Innovative methodologies in the concept of biorefinery for the analysis and derivatization of lignocellulose

Abstract

Lignocellulose biorefinery is considered an industry analogous to oil refinery, with the potential to meet the demand for renewable fuels, chemicals, and materials in the near future. However, compositional characterization processes of potential lignocellulosic sources, in addition to treatment and heterogeneous conversion of extracted cellulose are some of the main limitations for expanding the diversity of products that can be obtained with high efficiency in biorefineries. In this work, a series of innovative methodologies were developed with focus on optimizing the processes of this industry. A new composition characterization method via peak deconvolution of derivative thermogravimetry curves (DTG) was applied to in natura biomass and pulps from corn cob (CC) and sugarcane bagasse (SB), in comparison to the standard method, with high precision (standard deviation <1.58%) and accuracy (standard error <5.74x10-2 , R2>0.9993 and F>750,926). In addition, the new method made it possible to assess the treatment efficiency and reactivity of cellulose. Then, the optimization of heterogeneous synthesis of carboxymethylcellulose (CMC), one of the most commercially important cellulose derivatives, was carried out from these residual celluloses by a D-Optimal experimental design with 28 experiments. Analysis of variance (ANOVA) and response surface methodology (RSM) results proved with high precision (F=67.27; p-value<0.0001; R2=0.928; standard deviation=7.0x10-4 ) and accuracy (low regression residuals) that the waste celluloses extracted are promising to produce CMC under milder conditions in comparison to literature, yielding about 279% (w CMC/w cellulose) of water-soluble CMC. Finally, a zinc molten salt hydrate was used as a solvent and reaction system for one-pot carboxymethylation of cellulose in a homogeneous medium, in a novel, more efficient, and environmentally friendly process. Carboxymethylation was proven after just 30 min of reaction by solubility tests and spectroscopic analyses, as well as the complexation of Zn2+ by carboxylate groups. X-ray diffraction and microscopic results proved this is a nanomaterial (10-36 nm) organized in a crystalline cubic microstructure formed by the aggregation of nanoparticles. Thus, the nanoZnCMC is the first cellulose-based biocoordination polymer reported in the literature. This material has potential high-tech applications, thus opening up a new chapter for studies in the homogeneous synthesis of innovative materials from renewable sources.