Evolution of phase composition, microstructure and resistance to attrition - Annual report 2009

Annual report VISTA 2009

Phase composition, microstructure and resistance to attrition of alumina-based supports for Fischer-Tropsch catalysts

Project director: Grande, Tor, NTNU

Post-doc/ scholar: Rotan, Magnus

Project duration: 01.08.07 - 31.07.11

Technical contact person in Statoil: Rytter, Erling

Division head: Grislingås, Arne

Project number: 6453

Object

Statoil have in recent years spent considerable effort to develop its own catalyst, including the catalyst support, for a Fischer-Tropsch process for conversion of natural gas to liquid products such as diesel. This GTL conversion takes place in a slurry bubble column reactor where the catalyst and the catalyst support are exposed to considerable wearing. The catalyst support for the Co-based catalyst was initially based on γ-alumina, but in order to improve the resistance to attrition and abrasion of the catalyst support, a strong catalyst support have been developed by chemical and physical modification of the alumina support. The modified version of the support is obtained by infiltration of salts precursor solution of oxides such as NiO, MgO and CoO. The main objective in this project is to attain a fundamental understanding of how the mechanical stability of the catalyst support has been achieved. This is crucial for further improvements and optimized preparation conditions. We will focus on the effect of the processing procedure of the support, the thermal evolution during heat treatment and we will also characterize the resistance to attrition and abrasion by using an American standard test method (ASTM) and in addition look at alternative methods to characterize the mechanical performance.

Status:

In 2009 the scholar has finished compulsory courses and teaching duties. The scholar has also submitted the first articles, which now has been published. The investigation of the mechanical stability by Vickers indentation has been continued with several different supports. The hardness data have been correlated with the corresponding data from attrition measurements (ASTM d5757) of the same samples. The correlation between the Vickers hardness and attrition resistance are good and the Vickers indentation method is therefore an alternative method to characterize the mechanical properties of the support. Substantial analysis of the in situ high temperature X-ray Diffraction (HTXRD) data of impregnated porous supports has also been performed, which will be summarized in a paper which will be published in 2010. Investigation of the catalyst supports by transmission electron microscopy (TEM) has been initiated in 2009. Electron microscopy will be the main focus in 2010. The most important realisation in 2009 was the demonstration of the importance of the formation of the spinel phase on the mechanical performance of the support particles. This influence was proved by a support impregnated with manganese oxide. Under heat treatment in air, the manganese oxidized without reacting with the alumina and hence the strength was not improved. Heat treatment under reducing conditions however gave 60 wt% of the spinel phase and improved the strength by 500% compared to the sample treated in air measured by Vickers hardness.

Publications:

M. Rotan, J. Tolchard, E. Rytter, M.-A. Einarsrud and T. Grande, On the solid solution of the spinel phase in the system NiO-Al2O3, Journal of Solid State Chemistry, 2009, 182 (12), 3412-3415.