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Патент USA US3047657

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July 31, 1962
N. L. CARR
PROCESS FOR THE CATALYTIC HYDROISOMERIZATION
OF CRUDE NORMAL-PENTANE
3,047,645
Filed Dec. 7, 1959
I20
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I50
Pm:
I60
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I80
760
110
780
REACTION
790
800
TEMP. , "F.
INVENTOR.
NORMAN L. CARR
BYZW/S/IOZVj
ATTORNEY
r.
grates ?
red
$041645
Patented July 31, 1962
2
1
fouling of the catalyst and a general decline in catalytic
3,047,645
activity on extended use.
PROCE§5 FOR Tm CATALYTIC HYDROEGMERL
ZATION 0F CRUDE NQRMAL-PENTANE
It is therefore necessary to
balance the requirement of high reaction rate against
the disadvantages of a high aging rate (rate of decline
of activity) for the catalyst. In the Folkins et al. appli~
Norman L. Carr, Allison Park, Pa., assignor to The Pure
Oil Company, Chicago, Ill., a corporation of Uhio
Filed Dec. 7, 1959, Ser. No. 857,635
7 Claims. (Cl. 260-68355)
cation, data are presented which de?ne an excellent proc
ess for isomerization of a substantially pure n-parai?n
hydrocarbon, and it is indicated that mixtures of hydro
carbons could be isomerized satisfactorily at process con
This invention comprises a novel process for the cata
lytic hydroisomerization of a crude n~pentane cut con 10 ditions which represent compromise values between the
optimum values for the individual hydrocarbons. It has
taining a small amount of other closely related alkanes
been found, however, that mixtures of hydrocarbons can
be isomerized under the general conditions set forth in
Folkins et al. application only at temperatures less than
about 740° R, which do not result in coke fouling and
excessive aging rate for the catalyst. When a hydro
carbon cut is used, which corresponds to a particular
hydrocarbon fraction, such as n-pentane or n-hexane, the
cut usually' contains up to about 10% vol. of other hydro
and naphthenes. In particular, the invention is concerned
With an isomerization process which effects a maximum
isomerization rate for n-pentane, while maintaining a
substantially zero fouling rate or aging rate for the cata
lyst used.
According to this invention, it has been found that the
isomerization of a pentane feed stock containing up to
about 10% vol. of hydrocarbon impurities consisting
carbons as impurities, particular naphthenic hydrocar
bons and the adjacent para?in hydrocarbons. Thus, a
predominantly of hexanes ‘and cyclopentane can be car
ried out at high reaction rate‘ and low catalyst aging rate
by processing the pentane feed and hydrogen in the pres
n-pentane cut used for the feed to an isomerization proc
ence of a catalyst consisting of 0.5-0.75% wt. palladium
ess would ordinarily contain up to 10% vol. of hydro
on small silica-alumina (containing 70-90% silica) pel
carbon impurities consisting essentially of n-hexane and
The inclusion of these hydrocarbon im
purities in the n-pentane ‘feed introduces problems into
lets at a hydrogen partial pressure of 375-425 p.s.i.a. 25 cyclopentane.
and a hydrocarbon partial pressure and a reaction tem
perature which lie within the shaded area of the drawing.
Isomerization has recently come into prominence as
a unit process in the petroleum industry for increasing
the octane number of low-molecular-weight, liquid ali
phatic hydrocarbons. In particular, the isomerization of
n-pentane and n-hexane has been extensively investigated.
the isomerization process for which there were previously
no solutions.
The inclusion of an appreciable amount
of naphthenic hydrocarbons, such as cyclopentane and
30 cyclohexane in an isomerization feed usually results in
The isopentanes and isohexanes have substantially in
creased octane numbers over the corresponding normal
paraffins. In the copending patent application of Hillis
O. Folkins et al., Serial No. 691,996, ?led October 23,
1957, there is described an isomerization process which
utilizes a solid refractory catalyst consisting of a small
amount of palladium supported on an acidic silica-alu
a rapid coke fouling and high aging rate. The catalyst
aging rate is also affected by the catalyst pellet size and
the palladium metal content.
I have previously shown in my paper “Kinetics of
Catalytic isomerization of n-Pentane,” read before the
Division of Petroleum Chemistry, American Chemical
Society, April 1959 meeting, that for any speci?c com
bination of catalyst, reaction temperature, and feed stock
composition, there is an optimum total pressure at which
mina hydrocarbon cracking catalyst. In that patent ap 40 maximum isomerization rate is obtained at each hydro
gen/hydrocarbon ratio. However, many of the maxi
plication, the process is described as being applicable
to the isomerization of n-C4-C7 hydrocarbons at tem
mum isomerization reaction rates are accompanied by
peratures below 800° F. and being highly selective in
excessively high catalyst fouling rates, because, in gen
the conversion of n-pentane and n-hexane to their re
eral, both rates are increased by increasing the same re
spective isomers. Folkins et al. describe their isomeriza
tion process in detail ‘and set forth speci?c ranges of
conditions of temperature, pressure, space velocity, and
hydrogen/hydrocarbon mol ratio, which are desirable for
optimum yields of the C4-C7 isomers. ‘If the thermo
dynamic data for the formation of various hydrocarbon 50
isomers are examined, it is seen that the formation of
branched-chain C4—C'1 alkanes is favored at lower tem
action variables, viz., temperature, hydrocarbon partial
pressure, molecular weight of the feed stock, and naph
thene concentration in the feed stock.
‘It is therefore one object of this invention to provide a
new and improved process for the isomerization of an
impure hydrocarbon feed which consists predominantly of
n-pentane containing a small amount of other hydrocar
bons as contaminants.
A further object of this invention is to isomerize a
n-pentane feed containing up to 10% vol. of hydrocarbon
pass for ‘formation of branched-chain isomers of the
lower alkanes should be obtained at room temperature. 55 impurities consisting essentially of hexanes and cyclopen
tane, using a catalyst consisting of 0.5-0.75% wt. palla
It has been found, however, that the conversion of nor
peratures. Thus, theoretically the maximum yield per
mal para?ins to isoparaf?ns requires a moderately high
dium on an acidic silica-alumina support, under condi
ency toward hydrocracking and aromatization in prefer
cline of catalyst activity is elfectively mitigated, while
maintaining very high reaction rates.
tions of temperature, pressure, and hydrogen/hydrocar
temperature and a suitable catalyst if substantial yields
bon ratio which effect a maximum isomerization reaction
of isoparaf?ns are to be obtained. The palladium on
silica-alumina catalysts ‘are effective in the isomerization 60 rate at a substantially zero aging rate for the catalyst.
Another object of this invention is to provide an im
of n-pentane and n~hexane at temperatures of the order
proved catalytic isomerization process in which the de
of 650—800° F. At higher temperatures, there is a tend
ence to the isomerization reaction, while at lower tem
peratures the isomerization reaction rate is very slow. It
has thus become important to determine the conditions
which are conducive to ‘a high rate of isomerization
without excessive promotion of undesired side reactions,
A feature of this invention is the provision of an im
proved isomerization process using an isomerization cat
alyst consisting of 0.5~0.75% wt. palladium on an acidic
silica-alumina (70-90% wt. silica) support in which the
reaction temperature and partial pressures of pentane and
such as hydrocra-cking and aromatization. It has also
been found that at elevated temperatures, while there 70 hydrogen are carefully controlled to provide a maximum
isomerization reaction rate at a substantially Zero aging
is a substantial increase in the rate of the isomeriza
rate for the catalyst.
tion reaction, there is a substantial tendency toward coke
3,047,645
3
Another feature of this invention is the provision of an
improved isomerization process in which a sulfur-free hy
Zation reaction rate accompanied by a substantially zero
catalyst aging rate for an impure n-pentane feed, as pre
drocarbon feed consisting of n-pentane containing up to
viously described, using a catalyst consisting of 0.5—O.75 %
about 10% vol. of hydrocarbon impurities consisting es
wt. palladium on silica-alumina (containing 70-90% Wt.
sentially of hexanes and cyclopentane is isomerized by 5 silica) lie substantially along the curved line A—B (or
contact with an isomerization catalyst consisting of
surface, since the line extends along the “Z” axis in the
0.3—0.7% Wt. palladium supported on silica-alumina (con
range from 375-425 p.s.i.a hydrogen partial pressure in
taining 70-90% wt. silica), at a hydrogen pressure of
the attached drawing). Along the line (or surface) A—B,
375-425 p.s.i.a., hydrocarbon pressure of about l30~175
the isomerization rate constant is at a maximum value (in
p.s.i.a., and a reaction temperature of about 775~790° F., 10 the range from 8 to 12) and the catalyst aging rate is sub
all lying Within the shaded area of the drawing.
stantially Zero. A substantial increase in hydrogen par
Still another feature of this invention is the provision
tial pressure above 425 p.s.i.a. has been found to increase
of an improved isomerization process using a palladium
on silica-alumina catalyst in which catalyst pellets are used
the aging rate and decrease the isomerization rate, while
a substantial decrease in hydrogen partial pressure below
of a size and metal content which are highly resistant to 15 375 p.s.i.a. increases the aging rate but also increases the
aging and have a high activity for formation of isoparaf
isomerization rate. A decrease in hydrocarbon partial
?ns.
'
pressure below 130 p.s.i.a. decreases the isomerization rate
Other objects and features of this invention Will become
substantially without signi?cantly affecting the aging rate,
apparent from time to time throughout the speci?cation
while an increase in hydrocarbon partial pressure above
and claims as hereinafter related.
20 the limits de?ned by the line (or surface) A—B increases
In the accompanying drawing, to be taken as part of this
both isomerization rate and catalyst aging rate. A de
speci?cation, there is presented a graph showing the range
crease in the reaction temperature below 775° F. decreases
of isomerization reaction temperature and partial pressure
the isomerization rate very rapidly without aifecting the
of the crude n-pentane ‘feed at a hydrogen partial pressure
catalyst aging rate substantially, while increasing the tem
of 375-425 p.s.i.a., which results in a maximum isomeri 25 perature above the limits de?ned by the line (or surface)
zation reaction rate (K=8—12) and a substantially zero
A—B increases isomerization reaction rate, but also in
aging rate for the catalyst (0.5—0.75% wt. palladium on
creases the catalyst aging rate. .
an acidic silica-alumina support).
The catalysts containing 0.5-0.75% wt. palladium on
This invention consists essentially of a process for isom
silica-alumina (70—90% silica) are more active than cat
erization of an impure n-pentane feed containing up to 30 alysts containing less palladium and are more resistant to
about 10% vol. of hydrocarbon impurities such as hex
aging. Catalysts containing a higher proportion of palla
anes and cyclopentane. The n-pentane feed treated in
dium are not appreciably more active and are actually less
this process is ?rst subjected to a desulfurization process,
selective for formation of the desired isoparaf?ns. Cata
such as catalytic dehydrosulfurization, optionally includ
lysts which are ‘formed or broken into 1/16" pellets are
ing caustic- and water-washing and drying of the e?iuent,
much more resistant to aging than 1A" or 1A3" catalyst
or stabilization, to reduce the sulfur content to the range
pellets. Smaller catalyst pellets are impractical as they
of about 5-50 ppm. IThis hydrocarbon feed is heated to
tend to ‘be entrained by the feed at high flow rates and
an elevated temperature, preferably about 400°—800° F.
also increase the resistance of the reactor by a substan—
(although higher temperatures may be used), and passed
tial amount.
'
through a desulfurization reactor or guard case containing 40
The following non-limiting examples are illustrative of
a suitable desulfurizing reactant to ?x and remove sulfur
the scope of this invention.
without the release of hydrogen sul?de. Desulfurizing cat
alysts, which are well known in the prior art for removing
sulfur (as hydrogen sul?de) from hydrocarbons, include
EXAMPLE I
A 0.65% wt. palladium on 87/ 13 silica-alumina cat
various metals, such as copper, nickel, iron, molybdenum,
(1/16" pellets) was prepared by impregnating an
and cobalt, and their oxides and various compounds there 4:5 alyst
87/13 silica-alumina hydrocarbon cracking catalyst with
of, such as copper molybdate, cobalt molybdate, nickel
an acidi?ed solution of palladium chloride sufficient to
molybdate, etc., preferably supported on a silica, silica
produce the desired concentration of palladium metal.
alumina, or alumina support. Such materials are also ef
The impregnated catalyst thus produced was dried and
fective as reactants in a guard case to ?x and remove sul
reduced with hydrogen at -a temperature of 750 °—975° F.
fur without the release of hydrogen sul?de. The desul
to produce a highly active catalyst of the desired composi
furization catalyst may be the same as the catalyst used in
tion. This procedure for the preparation of the catalyst is
the isomerization reaction. Additonal details of this de
described in considerable detail in the aforementioned
sulfurization process and the need for using a totally de
copending application of Hillis O. Folkins et al. The cat
sulfurized feed are discussed in my copending application,
alyst which was thus prepared was used in carrying out a
Serial No. 731,778, ?led April 29, 1958, now Patent No.
number of experimental tests for catalyst aging under dif
2,951,888. This chemical treatment usually reduces the
ferent reaction conditions. In each case the hydrocarbon
sulfur content of the feed to less than about 1 ppm. and
feed consisted of 88% vol. n-pentane, 2% vol. isopentane,
may produce a’ sulfur content of practically zero. The
5% vol. cyclopentane, and 5% vol. n-hexane. The cyclo
completely desulfurized hydrocarbon feed is then passed
pentane
concentration used was slightly higher than would
to the isomerization reactor (containing the 0.5—~0.75% 60
be encountered in a n-pentane feed, but represented the
palladium on silica-alumina catalyst), with free hydrogen
at a partial pressure of 375—425 p.s.i.a., and at a reaction
temperture in the range of about 775 °—790° LR, and pen
tane feed partial pressure in the range of about 130-175
normal level which would be encountered in an isomeriza~
tion reactor as a result of cyclopentane build-up produced
by recycling. The hydrocarbon feed was desulfurized to
p.s.i.a., all lying within the shaded ‘area of the drawing. 65 a sulfur content less than about 1 ppm, as described in
my copending patent application, using a “guard-case”
Under these conditions of reaction, the n-pentane is con
containing
a desulfurization reactant consisting of 15%
verted to isopentane in a very high yield, approaching
reduced nickel molybdate on 75/25 silica-alumina. The
equilibrium, and at a very high reaction rate (rate con
desulfurized impure n~pentane feed was circulated over the
stant K=8—12) and at a catalyst aging rate of substan
tially zero. iAging, as it is used herein, means a change in 70 catalyst in an isomerization reactor for extended periods
catalyst activity with processing time under the test con
of time, up to about 100 hours, at different reaction condi
ditions used, and includes all possible “poisoning” action
tions of pressure, hydrogen/hydrocarbon ratio, and reac
from coke, trace sulfur, and other ‘forms of activity
changes which might be dependent upon the basic catalysts
tion temperature. In each experiment, the yield of isopen
or system. The process conditions for maximum isomeri
time to determine the aging rate of the catalyst, which is
tane was noted initially and after an extended period of
3,047,645
6
5
expressed in decrease of yield percent, per 100 hours of
process operation. The reaction rate constant for the iso
merization process under the conditions used as calculated
according to the equation:
These data are analyzed mathematically according to the
“steepest ascent” technique and are expressed graphically
in the drawing which shows the shaded area of tempera
ture and hydrocarbon partial pressure as being the area
K: (LWHSV) In I: 1 x]
of maximum isomerization reaction rate and substan
tially zero catalyst aging rate. This shaded area (which
should actually be considered a volume since it extends
along the Z aXis in the range from 375 to 425 p.s.i.a.,
where LWHSV is the liquid weight hourly space velocity
hydrogen partial pressure) represents the region in which
and x is the percent isopentane yield. The rate constant
the isomerization rate constant lies in the range from 8
to 12 and the catalyst aging rate is substantially Zero.
In Table I, from which the drawing is derived, the re
action rate constant “K” is shown in the left of each
column and the aging rate is set forth in parenthesis, ex—
pressed as decline in yield percent per 100 hours of
“as
K provides a basis for comparison of catalyst activity
under different conditions of temperature, space velocity,
etc.
A mixture of hydrogen and n-pent-ane (containing 10%
vol. C5 and C6 impurities) was passed over a 0.65% wt.
process operation.
palladium on 87/ 13 silica alumina catalyst (1/16" pellets)
at a temperature of 785° F. and liquid weight hourly space
EXAMPLE II
velocity of 5.0 for a period of 93 hours. The hydrogen
When
an
isomerization
catalyst is prepared consisting
partial pressure was 375 p.s.i.a. and the hydrocarbon par
tial pressure was 170 p.s.i.a. The initial yield of isopentane 20 of 0.65% wt. palladium on 75/25 silica-alumina (1/16"
pellets) and used in the isomerization of an impure n
was 54.4% and the ?nal yield was 52.5%. The reaction
pentane feed stock, as above described, the maximum
rate constant for the process under these conditions is
rate constant for the reaction is slightly less than the
11.8, while the aging rate for the catalyst is 2.0% decline
catalyst using 87/ 13 silica-alumina support. When this
per 100 hours of process operation.
A number of additional runs of the same type were car 25 catalyst is used in the isomerization of the impure n
pentane feed under different conditions of reaction tem
ried out in which the temperature and the partial pressures
perature, and partial pressures of hydrogen and pentane,
of hydrogen and the pentane feed were varied and determi
nations were made of the rate constant K and the aging
rate for the catalyst under the isomerization conditions
used. These data were obtained in a planned experi
mental program based on the so~called “steepest ascent”
technique which enabled me to determine the conditions
at which maximum isomerization rate is obtained together
with a substantially zero catalyst aging rate. In Table I
there are set forth in tabular form the rate constants and
aging rate for different hydrogen and pentane partial pres~
sures and ditferent isomerization reaction temperatures
it is found that the reaction rate is at a maximum and
the aging rate is substantially zero when the process con
ditions are maintained within the range speci?ed in the
shaded area of the drawing. In Table II, there are set
forth the rate constants and aging rates for the 0.65 %
wt. palladium on 75/25 silica-alumina catalyst for tem
peratures and pressures within and without the desired
range which shows that a maximum reaction rate and
substantially zero aging rate are obtained within the
shaded area of the drawing.
Table II
0.65% PALLADIUM ON 75/25 SILICA-ALUMINA CATALYST RATE
CONSTANT K AND AGING RATE (~—AY/l00 HRS.)
Pressure, p.s.i.a.
"I‘are.
Hydrogen
Hydrocarbon
375
Temperature ‘’ F.
750
_______
_ _ _ _-
.3(0)
5. 0(0)
_____
7. 6(0)
____ __
160
_____._
____.
_ _ _ _ __
6. 6(0)
7. 6(0)
325
140
_ _ _ _ _ _ _
. _ _ _ _
_ . _ _ _ _
_ _ _ _ __
8. 8(10)
300
175
_ _ _ _ _
_ _ _ _ _ _
_ _ _ _ 1 r
_ . . _ _ . _ _
600
130
_ _ _ _ _
_ _ _ _ _ _
_ _ . _ _-
8
480
180
_ _ _ . _
_ _ _ _ _ _
_ _ . _ _ _
_ . _ _ _ _ _ _
5(50)
r _ _ _ . _ _
3.
9(11)
carbon
Temperature ° F.
730
750
765
775
780
785
375
130
10.0(0)
375
425
425
375
450
600
400
425
255
600
300
150
150
140
170
140
150
165
175
140
190
175
.8 0.
250
250
6.5(40)
7. 0(0)
7. 8(0)
.2(3. 0)
5(7.
9. 0(5. 0)
7. 9(1. 0)
5)
______ __
_ _ _ _ . _ __
______ __
_ _ . _ _ _ __
The data in Table II also show that outside the range of
conditions indicated by the shaded area of the drawing,
Table I
Hydro-
790
175
4.
____ __
785
130
0.65% PALLADIUM ON 87/13 SILICA-ALUMINA CATALYST RATE CONSTANT K
AND AGING RATE (-AY/IOO HRS.)
gen
780
375
the 0.65% wt. palladium on 87/ 13 silica-alumina catalyst.
Hydro-
775
425
using the previously-described impure n-pentane feed and
Pressure p.s.i.a.
765
790
3,047,645
8
there is either excessive aging of the catalyst or an
uneconomically low reaction rate for the process.
of temperature and pressure, where ‘aging is slight, the
di?erence in palladium concentration between 0.35% and
0.65 % may be su?icient to prevent raging completely. In
EXAMPLE III
Table IV, aging rates are set forth for catalysts of differ
When palladium on silica-alumina catalysts are pre
5 ent size and palladium concentration under conditions
pared using palladium concentrations in the range from
which are conducive to moderate aging.
0.50 to 0.75% wt., it is found that there is relatively
little change in catalyst activity with palladium concentra
Table IV
tion. If the rate constant K for formation of isopentane
Feed: 88% l1-C5Hm, 2% l>C5H12, 5% cy-C5H1o, 5% n-CoHu
conditions :
in a pentane isomerization process is plotted against 10 Reaction
780° F. 8.3 LWHSV
H2-430 p.s.i.a. Hydrocarbon—185 p.s.i.a.
palladium metal concentration in a palladium on silica
Catalyst support : 7 5/25 silica-alumina
alumina catalyst, it is found that K increases linearly
with the metal content in the range from zero to about
0.5% wt. palladium. “K” reaches a maximum at about
Percent
Palladium
0.65-0.70% palladium and declines at higher palladium 15
concentrations. While it has been found that the combi
0.35
Particle Size, in.
it pellets __________ __
Aging Rate,
—AY/100 hrs.
5
nation of conditions of temperature and hydrogen and
0. 35
Lt extrudate _______ __
5
0.35
1A0 crooked pellets__
1.2
hydrocarbon partial pressures is somewhat unique for a
0.35
1A6 extrudate ______ __
1. 2
particular hydrocarbon feed containing a small amount of
0. 65
1A6 extrudate ______ __
0. 5~1. 0
hydrocarbon impurities with respect to a particular cata
lyst composition, still the range of conditions required
While I have described my invention with special em
does not vary substantially for catalysts of substantially
phasis
upon one or more speci?c embodiments, I wish it
the same activity, particularly in the region of maximum
to be understood that within the scope of the appended
activity. Therefore, catalysts in the range from 0.50
this invention may be practiced otherwise than as
to 0.75% wt. palladium on silica-alumina, containing 25 claims
speci?cally
described.
70-90% silica, vary slightly in activity with metal con
The
embodiments
of the invention in which an exclusive
tent, but have an optimum reaction rate and substantially
property or privilege is claimed. are de?ned as follows.
zero catalyst aging rate within the shaded area of the
I claim:
drawing. In Table III, there are set forth the reaction
1. A process for isomerization of a sulfur-free hydro
rate constants and catalyst aging rates for temperatures 30
carbon feed comprising n-pentane containing :an appreci
in the range from 750 to 790° F. and at different hydro
able amount of other C4-C7 hydrocarbon as impurities,
gen and hydrocarbon partial pressures for catalyst con
not exceeding about 10% vol. which comprises contacting
sisting of 0.50% wt. palladium on 87/13 silica-alumina.
said hydrocarbon feed and hydrogen with a catalyst con
Table III
35 sisting essentially of 0.5—0.75% wt. palladium on silica
RATE CONSTANT K AND AGING RATE (-AY/lOO HRS.) FOR
0.50% WT. PALLADIUM ON 87/13 SILIGA-ALUMINA
Pressure, p.s.i.a.
Temperature, ° F.
Hydrogen Hydrocarbon
375
130
750
5 0(0)
375
150
_________ __
425
150
___
425
140
___
600
150
......... __
300
175
5 5(70)
775
785
7. 7(0)
(0)
790
aiumina, containing 70—90% silica, at a hydrogen partial
pressure of 375—425 p.s.i.=a., and a hydrocarbon partial
pressure ‘of about 130-175 p.s.i.a. and reaction tempera
ture of about 775—790° F. lying within the shaded area
40 of the drawing, said process being characterized by a re
action rate constant of about 8-12, which remains con
stant for periods of operation in excess of 100 hrs.
2. A process in accordance with claim 1 in which the
8. 5(0)
________ __
(0
principal ‘hydrocarbon impurities are n-hexane and cyclo
__
___________ ._
9. 5(0)
8. 5(10)
________ ._
45
______________________________ _.
In this table, it should be noted that the reaction rate
constants and catalyst aging rates correspond to the
values within the shaded area of the drawings where a
maximum reaction rate is obtained and substantially zero
aging rate.
EXAMPLE IV
When palladium on silica-alumina catalysts ‘are pre
pared in different sizes and in ‘different palladium concen
trations, it is found that there is a de?nite relationship
between catalyst pellet size, palladium concentration, and
resistance to ‘aging. These catalysts increase in resistance
to aging with decrease in catalyst pellet size and with in 60
crease in palladium concentration up to about 0.75% wt.
Thus, catalyst pellets of 1A2" diameter are more resistant
to aging than pellets of 1A" diameter, ‘and 1A6" pellets
(extruded and cut into short lengths, or formed by break
ing 1A3" pellets in half) are even more resistant to aging. 65
Similarly, catalysts containing more than 0.50% Wt. pal
ladium are more resistant to aging than catalysts contain
ing lesser amounts of palladium. The ‘differences in aging
due to size and palladium concentration are most apparent
under conditions of temperature and pressure which are
pentane.
3. A process in accordance with claim 1 in which the
hydrocarbon pressure and reaction temperature lie sub
stantially on the line A-~B in the drawing.
4. A process in accordance with claim 1 in which the
catalyst support is 75 / 25 silica-alumina.
5. A process in accordance with claim 1 in which the
catalyst support is 87/ 13 silica-alumina.
6. A process in accordance with claim 3 in which the
catalyst comprises 0.65% wt. palladium on 87/13 silica~
alumina.
7. A process in accordance with claim 6 in which the
principal hydrocarbon impurities are nahexane ‘and cyclo
pentane.
References (Iited in the ?le of this patent
UNITED STATES PATENTS
2,550,531
2,798,105
2,830,013
Ciapetta ____- ________ __ Apr. 24, 1951
Heinemann et‘al. ____r ____ __ July 2, 1957
Northcott et a1. __/______ __ Apr. 8, 1958
2,831,908
2,906,798
2,925,453
2,944,096
Starnes et a1 ___________ __ Apr. 22,
Starnes et al ___________ __ Sept. 29,
Folkins et a1 ___________ __ Feb. 16,
Teter et a1 _____________ __ July 5,
conducive to catalyst aging, the larger pellets having lower 70
palladium content raging more rapidly. Under conditions
1958
1959
1960
1960
FOREIGN PATENTS
487,392
Great Britain ________ __ Oct. 21, 1952
1. “
5i
it
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