Evaluation of Manganese Catalysts for the Hydrogenative Deconstruction of Commercial and End‐of‐Life Polyurethane Samples

Abstract

Polyurethane (PU) is a thermoset plastic that is found in everyday objects, such as mattresses and shoes, but also in more sophisticated materials, including windmills and airplanes, and as insulation materials in refrigerators and buildings. Because of extensive inter-cross linkages in PU, current recycling methods are somewhat lacking. In this work, the effective catalytic hydrogenation of PU materials is carried out by applying a catalyst based on the earth-abundant metal manganese, to give amine and polyol fractions, which represent the original monomeric composition. In particular, Mn-Ph MACHO is found to catalytically deconstruct flexible foam, molded foams, insulation, and end-of-life materials at 1 wt.% catalyst loading by applying a reaction temperature of 180 °C, 50 bar of H 2 , and 0.9 wt.% of KOH in isopropyl alcohol. The protocol is showcased in the catalytic deconstruction of 2 g of mattress foam using only 0.13 wt.% catalyst, resulting in 90 % weight recovery and a turnover number of 905.

Switching between Hydrogenation and Olefin Transposition Catalysis via Silencing NH Cooperativity in Mn(I) Pincer Complexes

“… 19 This was typically confirmed in the studies where alkylation of the N–H functionality produced inactive (de)hydrogenation catalysts. 16h , 16i , 18a , 20 Our catalytic data ( Table 1 , entries 2–5) implies that for olefin transposition, this structure–activity relationship is inverted.…”

Hydrogenative depolymerization of silicon-modified polyureas

“…Having identified the need for selective depolymerization catalysts for silicon-modified polyurea derivatives, we initially studied the catalytic performance of various transition metal catalysts bearing pincer-type ligands. These complexes have only been very recently introduced as active catalysts for the hydrogenative depolymerization of polycarbonate, 29–35 polyurethane, 36–40 and polyurea, 28 however the hydrogenative depolymerization of SMPs has not yet been reported.…”

Manganese-catalyzed hydrogenation, dehydrogenation, and hydroelementation reactions

“…Soon after, in 2022, Skrydstrup developed a similar strategy for the hydrogenative degradation of PUs employing Ph MACHO–Mn( i ) complex Mn39 (Scheme 17, entry 2). 126 At a slightly lower H 2 pressure and temperature, PUs were converted to polyols and 4,4′- and 2,4′-methylene diphenyl diamine derivatives with a much higher TON.…”

“…Polyurethanes (PU) are thermoset polymers made of monomer units of isocyanates and polyols. 126 Polyurethanes contribute almost 8% of the plastic produced, and about 28 megatons of polyurethanes is used per year. 127 Although mechanical recycling is well known, this does not provide a final solution.…”