Page 352 - Refining Biomass Residues for Sustainable Energy and Bioproducts

320 Refining Biomass Residues for Sustainable Energy and Bioproducts

chemical for the production of other chemicals that include resins, polymers, herbi-
cides, pharmaceuticals, and flavoring agents, solvents, plasticizers, antifreeze
agents, and biofuels/oxygenated fuel additives can be derived from the LA
(Rackemann and Doherty, 2011). Based on the previous studies, LA has been pro-
duce from various biomass either through one-step reaction process (Ya’aini et al.,
2012; Ramli and Amin, 2014) or two-step reaction involving pretreatment method
(Wan Omar and Amin, 2016; Chin et al., 2015; Kang and Yu, 2016; Ramli et al.,
2014b; Jeong et al., 2017; Elumalai et al., 2016; Ma et al., 2016; Pulidindi and
Kim, 2018; Bevilaqua et al., 2013; Lopes et al., 2017). Previous works were
reported that the catalytic reaction of the biomass to LA required the existence of
both Bronsted and Lewis acid to demonstrate efficient polymerization of biomass
carbohydrate (Tiong et al., 2018; Ramli and Amin, 2015). The catalytic thermal
reaction also may involve the application of homogeneous (Ramli et al., 2014b;
Tiong et al., 2017) and heterogeneous (Ya’aini et al., 2012; Ramli and Amin, 2014)
catalysts.
The conversion of the lignocellulosic biomass to LA required pretreatment in
order to remove the lignin barrier that covers the cellulose and hemicellulose
structure of biomass. The biomass composition and operating conditions could
give a different effect on the pretreatments process and product (Hendriks and
Zeeman, 2009). Through the pretreatment process, the biomass complex structure
should break down efficiently, remove the lignin, and decrystallize the cellulose
fibers that can decrease the mass transfer limitation of the reaction for high con-
centration of sugar generation to convert to HMF and subsequently to LA
(Hendriks and Zeeman, 2009; Morone et al., 2015). Table 14.4 has shown the LA
production from the pretreated lignocellulosic biomass. There are various pretreat-
ment methods that have been applied on various biomasses for conversion to LA.
This includes ball milling (Chin et al., 2015), ozone (Wan Omar and Amin,
2016), steam explosion (Medina et al., 2016), ionic liquid (Ramlietal.,2014a,b),
ammonia soaking (Gozan et al., 2018), H 2 SO 4 (Kang and Yu, 2016; Jeong et al.,
2017), NaOH (Rackemann et al., 2016), andcombinedmethod(Ma et al., 2016;
Pulidindi and Kim, 2018; Lopes et al., 2017; Schmidt et al., 2017). Ball milling
pretreatment method provides pretreated biomass for further process such as acid
hydrolysis to LA. Ball milling can reduce the crystallinity of the cellulose to
enhance the reaction accessibility of catalysts at cellulose β-1,4-glycosidic bonds
(Zhao et al., 2006; Avolio et al., 2012). The physical pretreatment of biomass via
ball milling and steam explosion is presented clean and nontoxic alternative
method as compared to the chemical treatment via acid and base. Pretreatment or
one-pot reaction of biomass in ionic liquid becomes one of the suggested methods
for biomass conversion due to the ability of ionic liquid to depolymerize biomass
complex structure.
As for ionic liquid, special chemical properties make it work as dual solvent-
catalysts for catalytic biomass conversions in one pot such as pretreatment and
depolymerization (Xu et al., 2016). One-port biomass conversion in ionic liquid
was conducted as another alternatives to synthesis LA (Tiong et al., 2019; Ramli
and Amin, 2016). However, the separated pretreated biomass would still give a