Novel Preparation of Uniform Heterogeneous Catalysts Derived from Hydrotalcites

Abstract

Several heterogeneous catalysts were prepared starting from Mg-Al and Zn-Al hydrotalcites (HTs) and evaluated for oxidation, ozonation, dehydrogenation and reforming of hydrocarbons, and the CO shift reaction. All catalysts exhibited unique and excellent activities in these reactions. Fe/Mg/Al oxide catalysts prepared from Mg-Al(Fe) HT exhibited high activity for Baeyer-Villiger oxidation of various ketones and dehydrogenation of ethylbenzene. Ozonation activity of Cu/Mg/Al oxide catalysts similarly prepared from Mg(Cu)-Al HT was enhanced by the 'memory effect,' as reconstituted HT on the catalyst surface adsorbed oxalic acid and assisted in complete oxidation. Ni/Mg(Al)O catalysts prepared from Mg(Ni)-Al HT exhibited high and stable activity in steam reforming and oxidative reforming of methane and propane. Moreover, the activity of the Ni catalysts was improved by doping a trace amounts of noble metals by adopting the 'memory effect.' Use of these catalysts in the production of hydrogen for the PEFCs under daily start-up and shut-down operation showed that the catalysts were self-activated and the active Ni metal particles were self-regenerated during the reaction, resulting in high and sustainable activity. CO shift activity of Cu/Zn(Al)O catalysts was also improved by doping a trace Pt or Mg by adopting the memory effect of Zn(Cu)-Al HT in the precursor, resulting in the high sustainability.