Attrition resistance study of spray dried iron Fischer-Tropsch catalysts

Severe catalyst attrition encountered in the Fischer-Tropsch synthesis (FTS) using Slurry Bubble Column Reactors (SBCRs) has led to efforts to prepare more robust Fischer-Tropsch (F-T) catalysts, especially iron (Fe) F-T catalysts. Fe catalysts are preferred for FTS based on coal. However, the low activity of Fe necessitates the use of bulk Fe catalysts, which typically lack physical strength and undergo extensive phase changes during activation and reaction that can cause potential chemical attrition. To improve the attrition resistance of Fe F-T catalysts, spray drying has been recently used but the resulting catalysts differed significantly in both attrition resistance and catalytic properties. Therefore, the overall objectives of the present study were to develop methodology to predict attrition in SBCRs and to better understand those parameters affecting the attrition resistance of spray dried Fe F-T catalysts.; By comparing the morphology of catalysts resulting from SBCR use to those from several attrition tests, the attrition mechanism in SBCR's was identified to be primarily fracture. Of the attrition tests evaluated, the jet cup test was found to replicate satisfactory the catalysts attrition in an SBCR and was used as the major test throughout the subsequent studies of spray dried Fe catalysts.; Although the spray dried Fe catalysts studied were prepared under similar conditions, their physical attrition resistances in the calcined form were found to vary over a wide range. Particle density, among other catalyst particle properties, was found to closely relate to catalyst attrition performance. The type and concentration of SiO₂ incorporated was suggested to be the key parameter that controls catalyst inner structure and particle properties. After activation, most of the catalysts were found to possess similar or slightly better attrition resistance compared to the calcined catalysts. This is considered to be due to the increase in catalyst particle density. Chemical attrition was not found for catalysts having SiO₂ concentrations ≥9wt%.; These results of the work reported here have led to the developments of an attrition test for predicting attrition in an SBCR, a better understanding of catalyst attrition in SBCRs, and guidelines for the development of attrition resistant Fe F-T catalysts.