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Aggregation and precipitation of asphaltenes are relevant concerns during the extraction and processing of petroleum because of the severe damage they cause to the equipment for crude oil transportation. Studies show that the presence of resins can contribute to smaller aggregate formation and thereby reduce the asphaltene precipitation. Herein, we showed the investigation of the influence of resins on the size of asphaltene aggregates by diffusion-ordered spectroscopy (DOSY). The asphaltenes were extracted from crude oil by precipitation with n-heptane. The resins were extracted from the maltene fraction, and their samples were analyzed by 1H and 13C nuclear magnetic resonance spectroscopy. Aromatic and aliphatic hydrogen and carbon contents were estimated, including their subdivisions. From these results, we estimated the aromaticity factor (f a), the number of naphthenic rings (R N), the number of total rings (R T), the average length of alkyl chains (N alk), the aromatic condensation index (Φ), and the aromatic condensation degree (ξ), which were used to determine the asphaltene architecture. The asphaltene chemical structures were suggested for each sample (asphaltene 1 was predominantly continental, while asphaltenes 2 and 3 were archipelago), and the relative diffusion of asphaltene aggregates and resins in toluene-d 8 was determined by DOSY. Asphaltenes, resins, and their mixtures were prepared in toluene-d 8 at concentrations ranging from 5 to 7 wt %. The aspthaltenes/resins mixture proportions were 7:1; 7:2; 7:3; 1:1; and 2:1 wt %. Generally, the relative diffusion values of the solutions increased because of the addition of resins (asphaltenes/resins 7:3 > 7:2 > 7:1 wt %), indicating that their presence favors the formation of smaller aggregates.

A new analytical method was developed to quantify cocaine and some adulterants using nuclear magnetic resonance spectroscopy without the use of deuterated solvents.

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The study of petroleum asphalt cement (AC) aging is essential for the production of good quality pavements with high durability. Because of the complexity of this material, one of the biggest challenges is understanding the chemical variations that occur in the molecules present in the AC during the aging processes. This work proposes to study 15 standards of model compounds present in the AC composition, representing the fractions of saturated compounds (5-α-cholestane and hexatriacontane), aromatics (hexamethylbenzene, coronene, and benzo-[a]anthracene), nitrogenous compounds (acridine, carbazole, indole, and N,N′-Bis(3-pentyl)perylene-3,4,9,10-bis-(dicarboximide)), sulfur compounds (2-naphthalenethiol, 4,6diethyldibenzothiophene, and naphtho[1,2-b:6,5-b′]dithiophene(NDT)), and naphthenic acids (stearic (SA), pentadecanoic (PA), and sinapinic acids (ASN)), which were thermally aged by two methods: (i) they were subjected to a constant temperature of 80 °C, varying the time of analysis over 5, 10, 15, 30, and 60 days; and (ii) temperatures ranging from 80, 100, 120, to 140 °C for 15 days. The analyses of these compounds were performed by GC/MS, 1 H and 13 C NMR, ESI(−)MS (FT-ICR and LTQ), and FTIR. The results obtained showed that at 80 °C, from 15 days, only the indole standard compound showed the presence of thermal products, i.e., compounds detected from thermal aging of the standard model compounds. When the degradation temperature was increased from 100 to 140 °C, we observed the formation of thermal products at 100 °C in 6 out of 15 model compounds. However, at 140 °C, 12 of the 15 model compounds presented some type of degradation. Reactions of oxidation, polymerization, thermal aging, volatilization, and formation of double bonds were observed.

This review describes the chemical composition of asphalt, which is relevant for the development of materials with higher quality and durability. Asphalt aging can occur in the short term (during machining and storage periods) and the long-term (during the time the pavement is exposed to the environment). To understand the effect of aging on the chemical and physical properties of asphalt, we reviewed the short-term (rolling-thin film oven test (RTFOT) and its variations) and long-term (pressure aging vessel (PAV) and its variations) aging methods and the effects of the sun’s ultraviolet radiation (Suntest and its variations). We also explored the main chemical reactions that occur in the aging processes, such as oxidation, polymerization, and aromatization. For a more accurate assessment of the classes of compounds that undergo aging reactions, fractionation techniques have been developed over the years, such as separation of asphalt into saturates, naphthenic-aromatics, resins, asphaltenes, organic sulfides, nitrogenates, and oxygenates, among others. Despite several studies on the theme of asphalt aging, it is still necessary to understand the phenomena that occur in those processes.