## 4 Solketal Synthesis
### Recent Advances on the Continuous Process
A similar system was proposed by Li et al., followed by optimization in Aspen Plus software and comparison with a novel equipment, the reactive dividing-wall column (RDWC). The experimental parameters and results are shown in Table 4. As for the optimization results considering the energy consumption (reboiler duty), it was found that the ideal scenario is nine theoretical reaction stages, five theoretical rectifying stages, and six stages in the stripping section (solketal purification), with a G:A molar feed ratio of 1:2-3 and a reflux ratio of 2.4. The comparison of the optimized traditional process with the RDWC resulted in a reduction in energy consumption by 13.6%; therefore, the authors address the RDWC as a PI strategy. This column promotes a more efficient purification of the solketal because it simulates a distillation column (II) alongside the reactive distillation column (I) inside the same unit, as seen in Figure 9 [104]. \begin{table}
\begin{tabular}{c c c c c c} \hline
**Author** & **Catalyst** & **Catalyst** & **Reaction Conditions** & **Results** & **Observations** & **Ref** \\ \hline Reactive coupling & & & 1 glycerol:4 acetone  & & & \\  & & & 30 methanol:1 & & \\  & Amberlyst & & triacetin:4 acetone  & & \\  & 70–SO\({}_{3}\)H & & 6 methanol:1 & X\({}_{\text{gly}}\) = 80.6\% [FOOTNOTE:]Footnote 4: The experimental parameters and results are shown in Table 4. As for the optimization results considering the energy consumption (reboiler duty), it was found that the ideal scenario is nine theoretical reaction stages, five theoretical rectifying stages, and six stages in the stripping section (solketal purification), with a G:A molar feed ratio of 1:2-3 and a reflux ratio of 2.4. The comparison of the optimized traditional process with the RDWC resulted in a reduction in energy consumption by 13.6%; therefore, the authors address the RDWC as a PI strategy. This column promotes a more efficient purification of the solketal because it simulates a distillation column (II) alongside the reactive distillation column (I) inside the same unit, as seen in Figure 9 [104]. \begin{table}
\begin{tabular}{c c c c c c} \hline
**Author** & **Catalyst** & **Leading** & **Reaction Conditions** & **Results** & **Observations** & **Ref** \\ \hline Reactive coupling & & & & & \\ \hline \multirow{6}{*}{Eze, 2018} & & & 1 glycerol:4 acetone  & & & \\  & & & 30 methanol:1 & & \\  & & & triacetin:4 acetone  & & \\  & 70–SO\({}_{3}\)H & & 6 methanol:1 & X\({}_{\text{gly}}\) = 80.6\%  & & & \\  & 70–SO\({}_{3}\)H & & T = 323 K & X\({}_{\text{gly}}\) = 80.6\% [FOOTNOTE:]Footnote 4: Synthesis of biodiesel and solketal in one reactor. [ENDFOOTNOTE] & & \\  & Amberlyst & & P = N.A. & & \\  & A26–OH & & Sol = Methanol & & \\  & & & Space time = 0.5 h & & \\ \hline \multirow{6}{*}{Al-Saadi, 2019} & & & 10 methanol: 1 & & Silica gel added as \\  & DBSA (\(p\)– & & triacetin: 7 acetone & & dehydating agent to \\  & Dodecylbenzene & 0.5 mol & T = 323 K & Y\({}_{\text{solk}}\) = 82\% & overcome the \\ \cline{1-1}  & sulfonic acid) & & P = N.A. & & thermodynamic equilibrium \\ \cline{1-1}  & & & Space time = 8 h & & limitation. \\ \hline \end{tabular}
\end{table} 
Table 4: _Cont._Membrane reactors also approach PI by diminishing the thermodynamic limitations, i.e., removing water from the reaction medium. Pervaporation and vapor permeation are already industrially well-established processes for water removal; the challenges faced with the use of these technologies for solketal synthesis are the catalyst activity and the mass transfer limitation. Roldan et al. avoided these problems by using K10 montmorillonite as catalyst dispersed in the reaction medium, thus handling catalysis and water removal separately, and preventing membrane contact with the liquid phase by promoting vapor permeation [54, 119]. Qing et al., on the other hand, used a catalytically active membrane to react glycerol with cyclohexanone in a very similar system to solketal synthesis.