Decarboxylation to carbonate catalyst and carbonate production process

Abstract

The present application relates to a kind of decarboxylation carbonates catalyst and carbonate production process.The present application provides decarboxylation carbonates catalyst, which is supported catalyst, including active assistant modified carrier component, and alkali metal carbonate supported on carrier, and the active assistant is halogen element and / or halogen compound.The present application also provides the method for producing carbonate using the above method for producing carbonate.The decarboxylation carbonates catalyst provided by the present application is higher than prior art catalyst for oxalate decarboxylation reaction selectivity and conversion rate, and has good stability, long service life, can be used for fixed bed reactor continuous production carbonate, and is convenient for industrialization.

Description

Technical Field

[0001] This invention belongs to the field of chemical engineering, specifically relating to a decarbonylation catalyst for carbonate production and a carbonate production process. Background Technology

[0002] Carbonates, especially dimethyl carbonate, have attracted widespread attention both domestically and internationally in recent years as excellent solvents. The mainstream production methods include the phosgene process, transesterification, and methanol oxidative carbonylation. These methods use or generate large amounts of ethylene glycol, methanol, water, and other substances during the synthesis of dimethyl carbonate, making the preparation process relatively complex. In contrast, the preparation of dimethyl carbonate using dimethyl oxalate is a simple process, produces a high dimethyl carbonate content and few impurities in the product, and is easy to separate and purify, making it a superior method for carbonate synthesis. The reaction is as follows:

[0003]

[0004] Oxalate decarbonylation yields carbonates and carbon monoxide, and the reaction can occur in two forms: liquid-phase decarbonylation and gas-phase decarbonylation. Liquid-phase decarbonylation uses a batch reactor with a powdered catalyst dispersed in the oxalate ester, as described in CN1131818941A, which uses lithium silicate as the catalyst. In this process, oxalate undergoes liquid-phase decarbonylation to produce carbonates in the reactor. However, liquid-phase decarbonylation is a batch reaction, which suffers from long reaction times and difficulties in separating the catalyst from the product, making it unsuitable for continuous industrial production. Gas-phase decarbonylation typically employs a fixed-bed reactor, where oxalate esters enter the catalyst bed in gaseous form. For example, patent CN1221732A uses a solid base catalyst with activated carbon supporting a single alkali metal compound. Oxalate esters enter the reactor as a gas mixture (carried by an inert gas or evaporated from a solution). However, gas-phase decarbonylation, especially with pure oxalate feed, suffers from excessively high reaction temperatures, requiring temperatures above 200°C for complete conversion. Furthermore, using an inert gas or solvent to carry the oxalate leads to separation issues between the subsequent gas and liquid phase products, hindering industrial application. Zhang Haoyang, in his research on the decarbonylation of dimethyl oxalate to dimethyl carbonate, discovered that carbon-supported solid base catalysts are prone to deactivation. Patent CN202110781605 utilizes a Na2SiO3 catalyst to improve stability, but the catalyst's DMC selectivity drops significantly to 65%, indicating poor selectivity. This explains the lack of industrial application reports for this method. Therefore, it is necessary to develop a decarbonylation catalyst for oxalate that is suitable for industrial applications, exhibiting high activity, high selectivity, and long lifespan. Summary of the Invention

[0005] The purpose of this invention is to provide a decarbonylation catalyst for carbonate production, addressing the shortcomings of existing technologies, and to provide a carbonate production process. This catalyst features high activity, good stability, and long lifespan, exhibiting high selectivity and conversion rate in the decarbonylation reaction of oxalate, along with good stability and a long lifespan.

[0006] To achieve the above-mentioned objectives, the technical solution adopted by the present invention is as follows:

[0007] An oxalate decarbonylation catalyst for carbonate production is a supported catalyst comprising an active agent-modified support component and an alkali metal carbonate supported on the support, wherein the active agent is a halogen element and / or a halogen-containing compound.

[0008] The loading of the alkali metal carbonate is 1% to 20%, and the loading of the active auxiliaries is 0.1% to 10%.

[0009] Furthermore, the alkali metal carbonate is one or more of potassium carbonate, sodium carbonate, rubidium carbonate, and cesium carbonate.

[0010] Furthermore, the active agent is elemental fluorine and / or fluorine-containing compounds, elemental chlorine and / or chlorine-containing compounds, elemental bromine and / or bromine-containing compounds, elemental iodine and / or iodine-containing compounds; specifically, the active agent may be I2, as well as halogen-containing compounds such as CH3I, CBr4, NH4Br, KBr, KI, NaI, LiI, CsBr, FeI2, etc.

[0011] Furthermore, the carrier is activated carbon.

[0012] Furthermore, the carrier is selected from materials with a surface area of ​​400m². 2 / g~1200m 2 / g of activated carbon.

[0013] A method for preparing the above-mentioned catalyst for the decarbonylation of oxalate to carbonate is provided, comprising the following steps:

[0014] Step S1: Process the carrier;

[0015] Step S2: Carrier modification treatment: The carrier is modified by passing the active additive through solution or gas phase, then dried and calcined at high temperature to obtain the active additive modified carrier;

[0016] Step S3: Alkali metal carbonate loading. The alkali metal carbonate solution is poured into the active additive modified support by impregnation method. After the solution is completely absorbed, it is dried to obtain the catalyst for oxalate decarbonylation.

[0017] Further, in step S1: the activated carbon carrier is first soaked in a 0.1%–5% HCl or HNO3 solution for 0.5–12 hours, then washed with deionized water until neutral, then soaked in a 0.1%–5% alkaline solution for 0.5–12 hours, then washed with deionized water until neutral, and finally dried at 100°C–150°C for 2–4 hours; the alkali used can be selected from one or a mixture of more than one of NaOH, Na2CO3, KOH, K2CO3, and ammonia water.

[0018] Further, in step S2, the active additive modifies the carrier through solution or gas phase. The solution method involves immersing the treated carrier in a solution containing the active additive (halogen content 3-30%) for 2-4 hours, then air-drying and drying at 100-150°C for 1-5 hours; followed by calcination at 200-500°C for 2-5 hours. The gas phase method involves passing volatile halogens and / or halogen-containing compounds, such as organic halogen compounds, through an activated carbon carrier using hot nitrogen gas. The carrier after adsorbing the active additive is then calcined at 200-500°C for 2-5 hours.

[0019] Furthermore, in step S3, the mass concentration of the alkali metal carbonate solution is 5% to 30%. The modified support is impregnated with the solution, and after impregnation, it is air-dried for 2 to 12 hours and then dried at 100 to 150°C for 2 to 5 hours to obtain the desired catalyst.

[0020] According to the above scheme, under the condition that no precipitation occurs when the active additive is mixed with the alkali metal carbonate, the carrier can be improved by the active additive through solution: steps S2 and S3 can be combined, that is, the active additive and the alkali metal carbonate are mixed into a solution, the carrier is impregnated with the solution, and after impregnation, it is dried and then calcined to obtain the active additive modified carrier.

[0021] A process for producing carbonate by decarbonylation of oxalate is provided, wherein oxalate undergoes a gas-phase decarbonylation reaction under the catalysis of the above-mentioned catalyst to obtain crude carbonate.

[0022] According to the above scheme, after the oxalate is gasified in the gasification tower, it is carried into the decarbonylation reactor by the circulating gas. The decarbonylation reaction product is cooled and separated into liquid phase components, and carbonate is collected. The corresponding carbonate is used to absorb impurities in the circulating gas to purify the gas phase components. The purified gas phase components are then recycled back to the gasification tower to carry the oxalate.

[0023] According to the above scheme, the oxalate ester can specifically be dimethyl oxalate or diethyl oxalate.

[0024] According to the above scheme, the system can be kept running stably by adding fresh carbon monoxide, hydrogen or inert gas to the gas phase components.

[0025] According to the above scheme, when the circulating compressor fails, carbon monoxide or hydrogen can be used to carry oxalate through the catalyst bed in one go under compressor-free conditions.

[0026] According to the above scheme, the temperature for the decarbonylation reaction is 120℃~250℃.

[0027] Furthermore, the decarbonylation reactor is selected from fixed-bed reactors; the bed reaction temperature of the decarbonylation reactor is 170–200℃, the reaction pressure is 0.0–3 MPaG, and the liquid hourly space velocity of the dimethyl oxalate feed is 0.01–2 h⁻¹. -1 .

[0028] During the research process of this invention, the applicant discovered that the decarbonylation reaction of oxalate esters also involves the formation of other organic compounds such as alcohols and ethers. These reactions reduce the selectivity of the catalyst. Through research, the applicant found that treating the support with halogens and / or halogen-containing compounds can suppress side reactions during the decarbonylation of oxalate esters, improve the catalyst's activity and selectivity, and extend its lifespan. Compared with existing catalysts, the decarbonylation catalyst provided by this invention exhibits high selectivity and conversion rate, good stability, and long lifespan for the decarbonylation reaction of oxalate esters. It can be used in fixed-bed reactors for continuous production of carbonates, facilitating industrialization.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] (1) By using halogens or halides as active additives to modify activated carbon supports, the activity and stability of the catalyst are improved, and it has good selectivity.

[0031] (2) The catalyst also exhibits excellent decarbonylation activity of oxalate under a carbon monoxide atmosphere. Therefore, the carbon monoxide generated in the reaction can be used as the carrier gas for oxalate, avoiding the introduction of new impurities when using inert gases or solvents to carry oxalate. Using the carbon monoxide generated in the reaction as a circulating gas to carry oxalate into the reactor can reduce gas consumption and is more environmentally friendly.

[0032] (3) The reaction process provided by the present invention has a bed reaction temperature between 170 and 200°C and a required steam pressure of less than 1.5 MPa. It can use a low-pressure fixed bed reactor, and overcomes the disadvantage of batch reaction of the batch reactor. It can be continuously produced and is easy to realize industrialization.

[0033] (4) In the reaction process provided by the present invention, the gas phase components are washed and purified by the carbonate product generated by the reaction, which can avoid the introduction of new impurities into the system.

[0034] (5) By adding fresh carbon monoxide or H2, the proportion of circulating gas components can be adjusted to maintain stable system operation.

[0035] (6) In the reaction process provided by the present invention, when the circulating compressor fails, the catalyst bed can be continuously produced by adding carbon monoxide to carry oxalate through in one go under the condition of no compressor, so as to avoid production shutdown.

[0036] (7) The reaction process provided by this invention can be adapted to subsequent processes by changing the type of fresh gas (such as hydrogen, methane, etc.) added to the system, depending on the intended use of the purge gas. For example, if the purge gas is used for methanol synthesis, fresh hydrogen can be added to the system instead of carbon monoxide; if it is used for carbonyl synthesis, carbon monoxide is added. Attached Figure Description

[0037] Figure 1 This is a flow chart of the oxalate decarbonylation reaction. In the chart: 1. Oxalate vaporizer; 2. Reactor inlet heater; 3. Decarbonylation reactor; 4. Circulating gas heater; 5. Circulating gas cooler; 6. Circulating compressor; 7. Gas-liquid separator; 8. Circulating gas scrubbing tower. Detailed Implementation

[0038] In view of the deficiencies of the prior art, the inventors of this case, through long-term research and extensive practice, have proposed the technical solution of this invention. The technical solution of this invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0039] Catalyst preparation:

[0040] Example 1

[0041] With a specific surface area of ​​1000m 2 A g of activated carbon support was soaked in 1% (wt / wt) hydrochloric acid for 2 hours, washed with deionized water until pH neutral, and then soaked in 0.5% (wt / wt) sodium hydroxide for 2 hours. It was then washed with deionized water until neutral and dried at 120℃ for 1 hour to obtain a treated activated carbon support. The treated support was then mixed with 0.1% (by weight) of powdered iodine and placed in a sealed container. The container was heated to 130℃ to allow the iodine to sublimate and be adsorbed by the support, and this temperature was maintained for 3 hours. The container was then calcined in a muffle furnace at 250℃ for 2 hours to obtain a modified support. The modified support was impregnated with 15% K₂CO₃ solution, air-dried for 12 hours, and then dried at 130℃ for 4 hours to obtain a catalyst containing 8% K₂CO₃. This was designated as sample number 1.

[0042] Example 2

[0043] With a specific surface area of ​​500m 2A g of activated carbon support was soaked in 1.0% (wt / wt) nitric acid for 12 h, washed with deionized water until pH neutral, and then soaked in 1% (wt / wt) potassium hydroxide for 12 h. It was then washed with deionized water until neutral and dried at 120℃ for 2 h to obtain a treated activated carbon support. 2% (by weight) of CBr4 was vaporized and passed through the treated support using nitrogen gas. After adsorption, the support was calcined in a muffle furnace at 400℃ for 2 h to obtain a modified support. The modified support was impregnated with 15% Cs₂CO₃ solution, air-dried for 12 h, and then dried at 120℃ for 2 h to obtain a catalyst containing 8% Cs₂CO₃. This was designated as sample number 2.

[0044] Example 3

[0045] With a specific surface area of ​​600 m² 2 A g of activated carbon support was soaked in 1.5% (wt / wt) nitric acid for 2 h, washed with deionized water until pH neutral, and then soaked in 1% (wt / wt) ammonia water for 12 h. The activated carbon support was then washed with deionized water until neutral and dried at 110℃ for 2 h to obtain the treated activated carbon support. The treated support was impregnated with 3% NaI solution and dried at 150℃ for 3 h to obtain a modified support with a loading of 5%. The dried support was then calcined in a muffle furnace at 300℃ for 2 h to obtain the modified support. The modified support was impregnated with 15% Cs2CO3 solution, air-dried for 8 h, and then dried at 120℃ for 4 h to obtain a catalyst containing 10% Cs2CO3. This was designated as sample number 3.

[0046] Example 4

[0047] With a specific surface area of ​​1200 m² 2 A g of activated carbon support was soaked in 1.0% (wt / wt) nitric acid for 1 h, washed with deionized water until pH neutral, and then soaked in 1% (wt / wt) soda ash for 12 h. The activated carbon support was then washed with deionized water until neutral and dried at 140℃ for 2 h to obtain the treated activated carbon support. The support treated with 5% CsI solution was impregnated and dried at 150℃ for 3 h. The dried support was then calcined in a muffle furnace at 300℃ for 2 h to obtain a modified support with a loading of 6%. The modified support was impregnated with 15% Cs2CO3 solution, air-dried for 12 h, and then dried at 120℃ for 5 h to obtain a catalyst containing 8% Cs2CO3. This was designated as sample number 4.

[0048] Example 5

[0049] With a specific surface area of ​​800 m² 2A g of activated carbon support was soaked in 1.0% (wt / wt) nitric acid for 1 h, washed with deionized water until pH neutral, then soaked in 0.5% (wt / wt) potassium hydroxide for 3 h, washed again with deionized water until neutral, and dried at 110℃ for 4 h to obtain the treated activated carbon support. The treated support was impregnated with 10% LiBr solution, dried at 150℃ for 3 h, and then calcined in a muffle furnace at 300℃ for 2 h to obtain a modified support with a loading of 6%. The modified support was impregnated with 18% Na2CO3 solution, air-dried for 12 h, and then dried at 120℃ for 5 h to obtain a catalyst containing 12% Na2CO3. This was designated as sample number 5.

[0050] Example 6

[0051] With a specific surface area of ​​800 m² 2 A g of activated carbon support was soaked in 1.5% (wt / wt) hydrochloric acid for 4 hours, washed with deionized water until the pH was adjusted, and then soaked in 1% (wt / wt) sodium hydroxide for 4 hours. The activated carbon support was then washed with deionized water until neutral and dried at 150℃ for 1 hour to obtain the treated activated carbon support. The treated support was impregnated with 5% NH4I solution and dried at 100℃ for 5 hours. The container was then calcined in a muffle furnace at 300℃ for 2 hours to obtain a modified support with a loading of 5%. The modified support was impregnated with 18% K2CO3 solution, air-dried for 8 hours, and then dried at 120℃ for 4 hours to obtain a catalyst containing 10% K2CO3. This was designated as sample number 6.

[0052] Example 7

[0053] The support modification treatment was the same as in Example 6. The modified support was impregnated with a 10% Rb2CO3 solution, air-dried for 8 hours, dried at 120°C for 2 hours, and calcined at 250°C for 2 hours to obtain a catalyst containing 5% Rb2CO3. This was designated as sample number 7.

[0054] Example 8

[0055] With a specific surface area of ​​1000m 2 A g of activated carbon support was soaked in 1.0% (wt / wt) nitric acid for 12 h, washed with deionized water until pH neutral, and then soaked in 1% (wt / wt) KOH for 12 h. The activated carbon support was then washed with deionized water until neutral and dried at 140℃ for 3 h to obtain the treated activated carbon support. The treated support was impregnated with 10% KI solution and dried at 150℃ for 3 h. The dried support was then calcined in a muffle furnace at 400℃ for 2 h to obtain a modified support with a loading of 5%. The modified support was impregnated with 15% Rb₂CO₃ solution, air-dried for 12 h, and then dried at 120℃ for 5 h to obtain a catalyst containing 8% Rb₂CO₃. This was designated as sample number 8.

[0056] Comparative Example 1

[0057] The support was treated the same as in Example 6, but without the addition of NH4I. The acid-base treated support was directly impregnated with 18% K2CO3 solution, air-dried for 8 hours, and then dried at 120°C for 4 hours to obtain a catalyst containing 10% K2CO3. This was designated as Comparative Sample 1.

[0058] Comparative Example 2

[0059] The support was treated the same as in Example 4, but without CsI treatment. The acid-base treated support was directly impregnated with a 15% Cs₂CO₃ solution, air-dried for 12 hours, and then dried at 120°C for 5 hours to obtain a catalyst containing 8% Cs₂CO₃. This was designated as Comparative Sample 2.

[0060] To test the catalyst's reactivity, the catalysts from Examples 1-8 and Comparative Example 1 were applied to the decarbonylation of dimethyl oxalate to synthesize dimethyl carbonate.

[0061] Specific operating steps: A methanol-dimethyl oxalate solution is continuously fed into a multi-channel fixed-bed reactor packed with the catalysts from Examples 1-8 or Comparative Example 1, at a liquid space velocity of 0.4 h⁻¹. -1 Under the conditions of continuous reaction for 800 hours, the lifetime was investigated, and the results are shown in Table 1:

[0062] Table 1 Catalytic effects of catalysts in Examples 1-8 and Comparative Example 1

[0063]

[0064]

[0065] Note: After 270 hours of reaction, the DMO conversion rate of Comparative Example 1 sample began to decline rapidly, indicating inactivation.

[0066] CO-supported dimethyl oxalate was continuously fed into a multi-channel fixed-bed reactor packed with the catalysts of Example 4 and Comparative Example 2, at a liquid hourly space velocity (LHSV) of 0.5 h⁻¹. -1 The reaction was carried out continuously at a temperature of 190℃ for 400 hours. The results are shown in Table 2.

[0067] Table 2 Catalysts of Example 4 and Comparative Example 2

[0068] Example DMO conversion rate DMC Selectivity Lifespan (h) Example 4 100 99.2 >400 Comparative Example 2 90 95.6 380

[0069] Note: After 380 hours of reaction, the DMO conversion rate of Comparative Example 2 sample began to decrease, indicating inactivation.

[0070] Table 2 shows that the catalyst of the present invention also has good oxalate decarbonylation activity under CO, with high conversion rate, high selectivity, and good stability, making it suitable for CO-carried oxalate processes.

[0071] Process for the decarbonylation of oxalate esters to prepare carbonates:

[0072] To meet the industrial production needs of carbonates from oxalate decarbonylation, this invention provides, in addition to the aforementioned novel catalyst, a new process has been developed to address the shortcomings of existing technologies and leverage the characteristics of the catalyst. See details below. Figure 1 This process uses carbon monoxide from the decarbonylation reaction product as a carrier gas to carry oxalate through the catalyst bed. The recycle gas can be further washed with carbonate and reused. Fresh gas (CO / H2, etc.) can also be added as recycle gas, thereby adjusting the composition of the purge gas after recycling to make it suitable for subsequent process reactions.

[0073] like Figure 1 As shown: Oxalate is pumped to the oxalate vaporizer (1), vaporized in the vaporizer under the heating of circulating gas, and then enters the reactor inlet heater (2) to heat the mixed gas to the reaction temperature. The heated gas enters the decarbonylation reactor (3) for reaction. The gas after reaction is cooled by the circulating gas cooler (5) and then separated by the gas-liquid separator (7) to separate the gas and liquid. The liquid is sent to the carbonate refining system as a product to obtain refined carbonate. The gas enters the lower part of the circulating gas scrubbing tower (8) and carbonate is sprayed from the upper part of the tower. The carbonate absorbs the impurity components in the circulating gas to purify the circulating gas. Part of the circulating gas purified by carbonate enters the circulating compressor (6) for pressurization, and the other part is discharged as a release gas. The pressurized gas is mixed with fresh gas (CO / H2 / inert gas) added from the outside. The mixed gas is heated by the circulating gas heater (4) and then enters the lower part of the oxalate vaporizer.

[0074] The specific steps are as follows:

[0075] The heated oxalate ester is pumped into the upper middle part of the oxalate ester gasification tower. The oxalate ester flow rate is controlled based on the liquid hourly space velocity (LHSV), and the LHSV of the decarbonylation catalyst is 0.1–2.0 h⁻¹. -1 Oxalate is vaporized in the oxalate vaporization tower and carried out of the tower by the circulating gas. After being heated to 170-200°C by the reactor inlet heater, it enters the decarbonylation reactor. Unvaporized oxalate is discharged from the bottom of the vaporization tower to the oxalate recovery and purification system.

[0076] The recirculated gas from the oxalate reactor is cooled to 25–45°C by a recirculated gas cooler before going to the gas-liquid separator. Gas-liquid separation takes place in the gas-liquid separator, and crude carbonate liquid product is obtained at the bottom of the separator. The crude carbonate is sent to the carbonate refining system, and the recirculated gas after liquid separation goes to the bottom of the scrubbing tower.

[0077] The gaseous scrubbing agent is pumped into the upper middle part of the circulating gas scrubbing tower, where it contacts the circulating gas and absorbs impurities such as aldehydes, ethers, and alcohols. The scrubbing agent, having absorbed the impurities, is discharged from the bottom of the tower into the scrubbing agent refining system. The gaseous scrubbing agent is a solvent capable of absorbing aldehydes, ethers, and alcohols, such as diethylene glycol and ester compounds. More preferably, the scrubbing agent is a carbonate.

[0078] Part of the circulating gas from the scrubbing tower is used as circulating gas to boost the compressor, while the other part is discharged as purge gas. After purification, the discharged purge gas can be used as feed gas to produce corresponding chemicals such as oxalate, methanol, and methane.

[0079] Furthermore, the decarbonylation reactor is a fixed-bed reactor, with the reactor bed temperature controlled at 170–200°C and the circulating gas space velocity controlled at 100–3000 h⁻¹. -1 The system pressure is 0.01–3.0 MPag, which ensures that the oxalate conversion rate is ≥99%.

[0080] Furthermore, the pressurized circulating gas can be supplemented with gases such as CO and H2 to facilitate the stable operation of the system, and then heated to 150-200°C by the circulating gas heater. The heated circulating gas then enters the lower part of the oxalate gasification tower.

[0081] Furthermore, when the circulating compressor malfunctions or is unavailable, gases such as CO and H2 can be used directly as carrier gases to carry oxalate to the decarbonylation reactor. After the reaction is complete, the gas is cooled and separated into gas and liquid, and the non-condensable gas is discharged as a release gas.

[0082] The present invention will be described in detail below through examples and comparative examples. The catalysts used in the examples are all catalysts of Example 1.

[0083] Example 9

[0084] Set the system pressure to 0.25 MPag, start the circulating compressor 6, control the gas hourly space velocity through the catalyst bed to 300 h⁻¹, introduce cooling water into the circulating gas cooler 5, control the outlet temperature to 30–40 °C, control the inlet heater temperature of the decarbonylation reactor 3 to 192 °C, control the temperature of the circulating gas heater 4 to 200 °C, and simultaneously raise the catalyst bed temperature to 192 °C and stabilize it. Then, send dimethyl carbonate into the circulating gas scrubbing tower 8, with the dimethyl carbonate volumetric flow rate to the circulating gas volumetric flow rate ratio of 1:1000.

[0085] After the circulation stabilizes, liquid dimethyl oxalate is fed into the oxalate vaporization tower 1 at a liquid hourly space velocity (LHSV) of 0.3 h⁻¹, and the tower bottom is heated to ensure complete vaporization of dimethyl oxalate in the circulating gas. The vaporized dimethyl oxalate is carried by the circulating gas into the reactor inlet heater 2 and heated to 192°C, then enters the decarbonylation reactor 3. After the reaction, the gas is cooled to about 35°C by the circulating gas cooler 5. The liquid product dimethyl carbonate is separated in the gas-liquid separator 7. The gas component is sent to the circulating gas scrubbing tower 8 for washing and purification. To maintain stable system pressure, a portion of the purified gas component is discharged from the system as purge gas. This purge gas has a CO content ≥95% and can be used as a raw material for dimethyl oxalate synthesis, and is sent to the dimethyl oxalate synthesis system. The remaining circulating gas is sent to the circulating compressor 6 for pressurization to 0.27 MPag.

[0086] Alternatively, fresh CO can be added to the pressurized circulating gas from the outside to facilitate the stable operation of the system. The amount of fresh CO added is about 20% of the circulating gas volume. After the fresh CO and circulating gas are well mixed, they are heated to 200°C by the circulating gas heater 4 to the lower part of the oxalate gasification tower 1.

[0087] Example 10

[0088] Add H2 to the system to pressurize it to 0.40 MPag, start the circulating compressor 6, and control the gas space velocity through the catalyst bed to 600 h⁻¹. -1 Cooling water is introduced into the circulating gas cooler 5 to control the outlet temperature at 30-40℃. The temperature of the reactor inlet heater 2 is controlled at 192℃, and the temperature of the circulating gas heater 4 is controlled at 200℃. At the same time, the catalyst bed temperature is raised to 192℃ and stabilized. Then, dimethyl carbonate is sent to the circulating gas scrubbing tower 8. The ratio of dimethyl carbonate volume flow rate to circulating gas flow rate is 1:500.

[0089] After the circulation stabilizes, proceed at a liquid hourly rate of 0.4 h⁻¹. -1 Liquid dimethyl oxalate is fed into oxalate vaporization tower 1 and the tower bottom is heated to ensure complete vaporization of dimethyl oxalate in the circulating gas. The vaporized dimethyl oxalate is carried by the circulating gas into reactor inlet heater 2 and heated to 192°C, then enters decarbonylation reactor 3. After the reaction, the gas is cooled to about 35°C by circulating gas cooler 5. The liquid product dimethyl carbonate is separated in gas-liquid separator 7. The gas component is sent to circulating gas scrubbing tower 8 for washing and purification. To maintain stable system pressure, a portion of the purified gas component is discharged from the system as purge gas. This purge gas contains 65% H2 and 30% CO, with an H2 / CO ratio of approximately 2, close to the hydrogen-carbon ratio of syngas, and can be used as a raw material for methanol synthesis. This purge gas is washed, purified, and pressurized by methanol before being sent to methanol synthesis. The remaining circulating gas is sent to circulating compressor 6 and pressurized to 0.42 MPag.

[0090] Alternatively, fresh H2 can be added to the pressurized circulating gas from the outside to facilitate the stable operation of the system. The amount of fresh H2 added is about 30% of the circulating gas volume. After the fresh H2 is mixed with the circulating gas, it is heated to 200°C by the circulating gas heater 4 and then sent to the lower part of the gasification tower.

[0091] Example 11

[0092] When the circulating compressor 6 fails, the circulating gas scrubbing tower 8 stops spraying carbonate, the compressor is disconnected from the system, the valves before and after the compressor are closed, and fresh CO from the outside is used as the carrier gas for a one-way passage through the system. At this time, the vent valve is opened wide to maintain the system pressure at 0.25 MPag, and the gas hourly space velocity through the catalyst bed is controlled at 250 h⁻¹. -1 Cooling water is introduced into the circulating gas cooler 5 to control the outlet temperature at 30-40℃. The inlet heater temperature of the decarbonylation reactor 3 is controlled at 192℃, the circulating gas heater 4 temperature is controlled at 200℃, and the catalyst bed temperature is maintained at 192℃.

[0093] Based on a liquid air velocity of 0.2h -1 Liquid dimethyl oxalate is fed into the oxalate vaporization tower 1 and the tower bottom is heated to ensure complete vaporization of dimethyl oxalate. The vaporized dimethyl oxalate is carried by CO into the reactor inlet heater 2 and heated to 192°C. Then it enters the decarbonylation reactor 3. After the reaction, the gas is cooled to about 35°C by the circulating gas cooler 5. The liquid product dimethyl carbonate is separated in the gas-liquid separator 7. The CO content in the gas component is ≥97%, which can be used as a raw material for the synthesis of dimethyl oxalate and can be directly sent to the dimethyl oxalate synthesis system.

[0094] Comparative Example 3

[0095] Using fresh N2 from outside as the carrier gas, the system is passed through in a single pass. At this time, the vent valve is opened wide to maintain the system pressure at 0.25 MPag, and the gas space velocity through the catalyst bed is controlled at 250 h⁻¹. -1 Cooling water is introduced into the circulating gas cooler 5 to control the outlet temperature at 30-40℃, the reactor inlet heater 2 temperature is controlled at 192℃, the circulating gas heater temperature is controlled at 200℃, and the catalyst bed temperature is maintained at 192℃.

[0096] Based on a liquid air velocity of 0.2h -1Liquid dimethyl oxalate is fed into the oxalate vaporization tower 1 and the tower bottom is heated to ensure complete vaporization of dimethyl oxalate. The vaporized dimethyl oxalate is carried by N2 into the reactor inlet heater 2 and heated to 192°C. Then it enters the decarbonylation reactor 3. After the reaction, the gas is cooled to about 35°C by the circulating gas cooler 5. The liquid product dimethyl carbonate is separated in the gas-liquid separator 7. The gas composition is CO 14.8% and N2 82%. Since the CO content is low and CO and N2 are difficult to separate, the purge gas can only be vented. Compared with the previous embodiment, using nitrogen as the carrier gas not only wastes resources but also pollutes the environment.

[0097] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A process for the decarbonylation of oxalate esters to produce carbonates, characterized in that: Oxalate undergoes a gas-phase decarbonylation reaction under the catalysis of a catalyst for oxalate decarbonylation to obtain crude carbonate. The temperature of the gas-phase decarbonylation reaction is 120℃~250℃. The catalyst for oxalate decarbonylation is a supported catalyst, comprising an active agent-modified support component and an alkali metal carbonate supported on the active agent-modified support. The support is activated carbon, and the active agent is a halogen element and / or a halogen-containing compound. The halogen element is I2, and the halogen-containing compound is CH3I, CBr4, NH4Br, KBr, KI, NaI, LiI, CsBr, or FeI2 halogen-containing compound. The loading amount of the alkali metal carbonate is 1%~20%, and the loading amount of the active agent is 0.1%~10%.

2. The process for producing carbonates from oxalate esters by decarbonylation according to claim 1, characterized in that: The alkali metal carbonate is one or more of potassium carbonate, sodium carbonate, rubidium carbonate, and cesium carbonate.

3. The process for producing carbonates from oxalate esters by decarbonylation according to claim 1, characterized in that: The preparation of the catalyst for oxalate decarbonylation includes the following steps: Step S1: Process the carrier; Step S2: Carrier modification treatment: The carrier is modified by passing the active additive through solution or gas phase, then dried and calcined at high temperature to obtain the active additive modified carrier. Step S3: Alkali metal carbonate loading. The alkali metal carbonate solution is poured into the active additive modified support by impregnation method. After the solution is completely absorbed, it is dried to obtain the oxalate decarbonylation to carbonate catalyst.

4. The process for decarbonylating oxalate to produce carbonate according to claim 3, characterized in that: In the preparation of the catalyst for the decarbonylation of the oxalate ester, In step S1: the activated carbon carrier is first soaked in a 0.1%~5% HCl or HNO3 solution for 0.5~12 hours, then washed with deionized water until neutral, then soaked in a 0.1%~5% alkaline solution for 0.5~12 hours, then washed with deionized water until neutral, and finally dried at 100℃~150℃ for 2~4 hours; the alkaline solution uses a mixture of one or more of NaOH, Na2CO3, KOH, K2CO3, and ammonia water. In step S2, the active additive modifies the carrier through solution or gas phase. The solution method involves immersing the treated carrier in a solution containing 5-30% active additive for 2-4 hours, then air-drying it at 100-150°C for 1-5 hours, and finally calcining it at 200-500°C for 2-5 hours. The gas phase method involves passing volatile halogen elements and / or halogen-containing compounds through an activated carbon carrier using hot nitrogen gas, and then calcining the carrier after adsorbing the active additive at 200-500°C for 2-5 hours. In step S3, the mass concentration of the alkali metal carbonate solution is 5%~30%. The carrier modified with the active agent is impregnated in the solution. After impregnation, the carrier is air-dried for 2~12 hours and then dried at 100~150℃ for 2~5 hours to obtain the desired catalyst.

5. The process for decarbonylating oxalate to produce carbonate according to claim 1, characterized in that: After being gasified in the gasification tower, oxalate is carried by circulating gas into the decarbonylation reactor. The decarbonylation reaction product is cooled and separated into liquid phase components. Carbonate is collected and used to absorb impurities in the circulating gas, purifying the gas phase components. The purified gas phase components are then recycled back to the gasification tower to carry oxalate.

6. The process for decarbonylating oxalate to produce carbonate according to claim 1, characterized in that: The oxalate ester is dimethyl oxalate or diethyl oxalate; The process includes adding fresh carbon monoxide, hydrogen, or inert gas to the gas phase components; and in the event of a compressor failure, using carbon monoxide or hydrogen to carry oxalate through the catalyst bed in a single pass without a compressor.

7. The process for producing carbonates from oxalate esters by decarbonylation according to claim 1, characterized in that: The decarbonylation reactor is selected from fixed-bed reactors, with a bed reaction temperature of 170~200℃, a reaction pressure of 0.0~3MPaG, and a liquid hourly space velocity (LHSV) of oxalate feed of 0.01~2h. -1 .

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