R. R. Chada et al.
feedstock for the green and sustainable production of bio
based chemicals and 2nd generation bio fuels and is one of
the approaches to reduce environmental pollution to some
extent. Lignocellulosic biomass is the most abundant in agri-
culture residues and waste streams and is inexpensive, bio-
degradable and sustainable nature and in addition it avoids
the production of first generation fuels from sugars, starch
and vegetable oils. For the production of fuels via utiliza-
tion of first generation feed stocks creates negative impacts
like food versus fuel problems [2]. Lignocellulosic biomass
is mainly composed of three biopolymers such as cellulose
oxides [17], Al-TUD-1 [18], sulfonic acid functionalized
materials of carbon [19], ionic liquids and organosulfonic
acid functionalized SBA-15 [20, 21], organosilica hollow
nanospheres [22], zirconia bi-functionalized organosilica
modified heteropoly acid [23] and ZnTPA/Nb O [24]. Even
2
5
though those catalytic systems offer good catalytic activity,
the difficulty in preparation and usage of expensive precur-
sors are one of the drawbacks. Furthermore, most of these
reactions are conducted in batch conditions, in which, longer
reaction times, catalyst separation from reaction mixture,
disposal of effluents and reuse of catalyst are the notable
difficulties, which are unavoidable process limitations. In
this context, the production of AL in continuous process
at atmospheric pressure over facile, inexpensive, efficient,
stable and eco-friendly solid acid catalytic systems is more
advantageous.
(
40–50%), hemicellulose (25–30%) and lignin (15–20%).
Cellulose and hemicellulose polymers easily convert into
their respective monomeric sugars by lower energetic C–O
(
glycoside) bond cleavage. These sugars can be further con-
verted into fuels, fuel additives and chemicals in multiple
steps through various possible platform molecules [3–5].
Furfural is considered as an excellent platform molecule,
which can be easily converted into furfuryl alcohol (FAL)
over Cu/MgO and carbon–MgO catalysts in continuous
process [6, 7]. The alcoholysis of FAL to alkyl levulinates
It has reported that, the alcoholysis of FAL to produce
alkyl levulinates is significantly influenced by the acid site
density, strength and accessibility of active sites to reactants
[8, 25]. Hence, in the present investigation, preparation of
Al O /SiO , WO /SiO , ZrO /SiO , TiO /SiO solid acid
2
3
2
3
2
2
2
2
2
(
AL) has gained particular attention due to their potential
catalysts, determination of structural and textural charac-
teristics, estimation of type, distribution, nature and strength
of acidic sites and their correlation with the alcoholysis of
furfuryl alcohol in the formation of alkyl levulinates in the
fixed bed reactor has been delineated.
applications in transportation fuel, perfumery and flavouring
industries [2, 8]. AL are the main precursor for the synthesis
of valuable chemicals, such as γ-valerolactone. AL can also
be used as additives in gasoline and diesel transportation
fuels, which create enviable properties like cleaner combus-
tion, high lubricity, conductivity, decrease in emission of
toxic gases and particulate matter and also flow properties
even under cold conditions [9–11]. On the basis of physical
properties AL can be used as blending agents for diesel.
The blending of 20% ethyl levulinate (EL) to cotton seed oil
improves the fuel properties [12]. The swelling of engines
and percent hardness can be reduced with butyl levulinate
2 Experimental
2.1 Preparation of Various Solid Acid Catalysts
Various solid acid catalysts such as Al O /SiO , ZrO /
2
3
2
2
SiO , WO /SiO and TiO /SiO were prepared by wet
2
3
2
2
2
(
BL) and higher AL. EL (10 v/v%) and BL (20 v/v%) were
impregnation method using SiO (Aldrich Chemicals,
2
blended with diesel fuel and tested for Cummins ISB engine
and observed that engine-out smoke was reduced by 41.3 and
USA) as support and Al(NO ) ·9H O (S.D. Fine-Chem.
3
3
2
India), H N O W ·xH O (Aldrich Chemicals, USA),
2
6
6
40 12
2
5
5% respectively [11]. AL have been proposed as green sol-
ZrO(NO ) ·xH O (S.D. Fine-Chem. India) and TiCl (Chem-
3 2 2 4
vents due to lower vapour pressures compare to chlorinated
solvents and based on this property, Ferrer et al. claimed that
these can be used in metallic degreasing processes instead
of industrially used harmful trichloroethylene [13]. Conven-
tionally, AL have been synthesized by using inorganic liquid
acids such as HCl, H SO , H PO and HF. However, the
labs, India) are as precursors for Al O , WO , ZrO and TiO
2 3 3 2 2
respectively. In a typical method, requisite amount (10% by
weight) of the metal precursor dissolved in water was mixed
with SiO by continuous stirring and the mixture was dried
2
under constant manual stirring up to complete dryness. The
solid was dried in an air oven at 100 °C for 12 h, and then
calcined at 500 °C for 4 h in static air. The calcined Al O /
2
4
3
4
complications like corrosiveness, recyclability and environ-
mental issues hinder their industrial applications [14]. To
overcome these drawbacks, scientific community has made
several attempts to develop sustainable approaches for the
production of AL in green process and many researchers
have been explored the synthesis of AL from alcoholysis of
FAL over various solid acid catalysts. The most of reported
catalytic systems involve catalysts like ion exchange resins
2
3
SiO , ZrO /SiO , WO /SiO and TiO /SiO are designated
2
2
2
3
2
2
2
as AS, ZS, WS and TS respectively, which are collectively
known as MO/SiO .
2
2.2 Characterization
All of these catalysts were characterized by different tech-
niques. The X-ray patterns were recorded on an Ultima-IV
[
15], mesostructured aluminosilicates [16], sulfated metal
1
3