: Weigh 0.3 g of Cu 8.0 The ZSM-23 catalyst was packed into a fixed-bed reactor. Under an H2 atmosphere, the temperature was increased from room temperature to 120°C at a rate of 10°C / min and held for 1 h, then increased to 400°C at a rate of 2°C / min and held for 3 h. The H2 flow rate was 60 mL / min. After activation, the fixed-bed reactor temperature was lowered to the reaction temperature. A 1.0 wt.% cyclohexane hexadecanoic acid solution was then introduced into the fixed-bed reactor at a feed rate of 3.6 mL / h, an H2 flow rate of 30 mL / min, a reaction pressure of 2.0 MPa, and a weight hourly space velocity (WHSV) of 9.4 h⁻¹. -1 The reaction was carried out at a temperature of 260 ºC. After the reaction stabilized, the liquid products were collected and the conversion rate of hexadecanoic acid and the olefin products were quantitatively analyzed by gas chromatography. The conversion rate of hexadecanoic acid was 88.3%, and the selectivity for hexadecene was 60.2%.

[0051] Example 10: Accurately weigh 1.0 g of the treated Beta support, then dissolve 0.3041 g of copper nitrate trihydrate (Cu(NO3)2·3H2O) in 1.2 mL of distilled water. After complete dissolution, add the solution dropwise to 1.0 g of Beta powder. After impregnation, let it stand at room temperature for 12 h, then dry it in a 100 ºC oven for 12 h. The calcined catalyst is then pressed into tablets, pulverized, and sieved. A 20-40 mesh catalyst is calcined in a muffle furnace at 450 ºC for 3 h (heating rate 3 ºC / min) and labeled as Cu. 8.0 / Beta catalyst, wherein the Cu loading is 8.0 wt.%.

[0052] Performance evaluation: Weigh 0.3 g of Cu 8.0The / Beta catalyst was packed into a fixed-bed reactor and activated under H2 atmosphere. The temperature was increased from room temperature to 120°C at 10°C / min and held for 1 h, then increased to 400°C at 2°C / min and held for 3 h. The H2 flow rate was 60 mL / min. After activation, the fixed-bed reactor temperature was lowered to the reaction temperature. A 1.0 wt.% cyclohexane hexadecanoic acid solution was then introduced into the fixed-bed reactor at a feed rate of 3.6 mL / h, an H2 flow rate of 30 mL / min, a reaction pressure of 2.0 MPa, and a weight hourly space velocity (WHSV) of 9.4 h⁻¹. -1 The reaction was carried out at a temperature of 260 ºC. After the reaction stabilized, the liquid products were collected and the conversion rate of hexadecanoic acid and the olefin products were quantitatively analyzed by gas chromatography. The conversion rate of hexadecanoic acid was 100%, and the selectivity for hexadecene was 8.2%.

[0053] Example 11: Accurately weigh 1.0 g of treated SAPO-11 support, then dissolve 0.3041 g of copper nitrate trihydrate (Cu(NO3)2·3H2O) in 1.2 mL of distilled water. After complete dissolution, add the solution dropwise to 1.0 g of SAPO-11 powder. After impregnation, let it stand at room temperature for 12 h, then dry it in a 100 ºC oven for 12 h. The calcined catalyst is then pressed into tablets, pulverized, and sieved. A 20-40 mesh catalyst is calcined in a muffle furnace at 450 ºC for 3 h (heating rate 3 ºC / min) and labeled as Cu. 8.0 / SAPO-11 catalyst, wherein the Cu loading is 8.0 wt.%.

[0054] Performance evaluation: Weigh 0.3 g of Cu 8.0 The SAPO-11 catalyst was packed into a fixed-bed reactor. Under an H2 atmosphere, the temperature was increased from room temperature to 120°C at a rate of 10°C / min and held for 1 h, then increased to 400°C at a rate of 2°C / min and held for 3 h. The H2 flow rate was 60 mL / min. After activation, the fixed-bed reactor temperature was lowered to the reaction temperature. A 1.0 wt.% cyclohexane hexadecanoic acid solution was then introduced into the fixed-bed reactor at a feed rate of 3.6 mL / h, an H2 flow rate of 30 mL / min, a reaction pressure of 2.0 MPa, and a weight hourly space velocity (WHSV) of 9.4 h⁻¹. -1 The reaction was carried out at a temperature of 260 ºC. After the reaction stabilized, the liquid products were collected and the conversion rate of hexadecanoic acid and the olefin products were quantitatively analyzed by gas chromatography. The conversion rate of hexadecanoic acid was 92.1%, and the selectivity for hexadecene was 76.8%.

[0055] Figure 8To investigate the performance of different types of porous zeolite-supported Cu catalysts for the hydrogenation conversion of hexadecanoic acid, as shown in the figure, Cu... 8.0 / ZSM-5 and Cu 8.0 / Beta catalyst achieves complete conversion (100% conversion), while the conversion rates of other catalysts decrease in the following order: Cu 8.0 / SAPO-11 (92.1%) > Cu 8.0 / ZSM-22 (91.6%) > Cu 8.0 / ZSM-23 (88.3%) > Cu 8.0 / Y (58.6%). The selectivity for hexadecene decreases in the following order: Cu 8.0 / SAPO-11 (76.8%) > Cu 8.0 / ZSM-23 (60.2%) > Cu 8.0 / ZSM-22 (57.1%) > Cu 8.0 / ZSM-5 (29.8%) > Cu 8.0 / Y (8.9%) > Cu 8.0 / Beta (8.2%). These data indicate that relatively good hexadecene selectivity is achieved on Cu-based catalysts supported on ZSM-22, ZSM-23, SAPO-11, and MOR supports.

[0056] Example 12: Accurately weigh 1.0 g of the treated MOR support, then dissolve 0.3041 g of copper nitrate trihydrate (Cu(NO3)2·3H2O) in 1.2 mL of distilled water. After complete dissolution, add the solution dropwise to 1.0 g of MOR powder. After impregnation, let it stand at room temperature for 12 h, then dry it in a 100 ºC oven for 12 h. The calcined catalyst is then pressed into tablets, pulverized, and sieved. A 20-40 mesh catalyst is calcined in a muffle furnace at 450 ºC for 3 h (heating rate 3 ºC / min) and labeled as Cu. 8.0 / MOR catalyst, wherein the Cu loading is 8.0 wt.%.

[0057] Performance evaluation: Weigh 0.3 g of Cu 8.0 The MOR catalyst was packed into a fixed-bed reactor and activated under H2 atmosphere. The temperature was increased from room temperature to 120°C at a rate of 10°C / min and held for 1 h, then increased to 400°C at a rate of 2°C / min and held for 3 h. The H2 flow rate was 60 mL / min. After activation, the fixed-bed reactor temperature was lowered to the reaction temperature. A 1.0 wt.% cyclohexane octaate solution was then introduced into the fixed-bed reactor at a feed rate of 3.6 mL / h, an H2 flow rate of 30 mL / min, a reaction pressure of 2.0 MPa, and a weight hourly space velocity (WHSV) of 9.4 h⁻¹.-1 The reaction was carried out at a temperature of 260 ºC. After the reaction stabilized, the liquid products were collected and the conversion rate of octacarboxylic acid and the olefin products were quantitatively analyzed by gas chromatography. The conversion rate of octacarboxylic acid was 96.9%, and the selectivity for octaenes was 73.6%.

[0058] Example 13: Accurately weigh 1.0 g of the treated MOR support, then dissolve 0.3041 g of copper nitrate trihydrate (Cu(NO3)2·3H2O) in 1.2 mL of distilled water. After complete dissolution, add the solution dropwise to 1.0 g of MOR powder. After impregnation, let it stand at room temperature for 12 h, then dry it in a 100 ºC oven for 12 h. The calcined catalyst is then pressed into tablets, pulverized, and sieved. A 20-40 mesh catalyst is calcined in a muffle furnace at 450 ºC for 3 h (heating rate 3 ºC / min) and labeled as Cu. 8.0 / MOR catalyst, wherein the Cu loading is 8.0 wt.%.

[0059] Performance evaluation: Weigh 0.3 g of Cu 8.0 The MOR catalyst was packed into a fixed-bed reactor and activated under H2 atmosphere. The temperature was increased from room temperature to 120°C at a rate of 10°C / min and held for 1 h, then increased to 400°C at a rate of 2°C / min and held for 3 h. The H2 flow rate was 60 mL / min. After activation, the fixed-bed reactor temperature was lowered to the reaction temperature. A 1.0 wt.% solution of cyclohexane dodecanoic acid was then introduced into the fixed-bed reactor at a feed rate of 3.6 mL / h, an H2 flow rate of 30 mL / min, a reaction pressure of 2.0 MPa, and a weight hourly space velocity (WHSV) of 9.4 h⁻¹. -1 The reaction was carried out at a temperature of 260 ºC. After the reaction stabilized, the liquid products were collected and the conversion rate of dodecanoic acid and the olefin products were quantitatively analyzed by gas chromatography. The conversion rate of dodecanoic acid was 90.9%, and the selectivity for dodecene was 71.6%.

[0060] Example 14: Accurately weigh 1.0 g of the treated MOR support, then dissolve 0.3041 g of copper nitrate trihydrate (Cu(NO3)2·3H2O) in 1.2 mL of distilled water. After complete dissolution, add the solution dropwise to 1.0 g of MOR powder. After impregnation, let it stand at room temperature for 12 h, then dry it in a 100 ºC oven for 12 h. The calcined catalyst is then pressed into tablets, pulverized, and sieved. A 20-40 mesh catalyst is calcined in a muffle furnace at 450 ºC for 3 h (heating rate 3 ºC / min) and labeled as Cu. 8.0 / MOR catalyst, wherein the Cu loading is 8.0 wt.%.

[0061] Performance evaluation: Weigh 0.3 g of Cu 8.0 The MOR catalyst was packed into a fixed-bed reactor and activated under H2 atmosphere. The temperature was increased from room temperature to 120°C at a rate of 10°C / min and held for 1 h, then increased to 400°C at a rate of 2°C / min and held for 3 h. The H2 flow rate was 60 mL / min. After activation, the fixed-bed reactor temperature was lowered to the reaction temperature. A 1.0 wt.% solution of cyclohexane octadecanoic acid was then introduced into the fixed-bed reactor at a feed rate of 3.6 mL / h, an H2 flow rate of 30 mL / min, a reaction pressure of 2.0 MPa, and a weight hourly space velocity (WHSV) of 9.4 h⁻¹. -1 The reaction was carried out at a temperature of 260 ºC. After the reaction stabilized, the liquid products were collected and the conversion rate of octadecanoic acid and the olefin products were quantitatively analyzed by gas chromatography. The conversion rate of octadecanoic acid was 88.1%, and the selectivity for octadecene was 65.2%.

[0062] Examples 12-14 above studied Cu 8.0 The hydrogenation conversion performance of / MOR catalyst for octadic, dodecanoic, and stearic acid is shown in the following results. Figure 9 As shown, the Cu-based catalyst supported on the MOR support exhibits good versatility in the conversion of fatty acids to olefins with an equal number of carbon atoms.

[0063] Example 15: Accurately weigh 1.0 g of treated γ-alumina (γ-Al2O3) support, then dissolve 0.3041 g of copper nitrate trihydrate (Cu(NO3)2·3H2O) in 1.2 mL of distilled water. After complete dissolution, add the solution dropwise to 1.0 g of γ-Al2O3 powder. After impregnation, let it stand at room temperature for 12 h, then dry it in a 100 ºC oven for 12 h. The calcined catalyst is then pressed into tablets, pulverized, and sieved. 20-40 mesh catalyst is calcined in a muffle furnace at 450 ºC for 3 h (heating rate 3 ºC / min) and labeled as Cu. 8.0 / γ-Al2O3 catalyst, wherein the Cu loading is 8.0 wt.%.

[0064] Performance evaluation: Weigh 0.3 g of Cu 8.0The γ-Al₂O₃ catalyst was packed in a fixed-bed reactor. Under an H₂ atmosphere, the temperature was increased from room temperature to 120°C at a rate of 10°C / min and held for 1 h, then increased to 400°C at a rate of 2°C / min and held for 3 h. The H₂ flow rate was 60 mL / min. After activation, the fixed-bed reactor temperature was lowered to the reaction temperature. A 1.0 wt.% solution of cyclohexane hexadecanoic acid was then introduced into the fixed-bed reactor at a feed rate of 3.6 mL / h, an H₂ flow rate of 30 mL / min, a reaction pressure of 2.0 MPa, and a weight hourly space velocity (WHSV) of 9.4 h⁻¹. -1 The reaction temperature was 260 ºC. After the reaction stabilized, the liquid products were collected and quantitatively analyzed by gas chromatography to determine the conversion rate of hexadecanoic acid and the olefin products. The conversion rate of hexadecanoic acid was 100%, but hexadecene was not detected. The main product was hexadecane, with a selectivity of 95.8%.

[0065] Example 16: Accurately weigh 1.0 g of treated silica (SiO2) support, then dissolve 0.3041 g of copper nitrate trihydrate (Cu(NO3)2·3H2O) in 1.2 mL of distilled water. After complete dissolution, add the solution dropwise to 1.0 g of silica powder. After impregnation, let it stand at room temperature for 12 h, then dry it in an oven at 100 ºC for 12 h. The calcined catalyst is then pressed into tablets, pulverized, and sieved. A 20-40 mesh catalyst is calcined in a muffle furnace at 450 ºC for 3 h (heating rate 3 ºC / min) and labeled as Cu. 8.0 / SiO2 catalyst, wherein the Cu loading is 8.0 wt.%.

[0066] Performance evaluation: Weigh 0.3 g of Cu 8.0 The SiO2 catalyst was packed in a fixed-bed reactor. Under an H2 atmosphere, the temperature was increased from room temperature to 120°C at a rate of 10°C / min and held for 1 h, then increased to 400°C at a rate of 2°C / min and held for 3 h. The H2 flow rate was 60 mL / min. After activation, the fixed-bed reactor temperature was lowered to the reaction temperature. A 1.0 wt.% cyclohexane hexadecanoic acid solution was then introduced into the fixed-bed reactor at a feed rate of 3.6 mL / h, an H2 flow rate of 30 mL / min, a reaction pressure of 2.0 MPa, and a weight hourly space velocity (WHSV) of 9.4 h⁻¹. -1 The reaction temperature was 260 ºC. After the reaction stabilized, the liquid products were collected and quantitatively analyzed by gas chromatography to determine the conversion rate of hexadecanoic acid and the olefin products. The conversion rate of hexadecanoic acid was 24.2%, no hexadecene was detected, and the main product was hexadecanoic acid ester with a selectivity of 71.2%.

[0067] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for catalytically converting fatty acids into olefins with an equal number of carbon atoms using a Cu-based catalyst, characterized in that: Cu-based catalysts are used to catalyze the conversion of fatty acids into olefins with an equal number of carbon atoms; the Cu-based catalysts comprise a surface-modified porous zeolite support and metallic copper supported thereon.

2. The method according to claim 1, characterized in that: The porous zeolite support is one of ZSM-5, Y zeolite, Beta, ZSM-22, ZSM-23, SAPO-11, and mordenite.

3. The method according to claim 1, characterized in that: The surface modification method of porous zeolite carrier is as follows: zeolite and ammonium fluoride solution are mixed and treated at 80-120℃ for 3-5 h, filtered, and the filtered solid is stirred in dilute nitric acid solution at room temperature, then filtered, washed, dried, and calcined at 500-550℃ for 2-4 h to obtain the surface-modified porous zeolite carrier.

4. The method according to claim 1, characterized in that: The preparation method of Cu-based catalyst is as follows: soluble copper salt is dissolved in water, and the resulting copper solution is added dropwise to a surface-modified porous zeolite support. After standing and drying, the catalyst precursor is obtained by calcination at 400~500°C. After reduction and activation, Cu-based catalyst is obtained.

5. The method according to claim 1, characterized in that: The Cu loading in the catalyst ranges from 2.0 to 11.0 wt.%.

6. The method according to claim 5, characterized in that: The Cu loading in the catalyst ranges from 6.0 to 11.0 wt.%.

7. The method according to claim 1, characterized in that: The porous zeolite carrier is SAPO-11, ZSM-22, ZSM-23 or mordenite.

8. The method according to claim 4, characterized in that: The specific steps for using Cu-based catalysts to catalyze the conversion of fatty acids to olefins with equal carbon numbers are as follows: The prepared catalyst precursor is pressed into tablets, sieved, and then mixed evenly with quartz sand. The mixture is then placed in the isothermal zone of a fixed-bed reactor. The catalyst is activated under an H2 atmosphere, reduced, and then cooled to the reaction temperature. A cyclohexane solution containing fatty acids is fed into the reactor, and the catalytic reaction yields olefins with equal carbon numbers.

9. The method according to claim 8, characterized in that: The catalyst activation conditions were as follows: the catalyst was first heated from room temperature to 120 °C at a rate of 10 °C / min and held for 1 h, with an H2 flow rate of 60 mL / min; then the temperature was increased to 250-400 °C at a rate of 2 °C / min and held for 3 h, with an H2 flow rate of 60 mL / min. The catalytic reaction conditions were as follows: reaction pressure of 2.0 MPa, reaction temperature of 240-280 °C, H2 / feed liquid volume ratio of 500:1, and weight hourly space velocity of 9.4 h⁻¹. -1 .

10. The method according to claim 8, characterized in that: The fatty acid is CH3-(CH2). x -COOH, x=2~18.

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