Investigation of Surface Site of Ni Species on NiMo/Al 2 O 3 Hydrodesulfurization Catalyst Sulfided at High-Pressure by
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Investigation of Surface Site of Ni Species on NiMo/Al2O3 Hydrodesulfurization Catalyst Sulfided at High-Pressure by Means of DRIFTS Combined With Low-Temperature NO Adsorption Naoto Koizumi • Sungbong Jung • Yusuke Hamabe Hikotaro Suzuki • Muneyoshi Yamada
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Received: 12 October 2009 / Accepted: 27 January 2010 / Published online: 9 February 2010 Ó Springer Science+Business Media, LLC 2010
Abstract A high-pressure DRIFT chamber for low temperature NO adsorption was newly constructed, and used to probe surface sites of the Ni-Mo-S phase on NiMo/Al2O3 catalysts sulfided at high-pressure (1.1 MPa, 673 K). A sharp IR band was evolved at 1,765 cm-1 after NO adsorption at 186–199 K, whereas this band was not observed after NO adsorption at ambient temperature. The band at 1,765 cm-1 was observed neither in the spectra of Mo/Al2O3, Ni/Al2O3 nor their physical mixture even after NO adsorption at 186–199 K, suggesting that this band results from adsorption of nitrosyl species on the Ni-Mo-S phase. Keywords DRIFTS NO adsorption NiMo/Al2O3 hydrodesulfurization catalyst High-pressure sulfiding
1 Introduction Al2O3 supported Mo sulfide-based catalysts promoted with Co and/or Ni are widely used for hydrodesulfurization (HDS) of sulfur compounds in petroleum fraction. To understand the role of the Co and Ni promoters, extensive
N. Koizumi S. Jung Y. Hamabe H. Suzuki Department of Applied Chemistry, Graduate School of Engineering, Tohoku University, Aoba 6-6-07, Aramaki, Aoba-ku, Sendai 980-8579, Japan M. Yamada (&) Akita National College of Technology, 1-1, Iijima-Bunkyo-cho, Akita 011-8511, Japan e-mail: [email protected]
studies have been undertaken by using variety of experimental techniques [1–6]. Among them, in situ IR spectroscopy combined with adsorption of surface probe molecules such as CO and NO is a powerful tool for investigating adsorption properties of nm-sized sulfide clusters. Topsøe and Topsøe [3] used in situ FT-IR spectroscopy combined with NO adsorption to investigate adsorption properties of Co-Mo/Al2O3 catalysts sulfided at atmospheric pressure. They found that IR bands of NO adsorbed on Co sites were evolved at the expense of the ones of NO on Mo sites by the addition of small amount of the Co promoter to a Mo/Al2O3 catalyst. Thiophene HDS activity of the CoMo/Al2O3 catalyst correlated well with IR band intensity of NO adsorbed on the Co sites, not the Mo sites. Based on these results, they proposed that the addition of Co leads to the formation of the so-called Co-Mo-S phase as HDS active species, in which Mo atoms located at the edge site of MoS2 cluster are blocked with Co atoms. Later, the authors investigated effect of high-pressure sulfiding pretreatment on surface structure of CoMo/Al2O3 and NiMo(W)/Al2O3 catalysts by means of in situ DRIFTS combined with NO adsorption using a specially designed high-pressure chamber [7–10]. High-pressure (1.1–5.1 MPa) sulfiding pretreatment led to selective formation of Co and/or Ni sites, whereas Mo(W) sites were formed as well when the catalysts
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