THE SELECTIVITY CHANGES IN 1-HEXENE ISOMERIZATION AND ITS RELATION TO ACID PROPERTIES OF PD/SAPO-11, SAPO-11, HZSM-5, AND H-MORDENITE CATALYSTS

The activity and selectivity patterns for 1-hexene isomerrzation have been compared in the temperature range of 150-450°C for four different kinds of acidic zeolites (H-mordenite, HZSM-5, SAPO-11 and Pd/SAPO-11) differing both ir acid properties and geometric structure. At lower reaction temperatures (150-175°C) the predominant reaction pathway was double bond shift(DBS) and was not influenced by the type of catalyst. At higher temperatures significant shifts in selectivity were observed from DBS to cracking (C) or skeletal rearrangement (SR) depending on the type of catalyst. Temperature programmed desorption (TPD) patterns of chemisorbed NH3 were also determined. Three different peaks were found for the most of TPD patterns. The first peak might be associated with Lewis acidsite, and the other two peaks at higher temperatures might be associated with Brönsted acid-sites. It was found that significant loss of strong Brönsted acidity upon Pd loading on SAPO-11. A selectivity correlation at 350°C showed strong dependence of DBS and cracking on total acidity. The reaction seems well suited for investigation of the interrelation between pore structure and surface acidity in terms of these selectivity factors. © 1990 Korean Institute of Chemical Engineering.