Surface characterisation
TPD isopropylamine
Weak interaction between surface and amine, no Bronsted acidity;
density of amine adsorption similar to SiO2
(0.32µmol/m2 for β-SiC vs 0.36µmol/m2
for Aerosil-150).
The surface of the β-SiC is comparable to the surface of silica allowing an easy active phase deposition by conventional techniques.
Chemical stability
The SICAT β-SiC is resistant toward most aggressive media such acids and bases and the mechanical strength
and the BET surface area remain stable after 2-3 weeks aging at 20ºC in:
• HF (40% vol.), HCl (37% vol.), HNO3 (68% vol.), NaOH (10M)
The chemical inertness of the support allows to wash out the deactivated phase of the spent catalyst by chemical treatment
in order to recover the support and if needed for environmental and economical purpose to recover precious metals, metals and metal oxides.
Figure 1: A spent catalyst (Co/SiC) treated by a nitric acid solution (1M, 25ºC). The metal and the support were recovered. After impregnation of the washed support, the catalyst exhibited the same catalytic performances as a fresh catalyst.
Thermal stability and oxidation resistance
β-SiC offers strong thermal resistance. The mechanical strength and the BET surface area remain unchanged after thermal shocks, hydrothermal* and oxidative aging.
The aging conditions are described:
• Thermal shocks resistance (DIN model)
5 successive shocks from 600ºC to 20ºC, air
• Simulated regeneration conditions
165 cycles from 600ºC to 200ºC, air
• Stability in hydrothermal* conditions
270ºC, 55 bar steam, air during 4 months
*SBET drops to 18m2/g after 15 days then remains stable during time
• Oxidation resistance
500ºC, 30% vol. steam, air during 1 month
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