Fischer–Tropsch synthesis XAFS

The Effect of Water on the Activity and Selectivity for γ-Alumina Supported Cobalt Fischer–Tropsch Catalysts with Different Pore Sizes

“…Water decreased the reaction ate for all these catalysts. A negative impact on the Fischer-Tropsch activity for cobalt deposited on c-Al 2 O 3 due to addition of water is consistent with previous findings [3][4][5][6][7][8][9][10][11][12][13][14][15][16]. It is known for similar catalysts that water may act as an oxidation agent, producing non-active cobalt.…”

“…The catalyst lost activity in the presence of water, and it was found that small quantities of water (3-25 vol.%) led to mild reversible deactivation, whereas large amounts of water (>28 vol.%) deactivated the catalyst permanently. Jacobs et al [16] used XAS to define the role of water for the activity in the two partial pressure regimes. In the low partial pressure regime (<25 vol.%), XANES scans showed that the structure of cobalt remained intact.…”

Promotion Effects in Co‐Based Fischer—Tropsch Catalysis

“…Very recently, Jacobs et al have reported on Co-Pt/Al 2 O 3 catalysts investigated by EXAFS at the Pt L-edge, and they concluded that isolated Pt atoms interact with the supported cobalt clusters without forming Pt-Pt bonds. 107 The Co K-edge was used to verify that the cobalt cluster size increased slightly for those systems with Pt promotion, in which the cobalt reduction extent increased by a factor of two and the formation of Co aluminates was prevented.…”

Reaction performance and characterization of Co/Al2O3 Fischer–Tropsch catalysts promoted with Pt, Pd and Ru

“…Some researchers suggested that the low temperature peak is ascribed to the two-step reduction of relatively large crystalline Co 3 O 4 particles to Co 0 via CoO [5,14,15]. Whereas others proposed that the low temperature peak is ascribed to the reduction of Co 3 O 4 to CoO, though a fraction of the peak may likely correspond to the reduction of the large, bulk-like CoO species to Co 0 [7,16]. While the precise identity of the species is not clear, most researchers are in agreement that the broad high temperature peak is attributed to the reduction of highly dispersed cobalt surface species strongly interacting with Al 2 O 3 .…”

“…It is expected that, after the standard reduction at 673 K for 8 h, Co 3 O 4 has been completely reduced to CoO. Recent XANES study has shown that the broad high temperature peak of Co/Al 2 O 3 catalyst is due to the reduction of small CoO clusters interacting with the support [16]. Therefore, the H 2 consumptions of the catalysts after standard reduction could be assumed to correspond to the reduction of remaining CoO in the catalysts.…”