2. EXPERIMENTAL
Materials
PFAD was obtained from Bau Palm Oil Mill, Sarawak. Rice husk was
obtained from Selangor, Malaysia, washed and air dried prior to use.
Sodium hydroxide pallets (NaOH), sulfuric acid
(H2SO4) 99% and methanol were purchased
from Merck and used as received.
Preparation of Huskcatacid andHuskcatbase
Dried rice husks (1000g) was heated at 800 °C to form calcined rice husk
(RHA), and further treated with NaOH (20%) to produce activated ash
ARHA (200g). The activated ash was impregnated with concentrated
H2SO4 vi a sulfonation for 24 h.
The excess acid was decanted, and the residual wet solids were heated at
120 ºC for 18 h (Kaster et al., 2012) to form heterogeneousHuskcatacid .
Solid base catalyst Huskcatbase was prepared by soaking the
activated ash (RHA) in NaOH solution (5M) for 2 h, followed by
filtration. Sample was then heated at 700 ºC for 10 min (Perrichon and.
Durupty, 1988; Refaat, 2011) to afford Huskcatbase .
Characterization of Huskcatacid andHuskcatbase
The X-Ray Diffraction (XRD) patterns of calcined ash was obtained on a
Rigaku Miniflex X-ray diffractometer equipped with a scintillation
counter to generate pattern at ambient temperature. Surface morphology
of the catalyst was observed under Scanning Electron Microscope (SEM)
(JEOL 7500F-1) with magnification 10000x. Quantitative element
composition of the catalysts was characterized using Energy Dispersive
X-ray (EDX) (JEOL JSM-6390 LA). Specific surface area and total pore
volume of the catalysts were determined using Brunauer-Emmett-Teller
(BET) (Quantachrome ASIQC0000-3) with liquid nitrogen adsorption at 77
K.
Esterification and transesterification reaction of
PFAD
Due to high content of FFAs, the production of biodiesel from PFAD was
performed via esterification followed by transesterification
process. During esterification, Huskcatacid (0.5 g, 5%) was
added into methanol (10.0 mL) and heated at 65 ºC for 1 h in a round
bottom flask. Preheated PFAD (10.0 g) was added into the flask and
heating was continued for 24 h at 120 ºC. The mixture was cooled to room
temperature, filtered, and washed with methanol. The filtrate was
evaporated to eliminate water and excess methanol to obtain esterified
PFAD as a brown oil.
In transesterification process, Huskcatbase (1%, 0.1 g) was
added into a 10.0 mL methanol and heated at 65ºC for 1 h in a 3-neck
round bottom flask. The esterified oil (10.0 g) was added into the flask
and continued heating for 1 h. The mixture was cooled to room
temperature, filtered, and washed with methanol. The filtrate was
evaporated to remove excess methanol and formed layers of glycerol and
biodiesel [23], whereby the upper layer was collected as biodiesel.
The effect of reaction times (15 min, 30 min, 45 min, 60 min) employing
ratio 1:1 (methanol: oil) and 1% of catalyst was investigated. The acid
value and FFA (%) of the esterified oil was calculated using Equation 1
and Equation 2 (Banani et al., 2015).
Acid value (mgKOH/g) = (NKOH x MWKOH x
Vt)/ Ws Eq. 1
where, NKOH is the normality of KOH used,
MWKOH is the molecular weight of KOH (56.11 g/mol),
Vt is the volume of titrant used, and Wsis the mass of sample, g.
FFA % = AVs/2 Eq. 2
where, AVs = Acid value of PFAD, mgKOH/g
Analysis of Biodiesel
The esterified oil and biodiesel analysis were examined using Fourier
Transform Infrared (FTIR) (Thermo Scientific Nicolet iS10) with
zinc-selenide (Zn-Se) disc as the transmitter. The composition of the
biodiesel was analyzed using Gas Chromatography Mass Spectroscopy (GCMS)
(Shimadzu GC-MS model QP2010 Plus) with helium as gas carrier with
constant flow rate at 0.94 mL/min and linear velocity at 36.6 cm/sec.
Chromatographic separation was operated on a nonpolar capillary column,
BPX-5 (30.0 m x 0.25 µm x 0.25mm). MS was operated using electronic
impact (70 eV) in selected ion monitoring (SIM) mode. The injector port
was operated in splitless mode. The temperature of both injector and
interface were at 250 °C. The oven temperature was maintained at 10 °C/
min, which initiated at 110 °C and held for 1 min. The temperature was
increased to 220 °C at 20 °C/min and held for 8 min.