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Asphaltenes dissolution mechanism study by <i>in-situ</i> Raman characterization of a packed-bed microreactor with HZSM-5 aluminosilicates
摘要： Asphaltenes, the most aromatic component of heavy oil, are responsible for the fouling and impairment in flow lines, wellbores, and other production facilities in the petroleum industry. Aromatic solvents such as xylenes are commonly used for the asphaltenes’ cleaning process. Understanding the mechanism of asphaltenes’ dissolution in aromatic solvents is significant for the development of a remediation strategy. The reduction of a reactor’s characteristic length scale leads to the decrease in experimental period while providing high throughput information. Microfluidic systems with in-situ spectroscopy is an excellent platform for time-effective studies of the molecular behavior of asphaltenes in simulated sandstone reservoirs. Here, we injected the HZSM-5 zeolite nanoparticles (707 nm ·aggregate-1 in isopropanol solution) with varying Al2O3/SiO2 ratios (from 0 to 1/26) into the quartz porous media to represent reservoirs with different characteristic acidity. In-line UV-Vis spectroscopy enabled the direct measurement of the dissolution percentage, while in-situ Raman spectroscopy revealed where the dissolution took place within the porous media. In addition to bed occupancy, sheet sizes of asphaltenes molecules can also be determined by in-situ Raman spectroscopy. Our results show that the average sheet size of deposited asphaltenes molecules decreased from 2.97 ± 0.25 nm to 2.74 ± 0.26 nm after cleaning the porous media with xylenes. This trend is confirmed with the fluorescence emission spectra of dissolved asphaltenes molecules, where a 10-30 nm red-shift is present when referenced to asphaltenes source samples. These results provide an explanation to why the dissolution percentage of asphaltenes in aromatic solvents increases from 20.15 wt% to 51.00 wt% as the Al2O3 content increases. We can speculate that this increase in weight percentage is attributed to the differences in deposited asphaltenes molecules’ sheet size. These results reveal the importance of π-π interactions during asphaltenes dissolution process in the aromatic solvent. Our results provide the fundamental understanding of asphaltenes dissolution, which otherwise would be challenging to observe using any other analytical methods.
关键词： in situ Raman spectroscopy,Asphaltenes dissolution,Porous media
更新于2025-09-23 15:21:01
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In Situ Raman Spectroscopy on Silicon Nanowire Anodes Integrated in Lithium Ion Batteries
摘要： Rapid decay of silicon anodes during lithiation poses a significant challenge in application of silicon as an anode material in lithium ion batteries. In situ Raman spectroscopy is a powerful method to study the relationship between structural and electrochemical data during electrode cycling and to allow the observation of amorphous as well as liquid and transient species in a battery cell. Herein, we present in situ Raman spectroscopy on high capacity electrode using uncoated and carbon-coated silicon nanowires during first lithiation and delithiation cycle in an optimized lithium ion battery setup and complement the results with operando X-ray reflection diffraction measurements. During lithiation, we were able to detect a new Raman signal at 1859 cm?1 especially on uncoated silicon nanowires. The detailed in situ Raman measurement of the first lithiation/delithiation cycle allowed to differentiate between morphology changes of the electrode as well as interphase formation from electrolyte components.
关键词： silicon nanowires,lithium ion batteries,in situ Raman spectroscopy,operando XRD,solid electrolyte interphase
更新于2025-09-19 17:15:36
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In situ Raman spectroscopic evidence for oxygen reduction reaction intermediates at platinum single-crystal surfaces
摘要： Developing an understanding of structure–activity relationships and reaction mechanisms of catalytic processes is critical to the successful design of highly efficient catalysts. As a fundamental reaction in fuel cells, elucidation of the oxygen reduction reaction (ORR) mechanism at Pt(hkl) surfaces has remained a significant challenge for researchers. Here, we employ in situ electrochemical surface-enhanced Raman spectroscopy (SERS) and density functional theory (DFT) calculation techniques to examine the ORR process at Pt(hkl) surfaces. Direct spectroscopic evidence for ORR intermediates indicates that, under acidic conditions, the pathway of ORR at Pt(111) occurs through the formation of HO2*, whereas at Pt(110) and Pt(100) it occurs via the generation of OH*. However, we propose that the pathway of the ORR under alkaline conditions at Pt(hkl) surfaces mainly occurs through the formation of O2?. Notably, these results demonstrate that the SERS technique offers an effective and reliable way for real-time investigation of catalytic processes at atomically flat surfaces not normally amenable to study with Raman spectroscopy.
关键词： density functional theory,in situ Raman spectroscopy,electrochemical surface-enhanced Raman spectroscopy,oxygen reduction reaction,platinum single-crystal surfaces
更新于2025-09-10 09:29:36
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Oxidation of Epitaxial Silicene on Ag(111)
摘要： The high chemical reactivity of epitaxial silicene on Ag(111) still remains a debated subject in the literature. In particular results on the oxidation of epitaxial silicene and its related lifetime under ambient conditions are controversially discussed. Here, a detailed investigation of the oxygen exposure to epitaxial silicene layers investigated by means of X-ray photoemission and in situ Raman spectroscopy is reported. The results should clearly cease the discussion on the stability of epitaxial silicene against oxygen as it becomes completely oxidized after an exposure to only 100 L of oxygen. Such a small dose sets strict limits for ex situ studies of epitaxial silicene. Besides the formation of silicon oxide also the silver substrate surface oxidizes, suggesting that the silicene layer can hardly protect it, probably owing to the high number of domain boundaries within the silicene layer.
关键词： epitaxial silicene,2D materials,oxidation,in situ Raman spectroscopy,photoemission spectroscopy
更新于2025-09-10 09:29:36