The conditions of petroleum extraction may allow asphaltenes to precipitate, causing deposition that clogs wells, pipes and equipment, consequently reducing productivity. In this work, the solubility parameters and precipitation onset of polar fractions of heavy crudes from Brazilian fields were estimated using a simplified system of n-heptane/toluene mixtures. Asphaltenes were extracted by two different methods with regard to pressure and temperature. The samples were physically and chemically characterized, and both density (1053-1159 kg m-3) and molecular weight (1176-5316 g mol-1) were estimated based on the density of diluted asphaltenes in toluene solutions. The solubility of those fractions was studied as well as their solubility parameter (ca. 19-23 MPa0.5) based on regular solution theory, Flory-Hüggins theory and empirical correlation. The influence of asphaltene concentration (between 0.5 and 5.0 g L-1) on the solubility parameter and precipitation onset was studied, and a strong linear correlation between them was not found.
One of the methods used by the oil industry to increase production is to inject water, containing polymer, into the reservoir. The viscosity of the aqueous solution is primarily responsible for the efficiency of this method, and is achieved using polymers with high molar mass. However, polymer degradation can occur during pumping and fluid displacement in the porous medium, reducing the efficiency of the polymer flooding method. Therefore, it is important to monitor the molar mass of the polymer in the produced water. Size-exclusion chromatography (SEC) is a powerful method for determining average molar mass of polymers, but the impurities present in the produced water, such as salts and residual oil, can significantly affect the analysis. There is no method described in the literature for pretreating produced water before injecting it into the chromatograph. Therefore, the purpose of this work was to develop a reliable method for this pretreatment, without affecting the molar mass of the polymer. The results showed that an efficient method, which does not cause polymer degradation, must contain four steps: (i) heating, (ii) regular filtration, (iii) elution in poly(divinylbenzene) resin, and (iv) dialysis.
Predicting the compatibility of crude oils from different streams can be done by applying models that use the solubility parameter of the oils. The approximate solubility parameter value of a given crude oil can be calculated by observing the asphaltene precipitation onset caused by titration with n-heptane. For oils whose precipitation onset is not well defined, a small quantity of another petroleum with easily detected onset can be added. It would be ideal to always use the same petroleum for this addition, but this is obviously not possible. The purpose of this study was to replace this petroleum by a synthetic molecule. Therefore, molecules were selected and synthesized to obtain structures containing aromatic ring, aliphatic chain and heteroatom. The molecules were characterized by infrared spectrometry, gas chromatography-mass spectrometry, elemental analysis and gel permeation chromatography. Nitrated cardanol, polycardanol obtained by addition polymerization (PCA) and nitrated PCA presented the desired behavior. However, the concentration of the molecule in toluene needs to be adjusted in function of the characteristics of the petroleum. For a particular crude oil, when model molecule present solubility in a wider solubility parameter range, lower concentration will require to identify the precipitation onset of that oil.
Crude oils containing large quantities of waxes, and in situations where sudden temperature drops occur, a crystalline network can be formed, generating flow difficulties in production, transfer and offloading lines. Despite the scientific and economic importance of this phenomenon, correlations between the behavior of petroleum in relation to its pour point are scarce in the literature. In this work, nine crude oil samples were characterized regarding density, water content, wax fraction (one- and two-dimensional chromatography), pour point, yield stress and wax appearance temperature. The results showed that the storage conditions and oil characteristics had a strong influence on the pour point. Yield stress was influenced by initial temperature of the sample, cooling rate and shear rate during cooling. Finally, the content of aromatic compounds in oil with low concentration of n-alkanes can contribute to increase the pour point.
In this study, microparticles of poly(lactic acid) (PLA) were produced to encapsulate cardanol, varying molar mass of the polymer matrix, concentration of the emulsifier (PVA) and concentration of the chemical additive (cardanol). The droplet size distribution, polydispersity index, morphology, the interaction between cardanol and PLA, cardanol encapsulation efficiency and release profile of this chemical additive were assessed. The morphological characterization showed that the microparticles containing cardanol were presented as microcapsules up to a maximum cardanol concentration limit that could be incorporated. The addition of cardanol during the production of the microparticles led to an increase in the average diameter of the microparticles obtained, both those with low and high molar mass (MPLA3 and MPLA100, respectively), with the increase depending on the quantity of cardanol incorporated. DSC results showed a shift in melting point and a change in Tg and Tm with the incorporation of cardanol, suggesting an interaction between cardanol and PLA matrix. Higher encapsulation efficiency and slower release of cardanol were achieved when using microparticles with higher molar mass (MPLA100). The microparticles of MPLA100/1PVA/50C provided the slowest additive release among the formulations tested. Therefore, the processes for encapsulation and controlled release of cardanol in the PLA matrix were efficient.
Clays such as smectite have high technical and economic viability due to their large adsorption capacity. These properties can be improved by treatment with acids or other modifications. This paper describes experiments to prepare and characterize organoclays and to evaluate their ability to remove oil from contaminated water in comparison with clay in its natural state. We used natural smectite clay from the municipality of Presidente Dutra, Maranhão State, modified with the quaternary ammonium salt cetyltrimethylammonium bromide. Characterization was performed by X-ray diffraction, Fourier transform infrared spectroscopy, X-ray fluorescence, thermogravimetry and determination of surface area by the Brunauer-Emmett-Teller (BET) method. The results showed appropriate conditions of the organophilization process, indicating the intercalation of quaternary ammonium cations between the clay layers. The adsorption tests showed that the natural clay reduced the amount of oil contained in the aqueous medium by 76.16%, while the corresponding removal rates of all organoclays tested were above 92%, which makes them potentially applicable to remove oil from wastewaters.
Asphaltenes are blamed for various problems in the petroleum industry, especially formation of solid deposits and stabilization of water-in-oil emulsions. Many studies have been conducted to characterize chemical structures of asphaltenes and assess their phase behavior in crude oil or in model-systems of asphaltenes extracted from oil or asphaltic residues from refineries. However, due to the diversity and complexity of these structures, there is still much to be investigated. In this study, asphaltene (sub)fractions were extracted from an asphaltic residue (AR02), characterized by NMR, elemental analysis, X-ray fluorescence and MS-TOF, and compared to asphaltene subfractions obtained from another asphaltic residue (AR01) described in a previous article. The (sub)fractions obtained from the two residues were used to prepare model-systems containing 1 wt% of asphaltenes in toluene and their phase behavior was evaluated by measuring asphaltene precipitation onset using optical microscopy. The results obtained indicated minor differences between the asphaltene fractions obtained from the asphaltic residues of distinct origins, with respect to aromaticity, elemental composition (CHN), presence and content of heteroelements and average molar mass. Regarding stability, minor differences in molecule polarity appear to promote major differences in the phase behavior of each of the asphaltene fractions isolated.
The solubility parameter (δ) of a molecule is extremely important, since that new molecules are frequently developed to be applied in liquid systems. In this work, we looked for simple and reliable alternative techniques to determine δ of low and high molecular weight molecules. Pyrene, phenanthrene and naphthalene had their δ determined by microcalorimetry (µDSC), ultraviolet (UV) and calorimetry (DSC). UV results were similar to those obtained by DSC and to those cited in the literature. Polystyrene and sulfonated polystyrene samples had their δ determined by UV, µDSC and intrinsic viscosity ([η]). The [η] results were similar to those obtained by UV. UV procedure was relatively simple, easy operation and reliable for determining δ of molecules in a wide range of molar mass, can be used when developing new molecules. The µDSC procedure still requires some adjustments to become more accurate than [η] procedure.
O parâmetro de solubilidade (δ) de uma molécula é extremamente importante, visto que novas moléculas são frequentemente desenvolvidas para serem aplicadas em sistemas líquidos. Neste trabalho, nós buscamos técnicas alternativas simples e confiáveis para determinar δ de moléculas de baixa e alta massa molar. Pireno, fenantreno e naftaleno tiveram seus δ determinados por microcalorimetria (µDSC), ultravioleta (UV) e calorimetria (DSC). Resultados de UV foram similares àqueles obtidos por DSC e àqueles citados na literatura. Amostras de poliestireno e poliestireno sulfonado tiveram seus δ determinados por UV, µDSC e viscosidade intrínseca ([η]). Os resultados de [η] foram similares àqueles obtidos por UV. Procedimento de UV foi relativamente simples, de fácil operação e confiável para determinação de δ de moléculas de ampla faixa de massa molar, podendo ser utilizado no desenvolvimento de novas moléculas. O procedimento utilizando μDSC ainda requer alguns ajustes a fim de torná-lo mais preciso do que [η].
In the current scenario, there is growing interest in the products of degradation of rubber (natural and synthetic) for specific applications in different industry sectors, whose benefits in replacing conventionally used products are mainly related to sustainability. Since the degradation products of rubber can be used in different areas, several research groups may have the interest aroused by these products, but are not familiar with the aspects related to the chemical behavior of rubber. This review aims to bring together the key information in the published literature on the degradation of natural rubber, emphasizing metatheses reactions, oxidative damage and splitting of the double bond, in order to serve as a reference source for researchers from different fields interested in obtaining such kind of products. The structures and properties as well as additional chemical transformations resulting in oligomers of isoprene, functionalised oligomers and polymers based on both are also described.
Crude oil is produced as water-in-oil emulsion, and asphaltenes have been considered the main responsible by their stabilization. The aim of this work was to evaluate the influence of the asphaltenes subfractions on the stability of petroleum model emulsions and on the efficiency of demulsifiers. Model water-in-oil emulsions were prepared: aqueous phase of brine and oil phase of asphaltenes in toluene. Different asphaltenes fractions were used. The emulsions' stability was assessed by the bottle test, with and without adding demulsifier. The results show that a sample of asphaltenes with broad polarity distribution promotes greater emulsion stability than a sample with narrow distribution and intermediate polarity. Besides this, the efficiency of demulsifiers in separating the emulsions is directly related to the original stability of the emulsion. Measurements of the interfacial tension revealed the efficiency of displacement of the asphaltenes by the demulsifiers, which occurred more efficiently for the emulsions containing asphaltenes fractions with narrow distribution and intermediate polarity.
O petróleo é produzido na forma de emulsão água em óleo e os asfaltenos são considerados os principais responsáveis pela estabilização dessas emulsões. O objetivo deste trabalho foi avaliar a influência de diferentes frações asfaltênicas sobre a estabilidade de emulsões modelo de petróleo (salmoura em asfaltenos/tolueno) e sobre a eficiência de desemulsificantes. A estabilidade das emulsões foi acompanhada pelo ensaio de garrafa, com e sem a adição de desemulsificante. Os resultados mostram que a amostra de asfaltenos com larga distribuição de polaridade promove maior estabilidade da emulsão do que a amostra com distribuição mais estreita e polaridade intermediária. Além disso, a eficiência do desemulsificante na separação das emulsões está diretamente relacionada à estabilidade original da emulsão. Resultados de tensão interfacial evidenciaram a eficiência de deslocamento dos asfaltenos pelos tensoativos desemulsificantes, o que ocorreu com maior eficiência para as emulsões contendo frações de asfaltenos com distribuição estreita e polaridade intermediária.
A study was carried out to investigate the interaction between asphaltenes (in toluene solutions) and resins (in n-heptane solutions). To better understand the type of interaction between these fractions, it was quantified the resin uptake when asphaltenes (dissolved in toluene) were precipitated by a resin-containing n-heptane solution. These results indicated the asphaltene precipitation occurs together with a reduction in the resin concentration. The binding isotherm profiles indicated that saturation occurred in one case, while collective association following an initial plateau was observed for the other two samples. These results confirmed the hypothesis that resins can adsorb on asphaltenes but cannot prevent asphaltenes from flocculating and precipitating. Furthermore, microcalorimetric results suggested that the resin and asphaltene interact by weak van der Waals forces. These results are in stark contrast with the school of thought prevalent since the 1940s that resins can peptize and stabilize asphaltenes.
Foi realizado um estudo para investigar a interação entre asfaltenos (em soluções de tolueno) e resinas (em soluções de n-heptano). Para entender melhor o tipo de interação entre essas frações, quantificou-se o consumo de resina quando asfaltenos (dissolvidos em tolueno) foram precipitados com uma solução de n-heptano contendo resina. Os resultados indicaram que a precipitação de asfaltenos ocorre juntamente com a redução na concentração de resina. Os perfis das isotermas de ligação indicaram que a saturação ocorreu em um caso, em quanto que o efeito cooperativo com posterior platô inicial foi observado para duas outras amostras. Estes resultados confirmaram a hipótese de que resinas podem adsorver em asfaltenos, mas não podem evitar floculação e precipitação de asfaltenos. Além disso, resultados de microcalorimetria sugeriram que a resina e asfalteno interagem por forças fracas de van der Waals. Estes resultados estão em contraste com a escola de pensamento predominante desde a década de 1940 que advoga que as resinas podem peptizar e estabilizar asfaltenos.
The structure of the various asphaltenic subfractions found in crude oil was evaluated. For this purpose, C5 asphaltenes were extracted from an asphaltic residue using n-pentane as the flocculant solvent. The different subfractions were isolated from the C5 asphaltenes by the difference in solubility in different solvents. These were characterized by infrared spectroscopy, nuclear magnetic resonance, X-ray fluorescence, elementary analysis and mass spectrometry. The results confirmed that the subfractions extracted with higher alkanes had greater aromaticity and molar mass. However, small solubility variations between the subfractions were attributed mainly to the variation in the concentrations of cyclical hydrocarbon compounds and metals.
Water-in-crude oil emulsions are formed during petroleum production and asphaltenes play an important role in their stabilization. Demulsifiers are added to destabilize such emulsions,however the demulsification mechanism is not completely known. In this paper, the performances of commercial poly(ethylene oxide-b-propylene oxide) demulsifiers were studied using synthetic water-in-oil emulsions and model-systems (asphaltenes in organic solvent). No change in the asphaltene aggregate size induced by the demulsifier was observed. The demulsification performance decreased as the asphaltene aggregate size increased, so it can be suggested that the demulsification mechanism is correlated to the voids between the aggregates adsorbed on the water droplets surface.
Polymeric resins have been used as alternative materials for treating oily waters from the petroleum industry, which have already been treated by conventional methods. The objective of this work was to evaluate the purification degree of synthetic oily waters when treated in fixed bed columns packed with hydrophilic/lipophilic resins. Synthetic oily waters were prepared and fluorimetry was used to determine the total grease and oil content (TGOC) of the fresh oily water and the oily water eluted by the column. The results showed that the treated oily water presented a TGOC close to zero ppm. The kinetic study showed that the contaminant removal efficiency slightly depends on the system elution flow rate; optimum removal values were reached at a 7.0 mL/min flow rate. The passage of a water volume 11,087 times the volume of the column bed was not sufficient to observe its complete saturation. Preliminary tests of column regeneration and re-use showed its potential to be used for more than 1 cycle of oily water treatment.
Resinas poliméricas vêm sendo usadas como materiais alternativos para tratamento de águas oleosas, provenientes da indústria de petróleo, as quais já tenham sido tratadas por métodos convencionais. O objetivo deste trabalho é avaliar o grau de purificação de águas oleosas sintéticas, quando tratadas em colunas de leito fixo empacotadas com resinas poliméricas constituídas por segmentos hidrofílicos e lipofílicos. Foram preparadas águas oleosas sintéticas e a fluorimetria foi utilizada para determinar o teor total de óleos e graxas (TOG) nas amostras de água recém-preparada e após eluição pela coluna. Os resultados mostraram que amostras de água tratadas com a coluna apresentaram valor de TOG não superior a 1% do valor de TOG da água oleosa preparada. Um estudo cinético mostrou que a eficiência de remoção dos contaminantes depende ligeiramente da vazão de eluição do sistema, sendo que valores de desempenho ótimos foram alcançados a uma vazão de 7,0 mL/min. A passagem de um volume de água oleosa de 11.087 vezes o volume do leito da coluna não foi suficiente para atingir a completa saturação do sistema. Ensaios preliminares de regeneração e reutilização da coluna mostraram seu potencial de uso em mais de 1 ciclo de tratamento de água oleosa.
The preparation of bentonite-ionene complexes based on the adsorption of 2y-ionenes, where y = 4, 6, 10 or 12 and an ionene of the epichloridrin-dimethylamine EPI-DMA kind, was carried out in order to observe the behavior of the ionene spacer size in the expansion of the basal space (d-spacing, d001) of a Brazilian commercial bentonite. The complexes were characterized by adsorption spectromety in the infrared region, thermogravimetry, fluorescence and X-Ray diffraction. Ionenes were synthesized and characterized by infrared and nuclear magnetic resonance, the latter technique being useful for determining the average number molecular weight values. Based on the clay-ionenes complexes it could be observed that the ammonium polyquaternaries are adsorbed on the inner and outer clay surfaces, above the ion exchange capacity, CEC = 91 meq/100 g clay (calculated based on X-Ray fluorescence data). The clay basal expansion with the several polycations revealed that the spacer size is the most important factor, independent of ionene molecular weight values. Among the bentonite-ionene complexes, mainly between Bt-2,10 and Bt-2,12-ionene complexes which differ in molar mass by more than 30,000 g/mol, it was observed that the spacer size has no dependence on the ionene molecular weights.
A preparação de complexos bentonita-ionenos a partir da adsorção de tetrametil-[x,y]-ionenos, onde x= 2 e y= 4,6,10 ou 12, e o 2-hidróxi-3-cloro-ioneno, EPI-DMA, foi realizada com a finalidade de observar o comportamento do tamanho do espaçador do ioneno na expansão basal (d001) das camadas de uma bentonita comercial do Brasil. Os complexos foram caracterizados por espectrometria de absorção na região do infravermelho, termogravimetria, fluorescência e difração de raios X. A partir das análises por fluorescência e difração de raios X dos complexos, foi observado que os poli-quaternários de amônio são adsorvidos nas superfícies internas e externas da argila delaminada, acima da capacidade de troca catiônica, CTC = 91 meq/100g de argila (calculada a partir de dados de fluorescência de raios X). A expansão basal das camadas da argila com os diferentes policátions revelou que o tamanho do espaçador é o fator mais importante, independentemente das massas molares dos ionenos, tal como foi observado principalmente entre os complexos Bt-2,10- e Bt-2,12-ioneno, com massas molares de 12000 e 5000 g/mol, respectivamente.