Combined Enabling Technologies for Biodiesel Production in Flow Processes

Abstract

Alternative energy sources and fuels have been investigated to indemnify the higher demand of natural fuels that requires very long time for their formation. In the last 40 years several renewable energy sources have been developed. In this context biodiesel play an important role because its high heating values nearly equivalent to diesel fuels and its low environmental impact. The sustainability of the process is strongly related to the type of oil source and to the overall energy consumption. The aim of this chapter is to highlight the synergistic effects on process efficiency by combining different activation techniques such as microwaves, ultrasound, hydrodynamic cavitation and high-shear mixing. A big effort has been done in the search of new highly efficient reactors to produce biodiesel saving time and energy. Inefficient mass transfer is one of the main limitations in biphasic heterogeneous reactions such as transesterification. Although many types of vigorous mixing have been investigated to address this requirement, most of them suffer of high energy demand. The dielectric heating has been proved to dramatically enhance transesterification reaction because the excellent heat transfer if compared with conventional methods. Thanks to an optimal mass/heat transfer a full triglycerides conversion to methyl esters can be achieved in flow reactors in a very short time either in continuous or semi-continuous mode. Moreover, in accordance with international specifications and analytical ASTM standards, very fast treatments may produce a high-quality biodiesel. The high efficiency and the low energy consumption enable an easy scale up of the process.

Microwave, ultrasound and ball mill procedures for bio-waste valorisation

“…Highthroughput applications of enabling technologies would entail the use of flow US 65 and MW flow-reactors. 66…”

Harnessing cavitational effects for green process intensification

“…While several renewable energy sources have been developed over the last 40 years, biodiesel is able to play a particularly important role as its high heating values are nearly equivalent to those of diesel fuels and it has a low environmental impact. The sustainability of the biodiesel preparation process is closely related to the type of oil source used and to overall energy consumption [72]. Biodiesel has unique properties, including biodegradability, renewability and non-toxicity.…”

“…Non-edible oils, such as nagchampa, karanja, jatropha, neem and cotton, and waste sources, such as waste vegetable oil and waste-cooking oil (WCO), are considered to be good feedstocks for biodiesel synthesis [30,74], which involves the catalytic conversion of oils to glycerol and acid alkyl ester using methanol. However, this process has an inherent drawback; mass transfer resistance results in a lower reaction rate, with high energy, time and production costs [30,72,73]. Intensification technologies, such as microwave, UC and HC reactors, have been widely used to eliminate the mass transfer resistance caused by the immiscible reactants.…”

Biodiesel production process intensification using a rotor-stator type generator of hydrodynamic cavitation

“…With the aim of reducing energy consumption in biodiesel production, we have thoroughly investigated the effect of cavitation on the transesterification reaction of triglycerides over the last few years [16]. We have also investigated combinations of different enabling technologies both in batch and in flow processes [17][18][19]. Hybrid processes for biodiesel production that function upon a combination of sonochemical reactors and other intensification techniques have been thoroughly reviewed [20] as have continuous flow technologies [21].…”