resumo
In this work, yttrium containing dealuminated Beta zeolites (Y/deAlBeta) were synthesized and characterized by various spectroscopic techniques to improve understanding of ethanol upgrading over these materials. Characterization results indicate yttrium atoms partially condense with framework silanol nests formed during dealumination of parent Al-Beta supports. Active sites for conversion of ethanol and acetaldehyde to butadiene were quantified on a series of Y/deAlBeta catalysts (0.1-10 wt% yttrium) via ex situ chemisorption and transmission Fourier transformed infrared (FTIR) spectroscopy measurements by first measuring the integrated molar extinction coefficient (IMEC) for pyridine bound to Lewis acidic yttrium sites. In situ titrations with pyridine demonstrate that the number of sites quantified by ex situ chemisorption IR is quantitatively similar to the number of sites that catalyze butadiene formation, which varies (from 0.05 to 0.35) across the series of catalysts. In situ pyridine titrations impact butadiene site time yields (STY), but not crotonaldehyde STY, indicating that a distribution of yttrium sites is present, and that discrete yttrium site types participate in distinct steps in the pathway from ethanol to butadiene. Apparent kinetic parameters including activation energies and reaction orders were measured, these suggest differences in reactant (or reactant-derived intermediate) surface coverages result in higher STYs (per mol Y or per Lewis acidic Y site) for samples with low Y loadings relative to those with higher Y loadings. Isotopic labeling experiments evince the existence of other kinetically relevant steps in addition to the crotonaldehyde transformation to crotyl alcohol. Together, these findings provide further guidance into the heterogeneities in site structures in yttrium-containing zeolites and their relevance for the various steps in the pathway from ethanol to C4 4 products useful for production of sustainable aviation fuel and renewable butadiene.
palavras-chave
RAY-ABSORPTION SPECTROSCOPY; ACID SITES; ZN-Y/BETA; CATALYSTS; REACTIVITY
categoria
Chemistry; Engineering
autores
Borate, SN; Samad, N; Purdy, SC; Zhang, JY; Bornes, C; Cordon, MJ; Li, MJ; Mafra, L; Sutton, AD; Li, ZL; Harris, JW
nossos autores
Carlos Bornes
ColaboradorProjectos
agradecimentos
The authors acknowledge Mr. Ryan Kitchen and Ms. Mary Elizabeth Martin for assistance with zeolite synthesis. Drs. Jacklyn Hall and A. Jeremy Kropf (Argonne National Laboratory) are acknowledged for assistance with XAS data collection and analysis. Mr. Rob Holler and Mr. Johnny Goodwin from The University of Alabama Analytical Research Center (AARC) are acknowledged for their assistance in the collection of XRD patterns. S.N.B. and J.W.H. acknowledge financial support from the Oak Ridge Affiliated Universities 2021-2022 Ralph E. Powe Award, from DOE Subcontract #4000180427, and from DOE award #DE-EE0010304. J.W.H. also acknowledges a supplement to NSF award NSF-CBET-2050507, which resulted in collaboration with C.B. and L.M. for collection of the solid-state NMR data reported in this article.M.L., S.P. and A.S. acknowledges funding from Office of Energy Efficiency and Renewable Energy (EERE), Bioenergy Technologies Office (BETO), under contract DE-AC05-00OR22725 (ORNL) with UT-Battle, LLC, and in collaboration with the Chemical Catalysis for Bioenergy (ChemCatBio) Consortium, a member of the Energy Materials Network. Any opinions, findings, and conclusion or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the DOE.