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ÇëÎÊÎÒÔõôÔڲο¼ÎÄÏ×ÀïÒýÓÃÏÂÃæµÄ»áÒéÂÛÎÄ£¿¸ñʽÊÇÔõôдµÄ?лл´ó¼ÒÁË£¡ Studies in Surface Science and Catalysis Volume 34, 1987, Pages 523-534 Catalyst Deactivation 1987, Proceedings of the 4th International Symposium Copyright © 1987 Elsevier Science Publishers B.V. Published by Elsevier B.V. The Effect of Partial Reduction on the Thioresistance of Ni/Al2O3 Catalysts D. Dupreza and M. Mendeza aLaboratoire de Catalyse en Chimie Organique, UA CNRS 350, 40, Av. Recteur Pineau 86022 POITIERS CEDEX FRANCE Available online 4 January 2009. Abstract The effect of partial reduction on the thioresistance of the metals was evaluated on two series of nickel catalysts. The first series, comprising Ni/Al2O3 samples with variable metal loading (2 to 12 wt%) were characterized (metal area, degree of reduction), using two different methods: chemisorption of gases (H2, O2) and magnetism. Despite some discrepancies between the two methods of characterisation, it can be concluded that the presence of an unreduced phase improves the thioresistance of nickel, expressed as the number of molecules of thiophen required for deactivating one atom of surface nickel. For increasing the amount of unreduced nickel, a second series of catalysts was prepared by impregnation of nickel on NiO-Al2O3 supports (pre-spinelised at 700¡ãC). As a result, the catalysts were found to be particularly resistant to sulphur poisoning. In turn, three hypothesis were considered to interpret these results: trapping effects of sulphur by unreduced nickel species of the support, electronic effects (Ni¡ã-Ni2+ interactions) and geometric effects (dilution of the nickel surface by unreduced species). Complementary experiments (measurement of sulphur capacity by H2S chemisorption and evolution of electronic interaction by competitive hydrogenation) were used to clarify these interpretations. Trapping effects are likely but not sufficient to account for the improvment of thioresistance, which could be due also to geometric effects. |
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