Iminodiacetic acid synthesis in a microchannel reactor

The synthesis of iminodiacetic acid (IDA) by diethanolamine (DA) dehydrogenation over a Cu/ZrO₂ catalyst in a microchannel rector has been investigated and has been compared to the same synthesis in an autoclave. The output capacity of the microchannel reactor per unit volume of the reaction zone and per unit weight of the catalyst is 4.38 (g IDA)/(cm³ h) and 0.49 (g IDA)/(g Cat h), respectively, while the corresponding output capacities of the autoclave are 0.018 (g IDA)/(cm³ h) and 0.46 (g IDA)/(g Cat h). A kinetic analysis has demonstrated that IDA synthesis proceeds in two steps, yielding N-(2-hydroxyethyl)glycine as an intermediate product. A formal two-step kinetic scheme has been proposed, and the apparent rate constants of the reaction steps have been calculated. These rate constants for the synthesis in the microchannel reactor are several orders of magnitude higher than the corresponding constants for the synthesis in the autoclave. The output capacity per unit volume of the reaction zone for the microchannel reactor is two orders of magnitude higher than for the autoclave. This is evidence that the process in the submillimeter-sized channels is markedly intensified owing to the high heat and mass transfer efficiency.