| Summary: |
The main goal of the present project is the implementation of a process for the production of Solketal in a supercritical simulated moving bed reactor (SCSMBR), using as raw material the glycerol obtained as by-product during the production of biodiesels.
The valorisation of glycerol through its transformation into Solketal has been presented as one of the most promising solutions to absorb the glycerol surplus in the market resulting from the unrelenting growth of biodiesel production. This ketal, besides its traditional applications in the perfume, flavourings and pharmaceuticals industries, has presented interesting results when applied as a green fuel additive, particularly, due to its ability to reduce particulate emissions.
The Solketal synthesis can be performed through the reaction between glycerol and acetone, using an acid catalyst. This reaction is thermodynamically limited and this limitation can only be overcome by proceeding to the ketalization in a multifunctional, by means of the continuous removal of one of the products from the reaction medium. For this system, reactive distillation does not represent an attractive solution, due to restrictions in the compounds volatilities, and the lack of highly selective membranes hinders the application of membrane reactors. In this context, the simulated moving bed reactor (SMBR) that has proven in previous investigations, to be highly effective in acetalization reactions, was the selected technology. This technology, compared with conventional chromatographic reactors, takes advantage of a continuous counter-current operation mode, leading to high productivity values, since the equivalent height of a theoretical plate, measure of the efficiency of a chromatographic column, is about one third of the observed in batch processes. Simultaneously, SMBR has also demonstrated the capability to significantly reduce the consumption of desorbent and, consequently, the energy costs associated with its recovery.
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Summary
The main goal of the present project is the implementation of a process for the production of Solketal in a supercritical simulated moving bed reactor (SCSMBR), using as raw material the glycerol obtained as by-product during the production of biodiesels.
The valorisation of glycerol through its transformation into Solketal has been presented as one of the most promising solutions to absorb the glycerol surplus in the market resulting from the unrelenting growth of biodiesel production. This ketal, besides its traditional applications in the perfume, flavourings and pharmaceuticals industries, has presented interesting results when applied as a green fuel additive, particularly, due to its ability to reduce particulate emissions.
The Solketal synthesis can be performed through the reaction between glycerol and acetone, using an acid catalyst. This reaction is thermodynamically limited and this limitation can only be overcome by proceeding to the ketalization in a multifunctional, by means of the continuous removal of one of the products from the reaction medium. For this system, reactive distillation does not represent an attractive solution, due to restrictions in the compounds volatilities, and the lack of highly selective membranes hinders the application of membrane reactors. In this context, the simulated moving bed reactor (SMBR) that has proven in previous investigations, to be highly effective in acetalization reactions, was the selected technology. This technology, compared with conventional chromatographic reactors, takes advantage of a continuous counter-current operation mode, leading to high productivity values, since the equivalent height of a theoretical plate, measure of the efficiency of a chromatographic column, is about one third of the observed in batch processes. Simultaneously, SMBR has also demonstrated the capability to significantly reduce the consumption of desorbent and, consequently, the energy costs associated with its recovery.
Nevertheless, the performance of this technology can be further improved by using supercritical carbon dioxide as desorbent, as it will have a direct impact in the reduction of the outlet streams separation costs, since at these operating conditions it can be accomplished in a single unit by promoting the carbon dioxide depressurization and its change into the gaseous phase, collecting the purified target product in the liquid phase, and, at the same time, the use of this desorbent will enable a significant decrease of the mass transfer resistances, particularly noticeable in systems involving glycerol due to its physicochemical properties, since the diffusion coefficients in supercritical fluids are one to two orders of magnitude higher than those observed in liquids.
The synthesis of fuel additives by SCSMBR is an extremely innovative approach that will require an intense stage of experimental validation that can only be achieved through the construction and operation of a laboratory-scale unit, as proposed in this project.
The research team that will lead this project has developed an extensive know-how on the production of green fuel additives over the years, having successfully synthesized acetals such as dimethylacetal, diethylacetal, dibutyl acetal and glycerol ethyl acetal by SMBR (research supported by FCT), works internationally recognized with the 1st prize in the "Solvay Ideas Challenge 2003" and in the "IChemE Awards for Innovation and Excellence 2008" (the ABB Global Consulting Award for Sustainable technology) . Additionally, the knowledge generated by this team in p |