Effect of the electronic properties of Mo sulfide phase on the hydrotreating activity of catalysts supported on Al 2 O 3
- PDF / 321,795 Bytes
- 8 Pages / 593.972 x 792 pts Page_size
- 78 Downloads / 165 Views
Catalysis Letters Vol. 111, Nos. 1–2, October 2006 ( 2006) DOI: 10.1007/s10562-006-0126-7
Effect of the electronic properties of Mo sulfide phase on the hydrotreating activity of catalysts supported on Al2O3, Nb2O5 and Nb2O5/Al2O3 Angela S. Rocha,a Arnaldo C. Faro Jr,a Laetitia Oliviero,b Marc Antoine Le´lias,b Arnaud Travert,b Jacob van Gestel,b and Franc¸oise Mauge´b,* a
Dept. de Fı´sico-Quı´mica, Instituto de Quı´mica, UFRJ, Ilha do Funda˜o, CT, Rio de Janeiro, RJ, CEP 21949-900, Brazil b Laboratoire Catalyse & Spectrochimie, UMR CNRS-Ensicaen-Universite´ de Caen, Caen Cedex, 14050, France
Received 4 June 2006; accepted 29 June 2006
Activity in thiophene hydrodesulfurization (HDS) and in the three routes of 2,6-dimethylaniline (DMA) decomposition was examined on Mo sulfide catalysts supported on Al2O3, Nb2O5 and Nb2O5–Al2O3. Catalysts activity is enhanced when Mo phase is deposited on niobium-containing support. For HDS and for the hydrogenation route of DMA decomposition, the niobiumcontaining support strongly contributes to the catalyst activity whereas the activity of the Mo phase per Mo atom decreases with the increase of niobium amount in the support. By contrast, as for the DMA route, which leads to xylene formation (XYL), the activity of the Mo sulfide phase per Mo atom is strongly enhanced. The electronic properties of the MoS2 phase were studied by means of IR spectroscopy of CO adsorption. Comparison of m(CO/Mo) wavenumbers reveals an upward shift when Mo sulfide phase is deposited on Nb-containing support. The modification of the electronic properties of the sulfide phase is related to an interaction Mo–Nb either through the formation of a mixed Mo–Nb sulfide phase, or through the interaction MoS2 slabs – support whose strength depends on the support acidity. Hence, the beneficial effect for xylene formation route is attributed to a decrease of the electron density of the Mo sulfide phase that should strengthen the DMA adsorption on the sulfide phase. KEY WORDS: hydrotreatment; niobium; HDS; HDN; IR spectroscopy.
1. Introduction The need for decreasing pollutant emissions as well as the necessity of refining heavier petroleum feeds have stimulated a worldwide effort for the development of catalysts with better performance in hydrotreating processes. The conventional hydrotreating catalysts are based on pairs of metals in sulfide form, typically Co or Ni, combined with Mo or W, generally supported on alumina [1–3]. Thus, the development of new alternative catalysts can be done by changing the active sulfide phase, or by the proposition of new supports. The development of new supports is a quite attractive option, due to the importance of the acid–base properties of the catalysts in several hydrotreating (HDT) processes, as hydrodesulfurization (HDS), hydrodenitrogenation (HDN), hydrodearomatization (HDA) and hydrocracking (HCC) [3, 4]. Hence, the control of the support acidity should allow an adjustment of catalyst activity and selectivity. Niobium oxide in the hydrated form, also known as niobic acid (Nb2O5ÆxH
Data Loading...
