Adsorption and reaction of CO and hydrogen on iron-based Fischer–Tropsch synthesis catalysts

The role of potassium promoter in surface carbon hydrogenation on Hägg carbide surfaces

“…It is claimed that potassium promoter can enhance the activity of FTS [5] and water-gas shift reaction (WGS) [14], and increase the selectivity of the desired heavy hydrocarbons [15]. In addition, potassium promoter is known to promote CO adsorption and dissociation [16][17][18], improve (or suppress) H 2 adsorption [19][20][21], increase the carburization rate of iron catalysts [3], and suppress CH 4 formation [22]. Recently, K 2 O promotion has been proposed to modify the Fe crystallite morphology in stabilizing the more active facets [23].…”

Cu-Promoted Fe2O3/MgO-Based Fischer–Tropsch Catalysts of Biomass-Derived Syngas

“…The 250ºC peak probably corresponds to the reduction of surface Fe 3+ to mixture of Fe 3+ (100)) surfaces [30][31][32][33] . As reported in these studies, the CO desorbs from a clean Fe (100) surface to produce four CO desorption peaks, which were designated as three desorption peaks at temperature of -23, 67, and 157°C and are ascribed to the desorption of CO molecular states, while the fourth peak at ~ 527°C is attributed to desorption of dissociative CO adsorbed and recombined to desorb at this temperature 34 . The temperatures of the main CO desorption peaks in this study from carburized iron surfaces on all catalysts studied herein are far higher than those of the molecular CO on the Fe (100) surface and fall in the temperature range of dissociative CO desorption.…”

Effects of Zr and K Promoters on Precipitated Iron-Based Catalysts for Fischer–Tropsch Synthesis

“…If desorbed in thermal flashing, the required temperature for CO on iron carbide surfaces should be about 500°C, which is slightly lower than the CO desorption temperatures in our study. Therefore, the CO-TPD peaks on carburized catalysts are most likely to result from the strongly bound CO on iron carbide surfaces [29].These results imply that K largely improves the CO adsorption on carburized catalysts, which is in good consistence with the effect of K on CO adsorption on iron surfaces [32].…”

“…H 2 desorption peaks below 250°C are corresponding to the H species adsorbed on the metallic iron surface. The peaks at higher temperature ([350°C) may be ascribed to the cleavage of OH species on the difficultly reduced oxide surface in catalysts [29]. H 2 -TPD results indicate that K apparently suppresses the H 2 adsorption on catalyst surfaces.…”

“…This phenomenon has been rarely reported in previous studies. Also, there are few works studying on the CO adsorption on iron carbide surfaces [29,31]. The desorption temperatures of CO on carburized catalysts are close to that of the dissociative CO.…”