# Improving Sorbents for Glycerol Capture in Biodiesel Refinement
## 2 Results  
### Sorbents  
A previous study by [PERSON] et al. utilized sulfonation of a poly-(styrene-co-divinylbenzene) resin to increase hydrogen bonding with the material and binding of glycerol by the material [23]. The study did not consider the impact of the scaffold or the morphology of the resin on target adsorption. Because the chemical structures in proximity to the sulfonate groups as well as the density of the sulfonate groups is likely to impact the interaction of those groups with glycerol, a series of porous organosilicate materials were synthesized in which the pore wall composition was varied (Table 1). In some cases, S65, S85, E25, and E50, all sulfonated sites were included through pendant phenyl groups added to the materials following surfactant extraction; no sites for sulfonation were included in the base sorbent. In other cases, ED11 and D13, diethyl benzene groups comprise a portion of the scaffold walls. Sulfonation of the materials directly (ED11a(4) and D13a,b,c(6)) or sulfonation following grafting of additional phenyl groups was then completed. The schematic provided in Figure 1 illustrates the intended variations in the resulting materials (see also Table 1). Figure 1: Glycerol solvents. Schematics of the material variations are presented here showing both the groups within the sorbent scaffold (shaded area) and the groups added during post-synthesis processing. The numbers identify the type (1 through 6) and are used in the text to describe the sorbents as well as in the sorbent names. For example, S65-Ph(1) is a Type 1 sorbent while E50-Ph(2) is a Type 2 sorbent. As shown in Table 2, the various synthetic procedures lead to a variety of morphological characteristics. The Type 1 materials (Figure 1) provide a sodium-exchanged sulfonated phenyl group pendant on a silicate scaffold. Nitrogen sorption experiments on S65-Ph(1) and S85-Ph(1) yield type IV isotherms characteristic of mesoporous materials, showing steep increases in nitrogen adsorbed in the mid-pressure region (\(P/P_{0}\) ca. 0.4-0.7) corresponding to capillary condensation in mesopores (Figure 2). The silicate scaffolds have ordered mesostructures in which cylindrical mesopores are arranged with 2D-hexagonal packing; the pore sizes of 56 A (S65-Ph(1)) and 64 A (S85-Ph(1)) are influenced by the amounts of mesitylene, the micelle swelling agent, included in their syntheses [24; 25]. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Scaffold Description** & **Material** & **Type** & **Grafted** & **Phenyl Groups** & **Sulfonation** \\ \hline Silicate sorbent based on tetramethyl orthosilicate, 0.65 g presitylene used in synthesis & S65-Ph(1) & 1 & No & none \\ \hline Silicate sorbent based on tetramethyl orthosilicate, 0.85 g presitylene used in synthesis & S85-Ph(1) & 1 & Yes & standard \\ \hline Ethane-bridged organosilicate, 0.5 g presitylene used in synthesis & E25 & – & No & none \\  & E25-Ph(2) & 2 & Yes & standard \\ \hline Ethane-bridged organosilicate, 1.0 g presitylene used in synthesis & E50 & – & No & none \\  & E50-Ph(2) & 2 & Yes & standard \\ \hline  & ED11 & – & No & none \\ Organosilicate with mixed ethane and & ED11-Ph & – & Yes & none \\ diethylbenzene bridging groups & ED11a(4) & 4 & No & standard \\  & ED11-Ph1(3) & 3 & Yes & standard \\  & ED11-Ph2(3) & 3 & Yes & standard \\ \hline  & D13 & – & No & none \\  & D13a(6) & 6 & No & standard \\ Diethylbenzene-bridged organosilicate & D13b(6) & 6 & No & dilute \\  & D13c(6) & 6 & No & standard \\  & D13-Ph1(5) & 5 & Yes & standard \\  & D13-Ph2(5) & 5 & Yes & dilute \\ \hline Divinylbenzene resin, synthesized with water & PDVB-2 & – & No & standard \\ \hline Divinylbenzene resin, synthesized with no water & PDVB-3 & – & No & standard \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Sorbents described under this study.