Abstract
Most chemical reactions occur over multiple steps whose identity is
elucidated by experiment, yielding a reaction mechanism. Knowledge of
cognitive science suggests that mechanism elucidation can be viewed as
a knowledge-guided search within a combinatorial space. The MECHEM
computer program searches this space comprehensively for the simplest
plausible mechanisms. We use MECHEM to find mechanisms for
Fischer-Tropsch chemistry and CO2 reforming of methane, both
heterogeneous catalytic reactions of current importance. The results
reveal hundreds of equally simple mechanisms consistent with evidence.
Hence, mechanism elucidation in catalysis is a much harder problem
than is ordinarily realized.
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