Idoia Hita

Designing supported ZnNi catalysts for the removal of oxygen from bio-liquids and aromatics from diesel

This work describes the effect of the support (TiO2, hybrid 2TiO2–SiO2, SBA-15 and SBA-15 decorated with TiO2 particles) on the catalytic activity of ZnNi catalysts in the gas-phase hydrodeoxygenation (HDO or O-removal) of phenol and the liquid-phase hydrodearomatization (HDA) of synthetic diesel. These reactions are representative of the two major challenges of the hydrotreating unit embedded in a sustainable refinery: (i) decreasing oxygen content of bio-oils (produced in the pyrolysis of lignocellulosic biomass); and (ii) decreasing aromatics content in diesel. The fresh and deactivated catalysts were characterized by XRD, N2 adsorption–desorption, TPR, MS/TPD-NH3, XPS, SEM, HRTEM and coke combustion. Under steady-state conditions, the ZnNi catalyst supported on SBA-15 decorated with TiO2 particles displayed the highest activity in the hydrodeoxygenation of phenol (selectivity toward deoxygenated products > 95%) whereas the ZnNi/SBA-15 catalyst displayed the highest activity in the hydrodearomatization of synthetic diesel. It has been shown that dispersion of the active ingredient is favoured on the SBA-15 substrate. The relationship between structure and activity demonstrated that HDO and HDA reactions require optimized metal dispersion and acid function, metal dispersion being more important for HDA than for HDO reactions.

Experimental Studies on the Hydrotreatment of Kraft Lignin to Aromatics and Alkylphenolics Using Economically Viable Fe-Based Catalysts

Limonite, a low-cost iron ore, was investigated as a potential hydrotreatment catalyst for kraft lignin without the use of an external solvent (batch reactor, initial H2 pressure of 100 bar, 4 h). The best results were obtained at 450 °C resulting in 34 wt % of liquefied kraft lignin (lignin oil) on lignin intake. The composition of the lignin oil was determined in detail (elemental composition, GC-MS, GC×GC-FID, and GPC). The total GC-detectable monomeric species amounts up to 31 wt % on lignin intake, indicating that 92 wt % of the products in the lignin oil are volatile and thus of low molecular weight. The lignin oil was rich in low-molecular-weight alkylphenolics (17 wt % on lignin) and aromatics (8 wt % on lignin). Performance of the limonite catalyst was compared to other Fe-based catalysts (goethite and iron disulfide) and limonite was shown to give the highest yields of alkylphenolics and aromatics. The limonite catalyst before and after reaction was characterized using XRD, TEM, and nitrogen physisorption to determine changes in structure during reaction. Catalyst recycling tests were performed and show that the catalyst is active after reuse, despite the fact that the morphology changed and that the surface area of the catalyst particles was decreased. Our results clearly reveal that cheap limonite catalysts have the potential to be used for the depolymerization/hydrodeoxygenation of kraft lignin for the production of valuable biobased phenolics and aromatics.

Correlating the Process Variables and Products Involved in the Fluid Catalytic Cracking of Waste Feeds

Abstract: Associating the most influential parameters with the product distribution is of uttermost importance in complex catalytic processes such as fluid catalytic cracking (FCC). These correlations can lead to the information-driven catalyst screening, kinetic modeling and reactor design. In this work, a dataset of 104 uncorrelated experiments, with 64 variables, has been obtained in an FCC simulator using 6 types of feedstock (vacuum gasoil, polyethylene pyrolysis waxes, scrap tire pyrolysis oil, dissolved polyethylene and blends of the previous), 36 possible sets of conditions (varying contact time, temperature and catalyst/oil ratio) and 3 industrial catalysts. Principal component analysis (PCA) has been applied over the dataset, showing that the main components are associated with feed composition (27.41% variance); operational conditions (19.09%) and catalyst properties (12.72%). The variables of each component have been correlated with the indexes and yields of the products: conversion, octane number, aromatics, olefins (propylene) or coke, among others.

Insight into structure–reactivity relationships for the iron-catalyzed hydrotreatment of technical lignins

The viability of several technical lignins as a source for biobased platform chemicals was investigated via hydrotreatment using a cheap Fe-based limonite catalyst and without using a solvent. In general, high-quality oils (up to 29 wt% total monomers) with an average relative composition of 55% alkylphenolics and 27% aromatics were obtained. Detailed structural investigations showed that the S-G aromatic unit content of the lignins was the most important factor positively affecting overall oil yields. A second parameter was the lignocellulose processing method. Even though alkaline lignin isolation provides more recalcitrant lignins, their lower aliphaticity and methoxy group content partially limit char and gas formation. Finally, enhanced monomer yields could be obtained irrespective of the ether linkage content, and a high amount of β-O-4 linkages actually showed a slightly negative effect on monomer yields. Overall, the results demonstrate that this route is particularly suitable for processing residual lignin streams.