Coking behavior of a submicron MFI catalyst for ethanol to ethylene was studied in a pilot scale tubular reactor. The experimental results showed that the submicron MFI catalysts possessed high activity and stability. Ethanol conversion and ethylene selectivity over the fresh/regenerated catalyst were around 97.9%/96.2% and 99.1%/98.9%, respectively. The fresh catalyst illustrated an active duration of 1606 h while the regenerated of 2008 h, which implied the regeneration can enhance the stability. In the reactor, the coke mainly consisted of adsorbed substances at the forepart and of alkyl aromatics at the end, and the coke contents presented an approximate U-shape trend along the tube length. Further tests revealed that the loss of acidity rather than the pore volume should be responsible for the catalyst deactivation. (C) 2010 Elsevier B.V. All rights reserved.