LI Shanshan1, WAN Quan2, QIN Zonghua2, FU Yuhong2,3, GU Yuantao2,3
(1.School of Chemistry and Materials Science, Guizhou Normal University, Guiyang, 550001;
2.State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081;
3.University of Chinese Academy of Sciences, Beijing 100049)
Abstract: The ubiquitous interaction between nanopores and organic materials in the earth environment is critical to many substantial scientific issues, such as adsorption and preservation of organic matter, storage and recovery of oil and gas, and geological sequestration of carbon dioxide, etc. Yet, so far it still lacks systematic investigations of the interaction between nanopores especially micropores (< 2nm) and organic materials. In this work, we synthesized Stöber silica as a mineral micropore model and investigated its thermochemical properties by using TG/DSC-FTIR after the interaction with a series of organic solvents (including ethanol, n-propyl alcohol, n-butyl alcohol, and n-heptyl alcohol). Our results indicate that ethanol and propyl alcohol can easily enter Stöber silica’s micropores (pore diameter 0.8 nm). Under the catalysis of NH3, alkoxylation takes place between alcohols and surface silanol groups in and outside of the micropores. The removal temperature of alkoxyl groups outside of the pores decreases while the exothermic effect intensifies with increasing carbon chain length of the solvent. In contrast, the removal temperature of alkoxyl groups inside the pores increases with increasing carbon chain length, while the exothermic effect declines gradually. Without NH3 catalysis, due to the weakening of the alkoxylation, free ethanol and propyl alcohol molecules could exist inside the micropores and the removal temperature of alkoxyl groups inside the pores tends to decline with increasing carbon chain length of the solvent. Stöber silica’s microporous structure directly modulates the thermolysis behavior of organic alcohols under different atmospheres, and the evolved methane, ethylene, and propionic aldehyde may provide a reference for deep thermal behavior of organic materials confined in nanoporous structure.
Key words: micropore model; Stöber silica; TG/DSC-FTIR; organic matter; interaction
EARTH AND ENVIRONMENT Vol.45, No.3, Tot No.317, 2017, Page 374
