The particle length of fresh catalysts depends on the strength of the support/extrudates, which is determined by the strength of the green extrudates prior to drying and calcination. It is important to prepare extrusion batches with the right rheology, to ensure good flow properties of the paste through the die and green extrudate strength. After extrusion, the drying and calcination should be carried out in such a way as to minimise breakage. Temperature profiles and humidity are important. In addition, in commercial production it is important to minimise fall height and attrition in rotating equipment. A sampling and analysis plan can help you determine where the breakage occurs and what can be done to improve particle length.