Critical factors in operating catalytic reactors are the envelope density and porosity of the catalyst itself.
These properties are quickly and easily assessed with Micromeritics’ new GeoPyc 1360 in conjunction
with Micromeritics’ AccuPyc™ 1330.

Envelope density (sometimes called bulk density) is simply the weight of a quantity of catalyst divided by
the volume (including the pores) of the same quantity. It may be envisioned as the density that results
from using a volume measured with a zero-thickness but impenetrable film stretched over the exterior of
each and every catalyst pellet. It is thus different from the absolute density (variously termed skeletal,
true, or real density) which excludes pore spaces. Porosity can be directly calculated from a measure of
both envelope and absolute density.

The GeoPyc 1360 measures volume displacement of the catalyst with a free-flowing dry medium —
called DryFlo® — that conforms to exterior features but is unable to penetrate pores. Unlike other
methods such as mercury displacement and hot-wax dipping, the dry medium technique neither
contaminates nor destroys the tested sample.

The following table presents results for a variety of catalyst substrates. The first is Micromeritics’
standard reference sample (an extruded catalyst support, P/N: 004-16822-00). The remainder is from
other sources as are the mercury data offered in comparison. These substrates varied in shape from
extrudates about 1 mm in diameter, through round beads to nearly spherical tablets 5 mm in diameter. The GeoPyc 1360 permits calibration for shape with nonporous reference objects; short pieces of wire were used to simulate the extrudate, and glass beads of appropriate sizes were used to simulate the other
materials.

The greatest disparity in tabulated values amounts to 5.8%. Having tested sample No. 1 by mercury
porosimetry numerous times on different instruments with different operators, it is amply established that
these values are subject to variations as great as 3%. The table shows equally reliable results for the
GeoPyc.