KR20050095831A - Low pressure process for manufacture of 3-dimethylaminopropylamine(dmapa) - Google Patents

Abstract

An improved process for the production of 3-dimethylaminopropylamine in high purity from N,N-dimethylaminopropionitrile utilizing a low pressure hydrogenation process is described. The basic process comprises contacting the nitrile with hydrogen at low pressure in the presence of a catalyst under conditions sufficient to effect the conversion of the nitrile to the primary amine product.

Description

LOW PRESSURE PROCESS FOR MANUFACTURE OF 3-DIMETHYLAMINOPROPYLAMINE (DMAPA)} for the production of 3-dimethylaminopropylamine (DMPA)

This application is a continuation-in-part of Application No. 10 / 327,765, filed December 23, 2002, which claims priority therefrom.

The present invention generally relates to a process for producing dimethylaminopropylamine (DMAPA) from dimethylaminopropionitrile (DMAPN) using a hydrogenation process. More specifically, the use of a low pressure diamine hydrogenation process for the production of dimethylaminopropylamine from dimethylaminopropionitrile with exceptionally high selectivity using alkali metal hydroxide solutions and sponge (Raney ^® ) type catalysts It is about. In particular, low pressure hydrogenation of DMAPN to DMAPA is disclosed using a sponge nickel catalyst and a mixture having 50/50% by weight of sodium hydroxide and potassium hydroxide at low temperatures.

N, N-dimethylaminopropylamine (DMAPA, N, N-dimethyl-1,3-diaminopropane, 3-dimethylaminopropylamine) is an important intermediate in the large scale production of various industrial processes, for example DMAPA is a betaine and fat As an intermediate for the production of amine oxides and as a surfactant for the production of soft soaps and other products, it is an important intermediate. N, N-dimethylaminopropylamine is also used as starting material for the production of flocculants (by conversion to methacrylamide), road marking paints and polyurethanes. DMAPA is also known to inhibit corrosion in boiler water treatment and is an intermediate for gasoline and motor oil additives. Due to the widespread use of DMAPA and the fact that the products associated with it are produced in quantities of millions of pounds per year, due to the high costs associated with by-product contamination, N, N-dimethylaminopropylamine for producing high yields and selectivities There has been a constant attempt.

One of the most commonly used methods for commercial production of aliphatic amines, such as dimethylaminopropylamine, is the catalytic hydrogenation of aliphatic nitriles using batch or trickle bed hydrogenation techniques using ammonia to inhibit the formation of secondary amines. It was a response. However, significant amounts of ammonia are needed to carry out the reaction, are expensive to use ammonia industrially, and cause environmental problems. Over the years, several approaches have been tried to find the optimal technology for the production of DMAPA.

U.S. Patent No. 3,821,305 discloses a hydrogenation process in the liquid phase at a pressure and a temperature of 60 ~ 100 ℃ of 20 to 50 atm in the presence of a finely pulverized catalyst and Raney ^® caustic alkali base. As specifically described in this patent, hydrogen and nitrile are added to a liquid medium consisting of HMDA, water, caustic alkali base and catalyst, and the base content is in the range of 2 to 130 moles per mole of caustic alkali.

Zuckerman, US Pat. No. 4,739,120, discloses a process for catalytic hydrogenation of converting organic nitrile groups to primary amines using rhodium catalysts and inorganic or organic bases having a pH of 8 or greater. This reaction is disclosed to be carried out in a two-phase solvent system comprising an organic solvent and water that do not mix with each other.

U.S. Patent No. 4,885,391 discloses using a Raney ^® Co catalysts that promote the catalytic activity of chromium, sustained by the addition of water initiates a process for the hydrogenation of nitrile ₁₂ C ₄ ~ C. This process is carried out at a temperature of about 80-150 ° C. and a pressure of 400-2500 psig, without the use of any caustic base.

US 4,967,006 discloses the use of ammonia in alcohols instead of caustic bases for low reaction pressures. However, the use of alcohol can be problematic because it can often be difficult to remove and reuse, depending on the alcohol used, and can also result in the formation of unwanted byproducts during the reaction.

Borninkhof et al. In US Pat. No. 5,571,943 discloses a process for the production of primary amines by hydrogenation of mononitrile and / or dinitrile. As discussed in this patent, the nitrile is hydrogenated with a nickel and / or cobalt catalyst system on a carrier, optionally in the presence of a reaction medium-insoluble solid promoter, wherein the catalyst (and promoter) is non-acidic to be.

In U. S. Patent No. 5,789, 621 Schnurr et al. Disclose amine-containing compounds by hydrogenation of nitriles using cobalt and / or iron-containing catalysts at high temperatures (150-400 [deg.] C.) and hydrogen pressures of 0.1-30 MPa. Disclosed is a process for producing. This process is described in more detail as being carried out batchwise or continuously in a fixed-bed reactor using a downflow or upflow process with or without solvent.

United States Patent No. 5,840,989 Cordier et al., Discloses a process of hydrogenation reaction for specifically and doped (doped) the use of Raney ^® nickel catalyst and, using a catalyst doped with a nitrile to amine conversion. As described in the patent, in a further embodiment of the process, partly uses an aqueous liquid reaction medium and the remaining reaction medium uses a solvent such as an alcohol or an amide.

In U.S. Patent No. 5,869,653 is Johnson, discloses a continuous process for the hydrogenation of nitrites on Raney ^® Co catalysts in the presence of lithium hydroxide and water in the absence and a catalytic amount of ammonia. In order to reduce the nitrite to amine, the reaction is carried out at a hydrogen pressure of 1 ~ 300bar and a temperature of 60 ~ 160 ℃. As described, the catalyst is pretreated with lithium hydroxide to obtain the desired catalytic effect, or the reaction is carried out with lithium hydroxide present in the reaction medium itself.

Elsasser in US Pat. No. 5,874,625 discloses an industrial batch process for hydrogenation to reduce organic nitrite to primary amines. The process uses an aqueous alkali metal hydroxide, at least one Raney ^® catalyst, water, and hydrogen at a hydrogen pressure of 250-2500 psi and a temperature of 150-220 ° C. According to this disclosure, improvements in this process include reducing the water required in the system to about 0.2%, eliminating the step of drying the input and adding water.

In European Patent No. 0416,761, Kiel and Bauer described DMAPA as a byproduct, using a sponge cobalt or nickel catalyst and a small amount of calcium oxide or magnesium oxide and ammonia to control the selectivity of the reaction to obtain the desired primary amine. It is disclosed that, 3-propanediamine (PDA) can be made essentially free. The patent also shows that this process can be run at temperatures from 160 to 180 ° C at 2200 psig as a batch process.

Goodwin et al. In US Pat. No. 6,281,388 disclose a process for producing amines from nitriles using hydrogenation. This method involves placing both hydrogen and nitrile in a reactor containing catalyst, water, and inorganic bases, and providing a reaction medium to provide a constant bulk concentration of nitrile in at least one direction across the reactor to minimize the volume of the reactor. Mixing step. The process described above can be carried out at 25-50 atmospheres and temperatures of 60-120 ° C. using Raney ^® nickel catalysts and inorganic bases.

In US Pat. No. 6,469,211, Ansmann et al. Disclose a process for the hydrogenation of nitrite and nitrile to primary amines on activated Raney ^® catalysts based on aluminum alloys and at least one transition metal. This hydrogenation process is carried out in the absence of ammonia and basic alkali metal compounds or alkaline earth metal compounds.

In U.S. Patent Application Publication No. 2002/0058841, Ansmann et al. Described the specific macroporous molding based on an alpha-Al ₂ O ₃ aluminum alloy and at least one transition metal for the hydrogenation of nitriles to primary amines. Start activation and use of Raney ^® catalysts. As described in the patent application, the nitrile hydrogenation reaction is carried out in an organic solvent such as DMF or NMP at a pressure of 10-300 bar.

The periodical literature also discloses a method for the synthesis of DMAPA using hydrogenation techniques. For example, the study of hydrogenation of 3- (dimethylamino) propionitrile using a palladium catalyst is described in Krupka et al., Coll. Czech. Chem. Commun. 2000, Vol. 65 (11), 1805-1819. The effects of reaction conditions, catalyst type, and addition of ammonia or amines on the inputs to the hydrogenation selectivity are described. According to the results, these studies indicate that the preferred catalyst is Pd / SiO ₂ -Al ₂ O ₃ , and the formation of secondary amines and tertiary amines is preferred in the hydrogenation of 3- (dimethylamino) propionitrile on palladium. It shows that it is done.

Johnson et al. Catalysis of Organic Reactions, Vol. 82 (2000) discloses the use of a sponge catalyst modified with lithium hydroxide to control the selectivity of primary amines in batch nitrile hydrogenation. The LiOH modified sponge cobalt catalyst used provided high primary amine selectivity control upon conversion of nitrile to primary amine, but required high pressure (750 psig) to carry out the reaction.

However, even the methods listed above that are available for the synthesis of DMAPA are not suitable for use for commercial production of most of these compounds. Many uses of DMAPA require that the compound be of high purity and free of by-products. The methods described above produce compounds in acceptable yields in synthesis, but do not meet the stringent industrial requirements, such as the need to produce products in higher yields greater than 99% without by-products.

If the demand for high purity DMAPA with minimum byproduct contamination of <300 ppm is increased, N, N-dimethylaminopropyl with higher selectivity (generally no by-products), higher production rates, higher yields and greater than 99% purity There is a need for a method for efficiently preparing amines.

During the hydrogenation of nitriles, the use of alkaline materials in the presence of catalysts to improve the selectivity of primary amine formation has long been known. Depending on the catalyst and the conditions, the nitrile can be transformed into primary, secondary, or tertiary amines and most often a mixture of amine products is formed. For commercial reasons, only one of these products is the desired product, and generally the primary amine is the desired amine.

Early work in this field showed that the addition of ammonia to the hydrogenation mixture of nitriles strongly inhibited the formation of secondary amines and other byproducts. During the course of this study, routes have been proposed that represent a process for the hydrogenation of nitriles to amines, showing both products and by-products, for example, primary imines (1 ° imines) bound to the surface of nitrile. It is known to form during the hydrogenation of DMAPN. This species can be attacked by primary amines (1 ° amines), such as DMAPA, and then release ammonia in the reversible stage during the formation of secondary imines (2 ° imines). The hydrogenation of this 2 ° imine yields 3,3'-iminobis (N, N'-dimethylpropylamine (di- (3-dimethylaminopropyl) amine), which is a 2 ° amine. Is, for all practical purposes, the same as the reductive amination of aldehydes, and importantly, dimethylamine (DMA) and acrylonitrile (AN) derived from the reverse Michael addition of DMAPN to DMA and ACN. The presence of traces of impurities derived from starting nitrile DMAPNs, such as N, N, N ', N',-tetramethyl-1,3-propanediamine (TMPDA), creates problematic and difficult to remove by-products. Various other by-products are also possible, such as n-propylamine, resulting from excess water in the reaction medium.

Of all the by-products that can potentially form in catalytic hydrogenation of DMAPN to DMAPA, there is no damage to the formation of commercial products more than the formation of TMPDA or 2 ° amines. Both of these by-products are difficult to remove, and TMPDA cannot be separated from DMAPA by distillation. If contaminated DMAPA is used as an intermediate, these byproducts may form additional byproducts and impart undesirable properties to the target product. Most recently, a large and new DMAPA market has been developed that requires DMAPA as an intermediate containing less than 300 ppm of TMPDA.

Since amines of interest, such as N, N-dimethylaminopropylamine, are typically produced at billions of pounds per year, producing these products in high yields and selectivity is a challenge for companies. This is because even at high yields, even a few percent of ten minutes presents significant removal and disposal of by-products. From an economic point of view, these by-products can be unhandled and costly to dispose of without commercial use. As a result, it is beneficial to develop advanced and optimized techniques for controlling the selectivity and yield of primary amine products during the hydrogenation of N, N-dimethylaminopropionitrile.

As described herein, it has been found that, in addition to the sponge nickel catalyst, the introduction of Group IA alkali metal hydroxides, or mixtures thereof, allows for increased control of selectivity during hydrogenation of DMAPN to DMAPA. This process can be carried out at low hydrogenation pressure and temperature, thereby increasing both yield and selectivity to at least 99.0% and 99.98%, respectively, for the desired primary amine, 3-dimethylaminopropylamine. This process also has the advantage of producing less than about 300 ppm of difficult to remove by-products such as TMPDA and 2 ° amines. Further improvements associated with the present invention include low operating costs, reduced waste generation, and reduced disposal and disposal costs associated with such hydrogenation processes.

Although the present invention is directly related to the production process of 3-dimethylaminopropylamine, it also contains aliphatic and aromatic nitrites and derivatives thereof such as propionitrile, butyronitrile, tallow nitrite, acetonitrile, benzyl nitrite and the like. Applicable to any amine, including aliphatic and aromatic amines and derivatives thereof, such as hexamethylenediamine, propylamine, butylamine, benzylamine, tallowamine, ethylamine, etc., produced from a nitrile comprising The finely ground catalyst is dispersed in the liquid reaction medium.

In particular, the process for the production of 3-dimethylaminopropylamine with high yield and selectivity, together with the amines produced at pressures of 45-500 psig, more preferably 45-150 psig and temperatures of 70-100 ° C. This can be done by feeding hydrogen and nitrile to a liquid reaction medium containing finely ground nickel or cobalt catalyst dispersed in the base and the liquid component of the reaction medium. Preferably, catalysts that are sponge (eg, Raney ^® catalysts) nickel lose some of their activity during the hydrogenation, in the presence or absence of promoter metals such as chromium and / or iron.

As described in US Pat. No. 4,429,159 to Cutchens et al., Incorporated herein by reference, it is necessary to gradually regenerate the catalyst in the reaction medium to maintain a given level of catalytic activity within the catalytic mass. This regeneration involves transferring a certain amount of reaction medium containing the catalyst to the regeneration vessel, precipitating the catalyst, pouring the organic top layer back into the reaction vessel, and washing the catalyst with water to remove contaminants from the catalyst before circulating to the reactor. Is performed by. If addition of a small amount of new catalyst is necessary to increase the catalytic activity in the reactor, the circulated catalyst may consist of a mixture of fresh catalyst and circulated catalyst.

The most important point in the efficiency of the low pressure diamine hydrogenation process of the present invention is to introduce an effective amount of cheap caustic hydroxide into the sponge nickel catalyst in order to improve the selectivity of the reaction. The hydroxide is preferably a hydroxide of a Group IA ("alkali metal") element of the periodic table selected from the group consisting of lithium, sodium, potassium, rubidium, cesium, and mixtures thereof. More preferably, they are caustic alkali metal hydroxides sodium hydroxide, potassium hydroxide, cesium hydroxide, and mixtures thereof.

Suitable catalysts for use in the present invention are Raney ^® type catalysts, which are also known as "skeleton" or "sponge-type" metal catalysts. If the nickel and cobalt sponge catalysts both be used, because it is used for the sponge cobalt catalyst is related to the high cost, in the present invention, it is preferable to use a Raney ^® nickel catalyst.

Nickel catalyst used in the low-pressure hydrogenation process of the present invention is sponge nickel, or, Raney ^® nickel that mentioned already several times. This catalyst is commercially available from a number of sources (WR Grace and Co .; Degussa; Activated Metals), or can be found in literature, for example in Organic Syntheses Collected Volume 3, p. 181; And Reagents for Organic Synthesis, Fieser and Fieser. 1, pp. And a number of methods described in 723-731 and the references cited therein.

Another catalyst that can be used in the present invention is a cobalt catalyst. Such a cobalt catalyst used in the low-pressure hydrogenation process of the present invention is sponge cobalt, also known as Raney ^® Co. This catalyst is also commercially available from a number of sources and can be obtained by synthesis through several routes described in the literature.

Conventional promoters may be included or incorporated into the sponge catalyst in conventional amounts known to those skilled in the art. For example, such promoters suitable for introduction into the catalyst include Group VIa and Group VIII metals such as chromium, iron, molybdenum and the like.

N, N-dimethylaminopropionitrile (DMAPN) used as starting material (feedstock) in the present invention can be purchased commercially from various sources (Acros; Aldrich Chemical Co.). Alternatively, it may be synthesized and obtained by any process known in the art, such as obtained in the reaction of acrylonitrile and dimethylamine. This type of process, ie the reaction of acrylonitrile and dimethylamine in a blow column reactor, is described in German patent 27 09 966. Preferably, for use in the present invention, DMAPN is purchased commercially and is significantly free of n-propylamine and diaminepropane.

According to the invention, the hydrogenation of DMAPN to DMAPA takes place under conditions such that only a minimum amount of water is required for use in the reactor. The liquid portion of the reaction medium is divided into two phases, one is an aqueous solution of inorganic base and the other is an aqueous solution of catalyst. The amount of water suitable for use in the reduction reaction process is about 0.1 to 10% by weight of the reaction mixture weight, preferably about 2% by weight of the reaction mixture. In the ratio of water to the inorganic base, the preferred ratio range is 0.5 to 10 mol of water per 1 mol of caustic alkali.

The reduction reaction of the nitrile to the amine can be carried out under a hydrogen pressure of as low as 45 psig and as high as 500 psig. However, hydrogenation of DMAPN to DMAPA is preferably carried out under hydrogen pressure of 45-300 psig, more preferably 45-150 psig or 45-110 psig. The reduction reaction of the nitrile to the amine is carried out at a temperature of about 70 to about 100 ° C, more preferably 80 to 100 ° C, even more preferably 85 to 95 ° C. Most preferably, the reduction of DMAPN to DMAPA is carried out at about 100 psig and at about 90 ° C.

As described herein, pressure is measured in psig (lbs per square inch, gauge), where 1 psig = 0.068 atmospheres (or 0.069 bar). As a result, the reduction reaction of the nitrile to the amine according to the invention is preferably carried out under hydrogen pressure of about 3.0 atmospheres to about 10.2 atmospheres.

The process described herein for the hydrogenation of N, N-dimethylaminopropionitrile to N, N-dimethylaminopropylamine is surprisingly high in selection, while minimizing or avoiding formation of secondary amine by-products during the course of the reaction. The nitrile groups can be converted to primary amines in performance yields. As a result, the amine product DMAPA is produced with selectivity greater than 99.90% and with a yield of at least 99% (based on starting DMAPN). As described herein, selectivity refers to the amount of DMAPA formed from DMAPN, including the formation of byproducts that can be produced during the reaction. In particular, the process of the present invention exhibits at least DMAPN 99.60% selectivity to DMAPA, more preferably at least DMAPN 99.70% selectivity to DMAPA, even more preferably at least DMAPN 99.90% selectivity to DMAPA. The yield of DMAPA produced according to the invention is preferably at least 99% based on the starting DMAPN, and about 99.1%, about 99.2%, about 99.3%, about 99.4%, about 99.5%, about 99.6 based on the starting nitrile. %, About 99.7%, about 99.8%, and about 99.9%. Most preferably, the process of the present invention exhibits at least 99.98% selectivity and at least 99% yield from N, N-dimethylaminopropionitrile.

The hydrogenation can be in any conventional hydrogenation equipment suitable for carrying out the conversion. For example, suitable experimental devices include, but are not limited to, a stirred tank or loop reactor, a continuous stirred tank reactor, a continuous gas lift reactor, a fixed bed reactor, a trickle bed reactor, a bubble column reactor, or a sieve reactor. Preferred operating methods include those described in US Pat. No. 6,281,388, which is incorporated herein in its entirety.

The present invention is also expected to be applicable to high pressure and temperature and other hydrogenation processes that typically use sponge or Raney ^® type catalysts. Specific examples of such processes that are expected to be applicable are those that use a mixture containing a Raney ^® nickel catalyst and a strong caustic base. These processes would be expected to provide similar improvements as described herein for the low pressure hydrogenation of DMAPN to DMAPA. For example, low pressure hydrogenation of adiponitrile to hexamethylenediamine would be expected to provide similarly improved results.

The following examples are included to illustrate preferred embodiments of the present invention. It is to be appreciated by those skilled in the art that the techniques disclosed in the following examples represent techniques discovered by the inventors to function well in the practice of the invention, and thus can be considered to constitute a desirable form for their practice. . However, those of skill in the art should, in light of the present disclosure, appreciate that many changes can be made in the specific embodiments which are disclosed and still obtain a like or similar result without departing from the spirit and scope of the invention.

Example 1 Preparation of Caustic

The preparation of the caustic agent begins with obtaining boiled distilled water to remove dissolved carbon dioxide. Causticizer solutions are prepared at about 25% by weight in 100 g batches. A caustic agent (KOH, NaOH, etc.) was added to the degassed water (-60 mL) with stirring. After the caustic agent was completely dissolved, an additional amount of water was added to bring the total weight of the solution to 100 g. The solution is filtered and stored in a closed container until use to minimize absorption of CO ₂ from air.

Example 2 Hydrogenation Process

Equipped with a double turbine bladder, a dispersimax-type stirrer, a coil extending to the bottom to circulate the moving fluid from the thermostat bath for temperature control, and a molten, stainless steel metal sample port below the liquid level One liter autoclave reactor is used to react hydrogen with 3- (dimethylamino) propionitrile. Hydrogen is supplied from a cylinder equipped with a pressure gauge and a regulator so that when the pressure drops below the set pressure, hydrogen is added to the reactor. Hydrogen flows through the mass flow system. 3- (dimethylamino) propionitrile (Acros) was pumped into an Isco Model 500D syringe pump and placed in an autoclave. 37.5 g of a sponge nickel catalyst (Degussa MC502) was added to the autoclave along with iron and chromium to promote the hydrogenation reaction (the catalyst comprises about 85% nickel, 10% aluminum, 2% chromium, and 2% iron). ). The catalyst was washed three times with water and three times with 3-dimethylaminopropylamine (Acros; contaminated with 72 ppm TMPDA by GC analysis), each wash consisting of mixed catalyst and material in a 100 L graduated cylinder, The catalyst was precipitated and 50 mL of the clear liquid at the top layer was poured still. The autoclave was then charged with 50 mL of catalyst, water and 3-dimethylaminopropylamine slurry. Additionally, 265 mL of 100% 3-dimethylaminopropylamine in water and 6 mL of 25 wt% caustic solution were charged. The caustic agent solution is a mixture comprising 50 wt% sodium hydroxide and 50 wt% potassium hydroxide. The stirrer was turned on and the autoclave was heated to 60 ° C. The autoclave was then washed three times with nitrogen and then three times with hydrogen before the autoclave was pressurized to a hydrogen pressure of 7.805 atm. The autoclave was then heated to 90 ° C., the pressure checked and maintained for 5 minutes.

3- (dimethylamino) propionitrile containing 0.04% by weight of water was started to feed the autoclave at a rate of 5 mL / min using a syringe pump. Throughout the process, pressure and temperature were maintained at 7.805 atm and 90 ° C., respectively. After 27 minutes, the feed was stopped and 150 g samples were extracted from the autoclave for analysis. Thereafter, the supply was resumed under the same conditions as before. This process was then repeated seven cycles altogether.

The reaction mixture was sampled after each cycle and analyzed for purity, reaction progress, and (if any) the presence and amount of by-products formed. For the purpose of quantifying the byproduct impurities, they were analyzed by gas chromatography (HP 5890 series II; Phenomenex Zebron ZB-1 capillary column, Phenomenex Cat.No. 7HK-G001-36) with flame ion detector.

[Table 1]: per cycle, product analysis

n-pa = n-propylamine

dap = 1,3-diaminopropane

dmapn = dimethylaminopropionitrile

tmpda = N, N, N ', N'-tetramethyl-1,3-propanediamine

2 ° amine = 3,3'-iminobis (N, N-dimethylpropylamine)

Table 1 shows that when DMAPN is hydrogenated using a sponge nickel catalyst and a Group IA alkali metal hydroxide in accordance with the method of the present invention, the amount of secondary amine is usually maintained at 300 ppm or less throughout the entire reaction process. The amount of TMPDA formed from impurities found in the feed of DMAPA used to prepare the catalyst slurry is reduced during the reaction process, as a result of which the final product does not contain this common and difficult to remove by-product.

As is evident from the data shown in Table 1, the product 3- (dimethylamino) propylamine is produced with a molar yield of 99.98%, with a purity of> 99%, with no TMPDA or other secondary amine impurities in the final product, 2 Primary amines are present at less than 300 ppm.

Example 3 Hydrogenation of DMAPN with Various Added Alkali Metal Hydroxides and Sponge Nickel

Using the same methods described in detail in Examples 1 and 2, a series of processes were performed to determine the effect of the various alkali metal hydroxide additions on the sponge nickel catalyst for the hydrogenation reaction. 50% by weight sodium hydroxide and 50% by weight potassium hydroxide caustic solution, as defined in Example 2, was replaced with an aqueous solution of alkali metal hydroxides of the concentrations shown in Table 2. After the reaction of the number of cycles shown in Table 2, samples were removed for gc analysis. The amount of remaining DMAPN and the amount of various secondary amine byproducts produced were recorded. Conditions and results are clearly shown in Table 2.

[Table 2] Effect of alkali metal hydroxides on activity and selectivity

* See Table 1 for abbreviations

By using alkali metal hydroxides such as KOH, CsOH, and mixtures of KOH / NaOH, high DMAPN conversions, such as low concentrations of DMAPN remain in the product DMAPA within a reasonable time, and also maintain high selectivity to primary amines The progress of the reaction is clearly shown in Tables 1 and 2. The use of LiOH (step 5) shows that the amount of by-products formed is not much improved by using the same catalyst as in the other tests. From these results, in order to maintain a high ratio of selectivity in the hydrogenation reaction of dimethylaminopropionitrile to dimethylaminopropylamine, mixtures of KOH, CsOH, and KOH / NaOH are most effective as alkali metal hydroxides.

All methods and processes disclosed herein and claimed in the claims can be made and executed without undue experimentation in light of the present specification. Although the methods of the present invention have been described in accordance with preferred embodiments, modifications may be made to the methods and / or processes, and steps or successive steps of the methods described herein, without departing from the spirit, scope, and scope of the invention. Will be apparent to those skilled in the art. More specifically, any chemically relevant reagents may be replaced with the reagents described herein so long as they achieve the same or similar results. All such similar substitutions or variations apparent to those skilled in the art are considered to be within the spirit, scope and concept of the invention.

Claims (15)

A process for preparing N, N-dimethylaminopropylamine from N, N-dimethylaminopropionitrile by low pressure hydrogenation, comprising the following steps: Providing hydrogen and N, N-dimethylaminopropionitrile to a low pressure reactor comprising a sponge nickel catalyst, at least one Group IA alkali metal hydroxide, and water to form a reaction medium; Heating the reaction medium to a temperature of about 70 ° C. to about 100 ° C .; Applying a pressure of about 45 psig to about 500 psig to the reactor; And Hydrogenation of the nitrile to form N, N-dimethylaminopropylamine. The method of claim 1 wherein the selectivity of N, N-dimethylaminopropionitrile to N, N-dimethylaminopropylamine is at least about 99.60%. The method of claim 1 wherein the selectivity of N, N-dimethylaminopropionitrile to N, N-dimethylaminopropylamine is at least about 99.90%. The method of claim 1 wherein the Group IA alkali metal hydroxide is selected from the group consisting of sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide and mixtures thereof. The method of claim 1 wherein the Group IA alkali metal hydroxide is potassium hydroxide. The method of claim 1 wherein the Group IA alkali metal hydroxide is sodium hydroxide. The method of claim 1 wherein the Group IA alkali metal hydroxide is a mixture of sodium hydroxide and potassium hydroxide. The method of claim 1, wherein the temperature is 85 ℃ to 95 ℃. The method of claim 1, wherein the pressure is 45psig ~ 300psig. The method of claim 1, wherein the pressure is 45psig ~ 150psig. The method of claim 1, wherein the pressure is 45psig ~ 110psig. The method of claim 1 wherein the amount of water is from about 0.1% to about 10% by weight of the reaction medium. A process for preparing N, N-dimethylaminopropylamine from N, N-dimethylaminopropionitrile by low pressure hydrogenation, comprising the following steps: Providing hydrogen and N, N-dimethylaminopropionitrile to a low pressure reactor comprising a catalyst, at least one Group IA alkali metal hydroxide, and water to form a reaction medium; Heating the reaction medium to a temperature of about 70 ° C. to about 100 ° C .; Applying a pressure of about 45 psig to about 150 psig to the reactor; And Hydrogenation of the nitrile to form N, N-dimethylaminopropylamine. The method of claim 13, wherein the catalyst is a sponge nickel catalyst. The method of claim 13, wherein the catalyst is a cobalt catalyst.