Mechanism of Interaction between Surfactants and Surface Functional Groups of Jincheng Coal by XPS Analysis

摘要

Coalbed methane (CBM) is a kind of clean energy and CBM is adsorbed in coal seam. The surfactants arewidely used in CBM drilling and completion. The intensive research on the utilization of surfactants-basedproduct in coal technology is in progress in many laboratories. Jincheng coal has been modified by treating withseveral kinds of surfactants such as anionic surfactant sodium dodecylbenzene sulfonate (SDBS), cationicsurfactant cetyl trimethyl ammonium bromide(CTAB), non-ionic surfactant polyoxyethylenenonylphenylether(TX-10), and amphoteric surfactant Cocoamidopropyl Betaine (CAB). The impact of surfactant adsorptionon Jincheng coal has been investigated. Jincheng coal was crushed into a fine powder and immersed in differentsurfactant solution of certain concentration for 48h, respectively, then were filtered and dried in vacuum beforeanalyzed. The chemical compositions of the samples were monitored by X-ray photoelectron spectroscopy (XPS)after treated by different surfactants. C1s XPS spectra can be decomposed into four components correspondingto carbon atoms in different oxygen-containing functional groups, non-oxygenated C-C, carbon in C-O, carbonylcarbon C=O and carboxyl carbon O=C-O (COOH). The results show that the main form of carbon-functionalgroups is C-C on the coal surface. The C1s XPS spectra of the surfactant-treated (SDBS, CTAB and TX-10) coalshows the same functionalities but with less content of C-C and higher oxygenated carbons. The phenomenonindicates that surfactant-treated coal has much more oxygen containing functional groups. While the sampletreated by CAB has a similar C-C content compared with raw coal, and the O1s XPS spectra analysis is basicallyidentical with that of C1s XPS spectra. The results can be useful in studying other surfactant adsorption coalsystems.