Patented May 2, ‘1933
~ 1,906,440
PATENT OFFICE
UNITED STATES
WALTER 'VNWIRTH, 70F MILWAUKEE, WISCONSIN, ASSIGNOR TO vE. I. DU PONT DE
NEMOURS & COMPANY, OF vWILMINGTON, DELAWARE, A. CORPORATION OF DELA
WARE
-
PROCESS FOR THE MANUEAETURE OF PHOSPHORUS PEN'I‘AOHLORIDE
N0 Drawing.
, Application ?led Novemlier 27, 1931._ Serial No. 577,711.
This invention‘relates to a process‘ for the liquid, and thus necessarily decreasing the '1'“;
manufacture of phosphorus pentachloride. rate and e?iciency of the reaction‘ and in
More particularly, it relates to a process for creasingthe cost of the product.
It is accordingly an object of this inven
5 a form particularly adapted fornse in the tion to produce phosphorus pentachloride in _. 55
manufacturing phosphorus pentachloride 1n
preparation of organic acyl chlorides.
?nely divided form, suspended in a liquid
Organic acyl chlorides have generally been medium, and adapted for immediate use in
reactions requiring phosphorus pentachlo
prepared in the art by reacting the corre
sponding carboxylic acid with phosphorus ride.
pentachloride, in accordance with the fol
lowing equation:
15
It is a further object of this ‘invention to ,y60
Produce Phosphorus pentachloride in such a
physical form and suspended in such a
liquid medium as to be particularly adapted
to the manufacture of organic acyl-chlorides
(R =an
from the corresponding carboxylic acids.
oro'a
g n i c res‘idue) .
This method, however, was objectionable ~
on account of the difficult handling of phos
phorus pentachlorideand the violence of the
25
proceeds.
.
.
In my lmproved process, I select as ini
Accordingly, in U. S. Patent 1,359,071, a tial material either phosphorus or phos- 70.>
reaction.
20
55
Other and further important objects of ‘I
this invention will appear as the description
‘
‘
,
method of manufacturing acyl-chlorides was phorus trichloride. 'I suspend or- dissolve
proposed wherein the phosphorus penta this material in phosphorus oxychloride, and
chloride required is produced in situ during pass chlorine into the mixture, The quan
thereaction. Instead of starting with an tlty of phosphorus oxychloride used for this
organic acid and phosphoruspentachloride, purpose is preferably several times the
~75
this patent proposes to mix the organic acid weight of the phosphorus or phosphorus tri- "
with phosphorus trichloride, and then pass
in chlorine gas, which apparently reacts
?rst with the phosphorus trichloride to pro
duce phosphorus pentachloride, while the
latter immediately reacts with the organic
35
chloride used. In-the case where elemental
phosphorus is used, the chlorine reacts there
with ?rst to produce thetrichloride which
dissolves in the oxychloride.
In either case I ,
the trichloride, thus produced or initially
acid to convert the same into the correspond added, reacts with a further quantity of
ing acyl-chloride. The summarized equa chlorine to produce the ‘pentachloride
tion for the reaction is:
POI3 + Cl2->PCl5.
8.5
The oxychloride present is inert. toward
Now, the above process suffers from the ' chlorine. But its presence, I found, is high
objection that in many cases, particularly 1n ly bene?cial, in that it prevents-the penta
the case of aroyl acids, the phosphorus penta chloride from being formed in compact, 90
chloride is produced too suddenly and in too rocky form. Instead, the pentachloride is '
high concentration. If the chlorine is fed produced in very ?nely divided form, and
into the body 'of the liquid mixture'through may be distributed readily throughout the
a nozzle, solid phosphorus pentachloride oxychloride mass by mechanical agitation.
forms at once a hard, rocky incrustation at When the theoretical quantity of chlorine 9.5
the mouth of the nozzle, therebyimpeding has been absorbed, the mixture consists‘, sub
further, progress ofthe reaction. 'Accord stantially of phosphorus pentachloride sus
ingly, in practice the chlorine must be blown pended in phosphorus oxychloride} ‘Excess
over the surface of the liquid, thereby limit of chlorine does not materially affect the
50
ing the reaction zone to the surface of the composition ofthe mixture, since both the 100
40
2
1,906,440
pentachloride and oxychloride are inert to
ward chlorine.
This mixture is particularly suitable for
the manufacture of acyl chlorides from the
corresponding carboxylic acids. When an
organic acid is’added to this .mixture, re
action takes place in the usual manner, ex
cept that the reaction zone is distributed
10
16
chlorides. If Water is added to said suspen
sion it is converted, practically completely,
into phosphorus oxychloride and hydro
chloric acid.
PCl5 + H2O=POGl3 + 2HC1
Example 2
of phosphorus trichloride and
practically throughout the liquid mass, and 550v220jparts
parts
.of
phosphorus oxychloride are
is further facilitated‘by the ?ne form of the
charged into a flask, and chlorine gas'is ‘con
phosphorus pentachloride.
ducted through the solution until about 114
Since phosphorus oxychlorideis produced parts
have been absorbed. During this pro
as a by-product in the formation of acyl- cedure the temperature of the mixture is
chlorides, its introduction at the beginning kept
down below ‘60° (1, by externalcool
of the process does not complicate the latter ing. When
reaction is complete the mass
‘by any special recovery or separation steps. is cooled to the
room
temperature, and consists
On the contrary, the process is considerably
of a suspension of ?nely divided, crystalline,
simpli?ed, for instead of effectingv a com phosphorus
, plete separation of the organic acyl chloride oxychloride. pentachloride in phosphorus
from the phosphorus oxychloride in the ?nal
The above mixture, in View of the ?nely
product, it is sufficient in my process to sepa divided
form of ‘the phosphorus pentachlo
rate the reaction mass by distillation into
ride,
and
in View, of the nature of the diluent,
three fractions. The two extreme fractions
is
particularly
suitable for the manufacture
\ contain substantially pure acyl-chloride and
20
25
of acyl chlorides, as illustrated by the £01“.
phosphorus oxychloride, respectively, while lowing
example.
90
the'middle fraction containing a mixture of
the two may be used directly as suspending
medium for the next batchof reactants, and
2 therefore need not be further separated.
30
be
85
Although in the above discussion I illus
pentachloride in phosphorus oxychloride as. -
obtained in Example 2, there are stirred in
254
parts of p-nitro-benzoic acid. The tem
ufacture of organic acyl-chlorides, it will perature
rises very little, but as reaction ‘pro
95
be understood that my invention is applica
‘the benzoic acid body goes into solu
ble to other processes requiring phosphorus ceeds,
tion. When reaction is complete, the mass
pentachloride, particularly Where phosphor is distilled at a temperature gradually raised ~ 100
usoxychloride is produced in the reaction to
180° C. Most-of the'phosphorus ‘oxychlo
either as main product or by-product. As ride (about 728 parts) distils over during
examples of such other processes may be
fone chlorides from the corresponding sul~
fonic acids, the manufacture of thionyl chlo
ride from sulfur dioxide, or the manufac
.ture of phosphorus oxychloride itself from
phosphorus pentachloride and water.
to
Example 3
Into the cooled suspension of phosphorus
trated my invention as applied to the man
_ mentioned the manufacture of organic sul
45
85
this period. Application ofv a vacuum of 20
inches nowv brings over 48 parts more of- ~
I phosphorus oxychloride.
‘The undistilled
.
‘residue consists .of p-nitro-benzoyl chloride,
'in admixture with some residual phosphorus
oxychloride. It may be subjected to redis
‘under vacuum, but ordinarily it is, v»
NVithout limiting my invention to any tillation
su?iciently
pure for technical application 110
particular procedure, the following examples Without further
puri?cation.
'
are given to illustrate my preferred mode
In the case ‘of acyl chlorides Whose boil
of operation.' .Parts given are parts by . “ing point is close to that of phosphorus oxy
Weight.
7
"
-
Ewample 1
chloride, the distillation may be carried out
in the following manner. At ?rst the-‘(11S 115
62 parts of yellow phosphorus are charged ‘tillate consisting of'butk-a single component
into 337’ parts of phosphorus oxychloride is condensed. This may be pure oxy-chlo
and the mixture is warmed up to melt the ride‘ or pure acyl-chloride, dependingon the
phosphorus. Chlorine gas is now- passed boiling point-of the latter. The next frac—,- 55
into the mixture, while keeping down the
temperature, by the aid of cooling, at be
low 40° to 45° C. The reaction is complete
when about 360 parts of chlorine have been
absorbed. At this point the mass turns yel
60 low and consists of a rather dense suspension
tion containing a mixture of ‘both acyl chlo
120
ride and phosphorus oxychloride is collected
and condensed in a separate vessel. The dis
tillation is continued until theresidue in the
still consists of‘ the substantially pure second
component.
'
t
g
125
o'fl?ne crystals of phosphorus pentachloride The middle fraction containing both acyl
in liquid phosphorus oxychloride. The chloride and phosphorus oxychloride may be
V
used directly as diluent for the preparation
YThe above suspension is exceptionally Well of the next batch of phosphorus pentachlow
adapted to'the manufacture of organic acyl ride according to Examples '1_or 2, and the 130
yield is practically quantitative.
$5
1,906,440
mixture thus produced may be used for the
production of further quantities of acyl chlo
ride in accordance with Example 3. The
cycle may be repeated inde?nitely.
It will be understood that my preferred
process is susceptible to many Variations and
modi?cations without departing from the
spirit of this invention.
I claim:
10
1. The process of producing phosphorus
pentachloride in ?nely divided form which
comprises reacting with chlorine upon phos
phorus trichloride in phosphorus oxychlo
ride solution.
15
2. The process of producing phosphorus
pentachloride in ?nely divided form which
comprises preparing a solution of phosphor
us trichloride in phosphorus oxychloride,
and passing chlorine gas into this solution.
20
3. The process of producing phosphorus
pentachloride in ?nely vdivided form which
comprises suspending phosphorus in phos
phorus oxychloride, and passing in chlorine
gas in a quantity su?icient to produce ?rst
25
the trichloride and then the pentachloride
of phosphorus.
4:. The process of producing osphorus
pentachloride in ?nely divided orm which
comprises passing in substantially 360 parts
30
of chlorine gas into a mixture of substan
tially 62 parts of phosphorus in 337 parts
35
of phosphorus oxychloride maintained at a
temperature below 45° C.
5. The process of producing phosphorus
pentachloride in ?nely divided form which
comprises passing in substantially 114 parts
of chlorine into a solution of substantially
220 parts of phosphorus trichloride in 550
parts of phosphorus oxychloride while '
maintaining the temperature of the mass at
below 60° C.
6. The process of producing phosphorus
pentachloride in ?nely divided form which
comprises suspending phosphorus in phos
45
phorus oxychloride, and passing in chlorine‘
gas in a quantity sui?cient to convert the
phosphorus substantially completely into
phosphorus pentachloride.
50
55
60
65
In testimony whereof I a?ix my signature.
WALTER V. WIRTH.