Morphology and Size Distribution Characterization of Precipitated Asphaltene from Live Oil During Pressure Depletion

The size and morphology of asphaltene aggregates, precipitated from live oil by pressure depletion at the reservoir temperature was studied using scanning electron microscopy and atomic force microscopy. The experimental studies showed that the mean size of aggregates increased when pressure decreased. The results indicate that the morphology of aggregates was changed from amorphous spherical and elliptical shapes to irregular. A bimodal distribution function was able to describe the size distribution in pressure range of 500 to 3500 psi. At higher pressure, the unimodel was able to represent the size distribution. The results showed reduction in live oil stability and asphaltene aggregation with pressure drop.     

Equivalence classes of matrices inGL 2 (Q) andSL 2 (Q)

LetG denote either of the groupsGL ₂ (q) orSL ₂ (q). The mapping θ sending a matrix to its transpose-inverse is an automophism ofG and therefore we can form the groupG ⁺ =G. <θ>. In this paper conjugacy classes of elements inG ⁺ -G are found. These classes are closely related to the congruence classes of invertible matrices inG.     

Quantum chemical study of the nature of interactions between the boraphosphinine and alumaphosphinine with some of the mono- and divalent cations: cation–π or cation–lone pair?

Structural Chemistry - Quantum chemical study of the nature of interactions between the boraphosphinine (BP) and alumaphosphinine (AlP) with some of the alkali metal cations (Li+, Na+, K+) and...     

Ab initio study of aerogen-bonds between some heterocyclic compounds of benzene with the noble gas elements (Ne,Ar, and Kr)

Structural Chemistry - Ab initio calculations have been performed to study the complexes between the noble gas elements (Ae = Ne, Ar, Kr) with a series of benzene isoelectronic heterocyclic...     

Synthesis and Characterization of H3PW12O40 and H3PMo12O40 Nanoparticles by a Simple Method

In this study H₃PW₁₂O₄₀·9H₂O and H₃PMo₁₂O₄₀·6H₂O (HPA) particles were changed into nano forms by heat-treatment in an autoclave as a simple, repaid, inexpensive and one step method. The particle size of these nanoparticles was around 25 nm. The as-synthesized nanostructures were characterized by dynamic light scattering, X-ray powder diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy and inductively coupled plasma analyzer. Thermal stability of nanoparticles was surveyed by thermal gravimeter analyse. Acidity of prepared nanoparticles was investigated by pyridine adsorption method. Results showed rising acidity by declining particle size of HPA.     

N?H···S and S?H···N intramolecular hydrogen bond in β‐thioaminoacrolein: A quantum chemical study

The conformational study of β‐thioaminoacrolein was performed at various theoretical levels, HF, B3LYP, and MP2 with 6‐311++G(d,p) basis set, and the equilibrium conformations were determined. To have more reliable energies, the total energies of all conformers were recomputed at high‐level ab initio methods, G2MP2, G3, and CBS‐QB3. According to these calculations, the intramolecular hydrogen bond is accepted as the origin of conformational preference in thialamine (TAA) and thiolimine groups. The hydrogen bond strength in various resonance‐assisted hydrogen bond systems was evaluated by HB energy, geometrical parameters, topological parameters, and charge transfers corresponding to orbital interactions. Furthermore, our results reveal that the TAA tautomer has extra stability with respect to the other tautomers. The population analyses of the possible conformations by NBO predict that the origin of this preference is mainly due to the π‐electron delocalization in framework of TAA forms, especially usual π_C?C → π*_C?S and Lp (N) → π*_C?C charge transfers. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Reinvestigation of intramolecular hydrogen bond in malonaldehyde derivatives: An ab initio,AIM and NBO study

The RAHB systems in malonaldehyde and its derivatives at MP2/ 6‐311++G(d,p) level of theory were studied and their intramolecular hydrogen bond energies by using the related rotamers method was obtained. The topological properties of electron density distribution in O? H···O intramolecular hydrogen bond have been analyzed in term of quantum theory of atoms in molecules (QTAIM). Correlations between the H‐bond strength and topological parameters are probed. The results of QTAIM clearly showed that the linear correlation between the electron density distribution at HB critical point and RAHB ring critical point with the corresponding hydrogen bond energies was obtained. Moreover, it was found a linear correlation between the electronic potential energy density, V(r_cp), and hydrogen bond energy which can be used as a simple equation for evaluation of HB energy in complex RAHB systems. Finally, the similar linear treatment between the geometrical parameters, such as O···O or O? H distance, and Lp(O)→σ*_OH charge transfer energy with the intramolecular hydrogen bond energy is observed. © 2010 Wiley Periodicals, Inc., Int J Quantum Chem, 2011     

Vibrational assignment, structure and intramolecular hydrogen bond study of 3-amino-1-phenyl-2-buten-1-one

Fourier transform infrared and Fourier transform Raman spectra of 3-amino-1-phenyl-2-buten-1-one and its deuterated analogue were recorded in the regions 400-4,000 and 150-4,000 cm(-1), respectively. Furthermore, the molecular structure and vibrational frequencies of title compound were investigated by a series of density functional theoretical, DFT, and ab initio calculations at the post-Hartree-Fock (MP2) level. Although, the calculated frequencies are generally in agreement with the observed spectra but the DFT results are in much better quantitative agreement with the observed spectra than the MP2 results. The observed wavenumbers were analyzed and assigned to different normal modes of vibration of the molecule. The calculated geometrical parameters show a strong intramolecular hydrogen bond with a N...O distance of 2.621-2.668 A. This bond length is shorter than that of its parent, 4-amino-3-penten-2-one (with two methyl groups in the beta-position), which is in agreement with spectroscopic results. The topological properties of the electron density contributions for intramolecular hydrogen bond in 3-amino-1-phenyl-2-buten-1-one and 4-amino-3-penten-2-one have been analyzed in term of the Bader theory of atoms in molecules (AIM). These results also support the stronger hydrogen bond in the title compound with respect to the parent molecule.