Improved catalytic method for the reductive amination of poly(oxytetramethylene) glycols

Abstract: Poly(oxytetramethylene) diamines having the formula: H₂N-CH₂-CH₂-CH₂-CH₂-[-O-CH₂-CH₂-CH₂-CH₂-] n -O-CH₂-CH₂-CH₂-CH₂-NH₂ wherein n is 0 or 1 to 50, can be obtained in good yield and selectivity by the reductive amination of a poly(oxytetramethylene) glycol having the formula: HO-CH₂-CH₂-CH₂-CH₂-[-O-CH₂-CH₂-CH₂-CH₂-] n -O-CH₂-CH₂-CH₂-CH₂-OH wherein n is 0 to 50, when using a catalyst comprising, on an oxide-free basis, from 70 to 78 wt.% of nickel, 20 to 25 wt.% of copper, 0.5 to 5 wt.% of chromium, and 1 to 5 wt.% of molybdenum.

Description: This invention relates to a method for the catalytic reductive amination of a poly(oxytetramethylene) glycol in order to provide the corresponding poly(oxytetramethylene) diamine in high yield and with good selectivity. More particularly, this invention relates to an improvement in the method for the catalytic reductive amination of a poly(oxytetramethylene) glycol in the presence of hydrogen and ammonia under reductive amination conditions wherein the reaction is conducted in the presence of a catalyst composed of nickel, copper, chromium and molybdenum and containing, on an oxide-free basis, about 70 to about 78 wt.% of nickel, about 20 to about 25 wt.% of copper, about 0.5 to 5 wt.% of chromium and about 1 to 5 wt.% of molybdenum. Still more particularly, this invention relates to a process wherein a poly(oxytetramethylene) glycol, excess ammonia and hydrogen are passed through a bed of a pelleted nickel, copper, chromium, molybdenum catalyst on a continuous basis in order to continuously provide a reaction product comprising the poly(oxytetramethylene) diamine corresponding to the poly(oxytetramethylene) glycol feedstock. Methods for the preparation and use of poly(oxytetramethyl) glycols are disclosed in Smith et al. U. S. Patents No. 3,824,198, No. 3,824,219, and No. 3,824,220, patented July 16, 1974. Other patents disclosing methods for making and using poly(oxytetramethyl) glycols and poly[oxytetramethyl) diamines include Ubin et al. U. S. Patent No. 3,436,359 patented April 1, 1969 and Leir et al. U. S. Patent No. 4,833,213, patented May 23, 1989. The catalyst to be used in conducting the process of the present invention is suitably a catalyst of the type disclosed in Moss et al. U. S. Patent No. 3,151,115 wherein reductive amination catalysts are disclosed containing nickel, cobalt and copper or mixtures thereof and chromium oxide, molybdenum oxide, manganese oxides thorium oxide and mixtures thereof. The preferred catalyst disclosed by Moss et al. is a nickel, copper, chromia catalyst containing, on an oxide-free basis, from about 70 to 75 wt.% of nickel, about 20 to about 25 wt.% of copper and about 1 to about 5 wt.% of chromium. Renken et al. U. S. Patent No. 4,618,717, issued October 21, 1986 is directed to a method for reductively aminating ethylene glycol monoalkyl ethers in order to provide the corresponding primary amines using a catalyst composed of about 50 to 90 wt.% of nickel, about 10 to 50 wt.% of copper and about 0.5 to 5 wt.% of an oxide of chromium, iron, titanium, thorium, zirconium, manganese, magnesium or zinc. Larkin et al. U. S. Patent No. 4,766,245, issued August 23, 1988 discloses a method for reductively aminating polyoxyalkylene diols and triols in the presence of a Raney nickel/aluminum catalyst. This invention relates to a method for preparing poly(oxytetramethylene) diamines. Poly(oxytetramethylene) diamines are useful for the preparation of polyamide and polyurea elastomers. The poly(oxytetramethylene) diamines are conveniently prepared from the corresponding poly(oxytetramethylene) glycols, commonly referred to as polytetrahydrofuran glycols. However, when the poly(oxytetramethylene) diamines are prepared by catalytic reductive amination of the corresponding poly(oxytetramethylene) glycols, using hydrogenation/dehydrogenation catalysts, and in particular, nickel hydrogenation/dehydrogenation catalysts, problems are normally encountered in obtaining both a good yield and a good selectivity in converting the poly(oxytetramethylene) glycol to the desired poly(oxytetramethylene) diamine product. These and other problems are overcome in accordance with the present invention by conducting the reductive amination reaction in the presence of a catalyst composed of nickel, copper, chromium and molybdenum and containing, on an oxide-free basis, from about 70 to 78 wt.% of nickel, about 20 to about 25 wt.% of copper, about 0.5 to about 5 wt.% of chromium and about 1 to about 5 wt.% of molybdenum. The starting materials for the present invention are a nickel, chopper, chromia, molybdenum catalyst which may suitably be a powdered catalyst if the reaction is to be conducted in an autoclave on a batch basis or a pelleted catalyst if the reaction is to be conducted on a continuous basis in a continuous reactor. Also used as starting materials are ammonia, hydrogen and a poly(oxytetramethylene) glycol such as a poly(oxytetramethylene) glycol having the following formula: HO-CH₂-CH₂-CH₂-CH₂-[-O-CH₂-CH₂-CH₂-CH₂-] n -O-CH₂-CH₂-CH₂-CH₂-OH (I) wherein n represents 0 or a positive number having a value of 1 to about 50. In accordance with the present invention, a poly(oxytetramethylene) glycol feedstock is substantially quantitatively converted to the corresponding poly(oxytetramethylene) diamine with excellent yields and selectivities when the reaction is conducted in the presence of a catalyst composed of from about 70 to about 78 wt.% of nickel, about 20 to about 25 wt.% of copper, about 0.5 to about 5 wt.% of chromium and about 1 to about 5 wt.% of molybdenum. More particularly, an especially preferred catalyst composition of the present invention is one containing from about 70 to about 75 wt.% of nickel, about 20 to about 25 wt.% of copper, about 0.5 to about 3 wt% of chromium, and about 1 to about 3 wt.% of molybdenum. The reductive amination reaction of the present invention is suitably conducted at a temperature within the range of about 150° to about 220°C. and a pressure of about 100 to about 10,000 psig. (0.8 to 69 MPa), such as a pressure of about 100 to about 3,000 psig (0.8 to 20.8 MPa). The reductive amination is conducted in the presence of ammonia. Suitably, from about 1 to about 300 moles of ammonia per mole of poly(oxytetramethylene) glycol are employed, and more preferably, from about 10 to about 150 moles of ammonia are employed per mole of poly(oxytetramethylene) glycol. The reaction is also preferably conducted in the presence of added hydrogen. The amount of added hydrogen used may be about 0.1 to about 10 mole per mole of poly(oxytetramethylene) glycol. Preferably, from about 0.5 to about 80 mole of hydrogen per mole of poly(oxytetramethylene) glycol will be employed. The process of the present invention may be conducted batch-wise using an autoclave containing powdered catalyst, in which case the residence time is suitably from about 0.5 to about 5 hours. More preferably, the reaction is conducted on a continuous basis using a bed of pelleted catalyst through which the hydrogen, ammonia and poly(oxytetramethylene) glycol are passed. When the reaction is conducted on a continuous basis, the poly(oxytetramethylene) glycol is suitably charged to the catalyst bed at the rate of about 0.5 grams per hour of poly(oxytetramethylene) glycol per cc of catalyst. The reaction mixture formed as a result of the reductive amination of the poly(oxytetramethylene) glycol may be recovered and fractionated in any suitable manner, such as by fractional distillation, to obtain unreacted feed components, by-products and the desired poly(oxytetramethylene) diamine reaction product. Conversions of 90 wt.% or more and selectivities of 90% or more are obtainable with the process of the present invention, such that only minor quantities of unreacted feedstock and by-products are present in the reaction mixture. EXAMPLES The present invention will be further illustrated by the following specific examples. The nickel, copper, chromium, molybdenum catalyst used in conducting the batch and continuous experiments reported in the examples was a catalyst composed of about 75 wt.% of nickel, about 21 wt.% of copper, about 2 wt.% of chromium and about 2 wt.% of molybdenum. In Example 1, which was conducted in an autoclave, the catalyst was powdered. In the subsequent examples, which were conducted on a continuous basis in a continuous reactor, a bed of pelleted catalyst was employed. Example 1 A one-liter autoclave was charged with 299g of a 2000 molecular weight poly(oxytetramethylene) glycol, 48g of catalyst, and 90g of ammonia. The clave was then pressured to 350 psig (2.5 MPa) with hydrogen and heated over a 46-minute period to 220°C. It was held at that temperature for 3 hours. The reaction was then cooled and vented. The catalyst was removed by filtration and the product stripped at reduced pressure. The product had the following analysis: Total Acet. 0.847 meq/g Total Amine 0.688 meq/g Primary Amine 0.556 meq/g Example 2 A. In the following examples a tubular reactor filled with the Ni-Cu-Cr-Mo catalyst was used. Hydrogen, ammonia and the polyol (a 1000 molecular weight poly(oxytetramethylene) glycol) in the proportions of Example 1 were fed to the bottom of the reactor. The crude produced was then stripped under vacuum and analyzed. Ex. Temp °C Polyol SV Total Acet. meq/g Total Amine meq/g Primary Amine meq/g Total Amine % Primary Amine % 1 185 0.56 1.908 1.766 1.651 93 93 2 190 0.56 1.879 1.781 1.618 95 91 3 195 0.56 1.835 1.740 1.529 95 88 4 200 0.56 1.705 1.660 1.338 97 81 5 175 0.43 1.954 1.730 1.630 89 94 6 180 0.43 1.957 1.779 1.671 91 94 7 185 0.43 1.848 1.773 1.570 96 89 8 190 0.43 1.788 1.738 1.477 97 85 9 150 0.20 1.975 0.989 0.956 50 97 10 155 0.20 1.944 1.419 1.347 73 95 11 160 0.20 2.000 1.564 1.523 78 97 12 165 0.20 2.000 1.773 1.709 89 96 13 170 0.20 1.952 1.838 1.729 94 94 14 175 0.20 1.830 1.814 1.625 99 90 15 180 0.20 1.751 1.767 1.511 101 86 As can be seen in examples 1, 2, 6, 13 and 14, high total amine content as well as high primary amine content can be obtained by the process of the present invention. The examples also show that a variety of space velocities can be used and that for each space velocity there is an optimum temperature. B. This is a comparison example conducted under the conditions of Example 2A, except as noted. In this example, Raney Ni was used as the catalyst and a 1000 molecular weight polyol was used. Temp. °C Polyol Space Velocity Total Acet. meq/g Total Amine meq/g Primary Amine meq/g Total Amine % Primary Amine % 180 0.28 1.911 1.577 1.286 83 82 175 0.28 1.900 1.550 1.260 82 81 185 0.28 1.609 1.549 1.172 96 76 190 0.20 1.536 1.512 1.104 98 73 None of the reaction conditions gave high total amine content and high primary amine content. C. In this example conducted under the conditions of Example 1A, except as noted, a 650 molecular weight polyol and the catalyst in example A were used. Temp. °C Polyol Space Velocity Total Acet. meq/g Total Amine meq/g Primary Amine meq/g Total Amine % Primary Amine % 155 0.20 2.849 2.083 2.028 73 97 160 0.20 2.840 2.444 2.334 86 95 165 0.20 2.708 2.559 2.363 94 92 170 0.20 2.662 2.541 2.223 95 87 At 165°C. a product high in both total and primary amine was obtained. D. In this example, conducted under the conditions of Example 1A, except as noted, a 2000 molecular weight polyol and the catalyst in example A were used: Temp. °C Polyol Space Velocity Total Acet. meq/g Total Amine meq/g Primary Amine meq/g Total Amine % Primary Amine % 160 0.20 0.927 0.818 0.792 88 97 165 0.20 0.906 0.845 0.805 93 95 170 0.20 0.933 0.846 0.779 91 92 155 0.20 0.948 0.753 0.737 79 98 At 170°C., a product high in both total amine and primary amine was obtained. E. This is a comparison example conducted under the conditions of Example 1A, except as noted. In this example a Ni-Cu-Cr catalyst was used and a 1000 molecular weight polyol was used. Temp. °C Polyol Space Velocity Total Acet. meq/g Total Amine meq/g Primary Amine meq/g Total Amine % Primary Amine % 160 0.20 1.835 1.314 1.144 72 87 165 0.20 1.773 1.358 1.147 77 84 170 0.20 1.723 1.411 1.165 82 83 175 0.20 1.686 1.458 1.178 86 80 180 0.20 1.67 1.461 1.163 87 80 High amination and high primary amine content were not obtained with this catalyst.

Claims: A method for the production of a poly(oxytetramethylene) diamine having the formula: H₂N-CH₂-CH₂-CH₂-CH₂-[-O-CH₂-CH₂-CH₂-CH₂-] n -O-CH₂-CH₂-CH₂-CH₂-NH₂ wherein n is 0 or 1 to 50 by the reductive amination of a poly(oxytetramethylene) glycol in the presence of a catalyst, hydrogen and ammonia characterized by reacting a poly(oxytetramethylene) glycol having the formula: HO-CH₂-CH₂-CH₂-CH₂-[-O-CH₂-CH₂-CH₂-CH₂-] n -O-CH₂-CH₂-CH₂-CH₂-OH wherein n is 0 or 1 to 50, in the presence of a catalyst comprising, on an oxide-free basis, from 70 to 78 wt.% of nickel, 20 to 25 wt.% of copper, 0.5 to 5 wt.% of chromium, and 1 to 5 wt.% of molybdenum. A method according to Claim 1 characterized in that the catalyst comprises, on an oxide free basis, from 70 to 75 wt.% of nickel, 20 to 25 wt.% of copper, 0.5 to 3 wt.% of chromium, and 1 to 3 wt.% of molybdenum. A method according to Claim 1 or 2 characterized in that the catalytic reductive amination is carried out at a temperature of 150 to 220°C. and a pressure of 100 to 10,000 psig. (0.8 to 69MPa). A method according to any one of Claims 1 to 3 characterized in that the poly(oxytetramethylene) glycol, ammonia and hydrogen are passed through a bed of the catalyst in pelletized form at a space velocity of 0.1 to 20 grams per hour of poly(oxytetramethylene) glycol, per cm³ of catalyst.

Inventors: LARKIN JOHN MICHAEL, ZIMMERMAN ROBERT LEROY, LARKIN, JOHN MICHAEL, ZIMMERMAN, ROBERT LEROY
Applicants: HUNTSMAN CORP, HUNTSMAN CORPORATION
Application year: 1990
Main classification: C08G65
IPC codes: C08G65, B01J23, C07C213, C07C217, C07B61