Test Methods for Determining Asphaltene Stability in Crude Oils

The high cost of remediating asphaltene deposition in crude oil production and processing has necessitated the development of test methods for determining the stability of asphaltenes in crude oils. In the current work, the stability of asphaltenes in crude oils of varying API gravity is predicted using the Oliensis Spot Test, the Colloidal Instability Index, the Asphaltene-Resin ratio, and a solvent titration method with NIR solids detection. The test methods are described in detail and experimental data from them presented. The experimental stability data were validated via correlation with field deposition data. The effectiveness of the various tests as predictors of the stability of asphaltenes in oils is discussed. The Colloidal Instability Index and the solvent titration method were found to predict a crude oil's propensity towards asphaltene precipitation better than both the Asphaltene-Resin ratio and the Oliensis Spot Test. For oils with low asphaltene content where most stability tests fail, live oil depressurization is proposed as the test for predicting the stability of asphaltenes.     

机场沥青的技术要求与标准

机场道面和公路路面处于不同状态下工作。用于机场道面的沥青材料应是优质沥青，并且符合机场沥青的技术要求。此外，本文还对优质沥青的生产、市场等问题进行了讨论。     

季铵盐型阳离子沥青乳化剂的合成及影响因素研究

采用某酚、环氧氯丙烷、三乙胺同时加料的方法合成了季铵盐型阳离子沥青乳化剂，对合成的轧化剂轧化沥青的性能进行了测试。重点研究了溶剂、反应温度、反应时间对该合成反应的影响，并确定了最佳反应条件为甲醇和水的混合溶剂为较适宜的溶剂；最佳的反应温度为70C；反应时间4h为宜。     

Application of rheological characteristics of modified bitumen to predict the fatigue life of asphalt mixtures

Fatigue is defined as a fracture phenomenon due to a repetitive load or a variable dynamic load that occurs at a lower load than the ultimate static load. Fatigue stability of an asphalt mixture is its ability of enduring the repetitive flexural loads. In this study, the carbon nanotubes are used as the bitumen modifier in the way that the prepared samples contain 0%, 0.3%, 0.6%, 0.9%, 1.2%, and 1.5% carbon nanotubes. Then, the classic and rheological experiments are conducted on these samples. This additive improves the classical properties of bitumen (softening point, penetration degree, and so on) and also the fatigue parameter of bitumen (i.e., G*Sinδ) in comparison to the standard bitumen. Using the rheological graphs, it can be predicted that adding the carbon nanotubes to bitumen might improve the fatigue life of the asphalt mixtures. To evaluate the accuracy of this prediction, the fatigue experiment are performed on the prepared beam samples using a four-point loading in the case of constant strain (600 microstrain) with a semi-sinusoidal wave at 20°C. The end of the samples’ fatigue life is 50% reduction in their initial rigidity. It is observed that with an increase in the percentage of carbon nanotube in fatigue samples, the fatigue life of asphalt mixtures remarkably increases.     

Measurement of bitumen–tyre adhesion temperatures at realistic loading rates

A small-scale apparatus was constructed to measure the ‘adhesion temperature’, at which bitumen ‘pick-up’ onto tyre rubber (and subsequent tracking) occurs. Loading frequencies equivalent to traffic speeds of over 100 km hr^?1 and realistic tyre footprint pressures were used. The adhesion temperature increased with loading frequency, but all of the bitumens and polymer-modified bitumens studied had adhesion temperatures (i.e. the temperature at which the bitumen failed cohesively) at or below 60 °C, a temperature easily reached in the field. The results confirm the findings of an earlier slow-speed study (at 1.6 km hr^?1) and indicate that the adhesion temperature under realistic loading conditions is governed by the properties of the bitumen, i.e. the bitumen yield stress is lower than that of the adhesive bond formed as the tyre traverses the bitumen.     

Monitoring of bitumen hardening with a non-destructive ultrasonic shear wave reflection technique

The article presents a possibility of using a non-destructive ultrasonic shear wave reflection technique for monitoring hardening process of bitumen. The technique relies on the use of a new measuring instrument called USWR-4 Hardening meter, which was developed to be applicable directly in situ and has been effectively used for cement-based materials so far. It works on the principle of continuous measurement of change of a shear wave reflection coefficient. Three different types of paving grade and two polymer-modified bitumens were used. Results show that the presented ultrasound technique can effectively track a temperature-dependent hardening process of bitumen.     

Remote bitumen content estimation of Athabasca oil sand from hyperspectral infrared reflectance spectra using Gaussian singlets and derivative of Gaussian wavelets

Modeling of the total bitumen content, TBC, in Athabasca oil sands was undertaken on the basis of its hyperspectral reflectance spectra. Spectra (8 cm⁻¹ resolution) were obtained that covered both the short-wave infrared and thermal infrared (TIR: 3.00-30.00 μm). Two methods, Gaussian fitting and wavelet analyses, were investigated to identify useful bitumen features as well as the best removal of the baseline. We aim to obtain the best determination of the TBC for a suitable suite of test and validation oil sands samples. The Gaussian model relied explicitly on features at 2.282 and 2.532 μm though these were only two of 10 features simultaneously fit with a quadratic baseline to the range of 2.230-2.603 μm of the spectra. The wavelet model relied on bitumen features selected at 2.274, 2.396 and 3.725 μm that could be isolated from the baseline and noise. Both models yielded similar dispersion in their estimates of TBC (±∼1-2%) while the wavelet model proved to be more robust when applied to the validation and blind data suites. We also considered the effects of using the L2 optimization (classical least-squares) and L1 optimization (minimization of largest outlier) schemes for both models. Both schemes produced similar results for the model suite of samples for TBC but the L1 was superior when applied to the validation and blind data suites. The wavelet model using the L1 optimization appeared to be quite robust producing estimates of TBC (±∼1.0-1.7%).     

Prediction of bitumen content in oil sand based on FT-IR measurement

FT-IR spectra of bitumen are utilized to propose simple prediction method of bitumen content in oil sand. Analysis and fractionation of Athabasca oil sand were carried out by standard method. A fraction of bitumen dissolved in tetrahydrofuran (THF) was 9.1 wt% and insoluble fraction was found as concomitantly clean clay (sand). The asphaltene fraction of oil sand was 1.42 wt%, which has higher sulfur content and lower H/C molar ratio than that of maltene. The clean clay and bitumen were used to prepare clay/bitumen composites. FT-IR spectra of different clay/bitumen composite were measured and compared. From analysis of the absorbance data, the empirical equation to predict bitumen content in oil sand was acquired using linear least square fitting. Using this equation, bitumen content of Athabasca oil sand was predicted to have a value of 10.5 wt% which is similar to 9.1 wt% of bitumen content extracted by THF solvent from oil sand.     

Oxidized rapeseed oil methyl ester as a bitumen flux: Structural changes in the ester during catalytic oxidation

Structural changes occurring in the rapeseed oil methyl ester upon catalytic oxidation at 200 °C were examined. Oxidative decomposition of fatty acid chains to lower molecular weight compounds and the formation of oligomers were the major oxidation pathways at 200 °C. FT-IR and ¹H NMR examinations, as well as the fall in iodine number, revealed the disappearance of double bonds. Quantitative analysis of the rapeseed oil methyl ester and the liquid products of its oxidation showed that oxidation of fatty acid methyl esters possessing three and two double bonds was practically complete whereas for structures possessing one double bond the loss of unsaturation amounted to 25% only. The decrease in iodine number from about 110 to about 65 and the 1.5-fold increase in molecular weight of the liquid products in the course of 25-h oxidation suggest that only a part of the unsaturated bonds in the fatty acid methyl ester was engaged in the formation of liquid oligomers and volatile oxidation products. The addition of dicumyl peroxide promoted the formation of organic peroxides during the initial stage of oxidation, which resulted in a higher molecular weight of the liquid products. The volatile oxidation products were found to contain lower molecular weight aldehydes, ketones, free fatty acids and their methyl esters, alkylfurans, lactones, n- and isoalkanes. The reaction schemes for their formation were presented. The results of the study are of importance to the optimization of the conditions for oxidation of the ester in order to obtain a quality ecological bitumen flux.     

The effect of asphaltene on thermal properties of bitumen

Chemical composition and any variation of four main components of bitumen (asphaltene, saturated, naphthene aromatic and polar aromatic) have effective impact on its properties and especially, thermal properties. In other words, in order to have asphalt pavements with reasonable temperature susceptibility and thermal stability, first of all it is essential to know the effect of these components on bitumen properties. Therefore, in this research these effects were investigated and it was found that penetration index (PI) and penetration viscosity number (PVN) of bitumen were increased with increasing in asphaltene content.Thermal behavior of bitumen in an oxidizing environment was also studied using thermogravimetric analysis (TGA) technique. The results showed that increasing the asphaltene content of bitumen decreases the temperature susceptibility and improves the resistance of samples to thermal decomposition.