Novel atomization-assisted phosgenation for TDI synthesis from TDA: A theoretical study on single droplet reactivity

• Published in: Chemical engineering science Vol. 280; p. 119018
• Main Authors: Hou, Zitong, Chen, Haifeng, Mao, Jianyong, Ge, Jijun, Bi, Rongshan
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 05.10.2023
• Subjects: Atomization; Droplet reactivity; Phosgenation; Toluene diamine; Toluene diisocyanate; Toluene diamine; Toluene diisocyanate; Phosgenation; Atomization; Droplet reactivity
• ISSN: 0009-2509; 1873-4405
• DOI: 10.1016/j.ces.2023.119018

Heating organic amines (TDA) to the superheated liquid state, they are injected into a spray reactor through a nozzle, while phosgene enters in a high-temperature gas phase from an injection stream. Inside the reactor, organic amines rapidly flash boil and most of them atomize into uniformly small droplets, while a small amount of them flash vaporize into gas. The gaseous organic amines act as the reaction initiator, quickly reacting with phosgene and releasing heat. The released heat partially vaporizes the liquid organic amine droplets, and the resulting gaseous organic amines react with phosgene to release more heat, and the process continues in a cycle until the reaction is complete. The initial amount of organic amine in gas phase, which acts as the initiator, can be controlled by adjusting the overheating temperature difference of the organic amine, while the size and distribution of the droplets can be adjusted by the injector structure, operating conditions, and reaction ratio. [Display omitted] •A new phosgenation reaction mechanism based on flashing atomization was proposed.•Single TDA droplet reaction model under high temperature environment was established.•The results proved the feasibility of the new mechanism.•The superiority of the proposed method was validated by compare with gas phase method. TDI is a highly versatile chemical product with a significant market demand. The state-of-the-art production method is gas phase phosgenation, but it has drawbacks of high energy consumption and unwanted side reactions at high temperatures. In this study, we propose a novel atomization-assisted phosgenation method for TDI synthesis from toluene diamine (TDA) that addresses these limitations. The proposed method involves atomizing TDA in a reactor and introducing in the form of micro-droplets, which reduces the energy consumption required for TDA vaporization and superheating. Through a comprehensive theoretical investigation of droplet reactivity and a comparative analysis of reaction conditions, we have demonstrated that the method proposed in this study has the potential to achieve higher product yield and a reduced probability of side reactions, thus highlighting its superiority over conventional methods. This study demonstrates the feasibility and superiority of the atomization-assisted phosgenation method and its potential application in industrial TDI production.