The catalytic upgrading of polyethylene-derived pyrolysis oils using ZSM-5 zeolites enables the cost-effective production of valuable chemicals from plastic waste, fostering a circular economy through resource recycling. To achieve high-performance catalyst design, balancing active site accessibility and selectivity is crucial. Here, we report a monolithic ZSM-5 @nano-ZSM-5 core-shell catalyst (mZ@nZ) fabricated via vat photopolymerization, in situ crystal engineering, and a one-step desilication-recrystallization treatment. The micromorphologies and microstructures of the core-shell catalysts are investigated using electron microscopies and physical adsorption methods. The mZ@nZ catalyst features a self-supporting face-centered cubic macrostructure with a layer of compositionally heterogeneous ZSM-5 zeolites, which comprises a catalytically benign nano-ZSM-5 shell (Si-rich) and a catalytically active ZSM-5 core (Al-rich). Abundant mesopores are created in mZ@nZ through desilication and zeolite agglomeration processes. This design offers three significant advantages: (1) enhanced active site accessibility via in situ zeolite growth, (2) surface passivation using a Si-rich shell to minimize side reactions, and (3) improved diffusion facilitated by the hierarchical structure, reducing light olefin secondary reactions and coke formation. Compared to pristine monolithic ZSM-5 and a reference pelletized catalyst, the mZ@nZ catalyst demonstrates superior performance in terms of higher light olefin yields and selectivities, with enhanced resistance to coking in the model compound and real LDPE pyrolysis oil cracking reactions. This research showcases a rational design approach at both macroscopic and microscopic scales, offering valuable insights for advancing polyolefin waste upgrading and novel zeolite catalyst design.

使用 ZSM-5 沸石对聚乙烯衍生的热解油进行催化升级，可以从塑料废物中经济高效地生产有价值的化学品，通过资源回收促进循环经济。为了实现高性能催化剂设计，平衡活性位点的可及性和选择性至关重要。在这里，我们报道了一种通过还原光聚合、原位晶体工程和一步脱硅-重结晶处理制备的整体式 ZSM-5 @nano-ZSM-5 核壳催化剂 (mZ@nZ) 。使用电子显微镜和物理吸附方法研究了核壳催化剂的微观形貌和微观结构。mZ@nZ 催化剂具有自支撑面心立方宏观结构，具有一层组成异质 ZSM-5 沸石，其中包含催化良性纳米 ZSM-5 壳（富硅）和催化活性 ZSM-5 核（阿尔富）。通过脱硅和沸石团聚过程，在 mZ@nZ 中产生丰富的中孔。该设计具有三个显着优点：(1) 通过原位沸石生长增强活性位点的可及性，(2) 使用富硅壳进行表面钝化以最大限度地减少副反应，以及 (3) 分层结构促进了扩散，减少了光烯烃副反应和焦炭形成。与原始的整体式 ZSM-5 和参考颗粒催化剂相比，mZ@nZ 催化剂在更高的轻质烯烃产率和选择性方面表现出优异的性能，并且在模型化合物和真正的 LDPE 热解油裂化反应中具有增强的抗结焦性。这项研究展示了宏观和微观尺度上的合理设计方法，为推进聚烯烃废物升级和新型沸石催化剂设计提供了宝贵的见解。