Insight into the correlation between the adsorption-transformation behaviors of methylthiophenes and the active sites of zeolites Y

Correlation between the adsorption-transformation behaviors of 2-methylthiophene and 3-methylthiophene and the active sites of NaY, HY and rare earth ion-exchanged ultra-stable Y (REUSY) zeolites have been studied by using an in situ FTIR technique and an intelligent gravimetric analyser-mass spectrometer (IGA-MS) coupling technique. The results show that the bridging hydroxyls (OH) of Si and Al atoms located in the supercage of zeolites Y are the preferred active sites, leading to the protonation and cracking reactions of the methylthiophenes. The AlO+ active sites in the HY, and the Al(OH)(2+) and RE(OH)(2+) active sites in the REUSY both can make the oligomerization reaction occur at 303 and 373 K, and especially, the RE(OH)(2+) active sites significantly improve the oligomerization abilities. Besides, the activities and selectivities of the protonated 2-methylthiophene and 3-methylthiophene play a decisive role in the oligomerization pathways. As system temperatures of > 473 K, the oligomerization reaction is restricted, while the cracking reaction is improved. Thereby, modulation of the key active sites in adsorbents and system temperatures will be a good prospect for ultra-deep desulfurization in the future. (C) 2016 Elsevier B.V. All rights reserved.