CA1096401A - Preparation of acrylamide - Google Patents

Abstract

PREPARATION OF ACRYLAMIDE

ABSTRACT OF THE DISCLOSURE
Acrylamide may be prepared by the hydrolysis of acrylonitrile by treating the acrylonitrile with water in the presence of a copper catalyst which has been prepared by volatilizing copper metal at a tem-perature in the range of from about 1000° to about 1500° C. in vacuo and condensing the vapors in the presence of an organic solvent.

Description

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PREPARATION OF ACRYLAMIDE ~ ~ , SPEGIFICATION

: This invention relates t~ a method for the preparation o~ ac~yl- ~ :
; amide. More specifically the lnventlon is concerned with a process for preparing acrylamide~whereby acrylonitrile ;s hydrolyzed in the presence of copper-containing cata7ysts which have been prepared jD a certai~n manner.

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Acrylamide is used in flocculents, paper strengtheniny agerlts and most recently as an additlve -For tertiary oil recovery. For example, polyacrylamide flocculents cause a more rapid agglomeration and sedimenta-tion than do conventional inorganic flocculen-ts such as Ferrous sulfate or aluminum sul-fate. Consequently, since pollution with industr-lal waste water has grown the demand for thick polyacrylamide Flocculents has also grown. In addition to its use as a Flocculent, polyacrylamide also displays a higher improviny effect on the dry strength oF paper than do other paper strengthening agents such as starch or urea-Formaldehyde resins. Therefore ln v;ew of the increasing use of acrylamide in the above-mentloned fields~
it has become more important to develop a method whereby improved yields of the desîred product may be obta;ned without having to have the attendant worry of disposal of unwanted side products or unnecessary separation steps.
It ;s therefore an object o-F this invention to provide an improved process for the preparation of~acrylamide.
A further abject of this invention is to provide an improved process for the production;of acrylamide using copper catalysts whi~ch have been prepa~red in a certain manner. ~
In one aspect an~emobidment of this invention resldes in a process for the preparation of acrylamide which comprises treating acrylonitrile with water ln the presence oF a copper catalyst which;has been prepared by~volatîlizing copper metal, subsequently cooiîng the copper vapors in the presence of an organic sol~vent, and heating to ambient temperature, and recovering the resultant acrylamide~
, A specific embodiment of this invention is found in a process For : :
the preparation of acylamide whlch comprises treating acrylonitrile :

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in the presence of a copper catalyst in which copper me~.al has been sub-jected to volatilization at a temperature in the range of ~rom about 1000 to about lS00 C. in vacuo and subseguently cooled in the presence 5 oF tetrahydrofuran, and thereaFter recovering the resultant acrylamide.
Other objects and embodiments will be found in the following further detalled description of the present invention.
The desired product is.prepared, according to the process of this in~ention, by treating acrylonitrile with water in the presence of certain catalytic compositions of matter which are prepared 1n a manner hereinafter set forth in greater detail. By utilizing a copper-containing ca-talyst which has been prepared according to the process o~ this inven-tion, the desired product will be obtained in a very high.selectivity, the percentage of byproducts such as beta-hydroxypropionyl which results from :; 15 the hydration of the do:uble bond o~ the acrylonitrile, being negligible.
In addition, the copper will also act as an excellent inhibitor for preventing the polymerization of acrylamide and in addition;wlll not suffer from a fast rate of poisoning which is usually caused by the polymeriza-tion of acr~lamide which occurs during the reaction. Another~factor which 20: is present in the catalyst prepared according to the process of this inven~
. : tion is the relatively high activity. This high activity~will be lllus-trated in the exampl:es which are appended a:t the end of the specification .. . .... , ... . .................... : ~ , :~ and is in contrast to other copper-containing catalysts prepared ln various other ways. For example, as will be hereinafter shown in greater detail, copper which has been prepared by reduction of CuO powder with molecular :
: hydrogen showed the usual activity. Copper oxide needles or powder which ~ :are:reduced with molecular hydrogen and therea-fter used as a Fixed bed ~, - ~1 40~

catalyst or ;n a stirred tank reactor will l;kewise show a very low activity. In contradistinction to this, a catalyst which is prepared by vaporizing copper in an apparatus such as that which is shown in an article in Accounts o~ Chemical Research, 8, 1975 by K. J. Klabunde S followed by condensa~ion of the vapor on walls which have been cooled with liquid nitrogen and on which a solvent of the type herein~fter set forth in ~reater detail is also condensed will Form a complex between the metal atoms and the solvent which is stable as a solution at low tempera~
tures. Upon heating the solution ~o the room or ambient temperature, the com~lex is decomposed and the resultiny copper is present as a very finely dispersed me~al powder, the size of the particles of the metal powder being dependent namely upon the na-ture of the solvent which is employed in the separation of the catalyst.
In the preFerred ernbodiment of the inven-~ion the solvents which are employed will comprise poiar solvents such as ethers, amines, alco- ;
hols, etc. Some spec;~ic examples of solvents which may be employed to form the catalyst of the present inven~ion will include alkyl, aryl and heterocyclic ethers such as dimethyl ether, diethyl ether, dipropyl ether, diphenyl ether, dibenzyl ether, di-p-~olyl ether, tetrahydrofuran, tetra-hydropyran, dioxane, etc.; alkyl and aromatic amines such as trimethyl amine, tr1ethyl amine, tripropyl amine, tributyl amine, aniline, substi- :
t~ted anillnes such as isomeric d;methyl anilines, diethyl an;lines, ~i-propyl anilines, pyridines alkyl pyridines, nitriles such as acrylDnitrile;
propionitrile, butyronitrile~ etc.; alcohols both alkyl and aryl such as methyl alcohol,. ethyl alcohol, n-propyl alcohol, isopropyl alcohol, bulyl alcohol, benzyl alcohol~ etc. It is to be understood that the aforemen~
tioned polar solvents are only representative of the class of compounds - 5 - , 1~9~

wilich may be employed, and that the present invention is not necessarily limited thereto The process of this inven~ion, in which the catalyst which is used is prepared according to the me~hQd set forth in the aforementioned article in Accounts of Chemical Research, that is, hy vaporizing copper metal, thereafter cooling and condensing the copper vapors in a solvent, may be effected by~treating the acrylonitrile wi~h water in the presence of said catalyst in an appropriate apparatus~such as a Fischer-Porter apparatus. The acrylonitr1le is hydrolyzed at temperatures rangi~n~g~ from about 60 to about 160 C. for a perlod of time which may range~from~about~
- 0.5 up to about 10 hours or more in duration. While in the preferred ~embodiment of the invention, the reaction is effected at a pressure~of about 60 pounds per square inch, lt is also contemplated with~in the scop~
of this invention that superatmospheric pressures ranging~up~to about 1~0 atmospheres may be employed, the s;uperatmospher;c ~pressure being aFforded~
by~the ~1ntroduction of a substant1~a11y~inert gas~such~as nitrogen into~
the~reaction zone.~;Upon complet10n 0f the react1;on~period the~1iquid - reaction product is separated from the catalyst by~decantat1on~or f1ltra~
tion. If there are~ two phases or layers, the~organic 1ayer is separated~from~
~;20~ the aqueous l~ayer and recycled to~the reactor. The~aqueous layer which:
contains unreacted acrylonitrile and acrylamide is s~ubjected to~dist;lla ti~on ~or~removal of unreacted acry1~onltr11e~while the rema1n1ng~à~queous acrylamida~solut1on can~be used;as~;such or;concentra~ed to the~desired~
level by evaporation of;the~water. In ~he event that crystalline acryl-: ~ : - :
am1de constitutes the~desired product~ t may ba abtained by~comp1ete evapo~ration of all of the~water which is~present.
lt is also contemplated~within~the scope of this invention that; ~ ;
the desired acrylamide may be prepared ln a continuous manner oF~operation~
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l~hen such a type of operation is employed, the s~arting material compr~sln-J
the acrylonitrile is continuously charged to a reaction vessel which is maintained at the proper operating conditions o-f temperature and pressure and which will contain a catalyst which has been prepared by vaporizing copper m~tal and thereafter cooling the vaporized copper in the prèsence of a polar solvent of the type hereinbefore set Forth ;n greater detail.
The water will also be continuously charged to the reaction zone through a separate line or, if so desired, it may be admixed with the acrylonitrile prior to entry into said reactor and the resulting mixture charged thereto in a single stream. Upon completion of the residence time, the reactor effluent is continuously withdrawn through a filter and the aqueous layer is separated From the organic layer. The organic layer, if one is present, is separated and recycled.~ Unreacted acrylonitrile is stripped o~F from the water layer which is concentrated to a point where it contains from 15- 30 to 50% acrylamide, which is a~salable material. Because of the high~
selectivity of the reactlon, (i.e., 100%) no purification step is required.
The Following examples are given for purposes of illustrating the process of this invention as well as comparing the prior art cata-lysts with the catalyst herein described. It is to be understood that these examples are given merely for purposes of illustration and th~t the present invention is not necessarily limited thereto.
EXAMPLE I
To illustrate the hydrolysis of acrylonitrile to acrylamide using a catalyst of the type set forth in the prior art, such a catalyst was prepared by reducing 0.3 grams of copper oxide powder with molecular hydrogen at a temperature ln the range of from 150~ to 200 C. in a Fischer~
Porter pressure apparatus. Upon completion of the reduction, 7.2 grams :

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of acrylamide and 21 grams of water were added to the resultiny red copper powder under a nitrogen atmosphere The reaGtion was efFected at a tem-perature oF 120 C. for a period oF 6 hours, at the end of ~/hich time there was no detectable amoun-t of acrylamide formed.
The procedure set ~orth in the above paragraph was repeated with the exception that 4 grams of a reduced copper oxide powder was used as a catalyst in place oF the 0.3 grams. AFter 6 hours o~ reaction time at a temperature of 120 C., a gas-liquid chromatographic analysis disclosed that 20% of the acrylonitrile was converted, the conversion product comprising a7% acrylamide and 3% beta-hydroxypropionitrile.
EXAMPLE II
This example illustrates the unexpected activity of a catalyst~:
which was prepared by vaporizing copper on a liquid nitro~en temperature con~r~lled wall ln which tetrahydrofuran was also condensed. The result-;: 15 ing solution comprised a metal-solvent complex which was stable at low :;
temperatures. After heating the complex to room temperature, a black precipitate formed and the tetrahydrofuran was removed in vacuum. There-: a~ter 0.1 gram oF the vaporized~copper catulyst was pluced in a nitrogen~
atmosphere in a Fis~cher-Porter apparatus provided with a magnetic stirrer, along with 21 cc of water and 9 cc (7.2 grams) of acrylonitrile. The solution was heated to.a temperature o~ 120 C. and maintained thereat for a pe:riod of 6 hours, during which~time the pressure~in ~he reactor reached ~ :
: 70 psi (pounds per square inch). ~At the end o~ the 6-hour period:of time, : the solution which was recovered was clear and ln one phase, th~e ~;nely divided copper which resulted from the decomposition o~ the complex settling to the bot~om of the so1utlon. The solution-was then subjected to gas chromatographic analysis which disclosed that there had been a 40/O

' con~ersion oF the acrylonikrile to acrylamide with no beta-hy~roxypropio~
nitrile being de-tected by the analysis.
It should be noted from a comparison of t.he above examples that by utiliziny a copper-containing catalyst which was vaporized and condensed wi~h a solven-t to form a complex, the decomposi~ion of said complex result-ing in the obtention of finely divided copper particles, resultea in a conversion of acrylonitrile to acrylamide which was substantially greater than that which was obtained when using a conventional or prior art copper catalyst. In addition, the amount of catalyst which was used in this example was considerably less than the amount of catalyst which was used in the preceding example.
EXAMPLE II~
The experiment set forth in Example II was repeated utilizing - 0.2 grams of the vaporized copper catalys~ which had been prepared in a manner similar to that set forth ln the above examples. After heating the acrylonitrile in the presence of 0.2 grams of the catalyst for a period of 6 hours at 120 C.~ the reaction mixture was centriFuged. The slngle phase reaction product was subjected to gas-liquid chromatographic analysis, said analysis showing that there had been.an 80% conversion o~ the acrylo-nitrile to acrylamide with no detectable amount o-F be~a-hydroxypropio-nitrile being formed as a by-product.
~ Ihen the experiment was repeated using 0.26 grams~of vaporized copper catalyst along wlth 21 cc of water and 9 cc o~ acrylonitrile at identical operating conditions, a gas-liquid chromatographic analysis of the reac~ion product showed that there had been a complete conversion of acrylonitrile to acrylamide.

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EXAi~iPLE IV
In this example a copper catalyst was prepared by vaporizing copper inetal in a manner similar to that set Forth in Example II above, the exception being that acrylonitrile was used as a solvent in place of S the tetrahydro-~uran. After recovering the metal-solvent complex, it was heated ta room temperature, a slurry being formed which contained 0.25 grams of copper and 25 grams oF acrylonitrile This slurry along with 75 grams of water were placed in a Fischer Porter apparatus similar to that described in Example I above. The reaction was effected in a nitrogen atmosphere for a period of 6 hours at 120 C. At the end oF this time, a gas-liquid chromatographic analysis disclosed that 36% of the acrylo-nitrlle had been converted to acrylamide.
EXAMPLE V
To illustrate the contlnued activity of a catalyst whlch has been prepared according to the method~hereinbefore set forth, the catalys~ which was utilized in Example II was isolated and reused in an experiment~similar to that set forth in Example II~ab~ove. After a reaction tlme of 6 hours at 120 C. using 9 cc of acrylonitrile and 21 cc oF water,~the reaction ;
product was subjected to gas-liquid chromatographi~c analysis which dis~
closed that 36% of the acrylonitrlle had been converted to acrylamide.
This illustrates that the catalyst retained its actlvity and therefore may be reused for a number of cycles to convert acrylonitrile to acryl-:
amide.
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Claims (11)

I CLAIM AS MY INVENTION:

1. A process for the preparation of acrylamide which comprises treating acrylonitrile with water in the presence of a copper catalyst which is prepared by volatilizing copper metal, subsequently cooling the copper vapors in the presence of an organic solvent and heating to ambient temperature, at hydrolysis conditions, and recovering the resultant acryl-amide.

2. The process as set forth in Claim 1 in which said hydrolysis conditions include a temperature in the range of from about 60° to about 160° C.

3. The process as set forth in Claim 1 in which said copper is volatilized at a temperature in the range of from about 1000° to about 1500° C. in vacuo.

4. The process as set forth in Claim 1 in which said organic solvent is an ether.

5. The process as set forth in Claim 4 in which said ether is tetrahydrofuran.

6. The process as set forth in Claim 4 in which said ether is tetrahydropyran.

7. The process as set forth in Claim 1 in which said solvent is acrylonitrile.

8. The process as set forth in Claim 4 in which said ether is dioxane.

9. The process as set forth in Claim 1 in which said copper catalyst is absorbed on a solid support.

10. The process as set forth in Claim 9 in which said support is alumina.

11. The process as set forth in Claim 9 in which said support is silica.