Developing structure-performance relationships with the underlying goal of optimizing known zeolite catalysts involves the manipulation of their physicochemical properties. Here, we systematically assessed the impact of mesoscopic gradients in acid site concentration, which has received little attention in the design of zeolite catalysts for hydrocarbon upgrading. A series of core-shell MEL-type zeolites were synthesized with catalytically active ZSM-11 cores and passivated silicalite-2 shells of varying thickness. Our findings revealed that ZSM-11@silicalite-2 particles with ultrathin shells (< 10 nm) have enhanced mass transport, characteristic of relatively smaller particles, compared to the corresponding ZSM-11 core. Catalytic testing using the methanol-to-hydrocarbon (MTH) reaction showed that core-shell zeolites exhibit longer lifetimes, higher total turnovers, and an unexpected promotion of the aromatic cycle in the hydrocarbon pool mechanism. Time-resolved acid titration of core and core-shell catalysts confirmed that the siliceous shell introduces a hydrophobic exterior that impacts molecular diffusion. In comparison, prepared MFI core-shells (ZSM-5@silicalite-1) showed similar enhancement in catalyst performance. Moreover, we prepared egg-shell configurations of each zeolite, silicalite-2@ZSM-11 and silicalite-1@ZSM-5, comprised of an inert core and catalytically active shell. This inverse design of the egg-shell created pseudo nanosheets with total turnovers that were markedly higher than their homogeneous counterparts. Collectively, this study demonstrated that mesoscopic gradients in acid concentration via the design of core-shell and egg-shell zeolites markedly improve catalyst performance over conventional analogues for hydrocarbon upgrading.

开发结构-性能关系与优化已知沸石催化剂的潜在目标涉及对其物理化学性质的操纵。在这里，我们系统地评估了细观梯度对酸位浓度的影响，这在用于烃类升级的沸石催化剂的设计中很少受到关注。合成了一系列具有催化活性的 ZSM-11 核和不同厚度的钝化硅沸石-2 壳的核-壳 MEL 型沸石。我们的研究结果表明，与相应的 ZSM-11 核相比，具有超薄壳（< 10 nm）的 ZSM-11@silicalite-2 颗粒具有增强的质量传输，这是相对较小颗粒的特征。使用甲醇制烃 (MTH) 反应的催化测试表明，核壳沸石具有更长的寿命，更高的总转化率，以及烃池机制中芳香循环的意外促进。核和核-壳催化剂的时间分辨酸滴定证实，硅质壳引入了影响分子扩散的疏水外部。相比之下，制备的 MFI 核壳（ZSM-5@silicalite-1）表现出类似的催化剂性能增强。此外，我们制备了每种沸石的蛋壳结构，silicalite-2@ZSM-11 和silicite-1@ZSM-5，由惰性核和催化活性壳组成。蛋壳的这种反向设计产生了总周转率明显高于同质对应物的假纳米片。总的来说，