Transacetalization of Solketal: A Greener Route to Bioglycerol‐Based Speciality Chemicals

Abstract

In the present study the potential of solketal transacetalization reaction has been demonstrated as an effective method of synthesis of acetals of glycerol and lipophilic carbonyl compounds (2‐ethylhexanal, n‐decanal, cyclopentanone, cyclohexanone). In solketal transacetalization with 2‐ethylhexanal reaction rate was significantly higher than of direct acetalization of glycerol both with and without a solvent because on the contrary to glycerol solketal is freely miscible with lipophilic compounds. Unlike the direct acetalization, reaction rate increased along with the temperature with no losses in equilibrium conversion. Furthermore, by stripping of by‐product acetone from the reaction zone we have succeeded in increasing the product yield in one‐pot synthesis to 97–98%, so that no further purification is needed. Finally, transacetalization was shown to be catalyzed with solid acids much more efficiently than the direct reaction (the cheap and eco‐friendly montmorillonite K‐10 catalyst was found to be the most active). Based on the regulations revealed, a green atom‐efficient synthetic protocol to obtain higher glycerol acetals and ketals has been proposed.

The Joint Synthesis of 1,2-Propylene Glycol and Isopropyl Alcohol by the Copper-Catalyzed Hydrogenolysis of Solketal

“…6 It also should be noted that except for the free ethylene glycol, its ketal with acetone (2,2-dimethyl-1,3dioxolane, DMD) was detectedtheoretically, in the reaction system the reactions of transacetalization between solketal, TMD, and ethylene glycol could take place. 28,36 It is also important that the selectivity to 1,3-PG was, in general, significantly lower than it usually is in the copper-catalyzed glycerol hydrogenolysis. For example, in the copper-catalyzed glycerol hydrogenolysis, a considerable selectivity to 1,3-PG was detected, which could vary from 0.1 to 10 mol %.…”

Bio-Based Solvents and Gasoline Components from Renewable 2,3-Butanediol and 1,2-Propanediol: Synthesis and Characterization

“…Thus, to obtain the maximum ketal yields lower temperatures are preferred. At the same time, the thermodynamic stability of the cyclic ketal products depends on the molecular structure of the precursor diols and carbonyl compounds, what is supported by the different equilibrium yields obtained either within the reactions of the diol with the different carbonyl compounds [48][49][50] or in transacetalization (transketalization) reactions [51]. In order to determine the thermodynamic equilibrium for the reactions of interest (yielding the corresponding cyclic acetals from 1,2-PD and 2,3-BD) and to evaluate the relation between the reactants molecular structure and the reaction thermodynamic, experimental measurements of the equilibrium constant temperature dependence were conducted.…”

Solventless transacetalization of solketal over Amberlyst catalysts into valuable bio‐based chemicals

“…In a solventless system, reaction of glycerol with long‐chain and/or bulky aldehyde or acetal would be totally hindered by mass transfer due to the high viscosity and hydrophilicity of glycerol, as well as its poor miscibility with the other reagents resulting in low yield. The literature also reported poor reactivity due to coagulated catalyst caused by glycerol, 15 which is normally tackled by use of solvent and high reaction temperature 17–19 . Additional interest in this transformation has been generated by the fact that direct acetalization employing carbonyl compounds produces water as by‐product which has a detrimental effect on catalysts and the overall position of equilibrium.…”