ae8b00145_si_001.pdf (1.7 MB)
Stability of Molten-Phase Cs–V–O Catalysts for SO3 Decomposition in Solar Thermochemical Water Splitting
journal contribution
posted on 2018-04-19, 00:00 authored by Alam S.
M. Nur, Takayuki Matsukawa, Asuka Ikematsu, Masato MachidaSupported molten
cesium vanadate catalysts (Cs–V–O/SiO2) showed
activities comparable to that of a reference Pt catalyst (1 wt % Pt/TiO2) for SO3 decomposition at moderate temperatures
(∼600 °C), which is essential as an O2 evolution
reaction in solar thermochemical water splitting cycles. Stability
testing of the catalyst over a 1000 h continuous reaction at 600 °C
resulted in deactivation by ∼20% of the initial activity. Kinetic
analysis of the activity versus time-on-stream indicated that the
observed deactivation behavior can be divided into an induction period
(≤100 h) and an acceleration period (>100 h). The deactivation
is mainly caused by the vaporization loss of active components (Cs
and V) from the molten phase. At the earliest stage, most vapor is
generated in the upstream section of the catalyst bed and then redeposits
therebelow. Upon repeating these vaporization and deposition cycles,
Cs and V move gradually downstream. During this induction period,
the deactivation is not obvious because the total Cs and V content
of the catalyst bed remains almost unchanged. After this period, however,
detachment of Cs and V from the downstream end of the catalyst bed
induces accelerated deactivation. The vaporization loss was found
to be significantly suppressed by inverting the catalyst bed every
100 h during the stability test. Consequently, this operation reduced
the extent of catalyst deactivation from 20% to less than 10% of the
initial activity.