close

Вход

Забыли?

вход по аккаунту

?

Патент USA US3032592

код для вставки
May 1, 1962
H. ZIMA
3,032,582
PROCESS FOR THE PRODUCTION OF CYANOGEN AND CYANIC ACID
BY OXIDATION OF HYDROGEN CYANIDE AND THE PREPARATION
OF‘ URETHANES AND ALLOPHANIC ACID ESTERS THEREFROM
Filed May 12, 1958
INVENTOR
Herbert? Z12mm
ATTo-N Ys
United States atentO Mice
3,032,582
Patented May 1, 1962
2
1
of the product primarily desired. For the preparation of
3,032,582
PROCESS FOR THE PRODUCTION OF CYANOGEN
AND CYANIC ACID BY OXIDATION OF HYDRO
GEN CYANIDE AND THE PREPARATION OF
URETHANES AND ALLOPHANIC ACID ESTERS
THEREFROM
Herbert Zima, Darmstadt, Germany, assignor to Rohm &
Haas G.m.b.H., Darmstadt, Germany
Filed May 12, 1958,,Ser. No. 734,726
Claims priority, application Germany May 15, 1957
10 Claims. (Cl. 260-482)
This invention relates to an improved method for oxid
izing hydrogen cyanide.
cyanogen, the mol ratio of oxygen to hydrogen cyanide
should be at least 1:4, as indicated in Reaction I, whereas
for the preparation primarily of cyanic acid, the mol ratio
should be increased to at least 1:2, ‘as indicated in Reac—
tion II.
Whereas cyanogen is a relatively stable compound,
even at high temperatures, cyanic acid polymerizes readily
to form cyanuric acid or cyamelide or undergoes other
Such polymerization or other conversions,
which are generally considered undesirable, are prefer
10 conversions.
ably inhibited by rapidly cooling the gaseous reaction
products immediately after they are formed in the catalytic
reaction zone.
It is well known that hydrogen cyanide can be oxidized
The rapid cooling of the reaction gases immediately
15
upon contact with air or other oxygen-containing gas.
after
they leave the catalytic reaction zone can be accom
The products of such oxidation are cyanogen, cyanuric
plished in any desired manner or combination of Ways.
acid, cyamelide, melamine, urea and even nitrogen. oxides,
One means of rapid cooling is that of imparting a high
depending upon the catalyst employed, the ratio of hydro
velocity,
and therefore reduced pressure, to the reaction
gen cyanide to oxygen, the speed of ?ow and the tem
perature involved. The method of the present invention 20 gases immediately upon leaving the catalytic reaction zone
and then directing the gases to an adjacent cooling cham
is not concerned with such complete oxidations as those
ber.
Another means is that of injecting into the stream of
involved in the formation of nitrogen oxides but primarily
reaction gases, immediately-upon their departure from
with the preparation of cyanogen and cyanic acid as Well;
the catalytic reaction zone, a cooling’?uid which may be
as the preparation of secondary reaction products derived
inert to the reaction gases or be capable of reacting with
25
from the cyanogen and cyanic acid.
them
to ‘form one or more preselected derivatives. This
vThe oxidation of hydrogen cyanide is believed to take
may be accomplished by spraying a precooled liquid or
place in accordance with the following'reactions:
blowing a precooled or compressed gas into the gaseous
reaction product stream. Thus, for example, a rapid
30 chilling can be effected by-blowing into the hot reaction
gases a precooled and possibly compressed stream of
A technically feasible method for oxidizing hydrogen
precooled nitrogen. On the other hand, a rapid chilling
cyanide to cyanogen in accordance with Reaction I has
heretofore been proposed. It comprises bringing hydro
and simultaneous desired secondary reaction may . be
achieved by spraying into the hot reaction gases a pre
metallic silver catalyst at temperatures ranging from about 35 cooled alcohol which will not only effect the desired cool
ing of the reaction gases but react with them to produce
300 to about 600° C. ' Unfortunately, however, the yields
gen cyanide into contact with air in the presence of a
obtainable by means of this process are reported to be a
a urethane 'and/ or an allophanic acid ester. ‘It has been
shown to be particularly desirable, when the process is
directed primarily to the production of cyanogen and/or
sired from the point of view of commercial operation.
This low yield is believed to be due to‘ 'thefact'that a 40 cyanic acid, to inhibit the vformation of unwanted by
products of hydrogen cyanide oxidation by effecting the
considerable number of solid by-products of varying com
chilling with the aid of precooled gases that are inert to
position are formed, especially during continuous opera
the products of ‘reaction and are blown into the gaseous
tion. Such solid materials include polymerization prod
'stream thereof. While it is to be understood that the
ucts of cyanic acid, urea and ammonium cyanate which
collect in the apparatus, interfere with its operation, have 45 temperature to which the reaction gases are to be cooled
in accordance with the method of the invention depends
no practical utility, and contribute to the formation of
upon
the particular products desired and the yield re
other undesirable by-products and in general add consider
quired, and that the temperature may therefore vary wide
ably to the expense of the method and the cost of the
ly, it has been found generally desirable to cool the gases
apparatus. An ef?cient method of industrial utility for
immediately
after leaving the reaction zone to a tem
producing cyanic acid as indicated {in Reaction II is not 50
perature of approximately 0'’ C.
known to have been described.
The separation of cyanogen and/or cyanic acid, or of
It has now been found that oxidation of hydrogen
maximumof about 22.8%, which leaves much to be de
cyanide will proceed smoothly, with excellent yields of
their derivatives, can readily be carried out in known
cyanic acid and cyanogen, by bringing it into contact with
manner, e.g., by washing, crystallization, or otherwise,
a catalyst comprising metallic gold.
?uid such as an alcohol or chloroform circulated there
most desirably in an absorption tower having a suitable
oxygen at an elevated temperature and in the presence of 55
The catalyst is preferably in the form of a ?ne Wire
through.
It is to be understood of course that when
chloroform is employed the absorption tower must be
suitably
cooled.
precipitated in a ?nely divided form. It is also within the
A typical embodiment of the apparatus of the inven
scope of the invention to employ, as catalyst, combinations 60 tion is shown in the accompanying drawing. The em
of metallic gold with other catalytically active metals
bodiment illustrated comprises a tubular section 1 con
mesh or a porous carrier upon which gold has been
such as copper and silver.
The temperature conditions of the reaction are desirably
taining a catalytic reaction zone 2 provided with a wire
mesh catalyst 4 and having a restricted exit opening 6
within the range of about 300 to 700° C., a somewhat
leading to a chilling chamber 7 of substantially greater
65
narrower range between about 500 and 650° C. being
cross section than the catalytic reaction zone 2. The
preferred for optimum results. One or both the gases to
chamber 7 is shown as provided with two injection
nozzles 9 and as being connected to the catalytic reac
be reacted may desirably be preheated and the catalyst
may also be heated, e.g., electrically, to produce the de
sired elevated temperature and initiate the oxidiation.
The relative proportions of oxygen-containing gas, e.g.,
air, and hydrogen cyanide are dependent upon the identity
tion zone by a suitably ?anged and packed connection
shown generally at 10.
In operation, the hydrogen cyanide and air or other
oxygen-containing gas is introduced through the tube 1
3,032,582
3
4. A method of oxidizing hydrogen cyanide which com
to the catalytic reaction zone 2 wherein, upon contact
with the catalyst 4 at an elevated temperature, the hy
drogen cyanide is converted into the desired oxidation
products. The movement of the reaction gases is ac
celerated by passage through the restricted opening or
prises bringing it into contact with oxygen at a tempera
ture between about 300° and 700° C. in a catalytic zone
containing metallic gold and rapidly cooling the reaction
products of said oxidation immediately after their removal
ori?ce 6 whereupon they enter the chilling chamber 7
from the catalytic zone.
’
in Which they are further rapidly cooled by contact with
a precooled ?uid injected by means of the nozzles 9.
5. Method as de?ned in claim 4 wherein the oxidation
products are chilled to a temperature of approximately
0° C.
The advantages and utility as well as further details
6. Method as de?ned in claim 4 wherein the rapid cool
of the operation of applicant’s method will become fur 10
ing of the oxidation products is effected by injecting a
precooled ?uid into a stream of said products upon depar
ture from the catalytic “zone.
7. Method as de?ned in claim 6 wherein the precooled
ther apparent from the following example included to
illustrate the best mode now contemplated of carrying
out the invention.
Example
A mixture of 32.6 l.p.h. ,(liters per hour) air and 12.9
l.p.h. hydrogen cyanide was fed through reactor tube 1
15 ?uid is a liquid.
8. Method as de?ned in claim 6 wherein the precooled
?uid is a gas.
of vanadium alloy steel for contact at 630 to 640° C.
9. A method for preparing cyanic acid which com
prises, oxidizing hydrogen cyanide with at least a stoi
with three electrically heated gold Wire mesh screens 4
in which the diameter of the wire was 0.2
and the 20
chiometric amount of oxygen by contact thereof at
width of the mesh was 0.5 mm. The screens had diam
a temperature between about 300° and 700° C. with a
eters of 20 mm. and were spaced 5
apart. The
catalyst comprising metallic gold.
gaseous products of reaction were chilled to about 0°
C. by blowing in nitrogen cooled to a temperature of
about —.150° C- and then passed through an absorption
tower (not shown) containing alcohol.
10. in the method of making urethanes and allophanic
acid esters by reacting cyanic acid and cyanogen with an
25
alcohol, the improvement of continuously forming cyanic
acid and cyanogen by continuously contacting ‘hydrogen
It was found that 86% of the hydrogen cyanide had
cyanide with oxygen at a temperature between about 300°
been oxidized; the yields of cyanic acid, cyanogen and
and 700° .C. in the presence of an oxidation catalyst com
CO2 were 56%,, 1% and 37%, respectively, based on
prising
metallic gold, and then cooling the gases thus
the hydrogen cyanide consumed.
30 formed by injection thereinto of a precooled alcohol to
It is to be understood that numerous modi?cations will
be reacted therewith.
readily become apparent to those skilled in the art upon
readily this description. All such modi?cations are in
References Cited in the tile of this patent
tended to be included within the scope of ‘the invention
as de?ned in the appended claims.
UNITED STATES PATENTS
35
'
I claim:
1. A method of oxidizing hydrogen cyanide which
comprises bringing it into contact with oxygen at a
temperature between about 300° and 700° C. in the
presence of an oxidation catalyst comprising metallic gold. 40
2. Method as de?ned in claim 1 wherein the catalyst
comprises vmetallic gold wire mesh.
3. Method as de?ned in claim 1 wherein the catalyst
comprises metallic gold on a porous carrier.
2,712,493
2,723,185
Moje
____u
__."".'_"."I"—T_'—__'.'
___
_ _ _ _ __ July 5,
1955
' Hulemer __,_____,___,_>_,_____ Nov. 8, 1955
2,884,308
Fierce et al. ___‘____.__v____ Apr. 28, 1959
2,916,534
Schnallus et all. _______ __ Dec. 8, 1959
OTHER REFERENCES
131011111 et ah ‘fAllQphanates.” Chemical Reviews, Vol
51, 1952, page 472.
Документ
Категория
Без категории
Просмотров
0
Размер файла
312 Кб
Теги
1/--страниц
Пожаловаться на содержимое документа