Water-gas shift catalysts

Eu Q, Saltsburg H, Elytzani-Stephanopoulos M. 2003. Active nonmetallic Au and Pt species on ceria-based water-gas shift catalysts. Science 301 935-938. 

Catalytic upgrading of the hydrogen-rich syngas (tar and hydrocarbon conversion, possibly in combination with filtration, also water gas shift catalyst use and... 

Major differences were noted between the systems derived from Fe(CO)c and M(CO) (M = Cr, Mo, and W) with respect to the effect of the base concentration on the reaction rate. Thus in the case of the catalyst system derived from Fe(CO)5 tripling the amount of KOH while keeping constant the amounts of the other reactants had no significant effect on the rate of H2 production (11). However, in the case of the catalyst system derived from W(CO)g the rate of production increased as the amount of base was increased regardless of whether the base was KOH, sodium formate, or triethylamine (12). This increase may be interpreted as a first order dependence on base concentration provided some solution non-ideality is assumed at high base concentrations. Similar observations were made for the base dependence of H2 production in catalyst systems derived from the other metal hexacarbonyls Cr(CO) and Mo(CO) (12). Thus the water gas shift catalyst system derived from Fe(CO)5 has an apparent zero order base dependence whereas the water gas shift catalyst systems derived from M(CO)g (M - Cr, Mo, and W) have an approximate first order base dependence. Any serious mechanistic proposals must accommodate these observations. 

The by-product, representing a relatively reduced form of sulfur, is a reasonable model for the sulfur impurities in the synthesis gas obtained from sulfur-rich coal. This sodium sulfide test of sulfur resistance of water gas shift catalyst systems generated in basic solutions is a very severe test since the quantities of sulfur involved are much larger than those likely to be found in synthesis gas made from any sulfur-rich coals. 

The activation energies of these water gas shift catalyst systems were determined by rate measurements as a function of temperature. Thus on the basis of rate measurements at the five temperatures 180, 160, 150, 140, and 130°C the activation energy of the catalyst system derived from Fe(C0)5 was estimated at... 

Flytzani-Stephanopoulos and coworkers—urea method for preparing high surface area ceria/substituting noble metals with base metals/cationic active sites for Au and Pt-ceria catalysts/deactivation by hydroxycarbonates and improved stability with 02 co-feeding. Li et al.396 reported on low temperature water-gas shift catalysts in their search for a replacement catalyst for Cu/ZnO suitable for use in a fuel... 

Kim and Thompson—site blocking by formates/carbonates over Au/ceria catalysts linked to deactivation. Kim and Thompson437 reported on the deactivation of Au/ceria catalysts. The ceria was prepared by the decomposition of cerium carbonate (BET SA ceria calcined at 400 °C = 203 m2/g) or obtained from Rhodia (BET SA ceria calcined at 400 °C = 155 m2/g). Au was added by precipitation of HAuC14, resulting in a particle distribution between 1 and 10 nm, with the majority of clusters between 2 and 7 nm, as examined by HR-TEM. The experimental catalyst was tested with respect to the Sud-Chemie water-gas shift catalysts, consisting of Cu-Zn-Al with surface area 60 m2/g, and results are reported in Table 87. 

Does any industrial water-gas shift catalyst exist that can reach equilibrium CO conversion at 410 K for Question 3 a ... 

Although in many WGS applications cases conventional HTS catalysts are used, for some applications water-gas shift catalysts may be needed that operate at temperatures above the current industrial standard. Also, stability in a steam atmosphere, during regeneration of a SEWGS reactor, is an issue. 

Alternative water gas shift catalysts developed at ANL have shown activity comparable to commercially available shift catalysts but with the advantage that ANL s catalyst can be exposed to oxidizing/reducing environments without any loss in activity. This is very important as... 

Ruettinger, W., Ilinieh, O., Farrauto, R.J. 2003. A new generation of water gas shift catalysts for fuel eell applieations. J Power Sourees 118 61-65. 

Two homogeneous metal complex water-gas shift catalyst systems have recently appeared 98, 99). The more active of these comes from our Rochester laboratory (99, 99a). It is composed of rhodium carbonyl iodide under CO in an acetic acid solution of hydriodic acid and water. The catalyst system is active at less than 95°C and less than 1 atm CO pressure. Catalysis of the water-gas shift reaction has been unequivocally established by monitoring the CO reactant and the H2 and C02 products by gas chromatography The amount of CO consumed matches closely with the amounts of H2 and C02 product evolved throughout the reaction (99). Mass spectrometry confirms the identity of the C02 and H2 products. The reaction conditions have not yet been optimized, but efficiencies of 9 cycles/day have been recorded at 90°C under 0.5 atm of CO. Appropriate control experiments have been carried out, and have established the necessity of both strong acid and iodide. In addition, a reaction carried out with labeled 13CO yielded the same amount of label in the C02 product, ruling out any possible contribution of acetic acid decomposition to C02 production (99). 

Our present working hypothesis for the mechanism of this water-gas shift catalyst system remains essentially the same as it was initially presented (99). The catalytic cycle consists of two separate reactions, with the rhodium alternating between the Rh(I) and Rh(III) oxidation states. 

Ford and co-workers have also recently developed a homogeneous catalyst system for the water-gas shift reaction (95). Their system consists of ruthenium carbonyl, Ru3(CO)12, in an ethoxyethanol solvent containing KOH and H20 under a CD atmosphere. Experiments have been conducted from 100-120°C. The identity of the H2 and CD2 products has been confirmed, and catalysis by both metal complex and base has been verified since the total amount of H2 and COz produced exceeds the initial amounts of both ruthenium carbonyl and KOH. The authors point out that catalysis by base in this system depends on the instability of KHC03 in ethoxyethanol solution under the reaction conditions (95). Normally the hydroxide is consumed stoichiometrically to produce carbonate, and this represents a major reason why a water-gas shift catalyst system has not been developed previously under basic conditions. As has been noted above, coordinated carbonyl does not have to be greatly activated in order for it to undergo attack by the strongly nucleophilic hydroxide ion. Because of the instability of KHC03... 

Protonation of a carbonyl oxygen rather than the metal may be encouraged in this case by the high coordination number of vanadium. This would then promote halide attack on the carbonyl carbon to yield an intermediate hydroxyhalocarbene, which reacts further to yield the indicated products. This system represents a potential photoassisted water-gas shift catalyst system since H3V(CO)3(diars) upon photolysis with a mercury vapor lamp yields H2, and in the presence of CO regenerates the starting complex HV(CO)4(diars). The feasibility of coupling these two reactions in the same reaction solution remains to be demonstrated. 

Reuse et al. [24] applied a reactor carrying micro structured plates for methanol steam reforming over commercial copper-based low-temperature water-gas shift catalyst from Sud-Chemie. The reactor took up 20 plates made of FeCrAl alloy of size 20 mm x 20 mm x 0.2 mm. The channel size was 200 pm x 100 pm (Figure 2.5). The catalyst was conditioned by oxygen and hydrogen treatment. 

Water-gas Shift 3 [WGS 3] Sandwich-type Reactor ([HCR 4]) Applied to Water-gas Shift Catalyst Testing... 

Several Alkane Activation and Water-Gas Shift Catalysts Applied Catalysis A General, 101 (1993) 317-338. 

ANALYSIS OF DEACTIVATION OF A WATER GAS SHIFT CATALYST CoMoK/A1203 IN AN AMMONIA PLANT... 

Loffler DG, McDermott SD, Renn CN. Activity and durability of water-gas shift catalysts used for the steam reforming of methanol. J Power Sources. 2003 114(1) 15—20. 

The chances of success are greater if one tries to develop a homogeneous water gas shift catalyst rather than a steam reformation catalyst. Why ... 

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