Organic compounds -- part of the class 532-570 series – Organic compounds – Nitriles
Reexamination Certificate
2003-03-10
2004-05-18
Tsang, Cecilia (Department: 1626)
Organic compounds -- part of the class 532-570 series
Organic compounds
Nitriles
Reexamination Certificate
active
06737540
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a selective hydrogenation process for producing aminonitriles in the presence of a fluoride additive.
BACKGROUND OF THE INVENTION
Aminonitriles are a class of important chemicals that have a variety of industrial applications. For example, aminonitriles can be used as monomers for producing high molecular weight polyamides. Specifically, 6-aminocapronitrile can be used to produce nylon 6.
Aminonitriles can be produced by catalytic partial hydrogenation of dinitriles. See, for example, U.S. Pat. No. 2,208,598, U.S. Pat. No. 2,257,814, U.S. Pat. No. 2,762,835, U.S. Pat. No. 3,322,815, U.S. Pat. No. 3,350,439, U.S. Pat. No. 3,591,618, U.S. Pat. No. 4,389,348, U.S. Pat. No. 4,601,859, U.S. Pat. No. 5,151,543, U.S. Pat. No. 5,296,628, U.S. Pat. No. 5,512,697,U.S. Pat. No. 5,527,946, U.S. Pat. No. 6,080,884, DE848654, DE-A-19636768 and WO99/47492 (corresponding to U.S. Pat. No. 6,080,884 and U.S. patent application Ser. No. 09/268,148, filed Mar. 15, 1999) all of which are incorporated by reference herein for all purposes as if fully set forth. However, the yield of and selectivity to a desired aminonitrile using some of the known processes may not be as high as desired, and the amount of the complete hydrogenation product (diamine) is also generally higher than desired.
WO99/47492 mentioned above describes the use of certain carbonyl group-containing compounds as additives in the partial hydrogenation process to improve the yield of and/or selectivity to the desired aminonitrile product, and/or reduce the amount of fully hydrogenated product (diamine) produced.
We have now found new classes of compounds that also effectively function as improved yield and/or selectivity additives in the partial hydrogenation processes such as, for example, those mentioned in previously incorporated WO99/47492.
SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention, there is provided a process for the partial hydrogenation of a dinitrile to an aminonitrile, comprising the step of contacting the dinitrile with a hydrogen-containing fluid in the presence of (a) a solvent comprising liquid ammonia, an alcohol, or both; (b) a hydrogenation catalyst; and (c) an additive comprising a fluoride compound.
In accordance with another aspect of the present invention, there is provided an improved process for preparing an aminonitrile from a corresponding dinitrile by contacting the dinitrile with a hydrogen-containing fluid in the presence of a solvent and a hydrogenation catalyst, wherein the improvement comprises contacting the dinitrile, hydrogen-containing fluid, solvent and hydrogenation catalyst in the further presence of an additive comprising a fluoride compound.
Another aspect of the present invention relates to a method for improving the yield of and/or selectivity to an aminonitrile obtained by partially hydrogenating a corresponding dinitrile with a hydrogen-containing fluid in the presence of a solvent and a hydrogenation catalyst, comprising the step of partially hydrogenating the dinitrile in the further presence of an effective amount of an additive comprising a fluoride compound.
In yet another aspect of the present invention, there is provided a catalyst composition comprising a combination of (1) a hydrogenation catalyst suitable for partially hydrogenating a dinitrile to an aminonitrile; and (2) an additive comprising a fluoride compound.
An advantage of this invention is that an aminonitrile can be produced in higher yield and/or having a higher selectivity to the aminonitrile with the fluoride additive than without. Other objects and advantages will become more apparent as the invention is more fully disclosed herein below.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
According to this invention, a dinitrile is contacted with a hydrogen-containing fluid in the presence of a solvent, a catalyst and the fluoride additive.
Suitable dinitriles for use herein have the general formula R(CN)
2
, wherein R is a hydrocarbylene group selected from the group consisting of an alkylene, arylene, alkenylene, alkarylene and aralkylene group. One dinitrile or combinations of different dinitriles may be used. Preferred hydrocarbylene groups contain from 2 to 25, more preferably 2 to 15, and most preferably 2 to 10 carbon atoms per group. In other words, preferred dinitriles contain from 4 to 27, more preferably 4 to about 17, and most preferably 4 to 12, carbon atoms per dinitrile molecule. The preferred type of hydrocarbylene group is an alkylene group.
Examples of suitable dinitriles include, but are not limited to, adiponitrile; methylglutaronitrile; alpha,omega-butanedinitrile; alpha,omega-pentanedinitrile; alpha,omega-heptanedinitrile; alpha,omega-nonanedinitrile; alpha,omega-dodecanedinitrile; alpha,omega-pentadecanedinitrile; alpha,omega-icosanedinitrile; alpha,omega-tetracosanedinitrile; 3-methylhexanedinitrile; 2-methyl-4-methyleneoctanedinitrile; and combinations of two or more thereof.
Preferably the carbon atoms of the starting dinitrile are arranged in a branched or linear chain. Preferred examples are adiponitrile (hydrogenated to 6-aminocapronitrile), methylglutaronitrile (hydrogenated to two isomeric aminonitriles: 5-amino-
2-
methylvaleronitrile and 5-amino-4-methylvaleronitrile) and alpha,omega-dodecanedinitrile (hydrogenated to the corresponding aminonitrile). The preferred dinitrile is adiponitrile because its selective hydrogenation product, 6-aminocapronitrile, is a well-known monomer for polymerization applications.
Any hydrogen-containing fluid can be used in the invention as long as there is sufficient hydrogen in the fluid to selectively hydrogenate a dinitrile to an aminonitrile. The term “fluid” refers to liquid, gas or both. The hydrogen content in the fluid can range from 1 to 100%, preferably about 50 to about 100%, and most preferably 90 to 100% by volume. The presently preferred hydrogen-containing fluid is substantially pure hydrogen gas.
The molar ratio of hydrogen (in the hydrogen-containing fluid) to dinitrile is not critical as long as sufficient hydrogen is present to produce the desired aminonitrile. Hydrogen is generally used in excess. Hydrogen pressures are generally in the range of about 50 to about 2000 psig (about 0.45 to about 13.89 MPa), with from about 200 to about 1000 psig (about 1.48 to about 7.00 MPa) preferred.
Any solvent that comprises either liquid ammonia or an alcohol can be used in the invention. The concentration of liquid ammonia in the solvent can range from about 20 to about 100%, preferably about 50 to about 100%, and most preferably about 80% to about 100%, by weight of total solvent. A substantially pure liquid ammonia is preferred. However, if an alcohol is also present in the solvent, the concentration of ammonia can be adjusted based on the quantity of alcohol used, which is discussed in further detail below. The molar ratio of ammonia to dinitrile is preferably about 1:1 or greater, and is generally in the range of from about 1:1 to about 30:1, more preferably from about 2:1 to about 20:1.
Any alcohol that can facilitate the selected hydrogenation of a dinitrile to an aminonitrile can be used in this invention. Preferred are alcohols with 1 to 10, more preferably 1 to 4, carbon atoms per molecule. Examples of suitable alcohols include, but are not limited to, methanol, ethanol, propanol, isopropyl alcohol, butanol, isobutyl alcohol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, and combinations of two or more thereof. The most preferred alcohol (when used) is methanol. The alcohol can generally be present in the solvent in the concentration of from about 20 to about 100%, preferably about 30 to about 99%, by weight based on the total solvent weight.
Typically when an alcohol is use, the solvent further comprises a base that is substantially soluble in the solvent. The term “substantially” refers to “more than trivial”. Preferred bases are ammonia, an ammonium base or an inorganic base such as, for example, alkali metal oxides, alkaline earth metal o
E. I. Dupont de Nemours and Company
Sackey Ebenezer
Tsang Cecilia
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