KR101129878B1 - Use of Modifiers in a Dinitrile Hydrogenation Process - Google Patents

Abstract

Catalysts and quaternary ammonium hydroxide, cyanide, fluoride and thiocyanides; Quaternary phosphonium hydroxide; Carbon monoxide; And a hydrogenation of the dinitrile to produce aminocapronitrile and hexamethylenediamine, wherein the dinitrile is contacted with hydrogen in the presence of a modifier selected from the group consisting of hydrogen cyanide.

Modifiers, Dinitrile, Hydrogenation

Description

Use of Modifiers in a Dinitrile Hydrogenation Process

The present invention relates to hydrogenation of aliphatic dinitriles for the preparation of diamines and / or aminonitriles, for example hydrogenation of adiponitriles for the preparation of hexamethylenediamine and / or 6-aminocapronitrile.

Dinitrile is a common feedstock in the chemical, pharmaceutical, and agrochemical industries. These can be converted to diamines and / or aminonitriles which are used in the polymer intermediates, surfactants, chelating agents, and chemical synthetic intermediates or used as such materials via hydrogenation. As a specific example, adiponitrile may be converted to 6-aminocapronitrile and / or hexamethylenediamine by hydrogenation. Hexamethylenediamine is an intermediate in the preparation of nylon 6,6. 6-aminocapronitrile can be used as an intermediate in the preparation of nylon 6.

Typical methods for preparing hexamethylenediamine include hydrogenation of adiponitrile with reduced iron oxide or cobalt oxide catalysts at high pressures and temperatures. US 6110856 describes the use of cobalt and iron based catalysts in a hydrogenation process of adiponitrile to a mixture of aminocapronitrile and hexamethylenediamine. The process yields 37% aminocapronitrile at 75% adiponitrile conversion and thus does not produce aminocapronitrile with high selectivity. Low pressure processes are known for the simultaneous preparation of aminocapronitrile and hexamethylenediamine. US 5,151,543 describes the hydrogenation of dinitriles, including adiponitrile in the presence of a solvent. US 6,258,745, US 6,566,297, US 6,376,714, WO 99/47492 and WO 03/000651 A2 all describe the hydrogenation of dinitriles to aminonitriles in the presence of a low pressure, ie, a selector for reactions below about 13.89 MPa (2000 psig).

For the simultaneous preparation of aminonitrile and diamine, it would be advantageous to use commercial equipment currently used for the preparation of hexamethylenediamine and operating at high pressure, ie, above 13.89 MPa (2000 psig). It would also be advantageous to operate these methods with increased selectivity to aminocapronitrile than is possible under operating conditions known in the art.

Summary of the Invention

Thus, the present invention is a dinitrile hydrogenation process for the simultaneous preparation of aminocapronitrile and hexamethylenediamine, which process treatment of dinitrile with hydrogen in the presence of a catalyst and a modifier at a pressure of at least about 15.27 MPa (2200 psig) Wherein the catalyst comprises an element selected from the group consisting of Fe, Ru, Co, and Ni, wherein the modifier is quaternary ammonium hydroxide, quaternary ammonium cyanide, quaternary ammonium fluoride, quaternary ammonium thiocyanate, At least one element selected from the group consisting of quaternary phosphonium hydroxide, carbon monoxide, and hydrogen cyanide.

In the present invention, aliphatic or alicyclic dinitriles can be hydrogenated to diamines or mixtures of diamines and aminonitriles using a catalyst at pressures above 15.27 MPa (2200 psig). For example, adiponitrile can be hydrogenated with hexamethylenediamine or a mixture of hexamethylenediamine and 6-aminocapronitrile. The process uses one or more modifiers to maintain or enhance the selectivity of the process for making aminonitriles. These modifiers may react with the catalyst surface or may modify the reactivity of dinitrile and / or aminonitrile. Modifiers may include hydroxide, cyanide, fluorinated or thiocyanated quaternary ammonium salts, or quaternary hydroxide phosphonium salts or carbon monoxide or hydrogen cyanide. In particular, the modifiers of the present invention are not expected to accumulate in the incinerator refractory bricks upon removal of these or their decomposition products from the crude product obtained from the above-mentioned dinitrile hydrogenation, or anticipate that they will require disposal through deep wells. It doesn't work.

Suitable aliphatic or cycloaliphatic dinitriles for use herein have the general formula R (CN) ₂ , wherein R is a saturated hydrocarbylene group. Saturated hydrocarbylene groups contain carbon and hydrogen atoms in a branched or straight chain or in a ring and do not include double or triple bonds between any pair of carbon atoms. Preferred hydrocarbylene groups contain 2 to 25, more preferably 2 to 15, and most preferably 2 to 10 carbon atoms per group. In other words, preferred dinitriles comprise 4 to 27, more preferably 4 to about 17, and most preferably 4 to 12 carbon atoms per dinitrile molecule. Preferred types of hydrocarbylene groups are linear alkylene groups.

Examples of suitable dinitriles include adiponitrile; Methylglutaronitrile; Succinonitrile; Glutaronitrile; Alpha, omega-heptanedinitrile; Alpha, omega-octanedinitrile, alpha, omega-decanedinitrile, alpha, omega-dodecanedinitrile; And combinations of two or more thereof. Preferred embodiment is adiponitrile (ADN).

The catalyst in the process is a suitable hydrogenation catalyst for hydrogenating dinitrile to diamines or mixtures of diamines and aminonitriles. Preference is given to catalysts based on iron, cobalt, nickel, or ruthenium and combinations thereof which may be present as metals or metal compounds. Most preferred are catalysts comprising iron. The catalytic element may comprise about 1 to 99%, preferably about 50 to 85 wt%, of the total catalyst weight. The catalyst may also include one or more promoters selected from the group consisting of aluminum, silicon, titanium, vanadium, magnesium, chromium, sodium, potassium and manganese. The promoter may be present at a concentration of about 15% or less, preferably about 0.05 to 2 wt%, based on the total catalyst weight.

The degree of beneficial effect of the present invention may vary depending on the structure of the dinitrile, the identity of the catalytic elements, and the identity of the modifiers, but it is understood that even a small improvement in selectivity can have a significant economic impact in large industrial processes. It is important.

The catalytic element can also be supported on inorganic supports such as alumina, magnesium oxide, and combinations thereof. The element may be supported on the inorganic support by certain means known to those skilled in the art, such as, for example, impregnation, coprecipitation, ion exchange, and combinations of two or more thereof. When the catalytic element is supported on an inorganic support or is a component of an alloy or solid solution, the catalytic element is generally present in the range of about 0.1 to about 60 wt% and preferably about 1 to about 50 weight percent based on the total catalyst weight. do.

The catalyst may be present in any suitable physical shape or form. It may be in flowable form, extrudates, tablets, spheres, or a combination of two or more thereof. When using a method using a fixed bed catalyst, the catalyst is in the form of granules having a particle size in the range of about 0.76 to 10.2 mm (0.03 to 0.40 inch). When using a slurry-phase catalyst, the catalyst is in finely divided form, preferably less than about 100 μm in size and most preferred range is from 20 to 75 μm.

The molar ratio of catalyst to dinitrile can be any ratio as long as the ratio can catalyze the selective hydrogenation of dinitrile. The weight ratio of catalyst to dinitrile is generally in the range of about 0.0001: 1 to about 1: 1, preferably about 0.001: 1 to about 0.5: 1.

The modifier of the present invention may be selected from the group consisting of quaternary ammonium hydroxide, quaternary ammonium cyanide, quaternary ammonium fluoride, quaternary ammonium thiocyanate, quaternary phosphonium hydroxide, carbon dioxide and hydrogen cyanide. The term quatern describes a nitrogen or phosphorus atom having four bonds to the atom and having a formal charge of +1. Ammonium ions (NH ₄ ⁺ ) and tetraalkylammonium ions are included within the definition of quaternary ammonium. One or more modifiers may be used in the reaction. Examples of suitable modifiers are tetramethylammonium hydroxide, tetrabutylammonium cyanide, tetraethylammonium fluoride, tetrabutylammonium thiocyanate and tetrabutylphosphonium hydroxide. Preferred modifiers are quaternary ammonium hydroxide and quaternary ammonium cyanide. Examples of suitable tetraalkylammonium hydroxide compounds are tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide and tetrabutylammonium hydroxide. Examples of suitable tetraalkylammonium cyanide compounds are tetramethylammonium cyanide, tetraethylammonium cyanide and tetrabutylammonium cyanide. It should be noted that various hydrated forms, such as, for example, tetramethylammonium hydroxide pentahydrate, are included within the meaning of tetraalkylammonium hydroxide and tetraalkylphosphonium hydroxide.

The hydrogenation reaction has a temperature of about 50 to 250 ° C., preferably about 90 to 180 ° C. and a total pressure including hydrogen of about 15.27 to 55.26 MPa (2200 to 8000 psig), preferably about 20.78 to 34.58 MPa (3000 to 5000 psig) It can be carried out at a pressure. In a preferred mode of operation, the process is carried out continuously in a continuous stirred tank reactor (CSTR), a plug flow reactor (PFR), a slurry bubble column reactor (SBCR), or a trickle bed reactor. Continuous stirred tank reactors, also known as backmix reactors, are vessels in which the reactants are added in a continuous manner and the flow of the product stream is continuously withdrawn from the reactor. Mix sufficiently in a vessel provided with a mixing device, for example a mechanical stirrer, so that the composition in the reactor is uniform and identical to that in the outgoing product stream. A plug flow reactor is a tubular reactor in which the reactants are added in a continuous manner at one end of the tubular reactor and the product flows out continuously from the other end of the tube. There is no backmixing, ie the composition inside the reactor tube is not uniform. It is possible to backmix in the PFR by recycling the product flow part back to the inlet of the reactor. It is also possible to achieve plug flow reactor behavior using multiple CSTRs in series. Slurry bubble column reactors are vessels in which the product flows continuously from the top of the reactor, while the liquid reactant and gas are continuously fed at the bottom of the reactor. The gas is present in the reactor with bubbles which rise while at the same time providing mixing with the solid powder catalyst (average particle size 20-200 μm). The catalyst can be removed continuously with the product and added continuously by addition with the liquid feed. The trickle bed reactor is a tubular reactor in which the catalyst is fixed while the reactants are added at the top of the reactor and flow to the bottom where the product is continuously discharged. The gaseous reactants may flow in the same direction as the liquid or may flow in the opposite direction from the bottom of the reactor to the top.

The choice for the reactor does not limit the invention and can also be carried out in batch mode.

The method can be operated in the absence or presence of a solvent. In the present invention, a solvent is defined as a substance added to the reaction mixture and contributing to solvating one or more reaction components, increasing the volume of the reaction mixture, providing a medium for the transfer (or removal) of the reaction heat, and the final product It is not incorporated into or alters the properties of the final product. The solvent list is ammonia; Amines such as triethylamine; Alcohols such as methanol, ethanol, propanol, and butanol; Ethers such as tetrahydrofuran and dioxane; Amides such as diethylacetamide and N-methylpyrrolidinone; And esters such as ethyl acetate and dimethyladipate. Preferred solvent is ammonia. The solvent may be present in the reaction mixture at about 20 to 90 weight percent, preferably about 30 to 50 weight percent.

The modifier and dinitrile can be introduced separately or as a solution premixed with diamine, aminonitrile, water, solvent or a specific combination thereof into the reactor comprising the catalyst. The modifier may be added in a weight ratio with dinitrile of about 1: 5000 to 1:30, preferably about 1: 2000 to 1: 500.

Yields of diamines and / or aminonitriles, such as hexamethylenediamine and / or 6-aminocapronitrile, may include operations including temperature, pressure, hydrogen flow rate, amount and type of catalyst, amount and modifier of modifier, etc. Depends on the condition For the purposes of the present invention, the term "space velocity" is defined as the unit weight of dinitrile fed into the reactor per hour, per unit weight of catalyst. Typically, dinitrile should be added to the reactor such that the space velocity of dinitrile is in the range of about 0.5 to 20 h ⁻¹ . The most preferred space velocity can be easily determined by one skilled in the art using the prior art.

While it is possible for the modifier to react with the elements of the catalyst forming the modifier / catalyst element complex, it does not mean that the present invention is limited by a particular theory. The resulting complex may contain Group VIII elements in the metal state or possibly in the oxidized state. The reaction of the modifier with the catalytic element may be irreversible but there may also be a reversible equilibrium reaction. The interaction of the modifier with the catalyst can alter the reactivity of the catalyst, improve the selectivity of aminonitrile preparation, inhibit secondary amine oligomer formation, and possibly increase the life of the catalyst.

The catalyst and modifier may be introduced separately into the reactor and contact with dinitrile, but the catalyst may be in contact with the modifier in advance. This can be done in water and / or a solvent, for example alcohol, ether, ester, ammonia, or a combination of two or more thereof.

The molar ratio of hydrogen to dinitrile is not critical as long as sufficient hydrogen is provided to prepare aminonitrile and / or diamines such as 6-aminocapronitrile and / or hexamethylenediamine. Hydrogen is generally used in excess.

Diamines and / or aminonitriles such as hexamethylenediamine and / or 6-aminocapronitrile can be recovered from the reaction product via conventional purification procedures such as recrystallization or preferably distillation. Unreacted dinitrile can be recycled back to the hydrogenation reactor to additionally obtain diamines and / or aminonitriles.

Hydrogenation of adiponitrile (ADN) is accomplished by first converting ADN to aminocapronitrile (ACN) followed by conversion of ACN to hexamethylenediamine (HMD), as shown in the following scheme. And the first stage has a rate constant 2k ₁ and the second stage has a rate constant k ₂ ).

ADN → ACN → HMD

The value k ₁ / k ₂ = 1 in this model describes a non-selective catalyst and the maximum yield of ACN will be 50% in a well mixed batch reaction. It is desirable to maximize the k ₁ / k ₂ value.

Comparative Example 1.

The 1-L stainless steel pressure vessel was filled with 216 g of adiponitrile and 20 g of powder, reduced iron catalyst. The vessel was sealed, purged with hydrogen and filled with 225 g of ammonia. It was heated to 150 ° C. and pressurized to 4500 psig (31 MPa). As hydrogen was consumed, hydrogen was constantly replenished from the pressurized cylinder to maintain an operating pressure of 4500 psig (31 MPa). After 70 minutes the reaction was stopped and the sample was analyzed by gas chromatography. The analysis showed that the reaction product contained 12 wt% adiponitrile (ADN), 45 wt% 6-aminocapronitrile (ACN), and 36 wt% hexamethylenediamine. The k ₁ / k ₂ value was 1.1.

Examples 2-4.

The experiment of Example 1 was repeated except that 0.2 g of modifier agent was added to the reaction mixture with ADN. The results are shown in Table 1. TBACN = tetrabutylammonium cyanide, TEAF = tetraethylammonium cyanide, TMAHP = tetramethylammonium hydroxide pentahydrate.

Claims (7)

Group consisting of iron-containing catalyst and quaternary ammonium hydroxide, quaternary ammonium cyanide, quaternary ammonium fluoride, quaternary ammonium fluoride, quaternary phosphonium hydroxide, and hydrogen cyanide at pressures above about 15.27 MPa (2200 psig) A method of dinitrile hydrogenation for the simultaneous preparation of aminonitrile and diamine, comprising contacting dinitrile with hydrogen in the presence of a modifier that is at least one element selected from, wherein selectivity of aminonitrile is preferred over diamine. The method of claim 1 wherein the temperature is in the range of about 50 ° C. to 250 ° C. 7. The method of claim 1, wherein the pressure is in the range of about 20.7 to 34.5 MPa (3000 to 5000 psig). delete The method of claim 1 wherein the modifier comprises quaternary ammonium cyanide or quaternary ammonium hydroxide salts. The method of claim 1 wherein the dinitrile is adipononitrile. A method of simultaneously producing an aminonitrile and a diamine by hydrogenating dinitrile in the presence of a catalyst and a modifier at a pressure of at least about 15.27 MPa (2200 psig), wherein the catalyst comprises iron and the modifier is quaternary ammonium hydroxide, 4 cyanide. At least one element selected from the group consisting of quaternary ammonium, quaternary ammonium fluoride, quaternary ammonium thiocyanate, quaternary phosphonium hydroxide, and hydrogen cyanide, whereby the selectivity of aminonitrile is preferred over diamine Way.