U.S. patent number 3,567,921 [Application Number 04/870,860] was granted by the patent office on 1971-03-02 for apparatus for the continuous photohalogenation of hydrocarbons.
This patent grant is currently assigned to Phillips Petroleum Company. Invention is credited to Allan D. Holiday.
United States Patent |
3,567,921 |
Holiday |
March 2, 1971 |
APPARATUS FOR THE CONTINUOUS PHOTOHALOGENATION OF HYDROCARBONS
Abstract
A photohalogenation apparatus having a gas liberation region
above a reaction region, a gas outlet, a feed inlet and a product
recovery outlet. A light source is associated with the reaction
region to promote the halogenation reaction. Reactants flow
downwardly in the vertical apparatus; the halogenated product being
recovered from the lower portion of the apparatus.
Inventors: |
Holiday; Allan D.
(Bartlesville, OK) |
Assignee: |
Phillips Petroleum Company
(N/A)
|
Family
ID: |
27087366 |
Appl.
No.: |
04/870,860 |
Filed: |
September 22, 1969 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
614932 |
Feb 9, 1967 |
3944844 |
Feb 10, 1970 |
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Current U.S.
Class: |
250/428; 250/437;
250/493.1 |
Current CPC
Class: |
B01J
19/123 (20130101); C07C 17/10 (20130101); Y02P
20/582 (20151101) |
Current International
Class: |
C07C
17/10 (20060101); C07C 17/00 (20060101); B01J
19/12 (20060101); G01j 003/42 () |
Field of
Search: |
;23/285 ;204/162,163,193
;250/43,45,46,48 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Lindquist; William F.
Parent Case Text
This is a division of application Ser. No. 614,932, filed Feb. 9,
1967.
Claims
I claim:
1. A photohalogenation reactor comprising:
a. a vertical pressure vessel;
b. an ultraviolet light source mounted in fixed relation with and
in light communication with the interior of said vessel to promote
halogenation within said vessel;
c. means for energizing said light source;
d. inlet means communicating with the upper mid portion of said
vessel for introducing fluid feed mixture into said reactor and
maintaining a liquid level within said reactor, said liquid level
thus defining the upper limits of an initial reaction region and
the lower limits of a gas liberation region within said vessel;
e. outlet means communicating with a mid portion of said vessel for
removing a portion of partially reacted reactants from said
reactor, thus defining the lower limits of said initial reaction
region and the upper limits of a reaction completion region;
f. outlet means communicating with said vessel proximate to the
bottom of said vessel for recovering liquid reaction products from
said reaction completion region;
g. outlet means communicating with said vessel proximate to the top
of said vessel for recovering gaseous reaction products from said
gas liberation region; and
h. means for maintaining the rate of reaction in the reaction
completion region over the rate of reaction maintained in the
initial reaction region.
2. The apparatus of claim 1 wherein said vessel comprises a
cylindrical vessel.
3. The apparatus of claim 1 including means connected to said
partially reacted reactant outlet means for recycling, cooling, and
mixing the partially reacted portion with fresh feed
constituents.
4. The apparatus of claim 1 including means for mixing the liquid
reactants in the said reaction region.
5. The apparatus of claim 1 wherein said light source is mounted
inside said vessel and said means for maintaining the rate of
reaction of the reaction completion region comprises a plurality of
vertically disposed light sources.
6. The apparatus of claim 1 wherein said light source is mounted
inside said vessel and said means for maintaining the rate of
reaction in the reaction completion region comprises means for
reducing the space between vessel walls and said light source as
compared to the space between vessel walls and said light source in
the initial reaction region.
7. The apparatus of claim 6 wherein said initial reaction region
and said reaction completion region are cylindrical and said
reaction completion region has a smaller diameter than said initial
reaction region.
8. The apparatus of claim 6 wherein said space reducing means
comprises a sleeve which is adjustable to provide for altering the
residence time in said reaction completion region.
9. The apparatus of claim 1 wherein said light source is mounted
inside said vessel and the means for maintaining the rate of
reaction in the reaction completion region comprises baffles to
divert the flow of reactants in close proximity to said light
source.
Description
This invention relates to the photohalogenation of hydrocarbons. In
one aspect the invention relates to a method of producing a high
yield of a desired halogenated hydrocarbon derivative. In another
aspect the invention relates to a photochemical reaction
apparatus.
In some direct hydrocarbon halogenation methods, light of a
suitable wave length is used to promote the reaction of the
hydrocarbon and the halogen. These processes are sensitive to the
presence of oxygen and other impurities which inhibit the action of
the light and it is often necessary to provide supplemental
quantities of light over that theoretical amount necessary to
promote the reaction in order to obtain an economic yield.
At high conversion rates in a direct halogenation process, the
monohalogenated derivative formed in the first stages of the
reaction reacts with the halogen to produce more highly halogenated
derivatives. Thus, in operations where it is desired to obtain high
yields of the monohalogenated derivative, it is necessary to limit
the rate of conversion.
It is an object of this invention to halogenate hydrocarbons.
Another object of this invention is to produce high yields of
monohalogenated hydrocarbons at a relatively high rate of
conversion.
Another object of this invention is to provide a single stage
reaction vessel for photohalogenating hydrocarbons.
Another object of this invention is to provide a photohalogenation
process which is relatively tolerant to the presence of oxygen and
other impurities.
These and other objects will be apparent to one skilled in the art
upon consideration of the following specification, drawings, and
claims.
FIG. 1 illustrates one embodiment of the apparatus of the
invention.
FIG. 2 illustrates the apparatus of FIG. 1 in conjunction with a
preferred feed and recycle system.
FIG. 3 illustrates another embodiment of the apparatus of the
invention.
FIG. 4 illustrates another embodiment of the apparatus of the
invention.
FIG. 5 illustrates another embodiment of the structure of the
reaction completion region.
According to the invention, there is provided a photohalogenation
reactor comprising a vertical pressure vessel having a gas
liberation region in the upper portion of the vessel, a reaction
region in the mid and lower portion of the vessel, a suitable light
source to promote halogenation in the reaction region of the
vessel, means for introducing premixed feed into the reaction
region, means for removing gaseous reaction products from the gas
liberation region and means for removing the liquid reaction
products.
Further, in accordance with the invention, there is provided a
reactor comprising a vertical pressure vessel having a gas
liberation region in the upper portion of the vessel, an initial
reaction region in the midportion of the vessel and a reaction
completion region in the lower portion of the vessel.
Further in accordance with the invention, associated with the
reaction vessel are means for removing and recycling a portion of
the partially reacted reactants to be mixed with the feed.
Further in accordance with the invention, a mixture of a halogen
and a hydrocarbon is introduced in into the reaction region of a
halogenation zone wherein downflow mixing conditions are
maintained; light of suitable wave length and intensity is supplied
to promote the halogenation reaction; gaseous reaction products are
recovered from a gas liberation region of the halogenation zone
above said reaction region and products from the completion of the
halogenation reaction are recovered from a lower portion of the
halogenation zone below said reaction region. A portion of the
partially reacted feed mixture can be removed from the lower
portion of the reaction region, cooled to desired temperature, and
recycled to the feed mixture.
The light source can be exterior to the vessel or can be disposed
within the vessel. When an exterior light source is used, the
vessel can be fabricated from any suitable transparent material,
such as glass or quartz, or of opaque material, such as metal, and
have transparent windows through the walls thereof for the
admission of light. When the light source is disposed within the
vessel, the vessel can be constructed of any suitable material, for
example, Monel metal, nickel or glass-lined steel.
The gas liberation region is defined by the top of the vessel and
the liquid level of reactants in the vessel, the upper limit of the
reaction region being defined by the liquid level of the reactants
which will rise above the feed inlet means, and the lower limits of
the reaction region being defined by the bottom of the vessel. When
a portion of the partially reacted reactants are recycled, the
recycle outlet means defines the lower limits of the initial
reaction region and the upper limits of a reaction completion
region.
To ensure that the reaction is catalyzed substantially uniformly
during the reaction, mixing is provided in the reaction region. The
mixing can be mechanically induced, for example, by stirring
devices, or can result from reactant flow patterns in the reactor.
It is preferred to provide for mixing by introducing the premixed
feed tangentially at sufficient velocity to create a downward
helical flow pattern while catalyzing the reaction under conditions
resulting in the evolution of gases during the reaction, thus
creating turbulence. The reaction region can be of sufficient size
to allow substantial completion of the reaction.
The reaction completion region functions to react the remaining
halogen with the hydrocarbon so that the halogenated hydrocarbon
product is substantially free of any unreacted halogen. This can be
effected by balancing the residence time in that region with the
intensity of light supplied to the region. Extra light sources can
be disposed in the reaction completion region so as to more rapidly
promote the final reaction, or the reaction completion region can
comprise a zone which is of reduced annular space so that the light
does not travel as great a distance through the liquid. If desired,
baffles can be employed to direct the flow of the liquid into
proximity with the light source to effect completion of the
reaction.
Hydrogen halide, evolved during the halogenation reaction, passes
upwardly through the downwardly flowing liquids and disengages from
the liquid in the gas liberation region. These vapors are removed
from the gas liberation region at a rate which eliminates any
danger of explosion.
Referring now to FIG. 1 the photohalogenation reactor 10 is
depicted as having a cylindrical shell comprising a larger diameter
11 with a top plate 12 and a smaller diameter 13 containing an
outlet 14 in the bottom. An ultraviolet light source 16 extends
through a central opening in top 12 into the reaction regions. The
housing of the light source can be of any suitable material, such
as glass or quartz, which is heat resistant, inert to halogens and
transparent to light. Lamps can be employed to provide light having
a wave length of about 2000 to 7000 Angstrom units. Any suitable
power source 17 can be used to energize light source 16. Guides 18
position the light source 16 stably within reactor 10. Premixed
feed is introduced into reactor 10 through conduit 19. Conduit 19
enters reactor 10 tangentially so that the feed can be introduced
to create a downward helical flow pattern in the reactor and
provide mixing. The liquid level 21 of the reactors, above the
entry point of conduit 19, determines the lower limit of a gas
liberation region 22 and the upper limit of an initial reaction
region 23. During the photohalogenation reaction, the reactants
flow downwardly and a portion of the partially reacted reactants is
removed via conduit 24 to be recycled as shown in FIG. 2. The point
at which conduit 24 is positioned, as shown by phantom line 26,
defined the lower limits of initial reaction region 23 and the
upper limit of a reaction completion region 27.
Reaction completion region 27 is shown as being contained within
the lesser diameter 13 thus reducing the distance the light must be
transmitted through the liquid and increasing the effectiveness of
the light in catalyzing the reaction of any free halogen. Liquid
halogenated effluent is removed via outlet 14 and transferred to
various separation and/or process steps. Gaseous reaction products
evolved during the halogenation are removed from gas liberation
region 22 through conduit 28.
FIG. 2 illustrates one embodiment of a system for recycling the
partially reacted reactants and mixing them with fresh feed
constituents. The partially reacted reactants are removed from
reactor 10 via conduit 24 and cooled to a desired temperature in
heat exchanger 30, thus providing temperature control of the
photohalogenation reaction. The amount of cooling is determined by
the feed rate, recycle rate, and temperature level desired to be
maintained in reactor 10. The cooled recycle portion is removed
from heat exchanger 30 through conduit 31 by pump 32. Fresh
hydrocarbon feed is admixed with the recycled portion in conduit 31
through conduit 33. The action of pump 32 provides for the intimate
mixing of the fresh hydrocarbon feed with the recycle portion. Pump
32 transfers the mixture of fresh hydrocarbon and recycle through
conduit 34 to conduit 19. Fresh halogen feed, either liquid or
gaseous, stored in tank 35 flows through conduit 36, admixing with
the feed constituents in conduit 34 to form the premixed feed which
is introduced into reactor 10 through conduit 19.
FIG. 3 illustrates another embodiment of photochemical reactor 10
having a cylindrical shell 41, a pressure sealed top 42 and bottom
43, a feed conduit 44, a recycle conduit 46, a gas recovery conduit
47, and liquid product recovery outlet 48. The reaction completion
region, defined by the position of recycle conduit 46 and bottom
43, contains a sleeve 49 to reduce the annular space between the
cylindrical shell source and lamp 50 to ensure promotion of the
complete reaction. If desired the sleeves may be fabricated so that
they are adjustable thus allowing the annular space to be varied
providing for different residence times in reaction completion
region.
FIG. 4 illustrates a photochemical reactor 10 in which the reaction
completion region is provided with a plurality of lamps 51 and 52
in addition to the primary light source 53 to ensure the completion
of the reaction.
FIG. 5 depicts the reaction completion zone as containing a
plurality of circular baffles 61 disposed in planes horizontal to
light source 62 to direct the flow of the liquid in proximity with
the light source.
Often it is desirable to chlorinate or brominate cyclic or acyclic
hydrocarbons having 4 to 20 carbon atoms per molecule. Practice of
the method and use of the apparatus of this invention results in
high yields of the monohalogenated derivative at relatively high
conversion rates without the expensive duplication of equipment
necessary in conventional halogenating practices. In addition,
halogenation can be carried out at oxygen impurity contents not
feasible in conventional practice.
The following examples will serve to further illustrate the
invention.
EXAMPLE I
For pilot plant tests, a reactor as shown in FIG. 1 was constructed
of a Pyrex glass tube with an upper 2-inch diameter and a lower
1-inch diameter. Two 250-watt ultraviolet lamps were mounted
external to the reactor at a distance of about 3 inches. These
lamps emitted light in the range of about 2000 to 6000 Angstroms.
Using the feed system illustrated in FIG. 2, a premixed feed
comprising liquid cyclohexane, gaseous chlorine, and partially
reacted recycled reactants was introduced into initial reaction
region 23 of reactor 10. The gaseous chlorine went into solution,
providing a completely liquid feed. The amount of recycle liquid
was varied during different runs. The recycled portion was cooled
to provide a premixed feed temperature of 100.degree. F. when added
to the fresh feed constituents. The liquid reaction product was
recovered from reaction completion region 27 at a rate of about 4.4
gallons per hour and analyzed to determine its composition.
Hydrogen chloride gas was recovered from gas liberation region 22.
The conditions, effluent analysis, and results of the different
runs are tabulated below. ##SPC1##
It can be seen that a single stage reaction carried out in the
downflow reactor of this invention resulted in an average of 25.6
percent conversion of the cyclohexane to a chlorinated derivative
having an average ratio of 9.1 mols monochlorocyclohexane to 1
dichlorocyclohexane mol. The reaction can be carried out at
pressures in the range of atmospheric pressure to 200 p.s.i.g,
temperatures of from 0.degree. F. to 250.degree. F. and at a volume
recycle ratio of from 1 to 1 to 30 to 1 of recycle component to
fresh hydrocarbon feed.
For comparison cyclohexane was chlorinated in an adiabatic upward
flow photochlorination reactor which did not contain the different
regions and in which there was plug flow as opposed to the mixed
flow in the reactor of this invention.
A single pass in the abiabatic plug flow reactor resulted in a 12
percent conversion with a 14 to 1 monochlorocyclohexane to
dichlorocyclohexane ratio, while a second pass of the effluent
through the same reactor (simulating a two-stage reactor) resulted
in a 24 percent conversion with a 7 to 1 monochlorocyclohexane to
dichlorocyclohexane ratio.
Thus, it can be seen that photochlorination of cyclohexane in the
reactor of this invention produces in a single stage a greater
percent conversion with a greater quantity of monochlorocyclohexane
in the product than does a two-stage reaction carried out in a plug
flow reactor, a type of reactor conventionally used in many
halogenation processes. Monochlorocyclohexane can be
dehydrohalogenated to obtain cyclohexane, a useful olefin.
EXAMPLE II
Cyclohexane was chlorinated using the reactor and the light source
described in Example I, and the feed system illustrated in FIG. 2.
Air was injected into the discharge of recycle pump 30 at various
rates to test the effect of oxygen inhibiting. The amount of free
chlorine in the hydrogen chloride gas product and the liquid
chlorinated product was determined. The table below presents the
results of runs made with differing recycle and air injection
rates. ##SPC2##
The conversion rates and monochloro to dichloro ratios were
equivalent to those obtained in Example I. It can be seen that a
satisfactory liquid product can be made by oxygen levels above 600
parts per million in the chlorine feed. The maximum tolerable
amount for plug flow adiabatic reactors is about 100 parts per
million of oxygen in the chlorine, which is less than the 200 parts
per million level of oxygen in commercial chlorine. The high oxygen
tolerance of the reactor of this invention is not completely
understood but it is believed that liberation of hydrochloric acid
gas and its upward passage through the liquid purges the liquid
phase of the oxygen and allows the chlorination reaction to be
completed without excessive supplemental quantities of light.
EXAMPLE III
Normal heptane was chlorinated in the reactor of this invention
with air being introduced at the discharge of recycle pump 30 shown
in FIG. 2. Runs were made at various feed and recycle rates,
temperatures, and air injection rates. The conditions and results
of these runs are tabulated below: ##SPC3##
It can be seen that the single stage reaction resulted in an
average 22.8 percent conversion of the normal heptane to a
chlorinated derivative. Further, the injection of oxygen into the
system did not retard the reaction or leave excessive unreacted
chlorine in the product. The chloroheptane product can be used for
producing alkyl aromatics by alkylation or can be
dehydrohalogenated to obtain an olefin.
EXAMPLE IV
A mixture of normal paraffins comprising about 10 weight percent
n-decane, 30 weight percent n-undecane, 35 weight percent
n-dodecane, and 25 weight percent n-tridecane was chlorinated using
the apparatus and conditions set forth in Example III. The
conditions and results of different runs with the normal paraffins
are tabulated below: ##SPC4##
The example shows that the single stage reaction in the reactor of
this invention produced relatively high conversion rates of the
paraffins to chlorinated derivatives in the presence of oxygen.
EXAMPLE V
The data in Examples I through IV were obtained using gaseous
chlorine feed. To determine the effect of liquid chlorine, runs
were made chlorinating cyclohexane, normal heptane, and the mixture
of normal paraffins described in Example IV with liquid chlorine
using the feed system and reactor described in Example I. The
conditions and results of the runs utilizing liquid chlorine are
tabulated below: ##SPC5##
It can be seen that the single stage reaction utilizing liquid
chlorine produced results comparable to the results obtained using
gaseous chlorine. Utilizing liquid chlorine is advantageous in that
it eliminates one source of oxygen impurities in the system.
Reasonable modification and variation are within the scope of the
invention which provides a novel method of and apparatus for
photohalogenating hydrocarbons.
* * * * *