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Environmental science & technology 55(11), 7246-7255 (2021). doi:10.1021/acs.est.1c01512, Published by American Chemical Society, Columbus, Ohio

Continuous catalytic cracking of polyethylene over a spent fluid catalytic cracking (FCC) catalyst was studied in a conical spouted bed reactor (CSBR) with fountain confiner and draft tube. The effect of temperature (475–600 °C) and space‐time (7–45 gcat min gHDPE −1) on product distribution was analyzed. The CSBR allows operating with continuous plastic feed without defluidization problems and is especially suitable for catalytic pyrolysis with high catalyst efficiency. Thus, high catalyst activity was observed, with waxes yield being negligible above 550 °C. The main product fraction obtained in the catalytic cracking was made up of C5−C11 hydrocarbons, with olefins being the main components. However, its yield decreased as temperature and residence time were increased, which was due to reactions involving cracking, hydrogen transfer, cyclization, and aromatization, leading to light hydrocarbons, paraffins, and aromatics. The proposed strategy is of great environmental relevance, as plastics are recycled using an industrial waste (spent FCC catalyst)., One man's trash: The use of FCC spent catalyst in a fountain confined spouted bed reactor demonstrates great potential for plastics valorization. A complete polymer conversion towards valuable products as light olefins and gasoline‐range hydrocarbons is obtained. This strategy is of great environmental interest as plastics are recycled using a waste catalyst.

The effect of heat treatment on the gas barrier of the polymer-coated board further coated with an Al 2 O 3 layer by atomic layer deposition (ALD) was studied. Heat treatment below the melting point of the polymer followed by quenching at room temperature was used for the polylactide-coated board [B(PLA)], while over-the-melting-point treatment was utilized for the low-density polyethylene-coated board [B(PE)] followed by quenching at room temperature or in liquid nitrogen. Heat treatment of B(PLA) and B(PE) followed by quenching at room temperature improved the water vapor barrier. However, because of the changes in the polymer morphology, quenching of B(PE) with liquid nitrogen impaired the same barrier. No improvement in oxygen barrier was observed explained by, e.g., the spherulitic structure of PLA and the discontinuities and possible short-chain amorphous material around the spherulites forming passages for oxygen molecules. This work emphasizes the importance of a homogeneous surface prior to the ALD growth Al 2 O 3 barrier layer.