Solketal Production in a Fixed Bed Adsorptive Reactor through the Ketalization of Glycerol

Abstract

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.

Continuous Valorization of Glycerol into Solketal: From the Fixed-Bed Adsorptive Reactor to the Simulated Moving-Bed Reactor

“…7 Despite solketal's most common use as a solvent in resins, paints coatings, and cleaning agents, the most studied and most promising solketal application is as a fuel additive due to the capability of enhancing fuel octane number and oxidation stability, diminishing particle emissions and gum formation, and enhancing liquid properties at low temperatures. 4,12 This last property is what makes solketal a possible jet fuel additive. The aviation sector is one of the least developed in using renewable energy (less than 0.01% in 2018) 13 since it is very restrictive to alternative fuels for safety reasons and due to not having interest in redesigning engines.…”

“…1−3 The main disadvantage of this industry is the massive amount of lowpurity glycerol generated as a byproduct at a rate of 10−12% (w/w) and purity of 50−55%. 4 To alleviate the gut of crude glycerol in the market, there has been an extensive search for alternative processes able to absorb this compound. Solketal is derived from glycerol ketalization with acetone (Figure 1) in the presence of an acid catalyst.…”

Improving the Performance of a Simulated Moving Bed Reactor for the Synthesis of Solketal by Implementing Multifeed Strategy

“…The adsorption equilibrium isotherms for acetone, glycerol, solketal, water, and ethanol over Amberlyst-35, at 313 K, were determined in a previously published work through a frontal analysis methodology with binary nonreactive mixtures composed by ethanol and one of the reactants or products. 53 The results were described through a competitive multicomponent Langmuir adsorption model (eq 1). The estimated monolayer capacities, Q i , and equilibrium constants, K i , are presented in Table 1.…”

“…Multicomponent Langmuir Adsorption Equilibrium Parameters of the Species Involved in the Synthesis of Solketal in Amberlyst-35 at 313 K53 …”

Process Intensification in Chemical Reaction Engineering

“…For a reversible reaction, the chromatographic separation permits working over the chemical equilibrium, offering different advantages compared with classical packed bed reactors: (i) conversion enhancement, overcoming equilibrium limitations; (ii) separation of the products; and (iii) enhancement of the selectivity of complex reaction networks [51,52]. This system is well suited for esterification or ketalization reactions, where water must be removed on-stream to achieve full conversion of the reactant [52][53][54][55]. Its industrial application is unrealistic, as it is in effect a semi-batch system; therefore, the analogy of the simulated moving bed reactor was developed, where the feed/extract/raffinate position of a packed bed is switched automatically in different positions of the packed bed in order to simulate the motion of the catalytic bed with the operation time [56,57], leading to a continuous operation.…”