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Effects of processing parameters on the morphology of precipitated manganese oxide powders / Zhao, Qiang in Industrial & engineering chemistry research, Vol. 48 N°3 (Février 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N°3 (Février 2009) . - p. 1490–1494 Titre : Effects of processing parameters on the morphology of precipitated manganese oxide powders Type de document : texte imprimé Auteurs : Zhao, Qiang, Auteur ; Shih, Wan Y., Auteur ; Shih, Wei-Heng, Auteur Année de publication : 2009 Article en page(s) : p. 1490–1494 Langues : Anglais (eng) Mots-clés : Manganese  oxide  powders Résumé : It is desirable that the surface area of catalytic materials can be controlled by adjusting the processing parameters. In this paper we report that the morphology of precipitated manganese oxide powders after 500 °C calcination is affected by the volume ratio between the manganese nitrate precursor and ammonium hydroxide and also by the concentration of the precursor solution. When a large amount of ammonium hydroxide (nominal concentration of NH4OH in the final suspension greater than 4 N) was used, the synthesized powder had plate-like particles with higher specific surface area compared to spherical particles made by a small amount of ammonium hydroxide (nominal concentration of NH4OH less than 1 N). Thinner plates were synthesized from the system with lower nominal concentration of Mn(NO3)2, resulting in even higher specific surface area. The surface area differences between these powders synthesized by different conditions decreased as the calcination temperatures increased from 500 to 900 °C because the high calcination temperatures eliminated the morphology difference among them. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801173e [article] Effects of processing parameters on the morphology of precipitated manganese oxide powders [texte imprimé] / Zhao, Qiang, Auteur ; Shih, Wan Y., Auteur ; Shih, Wei-Heng, Auteur . - 2009 . - p. 1490–1494. Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N°3 (Février 2009) . - p. 1490–1494 Mots-clés : Manganese  oxide  powders Résumé : It is desirable that the surface area of catalytic materials can be controlled by adjusting the processing parameters. In this paper we report that the morphology of precipitated manganese oxide powders after 500 °C calcination is affected by the volume ratio between the manganese nitrate precursor and ammonium hydroxide and also by the concentration of the precursor solution. When a large amount of ammonium hydroxide (nominal concentration of NH4OH in the final suspension greater than 4 N) was used, the synthesized powder had plate-like particles with higher specific surface area compared to spherical particles made by a small amount of ammonium hydroxide (nominal concentration of NH4OH less than 1 N). Thinner plates were synthesized from the system with lower nominal concentration of Mn(NO3)2, resulting in even higher specific surface area. The surface area differences between these powders synthesized by different conditions decreased as the calcination temperatures increased from 500 to 900 °C because the high calcination temperatures eliminated the morphology difference among them. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801173e

Redox activity and NO storage capacity of MnOx−ZrO2 with enhanced thermal stability at elevated temperatures / Zhao, Qiang in Industrial & engineering chemistry research, Vol. 49 N° 4 (Fevrier 2010) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 49 N° 4 (Fevrier 2010) . - pp 1725–1731 Titre : Redox activity and NO storage capacity of MnOx−ZrO2 with enhanced thermal stability at elevated temperatures Type de document : texte imprimé Auteurs : Zhao, Qiang, Auteur ; Shih, Wan Y., Auteur ; Chang, Hsiao-Lan, Auteur Année de publication : 2010 Article en page(s) : pp 1725–1731 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Oxides  MnOx  ZrO2  Redox  Heat  treatment. Résumé : MnOx−ZrO2 mixed oxides are very active catalysts for oxidation or combustion applications due to their excellent redox activity. Recently, they have also shown promising results for NO storage in emission control. Despite the versatile applications, a systematic study on the redox activity and NO storage capacity of MnOx−ZrO2 with their thermal stability at high temperatures is still missing. In this paper the evolution of these properties in the temperature range 500−900 °C is reported. It was found that there is a dramatic deterioration in redox activity and NO storage capacity when the calcination temperature increases to 900 °C, which is attributed to the loss of thermal stability at this high temperature. On the other hand, doping with La can hinder the sintering of MnOx−ZrO2 particles and therefore increase the surface area of the mixed oxides calcined at 900 °C. Correspondingly, La-doped MnOx−ZrO2 mixed oxides show much improved redox activity and NO storage capacity even after 900 °C heat treatment. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901234x [article] Redox activity and NO storage capacity of MnOx−ZrO2 with enhanced thermal stability at elevated temperatures [texte imprimé] / Zhao, Qiang, Auteur ; Shih, Wan Y., Auteur ; Chang, Hsiao-Lan, Auteur . - 2010 . - pp 1725–1731. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 4 (Fevrier 2010) . - pp 1725–1731 Mots-clés : Oxides  MnOx  ZrO2  Redox  Heat  treatment. Résumé : MnOx−ZrO2 mixed oxides are very active catalysts for oxidation or combustion applications due to their excellent redox activity. Recently, they have also shown promising results for NO storage in emission control. Despite the versatile applications, a systematic study on the redox activity and NO storage capacity of MnOx−ZrO2 with their thermal stability at high temperatures is still missing. In this paper the evolution of these properties in the temperature range 500−900 °C is reported. It was found that there is a dramatic deterioration in redox activity and NO storage capacity when the calcination temperature increases to 900 °C, which is attributed to the loss of thermal stability at this high temperature. On the other hand, doping with La can hinder the sintering of MnOx−ZrO2 particles and therefore increase the surface area of the mixed oxides calcined at 900 °C. Correspondingly, La-doped MnOx−ZrO2 mixed oxides show much improved redox activity and NO storage capacity even after 900 °C heat treatment. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901234x