204
easily in the presence of water. On the other hand, higher amounts of protonic
groups are present in Nafion, but their catalytic activity is very much lower than the
conventional catalyst, concentrated sulfuric acid [6, 56]. Owing to these disadvantages, a new class of low-cost carbon-based catalysts were developed which offer an
environmentally benign and economically feasible biodiesel production process.
The low-cost alternative SACs for the high-cost traditional SACs are carbonbased SACs derived from various natural and waste materials. The low-cost carbonbased SACs which show high potential for esterification can be derived using sugars
(glucose and sucrose), polysaccharides (starch and cellulose), and biomass (coconut
shell, bamboo, wood powder, lignin, and bagasse). Owing to various other prolific
applications and higher cost of sugars and polysaccharides, more attention was
given to the environmentally benign and cheaper carbon alternatives like biomass.
Therefore, much research was still in progress to find various potential waste biomass materials and their transformation to value-added products. As a part of this
novel approach, corncob was used to synthesize SAC for biodiesel production [5].
4.1 Corncob-Based Catalyst
A fresh corncob was made free from kernels, sun-dried, ground, and screened to a
size between 72 and 100 mesh numbers. To increase the surface area of carbon,
phosphoric acid was impregnated at various ratios for different intervals of time and
kept for soaking at room temperature. Then the samples were carbonized and
washed thoroughly using dilute HCL and hot deionized water to remove phosphates
and polyphosphates formed on the surface. Finally, the carbonized samples were
sulfonated using the concentrated sulfuric acid at various temperatures for different
intervals of time in the presence of an inert atmosphere [5]. A detailed parametric
study was done involving all the catalyst preparation variables such as impregnation
time and ratio, carbonization time and temperature, and sulfonation time and temperature. The final synthesized catalyst was analyzed qualitatively using FTIR for
the presence of various functional groups (-SO 3 H, -COOH, and -OH). The structural properties of the catalyst were evaluated by X-ray diffraction (XRD). The surface area, average pore diameter, pore volume, and pore size distribution were
estimated using adsorption-desorption isotherm data fitted to Brunauer-EmmettTeller (BET) equation.
A three-necked round-bottom flask of 250 mL capacity was fitted with a Dean
and Stark apparatus and used to test the catalyst activity for esterification of oleic
acid and methanol. The reaction was carried out at 338 K and 1:9 oleic acid to
methanol molar ratio using 10 wt% catalyst [5]. The optimal catalyst synthesis
parameters were found to be as impregnation time = 5 h and ratio = 1, carbonization
time = 8 h, and temperature = 723 K and sulfonation time = 15 h and
Z. Hussain et al.
easily in the presence of water. On the other hand, higher amounts of protonic
groups are present in Nafion, but their catalytic activity is very much lower than the
conventional catalyst, concentrated sulfuric acid [6, 56]. Owing to these disadvantages, a new class of low-cost carbon-based catalysts were developed which offer an
environmentally benign and economically feasible biodiesel production process.
The low-cost alternative SACs for the high-cost traditional SACs are carbonbased SACs derived from various natural and waste materials. The low-cost carbonbased SACs which show high potential for esterification can be derived using sugars
(glucose and sucrose), polysaccharides (starch and cellulose), and biomass (coconut
shell, bamboo, wood powder, lignin, and bagasse). Owing to various other prolific
applications and higher cost of sugars and polysaccharides, more attention was
given to the environmentally benign and cheaper carbon alternatives like biomass.
Therefore, much research was still in progress to find various potential waste biomass materials and their transformation to value-added products. As a part of this
novel approach, corncob was used to synthesize SAC for biodiesel production [5].
4.1 Corncob-Based Catalyst
A fresh corncob was made free from kernels, sun-dried, ground, and screened to a
size between 72 and 100 mesh numbers. To increase the surface area of carbon,
phosphoric acid was impregnated at various ratios for different intervals of time and
kept for soaking at room temperature. Then the samples were carbonized and
washed thoroughly using dilute HCL and hot deionized water to remove phosphates
and polyphosphates formed on the surface. Finally, the carbonized samples were
sulfonated using the concentrated sulfuric acid at various temperatures for different
intervals of time in the presence of an inert atmosphere [5]. A detailed parametric
study was done involving all the catalyst preparation variables such as impregnation
time and ratio, carbonization time and temperature, and sulfonation time and temperature. The final synthesized catalyst was analyzed qualitatively using FTIR for
the presence of various functional groups (-SO 3 H, -COOH, and -OH). The structural properties of the catalyst were evaluated by X-ray diffraction (XRD). The surface area, average pore diameter, pore volume, and pore size distribution were
estimated using adsorption-desorption isotherm data fitted to Brunauer-EmmettTeller (BET) equation.
A three-necked round-bottom flask of 250 mL capacity was fitted with a Dean
and Stark apparatus and used to test the catalyst activity for esterification of oleic
acid and methanol. The reaction was carried out at 338 K and 1:9 oleic acid to
methanol molar ratio using 10 wt% catalyst [5]. The optimal catalyst synthesis
parameters were found to be as impregnation time = 5 h and ratio = 1, carbonization
time = 8 h, and temperature = 723 K and sulfonation time = 15 h and
Z. Hussain et al.