Miguel Angel Gutiérrez-Ortiz

Aviation is a major contributor to greenhouse gas emissions, and thus developing renewable alternatives such as lignin-derived biofuels is critical. Current catalytic routes for hydrodeoxygenation of bio-oil model compounds, such as isoeugenol, fail to produce the desired aromatics to cycloalkane ratios required for aviation fuels. We hypothesized that tailoring metal-support interactions in a nickel aluminate spinel catalyst can enable selective formation of hydrocarbon blends meeting fuel specifications. Hydrodeoxygenation of isoeugenol was conducted in a batch reactor using a nickel aluminate spinel catalyst synthesized via a one-pot sol-gel method. Reactions were conducted at 250–300 °C and 20–40 bar hydrogen pressure, and products were analyzed by gas chromatography-mass spectrometry to determine yields of aromatics, cycloalkanes, and intermediates. Catalyst structure and surface properties were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, and electron microscopy to establish structure–performance relationships. Under optimized conditions of 275 °C at 20 bar H ₂ , aromatic and cycloalkane yields reached 16 wt% and 30 wt%, respectively. Reaction trends showed that elevated temperatures favor cycloalkane formation while hydrogen pressure controls intermediate conversion. The moderate Lewis acidity combined with medium-sized Ni ⁰ crystallites promote selective hydrogenation and deoxygenation while minimizing over-hydrogenation. This catalytic system produces fuel-grade hydrocarbon mixtures in a single step, exceeding previously reported performance. These findings provide a practical route for lignin valorization and the production of renewable aviation fuels with reduced greenhouse gas emissions.

Biomass valorization is an essential strategy for converting organic resources into valuable energy and chemicals, contributing to the circular economy, and reducing carbon footprints. Glycerol, a byproduct of biodiesel production, can be used as a feedstock for a variety of high-value products and can contribute to reducing the carbon footprint. This study examines the impact of surface-level modifications of Mg, Cu, and Sn on Ni-Ce-Zr catalysts for the hydrogenolysis of glycerol, with in situ generated hydrogen. The aim of this approach is to enhance the efficiency and sustainability of the biomass valorization process. However, the surface modification resulted in a decrease in the global conversion of glycerol due to the reduced availability of metal sites. The study found that valuable products, such as H₂ and CH₄ in the gas phase, and 1,2-PG in the liquid phase, were obtained. The majority of the liquid fraction was observed, particularly for Cu- and Sn-doped catalysts, which was attributed to their increased acidity. The primary selectivity was towards the cleavage of the C–O bond. Post-reaction characterizations revealed that the primary causes of deactivation was leaching, which was reduced by the inclusion of Cu and Sn. These findings demonstrate the potential of Cu- and Sn-modified Ni-Ce-Zr catalysts to provide a sustainable pathway for converting glycerol into value-added chemicals.

A morphological strategy consisting of nanocasting synthesis of nickel aluminate spinel precursor was addressed. Two nanocasted catalysts were synthesized involving different template-removal procedures (i.e., Teflon-assisted calcination vs. NaOH washing) for spinel recovery. As a reference, spinel NiAl₂O₄ supported by SBA-15 and bare nickel aluminate spinel were selected. The obtained solids were characterized in detail, examining their textural, acid–base, structural and compositional characteristics, either in the calcined or reduced forms. The as-obtained catalysts’ performance was evaluated in the aqueous-phase reforming of glycerol at 235 °C and 35 bar. Exhausted samples were also characterized to enlighten changes in catalyst properties during the aqueous-phase reaction. NiAl/SBA-15 and NiAl-NCF catalyst showed very poor catalytic performance for the glycerol transformation. NiAl-NCN catalyst presented improved activity with respect to NiAl, with a 20% higher hydrogen production rate but, as a drawback, higher methane formation for a whole range of glycerol conversions. Exhausted catalyst indicated nickel oxidized in liquid phase reaction.

Bimetallic Pt-Co catalysts derived from cobalt aluminate spinel were investigated in the liquid-phase water–gas shift (WGS) reaction and CO hydrogenation. Liquid-phase WGS is a key reaction in the aqueous-phase reforming (APR) of polyols; thus, WGS activity is essential to formulate good APR catalysts. In this work, catalysts with different Pt/Co molar ratios were synthesized together with a reference Pt/alumina. All the synthesized catalysts were characterized by various techniques in order to gain knowledge on their structural and surface characteristics. WGS activity was tested with a feedstream of CO/H₂O = 1/15 (space-time of 76.8 kg_cat·s/mol_CO), isothermal operation at 260 °C and 50 bar, for 10 TOS. Bimetallic Pt-Co catalysts showed improved activity in liquid-phase WGS in comparison to bare Co or Pt catalysts, which was ascribed to the synergistic effect. Despite being subjected to an increased hydrogen concentration in the feedstream (H₂/CO between 0 and 12/3), these catalysts maintained a preferential selectivity towards WGS activity. In addition, the effect of temperature (220–260 °C) and pressure (25–50 bar) was investigated over a catalyst with 0.3Pt/CoAl. CO conversion and CO₂ yield were more sensitive to temperature, while a higher pressure favored methane production. The measured activation energy in the 220–260 °C temperature range was 51.5 kJ/mol.