PRODUCTION OF ISOPARAFFINS Cracking of Petroleum Fractions in the Presence of Aluminum Chloride V. 1. KOMAREWSKY AND LEE WARSON ILLINOIS INSTITUTE OF TECHNOLOQY, CHICACaO. ILL.
bon complex. The lower layer on decomposition with water forms aluminum hydroxide, hydrogen chloride, and a highly unsaturated hydrocarbon layer. I n cracking of natural hydrocarbon mixtures in the presence of aluminum chloride, two facts are apparent: The product in the upper layer is saturated, and isoparaffins are the principal upper-layer hydrocarbons. These products can readily be explained by the reactions mentioned above. Thus any hydrocarbon decomposing under the action of aluminum chloride and forming unsaturated fragments will , form a saturated product by the processes of alkylation, intermolecular dehydrogenation-hyd:o:ogenation, and conjunct polymerization. For example, PARAFFIN HYDROC.4RBONS :
c-c-c-c-c-c-c-c +c-c--c-c + c=c-c-c + c-c-c* + c=c--c-c + I c I
C
A&
COURTESY. UNIVERSAL OIL PROOUOTS COMPANY
Modern Catalytic Cracking U n i t
or
c-c-c-c-c-c
A
EARLY as 1878 Friedel and Crafts showed that hydro'carbons undergo decompos$ion in the presence of aluminum chloride to products of lower molecular weight. Of particular interest is the work of McAfee (25),who developed a cracking process for the production of gasoline from petroleum using anhydrous aluminum chloride as catalyst. An extensive literature, mostly patents (8, 4, 6, I,$), has appeared on the subject. The McAfee process, however, did not find wide practical application. The action of anhydrous aluminum chloride on pure hydrocarbons has been extensively studied during the last decade (1, 6, 17). As a result of these studies, many interesting reactions have been discovered; of particular importance are: (a) the alkylation of paraffins by olefins (9), ( b ) the alkylation of cycloparaffins by olefins ( I I ) , (c) the phenomenon of destructive alkylation ( 7 ) , (d) isomerization (3, l a ) , (e) intra- and intermolecular hydrogenation-dehydrogenation ( I O ) , and if) conjunct polymerization (8, I d ) . These reactions are usually accompanied by the formation of two layers. The upper layer contains hydrocarbons and the lower layer contains the so-called aluminum chloride-hydrocar-
(1)
b
* Isonierization can occur also prior t o decomposition of the starting ma-
terial.
CYCLOPARAFFIN HYDROCARBONS:
r n
1**
** Possible intermediate products which have not been isolated. I n addition to undergoing destructive alkylation and intermolecular dehydrogenation, cycloparaffin hydrocarbons have the tendency to isomerize 'with consequent degradation of the ring (19, 80) and thus of finally transforming into isoparaffins by 323
INDUSTRIAL AND ENGINEERING CHEMISTRY
324
the process of decycliestion-hydrogenation. drogen is formed as in reaction 3.
The necessary hy-
Part of the unsaturated hydrocarbons will form, with aluminum chloride, a lower layer and also undergo a conjunct polymerization with the formation of cycloparaffins, aromatics, and isoparaffins (8, 1 2 ) :
c=c
1
Vol. 37, No. 4
72 -3 A c=c-e-c
J
+3H2
--f
+
Ht I
A ~ o h r . 4 ~HYDROCARBONS. 1~ These
hydrocarbons are the most stable under the conditions of aluminum chloride cracking. However, the similar reactions of destructive alkylation, intermolecular dehydrogenation, and dealkylation can take place. Because of the fact that they constitute a rather small part of straight-run petroleum products (16), their behavior does not change the overpll postulated results. The unsaturated hydrocarbons formed as the result of cracking can also alkylate any other hydrocarbon present, and thus all classes of hydrocarbons can interact:
c c c-A-c-A-c
b
+c--c-c I
C
+ c=c--c
----f
c
oc
