Catalytic flash pyrolysis of Scenedesmus sp. post-extraction residue using low-cost HZSM-5 catalyst with the perspective to produce renewable aromatic hydrocarbons

Recovering renewable chemicals from de-fatted microalgal residue derived from lipid extraction within the algal-derived biofuel sector is crucial, given the rising significance of microalgal-derived biodiesel as a potential substitute for petroleum-based liquid fuels. As a circular economy strategy, effective valorization of de-fatted biomass significantly improves the energetic and economic facets of establishing a sustainable algal-derived biofuel industry. In this scenario, this study investigates flash catalytic pyrolysis as a sustainable pathway for valorizing Scenedesmus sp. post-extraction residue (SPR), potentially yielding a bio-oil enriched with upgraded characteristics, especially renewable aromatic hydrocarbons. In the scope of this study, volatile products from catalytic and non-catalytic flash pyrolysis were characterized using a micro-furnace type temperature programmable pyrolyzer coupled with gas chromatographic separation and mass spectrometry detection (Py-GC/MS). Flash pyrolysis of SPR resulted in volatile products with elevated oxygen and nitrogen compounds with concentrations of 46.4% and 26.4%, respectively. In contrast, flash pyrolysis of lyophilized microalgal biomass resulted in lower concentrations of these compounds, with 40.9% oxygen and 17.3% nitrogen. Upgrading volatile pyrolysis products from SPR led to volatile products comprised of only hydrocarbons, while completely removing oxygen and nitrogen-containing compounds. This was achieved by utilizing a low-cost HZSM-5 catalyst within a catalytic bed at 500 °C. Catalytic experiments also indicate the potential conversion of SPR into a bio-oil rich in monocyclic aromatic hydrocarbons, primarily BETX, with toluene comprising over one-third of its composition, thus presenting a sustainable pathway for producing an aromatic hydrocarbon-rich bio-oil derived from SPR. Another significant finding was that 97.8% of the hydrocarbon fraction fell within the gasoline range (C5-C12), and 35.5% fell within the jet fuel range (C8-C16). Thus, flash catalytic pyrolysis of SPR exhibits significant promise for application in drop-in biofuel production, including green gasoline and bio-jet fuel, aligning with the principles of the circular economy, green chemistry, and bio-refinery.

Energetic characterization and evaluation of briquettes produced from naturally colored cotton waste

Cotton crops generate millions of tons of lignocellulosic waste in Brazil that could be used in energy generation; however, the main destination of this raw material is soil incorporation. The aim of this work was to perform an energetic characterization and evaluation of briquettes produced from different agricultural waste of naturally colored cotton for power generation. The cultivars Brasil Sementes (BRS) Jade and Topazio were studied, with white cotton (BRS 286) as standard for comparison purposes. Two different parts of each species, stalk and cotton shell, were analyzed by bulk density, proximate analysis, higher heating value, cellulose, hemicellulose, protein, fat and lignin content, thermogravimetric analysis, and briquette mechanical strength. The results of the energetic characterization indicated a higher energetic potential of the colored species when compared with the white cotton, especially because of the volatile matter content, fixed carbon, and higher heating value. The briquette mechanical strength was higher in the samples formulated by a mixture of stalk and shell. Finally, it was concluded that the waste from colored cotton cultivars, Jade and Topazio, is capable to generate briquettes with good mechanical and physico-chemical characteristics, especially those formed by the mixture of stalk and shell.

Sulfur removal from model fuel by Zn impregnated retorted shale and with assistance of design of experiments

There is global concern about acid rain and other pollution which is caused by the consumption of oil. By decreasing sulfur content in the oil, we can reduce unwanted emissions and acid rain. Shale was used which is a solid waste generated in the pyrolysis of shale, impregnated with Zn as an adsorbent which removes sulfur present in fuels from the hexane/toluene model solution. An influence of the agitation time (60-180 min), temperature (25-35 °C), adsorbent mass (0.1-0.25 g), and initial sulfur concentration (100-250 ppm) factorial 24 with three central points totaling 19 experiments was applied to investigate the effect of the variables on the efficiency of sulfur removal in fuels. The values of the parameters tested for maximum sulfur removal were obtained as follows: contact time = 180 min, temperature = 35 °C, adsorbent mass = 0.25 g, and initial sulfur concentration = 100 ppm. The mathematical model proposed with R² 99.97% satisfied the experimental data. This may provide a theoretical basis for new research and alternative uses for tailings of schist industrialization in order to evaluate its potential.