RESUMO

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.

Assuntos

RESUMO

The vertical distribution of phytoplankton is of fundamental importance in the structure, dynamic, and biogeochemical pathways in marine ecosystems. Nevertheless, what are the main factors determining this distribution remains as an open question. Here, we evaluated the relative influence of environmental factors that might control the coexistence and vertical distribution of pico-nanoplankton associated with the OMZ off northern Chile. Our results showed that in the upper layer Synechococcus-like cells were numerically important at all sampling stations. Pico-nano eukaryotes and phototrophic nanoflagellates (PNF) also showed high abundances in the upper layer decreasing in abundance down to the upper oxycline, while only Prochlorococcus showed high abundances under oxycline and within the oxygen-depleted layer. Statistical analyses evidenced that temperature, oxygen, and carbonate chemistry parameters (pH and dissolved inorganic carbon, DIC) influenced significantly the vertical distribution of phototrophic pico-nanoplankton. Additionally, we experimentally-evaluated the combined effect of low pH/low O2 conditions on a nanophytoplankton species, the haptophyte Imantonia sp. Under control conditions (pH = 8.1; O2 = 287.5 µM, light = 169.6 µEm-2s-1), Imantonia sp. in vivo fluorescence increased over fifty times, inducing supersaturated O2 conditions (900 µM) and an increasing pH (8.5), whereas upon an experimental treatment mimicking OMZ conditions (pH = 7.5; O2 = 55.6 µM; light = 169.6 µEm-2s-1), in vivo fluorescence declined dramatically, suggesting that Imantonia sp. did not survive. Although preliminary, our study provides evidence about the role of low pH/low O2 conditions on the vertical distribution of nanophytoplankton, which deserve future attention through both fieldwork and more extended experimental experiences.

Assuntos

RESUMO

In this work, the deoxygenation of organic liquid products (OLP) obtained through the thermal catalytic cracking of palm oil at 450 °C, 1.0 atmosphere, with 10% (wt.) Na2CO3 as a catalyst, in multistage countercurrent absorber columns using supercritical carbon dioxide (SC-CO2) as a solvent, with an Aspen-HYSYS process simulator, was systematically investigated. In a previous study, the thermodynamic data basis and EOS modeling necessary to simulate the deoxygenation of OLP was presented. This work addresses a new flowsheet, consisting of 03 absorber columns, 10 expansions valves, 10 flash drums, 08 heat exchanges, 01 pressure pump, and 02 make-ups of CO2, aiming to improve the deacidification of OLP. The simulation was performed at 333 K, 140 bar, and (S/F) = 17; 350 K, 140 bar, and (S/F) = 38; 333 K, 140 bar, and (S/F) = 25. The simulation shows that 81.49% of OLP could be recovered and that the concentrations of hydrocarbons in the extracts of absorber-01 and absorber-02 were 96.95 and 92.78% (wt.) on a solvent-free basis, while the bottom stream of absorber-03 was enriched in oxygenated compounds with concentrations of up to 32.66% (wt.) on a solvent-free basis, showing that the organic liquid products (OLP) were deacidified and SC-CO2 was able to deacidify the OLP and obtain fractions with lower olefin contents. The best deacidifying condition was obtained at 333 K, 140 bar, and (S/F) = 17.

Assuntos

RESUMO

In this work, the production of renewable hydrocarbons was explored by the means of waste cottonseed oil (WCSO) micropyrolysis at 500 °C. Catalytic upgrading of the pyrolysis vapors was studied using α-Al2O3, γ-Al2O3, Mo-Co/γ-Al2O3, and Mo-Ni/γ-Al2O3 catalysts. The oxygen removal efficiency was much lower in non-catalytic pyrolysis (18.0%), whilst γ-Al2O3 yielded a very high oxygen removal efficiency (91.8%), similar to that obtained with Mo-Co/γ-Al2O3 (92.8%) and higher than that attained with Mo-Ni/γ-Al2O3 (82.0%). Higher conversion yields into total renewable hydrocarbons were obtained with Mo-Co/γ-Al2O3 (61.9 wt.%) in comparison to Mo-Ni/γ-Al2O3 (46.6%). GC/MS analyses showed a relative chemical composition of 31.3, 86.4, and 92.6% of total renewable hydrocarbons and 58.7, 7.2, and 4.2% of oxygenated compounds for non-catalytic bio-oil (BOWCSO), BOMoNi and BOMoCo, respectively. The renewable hydrocarbons that were derived from BOMoNi and BOMoCo were mainly composed by olefins (35.3 and 33.4%), aromatics (31.4 and 28.9%), and paraffins (13.8 and 25.7%). The results revealed the catalysts' effectiveness in FFA decarbonylation and decarboxylation, as evidenced by significant changes in the van Krevelen space, with the lowest O/C ratio values for BOMoCo and BOMoNi (O/C = 0-0.10) in relation to the BOWCSO (O/C = 0.10-0.20), and by a decrease in the presence of oxygenated compounds in the catalytic bio-oils.

RESUMO

The chemical speciation of iron (Fe) in oceans is influenced by ambient pH, dissolved oxygen, and the concentrations and strengths of the binding sites of dissolved organic matter (DOM). Here, we derived new nonideal competitive adsorption (NICA) constants for Fe(III) binding to marine DOM via pH-Fe titrations. We used the constants to calculate Fe(III) speciation and derive the apparent Fe(III) solubility (SFe(III)app) in the ambient water column across the Peruvian shelf and slope region. We define SFe(III)app as the sum of aqueous inorganic Fe(III) species and Fe(III) bound to DOM at a free Fe (Fe3+) concentration equal to the limiting solubility of Fe hydroxide (Fe(OH)3(s)). A ca. twofold increase in SFe(III)app in the oxygen minimum zone (OMZ) compared to surface waters is predicted. The increase results from a one order of magnitude decrease in H+ concentration which impacts both Fe(III) hydroxide solubility and organic complexation. A correlation matrix suggests that changes in pH have a larger impact on SFe(III)app and Fe(III) speciation than DOM in this region. Using Fe(II) measurements, we calculated ambient DFe(III) and compared the value with the predicted SFe(III)app. The underlying distribution of ambient DFe(III) largely reflected the predicted SFe(III)app, indicating that decreased pH as a result of OMZ intensification and ocean acidification may increase SFe(III)app with potential impacts on surface DFe inventories.

Assuntos

RESUMO

The chemical conditions of the Argentine Basin (western South Atlantic Ocean) water masses are evaluated with measurements from eleven hydrographic cruises to detect and quantify anthropogenic and natural stressors in the ocean carbon system. The database covers almost half-century (1972-2019), a time-span where the mean annual atmospheric carbon dioxide concentration (CO2atm) increased from 325 to 408 ppm of volume (ppm). This increase of atmospheric CO2 (83 ppm, the 64% of the total anthropogenic signal in the atmosphere) leads to an increase in anthropogenic carbon (Cant) across all the water column and the consequent ocean acidification: a decrease in excess carbonate that is unequivocal in the upper (South Atlantic Central Water, SACW) and intermediate water masses (Sub Antarctic Mode Water, SAMW and Antarctic Intermediate Water, AAIW). For each additional ppm in CO2atm the water masses SACW, SAMW and AAIW lose excess carbonate at a rate of 0.39 ± 0.04, 0.47 ± 0.05 and 0.23 ± 0.03 µmol·kg-1·ppm-1 respectively. Modal and intermediate water masses in the Argentine Basin are very sensitive to carbon increases due low buffering capacity. The large rate of AAIW acidification is the synergic effect of carbon uptake combined with deoxygenation and increased remineralization of organic matter. If CO2 emissions follows the path of business-as-usual emissions (SSP 5.85), SACW would become undersaturated with respect to aragonite at the end of the century. The undersaturation in AAIW is virtually unavoidable.

RESUMO

The hydraulic characteristics of the Gualaxo do Norte River (RGN), a tributary of the upper Rio Doce basin, were affected in November 2015 by the rupture of the iron ore tailings dam at Fundão, in Bento Rodrigues, Mariana, Minas Gerais. We analyzed two sections of the RGN, located upstream and downstream of the Fundão dam. Measurements were taken at 11 stations along the main river in distinct seasonal periods, including river depth, river width, velocity, and flow. We also calculated the deoxygenation coefficient (K1) and the reaeration coefficient (K2) and collected elaborate bathymetric profiles of the sections. Anthropogenic interference influenced the river's hydraulic characteristics mainly in relation to the depth. In upstream sections, the changes are believed to be due to mining activities at the head of the river, while downstream effects were due to the introduction of iron ore tailings coming from the rupture of the Fundão dam. Despite these influences, deoxygenation coefficient values were typical for clean water, and the reaeration coefficient findings show that the RGN is efficient at biological degradation of the organic matter even receiving untreated domestic sewage from riparian communities. With the results obtained in this work, we seek to replicate a source of information about the current state of the region and to contribute information to future river planning, control, and restoration projects.

Assuntos

RESUMO

RESUMO Os objetivos do presente trabalho foram realizar uma caracterização físico-química de diferentes águas residuárias agroindustriais (ARA) e aplicar modelos cinéticos de primeira e de segunda ordem para verificar qual deles descreve melhor a progressão da demanda bioquímica de oxigênio (DBO) e para determinar coeficientes cinéticos aeróbios de remoção da matéria orgânica das ARA. Efetuou-se o ensaio de progressão da DBO pela incubação de ARA em um sistema respirométrico (Oxitop®). Os modelos cinéticos de primeira e de segunda ordem foram avaliados por erro quadrático médio (RMSE), erro quadrático médio normalizado (NRMSE) e critério de informação de Akaike (AIC). A cinética de biodegradação aeróbia das ARA avaliadas ajustou-se melhor ao modelo de primeira ordem em termos de DBO total e solúvel. Na progressão de DBO total, o maior coeficiente de desoxigenação de primeira ordem (k') foi o da água residuária de abatedouro - ARB (0,56 d-1) - e o menor foi o da água residuária de suinocultura - ARS (0,16 d-1). Os coeficientes de desoxigenação determinados no presente trabalho mostraram-se representativos, podendo ser utilizados para a simulação de processos de degradação da matéria orgânica em condições aeróbias.

ABSTRACT The aim of the present work was to perform a physicochemical characterization of different agroindustrial wastewaters (AIW), to apply first and second order kinetic models to verify which one best describes the progression of the biochemical oxygen demand (BOD) and to determine the aerobic kinetics coefficients of organic matter removal from AIW. The BOD progression assay was performed from the incubation of AIW in a respirometric system (Oxitop®). The first and second order kinetic models were evaluated by mean square error (RMSE), normalized mean square error (NRMSE), and Akaike Information Criterion (AIC). The aerobic biodegradation kinetics of the AIW evaluated was better fitted to the first order model in terms of total and soluble BOD. In the total BOD progression, the highest coefficient of first-order deoxygenation (k ') was that of slaughterhouse wastewater (SW; 0.56 d-1) and the lowest was that of swine wastewater (SSW; 0.16 d-1). The deoxygenation coefficients determined in the present work were representative, and can be used for the simulation of degradation processes of organic matter under aerobic conditions.

RESUMO

Herein, we describe a selective late-stage deoxygenation of sulfoxides based on a novel application of chlorosulfonium salts and demonstrate a new process using these species generated in situ from sulfoxides as the source of electrophilic chlorine. The use of highly nucleophilic 1,3,5-trimethoxybenzene (TMB) as the reducing agent is described for the first time and applied in the deoxygenation of simple and functionalized sulfoxides. The method is easy to handle, economic, suitable for gram-scale operations, and readily applied for poly-functionalized molecules, as demonstrated with more than 45 examples, including commercial medicines and analogues. We also report the results of competition experiments that define the more reactive sulfoxide and we present a mechanistic proposal based on substrate and product observations.

Assuntos

RESUMO

The influence of reactor temperature of 300  and 600 °C and the acidity of the ZSM-5 and HZSM-5 catalysts on the pyrolysis product yields of the pineapple crown leaves have been investigated in a fixed bed reactor Py-GC/MS. The ZSM-5 catalyst was hydrothermally synthesized with a Si/Al ratio 50, using residual diatomite and rice husk ash as alternative sources of Al and Si for catalyst cost reduction. For the HZSM-5 synthesis, calcined ZSM-5 was activated by ion exchange between Na+ and H+. The catalysts structure was confirmed by the XRD and Rietveld treatment, SEM, FTIR, FRX, TGA and BET results. Analytical pyrolysis of the biomass was carried out at 500 °C in a Py-5200 HP-R pyrolyzer connected to the GC/MS and the pyrolysis vapors were transported to a catalytic bed at 300 and 600 °C. The results showed that the increase in the catalytic bed temperature promoted increased the aromatic content. The main pyrolysis products of the PCL were oxygenated compounds that were converted at 600 °C using the HZSM-5 catalyst into high value renewable aromatic compounds for the chemical industry, such as benzene, toluene, xylene, etilbenzene, thereby confirming the deoxygenation activity of synthesized catalyst to produce renewable aromatics compounds which are important platform chemicals and precursors for jet fuels, gases, polymers and solvents.

Assuntos

RESUMO

Efficient synthesis of 3-deoxy-1,2-O-isopropylidene-ß-D- and ß-L-threo-pentofuranose (1,2-O-isopropylidene-ß-D- and ß-L-cordycepose) was accomplished starting from D- and L-arabinofuranose derivatives, respectively, by the action of LiBH(Et)3 on corresponding intermediate 3-O-lyxofuranosyl trifluoromethanesulfonates.

Assuntos