PhD Defense of Mateus FREITAS PAIVA

Prof. Dorota RUTKOWSKA-ŻBIK

Thesis reviewer

Jerzy Haber Institute of Catalysis and Surface Chemistry - Polish Academy of Sciences - (Poland)

Prof. Elinor SCOTT 

Thesis reviewer

University of Wageningen - (Netherlands)

Dr. Olivier HERBINET 

Thesis reviewer

Université de Lorraine - (France)

Dr. Dorothée LAURENTI

Member

CNRS / University of Lyon - (France)

Dr. Guillaume VANHOVE

Thesis supervisor

University of Lille - (France)

Prof. Fábio BELLOT NORONHA

Thesis Co-supervisor

National Institute of Technology - (Brazil) / Centrale Lille - (France)

Prof. Harry BITTER 

Invited

University of Wageningen - (Netherlands)

Dr. Robert WOJCIESZAK

Invited

CNRS / University of Lorraine - (France)

Biorefineries; Lignocellulosic biomass; Fractionation; Catalysis; Combustion kinetics

The integral valorization of lignocellulosic biomass through efficient and sustainable technologies is essential for the production of renewable fuels and chemicals. This thesis investigates the use of Molten Salt Hydrate (MSH) systems as a reaction medium for the solubilization and depolymerization of biopolymers, such as cellulose and hemicellulose. The main objective was to maximize biomass conversion and the production of high-value platform molecules, while also enabling the valorization of residual lignin, through catalytic processes. Comparative studies were conducted on different MSHs, such as LiBr and ZnCl₂, and heterogeneous solid catalysts, including polymer resins, metal oxides, and zeolites, assessing their stability and efficiency in converting carbohydrate fractions from both commercial sources and real biomass (agro-industrial residues like wheat straw, sugarcane bagasse, and woods like eucalyptus and pinus). The results indicate that MSH systems are promising for the efficient fractionation of biomass, enabling the extraction of cellulose and hemicellulose fractions and their subsequent one-pot conversion under mild optimized conditions (90°C, 2h), yielding considerable amounts of monosaccharides and other platform compounds (e.g., 99.8% xylose obtained from wheat straw extraction), while also allowing the isolation of high-purity lignins (>99.6%). These molten lignins were then characterized by different techniques and subjected to reductive catalytic depolymerization (RCD) using a 1%Pd/TiO₂ catalyst, demonstrating their potential for conversion (≥ 50%) into bio-oils containing aromatic monomeric compounds that can be used as precursors for sustainable hydrocarbons. Finally, the study focused on investigating the low-temperature combustion kinetics of two of these cited hydrocarbons, n-propylbenzene (PBZ) and n-propylcyclohexane (PCH), under engine-relevant conditions, measuring their ignition delay times (IDT) in a well-controlled environment through experimental and computational modeling approaches to understand the reaction pathways (reactivity) and the oxidation mechanisms involved.