Table 2. The surface areas, acid density, and turnover frequency (TOF) of sulfonated silica monoliths.
| Catalyst | S BET a (m2 g−1) | S meso-BET (m2 g−1) | V BJH b (cm3 g−1) | –SO3H densityc (mmol g−1) | TOFd (h−1) |
|---|---|---|---|---|---|
| H-(0.9) SO3-TEOS monolith | 9.4 | 9.0 | 0.007 | 0 | — |
| H-(0.9) SO3-TEOS + SDS monolith | 200.9 | 25.8 | 0.05 | 0.49 | — |
| H-(0.9) SO3-HS-30 | 117.3 | 114.5 | 0.14 | 0.44 | — |
| H-(0.9) SO3-0%-silica | 243.2 | 241.6 | 0.67 | 0.71 | 10.9 |
| H-(0.9) SO3-25%-silica | 239.7 | 237.2 | 0.62 | 0.71 | 19.4 |
| H-(0.9) SO3-50%-silica | 225.3 | 220.2 | 0.57 | 0.67 | 24.1 |
| H-(0.9) SO3-75%-silica | 232.7 | 223.1 | 0.63 | 0.73 | 32.1 |
| H-(2.7) SO3-75%-silica | 258 | 252.7 | 0.68 | 0.69 | 27.8 |
| H-75%-silica | 219.7 | 212.1 | 0.61 | 0 | — |
a
BET method applied to the N2 isotherm (p/p0 0.05–0.3).
b
Surface area and pore volume of mesopores determined by the BJH method.
c
Based on the S content from elemental analysis.
d
Based on the free fatty acid conversion in the first hour of the reaction.