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Controlling the selectivity–stability tradeoff in zeolite catalysis: oligomerization–alkylation, cracking, and methanol-to-hydrocarbons 


    Problem Statement

    Olefins and aromatics are commodity chemicals used in producing plastics (in the petrochemical industry), lubricants, plasticizers, and surfactants, among other products. However, there is an imbalance between their production and demand, which reactions like oligomerization, alkylation, and cracking over zeolites could help address. At the same time, zeolites serve as excellent catalysts for converting methanol to hydrocarbons (MTH), olefins (MTO), or aromatics (MTA). These processes aim to produce light hydrocarbons such as propylene or to convert ethylene into higher-value alpha-olefins, aromatic hydrocarbons (BTX), and jet fuel.


    Our focus in this project is to synthesize, modify, and develop new catalysts with engineered porosity at multiple scales: from hierarchical and hollow zeolites to catalytic particles, bodies, or technical catalysts intended for implementation. Additionally, we incorporate various metals (e.g., Ni, Cr, Zn) to influence the selectivity toward the desired products.

    We utilize various reactors, including forced dynamic, operando, high-throughput packed-bed, and batch reactors.

    OLG-O2H

    Goals

    • Control the catalyst structure to balance selectivity and stability.
    • Metal modulation: Use Ni, Cr, Zn to bias reaction pathways and improve selectivity to target hydrocarbons.
    • Deactivation control: Reduce coke formation and extend catalyst lifetime with regeneration strategies.
    • Reactor optimization: Shape catalysts into bodies/extrudates and validate 100 h continuous stable operation.

    Related People

    Faseeh Kulangara Kandiyil
    Hend Omar Mohamed
    Kiruthika Jayaseelan

    Related Publications

    Implications of Co-Feeding Water on the Growth Mechanisms of Retained Species on a SAPO-18 Catalyst during the Methanol-to-Olefins Reaction

    by Valecillos, Hita, Sastre, Aguayo, Castaño
    ChemCatChem Year: 2021 DOI: https://doi.org/10.1002/cctc.202100124

    Abstract

    The dynamics of retained and deactivating species in a SAPO-18 catalyst during the methanol-to-olefins reaction have been followed using a combination of ex-situ and in-situ techniques in differential and integral reactors.The retained species were analyzed using extraction, in-situ FTIR and in-situ UV-vis spectroscopies combined with online product analysis (gas chromatography and mass spectrometry). The composition of the extracted soluble species was determined using gas chromatography-mass spectrometry and that of the insoluble species using high-resolution mass spectrometry. We observe a decrease in the formation and degradation rates of retained species when co-feeding water, whereas the extent of the decreases is the same across the entire spectrum of retained molecules. This indicates that co-feeding water unselectively quenches the formation of active and deactivating species. At the same time, the catalyst has an extended lifetime when co-feeding water due to the diffusion of species (particularly olefins) out of the SAPO-18 crystals, and subsequent growth of heavy polycyclic aromatic structures that imply less deactivation. These conclusions can be extrapolated to other MTO catalysts with relatively similar pore topology such as SAPO-34 or SSZ-13 structures.

    Keywords

    O2H CRE