Use of Nitrogen-Containing Carbon Supports To Control the Acidity of Supported Heteropolyacid Model Catalysts Academic Article uri icon

abstract

  • © 2018 American Chemical Society. Physical and chemical properties of heteropolyacids (HPAs), e.g., H3PMo12O40 supported on nitrogen-containing carbon materials, were investigated. Supports included nitrogen-doped graphitic carbons (N-C-1000 (2 N at.%) and N-C-600 (19 N at.%)) and mesoporous graphitic carbon nitride (mpgC3N4 (53 N at.%)). The ability to disperse HPAs without crystallite formation followed the trend N-C-600 < N-C-1000 activated carbon (C) < mpgC3N4. HPAs preferentially interact with pyridinic nitrogen and surface NH2 groups; the latter lead to ammonium HPA salt crystallites observed via X-ray diffraction (XRD). At low coverage, HPAs are molecularly dispersed on all four supports. At comparable polyoxometalate coverages, C and N-C-1000 showed similar dehydration/oxidation activities in methanol oxidation. However, N-C-600 and mpgC3N4 exhibited lower activities for both reactions. The much-greater decrease in dehydration vs oxidation activity on nitrogen-rich supports led to higher catalyst oxidation selectivities. This work demonstrates that acid site populations of HPA catalysts can be controlled via support nitrogen content.

altmetric score

  • 0.25

author list (cited authors)

  • Zhao, X., Li, X., Chen, J., & Barteau, M. A.

citation count

  • 3

publication date

  • October 2018