Characterization and Langmuir film properties of asphaltenes extracted from Arabian light crude oil

Lobato, Marcos D.; Pedrosa, José M.; Hortal, Ana R.; Martínez–Haya, Bruno; Lebrón-Aguilar, Rosa; Lago, S.

doi:10.1016/j.colsurfa.2006.12.011

Cited by 39 publications

(83 citation statements)

References 29 publications

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“…On the other hand, the deposition from the 4 mg ml −1 solution yielded an irregular film of alternating domains depleted of asphaltenes with domains of high local asphaltene density. The microscopic inspection of these films revealed that such island–like structure was associated to the ‘flocculation’ of asphaltene aggregates with sizes of several tens of microns 22…”

Section: Methodsmentioning

confidence: 99%

“…The complexity and heterogeneity of asphaltenes has become a defiant benchmark for analytical techniques. Therefore, this topic has motivated intense experimental efforts in the past years22–40 and, not surprisingly, it has also constituted a source of constructive controversy around the potentiality and limitations of the different experimental methods and the interpretation of the observations.…”

Section: Introductionmentioning

confidence: 99%

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Laser desorption/ionization determination of molecular weight distributions of polyaromatic carbonaceous compounds and their aggregates

et al. 2007

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Molecular weight distributions (MWDs) of model polyaromatic hydrocarbons (PAHs) and complex asphaltene samples have been investigated in laser desorption/ionization mass spectrometry (LDI-MS)experiments. Special efforts are devoted to the characterization of aggregation effects during the desorption process. It is found that non-covalent clusters of the PAHs and asphaltenes form readily in the desorbing plume. Aggregation is favoured in the experiments performed on dense samples at high laser energy and under continuous ion extraction conditions. In the absence of polar groups in the analyte molecules, the aggregation propensity correlates well with the size of the polycondensed system and with its degree of pericondensation, in qualitative agreement with previous theoretical predictions. For the polydispersed asphaltenes from two different crude oils, MWDs peaking at masses smaller than 500 amu with a highmass tail extending up to about 3000 amu have been observed, yielding average weights around 900 amu. Such MWDs are in good agreement with previous mass spectrometric measurement, as well as with diffusion studies in solution. In addition, stable asphaltene aggregates have been detected giving rise to two broad bands in the mass spectrum corresponding to average molecular weights of 2200-3100 amu and 15 000-19 000 amu, respectively. It is concluded that the strong aggregation propensity of asphaltenes is likely to be responsible for the apparent inconsistency between the MWD for these compounds determined by different groups in independent LDI-MS experiments. The reliability of different sample preparation procedures, including solvent-free methods, is discussed, and strategies are outlined that serve to apply the potentiality of LDI mass spectrometry to the characterization of covalent and non-covalent compounds in complex carbonaceous systems.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Laser desorption/ionization determination of molecular weight distributions of polyaromatic carbonaceous compounds and their aggregates

et al. 2007

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“…In fact, taking into account the typical densities of ¾0.4 µg cm 2 determined experimentally for asphaltene monolayers on the smooth air-water interface, 15 the samples with the lower average densities employed in this work, and, in particular, the 0.03 and 1.2 µg cm 2 cases, are expected to provide a nonhomogeneous, nanometric, incomplete coating of the irregular surface of the stainless steel sample plate. Under these conditions, it can be understood that the increase of the sample concentration results in an enhancement of the amount of material desorbed by each laser shot.…”

Section: Samples With Low and Intermediate Asphaltene Concentrationsmentioning

confidence: 98%

On the determination of molecular weight distributions of asphaltenes and their aggregates in laser desorption ionization experiments

et al. 2006

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Molecular weight distributions (MWD) of asphaltenes and their aggregates have been investigated in laser desorption ionization (LDI) mass spectrometric experiments. A systematic investigation of the dependence of the measured MWD on the asphaltene sample density and on the laser pulse energy allows the assignment of most probable molecular weights within 300-500 amu and average molecular weights of 800-1000 amu for the monomeric asphaltenes, as well as for the estimation of the contribution from asphaltene clusters in typical LDI measurements. The results serve to reconcile the existing controversy between earlier mass spectrometric characterizations of asphaltenes based on laser desorption techniques by different groups. Furthermore, the MWD measurements performed on particularly dense samples yield an additional differentiated broad band peaking around 9000-10,000 amu and extending over 20,000 amu, not observed previously in LDI experiments, thereby revealing a strong propensity of the asphaltenes to form clusters with specific aggregation numbers, which is in qualitative agreement with previous theoretical predictions and with the interpretation of measurements performed with other techniques.

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“…Many materials and biological systems in nature are mainly suspensions composed of disks, such as clay [1][2][3], asphaltenes [4,5], histone octamer disks in nucleosomes [6], and red blood cells [7]. Theoretical studies [8,9] and computer simulations [10][11][12] have confirmed that disks can undergo different liquid crystal transitions at high concentrations due to their excluded volumes.…”

Section: Introductionmentioning

confidence: 97%

“…The study of this transition can facilitate an understanding of the behavior of asphaltenes [5] to produce soft matrices of functional molecules [22], to promote the disklike mesogens to be used as templates for the preparation of mesoporous materials [23,24], * zcheng@tamu.edu and to initiate the use of nanoplatelets in semiconductors [21] and solid state photovoltaic cells [25]. In addition, a better understanding of the optical and electronic properties [26,27] of the nematic discotic phase can serve in the development of new liquid crystal display (LCD) devices [24,28,29].…”

Section: Introductionmentioning

confidence: 99%

Aspect ratio and polydispersity dependence of isotropic-nematic transition in discotic suspensions

Mejı́a

Chang

et al. 2012

Phys. Rev. E

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Characterization and Langmuir film properties of asphaltenes extracted from Arabian light crude oil

Cited by 39 publications

References 29 publications

Laser desorption/ionization determination of molecular weight distributions of polyaromatic carbonaceous compounds and their aggregates

Laser desorption/ionization determination of molecular weight distributions of polyaromatic carbonaceous compounds and their aggregates

On the determination of molecular weight distributions of asphaltenes and their aggregates in laser desorption ionization experiments

Aspect ratio and polydispersity dependence of isotropic-nematic transition in discotic suspensions

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