A review of recent developments on kinetics parameters for glycerol electrochemical conversion – A by-product of biodiesel

Abstract

Solilltkln \'•rilobb Cam:crcritlo.molsl>vcrol Céll\Cefll'll.ioncild«trol)'II: pllor'"'tloemtJI) / I! a Glycerol is a by product produced from biodiesel, fatty acid, soap and bioethanol industries. Today, the value of glycerol is decreasing in the global market due to glycerol surplus, which primarily resulted from the speedy expansion of biodiesel producers around the world. Numerous studies have proposed ways of managing and treating glycerol, as well as converting it into value added compounds. The electrochem ical conversion method is preferred for this transformation due to its simplicity and hence, it is discussed in detail. Additionally, the factors that could affect the process mechanisms and products distribution in the electrochemical process, including electrodes materials, pH of electrolyte, applied potential, current density, temperature and additives are also thoroughly explained. Value added compounds that can be produced from the electrochemical conversion of glycerol include glyceraldehyde, dihydroxyacetone, gly colic acid, glyceric acid, lactic acid, 1 :i. propanediol, 1,3 propanediol, tartronic acid and mesoxalic acid. These compounds are found to have broad applications in cosmetics, pharmaceutical, food and polymer industries are also described. This review will be devoted to a comprehensive overview of the current sce nario in the glycerol electrochemical conversion, the factors affecting the mechanism pathways, reaction rates, product selectivity and yield. Possible outcomes obtained from the process and their benefits to the industries are discussed. The utilization of solid acid catalysts as additives for future studies is also suggested

On the Mechanistic Origins of the pH-Dependency in Au-Catalyzed Glycerol Electro-Oxidation: Insight from First Principles Calculations

“…In alkaline media, GLA has been identified as the main product or reaction intermediate towards more oxygenated species but the formation of DHA cannot be ruled out a priori or based on current experimental data. 1,7,18,19,21,80,81 Figure 6 18,19,29,[40][41][42]82 This clearly indicates that both GLY and OH are simultaneously present on the surface at the experimentally relevant EOG conditions around the onset potential region in > 0.7 V RHE . Therefore, the computational model for Au-catalyzed alkaline EOG should explicitly take into account the influence of OH groups and thus two OH groups, corresponding to 1/6 ML coverage, were added to the Au(111) surface.…”

“…These include e.g., organic acids, aldehydes, and ketones such as glyceric acid (GLA), glyceraldehyde (GLD), dihydroxyacetone (DHA) and so forth. To utilize and upgrade the excess glycerol, various approaches such as thermocatalytic oxidation, 5-10 catalytic decomposition [11][12][13] and hydrodeoxygenation, 14,15 and electrocatalytic oxidation [16][17][18][19][20][21][22][23][24][25][26] have been recently considered.…”

“…To improve selectivity towards the oxygen-rich products and to facilitate milder reaction conditions, the electrocatalytic oxidation of glycerol (EOG) has emerged as a highly competitive alternative. 21,24,26 EOG can be efficiently operated at ambient reaction conditions eliminating the need for additional chemical oxidants such as oxygen or hydrogen peroxide. The electrocatalytic approach also allows finer control of activity and selectivity by modulating the applied electrode potential, electrolyte, and pH.…”

“…Furthermore, solution pH substantially affects the conversion, activity, selectivity, and yield. 5,19,21 In highly alkaline conditions, the oxidation of GLY is considered to take place via the primary hydroxyl group producing glyceraldehyde (GLD). However, GLD is very unstable under these conditions and it quickly oxidizes to the first primary product, glyceric acid (GLA).…”

Glycerol waste to value added products and its potential applications

“…The biodiesel industry produces energy and sells the commodity that lacks the treatment with crude glycerol. Crude glycerol by combustion and uncontrolled burning leads to severe risks to human health due to the formation of unsaturated aldehyde [ 31 ].…”