**3. Fatty acid alkylesters production assisted by radio frequency**

Radio waves, whose wavelengths range from more than 104 m to about 0.1 m, are the result of charges accelerating through conducting wires. They are generated by such electronic devices as LC oscillators and are used in radio and television communication systems (Serway and Jewett, 2004).

Radio frequency (RF) heating is a promising dielectric heating technology which provides fast heat generation through a direct interaction between an RF electromagnetic field and the object being heated (Piyasena et al., 2003). Compared to microwave heating, a popular

1:27

1:20

Some examples about the obtaining of biodiesel making a response surface methodology (RSM) was used to analyze the influence of the process variables (oil to methanol ratio, catalyst concentration, and reaction time) on the fatty acid methyl ester conversion, are shown in Table 3, where is confirmed that the microwave energy has a significant effect on

> **Oil to alcohol molar ratio**

(wt/vol)

33.83% (w/w) 33.4% (w/w)

Table 3. Recent examples of optimization of reaction conditions a for production of biodiesel

Radio waves, whose wavelengths range from more than 104 m to about 0.1 m, are the result of charges accelerating through conducting wires. They are generated by such electronic devices as LC oscillators and are used in radio and television communication systems

Radio frequency (RF) heating is a promising dielectric heating technology which provides fast heat generation through a direct interaction between an RF electromagnetic field and the object being heated (Piyasena et al., 2003). Compared to microwave heating, a popular

2.5 EtOH 1:9 Synthos 3000-Anton

Domestic MW 1000W 60C, 1h 75C, 1h 105C, 1h 90C, 1h 115C, 1h

Domestic MW 1000W 60C, 3h 75C, 3h 105C, 3h 90C, 3h 115C, 3h

800W 70C, 5 min

**Microwave reaction conditions** 

Domestic MW 800W 60C, 4min

Domestic MW 800W 60C, 190s 60C, 150s

Paar. 1400W. 30C, 15min

99.9 99.87 88.39 83.19 81.63

8.63 49.51 67.59 52.00 54.59 (Mazo and Rios, 2010a)

(Mazo and Rios, 2010b)

97.4 (Suppalakpanya et al., 2010a)

> **Ester conversion (%)**

45.2 22.9

87.4 89.9

64.18 (Patil et al., 2011)

**Ref.** 

(Nogueira et al., 2010)

(Venkatesh et al., 2011)

IsoprOH IsoBuOH 2-BuOH IsopentOH

IsoprOH IsoBuOH 2-BuOH IsopentOH

Palm KOH 1.5 EtOH 1:4 Domestic MW

**2.3 Optimization production biodiesel under MW irradiation** 

**Catalyst amount (%wt)** 

3.73 1.33

from various feedstocks using response surface methodology

**Alcohol**

MeOH MeOH

**3. Fatty acid alkylesters production assisted by radio frequency** 

Palm NaOCH3 0.9 MeOH

Palm K2CO3 3.0 MeOH

Table 2. Microwave assisted transesterification.

esterification and transesterification reactions.

Dry algae KOH 2.0 MeOH 1:12

**Oil Catalyst** 

Macauba Novozyme 435

Pongamia pinnata

Lipozyme IM

Esterification: H2SO4

KOH

(Serway and Jewett, 2004).

Transesterification:

dielectric heating technology, RF heating systems are simpler to configure and have a higher conversion efficiency of electricity to electromagnetic power (Wang et al., 2003). Moreover, RF energy has deeper penetration into a wide array of materials than microwave energy, increasing feasibility of RF heating for industrial scale applications.

Very few publications have been obtained by this alternative heating method, which use a RF heating apparatus (SO6B; Strayfield Fastran, UK). The distance between the two electrodes was fixed at 15 cm. A 150-mL conical flask coupled with a water-cooling reflux condenser was used as a reactor. Schematic diagram and photograph are shown in Fig. 1.

Fig. 1. a) Schematic diagram of RF heating apparatus (Lui et al., 2010) and b) Photograph of RF heating apparatus (Lui et al., 2008).

Applications to obtaining biodiese using different oils, reaction conditions and catalysts are described below:
