The direct functionalization of the
carbon–carbon double
bonds of castor oil and its derivatives is of major interest to access
biosourced building blocks. In particular, polyol derivatives can
be produced in this way and find application in the field of bio-based
polyesters and polyurethanes. In this study, we described the synthesis
of polyhydroxylated derivatives via a hydrohydroxymethylation reaction
consisting of two consecutive Rh-catalyzed reactions: a hydroformylation
reaction followed by a hydrogenation reaction of formyl groups. A
catalytic system based on Rh(acac)(CO)2 and a trialkylamine
proved to be active both in hydroformylation of carbon–carbon
double bonds and reduction of the resulting aldehydes into primary
alcohols. By optimizing the reaction conditions, yields in alcohols
of 74 and 80% were reached for castor oil and ethyl ricinoleate, respectively.
Electrochemical reduction of pressurized CO2 is proposed as an interesting approach to overcome the main hurdle of the CO2 electrochemical conversion in aqueous solution, its low solubility (ca. 0.033 M), and to achieve good faradaic efficiency in CO using simple sheet silver cathodes and undivided cells, thus lowering the overall costs of the process. The effect on the process of CO2 pressure (1–30 bar), current density, nature of the supporting electrolyte and other operative conditions, such as the surface of the cathode or the mixing rate, was studied to enhance the production of CO. It was shown that pressurized conditions allow to improve drastically the current efficiency of CO (CECO). Furthermore, at relatively high pressure (20 bars), the utilization of simple sheet silver cathodes and silver electrodes with high surfaces gave similar CECO. The stability of the system was monitored for 10 h; it was shown that at a relatively high pressure (15 bar) in aqueous electrolyte of KOH using a simple plate silver cathode a constant current efficiency of CO close to 70% was obtained.
Graphic abstract
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