VK68
The power of no cesium
VK68 is a cesium-free catalyst designed for lean gases in the lower beds of sulfuric acid plants, typically downstream of intermediate absorption towers.
TOPSOE™ VK68 is optimized for operation in lean gases from 400°C and above, which is typical of the fourth pass in 3+1 double-absorption plants. Under these conditions, VK68 provides several times the activity of conventional potassium-promoted catalysts. At approximately 420°C and above, its activity matches that of the high-performance VK69 catalyst, while still providing a significant activity advantage at temperatures between 400°C and 420°C.
The high activity of VK68 creates new opportunities for double-absorption plants to achieve many of the proven benefits associated with VK69, and because VK68 contains no cesium – the largest contributor to Cs-promoted catalyst cost – it offers a cost-effective alternative for suitable applications.
For example, for a typical S-burning plant, VK68 installed in the final pass can provide:
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Up to 35% reduction in SO₂ emissions, potentially reducing or eliminating the need for costly tail-gas scrubber systems.
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Up to 30% increase in acid production, together with a corresponding increase in steam generation.
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Double-digit emission levels, well below 100 ppm, without the need for an expensive cesium-containing catalyst.
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A practical solution for debottlenecking challenges in the upper beds, such as rapid deactivation in the first passes, or flow-distribution issues.
Activity
VK68 catalyst activity has been measured under lean gas conditions, demonstrating that from 420°C onward it fully matches the superior activity of VK69 – delivering 2 to 3 times higher activity than VK38. Even below that point, in the 400–420°C range, VK68 already shows outstanding performance, reaching up to 2 times higher activity than conventional VK38 and 1.5 times higher than VK38+, making it by far the most active cesium-free catalyst on the market for this application, even outperforming most cesium catalyst. These high performance levels have also been verified in the first full-scale sulfuric acid plant using VK68.
