Effect of the Cr2O3 Promoter on Pt/WO3-ZrO2 Catalysts for n-Heptane Isomerization

Abstract

Isomerate, the product of a light naphtha Isomerization unit, is a clean, high-octane gasoline blending component, which is free of sulfur content, aromatics, and olefins. However, the isomerization of the long-chain alkanes, such as n-heptane, is pretty difficult. As a result, this process has not been commercialized yet. In recent years, much attention has been paid to Pt/WO3/ZrO2 as an n-heptane isomerization catalyst due to its good thermal stability, strong acidity, simplicity of preparation, reusability and good isomerization activity. In this work, the Pt/WO3/ZrO2 catalyst was modified by various loading of metal Cr to improve the catalytic performance. The effects of WO3 content, Cr metal loading and calcination temperature on the catalyst characters and catalytic activity were studied. It is shown that Cr-Pt/WO3/ZrO2 with the loading of 18 wt% WO3 and 1.0–1.4 wt% Cr, prepared at the calcination temperature of 800 °C, has the highest activity. It was found that the octane number increases by 28 units through the isomerization of light naphtha feedstocks. In addition, the study on the stability of Cr-Pt/WO3/ZrO2 indicates that the catalyst is not deactivated after 500 h of the n-heptane isomerization reaction.