Coking-Resistant Polyethylene Upcycling Modulated by Zeolite Micropore Diffusion.

Although the mass production of synthetic plastics has transformed human lives, it has resulted in waste accumulation on the earth. Here, we report a low-temperature conversion of polyethylene into olefins. By mixing the polyethylene feed with rationally designed ZSM-5 zeolite nanosheets at 280 °C in flowing hydrogen as a carrier gas, light hydrocarbons (C1-C7) were produced with a yield of up to 74.6%, where 83.9% of these products were C3-C6 olefins with almost undetectable coke formation. The reaction proceeds in multiple steps, including polyethylene melting, flowing to access the zeolite surface, cracking on the zeolite surface, formation of intermediates to diffuse into the zeolite micropores, and cracking into small molecules in the zeolite micropores. The ZSM-5 zeolite nanosheets kinetically matched the cascade cracking steps on the zeolite external surface and within micropores by boosting the intermediate diffusion. This feature efficiently suppressed the intermediate accumulation on the zeolite surface to minimize coke formation. In addition, we found that hydrogen participation in the cracking process could hinder the formation of polycyclic species within zeolite micropores, which also contributes to the rapid molecule diffusion. The coking-resistant polyethylene upcycling process at a low temperature not only overturns the general viewpoint for facile coke formation in the catalytic cracking over the zeolites but also demonstrates how the polyethylene-based plastics can be upcycled to valuable chemicals. In addition to the model polyethylene, the reaction system worked efficiently for the depolymerization of multiple practically used polyethylene-rich plastics, enabling an industrially and economically viable path for dealing with plastic wastes.

Olfaction alters spatial memory strategy of scatter-hoarding animals.

Although it has been suggested that olfaction is closely interconnected with hippocampal systems, whether olfaction regulates spatial memory strategy remains never known. Furthermore, no study has examined how olfaction mediates spatial memory established on the external objects, for example, caches made by scatter-hoarding animals. Here, we experimentally induced nondestructive and reversible olfaction loss of a scatter-hoarding animal Leopoldamys edwardsi, to test whether and how olfaction regulates spatial memory to mediate cache recovery and pilferage. Our results showed that the normal L. edwardsi preferred to pilfer caches of others rather than to recover their own using accurate spatial memory (35.7% vs. 18.6%). Anosmic L. edwardsi preferred to recover the caches they made prior to olfaction loss rather than to pilfer from others relied on spatial memory (54.2% vs. 36.0%). However, L. edwardsi with anosmia showed no preference either to the caches they established after olfaction loss or caches made by others (25.8% vs. 29.1%). These collectively indicate that olfaction loss has a potential to affect new memory formation but not previously established spatial memory on caches. Our study first showed that olfaction modified spatial memory strategy in cache recovery and pilferage behaviors of scatter-hoarding animals. We suggest that future studies pay more attention to the evolution of olfaction and its relationship with spatial memory strategy.