基础油在热处理、超声和磁场作用下的太赫兹频段分子动力学

Molecular Dynamics of Lube Base Oil Subjected to Annealing,Ultrasonic and Magnetic Treatments in Terahertz Band

利用太赫兹时域光谱技术研究了基础油在热处理、超声和磁场作用下的动力学过程及相互作用机制。由于超声处理过程中声空化作用引起高温高压,而样品在热处理中的作用能量较低,基础油在超声处理后的折射率变化大于其在热处理和磁场作用下的变化。样品在1.7 THz和2.3 THz处有较明显的吸收峰,该吸收来源为分子间的相互作用,以这两处的吸收峰为研究对象,利用分子间相互作用的强弱变化分析了基础油与磁场的相互作用机制。研究结果表明太赫兹时域光谱技术能够实现有机化学物质在物理场作用下的降解机制研究,易操作,数据处理简单,重复性好。

The related petroleum products need to be upgraded using various microbial degradation,thermal and chemical methods to avoid potential hydrocarbon contamination. Although these techniques are commonly used, they have several limitations, such as high energy consumption, high cost, poor efficiency,and environmental pollution. To date,considerable attention has been paid to the degradation of related petroleum products by ultrasonic and magnetic methods. Ultrasound methods have the advantages of easy operation, mild conditions, high efficiency, low cost, and environmental friendliness.Comparatively,some authors have shown that magnetic and electric methods may improve the rheological properties of crude oil. Apart from this study,to our knowledge,no work studying the effects of the ultrasonic or magnetic treatment of Lube Base Oil(LBO)has been performed to date,and the interaction between the ultrasonic/magnetic fields and organic compounds needs further study. The use of these physical fields to treat and degrade petroleum products has sparked considerable controversy. Terahertz Time-Domain Spectroscopy(THz-TDS)has recently received considerable attention with the expectation that it will provide new insights into complex petroleum systems, such as optical property and spectroscopic studies of the selected lubricating oil and probes of the disaggregation of crude oil. In this paper,the degradation mechanism and molecular dynamics of LBO subjected to annealing,ultrasonic and magnetic treatments were compared and investigated using THz-TDS. The thermal degradation of the Korea105 was assessed by means of an annealing treatment at 110 ° C. The ultrasonication times for the samples were 4(us4h),6(us6h),and 12 hours(us12h). The magnetic treatment times were controlled at4(mag4h),6(mag6h),and 12 hours(mag12h). By comparison with reference and sample pulse,and use of a numerical fast Fourier transform,the refractive index n(ω)and the absorption coefficient α(ω)of the samples were calculated. The change of refractive index of LBO under ultrasonic field is higher than that under annealing and magnetic treatment, owing to the high temperature and pressure rise due to ultrasound,whereas heat interacts on longer timescales at lower energies. Moreover,the absorption peaks of the original Korea105 at 1.7 THz and 2.3 THz corresponding to intermolecular interactions were selected as marker bands to illustrate the interaction mechanism. The absorption peaks of samples varied significantly after annealing,ultrasonic and magnetic treatments. The sonication of Korea105 proceeds by three categories of reactions,i. e.,free-radical generation,propagation,and termination. The principle sonochemical process in LBO appears to be C-C bond cleavage and the recombination of alkanes and aromatics,according to the disappearance of or significant shift in the absorption peaks at the two positions corresponding to the intermolecular and parallel alkane interaction forces for all the LBOs after ultrasonic treatment. The effect of a magnetic field on the viscosity of related petroleum oil is very controversial and the controversy was simplified to two aspects. Several researchers have determined that the viscosity of paraffin-based crude oil increases after exposure to a strong magnetic field at 1.5 T for an extended time. In contrast,other studies have found that the magnetic field reduced the viscosity. Our experiments regarding the increasing viscosity of Korea105 verified the first aspect. The increase in the viscosity of Korea105suggests that the strong magnetic field and long interaction time induced the aggregation and orientation of the organic molecules. The results obtained in this work demonstrate that THz-TDS is a powerful tool that can provide evidence for the degradation mechanism of organic molecules subjected to different physical treatment methods.