Preparation of Cellulose Nanofibrils with the Pretreatments using Inexpensive Protic Ionic Liquids based on Dimeric Oxalic Acid Anions

Graphical Preparation of CNFs with pretreatments of inexpensive alkanolamine-based PILs with dimeric oxalic acid anions was investigated. Cation type and PIL content influenced the yields and physicochemical properties of prepared CNFs. The cations and anions in PILs cooperatively enhanced CNFs production. CNF yield of 85.0 % was obtained with [MEA][(HOA)(H 2 OA)] 30% . Preparation of cellulose nanofibrils (CNFs) with the pretreatments using alkanolamine-based protic ionic liquids (PILs) with dimeric oxalic acid anions ([(HOA)(H 2 OA)] − ) was fully investigated. The cation type [ethanolamine ([MEA] + ), diethanolamine ([DEA] + ), triethanolamine ([TEA] + )], and water addition greatly influenced the CNF yields. Under the pretreatment conditions of 110 °C and 3 h, the CNF yields with different PIL-based systems followed the order: [MEA][(HOA)(H 2 OA)]>[DEA][(HOA)(H 2 OA)]>[TEA][(HOA)(H 2 OA)], similar to their swelling capacities. The highest CNF yield of 85.0 % was obtained after the pretreatment with [MEA][(HOA)(H 2 OA)]-water containing 30 wt % PILs. The optimal pH range of PILs-water was 1.10–1.15. The good recyclability indicated that these inexpensive PILs can be employed as a simple and efficient pretreatment system for preparing CNFs. The physicochemical properties of the prepared CNFs were greatly changed by varying the PILs’ pretreatment systems. The thermal stability of CNFs was intimately connected with the crystalline structures and hydrogen bonding modes.