Complex sentence: Cobalt-based catalysts are highly active, although iron may be more suitable for low-hydrogen-content synthesis gases such as those derived from coal due to its promotion of the water-gas-shift reaction.
Split into simpler sentences: Cobalt-based catalysts are highly active, although iron may be more suitable for certain applications. Synthesis gases derived from these hydrogen-poor feedstockes has a low-hydrogen-content and require the water-gas-shift reaction.