Rimer, Jeffrey D.2021-08-13December 22020-12December 2Portions of this document appear in: Le, Thuy T., Aseem Chawla, and Jeffrey D. Rimer. "Impact of acid site speciation and spatial gradients on zeolite catalysis." Journal of Catalysis 391, no. C (2020).; Rimer, Jeffrey D., Aseem Chawla, and Thuy T. Le. "Crystal engineering for catalysis." Annual review of chemical and biomolecular engineering 9 (2018): 283-309.; Shen, Yufeng, Thuy T. Le, Donglong Fu, Joel E. Schmidt, Matthias Filez, Bert M. Weckhuysen, and Jeffrey D. Rimer. "Deconvoluting the competing effects of zeolite framework topology and diffusion path length on methanol to hydrocarbons reaction." Acs Catalysis 8, no. 12 (2018): 11042-11053.; Hwang, Andrew, Thuy T. Le, Zhichen Shi, Heng Dai, Jeffrey D. Rimer, and Aditya Bhan. "Effects of diffusional constraints on lifetime and selectivity in methanol-to-olefins catalysis on HSAPO-34." Journal of Catalysis 369 (2019): 122-132.https://hdl.handle.net/10657/8092Zeolites, with their diverse framework topology and tunable acidity, are highly utilized as commercial catalysts with one of the most popular applications being the production of hydrocarbons from methanol (MTH). Although MTH is a commercial reaction, there are various mechanistic aspects that are not fully understood, and ongoing efforts are focused on ways to improve catalyst performance and establish fundamental understandings of structure-performance relationships. One of the critical challenges in this area of research is the inherent complexity of zeolite synthesis, which can result in catalysts with a range of compositions, morphologies, and defects. This dissertation aims to better correlate the physicochemical properties of zeolites with their catalytic performance through the development of characteristic descriptors and elucidating the effect of compositional (acid site) gradients using MTH as a benchmark reaction. We first investigated the introduction of defects that occurs during zeolite ZSM-5 crystallization as a result of complex nonclassical crystallization mechanisms using time-resolved dissolution studies coupled with ex situ electron and scanning probe microscopy. Our findings reveal that ZSM-5 (MFI framework) undergoes multiple stages of growth (both classical and nonclassical), which can lead to catalysts with a high concentration of crystalline defects. These defects can affect mass transport properties of zeolites and consequentially catalytic performance. To quantitatively assess the impact of mass transport limitations in zeolites, we investigated the use of experimentally obtained diffusional timescales to account for the effect of diffusional constraints, imposed by crystallite size and defects, on catalytic lifetime in MTH reaction for three zeolites/zeotypes: ZSM-5 (MFI), ZSM-11 (MEL), and SAPO-34 (CHA). Lastly, using the developed descriptors, we focused on elucidating the impact of mesoscopic compositional gradients within zeolite catalysts on MTH catalyst performance. In recent years, improvements in the design and optimization of zeolite catalysts have shifted toward modulation of elemental composition, including the characterization and understanding of acid site speciation and distribution within zeolite particles; however, mesoscopic compositional gradients within zeolite catalysts is often overlooked. Here, we reported a one-pot synthesis of ZSM-5 with compositional gradient (i.e., zoning) and investigated its performance in MTH. We demonstrated that Si-zoned ZSM-5 exhibits improved lifetime in comparison to its homogeneous counterpart due to the reduction of diffusion limitations and the suppression of external coking as a result of its siliceous (passivated) exterior. We further expanded this study to determine the effect of siliceous shell thickness in core-shell zeolite catalysts (i.e., zoning analogues), which show similar improvement in lifetime, albeit with different trends in selectivity. Our findings suggest that there are distinct differences at the exterior-interior interface for zoned and core-shell catalysts that can influence mass transport properties and impact product selectivity.application/pdfengThe author of this work is the copyright owner. UH Libraries and the Texas Digital Library have their permission to store and provide access to this work. UH Libraries has secured permission to reproduce any and all previously published materials contained in the work. Further transmission, reproduction, or presentation of this work is prohibited except with permission of the author(s).Heterogeneous catalysiszeolitemethanol-to-hydrocarbons2021-08-13Thesisborn digital