Chemical repurposing has emerged as a promising route to valorize "end-of-use" plastic waste and mitigate its release to the environment. In this work, we applied silica-supported cobalt (5 wt % Co/SiO 2 ) catalysts to produce liquid-range hydrocarbons (C 5 −C 30 ) in the batch phase at 200−300 °C, 20−40 bar H 2 , and 2−36 h with high selectivity and investigated the reaction pathways, the influence of catalyst phase on the product yields and selectivity, and the catalyst deactivation mechanisms. Reaction conditions were optimized for improving liquid product yields at 275 °C, 30 bar H 2 , and 8 h reaction time, giving a 55% liquid product yield (C-mole basis), comprising 75% of nonsolid products, with gas yields limited to ∼19%. By tracking product evolution over time and with varying cobalt surface density, we propose a multipathway mechanism, including a dominant, nonterminal C−C cleavage route on the polymer chain over the catalyst, which drives the high liquid product selectivity. The catalyst also showed recyclability over four reactions with reduced activity and a shift in yield toward liquid products after the first reaction. It was effectively regenerated by calcination under air at 450 °C. We combined the reactivity data with powder X-ray diffraction (PXRD), thermogravimetric analysis coupled with mass spectrometry (TGA-MS), and catalyst surface areas via N 2 physisorption of various fresh, spent, recycled, and regenerated catalysts to attribute the reduced activity and selectivity shift mainly to the presence of a recalcitrant polymer species embedded on the catalyst, comprising 10.5−18.5 wt % of the spent catalyst, which obstructs access to active sites and increases liquid selectivity and overshadows the influence of carbonaceous coke or catalyst phase reduction to Co. Moreover, we successfully applied the catalyst to various postconsumer polyethylene (HDPE and LDPE) samples. These results move the field toward more sustainable and economically viable catalysts for the chemical upcycling of waste plastics.

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The thermocatalytic conversion of carbon dioxide (CO2) into valuable hydrocarbons presents a promising solution for mitigating anthropogenic CO2 emissions while producing drop‐in replacements for fossil‐derived products. Among the two tandem mechanisms for the direct hydrogenation of CO2, the methanol synthesis coupled with the methanol to hydrocarbon (MTH) reaction offers an improvement over the reverse water‐gas shift coupled with Fischer‐Tropsch synthesis reaction (RWGS‐FTS), as it is not limited Anderson‐Schulz‐Flory distribution and yields higher selectivity towards specific products (e.g., olefins, aromatics, higher hydrocarbons). Herein, we focus on the recent progress achieved through this pathway and outline the existing knowledge gaps. We discuss the challenges involved in the process and highlight the key descriptors in the selection of catalyst components. Finally, we present several potential solutions to circumvent the current challenges, aiming to expedite the advancement of this route toward an efficient CO2 hydrogenation process.

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Widespread plastic pollution has led to an environmental crisis, motivating new and effective methods for recycling and upcycling “end-of-use” plastics. In this review, we highlight recent advances in chemical recycling and upcycling pathways, namely, hydroconversion, pyrolysis, and solvent treatment for the deconstruction and valorization of post-consumer plastics. We highlight the advances in the design of supported metal catalysts (Pt, Ru, Zr), for the hydroconversion of plastics, especially polyolefins (PO) and polyesters. We deduce mechanistic insights by comparing and contrasting small alkane and PO hydroconversion reactions. We also review the two types of solvent treatments: chemical solvent treatment (solvolysis) for condensation polymers and solvent extraction for composite polymers. Further, we discuss advances in pyrolysis and cross alkane metathesis to deconstruct POs into liquid hydrocarbons, and finally, the functionalization of POs into vitrimers and adhesives. We highlight the challenges and envision the path forward in optimal catalyst and process design that will enable the development of chemical upcycling technologies for building a circular plastic economy.