Influence of tabletting pressure upon internal morphology of a Fe2O3Cr2O3catalyst

Abstract

A study on the influence of tabletting pressure upon the internal morphology of Fe 2 O 3 -Cr 2 O 3 catalytic system shows the behaviour of that system at crystallite level or even below it. On increasing tabletting pressure of catalytic powder, remanent stresses are left in the tablets formed which can be calculated in terms of the remanent strain. The macrostresses are constant and small at tabletting pressures ranging within 10 8 − 5 × 10 8 Pa and increase linearly between 6 × 10 8 and 14 × 10 8 Pa. The microstresses take measurable values only in samples tabletted at pressures higher than 7 × 10 8 Pa. Besides the formation of remanent stresses, the increase of tabletting pressure brings about the overall change of porous structure and mechanical resistance of the catalytic system. The remanent stresses that appeared at tabletting result in cracks along some planes which, in most instances, are parallel to the planar faces of tablets. The maximum acceptable tabletting pressure of the catalytic system studied amounts to 5 × 10 8 Pa.