Page 362 - Refining Biomass Residues for Sustainable Energy and Bioproducts

Pretreatment of agroindustry waste by ozonolysis for synthesis of biorefinery products 327

Low yield of ethyl levulinate was obtained by a one-pot process of OPF conver-
sion in [SMIM][FeCl 4 ] compared to a two-step reaction process. The one-step pro-
cess may require long reaction time or high reaction temperature for biomass
conversion to ethyl levulinate. One-step conversion of OPF in [SMIM][FeCl 4 ]
required 12.0 h for reaction (Ramli and Amin, 2016) while wheat straw to ethyl

levulinate conversion was conducted at 200 C in [HSO 3 -BMIM][HSO 4 ](Guan
et al., 2018) to obtain 12.8% and 16.2% of ethyl levulinate, respectively. In order to
improve the synthesis of alkyl levulinate, it is possible to conduct a pretreatment
process to remove the biomass lignin or other extractives. This pretreatment can be
conducted either using a suitable ionic liquid to remove lignin or physically used
ball milling method to break down the lignin of biomass. As provided by ozone pre-
treatment, the process can remove the lignin with less effect on the hemicellulose
and cellulose structures (Travaini et al., 2016c). The pretreated biomass applied
may improve the current reaction condition of the hydrolysis and esterification reac-
tion such as reducing the reaction time and temperature. As mentioned in the dis-
cussion on LA production from pretreated biomass in Section 14.3.3, optimum
yield was obtained at low reaction time compared to raw biomass. Thus high LA
concentration produced can be used to synthesize optimum alkyl levulinate yield.

14.3.4.3 Carboxymethyl cellulose
Carboxymethyl cellulose, also known as CMC, is a linear, long chain, water solu-
ble, anionic polysaccharide derived from cellulose that could potentially be synthe-
sized from ozonated lignocellulosic biomass, especially agroindustry waste. CMC is
widely used as thickening, binding, emulsifying, film-forming, lubricating, dispers-
ing, stabilizing, and gelling agents and is especially useful as additives in food,
pharmaceutical, and cosmetic industries (Chang and Zhang, 2011). CMC is synthe-
sized by two simple reaction steps, namely, alkalization followed etherification pro-
cess. Recently, some agroindustry waste materials have been utilized to be the raw
material for the synthesis of CMC such as bamboo shaving (Chen and Lou, 2014),
corn husk (Mondal et al., 2015), sugarcane bagasse, cotton stalk (Zhang et al.,
2011), durian rind (Rachtanapun et al., 2012), granular potato starch (Tijsen et al.,
2001), orange peel (Ya¸sar et al., 2007), and EFB (Eliza et al., 2015). The optimum
condition and properties of these agroindustry wastes are shown in Table 14.7.
Besides using hydrogen peroxide as the oxidizing agent, the cellulose to be used
in the synthesis of CMC could also be extracted by bleaching various agroindustry
wastes, such as spent tea leaves, sugarcane bagasse, coconut fibers, oil palm fibers,
dried duckweed, and palm kernel cake, with specific amounts of acetic acid and
sodium chlorite as described in Huang et al. (2017). It was found that the spent tea
leaves, sugarcane bagasse, and palm kernel cake had the highest moisture content
and cellulose yield, and all the agroindustry wastes could potentially be converted
into CMC. However, the maximum degree of substitution (DS) of each agroindustry
waste was different due to their varying cellulose content.
The experimental, modeling, and optimization of CMC production from sugar-
cane bagasse was studied by Golbaghi et al. (2017) using steam explosion pulping.