An effective synthesis of bio-based pentamethylene diisocyanate in a jet loop reactor

A highly efficient jet loop reactor (JLR) with a submerged nozzle was developed to enhance the mixing and dispersion capacity of a phosgenation reaction, which was implemented in the preparation of pentamethylene diisocyanate (PDI). Model test of air–water two-phase flow was carried out first, which provided references for the control conditions of the phosgenation of 1,5-pentanediamine (PDA). Carbon dioxide (CO₂) was used to protect PDA as 1,5-pentanediamine carbonate (PDAC). Both the carbonate-forming and phosgenation reactions were preferably carried out in the JLR. The phosgene inlet pressure, asynchronous speed of the circulating pump, PDI content, and reaction completion time in the JLR system were investigated. Interestingly, we found that the PDI content exceeded 0.6–0.7%, the yields of PDI exceeded 7–8.5%, and the reaction time was decreased by approximately 50% compared to that of the traditional stirred-tank reactor (STR). The JLR is thus applicable for the preparation of PDI and is superior to the STR system.