Selective Electrooxidation of Glycerol Into Value-Added Chemicals: A Short Overview

Abstract

A comprehensive overview of the catalysts developed for the electrooxidation of glycerol with the aim of producing selectively value-added compounds is proposed in the present contribution. By presenting the main results reported in the literature on glycerol electrooxidation in acidic and alkaline media, using different kinds of catalytic materials (monometallic catalysts based on platinum group metals and non-noble metals, multimetallic alloys, or modification of surfaces by adatoms, etc.) and under different experimental conditions, some general trends concerning the effects of catalyst composition and structure, of reaction medium and of the electrode potential to enhance the activity for the glycerol oxidation reaction and of the selectivity toward a unique value-added product will be presented and discussed. The objective is to provide a guideline for the development of electrochemical systems which allow performing the electrooxidation of glycerol at the rate and selectivity as high as possible.

Recent Advances in Glycerol Catalytic Valorization: A Review

“…Special attention must be paid to polyoxomethalates, which have exhibited an interesting activity under mild conditions (60 • C), even with crude glycerol (Table 6), and could be supported as a catalyst modifier [190]. Another emerging option for performing room temperature oxidation processes is electrocatalysis due to its effective activity and selectivity to a specific compound, produced by tuning the structure of the electrocatalyst and/or the electrode potential [202][203][204][205]. Even though base addition is environmentally undesirable, in this process, whilst an inorganic base can act as an electrolyte for the reaction, other buffers can be applied [205].…”

Glycerol Electro-Oxidation in Alkaline Media and Alkaline Direct Glycerol Fuel Cells

“…The reaction pathway for the glycerol electrooxidation in alkaline medium with C-C bond cleavage and in the absence of the oxidation of the secondary OH is shown in Figure 1 [2,10,[19][20][21][22][23][24]. Various reaction pathways were proposed for GLY oxidation to C2/C1 compounds (see Figure 1): in most of these pathways, GLA is the C3 compound that undergoes the breaking of one of two C-C bonds [10,[19][20][21][22][23], followed by TA [2,20,24], MOA [2,19] and also GLY [2], to form C2 and C1 compounds, while C2 compounds, such as GA [20], Glyoxylate (GOA) [21,24] and OA [24], undergo C-C bond cleavage to form FA and carbonate. Sandrini et al [25] reported that the GOR mechanism on Pt begins with glycerol dehydrogenation to alkoxydes followed by the formation of aldehyde intermediates adsorbed as η 1 (O)-aldehyde and η 1 (C)-acyl geometry, respectively.…”

“…Glycerol oxidation on Pd lead to a selectivity towards GALD and GLA at low potentials, and then towards HPA, dicarboxylates and products derived by C-C bond cleavage (C2 and C1 compounds) at higher potentials [18,26]. It has to be denoted that the structure and morphology of the catalysts can play a role for the selectivity: GLA and TA were obtained on Pd/C, and HPA on Pd nanofoam [2].…”

“…Representation of the possible pathways of GLY electrooxidation on precious metal and precious metal-based catalysts in an alkaline medium with C-C bond cleavage and in the absence of the oxidation of the secondary OH, based to the pathways reported in various schemes [2,10,[19][20][21][22][23][24].…”

“…Thus, a serious problem in biodiesel production is the consequent production of glycerol as a by-product with a low commercial value. Different methods have been developed to transform glycerol into value-added chemicals [2,3]. Among the products of glycerol oxidation, almost all C3 oxidation compounds are of high commercial value.…”