Biodiesel production from Tung oil and blended oil via ultrasonic transesterification process

The effects of ultrasonic irradiation time (tUS) on the transesterification yield (YF) of biodiesel from Tung (Vernicia fordii) and blended oils with CH3OH and KOH, and on some properties of biodiesel such as acid value (AV), iodine value (IV), kinematic viscosity (KV), density and cold filter plugging point (CFPP) were investigated. The blended oil is consisted of 20, 50 and 30% of Tung, canola and palm oils, respectively. The molar ratio of methanol to oil is 6:1 and the catalyst concentration is 1 wt.%. Temperature and ultrasonic frequency were kept at 20–30 °C and 25 kHz, respectively. The tUS was set in the range of 1–30 min. The results showed that YF reaches high value of 87–91% for Tung oil as tUS ≥ 5 min, while of about 92–94% for blended oil as tUS ≥ 1 min. At tUS = 10 min, the properties of biodiesel produced from Tung oil are with AV of 0.11 mg KOH/g, IV of 159.36 mg I2/100 g, KV of 9.17 mm2/s, density of 905 kg/m3 and CFPP of −16 °C, while those from blended oil are with AV of 0.11 mg KOH/g, IV of 120.35 mg I2/100 g, KV of 5.54 mm2/s, density of 887 kg/m3 and CFPP of −5 °C. Comparing these values with the ASTM-D6751 standards with AV < 0.5 mg KOH/g, KV = 1.9–6 mm2/s and density = 860–900 kg/m3 pointed out that the Tung oil should be blended with other oils in order to produce biodiesel satisfying the biodiesel standards. Moreover, the results indicated that a certain enough time, say 5 min, is needed to provide sufficient cavity heating and mixing via ultrasonic wave ensuring good properties of biodiesel produced. The KV of biodiesel using blended oil decreases from 6.26 mm2/s at tUS = 1 min to 5.54 mm2/s at tUS = 5 min, thus meeting the ASTM-D6751 value of 1.9–6.0 mm2/s. The information obtained in this study is useful for the proper use of Tung oil in conjunction with other edible oils for the production of biodiesel with satisfactory qualities and the rational design and operation of ultrasonically catalytic transesterification process.