Mestrado em Química
URI Permanente para esta coleção
Nível: Mestrado Acadêmico
Ano de início: 2006
Conceito atual na CAPES: 5
Ato normativo: Homologação da 85ª Reunião do CTC-ES, Parecer CNE/CES nº 163/2005.
Processo nº 23001.000081/2005-56 do Ministério da Educação.
Publicado no DOU 28/07/2005, seção 1, página 11)
Periodicidade de seleção: Anual
Área(s) de concentração: Química
Url do curso: https://quimica.vitoria.ufes.br/pt-br/pos-graduacao/PPGQ/detalhes-do-curso?id=954
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- ItemAplicações da espectrometria de massas de resssonância ciclotrônica de íons por transfromada de Fourier (FT-ICR MS) em petroleômica(Universidade Federal do Espírito Santo, 2013-08-23) Pereira, Thieres Magaive Costa; Cunha Neto, Alvaro; Vaz, Boniek Gontijo; Lopes, Rosana CardosoPetroleum is a complex mixture, being one of the most challenging mixtures for chemical analyzes. Many techniques are employed to characterize constituents of the oil. However , when we combine the highest resolving power and accuracy of mass spectrometry , especially Ion Cyclotron Resonance Fourier Transform ( FT - ICR MS ) with sources of atmospheric pressure ionization , an assignment need more than 20 000 organic compounds in the oil can be obtained. In the oil industry there is a great interest in the analysis of asphaltenes and naphthenic acids due to problems such as corrosion and deposit formation, which increases production costs. Therefore this study aims to evaluate the thermodegradation of naphthenic acids, besides the use of sources of ESI, APCI, APPI, MALDI and LDI for the acquisition of new data on the characterization of asphaltenes . Two test oils were used in thermodegradation of the oil with an acidity of 2.38 mg KOH g -1 and Oil B with 4.79 mg KOH g- 1 which were treated at 280 , 300 and 350 ° C for a period of 2 , 4 and 6 hours. Generally, the major classes identified for both samples O2, NO2, and C, respectively. A slight reduction of NAT and relative abundance refers to the class O2 were observed as a function of temperature and aging time (T = 280 ? 300 ° C t = 2 ? 6 h), and the heat treatment temperature at 350 ° C showed a determinant for the removal of class O2. The chemical asphaltenes Brazilian samples was evaluated using five different methods of ionization in both modes of ionization: positive and negative, then the molecular weight distribution, distribution class, typical plots versus carbon number and DBE van Krevelen diagrams were obtained and discussed. An unusual behavior was observed for the LDI and MALDI source ( ± ) FT - ICR MS . A comprehensive profile of m / z 500-3000, with spacing of 24 Da was observed, and this corresponds to allotropes of fullerene C60. In general, the asphaltenes had an heteroatómicas high proportion of species such as HC , HC [ H] , N, [ H] , N2O N2O [ H] N2, N2 [ M ] O O [ H] to mode (+) and N, [ H ] , NO [ H] , NO , NO2, [ H] , N2O N2O [ H ] for the negative mode . In the diagrams DBE against the carbon number , the asphaltenes shown for each value of DBE composed of a small amplitude with respect to NC, thus providing images that form a line of 45 ° between the axes CN and DBE. This indicates that these compounds do not exhibit large chain alkyl, composed mainly of aromatic rings. In general diagrams van Krevelen showed a high proportion of compounds ratio H / C ~ 0.7, confirming the existence of highly aromatic species
- ItemComparação de ácidos naftênicos por ressonância magnética nuclear e ouras técnicas analísticas(Universidade Federal do Espírito Santo, 2016-05-19) Corti, Mayara Modenesi; Cunha Neto, Álvaro; Lacerda Júnior, Valdemar; Franca, Hidelgardo Seibert FrancaNaphthenic acids are a diverse group of carboxylic acids present in petroleum. The presence of these compounds in the oil is harmful to the refining equipment since according to oil’s composition, they can cause corrosion, emulsions and precipitates formation, consequently, leading to great losses in production. Corrosion in oils processing is related to sulfur compounds content in the oil and to the type of acid present, being the latter of smaller chain and having the acidic hydrogen more available to attack. Precipitates formation is associated to the acids transformation (generally of longer chain) in poorly soluble salts, which deposit in the transfer ducts. NMR technique was used in this work to differentiate the types of naphthenic acids extracted from oil and calcium naphthenates. For samples extracted from oil, it was possible to observe a content of approximately 8% of aromatic hydrogens and 90% of alkyl. Among the last quantity, the large variety of Ha, Hß and H? levels indicates the structural diversity of the compounds present in the oil extracted samples. With the pH extraction increasement, it was noticed a decrease in Ha and a raise in Hß and H? contents, indicating the greater complexity of the extracted structures. For samples extracted from calcium naphthenates, contents of almost 5% of aromatic hydrogens and 95% of alkyl were observed, however, for these samples, no significant variation was noticed between the different extractions, what indicates that these compounds have similar compositions. A higher content of Hß was observed in comparison to Ha and H?, which attests these compounds have many ramifications near the aromatic ring, showing a structure with a pronounced alkyl chain, similar to that described in literature for ARN. In conclusion, it was possible to differentiate these two types of samples using NMR, since the aromatic and alkyl hydrogens contents are characteristic for each kind of naphthenic acid extracted from oil or calcium naphthenate.
- ItemEstudo da degradação de petróleos ácidos por técnicas analíticas de alta resolução(Universidade Federal do Espírito Santo, 2016-11-25) Barros, Eliane Valéria de; Romão, Wanderson; Silva, André Romero da; Cunha Neto, ÁlvaroIn the refining process of petroleum the corrosion caused by naphthenic acids (NA) is one of the most aggressive,and it can be accentuated when in presence of other compounds usually found in oil. Herein, oils samples weresubjected to thermal degradation process aiming the understanding of its behavior at the molecular level and to evaluate its physicochemical properties as a function of degradation time. In the first part of this study, anacid oil sample was subjected tothermal degradation process at 350 °C. Additionally, the oil was characterized by classic and high resolution analytical techniques. The obtained results showed that the oil exposed to longer degradation times presented characteristics of “lighter” oil due to mainly disaggregation of resins and asphaltenes. Total Acid number (TAN) measurements displayed a decrease of 68.3% (from 2.0 to 0.75 mg KOH g-1) of its initial value after 36h of degradation at 350 oC. Other important changes observed included an increase in API gravity (of two decimal places from 17 to 19), and decreases in the pour point from -12 to -36 oC, in the kinematic viscosity in 86.5% and of total sulfur content in 5.2% (from 0.58 to 0.55 wt%). The HTGC and NMR results showed that the saturated fraction is not affected during the thermal stress process, whereas a subtle increase in the number of aromatic compounds was observed as a function of degradation time. This behavior can be attributed to the disaggregationof resins and asphaltenes as well as to the decarboxylation process that was confirmed by ESI(-)-FT-ICR MS, where a reduction of average mass molar distribution from 466 to 450 Da was observed.In the second part of the work, a second sample of oil was degraded at 320 ° C and characterized by ESI (--FT-ICR MS and 1H NMR. Different extraction methodologies were used to investigate the behavior of the acidic species present. Regarding the collective extractions of NAs, solid phase extraction (SPE) was more efficient in relation to liquid-liquid extraction. Since the results of ESI(-)-FT-ICR MS showed an increase in the amplitude of observation of the acidic compounds and a greater number of compounds of class O2, which corresponded to almost 100% of all the processing. The integrations of the 1H NMR spectra of the acid fractions as a function of the molecular weight (Mw) emphasized the expressive presence of alkyl compounds, which had already been observed in the first part of the work. The successive removals of the acids of smallercarbon chains which reduced the ionic suppression on the larger acid species. The MS results of the extracts as a function of Mwdid not show typical Gaussian spectra for the last fractions (degraded for 24 and 72 hours), suggesting that cracking reduced the number of acid species for times of major degradation. The DBE versus NC graphs of the extracts of all samples (original oil and degraded at 24 and 72 hours) showed that there is an increase in the number of cyclizations, which corroborated with the previous results regarding the increase of the aromatic content.The reduction of the resin and asphaltenes content due to the thermal degradationsuggestthe"transformation" of heavy oil into considered "lighter" oils.
- ItemExtração e caracterização de ácidos naftênicos por espectrometria de massas de altíssima resolução e exatidão (ESI-FT-ICR MS)(Universidade Federal do Espírito Santo, 2012-03-09) Colati, Keroly Alaíde Pascoal; Castro, Eustáquio Vinicius Ribeiro de; Romão, Wanderson; Vaz, Boniek GontijoNaphthenic acids are present in crude oil as a complex mixture of compounds with a wide structure variation. These compounds are mainly responsible for corrosion problems, formation of stable emulsions and unwanted deposits. The total acid number (TAN) is the classical way of monitoring the acidity in oils. TAN increase is usually associated with the oil corrosion rate. Naphthenic acids can be obtained from crude oils by procedures extraction such as liquid/liquid extraction with alkaline solutions, solid/liquid extraction and others. Instrumental methods of analysis such as Infrared Spectroscopy (FTIR) and Mass Spectrometry of high resolution accuracy coupled to electrospray source (ESI (-) FT-ICR MS) have been used for characterization of acidic components in petroleum. Thus, the main objective of this study was to characterize naphthenic acid extracted from two samples (AM1 and AM2) of oil with high NAT value using the technique ESI (-) FT-ICR MS. Naphthenic acids were extracted by alkaline alcoholic solutions of pH 7, 10 and 14. TAN analyses were performed in the original oil and residual. ESI (-) FT-ICR MS and FTIR analysis were made in the original oils, waste and acidic fractions. The extraction process was very satisfactory. The TAN reduction was of 92% for AM1 and AM285% for both extracted at pH 14. It was verified by FTIR analysis the concentration of carboxylic acids in acidic fractions by increase absorption in the region of 1706 cm-1. Is was also observed the presence of nitrogen compounds by absorption in 3380 cm-1. MS analysis showed that for both oil samples acidic species are concentrated in a range of m/z 200 to 650 centered in 360 Da. The O2 class carbon distribution is C14-C46 and DBE = 2-14. O2species contained in the oil samples showed mostly DBE in the range 3 to 4 with no change during extraction process. In waste oil sample AM1 was detection of species with DBE < 3 which were not detected in the original oil. N, NO2 and O2 class were the most abundant for all samples analyzed. N class remain in residual oil showing migration in low proportion for the acid fractions 14. Therefore, the extraction method was very efficient for reducing the total acidity of the oil samples, as well as the assignment of the molecular weight was obtained with excellent accuracy thus enabling very satisfactory characterization of naphthenic acids presents by ESI (-) FT-ICR MS.
- ItemUso da microcromatografia gasosa no estudo da evolução do gás CO2 no processo de destilação laboratorial de petróleo(Universidade Federal do Espírito Santo, 2017-02-20) Lima, Tamires Aliprandi; Castro, Eustáquio Vinicius Ribeiro de; Ferreira, Ernesto Correa; Cunha Neto, ÁlvaroPetroleum remains the largest non-renewable source of energy in the world. In its raw state it has little use. However, its derivatives have high economic value. In the steps of primary processing of petroleum, a few compounds of natural occurrence are undesirable, such as the naphthenic acids, resins, asphaltenes, and metal and sulfur compounds. The corrosive power of naphthenic acids worries petroleum industries due to the damage caused in the pipes and refineries. Recent studies indicate that a portion of these acids when subjected to elevated temperatures (greater than 280°C) can undergo decarboxylation reactions and thermal degradation, forming carbon dioxide (CO2) and smaller chains acids such as degradation products. The smaller chains acids along with naphthenic acids, which remained preserved are corrosive and CO2when in contact with water forms carbonic acid (H2CO3), which may contribute to corrosion rates in refining equipment. In this paper a new methodology for "online" quantification of CO2released in petroleum distillation process was developed. The developed methodology wasbased on micro gas chromatography technique. The quantitative data ofthe CO2concentration generated by micro chromatograph were related to the values of the distillation temperature, thereby obtaining a variation in the concentration of CO2, in accordance with the oil distillation temperature. The results show that the distillate petroleum presents a tendency in the formation of CO2gas from temperatures above 230 °C. In an attempt to elucidate the possible origin of this gas, it was necessary to assume one decarboxylation mechanism for such acids