Synthesis of dimethyl carbonate catalyst, its preparation method and application

Abstract

The present application relates to a kind of synthetic dimethyl carbonate catalyst and its preparation method and application.The catalyst includes supported palladium metal active site and modified clay carrier.Modified clay carrier is prepared by acid treatment, base treatment and ion exchange mode with layered structure clay as matrix, and the stability of noble metal active site is improved by using transition metal ion introduced by clay modification.The catalyst has the characteristics of high catalytic activity and good stability in carbon monoxide and methyl nitrite gas-phase carbonylation reaction.

Description

Technical Field

[0001] This invention relates to a catalyst for the synthesis of dimethyl carbonate, its preparation method, and its application, belonging to the field of catalyst preparation technology. Background Technology

[0002] Dimethyl carbonate (DMC) is an important organic chemical intermediate. Due to the presence of carbonyl, methyl, methoxy, and carbonylmethoxy groups in its molecular structure, it can be widely used in organic synthesis reactions such as carbonylation, methylation, methoxylation, and carbonylmethylation, earning it the reputation as a "new cornerstone" of modern organic synthesis. Furthermore, DMC can be used to prepare electrolytes for lithium-ion batteries, playing a crucial role in the development of new energy vehicles.

[0003] Currently, there are many process technologies available for the production of dimethyl carbonate, such as the phosgene process, the methyl nitrite carbonylation process, and the urea alcoholysis process. Among these, the methyl nitrite carbonylation process, using methyl nitrite and carbon monoxide as raw materials, has received widespread attention. Highly active and stable catalysts are crucial for this technology. Currently, the catalysts used in industrialized technologies are palladium catalysts supported on activated carbon. These catalysts require additional chlorine to maintain stability, leading to problems such as equipment corrosion and the presence of chlorine impurities in the products. Developing highly active, chlorine-free catalysts is currently a hot research topic in academia and a focus of industrial attention.

[0004] Molecular sieve catalysts supported on palladium metal active sites are currently the best-performing class of carbonylation catalysts for methyl nitrite without chloride. Researchers at Ube Industries, Ltd. in Japan (Journal of the Chemical Society, Faraday Transactions, 1997, 93(2):3721-3727) reported the preparation of a methyl nitrite carbonylation catalyst without chloride chloride by impregnating NaY molecular sieves with supported palladium metal, but the space-time yield of dimethyl carbonate was only 180 g / (LCat.) -1 h -1 Patent CN110844918B discloses a method for improving catalyst activity by doping titanium and phosphorus into a Y-type molecular sieve support, but the activity of this catalyst is still lower than that of current chlorine-containing catalysts. Researchers at China University of Petroleum (Journal of Energy Chemistry, 2021, 52:191-201) reported the application of a palladium-supported chlorine-free catalyst using EMT molecular sieves in the carbonylation of methyl nitrite to dimethyl carbonate. This catalyst maintained stable activity for 130 hours, but its catalytic activity was still relatively limited. Based on their published conversion and selectivity estimates, the space-time yield of dimethyl carbonate is approximately 280 g / (LCat.). -1 h-1 Despite the extensive work done by numerous scientists and engineers in developing chlorine-free methyl nitrite carbonylation catalysts, the preparation of highly active chlorine-free catalysts remains a challenge. Summary of the Invention

[0005] The present invention aims to provide a catalyst for the synthesis of dimethyl carbonate and a method for its preparation. The catalyst is characterized by comprising a modified layered clay support and noble metal active sites, wherein the stability of the noble metal active sites is improved by introducing transition metal ions through clay modification.

[0006] According to one aspect of the present invention, a catalyst for synthesizing dimethyl carbonate is provided, the catalyst comprising a modified layered clay support and a palladium active component supported on the surface of the modified layered clay support.

[0007] In the catalyst, the mass ratio of the palladium active component to the modified layered clay support is 0.0005 to 0.02:1.

[0008] The mass of the palladium active component is expressed as the mass of palladium element.

[0009] According to another aspect of the present invention, a method for preparing the above-mentioned catalyst for synthesizing dimethyl carbonate is provided, comprising the following steps:

[0010] The modified layered clay support was added to an aqueous solution containing a palladium precursor and an alkali, impregnated, then centrifuged, washed with deionized water, and dried to obtain the catalyst for the synthesis of dimethyl carbonate.

[0011] The palladium precursor is selected from at least one of palladium nitrate, palladium chloride, ammonium chloropalladate, potassium chloropalladate, and tetraamminepalladium chloride.

[0012] The alkali is selected from at least one of ammonia, sodium hydroxide, and potassium hydroxide;

[0013] In the aqueous solution containing the palladium precursor and the base, the molar concentration of the palladium precursor is 0.65–1.75 mmol / L;

[0014] Optionally, in the aqueous solution containing the palladium precursor and the base, the molar concentration of the palladium precursor is any value or a range between 0.65 mmol / L, 0.75 mmol / L, 1 mmol / L, 1.25 mmol / L, 1.5 mmol / L and 1.75 mmol / L.

[0015] The liquid-to-solid ratio of the aqueous solution containing palladium precursor and alkali to the modified layered clay carrier is 10-200:1 mL / g.

[0016] Optionally, the liquid-to-solid ratio of the aqueous solution containing the palladium precursor and alkali to the modified layered clay carrier is any value or a range between 10:1 mL / g, 50:1 mL / g, 100:1 mL / g, 150:1 mL / g, and 00:1 mL / g.

[0017] The impregnation temperature is 20–80°C;

[0018] Optionally, the impregnation temperature is any value among 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, and 80°C, or a range between any two.

[0019] The soaking time is 1 to 30 hours;

[0020] Optionally, the immersion time is any value among 1h, 5h, 10h, 15h, 20h, 25h and 30h or a range between any two.

[0021] The drying temperature is 80–250°C;

[0022] Optionally, the drying temperature is any value among 80°C, 100°C, 150°C, 200°C, and 250°C, or a range between any two.

[0023] The drying time is 1 to 30 hours;

[0024] Optionally, the drying time is any value among 1h, 5h, 10h, 15h, 20h, 25h, and 30h, or a range between any two.

[0025] The aqueous solution containing the palladium precursor and the base has a pH of 8 to 10.

[0026] Optionally, the pH of the aqueous solution containing the palladium precursor and the base is any value among 8, 9, and 10, or a range between any two.

[0027] The modified layered clay carrier is obtained through the following steps:

[0028] Acid-base modified clay is mixed with an aqueous solution containing transition metal ions, subjected to ion exchange, then centrifuged, washed with deionized water, dried, and calcined to obtain the modified layered clay carrier.

[0029] The aqueous solution containing transition metal ions is selected from zinc nitrate aqueous solution and / or zinc chloride aqueous solution;

[0030] In the aqueous solution containing transition metal ions, the molar concentration of the transition metal ions is 0.1–0.5 mol / L;

[0031] Optionally, in the aqueous solution containing transition metal ions, the molar concentration of the transition metal ions is DD220843I-DL

[0032] The concentration can be any value among 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, and 0.5 mol / L, or any range between two of them.

[0033] The temperature for ion exchange is 50–95°C;

[0034] Optionally, the temperature of the ion exchange is any value among 50°C, 60°C, 70°C, 80°C, 90°C, and 95°C, or a range between any two.

[0035] The ion exchange time is 1–8 hours;

[0036] Optionally, the ion exchange time is any value among 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, and 10h, or a range between any two.

[0037] The liquid-to-solid ratio of the aqueous solution containing transition metal ions to the acid-base modified clay is 5–100:1 mL / g.

[0038] Optionally, the liquid-solid ratio of the aqueous solution containing transition metal ions to the acid-base modified clay is any value among 5:1 mL / g, 10:1 mL / g, 50:1 mL / g, and 100:1 mL / g, or any range between two of them.

[0039] The temperature of the drying process I is 100–240°C;

[0040] Optionally, the temperature of the drying I is any value or a range between 100℃, 120℃, 140℃, 160℃, 180℃, 200℃, 220℃, and 240℃.

[0041] The drying time for step I is 1–30 hours;

[0042] Optionally, the drying time I is any value among 1h, 5h, 10h, 15h, 20h, 25h, and 30h, or a range between any two.

[0043] The calcination temperature is 400–600°C;

[0044] Optionally, the roasting temperature is any value among 400°C, 500°C, and 600°C, or a range between any two.

[0045] The roasting time is 1 to 30 hours.

[0046] Optionally, the roasting time is any value among 1h, 5h, 10h, 15h, 20h, 25h, and 30h, or a range between any two.

[0047] The acid-base modified clay is obtained through the following steps:

[0048] a: The layered clay was mixed with an acidic solution, stirred, then centrifuged, washed with deionized water, and dried to obtain acid-modified clay.

[0049] b: The acid-modified clay obtained in step a is mixed with an alkaline solution, treated in an autoclave, then centrifuged, washed with deionized water, and dried to obtain the acid-base modified clay.

[0050] The layered clay is selected from concave clay and / or sepiolite;

[0051] The acidic solution is selected from at least one of sulfuric acid solution, hydrochloric acid solution, nitric acid solution, and phosphoric acid solution;

[0052] The concentration of the acidic solution is 0.1–3 mol / L;

[0053] Optionally, the concentration of the acidic solution is any value or a range between 0.1 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L and 3 mol / L.

[0054] The temperature for the stirring process is 20–80°C;

[0055] Optionally, the temperature of the stirring treatment is any value among 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, and 80°C, or a range between any two.

[0056] The stirring process takes 1 to 8 hours.

[0057] Optionally, the stirring time is any value among 1h, 2h, 3h, 4h, 5h, 6h, 7h and 8h or a range between any two.

[0058] The liquid-to-solid ratio of the acidic solution to the layered structure is 5-100:1 mL / g;

[0059] Optionally, the liquid-to-solid ratio of the acidic solution to the layered structure is any value among 5:1 mL / g, 10:1 mL / g, 50:1 mL / g, and 100:1 mL / g, or any range between two of them.

[0060] The temperature of the drying II process is 120–200°C;

[0061] Optionally, the temperature of the drying II is any value or a range between 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C and 200°C.

[0062] The drying time for step II is 1–30 hours;

[0063] Optionally, the drying time II is any value among 1h, 5h, 10h, 15h, 20h, 25h, and 30h, or a range between any two.

[0064] The alkaline solution is selected from at least one of sodium hydroxide solution, lithium hydroxide solution, and potassium hydroxide solution;

[0065] The concentration of the alkaline solution is 0.2–2 mol / L;

[0066] Optionally, the concentration of the alkaline solution is any value among 0.2 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L, and 2 mol / L, or a range between any two.

[0067] The temperature in the autoclave is 120–200°C;

[0068] Optionally, the temperature processed in the autoclave is any value or a range between 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C and 200°C.

[0069] The processing time in the autoclave is 1 to 8 hours;

[0070] Optionally, the treatment time in the autoclave is any value among 1h, 2h, 3h, 4h, 5h, 6h, 7h, and 8h, or a range between any two.

[0071] In step b, the liquid-to-solid ratio of the alkaline solution to the acid-modified clay is 5-100:1 mL / g.

[0072] Optionally, the liquid-solid ratio of the alkaline solution to the acid-modified clay in step b is any value among 5:1 mL / g, 10:1 mL / g, 50:1 mL / g, and 100:1 mL / g, or any range between the two.

[0073] The temperature of the drying III process is 120–200°C;

[0074] Optionally, the temperature of the drying III is any value or a range between 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C and 200°C.

[0075] The drying time for the third stage is 1 to 30 hours.

[0076] Optionally, any value from 1h, 5h, 10h, 15h, 20h, 25h, 30h, or a range between any two.

[0077] The preparation process of the catalyst includes the following steps:

[0078] a) Add the palladium precursor to water or alcohol, stir thoroughly to dissolve, and add an alkaline solution to adjust the pH to 8-10 to prepare a palladium-supported precursor solution.

[0079] b) The modified layered clay support was added to the palladium-supported precursor solution, stirred and impregnated, then washed with deionized water, centrifuged, and dried to prepare a catalyst for the synthesis of dimethyl carbonate.

[0080] The preparation process of the modified layered clay carrier includes the following steps:

[0081] a) Add layered clay to an acid solution, stir and acid-treat for 1-8 hours, then wash with deionized water and centrifuge to obtain acid-modified clay.

[0082] b) Add the acid-modified clay obtained in step a) to an alkaline solution, treat with alkali in an autoclave for 1-8 hours, wash with deionized water, and centrifuge to obtain acid-alkali modified clay.

[0083] c) The acid-base modified clay obtained in step b) is added to a solution containing transition metal ions for ion exchange for 1 to 8 hours, then washed with deionized water, centrifuged, dried, and calcined at 400 to 600°C to obtain a modified layered clay carrier.

[0084] According to another aspect of the present invention, a method for synthesizing dimethyl carbonate is provided, comprising the following steps:

[0085] The material containing carbon monoxide and methyl nitrite is contacted with a catalyst and reacted to obtain a product containing dimethyl carbonate.

[0086] The catalyst is selected from the above-mentioned supported noble metal catalysts or the supported noble metal catalysts prepared by the above-mentioned preparation method.

[0087] The feed volume hourly space velocity of the material is 200–10000 h⁻¹. -1 ;

[0088] Optionally, the feed volume hourly space velocity of the material is 200 h⁻¹. -1 500h -1 1000h -1 2000h-1 3000h -1 4000h -1 5000h -1 6000h -1 7000h -1 8000h -1 9000h -1 and 10000h -1 Any value in the range or any value between the two.

[0089] The reaction temperature is 90–150°C;

[0090] Optionally, the temperature of the reaction is any value or a range between 90°C, 100°C, 110°C, 120°C, 130°C, 140°C and 150°C.

[0091] The reaction pressure is 0.1–1 MPa.

[0092] Optionally, the pressure of the reaction is any value among 0.1 MPa, 0.5 MPa, and 1 MPa, or a range between any two.

[0093] The advantages of this invention are:

[0094] The catalyst uses a modified layered clay support, which is suitable for stabilizing palladium metal activity.

[0095] The catalyst exhibits high catalytic activity and good stability in the gas-phase carbonylation reaction of carbon monoxide and methyl nitrite. Detailed Implementation

[0096] The present invention will now be described in detail with reference to the embodiments, but the present invention is not limited to these embodiments.

[0097] Unless otherwise specified, all raw materials used in the embodiments of this invention were purchased commercially.

[0098] In the examples, the elemental composition of the catalyst was determined using an Axios 2.4KW X-ray fluorescence analyzer (XRF) from PANAbalytical, and the catalyst loading was calculated based on its elemental composition.

[0099] In this embodiment, the analysis method and the calculation of conversion rate and selectivity are as follows:

[0100] The products were analyzed online using an Agilent 7890A chromatograph. Methyl nitrite, dimethyl carbonate (DMC), dimethyl oxalate (DMO), methyl formate (MF), methyl acetal (DMM), and methanol (MeOH) were analyzed using a flame ionization detector (FID), while carbon monoxide, carbon dioxide, and nitrogen were analyzed using a thermal conductivity detector (TCD).

[0101] Using carbon monoxide conversion rate X CO Selectivity of dimethyl carbonate based on carbon monoxide DMC / CO space-time yield of dimethyl carbonate (STY(gDMC·Lcat)) -1 ·h -1 The activity of the catalyst is evaluated using indicators such as [list of indicators]. The calculation methods for each indicator are as follows:

[0102]

[0103]

[0104] STY = X CO ×S DMC / CO ×[CO] in ×M DMC

[0105] [CO] in and [MN] in [CO] and [MN] represent the molar flow rates (mol / h) of CO and MN at the reactor inlet, respectively; out [MN] out [DMC] out [DMO] out and [CO2] out These represent the molar flow rates (mol / h) of CO, MN, DMC, DMO, and CO2 at the reactor outlet, respectively; M DMC This represents the molar mass of DMC.

[0106] Example 1: Preparation of Catalyst Support

[0107] 1) Acid-modified clay

[0108] Layered clay was added to an acid solution and subjected to acid treatment with magnetic stirring at 300 r / min. The clay was then washed with deionized water, centrifuged, and dried at 200℃ to obtain acid-treated clay samples A-1 to A-8. Table 1 shows the type of layered clay used, the type and concentration of the acid solution, the liquid-to-solid ratio, the treatment temperature, and the treatment time for each acid-modified sample.

[0109] Table 1 Treatment conditions for acid-modified clay samples A-1 to A-8

[0110]

[0111]

[0112] 2) Acid-base modified clay

[0113] Acid-modified clay samples (one of A-1 to A-8) were added to an alkaline solution, stirred and mixed thoroughly, and then transferred to an autoclave for alkaline treatment in a dynamic oven. After treatment, the samples were washed with deionized water, centrifuged, and dried at 200℃ to obtain acid- and alkali-modified clay samples B-1 to B-8. The types of parent materials used, types and concentrations of alkaline solutions, liquid-to-solid ratios, treatment temperatures, and treatment times for each acid- and alkali-modified sample are shown in Table 2.

[0114] Table 2 Treatment conditions for acid-base modified clay samples B-1 to B-8

[0115]

[0116] 3) Modified layered clay carrier

[0117] Acid-base modified clay sample (one of B-1 to B-8) was added to the ion exchange precursor solution, and ion exchange was performed under magnetic stirring at 300 r / min. The sample was then washed with deionized water, centrifuged, dried at 200℃, and calcined to obtain the modified clay. Layered structure Clay carrier samples Z-1 to Z-8. Various modifications. Layered structure The types of parent materials used in the clay carrier samples, the types and concentrations of ion exchange precursors, the liquid-to-solid ratio, the exchange temperature, the exchange time, and the calcination temperature are shown in Table 3.

[0118] Table 3 Modification Layered structure Ion exchange treatment conditions for clay carrier samples Z-1 to Z-8

[0119]

[0120] Example 2: Preparation of catalyst for the synthesis of dimethyl carbonate

[0121] Add the palladium precursor to deionized water, stir thoroughly to dissolve, and add alkaline solution dropwise to adjust the pH to the range of 8-10 to prepare a palladium-supported precursor solution.

[0122] Two g of the modified layered clay support (one of Z-1 to Z-8) prepared in Example 1 was added to the above palladium-supported precursor solution. The solution was impregnated for 8 hours under magnetic stirring at 300 r / min, then washed with deionized water, centrifuged, and dried at 200 °C to prepare supported dimethyl carbonate synthesis catalysts C-1 to C-10. The support used in the preparation of the above dimethyl carbonate synthesis catalysts, the type and concentration of palladium precursors, the pH value of the palladium precursor solution and the pH adjustment solution, the impregnation liquid-to-solid ratio, the impregnation temperature, and the palladium mass loading are shown in Table 4.

[0123] Table 4. Preparation conditions of catalysts C-1 to C-10 for the synthesis of dimethyl carbonate.

[0124]

[0125] Example 3 Evaluation of the carbonylation reaction of methyl nitrite

[0126] The performance of catalysts C-1 to C-10 prepared in Example 2 for the carbonylation of methyl nitrite was evaluated using a fixed-bed reactor with an inner diameter of 8 mm and a catalyst loading of 2 mL. The reaction used carbon monoxide (CO) and methyl nitrite (MN) as feedstocks, with nitrogen (N2) as dilution gas. The feed rate was accurately controlled using a mass flow controller. The volume ratio of carbon monoxide, methyl nitrite, and nitrogen in the feed was 8:20:72. The reaction conditions and catalytic activity of catalysts C-1 to C-10 for the gas-phase carbonylation of methyl nitrite to dimethyl carbonate are shown in Table 3.

[0127] Table 3. Catalytic conditions and activity of catalysts C-1 to C-10 for the carbonylation of methyl nitrite. a

[0128]

[0129]

[0130] The reaction was sampled and analyzed every 1 hour, and the above reaction results are the average value over 50 hours.

[0131] b. Calculation formula: [(dimethyl carbonate space-time yield after 1 hour of reaction) - (dimethyl carbonate space-time yield after 50 hours of reaction)] × 100% / (dimethyl carbonate space-time yield after 1 hour of reaction).

[0132] The above description is merely a few embodiments of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any modifications or alterations made by those skilled in the art without departing from the scope of the technical solution of the present invention using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A catalyst for synthesizing dimethyl carbonate, characterized in that, The catalyst comprises a modified layered clay support and a palladium active component supported on the surface of the modified layered clay support. In the catalyst, the mass ratio of the palladium active component to the modified layered clay support is 0.0005~0.02:1; The mass of the palladium active component is expressed as the mass of palladium element; The modified layered clay carrier is obtained by the following preparation method: Acid-base modified clay is mixed with an aqueous solution containing transition metal ions, subjected to ion exchange, then centrifuged, washed with deionized water, dried, and calcined to obtain the modified layered clay carrier. The aqueous solution containing transition metal ions is selected from zinc nitrate aqueous solution and / or zinc chloride aqueous solution; The layered clay is selected from attapulgite and / or sepiolite; The acid-base modified clay is obtained by the following preparation method: a: The layered clay was mixed with an acidic solution, stirred, then centrifuged, washed with deionized water, and dried to obtain acid-modified clay. b: The acid-modified clay obtained in a is mixed with an alkaline solution, treated in an autoclave, dried (III), then centrifuged and washed with deionized water to obtain the acid-base modified clay; The temperature in the autoclave is 120~200 ℃; The processing time in the autoclave is 1 to 8 hours.

2. A method for preparing the catalyst for synthesizing dimethyl carbonate according to claim 1, characterized in that, Includes the following steps: The modified layered clay support was impregnated in an aqueous solution containing a palladium precursor and an alkali, and then dried to obtain the catalyst for the synthesis of dimethyl carbonate.

3. The preparation method according to claim 2, characterized in that, The palladium precursor is selected from at least one of palladium nitrate, palladium chloride, ammonium chloropalladate, potassium chloropalladate, and tetraamminepalladium chloride. The alkali is selected from at least one of ammonia, sodium hydroxide, and potassium hydroxide; In the aqueous solution containing the palladium precursor and the base, the molar concentration of the palladium precursor is 0.65~1.75 mmol / L; The liquid-to-solid ratio of the aqueous solution containing palladium precursor and alkali to the modified layered clay carrier is 10~200:1mL / g. The impregnation temperature is 20~80℃; The soaking time is 1~30 h; The drying temperature is 80~250℃; The drying time is 1~30 h; The aqueous solution containing the palladium precursor and the base has a pH of 8 to 10.

4. The preparation method according to claim 2, characterized in that, The aqueous solution containing transition metal ions has a molar concentration of 0.1~0.5 mol / L. The ion exchange temperature is 50~95℃; The ion exchange time is 1-8 h; The liquid-to-solid ratio of the aqueous solution containing transition metal ions to the acid-base modified clay is 5~100:1 mL / g; The temperature of the drying process I is 100~240℃; The drying time for step I is 1~30 h; The calcination temperature is 400~600 ℃; The roasting time is 1 to 30 hours.

5. The preparation method according to claim 2, characterized in that, The acid-base modified clay is obtained by the following preparation method: a: The layered clay was mixed with an acidic solution, stirred, then centrifuged, washed with deionized water, and dried to obtain acid-modified clay. b: The acid-modified clay obtained in a is mixed with an alkaline solution, treated in an autoclave, dried (III), then centrifuged and washed with deionized water to obtain the acid-base modified clay.

6. The preparation method according to claim 5, characterized in that, The acidic solution is selected from at least one of sulfuric acid solution, hydrochloric acid solution, nitric acid solution, and phosphoric acid solution; The molar concentration of the acidic solution is 0.1~3 mol / L; The temperature of the stirring process is 20~80℃; The stirring process takes 1 to 8 hours. The liquid-to-solid ratio of the acidic solution to the layered clay is 5~100: 1 mL / g; The temperature of the drying process II is 120~200 ℃; The drying time for step II is 1~30 h; The alkaline solution is selected from at least one of sodium hydroxide solution, lithium hydroxide solution, and potassium hydroxide solution; The molar concentration of the alkaline solution is 0.2~2 mol / L; In step b, the liquid-to-solid ratio of the alkaline solution to the acid-modified clay is 5~100: 1 mL / g; The temperature of the drying process III is 120~200 ℃; The drying time for the third stage is 1 to 30 hours.

7. A method for synthesizing dimethyl carbonate, characterized in that, Includes the following steps: Materials containing carbon monoxide and methyl nitrite are contacted with a catalyst and reacted to obtain a product containing dimethyl carbonate. The catalyst is selected from the supported noble metal catalyst of claim 1 or the supported noble metal catalyst prepared by the preparation method of any one of claims 2 to 6.

8. The method according to claim 7, characterized in that, The feed volume hourly space velocity of the material is 200–10000 h⁻¹. -1 ; The reaction temperature is 90~150 ℃; The reaction pressure is 0.1~1 MPa.

Images