October

Biochar Supported Cao As Heterogeneous

Catalyst For Biodiesel Production
Lakhya Jyoti Konwar
Department of Energy , Tezpur University, Tezpur, Assam, India
Singh Chutia
Department of Energy , Tezpur University, Tezpur, Assam, India
Jutika Boro
Department of Energy , Tezpur University, Tezpur, Assam, India
Rupam Kataki
Department of Energy , Tezpur University, Tezpur, Assam, India
Dhanapati Deka
Department of Energy , Tezpur University, Tezpur, Assam, India

Abstract
In this paper we report an environmentally benign biodiesel production using
biochar supported CaO as a heterogeneous catalyst. Both the active part as well
as catalyst support reported in this work has been derived from waste materials
(i.e. waste shells of Turbonillastriatula and deoiled cake of
MesuaferreaLinnseeds). The catalyst was prepared by impregnation method and
optimal reaction conditions for achieving maximum yield were investigated. Under
optimal conditions biodiesel yields <90 was obtainedwith biochar supported CaO
which was similar to the yield reported for shell derived CaO catalyst.

Keywords: Biochar; CaO, Waste shell; Mesuaferrea; Pyrolysis;Biodiesel

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Introduction
Biodiesel is an alternative diesel fuel derived from vegetable oils or animal fats.
Owing to its properties which are similar to petroleum-based diesel, it can be used
either as a substitute for diesel fuel or more commonly in fuel blends [1-2]. It also
presents an alternative to petroleum diesel for reducing emissions of gaseous
pollutants such as CO, SOx, particulate matter and organic compounds [3]. Amongst
the available methods, transesterification is the easiest and most cost effective way to
produce biodiesel [1]. Transesterification also called alcoholysis is the reaction of a
fat or oil with an alcohol to form esters and glycerol. In the reaction, 1 mol of
triglyceride reacts with 3 mol of methanol in presence of catalysts. Usually
transesterification of vegetable oil to biodiesel (fatty acid methyl ester, FAME) can be
catalyzed by bases, acids and enzymes [5, 6]. The industrial synthesis of biodiesel
uses homogeneous catalyst KOH, NaOH, in a liquid-phase reaction [7]. However,
transesterification with these catalysts has disadvantages related with catalyst
separation and reusability. To address these issues, heterogeneous catalyst have been
considered a viable alternative since they eliminate the usual difficulties related to
homogenous catalyst and can be reused several times [9-11].Due to the high cost and
complex syntheis of existing heterogeneous base catalysts such as supported alkaline
catalysts, alkali earth oxides, mixed metal oxides, dolomites, perovskite-type
catalysts, and zeolites, hydrocalcites [12-13]; research for production of biodiesel has
been focused towards renewable “green catalyst” prepared either from biomass or
from waste generated in the households. Recently renewable heterogeneous catalysts
such as carbon-based catalysts (activated carbon, biocharetc) [14-18] and metal
oxides catalysts derived from shells: shrimp shell, eggshells [13,19,20] have gained
much importance owing to their low material costs which could significantly bring
down the biodiesel production cost. In our previous studies we reported biodiesel
synthesis from vegetable oils using CaO derived from waste shells of
Turbonillastriatulaas heterogeneous catalyst. [12]. Comparative studies with
commercial grade CaO showed no difference in terms of activity for
transesterification of soybean oil [21]. However, the catalyst was plagued by
problems like very low surface area, sensitivity to the presence of water, leaching of
active sites by polar species(e.g., glycerol) and competed with soap forming side
reactions. To overcome such limitations CaO can be impregnated into supports such
as silica and alumina or carbon materials such as activated carbon, nanoporous

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carbon, nanotubes etc[22]. Carbon materials have recently gained attention as catalyst
supports, owing toproperties like: high stability in acidic, basic media and possibility
of tailoring both their texture and surface chemistry. In this context biochar is also a
potential candidate as it mirrors charcoal in all aspects. Surface chemistry of biochar
may be modified to have very high area (by physical or chemical activation) similar to
charcoal [23].In the present study we used activated biocahar as support and
impregnated it with the CaO derived from waste shells obtained by calcination of
waste Turbonillastriatulashells. The physical and chemical properties of this biochar-
supported CaO material were evaluated and catalytic properties were studied in the
transesterification of Mesua F. oil with methanol.

Materials And Methods

Waste shells of T. striatula were obtained from a local household of Chirang district
of Assam, India. Synthesis-grade methanol (
and all necessary solvents were purchased from Merck Limited, Mumbai, India and
were used as received. MesuaferreaLinn oil was extracted by soxhlet extraction from
the powdered seeds. The raw oil was pretreated in order to reduce its acid value which
was found to be 16mg/KOH.

Preparation Of Biochar Supported Cao Catalysts

The active phase of the catalyst, CaO was produced by the high temperature
calcination of Waste shells of T. striatulaas described elsewhere [12]. For preparing
support biochar produced from MesuaferreaLinn deoiled cakes were used,since
biochar produced by fast pyrolysis have very low surface area, [23, 24] it was than
subjected to chemical activation (with 7 M KOH) in order to increase the surface area.
The biochar-supported CaO (BCh-CaO) catalystwas prepared by the wet
impregnation method. Typically, a Ca-containing solution was prepared by dissolving
20 g CaO produced earlier in minimum amount of dilute HNO 3(aq). To this solution,
a 20 g of dried and powdered support was added and the resultant mixture was stirred
for about 2 h at room temperature. Thereafter, it was heat treated at a calcination
temperature of 600 C under atmospheric pressure. The resulting material from
hereafter was treated as catalyst.

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Catalyst Characterization And Testing

The powder X-ray diffractograms of catalyst samples were recorded on a
Rigakuminiflexdiffractometer (Cu- Å) in 2 –70 at a
scanning rate of 2 °C min –Emmett– Teller (BET) surface area and
pore size were measured by the multipoint N 2 adsorption–desorption method with
ASAP® 2020 Accelerated Surface Area and PorosimetryAnalyzer, USA at liquid
nitrogen temperature (-196 ºC). SEM and EDX were performed on a Jeol, JSM-
6290LV instrument. IR spectra were recorded in KBr pallets on a Nicolet (Impact
410) FT-IR spectrophotometer. The chemical composition of the catalyst was
estimated by Energy-dispersive X-ray spectroscopy (EDX). The basic strength (H_)
and basicity were determined according to the methods based on the colour change of
Hammet indicators. The catalytic performance of biochar supported-CaO (BCh-CaO)
catalystwas evaluated in the transesterification of pretreatedMesuaferreaLinnoil with
methanol. The transesterification reactions were performed in a 100 ml three-neck
round-bottom flask equipped with magnetic stirring, thermometer and a reflux
condenser. Oil conversions were determined from the 1H NMR. Sample aliquots were
drawn periodically from the reactor and analyzedby 1 H NMR on a Jeol JNM-ECS400
NMR spectrometer at 25.5 C with CDCl3 and TMS as solvent and internal standard
respectively [25]. The yield ofmethyl esters was calculated as follow:
2A
Yield = 100
3ACH
Where,AMe = integration value of the methoxy protons of the methyl esters and
ACH -methylene protons.

Results And Discussion

The catalyst changed the colour of phenolphthalein (H_ = 8.2) from colorless to pink,
the colour of indigo carmine (H_=12.2) from blue to green and the colour of 2,4-
dinitroaniline (H_ = 15) from yellow to mauve but failed to change the colour of 4-
nitroaniline (H_ = 18.4). As such, the catalyst’s basic strength was designated as 15 <
H_ < 18.4, and it was considered as a strong base for the transesterification reaction.
Fig. 1 shows the XRD patterns of shell-CaOand BCh-CaO respectively. New peaks
corresponding to the graphite carbon appeared in the XRD pattern of the prepared
catalyst (BCh-CaO) along with the peaks of CaO. It was observed that major peaks

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fundamental peaks for calcium oxide corresponding to JCPDS file no. 00-003-1123.
The presence of carbon is indicated by the peak for 2= 29.26 which corresponds to
JCPDS file no.01-074-2328. This indicates that the activated supported carbon
catalyst consists of calcium oxide and carbon. Both shell-CaO and BCh-CaO shows

for calcium oxide (JCPDS file no. 48-1467). The Diffractograms of produced biochar
was quite similar to biochars as per literature [24,26], while the graphitic basal planes

in the activated samples.

Shell-CaO BCh-CaO
500
(b)
160 (c)

140
400
120

300 100

80
200
60

40
100
20

0 0

-20
0 10 20 30 40 50 60 70 80 10 20 30 40 50 60 70

2 q degree 2 q degree

Figure 1: XRD patterns of Active phase and Supported Catalyst

Figure 2: EDX spectra of BCh-CaO catalyst

The morphology of the catalyst (BCh-CaO) was observed by scanning electron

micrographs (not shown here). The SEM images of the samples showed a good
dispersion of CaO on the surface of activated biochar. It was observed that although
biochar could retain its initial structure (which is supported by XRD pattern also) the
CaO species were highly distributed on the surface of the support. It could be seen
that the particles distinctly filled up all the pores of the support indicating that the
resulting sample may have high activity.This conclusion is also supported by the
surface area measurements. It was observed that there was a significant reduction in

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BET surface area of activated biochar from (456 m2/g) to the BCh-CaO catalyst (57.7
m2/g) which indicates that the CaO molecules were successively impregnated into the
pores of the activated carbon.The chemical composition of the catalyst was estimated
by Energy-dispersive X-ray spectroscopy and the findings are shown in Fig. 2. It was
observed that the major constituent elements present in the BCh-CaO catalyst were
calcium, carbon and oxygen having weight % of 27.78, 17.66 and 54.55 respectively.
This result supports the finding in XRD analysis and hence establishes that the
catalyst proposed in this study is mainly composed of CaO particles dispersed on
activated carbon.Biochar supported CaO (BCh-CaO) was found to be active in
transesterification of MesuaferreaL.oil.To study the influence of different parameters
on activity (FAME yield), reactions were carried out at different temperatures with
varying methanol to oil molar ratio and catalyst amounts. The results are presented in
Table 1. From the results it was observed that the catalytic activity of developed BCh-
CaO catalyst was almost similar to the shell-CaO catalysts [13, 21] which could be
attributed to the very high loading (50% w/w of support) of active CaO particles. The
key parameters affecting biodiesel yield were temperature and catalyst loading.In our
study, use of 3 (Wt. %) catalyst loading produced the best results yield of 96% with
12:1 alcohol to oil ratio at 65 C (Entry 6).

Entry no Temperature Catalyst Methanol/oil Time Biodiesel

( (Wt. %) (molar ratio) Yield
1 65 1 6/1 6 61
2 65 2 6/1 6 88
3 65 3 6/1 6 92.4
4 65 3 6/1 6 94.3
5 80 3 9/1 6 95.7
6 65 3 9/1 6 96
7 95 3 12/1 6 85.6
8 70 3 6/1 6 93
9 33 1 6/1 6 20
10 33 2 9/1 6 25.9
11 33 3 6/1 6 27.2
12 65 3 12/1 6 56
13 70 2 3/1 6 91

14 70 2 9/1 6 91.4

Table 1: Influence of different parameters on yield (Temperatures, methanol to oil

molar ratio and catalyst loading)

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Conclusion
In this work we successfully employed biochar supported CaO (BCh-CaO) as a
heterogeneous catalyst in theproduction of biodiesel from MesuaferreaL.oil. The
catalyst reported was synthesized entirely by processing waste materials. The active
part of the catalyst (i.e. CaO) was derived from waste shells of Turbonillastriatula
andthe support (i.e. activated biochar) was prepared from deoiled cake of Mesuaferrea
Linn seeds. Use of this novel approach makes thebiodiesel synthesis process
environmentally benign. It showed high activity and very high yield upto96% was
achieved in 6 h using 3 Wt. % catalyst 12/1 (methanol/oil molar ratio) at reaction
temperature of 65 C.

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