# Improving Sorbents for Glycerol Capture in Biodiesel Refinement
## 2 Results
### Sorbents
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Material** & **Type** & **Surface** & **Pore Volume** & **Pore** & **\#+** & **k** & **St.** \\  & **Area (m2/g)** & **(cm2/g)** & **Diameter** (Å) & mg/g & **ug/m2** & **(U/mg)** & **n** & **Chi2** & **Error** \\ \hline S65 + & – & 591 & 0.675 & 65 & – & – & – & – & – \\ S85 + & – & 552 & 0.716 & 75 & – & – & – & – & – \\ S65-Ph(1) & 1 & 525 & 0.542 & 56 & 37.3 & 72.4 & 2.78 & 1 & 0.334 & 0.160 \\ S85-Ph(1) & 1 & 578 & 0.626 & 64 & 24.5 & 42.4 & 1.92 & 1 & 0.008 & 0.024 \\ E25 + & – & 1088 & 1.32 & 88 & – & – & – & – & – \\ E50 t & – & 1143 & 1.050 & 76 * & – & – & – & – & – \\ E25-Ph(2) & 2 & 803 & 0.740 & 64 & 12.0 & 14.9 & 4.78 & 1 & 0.018 & 0.361 \\ E50-Ph(2) & 2 & 883 & 0.664 & – & 5.2 & 5.90 & 10.8 & 1 & 0.023 & 0.042 \\ ED11 + & – & 711 & 0.817 & 55 & 38.8 & 55.4 & 0.461 & 1 & 0.001 & 0.012 \\ ED11-Ph+ & – & 498 & 0.560 & 57 & – & – & – & – & – \\ ED11a(4) & 4 & 87 & 0.111 & 55 & 18.0 & 207 & 0.920 & 1 & 0.022 & 0.047 \\ ED11-Ph(13) & 3 & 147 & 0.151 & 48 & 21.3 & 145 & 13.5 & 1 & 0.057 & 0.069 \\ ED11-Ph2(3) & 3 & 27 & 0.047 & 50 & 12.2 & 452 & 24.0 & 1 & 0.007 & 0.031 \\ D13 + & – & 427 & 0.642 & 74 & 0.006 & 137.0 & 0.011 & 1 Type 2 materials provide the same pendant functional group on an ethane-bridged organosilicate sorbent. The base E50 scaffold has been functionalized and studied previously for adsorption applications [26]. It has a combination of disordered micropores and mesopores, evidenced in the adsorption branch of its nitrogen sorption isotherm by an initial increase in the low relative pressure region and gradual increase throughout the mid and high relative pressure regions (Figure 3). No defined peak is observed in the pore size distribution of E50-Ph(2) after functionalization (Figure 3); an indistinct feature ca. 76 A is present in the base material. E25, synthesized with half the amount of mesitylene used for E50, does produce a distinct pore size distribution peak at 64 A following functionalization (Figure 3). The type IV nitrogen sorption isotherm shape with steep adsorption step in the mid relative pressure region is similar to those of ordered S65-Ph(1) and S85-Ph(1). The E25-Ph(2) and E50-Ph(2) products have the highest surface areas (>800 m\({}^{2}\)/g) and pore volumes (>0.6 cm\({}^{3}\)/g) of the sorbents used in this study. Type 3 materials based on ED11 have 50% ethane bridging groups with the remainder comprised of diethylbenzene groups, allowing for direct sulfonation of phenylene groups within the pore walls, as well as the grafted phenyl groups. Type 4 refers to sodium-exchanged sulfonated ED11 with no grafted phenyl moieties (ED11a(4)). Direct functionalization of the scaffold walls leads to notably low values for surface area and pore volume (Table 2), despite the base ED11 material having values ca. 700 m\({}^{2}\)/g and 0.8 cm\({}^{3}\)/g. Most products sulfonated with undiluted H\({}_{2}\)SO\({}_{4}\) display Type II nitrogen sorption isotherms indicative of relatively non-porous materials (e.g., ED11-Ph2(3) in Figure 4). Figure 3: Nitrogen sorption analysis for ethane bridged sorbents. (**a**) Nitrogen adsorption/desorption isotherms for E25 (black), E25-Ph(2) (red), E50 (blue), and E50-Ph(2) (green); (**b**) Pore size distributions for the sorbents colored as in (**a**). Figure 2: Nitrogen sorption analysis for sulfonated sorbents. (**a**) Nitrogen adsorption/desorption isotherms for S65 (black), S65-Ph(1) (red), S85 (blue), and S85-Ph(1) (green); (**b**) Pore size distributions for the sorbents colored as in (**a**). Types 5 and 6 solvents based on D13 have the highest concentration of diethylbenzene bridging groups in their scaffold walls, being synthesized with bis(trimethoxysilylethyl)benzene as the sole silane precursor. Type 5 also includes grafted pendant phenyl moieties. The base D13 scaffold exhibits impressive porosity characteristics for a templated material synthesized from this relatively flexible bridged-silane, with a surface area ca.