Ultrasonic radiation

In biodiesel production, the two main reactions involved are the esterification of free fatty acids to biodiesel and the transesterification of triglycerides to biodiesel. The purpose of ultrasonic chemical radiation is to increase catalyst surface activation by homogenizing reactants and catalysts, thereby providing more microchannels for emulsification with reactants, thereby increasing the reaction rate. The use of ultrasonic additives in homogeneous transesterification reactions is the most common process for producing biodiesel. It does not affect the thermodynamic equilibrium of the reaction but can improve the mass transfer performance and thus the reaction rate to achieve the same chemistry in the shortest time. reaction. This reaction process relies on the flow and acoustic energy provided by the sonochemical radiation produced by the passage of sound waves. The reaction mechanism of sound waves involves sine waves, which provide positive and negative pressure to create cavitation bubbles and release energy. In biodiesel production, by combining ultrasonic energy input with other reaction processes, transesterification and esterification reactions can be significantly improved to produce high-quality biodiesel at low cost and in less time.

Supercritical

Supercritical transesterification (SCT) is a promising alternative to traditional processes for the production of biodiesel. SCT provides a catalyst-free process with faster reaction times, allowing direct triglyceride transesterification and free fatty acid esterification, with higher final product purity. Furthermore, this catalyst-free reaction provides better phase solubility and lower mass transfer limitations. In the SCT process, feedstock and alcohol are fed into the reactor, where they are subjected to temperatures and pressures that exceed the alcohol's critical point. Under these conditions, the physical properties of alcohol change, such as diffusivity, density, viscosity, etc. Under high temperature and high pressure, the fluid (alcohol) enters the supercritical region. In this region, the fluid has the properties of both gas and liquid, presenting a non-condensable fluid with a density between gaseous and liquid states. This fluid has reduced viscosity and increased mass diffusivity, allowing greater mass transfer properties. Under supercritical conditions, it can be better dissolved in alcohol to form a uniform phase. The main parameters affecting the supercritical transesterification reaction are temperature, pressure, molar ratio of solvent to oil and reaction time.