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Calcined NiMgMn LDH Modified with Noble Metals in Total Oxidation of toluene
|Zuzana Mikulová 1, Jana Balabánová 1, František Kovanda 2, Květa Jirátová 1|
1. Czech Academy of Sciences, Institute of Chemical Process Fundamentals (ICPF), Rozvojová 135, Prague 16502, Czech Republic
Volatile organic compounds (VOCs) in industrial gases represent a serious environmental problem. The VOCs in the air can be reduced applying the process of total catalytic oxidation. Catalysts with noble metals are currently preferred as they are highly active and stable but expensive. Metal oxide alternatives are cheaper but less stable. Combination of both groups of active materials could give highly active catalysts with sufficient stability. In our previous study we found high activity of the calcined NiMgMn LDH in total oxidation of VOC in air. Now we attempted to improve its catalytic properties by introducing of small amount (0.1 wt%) of noble metals from different precursors and to reveal their effect on physical chemical properties and the activity in total oxidation of toluene. The Ni-Mg-Mn LDH precursor was prepared by coprecipitation. The calcined product was either impregnated by solutions of various noble metal salts or by their microemulsions. The catalysts were characterized by SBET, XRD, TPR and XPS. Activity in toluene total oxidation was examined. A well-crystalline Ni-Mg-Mn LDH was obtained after precipitation, with small fraction of crystalline MnCO3. After calcination, mixed oxide phases were formed. XPS analysis showed enrichment of its surface by Ni and Mn (surface concentrations Ni:Mg:Mn-41:11:48 at.%). Temperature T50 (corresponding to 50% toluene conversion) was 153°C and after 15 h increased to 180°C. Modification of the parent catalyst with noble metals did not change initial catalytic activity too much (T50 152+-2°C). However, substantial difference was observed in catalyst stability. After 15 h examination, the T50 value for the NiMgMn catalyst (180°C) decreased for the modidied catalysts in the following order: AgNO3 (174), Pd(NO3)2 (170), H2PtCl6-Me (170), (NH3)4Pt(NO3)2-Me (166). Acknowledgement This work was supported by the Grant Agency of the Czech Republic (grants No. 104/04/2116 and GD203/03H140).
Presentation: Poster at E-MRS Fall Meeting 2006, Symposium B, by Zuzana Mikulová
See On-line Journal of E-MRS Fall Meeting 2006
Submitted: 2006-05-15 12:03 Revised: 2009-06-07 00:44