La-Modified SBA-15 Prepared by Direct Synthesis: Importance of Determining Actual Composition

• Published in: Catalysts Vol. 14; no. 7; p. 436
• Main Authors: Gloribel Morales Hernández, José Escobar, José G. Pacheco Sosa, Mario A. Guzmán Cruz, José G. Torres Torres, Paz del Ángel Vicente, María C. Barrera, Carlos E. Santolalla Vargas, Hermicenda Pérez Vidal
• Format: Journal Article
• Language: English
• Published: MDPI AG 01-07-2024
• Subjects: lanthanum; materials composition; phenol HDO; platinum; SBA-15
• ISSN: 2073-4344
• DOI: 10.3390/catal14070436

Lanthanum (La) integration (at various nominal contents) in SBA-15 prepared under acidic medium was intended from corresponding direct nitrate addition during mesoporous silica formation. Materials were impregnated with Pt (1.5 wt%) and studied through several textural (N2 physisorption), structural (XRD, TG-DTG), and surface (FTIR, STEM-HAADF, SEM-EDS, NH3, and CO2 TPD) instrumental techniques. Pt-impregnated solids were tested in phenol hydrodeoxygenation (HDO, T = 250 °C, 3.2 MPa, batch reactor, n-decane as solvent). Catalytic activity (in pseudo-first-order kinetic constant, kHDO basis) was not directly related to Pt dispersion, which was not determined by nominal rare earth content. Determining the actual composition of modified SBA-15 materials is crucial in reaching sound conclusions regarding their physicochemical properties, especially when La modifier is directly added during mesoporous matrix formation, where efficient interaction among constituents could be difficult to get. Otherwise, results from some characterization techniques (N2 physisorption and FTIR, for instance) could be misleading and even contradictory. Indeed, extant modifier precursors, when under SBA-15 synthesis conditions, could affect the properties of prepared materials even though they were absent in obtained formulations. Performing simple compositional analysis could eliminate uncertainties regarding the role of various modifiers on characteristics of final catalysts. However, several groups have failed in doing so.