Continuous co-product separation by organic solvent nanofiltration for the hydroaminomethylation in a thermomorphic multiphase system

While homogeneous catalysts can be used to efficiently produce intermediate and specialty chemicals, the separation of the precious catalyst from products, by-products or co-products can be a major challenge. Consequently, novel processes need to be developed to effectively separate and reuse the active catalyst, while avoiding accumulation of the various reaction products. Therefore, this work presents the development and demonstration of a hybrid, continuous reaction and separation process for the catalytic auto-tandem hydro-aminomethylation (HAM) reaction. Herein, long-chain alkenes are converted to valuable higher aliphatic amines with high atom economy, while producing only water as co-product. Since the HAM is a rhodium-catalyzed reaction, a thermomorphic multiphase system is used as an integrated catalyst recycling strategy, which is further combined with a membrane-based separation of the co-product via organic solvent nanofiltration. Based on initial screening of various membranes and investigation on the water influence on the phase separation after the reactor, the full process for the HAM of 1-decene with diethylamine with separation of the co-product water was operated continuously for 75 h in a miniplant. The continuous operation of the process successfully demonstrated stable process operation, avoiding a steady accumulation of water while maintaining high catalyst rejection between 97% and 99.3%. The overall leaching of rhodium was kept below 3% of the total amount supplied. This corresponds to a loss of only 11 mg of catalyst per kg of product.

Automated summary

This study developed a hybrid, continuous reaction and separation process for catalytic auto-tandem hydro-aminomethylation (HAM) reaction, demonstrating efficient production of valuable higher aliphatic amines and avoidance of product accumulation through effective separation and reuse of active catalyst. With an integrated catalyst recycling strategy and membrane-based separation of co-product, the process operated continuously for 75 hours, showing stable process operation and high catalyst rejection rates.