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Pretreatment of agroindustry waste by ozonolysis for synthesis of biorefinery products 325

14.3.4.2 Alkyl levulinate

Generally, the acid-catalyzed reaction of biomass or its derivatives are required for
the preparations of HMF, LA, and alkyl levulinate. Biomass and its derivatives that
include reducing sugars and cellulose can be applied as the feed for reaction to pro-
duce HMF, LA, and alkyl levulinate. Alkyl levulinate is one of the alternative
biofuel-based products as it could be derived from a renewable source such as lig-
nocellulosic biomass. Alkyl levulinate shows a potential as a solvent, an additive,
and a precursor for chemical synthesis as described by De ´molis et al. (2014). Alkyl
levulinate becomes more compressible as the solvent due to hydrogen-bond net-
work of molecules and retains much lower vapor pressures compared to usual sol-
vents (De ´molis et al., 2014). Besides, alkyl levulinate can be used as fuel additives
to improve engine performance, fuel stability, and quality by reducing carbon mon-
oxide and nitrogen monoxide emissions (Pasquale et al., 2012; Badgujar and
Bhanage, 2015). In chemical synthesis the alkyl levulinate was used as a building
block for chemical transformation such as γ-valerolactone (GVL) (De ´molis et al.,
2014). As stated by Maldonado et al. (2012), ethyl levulinate can be applied as a
precursor for the production of GVL dubbed as advanced biofuel.
In alkyl levulinate synthesis, Melero et al. (2013) stated that the potential route
can be via LA, furfuryl alcohol, 5-chloromethylfurfural, and cellulosic biomass
(carbohydrate). As publicized by the previous study, model compound of LA has
been used to synthesized methyl levulinate (Melero et al., 2013), ethyl levulinate
(Kong et al., 2016; Zainol et al., 2019), butyl levulinate (Maheria et al., 2013),
and octyl levulinate (Nandiwale et al., 2014). Besides, the furfuryl alcohol also
shows possible alternative in derived levulinate ester (Maldonado et al., 2012;
Song et al., 2015). As focused in this chapter, the biomass has been utilized for
alkyl levulinate production especially for ethyl levulinate. Based on Table 14.6,
the biomass has been utilized in one-pot reaction for synthesis alkyl levulinate.
There has been no study conducted using pretreated biomass to synthesize ethyl
levulinate. However, there is a study that conducted the extraction process via
pressing method on the oil palm trunk to synthesize methyl levulinate (Jahar

et al., 2019). The reaction was conducted using H 2 SO 4 and HCl at 180 C for 2.0 h
to produce 43.75% and 16.37% of methyl levulinate, respectively. This shows the
ability of the H 2 SO 4 to catalyze the reaction at lower reaction time to produce
high yield of methyl levulinate. Besides, the previous studies conducted the reac-
tion using a two-step process where the raw biomass was converted to LA and
subsequently to ethyl levulinate (Tiong et al., 2017; Tiong et al., 2019; Ramli and
Amin, 2016). Currently, the conversion of biomass such as EFB, oil palm meso-
carp fiber (OPMF), and OPF to ethyl levulinate was conducted in ionic liquid due
to its efficiency in depolymerizing the biomass structure and catalyzing the reac-
tions. In a two-step reaction process, InCl 3 [HMIM] [HSO 4 ] was used to esterify
LA from EFB and OPMF in ethanol to produce 18.7% and 21.1% of ethyl levuli-
nate, respectively (Tiong et al., 2019). Besides, [SMIM][FeCl 4 ]have alsobeen
applied to convert LA from OPF to ethyl levulinate where 20.1% of yield was
produced (Ramli and Amin, 2016).