Evaluation of the acid properties of porous zirconium-doped and undoped silica materials

• Published in: Journal of solid state chemistry 2006-07, Vol.179 (7), p.2182-2189
• Main Authors: Fuentes-Perujo, D., Santamaría-González, J., Mérida-Robles, J., Rodríguez-Castellón, E., Jiménez-López, A., Maireles-Torres, P., Moreno-Tost, R., Mariscal, R.
• Format: Article
• Language: English
• Subjects: 1-butene isomerization; ACETONITRILE; ADSORPTION; BUTENES; Catalysis; Catalytic reactions; Chemistry; Condensed matter: structure, mechanical and thermal properties; Defects and impurities in crystals; microstructure; DOPED MATERIALS; Doping and impurity implantation in other materials; Exact sciences and technology; FOURIER TRANSFORMATION; General and physical chemistry; INFRARED SPECTRA; ISOMERIZATION; Isopropanol decomposition; LEWIS ACIDS; MATERIALS SCIENCE; MCM-41; MOLECULAR SIEVES; PH VALUE; Physics; POROUS MATERIALS; Porous silica; PYRIDINE; SILICA; Structure of solids and liquids; crystallography; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; X-RAY DIFFRACTION; X-RAY PHOTOELECTRON SPECTROSCOPY; ZIRCONIUM; Zirconium oxide; ZIRCONIUM OXIDES
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1016/j.jssc.2006.04.018

A series of porous silica and Zr-doped silica molecular sieves, belonging to the MCM-41 and MSU families, were prepared and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and N 2 adsorption at 77 K. Their acid properties have been evaluated by NH 3-TPD, adsorption of pyridine and deuterated acetonitrile coupled to FT-IR spectroscopy and the catalytic tests of isopropanol decomposition and isomerization of 1-butene. The acidity of purely siliceous solids were, in all cases, very low, while the incorporation of Zr(IV) into the siliceous framework produced an enhancement of the acidity. The adsorption of basic probe molecules and the catalytic behaviour revealed that Zr-doped MSU-type silica was more acidic than the analogous Zr-MCM-41 solid, with a similar Zr content. This high acidity observed in the case of Zr-doped silica samples is due to the presence of surface zirconium atoms with a low coordination, mainly creating Lewis acid sites. The adsorption of basic probe molecules and the catalytic behaviour have revealed that MSU-type materials are more acidic than the analogous MCM-41 solids, mainly after the incorporation of zirconium into the silica framework.