CA1276166C

CA1276166C - Carbonylation process

Info

Publication number: CA1276166C
Application number: CA000503125A
Authority: CA
Inventors: John H. Grate; Donald H. Valentine; David R. Hamm
Original assignee: Haldor Topsoe AS
Current assignee: Topsoe AS
Priority date: 1985-03-04
Filing date: 1986-03-03
Publication date: 1990-11-13
Anticipated expiration: 2007-11-13
Also published as: DK511286D0; BR8605693A; FI864485A; NO166711B; DK511286A; EP0215848A4; WO1986005179A1; NO166711C; AU5540386A; EP0215848A1; KR940003065B1; FI864485A0; KR860007208A; NO864387D0; NO864387L; AU586591B2

Abstract

ABSTRACT
The invention provides a process for carbonylating a nitrogen-containing organic compound, selected from the group consisting of nitro, nitroso, azo, and azoxy compounds, by reacting said nitrogen-containing organic compound, with carbon monoxide, wherein the improvement comprises the step of:
(a) reacting said nitrogen-containing compound with carbon monoxide, in the presence of a primary amine and a catalyst, essentially free of redox active metal components selected from the group consisting of rhodium and ruthenium.

Description

CARBONYLATION PROCESS

BACKGROUND OF THE INVENTION

1. Field Q~ ~he I~yQn~ion This invention relates to a proce~s for the carbonylation of a nitrogen-containing organlc compound by reacting said compound with carbon monoxide in the presence of a rhodium or ruthenium catalyst.

2. ~es~LiR~i2n-c-th~-a~
Variou~ patents have disclosed methods for carbonylating nitrogen-containing organic compounds -e.g., nitro compounds, amines, azo- and azoxy compounds, -:
to urethanes in the presence of a platlnum group metal-containing catalyst usually a palladium or rhodium-containing catalyst and most often a palladium or rhodium halide-containing catalyst. Generally, a co-catalyst ;
. , .

~' i6 (promoter) has been needed in combination with the platinum ~r`oup metal-containing catalyst in order to obtain improved rates o~ reactionO The vast majority of prior art processes use, as a co-catalyst, a halide salt of a metal which is redox-active under the reaction conditions, usually iron, and most often iron chlorides.
The co-catalyst is used in substantial molar excess compared to the main catalyst in order to obtain the desired reaction rate. These large quantities of redox-active metal halides are troublesome to separate ~rom the reaction product and cause substantial corroslon problems.
A few references have taught the addition o a primary amino compound (and/or related compounds, such as urea, biurets, and allophanates) to urther improve the rate and selectivity of reactions catalyzed by a platinum group metal compound in combination with a redox-active metal halide-cocatalyst. U.S. Patent 4rl78~455 discloses that, in a process for converting nitroaromatic to urethane catalyzed by a platinum, palladium, rhodium, or ruthenium compound and a Lewis~acid promoter, the rate and selectivity are improved by adding to the reaction, an organic primary amino compound, a urea compound, a biuret compound, an allophanate compound, or a mixture thereof.
The preEerred Lewis acid promo~ers are redox-active metal : salts, especially iron chlorides. This patent illustrates (by example) only palladium catalysts with iron chloride promoters. A careful study of the examples reveals that the starting nitroaromatic and the primary amino compound (or related compound) are both converted, in net, to urethane. Thus, when the primary amino compound or urea compound contains the same aryl group as the starting nitroaromatic compound the reported yield o urethane, based on only the nitroaromatic converted, exceeds 100~.

. . .

~ ;27~

This patent also teaches the use of tertiary amines, ~.g.
pyridine, in large molar excess compared to the palladium catalyst to prevent corrosion. See also U.S. Patent 4,169,269 wherein a tertiary amine, e.g. pyridine, in large molar excess i5 utilized to ~uppress corrosion in a process utilizing a catalyst system comprising (1) palladium, ruthenium/ rhodium or compounds thereof, and ~2) a Lewis ~cid, e.gt ferric chloride. Similarly, U.S. Patents 4,219,661; 4,262,130; and 4l339,592 teach palladium catalysts with iron oxide and iron chloride co-catalysts in which addition of tertiary amines is one embodiment.
U.S. Patent 4,297,501 discloses a process in which mixtures of a primary a~ine and a nitroaromatic are carbonylated to urethane with a Group VIII noble metal compound and an oxychloride compound capable o~ undergoirlg redox reactions. In the preferred embodiment o~ U.S.
4,297,501, the nitroaromatic corresponds to the primary amine, and the patent teaches the following reaction stoichiometry:

2RNH2 + RN02 ~ 3CO ~ 3R'OH--~ 3RNEICO2R' ~ 2H20 (1) U.S. 4,297,S01 further teaches that when nitroaromatic is present in excess of the 1:2 ratio relative to amine, the remaining nitroaromatic is converted to urethane by the followlng reaction stoichlometry:

RNO2 ~ 3CO ~ R'OH RN~CO2R' ~ 2CO2 ~2) It can be seen from the above equations that when primary amine is initially preseilt, in processes which convert nitroaromatic to urethane uslng Group V~II noble 27~

metals, the primary amine is, in net, consumed to alco make urethane. (See equation (1) above). Once the primary amine is consumed to low levels, any rema;ning nitrobenzene is converted to urethane via reaction equation (2) above. Since the primary amine is already consumed to low levels, it is no longer available to favorably influence the rate of the process accordiny to said reaGtion (2)o U.S. 4,304,922 similarly discloses a process in which mixtures of N,N'-diaryl urea and nitroaromatic are carbonylated to urethane with the~same catalyst/co~
catalyst systems of U.S. 4,297rS01~ Illustrated by examples are PdC12, RhC13, IrC13, PtCl~
and RUC13 as Group VIII noble metal compounds. Iron oxychloride and several other redox active metal oxides and chlorides are illustrated as co-catalysts. In examples in which redox active metal oxides are used, anilinium hydrochloride is also added to provide active anionic chloride. In the preferred embodiment of this patent, the N,N'-diaryl urea and nitroaromatic have the same aryl groups, and the patent ~eaches that the following reaction stoichiometry is obtained:

2RNHCONHR ~ RNO2 + 3CO -1 5~' OEI~ 5RNIICO2R' ~ 2E120 ~3~

It is known that N,N' diarylureas react wi~h alcohols to produce urethane plus amins; see for Example U.S.
Patent 2,409,712, wherein the ~ollowing reactlon is disclosed:

RNEICONEIR ~ R' OH--~ RNIIC02R' ~ RNH2 ~ 4) .

It can be seen that once this occurs under the reaction conditions, the same process as UOS~ 4,297,501 is obtained according to equation (1) above. (Twice equation (4) plus equation (1) equals equation (3)). It can further be seen that both N,N'-diaryl urea and arylamine are, in net, consumed in the process to make urethane.
Example 11 of U.S. Patent 4,304,922 illustrates that when RhC13 is used as catalyst in combination with iron oxychloride as co-catalyst, nitrobenzene and N/N'-diphenylurea (1:2 molar ratio) are both consumed (100% and 99% conversion, respectively) to give urethane product 99~
selectivity based on nitrobenzene plus N,N'-diphenylurea).
Japan Rokai 55-7227 discloses a process in which molecular hydrogen is added, to a process for carbonylating nitroaromatic, in the presence of a palladium catalyst, to increase the reaction rate. The description of the invention specifies a palladium catalyst, accompanied by promoters such as tertiary amines, iron and vanadium compounds, and chlorine ions~
All illustrated examples use a supported palladium-selenium on carbon catalyst promoted with pyLidlne and either FeC12 or VOC13 (these are redox-active metal chlorides), The patent ~eaches that the addition of hydrogen causes hydrogenatlon of a fraction o~ the nitroaromatic to generate the corresponding primary arylamine 1LL~ . The process i5 thus generically similar to that of U.S. 4,178~455, discussed above, which illustrates by example the addition oE primary arylamine to a reaction wlth a supported palladium catalyst promoted with FeC13. Thus, it may be concluded that primary amine generated ~rom hydrogen will in net be consumed in the reaction to make urethane. Indeed, Japan Ko~ai 55-7227 teaches that any primary amine remalnlng at the end oE a ~ ~7~

reaction can be returned to another reaction with more nitroaromatic, in which case the primary amine is easily conYerted to urethane.
In U.S. Patent 4,474,978 a process is disclosed for converting a nitroaromatic to a urethane ln the presence o a primary amine and a catalyst system based on palladium complexed with Group VA-chelate ligands, including bis phosphine ligands and bis-tertiary amino-containing ligands~ The patent teaches ~hat redox active metal co-catalysts are not needed when these ligand~ are used. The paten~ teaches that the primary amine and/or urea are co-converted with the nitroaromatic to urethane.
Thus, the process, in net, consumes added amine or urea;
But, this patent does not suggest the use of ruthenium or rhodium with said ligands.
Thus, it ls clear that, ln the processes clted above, as the primary amine and/or urea compound ls converted, in net, to urethane, its concentration decreases and its effects on reaction rate and selectivity must also decrease. Eventually, as nitroaromatic continues to be converted, either in a ba~ch process or in a continuous process (with recycle of the remaining amine), the primary amine will be consumed to a low concentration. In order to maintain t~e improved rates and selectivities, which are obtained by the original addition oE primary amlne, urea, hydrogen, etc., it is necessary to provide additional`primary amine, urea, hydrogen, etc. as the primary amine is consumed.
A few references teach the use o rhodium catalysts, in the absence of a redox-active metal co-catalysts, for the carbonylation of nitrogen-containing organic compounds to urethanes. ~owever, these reEerences do not teach the initial addition oE primary amines, ureas, hydrogen, etc.

' - ' , ' .

~ ~ 7 ~ ~ 6 ~

to obtain improved activity. For example, U.S. Patent 3,338,956 discloses a metal carbonyl catalyst of Group VIA, VIIA, or VIII~ for this reaction. The only such catalyst exemplified, however, is rhodium chlorocarbonyl and the rates of reaction are relatively slow.
U.S. Patent 3r993l685 teaches the addition of tertiary amines, especially pyridine, to platinum group metal catalysts to obtain improved activity in the absence of redox-active metal co-catalysts. Rhodium chloride and hydridocarbonyl tris (triphenyl-phosphine) rhodium in combination with pyridine are exemplified.
U.S. Patent 4,052,437 discloses the use of rhodium oxide as catalyst, preferentially in nitrilic solvent.
Rh6(Co)l6 as a catalyst i5 also exemplified in this patent. There ls no suggestion that the inltial addltion of a primary aryl amine to the process disclosed in thls patent would improve the rate.
An article in the Journal o~ Organic Chemistry 37~
2791 (1972) describes a reaction in which nitro benzene in the presence o~ ethanol is carbonylated in low yield to urethane (<10~) and urea (<5%) with a catalyst comprising Rh6(Co)l6 in pyridine solvent. The major product was aniline. A related article in Helveti¢a Chimica Acta 55, 2637 (1972) describes a reaction in which nitrobenzene is reacted with carbon monoxide and hydrogen to urea with a catalyst comprising Rh6(CO)16 in pyridine solvent~ The pyridine is used in high concentration or excess to enable its function as a solvent for the reaction.
None of the above cited art, which discloses the use o~ rhodium catalysts (in the absence of redox-active metal co-catalysts) ~or the carbonylation oE nitro-organics to urethanes, discloses the initial addition of primary - .

6~

amine, urea~ hydrogen, etc. Moreover, the efEect of initially adding primary amine to such catalysts is not predictable. Finally, the result obtained by adding a primary amine to a rhodium or ruthenium catalyst system essentially free from redox-active metal components, is substantially different from the result obtained when a primary amine is added to either Group VIII metal catalysts (including ruthenium, rhodium and palladium) in the presence of redox active metal co-catalysts or certain palladium catalysts in the absence of ~edox active metal co-catalysts.
Ruthenium compounds have been utilized in the reduction of organic nitro compounds to the cGrrresponding amines with mixtures of hydrogen and carbon monoxide. ~t was reported in U.S. 3,729,512 that urea is a by~roduct of the reaction of nltrobenzene with hydrogen and carbon monoxide to give aniline using Ru3(C0)12 catalyst. It was also reported that the reduction of the organic nitro compound with carbon monoxide and ethanol, in the absence of H2, resulted in a mixtu~e Q amine ~nd a urethane. The patentee was not concerned with the preparation of a urethane product; therefore, there was no attempt to increase the selectivity above ~he approximately ~2 percent, urethane, that was obtained.
It is an object of this invention to provide a process for the conversion of nitro-~romatic to urethane in good rate and selectivity, without requiring continual addition of primary amine, urea, hydrogen, etc~ to maintain the rate and selectivity.
Xt is a further object of this invention to effectively carry out tha above process in the absence o redox-active metal halide co-catalysts.

g--Other objects and advantages of this invention will become apparent ~rom a carcEul read;ng o~ the specification below.

SUMM~RY OF THE INVENTI~N
It has now been surprisingly found that, in a process for carbonylating nitrogen-containing organic compounds selected from the group consisting of nitro, nitroso, azo and azoxy compounds, by reacting said nitrogen~containing organic compound, with carbon monoxide, the improvement comprises: .
(a) reacting said nitrogen-containing compound with carbon monoxide, in the presence of a primary amine and a catalyst, said catalyst being essentially free of redox active metal halide components, and comprising ruthenium or rhodium.
Furthermore, the present invention provides a process for converting a nitrogen-containing organic compound, selected from the group consisting oE nitro, nitroso, azo, and a~oxy compounds, into a carbamic acld derivative by reacting said nitroyen-con~aining organic compound with carbon monoxide wherein the improvement comprises the steps of:
(a) mixing a primary amine with said nitrogen-containing organic compound to provide a solution, - (b) contacting ~he solution of step (a~ with carbon monoxide, in the presence of a catalyst essentially free of redox active metal halide components and comprising rhodium or ruthenlum at conditions suEficient to convert said nitrogen-containing organic compound into sald carbamic acid derivative .

~ ~t~6~

--10-- , Said carbamic acid derivative may be a urethane or a urea (depending on whether a hydroxyl containing organic compound is included in the solution o~ step (a~O) If the solution of step (a) includes only the nitrogen-containing compound and the primar~ amine --and any inert solvent--the carbamic acid derivative will be a urea, which may be separated and alcoholyzed to the urethane in a separate step.
~inally, the present invention provides a process for preparing a urethane by reacting a nitrogen-containing organic compound, selected from the group consisting of nitro, nitroso, azo and azoxy compounds, with carbon monoxide and a hydroxyl-containing vrganic compound, the improvement which comprises the steps of:
(a) adding a primary amine to a solution comprising said nitrogen-containing organic compound, (b) reacting said solution with carbon monoxide, in the presence of a catalyst consisting essentially of rhodium or ruthenium, (c) recovering a urethane, and (d) recovering a primary amine, in an amount equal or greater than the primary amine in the primary amine-containing solution of step ~a).
Whether the process of the present invention is practiced to obtain urethane, directly, or upon separate alcoholysls of a urea, the primary amine recovered i9 equal to or greater than the primary amine initially provided in the reactant solution. Thus, in a cont~nuous process, the primary amine can be constantly recycled and no further addition o~ primary amine, urea, hydrogen, etc. is needed to maintain the desired rate and selectivities.
While not wishing to be bound by kheory, it appears that, in the rhodium or ruthenium-catalyzed carbonylation i6 o the above nitrogen-containing organic compound to the corresponding urethane~ in the absence of a redox-active metal halide co-catalyst, the urethane is produced by oxidative carbonylation of the corresponding primary amine. This oxidative carbonylation also provides hydrogen atom equivalents for the reduction of the nitrogen-containing organic compound to the primary amine.
These reactions which are illustrated below ~wherein [E~]
represents the rhodium or ruthenium hydrogen carrier) must be effectively coupled to provide the desired selectivity to the urethane.
Oxidative carbonylation: C6H5NE12 ~ C0-~CE130~ C~H5NHC02CH3-~2[H]
Reduction/hydrogenation: C6~5~02 ~ 2C0+2[H]--~C6H5NH2~2C02 Net Reaction: C6H5N2 ~ 3CO~CH30H-~C~H5NE1C02C~13~2C02 Thus, the primary amine (illustrated by aniline) is an intermediate in the fornlation of urethane from the nitrogen-containing organic compound, but is not in net produced or consumed by the desired net reaction. It has been ~ound that the primary amine is not in net consumed and the desired reaction stoichiometry is obtained even when pr~mary amine is initially added to the reaction. It has been further ~ound that the rate of conversion of nitrogen-containing organic compound to urethane and the selectivity of the reaction are increased when the initial amount of primary amine added to the reaction is increased. The ini~ial amount o primary amine and itB
favorable e~ects on the rate and selectivity of the reaction persist for the conversion o~ an inde~inite amount of nitrogen-containing or~anic compound to urethane.

- .

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The primary amine can be provided directly or by the in situ alcoholysis of a urea~ bluret, or allophanate compound. Uxea is alcoholyzed ~o form amine and urethane:
RNHCON~IR ~ E~'O~I~RNH2 t RNHC02R' siurets and allophanates similarly provide primary amine by alcoholysis under the reaction conditions.
In a carbonylation reaction wherein no primary amine, urea, biuret, or allophanate is present, initially, a fraction of the nitrogen-containing compound (e.g.
nitrobenzene) can be reduced to the primary amine (aniline) by added hydrogen. It has been found that the reduction of the nit~ogen-containing organic compound to a prima~y amine in the p~e~ence of hydrogen is rapid and provided that the molar xatio o~ hydrogen to the nitrogen-containing organic compound is less than 1, the remainder o~ the nitrogen-containlng organic compound is converted to urethane by the desired reac~ion stoichiometry. The primary amine may also be provlded in situ by the addition of water, iD which case a fraction of the nitrogen-containing compound is reduced to primary amine by hydrogen equivalents obtained from shifting water and carbon monoxide to carbon dioxide.
In the initial absence oE primary amine, hydrogen or water in a urethane production reaction, the hydrogen equivalents required to initially reduce nitrogen-containing organic compound to the primary amine are derived by dehydrogenation oE the alcohol. ~In the scheme illustrated below R represents a hydrogen or hydrocarbyl radical.) .

-13~
~lcohol Dehydrogenation: R2 CHOH~ R~C=O ~ 2[~1]
Reduction/
Hydrogenation: c6i~5NO2 + 2co ~ 2[~] C6H5NH2 ~ 2C2 Net Reaction C6H5N02 ~ 2Co ~ R2C110~1 ~C6H5NH2 -~ 2C2 ~R2C=O

However, the carbonyl compounds which result from dehydrogenation of alcohol react with the primary amine to ~orm undesired condensation products and water.
~dditional nitrogen-containing compound may then be reduced to the primary amine by hydrogen equivalents derived from water by the shift reaction.
When sufficient primary amine is initially present in the reaction solution, alcohol dehydrogenation is undesired because it converts the nitrogen-containing organic compound to primary amine and higher products instead of urethane. It has been ound that methanol is less susceptible to dehydrogenation to the aldehyde than ethanol and higher alcohols, in the presence o~ the ruthenium catalysts utilized in the process of the instant invention. Therefore, the use of methanol improves the yield of urethane obtained in the carbonylation reaction product mixture and the combination o~ methanol and a primary amine in the process of the instant invention results in both an increi~sed yield o~ urethane and an increased reaction rate Since oxidative carbonylation of amlne to yield urethane and dehydrogenation of alcohol to carbonyl compound compete as sources of hydrogen equivalents ~or reduction of the nitrogen containing organic compound, the selectivity of urethane production is increased by increasing the amine-to-alcohol ratio. The amine-to-alcohol ratio is increased by increasing the am~ne concentration and/or by decreasing the alcohol -7~

concentration. The primary amine may become the major reaction solution component and act as solvent. The alcohol concentration may be independently decreased by using an inert solvent in place of excess alcohol in the initial reaction solution.
It has been found that during the course of reactions in which amine ls initially present, N,N'-disubstituted urea is present in the reaction mixture during the reaction. When nitrobenzene is reacted with alcohol, aniline, or many inert solvents as solvent, the N, N'-diphenyl-urea appears as a solid in samples of the reaction mixture which are cooled. The solid has been filtered rom the solution componen~s of such samples (includ$ng the soluble catalyst), and characterized as N,N'-diphenyl urea.
The amount of urea presen~ during the reaction depends on the amine-to-alcohol ratio initially presentO
The higher the ratio, the higher the amount of urea present. When enough alcohol is provided, however, little or no urea persists to the end of the reaction. At the end oE the reaction it is substantially reacted with alcohol to make urethane according to equation (4). Some or perhaps all of the urethane appears ~o be formed via oxidative cabonylation to amine to urea, followed by urea alcoholysis:

2C6H5Nli2 ~ CO ~ C6E15NHÇONHC6H5 ~ 2111], - C6H5N02 ~ 2CO -~ 2[H]~ -' C6H5N~2 ~ 2C2 C6H5N02 ~ C6H5NH~ ~ 3CO ~ C6ll5NHCONHC6H5 ~ 2C02 then, ~6~15NHcoN~lc6Hs ~ ROII ~ C6H5NHCO2R ~ C6~lSNEl2 .
C6H5NO2 -~ 3CO ~ ROH ~ C6HsMHC02~ ~ 2C2 , ~.~7~

If the amine-to-alcohol ratio becomes quite high or if insufficient alcohol is provided, urea will persis~ at the end of the reac~ion. If little or no alcohol is provided, urea will become the major reaction product. It can be seen that the urea production consumes one equivalent of initially added amine ~or each equivalent of urea produced~ This consumed amine can be separately recovered by reacting the urea with the alcohol to make urethane in a ~eparate step In a carbonylation reaction to produce urea~ wherein no primary amineS urea, biuret or allophanate is present, initially, a fraction o~ the nitrogen-containing organic compound (e,~. nitrobenzene) can be reduced to the primary amine (aniline) by added hydrogen. Again, if the molar ratio o hydrogen to the nitrogen-containing organic compound is less than 1, the remainder of the nitrogen-containing oryanic compound is converted to urea by the desired reaction stoichiometry. In a batch process, an improved yield of urea is obtained ~hen from 50 to about 60 percent of the nitrogen-containing organic compound is converted to primary amine, b~ hydrogenation, with the maximum being obtained at S0 percent conversion.
Since there is no alcohol present in the urea production reaction, side reactions of the alcohol ~dehydrogenation, dehydration) which reduce selectivity are avoided. Thus, at the same initial amine concentration, the yield oE urea in the absence of alcohol can exceed the yield oE urethane in the presence of alcohol.
Because one equivalent o~ amlne is consumed in the urea production reaction, the amine concentration decreases during the reaction, and the observed rate of nitrogen-containing organic compound conversion . . .. .. .

~ ~6~66 `1~
coeespondingly decreases during the reaction. (If the molar ratio of nitrogen-containing organlc compound to the primary amine is greater than 1, not all of the nitrogeJI-containinq compound will be converted to urea~ Thus, in the absence of alcohol, there will be unreacted nitrogen-containing organic ccmpound left when all of the primary amine is consumed into urea. I the amine is used in large excess to the nitro compound (as solvent, for example) however, the fractional changes in amine concentration and rate of urea production are small or insignificant.
By proYiding amine at higher concentrations in excess of nitrogen-containing organic compoundl the rate of urea production is increased and the nitro compound can be conveniently 100% converted. Urea yields near 100~ may thus be obtainedr Since the urea alcoholysis to urethane is essentially quantitative, the overall selectivity of urethane synthes~s can be increased by separating the urea synthesis and urea alcoholysis into two process steps, 80 that the selectivity reducing reactions o the alcohol in the catalytlc carbonylation step are avoided.

76~

DETAILED DESCRIPTION OF THE INVENTION
The nitrogen-containing organic compound useful in the process of this invention will contain at least one non-cyclic group in which a nitrogen atom is directly attached to a single carbon atom and through a double bond to oxygen or another nitrogen atom. The nitrogen-containing organic compound is selected from ~he group consisting of nitro, nitrosor aæo and azoxy compounds.
Examples o suitable nltrogen-containing organic compounds for use in the process o~ this invention are compounds represented by the general formulae:
I R ~NOx)y and II Rl-RN-N (O)z ~ ~2 wherein Rl and R2 are radicals independently selected ~rom the group consisting o~ Cl to C2~ hydrocarbyl radicals and substituted derivatives thereof, x is an integer of from 1 to 2, y is an integer of from 1 to 3, and z i3 an integer of from O to 1. The substituted hydrocarbyl radical may include hetero atoms selected from the group conslsting of halogen, oxygen, sulfur, nitrogen and phosphorus atoms.
The nitrogen-containing compounds represented by formula I include nitro compounds (wherein x is 2) and nitroso compounds (wherein x is 1~. Suitable nitro compounds are mononitro compounds such as nitrobenzene, alkyl and alkoxy nitrobenzenes wherein ~he alkyl group contains up to 10 carbon atoms, aryl and aryloxy nitrobenzenes, wherein the aryl group is phenylr toyl, naphthyl, xylyl, chlorophenyl, ~hloronitrobenzenes, aminonitrobenzenes, carboalkoxyamino nitrobenzenes wherein the alkoxy group has up to 10 carbon atoms, aryl and aryloxy dinitrobenzenes, trinikro compounds such as trinitrobenzene, alkyl and alkoxytrinitroben2enes, aryl and aryloxytrinitrobenzenesr the substituents being any of ~ ~:76~

those already mentioned and chlorotrinitrvbenzenes as well as similarly substituted mono and polynitro derivatives o~ the naphthalene, diphenyl, diphenylmethane, anthracene and phenanthrene series. Substituted or unsubstituted aliphatic nitro compounds such as nitromethane, nitrobutane, 2,2'-dimethyl nitrobutane, nitrocyclopentane, 3-meth~lnitrobu~ane, nitrooctadecane, 3-nitropropene-1, phenyl nitromethane, p-bromophenyl nitromethaner p-methoxy phenyl nitromethane,dinitroethane, dinitrohexane, dinitrocyclohexane, di-(nitrocyclohexyl)-methane are also suitable. The above nitro compounds may include more than one of the above substituents (in addition to ~he nitro group(s) such as in nitroaminoalkylbenzenes"
nitroalkylcarboalkoxyamino benzenes, etc. From this group of nitro compounds nitrobenzene, nitrotoluene, dinitrobenzene, dinitrotoluene, trinitrobenzene, trinitrotoluene, mononitronaphthalene, dinitronaphthalene, 4,4'-dinitrodiphenylmethane, nitrobutane, nitrocyclohexane, p-nitrophenylnitromethane.
dinitrocyclohexane, dinitromethylcyclohexane, dinitrocyclohexylmethane, nitroaminotoluene and nitrocarboalkoxyaminotoluene are pre~erred and in particular aromatic nitro compounds especially 2,4-and 2,6-dinitrotoluenes, meta and para dinitrobenzenes, and 5-nitro-2-methyl-carboalkoxyamino~,2-nitro-5-methyl-carboallcoxyamino-t and 3-nitro-2-methyl~carboalkoxyamino benzenes.
Examples of sultable nitroso compounds are the aromatic nitroso compounds such as nitrosobenzene, nitrosotoluene, dinitrosobenzene, dinitrosotoluene and the aliphatic nitroso compounds such as nitrosobutane, nitrosocyclohexane and dlnitrosomethylcyclohexane.

~ ~7 ~ ~6 ~

The nitrogen~containing compounds represented by Formula II include both azo compounds ~wherein z is O) and azoxy compounds ~wherein z is l)o Suitable compounds represented by Formula II include azobenzene, nitroazobenzne, chloroazobenæene, alkyl or aryl substituted a~obenzener azoxybenzene, nitroazoxybenzene, chloroazoxybenzene, etc.
The primary amine compound utilized in this invention may be selected from the group consisting o~ compounds xepresented by the general formula:
IV Rl (NH2)y wherein Rl and Y are as de~ined above. Examples of such primary amines include methylamine, ethylamine, butylamine, hexylamine~ ethylenediamine, propylenediamine, butylenediamine, cyclohexylamine, cyclohexyldiamlne, aniline, p-toluidine, o-m-and p-diaminobenzenes, amino-methylcarbanilic acid esters, especially the 5-amino-2 methyl-, 2-amino-5-methyl-, and 3-amino-2-methyl carboalkoxyaminobenzenes, wherein said alkoxy group has up to lO cabon atoms, o-, m- and p-nitroanilines, nitroaminotoluenes, especially those designated above, o-and p-phenylenediamine, benzylamine, v-amino-p-xylene, l-aminophthaline, 2,4-and 2,6-diaminotoluenes, 4,41_ diaminodibènzyl, bis (4-aminophenyl) thioether~ bis (4-aminophenyl) sulfone,~ 2,4,6-triaminotoluene, o-, m-and p-chloroanilines, p-bromoaniline, l-fluoro-2,4-diaminobenzener 2~-4-diaminophenetole, o,-m- and p-aminoanisoles, ethyl p-aminobenzoate, 3-aminophthalic anhydride, etc. These primary amino compound3 may be used alone or in combination.
Among the above enumerated primary amino compounds, those which can be derived from the startlng nitro .

~ ;~76~

~ 20-compound are preferred. For example, when nitrobenzene is used as the starting aromatic nitro compound, aniline is preferred. Similarly, 2-amlno-4-nitrotoluene, 4-amino-2-nitrotoluene, and 2,4-diaminotoluene are preferably used when the starting aromatic nitro compound is 2,4-dinitrotoluene, while 2-amino-6-nitrotoluene, and 2,6-diaminotoluene are preferably used when the starting aromatic nitro compound is 2,6~dinitrotoluene.
The primary amine compound can be provided by the in-situ decomposition of the corresponding urea or biuret as represented by compounds having the general formulae:
RNH ~ NHR

and Rl~H - ~ - N - ~ - NHR
~1 ' respectively, wherein ~1 is as defined above. Of course, since the above urea and biuret will comprise more than one radical, Rl may represent different radicals in the same compound. That is non-symmetrical ureas and biurets, e.g.
CH3NH~1 - NHC2~15 are within the scope of the invention.
In the process of this invention, no particular limitation is placed on the amount of primary amine used~
However, it is preferably used in an amount equal to from 0.1 to 100 moles per gm-atom oE nitrogen in the nitrogen-contalning organlc compound.
The process of the invention may be carried out in the absence o~ solvent but the use of a sol~ent is not precluded. Suitable solvents include, for example, aromatlc solvents such as benzene, toluene, xylene, etc.;

~ ;~7~i~6Ei;

nitriles such as acetonitrile, benzonltrile, etc.;
s~lfolles such as sulfolane, etc.; hal~genated aliphatic hydrocabons such as 1,1,2-trichloro 1,,2,2,-trifluoroethane, etc.; halogenated aromatic hydrocarbons such as monochlorobenzene, dichlorobenzene, trichlorobenzene, etc.; ~e~ones; esters; and other solvents such as tetrahydroEuran, 1,4-dioxane, 1,2-dimethoxyethane, etc.
The hydroxy-containing organic compounds for use in the process of this invention include compounds represented by the general ~ormula III Rl (OH)y wherein Rl and y are de~ined above.
Hydroxy compounds suitable for use in the process of the present invention may be, for example, mono- or polyhydric alcohols containil3g primary, secondary or tertiary hydroxyl groups as well as mono- and polyhydric phenols. Mixtures o these hydroxy compounds may also be used. The alcohols may be aliphatic or aromatic and may bear other substituents in addition to hydroxyl gro~ps but the substituents should texcept as hereinafter described) preferably be non-reactive to carbon monoxide under the reaction conditions. Especially suitable compounds are phenol and monohydric alcohols such as methyl, ethyl, n~ ;
and sec-propyl, n-, lso, sec-and tert butyl, amyl, hexyl, lauryl, cetyl, benzylr chlorobenzyl and methoxybenzyl alcohols as well as diols such as ethylene glycol, diethylene glycol, propylene glycol and dipropylene glycol, triols such as glycerol, trimethylol propane, hexanetriol, tetrols such as pentaerythritol and the ethers o~ such polyols providing that at least one hydroxyl group remains unetheriEied. The etheriying group in such ether alcohols normally contains up to 10 carbon atoms and is preferably an alkyl, cycloalkyl or aralkyl gro~p which may be substituted with, for example, a halogen or an alkyl group.
The most preferrea hydroxyl-containing organic compound for use in the process of this invention is methyl alcohol or a similar lower alkanol, e.g. a Cl to C5 alcohol.
The process o~ this invention includes the use of any mixture o~ nitro compounds, nitroso compound~, azo or azoxy compounds with any mixture oE hydroxy compounds and also the use of compounds containing both functions, l.e.
hydroxynitro compounds, hydroxynitroso compounds, hydroxyazo and hydroxyazoxy compounds such as 2-bydroxynitroethane, 2-hydroxynitrosoethane, nitrophenols, nitronaphthols, nitrosophenols, nitrosonaphthols, hydroxyazobenznes and hydroxyazoxybenzenes. Mixtures o these nitrogen-containing compounds may also be used.
This process of the invention has been ~ound to proceed most smoothly to give the hlghest yield~ when employing nitro compounds. It is accordingly preferred to use nitro compounds rather than n~troso, azo or azoxy compounds.
The catalyst utilized in the process o~ this invention may be selected rom the group consisting o~
rhodium or ruthenium salts, e.g. the halides, nitrate, sulfate, acetate,~formate, carbonate, etc. and rhodium or ruthenium complexe~ (especially rhodium or ruthenium carbonyl complexes) including ligands capable of coordlnating with the rhodium or ruthenium atom~ The complex may include one or more rhodium or ruthenium atoms and suitable ligands may include carbon-carbon unsaturated groups as in ethylene, isobutylene, cyclohexener norbornadiene, cyclooctatetraene. Other suitable ligands -~3-include acetylacetonate (acac), hydrogen atoms, carbon monoxide, nitric oxide, alkyl-radicals, alkyl or aryl nitriles or ison triles, nltrogen-containing heterocyclic compounds such as pyridine, piperidine, and organo phosphines, arsines or stilbines.
In one embodiment of this invention a rhodium or ruthenium catalyst for use in the present process further comprises a polyamino ligand having at least two tertiary amino groups capable of coordinating with rhodium. For example, such polyamino ligand may be selected from the group o~ compounds represented by the general formula:
R3 ~ / R7 N (CR5R6)n N
R4 / ~ R8 wherein R3, R4, R7 and R8, which may be the same or dif~erent, each represent an alkyl, aryl, alkaryl or aralkyl group which may be substituted by one or more inert substituents or R3 and R4 and/or R7 and ~8 may orm a ring structure together with the atom M to which they are attached; R5 and R6, which may be the same or different, each represent a hydrogen atom or a lower alkyl ~roup and may form a ring struc~ure together with the atom N and R3, ~4, R7 and/or R~ and n is an integer, pre~erably n varies from 1 to about 5, e.g~ 1 to 3.
Examples o~ ligands according to the general ~ormula are l,2-bis(diethylamino)ethane 1,2-bis(dimethylamino)propane, l,2-~is(dimethylamino)ethane, 1,2-bis(di-t-butylamino)ethane, 1,2-bis~diphenylamino)ethane, 1,2-bis(diphenylamino)propane, 1,2-bis(diphenylamino)butane, 2,2'-bipyridine, 2,2'-biquinoline, bispyridylglyoxal, and l,10-phenanthroline and derivatives thereof. Preference ls given to the use o 2,2'-bipyridine and l,10-phenanthroline.

, ~ ~7~

.
In another embodiment of the instant invention the catalyst utiliæed in the process of this ~nvention may comprise a bis-phosphino rhodium or ruthenium compound.
The bis-phosphino rhodium or ruthenium compound may also include the above anions, i.e. sulfate, acetate, trifluoroacetate, formate, carbonate, etc. and/or other ligands, discussed above, cpable of coordinating with the rhodium or ruthenium atom. The bis-phosphino rhodium or ruthenium compound may include more than one rhodium or ruthenium atom.
The bis-phosphino ligand of the rhodium or ruthenium catalyst may be represented by the general formula:
(R3) (R4) P-Rg-P (R7) (Rg) wherein ~3, R~, ~7 and R8 are as de~ined above and ~9 is a divalent radical providing sufficient spacing to enable both phosphorus atoms to coordinate with a rhodium or ruthenium atom. Rg may be a hydrocarbyl having from 1 to 10 atoms or a substituted derivative thereof including one or more heteroatoms selected rom the group connsisting of haloyen, oxygen, sul~ur, nitrogen, and phosphorus atom.
Preferably, Rg comprises Erom 2 to G carbon atoms.
Examples of suitable bis phosphine ligands include bis(1,2-diphenylphosphino)benzene, bis(1,2-diphenylphosphino)-ethane, bis~3,3-diphenylpho~phino)propane, etc.
Examples o~ ruthenium compounds which are suitable as catalysts ~or the process o~ this invention include:
Ru(CO)3lbis(1,2-diphenylphosophino)ethane]
Ru(CO)3[bis(1,2-dlphenylphosphino)benzene]
Ru(CO)3[bis(1,3-diphenylphosphino)propane]
The rhodium or the ruthenium catalyst is preferably utilized as a homogeneous catalyst and therefore one criteria ~or t~e selection o~ the rhodium or ruthenium compound is its solubility und~r the conditlons of reaction in the mixture QE the nitrogen-containing organic compound and the primary amino compound (and, if desired, the hydroxyl-containing organic compound). The rhodium or ruthenium compound i5 also selected with a vlew toward the catalytic activity of the compound. Mixtures of rhodium and ruthenium compounds may be used.
The rhodium or ruthenium compound comprising a polyamino ligand or a bls-phosphino ligand may be preformed or formed ln~ in the reaction solution by separately dissolving a ~hodium or a ruthenium compound and the respectlve l~gand. Since the catalyst is utillzed in very low concentration, it ls preferred that the compound is preformed to ensure that uch llgand will be coordinated with the rhodium or ruthenium during the reaction.
The rhodlum or ruthenium catalyst may be used in m~xture with co-catalysts or promoters 80 long as the co-cataly3t~ unllkè the redox-actiYe metal halide co-~o catalysts of the prior art, does not change the reactivityo~ the catalyst system to con~ume added amine~. Mono-tertiary amines are one class of ~uitable promoter~ for the rhodium cataly~ts o~ this invention. Suitable mono~
tertiary amlnes are ~hose descr~bed in U.S. 3~993,6~5.
Preferably the catalyst is free of halide to avoi~d corrosion problems.
In carrying out the process of the invention, -the hydroxyl-containing organic compound and carbon monoxide may be used in amounts equal to at least 1 mole per gm-atom of nitrogen in the nitrogen-containing compound.
When it is desired to obtain the urethane product, directly, preferably the hydroxyl-containing organic compound is used in excess. When it is desired to obtain r~ ~
~1 ~ ~7~

a urea product, then the primary amine iSJ preferably;
used in excess.
The amount oE the rhodium or ruthenium compound used as the catalyst may vary widely according to the type thereof and other reaction cond~ tions. However, on a weight basis, the amount of catalyst is generally in the range o~ from 1 X 10-5 to 1 part, and preferably from 1 X
10-4 to 5 X 10~1 parts, per gram-atom of nitrogen in the startin~ nitrogen~containing organic compound when expressed in terms of its metallic component.
The reaction temperature is generally held in the range of 80 to 230 COt and preferably in the range of from 100 to 200 C.
The reaction pressure, or the initial carbon monoxide pressure, is generally in the range of ~rom 10 to 1,~00 kg/cm2G, and preEerably from 30 to 500 kg/cm2G.
The reaction time depends on the nature and amount of the nitrogen-containing organic compound used, the reaction temperature, the reaction pressure~ the type and amount of catalyst used, the type of reactor employed, and the like, but is generally ln the range oE from S mlnutes to 6 hours. After completion of the reaction, the reaction mixture is cooled and the gas is discharged from the reactor. Then, the reaction mixture is subjected to any conventional procedure including filtratlon, distillation, or other suitable separation steps, whereby the resulting urethane or urea is separated from any unreacted materialsr any by-products, the solvent, the catalyst, and the like.
The urethanes and the ureas prepared by the process of the invention have wlde applications in the manufacture o~ agricultural chemicals, isocyanates, and polyuretllanes.

~ ;~7~

The invention is more fully illustrated by the f ollowing examples. However, they are not to be construed to limit the scope oE the inven~ion.
In each of the following examples9 the reaction was conducted in batch mode in a 300 ml stainless steel autoclave reactor equipped with a stlrring mechanlsm which provides constant dispersion o~ the gas through the liquid solution. Heating of the reaction is provided by a jacket-type furnace controlled by a proportioning controller. The autoclave is equipped with a high pressure sampling system for removal of small samples of the reaction solution during the reaction in order to monitor the reaction progress. Reaction solutions were prepared and maintained under anaerobic conditions.
Reaction samF~es were analyzed by gas chromatography.
The ~ollowing examples are shown for the purpose o~
illustration only and should not be deemed as limitlng the scope o~ the invention.

~ .
75 ml o~ a solution conta~ning 12.31g (0.100 mole) nitrobenzene, 4.66g (0.050 mole) aniline~ and 2068g t-butylbenzene (internal sandard for gas chromatographic analysls~ in methanol and 0012~g (0.20 mlllimole) Ru3(C0)12 were placed in the reaction vessel. The gas volume in the vessel was replaced with carbon monoxide at 1000 pslg at ambient temperature. The reactor contents were then heated to 160C. Complete conversion of nltrobenzene occurred over 805 hours at 160C and yielded 0.076 mole methyl N-phenyl carbamate (76~ selectivity based on nitrobenzene) and 0~067 mole aniline (17~
selectivity to additlonal aniline based on nitrobenzene).
The balance consis~ed o~ undesired side-products formed -~8-by aniline-formaldehyde condensations and ensuing reactions.

, x~m~l~ 2 The procedure was the same as for Example 1 except that 9.32g ~0.100 mole) aniline was lnitlally provided to the reaction. The volume of methanol ws reduced so that the total solution volume was again 75 ml. Complete conversion of nitrobenzene occurred over 3.5 hours at 160C and yielded 0.088 mole methyl N-phenylcarbamate (88~ selectivity based on nitrobenzene) and 0.112 mole aniline ~12~ selectivi~y to additional aniline based on nitrobenzene).

~omparativ~ E~ample 1 The procedure was the same as or Example 1 with the exception tha~ no aniline was introduced to the reaction.
Complete nitrobenzene conversion re~uired 26 hours at lG0~ Selectivities based on nitro~enzene were 38 pecent to methyl N-phenylcarbamate, 32 percent to aniline, 12 percent total to formylidene aniline and N-methylaniline. The balance was converted to higher molecular weight products derived from aniline.
It can be seen by comparison oE Examples 1, 2 and Comparative Example 1 that the rate and selectivity oE the reaction are improved by intially pro~lding increasing amounts o~ amine to the reaction.
Relative to Example 1 and 2, the amine concentration and amine-to-alcohol ratio may be further increased by replacing more alcohol in the initial solution with amine. Amine may become the major reaction solution component and thus act as solvent for the reaction.

. ~ . ' . .
. !

~ ~7~l6~i The amine-to-alcohol ratio may also be increased by simply replacing some of khe excess alcohol with an lnert solvent.

Example 3 ~ he procedure was the same as ~xample 1 except only 6.40g (0.200 mole) methanol was initially provided to the reaction solution. Toluene was added as an lnert solvent to again give a total solution volume of 75 ml. Complete conversion of nitrobenzene occurred in 8.5 hour~ at 160C
yielding 0.095 mole methyl N-phenyl carbamate 195~
selectivity based in nitrobenzene) and 0.054 mole aniline (4~ selectivity to additional aniline based on nitrobenzene).
It can be seen by comparison of Examples 1 and 3 that reducing the alcohol concentration in the solution, for example by using an inert solvent, increases the selectivity of the reaction without any decrease in the rate of urethane production. Thus, in Example 1, wherein the ratio of methanol to nltrobenzene was 15.1, the selectivity was 76~, while in this Example, wherein the ratio of methanol to nitrobenzene was 2:1, the ~electlvity was increased to 95~. (Decreasing the ratlo of methanol to nitrobenzene to almost 1:1, would be expected to further increase selectivity.) In view o~ the above, it is preferable to provide a ratio of methanol (or other hydroxy-containing organic compound) to nitrobenzene (or other nitroyen~containing organic compound) of less than 15:1, more preferably a rakio of from l:I to 5sl, mosk preferably a ratio of from 1:1 to 3~1, e.g. about 2:1~

The procedure was the same a~ for Example 3 except that no methanol is provided to the reaction. ~dditional toluene solvent was added to again give 75 ml total reaction solution. AEter 10 hours at 160C, 0~048 mole nitrobenzene and 0.008 mole aniline remained (52~ and 42%
conversion, respectively). The mixture contained copious amounts o a white organic colid. ~fter cooling, the solid was filtered and characterized (IR, NMR) as predominantly N,N'-diphenyl urea. The spectra and the excess consumption of nitroben~ene over aniline indicate that N,N',N"-triphenylbiuret was also present.
Durin~ the course of the urea synthesis of Example 4, the observed rates of nitrobenzene and aniline conversion decreased as the aniline was consumed. However, the aniline-dependent rate of nitrobenzene conversion to urea in this experiment was approximately equal to the anil~ne-dependent rates of nitrobenzene conversion to urethane in the experiments o Examples 1 and 4. This shows ~hat urea synthesis is kinetically competent to account for all of urethane synthesis in ~he presence o alcohol.

Example_5 10.60g (0.050 mole) N,N'-diphenylurea and methanol to gi~e 75 ml total mixture volume were heated from room temperature to 160C over approximately one hour~ On reaching 160C, the mixture contained 0.035 mole each of methyl N-phenyl carbamate and aniline~ and unreacted N,N'-diphenylurea. ~fter 45 minutes at 160C, the solution contained 0.050 mole each of methyl N-phenyl carbamate and aniline! representing quantitative urea alcoholysis.
From this example, it can be seen that the urea alcoholysis occurs in the absence of an added catalyst.
The data obtained also indicate tha~ uncatalyzed urea alcoholysis is klnetically competent to account or all Of ~31-the urethane synthesis in the catalytic conversion of nitro compounds in the presence of alcoholO

Example 6 The procedure was the same as for Example 1 except that 0.23y (1.40 millimole) tetraethylammoniumchloride was also provided to the reaction. Complete conversion of nitrobenzene occurred over 6.0 hours at 160C and yielded O.Q77 mole methyl N-phenylcarbamate (77% selectivity based on nitrobenzene) and 0.071 mole aniline ~21% selectivity to additional aniline based on nitrobenzene)c Comparative Example 2 The procedure was the same as for Example 6 except t~at no aniline was initially provided to the reaction Commplete nitrobenzene conversion required 15 hours at 160C. Selectivities based on nitrobenzene were 60% to methyl N-phenylcarbamate and 34% to aniline.
Comparison of Example 6 with Comparative Example 2 shows that the rate and selectivity oE the reaction are improved by initially providing primary amine to the reaction, when the reaction also includes chloride ion.
Example 6 also shows that the amine is not, in net, consumed when the reaction contains chloride lon. Thus, in the prior art processes in which the amine is consumed in the presence o~ redox-active metal chloride co-catalysts, it is the additional presence of the redox-active metal which causes the amlne consumption.
, .
Example 7 75 ml o~ a solution containing 3.07g (0 025 mole) nitrobenzene, 11.6~ (0.125 mole) aniline, and 2.74g t-butylbenzene ~internal standard) in toluene and 0.1289 ';
..

~.~76~

(0.20 mlllimole) Ru3(CO~12 were placed in the reaction vessel. The gas in the vessel was replaced with carbon monoxide at 1000 psig at ambient temperature~ The reactor contents were then heated to 160C. ~fter 1.5 hours at 160Cr the reactor contents were cooled to am~ient temperature. The sampling system was clogged with solld ~,N'-diphenylurea 30 ml of methanol was then injected into the vessel and the gas in the vessel was vented and replaced with nitrogen at 1000 psig. The reactor contents were then reheated to 1~0C. After 1.0 hour at 160C, the reactor contents were cooled. The resulting solution contained no nitrobenzene, 0.023 mole methyl N-phenylcarbamate (92% selectivity on nitrobenzene) and 0.126 mole aniline.
.
Comparative Exam~le 3 The procedure was the same as ~or Example 7 except that no aniline was lnitially provided ~o the reaction.
Additional toluene solvent was added to again give a total initial solution volume of 75 ml. After 1.5 hours at 160C under carbon monoxide, 0.023 mole ~itrobenzene remained and no products were observed by the gas chromatographic analytical system. The mixture was cooled, methanol was added, and the gas was changed to nitrogen as in Example 7. Ater 1.0 hours at 160C under nitrogen, the solution contained O.Q13 mole nitrobenzene, 0.003 mole aniline, O.OQl mole N-methylene aniline, 0.004 mole N-methyl aniline, and less than 0.001 mole methyl N-phenyI carbamate.

.

Claims

1. A process for reacting a solution containing a nitrogen containing organic compound, selected from the group consisting of nitro, nitroso, azo and azoxy compounds, with carbon monoxide to obtain a carbamic acid derivative selected from the group consisting of urethane and N,N'-disubstituted urea, which comprises providing a primary amine in said solution and reacting said nitrogen-containing organic compound with carbon monoxide in the presence of a catalyst selected from the group consisting of ruthenium and rhodium, and essentially free of redox-active metal components; with the proviso that, in a batch process, when said carbamic acid derivative is an N,N'-disubstituted urea and said primary amine is provided by the in-situ reduction of the nitrogen-containing organic compound, by hydrogen, to said primary amine, then from 50 to about 60 percent of said nitrogen-containing organic compound is hydrogenated to maximize the yield of said N,N'-disubstituted urea.

2. The process of claim 1 wherein said nitrogen-containing organic compound is a nitro compound.

3. The process of claim 2 wherein said nitro compound is an aromatic nitro compound.

4. The process of claim 3 wherein said primary amine is an aromatic amine corresponding to said aromatic nitro compound.

5. The process of claim 4 wherein said catalyst is selected from the group consisting of rhodium and ruthenium carbonyl complexes.

6. The process of claim 4 wherein said N,N'-disubstituted urea is recovered and subsequently converted to a urethane by alcoholysis in the presence of a hydroxyl-containing organic compound.

7. The process of claim 3 wherein said nitrogen-containing organic compound is carbonylated in the presence of a hydroxyl-containing organic compound and said carbamic acid derivative is a urethane.

8. The process of claim 6 further comprising recovering a primary amine, upon alcoholysis of said urea, in an amount equal to or greater than the primary amine initially provided in the solution.

9. The process of claim 7 further comprising recovering a primary amine in an amount equal to or greater than the primary amine initially provided in the solution.

10. The process of claim 7 wherein said hydroxyl-containing organic compound is methanol.

11. The process of claim 5 wherein said catalyst commprises a bisphosphino ligand.

12. The process of claim 5 wherein said catalyst comprises a poly tertiary amino ligand.

13. The process of claim 7 wherein the molar ratio of said hydroxyl-containing organic compound to said aromatic nitro compound is less than 15:1.

14. The process of claim 7 wherein the molar ratio of said hydroxyl-containing organic compound to said aromatic nitro compound is between 1:1 and 3:1.

15. The process of claim 3 wherein said aromatic nitro-compound is selected from the group consisting of nitrobenzene, nitroanisole, dinitrotoluene, nitromesitylene, bis(4-nitro-phenyl) methane, nitroaminotoluene and nitrocarboalkoxyaminotoluene.

16. The process of claim 15 wherein said primary amine is selected from the group consisting of p-toluidine, aniline, diaminotoluene, bis(4-aminophenyl) methane, aminonitrotoluene, and aminomethylcarboalkoxybenzene.

17. The process of claim 2 wherein said nitro containing organic compound is converted into the corresponding carbamic acid derivative, by reacting said nitrogen-containing organic compound with carbon monoxide at a temperaure of from about 100°C. to 200°C. and a carbon monoxide pressure in the range of from 30 to 500 kg/cm2G .

18. The process of claim 6 wherein the molar ratio of the primary amine and the nitrogen-containing organnic compound is greater than 1:1.

19. The process of claim 13 wherein said solution further comprises an inert solvent.