Aggregates Structure Analysis of Petroleum Asphaltenes with Small-Angle Neutron Scattering

Abstract

The objective of this study is to examine changes in the structures of petroleum asphaltene aggregates in situ with small-angle neutron scattering (SANS). Asphaltenes were isolated from three different crude oils: Maya, Khafji, and Iranian Light. An aliquot of the 5 wt % asphaltene solution in deuterated Decalin, 1-methylnaphthalene, or quinoline was loaded in a special stainless steel cell for SANS measurements. SANS data measured at various temperatures from 25 to 350 °C showed various topological features different with asphaltene or solvent species. A fractal network was formed only with asphaltene of Maya in Decalin, and it remained even at 350 °C. In all of the solvents, asphaltenes aggregate in the form of a prolate ellipsoid with a high aspect ratio at 25 °C and got smaller with increasing temperature. That became a compact sphere with the size of around 25 Å in radius at 350 °C.

Composition and Heavy Oil Rheology

“…I5 and I9 have probably close sizes at high temperature. We can also assume like [27] that Figure 16 Huggins coefficient in xylene. asphaltenes are more numerous and so more closer.…”

Asphaltenic aggregates are polydisperse oblate cylinders

“…Various experimental techniques have previously been applied to study the aggregation behavior of asphaltenes in solution including: near-infrared spectroscopy [10,11], pulsed-field gradient spin echo nuclear magnetic resonance [12,13], vapor pressure osmometry [8,14,15], viscosity measurements [16][17][18][19], small-angle X-ray scattering (SAXS) [14,17,[20][21][22][23][24][25], and small-angle neutron scattering (SANS) [8,14,16,[21][22][23][26][27][28][29][30][31][32][33][34][35][36][37][38][39]. Small-angle scattering methods, such as SAXS and SANS, have been useful for deducing the sizes of asphaltenic aggregates in solution based on assumed particle morphologies.…”

Characterization of asphaltenic material obtained by treating of vacuum residue with different reactive molecules

“…Our XRD, SEM and TGA results and physical properties suggest that the improvement of the hardness properties of a bitumen is mainly due to (i) increase in asphaltene content, (ii) compactness of asphaltene and (iii) the degree of polymerization. Increase in number of graphene layers into the treated bitumen suggests that the reactive molecules help to form a three dimensional networking by linking one asphaltene structure to another may be pi-bonding [5]. This type of networking structure is more when the reactive molecule bigger is in size like C18-acrylate.…”

“…The aggregation of asphaltenes has been studied by in situ with small angle neutron scattering [5]. Maya, Khafji and Iranian light were used for the different sources of the asphaltene.…”