Hortal Sánchez, Isabel

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    Conversion of carbohydrates to alpha-hydroxy-acids over Lewis acidic HF-, SN- and ZR- beta zeolite catalysts using gamma-valerolactone and water as solvent
    (2019-07-10) Hortal Sánchez, Isabel; Cardona Martínez, Nelson; College of Engineering; Hernández Maldonado, Arturo J.; Pagán Torres, Yomaira; Department of Chemical Engineering; Mathanker, Sunil K.
    The incorporation of Sn, Hf and Zr in the structure of Beta zeolite using a post-synthetic method gives catalysts with Lewis acidity that are effective for the conversion of C6 sugars to alpha-hydroxy acids (AHAs), such as lactic acid. Sn-Beta zeolite with a Si/Sn of 561 has the best catalytic performance both in water and in a 9:1 mixture of gamma-valerolactone (GVL) and water. The use of GVL as cosolvent with water improves the activity, selectivity and stability of the catalysts for the conversion of C6 carbohydrates to AHAs. Glucose conversion in GVL:water 9:1 is a viable pathway for AHAs production. The use of toluene at room temperature is an effective method for the extraction of the products from GVL. At room temperature the combination forms a bi-phasic solvent system giving an organic phase rich in GVL and toluene and an aqueous phase rich in AHAs and water.
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    Valorization of carbohydrates using polar aprotic solvents and acid Beta catalysts
    (2024-06-28) Hortal Sánchez, Isabel; Cardona Martínez, Nelson; College of Engineering; Pagán Torres, Yomaira; Acevedo Vélez, Claribel; Velázquez Figueroa, Carlos; Department of Chemical Engineering; Huertas Miranda, Javier A.
    Dependence on fossil fuels depletes resources and harms the environment, necessitating the search for ecologically acceptable and viable alternatives. Biorefineries are proposed as a potential replacement for traditional refineries, using biomass residues as feedstock for chemical synthesis. Acid Beta zeolite catalysts are effective in converting carbohydrates from sustainable biomass into various value-added compunds ¹,² this study investigated the effects of synthesis, characterization, solvent, and acid on the catalytic performance of materials in converting carbohydrates to lactic acid (LA), 5-hydroxymethylfurfural, difructose anhydride (DFA), and 1,6-anhydrosugars. We developed a method for Sn-Beta zeolite synthesis using heptane as a solvent during grafting, achieving over 2% tin content without detectable extraframework tin oxide. Water is essential for producing LA, from C6 sugars using Sn-Beta as a catalyst. Additionally, acetone-H₂O versus gamma-valerolactone (GVL)-H₂O improved LA yield at similar conversion. At 76% conversion, acetone-water 9:1 displayed a 36% yield towards LA versus 18% in GVL-water 9:1. Acetone not only improves the yield to LA but is cheaper, reduces the yields of formic and acetic acid and is easier to separate from the product mixture. On the other hand, the use of pure GVL shifts the product distribution towards dehydrated molecules, yielding DFA from fructose and 1,6-anhydrosugars from aldohexoses. Maximum yields were 75% of DFA at 94% of fructose conversion and 73% of 1,6-anhydromannose yield at 91% of mannose conversion. Both Lewis and Brønsted acid Beta catalysts are effective. To our knowledge, this study is the first to report the production of 1,6-anhydrosugars and DFA from fructose and aldohexoses, respectively, in pure GVL using acid Beta zeolites. This work underscores the importance of solvent selection in catalytic biomass conversion processes and provides novel insights into producing value-added chemicals from carbohydrates.