Contact Section - Catalysts - BASF
February 23, 2003

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.

04-110

Type 04-110 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.

04-111

Type 04-111 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.

04-115

Type 04-115 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.