The pyrolysis of waste tires offers an environmentally friendly solution to the global tire waste problem. Pyrolytic carbon black (PCB) is an important by-product that can be reintroduced into industrial processes. This study aimed to improve the commercial viability of PCB by reducing its ash content. Pyrolysis was optimized at 420 °C for 4 h with a nitrogen flow rate of 1 L min-1. Demineralization, crucial for minimizing ash, was carried out using acid and alkali treatments (H2SO4, HNO3, HCl, NaOH). Two demineralization strategies were tested, one using fresh acid for three cycles and the other reusing the solution. The most effective method used 1 M HNO3 at 80 °C for 1 h, reducing the ash content to 1.7

Natural gas remains an important global source of energy. Usually, sour gas from the well or refinery stream contains H2S among other contaminants that should be removed to fulfill permissible standards of use. Despite the use of different gas-liquid sour gas upgrading technologies, ionic liquids (ILs) have been recognized as promising materials to remove H2S from sour gas. However, data concerned with thermodynamic solution functions of H2S in ILs have scarcely been reported in the literature. In this work, solution H-1 NMR spectroscopy was employed for quantifying H2S soluble in [BMIM][Cl] and for gaining a better understanding of the H2S-IL interaction. Experiments were carried out in a Young-Tap NMR tube containing a saturated solution of H2S/CH4/[BMIM][Cl] and recording spectra from 298 to 333 K. The thermodynamic solution functions, determined from the Van't Hoff equation, showed that solubility of the H2S in the [BMIM][Cl] is an exothermic gas-liquid physisorption process (Delta H-sol degrees = -66.13 kJmol(-1)) with a negative entropy change (Delta S-sol degrees = -168.19 JK(-1) mol(-1)). H-1 NMR spectra of the H2S/[BMIM][Cl] solution show a feature of strong solute-solvent interactions. However, solubility enthalpy is a fifth of the H-S bond energy value. Results from H-1 NMR spectroscopy also agree with those from the bench dynamic experiments.

Activated carbons (ACs) from olive stone were prepared using CO2, steam, KOH, and H3PO4 as activating agents. The resultant activated carbons were characterized by proximate and ultimate analysis, N2 adsorption (Brunauer-Emmett-Teller (BET) method), iodine number, Boehm titration, temperature-programmed desorption (TPD), and Fourier transform infrared spectroscopy (FTIR). Ammonia (NH3) was used as a test molecule to be adsorbed. The BET surface areas of the ACs obtained ranged from 1000 to 1986 m2 g-1. Type I isotherms were obtained for all the samples, although steam and H3PO4 ACs showed a significant mesopore contribution. KOH activation resulted in carbon with a high microporosity (98%) and high iodine adsorption (1030 mg g-1). KOH AC prepared with a KOH/pyrolyzed char weight ratio of 2 and at 900 °C showed the highest NH3 adsorption (252 mg g-1), favored by the high microporosity and adequate acidity. Chemical activation (KOH and H3PO4) promotes higher NH3 adsorption than the physical ACs prepared (CO2 and steam). Langmuir and Freundlich adsorption equilibrium models were used to correlate the NH3 adsorption isotherms, obtaining the best fit for the Freundlich equation. The results indicated that olive stone-based activated carbon could be used for commercial AC to remove NH3 from gaseous streams.

Commercial forest plantations in Chile are dominated by pine (Pinus radiata) and eucalyptus (Eucalyptus globulus). Tree bark is the main by-product of the forestry industry and has low value, but great potential for use as an agricultural substrate. However, the direct use of bark fibers may cause plant phytotoxicity due to the presence of polyphenolic and other compounds. This study aims to evaluate the physicochemical properties of E. globulus and P. radiata bark after water extraction treatments. The phytotoxicity of the resulting extracted bark alone and that mixed with commercial substrates (coconut fiber, moss, peat, and composted pine) at different ratios (25 to 75 wt%) were assessed using the Munoo-Liisa vitality index (MLVI) test. For all treatments, the seed germination and growth of radish (Raphanus sativus) and Chinese cabbage (Brassica rapa) species were evaluated and compared to a commercial growing medium (peat) as a control. The optimal mixture for seed growth was determined to be 75% extracted E. globulus bark fiber and 25% commercial substrates such as peat (P), coconut fiber (C), moss (M), and composted pine (CP), as indicated by the MLVI and germination results. Two phytostimulant products, chitosan and alginate-encapsulated fulvic acid, were added to the best substrate mixture, with the purpose of improving their performance. Encapsulated fulvic acid at 0.1% w/v was effective in promoting plant growth, while chitosan at all of the concentrations studied was effective only for mixture 75E-25CP. The mixture of E. globulus fiber and commercial substrates, containing a high proportion of water-extracted fiber (75%), shows the potential to be used in the growth of horticultural crops and in the plant nursery industry.

Addition of Pt and CeO 2 to Ni/Al 2 O 3 catalysts for the partial oxidation of methane was evaluated. The catalysts were prepared by the incipient wetness impregnation method, Pt and Ni loading of monometallic catalysts were 0.8 and 13% respectively, while Pt content for bimetallic catalysts varied between 0.25 and 1%. The catalysts characterization included N 2 physisorption, XRF, TPR, CO chemisorption, FTIR of adsorbed CO and XPS. The partial oxidation of methane was carried out from at room temperature up to 700 °C (CH 4 /O 2 =2). Ni and CeO 2 addition caused a decrease in the surface area and pore volume, while Pt addition did not affect such parameters. XPS results reported that Pt and Ni addition to CeO 2 /Al 2 O 3 leads to a decrease in the NiAl 2 O 4 surface species. TPR profiles showed that Ni and CeO 2 reducibility was favored by Pt addition. CO chemisorption indicated a low dispersion of Ni catalysts, which increased with Pt addition. FTIR analysis revealed a predominant Pt contribution in the bimetallic catalysts. The catalytic activity tests showed that CeO 2 addition improved the catalytic performance of monometallic catalysts; however, bimetallic catalysts were adversely affected by such promoter. Furthermore, the Pt addition causes an increase in the catalytic activity of bimetallic catalysts due to favored Ni reducibility.

The present study shows porous activated carbon obtained from Chenopodium quinoa Willd and Quillaja saponaria and their use as potential adsorbents to remove three types of dyes from aqueous solutions. The adsorption results were compared with commercial charcoal to check their efficiency. All porous carbon materials were activated using carbon dioxide and steam and fully characterized. Moreover, the steam-activated samples exhibited a high total pore volume with a BET surface area of around 800 m2 g−1. Batch adsorption experiments showed that commercial charcoal is the charcoal that offered the best adsorption efficiency for tartrazine and sunset yellow FCF. However, in the case of crystal violet, all activated carbons obtained from Chenopodium quinoa Willd and Quillaja saponaria showed the best captures, outperforming commercial charcoal. Molecular dockings of the dyes on the commercial charcoal surface were performed using AutoDock Vina. The kinetic results of the three isotherm’s models for the present data follow the order: Langmuir~Freundlich > Temkin.

Resumen Se estudió un catalizador industrial de CuO/ZnO/Al2O3 fresco y usado, empleado en la reacción de desplazamiento del gas de agua (WGSR). Las muestras fueron caracterizadas mediante Fluorescencia de rayos X, Difracción de rayos X, Reducción a Temperatura Programada y quimisorción de CO. El desempeño catalítico del catalizador fresco fue evaluado bajo 3 ciclos consecutivos de la reacción a baja temperatura (200-250 °C). Los catalizadores usados presentaron una disminución del área superficial, así como una modificación de la estructura cristalina, pérdida de superficie metálica del cobre y presencia de azufre. La reacción de WGSR se favoreció a 250 °C, registrando altas conversiones de CO (≈90%) para la muestra fresca durante 3 ciclos sucesivos de reacción. Los catalizadores usados aún mantienen una alta actividad (≈80%), con excepción de la muestra más cercana al tope del reactor, la cual podría estar más afectada como consecuencia de un alto contenido de azufre y/o la condensación de agua durante el enfriamiento. Abstract Fresh and spent CuO/ZnO/Al2O3 industrial catalyst used in a water-gas shift reaction (WGSR) was studied. The samples were characterized by X-ray fluorescence, X-ray diffraction, Temperature programmed reduction and CO chemisorption. The catalytic performance was evaluated under consecutive cycles of WGSR at low temperature (200-250 °C). The spent catalysts exhibited a decrease in surface area, as well as a modification of the crystalline structure, loss of Cu metallic surface and presence of sulfur. WGSR was favored at 250 °C, registering high CO conversions (≈90%) for the fresh sample during successive reaction cycles. The spent catalysts kept a high activity (≈80%), except for the catalyst portion collected at the reactor’s top, which could be more affected because of high sulfur content and/or water condensation during the reactor’s cooling. https://doi.org/10.22209/rt.v43n3a06

Resumen Se prepararon catalizadores de Pd soportados sobre CexZr1-xO2/SiO2 (x=0; 0,3; 0,7 y 1 en términos de relación molar), los cuales se sometieron a varios ciclos continuos de la reacción de oxidación parcial de metano hasta 700 °C en condiciones de alimentación estequiométricas (CH4/O2=2). Los catalizadores fueron caracterizados mediante Reducción a Temperatura Programada (RTP) antes y después de reacción. Los resultados de RTP indicaron que la adición de Zr desplazó la reducibilidad del óxido de cerio a más baja temperatura y la formación de la fase β-PdHx después tres ciclos de reacción, sugiriendo la presencia de aglomerados de PdO. Los catalizadores con 1% de Pd fueron los más activos, ocurriendo posiblemente una reestructuración de las partículas de PdO causado por los pasos de reducción y oxidación repetidos. Los catalizadores de Pd/CexZr1-xO2/SiO2 exhibieron actividades catalíticas más altas que los usados como referencia (Pd/ZrO2/SiO2 y Pd/CeO2/SiO2) con carga de Pd de 0,5%. Aunque la conversión de CH4 disminuyó durante los ciclos de reacción entre un 4 y 49% dependiendo del tipo de soporte, el catalizador 1%Pd/Ce0,7Zr0,3O2/SiO2 fue el más activo (~40% conversión de CH4) y con mayor estabilidad a 600 °C (60% conversión de CH4), manteniendo la selectividad a gas de síntesis (H2/CO=1,5). Abstract Six Pd catalysts supported on CeO2/SiO2, ZrO2/SiO2 and CexZr1-xO2/SiO2 (x= 0; 0.3;0.7 and 1 in terms of molar composition) were prepared and submitted to several reaction cycles of the partial oxidation of methane up to 700 °C, under stoichiometric feeding conditions (CH4/O2=2). The catalysts were characterized by Temperature Programmed Reduction (TPR) before and after the reaction. TPR results indicated that Zr addition displaced the reducibility of cerium oxide at lower temperature and the formation of the β-PdHx phase after three reaction cycles, suggesting the presence of PdO agglomerates. 1%Pd catalysts were more active, with the possible restructuring of the PdO particles caused by the repeated reduction and oxidation steps. Pd/CexZr1-xO2/SiO2 catalysts exhibited higher catalytic activities than Pd/ZrO2/SiO2 and Pd/CeO2/SiO2 references samples with Pd loading of 0,5%. Although the CH4 conversion decreased during the reaction cycles between 4 and 49% depending on the support, 1%Pd/Ce0,7Zr0,3Ox/SiO2 catalyst was the most active (~40% CH4 conversion) and high stability at 600 °C (60% CH4 conversion), keeping the syngas selectivity (H2/CO=1.5). https://doi.org/10.22209/rt.v43n3a07

ResumenSe estudió un catalizador industrial de CuO/ZnO/Al2O3 fresco y usado, empleado en la reacción de desplazamiento del gas de agua (WGSR). Las muestras fueron caracterizadas mediante Fluorescencia de rayos X, Difracción de rayos X, Reducción a Temperatura Programada y quimisorción de CO. El desempeño catalítico del catalizador fresco fue evaluado bajo 3 ciclos consecutivos de la reacción a baja temperatura (200-250 °C). Los catalizadores usados presentaron una disminución del área superficial, así como una modificación de la estructura cristalina, pérdida de superficie metálica del cobre y presencia de azufre. La reacción de WGSR se favoreció a 250 °C, registrando altas conversiones de CO (≈90%) para la muestra fresca durante 3 ciclos sucesivos de reacción. Los catalizadores usados aún mantienen una alta actividad (≈80%), con excepción de la muestra más cercana al tope del reactor, la cual podría estar más afectada como consecuencia de un alto contenido de azufre y/o la condensación de agua durante el enfriamiento. AbstractFresh and spent CuO/ZnO/Al2O3 industrial catalyst used in a water-gas shift reaction (WGSR) was studied. The samples were characterized by X-ray fluorescence, X-ray diffraction, Temperature programmed reduction and CO chemisorption. The catalytic performance was evaluated under consecutive cycles of WGSR at low temperature (200-250 °C). The spent catalysts exhibited a decrease in surface area, as well as a modification of the crystalline structure, loss of Cu metallic surface and presence of sulfur. WGSR was favored at 250 °C, registering high CO conversions (≈90%) for the fresh sample during successive reaction cycles. The spent catalysts kept a high activity (≈80%), except for the catalyst portion collected at the reactor’s top, which could be more affected because of high sulfur content and/or water condensation during the reactor’s cooling. https://doi.org/10.22209/rt.v43n3a06

Resumen Se prepararon catalizadores de Pd soportados sobre CexZr1-xO2/SiO2 (x=0; 0,3; 0,7 y 1 en términos de relación molar), los cuales se sometieron a varios ciclos continuos de la reacción de oxidación parcial de metano hasta 700 °C en condiciones de alimentación estequiométricas (CH4/O2=2). Los catalizadores fueron caracterizados mediante Reducción a Temperatura Programada (RTP) antes y después de reacción. Los resultados de RTP indicaron que la adición de Zr desplazó la reducibilidad del óxido de cerio a más baja temperatura y la formación de la fase β-PdHx después tres ciclos de reacción, sugiriendo la presencia de aglomerados de PdO. Los catalizadores con 1% de Pd fueron los más activos, ocurriendo posiblemente una reestructuración de las partículas de PdO causado por los pasos de reducción y oxidación repetidos. Los catalizadores de Pd/CexZr1-xO2/SiO2 exhibieron actividades catalíticas más altas que los usados como referencia (Pd/ZrO2/SiO2 y Pd/CeO2/SiO2) con carga de Pd de 0,5%. Aunque la conversión de CH4 disminuyó durante los ciclos de reacción entre un 4 y 49% dependiendo del tipo de soporte, el catalizador 1%Pd/Ce0,7Zr0,3O2/SiO2 fue el más activo (~40% conversión de CH4) y con mayor estabilidad a 600 °C (60% conversión de CH4), manteniendo la selectividad a gas de síntesis (H2/CO=1,5). AbstractSix Pd catalysts supported on CeO2/SiO2, ZrO2/SiO2 and CexZr1-xO2/SiO2 (x= 0; 0.3;0.7 and 1 in terms of molar composition) were prepared and submitted to several reaction cycles of the partial oxidation of methane up to 700 °C, under stoichiometric feeding conditions (CH4/O2=2). The catalysts were characterized by Temperature Programmed Reduction (TPR) before and after the reaction. TPR results indicated that Zr addition displaced the reducibility of cerium oxide at lower temperature and the formation of the β-PdHx phase after three reaction cycles, suggesting the presence of PdO agglomerates. 1%Pd catalysts were more active, with the possible restructuring of the PdO particles caused by the repeated reduction and oxidation steps. Pd/CexZr1-xO2/SiO2 catalysts exhibited higher catalytic activities than Pd/ZrO2/SiO2 and Pd/CeO2/SiO2 references samples with Pd loading of 0,5%. Although the CH4 conversion decreased during the reaction cycles between 4 and 49% depending on the support, 1%Pd/Ce0,7Zr0,3Ox/SiO2 catalyst was the most active (~40% CH4 conversion) and high stability at 600 °C (60% CH4 conversion), keeping the syngas selectivity (H2/CO=1.5). https://doi.org/10.22209/rt.v43n3a07

The bioconvection of gravitactic microorganisms, through linear analysis and numerical simulation is presented. Using the basic state as initial condition for both microorganisms and streamlines, the critical Rayleigh number and the bioconvection are predicted. The dynamic microorganisms’ behavior is influenced by the initial spatial distribution. The stability of the system is dependent on the horizontal wave component that is inversely related to wavelength. The pattern length and the instability of the process are associated with the horizontal component of the wave number and the characteristic wavelength, respectively. Using complex and real eigenvalues, five unstable and three stable rolls are found respectively. The three stable rolls is the dominant pattern when varying the principal variables of this bioconvective process.

In this work, the FENE dumbbell model under small- and large-amplitude oscillatory shear flows using a micro-macro approach is presented. This approach involves the evolution of an ensemble of Brownian Configuration Fields which describes the polymer dynamics of the microscopic scale and the momentum equation describes the macroscopic scale. The Lissajous curves for the shear stress and the first normal stress difference versus the instantaneous strain or strain rate for the elastic or viscous projection are shown. The influences of the solvent/polymer viscosity ratio, the maximum extension length, and the relation between strain rate and frequency are analyzed. An important finding is the self-intersection of the Lissajous curves, which forms secondary loops for short extension lengths and high Weissenberg/Deborah dimensionless numbers ratio.

In this work, the numerical simulation of the non-isothermal steady co-extrusion fiber spinning with flowinduced crystallization is explored. The model is based on the formulation originally proposed by China et al. in which Newtonian and Phan-Thien-Tanner (PTT) fluids are considered the core and the skin layer, respectively. The polymeric flow rate fraction, Deborah dimensionless number and the PTTs parameters on the temperature, the velocity and the crystallization profiles are analyzed. The numerical results show: the temperature profile is sensitive to the polymeric layer flow rate and the deformation parameters (shear thinning and extensional), the tensile stress induced crystallization parameter has a strong influence at the onset of the process, increasing drastically temperature and crystallinity.

A numerical solution for axis-symmetrical fluid flow through a smooth constriction using the alternating direction implicit finite volume method and the fractional-step-method is presented. The wall is modelled with a smooth contraction mapped by a sinusoidal function and the flow is supposed to be axis-symmetric. A pressure boundary condition is set at the inlet and the resulting pressure gradient field drives fluid flow which is always in laminar regime. This study presents results for a non-Newtonian fluid using the Ostwaldde Waele constitutive model. Moreover, a transient network representing three different microstructures, immersed in the fluid, is evolved by viscous dissipation and an isothermal process is considered. The time dependent evolution of the transient network is represented by a set of kinetic equations with their respective forward and reversed constants. The numerical predictions show that, at a fixed Reynolds number, the viscous dissipation and the grade of structure restoration or breakage is influenced by constriction severity due to the energy generated during fluid flow. A 50% reduction in transversal section generates secondary flow downstream and vortex shedding, whereas a 10% and 25% constrictions presents a thin boundary layer and no secondary flow near the constricted wall.

In this work, the micro-macro approach is used to simulate the flow of dilute polymer solutions by means of a kinetic model coupled with the dynamics of a transient network. The transient network modeling is based on the original formulation, in which the kinetics of microstates describes the complexity of interactions among the macromolecules suspended in a Newtonian solvent (Rincón et al, J Non-Newton Fluid 131:64–77, 2005). The average concentration of microstates, at a given time, defines a variable maximum segment length (variable extensibility) of the molecular FENE model. The non-Newtonian contribution to the extra stress tensor is computed according to the Brownian configuration-fields method. Comparisons with the Oldroyd-B model validates its limiting behavior. Numerical results show the influence of the solvent to total viscosity ratio and shear rate, on the transient and steady rheological phenomena of complex fluids with microstates.

Pd/Ce0.6Zr0.4Ox/SiO2 and Pd/Ce0.73Tb0.27Ox/SiO2 catalysts were prepared by incipient wetness impregnation method using aqueous solutions of Ce(NO3)(3)center dot 6H(2)O, ZrO(NO3)(2)center dot nH(2)O, Tb(NO3)(3)center dot 5H(2)O and Pd(NO3)(2)center dot nH(2)O precursors. The catalysts were characterized by X-ray diffraction (XRD), Temperature Programmed Reduction (TPR-H-2), CO Chemisorption, Oxygen Storage Capacity (OSC) and Infrared spectroscopy of adsorbed CO (FTIR-CO). The catalytic activity was measured in the methane oxidation reaction. XRD patterns showed that after two activity cycles, the solids crystallinity was not modified, while TPR results revealed that reduction maxima were shifted to lower temperatures, indicating an improvement in sample reducibility. The CO/Pd ratio diminished with increasing the reduction temperature, suggesting both, Pd inward diffusion/covering by Ce3+ ions (geometrical effects) and/or increase in Pd particles size. The IR spectrum of adsorbed CO reported the presence of cationic palladium species interacting with CO regardless of reduction temperature as well as carbonate species and weak interactions with ceria and silica. Zr and Tb containing samples presented a high and stable OSC after undergoing various OSC cycles. The catalytic activity was enhanced after two reaction cycles due to the formation of large PdO particles. T-50 values indicated that reduction treatments prior to methane reaction generated more active catalytic species than those obtained by oxidation treatment; however, such active species were not stable at high temperatures.

Se prepararon catalizadores de Pd soportados sobre Al2 O3 , CeO2 /La2 O3 -Al2 O3 , Ce0,73Tb0,27Oδ-x/La2 O3 -Al2 O3 y Ce0,6Zr0,4Ox / La2 O3 -Al2 O3 , utilizando la tecnica de impregnacion a humedad incipiente. Los catalizadores fueron caracterizados mediante las tecnicas de Fluorescencia de Rayos X (FRX), Difraccion de Rayos X (DRX), Reduccion a Temperatura Programada (RTP), Quimisorcion de CO y Capacidad de Almacenamiento de Oxigeno (CAO). La actividad catalitica se estudio mediante la reaccion de reduccion de NO por CO en condiciones de alimentacion estequiometricas. Los patrones de DRX mostraron que la cristalinidad de las muestras no es afectada por los tratamientos termicos. Los resultados de RTP indicaron que la adicion de Tb o Zr promovio la reducibilidad del oxido de cerio a mas baja temperatura y la formacion de la fase β-PdHx despues de dos ciclos de reaccion, asi como un incremento en la CAO. La actividad catalitica mejoro luego de dos ciclos de reaccion, siendo el catalizador mas activo el de 0,5%Pd/Ce0,6Zr0,4Ox /La2 O3 -Al2 O3 . Este resultado sugiere cambios en la especies de PdO que junto con el oxido mixto CeZr, generan especies de mayor actividad