Which expert has process information on adipic acid and polyoxymethylene?

In industrial production, adipic acid is generally obtained by oxidizing cyclohexane to produce a mixture containing cyclohexanol and unreacted cyclohexane; after distillation, pure cyclohexanol is obtained. Adipic acid is produced through oxidation with nitric acid. The main manufacturers in China include Shenma Industry in Pingdingshan, Liaoyang Petrochemical, and Taihua Co., Ltd.

1.2.2 Reaction mechanism of ADA production by nitric acid oxidation – a patented technology from DuPont in 1927. 　 OH O O H NO O H NO2 O NO NO2 OH O NOH NO2 OH O O OH HNO3 HNO2, H2O HNO3 HNO2 HNO2 NH2OH HNO2 H2O H2O 2H2O (Nitrooxime acid) Reaction mechanism for the production of ADA via nitric acid oxidation HNO2 H2O • For every 1 kg of ADA produced, 0.25 kg of N2O is generated. • Control steps: Nitrooximate (NA) → ADA • By-products: Gluconic acid, Succinic acid http://pu.**.com

If you have any production-related materials, please send them to me at lzq209@sina.com; no need to send the laboratory materials

Reply to 1# l2211142: If you have any, please give me some too. My email is sunjiguang111222@163.com; I work in the adipic acid industry as well – we’re in the same field

This post was last edited by Oath-taking on 2011-11-5 15:41. The production processes for polyoxymethylene include two types: the homopolymerization process for polyoxymethylene and the copolymerization process for it. The production process for homopolymerous formaldehyde is represented by the process used by DuPont in the United States. In this process, a 50% aqueous solution of formaldehyde is used as the raw material; it first reacts with higher alcohols to form hemiacetals. These hemiacetals are then dehydrated and thermally decomposed to produce high-concentration formaldehyde gas, which is subsequently purified to yield anhydrous formaldehyde suitable for polymerization. Anhydrous formaldehyde is subjected to suspension polymerization in an inert solvent containing a catalyst, followed by processes such as centrifugation and drying to obtain a powdery crude polymer. The crude polymer is then stabilized through esterification termination using acetic anhydride. After stabilization, the polymer is mixed evenly with various additives, and then extruded and granulated to produce the final polyoxymethylene granules. The production process for copolymerized formaldehyde is represented by the process used by Celanese Corporation in the United States. The raw material, formaldehyde, is first concentrated; the concentrated formaldehyde is then used, in the presence of a catalyst, to produce triformaldehyde, which is subsequently purified through processes such as further concentration and distillation to yield high-purity triformaldehyde. Pure trioxane and the second monomer, pentaerythritol, undergo copolymerization in the presence of a catalyst. The crude polymer is produced through grinding and passivation, followed by post-treatment during which various additives are added; finally, extrusion granulation yields the finished copolymer formaldehyde granules. Brief description of the polyoxymethylene production process at Poland’s ZAT company: It mainly consists of a formaldehyde concentration unit, a trioxymethane unit, a pentaerythritol unit, a butyl acetal unit, a polymerization unit, and a packaging unit. 1) Formaldehyde concentration unit: Fresh formaldehyde from the formaldehyde production unit enters the formaldehyde evaporator for vacuum concentration; the concentrated liquid formaldehyde is then sent to the paraformaldehyde synthesis reactor and the pentaerythritol synthesis reactor as raw materials. The dilute formaldehyde at the top of the formaldehyde evaporator enters the methanol recovery tower after condensation. The crude methanol separated from the top of the methanol recovery tower is sent to the methanol plant for purification, while the dilute formaldehyde separated from the bottom of the tower undergoes alkaline neutralization before being fed into a pressurized distillation tower. The 37% formalin aqueous solution obtained after condensing the formalin vapor at the top of the tower is recycled back to the formalin vacuum evaporator as a raw material. 2) Triomethylene formaldehyde units: Concentrated formaldehyde from the formaldehyde evaporator enters the triomethylene formaldehyde synthesis reactor, where it is synthesized into triomethylene formaldehyde under the action of a catalyst. The reaction products are vaporized and sent to the paraformaldehyde distillation tower, while the liquid remaining in the reactor is returned to the paraformaldehyde synthesis reactor. The products from the top of the tower enter the light components tower after being condensed. The kettle liquid then enters the trimerization concentration tower. The formalin aqueous solution separated from the bottom of the polymerization concentration tower is recycled back to the formalin evaporator, while the gas phase at the top of the tower is sent to the paraformaldehyde crystallizer after condensation. A suspension of triomethylenemethane crystals is generated and fed into a centrifuge for liquid-solid separation; the mother liquor obtained from this separation is recycled back to the crystallizer, while the triomethylenemethane crystals are melted and then fed into a triomethylenemethane dehydration tower. The polyoxymethylene at the top of the tower is recycled back to the crystallizer, while the concentrated polyoxymethylene at the bottom of the tower is treated with an alkali and then sent to a sedimentation tank for reuse. Concentrated paraformaldehyde is sent to the polymerization purification tower, while the liquid from the reactor is returned to the alkali sedimentation tank. The gas phase at the top of the tower is condensed and then sent to the polymerization refining tower for distillation. The concentrated paraformaldehyde at the top of the tower is returned to the polymerization crystallization system. 3) The dioxolane units are formed by reacting concentrated formaldehyde from the formaldehyde evaporator with ethylene glycol in the tank area; after forming a hemiacetal, this mixture enters the hemiacetal reactor where dioxolane is synthesized under the action of a catalyst. The gaseous products generated are sent to the dioxolane synthesis tower, where formaldehyde and dioxolane are separated from each other. The bottom liquid from the tower is returned to the dioxolane synthesis reactor, while the vapor at the top of the tower enters the dioxolane distillation tower after being condensed. The vapor at the top of the tower enters the pentaerythritol extraction tower after being condensed. The liquid from the bottom of the extraction tower is sent to the alkali solution regeneration system. The material coming out of the upper part of the extraction tower enters the evaporator; the vapor generated is condensed and then sent to the dioxolane distillation tower for purification. Water is separated from the top of the tower, while the purified dioxolane at the bottom of the tower is sent to the polymerization process. 4) Butyl acetal units: Purified trioxane derived from trioxane units and butanol are fed into the butyl acetal reactor, where butyl acetal is synthesized under the action of a catalyst. The product is fed into a distillation kettle and distillation tower system for batch distillation. The butyl acetal product obtained from the top of the butyl acetal distillation tower is sent to the polymerization process. 5) Polymerization units: high-purity trioxane and high-purity dioxolane are metered and fed into the polymerization reactor along with a catalyst and a molecular weight regulator, where they undergo polymerization to produce copolymerized formaldehyde. The crude polymer produced by the polymerization reactor is sent to a grinding system for grinding. A terminator is added to the powder during transportation to terminate the polymerization reaction. The powder obtained from the grinding and passivation process enters a tray dryer to remove unreacted triomethylenemethane; this triomethylenemethane is recovered by being absorbed by the grinding monomer and then sent to the polymerization triomethylenemethane recovery tower, where the vapor at the top of the tower is condensed and returned to the triomethylenemethane unit. The powder dried by the dryer is conveyed by air to the powder silo. The dried powder coming from the powder silo is metered along with several additives and thoroughly mixed, then sent to the degassing and granulation process. The uniformly blended powder undergoes vacuum degassing in a twin-screw extrusion granulator. The removed unstable monomer is sent to a degassing absorption tower to recover formaldehyde, which is then returned to the formaldehyde concentration unit. The pellets produced by the extrusion granulator are dried and cooled before being sent to the finished pellet silo. The production process of polyoxymethylene is divided into two types: the homopolymerized polyoxymethylene production process and the copolymerized polyoxymethylene production process. The production process for homopolymerous formaldehyde is represented by the process used by DuPont in the United States. In this process, a 50% aqueous solution of formaldehyde is used as the raw material; it first reacts with higher alcohols to form hemiacetals. These hemiacetals are then dehydrated and thermally decomposed to produce high-concentration formaldehyde gas, which is subsequently purified to yield anhydrous formaldehyde suitable for polymerization. Anhydrous formaldehyde is subjected to suspension polymerization in an inert solvent containing a catalyst, followed by processes such as centrifugation and drying to obtain a powdery crude polymer. The crude polymer is then stabilized through esterification termination using acetic anhydride. After stabilization, the polymer is mixed evenly with various additives, and then extruded and granulated to produce the final polyoxymethylene granules. The production process for copolymerized formaldehyde is represented by the process used by Celanese Corporation in the United States. The raw material, formaldehyde, is first concentrated; the concentrated formaldehyde is then used, in the presence of a catalyst, to produce triformaldehyde, which is subsequently purified through processes such as further concentration and distillation to yield high-purity triformaldehyde. Pure trioxane and the second monomer, pentaerythritol, undergo copolymerization in the presence of a catalyst. The crude polymer is produced through grinding and passivation, followed by post-treatment during which various additives are added; finally, extrusion granulation yields the finished copolymer formaldehyde granules. Brief description of the polyoxymethylene production process at Poland’s ZAT company: It mainly consists of a formaldehyde concentration unit, a trioxymethane unit, a pentaerythritol unit, a butyl acetal unit, a polymerization unit, and a packaging unit. 1) Formaldehyde concentration unit: Fresh formaldehyde from the formaldehyde production unit enters the formaldehyde evaporator for vacuum concentration; the concentrated liquid formaldehyde is then sent to the paraformaldehyde synthesis reactor and the pentaerythritol synthesis reactor as raw materials. The dilute formaldehyde at the top of the formaldehyde evaporator enters the methanol recovery tower after condensation. The crude methanol separated from the top of the methanol recovery tower is sent to the methanol plant for purification, while the dilute formaldehyde separated from the bottom of the tower undergoes alkaline neutralization before being fed into a pressurized distillation tower. The 37% formalin aqueous solution obtained after condensing the formalin vapor at the top of the tower is recycled back to the formalin vacuum evaporator as a raw material. 2) Triomethylene formaldehyde units: Concentrated formaldehyde from the formaldehyde evaporator enters the triomethylene formaldehyde synthesis reactor, where it is synthesized into triomethylene formaldehyde under the action of a catalyst. The reaction products are vaporized and sent to the paraformaldehyde distillation tower, while the liquid remaining in the reactor is returned to the paraformaldehyde synthesis reactor. The products from the top of the tower enter the light components tower after being condensed. The kettle liquid then enters the trimerization concentration tower. The formalin aqueous solution separated from the bottom of the polymerization concentration tower is recycled back to the formalin evaporator, while the gas phase at the top of the tower is sent to the paraformaldehyde crystallizer after condensation. A suspension of triomethylenemethane crystals is generated and fed into a centrifuge for liquid-solid separation; the mother liquor obtained from this separation is recycled back to the crystallizer, while the triomethylenemethane crystals are melted and then fed into a triomethylenemethane dehydration tower. The polyoxymethylene at the top of the tower is recycled back to the crystallizer, while the concentrated polyoxymethylene at the bottom of the tower is treated with an alkali and then sent to a sedimentation tank for reuse. Concentrated paraformaldehyde is sent to the polymerization purification tower, while the liquid from the reactor is returned to the alkali sedimentation tank. The gas phase at the top of the tower is condensed and then sent to the polymerization refining tower for distillation. The concentrated paraformaldehyde at the top of the tower is returned to the polymerization crystallization system. 3) The dioxolane units are formed by reacting concentrated formaldehyde from the formaldehyde evaporator with ethylene glycol in the tank area; after forming a hemiacetal, this mixture enters the hemiacetal reactor where dioxolane is synthesized under the action of a catalyst. The gaseous products generated are sent to the dioxolane synthesis tower, where formaldehyde and dioxolane are separated from each other. The bottom liquid from the tower is returned to the dioxolane synthesis reactor, while the vapor at the top of the tower enters the dioxolane distillation tower after being condensed. The vapor at the top of the tower enters the pentaerythritol extraction tower after being condensed. The liquid from the bottom of the extraction tower is sent to the alkali solution regeneration system. The material coming out of the upper part of the extraction tower enters the evaporator; the vapor generated is condensed and then sent to the dioxolane distillation tower for purification. Water is separated from the top of the tower, while the purified dioxolane at the bottom of the tower is sent to the polymerization process. 4) Butyl acetal units: Purified trioxane derived from trioxane units and butanol are fed into the butyl acetal reactor, where butyl acetal is synthesized under the action of a catalyst. The product is fed into a distillation kettle and distillation tower system for batch distillation. The butyl acetal product obtained from the top of the butyl acetal distillation tower is sent to the polymerization process. 5) Polymerization units: high-purity trioxane and high-purity dioxolane are metered and fed into the polymerization reactor along with a catalyst and a molecular weight regulator, where they undergo polymerization to produce copolymerized formaldehyde. The crude polymer produced by the polymerization reactor is sent to a grinding system for grinding. A terminator is added to the powder during transportation to terminate the polymerization reaction. The powder obtained from the grinding and passivation process enters a tray dryer to remove unreacted triomethylenemethane; this triomethylenemethane is recovered by being absorbed by the grinding monomer and then sent to the polymerization triomethylenemethane recovery tower, where the vapor at the top of the tower is condensed and returned to the triomethylenemethane unit. The powder dried by the dryer is conveyed by air to the powder silo. The dried powder coming from the powder silo is metered along with several additives and thoroughly mixed, then sent to the degassing and granulation process. The uniformly blended powder undergoes vacuum degassing in a twin-screw extrusion granulator. The removed unstable monomer is sent to a degassing absorption tower to recover formaldehyde, which is then returned to the formaldehyde concentration unit. The pellets produced by the extrusion granulator are dried and cooled before being sent to the finished pellet silo.

I once specifically looked for information on polyoxymethylene, but there was very little of it:(

What is the equipment located above the ADA1# resin reactor? What is its function?