The etherification of glycerol with isobutene to synthesize di-tert-butyl glycerol ethers (DTBG) and tri-tert-butyl glycerol ether (TTBG) was studied on acid-treated HY zeolites. Compared to the parent commercial HY, both activity and selectivities to the desired ethers were doubled after optimal acid treatments. At 70 degrees C with 1 wt% catalyst loading, the glycerol conversion and the selectivities to DTBG and TTBG after 7 h were 85% and 58%, respectively on a citric acid washed HY. The catalyst showed higher selectivity than an acidic resin (SAC-13) and was reusable. Similar performance was also achieved using nitric acid solutions. Although the acid wash resulted in fewer acid sites due to dealumination, the zeolite crystalinity was retained. Besides increased acid strength, enlarged surface area and pore volume from the generation of mesopores were observed, which were likely to be the key factors for the improved catalytic performance by facilitating mass transfer. (C) 2010 Elsevier B.V. All rights reserved.