Focus of the two preceding papers within this publication series were the development and manufacturing of technical catalysts at the Leuna Werke company from 1921 - 1945 (part I) and 1950 - 1991 (part II) for the reforming and isomerization catalysts. This article describes the genesis of the hydrofining group of catalysts as cornerstones of the GDR economy. 36 catalysts and 15 special aluminum oxides, X-ray amorphous as well as crystalline aluminum silicates, were developed and brought into service for the Leuna hydrogenation and other refineries. During that time, a vast knowledge base was generated; new chemical processes were pioneered and equipped with tailor-made catalysts developed in Leuna.