Page 148 - Principles of Catalyst Development

136 CHAPTER 7
be expected and requested, and to present guidelines for the selection of
appropriate tests.
Historically, organizations in catalyst development and use have evol-
ved their own analytical procedures and equipment. Although similar in
many respects, sufficient differences emerged to make precise comparisons
meaningless. For example, measurements of particle crushing strength were
reported not only in a wide range of unit systems but also in unit dimensions.
Test results were dependent on the apparatus used, so that relative assess-
ment was pointless. Recognizing that characterization is one area where
cooperation is possible and desirable, the industry has taken measures to
standardize testing procedures and equipment. In the United States, a
committee of the American Society for Testing of Materials (ASTM) was
established in 1974 to develop accepted methods. 11 <i2,193) Similar but less
organized efforts started in Europe,1194! the Soviet Union,( 195) and Japan. II961
The A TM Committee D-32 is now issuing detailed descriptions and more
will be forthcoming. Whenever possible, this chapter conforms to recom-
mendations from the committee's deliberations.

7.2. BULK PROPERTIES

The most important bulk properties for either powders or particles are
(1) composition, and (2) phase structure.

7.2.1. Composition

Qualitative and quantitative identification of elemental components of
the catalyst is a basic necessity. This includes not only the principal and
impurity components added during preparation but also contamination
deposited during use. These deposits include: (l) rust and other debris, (2)
poisons from the feed, such as S, As, Pb, and Cl, (3) secondary contamina-
tions in the feed such as Ni, Fe, Y, Ca, and Mg, and (4) carbon deposited
as coke during fouling. In the case of particles, determination of the
composition profile is useful in diagnosis. The field of analytical chemistry
has developed a vast array of methods. Physical and chemical, destructive
and nondestructive, "wet" and instrumental, all are legitimate possibilities
for application in catalysis. Those receiving the most attention are as follows.

7.2.1.1. Solution Methods

Each element is susceptible to some type of "wet'" test, a fact familiar
to every student of quantitative analysis. Usually the element of interest is