Study On Stability Behaviors And Mechanism Of Asphaltene Stabilizer To Asphaltenes

Six asphaltene stabilizers with different molecular structures,4-dodecylbenzenesulfonic acid(4-ADBS),4-dodecylbenzene aniline(4-DA),4-dodecylbenzenesulfonic acid(4-DDP),2-dodecylbenzenesulfonic acid(2-ADBS),polyisobutylene succinimide benzenesulfonic acid(APS2),polyisobutylene succinimide sulfonic acid(APS3)were selected,according to the properties and structural characteristics of the stabilizers,such as acidity and alkalinity,relative positions of polar and non-polar groups,etc.,asphaltene in oil sand asphalt from Canada was used as a raw material to study the effects of structure characteristics and contents of the asphaltene stabilizers on the stability of asphaltene by ultraviolet-visible spectroscopy,X-ray photoelectron spectroscopy(XPS),infrared spectroscopy,viscosity determination,dynamic light scattering(DLS),X-ray diffraction(XRD),etc.The mechanism that the stabilizers stabilize asphaltene was deduced from macro and micro properties.The molecular structure of asphaltene in the oil sand asphalt was studied by infrared spectroscopy,XPS,nuclear magnetic resonance,elemental analysis,etc.;an average molecular structure model was created;and the polar groups in asphaltene molecules were determined,to lay a theoretical foundation for further analysis of the interaction between stabilizers and asphaltene.The stabilization effect of stabilizer on asphaltene in toluene-n-heptane solution was studied by ultraviolet-visible spectroscopy.The results show that the stabilization effect on asphaltene can be improved by increasing the concentration of stabilizer.When the concentration of stabilizer reaches a certain level,the asphaltene stabilization efficiency reaches maximum value and no longer changes with the concentration of asphaltene.The stabilizers have the asphaltene stability in toluene-n-heptane solution in the following descending sequence: APS2>APS3>4-ADBS>2-ADBS>4-DDP>4-DA,showing that the sulfonic group as a polar group in the stabilizer interacts with asphaltene more strongly than boric acid group;the results that 2-ADBS and 4-ADBS stabilize asphaltene show that the stabilizer with polar group and non-polar group at the positons para to benzene ring has the molecular steric structure more conducive to dense alignment of stabilizer molecules on asphaltene surface and therefore protect asphaltene more strongly than the stabilizer with polar group and non-polar group at the positons ortho benzene ring.4-DA,4-DDP and 4-ADBS have different stabilization effects on asphaltene,reflecting that the effect of their acidity and alkalinity on the asphaltene stability in the following descending sequence: acid group > neutral group(hydroxyl)> alkaline group(amine group).The effect of the stabilizers on asphaltene association number in asphaltene-toluene-nheptane solution was obtained by processing the viscosimetry and dynamic light scattering results.The results show that the stabilizer adsorbed on asphaltene surface inhibits the aggregation of asphaltene molecules and reduces the association number of asphaltene molecules in the presence of stabilizer,which further reflects the stabilization effect of stabilizer on asphaltene,in agreement with the conclusion obtained by ultraviolet radiation.The number of layers or the aggregation number of asphaltene solids was determined by XRD.All the aggregation numbers of asphaltene after adsorbed stabilizers are less than 6,the aggregation number of pure asphaltene solids.Therefore,it can be roughly considered that the asphaltene in the solution is unstable when the aggregation number of asphaltene in the solution is equal to or greater than 6,and stable when the aggregation number is less than 6.The adsorption effects of asphaltene on the stabilizers were analyzed by infrared spectroscopy and XPS.The infrared spectroscopy results show that stabilizer molecules adsorbed on the surface of asphaltene is the basic reason why the stabilizers reduce the aggregation number of asphaltene and improve the stability of asphaltene in toluene-n-heptane solution.In addition,the change of O-H peak in infrared spectra and the change of N,O and S groups in XPS indicate that hydrogen bonding occurs between stabilizer molecules and asphaltene molecules.Based on the above analysis,it is preliminarily inferred that the mechanism that the stabilizers stabilize asphaltene is that strong polar groups,such as sulfonate,imino,hydroxyl,amino,etc.,in the stabilizers,readily make the relevant polar groups in the asphaltene molecules provide strong hydrogen bonding effects,etc.,while the long chain structure of the stabilizers spatially protects asphaltene,inhibits the association of asphaltene molecules,reduces the association number.Thus,the stabilizers stabilize the asphaltene molecules.