Cellulose nanocrystals (CNCs) with different degrees of amination to enhance tolerance to Fe (III) and enhance oil displacement performance

Cellulose nanocrystals (CNCs) have been widely concerned in enhanced oil recovery (EOR) due to their abundant resources, small size and easy modification. In crude oil extraction, Fe (III) is increasingly produced. However, CNCs are very sensitive to Fe (III) and easy to aggregate, which brings obstacles to the application of CNCs. In order to improve the tolerance of CNCs to Fe (III), the surface of CNCs was modified with Aminopropyltrimethoxysilane (APTMS), N-[3-Trimethoxysilyl)propyl]ethylenediamine (TMPED) and N-[3-(trimeth-oxysilyl)propyl]diethylenetriamine (TMPDET), respectively. The products were named CNC-APTMS, CNC-TMPED and CNC-TMPDET. The N content in CNC-APTMS, CNC-TMPED and CNC-TMPDET are 1.36 wt%, 2.03 wt% and 2.17 wt%, respectively. The adsorption amount of Fe (III) by CNCs, CNC-APTMS, CNC-TMPED and CNC-TMPDETDT are ~155 mg/g, ~ 13 mg/g, ~ 29 mg/g and ~ 18 mg/g, respectively. This indicates that compared to CNCs, the modified CNCs improve significantly the tolerance to Fe (III). Moreover, compared to CNCs, in the presence of Fe (III), there is less remaining oil in the glass model after modified CNCs dispersion flooding. The improvement of tolerance to Fe (III) and the excellent oil displacement performance of the modified CNCs in the presence of Fe (III) make them the potential green oil displacement agents.