Pd catalysts supported on silica were tested for H2O 2 direct synthesis under very mild (1 bar, 20C, no halide addition) and nonexplosive conditions. Other catalytic tests were performed at higher pressure using a solvent expanded with CO 2. The optimum Pd content is 1.5 w t.%. Calcination is mandatory to preserve catalytic performance and recycle the catalyst. A comparison among Pd samples with similar metal content over different supports was performed under identical experimental conditions, showing that Pd/ SiO2 gives the highest selectivity (constant at 60%). At the same time, the produc tivity follows the trend: Pd= SiO2> Pd= ZrO2= SO¼4> Pd= ZrO2> Pd= CeO 2= SO¼4> Pd= CeO2 . HRTEM and chemisorption results clearly indicate that a high Pd dispersion is not advisable to observe good catalytic performance. On the contrary, the presence of less energetic Pd sites exposed at the surface of big particles of Pd/SiO 2, where oxyg en can chemisorb without dissociation, is a necessary condition to produce H 2O2

When high metal dispersion has a detrimental effect: Hydrogen peroxide direct synthesis under very mild and nonexplosive conditions catalyzed by Pd supported on silica

MENEGAZZO, FEDERICA;SIGNORETTO, Michela;PINNA, Francesco;STRUKUL, Giorgio;
2012-01-01

Abstract

Pd catalysts supported on silica were tested for H2O 2 direct synthesis under very mild (1 bar, 20C, no halide addition) and nonexplosive conditions. Other catalytic tests were performed at higher pressure using a solvent expanded with CO 2. The optimum Pd content is 1.5 w t.%. Calcination is mandatory to preserve catalytic performance and recycle the catalyst. A comparison among Pd samples with similar metal content over different supports was performed under identical experimental conditions, showing that Pd/ SiO2 gives the highest selectivity (constant at 60%). At the same time, the produc tivity follows the trend: Pd= SiO2> Pd= ZrO2= SO¼4> Pd= ZrO2> Pd= CeO 2= SO¼4> Pd= CeO2 . HRTEM and chemisorption results clearly indicate that a high Pd dispersion is not advisable to observe good catalytic performance. On the contrary, the presence of less energetic Pd sites exposed at the surface of big particles of Pd/SiO 2, where oxyg en can chemisorb without dissociation, is a necessary condition to produce H 2O2
2012
290
File in questo prodotto:
File Dimensione Formato  
J.Catal 2012.pdf

non disponibili

Tipologia: Documento in Post-print
Licenza: Accesso chiuso-personale
Dimensione 844.65 kB
Formato Adobe PDF
844.65 kB Adobe PDF   Visualizza/Apri

I documenti in ARCA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10278/29709
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 54
  • ???jsp.display-item.citation.isi??? 53
social impact