Application Research of n-Heptadecane

Introduction

N-Heptadecane (Figure 1), a congener of n-alkanes, was proved as the molecular marker of algae by the analysis of paleoenvironmental sediment records of hydrocarbons and extracts of algae cells. It was synthesized from stearic acid of lipids through decarboxylation pathway. Sedimentary study showed that n-heptadecane posed a distinct peak in eutrophic lake. Therefore, n-heptadecane has been successfully utilized to reflect algae biomass and distinguish the dominating sources of the sedimentary organic matter in eutrophication-related studies, eventhough some species could not be detected via n-heptadecane. n-Heptadecane has the melting point of 22℃, freezes in winter, and is difficult to treat compared to n-hexadecane. The following text lists the research on the application of n-heptadecane in different fields.

1. Production of Sustainable Aviation Fuel by Hydrocracking of n-Heptadecane Using Pt-Supported Y-Zeolite-Al₂O₃ Composite Catalysts

Hydrocracking of fat or Fischer-Tropsch (FT) wax from biomass to produce the jet fuel of sustainable aviation fuel has been one of the key reactions. n-Heptadecane, which is one of the model diesel fractions produced from fat or FT wax, has hardly been used for hydrocracking of hydrocarbon for jet fuel production,while n-hexadecane has often been used as one of the model compounds for this reaction. The purpose of this study is to selectively obtain sustainable aviation fuel (SAF), the intermediate fraction with the highest economic value, through the hydrocracking of n-heptadecane(C17) as a model raw liquid from hydrotreatment of a fat or cracking of FT wax. Al₂O₃ with mesopores as a matrix component, HY-zeolite, and binder (alumina-sol) were kneaded to prepare a HY-zeolite-Al₂O₃ composite support. It was found for the first time that hydrocracking of n-heptadecane by the 0.5 wt % Pt/50 wt % HY-zeolite (SiO₂/Al₂O₃ = 100)-50 wt % Al₂O₃ composite catalyst gave the C8−C15 fraction with a selectivity of 74% and a conversion of 99% at 295℃ and 0.5MPa.

2. n-Heptadecane can be utilized to represent algae cell density dynamics in water environment

The monitoring and prediction of algae cell density are the fundamental supports for eutrophication management. As the molecular marker of algae, n-heptadecane has been successfully utilized to reflect algae biomass in sedimentary studies. However, whether biogenic n-heptadecane (bio C17) can be utilized to represent algae cell density dynamics in water environment still remains an issue. Current study aims to provide novel evidences from both field investigation and laboratory validation for it. Firstly, He et al. found a strinkingly positive correlation between algae cell density dynamics and n-heptadecane variations (p = 4.34 × 10–10) via meta-analysis using field dataset in Lake Chaohu. Then, they selected Microcystis aeruginosa, Chlorella vulgaris and Melosira sp. as model species of cyanobacteria, green algae and diatom, respectively, for laboratory validation. Our results illustrated that n-heptadecane was synchronized with the growth for cyanobacteria and green algae but not for diatom. The association between n-heptadecane and algae cell density was species-dependent, and the relationship between n-heptadecane and cell density was linear within 107 cells∙mL–1 . Therefore, we established and optimized a generalized additive model to fit observed algae cell density in Lake Chaohu. In the optimal model, n-heptadecane, Pielou evenness index J and Shannon-Wiener index H’ were included, totally explaining 66% of the variance of algae cell density. Model comparisons revealed that considering algae community could indeed improve the interpretation of algae cell density in natural environment. In conclusion, our study provided novel evidences that n-heptadecane can be utilized to represent the cell density dynamics of cyanobacteria and green algae in the environment.

3. Evaluation of n-heptadecane for thermal regulation enhancement in buildings

The growth of high-efficiency phase change material (PCM) nanocomposites with good heat conduction and substantial thermal capacity was of vital significance for practical matters in the sustainable utilization of energy. A novel leakage-proof n-heptadecane-graphene nanocomposite was prepared by a direct impregnation procedure from n-heptadacne as a PCM and nanographene as a skeleton. The creation of shape-stabilized nanocomposite was checked with X-ray diffraction (XRD), Raman, and Fourier transform infrared (FTIR) spectroscopy. The scanning electron microscopy (SEM) analysis illustrated that the n-heptadecane and graphene had favourable compatibility and there was no phase separation and graphene accumulation. Thermal analysis showed that the shape-stabilized nanocomposite not only had a good phase transition enthalpy (101.7 J/g) and n-heptadecane content (45.6 %) but also possessed appropriate thermal stability. The heat conduction of the obtained mesoporous nanocomposite was up to 1.527 W/mK, with a growth of 808 % compared to pure n-heptadecane. Furthermore, the optimized nanocomposite held auspicious thermal reliability, being exposed to 400 thermal cycles. Moreover, the thermoregulation tests demonstrated that the gypsum boards containing optimized nanocomposite showed a slow heat release rate and improved the building temperature profile over only the gypsum board. By virtue of the combination of n-heptadecane and thermal conductive nanographene, the obtained engineered nanocomposite might be regarded as a smart material for energy-conserving and temperature regulation in buildings.[3]

References

[1] Mitsuoka S, Murata K, Hashimoto T, et al. Production of Sustainable Aviation Fuel by Hydrocracking of n-Heptadecane Using Pt-Supported Y-Zeolite-Al2O3 Composite Catalysts. ACS Omega. 2024;9(3):3669-3674. Published 2024 Jan 8. doi:10.1021/acsomega.3c07678

[2] He Y, Wang T, Xu F. Can biogenic n-heptadecane be utilized to represent algae cell density dynamics in water environment? Evidences from field investigation and laboratory validation. Water Res. 2022;214:118219. doi:10.1016/j.watres.2022.118219

[3] Amirkhani Khabisi M, Roudini G, Barahuie F, Sheybani H, Ibrar M. Evaluation of phase change material-graphene nanocomposite for thermal regulation enhancement in buildings. Heliyon. 2023;9(11):e21699. Published 2023 Oct 29. doi:10.1016/j.heliyon.2023.e21699

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