Optimization of a catalyst system through the sequential application of experimental design techniques

The selective oligomerisation of ethylene to higher alpha olefins is an area of much recent interest. In this regard, Sasol Technology R{&}D has developed a homogeneous catalyst system based on bis-sulfanylamine (SNS) complexes of chromium for the selective trimerisation of ethylene to 1-hexene. It is activated by methylaluminoxane (MAO), which is an extremely expensive activator. This paper discusses how, through the sequential application of experimental design and response surface techniques, the activator requirements of the catalyst system were reduced 12 times, whilst improving the catalyst activity on a g/g Cr/h basis ca. three times and the activity on a g/g MAO basis ca. nine times. This reduction in the amount of MAO required led to economically attractive catalyst activities for the production of 1-hexene, and would not have been possible without the use of experimental design techniques. This paper will demonstrate the process of investigation through the use of sequential experimental design in practice.