Preparation method and application of cellulose-derived porous carbon supported copper catalyst
By preparing a copper catalyst supported on cellulose-derived porous carbon, the problem of easy aggregation of copper species under reaction conditions in traditional activated carbon-supported copper catalysts was solved, achieving uniform dispersion and stability of copper species and improving the catalytic performance of dimethyl carbonate synthesis.
Patent Information
- Application Number
- CN202610169898.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-02-06
- Publication Date
- 2026-04-07
AI Technical Summary
In existing dimethyl carbonate synthesis processes, copper species tend to agglomerate under reaction conditions in traditional activated carbon-supported copper catalysts, leading to reduced dispersion of active sites. Furthermore, the pore structure restricts mass transfer and accessibility of active sites, thus requiring improvement in catalytic activity.
Using microcrystalline cellulose as raw material, a cellulose-derived porous carbon material with a large specific surface area was prepared by impregnation with zinc salt solution, high-temperature carbonization at 900~1000℃ and washing with nitric acid. Copper species were then loaded using an equal-volume impregnation method and reduced at 350~400℃ to obtain a cellulose-derived porous carbon-supported copper catalyst.
The copper particles in the catalyst are uniformly distributed without obvious agglomeration, which improves the dispersibility and stability of copper species and significantly enhances the catalytic performance of methanol oxidative carbonylation to synthesize dimethyl carbonate, with a maximum methanol conversion rate of 9.0%.
Smart Images
Figure CN121797315A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of catalyst preparation technology, specifically to a method for preparing and applying a cellulose-derived porous carbon-supported copper catalyst. Background Technology
[0002] Dimethyl carbonate (DMC) is an environmentally friendly chemical product. The DMC molecule contains a variety of functional groups such as methyl, carbonyl, methoxy, and methoxycarbonyl, and can be used in reactions such as methylation, carbonylation, methoxylation, and transesterification. It has important application value in the fields of organic synthesis and fine chemicals.
[0003] Traditional synthesis processes for dimethyl carbonate mainly include the phosgene method, urea alcoholysis method, transesterification method, and methyl nitrite carbonylation method. These methods suffer from severe pollution, high raw material costs, and low product yields. Direct CO2 synthesis methods typically have low conversion rates due to the thermodynamic stability and kinetic inertness of CO2 molecules. The methanol oxidative carbonylation method, using methanol, carbon monoxide, and oxygen as raw materials, offers high product selectivity, with water as the only byproduct, making it environmentally friendly and a green chemical route for clean coal utilization, thus attracting widespread attention.
[0004] In existing catalytic systems for the oxidative carbonylation of methanol to dimethyl carbonate, activated carbon-supported copper catalysts are commonly used. However, under certain reaction conditions, copper species at the active sites are prone to aggregation, leading to reduced dispersion of active sites and deactivation. Furthermore, the pore structure of traditional activated carbon materials is predominantly microporous, limiting mass transfer and accessibility to active sites. Active copper species are mostly dispersed on the outer surface of the support, making it difficult to maintain stable dispersion during the reaction, thus hindering catalytic activity improvement.
[0005] Introducing mesoporous structures can provide mass transfer channels, promote the diffusion of reactants and products, improve the utilization of active sites, and further improve the dispersibility of copper particles. Therefore, previous studies have attempted to construct hierarchical porous carbon supports with both micropores and mesopores for loading copper species. However, the preparation of existing hierarchical porous carbon materials often relies on complex templates and cumbersome processes, making it difficult to reproducibly control the pore size distribution and micro / mesopore ratio. Furthermore, after loading copper, the dispersibility and stability of copper species are still insufficient, leaving room for further improvement in catalytic performance. Summary of the Invention
[0006] To address the aforementioned technical problems, this invention provides a method for preparing and applying a cellulose-derived porous carbon-supported copper catalyst. The technical solution of this invention is as follows: In a first aspect, a method for preparing a cellulose-derived porous carbon-supported copper catalyst is provided, comprising: S1, using microcrystalline cellulose as raw material, is prepared by impregnation with zinc salt solution of equal volume, high-temperature carbonization at 900~1000℃ and washing with nitric acid to produce cellulose-derived porous carbon with a large specific surface area, which serves as a catalyst support. S2, copper species are loaded onto the catalyst support using an equal-volume impregnation method, and then reduced at 350~400℃ to obtain a cellulose-derived porous carbon-supported copper catalyst.
[0007] Preferably, S1 includes: S11, add microcrystalline cellulose at a concentration of 0.3~1.5 mol·L⁻¹ -1 The sample was ultrasonically treated in a zinc salt solution at an ultrasonic frequency of 80-100 kHz for 30-60 min, and then allowed to stand at room temperature for 12-36 h. After standing, the sample was placed in a forced-air drying oven and dried at 60-80℃ in an air atmosphere for 12-24 h. The dried sample was then ground to obtain an impregnated powder sample. The molar ratio of microcrystalline cellulose to zinc salt was 1:0.5-1:2.5. S12, the impregnated powder sample is placed in a high-temperature tube furnace, and an airflow of 20~30 mL·min is introduced. -1 Argon gas, at 2~10℃·min -1 The temperature was increased to 900-1000℃ at a rising rate, and then kept at a constant temperature for 30 minutes before being naturally cooled to room temperature to obtain a carbonized powder sample. S13, the carbonized powder sample obtained in S12 is immersed in 0.5~2.0 mol·L⁻¹ water. -1 The filter cake was placed in a nitric acid solution for 12-24 hours, then filtered, and washed with deionized water until the filtrate was neutral. It was then dried at 60-80℃ for 12-24 hours to obtain a cellulose-derived porous carbon material with residual Zn species removed, which was used as a catalyst support.
[0008] Preferably, S2 includes: S21, weigh 0.2~0.8g Cu(NO3)2·3H2O, add 20~60mL deionized water, stir until completely dissolved to obtain copper nitrate solution; then add 0.3~1.0g catalyst support to copper nitrate solution, stir for 9~15h, and dry the resulting suspension at 40~60℃ for 24~48h to obtain catalyst precursor; S22, the catalyst precursor obtained in S21 is placed in a high-temperature tube furnace, and a flow rate of 20~30 mL·min is introduced. -1 Argon gas, at 2~4℃·min -1 The temperature was increased to the reduction temperature of 350-400℃ at a certain heating rate, and then kept at a constant temperature for 2-4 hours before being naturally cooled to room temperature to obtain a cellulose-derived porous carbon-supported copper catalyst.
[0009] Preferably, in step S11, microcrystalline cellulose is added at a concentration of 0.6 mol·L⁻¹. -1 The sample was ultrasonically treated in a zinc salt solution at an ultrasonic frequency of 80-100 kHz for 60 min and then allowed to stand at room temperature for 24 h. The sample was then placed in a forced-air drying oven and dried at 60 ℃ for 18 h in an air atmosphere. The dried sample was then ground to obtain an impregnated powder sample. The molar ratio of microcrystalline cellulose to zinc salt was 1:1. In step S12, the impregnated powder sample is placed in a high-temperature tube furnace, and an airflow of 25 mL / min is introduced. -1 Argon gas, at 5~10℃·min -1 The temperature was increased to 900-1000℃ at a rising rate, and then kept at a constant temperature for 30 minutes before being naturally cooled to room temperature to obtain a carbonized powder sample. In step S13, the carbonized powder sample obtained in step S12 is immersed in 2.0 mol·L⁻¹ water. -1 The filter cake was placed in a nitric acid solution for 12 hours, then filtered, washed with deionized water until the filtrate was neutral, and then dried at 60°C for 12 hours.
[0010] Preferably, in step S21, 0.565g of Cu(NO3)2·3H2O is weighed, 50mL of deionized water is added, and the mixture is stirred until completely dissolved to obtain a copper nitrate solution; then 1.0g of catalyst support is added to the copper nitrate solution, and after stirring for 12h, the resulting suspension is dried at 50℃ for 24h to obtain the catalyst precursor.
[0011] Preferably, when the zinc salt solution is a zinc nitrate solution, the resulting catalyst support is a mesoporous, microporous cellulose-derived carbon material.
[0012] Preferably, when the zinc salt solution is a zinc chloride solution, the resulting catalyst support is a microporous cellulose-derived carbon material.
[0013] In a second aspect, an application of a cellulose-derived porous carbon supported copper catalyst is provided, wherein the cellulose-derived porous carbon supported copper catalyst is prepared by the preparation method described in the first aspect, and the cellulose-derived porous carbon supported copper catalyst is used for the oxidative carbonylation of methanol to synthesize dimethyl carbonate.
[0014] Preferably, the cellulose-derived porous carbon-supported copper catalyst is used in the reaction of methanol oxidative carbonylation to synthesize dimethyl carbonate, specifically including: S3, weigh 0.1~0.3g of cellulose-derived porous carbon supported copper catalyst and 10~30mL of methanol, put them into a microreactor, introduce oxygen at 0.2~0.5MPa at 20~30℃, then introduce carbon monoxide until the total pressure is 3.0~4.0MPa, and then introduce it at 200~400r·min. -1Stir at a certain rate and react at 110~130℃ for 2~3 hours, then stop heating and allow to cool naturally to room temperature.
[0015] Preferably, in step S3, 0.15 g of cellulose-derived porous carbon-supported copper catalyst and 10 mL of methanol are weighed and placed in a microreactor. Oxygen is introduced at 0.2 MPa at 25°C, followed by the introduction of carbon monoxide until the total pressure reaches 4.0 MPa, at a rate of 400 r·min. -1 Stirring at a certain rate, reacting at 110℃ for 2 hours, then stopping heating and allowing to cool naturally to room temperature.
[0016] All of the above-mentioned optional technical solutions can be combined arbitrarily, and the present invention will not provide a detailed description of the structure after each combination.
[0017] By means of the above solution, the beneficial effects of the present invention are as follows: This invention uses microcrystalline cellulose as a carbon source, which is impregnated with zinc salt and then carbonized and activated under an inert atmosphere. Residual zinc-containing components are removed by acid washing to obtain cellulose-derived porous carbon materials with tunable pore structures. By selecting different zinc salts (such as zinc nitrate hexahydrate or zinc chloride), porous carbon supports with different pore structure characteristics can be obtained: activation with zinc nitrate yields microporous carbon materials containing mesopores, while activation with zinc chloride yields microporous carbon materials.
[0018] Because the catalyst support has a well-developed porous structure, it can provide anchoring sites for copper species and improve their accessibility and dispersion. As a result, the copper catalyst supported on cellulose-derived porous carbon has good copper species dispersion and stability, which is beneficial to improving the catalytic performance of methanol oxidative carbonylation reaction.
[0019] In the cellulose-derived porous carbon-supported copper catalyst obtained in this invention, copper particles are uniformly distributed on the catalyst support without significant agglomeration. In the methanol oxidative carbonylation to dimethyl carbonate synthesis reaction, this catalyst exhibits high catalytic performance, with a maximum methanol conversion rate of 9.0%.
[0020] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the following detailed description is provided with reference to the embodiments of the present invention and in conjunction with the accompanying drawings. Attached Figure Description
[0021] Figure 1 The nitrogen physisorption-desorption isotherms of cellulose-derived porous carbon prepared in Examples 1, 2, 3, 4 and Comparative Examples 1, 2, 3 of this invention are shown.
[0022] Figure 2 Transmission electron microscopy (TEM) images of the cellulose-derived porous carbon-supported copper catalysts prepared in Example 1 and Comparative Example 1 of this invention.
[0023] Figure 3 These are scanning electron microscope images of the cellulose-derived porous carbon prepared in Examples 1, 3 and Comparative Example 1 of the present invention. Detailed Implementation
[0024] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.
[0025] The method for preparing a cellulose-derived porous carbon-supported copper catalyst provided in this invention includes: S1, using microcrystalline cellulose as raw material, is prepared by impregnation with zinc salt solution of equal volume, high-temperature carbonization at 900~1000℃ and washing with nitric acid to produce cellulose-derived porous carbon with a large specific surface area, which serves as a catalyst support.
[0026] In one specific embodiment, S1 includes: S11, add microcrystalline cellulose at a concentration of 0.3~1.5 mol·L⁻¹ -1 The sample was ultrasonically treated in a zinc salt solution at an ultrasonic frequency of 80-100 kHz for 30-60 min and then allowed to stand at room temperature for 12-36 h. The sample was then placed in a forced-air drying oven and dried at 60-80 ℃ for 12-24 h in an air atmosphere. The dried sample was then ground to obtain an impregnated powder sample. The molar ratio of microcrystalline cellulose to zinc salt was 1:0.5 to 1:2.5.
[0027] Preferably, in step S11, microcrystalline cellulose is added at a concentration of 0.6 mol·L⁻¹. -1 The sample was ultrasonically treated in a zinc salt solution at an ultrasonic frequency of 80-100 kHz for 60 min and then allowed to stand at room temperature for 24 h. The sample was then placed in a forced-air drying oven and dried at 60 ℃ for 18 h in an air atmosphere. The dried sample was then ground to obtain an impregnated powder sample. The molar ratio of microcrystalline cellulose to zinc salt was 1:1.
[0028] S12, the impregnated powder sample is placed in a high-temperature tube furnace, and an airflow of 20~30 mL·min is introduced. -1 Argon gas, at 2~10℃·min -1 The temperature was increased to 900-1000℃ at a certain heating rate, and then kept at a constant temperature for 30 minutes before being naturally cooled to room temperature to obtain a carbonized powder sample.
[0029] Preferably, in step S12, the impregnated powder sample is placed in a high-temperature tube furnace, and an airflow rate of 25 mL / min is introduced. -1 Argon gas, at 5~10℃·min -1The temperature was increased to 900-1000℃ at a certain heating rate, and then kept at a constant temperature for 30 minutes before being naturally cooled to room temperature to obtain a carbonized powder sample.
[0030] S13, the carbonized powder sample obtained in S12 is immersed in 0.5~2.0 mol·L⁻¹ water. -1 The filter cake was placed in a nitric acid solution for 12-24 hours, then filtered, and washed with deionized water until the filtrate was neutral. It was then dried at 60-80℃ for 12-24 hours to obtain a cellulose-derived porous carbon material with residual Zn species removed, which was used as a catalyst support.
[0031] Preferably, in step S13, the carbonized powder sample obtained in step S12 is immersed in 2.0 mol·L⁻¹ water. -1 The filter cake was placed in a nitric acid solution for 12 hours, then filtered, washed with deionized water until the filtrate was neutral, and then dried at 60°C for 12 hours.
[0032] S2, copper species are loaded onto the catalyst support using an equal-volume impregnation method, and then reduced at 350~400℃ to obtain a cellulose-derived porous carbon-supported copper catalyst.
[0033] In one specific embodiment, S2 includes: S21, weigh 0.2~0.8g Cu(NO3)2·3H2O, add 20~60mL deionized water, stir until completely dissolved to obtain copper nitrate solution; then add 0.3~1.0g catalyst support to copper nitrate solution, stir for 9~15h, and dry the resulting suspension at 40~60℃ for 24~48h to obtain catalyst precursor.
[0034] Preferably, in step S21, 0.565g of Cu(NO3)2·3H2O is weighed, 50mL of deionized water is added, and the mixture is stirred until completely dissolved to obtain a copper nitrate solution; then 1.0g of catalyst support is added to the copper nitrate solution, and after stirring for 12h, the resulting suspension is dried at 50℃ for 24h to obtain the catalyst precursor.
[0035] S22, the catalyst precursor obtained in S21 is placed in a high-temperature tube furnace, and a flow rate of 20~30 mL·min is introduced. -1 Argon gas, at 2~4℃·min -1 The temperature was increased to the reduction temperature of 350-400℃ at a certain heating rate, and then kept at a constant temperature for 2-4 hours before being naturally cooled to room temperature to obtain a cellulose-derived porous carbon-supported copper catalyst.
[0036] It should be noted that when the zinc salt solution is zinc nitrate hexahydrate solution, the resulting catalyst support is a microporous carbon material containing mesopores (micropore specific surface area ratio of 82-86%). When the zinc salt solution is zinc chloride solution, the resulting catalyst support is a microporous carbon material (micropore specific surface area ratio of over 90%).
[0037] It should be noted that the cellulose-derived porous carbon-supported copper catalyst prepared in the embodiments of the present invention should be stored in a dry and oxygen-free container, and the container for storing the catalyst should be placed in an environment with an ambient temperature of 10~35℃ and a relative humidity of ≤5%.
[0038] This invention also provides an application of a cellulose-derived porous carbon supported copper catalyst, which is prepared using the preparation method described in the above embodiments. The cellulose-derived porous carbon supported copper catalyst is used for the oxidative carbonylation of methanol to synthesize dimethyl carbonate.
[0039] In one specific embodiment, the cellulose-derived porous carbon-supported copper catalyst is used in the reaction of methanol oxidative carbonylation to synthesize dimethyl carbonate, specifically including: S3, weigh 0.1~0.3g of cellulose-derived porous carbon supported copper catalyst and 10~30mL of methanol, put them into a microreactor, introduce oxygen at 0.2~0.5MPa at 20~30℃, then introduce carbon monoxide until the total pressure is 3.0~4.0MPa, and then introduce it at 200~400r·min. -1 Stir at a certain rate and react at 110~130℃ for 2~3 hours, then stop heating and allow to cool naturally to room temperature.
[0040] Preferably, in step S3, 0.15 g of cellulose-derived porous carbon-supported copper catalyst and 10 mL of methanol are weighed and placed in a microreactor. Oxygen is introduced at 0.2 MPa at 25°C, followed by the introduction of carbon monoxide until the total pressure reaches 4.0 MPa, at a rate of 400 r·min. -1 Stirring at a certain rate, reacting at 110℃ for 2 hours, then stopping heating and allowing to cool naturally to room temperature.
[0041] To verify the pore structure characteristics of the cellulose-derived porous carbon-supported copper catalyst prepared in the embodiments of the present invention and its beneficial effect in the synthesis of dimethyl carbonate by methanol oxidative carbonylation, the following examples and comparative examples are provided, all of which are used to synthesize dimethyl carbonate.
[0042] Example 1: (1) Weigh out microcrystalline cellulose and add it to a concentration of 0.6 mol·L -1The sample was ultrasonically treated with a frequency of 100 kHz for 60 min in a zinc nitrate hexahydrate solution and then allowed to stand at room temperature for 24 h. The sample was then placed in a forced-air drying oven and dried at 60 °C for 24 h in an air atmosphere. The dried sample was then ground to obtain an impregnated powder sample. The molar ratio of microcrystalline cellulose to zinc salt was 1:1.
[0043] (2) Place the impregnated powder sample in a high-temperature tube furnace and introduce a flow rate of 30 mL / min. -1 Argon gas, at 5℃·min -1 The temperature was increased to 1000℃ at a certain rate, and then kept constant for 30 minutes before being naturally cooled to room temperature to obtain a carbonized powder sample.
[0044] (3) Immerse the carbonized powder sample in 1.0 mol·L⁻¹ water. -1 The cellulose-derived carbon material was dried at 60°C for 12 hours in a nitric acid solution, followed by filtration. The filter cake was washed with deionized water until the filtrate was neutral, and then dried at 60°C for 12 hours to obtain cellulose-derived carbon material with residual Zn species removed, which was used as a catalyst support.
[0045] (4) Weigh 0.565g Cu(NO3)2·3H2O, add 50mL of deionized water, stir until completely dissolved to obtain copper nitrate solution; then add 1.0g catalyst support to copper nitrate solution, stir for 12h, and dry the resulting suspension at 50℃ for 24h to obtain catalyst precursor.
[0046] (5) Place the catalyst precursor in a high-temperature tube furnace and introduce it at a flow rate of 30 mL·min. -1 Argon gas, at 2℃·min -1 The temperature was increased to the reduction temperature of 350℃ at a certain rate, and then kept at a constant temperature for 4 hours before being naturally cooled to room temperature to obtain a cellulose-derived porous carbon supported copper catalyst.
[0047] (6) Weigh 0.15 g of cellulose-derived porous carbon supported copper catalyst and 10 mL of methanol, put them into a microreactor, introduce oxygen at 0.2 MPa at 25 °C, and then introduce carbon monoxide until the total pressure is 4.0 MPa, and then introduce it at 400 r·min. -1 Stirring at a certain rate, reacting at 110℃ for 2 hours, then stopping heating and allowing to cool naturally to room temperature.
[0048] Example 2: The other steps are the same as in Example 1, except that in step (1), microcrystalline cellulose is weighed and added to a concentration of 0.9 mol·L⁻¹. -1 The solution of zinc nitrate hexahydrate was ultrasonically treated at a frequency of 100 kHz for 60 min, and then left to stand at room temperature for 24 h, followed by drying at 60 ℃ for 24 h; wherein the molar ratio of microcrystalline cellulose to zinc salt was 1:1.5.
[0049] Example 3: The other steps are the same as in Example 1, except that in step (1), microcrystalline cellulose is weighed and added to a concentration of 0.6 mol·L⁻¹. -1 The microcrystalline cellulose was ultrasonically treated with an ultrasonic frequency of 80 kHz for 60 min in a zinc chloride solution, and then allowed to stand at room temperature for 24 h, followed by drying at 60 °C for 24 h; wherein the molar ratio of microcrystalline cellulose to zinc salt was 1:1.
[0050] Example 4: The other steps are the same as in Example 1, except that in step (1), the concentration of microcrystalline cellulose added is 0.9 mol·L⁻¹. -1 The solution of zinc chloride was ultrasonically treated at a frequency of 100 kHz for 60 min, and then left to stand at room temperature for 24 h, followed by drying at 60 ℃ for 24 h; wherein the molar ratio of microcrystalline cellulose to zinc salt was 1:1.5.
[0051] Comparative Example 1: The other steps are the same as in Example 1, except that in step (1), microcrystalline cellulose is weighed and added to an equal volume of distilled water, ultrasonically treated at a frequency of 100 kHz for 60 min, and then left to stand at room temperature for 24 h, and then dried at 60 ℃ for 24 h.
[0052] Comparative Example 2: The other steps are the same as in Example 1, except that in step (2), the flow rate is 30 mL·min. -1 Argon gas, at 5℃·min -1 The temperature was increased to 900℃ at a certain rate, and then kept constant for 30 minutes before being allowed to cool naturally to room temperature.
[0053] Comparative Example 3: The other steps are the same as in Example 1, except that in step (1), microcrystalline cellulose is weighed and added to a concentration of 0.6 mol·L⁻¹. -1 The solution of zinc chloride was ultrasonically treated at an ultrasonic frequency of 80 kHz for 60 min, and then allowed to stand at room temperature for 24 h, followed by drying at 60 °C for 24 h. In step (2), the flow rate was 30 mL / min. -1 Argon gas, at 5℃·min -1 The temperature was increased to 900℃ at a certain rate, held at a constant temperature for 30 minutes, and then naturally cooled to room temperature. The molar ratio of microcrystalline cellulose to zinc salt was 1:1.
[0054] The reaction performance was obtained using methanol conversion rate and methanol selectivity for DMC as indicators, as shown in Table 1.
[0055]
[0056] Comparing the specific surface area data of Examples 1-4 with Comparative Example 1, it can be seen that the specific surface area of the carrier obtained after activating microcrystalline cellulose with zinc salts such as zinc nitrate hexahydrate or zinc chloride and then carbonizing it at a high temperature of 900-1000℃ is significantly increased compared with the material without zinc salts. The specific surface areas of Examples 1-4 reached 763, 829, 821, and 981 m², respectively. -2 ·g -1 All of them are higher than the 597 m of Comparative Example 1. -2 ·g -1 Meanwhile, the methanol conversion rates in Examples 1-4 were 6.3%-9.0%, higher than the 5.6% in Comparative Example 1. These results indicate that the cellulose-derived porous carbon support prepared by zinc salt activation has a larger specific surface area and higher catalytic activity.
[0057] By comparing the mesoporous specific surface areas of Examples 1-2 and Examples 3-4, the mesoporous specific surface areas of the samples prepared using zinc nitrate hexahydrate (Examples 1-2) were 129 and 155 m², respectively. -2 ·g -1 The values were significantly higher than those of the samples prepared using zinc chloride (Examples 3-4) at 3 and 5 m. -2 ·g -1 This demonstrates that the mesoporous structure of the carrier can be controlled by changing the type of zinc salt. The introduction of the mesoporous structure is beneficial to improving pore connectivity and mass transfer conditions, and increasing the accessibility of active sites. Accordingly, the methanol conversion rate of Example 1 reached 9.0%, which is higher than the 6.3% of Example 3.
[0058] Comparing Example 1 with Comparative Example 2, and Example 3 with Comparative Example 3, it is evident that compared to carbonization at 900℃, carbonization at 1000℃ resulted in a similar mesopore specific surface area, while the micropore specific surface area increased. This indicates that increasing the carbonization temperature has a smaller impact on mesopore size and is more likely to promote the formation of microporous structures. Under the premise of similar mesopore specific surface areas, Example 1 achieved a methanol conversion rate of 9.0%, higher than the 5.6% of Comparative Example 2, suggesting that increased microporous structure may further enhance catalytic activity.
[0059] To further investigate the structure and performance of the cellulose-derived porous carbon-supported copper catalyst, this invention employs various characterization methods to analyze Examples 1-4 and Comparative Examples 1-3: Figure 1 The nitrogen physisorption-desorption isotherms showed that the samples in Examples 1, 2, and Comparative Example 2 exhibited a mixed type I / IV isotherm characteristic, reflecting a pore structure that combines micropores and mesopores. In Examples 3, 4, and Comparative Example 3, the samples exhibited type I isotherm characteristics, indicating that the pore structure of the samples was mainly microporous. Figure 2TEM (transmission electron microscopy) images show that the copper particles in Example 1 are smaller in size, uniformly distributed and without obvious agglomeration, while the copper particles in Comparative Example 1 are more obviously agglomerated, indicating that the porous carbon support obtained by zinc salt activation is beneficial to the dispersion of copper species. Figure 3 The SEM (scanning electron microscope) images show that the material of Example 1 is composed of stacked sheet-like carbon structures with abundant pores, which is beneficial for providing anchoring points for copper species; the material of Example 3 is mainly composed of microporous structures with fewer mesopores; the material of Comparative Example 1 retains more cellulose morphology and has a relatively dense surface with relatively few pore structures, which is not conducive to the anchoring and dispersion of copper species.
[0060] In summary, addressing the limitations of traditional activated carbon materials, such as their predominantly microporous structure and restricted accessibility of active sites and stable dispersion of copper species, this invention utilizes microcrystalline cellulose as the carbon source and zinc salts as activators and templates to prepare materials with a high specific surface area and tunable pore structure (a maximum specific surface area of 981 m²). -2 ·g -1 The highest specific surface area of micropores is 976 m². -2 ·g -1 Mesoporous specific surface area up to 155 m² -2 ·g -1 The catalyst exhibits high catalytic performance in the methanol oxidative carbonylation to synthesize dimethyl carbonate, with a maximum methanol conversion rate of 9.0%.
[0061] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for preparing a copper catalyst supported on cellulose-derived porous carbon, characterized in that, include: S1, using microcrystalline cellulose as raw material, is prepared by impregnation with zinc salt solution of equal volume, high-temperature carbonization at 900~1000℃ and washing with nitric acid to produce cellulose-derived porous carbon with a large specific surface area, which serves as a catalyst support. S2, copper species are loaded onto the catalyst support using an equal-volume impregnation method, and then reduced at 350~400℃ to obtain a cellulose-derived porous carbon-supported copper catalyst.
2. The method for preparing the cellulose-derived porous carbon-supported copper catalyst according to claim 1, characterized in that, S1 includes: S11, add microcrystalline cellulose at a concentration of 0.3~1.5 mol·L⁻¹ -1 The sample was ultrasonically treated in a zinc salt solution at an ultrasonic frequency of 80-100 kHz for 30-60 min, and then allowed to stand at room temperature for 12-36 h. After standing, the sample was placed in a forced-air drying oven and dried at 60-80℃ in an air atmosphere for 12-24 h. The dried sample was then ground to obtain an impregnated powder sample. The molar ratio of microcrystalline cellulose to zinc salt was 1:0.5-1:2.
5. S12, the impregnated powder sample is placed in a high-temperature tube furnace, and an airflow of 20~30 mL·min is introduced. -1 Argon gas, at 2~10℃·min -1 The temperature was increased to 900-1000℃ at a rising rate, and then kept at a constant temperature for 30 minutes before being naturally cooled to room temperature to obtain a carbonized powder sample. S13, the carbonized powder sample obtained in S12 is immersed in 0.5~2.0 mol·L⁻¹ water. -1 The filter cake was placed in a nitric acid solution for 12-24 hours, then filtered, and washed with deionized water until the filtrate was neutral. It was then dried at 60-80℃ for 12-24 hours to obtain a cellulose-derived porous carbon material with residual Zn species removed, which was used as a catalyst support.
3. The method for preparing the cellulose-derived porous carbon-supported copper catalyst according to claim 1, characterized in that, S2 includes: S21, weigh 0.2~0.8g Cu(NO3)2·3H2O, add 20~60mL deionized water, stir until completely dissolved to obtain copper nitrate solution; then add 0.3~1.0g catalyst support to copper nitrate solution, stir for 9~15h, and dry the resulting suspension at 40~60℃ for 24~48h to obtain catalyst precursor; S22, the catalyst precursor obtained in S21 is placed in a high-temperature tube furnace, and a flow rate of 20~30 mL·min is introduced. -1 Argon gas, at 2~4℃·min -1 The temperature was increased to the reduction temperature of 350-400℃ at a certain heating rate, and then kept at a constant temperature for 2-4 hours before being naturally cooled to room temperature to obtain a cellulose-derived porous carbon-supported copper catalyst.
4. The method for preparing the cellulose-derived porous carbon-supported copper catalyst according to claim 2, characterized in that, In step S11, microcrystalline cellulose is added at a concentration of 0.6 mol·L⁻¹. -1 The sample was ultrasonically treated in a zinc salt solution at an ultrasonic frequency of 80-100 kHz for 60 min and then allowed to stand at room temperature for 24 h. The sample was then placed in a forced-air drying oven and dried at 60 ℃ for 18 h in an air atmosphere. The dried sample was then ground to obtain an impregnated powder sample. The molar ratio of microcrystalline cellulose to zinc salt was 1:
1. In step S12, the impregnated powder sample is placed in a high-temperature tube furnace, and an airflow of 25 mL / min is introduced. -1 Argon gas, at 5~10℃·min -1 The temperature was increased to 900-1000℃ at a rising rate, and then kept at a constant temperature for 30 minutes before being naturally cooled to room temperature to obtain a carbonized powder sample. In step S13, the carbonized powder sample obtained in step S12 is immersed in 2.0 mol·L⁻¹ water. -1 The filter cake was placed in a nitric acid solution for 12 hours, then filtered, washed with deionized water until the filtrate was neutral, and then dried at 60°C for 12 hours.
5. The method for preparing the cellulose-derived porous carbon-supported copper catalyst according to claim 3, characterized in that, In S21, 0.565g of Cu(NO3)2·3H2O was weighed, 50mL of deionized water was added, and the mixture was stirred until completely dissolved to obtain a copper nitrate solution. Subsequently, 1.0g of catalyst support was added to the copper nitrate solution, and the mixture was stirred for 12h. The resulting suspension was then dried at 50℃ for 24h to obtain the catalyst precursor.
6. The method for preparing the cellulose-derived porous carbon-supported copper catalyst according to claim 2 or 4, characterized in that, When the zinc salt solution is a zinc nitrate solution, the resulting catalyst support is a mesoporous, microporous cellulose-derived carbon material.
7. The method for preparing the cellulose-derived porous carbon-supported copper catalyst according to claim 2 or 4, characterized in that, When the zinc salt solution is a zinc chloride solution, the resulting catalyst support is a microporous cellulose-derived carbon material.
8. The application of a cellulose-derived porous carbon-supported copper catalyst, characterized in that, The cellulose-derived porous carbon supported copper catalyst is prepared by the preparation method described in any one of claims 1 to 7, and the cellulose-derived porous carbon supported copper catalyst is used for the oxidative carbonylation of methanol to synthesize dimethyl carbonate.
9. The application of the cellulose-derived porous carbon-supported copper catalyst according to claim 8, characterized in that, The cellulose-derived porous carbon-supported copper catalyst is used in the reaction of methanol oxidative carbonylation to synthesize dimethyl carbonate, specifically including: S3, weigh 0.1~0.3g of cellulose-derived porous carbon supported copper catalyst and 10~30mL of methanol, put them into a microreactor, introduce oxygen at 0.2~0.5MPa at 20~30℃, then introduce carbon monoxide until the total pressure is 3.0~4.0MPa, and then introduce it at 200~400r·min. -1 Stir at a certain rate and react at 110~130℃ for 2~3 hours, then stop heating and allow to cool naturally to room temperature.
10. The application of the cellulose-derived porous carbon-supported copper catalyst according to claim 9, characterized in that, In step S3, 0.15 g of cellulose-derived porous carbon-supported copper catalyst and 10 mL of methanol were weighed and placed in a microreactor. Oxygen was introduced at 0.2 MPa at 25°C, followed by carbon monoxide until the total pressure reached 4.0 MPa, and the reaction was carried out at a rate of 400 r·min. -1 Stirring at a certain rate, reacting at 110℃ for 2 hours, then stopping heating and allowing to cool naturally to room temperature.