Transformation of CO2 to Carbon Nanotubes by Catalytic Chemical Vapor Deposition using a Metal-Supported Hierarchical Zeolite Template.

The conversion of CO2 into valuable substances is a topic of great interest in current research. Carbon nanotubes (CNT) have emerged as highly promising materials for CO2 conversion. In this study, we successfully developed a catalyst by loading active transition metals (Fe or Ni) onto hierarchical zeolite for CNT synthesis. Our catalyst demonstrated excellent performance under synthetic conditions. The most favorable CNT was obtained using the 25 wt.% FeHieFAU catalyst, which exhibited a diameter size of 23.1 nm, a CNT yield of 15.4 %, and an ID /IG ratio of 0.56, indicating high quality. Additionally, we investigated the beneficial effects of the synthesized CNT by testing their current response. Notably, the current response of the synthesized CNT surpassed that of commercial CNT when using a 0.5 M H2 SO4 supporting electrolyte and cyclic voltammetry (V vs. Ag/AgCl). These findings highlight the significant contributions of the small diameter and superior quality of our synthesized pure CNT, which offer potential improvements in current response compared to commercial CNT. This research opens new avenues for utilizing CNT in CO2 conversion and electrochemical applications.

Characterization of fractionated asphaltenes by UV-vis and NMR self-diffusion spectroscopy.

Asphaltenes have been fractionated by liquid/liquid extraction, yielding four subfractions. The characteristics of fractionated asphaltenes were studied with respect to solubility, aromaticity, heteroatom content, and diffusion behavior. It was observed that asphaltenes from the four subfractions showed variations in their tendency to flocculate and also distinct differences in aromaticity. Furthermore, NMR self-diffusion studies showed that the average diffusion coefficients varied for asphaltenes from the different subfractions. The results suggest a variation in average size and stability between asphaltenes, depending on what subfraction they belong to. The subfraction that consisted of asphaltenes with the largest average size and the highest aromaticity was also found to contain the asphaltenes that had the strongest tendency to flocculate.