Catalytic materials prepared from natural clinoptifolite by ion exchange and acid treatment have been successfully used in the gas phase conversion of acetaldehyde and formaldehyde into acrolein. The modifications made on the raw clinoptilolite have generated important changes of the texture and catalytic sites. The results in catalysis showed that the nature and the amount of condensation products strongly depend on the acid-base properties of catalysts. The highest stability, activity and selectivity to acrolein have been proved by the catalysts having high number and strength of basic sites. (C) 2008 Elsevier B.V. All rights reserved.