Preparation of thermally stable high surface area mesoporous tetragonal ZrO2 and Pt/ZrO2:: An active hydrogenation catalyst

Thermally stable mesoporous tetragonal zirconia with high surface area (153 m(2)/g at 700 degrees C) has been prepared by using bifunctional ethylene diamine as both precipitating agent for ZrOCl2 to ZrO(OH)(2) and colloidal protecting agent for the ZrO(OH)(2) nanoparticles. The zirconia sample was found to possess the tetragonal crystal phase exclusively. This approach avoids traditional bases such as NH3, NaOH and expensive surfactants and copolymers, which are usually employed as templates for the synthesis of high surface area and thermally stable metal oxides. Pt nanoclusters of size similar to 20-30 angstrom have been prepared in a single step chemical reduction method in aqueous media. The Pt nanoclusters have been deposited on mesoporous (pore size approximate to 35-45 angstrom) hydrous zirconia by adopting the 'precursor' route. The Pt nanoclusters have been found almost evenly dispersed in the hydrous zirconia matrix without aggregation. The ethylene diamine likely serves as a link between the support (ZrO(OH)(2)) and Pt nanoclusters. The Pt/ZrO2 catalyst has been found to be highly active for 1-hexene hydrogenation reactions with a turnover frequency of about 20,000 h(-1). All systems have been characterized by TEM, EDX, SEM, X-ray diffraction, N-2 adsorption-desorption isotherms and TGA. (c) 2005 Elsevier Inc. All rights reserved.