8 Oleochemistry Products
213
The transformation of glycerol to different valuable derivatives by conversion of
crude glycerol (CG), which is a waste by-product of biodiesel production has been
rarely reported because of the CG impurity. The direct etherification of glycerol
has been extensively explored to synthesize polyglycerols which are known as nonionic surfactants that can stabilize suspensions and emulsions. Thus, polyglycerols
have various biomedical applications and are widely used as cosmetic ingredients,
polymer additives, nutritional additives and lubricants [110].
Glycerol has the potential to become an available and sustainable raw material,
due to its low cost and intrinsic properties including having a reactivity that can
be increased by transformation into glycerol carbonate by heterocyclization. The
oligomerization of glycerol carbonate, assisted by the glycerol, results in the production of polyhydroxylated oligomers rich in linear carbonate groups. The polar
moieties of these oligomers were supplied by glycerol and glycerol carbonate rather
than ethylene oxide as in most commercial surfactants. The insertion of linear carbonate groups into the glycerol-based skeleton rendered the oligomers amphiphilic,
resulting in a decrease in air/water surface tension. The polar head is constituted of
homo-oligomers (oligoglycerol and/or oligocarbonate) and hetero-oligomers (oligo(glycerol-glycerol carbonate)). Coprah oligoesters had the best surfactant properties, outperforming molecules of fossil origin. The oligo-(glycerol carbonateglycerol ether) with relatively low molecular weights showed properties of relatively high-molecular-weight molecules, and constitute a viable ‘green’ alternative
to ethoxylated surfactants [87].
Fully bio-sourced lauroyl oligoester surfactants, based on poly(glycerolsuccinate) as polar head group with controllable sizes and topologies were prepared without solvent nor catalyst. The alkyl chain was either derived from lauric
acid or from glycerol α-monolaurate. The oligoester surfactants were characterized
by quantitative 13C NMR, acid values and size exclusion chromatography. Their
surface activity, foamability, foam stability, wetting power, solubilization properties and biodegradability were investigated proving their potential use in a wide
set of applications in replacement of petrochemical surfactants. Relative impacts
of the succinic acid/glycerol monomer ratios and of the strategies of synthesis on
the physico-chemical behaviour, on the biodegradability and on the stability of the
lauroyl poly(glycerol-succinate) surfactants were underlined [3].
Fatty acid soaps
Usually fats and oils are hydrolyzed to glycerol and fatty acid. Fatty acids can be
purified by distillation in a specific fraction before the saponification reaction. Soaps
of fatty acids are subsequently produced by the neutralization with various bases,
resulting in a fatty acid soap with different positively charged counterions, for example, Na, K, NH 4 . Unlike fatty acids, soaps are generally water soluble and display
strong surfactant properties. The solubility and surface-active properties can be tuned
by the nature and combination of fatty acids, counterions and the extent of polarization. Fatty acid methyl ester salts, synthesized from renewable resources, are
an example of green surfactants used in eco-friendly washing detergents because
of their excellent detergent properties, biodegradability and enzyme stability [207].
213
The transformation of glycerol to different valuable derivatives by conversion of
crude glycerol (CG), which is a waste by-product of biodiesel production has been
rarely reported because of the CG impurity. The direct etherification of glycerol
has been extensively explored to synthesize polyglycerols which are known as nonionic surfactants that can stabilize suspensions and emulsions. Thus, polyglycerols
have various biomedical applications and are widely used as cosmetic ingredients,
polymer additives, nutritional additives and lubricants [110].
Glycerol has the potential to become an available and sustainable raw material,
due to its low cost and intrinsic properties including having a reactivity that can
be increased by transformation into glycerol carbonate by heterocyclization. The
oligomerization of glycerol carbonate, assisted by the glycerol, results in the production of polyhydroxylated oligomers rich in linear carbonate groups. The polar
moieties of these oligomers were supplied by glycerol and glycerol carbonate rather
than ethylene oxide as in most commercial surfactants. The insertion of linear carbonate groups into the glycerol-based skeleton rendered the oligomers amphiphilic,
resulting in a decrease in air/water surface tension. The polar head is constituted of
homo-oligomers (oligoglycerol and/or oligocarbonate) and hetero-oligomers (oligo(glycerol-glycerol carbonate)). Coprah oligoesters had the best surfactant properties, outperforming molecules of fossil origin. The oligo-(glycerol carbonateglycerol ether) with relatively low molecular weights showed properties of relatively high-molecular-weight molecules, and constitute a viable ‘green’ alternative
to ethoxylated surfactants [87].
Fully bio-sourced lauroyl oligoester surfactants, based on poly(glycerolsuccinate) as polar head group with controllable sizes and topologies were prepared without solvent nor catalyst. The alkyl chain was either derived from lauric
acid or from glycerol α-monolaurate. The oligoester surfactants were characterized
by quantitative 13C NMR, acid values and size exclusion chromatography. Their
surface activity, foamability, foam stability, wetting power, solubilization properties and biodegradability were investigated proving their potential use in a wide
set of applications in replacement of petrochemical surfactants. Relative impacts
of the succinic acid/glycerol monomer ratios and of the strategies of synthesis on
the physico-chemical behaviour, on the biodegradability and on the stability of the
lauroyl poly(glycerol-succinate) surfactants were underlined [3].
Fatty acid soaps
Usually fats and oils are hydrolyzed to glycerol and fatty acid. Fatty acids can be
purified by distillation in a specific fraction before the saponification reaction. Soaps
of fatty acids are subsequently produced by the neutralization with various bases,
resulting in a fatty acid soap with different positively charged counterions, for example, Na, K, NH 4 . Unlike fatty acids, soaps are generally water soluble and display
strong surfactant properties. The solubility and surface-active properties can be tuned
by the nature and combination of fatty acids, counterions and the extent of polarization. Fatty acid methyl ester salts, synthesized from renewable resources, are
an example of green surfactants used in eco-friendly washing detergents because
of their excellent detergent properties, biodegradability and enzyme stability [207].