Asphaltenes: Aggregates in Terms of A1 and A2 or Island and Archipielago Structures.

In this work several issues related to asphaltenes and asphaltene aggregates such as isolation of real asphaltene molecules and comparison of these with average structures obtained using regular analytics laboratory techniques are presented. Several molecular organic models were used to simulate asphaltene in solution and aggregates formation in the two solvents toluene and THF employed. The results, obtained from simulation calculations using molecular dynamics were compared with experimental chromatography results obtained using the micro gel permeation chromatography (µGPC), inductively coupled plasma (ICP) mass spectra (MS) combined technique (GPC ICP MS for short). In this case reasonable hydrodynamic ratios and size distribution were obtained for asphaltenes and their corresponding subfractions A1 and subfraction A2. Comparison between experimental sample profiles, transmission of electron microscopy (TEM) data, and molecular dynamics allows for estimation of hydrodynamic ratios of around 8 nm. Highly aromatic and island type molecular model A30 and continental type molecular model A40 were employed in the molecular dynamics to built colloids. In this case open-like colloids (A40) and compact-like colloids A30 were obtained. Subjects such as trapped compounds (TC), metallic porphyrins, and colloidal dipole moments were also studied. Studies of the adsorption behavior of asphaltenes on several macroscopic and nanoscopic surfaces are presented and show the tendency of the asphaltene to adsorb in aggregate form.

Catalytic Conversion of n-C7 Asphaltenes and Resins II into Hydrogen Using CeO2-Based Nanocatalysts.

This study focuses on evaluating the volumetric hydrogen content in the gaseous mixture released from the steam catalytic gasification of n-C7 asphaltenes and resins II at low temperatures (<230 °C). For this purpose, four nanocatalysts were selected: CeO2, CeO2 functionalized with Ni-Pd, Fe-Pd, and Co-Pd. The catalytic capacity was measured by non-isothermal (from 100 to 600 °C) and isothermal (220 °C) thermogravimetric analyses. The samples show the main decomposition peak between 200 and 230 °C for bi-elemental nanocatalysts and 300 °C for the CeO2 support, leading to reductions up to 50% in comparison with the samples in the absence of nanoparticles. At 220 °C, the conversion of both fractions increases in the order CeO2 < Fe-Pd < Co-Pd < Ni-Pd. Hydrogen release was quantified for the isothermal tests. The hydrogen production agrees with each material's catalytic activity for decomposing both fractions at the evaluated conditions. CeNi1Pd1 showed the highest performance among the other three samples and led to the highest hydrogen production in the effluent gas with values of ~44 vol%. When the samples were heated at higher temperatures (i.e., 230 °C), H2 production increased up to 55 vol% during catalyzed n-C7 asphaltene and resin conversion, indicating an increase of up to 70% in comparison with the non-catalyzed systems at the same temperature conditions.