Cellulose from oil palm empty fruit bunch fiber and its conversion to carboxymethylcellulose
Benyathip Yimlamai, Wanna Choorit, Yusuf Chisti, Poonsuk Prasertsan
Abstract
Abstract BACKGROUND Higher‐value products, such as cellulose and carboxymethylcellulose (CMC), may be produced from lignocellulosic agroindustrial residues, such as oil palm empty fruit bunch (EFB) fibers that are presently underutilized or discarded. Recovery of cellulose from EFB and its conversion of CMC are discussed as methods of creating value and reducing the environmental impact of EFB. RESULTS Cellulose was recovered from EFB fibers and converted to water soluble CMC. Cellulose isolation used a two‐step sequential treatment involving peracetic acid (PA) (50 g dry EFB L −1 PA, 35 °C, 9 h) for initial delignification, and then alkaline peroxide (AP) (50 g delignified‐EFB L −1 AP, 45 °C, 12 h). This treatment removed 91.5% of lignin in the original EFB fiber. The recovered solids, designated as cellulose‐EFB, were comprised of 83.7 ± 3.4% cellulose, 5.6 ± 0.3% hemicellulose, 1.7 ± 0.0% lignin, and 1.7 ± 0.1% ash. A two‐step process with an initial alkalization {3 g cellulose‐EFB in 99 mL solvent [10:1 by vol mixture of ethanol (95%) and 35% NaOH], 30 °C, 2 h} followed by etherification was used to convert cellulose‐EFB to CMC sodium salt. The conversion yield was 50% of the theoretical maximum. CONCLUSION The best conditions for preparing CMC from cellulose‐EFB were a 2 h treatment with 35% (wt/vol) NaOH during alkalization at 30 °C, followed by etherification at 55 °C. The CMC had a degree of substitution of 0.16 and a water solubility of 6.8 g L −1 at 30 °C. © 2021 Society of Chemical Industry