Synthesis of tungsten carbide on Al-SBA-15 mesoporous materials by carburization

• Published in: Microporous and mesoporous materials Vol. 219; pp. 19 - 28
• Main Authors: Álvarez, M.G., Chimentão, R.J., Tichit, D., Santos, J.B.O., Dafinov, A., Modesto-López, L.B., Rosell-Llompart, J., Güell, E.J., Gispert-Guirado, F., Llorca, J., Medina, F.
• Format: Journal Article Publication
• Language: English
• Published: Elsevier Inc 01.01.2016
• Subjects: Al-SBA-15; Alumina; Alumini; Aluminum; Catalysts; Crystal; Difracció; Enginyeria dels materials; Enginyeria química; Hydrogen-production; Indústries químiques; Mesoporous silica; Molybdenum; Natural-gas lng; Raigs X; Raman-spectroscopy; SBA-15; Silica; Tungsten carbide; X-rays - Diffraction; Àrees temàtiques de la UPC; Tungsten carbide; Al-SBA-15; SBA-15; Mesoporous silica
• ISSN: 1387-1811; 1873-3093
• DOI: 10.1016/j.micromeso.2015.07.018

Aluminum was incorporated into SBA-15 supports at molar ratios Si/Al = 10 and 2 by the pH-adjusting method. The calcined mesoporous Al-SBA-15 supports, as well as the Al-free SBA-15 support, were impregnated with ammonium paratungstate ((NH4)10·[H2W12O42]·4H2O) aqueous solution. Tungsten carbide (W2C) was synthesized by temperature programmed carburization (TPC) from the WO3 supported on Al-SBA-15 and SBA-15 in a flow of CH4/H2. These resultant materials were characterized by powder X-ray diffraction (XRD), N2 adsorption/desorption, 27Al NMR and Raman spectroscopies, and transmission electron microscopies (TEM and HRTEM). W2C species were obtained after the carburization process in all the materials. The mesoporous structure of the SBA-15 supports was preserved at all synthesis steps. XRD and TEM analyses revealed that the introduction of aluminum species into the SBA-15 greatly enhanced the dispersion of WO3 and W2C phases during the calcination and carburization steps, respectively. In situ XRD measured during the carburization in a synchrotron facility provided further details of the reduction of tungsten trioxide species as a function of temperature. The presence of aluminum in the SBA-15 notably affected the distribution and the reduction temperature of the tungsten oxide species. [Display omitted] Schematic representation of the evolution of the tungsten crystallographic phases supported on Al-SBA-15 material during the TPC process. •The mesoporous structure of the SBA-15 was preserved after the carburization.•The introduction of Al in the SBA-15 enhanced the dispersion of tungsten species.•The presence of Al in the SBA-15 raised the reduction temperature of WOx species.