VK68 Catalyst

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:

• Up to 35% reduction in SO₂ emissions, potentially reducing or eliminating the need for costly tail-gas scrubber systems.

• Up to 30% increase in acid production, together with a corresponding increase in steam generation.

• Double-digit emission levels, well below 100 ppm, without the need for an expensive cesium-containing catalyst.

• 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.