In this work, phosphorus-modified ZSM-5 zeolites were used to transform ethanol to propylene. The selectivity of propylene formation depended strongly on the phosphorus content in the zeolites; the highest propylene yield (32%) was observed over H-ZSM-5(80) modified with phosphorus at a P/Al molar ratio of 0.5. The enhancement of propylene selectivity with increasing phosphorus content was attributed to reduction of strong acid sites on the H-ZSM-5. Modification of the zeolite with phosphorous also improved the material's catalytic stability. (C) 2010 Elsevier B.V. All rights reserved.