Section III - Paper 17 - PD 7
u. s. A.
REACTIONS AND MECHANISMS OF THE ISOMAX PROCESS
Vladimir Haensel" - E. L. Pollitzer" - C. H. Watkins*
Abstract. ISOMAX is discussed in terms of the reactions
which occur in this hydrocracking process. These reactions
are interpreted in terms of alternate mechanisms of over-
all reactions with indications of rate limiting steps.
Product distributions are given and interpreted with re-
spect to the types of the parent molecules. Laboratory
and pilot plant studies on various stocks together with the
results of commercial operation will be discussed.
The Isomax' process has been the subject of a
number of technical papers's2, so that a lengthy
review of the process is not necessary. This paper
concerns itself primarily with the chemistry of the
process and also presents some of the results ob-
tained from the recent commercial operations.
The Isomax process usually consists of two steps.
The first serves to remove nitrogen, oxygen, Sulfur
and metal contaminants from the feedstock, while
the second step effects the hydrocracking into the
desired hydrocarbon fractions. The first step can,
therefore, be looked upon as a purification or clean-
up step while the second step can be considered as
a true hydrocracking part of the process. The first
step will produce some hydrocracking; however, its
main function is that of feed preparation for the
First Step or Purification Reactions
In considering the performance of the first step
it has been thought for some time that, in order to
provide a suitable charge stock for the second stage,
the most important impurity to be removed from
the feedstock is combined nitrogen. Considerable
work has been done in processing clean oils which
Résumé. On étudie les réactions entrant en jeu dans le
procédé d'hydrocraquage ISOMAX. Elles sont interpré-
tées par différents mécanismes de l'ensemble des réac-
tions et on indique les étapes limitant la vitesse réaction-
La répartition des produits est présentée et interprétée
en fonction des types de molécules mères. L'article ana-
lyse pour terminer les études de diverses charges effec-
tuées en laboratoire et sur pilote ainsi que les résultats
obtenus à l'échelon industriel.
have been contaminated with various nitrogen
compounds. From the results of this work, the fol-
lowing conclusions have been drawn:
(I) All of the added nitrogen impurities are very
readily removed from the clean oil.
(2) When a gas oil or a nitrogen-containing poly-
cyclic aromatic hydrocarbon is processed under
the same conditions, the nitrogen removal is less
(3) The nitrogen removal is facilitated as the oper-
ating pressure is increased.
These conclusions are substantiated by the re-
sults shown in Table I.
The results indicate that the removal of natur-
ally-occurring nitrogen compounds from technical
methylnaphthalene is more difficult than the remo-
val of nitrogen comp