Glycerol valorization: conversion to lactic acid by heterogeneous catalysis and separation by ion exchange chromatography

Abstract

The consumption and production of biodiesel has grown dramatically in recent decades, motivated by a strong interest in renewable energy. This has generated a surplus of its main by‐product, glycerol. Several catalytic processes have been proposed to generate alternatives for using this excess glycerol, mainly focusing on its transformation into high value‐added chemical products. Various products, ranging from syngas to organic acids, such as acrylic or lactic acid, along with 1,2‐propanediol, 1,3‐propanediol, glycerol ethers or even polymers, have been produced starting from glycerol. Among this multitude of possibilities, the production of lactic acid is one of the most interesting alternatives to valorize glycerol, because of the wide range of applications described for this organic acid. This review focuses on recent studies dealing with the catalytic conversion of glycerol to lactic acid, using different heterogeneous catalysts, and evaluates the factors influencing the oxidation catalytic process and the proposed reaction mechanisms. Finally, recent studies on the separation and purification of lactic acid using ion exchange chromatography resins are also reported. © 2019 Society of Chemical Industry and John Wiley & Sons, Ltd

Recent Advances on Purification of Lactic Acid

“…[7] Chemical synthesis from petroleum always results in a racemic mixture of DL-LA, which demands the use of toxic additives and multiple energy-intensive procedures. [13] According to the strains used and fermentation conditions, D (À ) or L (+)-LA are commonly produced separately or in a mixture form ( Figure 3). [14] Biological fermentation can be divided into Rhizopus fermentation and bacterial fermentation.…”

“…[8] Compared with the biological fermentation method, the chemical synthesis route is based on lactonitrile in the petrochemical industry (Figure 4(a)). [13] The acetaldehyde converted from petroleum first reacts with hydrogen cyanide (HCN) to obtain lactonitrile under high pressure. Crude lactonitrile is then purified by distillation and subsequently hydrolyzed to LA.…”

“…[18,19] Transformation from glycerol is one of the most attractive approaches (Scheme 2). [13] Conversion of glycerol can occur easily at elevated temperature (> 260°C) in alkaline medium (Figure 4(b)). [20] As alternative processes, catalytic dehydrogenation and oxidation of glycerol can be achieved over various metal catalysts, such as Pt, Pd, Au, Cu, Ni, and Co. [21][22][23][24] Catalyst metal leaching is a big challenge for LA production, because LA has a unique leaching performance and mineral dissolution ability.…”

Glycerol Selective Oxidation to Lactic Acid over AuPt Nanoparticles; Enhancing Reaction Selectivity and Understanding by Support Modification

“…Initially, emphasis was placed on the design and synthesis of heterogeneous catalysts, which could selectively oxidise glycerol to glyceric (GLA) and tartronic acid (TA), avoiding any C−C cleavage, which have previously been associated with the formation of H 2 O 2 during the reaction . Recently however, much more attention has been given to the formation of lactic acid (LA) from glycerol . LA has a number of different applications, perhaps the most notable is its use as a feedstock for the formation of polylactic acid.…”

Valorization of Glycerol through the Enzymatic Synthesis of Acylglycerides with High Nutritional Value

“…Furthermore, glycerol is the most important byproduct of the biodiesel industry and represents 10% by weight with respect to the biofuel produced [1]. Due to the global growth in the use of biofuels, the saturation of the market for this alcohol has taken place, and world production of three million tons was estimated for the year 2020, while the demand will be only 500,000 tons [2].…”