279 1
Communications to the Editor
Homogeneous Catalysis of the Water Gas Shift Reaction Using Rhodium Carbonyl Iodide
A 0
Sir:
The water gas shift reaction, eq I , H2O
+ CO
+ H2
+ CO2
(1)
has been of great industrial importance for over 40 years.' The reaction finds application in the large scale production of hydrogen for ammonia synthesis,2 in increasing the H2:CO ratio for methanation and Fischer-Tropsch synthesis,' and in the treatment of combustion exhaust gases through CO removal and Hz generation for reducing nitrogen and sulfur oxide^.^ Heterogeneous catalysts for eq 1 fall into two distinct categories, based either on Fe304 and related oxides a t temperatures exceeding 350 "C, or on copper metal in the range 200-250 OC.* Under ambient conditions, the reaction is slightly favored thermodynamically (AH0198 = +0.68 kcal/ mol; AGO298 = -4.76 kcal/mol), but a t higher temperatures the equilibrium becomes significantly less favorable for product formation ( K equals 1.45 X I O 3 and 26.9 a t 127 and 327 O C , respectively4). The mechanism of the heterogeneously catalyzed reaction has been much s t ~ d i e d .To ~ , date, ~ few reports have appeared on the homogeneous catalysis of eq 1 ,6-8 the most recent one being by Ford and co-workers using R U ~ ( C O ) , ~We . * herein wish to report a more active homogeneous catalyst system for the water gas shift reaction which functions at low temperatures (
