**4.1.2 Experimental procedure**

25 ml of refined castor oil containing 8.4% FFA was charged with 1 litre dry methanol in a 1.5 litres round-bottomed flask fitted with a condenser and fused calcium chloride guard tube on a preheated oil bath under vigorous stirring. To it was added 1.25gm (5%) catalyst A and stirred at 600 rpm under heating at 700C (external) for 5 hours. Occasionally TLC was monitored to check the progress of the reaction. After completion, the reaction mixture was distilled to recover methanol. The product with the catalyst remained after separation of methanol was obtained with glycerol as a separate layer. Methyl ester of castor oil along with glycerol layer was decanted out from the solid catalyst surface. Glycerol separated as the bottom layer was taken out from the methyl ester of castor oil (CastMe) layer. The solid catalyst was washed several times with petroleum ether and dried at 1500C for 24 hours in a hot air oven for subsequent runs. The product isolated was found to have yield 95%. During the period of the reactions, samples were taken out at regular intervals and analysed on GC (Fig. 1) using carrier gas nitrogen at flow rate of 2.5kg/cm2. Triglyceride, diglyceride, monoglyceride and methyl ester CastMe as transesterified product were quantified by comparing the peak areas of their corresponding standard.

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Fig. 3. FTIR of CastMe

Avenue for Castor Oil Biodiesel: Use of Solid Supported Acidic Salt Catalyst 387

The corresponding significant FT IR frequencies (Fig 3) and superimposable FTIR spectra of CastMe and standard methyl ricinoleate (Fig 4) and 300 MHz NMR spectral data (Fig5) of

**FT IR (Cm-1, thin film):** 1742 (COOMe str),2855 & 2928(CH str),3407(OH str) (Fig 3):

Fig. 4. Superimposable FTIR spectra of CastMe and standard methyl ricinoleate

**1HNMR( ppm,CDCl3)** :: 1.96(s,1H,OH), 1.23-2.24(m, nH,(CH2)nMe), 3.55-3.57(m,1H,CH-OH), 3.57(s,3H,COOMe), 5.25-5.47(m, nH, olefinic protons),(n=different numbers of protons of fatty acids), the hydroxyl group present in ricinoleic acid, the major constituent of castor oil imparts unique properties. Because of the branching created by it causes the low cetane number and higher viscosity (Knothe et al, 2008). However the advantage of the present method is that unlike other acidic catalyst, this catalyst system does not facilitate any

methyl ester of castor oil (CastMe) have been as given below.

Fig. 1. GC of standard ricinoleic acid methyl ester

Fig. 2. GC of CastMe

#### **4.1.3 Physical properties of CastMe determined by ASTM D6751 standard**

The physical properties of CastMe viz. kinematic viscosity, density, pour point, and cloud point have been determined following standard ASTM D675 method and given in the Table 1 along with reported (Forero, C.L.B., 2004) values of corresponding castor oil, petrodiesel and methyl esters of few other vegetable oils. In Table 2 suggested ASTM standard for pure biodiesel (100%) were given. The properties of CastMe are comparable to those of petrodiesel and acceptable within what is specified for 100 % pure biodiesel as per ASTM standard except that of viscosity and cetane numbers which are the bottlenecks. However, 10% or 20% blended CastMe with petrodiesel that are known as B10 and B20 have their kinetic viscosity 4.54 & 4.97 mm2/s and are within ASTM standard.

The corresponding significant FT IR frequencies (Fig 3) and superimposable FTIR spectra of CastMe and standard methyl ricinoleate (Fig 4) and 300 MHz NMR spectral data (Fig5) of methyl ester of castor oil (CastMe) have been as given below.

**FT IR (Cm-1, thin film):** 1742 (COOMe str),2855 & 2928(CH str),3407(OH str) (Fig 3):

Fig. 3. FTIR of CastMe

386 Biodiesel – Feedstocks and Processing Technologies

Fig. 1. GC of standard ricinoleic acid methyl ester

**4.1.3 Physical properties of CastMe determined by ASTM D6751 standard** 

kinetic viscosity 4.54 & 4.97 mm2/s and are within ASTM standard.

The physical properties of CastMe viz. kinematic viscosity, density, pour point, and cloud point have been determined following standard ASTM D675 method and given in the Table 1 along with reported (Forero, C.L.B., 2004) values of corresponding castor oil, petrodiesel and methyl esters of few other vegetable oils. In Table 2 suggested ASTM standard for pure biodiesel (100%) were given. The properties of CastMe are comparable to those of petrodiesel and acceptable within what is specified for 100 % pure biodiesel as per ASTM standard except that of viscosity and cetane numbers which are the bottlenecks. However, 10% or 20% blended CastMe with petrodiesel that are known as B10 and B20 have their

Fig. 2. GC of CastMe

Fig. 4. Superimposable FTIR spectra of CastMe and standard methyl ricinoleate

**1HNMR( ppm,CDCl3)** :: 1.96(s,1H,OH), 1.23-2.24(m, nH,(CH2)nMe), 3.55-3.57(m,1H,CH-OH), 3.57(s,3H,COOMe), 5.25-5.47(m, nH, olefinic protons),(n=different numbers of protons of fatty acids), the hydroxyl group present in ricinoleic acid, the major constituent of castor oil imparts unique properties. Because of the branching created by it causes the low cetane number and higher viscosity (Knothe et al, 2008). However the advantage of the present method is that unlike other acidic catalyst, this catalyst system does not facilitate any

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**5. Results and discussion** 

maximum yield of CastMe up to 95%.

Avenue for Castor Oil Biodiesel: Use of Solid Supported Acidic Salt Catalyst 389

Potassium bisulphate (PBS) impregnated microporous silica has been evaluated as solid acid catalyst for biodiesel production from refined castor oil containing 8.4% FFA compared to other support viz. alumina with 95% yield. The determination of surface area, pore volume and pore diameter and also FTIR spectra of KHSO4 supported on microporous silica revealed that KHSO4 is well dispersed very evenly generating Bronsted acid site that is responsible for its higher activity.The FT IR spectrum of pure KHSO4,pure silica gel and

KHSO4 supported silica gel (Fig-6) have been depicted below.

Fig. 6. FT IR spectra of pure KHSO4,Pure SiO2 and KHSO4 supported on SiO2

The pure silica FTIR spectra of KHSO4 exhibited typically six major bands located at 577,852,886,1009,1070 and 1179 cm-1 which are stretching modes of oxygen bonded to sulphur and hydrogen. In supported KHSO4 catalyst no clear bands were observed. These results indicated that KHSO4 is highly dispersed on the surface of support SiO2. A 40:1 alcohol to oil ratio at 700C (external) temperature and 5 wt% catalysts loading gave a

The textural properties (Kulkarni et al, 2006) of the catalyst were summarized in Table 3. The surface area of microporous silica of 60-100 mesh particle size has 300m2/g and pore volume 1.15cm2/g and its average pore diameter is 150 A0. After loading 50 wt% of KHSO4 the accessible surface area of silica gel left was only 55.45m2/g and pore volume and average pore diameter were reduced to 0.13cm2/g and 98.9 A0. The reason is attributed to uniform dispersing of KHSO4 on the surface leaving only 55.45m2/s surface and pore plugging of the support. The same reaction when carried out in a similar fashion supporting KHSO4 on alumina surface, the reaction gives very poor or no yield at all. It may be due to too narrow micropores of alumina which cannot accommodate KHSO4 molecule to disperse uniformly to enhance catalytic activity (Kulkarni et al, 2006) although its surface area is higher (260m2/g). Even though alumina is an interesting support it is assumed that the surface basicity could bring about decomposition of KHSO4. It means that particles of

methanol olefin etherification (Goodwin et al,2002) even though the constituent of the oil do possess olefinic bonds .

Fig. 5. 1HNMR (300MHz) of CastMe


Table 1. Physical values of castor oil methyl ester (CastMe) determined along with values of other vegetable oil methyl esters


Table 2. Suggested standard for pure (100%) biodiesel as per ASTM.
