Abstract:
This invention relates to an improved hydrogenation process for the preparation of etheramines. In the process, cyanoethylated alcohols, i.e., the reaction product of an alcohol with (meth)acrylonitrile, are contacted with hydrogen in the presence of a sponge cobalt catalyst. The improvement in the process resides in effecting the hydrogenation process utilizing a cyanoethylated alcohol feedstock contaminated with byproduct acrylonitrile and utilizing a solvent that solubilizes byproduct (meth)acrylonitrile present in the feedstock. Specific classes of solvents employed are ethers and amides.

Description:
BACKGROUND OF THE INVENTION 
     Cyanoethylethers are widely used as a feedstock for the production of primary amines. These cyanoethylethers are commonly produced by the reaction of acrylonitrile or methacrylonitrile with an alcohol. Diaminopropyldiethyleneglycol (DAPDEG) is a valuable diprimary amine produced by a two step process involving the cyanoethylation of diethylene glycol followed by hydrogenation of the thus formed bis(2-cyanoethyl)diethylene glycol. One of the problems encountered during the hydrogenation of cyanoethylated alcohols, and, particularly in the hydrogenation of bis(2-cyanoethyl)diethyleneglycol, is the continuous loss of catalyst activity and selectivity to the product. 
     The following patents and articles are representative of the art in the cyanoethylation of alcohols such as glycols. 
     U.S. Pat. No. 4,313,004 discloses the hydrogenation of cyanoethers in the presence of ammonia and sodium hydroxide over a nickel catalyst at elevated pressures (800-2000 psig) and temperatures of 90-160° C. It is suggested that the hydrogenation may be carried out in the presence or absence of a solvent. To minimize cleavage, the nitrile is added incrementally to the hydrogenation reactor. High yields of diamines (95-98%) are obtained. 
     U.S. Pat. No. 5,869,653 disloses a process for the catalytic hydrogenation of nitrites formed by the cyanoethylation of glycols or the cyanoethylation of amines in the presence of a sponge or Raney cobalt catalyst. Lithium hydroxide is added to achieve high rates of primary amine formation. 
     U.S. Pat. No. 5,075,507 discloses a process for the separation of unreacted acrylonitrile in a process for the cyanoethylation of glycols. In the process, a primary of secondary amine is added to the reaction medium. The process may be carried out in the presence or absence of a solvent which solvents include alcohols and hydrocarbons. 
     SUMMARY OF INVENTION 
     This invention relates to an improved hydrogenation process for the preparation of etheramines, wherein cyanoethylated alcohols, i.e., the reaction product of an alcohol with (meth)acrylonitrile, are contacted with hydrogen in the presence of a catalyst. The improvement in the process resides in effecting the hydrogenation process utilizing an ether or amide solvent that solubilizes byproduct (meth)acrylonitrile and poly(meth)acrylonitrile present in the feedstock or produced during the hydrogenation. 
     Significant advantages can be achieved by the use of specific types of solvents in the catalytic hydrogenation of cyanoethylated alcohols, particularly cyanoethylated ether glycols. These include:
         an ability to reduce the catalyst levels necessary to maintain reaction rate in the hydrogenation process; and,   an ability to use the catalysts over many cycles without regenerative treatment.       

    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The cyanoethylated ethers, which constitute the basis of the feedstock for the improved hydrogenation process, are formed by the reaction of acrylonitrile or methacrylonitrile with an alcohol. In carrying out that reaction, a byproduct comprised of unreacted (meth)acrylonitrile and polymerized (meth)acrylonitrile is formed and small amounts remain after purification. It is believed that the presence of byproduct (meth)acrylonitrile is believed to be a major contributor to catalyst deactivation during conversion of the nitrile to the amine. It is also thought that some byproduct (meth)acrylonitrile, in polymerized form, is generated in the hydrogenation process and this too, contributes to catalyst deactivation. Catalyst deactivation, it is thought, is caused by byproduct and unreacted (meth)acrylonitrile being polymerized within the catalyst sites or polymerized (meth)acrylonitrile adsorbed on the surface of the catalyst. 
     It has been found that effecting the hydrogenation of cyanoethylated alcohols, as distinguished from cyanoethylated amines, in the presence of select solvents can improve catalyst activity and catalyst life. The improvement in the hydrogenation process resides in the use of an ether or amide solvent to overcome a substantial problem of rapid catalyst deactivation. In the past, common practice involved the use of a small amount of water, an alcohol, or a hydrocarbon as a carrier in the hydrogenation process. 
     Solvents to be used for the hydrogenation of cyanoethylated alcohols and the formation of aminoethylated alcohols and found to contribute to catalyst life include lower C 1-8  alkyl and cycloalkyl ethers such as tetrahydrofuran, dimethyl ether, diethyl ether, dibutyl ether and methyl-tertiary-butyl ether. Specific amides include C 1-8  alkyl amides and C 5-10  cyclic amides, such as dimethylformamide, acetamide, N-methylpyrrolidone, etc. Mixtures of solvents cited herein can also be used. 
     The level of ether and amide solvent employed is not critical. Functionally, there should be sufficient solvent present in the reaction medium to effect washing of the catalyst surface and removal of byproduct (meth)acrylonitrile. It should also be present in an amount to at least partially dissolve polymerized (meth)acrylonitrile on the surface of the catalyst. The major side effect of excessive levels of solvent is one of increased recovery cost. Typical solvent levels for the hydrogenation process are from 5 to 100%, preferably from 20 to 50%, by weight of the cyanoethylated alcohol to be hydrogenated. 
     The cyanoethylated derivatives suited as feedstocks for hydrogenation and conversion to the aminopropyl alcohol are based on the reaction of alcohols with (meth)acrylonitrile. Representative alcohols are monoalcohols, polyols, and ether derivatives thereof. Specifically, suited for forming cyanoethylated derivatives are the C 1 -C 30  alkanols and C 1-8  alkylether alcohols, aliphatic glycols, aliphatic ether glycols and polyols. Representative C 1-30  and preferably C 1-8  alkanols include methanol, ethanol, ethanol, the propanols, the butanols, and hexanol. The C 1-8  alkylether alcohols include methoxy methanol, methoxy ethanol, ethoxy ethanol, ethoxy propanol, propoxy ethanol and propoxy propanol. Representative aliphatic glycols include the C 2-8  aliphatic glycols such as ethylene glycol, propylene glycol, butylene glycol, and pentane glycol, and the ether glycols such as diethylene glycol, and dipropylene glycol. Representative polyols include glycerin, sorbitol, and mannitol as well as polymeric polyether polyols having a number average molecular weight of up to about 4 million. Specific examples of polymeric polyols include polyethylene glycol, polypropylene glycol, polybutylene polyol and polytetrahydrofuran. 
     Favored cyanoethylethers produced by the cyanoethylation of such alcohols include methoxypropionitrile, ethoxypropionitrile, biscyanoethylether, bis-(2-cyanoethyl)ethylene glycol, bis-(2-cyanoethyl)diethylene glycol, mono-(2-cyanoethyl)diethylene glycol, and bis(2-cyanoethyl)tetramethylene glycol, mono and polycyanoethylated glycerin, mono and polycyanoethylated sorbitol and mono and polycyanoethylated mannitol. 
     The hydrogenation of the cyanoethylated alcohols can be conducted in conventional hydrogenation equipment, e.g., a stirred tank or loop reactor, a continuous stirred tank reactor, a continuous gas lift reactor, a fixed-bed plug flow reactor, a trickle-bed reactor, a bubble column reactor or a sieve-tray reactor. Preferred methods of operation include semi-batch and continuous back-mix. 
     The reduction of the cyanoethylated alcohol with hydrogen to the amine is generally carried out under a hydrogen pressure of from 1 to 300 bars, typically from 5 to 80 bars, and at temperatures of from about 60 to 160° C. Typical reaction times range from 15 to 600 minutes. 
     The catalyst used in the hydrogenation process is conventional in the art although typically the catalytic metal is sponge cobalt, or as it is sometimes called, Raney cobalt. Raney nickel, nickel, palladium, platinum, rhodium and ruthenium metals carried on a support such as alumina, silica, and the like, can also be used. Conventional promoters may be present in the catalyst in conventional amounts. Examples of promoters include Group VI and Group VIII metals such as chromium, iron, molybdenum, nickel, and so forth. Lithium hydroxide is also used as a preferred promoter. 
     The following examples are provided to illustrate various embodiments of the invention and are not intended to limit the scope thereof. 
     CONTROL EXAMPLE 1 
     Semi-Batch Hydrogenation of Cyanoethylated Diethylene Glycol in the Presence of Water 
     In a one-liter batch reactor a heel was formed by adding 266 grams of water, 13.1 grams of Grace 2724 sponge cobalt catalyst to a reactor. The reactor was pressure cycled three times with nitrogen, three-times with hydrogen, and then, heated to 60° C. To this reactor was incrementally added 310 grams of nitrile feed in four hours. The nitrile feed was made by reacting diethylene glycol (DEG) (LiOH present in an amount of 1000 ppm) with acrylonitrile at a molar ratio of 1:1.3 such that equimolar concentrations of monocyanoethyl (DEG) and dicyanoethylDEG were present. Once the hydrogenation was over the product was removed using a filter, and then, the subsequent runs were started using the same catalyst with fresh solvent and feed. The subsequent hydrogenation reactions then were carried out at 800 psig (56 bar) and 60° C., semi batch. The results are shown in the Table. 
     CONTROL EXAMPLE 2 
     Semi-Batch Hydrogenation of Cyanoethylated Diethylene Glycol in the Presence of Methanol 
     In a one-liter batch reactor a heel was formed by adding 254 grams of methanol, 8.5 grams of Grace 2724 sponge cobalt catalyst to a reactor. The reactor was pressure cycled three times with nitrogen, three-times with hydrogen, and then, heated to 120° C. To this reactor was incrementally added 423 grams of nitrile feed in five hours. The nitrile feed was made by reacting DEG (LiOH present at 1000 ppm) with acrylonitrile at a molar ratio of 1:2.03 such that the concentration of dicyanoethyl DEG and monocyanoethyl DEG in the reaction product was about 9:1. Once the hydrogenation was over the product was removed using a filter, and then, the subsequent runs were started using the same catalyst with fresh solvent and feed. The subsequent hydrogenation reactions were carried out at 800 psig (56 bar) and 120° C. The results are shown in the Table. 
     CONTROL EXAMPLE 3 
     Semi-Batch Hydrogenation of Cyanoethylated Diethylene Glycol in the Presence of Diaminopropydiethyleneglycol 
     In a one-liter batch reactor a heel was formed by adding 302 grams of DAPDEG, 15 grams of Grace 2724 sponge cobalt catalyst. The reactor was pressure cycled three times with nitrogen and three times with hydrogen. Then, under hydrogen pressure, the contents were heated to 125° C. To this reactor was incrementally added 301 g of nitrile feed in four hours. The nitrile feed was made by reacting DEG (LiOH present at 1000 ppm) with acrylonitrile at a molar ratio of 1:2.1 such that the concentration of dicyanoethyl DEG and monocyanoethyl DEG was about 9:1 in the product. Once the hydrogenation was over the product was removed using a filter, and then, the subsequent runs were started using the same catalyst with fresh solvent and feed. The hydrogenation was carried out at 900 psig (63 bar) and 125° C. The results are shown in the Table. 
     EXAMPLE 4 
     Semi-Batch Hydrogenation of Cyanoethylated Diethylene Glycol in the Presence of Dimethylformamide 
     In a one-liter batch reactor a heel was formed by adding 120 grams of dimethylformamide (DMF), 7.2 grams of Grace 2724 sponge cobalt catalyst. The reactor was pressure cycled three times with nitrogen and three times with hydrogen. The contents were heated to 120° C. To this reactor was incrementally added 360 grams of nitrile feed in four hours. The nitrile feed was made by reacting DEG (LiOH present at 1000 ppm) with acrylonitrile at a molar ratio of 1:2.03 such that the concentration of dicyanoethyl DEG and monocyanoethyl DEG was about 9:1 in the product. Once the hydrogenation was over the product was removed using a filter, and then, the subsequent runs were started using the same catalyst with fresh solvent and feed. The subsequent hydrogenation reactions were carried out at 800 psig (56 bar) and 120° C. The results are shown in the Table. 
     EXAMPLE 5 
     Semi-Batch Hydrogenation of Cyanoethylated Diethylene Glycol in the Presence of Methyl-Tertiary-Butylether 
     In a one-liter batch reactor a heel was formed by adding 120 grams of methyl-tertiary-butylether (MTBE), 7.2 grams of Grace 2724 sponge cobalt catalyst. The reactor was pressure cycled three times with nitrogen and three times with hydrogen. The contents were heated to 120° C. To this reactor was incrementally added 360 grams of nitrile feed in five hours. The nitrile feed was made by reacting DEG (LiOH present at 1000 ppm) with acrylonitrile at a molar ratio of 1:2.03 such that the concentration of dicyanoethyl DEG and monocyanoethyl DEG was about 9:1 in the product. Once the hydrogenation was over the product was removed using a filter, and then, the subsequent runs were started using the same catalyst with fresh solvent and feed. The subsequent hydrogenation reactions were carried out at 800 psig (56 bar) and 120° C. The results are shown in the Table. 
     EXAMPLE 6 
     Semi-Batch Hydrogenation of Cyanoethylated Diethylene Glycol in the Presence of Tetrahydrofuran 
     In a one-liter batch reactor a heel was formed by adding 120 grams of tetrahydrofuran (THF), 7.3 grams of Grace 2724 sponge cobalt catalyst. The reactor was pressure cycled three times with nitrogen and three times with hydrogen. The contents were heated to 120° C. To this reactor was incrementally added 360 grams of nitrile feed in four hours. The nitrile feed was made by reacting DEG (LiOH present at 1000 ppm) with acrylonitrile at a molar ratio of 1:2.03 such that the concentration of dicyanoethyl DEG and monocyanoethyl DEG was about 9:1 in the product. Once the hydrogenation was over the product was removed using a filter, and then, the subsequent runs were started using the same catalyst with fresh solvent and feed. The subsequent hydrogenation reactions were carried out at 800 psig (bar) and 120° C. The results are shown in the Table. 
     
       
         
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                   
                 TABLE 
               
             
             
               
                   
                   
               
               
                   
                 Catalyst 
                   
                 Selectivity of Products % 
               
             
          
           
               
                 Catalyst Use 
                 Addition 
                 Temp. 
                 Pressure, 
                 loading, 
                   
                   
                 Mono 
                   
                 APDAP 
                 DAPDEG 
                 Heavies/ 
               
               
                 # 
                 Time, hrs 
                 ° C. 
                 psig 
                 % 
                 Heel 
                 DEG 
                 APDEG 
                 DAPDEG 
                 DEG 
                 SEC A 
                 Others 
               
               
                   
               
             
          
           
               
                 Control 
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 Ex. 1 
               
               
                 1 
                 4 
                 60 
                 800 
                 4.2 
                 46% Water 
                 8.60 
                 39.24 
                 52.12 
               
               
                 2 
                 4 
                 60 
                 800 
                 4.2 
                 46% Water 
                 12.62 
                 40.50 
                 46.91 
               
               
                 3 
                 4 
                 60 
                 800 
                 4.2 
                 46% Water 
                 19.48 
                 42.20 
                 38.30 
               
               
                 4 
                 4 
                 60 
                 800 
                 4.2 
                 46% Water 
                 25.39 
                 42.60 
                 31.36 
               
               
                 Control 
               
               
                 Ex. 2 
               
               
                 1 
                 5 
                 120 
                 800 
                 2 
                 37% Methanol 
                   
                 8.1 
                 89.5 
                 1.1 
                 1.3 
               
               
                 2 
                 5 
                 120 
                 800 
                 2 
                 37% Methanol 
                   
                 16.4 
                 72.2 
                 1.5 
                 9.8 
               
               
                 3 
                 5 
                 120 
                 800 
                 2 
                 37% Methanol 
                   
                 22.2 
                 32.9 
                 6.9 
                 15.6 
                 22.2 
               
               
                 Control 
               
               
                 Ex. 3 
               
               
                 1 
                 4 
                 125 
                 900 
                 5 
                 50% DAPDEG 
                   
                 11.73 
                 86.23 
                 2.04 
               
               
                 2 
                 4 
                 125 
                 900 
                 5 
                 50% DAPDEG 
                   
                 17.7 
                 79.67 
                 2.6 
               
               
                 3 
                 4 
                 125 
                 900 
                 5 
                 50% DAPDEG 
                   
                 23.5 
                 72.52 
                 4 
               
               
                 4 
                 4 
                 125 
                 900 
                 5 
                 50% DAPDEG 
                   
                 28.26 
                 65.42 
                 6.32 
               
               
                 Ex. 4 
               
               
                 1 
                 5 
                 120 
                 800 
                 2 
                 25% DMF 
                   
                 7.6 
                 87.3 
                 0.6 
                 2.8 
                 1.7 
               
               
                 2 
                 5 
                 120 
                 800 
                 2 
                 25% DMF 
                   
                 7.6 
                 89.5 
                 0.7 
                 1.5 
                 0.7 
               
               
                 3 
                 5 
                 120 
                 800 
                 2 
                 25% DMF 
                   
                 8.1 
                 90 
                 0.4 
                 0.6 
                 0.9 
               
               
                 4 
                 5 
                 120 
                 800 
                 2 
                 25% DMF 
                   
                 8.7 
                 89.6 
                 0.4 
                 0.8 
                 0.5 
               
               
                 5 
                 5 
                 120 
                 800 
                 2 
                 25% DMF 
                   
                 9.2 
                 88.5 
                 0.5 
                 0.8 
                 1.0 
               
               
                 6 
                 5 
                 120 
                 800 
                 2 
                 25% DMF 
                   
                 9.4 
                 88.6 
                 0.5 
                 0.6 
                 0.9 
               
               
                 7 
                 5 
                 120 
                 800 
                 2 
                 25% DMF 
                   
                 9.4 
                 88.5 
                 0.4 
                 0.6 
                 1.1 
               
               
                 8 
                 5 
                 120 
                 800 
                 2 
                 25% DMF 
                   
                 7.4 
                 90 
                 0.8 
                 1 
                 0.8 
               
               
                 9 
                 5 
                 120 
                 800 
                 2 
                 25% DMF 
                   
                 7.9 
                 90.1 
                 0.5 
                 0.8 
                 0.7 
               
               
                 Ex. 5 
               
               
                 1 
                 5 
                 120 
                 800 
                 2 
                 25% MTBE 
                   
                 9.1 
                 89 
                 1.1 
                 0.8 
               
               
                 2 
                 5 
                 120 
                 800 
                 2 
                 25% MTBE 
                   
                 7.3 
                 92.7 
               
               
                 3 
                 5 
                 120 
                 800 
                 2 
                 25% MTBE 
                   
                 7 
                 93 
               
               
                 4 
                 5 
                 120 
                 800 
                 2 
                 25% MTBE 
                   
                 7 
                 93 
               
               
                 Ex.6 
               
               
                 1 
                 5 
                 120 
                 800 
                 2 
                 25% THF 
                   
                 6.8 
                 92.8 
                 0.4 
               
               
                 2 
                 5 
                 120 
                 800 
                 2 
                 25% THF 
                   
                 6.9 
                 93.1 
                 0 
               
               
                 3 
                 5 
                 120 
                 800 
                 2 
                 25% THF 
                   
                 7 
                 93 
                 0 
               
               
                   
               
               
                 DEG—diethyleneglycol 
               
               
                 DAPDEG—diaminopropyldiethyleneglycol 
               
               
                 DAPDEG Sec A—DAPDEG Secondary Amine 
               
               
                 Mono APDEG—mono aminopropyldiethylene glycol 
               
               
                 APDAPDEG—AminopropylDAPDEG 
               
             
          
         
       
     
     Control Example 1 shows the selectivity to the diaminopropyl diethylene glycol (DAPDEG) in the first use was 52% and by the 4 th  use the selectivity dropped to 31%, showing significant catalyst deactivation. This example shows that water is not very effective as a carrier/solvent in preventing catalyst deactivated in the hydrogenation process. 
     Control Example 2 shows the selectivity to DAPDEG in the first use was 89%. By the 3 rd  use, the catalyst was severely deactivated and the selectivity to DAPDEG dropped to 33%. 
     Control Example 3 shows the selectivity to the DAPDEG in the first use was 86% and by the 4 th  use the catalyst was severely deactivated and the selectivity DAPDEG drops to 65%. The data from Control Examples 2-3 show that similar to water, methanol, and DAPDEG are not effective as solvent/carriers in preventing catalyst deactivation. 
     Example 4 surprisingly shows the selectivity to DAPDEG was 87% in the first use and did not show rapid deactivation with use. Over a period of 9 uses, the selectivity did not change. These results clearly show that using DMF as a solvent is beneficial in the hydrogenation of cyanoethylalcohols to aminoethers. Also, with DMF as a solvent, it was possible to use a 2% catalyst loading compared to greater than 3% used in Control Examples 1-3 to achieve the same level of conversion. 
     Example 5 shows excellent results of a 2% catalyst level and excellent conversion over 4 uses. 
     Example 6 shows excellent results of a 2% catalyst level and excellent conversion over many uses. 
     In summary, the data in Table 1 show that the use of certain ethers or amide solvents can reduce the rate of catalyst deactivation in the hydrogenation of cyanoethyl ethers. For example, the results show that after 9 uses of the catalyst (Example 4) there is no loss of selectivity, compared to losses of greater than 40% selectivity in the first 3 uses of the catalyst employing the solvents of Control Examples 1-3. As a result, it is possible to use one half to one fourth of the traditional loading of the catalyst with no significant deactivation in about 10 uses. Commercially, it is desirable to obtain at least 8 uses of the catalysts prior to effecting regeneration.