ERTC 2025
Novel textured sphere technology for new high-performance WGS catalysts
Emmanuel Iro, Richard Caulkin, Sergio A. Robledo, and Carl Keeley UNICAT Catalyst Technologies, LLC
Water-gas shift overview The water-gas shift (WGS) reaction max- imises hydrogen (H₂) yield by converting carbon monoxide (CO) to more hydrogen. This reaction can be represented as:
Shift catalyst overview
Temperature range (°C) Catalyst
Composition
Poisoning
Sintering
Magshift™
Traditional catalyst 1 Traditional catalyst 2 Traditional catalyst 3 Traditional catalyst 4
310 and 450
High-temperature shift
Typically contain iron oxide with chromium
Prone to deactivation by sulphur compounds
(HTS) catalysts
CO + H₂O ⇌ CO₂ + H₂
190 and 330
Medium-temperature shift (MTS) catalysts
Often contain a mix of
Sensitivity to sulphur
Susceptible to
copper, zinc, and alumina poisoning
sintering
Being an equilibrium reaction means the reaction can shift either to the products or to the reactants, depending on several fac- tors, such as temperature, pressure, vol- ume, the molar ratio of the feed, and the presence of a catalyst.¹ This reaction increases the total hydro- gen yield, making it a vital component of the hydrogen economy. Furthermore, removing carbon monoxide is crucial for many hydrogen applications, as it acts as a poison for many different catalyst sys- tems. 2 Depending on the operating condi- tions, several shift catalysts can be used ( Table 1 ). Description of the New Catalysts Traditional medium temperature shift (MTS) and low temperature shift (LTS) cat- alysts consist of copper oxide (CuO) dis- persed on a mixed support matrix of zinc oxide (ZnO) and alumina (Al₂O₃). The ZnO supports the CuO and inhibits copper crys- tallite sintering, maintaining stable cata- lyst activity. Similarly, alumina plays a crucial role in maintaining the dispersion of the active copper component, preventing sintering and enhancing thermal stabil- ity. Furthermore, alumina contributes to the overall surface area of the catalyst, improving the dispersion and providing more area for impregnating the active cop- per crystals, thereby ensuring sustained catalyst activity. Traditional catalysts are mainly formed by hydraulic pressing (tabletting). Tabletting results in a pore size distribution that biases towards micropore formation ( Figure 1 ), rendering a significant portion of the surface area and active copper inac- cessible due to diffusion limitations. Tabletting is commonly employed to impart mechanical strength to the cata- lyst particle. Carrier formulation develop- ment was conducted specifically for the WGS textured sphere catalyst. The pre- cise alumina particle size distribution within the supports has been meticulously engineered through experimental design to provide optimal physical and chemical properties tailored to the shift reaction. These properties include high cal- cined strength to enhance pellet mechanical integrity and hydrothermal stability, reduced pellet brittleness, improved Brunauer, Emmett and Teller (BET) surface area, and the necessary surface acidity. Furthermore, the shift catalyst carriers developed exhibit signifi-
150 to 250
Low-temperature shift
Usually based on a copper- Sensitivity to sulphur
Susceptible to
(LTS) catalysts
zinc oxide mix with a small amount of alumina
poisoning
sintering
Magshift™ MTS
Time on stream (h)
Table 1
Figure 2 Comparison of traditional MTS catalysts with Magshift MTS catalyst a
10 12 14 16
Magshift™ catalyst Traditional WGSR catalyst
0 2 4 6 8
Magshift™
Traditional catalyst 1 Traditional catalyst 2 Traditional catalyst 3 Traditional catalyst 4
Lab-produced Magshift™ LTS™
0.001
0.01
0.1
1
10
100
1000
Pore diameter, um
Time on stream (h)
Figure 1 Comparison of pore volume for traditional shift catalysts with Magshift
Figure 3 Comparison of traditional LTS catalysts with Magshift LTS catalyst b
cantly higher mean pore volume than tradi- tional shift catalysts. This pore volume has been designed within a specific size range to optimise the water-gas shift reaction (WGSR) performance (Figure 1). Therefore, the Magshift TM carrier tech- nology offers two primary advantages. The manufacturing method inherently pro- duces a robust matrix without necessitat- ing the compression of particles to achieve strength, thus incorporating mesopores and macropores that facilitate the utilisa- tion of the internal surface area. UNICAT’s research and development efforts successfully synthesised the cop- per-alumina-based textured sphere cat- alyst using its novel production method. This method enables copper to strongly interact with the alumina support, thereby eliminating the need for zinc or chromium promoters in the finished catalyst, which would otherwise compete for valuable surface area with the copper crystalline structure. This allows for better-dispersed, smaller copper crystals and enhanced resistance to thermal sintering. Additionally, the unique textured sphere shape reduces drag and enables reactants to contact a greater geometric surface area of the particle, thereby enabling a closer approach to equilibrium (ATE). Moreover, UNICAT can create the textured spheres in sizes ranging from 14mm to 32mm for WGS reactors. Such sizes are not feasible with traditional shift catalysts, which are limited to 3mm to 6mm cylindrical pellets, sometimes with holes or cut-outs.
copper sintering and extending the cata- lyst’s life-time-on-stream. A comparison of the pore structures of traditional shift catalysts and Magshift is shown in Figure 1. Magshift MTS In testing conducted at UNICAT’s pilot plant facilities in Dewsbury, UK, the Magshift MTS catalyst demonstrated per- formance comparable to commercially available catalysts. The hydrogen and CO₂ yields were consistent with those of com- petitive products. Under MTS test conditions, the tex- tured sphere catalyst exhibited slightly higher activity than the other catalysts (Traditional catalysts 2-4), consistently achieving 100% conversion throughout the test duration ( Figure 2 ). Traditional catalysts 2-4 also demon- strated high activity, achieving 97-98% conversion. However, Traditional catalyst 1 performed poorly at the elevated MTS test temperature of 300°C, with conver- sion rates ranging from 0.8% to 1.4%. This suboptimal performance could be attributed to the sintering of copper oxide under the pilot-plant test conditions. Magshift LTS In testing conducted at UNICAT’s pilot plant, the Magshift LTS catalyst dem- onstrated performance comparable to commercially available catalysts. All the catalysts were first heated under nitro-
did you know? the unique textured sphere shape reduces drag and enables reactants to contact a greater geometric surface area of the particle, thereby enabling a closer approach to equilibrium (ATE) Traditional WGS catalysts have more than 90% microporous structures. Suppose the supplier increases pellet sizes beyond 6mm to reduce pressure drop issues for its customers. In that case, the catalyst performance significantly deteriorates, as the reactant gases strug- gle to reach the active sites due to diffu- sion limitations. In contrast, Magshift has more than 70% macropores, allowing reactant gases to easily access all active sites. The exten- sive pore size network also facilitates the quick dissipation of formed products and heat from exothermic reactions, reducing
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