Thermoporosimetry of n-alkanes for characterization of mesoporous SBA-15 silicas – Towards deeper understanding the effect of the probe liquid nature

• The origin of the complex shape of PSD pro files derived from alkanes thermoporosimetry (TPM) experiments was explained.
• The influence of solid to liquid mass ratio and the degree of pore cover on the TPM results was studied and evaluated.
• Even-odd effect was observed: two kinds of solid phase was demonstrate by even-alkanes TPM, one phase in case of nC7-TPM.
• h-heptane was found to be the most advisable for n-alkane thermoporosimetry.
• The interaction of the alkane molecules with the pore walls was found to have a negligible impact on TPM results.

Thermoporosimetry (TPM), based on DSC measure melting point depression of n-alkane confined in mesopores, can provide very useful information about the porous properties of studied material as long as the obtained results are well understand and described. In this paper we reported original and detailed results concerning the nature of the alkanes confined inside the channels of a series of mesoporous SBA-15 silicas, differing by size of the unit cell. The complex character of pore size distribution profiles, known from our earlier works, was investigated and finally evaluated. For the first time the impact of such factors as solid to liquid mass ratio, the degree of pore cover and freezing time on the n-alkane TPM results was explained. Additionally, the even-odd effect on alkane TPM was evaluated. Based on FT-IR investigations the interactions between the probe molecules and the pore walls were found to be negligible.

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