Fourier transform infrared spectroscopy analysis for hydrothermal transformation of microcrystalline cellulose on montmorillonite

• Hydrothermal treatment of cellulose with montmorillonite (Mt) at 200 °C for 16 h
• Using IR spectra and derivatives to probe interactions between Mt and cellulose
• To detect and discuss the formation of aliphatic CHx and aromatic groups
• ‘A Factor’ and CH3/CH2 ratio correlated with the amount of montmorillonite used.
• Montmorillonite-assisted hydrothermal treatment of cellulose yielded kerogen analogs.

Specifying the interactions between montmorillonite and cellulose is helpful for understanding the evolution of biomass in soil and the geological formation of fossil fuels in nature. In this work, Fourier transform infrared spectroscopy was used to investigate the hydrothermal transformation of microcrystalline cellulose on montmorillonite. A series of samples were obtained from hydrothermal treatments of microcrystalline cellulose with montmorillonite in various ratios at 200 °C for 16 h. The resulting solid samples were analyzed by using Fourier transform infrared (FTIR) spectroscopy. The subtle changes before and after hydrothermal treatments were particularly studied by using mathematical methods to generate second derivatives of absorbance spectra. It was found that there were interactions between montmorillonite and microcrystalline cellulose during the hydrothermal process. In the presence of montmorillonite, the cellulose was transformed to yield a product with aliphatic CHx and aromatic groups. These were further confirmed by the FTIR spectra of the samples which were further treated by using an HCl/HF acid solution to remove the montmorillonite in them (demineralization). The structural parameters (‘A Factor’, ‘C Factor’ and CH3/CH2 ratio) were calculated. The values of the ‘A Factor’ and CH3/CH2 ratio of the resulting solid samples increased with the increase of montmorillonite. The values of ‘C Factor’ were little affected by the montmorillonite minerals. The findings suggested that montmorillonite-assisted hydrothermal treatment of cellulose was able to produce kerogen analogs.

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