NiMo/MCM-41 Catalysts for the Hydrotreatment of Polychlorinated Biphenyls
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NiMo/MCM-41 Catalysts for the Hydrotreatment of Polychlorinated Biphenyls Franklin J. Me´ndez • Ernesto Bastardo-Gonza´lez • Paulino Betancourt • Luis Paiva • Joaquı´n L. Brito
Received: 26 April 2012 / Accepted: 29 October 2012 / Published online: 11 December 2012 Springer Science+Business Media New York 2012
Abstract MCM-41 type mesoporous materials of pure silicon and aluminosilicates (with Si/Al atomic ratios of 20 and 40) were prepared by a facile synthesis method and used to support NiMo catalysts. Characterization by XRD showed typical patterns of this type of mesoporous solids with a partial collapse of the structure on increasing Al content. In addition, signals attributed to the formation of MoO3, NiO and Al2(MoO4)3 in the transition-metal containing catalysts were observed. The 29Si-NMR-MAS spectra showed that local arrangement of the Si–O–Si bonds was regular, independently of the solid being pure or modified with Al, while the 27Al-MAS-NMR spectra of the aluminosilicates showed both structural and non-reticular species. The N2 adsorption–desorption curves showed type IV isotherms, with considerable diminution in the BET areas once the metals were incorporated. The catalytic results in thiophene hydrodesulfurization (HDS) and polychlorinated biphenyl hydrodechlorination (HDCl) revealed a considerable catalytic activity for all prepared
F. J. Me´ndez P. Betancourt (&) J. L. Brito (&) Laboratorio de Fisicoquı´mica de Superficies, Centro de Quı´mica, Instituto Venezolano de Investigaciones Cientı´ficas, Apartado 20632, Caracas 1020, Venezuela e-mail: [email protected] J. L. Brito e-mail: [email protected] E. Bastardo-Gonza´lez (&) Laboratorio de Quı´mica de Superfı´cies, Departamento de Quı´mica, Universidad de Oriente, Cumana´, Venezuela e-mail: [email protected] P. Betancourt L. Paiva Laboratorio de Tratamiento Catalı´tico de Efluentes, Centro de Cata´lisis, Petro´leo y Petroquı´mica, Universidad Central de Venezuela, Caracas, Venezuela
catalysts as compared with a commercial NiMo/Al2O3 one, being highest in the case of the NiMo/Al-MCM-41(40) one for HDS, and for NiMo/Al-MCM-41(20) in HDCl. The excellent properties for HDCl can be attributed to good dispersion of Ni and Mo active phases and to the bifunctional character of the catalysts, namely, to the participation of both coordinatively unsaturated sites of the NiMoS active phase and Brønsted acid sites of the support. Keywords Hydrodechlorination Hydrodesulfurization MCM-41 synthesis NiMo Sulfided catalysts
1 Introduction Considerable effort is aimed nowadays at improving hydrotreatment (HDT) catalysts, especially for the hydrodesulfurization (HDS) reaction [1]. From an environmental point of view, the main purpose of removing sulfur from petroleum and its derivatives is to reduce the sulfur dioxide emissions that result from using fossil fuel. Another important reason is that sulfur, even in low concentrations, poisons the noble metal catalysts in the catalytic reforming units that are used subsequently to HDT in
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