The valorization of waste polyolefins via mild temperatures is advantageous over high temperature thermal deconstruction processes such as pyrolysis. For this study, we investigate different bifunctional catalysts (Ru, Mo, Co) which are considered robust heterogenous catalytic systems active for the cleavage of C-C bonds. We further examine the behavior of those catalysts on a wide range of acidic and neutral supports such as silica or zeolite and provide a detailed structural investigation of these systems under hydrogenolysis reaction conditions using in situ/operando X-ray absorption spectroscopy (XAS) to understand the structure property relationships and the specific role the metals play in polypropylene and polyethylene deconstruction. We discuss several aspects such as the role of support, extent of reduction and intrinsic thermal properties to help shed light onto the catalytic chemistry and reactivity <i>in situ</i>/operando at the atomistic level<i>.</i> XAS measurements on the reduced Ru impregnated bifunctional catalysts indicate that there are differences in the average Ru nanoparticle size, with the estimated average particle smaller on the acidic supports over their neutral counterparts. In situ/operando XAS under hydrogenolysis (under ambient hydrogen flow conditions in model olefins butane or n-dodecane at 200°C) further revealed that the average local chemical environment remains unchanged. These studies, in combination with complimentary surface measurements, suggest the added role of support choice in steering selectivity for polymer chemical transformation and deconstruction. Knowledge obtained will help provide insight into the generation of deconstruction catalyst by design, guide further studies with more complex hydrocarbon sources and enable plastic transformation at large.

Tracking structural changes in metal-based hydrogenolysis catalysts for polyolefin deconstruction under mild temperature using in situ/operando X-ray absorption spectroscopy

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