Preparation, application and recycling of a catalytic microflow reactor based on polylactic acid

Highlights: • A novel catalytic microflow reactor based on polylactic acid is developed. • Pd nanoclusters are deposited on the surface of the microreactor channels. • The catalytic microreactor is more active than a commercial catalyst. • The catalytic microreactor maintains the same degradation of the neat material. • The catalytic microreactor is easily recyclable. In this work, novel catalytic microflow reactors prepared by 3D printing and based on polylactic acid (PLA), a compostable biopolymer of relevant industrial interest, were developed. To maintain the properties of the polymer bulk, the metal catalyst, namely palladium (Pd), was deposited in the form of nanoclusters on the surface of the inner walls of the microreactor. A functionalization reaction, i.e. aminolysis, was carried out to activate the channel surface to the metal precursor. The catalyst deposition approach, carried out in water, allowed obtaining a homogeneous distribution of Pd clusters with average dimensions of ca. 20 nm. Hydrogenation reactions performed in a batch system, using reactor sections, superficially decorated with Pd nanoclusters, demonstrated the excellent activity of the system and the absence of the catalyst leaching. In order to prove the effectiveness of the catalytic system under flow conditions, the elimination of the propargyloxy protecting group from Proc-4-methoxybenzylamine was performed using the activated microflow reactor. The higher catalytic activity, observed under flow conditions compared to a batch system, demonstrated the effectiveness of this configuration. Finally, the developed catalytic microreactor was shown to maintain the same degradation behavior as the neat material and to be easily recyclable.