Chemical Transient Kinetics Applied to CO Hydrogenation over a Pure Nickel Catalyst

Abstract

CO hydrogenation over unsupported Ni model catalysts has been studied by chemical transient kinetics (CTK) to provide insight into the time-dependent surface processes leading to hydrocarbon formation at atmospheric pressures. Buildup and backward transients were triggered by stepwise changes of the CO flow into the reactor. CTK data have been evaluated, for the first time, to allow counting of the number of surface carbon, oxygen, and hydrogen atoms from the onset of catalytic reaction conditions to steady state. In this manner, it is shown that the total amount of these atoms may considerably exceed the monolayer limit on Ni metal. Back transients from CO/H 2 to pure H 2 show that the intermediates react in two steps, of which the second occurs with a common first-order decay time for all hydrocarbons (C 1 to C 4 , in this case). This is in agreement with a chain growth mechanism, in which the C 1 most abundant surface intermediate (masi) is always of the same type. Indications have been obtained that a CO insertion mechanism is in operation to form this masi.

High Catalytic Activity in CO Oxidation over MnO x Nanocrystals

“…Mn 2 O 3 and Mn 3 O 4 . The oxalate route toward small metal and metal-oxide particles was previously reported by our group for Mn, Co, Ni and Cu in metallic or oxidized form [10,11] as well as for TiO 2 -supported Ag [12].…”

“…It has been shown, however, that metal oxalates may precipitate fast in either aqueous or non-aqueous solvants [11,12,14,15]. Subsequent thermal decomposition causes (crystal-) water, carbon monoxide and carbon dioxide to be released in variable amounts.…”

“…Subsequent thermal decomposition causes (crystal-) water, carbon monoxide and carbon dioxide to be released in variable amounts. In certain cases, provided that this decomposition is performed under inert gas conditions, only water and carbon dioxide are produced so that pure metal is obtained with relatively high specific surface area [11]. If on the other hand, the thermal decomposition is conducted in the presence of oxygen gas, metal oxides of variable stoichiometry are formed.…”

Fischer-Tropsch Synthesis on Multicomponent Catalysts: What Can We Learn from Computer Simulations?

“…Not only Fe, Co and Ru are being considered in this quest for novel catalysts for the Fischer-Tropsch synthesis reaction. Other transition metals (and alloys of different metals) are being considered, especially those from group VIIIA in the Periodic Table because they display some activity in the C-C coupling reaction during CO hydrogenation [13,[16][17][18][19][20][21][22][23][24][25][26][27][28][29]. Yet, this is not a trivial task since small variations in the catalyst composition change dramatically the reaction yield and/or selectivity.…”

Study of K/Mn‐MgO Supported Fe Catalysts with Fe(CO)5 and Fe(NO3)3 as Precursors for CO Hydrogenation to Light Alkenes

“…Ru, Fe, Ni and Co) are generally considered as the traditional catalysts for CO hydrogenation for Fischer-Tropsch synthesis (FTS). [4][5][6][7] Fe has attracted considerable attention because of its relatively high activity and light olefins selectivity in CO hydrogenation. [8,9] For supported iron catalysts, in the previous studies, the scientists have proved that the precursors could largely influence the activity and selectivity of catalysts.…”