Recent Advances in Glycerol Catalytic Valorization: A Review

Abstract

Once a biorefinery is ready to operate, the main processed materials need to be completely evaluated in terms of many different factors, including disposal regulations, technological limitations of installation, the market, and other societal considerations. In biorefinery, glycerol is the main by-product, representing around 10% of biodiesel production. In the last few decades, the large-scale production of biodiesel and glycerol has promoted research on a wide range of strategies in an attempt to valorize this by-product, with its transformation into added value chemicals being the strategy that exhibits the most promising route. Among them, C3 compounds obtained from routes such as hydrogenation, oxidation, esterification, etc. represent an alternative to petroleum-based routes for chemicals such as acrolein, propanediols, or carboxylic acids of interest for the polymer industry. Another widely studied and developed strategy includes processes such as reforming or pyrolysis for energy, clean fuels, and materials such as activated carbon. This review covers recent advances in catalysts used in the most promising strategies considering both chemicals and energy or fuel obtention. Due to the large variety in biorefinery industries, several potential emergent valorization routes are briefly summarized.

Catalytic Production of Glycolic Acid from Glycerol Oxidation: An Optimization Using Response Surface Methodology

“…A preliminary benchmark test was carried out with the initial conditions that corresponded to those evaluated in previous investigations carried out in our laboratory [5]. These conditions corresponded to a 0.3 M glycerol solution, a reaction temperature of 60 °C, 5 bar of oxygen, 0.5 g of catalyst, and a NaOH/glycerol molar ratio of 4.…”

“…Different glycerol valorization pathways have been studied to generate alternative energy carriers and to obtain high-value-added compounds of interest in different industrial applications, such as food, cosmetics, paints, and pharmaceuticals, among others [1,5].…”

“…The various identified routes to generate energy are combustion, pyrolysis, and hydrogen production (through reforming and/or partial oxidation). Combustion is an inexpensive process and is carried out without a catalyst, but glycerol presents a low heating value (18 MJ/kg) [5] and the production of CO2 is an environmental disadvantage. On the other hand, pyrolysis requires catalysts, from which H2/syngas, aldehydes, ketones, and aromatics of low molecular weight can be obtained.…”

Challenges & Opportunities on Catalytic Conversion of Glycerol to Value Added Chemicals

“…Earlier before, Corma reported that glyc-Figure 3. Reaction Mechanism for production of 1,2-Propanediol (1,2-PDO) [94]. erol dehydration at temperature 350 °C and 500 °C takes place in two pathways and declared that 66% will be directed to the formation of acetol and 33% towards acrolein.…”

Flame Pyrolysis Synthesis of Mixed Oxides for Glycerol Steam Reforming

“…Furthermore, the latter market is unable to sustain the increasing availability of glycerol. The development of glycerol transformation routes that have a large potential volume of production and do not require heavy purification of the feed is envisaged and, among these, the production of hydrogen by steam reforming appears promising [ 11 ].…”