Isomerization process

An aliphatic mono-olefin e.g. butene-2 is isomerized in the presence of a catalyst comprising zirconium phosphate and zirconium phosphate prepared from an aryl phosphonic acid to produce a corresponding terminal olefin selectively.

The invention relates to the selective isomerization of an aliphatic 
mono-olefin. In accordance with another aspect, this invention relates to 
the selective isomerization of an aliphatic mono-olefin having an internal 
double bond to produce and to improve yield of the corresponding terminal 
olefin. A further aspect of this invention relates to a catalyst for 
isomerizing aliphatic mono-olefins. 
BACKGROUND OF THE INVENTION 
Terminal olefins, also called 1-olefins or alpha-olefins, are useful as 
reactants for a number of commercially important processes such as 
hydroformylation, sulfonation, alkylation and acid oligomerization. In 
these processes they are more reactive than internal olefins. The 
homologous series of 1-olefins can be prepared by the thermal cracking of 
paraffinic hydrocarbons. However, olefins produced by catalytic cracking 
will generally have close to thermodynamic equilibrium composition 
determined by the cracking temperature for the mixture of normal and 
branched isomers. These isomers are frequently not easily separated. When 
the normal and branched isomers can be separated from each other as with 
butenes, then the normal olefins can be treated by the catalyst of this 
invention to provide a fraction that is enriched in 1-olefins. 
Accordingly, an object of this invention is to provide a process for the 
shifting of an internal double bond in an aliphatic mono-olefin 
hydrocarbon to the terminal position. 
Another object of this invention is to provide a catalytic process for 
shifting an internal bond in an aliphatic mono-olefin to the 1- or the 
terminal position. 
Another object of this invention is to provide a catalytic process for the 
selective isomerization or shifting of an internal unsaturation or double 
bond in an aliphatic mono-olefin to a terminal or 1-position. 
Other aspects, objects as well as the several advantages of the invention 
are apparent from a study of this disclosure and the appended claims. 
SUMMARY OF THE INVENTION 
According to the present invention the double bond of an aliphatic 
mono-olefin is shifted from an internal position to a terminal position by 
contacting said mono-olefin under isomerization conditions with a catalyst 
essentially comprising zirconium phosphate and zirconium phosphonate which 
has been prepared from an aryl phosphonic acid and a compound of 
zirconium. 
In accordance with one specific embodiment of the invention, the invention 
provides an isomerization process as described in which the catalyst used 
is prepared from aryl phosphonic acid and a compound of zirconium and used 
for the isomerization of mono-olefins having from 4 to 20 carbon atoms 
inclusive, to produce good yields of 1- or terminal double bond containing 
olefins. 
In a preferred embodiment a feed stream containing C.sub.4 hydrocarbons is 
treated with the invention catalyst for the production of butene-1 for 
example from butene-2. 
DETAILED DESCRIPTION 
The catalyst of this invention comprises zirconium phosphate and zirconium 
phosphonate prepared from an aryl phosphonic acid. 
The catalyst is typically prepared by adding a solution of a soluble aryl 
phosphonic acid to a solution of a suitable zirconium compound. The 
resultant precipitate is filtered, washed and dried for 2-100 hrs. at 
100.degree.-200.degree. C., although temperatures up to 350.degree. C. may 
be employed. Where catalyst activation is carried out below 200.degree. 
C., the use of inert atmosphere is optional. For catalyst activation at 
temperatures of 200.degree.-350.degree. C., the use of inert atmosphere, 
such as nitrogen, argon, or the like, is preferred. 
Suitable aryl phosphonic acids are compounds of the following general 
formula: 
##STR1## 
X can be a hydroxy group or a halide while the R groups can individually 
be H, alkyl, cycloalkyl, alkenyl, aryl, halo, nitro, cyano, sulfonato, and 
the like, and various combinations thereof. Exemplary compounds include 
4-methylbenzene phosphonic acid, 3-chlorobenzene phosphonic acid, benzene 
phosphonic acid dichloride, and phenyl phosphonic acid, and the like. 
Mixtures can also be employed. 
Compounds of zirconium which are applicable include the oxychlorides, 
halides, nitrates, sulfates, acetate, and the like, and mixtures thereof. 
Exemplary compounds include zirconyl chloride, zirconyl bromide, zirconyl 
iodide, zirconium tetrachloride, zirconium fluoride, zirconium nitrate, 
and the like. 
The aryl phosphonic acid component and zirconium compound employed are 
dissolved in any suitable solvent. Suitable solvents include polar 
solvents such as alcohols, nitriles and water. Water is preferred. 
Aliphatic mono-olefins having more than three carbon atoms are amenable to 
treatment by the catalyst of this invention. This includes branched chain 
as well as normal chain compounds. With both, the equilibrium 
concentration of the 1-olefin isomer increases with increasing 
temperature. In general, olefins being treated will have between 4 and 20 
carbon atoms. 
Such olefins include pentene-2, 2-methylbutene-2, hexene-2, hexene-3, 
3-methylpentene-2, heptene-2, heptene-3, octene-2, octene-3, octene-4, and 
the like as well as mixtures thereof. 
Especially preferred as feedstock to be treated with this catalyst are the 
isomeric n-butenes. 
In carrying out the isomerization reaction with the catalyst of the 
invention suitable reaction conditions or isomerization conditions can be 
used which effectively cause double bond isomerization of the olefins in 
the feed. In general, the temperature at which isomerization is effected 
with this catalyst is about 300.degree.-1100.degree. F. Preferably the 
temperature will be in the range of about 500.degree.-900.degree. F. 
Reaction pressure can vary appreciably and can be subatmospheric and 
preferably will not exceed about 500 psig to avoid condensation reactions 
that ultimately lead to excessive coke formation on the catalyst. 
Contact time of reactants on the catalyst expressed as liquid hourly space 
velocity (LHSV) can range between about 0.5 and 20. Preferably, LHSV will 
be between about 1 and 5.

EXAMPLE I 
Inventive catalyst A was prepared by adding a solution of 58 g (0.367 
moles) of phenylphosphonic acid, C.sub.6 H.sub.5 P(O)(OH).sub.2, dissolved 
in 600 mL of water to a solution of 58 g (.about.0.231 moles) of 
ZrO(NO.sub.3).sub.2.xH.sub.2 O in 600 mL of water. The precipitate was 
filtered, washed with hot water, and dried in an oven at 140.degree. C. 
for 4 days. The catalyst contained by analysis 38.0 wt% Zr, 17.1 wt% P, 
had 64.5 m.sup.2 /g surface area, and 0.294 mL/g pore volume. 
Control catalyst B was prepared by adding a solution of 54.0 g (0.409 
moles) of (NH.sub.4).sub.2 HPO.sub.4 in 400 mL of water to a solution of 
25 g (.about.0.100 moles) ZrO(NO.sub.3).sub.2.xH.sub.2 O dissolved in one 
liter of water. After being stirred for 5 minutes the precipitate was 
removed by filtration, washed with 1.5 L of hot water, dried in an oven, 
and finally calcined in air for 5 hours at 550.degree. C. The catalyst 
contained by analysis 42.7 wt% Zr and 13.0 wt% P, had 141 m.sup.2 /g 
surface area, and 0.437 mL/g pore volume. 
EXAMPLE II 
Runs were made using these catalysts to isomerize Phillips Pure Grade 
butene-2. Twenty-five mL portions of -14+45 mesh sieve fractions of 
catalysts were used. The catalyst was placed in a half-inch i.d. stainless 
steel reactor mounted vertically in a temperature controlled furnace; 
butene passed downflow at 2.0 LHSV, about 600.degree. F., and at 
atmospheric pressure. Effluent from the reactor flowed through a glass 
trap at room temperature, then through a glass sampling container that 
could be closed and removed for GLC analysis. Butene-2 feed to the reactor 
was either dry or saturated with water vapor at room temperature to add 
about 3 mole% water vapor to it. This was done to see if the presence of 
water induced acid behavior in the catalyst. Table I presents some 
pertinent information about these runs and the results of the gaseous 
product analysis. 
TABLE I 
__________________________________________________________________________ 
Run 1 2 3 4 5 6 7 8 9 10 11 12 
__________________________________________________________________________ 
Catalyst 
A A B B B B B B B B B B 
Water Added 
No Yes 
No No No No No Yes 
Yes 
Yes 
Yes 
Yes 
Time on stream, 
0.7 
1.3 
0.5 
1 2 3 5 0.5 
1 2 3 5 
Hr. 
CH.sub.4 
N.D. 
N.D. 
0.005 
0.004 
0.003 
0.001 
0.002 
0.005 
0.003 
0.002 
0.003 
0.002 
C.sub.2 's 
N.D. 
N.D. 
0.02 
0.01 
0.01 
0.003 
0.006 
0.02 
0.01 
0.01 
0.01 
0.006 
C.sub.3 H.sub.8 
0.001 
N.D. 
N.D. 
N.D. 
N.D. 
N.D. 
N.D. 
N.D. 
N.D. 
N.D. 
N.D. 
N.D. 
C.sub.3 H.sub.6 
0.04 
0.02 
0.82 
0.53 
0.31 
0.14 
0.18 
0.77 
0.54 
0.36 
0.31 
0.24 
i-C.sub.4 H.sub.10 
N.D. 
N.D. 
0.86 
0.47 
0.24 
0.15 
0.11 
0.77 
0.47 
0.27 
0.22 
0.16 
1-C.sub.4 H.sub.8 
19.1 
18.0 
18.1 
17.9 
16.7 
18.6 
18.2 
18.4 
18.7 
18.6 
18.0 
n-C.sub.4 H.sub.10 
0.30 
0.29 
0.98 
0.76 
0.57 
0.50 
0.46 
0.97 
0.78 
0.61 
0.56 
0.50 
i-C.sub.4 H.sub.8 
0.65 
0.44 
2.78 
2.14 
1.54 
1.19 
1.08 
2.51 
1.92 
1.44 
1.26 
1.07 
c-2-C.sub.4 H.sub.8 
30.7 
31.0 
28.1 
28.5 
28.5 
29.9 
29.6 
27.9 
29.0 
29.7 
29.8 
29.1 
t-2-C.sub.4 H.sub.8 
47.5 
47.9 
43.2 
43.9 
44.0 
44.5 
45.4 
42.7 
44.8 
46.1 
46.3 
44.8 
C.sub.4 H.sub.6 
N.D. 
N.D. 
N.D. 
N.D. 
N.D. 
N.D. 
N.D. 
N.D. 
N.D. 
N.D. 
N.D. 
N.D. 
C.sub.5.sup.+ 
1.89 
1.27 
5.21 
5.55 
6.99 
6.85 
4.55 
6.09 
4.09 
2.80 
2.91 
6.15 
__________________________________________________________________________ 
During runs 37 and runs 8-12 about 12 mL of liquid product collected in the 
effluent trap. Analysis by GLC showed these liquid fractions to be about 
60% C.sub.8 's, about 25% lighter, and about 15% heavier, indicating that 
catalyst B was active to oligomerize butene. No measurable quantity of 
liquid product was obtained from catalyst A. 
Table I shows that yields of propylene, isobutene, normal and isobutane, 
and C.sub.5 + hydrocarbons were all substantially lower with inventive 
catalyst A than which control catalyst B. The presence of water vapor in 
the feed is not considered to have affected the activity or the 
selectivity of the catalysts.