Investigations of activated carbon catalyst supports from different natural sources

Abstract

We have used a multi-technique approach to allow us to build a consistent picture of the carbons used for catalyst supports and suggest reasons for the differences between the supports. From the catalyst tests it is clear that the nature of the support has a major influence on the catalyst performance. In part, this is the result of the activation method, however, the hydrogen content of the support also influences the activity. SEM pictures show that the characteristic structures present in the starting material are preserved after carbonisation. The inelastic neutron scattering spectra show that this is also true at the atomic level, with carbons from different sources having different patterns of edge termination of the graphitic structures. That different patterns of edge termination are reflected in the INS spectrum in the out-of-plane C-H bending region around 880 cm À1 is supported by DFT calculations. XPS and SIMS measurements show that for all the carbons, oxygenated and non-aromatic structures are located at the surface of the materials and both decrease rapidly with depth. Comparison of a wood-derived activated carbon before and after impregnation with platinum showed changes that were consistent with reactions on the support during impregnation and reduction treatment in generating the final supported precious metal/carbon catalyst. In addition to redox activity in oxygenated sites enhanced sp 2 type disorder contributes to improved catalyst dispersion.

Characterisation of hydrocarbonaceous overlayers important in metal-catalysed selective hydrogenation reactions

“…This is supported by the observation of two peaks at 1365 and 1465 cm -1 in Figure 4 that can be assigned to unresolved CH 2 twist and wag modes and CH 2 scissors respectively [20]. We note that the spectrum is markedly different from that of solid propyne [14], see Figure 5, and also from that of amorphous carbon [21].…”

Quantification of surface species present on a nickel/alumina methane reforming catalyst

“…Whereas the former is becoming more prevalent, 10,19 somewhat surprisingly, there are very few studies on the use of neutrons to determine concentration data for retained species at catalyst surfaces. Noticeable exceptions are the work of Koon,20,21 Acharya et al, 22 Mitchell and Tomkinson 23 and Albers et al 24,25 Rather innovatively, Koon used a portable neutron source to determine the C : H ratio for coke deposits found on a chromia-alumina catalyst that have been used in the dehydrogenation of 1-butene. That work reports a C : H value of ca.…”

“…24 A subsequent study from the same team correlated the area of C-H bending bands with hydrogen content for a number of activated carbon catalyst support materials. 25 Whilst that work utilised the quantitative aspect of INS to characterise a series of materials used in catalyst preparative procedures, the work presented here seeks to use INS to obtain a quantitative assessment of surface species formed during the course of a reaction over a representative supported metal catalyst. Specifically, it examines an alumina-supported nickel methane reforming catalyst that has been operated at steady state in the methane 'dry' reforming reaction.…”

Non-hydrogenous Materials and Carbon

“…Model fragments with largely HI, all H2 and largely H3 were constructed and the vibrational spectra calculated by DFT [60] as shown in Fig. 11.16.…”