TITLE: Transient-Kinetic Study of Nickel-Catalyzed Methanation: Performance Report.

AUTHOR: P. Biloen.

INST.  AUTHOR: Pittsburgh Univ., PA.

SPONSOR: Department of Energy, Washington, DC.


PUB.  TYPE: Technical Report

PUB.  COUNTRY: United States

SOURCE: Department of Energy [DE],  1986,  23p.



The notion of a ''carbidic'' mechanism for methanation (and Fischer Tropsch hydrocarbon synthesis) has been challenged by isotopic transient-kinetic experiments. ''Carbidic mechanism'' is being utilized in the prevailing context for a global scheme characterized by an inventory of non-oxygen containing (''carbidic'') intermediates CH/sub x/-ad, serving as the precursors for methane and higher hydrocarbons. Platinum is known to be a methanation catalyst on the one hand, and being incapable of dissociating CO efficiently on the other hand. It therefore is implausible that methanation over platinum proceeds via a ''carbidic'' mechanism. Nickel dissociates CO efficiently and has been identified with the ''carbidic'' mechanism. Accordingly, an isotopic transient-kinetic comparison of platinum and nickel was performed. Fig. 1a and b give representative transient responses of Ni and Pt. In the pertaining experiments the feed at the inlet of a plug-flow reactor was switched abruptly from sup 12 CO/H sub 2 to sup 13 CO/H sub 2 . With on-line mass spectrometry the transient decay of sup 12 CH sub 4 and the transient ingrowth of sup 13 CH sub 4 was monitored at the reactor outlet. The transient response of platinum and nickel is clearly different. When changing from sup 12 CO/H sub 2 to sup 13 CO/H sub 2 , the production of sup 12 CH sub 4 over platinum ceases immediately, whereas over nickel it continues for some 100 s. 28 refs., 22 figs. (ERA citation 12:028262)