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dc.contributor.advisorPagán-Torres, Yomaira J.
dc.contributor.authorAlbarracin-Suazo, Sandra Cecilia
dc.date.accessioned2021-07-14T13:12:46Z
dc.date.available2021-07-14T13:12:46Z
dc.date.issued2021-07
dc.identifier.urihttps://hdl.handle.net/20.500.11801/2803
dc.description.abstractThe development of catalytic pathways to produce commodity chemicals from lignocellulosic biomass is promising for substituting non-renewable fossil feedstock use. This dissertation studied the catalytic performance of molybdenum-based materials for the selective cleavage of C-O bonds in biomass-derived compounds (1,4-anhydroerythritol, tartaric acid, and glycerol) to produce value-added chemicals. The reactions studied include the transformation of (i) 1,4-anhydroerythritol to tetrahydrofuran, (ii) tartaric acid to succinic acid, and (iii) glycerol to 1,2-propanediol and 1,3-propanediol.<br /> Hydrodeoxygenation reactions represent a transformation by which C-O bonds can be selectively cleaved. A heterogeneous MoO<sub>x</sub>-Pd/TiO<sub>2</sub> catalyst was active, selective, and stable in the hydrodeoxygenation of 1,4-anhydroerythritol to tetrahydrofuran. Results obtained from catalyst characterization studies (Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Diffuse Reflectance Infrared Fourier Transform Spectroscopy) and reaction kinetics indicate that hydrogen atoms dissociated over Pd nanoparticles promote the reduction of supported MoO<sub>x</sub> species from a Mo<sup>6+</sup> to Mo<sup>5+</sup>/Mo<sup>4+ </sup>oxidation state. The reduced Mo<sup>5+</sup> and Mo<sup>4+ </sup>centers facilitate the cleavage of vicinal hydroxyls in 1,4-anhydroerythritol to produce the intermediate 2,5-dihydrofuran, which undergoes subsequent hydrogenation to tetrahydrofuran.<br /> The hydrodeoxygenation of tartaric acid to succinic acid over MoO<sub>x</sub>-Pd/TiO<sub>2</sub> was also examined. The MoO<sub>x</sub>-Pd/TiO<sub>2</sub> catalyst exhibited the highest succinic acid production rates among supported oxophilic metal (MoO<sub>x</sub>, ReO<sub>x</sub>, WO<sub>x</sub>) and noble metal (Pd, Pt, Rh) combinations studied. Insights from catalyst characterization and kinetics indicate that an active Mo<sup>5+</sup> center is formed, cleaving internal C-O bonds from tartaric acid while leaving carboxylic acid end-groups intact.<br /> Another catalytic reaction reported in this dissertation is the hydrodeoxygenation of glycerol over Mo<sub>2</sub>C, and Cu promoted Mo<sub>2</sub>C. These catalysts were studied under continuous flow reaction conditions to determine reaction orders, apparent activation energy barrier, product selectivity, and catalyst stability. Reaction kinetic studies show selectivity trends for Mo<sub>2</sub>C and Cu-Mo<sub>2</sub>C powders that agree with the literature reported surface science and computational studies. Mechanistic insights suggest that the reaction proceeds through a concerted bond cleavage and formation pathway. The modification of the catalyst with Cu modifies the oxophilicity of the Mo site, and can be tailored to control the number of glycerol C-O bonds which are cleaved.en_US
dc.description.abstractEl desarrollo de vías catalíticas para producir productos químicos básicos a partir de biomasa lignocelulósica es prometedor para sustituir el uso de materias primas fósiles no renovables. Esta disertación estudió el desempeño catalítico de materiales a base de molibdeno para el rompimiento selectivo de enlaces C-O en compuestos derivados de la biomasa (1,4-anhidroeritritol, ácido tartárico y glicerol) para producir productos químicos de valor agregado. Las reacciones estudiadas incluyen la transformación de (i) 1,4-anhidroeritritol en tetrahidrofurano, (ii) ácido tartárico en ácido succínico y (iii) glicerol en 1,2-propanodiol y 1,3-propanodiol. Un catalizador heterogéneo de MoOx-Pd/TiO2 fue activo, selectivo y estable en la hidrodesoxigenación de 1,4-anhidroeritritol a tetrahidrofurano. Los resultados de los estudios cinéticos y de caracterización de los catalizadores indican que los átomos de hidrógeno disociados sobre nanopartículas de Pd promueven la reducción de especies de MoOx soportadas de un estado de oxidación de Mo6+ a oxidación Mo5+/Mo4+. Los centros de Mo5+ y Mo4+ facilitan el rompimiento de hidroxilos vecinales en 1,4-anhidroeritritol para producir tetrahidrofurano. La hidrodesoxigenación de ácido tartárico a ácido succínico sobre MoOx-Pd/TiO2 se estudió en reactores en tanda. El catalizador MoOx-Pd/TiO2 exhibió la rapidez de producción de ácido succínico más alta entre las combinaciones de metal oxofílico (MoOx, ReOx, WOx) y metal noble (Pd, Pt, Rh) estudiadas. Los conocimientos de la cinética y la caracterización del catalizador indican que se forma un centro Mo5+ que activa los enlaces C-O internos del ácido tartárico. Otra reacción catalítica reportada en esta disertación es la hidrodesoxigenación de glicerol sobre Mo2C, y Mo2C promovido por Cu. Estos catalizadores se estudiaron para determinar los órdenes de reacción, la barrera de energía de activación, selectividades de productos y estabilidad del catalizador. Los estudios cinéticos muestran que las tendencias de selectividad para Mo2C y Cu-Mo2C son consistentes con la literatura reportada en experimentos a vacío usando espectroscopia electrónica de pérdida de energía de alta resolución y estudios computacionales como la teoría de funciones de la densidad. Los resultados mecanísticos sugieren que la reacción procede a través de la formación y rompimiento de enlaces concertados. La modificación del catalizador con Cu altera la oxofilicidad del sitio Mo y se puede adaptar para controlar el número de enlaces C-O de glicerol que se rompen.en_US
dc.description.sponsorshipCenter for a Sustainable Water Energy Food Nexus (SusWEF) through the National Science Foundation Award No. OIA-1632824en_US
dc.language.isoenen_US
dc.subjectHydrodeoxygenationen_US
dc.subjectBiomassen_US
dc.subjectHeterogeneous catalysisen_US
dc.subjectReaction kineticsen_US
dc.subjectTetrahydrofuranen_US
dc.subject.lcshMolybdenumen_US
dc.subject.lcshBiomass conversionen_US
dc.subject.lcshNonrenewable natural resourcesen_US
dc.subject.lcshSuccinic aciden_US
dc.subject.lcshChemical kineticsen_US
dc.subject.lcshGlycerol - Effect of oxygen onen_US
dc.subject.lcshTetrahydrofuranen_US
dc.subject.lcshHeterogeneous catalysisen_US
dc.titleSelective hydrodeoxygenation of biomass-derived oxygenates over heterogeneous Mo-based catalystsen_US
dc.typeDissertationen_US
dc.rights.holder(c) 2021 Sandra C. Albarracin Suazoen_US
dc.contributor.committeeCuret-Arana, María C.
dc.contributor.committeeCardona-Martínez, Nelson
dc.contributor.committeeMartínez-Iñesta, María M.
dc.contributor.representativeOrtiz-Ríos, Gloribell
thesis.degree.levelPh.D.en_US
thesis.degree.disciplineChemical Engineeringen_US
dc.description.noteChapter 2 of this dissertation includes contents that will be published by the authors in ACS Sustainable Chemistry and Engineering from ACS. Chapter 3 of this dissertation is a reprint from an article published in ChemCatChem. Reprinted with permission from Nacy, A.; Lima e Freitas, L. F.; Albarracín‐Suazo, S.; Ruiz‐Valentín, G.; Roberts, C. A.; Nikolla, E.; Pagán‐Torres, Y. J. Selective C−O Bond Cleavage of Bio‐Based Organic Acids over Palladium Promoted MoOx/TiO2. ChemCatChem 2020, 13, 1294, 1294-1298. Copyright (2020) Wiley.en_US
dc.contributor.collegeCollege of Engineeringen_US
dc.contributor.departmentDepartment of Chemical Engineeringen_US
dc.description.graduationSemesterSummeren_US
dc.description.graduationYear2021en_US


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    Items included under this collection are theses, dissertations, and project reports submitted as a requirement for completing a graduate degree at UPR-Mayagüez.

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(c) 2021 Sandra C. Albarracin Suazo
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