abstracts - Институт катализа им. Г.К. Борескова

OP-II-34adsorption show that strongly coordinated pyridine leads to a poisoning of the catalyst.Besides, the correlation between deactivation and surface carboxylates accumulation indicatesthat basic oxygen atoms are also involved in the reaction mechanism. Our results suggest thatLewis acid-base pairs are active sites for THT decomposition on Zn/Al 2 O 3 additives. Wepropose that decomposition mechanism of THT proceeds by strong coordination of THT onLewis acid sites through the sulfur atom followed C-S bond breaking (beta-eliminationmechanism). This leads to the formation of a surface thiolate which is easily transformed intobutadiene by subsequent C-S cleavage, sulfur being released in the form of H 2 S.Contrary to THT, thiophene shows minute reactivity on Zn/Al 2 O 3 . This contrasts SCT-MAT results that show that Zn/Al 2 O 3 blended with a FCC catalyst is effective to reducethiophene and alkylthiophenes. As outlined in the literature, hydrogen transfer (HT) tothiophenic compounds is the main route for their desulfurization by the FCC catalyst.SRHTSRcrackingR-C 4+ H 2SScheme 1At reaction conditions, the cracking catalyst essentially gives rise to THTdehydrogenation, leading to thiophene whereas Zn/Al 2 O 3 is more active and much moreselective for THT decomposition (95 % vs. 45 %). Our results thus show that in actual FCCconditions, Zn/Al 2 O 3 additives lead to a reduction of gasoline thiophenic compounds by anefficient decomposition of tetrahydrothiophenes produced by hydrogen transfer on the FCCcatalyst.References:1 Habib Jr., E. T.; Zhao, X.; Yaluris, G.; Cheng, W. C.; Boock, L. T.; Gilson, J. P., inZeolites for Cleaner Technologies Ed. Guisnet, M.; Gilson, J. P. (Imperial College Press,London, 2002), 105.2 Kim, G.; Wormsbecher, R. F. US Patent 5,376,608, (1994).3 Hu, R.; Zhao, X.; Wormsbecher, R. F.; Ziebarth, M. S.; US patent application US2005/0205464 A1 (2005).4 Chester, W. C.; Roberie, T.; Timkent, H. K. C.; Ziebarth, M. S.; US patent applicationUS 2002/0179498 A1 (2002).274