The escalating crisis of global plastic pollution underscores an urgent need for truly sustainable and closed-loop technological solutions. While chemical recycling presents a promising route, its current reliance on fossil-derived hydrogen fundamentally undermines the process's environmental rationale. Herein, an innovative cascade catalytic system is introduced that directly addresses this challenge by employing the water-gas shift reaction (WGSR) as an in-situ hydrogen source. This integrated strategy enables the efficient conversion of polypropylene (PP) waste into high-value liquid fuels (C 5 -C 22 ). The process is driven by a rationally designed bifunctional catalyst, Ni-Fe 3 O 4 /USY. The reducible Fe 3 O 4 continuously generates active hydrogen species through the WGSR, while Ni finely tunes the redox properties required for CO activation. Concurrently, the acidic sites of the USY zeolite facilitate the selective cleavage of C-C bonds in the polymer chain. The results show that the well-designed tandem reaction achieves >99% conversion of post-consumer PP waste and a remarkably high liquid fuel yield of 83.2% under relatively mild conditions (340 °C). This study establishes a green and intensified pathway for plastic valorization, fundamentally circumventing the dependency on external fossil-based hydrogen and paving the way for more sustainable chemical recycling paradigms.
Selective catalytic oxidation of ammonia (NH 3 -SCO) to N 2 is crucial for abating residual NH 3 emissions, but existing catalysts struggle to combine low-temperature activity with high N 2 selectivity due to competitive Pt-NO interactions. Here we design a tandem confinement catalyst by depositing sub-nanometer Pt clusters (∼0.72 nm) inside the supercages of a Cu-exchanged USY zeolite via atomic layer deposition (ALD), creating intimately paired Pt–Cu active sites. This confined Pt/Cu-USY ALD catalyst achieves >90 % NH 3 conversion and >90 % N 2 selectivity across an exceptionally broad 170-300°C window under simulated exhaust conditions, surpassing all previously reported Pt-based NH 3 -SCO catalysts. The simultaneously enhanced low-temperature activity and high-temperature N 2 selectivity of the Pt/Cu-USY ALD catalyst can be attributed to the spatial confinement of Pt clusters within the Cu-USY framework, which leads to an expanded NO desorption window (150–350 °C). Detailed in situ studies further reveal that N 2 O 4 species preferentially serve as NO storage intermediates on the Pt/Cu-USY ALD catalyst surface at low temperatures, exhibiting significantly lower formation barriers compared to free nitrates, which dominate as intermediates in conventional Pt–Cu systems. This effectively mitigates free nitrate–induced site poisoning and overcomes the typical activity–selectivity trade-offs observed in conventional Pt–Cu dual-site catalysts.
SSZ-13 has been widely used in catalysis and adsorption due to its excellent hydrothermal stability and large specific surface area. It was reported that the long crystallization time was one of the primary challenges limiting its industrial progress. In this paper, we reported a novel solid-state grinding route of synthesizing SSZ-13 zeolite, which was based on interzeolite transformation strategy and promoted by sodium persulfate (Na 2 S 2 O 8 ). The effects of the amount of Na 2 S 2 O 8 and crystallization time on the purity and crystallinity of SSZ-13 zeolite were studied by XRD measurements in detail. The results indicated that the crystallization time could be significantly shortened from 72 to 24 h when the molar ratio of Na 2 S 2 O 8 /SiO 2 was changed from 0 to 0.01, proving that Na 2 S 2 O 8 has the ability of accelerating the crystallization of SSZ-13 as a hydroxyl radical reagent. Three typical SSZ-13 materials and a reference sample were used as the catalysts for methanol-to-olefins reaction (MTO) and their physicochemical properties were analyzed by SEM, N 2 physisorption and NH 3 –TPD techniques. The SEM characterization results showed that the crystal size of SSZ-13 synthesized in the presence of Na 2 S 2 O 8 was larger than that of the one in the absence of it. The NH 3 –TPD results showed that the introduction of Na 2 S 2 O 8 could modulate the acid properties of SSZ-13 zeolites. The MTO tests revealed that the catalytic lifetime of one sample with Na 2 S 2 O 8 promoter (SSZ-13-0.01M-24h) was much longer than that of the other three samples. The observed difference in catalytic stability was mainly attributed to their various concentrations of medium strong acid sites.
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