Brazilian Journal of Chemical Engineering最新文献

Heparin is a well-known substance commonly introduced in the bloodstream in many medical procedures to avoid thrombogenicity. Polymer membranes used for biomedical applications, such as in hemodialysis and blood oxygenators, must also have good antithrombogenic and biocompatibility characteristics. Recently developed polyetherimide/polyvinylpyrrolidone (PEI/PVP) hollow fiber membranes showed good potential as an alternative to clinically available membranes, as evaluated by the transport properties of blood-targeted molecules relevant in the treatment of patients with renal chronic diseases. Aiming at improving the hemocompatibility of these membranes, the incorporation of heparin onto their surface was sought as a promising attempt to achieve this goal. In this work, flat sheet PEI/ PVP membranes were prepared by the phase inversion technique and were functionalized through the covalent grafting of heparin. Characterization included the follow-up of hydrophilicity, protein adsorption, prothrombin time (PT), activated partial thromboplastin time (aPTT), hemolysis occurrence, platelet adhesion, and complement system activation. The results showed that heparinization resulted in more hydrophilic membranes (contact angle reduced from 76.5° to 58.5°) and in the reduction of protein adsorption by more than 50%. In contact with human blood, these membranes reduced the occurrence of platelet adhesion, increased aPTT from 34 to 46 s, and did not lead to complement system activation. Such PEI/PVP membranes have therefore remarkable antithrombogenic and biocompatibility characteristics, which are highly desired for use in biomedical applications such as hemodialysis filters.

A spinning disk reactor (SDR) was applied and tested successfully for precipitated calcium carbonate particles synthesis in liquid–liquid system which is poorly understood in literature. The proposed SDR reactor consists of a spinning disk rotating at 4000–16,000 rpm. The proposed SDR resulted in a high local supersaturation ratio due to the intense energy dissipation produced by a high-speed spinning disk. The higher rotational speed of SDR produces calcium carbonate nanoparticles with smaller mean particle sizes and higher aragonite content. At the rotating speed of 15,000 rpm, precipitated calcium carbonate nanoparticles with a size of around 975 nm were produced. In addition, aragonite content increased from 10 to 95 wt% by increasing disk speed from 4000 to 15,000 rpm.

Naphthenate deposits are a major obstacle in ensuring an economic and successful flow in the production and processing of crude oil. The formation of these deposits depends mainly on a specific group of high molecular weight tetrameric acids, sometimes called ARN. Among the challenges of identifying and characterizing the ARN of this complex matrix, we propose the use of a new analysis methodology for identifying these species in oil samples and naphthenate deposits with minimal sample preparation. Such methodology is based on an unconventional approach to the negative-mode electrospray ionization technique, combined with high resolution and precision mass spectrometry. The methodology proved to be promising and advantageous, since it requires a simpler sample preparation and a reduced consumption of reagents and analysis time. With good feasibility of application to identify the nature of deposits and to estimate, in an initial phase, the potential for inorganic scale and the need for oil treatment in production units.

The increasing accumulation of agricultural residues like rice husk (RH) and plantain peels (PP) poses environmental challenges, necessitating efficient waste management strategies. The study explores the potential of anaerobic co-digestion (AcoD) as a sustainable solution, specifically investigating its capacity for biogas generation from these agricultural residues. The primary objective is to determine the optimal substrate mixing ratios (SMRs) to maximize biogas yield. In-depth examination revealed that the highest biogas production reached a significant 2880 mL with a blend of 60% RH and 40% PP (RH60PP40). Additionally, the 80% RH and 20% PP composite (RH80PP20) demonstrated a substantial yield of 1996 mL. However, when plantain peels were used as the major substrate, biogas outputs decreased to 1250 mL and 173 mL for RH40PP60 and RH20PP80, respectively. Synergistic indexes (SI), measuring compatibility, reported values of 1.36 and 1.96 for the most promising samples, underscoring their optimal blending for biogas enhancement. From the perspective of digestate quality, plantain peel-based digestate (PP100D) stood out as a leading biofertilizer candidate due to its enriched nutrient profile. For the kinetic analysis, the logistic model was identified as the most predictive, outperforming the exponential and modified Gompertz models in mapping biogas production dynamics. Conclusively, the study accentuates that strategically optimized anaerobic co-digestion (AcoD) of RH and PP not only amplifies biogas outputs but also presents a viable, sustainable avenue for managing the environmental concerns associated with unchecked agricultural residue accumulation.

Abstract

Microwave assisted glycerol acetylation reactions in a monomode pilot reactor were performed in order to obtain glycerol derivatives as potential biodiesel additives. The reactions were carried out with acetic acid and acetic anhydride using sulfuric acid, pyridine and triethylamine as catalysts. The acetylation reactions yielded a mixture of mono, di and triacetin respectively with short irradiation time and high selectivity to triacetin. Pyridine exhibits 100% of selectivity to triacetin in 30 min of microwave heating with 0.88% (w/w_T) of catalyst concentration. Microwave-heating technology has been demonstrated as an alternative to reach a green chemistry and to this end becomes essential the knowledge of the dielectric properties of the materials involved in microwave heating in order to operate under optimal conditions. Dielectric properties of the pure reagents and during the glycerol acetylation under conventional heating were measured. High loss tangent were obtained for reactions mixtures employing H₂SO₄ and triethylamine and dielectric heating is dominated by ionic conductivity whereas with pyridine the dielectric heating of the reaction mixture is governed by dielectric relaxation process. Physical–chemical analysis of blended biodiesel with triacetin show values for viscosity, flash point, water content, density and acid number in accordance with current international standards. Gaseous emissions analyses of blended biodiesel showed significant reduction of CO emission (50%), CO₂ (25%) and 30% reduction in unburned hydrocarbon (UBHC) and 50% of NOx emissions. The best values were observed in the samples containing 5 and 10% of triacetin.

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In this work, the Ni/γ-Al₂O₃ (Ni/Al) and Ni/La₂O₃-γ-Al₂O₃ (Ni/La-Al) catalysts were synthesized using the all-in-one method and applied to dry methane reforming, with the aim of minimizing the effects of deactivation through the use of La and the application of monoliths. The characterization showed a smaller Ni crystallite size for the catalyst promoted by La, which was associated with better dispersion of its active phase. The monoliths showed a conversion rate around 15% higher than that of the powdered catalysts. By studying the deactivation of the monoliths and applying residual activity deactivation models (DMRA), it was possible to verify a fit with R² greater than 0.90 and RMSE values below 5%, with the model predicted and adjusted to the residual activity region. In addition, the highest and lowest deactivation of the structured systems was identified for WHSV values of 40 and 20 L h⁻¹ g⁻¹_cat, respectively. Finally, the regeneration of the catalysts with CO₂ proved to be superior to that with H₂, with a regeneration rate of 90% in the first two cycles.

The demand for permanent magnets is expected to increase in the 2021–2030 decade, which will require a commensurate increase in the production of samarium (Sm) and neodymium (Nd). Since these metals are considered critical and due to their abundance in Brazilian territory, the Brazilian government and mining companies must master the refining of these metals through autochthonous technologies. Thus, we developed a process to separate the light (La, Ce, Pr and Nd) from the medium (Sm, Eu and Gd) and heavy (Tb-Lu and Y) rare earth elements (REE) with D₂EHPA by empirical modeling of solvent extraction (SX) processes. The experimental methodology included three phases: equilibrium data acquisition from batch experiments, solvent extraction simulation, and continuous process trials to validate the model on a mini-pilot scale. Our simulation predicted 99.5% Sm organic recovery and 80% Nd aqueous recovery in a seven-stage process and 0.30 A/O ratio, validated in the continuous trial. This work paves the way for establishing Brazilian technology to obtain the constituent elements of permanent magnets.

The biggest challenges for E&P activities are the high viscosity of the oil, the geology of the formation, the high interfacial tensions (IFT) between fluids and the reservoir wetting conditions. Enhanced oil recovery (EOR) methods are applied to modify fluid–fluid and fluid–rock interactions in the reservoir, facilitating the oil displacement and, consequently, increasing the recovery factor. In this work, the use of silica nanofluids as EOR method to reduce the IFT and to change the wettability conditions of reservoir rock were evaluated. For experimental tests, crude oil from a reservoir in a Brazilian Pre-salt field was used as oleic phase. No significant change in IFT was observed with an increase in the concentration of SiNPs for both distilled water and low salinity water (1000 ppm) dispersant fluids. The significant reduction of the contact angle is observed for nanofluids with 0.02 wt% SiNP. Finally, the Amott test was performed in a carbonate rock sample to reaffirm the action of these chemicals in oil recovery, corroborating the potential of nanofluids to EOR applications. Thus, this work might contribute to a more rational design of nanoEOR strategies and technological innovations in carbonate reservoirs, especially those addressed to the South American Deepwater sector.

Graphical abstract