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Патент USA US2136785

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Patented Nov. 15', 1938
UNITED STATES. PATENT
OFFICE ‘
2,136,785
-.PROCESS FOR POLYMERIZING HYDRO
CARBONS
William N. Davis, Berkeley, Calm, ?ssig‘niir to
Standard Oil Company oi’ California, San
Francisco, Calif”, a corporation of Delaware
No Drawing. Application March a 1936,
Serial No; 67,920 ,.
(cl; 196-10)
' 4 Claims.
' This invention relates to a process for the poly
merization of normally gaseous ole?ne hydrocar
bons to low boiling liquids suitable for use as
motor fuels and ‘especially to a. process wherein
the polymerization is elfected by an acid-?lm
type of catalyst. More particularly the invention
pertains to a process suitable for use with a supply
particularly pertinent to a‘ process employing this '
type of catalyst that the present invention per
tains though its'applicabillty to processes em
ploying other catalysts such as the “solid acid”
type will be readily appreciated.
' As is well known, the bulk of gaseous ole?nes
which are at present readily available for poly
of ole?ne containing gas which is subject to wide ‘ merization to liquid motor fuels is produced dur
fluctuations in the amount available for poly
ing the cracking of petroleum oils. The amount
10 merization.
'
of gas produced, its total content of ole?nes and 10.
IThe polymerization of normally gaseous ole
the proportions of individual ole?nes are found
‘ ?nes to liquids boiling in the range of gasoline I to vary not only with the oil cracked but with
' and suitable as a motor fuel'became economi
cally possible with the widespread production of
15 vast quantities of'ole?nes containing from two
to ?ve carbon atoms per molecule as a bye-product
of the cracking of petroleum and-became par
ticularly desirable when it was discovered that
such polymers could be produced which could be
20 used as fuel in the modern high compression
motors with a high degree of freedom from det
onation: Both thermal and catalytic means ve
been extensively studied for effecting such poly
merization.
25
.
'the extent to which cracking is carried and the
speci?c combination of physical conditions under
which it is effected. Since for obvious reasons of 15
stock balance and product requirements it is the
exception rather than the rule for any commer
cial cracking plant to operate continually on the
same raw material to e?ect the same degree oi’
cracldng under the same conditions it follows 20'
that both the composition and the gross quantity
of gas which is available from any such plant to
an associated polymerization unit will be quite
variable. An even greater ?uctuation in the
Many advantages have now been demonstrated > quantity of gas produced is due to the unavoid
25
able intermittence in operation of the individual
units of any cracking plant resulting from the
to be more or less inherent in the catalytic meth
0d of polymerization and numerous speci?c cata
lysts have been developed to meet some particular
requirement imposed either by the raw material
30 available or the product desired or both.
frequency with which alterations and repairs are '
required by apparatus in such severe service.
i The trend toward smaller numbers and increased
In general the strong inorganic oxy-acids and size of individual cracking units has still further 30
‘ their salts or special derivatives have been found accentuated'this latter element 'of ?uctuation‘,
' l to constitute the preferred group of catalytically
active materials. Of these, the acids of phos
35 phorus have probably received the widest atten
tion and have been most highly developed in the
numerous special forms in which they have been
applied. Both the liquid and solid acids have
been used as such, various of the normal and
40 acid salts have been employed, the liquid acids
have been absorbed in highly porous silicious
materials such as diatomaceous earth and cal
cined to produce the so-called -“solid acid" cata
lysts and‘the liquid acids have been ‘adsorbed
45 in .thin ?lms on substantially non-porous inert
materials such as glassy quartz to give the “acid
?lm type” catalysts, each group with its own par
ticular set of characteristics.
Of these several groups of) phosphoric acid
50 catalysts the latter, acid-?lm type, has been found
The net- result is thus that a polymerization
unit to utilize the fluctuating supply of raw ma
terial from any actual cracking plant in an em 35
ciently continuous process for producing a uni
form polymer product must either comprise large
and expensive reserve storage facilities or possess
a de cc of elasticity not reasonably to be ex
pecte in the commercial operation of what is at 40
best a critical process.
,
The object of this invention is broadly to pro
vide a method of operating a catalytic polymer
ization process employing an acid-catalyst in a
smooth and continuous manner on a ?uctuating 45
supply of ole?ne containing raw material with
out recourse to the expedient of considerable re
serve gas storage. More speci?c objects will be
apparent from the description and discussion
which follows:
I
.
to possess a combination of characteristics which
The polymerization of gaseous ole?ne hydro
cause it to stand out as’the most nearly ideal
in meeting all of the requirements for vemcient,
economical, trouble-free, ?exible commercial op
eration. It is to ai'eature of operation which is
carbons to yield a liquid product which shall con
tain'no polymer higher than a trimer and in
certain instances none higher than the dimer
is a reaction which is different in many funda
50
2,186,785
Y 2
It has been further found that with phosphoric
-‘ , mental respects from the ordinary chemical re
action. In order, therefore, to understand the
operation of any process for e?ecting such a
polymerization these several points of peculiar
ity must be clearly appreciated.
'
Quite frequently when the supply of raw ma
' terial available for a continuous chemical proc
acid there is a concentration range in which the
rate of ole?ne polymerization is variable between
surprisingly wide limits with only slight changes
in the concentration of acid employed as the cat
alyst, all other factors remaining constant. The
following data are illustrative of this point. They
ess is for any reason reduced the rate of ?ow ' were obtained in operation with acid-?lm type
through the process is merely reduced in pro . catalysts in which phosphoric acid of the indi
cated strength was adsorbed on 10-20 mesh 10
portion and the only result is a reduction in out
put from the plant. The extent of an ole?ne broken glassy quartz particles supported in an
polymerization is however roughly proportional
‘"rin-ah O
to the length of time the polymerizable material
is subjected to the polymerizing conditions and
appropriate reaction tower.
TABLE I
Polymerizinq activity of phosphoric acids
hence to reduce the rate of passage to accommo
date a reduction in the supply of. raw material
would obviously result - in over-polymerization.
a, When
the degree of polymerization permissible in
the productionof a given product is limited to
dimerization or at most to trimerization any
such reduction in rate with its resultant over
polymerization is obviously untenable.
In many other well known instances-oi’ con
tinuous chemical processes a reduction in the
25 temperature of operation may be employed to
so
reduce the rate of the reaction to-accommodate
a reduction in the supply of raw material to the
process. The composition of a polymer liquid re
sulting from the polymerization of. a mixture of
several different ole?nes, such as is contained in
a gas produced in the cracking of petroleum, is
however directly dependent upon the temperature
at which polymerization is effected. Variation‘
is probably due in part to the different propor
35 tions of individual ole?nes which are polymerized
at different temperatures and in part to diner
ences in the amount of interaction between the
several individual ole?nes. In any event 'con
stancy of temperature is imperative to constant
composition of the polymer product and thus
precludes the utilization of reduced operating
'
Percent mro.
Gigéggys‘t‘l‘glggft'
an
0.90
m
I
1.60
?6m
110
15
20
3.50
12. 50
~
-
13.20
The practically constant rate of polymerization
effected by a catalyst in which the acid is at a
concentration of from 100 to 110% HIiPOA indi
cates the range in which operation would nor
mally occur and upon which a plant would be
designed to accommodate the maximum quantity
of gas ordinarily available. The approximately 30
four-fold change in rate between 100% and 95%
H3P04 would then be availed of to compensate
for any probable variations in gas supply.
It follows from these data, that by the adjust
ment of acid concentration in any liquid phos
phoric acid catalyst a constant percent polymer
ization may be maintained with varying rates of
gas passage while the conditions of pressure, tem
perature and degree of dilution, which determine
the nature and extent of polymerization are held 40
constant.
While apparently the form of cata
temperatures to compensate for‘ a reduction in lyst employed
or the means by which the acid
the amount of feed material available to a mixed
concentration is adjusted should make no dif
ole?ne polymerization process.
ierence in the result obtained, from the practical
In still other well known chemical processes it standpoint both may be of the utmost importance. 45
is possible to maintain a constant bulk of mate
With an acid-?lm type of catalyst in which the
rial through a given plant in spite of variations total
amount of acid is small, equivalent on the
I in amount of reactants available by cycling more
or less of some inert diluent.
Of the several
customary expedients for obtaining constant
process operation with variable materials supply
this latter is most nearly applicable to a poly
merization process though di?‘erences in the
degree of dilution of gaseous ole?nes may still
somewhat in?uence the nature of the polymer
product. The increased cost ofsuch operation
per unit of product is also against its adoption
wherever other methods are possible.
It has been discovered that still another
method of compensation may be employed in a‘
process for polymerizing gaseous ole?nes with
an acid catalyst and particularly with a phos
phoric acid ?lm type catalyst which is subject
average to about 3.5 pounds of phosphoric anhy
dride per bulk cubic foot of 10-20 mesh support,
the small amounts of water required and the 50
ready accessibility of the acid make possible very
rapid changes of several percent in acid concen
tration by simply varying'the water vapor con
tent of the gas to be polymerized. For any given
temperature of operation the partial pressure of
water vapor necessary to give the acid concen
tration desired may be approximated with‘su?l
cient accuracy from the data of Table II. _
TABLE 11
to none of the foregoing enumerated objections
Mm.
65 and which introduces no new dimculties of. its
own. This is based upon the fact that only the
rate and not the proportion or degree of polymer
ization of mixed gaseous ole?nes is in?uenced by
the concentration of the acid employed as cata»
70 lyst. This fact makes it possible to vary the
capacity of a given plant to accommodate a var
iable supply of raw material merely by appropri-'
ately varying the concentration of. the acid cata
lyst and without disturbing any of the factors
75 whichdetermine the composition of the product.
60
Water vapor pressure over phosphoric acid
solutions
Hg.
as.
11,204.". ______________________ _99.8 a H|PO|, 72.27 P105 .............. -1(D.5% H‘PO‘, 79.4 0 P10; _____________ _.
140
140
230
o.
0.
0.
400
400
540
400. 0
1(1). 0
70. 0
70
Having determined the temperature and per
centage polymerization of the ole?nes contained
in' the gas available, which together will lead to
the desired polymer product it becomes a simple
matter to determine the necessary rate of gas 75
8,186,785
3
passage‘ through a given catalyst chamber to e!
‘iect the proper percent of polymerization. There .in the gas to correspond to other conditions of -
operation and the changes necessary to accom
after it is‘ possible by varying the concentration of modate changes in such operation may obviously
acid in the catalyst in accord with the reaction be arrived at by a similar procedure from‘the
~ rates given in Table I, to maintain the percentage data of Tables I and II.
polymerization and hence the nature of the prod
It
has
been
found
that
the
heat
liberated
by
uct constant; in spite of variations in the amount the polymerization of normally gaseous ole?nes
of gas available. Obviously this may be accom
sufllcient that provision must be made for its
plished by varying the humidity 01’ the gas more is
controlled
dissipation in order to permit of close
10 or less inversely with the rate of gas passage.
temperature control in a polymerization process. 10
The acid concentration in a ?lm type catalyst has, for instance, been found that when a gas
~follows the humidity of the gas so rapidly that It
containing 40% of ole?nes is 95% polymerized
when means are provided for‘ correctly control- . suiiicient heat is generated to raise the tempera
ling the latter by the amount of gas entering the
15 catalyst chamber the constancy of the polymer
’
ture of the reaction mixture by over 200° F. The
removal of this energy'may be advantageously 15
product may be automatically insured. The provided
for by dividing the catalyst into two or
means‘ for adjusting the humidity of the gas and more series units and inserting ‘an e?icient cool
for coordinating the humidity with the amount ing stage therebetween. Such arrangement
or gas may obviously be selected at will without
20 departing from the foregoing principles and hence makes possible the removal of already formed
polymer product at the same time and ultimately 20
without departing from the spirit of this inven leads
to a higher recovery of oleilnes per passage
tion.
.
through the catalyst without excessive over poly
It has been round that gases from the crack
merization.
‘
ing of petroleum must be puri?ed by washing with
Ordinarily
the
?rst
section of a two unit sys
25 dilute acid, as disclosed and claimed in an ap
will contain from 10 to 20% of the catalyst 25
plication Serial No. 07,918 copending herewith tem
and will be responsible for about 50% of the
to remove traces of alkaline reacting catalyst reaction at the rate of gas passage for which it
poisons, usually present, in order to secure long was designed.‘ Ii’ then the rate or‘ gas passage is
catalyst‘life. It is also usually desirable to re
for any reason materially altered it is imperative
so move by an appropriate alkaline wash acid re
that the rate of polymerization be altered in com
. - acting sulfur bodies such as hydrogen sul?de and
merca'ptans, which if allowed to remain are con
densed during the polymerization reaction and
result in bodies which are di?lcult to remove from
the product.
.
Since both such puri?cation treatments are
usually e?ected by means of aqueous solutions
7 they must ‘obviously precede any humidity con
trol operation or be made a. part of such opera
d0
tion.
.
nensation in order to prevent a very serious dis
so,
turbance in the heat balance in the system. By
varying the activity of the catalyst in accord
with the process oi this invention a method of
compensation is provided which prevents any sub 35
stantial disturbance in the heat balance in an
operating plant.
ving now described my invention which ton
sists in a method of controlling the rate of.
I
The complete process of this invention may now
be illustrated by brief reference-to a speci?c ex
ample. An olefine containing gas such as de
rived‘ from the cracking of “a petroleum oil and
containing 30 to 40% total oie?nes'is fractionated
to give a cut consisting substantially oi butane
and the three isomeric 'butenes. It is then puri~
fled by washing with‘ a 5 to 10% solution of sul
furic acid and a solution or caustic soda.
Polymerization at a temperature of 300° F., a
50
pressure of about 200 pounds per square inch, a
polymerization oi’ normally gaseous ole?ne hydro 40
carbons by a phosphoric acid-?lm catalyst under
any given set of operating conditions by con
trolling the humidity oi the gas undergoing polymerization:
_
I claim:
45
1. In a process for the catalytic polymerization '
‘of normally gaseous ole?ne hydrocarbons by
means or ‘a phosphoric ‘acid-?lm catalyst the \
method of controlling the rate of polymerization
at constant temperature and pressure without
catalyst acid strength of about 100% HaPO4 and altering its nature or extent to maintain a con
a space velocity through the catalyst of about stant product during changes in the time of re
1.0 is desired. The partial water vapor pressure action which comprises the step of regulating the
humidity oi'the gas passing the catalyst in a
55 oi the puri?ed gas is accordingly adjusted to cor
respond to about 10.2 millimeters olmercury im ratio inverse to the rate oi’
age. ‘
55
mediately prior to passing‘ the gas over the'catam
2. In a process for the catalytic polymerization
lyst. It is soon found however that the rate 01’ of norlly gaseous olefine‘ hydrocarbons by .
gas- production at the cracking plant has been means of ‘a phosphoric acid ?lm catalyst the
00 reduced by about 20% and consequently there. method of quickly altering the e?’ective capacity
is sumcient gas available to maintain only a space ' of a given plant to accommodate changes in the
velocity of 0.80 through the catalyst which liner available supply ‘of ole?ne containinggas which
mltted without any compensating change will comprises the step'oi' regulating ‘the’v partial pres
give a considerable proportion of liquid polymer sure of water vapor associated with said ole?nes
65 boiling above the range which is permissible in in a ratio inverse to the quantity of gas entering
the particular product desired. The water vapor the catalyst unit.
05
.
pressure in‘ the gas is accordingly adjusted’to
3. A process for‘ the catalytic polymerization
about 25.0 millimeters. of mercury which quickly of normally gaseous ole?ne hydrocarbons to
brings the acid in the catalyst to about 98% liquids which comprises passing a gas containing
70 HaPOr' having a polymerizing-activity of approx» said oleilnes over a catalyst consisting. of a thin
imately 0.8 that 01' 100% acid.‘ Operation may film of phosphoric acid adsorbed on a non-porous 70
thus proceed with the reduced ?ow oi.’ gas and
the nature of the polymer product remain-un
ch
inert support maintained under polymerizing con
ditions of temperature and pressure and holding
‘said temperature‘ and pressure substantially con
e appropriate partial water vapor pressure stant while varying the supply of said ole?ne con
_ ged.
'
r
4
2,136,785
taining gas and simultaneously inversely varying
its water vapor content.
4. In a process for the catalytic polymerization
of normally gaseous ole?ne hydrocarbons to
5 liquid motor tuelsby means of a phosphoric acid '
?lm catalyst the method of maintaining the na
ture and extent of polymerization constant while
varying the time of reaction at constant tempera
ture and pressure which consists in varying the
partial pressure of water vapor in the gas mix
ture passing over the catalyst in inverse ratio to
the rate of passage.
WILLIAM N. DAVIS.
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