**4. Conclusions**

Carbon supports such as activated carbon and MWNTs can be irreversibly sulfonated to yield materials with sulfonic groups surface concentrations of about 3 milimols per gram.

Sulfonation of activated carbon does not yield materials with meaningful concentration values of surface acid sites unless a graphitic precursor such as naphthalene is coimpregnated during sulfonation.

MWNTs are more efficiently sulfonated at 230 ºC. In this case, only 1/6 of the surface carbon atoms are exposed.

Esterification of glycerol with acetic acid can be carried out at room temperature, but in these conditions, the selectivity is biased toward monoacetin because the esterification rate is low and monoacetin cannot be acetylated. The selectivity to TAG and DAG is increased at higher temperatures (e.g., 60% at 100 ºC).

Etherification of glycerol with tert-butyl alcohol is a complex reaction with many undesired by-products being produced. All catalysts tried were effective for converting glycerol, but obtaining selectivities higher than 70-80% to di- and tri-ethers is still a challenge.
