Avaliação e modelagem da absorção de H2S do gás natural em coluna de leito estagnado

Natural gas, although basically composed by light hydrocarbons, also presents contaminant gases in its composition, such as CO2 (carbon dioxide) and H2S (hydrogen sulfide). The H2S, which commonly occurs in oil and gas exploration and production activities, causes damages in oil and natural gas pipelines. Consequently, the removal of hydrogen sulfide gas will result in an important reduction in operating costs. Also, it is essential to consider the better quality of the oil to be processed in the refinery, thus resulting in benefits in economic, environmental and social areas. All this facts demonstrate the need for the development and improvement in hydrogen sulfide scavengers. Currently, the oil industry uses several processes for hydrogen sulfide removal from natural gas. However, these processes produce amine derivatives which can cause damage in distillation towers, can cause clogging of pipelines by formation of insoluble precipitates, and also produce residues with great environmental impact. Therefore, it is of great importance the obtaining of a stable system, in inorganic or organic reaction media, able to remove hydrogen sulfide without formation of by-products that can affect the quality and cost of natural gas processing, transport, and distribution steps. Seeking the study, evaluation and modeling of mass transfer and kinetics of hydrogen removal, in this study it was used an absorption column packed with Raschig rings, where the natural gas, with H2S as contaminant, passed through an aqueous solution of inorganic compounds as stagnant liquid, being this contaminant gas absorbed by the liquid phase. This absorption column was coupled with a H2S detection system, with interface with a computer. The data and the model equations were solved by the least squares method, modified by Levemberg-Marquardt. In this study, in addition to the water, it were used the following solutions: sodium hydroxide, potassium permanganate, ferric chloride, copper sulfate, zinc chloride, potassium chromate, and manganese sulfate, all at low concentrations (»10 ppm). These solutions were used looking for the evaluation of the interference between absorption physical and chemical parameters, or even to get a better mass transfer coefficient, as in mixing reactors and absorption columns operating in counterflow. In this context, the evaluation of H2S removal arises as a valuable procedure for the treatment of natural gas and destination of process by-products. The study of the obtained absorption curves makes possible to determine the mass transfer predominant stage in the involved processes, the mass transfer volumetric coefficients, and the equilibrium concentrations. It was also performed a kinetic study. The obtained results showed that the H2S removal kinetics is greater for NaOH. Considering that the study was performed at low concentrations of chemical reagents, it was possible to check the effect of secondary reactions in the other chemicals, especially in the case of KMnO4, which shows that your by-product, MnO2, acts in H2S absorption process. In addition, CuSO4 and FeCl3 also demonstrated to have good efficiency in H2S removal

Estudo da influência de tensoativos em sistemas microemulsionados na extração de gálio e alumínio

Gallium is an important material used in the electronic industry whose demand in the world market is increasing in view of its potential applications. A selective technique is required to allow for the production of the metal, separated from aluminium. Due to the fact that microemulsions constitute an attractive alternative to metal extraction procedures, microemulsified systems have been employed as gallium-selective extraction agents. Two surfactants have been synthesized: sodium 12-N,N-diethylamino-9,10-dihydroxyestearate (AMINE) and saponified coconut oil (SCO), both produced from raw materials readily available in Northeastern Brazil. Also, the commercial extraction agent KELEX-100, conventionally used with the same purpose, has been used in this work for comparison. The optimization of the extraction process with microemulsions was carried out by investigating the influence of some parameters, namely the type of cosurfactant, the cosurfactant/surfactant (C/S) ratio, the pH and concentration of metals in the aqueous phase. Pseudoternary diagrams, which are representative of the microemulsified systems under study, have been constructed in order to establish the boundaries of the regions where the several Winsor systems are formed. An experimental planning methodology (Scheffé Net) has been used to optimize the extraction. The extraction percentage values were as high as 100% for gallium and 99.99% for aluminium for the system with KELEX-100; 96.6% for gallium and 98.8% for aluminium for the system containing AMINE; and 88% for gallium and 85% for aluminium for the system with SCO. The microemulsified system chosen for presenting the best results in gallium extraction was composed by SCO/isoamyl alcohol/kerosene/Bayer licquor with a C/S ratio of 28 and pH of the original aqueous phase of 6.0. The selectivity that has not been observed in the extraction stage was accomplished in the reextraction process using HCl. For the KELEX-100 system, gallium was reextracted at 100% with 6M HCl and aluminium was reextracted at 100% with 0.8M HCl. For the AMINE system, the reextraction percentages were also 100% for both metals, using 6M HCl for gallium and 0.5M HCl for aluminium. On the other hand, the reextraction percentages for the system with SCO were as high as 84% for gallium and 92% for aluminium, with HCl in the same concentrations as those used in the AMINE system. Finally, an optimized system was applied in the gallium extraction process employing a reciprocating perforated-plates extractor. As a result, the metal content was extracted at a recovery rate of 95% for gallium and 97% for aluminium

Study of the interaction between cardiolipin bilayers and methylene blue in polymer-based Layer-by-Layer and Langmuir films applied as membrane mimetic systems

An increase of the reports involving mimetic systems has been observed. Briefly, these systems use biological phospholipids to exploit specific interactions between membrane-models and drugs. Here, the Layer-by-Layer (LbL) and Langmuir techniques were used to investigate the interaction between cardiolipin (CLP-negative phospholipid) and a cationic-like drug methylene blue (MB). Supported by a cationic polyelectrolyte (PAH), LbL films containing PAH/(CLP + MB) and PAH/(CLP + MB + AgNP) were grown up to 14 bilayers. The optical microscopy analysis revealed a decrease of the CLP vesicle sizes in the presence of MB as a possible consequence of the MB action onto the mechanical properties of the CLP membrane. From FTIR spectra, changes mainly related to peak position and band intensity and shape were observed in the spectra from PAH/CLP when in the presence of MB. The latter supports that the interactions between the phosphate and amine charged groups from CLP and PAH, respectively, established during the LbL film fabrication, besides the CLP hydrocarbon environment, are influenced by the presence of MB. Using the micro-Raman technique, a chemical mapping was build based on MB spectrum by resonance Raman scattering (RRS) and surface-enhanced resonance Raman scattering (SERRS). The later phenomenon was activated by Ag nanoparticles (AgNPs) trapped within the LbL film allowing collecting spectra for a single bilayer of PAH/(CLP + MB + AgNP). A rough estimation showed a SERRS amplification of 10(3) in comparison to RRS spectra. As a complementary approach, Langmuir films of CLP in the presence of co-spread MB were investigated through surface pressure vs mean molecular area (pi-A) isotherms. The results showed that for concentrations of MB below 100 mol%, the drug is expelled to water subphase for high values of surface pressure (condensed phase). For concentration at 100% and higher, the MB keeps bound to CLP floating monolayer. (C) 2010 Elsevier B.V. All rights reserved.

Piezoelectric biosensors for real-time monitoring of hybridization and detection of hepatitis C virus

The piezoelectric quartz crystal resonators modified with oligonucleotide probes were used for detection of hepatitis C virus (HCV) in serum. The gold electrodes on either rough or smooth surface crystals were modified with a self-assembled monolayer of cystamine. After activation with glutaraldehyde, either avidin or streptavidin were immobilized and used for attachment of biotinylated DNA probes (four different sequences). Piezoelectric biosensors were used in a flow-through setup for direct monitoring of DNA resulting from the reverse transcriptase-linked polymerase chain reaction (RT-PCR) amplification of the original viral RNA. The samples of patients with hepatitis C were analyzed and the results were compared with the standard RT-PCR procedure (Amplicor test kit of Roche, microwell format with spectrophotometric evaluation). The piezoelectric hybridization assay was completed in 10 min and the same sensing surface was suitable for repeated use. (C) 2004 Elsevier B.V. All rights reserved.

Immobilization of streptavidin in sol-gel films: Application on the diagnosis of hepatitis C virus

Recent advances have accelerated the development of biosensors for the analysis of specific gene sequences. In this kind of biosensor, a DNA probe is immobilized on a transducer and the hybridization with the target DNA is monitored by suitable methodology. In the present work, the streptavidin (STA) was encapsulated in thin films siloxane-poly(propylene oxide) hybrids prepared by sol-gel method and deposited on the graphite electrode surface by dip-coating process. Biotinylated 18-mer probes were immobilized through STA and a novel amperometric DNA biosensor for the detection and genotyping of the hepatitis C virus (genotypes 1, 2A/C, 2B and 3) is described. The HCV RNA from serum was submitted to reverse transcriptase-linked polymerase chain reaction (RT-PCR) and biotin-labeled cDNA was obtained. Thus, the cDNA was hybridized to the target-specific oligonucleotide probe immobilized on the graphite electrode surface and following the avidin-peroxidase conjugate was added. The enzymatic response was investigated by constant potential amperometry at -0.45 V versus Ag/AgCl using H2O2 and KI solutions. HCV RNA negative and positive controls and positive samples of sera patients were analyzed and the results were compared to commercial kit. The proposed methodology appeared to be suitable and convenient tool for streptavidin immobilization and diagnose of HCV disease. (c) 2006 Elsevier B.V. All rights reserved.

Atividade antiinflamatória, antiúlcera gástrica e toxicidade subcrônica do extrato etanólico de própolis

Avaliou-se a atividade antiinflamatória do extrato etanólico de própolis - EEP, . sobre o edema desencadeado por carragenina, dextrana e histamina. O EEP apresentou dose eficaz (DE50) de 650 mg/kg (v.o), inibindo significativamente o processo inflamatório desencadeado pela carragenina, mas não inibiu o produzido por dextrana. O EEP antagonizou ainda o efeito edematogênico produzido por histamina. Nas úlceras produzidas por estresse, o EPP inibiu de forma significativa a geração dos diversos tipos classificados. em todos os parâmetros analisados no estudo da toxicidade em fase de tratamento subcrônico , (hematológicos, bioquímicos e histopatológicos), o grupo tratado com o EEP não apresentou diferença significativa em relação ao grupo controle. Desta forma, sugere-se que na dose de 650 mg/kg (dose eficaz) não existe a presença de efeitos tóxicos que possam comprometer a utilização deste extrato.

Serotonin as a physiological substrate for myeloperoxidase and its superoxide-dependent oxidation to cytotoxic tryptamine-4,5-dione

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Dynamic mechanical properties for polyurethane elastomers applied in elastomeric mortar

Dynamic mechanical properties of a polyurethane (PU) elastomer and a mortar processed with the same elastomer (modified polytetramethylene ether glycol (PTMEG)) were studied. The results obtained showed that the liquid aromatic amine ETHACURE (R) 300, used as cure agent, can be used to substitute the aromatic amine MOCA (R), which is usually used as cure agent in high performance elastomers. The resulting mortar produced with ETHACURE (R) 300 presents similar dynamic-mechanical thermal properties when compared with MOCA (R). However, dynamic-mechanical thermal analysis studies showed that the mortar developed with ETHACURE (R) 300 presents some advantages such as the low values of tan d, indicating a good capacity of recovery of the strain after retreating an applied force. (c) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Síntese, caracterização e aplicação de MCM-41 funcionalizado com diisopropilamina no processo de adsorção do dióxido de carbono

Emissions of CO2 in the atmosphere have increased successively by various mechanisms caused by human action, especially as fossil fuel combustion and industrial chemical processes. This leads to the increase in average temperature in the atmosphere, which we call global warming. The search for new technologies to minimize environmental impacts arising from this phenomenon has been investigated. The capture of CO2 is one of the alternatives that can help reduce emis ions of greenhouse gases. The CO2 can be captured through the process of selective adsorption using adsorbents for this purpose. Were synthesized by hydrothermal method, materials of the type MCM-41 and Al-MCM-41 in the molar ratio Si / Al equal to 50. The synthesis of gels were prepared from a source of silicon, sodium, water and aluminum in the case of Al-MCM-41. The period of synthesis of the materials was 5 days in autoclave at 100°C. After that time materials were filtered, washed and dried in greenhouse at 100 º C for 4 hours and then calcined at 450 º C. Then the calcined material was functionalized with the Di-isopropylamine (DIPA) by the method of wet impregnation. We used 0.5 g of material mesopores to 3.5 mL of DIPA. The materials were functionalized in a closed container for 24 hours, and after this period were dried at brackground temperature for 2 hours. Were subsequently subjected to heat treatment at 250°C for 1 hour. These materials were used for the adsorption of CO2 and were characterized by XRD, FT-IR, BET / BJH, SEM, EDX and TG / DTG. Tests of adsorption of CO2 was carried out under the following conditions: 100 mg of adsorbent, temperature of 75°C under flow of 100 mL/min of CO2 for 2 hours. The desorption of CO2 was carried out by thermogravimetry from ambient temperature to 900ºC under flow of 25 mL min of He and a ratio of 10ºC/min. The difratogramas X-ray for the synthesized samples showed the characteristic peaks of MCM-41, showing that the structure of it was obtained. For samples functionalized there was a decrease of the intensities of these peaks, with a consequent reduction in the structural ordering of the material. However, the structure was preserved mesopores. The adsorption tests showed that the functionalized MCM-41 is presented as a material promising adsorbent, for CO2 capture, with a loss of mass on the desorption CO2 of 7,52%, while that in Al-MCM- 41 functionalized showed no such loss

Banana Peel Applied to the Solid Phase Extraction of Copper and Lead from River Water: Preconcentration of Metal Ions with a Fruit Waste

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Synthesis, characterization, and application of modified silica in the removal and preconcentration of lead ions from natural river water

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Síntese, caracterização e estudo fotofísico de complexos de 4,4- diaminoestilbeno-2,2-dissulfonato com íons lantanídeos

This is a work involving fundamental studies of chemistry where the synthesis and structural characterization, as well as a possible future application of these new compounds as luminescent sensors or sunscreen agents, complexes with 4,4 diaminostilbene-2,2-disulfonic (DSD) and trivalent lanthanide ions La3+, Nd3+, Eu3+, Gd3+ and Yb3+, were synthesized in the ratio of 3 mmol: 1 mmol (DSD: lanthanides). The complexes obtained with these ions were present in powder form and were characterized by complexometric titration with EDTA CHN Elemental analysis, molecular absorption spectroscopy in the ultraviolet region, the absorption spectroscopy in the infrared, thermal analysis (TG / DTG), Nuclear Magnetic Resonance - NMR 1H and Luminescence Spectroscopy. The complexometric titration and CHN analysis, confirmed the TG / DTG which suggest that these complexes have the following general chemical formulas: [La2(C14H12S2O6N2)2(H2O)2Cl2].7H2O,[Nd2(C14H12S2O6N2)2(H2O)2Cl2].6H2O,[Eu2(C14 H12S2O6N2)2(H2O)2Cl2].7H2O,[Gd2(C14H12S2O6N2)2(H2O)2Cl2].4H2O e [Yb2(C14H12S2O6N2)2(H2O)2].6H2O. The disappearance of the bands in the infrared spectrum at 2921 cm-1 and 2623 cm-1 and the displacement of the bands in the spectra of the amine complex indicate that the lanthanide ion is coordinated to the oxygen atoms and the sulfonate groups of the nitrogens amines, suggesting the formation of the dimer. The disappearance of the signal and the displacement signal SO3H amines in the 1H NMR spectrum of this complex are also indicative coordination and dimer formation. The Thermogravimetry indicates that the DSD is thermally stable in the range of 40º to 385°C and their complexes with lanthanide ions exhibit weight loss between 4 and 5 stages. The Uv-visible spectra indicated that the DSD and complexes exhibit cis isomers. The analysis of luminescence indicates that the complexes do not exhibit emission in the region of the lanthanides but an intense emission part of the binder. This is related to the triplet states of the ligand, which are in the lowest energy state emitting lanthanide ions, and also the formation of the dimer that suppress the luminescence of ion Eu3+. The formation of dimer was also confirmed by calculating the europium complex structure using the model Hamiltonian PM6 and Sparkle

Estudo de materiais mesoporosos funcionalizados com diferentes aminas para captura do dióxido de carbono através do processo de adsorção

Intensive use of machinery and engines burning fuel dumps into the atmosphere huge amounts of carbon dioxide (CO2), causing the intensification of the greenhouse effect. Climate changes that are occurring in the world are directly related to emissions of greenhouse gases, mainly CO2, gases, mainly due to the excessive use of fossil fuels. The search for new technologies to minimize the environmental impacts of this phenomenon has been investigated. Sequestration of CO2 is one of the alternatives that can help minimize greenhouse gas emissions. The CO2 can be captured by the post-combustion technology, by adsorption using adsorbents selective for this purpose. With this objective, were synthesized by hydrothermal method at 100 °C, the type mesoporous materials MCM - 41 and SBA-15. After the synthesis, the materials were submitted to a calcination step and subsequently functionalized with different amines (APTES, MEA, DEA and PEI) through reflux method. The samples functionalized with amines were tested for adsorption of CO2 in order to evaluate their adsorption capacities as well, were subjected to various analyzes of characterization in order to assess the efficiency of the method used for functionalization with amines. The physic-chemical techniques were used: X- ray diffraction (XRD), nitrogen adsorption and desorption (BET/BJH), scanning electron microscopy (SEM), transmission electron microscopy (TEM), CNH Analysis, Thermogravimetry (TG/DTG) and photoelectron spectroscopy X-ray (XPS). The CO2 adsorption experiments were carried out under the following conditions: 100 mg of adsorbent, at 25 °C under a flow of 100 ml/min of CO2, atmospheric pressure and the adsorption variation in time 10-210 min. The X-ray diffraction with the transmission electron micrographs for the samples synthesized and functionalized, MCM-41 and SBA-15 showed characteristic peaks of hexagonal mesoporous structure formation, showing the structure thereof was obtained. The method used was efficient reflux according to XPS and elemental analysis, which showed the presence of amines in the starting materials. The functionalized SBA -15 samples were those that had potential as best adsorbent for CO2 capture when compared with samples of MCM-41, obtaining the maximum adsorption capacity for SBA-15-P sample

Interações entre a carboximetilcelulose, carbonato de cálcio e bentonita: repercussões sobre as propriedades dos fluidos de perfuração aquosos

The role of carboxymethylcellulose (CMC) in association to calcium carbonate particles (CaCO3) in most water-based drilling fluids is to reduce the fluid loss to the surrounding formation. Another essential function is to provide rheological properties capable of maintaining in suspension the cuttings during drilling operation. Therefore, it is absolutely essential to correlate the polymer chemical structure (degree of substitution, molecular weight and distribution of substituent) with the physical-chemical properties of CaCO3, in order to obtain the better result at lower cost. Another important aspect refers to the clay hydration inhibitive properties of carboxymethylcellulose (CMC) in drilling fluids systems. The clay swelling promotes an undesirable damage that reduces the formation permeability and causes serious problems during the drilling operation. In this context, this thesis consists of two main parts. The first part refers to understanding of interactions CMC-CaCO3, as well as the corresponding effects on the fluid properties. The second part is related to understanding of mechanisms by which CMC adsorption occurs onto the clay surface, where, certainly, polymer chemical structure, ionic strength, molecular weight and its solvency in the medium are responsible to affect intrinsically the clay layers stabilization. Three samples of carboximetilcellulose with different molecular weight and degree of substitution (CMC A (9 x 104 gmol DS 0.7), CMC B (2.5 x 105 gmol DS 0.7) e CMC C (2.5 x 105 gmol DS 1.2)) and three samples of calcite with different average particle diameter and particle size distribution were used. The increase of CMC degree of substitution contributed to increase of polymer charge density and therefore, reduced its stability in brine, promoting the aggregation with the increase of filtrate volume. On the other hand, the increase of molecular weight promoted an increase of rheological properties with reduction of filtrate volume. Both effects are directly associated to hydrodynamic volume of polymer molecule in the medium. The granulometry of CaCO3 particles influenced not only the rheological properties, due to adsorption of polymers, but also the filtration properties. It was observed that the lower filtrate volume was obtained by using a CaCO3 sample of a low average size particle with wide dispersion in size. With regards to inhibition of clay swelling, the CMC performance was compared to other products often used (sodium chloride (NaCl), potassium chloride (KCl) and quaternary amine-based commercial inhibitor). The low molecular weight CMC (9 x 104 g/mol) showed slightly lower swelling degree compared to the high molecular weight (2.5 x 105 g/mol) along to 180 minutes. In parallel, it can be visualized by Scanning Electron Microscopy (SEM) that the high molecular weight CMC (2.5 x 105 g/mol e DS 0.7) promoted a reduction in pores formation and size of clay compared to low molecular weight CMC (9.0 x 104 g/mol e DS 0.7), after 1000 minutes in aqueous medium. This behavior was attributed to dynamic of interactions between clay and the hydrodynamic volume of CMC along the time, which is result of strong contribution of electrostatic interactions and hydrogen bounds between carboxylate groups and hydroxyls located along the polymer backbone and ionic and polar groups of clay surface. CMC adsorbs on clay surface promoting the skin formation , which is responsible to minimize the migration of water to porous medium. With the increase of degree of substitution, it was observed an increase of pores onto clay, suggesting that the higher charge density on polymer is responsible to decrease its flexibility and adsorption onto clay surface. The joint evaluation of these results indicate that high molecular weight is responsible to better results on control of rheological, filtration and clay swelling properties, however, the contrary effect is observed with the increase of degree of substitution. On its turn, the calcite presents better results of rheological and filtration properties with the decrease of average viii particle diameter and increase of particle size distribution. According to all properties evaluated, it has been obvious the interaction of CMC with the minerals (CaCO3 and clay) in the aqueous medium

Variação da pressão sistólica como indicadora precoce de hipovolemia e guia de reposição volêmica com solução hiperosmótica e hiperoncótica no cão

JUSTIFICATIVA E OBJETIVOS: Estudos introduziram novo método para avaliação da pré-carga, baseado na análise da variação da pressão sistólica (VPS) durante ventilação artificial. O objetivo desta pesquisa é avaliar se a VPS e sua derivada delta down (ddown) são indicadoras precoces de hipovolemia e guias de reposição volêmica com solução hiperosmótica e hiperoncótica. MÉTODO: Doze cães foram submetidos a sangramentos parciais de 5% da volemia até se atingir 20% da volemia (14 ml.kg-1). Antes (controle) e após cada sangramento foram realizadas análises hemodinâmicas, respiratórias e sangüíneas. Após, os cães foram submetidos à reposição com solução de NaCl a 7,5% em dextran 70 a 3,75% (SHD) (4 ml.kg-1) e novas análises dos atributos estudados foram realizadas aos 5 e 30 minutos após a reposição. RESULTADOS: A pressão arterial média diminuiu durante o sangramento e aumentou após a reposição, sem retornar aos valores do controle. As pressões da artéria pulmonar e do átrio direito (PAD) diminuíram antes e aumentaram após a reposição para valores semelhantes aos do controle. A pressão da artéria pulmonar ocluída (PAPO) diminuiu após o primeiro sangramento e manteve-se em valores abaixo aos do controle, mesmo após a reposição. O índice cardíaco não se alterou, mas aumentou após a reposição, para valores superiores aos do controle. O índice sistólico (IS) diminuiu antes e aumentou após a reposição, em níveis superiores aos do controle. Os índices de resistência vascular sistêmica (IRVS) e pulmonar (IRVP) não se alteraram antes, mas diminuíram após a reposição, com o IRVS em níveis inferiores aos do controle, e o IRVP em níveis semelhantes aos do controle. Os índices de trabalho sistólico dos ventrículos direito (ITSVD) e esquerdo (ITSVE) diminuíram durante o sangramento, mas aumentaram após a reposição, com o ITSVD em níveis superiores aos do controle e o ITSVE em níveis semelhantes aos do controle. A VPS e ddown aumentaram progressivamente durante o sangramento e diminuíram após a reposição, mas mantendo-se em valores superiores aos do controle. As maiores correlações de VPS e ddown foram com IS, PAPO, PAD e ITSVE. CONCLUSÕES: No cão, nas condições empregadas, a VPS e sua derivada ddown são indicadoras precoces de hipovolemia e guias sensíveis de reposição volêmica com SHD.