Contact Section - Catalysts - BASF
December 21, 2023

Introduction

In 1901, Badische Anilin- & Soda-Fabrik (BASF) was issued German Patents 113933 and 133933 which described their pioneering activities in the development of the contact process which employed a catalyst to promote the oxidation of  SO₂ and O₂ to give SO₃.  At this time the active ingredient in the catalyst was platinum.  Platinum catalysts exhibit high activity but were costly and were easily deactivated by poisons such as arsenic trioxide (As₂O₃). 

Development continued into alternative catalysts that did not suffer the disadvantages of platinum and were less costly to manufacture.  In 1913, BASF was issued German Patent 291792 and Swiss Patent 71326 for a catalyst consisting of vanadium pentoxide and alkali metal oxides on a porous silica carrier.  This new catalyst was first used in a commercial scale plant in 1915.  The results were successful and the remaining platinum catalysts was soon replaced with vanadium pentoxide catalyst.

Today, BASF offer 3 different types of catalyst in a variety of shapes for various situations in sulphuric acid plants.

Catalyst Types

The physical properties of the catalyst are provided in the following table and a brief description of each catalyst is given below.

Other Shapes

S6: 6 mm pellet
S8: 8 mm pellet
SS11x4: 11 x 4 mm star ring
SR10x5: 10 x 5 ring
SR11x4: 11x 4 ring

O4-110

Type O4-110 is a proven catalyst primarily used in the first converter bed.  The catalyst is suitable for sulphur combustion gases and for waste gases from metallurgical plants or from H₂S combustion (i.e. wet catalysis).  The catalyst possesses a low ignition temperature of 380^oC which is useful during initial plant start-ups.  Normal inlet temperatures are in the range of 410 to 430^oC.  Maximum operating temperature is 630^oC which makes it suitable for treating gases containing up to 13% SO₂.

O4-111

Type O4-111 is a highly active catalyst for use in catalyst beds after the first bed.  The higher activity results in closer approaches to the thermodynamic equilibrium.  Ignition temperatures can be as low as 360^oC depending on the gas composition.  Maximum operating temperatures are limited to 600^oC.

O4-115

Type O4-115 is a caesium based catalyst which allows normal inlet temperature down to 370 to 385^oC depending on gas composition.  The catalyst can be used as an ignition layer in the first pass or in the final pass.  The lower inlet temperatures allow gases containing up to 16% SO2 without thermally overloading the subsequent beds.  The ignition temperature of the catalyst is about 340^oC with a maximum operating temperature of 630^oC.

O4-116

Cesium promoted catalyst for the catalytic oxidation of SO₂ to SO₃ for the production of sulfuric acid. Because of its excellent low temperature activity, catalyst O4-116 is installed in the lower passes to improve the conversion and to reduce emissions.

Catalyst Shape

BASF has introduced a new catalyst shape they call Quattro in the O4-115 caesium formulation.

http://www.catalysts.basf.com/p02/USWeb-Internet/catalysts/en/content/microsites/catalysts/news/news255

BASF has introduced the new sulphuric acid catalyst O4-115 Quattro into the market. The new, cesium-based catalyst is unique due to its geometrical shape – a combination of four strands – leading to a 30 percent greater catalytic surface area compared to conventional sulphuric acid catalysts. For sulphuric acid producers, this translates into higher conversion in the catalyst bed, reduction of SO2 emissions, and improved performance in plants with limited catalyst volumes. Additionally, the O4-115 Quattro features enhanced physical and mechanical properties. Due to its improved catalyst hardness, which is reflected in a lower sieving loss, this new catalyst offers long-term stability and cost-efficient operation.

A reference plant operated by Domo Caproleuna GmbH has been using the new sulphuric acid catalyst O4-115 Quattro since 2016. With the new catalyst, the plant has seen an increase of the SO₂ conversion and a simultaneous capacity increase. Ulf Müller, Domo Caproleuna’s plant manager, is pleased with the BASF Quattro catalyst performance: “The right catalyst is a crucial factor for successfully operating a sulphuric acid production plant. Since we have been using the O4-115 Quattro catalyst, we are able to operate our plant in a much more efficient way.”