Studies of the Fischer-Tropsch Synthesis. XIV. Hägg Iron Carbide as Catalysts¹

Development and process evaluation of improved Fischer-Tropsch slurry catalysts. Final report

“…The higher WGS activity of H2 activated catalysts, in comparison to carbided catalysts, was also observed in several previous studies with iron catalysts (Koibel and Engelhardt, 1949; Anderson, 1984 (p. 45); Schultz et al, 1955). It was inferred that carbides are less active for the WGS than are reduced iron or magnetite.…”

Carbon Pathways, Sodium‐Sulphur Promotion and Identification of Iron Carbides in Iron‐based Fischer‐Tropsch Synthesis

“…The conversion of Fe x C phases into Fe 3 O 4 takes place if either of the H 2 O:H 2 or CO 2 :CO ratios are above critical molar ratios. [1,32,33,56,62,[75][76][77] In general, H 2 O is more potent Fe oxidant than CO 2 . [32,62,77] When moving along a fixed bed reactor towards the FTS reactor outlet, [64,78] or towards the inner core of the Febased catalyst material particle, [56] the reducing H 2 : CO mixture is progressively converted into H 2 O and CO 2 .…”

“…Due to the increasing H 2 O and CO 2 concentrations, the oxidation potential towards forming Fe 3 O 4 from Fe x C increases. [1,56,75,76] Up to around 100-200 μm depth from the particle surface, the Fe-based catalyst particle might remain under reductive environment at FTS reaction conditions. For depths beyond > 200-400 μm from the particle surface, the environment may become oxidative and Fe x C oxidation to Fe 3 O 4 can take over.…”

“…[1] Excessive inactive carbon deposition via the Boudouard reaction (Reaction 6) and/or carbon filament growth causes fragmentation of the, especially bulk, Fe-based catalyst materials into a fine powder. [1,3,4,76,79] The carbon deposition relates to metal carbide sintering in a two-fold manner: i) initially the availability of the FTS reaction active Fe x C sites may increase due to catalyst fragmentation into smaller Fe particles exposing new active Fe x C surface sites. However, ii) after a longer Time-on-Stream (ToS) the Fe tends to sinter into larger Fe particles, thereby resulting in a loss of the available Fe x C surface area.…”

Influence of carbon on iron in the hydrogenolysis of isopentane

“…Reduction in a high flow of H2 was done in the reactor for 45 hours at 450°C. Hagg carbide, FesC2, was prepared from the reduced catalyst in a glass tube according to the method of Shultz et al (1955), by passing CO at an hourly space velocity of 100 and slowly increasing the temperature from 200" to 300°C, to avoid overheating and oxidizing the catalyst. Carbided and used catalysts were kept under hexane during storage and handling to prevent oxidation.…”