Structures and Wettability Alterations of a Series of Bispyridinium Dibromides Exchanged with Reduced-Charge Montmorillonites

Abstract

Capillary rise tests were performed to investigate the influences that the structure of the modifier and layer charge of clay had on wetting properties of organoclays, which were prepared by ion exchange using bispyridinium dibromides (BPs) with different spacer length and the reduced-charge montmorillonites (RCMs). Their structures were examined by Fourier transformed infrared spectroscopy (FTIR), X-ray diffraction (XRD), and nitrogen adsorption–desorption isotherms. The results indicated that BPs had been successfully intercalated into interlayers and lay in the monolayer. The d001 basal spacing of organo-RCMs increased with the spacer length of BPs increasing, whereas it decreased gradually as the layer charge of the RCMs was decreased, independent of the type of BPs. Whether the organic modification made the Brunauer–Emmett–Teller (BET) surface area increase or decrease depended upon the size of the organic cations and the layer charge of the clays. The wettability alterations of the organo-RCMs for deionized water and cyclohexane were also compared. Both the spacer length of BPs and the layer charge of RCMs had important effects on the relative wettability of organo-RCMs. The hydrophilicity of organo-RCMs was increased with the spacer length of BPs increasing, namely, in the order as follows: C2-2Py-RCMs < C6-2Py-RCMs < C10-2Py-RCMs. In addition, the hydrophobicity was increased with a decrease in the layer charge. The results of this work were supposed to provide some reference information for regulating the wettability of the organo-RCMs by simultaneously controlling the type of modifiers along with the layer charge characteristics, to provide theoretical guidance for the favorable change in reservoir wettability.