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Synthesis of porous acid carbons for the conversion of glucose to HMF

Grant number: 20/04109-0
Support type:Scholarships in Brazil - Doctorate (Direct)
Effective date (Start): August 01, 2020
Effective date (End): February 29, 2024
Field of knowledge:Physical Sciences and Mathematics - Chemistry - Inorganic Chemistry
Principal researcher:Jean Marcel Ribeiro Gallo
Grantee:José Lucas Vieira
Home Institution: Centro de Ciências Exatas e de Tecnologia (CCET). Universidade Federal de São Carlos (UFSCAR). São Carlos , SP, Brazil

Abstract

Lignocellulosic biomass is the most promising renewable and green source to replace oil, and is also able to produce chemicals and fuels. One of the products obtained from it is 5-hydroxymethylfurfural (HMF), a very important intermediate in the chemical industry. It is obtained from the dehydration of monosaccharides, such as glucose and fructose, using acid catalysis. In the case of fructose, Brønsted acid catalysts are employed and high selectivities for HMF are obtained. Among the solid catalysts used in this reaction, the sulfonated resins Amberlyst 15 and Amberlyst 70 are the ones that present better yields and higher reaction rates for the formation of HMF, however the first resin is commonly used above its optimal operating temperature, and the second stopped being produced recently. Therefore, in this project, we propose the synthesis of different sulfonated carbons with Brønsted acidity and high thermal stability to dehydrate fructose directly to HMF. In the case of glucose, on the other hand, a combination of Lewis and Brønsted acid must be used to produce HMF with high selectivities. In this case, the Lewis site isomerizes glucose in situ to fructose, which is later dehydrated to HMF in the Brønsted sites. Among the bifunctional solids used in this reaction, sulfonated resins modified by partial ionic exchange of protons for metals with Lewis acidity stand out as promising catalysts. Because of this, in this project, we propose the partial ion exchange of protons from Brønsted acid sulfonated carbons by nodes synthesized by cationic complexes with Lewis acid characteristic, in order to obtain a bifunctional material able to produce HMF from glucose. All synthesized materials will be characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), nitrogen physisorption at -196°C, Nuclear Magnetic Resonance in the solid state for the 13C nuclei (ssNMR 13C), Thermogravimetric Analysis (TGA) and Differential Thermal Analysis (DTA) under oxygen flow, Optical Emission Spectroscopy with Inductively Coupled Plasma (ICP-OES) and adsorption of probe molecules monitored by Fourier Transform Infrared spectroscopy (FTIR). In addition, we propose the optimization of experimental parameters by using the chemometrics statistical tool and the understanding of the reaction routes of monosaccharides dehydration using tools of chemical kinetics and kinetic modeling, in order to obtain physical-chemical parameters such as order of reaction of species, reactions rate constants and activation energies of the reactions. (AU)

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