Mixed fatty acid cellulose esters from diosmectite oxalate-assisted surface esterification. Investigating properties, techno-economics and sustainability

Abstract

Preparation of fatty acid cellulose esters (FACEs) is much mired in high costs, process complexity and requirements for specialized handling and safety. The present work proposes a novel oxalic acid clay-assisted surface esterification of microcrystalline cellulose (MCC) in a two-stage modified Fischer-Speier Esterification. The proposed method has substantial potential as a process with high reactant recyclability, esterification degree and FACEs with high degree of substitutions, ca. 0.86–2.16. The coconut oil esterifying agent rich in C₁₂-C₁₄ fatty acids has been directly used, reducing the need for derivatization steps. Optimization has been performed in terms of %weight proportions of the co-reactant, time, temperature, and the feedstock. FTIR, ¹H NMR and ¹³C NMR confirm the synthesis of a mixed FACE having either lauroyl or myristoyl fatty acid groups, in combination or by themselves. Thermal and XRD characterization further reveals high thermal stability up to ≥360 °C (by TGA/DTG) and crystallinity upto 23 % – 43 % (XRD) which provides significant appeal as potential thermoplastic material for additive utilization and blending. In this paper, we further demonstrate the applicability of the Green Chemistry Metrics (GCM) and the E-factor (ca. 0.18) approach to quantify how the above procedure compares with the tenets of Green Chemistry Principles, with reference to other reported methods to prepare FACE.

Synopsis

The article relates to sustainability in chemistry regarding novel cellulose modification characterized by high reactant recyclability, OH conversion and cost-effective use of green reagents and auxiliaries.