No abstract

Polyethylene terephthalate (PET) fibers are among the largest plastics in production. Used commonly in textiles, PET fibers are often blended with non-PET components such as cotton, dyes, and additives. As these non-PET components generate impurities during depolymerization, extracting a high-purity terephthalic acid (TPA) monomer from the chemical recycling of textiles is challenging. Here, we demonstrate the extraction of high-quality TPA from the impure crude digestion mixtures containing depolymerized PET fibers and non-PET components. Our approach uses reactive crystallization to turn TPA into a metal−organic framework (MOF). As TPA is the only component in the mixture capable of forming an extended, crystalline structure, TPA monomers are separated from impurities as MOF crystallizes. We demonstrate this concept on recycled TPA (rTPA) extracted from a polyester−cotton blend textile through alkaline hydrolysis, where the impure rTPA was used as an organic linker to prepare MOF . This MOF crystallization removed the trapped impurities. After MOF disassembly, colorless TPA, reminiscent of a virgin-grade monomer, was obtained (yield: 78%). These results demonstrate self-assembly-induced crystallization as a new strategy to selectively recover monomers from complex mixtures.

Hydrogen from water electrolysis is essential to energy and industrial decarbonization. Beyond being a carbon-neutral fuel to stabilize the intermittent nature of the renewable grid, hydrogen also plays a key role in manufacturing including ammonia and steel production. Intermediate-temperature water electrolysis (>200 °C) has several advantages. First, the thermodynamic requirement for water splitting decreases as temperature increases. Second, reaction kinetics are more facile at higher temperatures. We present water electrolysis using an intermediate-temperature solid acid electrolysis cells (SAECs), with CsH2PO4 (CDP) as an electrolyte. Inspired by Fujiwara et al., whose work demonstrated water electrolysis in SAEC1, we extend upon their work to understand the role of electrode materials on stability and efficiency. We analyze the microstructure of post-electrolysis SAFCs to understand the role of temperature and electrode composition on the degradation. We focus on the reaction kinetics of the oxygen evolution reaction (OER) on the anode and present the challenges that must be overcome by future materials. (1) Fujiwara, N.; Nagase, H.; Tada, S.; Kikuchi, R. Hydrogen Production by Steam Electrolysis in Solid Acid Electrolysis Cells. ChemSusChem 2021, 14 (1), 417–427. https://doi.org/10.1002/cssc.202002281.

Electrochemical activation of alkanes plays an enabling role for applications ranging from fuel cells to electro-production of materials and chemicals. Intermediate-temperature (>200 oC) electrochemical devices have improved diffusions, reaction kinetics, and feedstock flexibility. In this contribution, we present the electrochemical activation of alkanes using intermediate-temperature electrochemical devices. Our work is inspired by Duan et al. whose work showed that alkanes can be oxidized as fuel in protonic ceramic fuel cells1. We extend this concept and evaluate whether this electrochemical activation can activate longer-chain hydrocarbons to form industrial gases. We present a comparison of the electrochemical approach to pyrolysis, and in particular, its selectivity. Different electrocatalysts will be evaluated to test both electrochemical and thermal oxidation. Finally, we use small-molecule oxidation experiments to probe how the thermochemical reactions occur in parallel with the electrochemical conversion. We identify the products from these processes and propose the alkane activation mechanism. Duan, C.; Kee, R. J.; Zhu, H.; Karakaya, C.; Chen, Y.; Ricote, S.; Jarry, A.; Crumlin, E. J.; Hook, D.; Braun, R.; Sullivan, N. P.; O’Hayre, R., Highly durable, coking and sulfur tolerant, fuel-flexible protonic ceramic fuel cells. Nature 2018, 557 (7704), 217-222.