Sulfonated niobia (HY-340 CBMM) and pillared clay (Fluka) were tested in the catalytic conversion of glycerol by etherification reactions. The solids were treated with concentrated fuming sulfuric acid (AS100 and NS100), and a 30% aqueous solution of this acid (AS30 and NS30). Both the presence of sulfur and the increase in the acidity of the solids demonstrate the suitability of the sulfonation process, especially in samples treated with concentrated fuming sulfuric acid. The best catalyst for the reaction of etherification with tert-butyl alcohol was AS100, with a glycerol conversion of 95% after 5 h at 393 K and yield of 60.3, 33.2 and 5.4%, respectively for mono-tert-butyl-glycerol (MTBG), di-tert-butyl-glycerol (DTBG) and tri-tert-butyl-glycerol (TTBG). (C) 2014 Elsevier B.V. All rights reserved.