Surfactants and nanoparticles play crucial roles in controlling the oil-water interfacial phenomenon. The natural oil-wet mineral nanoparticles that exist in crude oil could remarkably affect water-oil interfacial characteristics. Most of recent studies focus on the effect of hydrophilic nanoparticles dispersed in water on the oil-water interfacial phenomenon for the nanoparticle enhanced oil recovery. However, studies of the impact of the oil-wet nanoparticles existed in crude oil on interfacial behaviour are rare. In this study, the impacts of Span 80 surfactant and hydrophobic SiO2 nanoparticles on the crude oil-water interfacial characteristics were studied by measuring the dynamic and equilibrium crude oil-water interfacial tensions. The results show the existence of nanoparticles leading to higher crude oil-water interfacial tensions than those without nanoparticles at low surfactant concentrations below 2000 ppm. At a Span 80 surfactant concentration of 1000 ppm, the increase of interfacial tension caused by nanoparticles is largest, which is around 8.6 mN/m. For high Span 80 surfactant concentrations, the less significant impact of nanoparticles on the crude oil-water interfacial tension is obtained. The effect of nanoparticle concentration on the crude oil-water interfacial tension was also investigated in the existence of surfactant. The data indicates the less significant influence of nanoparticles on the crude oil-water interfacial tension at high nanoparticle concentration in the presence of Span 80 surfactant. This study confirms the influences of nanoparticle-surfactant interaction and competitive surfactant molecule adsorption on the nanoparticles surfaces and the crude oil-water interface.

Goethite (α-FeOOH) nanorods could be prepared by a surfactant directed approach in aqueous solution at ambient conditions. In this approach, it is observed that the surfactants (e.g, cetyltrimethylammonium bromide (CTAB) and tetraethylamine chloride (TEAC)) play a key role in the growth of goethite nanorods under the reported conditions. The molecular dynamics (MD) method is used to understand the underlying principle governing particle formation and growth through the analysis of the interaction energies between the crystal surfaces and the surfactant molecules. The findings will be useful for understanding the growth mechanism of anisotropic particles and their surface coatings with heterogeneous materials for desired functional properties.

In thermal cracking and collision-induced dissociation (CID) processes, molecules/ions mainly undergo cleavage reactions. In theory, the cleavage reaction is preferred for weak bonds in both processes. The present study investigates the thermal cracking and CID behavior of polar compounds in vacuum residue. By controlling the thermal reaction temperature and collision energy, different degrees of fragmentation were achieved. The molecular composition before and after the cracking process was analyzed through electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS). There was a correlation between the reaction temperature and the collision energy for the average carbon number value. Both desulfurization and decarboxylation were also observed in two processes due to the low C-S bond energy and poor stability of carboxylic acid groups. Nevertheless, the two processes still had some differences in reaction selectivity. Polar species tended to be directly dealkylated down to the C1–C5 substituted aromatic core in the CID process, showing a discontinuity in the carbon number vs. double bond equivalence (DBE) distribution for the CID product. On the contrary, the carbon number distribution in the thermal reaction showed a continuously reduced trend. In summary, the CID process can qualitatively reflect the cracking behavior. However, the product structural distribution of the thermal cracking product cannot be fully predicted, especially for sidechain cracking reactions. In addition, the research results can provide a new method to realize the simulation of the thermal cracking without energy and time consumption, so as to guide the selection of the feedstock and optimization of the reaction condition.

No abstract