Review of Non-Thermal Plasma Technology for Hydrogenation of Vegetable Oils and Biodiesel

The hydrogenation of lipid derivative compounds has received much attention as it is one of the key chemical reactions of industrial processes to improve the physical and chemical properties of those compounds such as thermal resistance, cold flow properties, oxidative stability, etc. The principle of hydrogenation of vegetable oil for margarine production relies on the addition of hydrogen to the carbon double bond positions of fatty acid molecules to become a single bond, increasing the saturated fatty acids until the texture becomes semi-solid. The partial addition of hydrogen to biodiesel improves its oxidation resistance. At present, industrial-scale using catalytic hydrogenation of lipid derivative compounds operates under high temperature and high-pressure environments, leading to a high trans-fat content in the products and requiring catalyst separation from the product. Non-thermal plasma (NTP) technology as a green process can be deployed to substitute conventional hydrogenation, on a laboratory scale for the time being, because no catalyst is required and the process can occur at near ambient temperature and low or atmospheric pressure. Moreover, trans-fat formation is several times lower than that of catalytic hydrogenation. The present review article provides more insight into the various types of NTP technology for lipid derivative compounds hydrogenation, including discussions on different experimental setup configurations, parameters affecting plasma hydrogenation, properties of synthesized products, as well as the advantages and drawbacks of environmentally-friendly plasma hydrogenation compared to conventional catalytic hydrogenation.