Olefin hydroisomerization multiphase cobalt-nitrogen-carbon catalyst, preparation method and application

Abstract

The invention provides an olefin hydroisomerization heterogeneous cobalt-nitrogen-carbon catalyst, a preparation method and application. The invention belongs to the technical field of fine chemical engineering. According to the technical scheme, a cobalt and zinc bimetal organic framework material is adopted as a precursor, and the cobalt-nitrogen-carbon catalyst is prepared through roasting in an inert atmosphere. The catalyst is simple in preparation process, low in cost, good in stability and easy to separate. The terminal olefin can be efficiently converted into the internal olefin only by using a small amount of catalyst, the required time is short, the conversion rate is high, the reaction selectivity is good, and the E / Z ratio is high.

Description

Technical Field

[0001] The present invention relates to the technical field of fine chemicals, in particular to a heterogeneous cobalt-nitrogen-carbon catalyst for olefin hydroisomerization, a preparation method and an application thereof. Background Art

[0002] The isomerization of terminal olefins to the corresponding internal olefins is a key reaction in the flavoring, pharmaceutical, food, and petrochemical industries due to its excellent controllability and atom economy. For example, in the flavoring industry, 1,2-dimethoxy-4-allylbenzene (methyl eugenol) isomerizes to produce isoeugenol, and 4-allylanisole isomerizes to produce anethole. In the pharmaceutical industry, the synthesis of rosuvastatin, cyclosporine, and licalin A also requires the isomerization of terminal olefins. In the petrochemical industry, 1-butene isomerizes to produce 2-butene.

[0003] Acid-catalyzed olefin isomerization generally has a faster reaction rate, but such acid catalysts are often prone to olefin polymerization. Furthermore, the strong acidity can corrode equipment and is difficult to recover (CN 202311857256.X, CN 202310193854.5, CN202210331369.5, CN 201410483078.3, CN 202110981905.1, CN 201210065262.7). For example, in the patent application document (CN 201910738800.6), alumina is mainly used as the catalyst body. The acid amount and acid type of the catalyst are adjusted by main group element modification, thereby improving the catalyst activity. The acid distribution on the catalyst surface is then adjusted by metal modification (Co, Ni, Mo, Cu, Ti and V), thereby improving the catalyst's isomerization selectivity. However, the isomerization reaction temperature is 300°C-500°C, and the reaction conditions are extremely harsh. Base-catalyzed olefin isomerization can promote the inward shift of the allylic double bond, but the reaction time is long, the yield is low, the required temperature is high, and waste discharge and product separation are difficult (CN 201310435210.9, CN 202010041752.8, CN 201710993559.2). For example, a patent application (CN 202111009152.4) uses a magnesium oxide-modified mixed catalyst. However, this catalyst yields only 50%-70% of olefins, making it unsuitable for industrial production. While photocatalytic olefin isomerization operates under mild conditions, it requires specialized equipment and is difficult to commercialize (CN 202011252431.9).

[0004] In addition to solid acid, alkali and photocatalyst, the olefin isomerization catalyst reported in existing literature and patents is mainly a homogeneous metal catalyst (CN 202280023356.X), but homogeneous catalysts are difficult to separate and recycle, and most of them use precious metal catalysts (e.g., Ru, Ir, Pd, etc.), which reduces the economy of the reaction. At present, there are fewer reports on heterogeneous catalysts for olefin isomerization reactions. For example, Amanda K.Cook et al. (Journal of the American Chemical Society, 2024, 146 (22), 15596-15608) use Ni [P (OEt) 3] 4 and SZO 300 The combination of these two catalysts yields an efficient heterogeneous catalyst for olefin isomerization, which requires either acidic or solid acid conditions. et al. (ChemCatChem, 2017, 9(15), 2930-2934) used a carbon nitride-coated NiCo alloy catalyst to catalyze the isomerization of 4-allylanisole, but the reaction time was long, requiring 24 h, and the E / Z ratio was only 84:16. In addition, this method used silane as a hydrogen source, generating organic waste.

[0005] Regarding hydroisomerization catalysts, a patent application (CN 202311857256.X) describes the use of a Pd / Al2O3 catalyst to isomerize 3-methyl-3-butene-1-ol to 3-methyl-2-butene-1-ol. This catalyst, which uses the precious metal Pd, is expensive and unfavorable for industrial production. Another patent application (CN 202011063173.X) describes the isomerization of β-pinene to α-pinene using a modified activated carbon catalyst loaded with PdCu on a metal. Furthermore, patent applications (CN 201310435210.9 and CN 202211291748.2) describe the isomerization of 1-butene to 2-butene using metal oxide-supported iron, copper, nickel, cobalt, and palladium catalysts. However, the catalyst's universality was not tested in these cases.

[0006] Therefore, it is of great significance to develop a catalyst with low cost, mild reaction conditions and good universality. Summary of the Invention

[0007] The present invention aims to provide a heterogeneous cobalt-nitrogen-carbon catalyst for olefin hydroisomerization, a preparation method and an application thereof. The catalyst has low cost, high activity, high selectivity, good universality and is easy to separate in the olefin isomerization reaction.

[0008] The present invention is achieved in that:

[0009] The heterogeneous cobalt-nitrogen-carbon catalyst for olefin hydroisomerization provided by the present invention is a metal-organic framework-derived heterogeneous cobalt-nitrogen-carbon catalyst, and its preparation method is as follows:

[0010] (1) Cobalt nitrate hexahydrate [Co(NO3)2·6H2O] and zinc nitrate hexahydrate [Zn(NO3)2·6H2O] are dissolved in a solvent in a certain proportion to obtain a mixed metal salt solution; 2-methylimidazole is dissolved in a solvent to obtain a 2-methylimidazole solution; the mixed metal salt solution is added dropwise to the 2-methylimidazole solution and stirred at room temperature for 30 minutes; the resulting purple precipitate is collected, centrifuged, washed three times with ethanol, and dried to obtain a purple powder.

[0011] (2) The purple powder obtained in step (1) was placed in a tube furnace, heated at a high temperature of 5°C / min in flowing nitrogen, and pyrolyzed at 700, 800, 900, and 1000°C for a certain time, and then naturally cooled to room temperature to obtain Co / CN-T black solid powder, where T represents the pyrolysis temperature.

[0012] In step (1), the molar ratio of Co(NO3)2·6H2O to Zn(NO3)2·6H2O is 1:5 to 1:20, preferably 1:10.

[0013] In step (1), the solvent is methanol, ethanol, isopropanol, tetrahydrofuran, acetonitrile or acetone; preferably, the solvent is methanol.

[0014] In step (1), the molar ratio of the mixed metal salt to 2-methylimidazole is 1:1 to 1:5, preferably 1:4.

[0015] In step (2), the calcination temperature in nitrogen is 700, 800, 900 and 1000° C., preferably 800° C.; the constant temperature holding time is 1-4 hours, preferably 3 hours.

[0016] The heterogeneous cobalt-nitrogen-carbon catalyst for olefin hydroisomerization prepared by the above method has cobalt as its active metal. The catalyst is used for olefin isomerization reactions including but not limited to allylbenzene, 1,4-butenediol, methyl eugenol, 4-allyl anisole, and the like. For example, the catalyst is used for olefin isomerization reactions of 4-allyl anisole, allylbenzene, 1-allyl-2-methylbenzene, 1,4-butenediol, 1,2-dimethoxy-4-allylbenzene (methyl eugenol), eugenol, 3-allyl-2-hydroxybenzaldehyde, 1-allylnaphthalene, N-allylcarbazole, 2-allylphenol, allylpentafluorobenzene, 1-octene, allylcyclohexane, allyl cyanide, 1-(allyloxy)-4-methylbenzene, 3-methyl-3-butene-1-ol, and the like.

[0017] The catalyst prepared in the present invention is applied to the isomerization reaction of olefins, and the experimental conditions are as follows:

[0018] The raw materials (0.5 mmol), Co catalyst (20 mg), and solvent (20 mL) were mixed and added to a polytetrafluoroethylene-lined reactor. The reactor was installed and airtightness checked. The air in the reaction system was replaced with hydrogen three times and then filled with hydrogen to 1 atmosphere. Stirring was then started at 300 rpm and the isomerization reaction was carried out by heating to 80-160°C at 5°C / min. After the reaction was completed, the apparatus was cooled to room temperature, the residual reaction gas was released, and the reactor was disassembled. The reaction liquid was separated from the catalyst and analyzed using a gas chromatograph equipped with a hydrogen flame ionization detector.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The heterogeneous cobalt-nitrogen-carbon catalyst of the present invention is prepared by a mixing-drying-calcination process, which is simple and safe to operate. It uses non-precious metal Co as a catalyst, has the characteristics of low cost and easy separation. It exhibits good activity, selectivity, high E / Z ratio, stability in olefin isomerization reactions, and has good substrate universality. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 These are the nitrogen adsorption and desorption curves of Co / CN-700, Co / NC-800, Co / CN-900 and Co / CN-1000.

[0022] Figure 2 These are the X-ray powder diffraction (XRD) spectra of Co / CN-700, Co / NC-800, Co / CN-900, and Co / CN-1000.

[0023] Figure 3 Transmission electron microscopy (TEM), element mapping, and spherical aberration-corrected transmission electron microscopy images of Co / NC-800.

[0024] Figure 4 This is the extended X-ray absorption fine structure spectrum of Co / NC-800. DETAILED DESCRIPTION

[0025] The technical solution of the present invention will be described in detail below with reference to the embodiments. The following embodiments are only used to more clearly illustrate the technical solution of the present invention and are therefore only used as examples and are not intended to limit the scope of protection of the present invention.

[0026] Example 1

[0027] Catalyst preparation: 0.32 g of Co(NO₃)₂·6H₂O and 3.24 g of Zn(NO₃)₂·6H₂O were mixed and dissolved in 120 mL of methanol (Solution 1). Then, 4.02 g of 2-methylimidazole was dissolved in 40 mL of methanol (Solution 2). Solution 1 was added dropwise to Solution 2 and stirred at room temperature for 30 min. The precipitate was collected by centrifugation at 8000 rpm for 5 min, washed twice with ethanol, and dried under vacuum at 60°C overnight. The resulting powder was placed in a tube furnace and heated at a rate of 5°C / min under flowing nitrogen to specific temperatures (700, 800, 900, and 1000°C), respectively. The temperature was maintained for 3 h, and then naturally cooled to room temperature. The catalysts are designated Co / NC-T (T = 700, 800, 900, and 1000°C).

[0028] Figure 1 The nitrogen adsorption and desorption curve of Co / NC-T catalyst is shown in Fig. Figure 1 It can be seen that the catalysts prepared in the present invention are all mesoporous materials and have a relatively high specific surface area (see Table 1), which is conducive to the smooth progress of the catalytic reaction.

[0029] Table 1 Specific surface area and pore size analysis data of catalysts at different calcination temperatures in the present invention

[0030]

[0031] Figure 2 is the XRD spectrum of Co / NC-T catalyst. Figure 2 It can be seen that obvious characteristic diffraction peaks of metallic Co were observed on Co / NC-900 and Co / NC-1000 catalysts, but no characteristic diffraction peaks of metallic Co appeared on Co / NC-800 and Co / NC-700 catalysts, indicating that the Co species are highly dispersed on the carbon nitride support.

[0032] Figure 3 ab are transmission electron microscopy (TEM) images of the Co / NC-800 catalyst. No Co nanoparticles or nanoclusters were found in the TEM images, indicating that the cobalt in the Co / NC-800 catalyst is atomically dispersed on the carbon nitride support; element mapping results ( Figure 3 ce) also shows that the three elements C, N, and Co are uniformly dispersed on the carbon nitride support; the spherical aberration corrected transmission electron microscopy image of the Co / NC-800 catalyst ( Figure 3 f) A large number of Co single atoms (marked with circles) were found, but no obvious Co nanoparticles or nanoclusters were found, indicating that the single-atom Co / NC-800 catalyst was successfully prepared in the present invention.

[0033] Figure 4This is the extended X-ray absorption fine structure spectrum of the Co / NC-800 catalyst. No obvious diffraction peak of the Co-Co bond was observed in the figure, only the Co-N peak was observed, indicating that the single-atom Co / NC-800 catalyst was successfully prepared.

[0034] Example 2

[0035] In the isomerization reaction of 4-allylanisole, the catalyst prepared in Example 1 was screened, and the steps were as follows:

[0036] The equation for the isomerization reaction of 4-allylanisole is as follows:

[0037]

[0038] 4-Allylanisole (0.5 mmol), Co catalyst (20 mg), and methanol (20 mL) were mixed and added to a polytetrafluoroethylene-lined reactor. The reactor was installed and airtightness checked. The air in the reaction system was replaced with hydrogen three times and then filled with hydrogen to 1 atmosphere. Stirring was then started at 300 rpm and the isomerization reaction was initiated by heating to 120°C at 5°C / min. After the reaction was completed, the apparatus was cooled to room temperature, the residual reaction gas was released, and the reactor was disassembled. The reaction liquid was separated from the catalyst and analyzed by gas chromatograph equipped with a hydrogen flame ionization detector. The results are shown in Table 2.

[0039] Table 2 Effect of calcination temperature of catalyst on isomerization reaction of 4-allylanisole in the present invention

[0040]

[0041] As can be seen from Table 2, the Co / NC-800 catalyst has the best catalytic effect in the isomerization reaction of 4-allylanisole. The yields and E / Z ratios of other catalysts are lower than those of the Co / NC-800 catalyst, thus confirming that Co / NC-800 is the optimal catalyst.

[0042] Example 3

[0043] Under the action of the optimal catalyst in Example 2, the solvent for the isomerization reaction of 4-allyl anisole was screened, and the steps were as follows:

[0044] 4-Allylanisole (0.5 mmol), Co / NC-800 (20 mg), and solvent (20 mL) were mixed and added to a polytetrafluoroethylene-lined reactor. The reactor was installed and airtightness checked. The air in the reaction system was replaced with hydrogen three times and then filled with hydrogen to 1 atmosphere. Stirring was then started at 300 rpm and the isomerization reaction was initiated by heating to 120°C at 5°C / min. After the reaction was completed, the apparatus was cooled to room temperature, the residual reaction gas was released, and the reactor was disassembled. The reaction liquid was separated from the catalyst and analyzed by gas chromatograph equipped with a hydrogen flame ionization detector. The results are shown in Table 3.

[0045] Table 3 Effect of solvent on the isomerization reaction of 4-allyl anisole in the present invention

[0046]

[0047] As can be seen from Table 3, the Co / NC-800 catalyst has the best catalytic effect on the isomerization reaction of 4-allylanisole in methanol solvent, thus confirming that methanol is the best solvent.

[0048] Example 4

[0049] Under the optimal conditions in Examples 2 and 3, the reaction temperature for the isomerization reaction of 4-allyl anisole was screened by the following steps:

[0050] 4-allyl anisole (0.5 mmol), Co / NC-800 (20 mg), and methanol (20 mL) were mixed and added to a polytetrafluoroethylene-lined reactor. The reactor was installed and airtightness checked. The air in the reaction system was replaced with hydrogen three times and then filled with hydrogen to 1 atmosphere. Stirring was then started at 300 rpm and heated to T°C (T = 100, 120, and 140°C) at 5°C / min to initiate the isomerization reaction. After the reaction was completed, the apparatus was cooled to room temperature, the residual reaction gas was released, and the reactor was disassembled. The reaction solution was separated from the catalyst and analyzed using a gas chromatograph equipped with a hydrogen flame ionization detector. The results are shown in Table 4.

[0051] Table 4 Effect of reaction temperature on the isomerization reaction of 4-allyl anisole in the present invention

[0052]

[0053] As can be seen from Table 4, under the action of Co / NC-800 catalyst, the conversion rate of the isomerization reaction is low at 100°C, while a large amount of overhydrogenation products appear at 140°C. Therefore, it is determined that the catalytic effect of Co / NC-800 catalyst is best at 120°C.

[0054] Example 5

[0055] Under the optimal conditions in Example 4, the hydrogen pressure or partial pressure for the isomerization reaction of 4-allylanisole was screened as follows:

[0056] 4-Allylanisole (0.5 mmol), Co / NC-800 (20 mg), and methanol (20 mL) were mixed and added to a polytetrafluoroethylene-lined reactor. The reactor was installed and airtightness checked. The air in the reaction system was replaced with hydrogen three times and then filled with hydrogen to specific pressures (0.1, 0.5, and 1.0 MPa, respectively). Stirring was then started at 300 rpm and the isomerization reaction was initiated by heating to 120°C at 5°C / min. After the reaction was completed, the apparatus was cooled to room temperature, the residual reaction gas was released, and the reactor was disassembled. The reaction liquid was separated from the catalyst and analyzed by gas chromatograph equipped with a hydrogen flame ionization detector. The results are shown in Table 5.

[0057] Table 5 Effect of hydrogen pressure or partial pressure on the isomerization reaction of 4-allyl anisole in the present invention

[0058]

[0059] It can be seen from Table 5 that under the action of Co / NC-800 catalyst, the hydrogen pressure or partial pressure has little effect on the activity and selectivity of the product. Therefore, it is determined that the catalytic effect is best when the hydrogen pressure or partial pressure is 0.1 MPa.

[0060] Example 6

[0061] Under the optimal conditions in Example 4, the universality test of the Co / NC-800 catalyst in the isomerization reaction was performed as follows:

[0062] The reactants (0.5 mmol), Co / NC-800 (20 mg), and methanol (20 mL) were mixed and added to a polytetrafluoroethylene-lined reactor. The reactor was installed and airtightness checked. The air in the reaction system was replaced with hydrogen three times and then filled with hydrogen to 1 atmosphere. Stirring was then started at 300 rpm and the isomerization reaction was initiated by heating to 120°C at 5°C / min. After the reaction was completed, the apparatus was cooled to room temperature, the residual reaction gas was released, and the reactor was disassembled. The reaction liquid was separated from the catalyst and analyzed by gas chromatograph equipped with a hydrogen flame ionization detector. The results are shown in Table 6.

[0063] Table 6 Universality of the optimal catalytic system in the present invention for olefin isomerization reaction

[0064]

[0065]

[0066] a The product is 2-hydroxytetrahydrofuran, which has no cis-trans isomers.

[0067] As can be seen from Table 6, the substrate universality of the isomerization reaction is good under the action of Co / NC-800 catalyst.

[0068] Example 7

[0069] Under the optimal conditions in Example 4, the cyclic stability test of the Co / NC-800 catalyst in the isomerization reaction was carried out as follows:

[0070] The reactants (0.5 mmol), Co / NC-800 (20 mg), and methanol (20 mL) were mixed and added to a polytetrafluoroethylene-lined reactor. The reactor was installed and airtightness checked. The air in the reaction system was replaced with hydrogen three times and then filled with hydrogen to 1 atmosphere. Stirring was then started at 300 rpm and the isomerization reaction was initiated by heating to 120°C at 5°C / min. After the reaction was completed, the apparatus was cooled to room temperature, the residual reaction gas was released, and the reactor was disassembled. The reaction liquid was separated from the catalyst, and the catalyst was recovered by centrifugation and used for the next reaction. The resulting reaction liquid was analyzed by gas chromatograph equipped with a hydrogen flame ionization detector. The results are shown in Table 7.

[0071] Table 7 Cyclic stability test of the optimal catalyst Co / NC-800 in the present invention

[0072]

[0073]

[0074] Table 7 shows the relationship between the number of cycles and yield in the isomerization reaction of 4-allylanisole using the optimal catalyst Co / NC-800 prepared in the present invention. The recovered catalyst was reused five times without significant loss of activity. These results demonstrate the excellent stability of the heterogeneous Co / NC-800 catalyst.

[0075] Experimental results show that the Co / NC-800 catalytic system exhibits superior selectivity, efficiency, stability, and reactant compatibility compared to other catalysts calcined at other temperatures. Furthermore, the catalytic system employs a simple recovery process, which will facilitate its industrial application.

[0076] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent replacements and improvements made by any technician familiar with this technical field within the technical scope disclosed by the present invention should be included in the scope of protection of the invention.

Claims

1. A method for preparing a heterogeneous cobalt-nitrogen-carbon catalyst for olefin hydroisomerization, characterized in that: The steps include: (1) dissolving cobalt nitrate hexahydrate and zinc nitrate hexahydrate in a solvent to obtain a mixed metal salt solution; dissolving 2-methylimidazole in a solvent to obtain a 2-methylimidazole solution; adding the mixed metal salt solution dropwise to the 2-methylimidazole solution, and stirring at room temperature for 30 minutes; collecting the resulting precipitate, centrifuging, washing, and drying to obtain a powder; (2) The powder obtained in step (1) was placed in a tube furnace, heated at a rate of 5°C / min in flowing nitrogen, kept at a constant temperature, and then naturally cooled to room temperature to obtain a black solid powder.

2. The method for preparing a heterogeneous cobalt-nitrogen-carbon catalyst for olefin hydroisomerization according to claim 1, wherein: In step (2), the calcination temperature in a nitrogen atmosphere is 700-1000° C., and the constant temperature holding time is 1-5 hours.

3. The preparation method of the heterogeneous cobalt-nitrogen-carbon catalyst for olefin hydroisomerization according to claim 1, wherein: The molar ratio of cobalt nitrate hexahydrate to zinc nitrate hexahydrate in step (1) is 1:5 to 1:

20.

4. The method for preparing a heterogeneous cobalt-nitrogen-carbon catalyst for olefin hydroisomerization according to claim 1, wherein: The solvent selected in step (1) is methanol.

5. A heterogeneous cobalt-nitrogen-carbon catalyst for olefin hydroisomerization prepared by the method according to any one of claims 1 to 4. The heterogeneous cobalt-nitrogen-carbon catalyst for olefin hydroisomerization according to claim 5 is used in olefin isomerization reactions.

7. The use according to claim 6, characterized in that: The olefin hydroisomerization heterogeneous cobalt nitrogen carbon catalyst is applied to the olefin isomerization reaction, and the specific steps are as follows: The raw materials, catalyst and solvent are mixed and added to a reactor equipped with a polytetrafluoroethylene liner; the reactor is installed and the air tightness is checked, the air in the reaction system is replaced with hydrogen three times, and then hydrogen is filled to 1 atmosphere of pressure, and then stirring is started at a speed of 300 r / min, and the isomerization reaction is carried out by heating to 80-140°C at a speed of 5°C / min; after the reaction is completed, the device is cooled to room temperature, the residual reaction gas is released, and the reactor is disassembled; the reaction liquid and the catalyst are separated, and the obtained reaction liquid is analyzed by a gas chromatograph equipped with a hydrogen flame ionization detector.

8. The use according to claim 7, characterized in that: The solvent is methanol, ethanol, isopropanol, tetrahydrofuran, acetonitrile or acetone.

9. The use according to claim 7, characterized in that: Heat to 120-140°C for isomerization reaction.

10. The use according to claim 7, characterized in that: The catalyst is used for the olefin isomerization reaction of 4-allylanisole, allylbenzene, 1-allyl-2-methylbenzene, 1,4-butenediol, 1,2-dimethoxy-4-allylbenzene (methyl eugenol), eugenol, 3-allyl-2-hydroxybenzaldehyde, 1-allylnaphthalene, N-allylcarbazole, 2-allylphenol, allylpentafluorobenzene, 1-octene, allylcyclohexane, allyl cyanide, 1-(allyloxy)-4-methylbenzene or 3-methyl-3-butene-1-ol.

Images