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

Abstract:

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 ((NH<inf>4</inf>)<inf>10</inf>·[H<inf>2</inf>W<inf>12</inf>O<inf>42</inf>]·4H<inf>2</inf>O) aqueous solution. Tungsten carbide (W<inf>2</inf>C) was synthesized by temperature programmed carburization (TPC) from the WO<inf>3</inf>supported on Al-SBA-15 and SBA-15 in a flow of CH<inf>4</inf>/H<inf>2</inf>. These resultant materials were characterized by powder X-ray diffraction (XRD), N<inf>2</inf>adsorption/desorption,²⁷Al NMR and Raman spectroscopies, and transmission electron microscopies (TEM and HRTEM). W<inf>2</inf>C 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 WO<inf>3</inf>and W<inf>2</inf>C 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.

Año de publicación:

2016

Keywords:

• Tungsten carbide
• SBA-15
• Al-SBA-15
• Mesoporous silica

Fuente:

scopus