Improving the stability of La-exchanged zeolite Y catalysts in the vapor-phase isomerization of endo-tetrahydrodicyclopentadiene by co-feeding steam

Abstract

• La 3+ exchanged zeolite Y is more effective than HY catalyst for isomerizing endo-THDCPD to its exo isomer in vapor phase. • LaY catalyst has more Brönsted acidity and more moderate acid sites than HY catalyst. • Deactivated LaY catalyst could be completely recovered after calcination in air. • Improved stability of LaY catalyst was observed in the presence of a small amount of steam. The activities of La-exchanged zeolite Y (LaNaY) catalysts were investigated and compared with that of HNaY catalyst for the vapor-phase isomerization of endo-tetrahydrodicyclopentadiene (endo-THDCPD) to exo-THDCPD. HNaY and LaNaY catalysts were characterized by means of X-ray diffraction (XRD), nitrogen adsorption, NH 3 -TPD, pyridine-adsorbed Fourier Transformation Infrared Spectroscopy (FTIR). The LaNaY catalysts with La loading of 2-5 wt% showed better catalytic performance than the HNaY catalyst. All catalysts deactivated gradually with number of run. The activity of the deactivated LaNaY catalyst could be completely recovered after calcination in air for 4 h at 550 °C. The effect of steam co-feeding on the stability of the LaNaY catalyst was investigated. The results show that the stability of the LaNaY catalyst was improved by co-feeding steam compared to those in the absence of steam, which was attributed to the replacement of adamantane adsorbed on the active sites of the catalyst by competitive adsorption of water. In the presence of 5 % steam, the effect of temperature on the stability of the LaNaY catalyst was also studied. A high and stable activity was observed at 185 °C.