Surface nature of nanoparticle zinc-titanium oxide aerogel catalysts

• Published in: Applied surface science Vol. 254; no. 15; pp. 4500 - 4507
• Main Authors: Wang, Chien-Tsung, Lin, Jen-Chieh
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 30.05.2008; Elsevier Science
• Subjects: Aerogels; Catalysts; Chemistry; Colloidal state and disperse state; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Electrochemistry; Electrodes: preparations and properties; Electron and ion emission by liquids and solids; impact phenomena; Exact sciences and technology; General and physical chemistry; Methanol oxidation; Nanoparticles; Photoemission and photoelectron spectra; Physics; Porous materials; Zinc titanate; Nanoparticles; Aerogels; Zinc titanate; Catalysts; Methanol oxidation; Particle size; Nanoparticle; Inorganic compound; Surface structure; Anions; Oxidation; Infrared spectrum; Methanol; Lewis acid; Oxygen; Aerogel; Vacancy; Transition element compounds; Carbon; X ray diffraction; Electron electron interaction; Catalyst activity; Catalyst; Zinc Titanates; X-ray photoelectron spectra
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2008.01.024

Nanoparticle zinc-titanium oxide materials were prepared by the aerogel approach. Their structure, surface state and reactivity were investigated. Zinc titanate powders formed at higher zinc loadings possessed a higher surface area and smaller particle size. X-ray photoelectron spectroscopy (XPS) revealed a stronger electronic interaction between Zn and Ti atoms in the mixed oxide structure and showed the formation of oxygen vacancy due to zinc doping into titania or zinc titanate matrices. The 8–45 nm aerogel particles were evaluated as catalysts for methanol oxidation in an ambient flow reactor. Carbon dioxide was favorably produced on the oxides with anion defects. Titanium based oxides exhibited a high selectivity to dimethyl ether, so that a strong Lewis acidic character suggested for the catalysts was associated primarily with the Ti 4+ center. Both methanol conversion and dimethyl ether formation rates increased with increasing the zinc content added to the oxide support. Results demonstrate that cubic zinc titanate phases produce new Lewis acid sites having also a higher reactivity and that the nature of the catalytic surface transforms from Lewis acidic to basic characters due to the presence of reactive oxygen vacancies.