Catalyst for the production of dimethyl carbonate by indirect gas phase process, production method and use
By employing a Pd complex structure with transition metal phosphides in the catalyst, the problem of catalyst performance instability was solved, achieving highly selective and efficient dimethyl carbonate synthesis with good catalytic performance and service life.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- NINGBO INST OF MATERIALS TECH & ENG CHINESE ACAD OF SCI
- Filing Date
- 2024-01-04
- Publication Date
- 2026-07-03
AI Technical Summary
Existing catalysts suffer from unstable catalytic performance, low selectivity, and low space-time yield in the preparation of dimethyl carbonate.
A two-component metal phosphide is used as the catalytic active component, in which Pd forms a complex structure with transition metals through a complexing agent and is supported on a γ-Al2O3 catalyst support to prevent Pd ion precipitation and improve the uniform distribution and utilization rate of the active component.
It significantly improves the catalytic performance and stability of the catalyst, especially the selectivity and space-time yield of dimethyl carbonate synthesis under low temperature and low pressure.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of catalysis technology, specifically to the field of catalysis technology for the gas-phase synthesis of dimethyl carbonate from CO, and more specifically, to a catalyst, preparation method, and application for the indirect gas-phase preparation of dimethyl carbonate. Background Technology
[0002] Dimethyl carbonate (DMC) is an important organic chemical raw material. Its methyl, methoxy, and hydroxyl functional groups give it relatively active chemical properties, making it widely used in organic synthesis, pharmaceutical synthesis, engineering plastics, green additives, and cleaning agents for color television picture tubes. In recent years, driven by the booming development of the domestic lithium battery industry, there has been a shortage of lithium battery electrolyte solvents, such as dimethyl carbonate. Therefore, the development of electronic-grade dimethyl carbonate technology is both necessary and urgent.
[0003] Currently, methods for synthesizing dimethyl carbonate include the phosgene method, methanol oxidative carbonylation, transesterification, urea alcoholysis, and methyl nitrite gas-phase carbonylation. In recent years, the methanol oxidative carbonylation method, with its advantages of lower cost and greener raw materials, has gained popularity. The methanol oxidative carbonylation gas-phase indirect method first reacts methanol, O2, and NO to produce methyl nitrite. The generated methyl nitrite then reacts with CO to produce dimethyl carbonate and NO. NO can be recycled to produce methyl nitrite. This route has advantages such as mild reaction conditions and high product quality, and has good development prospects.
[0004] Chinese invention patent CN11659456A discloses a dedicated catalyst for the synthesis of dimethyl carbonate and its preparation method. The catalyst's main active component is Pd, its co-active component is Cu, and its support is an oxide-modified Y-type molecular sieve, belonging to a chlorine-free catalyst system. The catalyst's key feature is the introduction of metal ions into the pores of the molecular sieve using an ultrasonic-assisted method, followed by the addition of an alkaline solution to precipitate the metal ions. This precipitate is then decomposed through high-temperature calcination, resulting in the metal oxide-modified Y-type molecular sieve support. This support reduces the acidic sites on the molecular sieve surface, effectively inhibiting the decomposition of methyl nitrite during dimethyl carbonate preparation, thereby improving the catalyst's selectivity and space-time yield for dimethyl carbonate.
[0005] Chinese invention patent CN107376954A discloses a catalyst and its preparation method for the gas-phase synthesis of dimethyl carbonate from CO and methyl nitrite under low-temperature and low-pressure conditions. This catalyst is a Wacker-type catalyst with Pd-Cl-Cu supported on γ-Al₂O₃ and doped with an alkali metal element. In this catalyst, Pd... 2+ To provide reactive sites, Cu 2+PdO reduced by CO is oxidized to form Pd again. 2+ , and Cl - It plays a role in electron transfer. This catalyst has the advantages of stable use and long lifespan, and the alkali metal element in the catalyst can be used as an auxiliary agent to improve the catalytic performance.
[0006] To address the aforementioned technical problems, this invention provides a catalyst for the indirect gas-phase preparation of dimethyl carbonate, employing a two-component metal phosphide as the catalytically active component. One component is a Pd phosphide, and the other is a transition metal phosphide. Furthermore, Pd and the transition metal form a complex structure through a complexing agent, which can significantly improve the stability of the catalytic performance of the prepared catalyst. Summary of the Invention
[0007] In view of this, the purpose of the present invention is to provide a catalyst, preparation method and application for the indirect gas-phase preparation of dimethyl carbonate, which has excellent catalytic performance, stable use and long life, and in particular, has extremely high selectivity and space-time yield when applied to the catalytic synthesis of dimethyl carbonate.
[0008] To achieve the above objectives, this invention provides a catalyst for the indirect gas-phase synthesis of dimethyl carbonate. This catalyst is a supported catalyst, composed of a main active component, a co-active component, and a catalyst support. The main active component includes a Pd phosphide; the co-active component is a transition metal phosphide; the main active component and the co-active component are supported within the catalyst support. The Pd ions in the main active component and the transition metal ions in the co-active component are complexed with a complexing agent to form a Pd-transition metal complex, preventing Pd ions from precipitating during material preparation and maximizing their utilization.
[0009] Preferably, the auxiliary active component includes a phosphide of at least one of the transition metals Cu, Fe, Co, and Ni.
[0010] Preferably, the main active component includes one or more of Pd6P, Pd3P, Pd5P2, and PdP2.
[0011] Preferably, the loading rate of the main active component is 0.1% to 5%.
[0012] Preferably, the loading rate of the co-active component is 0.01%-2%.
[0013] Preferably, the complexing agent is ethylenediamine. The purpose of adding the complexing agent is to complex Pd ions and various transition metal cations in the solution, preventing the formation of corresponding hydroxide precipitates during stirring after the phosphating agent (diammonium hydrogen phosphate) is added to the solution.
[0014] Preferably, the catalyst support is γ-Al₂O₃, and the specific surface area of the γ-Al₂O₃ support is 30-300 m². 2 / g, pore volume of 0.1-1.5m 2 / g, pore size is 3-20m.
[0015] To achieve another objective, the present invention also provides a method for preparing the above-mentioned catalyst, the specific steps of which include:
[0016] S1. Dissolve Pd ions and transition metal ions in water, adjust the pH to acidic, and obtain a precursor solution;
[0017] S2. Add the complexing agent to the precursor solution to carry out a complexation reaction and obtain a complex with a Pd-transition metal complex structure;
[0018] S3. Add a phosphating agent to the complex to form a mixture of Pd phosphide and transition metal phosphide;
[0019] S4. The mixture is added dropwise to the catalyst support, impregnated, dried, and calcined to obtain the supported catalyst.
[0020] The phosphating agent includes an aqueous solution of diammonium hydrogen phosphate.
[0021] Preferably, the concentration of Pd ions in the solution is 10–500 mmol / L, and the concentration of transition metal ions in the solution is 15–800 mmol / L.
[0022] Preferably, in the catalyst, the mass ratio of the catalyst support to Pd is 50:1 to 1000:1.
[0023] Preferably, in S4, drying is performed by ultrasonication, heating, or drying in a drying oven to remove the solvent from the catalyst surface.
[0024] Preferably, in S4, the calcination temperature is 200°C and the calcination time is more than 2 hours.
[0025] The catalyst prepared using the above technical solution is used in the indirect gas-phase method for the oxidative hydroxylation of methanol to prepare dimethyl carbonate. In particular, the reaction of mixing NO, O2, methanol and CO can efficiently synthesize dimethyl carbonate at relatively low temperature and pressure.
[0026] Specifically, methanol, O2, and NO are first mixed and reacted to obtain methyl nitrite; the generated methyl nitrite reacts with CO under the action of the above catalyst in a low-pressure gas phase reaction to generate dimethyl carbonate.
[0027] Preferably, the low-pressure gas-phase reaction includes using nitrogen as a diluent and mixing in a trace amount of HCl gas. The reaction conditions include a CO space velocity of 250–1000 h⁻¹. -1 The space velocity ratio of methyl nitrite to CO was 1:2 to 2:1, the space velocity ratio of N2 to CO was 2:1 to 8:1, and the amount of HCl mixed in was 50-500 ppm; the reaction temperature was controlled at 110-130℃, the reaction pressure was controlled at 0.2-1 MPa, and the reaction time was 3-5 h.
[0028] In the catalyst provided by the technical solution of this invention, Pd 2+ To provide the main reactive sites, transition metal ions, acting as co-reactive substances, oxidize Pd reduced by CO. 0 Pd is formed again 2+ Therefore, this catalyst has the advantage of a longer lifespan compared to common noble metal catalysts. Furthermore, the presence of P increases the interaction between the main active component Pd and the co-active components, transition metals, and the alumina support. This results in extremely small palladium and transition metal particles with excellent dispersibility, which can significantly improve the catalyst's catalytic performance.
[0029] The beneficial technical effects obtained by this invention are as follows:
[0030] 1. By adopting the technical solution of the present invention, Pd and transition metal ions are complexed by a complexing agent during the preparation process to prevent the precipitation of hydroxide generated during stirring after the phosphating agent (diammonium hydrogen phosphate) is added to the solution. On the one hand, this can improve the uniform distribution of active components in the catalyst within the support, and on the other hand, it can increase the effective content of catalytically active components in the catalyst.
[0031] 2. The Pd in the catalyst provided by adopting the technical solution of the present invention 2+ To provide the main reactive sites, transition metal ions, acting as co-reactive substances, oxidize PdO reduced by CO to regenerate Pd. 2+ Therefore, this catalyst has the advantage of long service life. In particular, the presence of phosphide as the active component can increase the interaction between the main active component Pd and the co-active component transition metal and alumina support, making the palladium and transition metal particles extremely small and having good dispersibility, which greatly improves the catalytic performance of the catalyst. Detailed Implementation
[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.
[0033] This invention provides a supported catalyst for the indirect gas-phase synthesis of dimethyl carbonate, comprising a main active component, a co-active component, and a catalyst support; the main active component includes a Pd phosphide; the co-active component is a transition metal phosphide; the main active component and the co-active component are supported within the catalyst support; wherein, the Pd ions in the main active component and the transition metal ions in the co-active component are complexed with a complexing agent to form a Pd-transition metal complex structure.
[0034] In the catalysts mentioned above, the loading of Pd is 0.1 wt%-2.0 wt%, and the loading of transition metals is 0.1 wt%-2.0 wt%.
[0035] In some specific embodiments, the transition metal ion compound is one or more of copper chloride, ferric chloride, cobalt chloride, and nickel chloride, but is not limited thereto.
[0036] In some specific embodiments, the concentration of PdCl2 solution is 10–500 mmol / L, and the concentration of transition metal ion compound solution is 15–800 mmol / L.
[0037] In some specific embodiments, ethylenediamine is selected as the complexing agent; the molar ratio of the complexing agent to Pd in the catalyst is 1:10.
[0038] In some specific embodiments, the catalyst support is γ-Al₂O₃, with a specific surface area of 30-300 m². 2 / g, pore volume 0.1-1.5m 2 / g, with a pore size of 3-20nm.
[0039] Furthermore, the mass ratio of γ-Al2O3 to Pd is 50:1 to 1000:1.
[0040] The technical solution of the present invention will be further illustrated below through specific embodiments.
[0041] Example 1
[0042] This embodiment provides a supported catalyst, the preparation steps of which include:
[0043] Dissolve 18.8 mmol PdCl2 and 31.5 mmol CuCl2 in 100 g of water, mix well, add hydrochloric acid to adjust the pH to 1, and stir to obtain the precursor solution.
[0044] 100 μL of ethylenediamine was added to the precursor solution as a complexing agent to carry out the complexation reaction. Then, 60.6 mmol of diammonium hydrogen phosphate was added and stirred for 1 h. The solution was then slowly added dropwise to 100 g of γ-Al2O3 support while stirring continuously with a glass rod until the mixture was homogeneous.
[0045] The above mixture was impregnated at room temperature for 48 hours, then removed and evaporated at 120°C in a drying oven, and finally calcined at 200°C for 10 hours to obtain the supported catalyst.
[0046] The catalyst prepared by the above steps is designated as catalyst 1#, wherein the loading rate of Pd in catalyst 1# is 2.0 wt% and the loading rate of Cu is 2.0%.
[0047] Example 2
[0048] This embodiment provides a supported catalyst, the preparation steps of which include:
[0049] 14.1 mmol PdCl2 and 23.6 mmol CuCl2 were dissolved in 100 g of water and mixed thoroughly. Hydrochloric acid was added to adjust the pH to 1, and the mixture was stirred to obtain the precursor solution.
[0050] 75 μL of ethylenediamine was added to the precursor solution as a complexing agent for complexation. Then, 45.2 mmol of diammonium hydrogen phosphate was added and stirred for 1 h. The solution was then slowly added dropwise to 100 g of γ-Al2O3 support while continuously stirring with a glass rod until the mixture was homogeneous.
[0051] The above mixture was impregnated at room temperature for 48 hours, evaporated and dried in a drying oven at 120°C, and then calcined at 200°C for 10 hours to obtain the supported catalyst.
[0052] The catalyst prepared by the above steps is used as catalyst 2#, wherein the loading rate of Pd is 1.5 wt% and the loading rate of Cu is 1.5%.
[0053] Example 3
[0054] This embodiment provides a supported catalyst, the preparation steps of which include:
[0055] Dissolve 10 mmol PdCl2 and 16.7 mmol CuCl2 in 100 g of water, mix well, add hydrochloric acid to adjust the pH to 1, and stir to obtain the precursor solution.
[0056] 50 μL of ethylenediamine was added to the precursor solution for complexation, followed by the addition of 30.4 mmol of diammonium hydrogen phosphate and stirring for 1 h. The solution was then slowly added dropwise to 100 g of γ-Al2O3 support while continuously stirring with a glass rod until the mixture was homogeneous.
[0057] The above mixture was impregnated at room temperature for 48 hours, evaporated and dried in a drying oven at 120°C, and then calcined at 200°C for 10 hours to obtain the supported catalyst.
[0058] The catalyst prepared by the above steps is designated as catalyst 3#, wherein the loading rate of Pd is 1.0 wt% and the loading rate of Cu is 1.0%.
[0059] Example 4
[0060] This embodiment provides a supported catalyst, the preparation steps of which include:
[0061] Dissolve 4.7 mmol PdCl2 and 7.9 mmol CuCl2 in 100 g of water, mix well, add hydrochloric acid to adjust the pH to 1, and stir to obtain the precursor solution.
[0062] 25 μL of ethylenediamine was added to the precursor solution for complexation, followed by the addition of 15.2 mmol of diammonium hydrogen phosphate and stirring for 1 h. The solution was then slowly added dropwise to 100 g of γ-Al2O3 support while continuously stirring with a glass rod until the mixture was homogeneous.
[0063] The above mixture was impregnated at room temperature for 48 hours, evaporated and dried in a drying oven at 120°C, and then calcined at 200°C for 10 hours to obtain the supported catalyst.
[0064] The catalyst prepared by the above steps was used as catalyst 4#, with a Pd loading rate of 0.5 wt% and a Cu loading rate of 0.5%.
[0065] Example 5
[0066] This embodiment provides a supported catalyst, the preparation steps of which include:
[0067] Dissolve 18.8 mmol PdCl2 and 1.7 mmol CuCl2 in 100 g of water, mix well, add hydrochloric acid to adjust the pH to 1, and stir to obtain the precursor solution.
[0068] 50 μL of ethylenediamine was added to the precursor solution for complexation, followed by the addition of 30.4 mmol of diammonium hydrogen phosphate and stirring for 1 h. The solution was then slowly added dropwise to 100 g of γ-Al₂O₃ support while continuously stirring with a glass rod until homogeneous. The mixture was then impregnated at room temperature for 48 h, evaporated and dried at 120 °C in a drying oven, and finally calcined at 200 °C for 10 h to obtain the supported catalyst.
[0069] The catalyst prepared by the above steps was designated as catalyst 5#, with a Pd loading rate of 2 wt% and a Cu loading rate of 0.1%.
[0070] Example 6
[0071] This embodiment provides a supported catalyst, the preparation steps of which include:
[0072] Dissolve 18.8 mmol PdCl2 and 16.7 mmol CuCl2 in 100 g of water, mix well, add hydrochloric acid to adjust the pH to 1, and stir to obtain the precursor solution.
[0073] 75 μL of ethylenediamine was added to the precursor solution for complexation, followed by the addition of 45.2 mmol of diammonium hydrogen phosphate and stirring for 1 h. The solution was then slowly added dropwise to 100 g of γ-Al₂O₃ support while continuously stirring with a glass rod until homogeneous. The mixture was then impregnated at room temperature for 48 h, evaporated and dried at 120 °C in a drying oven, and finally calcined at 200 °C for 10 h to obtain the supported catalyst.
[0074] The catalyst prepared by the above steps was designated as catalyst 6#, with a Pd loading of 2 wt% and a Cu loading of 1%.
[0075] Example 7
[0076] This embodiment provides a supported catalyst, the preparation steps of which include:
[0077] Dissolve 18.8 mmol PdCl2 and 35.7 mmol FeCl3 in 100 g of water, mix well, add hydrochloric acid to adjust the pH to 1, and stir to obtain the precursor solution.
[0078] 100 μL of ethylenediamine was added to the precursor solution for complexation, followed by the addition of 60.6 mmol of diammonium hydrogen phosphate and stirring for 1 h. The solution was then slowly added dropwise to 100 g of γ-Al₂O₃ support while continuously stirring with a glass rod until homogeneous. The mixture was then impregnated at room temperature for 48 h, evaporated and dried at 120 °C in a drying oven, and finally calcined at 200 °C for 10 h to obtain the supported catalyst.
[0079] The catalyst prepared by the above steps was designated as catalyst 7#, with a Pd loading of 2.0 wt% and an Fe loading of 2.0%.
[0080] Example 8
[0081] This embodiment provides a supported catalyst, the preparation steps of which include:
[0082] Dissolve 18.8 mmol PdCl2 and 33.9 mmol CoCl2 in 100 g of water, mix well, add hydrochloric acid to adjust the pH to 1, and stir to obtain the precursor solution.
[0083] 100 μL of ethylenediamine was added to the precursor solution for complexation, followed by the addition of 60.6 mmol of diammonium hydrogen phosphate and stirring for 1 h. The solution was then slowly added dropwise to 100 g of γ-Al₂O₃ support while continuously stirring with a glass rod until homogeneous. The mixture was then impregnated at room temperature for 48 h, evaporated and dried at 120 °C in a drying oven, and finally calcined at 200 °C for 10 h to obtain the supported catalyst.
[0084] The catalyst prepared by the above steps was designated as catalyst 8#, with a Pd loading of 2.0 wt% and a Co loading of 2.0%.
[0085] Example 9
[0086] This embodiment provides a supported catalyst, the preparation steps of which include:
[0087] 18.8 mmol PdCl2 and 34.1 mmol NiCl2 were dissolved in 100 g of water and mixed thoroughly. Hydrochloric acid was added to adjust the pH to 1, and the mixture was stirred to obtain the precursor solution.
[0088] 100 μL of ethylenediamine was added to the precursor solution for complexation, followed by the addition of 60.6 mmol of diammonium hydrogen phosphate and stirring for 1 h. The solution was then slowly added dropwise to 100 g of γ-Al₂O₃ support while continuously stirring with a glass rod until homogeneous. The mixture was then impregnated at room temperature for 48 h, evaporated and dried at 120 °C in a drying oven, and finally calcined at 200 °C for 10 h to obtain the supported catalyst.
[0089] The catalyst prepared by the above steps was designated as catalyst 9#, with a Pd loading of 2.0 wt% and a Ni loading of 2.0%.
[0090] Comparative Example 1
[0091] This comparative example provides a supported catalyst, the preparation steps of which include:
[0092] Dissolve 2.3 mmol PdCl2 and 3.9 mmol CuCl2 in 100 g of water, mix well, add hydrochloric acid to adjust the pH to 1, and stir to obtain the precursor solution.
[0093] 13 μL of ethylenediamine was added to the precursor solution for complexation, followed by the addition of 7.6 mmol of diammonium hydrogen phosphate and stirring for 1 h. The solution was then slowly added dropwise to 100 g of γ-Al2O3 support while continuously stirring with a glass rod until the mixture was homogeneous.
[0094] The above mixture was impregnated at room temperature for 48 hours, evaporated and dried in a drying oven at 120°C, and then calcined at 200°C for 10 hours to obtain the supported catalyst.
[0095] The catalyst prepared by the above steps was used as catalyst 10#, with a Pd loading rate of 0.25 wt% and a Cu loading rate of 0.25%.
[0096] Comparative Example 2
[0097] This comparative example provides a supported catalyst, the preparation steps of which include:
[0098] Dissolve 1 mmol PdCl2 and 1.67 mmol CuCl2 in 100 g of water, mix well, add hydrochloric acid to adjust the pH to 1, and stir to obtain the precursor solution.
[0099] 13 μL of ethylenediamine was added to the precursor solution for complexation, followed by the addition of 4 mmol of diammonium hydrogen phosphate and stirring for 1 h. The solution was then slowly added dropwise to 100 g of γ-Al2O3 support while continuously stirring with a glass rod until the mixture was homogeneous.
[0100] The above mixture was impregnated at room temperature for 48 hours, evaporated and dried in a drying oven at 120°C, and then calcined at 200°C for 10 hours to obtain the supported catalyst.
[0101] The catalyst prepared by the above steps was designated as catalyst 11#, with a Pd loading rate of 0.1 wt% and a Cu loading rate of 0.1%.
[0102] Comparative Example 3
[0103] Dissolve 18.8 mmol PdCl2 and 31.5 mmol CuCl2 in 100 g of water, mix well, add hydrochloric acid to adjust the pH to 1, and stir to obtain the precursor solution.
[0104] Unlike Example 1, this example does not add the complexing agent ethylenediamine. Instead, 60.6 mmol of diammonium hydrogen phosphate is added and stirred for 1 hour. The solution is then slowly added dropwise to 100 g of the γ-Al2O3 support while continuously stirring with a glass rod until the mixture is homogeneous.
[0105] The above mixture was impregnated at room temperature for 48 hours, then removed and evaporated at 120°C in a drying oven, and finally calcined at 200°C for 10 hours to obtain the supported catalyst.
[0106] The catalyst prepared by the above steps is designated as catalyst 1#. In catalyst 12#, the loading rate of Pd is 2.0 wt% and the loading rate of Cu is 2.0%.
[0107] Comparative Example 4
[0108] Dissolve 4.7 mmol PdCl2 and 7.9 mmol CuCl2 in 100 g of water, mix well, add hydrochloric acid to adjust the pH to 1, and stir to obtain the precursor solution.
[0109] Similarly, without adding ethylenediamine for complexation, 15.2 mmol of diammonium hydrogen phosphate was added directly and stirred for 1 hour. The solution was then slowly added dropwise to 100 g of γ-Al2O3 support while continuously stirring with a glass rod until the mixture was homogeneous, thus obtaining a mixture.
[0110] The above mixture was impregnated at room temperature for 48 hours, evaporated and dried in a drying oven at 120°C, and then calcined at 200°C for 10 hours to obtain the supported catalyst.
[0111] The catalyst prepared by the above steps was used as catalyst 13#, with a Pd loading rate of 0.5 wt% and a Cu loading rate of 0.5%.
[0112] Catalysts 1# to 13# prepared in the examples and comparative examples were placed in a fixed-bed reactor to evaluate their catalytic performance in the low-pressure gas-phase reaction of CO with methyl nitrite. The reactor inner diameter was 25 mm, the catalyst loading was 100 mL, and 70 mL of inert ceramic beads were packed at the top and bottom of the catalyst bed. The reactor was temperature-controlled in three stages. The feedstock was a mixture of CO, methyl nitrite, and nitrogen, with an HCl content of 200 ppm and a CO space velocity of 1000 h⁻¹. -1 The space velocity ratio of methyl nitrite to CO was 1:1, and the space velocity ratio of N2 to CO was 4:1. The reaction temperature was controlled at 118–122 °C, and the reaction pressure was controlled at 0.2 MPa. The reaction lasted for 4 hours.
[0113] Finally, the products were analyzed using methods such as weighing and gas chromatography, and the catalytic performance was calculated, including catalyst space-time yield, conversion of methyl nitrite, and selectivity of dimethyl carbonate. Specific catalytic performance results are shown in Table 1.
[0114] The calculation method includes catalyst space-time yield: dimethyl carbonate content * product mass / catalyst volume * reaction time.
[0115] Conversion rate of methyl nitrite: the concentration ratio of methyl nitrite to nitrogen at the catalyst tail end / the concentration ratio of methyl nitrite to nitrogen at the catalyst front end.
[0116] Dimethyl carbonate selectivity was characterized by the dimethyl carbonate content in the product.
[0117] Table 1 Comparison of performance test results of catalysts prepared in Examples 1-11
[0118]
[0119] As shown in Table 2, the catalyst obtained by the technical solution of the present invention exhibits a conversion rate of methyl nitrite of 70-80%, a selectivity of 82-83% for dimethyl carbonate, and a space-time yield of 570-645 g / (Lcat.h) when catalyzing the synthesis of dimethyl carbonate. This indicates that the catalyst obtained by the technical solution of the present invention has good batch-to-batch stability under different conditions.
[0120] Experimental results show that the catalyst with added ethylenediamine exhibits better catalyst performance. This is because, during the preparation process, the addition of a complexing agent binds Pd ions and various transition metal cations in the solution together, effectively preventing the formation of corresponding hydroxide precipitates during stirring after the addition of the phosphating agent (diammonium hydrogen phosphate). This not only improves the uniform distribution of active components within the support but also increases the effective content of catalytically active components in the catalyst.
[0121] Furthermore, both the main active component and the co-active component in the catalyst are phosphides, which can enhance the interaction between Pd and transition metals and the alumina support. This results in extremely small palladium and transition metal particles with good dispersibility, which can greatly improve the catalytic performance of the catalyst.
[0122] The above are merely preferred embodiments of the present invention and do not limit the scope of protection of the present invention. For those skilled in the art, the present invention can have various modifications and variations. Any changes, modifications, substitutions, integrations, and parameter alterations to these embodiments within the spirit and principles of the present invention, achieved through conventional substitutions or by achieving the same function without departing from the principles and spirit of the present invention, fall within the scope of protection of the present invention.
Claims
1. A catalyst for the indirect gas-phase synthesis of dimethyl carbonate, comprising a main active component, a co-active component, and a catalyst support; The main active component includes Pd phosphide; The active component is a phosphide of the transition metal Cu; The main active component and the co-active component are loaded within the catalyst support; The catalyst support is γ-Al2O3; The catalyst is prepared by the following steps: dissolving Pd ions and transition metal Cu ions in water, adjusting the pH to acidic to obtain a precursor solution; adding ethylenediamine as a complexing agent to the precursor solution to carry out a complexation reaction to obtain a complex with a Pd-transition metal complex structure. A phosphating agent containing an aqueous solution of diammonium hydrogen phosphate is added to the complex to form a mixture of Pd phosphide and transition metal phosphide; the mixture is dropwise added to a catalyst support, impregnated, dried, and calcined to obtain the final product; wherein, the Pd ions in the main active component and the transition metal ions in the auxiliary active component are complexed by a complexing agent to form a Pd-transition metal complex structure, protecting the Pd ions and preventing them from precipitating during the material preparation process.
2. The catalyst for the indirect gas phase synthesis of dimethyl carbonate according to claim 1, characterized by that, The main active component includes one or more of Pd6P, Pd3P, Pd5P2, and PdP2.
3. The catalyst for the indirect gas-phase synthesis of dimethyl carbonate according to claim 1, characterized in that, The loading rate of the main active component is 0.1-2%.
4. The catalyst for the indirect gas phase synthesis of dimethyl carbonate according to claim 1, characterized by that, The loading rate of the co-active component is 0.01%-2%.
5. Catalyst for the synthesis of dimethyl carbonate by indirect gas phase synthesis according to any one of claims 1 to 4, characterized in that, The molar ratio of the complexing agent added to Pd in the supported catalyst is 1:
10.
6. The catalyst for the indirect gas phase synthesis of dimethyl carbonate according to claim 1, characterized by that, The specific surface area of the γ-Al₂O₃ support is 30-300 m². 2 / g, pore volume of 0.1-1.5m 2 / g, pore size is 3-20nm.
7. A method for preparing a catalyst for the indirect gas-phase synthesis of dimethyl carbonate as described in any one of claims 1-6, characterized in that, The specific steps include: S1. Dissolve Pd ions and transition metal Cu ions in water, adjust the pH to acidic, and obtain a precursor solution; S2. Ethylenediamine is added as a complexing agent to the precursor solution to carry out a complexation reaction, thereby obtaining a complex with a Pd-transition metal complex structure; S3. A phosphating agent containing an aqueous solution of diammonium hydrogen phosphate is added to the complex to form a mixture of Pd phosphide and transition metal phosphide; S4. The mixture is added dropwise to the catalyst support, impregnated, dried, and calcined to obtain the catalyst.
8. The use of a catalyst as described in any one of claims 1-6 in the synthesis of dimethyl carbonate.
9. A method for synthesizing dimethyl carbonate, comprising a methanol oxidative carbonylation gas-phase indirect synthesis method; firstly, methanol, O2, and NO are mixed and reacted to obtain methyl nitrite; the generated methyl nitrite is reacted with CO under the action of the catalyst described in any one of claims 1-6 in a low-pressure gas-phase reaction to generate dimethyl carbonate.
10. The method of synthesizing dimethyl carbonate according to claim 9, wherein, The low-pressure gas phase reaction includes using nitrogen as a diluent and mixing in a trace amount of HCl gas; The reaction conditions include a CO space velocity of 250–1000 h⁻¹. -1 The space velocity ratio of methyl nitrite to CO is 1:2 to 2:1, the space velocity ratio of N2 to CO is 2:1 to 8:1, and the amount of HCl mixed in is 50-500 ppm. The reaction temperature is controlled at 110~130℃, the reaction pressure is controlled at 0.2~1MPa, and the reaction time is 3~5h.