With the global biodiesel production growing as never seen before, encouraged by government policies, fiscal incentives, and emissions laws to control air pollution, there has been the collateral effect of generating massive amounts of crude glycerol, a by-product from the biodiesel industry. The positive effect of minimizing CO2 emissions using biofuels is jeopardized by the fact that the waste generated by this industry represents an enormous environmental disadvantage. The strategy of viewing “waste as a resource” led the scientific community to propose numerous processes that use glycerol as raw material. Solketal, the product of the reaction of glycerol and acetone, stands out as a promising fuel additive capable of enhancing fuel octane number and oxidation stability, diminishing particle emissions and gum formation, and enhancing properties at low temperatures. The production of this chemical can rely on several of the Green Chemistry principles, besides fitting the Circular Economy Model, once it can be reinserted in the biofuel production chain. This paper reviews the recent advances in solketal production, focusing on continuous production processes and on Process Intensification strategies. The performance of different catalysts under various operational conditions is summarized and the proposed industrial solketal production processes are compared.

Biodiesel production has been generating increasing amounts of glycerol as byproduct, therefore effective strategies are required to convert it into valuable chemicals to enhance the sustainability of the biodiesel production chain. In this work, solketal was synthesized by reacting glycerol with acetone (in the presence of ethanol) in a fixed bed adsorptive reactor packed with Amberlyst-35. Additionally, adsorption equilibrium isotherms for all the compounds of the process were determined at 313 K through a frontal analysis methodology, and the results were fitted through a competitive multicomponent Langmuir model. It was possible to conclude that water was the most adsorbed compound while solketal was the least. The potential for implementation of sorptionenhanced reactive processes was experimentally demonstrated since the conversion values transitorily attained during the solketal synthesis process were approximately 30% above the equilibrium values. Finally, all the experimental results were accompanied by numerical simulation using a comprehensive mathematical model that was able to accurately describe the results.

With the unprecedent global biodiesel production growth, massive amounts of crude glycerol have been generated as a byproduct of this industry. Solketal, the reaction product of glycerol and acetone, stands out as a promising jet fuel additive due to its antifreezing property. Solketal production via glycerol ketalization is thermodynamically limited, a problem surpassed by sorption-enhanced strategies. The fixed-bed column was used to determine the adsorption equilibrium parameters for 303 and 323 K through the frontal analysis methodology, and the experimental data for 303, 313, and 323 K were simultaneously fitted to the Langmuir adsorption isotherm. This procedure endows the estimated parameters with notable reliability and robustness. The study on the dynamic behavior of a fixed-bed adsorptive reactor was performed to assess the optimal reaction temperature and its influence on the physicochemical phenomena controlling the process. Solketal synthesis on a larger scale was studied through the fixed-bed model extension to the simulated moving-bed reactor, supporting the conclusion that 303 K is the best operational temperature, as a larger reactive separation region is obtained, with the additional benefit of operating under milder conditions.

The simulated moving bed reactor (SMBR) is a sorption-enhanced reactive technology that has been successfully applied to the synthesis of several organic compounds, due to its ability to overcome the thermodynamic limitations associated with reversible reactions. This work proposes the implementation of an innovative multifeed strategy that can considerably improve the performance of the SMBR, particularly for systems in which none of the reactants can be used as desorbent. A systematic design methodology based on the so-called "reactive-separation volumes" is developed and applied for the first time, and the results for the multifeed SMBR are compared to those obtained in a conventional SMBR. Due to its industrial relevance, the synthesis of solketal through the ketalization of glycerol and acetone was selected as a case study. The results demonstrated that the new SMBR operating mode can produce solketal with a purity of 97%, reaching a productivity of over 10 kg Solk L Ads −1 day −1 , while for a conventional unit this is barely possible. Moreover, it led to a reduction in desorbent consumption of 85%.