Collaborative Research: Advanced Zeolite-Composite Adsorbents with Fine-Tuned Pore Sizes for Molecular Sieving Separations

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PI: Yu, Miao / Liang, XinhuaProposal Number: 1402772 / 1402122Title: Collaborative Research: Advanced Zeolite-Composite Adsorbents with Fine-Tuned Pore Sizes for Molecular Sieving Separations Mixture separation constitutes a large and costly component of industrial processes. Various separation technologies, such as distillation, extraction, adsorption, and membrane separation, have been developed to separate mixtures utilizing different properties of components in the mixture. Among these technologies, separation processes based on adsorption, such as pressure swing adsorption (PSA) and temperature swing adsorption (TSA), have been widely used in industry. Development of more energy-efficient adsorptive gas separation processes strongly depends on the development of improved porous adsorbents, and porous adsorbents with favorable adsorption isotherms and selectivity for the separation of interest are always the focus of adsorption-based separation processes. Zeolites are one of the most promising adsorbents that may realize true molecular-sieving separation under harsh separation conditions, attributing to their uniform, molecular-sized pores and high chemical, thermal and mechanical stabilities. Despite of a large selection pool of zeolites/molecular sieves and available techniques to adjust their pore sizes, not all desired pore sizes can be obtained for target separations, especially for separation of molecules with very close sizes, such as N2 (kinetic diameter: 0.364 nm)/CH4 (0.38 nm), O2 (0.346 nm)/N2, and paraffin/olefin. Therefore, it is highly desirable to develop new strategies to further fine-tune the pore sizes of zeolite-based materials and fill the pore size gaps between different zeolites. The goal of this proposed research is to fine-tune the pore entrance of zeolites by depositing ultrathin microporous coatings to achieve effective separation for industrially important mixtures that traditional zeolites have difficulty to separate. Ultrathin microporous coatings will be deposited using molecular layer deposition (MLD) on the zeolites to fill the pore-size gaps between different zeolites an obtain enhanced fundamental understanding of deposition mechanisms and coating interactions with zeolite substrates. Specifically, the objectives of the proposed research are: (1) To develop a reliable and reproducible MLD process to deposit ultrathin organic/inorganic hybrid films (with precisely controlled properties) on zeolite substrates and obtain a fundamental understanding on the factors that affect the quality of MLD coatings; (2) To elucidate and understand the decomposition of hybrid MLD coating and pore-generation mechanisms under different conditions; (3) To characterize effective pore sizes of zeolite-composite adsorbents and establish the fundamental coating property-pore entrance size relationship; and (4) To rationally design zeolite composite adsorbents with desired pore sizes and investigate separation performance for target mixtures. This completely new concept may lead to effective adsorptive separation of difficult-to-separate mixtures.This proposed research is expected to have great scientific as well as technological impact on the synthesis of nanostructured zeolite-composite adsorbents with fine-tuned pore sizes for mixture separations and potentially for selective catalysis. If successful, the project will greatly benefit adsorption-based separation processes. It will represent a significant advance in the rational design of zeolite-based adsorbents. The proposed research has significant practical implications on industrially important gas mixture separations. It is anticipated that this study could serve as a model for the rational design of advanced sorbents for adsorption-based separation processes.The PIs have specific defined plans to engage a broad range of students in learning about nanomaterials and molecular sieves. Specific opportunities for minorities will be funded through targeted scholarships and projects during the summer. Both PIs are active in outreach programs for K-12 students in mainly underrepresented populations in the areas of both universities.