Low-temperature preparation method of ketene

Abstract

The invention relates to the technical field of chemical production, and provides a low-temperature preparation method of ketene. According to the method, the high-activity auxiliary is added in the acetic acid cracking process to initiate the acetic acid cracking reaction, so that the cracking temperature is reduced, the side reaction is reduced, the selectivity of ketene is improved, and the energy consumption is reduced; meanwhile, nitrogen oxide and the like generated after the aid is decomposed at high temperature have polymerization inhibition effect, so that the auto-polymerization of the gas-phase ketene can be prevented, the problem that the ketene is difficult to store is solved, and the effect of'one agent with double effects' is realized.

Description

Technical Field

[0001] This invention relates to the field of chemical production technology, and in particular to a low-temperature preparation method for ketene. Background Technology

[0002] Ketone is a simple and highly chemically reactive unsaturated organic acid anhydride compound. The accumulated double bonds in its molecular structure endow it with high reactivity, making it an important chemical intermediate that can be used to prepare various food additives and pharmaceutical intermediates.

[0003] Currently, ketene is typically produced industrially using a high-temperature acetic acid cracking process. This method uses acetic acid as a raw material, inducing a cracking reaction at high temperatures to produce ketene. However, this method involves high cracking temperatures (typically around 700-780℃), which leads to increased side reactions, decreased selectivity for the target product ketene, reduced raw material utilization and product purity, and hinders production efficiency. Simultaneously, ketene exhibits a strong tendency to self-polymerize, posing a significant challenge for stable storage. To address this self-polymerization problem, polymerization inhibitors such as hydroquinone are commonly used industrially, but traditional inhibitors have extremely limited effectiveness in inhibiting the polymerization of ketene in the gaseous phase. Summary of the Invention

[0004] In view of this, the present invention provides a low-temperature preparation method for ketene. The method provided by the present invention can lower the temperature of acetic acid cracking, reduce the occurrence of side reactions, improve the selectivity of ketene, and simultaneously inhibit the self-polymerization of ketene, thus solving the problem of difficult storage of ketene.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: A method for preparing ketene at low temperature, comprising the following steps: Acetic acid and additives are added to a pyrolysis furnace for pyrolysis reaction to obtain ketene; the pyrolysis furnace includes a convection section and a radiation section, and the acetic acid and additives are fed into the convection section of the pyrolysis furnace; the temperature of the pyrolysis reaction is ≤700℃; the additives include one or more of azobisisobutyronitrile, nitroalkanes, tetramethylpiperidine oxide, and polyamides.

[0006] Preferably, the nitroalkane includes one or both of nitromethane and nitromethane.

[0007] Preferably, the mass of the auxiliary agent is 0.1 to 2 wt% of the mass of the acetic acid.

[0008] Preferably, the acetic acid and the additive are mixed, and the resulting mixture is added to a pyrolysis furnace; the mixing temperature of the acetic acid and the additive is 35~45°C.

[0009] Preferably, the convection section of the pyrolysis furnace is provided with a main material inlet; the main material inlet is located in the region of the convection section from room temperature to 150°C; the mixture of acetic acid and additives is added from the main material inlet.

[0010] Preferably, the convection section of the pyrolysis furnace is further provided with a material auxiliary injection port; the material auxiliary injection port is located in the region of the convection section from 200°C to 600°C; the mixture of acetic acid and additives is added from the main material injection port and the material auxiliary injection port respectively; or a portion of the additives and acetic acid are mixed and added from the main material injection port, and the remaining additives are added from the material auxiliary injection port.

[0011] Preferably, the temperature of the pyrolysis reaction is 650~700℃.

[0012] Preferably, the pyrolysis reaction is carried out in the radiation section of the pyrolysis furnace; the residence time of the acetic acid and the additives in the radiation section is 1 to 2 seconds.

[0013] Preferably, the pyrolysis reaction to obtain pyrolysis products further includes gas-liquid separation of the pyrolysis products to obtain pyrolysis gas; the pyrolysis gas is a crude gaseous ketene product.

[0014] Preferably, after obtaining the crude gaseous ketene product, the method further includes purifying and refining the crude gaseous ketene product.

[0015] This invention provides a low-temperature preparation method for ketene, comprising the following steps: adding acetic acid and an auxiliary agent to a pyrolysis furnace for a pyrolysis reaction to obtain ketene; the pyrolysis furnace includes a convection section and a radiation section, and the acetic acid and auxiliary agent are fed into the convection section of the pyrolysis furnace; the temperature of the pyrolysis reaction is ≤700℃; the auxiliary agent includes one or more of azobisisobutyronitrile, nitroalkanes, tetramethylpiperidine oxide, and polyamide. This invention adds a highly active auxiliary agent during the acetic acid pyrolysis process to initiate the acetic acid pyrolysis reaction, thereby reducing the pyrolysis temperature, decreasing the occurrence of side reactions, improving the selectivity of ketene, and reducing energy consumption; simultaneously, the nitrogen oxides and other substances generated after the high-temperature decomposition of the auxiliary agent have a polymerization inhibitory effect, preventing the self-polymerization of gaseous ketene and solving the problem of difficult storage of ketene, achieving a "dual effect with one agent". Detailed Implementation

[0016] This invention provides a low-temperature preparation method for ketene, comprising the following steps: Acetic acid and additives are added to a pyrolysis furnace for pyrolysis reaction to obtain ketene; the pyrolysis furnace includes a convection section and a radiation section, and the acetic acid and additives are fed into the convection section of the pyrolysis furnace; the temperature of the pyrolysis reaction is ≤700℃; the additives include one or more of azobisisobutyronitrile, nitroalkanes, tetramethylpiperidine oxide, and polyamides.

[0017] This invention involves adding acetic acid and an auxiliary agent to a pyrolysis furnace for a pyrolysis reaction to obtain ketene. In this invention, the auxiliary agent includes one or more of azobisisobutyronitrile, nitroalkanes, tetramethylpiperidine oxide, and polyamides; the nitroalkanes include one or two of nitromethane and nitrobanane; the mass of the auxiliary agent is preferably 0.1-2 wt% of the mass of the acetic acid, specifically 0.5 wt% or 1 wt%.

[0018] In this invention, the acetic acid and the additive can be mixed, and the resulting mixture can be added to a pyrolysis furnace; the mixing temperature of the acetic acid and the additive is preferably 35~45℃, specifically 40℃; this invention does not have special requirements for the mixing time, as long as the additive can be dissolved in the acetic acid.

[0019] In this invention, the pyrolysis furnace includes a convection section and a radiation section, and the feeding position of the mixed material is the convection section of the pyrolysis furnace; according to the flow direction of the material, the temperature of the convection section gradually increases, thereby realizing the preheating and gasification of the material; specifically, the initial temperature of the convection section is room temperature, and the end temperature is 300~600℃.

[0020] In one specific embodiment of the present invention, the convection section of the pyrolysis furnace is provided with a main material inlet; the main material inlet is preferably located in the region of the convection section from room temperature to 150°C; the mixture of acetic acid and additives is added from the main material inlet.

[0021] In another specific embodiment of the present invention, the convection section of the pyrolysis furnace is preferably further provided with an auxiliary material feeding port; the auxiliary material feeding port is preferably located in the region of the convection section between 200°C and 600°C; in this invention, the mixture of acetic acid and additives can be added separately from the main material feeding port and the auxiliary material feeding port; or a portion of the additives and acetic acid can be mixed and added from the main material feeding port, and the remaining additives can be added from the auxiliary material feeding port. The present invention improves the yield of ketene by providing an auxiliary material feeding port. In this invention, when materials are added simultaneously through the main material feeding port and the auxiliary material feeding port, the types of additives in the two portions of materials can be the same or different, and the present invention does not impose specific limitations. In a specific embodiment of the present invention, a mixture of acetic acid and nitroalkanes can be added to the main material feeding port, and tetramethylpiperidine oxide can be added to the auxiliary material feeding port.

[0022] In this invention, the mixture is added to the convection section of the pyrolysis furnace at room temperature, and after being gasified and preheated in the convection section, it enters the radiation section where a pyrolysis reaction occurs.

[0023] In this invention, the temperature of the pyrolysis reaction is ≤700℃, preferably 650~700℃; the pyrolysis reaction is carried out in the radiation section of the pyrolysis furnace; the residence time of the acetic acid and the auxiliary agent in the radiation section is preferably 1~2 seconds, specifically 1.5 seconds. By adding the auxiliary agent, this invention can lower the temperature of the pyrolysis reaction, thereby reducing the occurrence of side reactions, lowering energy consumption, and improving the selectivity of ketene; simultaneously, the auxiliary agent itself decomposes to produce nitrogen oxides, which do not need to be separated from the ketene product and can act as polymerization inhibitors to prevent the self-polymerization of ketene, thus solving the problem of difficult ketene storage.

[0024] In this invention, the pyrolysis reaction yields pyrolysis products, and the pyrolysis products are further subjected to gas-liquid separation to obtain pyrolysis gas; the pyrolysis gas is a crude gaseous ketene product; the gas-liquid separation is carried out in a cooling separation section; this invention does not have special requirements for the cooling separation section, and any section well known to those skilled in the art can be used.

[0025] In this invention, after obtaining the gaseous crude ketene product, it is preferable to further purify and refine the gaseous crude ketene product; the purification and refining are carried out in a purification and refining section, and this invention does not have special requirements for the purification and refining section, and any section well known to those skilled in the art can be used.

[0026] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0027] Example 1 Azobisisobutyronitrile (AIBN) was weighed and dissolved in acetic acid under vigorous stirring at 40°C to obtain a mixture. The concentration of AIBN in acetic acid was 1 wt%. The mixture was fed into the pyrolysis furnace at room temperature through the main material inlet (located in the convection section at room temperature to 150°C) for pyrolysis. The pyrolysis temperature was controlled at 650°C, and the residence time was about 1.5 seconds. The acetic acid conversion rate was measured to be 89%, the yield of ketene in the product was 60%, and the polymerization rate of gaseous ketene in the storage tank after 168 hours (storage temperature -10°C) was 8.3%.

[0028] Comparative Example 1 The other conditions are the same as in Example 1, except that no additives are added.

[0029] The acetic acid conversion rate was measured to be 70%, and the ketene yield was 42%. The polymerization rate in the gaseous ketene storage tank after 168 hours (storage temperature of -10℃) was greater than 80%.

[0030] Example 2 Nitropropane was weighed and dissolved in acetic acid under vigorous stirring at 40°C to obtain a mixture. The concentration of nitropropane in acetic acid was 1 wt%. The mixture was fed into the cracking furnace at room temperature through the main material inlet (located in the convection section at room temperature to 150°C) for cracking. The cracking temperature was controlled at 650°C and the residence time was about 1.5 seconds. The acetic acid conversion rate was measured to be 85%, the yield of ketene in the product was 58%, and the polymerization rate of gaseous ketene in the storage tank after 168 hours (storage temperature of -10°C) was 5.3%.

[0031] Example 3 Nitropropane was weighed and dissolved in acetic acid under vigorous stirring at 40°C to obtain a mixture. The concentration of nitropropane in acetic acid was 0.5 wt%. The mixture was fed into the cracking furnace through the main material inlet (located in the convection section from room temperature to 150°C) at room temperature. At the same time, tetramethylpiperidine oxide was added at the auxiliary material inlet (located in the convection section from 200°C to 150°C). The mass of tetramethylpiperidine oxide was 0.5 wt% of acetic acid. The cracking reaction was carried out at a temperature of 650°C and a residence time of about 1.5 seconds. The acetic acid conversion rate was measured to be 91%, the yield of ketene in the product was 63%, and the polymerization rate of gaseous ketene in the storage tank after 168 hours (storage temperature of -10°C) was 7.5%.

[0032] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A process for the low temperature preparation of ethylene ketone, characterized in that, The method comprises the following steps: The acetic acid and the auxiliary agent are added into a cracking furnace to perform a cracking reaction to obtain ketene; the cracking furnace comprises a convection section and a radiation section, the acetic acid and the auxiliary agent are added into the convection section of the cracking furnace, the cracking reaction is performed at a temperature of ≤700 ℃, and the auxiliary agent comprises one or more of azobisisobutyronitrile, nitroalkane, tetramethylpiperidinium oxide and polyamide.

2. The production method according to claim 1, characterized by, The nitroalkane comprises one or both of nitromethane and nitropropane.

3. The production method according to claim 1, characterized by, The mass of the auxiliary agent is 0.1-2 wt% of the mass of the acetic acid.

4. The production method according to claim 1, characterized by, The acetic acid and the auxiliary agent are mixed, and the mixture is added into the cracking furnace; the mixing temperature of the acetic acid and the auxiliary agent is 35-45 ℃.

5. The production method according to claim 4, characterized by, The convection section of the cracking furnace is provided with a main material inlet; the main material inlet is arranged in a region with a normal temperature to 150 ℃, and the mixture of the acetic acid and the auxiliary agent is added from the main material inlet.

6. The production method according to claim 5, wherein The convection section of the cracking furnace is further provided with an auxiliary material inlet; the auxiliary material inlet is arranged in a region with a temperature of 200-600 ℃, and the mixture of the acetic acid and the auxiliary agent is added from the main material inlet and the auxiliary material inlet respectively, or part of the auxiliary agent is mixed with the acetic acid and added from the main material inlet, and the remaining part of the auxiliary agent is added from the auxiliary material inlet.

7. The preparation method according to claim 1, characterized in that, The cracking reaction is performed at a temperature of 650-700 ℃.

8. The method of claim 1, wherein, The cracking reaction is performed in the radiation section of the cracking furnace, and the residence time of the acetic acid and the auxiliary agent in the radiation section is 1-2 seconds.

9. The method of claim 1, wherein, The cracking reaction obtains a cracking product, and further comprises performing gas-liquid separation on the cracking product to obtain a cracking gas; the cracking gas is a gaseous ketene crude product.

10. The method of claim 9, wherein, After the gaseous ketene crude product is obtained, further comprising purifying and refining the gaseous ketene crude product.