Laureano Canoira

This study investigates the etherification of pyrolysis oils derived from pinewood (PWPYO) and sawdust (SWPYO) as a strategy to reduce their high acidity and improve their compatibility with fuel blends. Three etherification procedures were evaluated using potassium carbonate and ethyl iodide (Procedure 1), and ethyl iodide or sec-butyl iodide under phase-transfer catalytic conditions (Procedures 2 and 3, respectively). The upgraded oils were characterized by potentiometric titration, FTIR spectroscopy, and GC × GC–TOF–MS to assess acidity reduction and compositional changes. Significant decreases in acid value were achieved, particularly with Procedure 1, which reduced the acid value of PWPYO from 68.83 to 0.63 mgKOH g–1 and that of SWPYO from 84.78 to 1.38 mgKOH g–1. FTIR and chromatographic analyses confirmed the transformation of phenolic hydroxyl groups into ether functionalities. Medium-scale experiments using Procedure 1 successfully reproduced the acidity reduction and ether formation observed at laboratory scale, although mixing and mass-transfer limitations affected process efficiency. Solubility tests revealed limited miscibility with hydrocarbon fuels but stable blends with short-chain alcohols. Etherification proved to be an effective pretreatment to mitigate acidity in phenol-rich pyrolysis oils, although further optimization is required to improve fuel compatibility and scale-up performance.

This study evaluates the influence of seasonal harvesting conditions on biomass productivity, oil yield, and biodiesel-related FAME composition of native microalgae—predominantly Chlorella sp., with minor populations of Scenedesmus and Ankistrodesmus—cultivated in an open raceway pond integrated into a pig-slurry biogas plant in Soria, Spain. Processing biomass harvested across four seasons showed that oven drying at 45 °C yields stable seasonal biomass concentrations around 7.80–8.80 g/L, while extended outdoor air-drying during spring and summer reduces yields to 2.86 and 4.33 g/L due to the absence of active growth conditions. Lipids extracted via the Soxhlet method using a dichloromethane: methanol mixture (9:1 v/v) exhibited a wide range of 2.5–18.9 g oil per 100 g dry biomass. Marked seasonal variations were observed: winter samples demonstrated an outstanding lipid accumulation capability, yielding the highest oil production (18.9 g/100 g biomass and 1.47 g/L) and a crude ester content reaching 60.75% FAMEs, which reached a maximum of 93.3 wt.% after purification via column chromatography. Conversely, spring, summer, and autumn samples suffered from limited lipid accumulation, with dry-basis oil yields remaining below 4.2 g/100 g biomass. Extensive characterization confirmed that the residual biomass has limited application as a solid fuel because of its low higher heating values (−1) and exceptionally high ash contents, which climbed from 15.98–60.02% to 41.14–51.91% after extraction.

In this study, the feasibility of using a calcined Jatropha curcas shell (JCS) as a solid catalyst for biodiesel production was investigated. Thermogravimetric analysis (TGA) was applied to the precursor biomass to evaluate the stages of the thermal decomposition processes and to identify proper temperature intervals for biomass calcination, aiming to decarbonize to form oxides that have proven to behave as effective active sites. The kinetic parameters were defined by applying Kissinger’s isoconversional method. The activation of the precursor biomass was carried out at three calcination temperatures (700, 800, and 900 °C) and two calcination times (2 and 4 h) in order to evaluate the influence of these operating conditions on the structure, morphology, and catalytic activity of the catalyst. The catalyst was characterized by the Brunauer–Emmett–Teller method (BET), scanning electron microscopy with energy-dispersive X-ray (SEM/EDX), and X-ray diffraction (XRD). The effectiveness of the catalyst was assessed by oil’s transesterification at 60 °C, 2 h of reaction, and a 15:1 alcohol/oil molar ratio. The effects of catalyst loading (1, 3, and 5 wt %) and activation temperature of the catalyst on the yield and conversion to fatty acid methyl esters (FAMEs) were studied. The highest values of conversion and FAME yield were obtained with a 3% catalyst load (calcined at 800 °C for 2 h). Ester content and fatty acid profile were obtained by chromatographic analysis. The results of this study demonstrate that calcined JCS has a high potential as a heterogeneous catalyst for biodiesel production.

The production and use of terpene-based fuels represents a renewable source of energy in the transportation sector, especially in the aviation sector. The literature on the conversion of terpenes into valuable compounds is not new but has been based on the production of products for cosmetics and pharmaceutics. Several established chemical routes are also a way to develop drop-in fuels. The present work explores all the main chemical processes that can transform terpenes into more valuable fuels or additives, focusing on the use of heterogeneous catalysis, catalyst type, operating conditions, and reaction performance. α-pinene is the most studied catalyst, since it is the main component of turpentine. Isomerization is the most frequently applied chemical pathway used to enhance fuel properties, and a wide group of heterogeneous catalysts have been reported, with sulphonic acid resin catalysts, transition metals, alumina, and silicates being the most used. This work also explores the current production and commercialization of terpenes, as well as the challenges for their use as fuels at a commercial scale. The future challenge is to discover new catalysts or to improve the performance of the current products and reduce production costs. The feasibility of the production and commercialization of terpene-derived fuels is also linked to oil prices.

Kaolin waste dumps contain a huge volume of material that cannot be commercialized due to the presence of variable amounts of iron minerals, which impart a yellowish color to the kaolin. Elimination of iron from kaolin using either a chemical or a biological method was the aim of this study. The chemical leaching of iron from kaolin was carried out using response surface methodology to optimize the reaction conditions. Time was found to be the most influential variable, although oxalic acid must be present to leach 32% of the iron. Biological leaching was also assayed for 14 days using a Bacillus strain. The results of bacterial leaching of iron from kaolin showed <1% iron elimination.

Production of biojet fuel from turpentine shows a reduction of 93% of CO₂ eq. emissions. Manual harvesting and resin yield strongly influence the final cost. Cost-competitive for productivities higher than 6 kg of resin per pine per year.

The sodium form of Faujasite Y (Na-FAU) zeolite has been synthesized by the hydrothermal method, and it has been exchanged with ammonium sulphate and later with lanthanum (III) chloride solutions to obtain the La-FAU catalyst. The three zeolites Na-FAU, NH₄⁺-FAU and La-FAU have been characterized by microcrystalline X-ray diffraction, X-ray fluorescence, surface area, pore volume and Brönsted acid sites. The La-FAU catalyst has been successfully activated with boron trifluoride etherate, and it has been tested in the alkylation reaction of isobutane with isobutene up to 112 h of time on stream, since the raw La-FAU catalyst showed a rapid deactivation.