Alcohols and alcohols mixtures as liquid biofuels: A review of dielectric properties

Oils, pure alcohols and alcohols mixtures have a complicated dielectric behavior. The strong electric field of the ions affects intensively the molecular interaction of solvents. Microwave heating resides in the characterization of dielectric properties. Classified as biodiesel precursors, advances in microwave technology of alcohols have a significant potential in improving the biodiesel production. In this context, this review provides basic knowledge on the dielectric properties theory and the heating phenomenon in the microwave fields. The main goal of the paper is to provide an organized summary of the main chemical and physical properties of alcohols and links them to their corresponding research studies dealing with dielectric properties measurements. The review covers the dielectric constant and loss factor variations observed with temperature and frequency, the relaxation time and the tangent loss of various mixtures found in the literature. Moreover, the review provides an updated database for organic solvents and alcohols to account for their abilities to couple in microwave radiation. The aim of the work is building a rigid bridge between chemico-physical and dielectric properties so it can make an essential step towards improving biofuels production. This review opens new perspectives for further investigation of dielectric properties that are interesting for microwave heating studies.