Note: Descriptions are shown in the official language in which they were submitted.
PROCESS FOR PREPARING ALUMINUM
OR MAGNESIUM PHOSPHIDE
This invention relates ~o an improvement in the
production of the phosphide of aluminum or magnesium in
which the finely divided metal or an alloy of the two
metals is reacted with yellow phosphorus at a temperature
between 300 and 600C in an inert gas atmospherence and in
the presence of chlorine, bromine, iodine, or a compound
of such elements with phosphorus, sulfur, hydroger" ammo-
nium, zinc, or the metal being reacted.
According to a particularly preferred form, first
the finely divided or gritty metal is intimately mixed
.15 with the catalyst. The mixture is heated in a suitable
reactor capable of being enclosed in an inert gas atomos-
phere, for example, under nitrogen at normal pressure to
the reaction between 300 and 600C. When the desired reac-
tion temperature is reached liquid yellow phosphorus is
added at such a speed that the heat of reaction liberated
is led off without problem and the temperature can be main-
tained in the range between 300 and 600C.
.~
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It has now be found that this process can be made
still safer and be more readily controlled and above all be
made par-tially or even fully continuous if the finely divi-
ded metal is also slowly added into the reaction vessel.
According to the present invention there is provi-
ded a process for preparing aluminium or magnesium phosphide
by reacting the finely divided metal or an alloy of the two
metals and liquid yellow phosphorus at a termpera-ture bet-
ween 300 and 600 C in an inert gas atmosphere and in the
presence of a catalytically effective amount of -the element
chlorine, bromine, or iodine or a compound of such element
with phosphorus, sulfur, hydrogen, ammonium, zinc, or -the
metal being reacted, the improvement comprising slowly add-
]5 ing to the reaction vessel both the liqu~d phosphorus and the
finely divided metal.
If the process of the invention is carried out in
a substantially cylindrical reaction vessel, which is heated
Erom below the bo-ttom then there are clearly formed four
different zones which from the top to the bottom can be des-
cribed as follows:
Zone 1: In this uppermost zone there exists only
gas, namely a rnixture of -the inert gas employed and phos-
phorus vapor. Since in this zone in the most extreme case
-there is only reached a maximum tempera-ture of about 200 C,
the vapor pressure of -the phosphorus is rela-tively small so
that the gas mixture consists chiefly of the inert gas em-
ployed.
Zone 2: Here is the vaporization zone of the yellow
phosphorus. In this zone there prevail temperature which are
slightly above the boiling point of the yellow phosphorus.
Also in zone there exists only gas, which now indeed consis-ts
for the greatest part of phosphorus vapor.
2 -
4 6~~f31P~li
Zone 3: Here lS located in the uppermost layer of
the container filling the true
- 2a -
73
--3--
reaction zone ln whlch phospnorus vapor comes in
contact with tne flnel~ dividea metal and the
alreac~ formec ~nos?hiàe. In this zone whicn lS
at the reactio. tem?erature of 300 to 600C tnere
akes ?12ce the s rongl\~ e~othermic reaction between
the phosphor~s vz?cr and the flnely diviaea metal.
Since .ne pnos_hor~as vapor reacts very quickly with
the metal 1 does nct ~enetr2te very deeply into
the contalner fi_ilns but onlv about 10 to 15 c~.
There_ore witlln _he container filling the gas phase
in tne cirec.lo- rom the top cownwardlv very
raplcly has a o;ered phospnorus vapor content.
Zor.e ~.: In this lowermost zone tne
cas ?hase consis C practlcally only of inert ~as
because the phcs?ncruc vapor does not penetrate to
thls de?th. The solid material consists practicall-
only of the phosphide formec and contains perhaps
small amounts of unreacted metal. A sliaht excess
of metal makes certain that the ?hos?hide formed
is free OI phosphorus.
The forma~ion of tne previously aescribed
four zones within the reaction vessel then makes
possible a particula~ly simple and completely safe
form o~ the process of the invention. Thereby the
liquic yellow phosphorus is continuously addec into
the up?er part o the reaction vessel thus in the
gas space abo~e the container packing where lt can
be va?orized ~ilhout hindr2nce. It is especiallv
advantageous if the entrance for the liquid pnos-
phorus is locatec entirely above in the reaction
vessel thus ln aDove-mentioned zone 1. The finely
divided metal to be sure can also be added in the
upper part of the reaction vessel. Then however
the quick anc vigorous reaction ~ith the phosphorus
vapor already present makes
.. ~
necessary the use of special closing off devices for
the entrance in order to prevent the phosphorus
VG,-Or frcm penetrating into the conveying device for
the flnelv divided metal. Therefore it is more
advan,ageous to continuously add the finely divided
metal into the lower par, of the reaction vessel,
namely so that the entrance is in the region of the
container filling. This can occur in the above-
mentioned zone 3, the true reaction zone. Then it
is suitable to provide about the height of the
entrance for the metal a stirrer whose conveying
elements move the container packing along the
periphery of the container and thus provide for a
uniform distribution of the freshly added metal in
the reaction zone. However, it is still more
advantageous if the addition of the finely divided
metal takes place in the lowest part of the reaction
vessel, thus in the above-mentioned zone g. In
this case it is suitable to provide a stirrer whose
conveying elements move the container packing
along the periphery of the container and simul-
taneously provide for a thorough mixing vertically.
It is possible in the manner depicted
to continuously add equivalent amounts of finely
divided metal, which contains the catalyst mixed
therein, and liquid yellow phosphorus into the
reaction vessel and during the reaction to withdraw
from the lowest part of the reaction vessel, thus
from the above-mentioned zone 4, the phosphide
formed, which is free from unreacted phosphorus.
The withdrawal takes place through an~opening at
the bottom of the reaction vessel. ~t can be
carried out at will continuously or batchwise. In
continuous withdrawal the product is discharged in
an amount corresponding exactly to the rnetal and
phosphorus added. However, it is possible just as
well also to let it slowly build up in the lowermost
zone in the reaction vessel, thus the above-
mer,tioned zone 4, and then to discharge the phos-
phice formed batchwise. However, thereby attention
mus, be paid that actually there is only discharged
from this zone 4 material which no longer contains
unreacted phosphorus, and not perhaps also material
from the reaction zone, which can happen through
weisht control.
If the finely divided metal - as
described above - is fed into the lower part of
the reaction vessel, thus in the above-mentioned
zone 3 or zone 4, then there suffices as feeding
device a customary screw convever, because the
solid, gritty contai.ner filling serves at the same
time as closing off device. Should the process of
the invention be started in an empty reaction
vessel, it .is therefore suitable first to introduce
onlv f inely divided metal until the entrance for
the metal is covered, and only then to beg.in the
slow addition of the liquid phosphorus. However
it is still more advantageous if the reaction
vessel first is filled with the corresponding phos-
phide from an earlier production until it is above
the entrance for the metal, and then simultaneously
there is begun the addition of the liquid phosphorus
and the finelv divided metal.
The process of ,he invention is explained
in more detail in the following examples. Unless
olherwise stated all percents are weight percents.
Example 1
As reaction vessel there served a
cylindrical container having a diameter of about
80 crn and a height of about 100 cm which was provided
with a stirrer, a coolins system, temperature
probes at various heights, an inlet line for inert
gas and a line for waste gas. The bottom of the
container was heatable by a gas burner from the
outside to temperatures U? to 500C. Connected
thereto was a supply vessel for liquid phosphorus
having a pump which permitted at will the rotation
of the liquid yellow phosphorus in the supply vessel
or to feed it into the reaction vessel, as well as
a supply vessel for the finely divided metal to be
reacted with a conveying device for the adding of
the metal into the reaction vessel. At the bottcr~
of the reaction vessel there was located a small
opening provided with a locking off device for dis-
charge of product. For reasons of safety the reaction
vessel was provided with a rupture disc to counter
an~ possible increase in pressure. The reaction
vessel was rinsed before and after the reaction
with nitrogen, during the reaction the reaction
mixture was covered with argon. The waste gas was
led off over a water receiver having a glass fiber
filter and a post-connected activated,carbon filter.
Before the beginning of the reaction
there were located in the reaction vessel 50 kg of
73
magnesium phosphide from an earlier production, in
the supply vessel for the metal a mixture of 200 kg
of magnesium and 0.8 kg of iodine, in the supply
vessel for ~he liquid phosphorus this was rotated.
Then the reaction vessel W2S heated at the bottom
to 300C. Then there were fed into the reaction
vessel 10 kg of magnesium and the feeding in of the
liquid phosphorus was begun with a speed of 0.4 to
1 kg per minute. Simultaneously more magnesium
was also added. Through the heat of reaction the
temperature increased in the lower part of thte
xeaction vessel to 550C. Then the addition of the
phosphorus and the magnesium was so regulated that
the temperature was maintained at 550C and the
weight ratio between phosphorus and magnesium was
around 0.85:1. After about 180 kg of magnesium
phosphide had formed in the reaction vessel there
were discharged through the withdrawal opeing 100
kg of product within 10 minutes while continuously
adding further phosphorus and magnesium. The with-
drawal opening was again closed. After there had
again formed about 180 kg o~ magnesium phosphide.
this was a'gain discharged and subsequently the
entire process was again re2eated. After using up
the supply of 200 kg of magnesium the addition of
phosphorus was stopped. The product still located
in teh reaction vessel was again heated briefly and
discharged. Including the magnesium phosphide
present in the reaction vessel in the course of 5
hours there were discharged 415 kg of product having
a magnesium phosphide content of 92~.
Example 2
There were present in the reaction ~essel
described in Example 1 a mixture of 100 kg of
--&--
magnesium and 0.3 kg of iodine in the supply vessel
for the metal there was present a mixture of a
further 150 kg of magnesium and 0.5 ky of iodine.
Then the reaction vessel was heated at the bottom
of 300 C. Then phosphorus was added at such a
speed that the temperature in the lower part of the
reaction vessel slowly increased to 550C. Through
control of the addition of phosphorus this tempera-
ture was maintained until altogether 82 kg of
phosphorus was used. Then there were simultaneously
added magnesium and phosphorus in the weight ratio
1:0.83 at such 2 velocity that the temperature in
the lower part of tne reaction vessel continuously
remained between 500 and 550C. At the same time
there was continuously discharged through the
withdrawal opening product in such amount that it
exactly corresponded to the amount of magnesium and
phosphorus added thus altogether 150 kg of magnesium
and 123 kg of phosphorus. Finally the product still
found in the reaction vessel was heated again
briefly and further discharged continuously. The
yield in all amounted to 450 kg with an average
content of magnesium phosphide of 90~.
Example 3
There were present in the reaction vessel
described in Example 1 a mixture of 50 kg of a gritty
aluminum-magnesium alloy having a magnesi~un content
of 5~ and 0.2 kg of iodine. There was present in
the suppl~ vessel for the metal a mixture of a
further 200 kg of the alloy mentioned and 0.6 kg
of iodine. Then the reaction vessel was heated
at the bo-ttom to 450C. Then there was begun the
addition of phosphorus and alloy. Thereby the
phosphorus was first added with relatively greater
~ Z7~7
speed in order to compensate for the excess of alloy
present, until ln all there was reached a weight
ratlo of phosphorus to alloy o~ 1. The heat~ng
remined on until a temperature of 500C was reached
in the lower part of the reaction vessel. Subse-
~uently there were added more phosphorus and alloy
in the wieght ratio of 1.1:1 until the reaction
vessel contained about 200 kg of product. From
this point on tnere was continuously discharged
through the withdrawal opening product at the same
velocity that phosphorus and alloy were added. The
addition was so adjusted that the temperature dic
not exceed 550C. After use of the entire alloy
the addition of the phosphorus was stopped, the
heating set in operation and the remainder of the
product continuously further discharged. In all
there were obtained 520 kg of gritty product with
a phosphide content of 90~ of theory.
Example 4
There were present in the reaction vessel
described in ~xample 1 130 kg of aluminum phosphide
from an earlier production, in the suppl~7 vessel for
th~ metal there was a mixture of 250 kg of aluminum
and 1 kg of iodine. Then the reaction vessel was
heated at the bottom to 480C and there were
introduced 20 kg of aluminum. Then there were
simultalleously added aluminum and phosphorus and
after reacting a temperature of 500C the heating
stopped. The excess of metal present was compen-
sated for by an at first somewhat quicker addition
of phosphorus, then there took place the addition
of aluminum and phosphorus with a constant weight
ratio of 1:1.1 at such velocity that the temperature
--10--
of i70 C was not exceeded. After there were found in
the reaction vessel ln all 230 kg of product there was
discharged 130 kg of product with constant
addition of aluminum and phosphorus. This process
was repeated until the 250 kg of aluminum were use~
up. In all there were discharged 501 kg of product
with an aluminum phosphide content of 95~, around
a fur.her lii kg was left in the reaction vessel as
a heel for ~he next product.
