Organic compounds -- part of the class 532-570 series – Organic compounds – Amino nitrogen containing
Reexamination Certificate
2001-11-07
2004-01-13
Davis, Brian (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Amino nitrogen containing
C564S415000, C564S491000, C564S492000, C564S493000, C502S301000
Reexamination Certificate
active
06677486
ABSTRACT:
The present invention relates to a process for hydrogenating nitrites to primary amines over an activated macroporous Raney catalyst, to a process for producing the Raney catalysts and to the Raney catalysts themselves.
It is known that nitrites and iminonitriles can be hydrogenated in the liquid phase over Raney catalysts.
EP-A-0 382 508 describes the semicontinuous hydrogenation of polynitriles in the liquid phase over Raney cobalt catalysts in the presence of anhydrous ammonia.
U.S. Pat. No. 5,869,653 describes a continuous process for hydrogenating nitrites over Raney cobalt catalysts in the absence of ammonia, which is carried out in the presence of catalytic amounts of lithium hydroxide and water.
U.S. Pat. No. 4,895,994 discloses a Raney catalyst having a BET surface area of from 20 to 80 m
2
/g and a proportion of macropores of from 0.01 to 70% by volume, based on the total pore volume, which is produced by mixing the Raney alloy with a high molecular weight polymer, shaping the mixture to form a shaped body, calcining the composition firstly at from 300 to 700° C. and subsequently at from 850 to 1200° C. in the presence of oxygen and leaching aluminum from the calcined shaped body by treatment with 6 N NaOH at from 90 to 100° C. The catalyst which has been activated in this way is subsequently washed repeatedly with water until the pH of the washings is <9. The Raney catalyst is used, inter alia, for hydrogenating nitrites to amines.
EP-A-0 842 699 discloses a process for producing an activated, metal powder-free, macroporous fixed-bed metal catalyst of the Raney type based on an alloy of aluminum and at least one metal of transition group VIII of the Periodic Table, which comprises the steps (1) preparing a kneadable composition comprising the alloy, a shaping aid, water and a pore former, (2) shaping the kneadable composition to give a shaped body, (3) calcining the shaped body and (4) treating the calcined shaped body with an alkali metal hydroxide. After treatment of the shaped body with alkali metal hydroxide, the activated catalyst is washed with water until the pH of the washings has dropped to 7.5. The catalyst obtained in this way has a macropore content of more than 80% by volume. The catalyst is used for hydrogenating nitrites to primary amines.
Such a process is also disclosed in DE-A 44 46 907, in which polyvinyl alcohol and water or stearic acid are used as auxiliaries.
A disadvantage of the Raney catalysts of the prior art is that they have aluminum oxides and aluminum hydroxides having acidic and/or basic properties, e.g. Al(OH)
3
, AlOOH or &ggr;-Al
2
O
3
, on their surface and these can lead to secondary reactions in the hydrogenation of the nitrites. Examples of such secondary reactions are dissociation of the nitrile or an amine-imine condensation. Particularly for extender nitrites which are obtainable by addition of formaldehyde and hydrocyanic acid onto nucleophilic centers or Michael nitrites which are obtainable by addition of acrylonitrile onto nucleophilic centers, the hydrogenation has to be carried out under particularly gentle conditions since these nitrites are unstable and can be redissociated into their starting materials. In addition, some of the Raney catalysts described have a relatively low proportion of macropores, e.g. the catalysts described in U.S. Pat. No. 4,895,994, which has an adverse effect on mass transfer in the catalyst.
It is an object of the present invention to provide a process for the gentle hydrogenation of nitrites which displays high selectivity in respect of the formation of primary amines and in which secondary reactions such as dissociation of the nitrites are avoided.
We have found that this object is achieved by a process for hydrogenating nitrites to primary amines over an activated, alpha-Al
2
O
3
-containing, macroporous Raney catalyst based on an alloy of aluminum and at least one transition metal selected from the group consisting of iron, cobalt and nickel, and, if desired, one or more further transition metals selected from the group consisting of titanium, zirconium, chromium and manganese, which is obtainable by a process comprising the steps in the order (a)-(f):
(a) preparing a kneadable composition comprising the alloy, a shaping aid, water and a pore former;
(b) shaping the kneadable composition to form a shaped body;
(c) calcining the shaped body;
(d) activating the calcined shaped body by treatment with aqueous alkali metal hydroxide solution;
(e) rinsing the shaped catalyst body with aqueous alkali metal hydroxide solution;
(f) rinsing the shaped catalyst body with water.
The object is also achieved by a process for producing the macroporous Raney catalyst and by the macroporous Raney catalyst itself.
The production of the Raney catalyst used according to the present invention is described in more detail below.
According to the present invention, a kneadable composition is firstly prepared from an alloy of aluminum and at least one transition metal selected from the group consisting of iron, cobalt and nickel, and, if desired, one or more further transition metals selected from the group consisting of titanium, zirconium, chromium and manganese, a shaping aid, water and a pore former. Preferred transition metals are nickel and cobalt, and particular preference is given to solid solutions of nickel in cobalt or of cobalt in nickel in which the dissolved metal is present in a concentration of from 0.05 to 50% by weight. To increase the activity and selectivity, the alloy may further comprise at least one additional transition metal selected from the group consisting of titanium, zirconium, chromium and manganese as promoter, generally in concentrations of from 0.01 to 15% by weight, preferably from 0.05 to 5% by weight, based on the total amount of transition metals. The weight ratio of aluminum to transition metals is generally in the range from 30 to 70% by weight of aluminum and from 30 to 70% by weight of transition metal.
The aluminum alloy is produced in a manner known per se, for example as described in DE 21 59 736, whose contents relating to the production of alloys of aluminum and the specified transition metals is hereby incorporated by reference into the present application.
As shaping aids, it is possible to use all shaping aids used in the prior art as are mentioned, for example, in the U.S. Pat. Nos. 4,826,799 and 4,895,994. Preference is given to using waxes such as wax C micropowder PM from HOECHST AG, fats such as magnesium or aluminum stearates, or carbohydrate-containing polymers such as Tylose (methylcellulose); particular preference is given to using stearic acid and Tylose. The amount of shaping aid present in the kneadable composition is generally from about 0.1 to about 3% by weight, preferably from about 0.2 to about 2% by weight, more preferably from about 0.5 to about 1% by weight.
As pore formers, it is possible to use any polymers which have a molar mass of from greater than 6000 to about 500,000 g/mol. Their molar mass is preferably from about 10,000 to about 200,000 g/mol, more preferably from about 13,000 to about 150,000 g/mol and in particular from about 13,000 to about 50,000 g/mol.
Examples of polymers which can be used as pore formers in the process of the present invention are polyvinyl chloride, copolymers of an olefin with polar comonomers, e.g. ethylene or propylene with polyvinyl chloride, polyvinylidene chloride copolymers, ABS polymers, polyethylene copolymers with vinyl acetate, alkylacrylates, acrylic acid, chlorinated polyethylenes, chlorosulfonated polyethylenes, thermoplastic polyurethanes, polyamides such as nylon-5, nylon-12, nylon-6/6, nylon-6/10, nylon-11, fluorine-containing plastics such as FEP, polyvinylidene fluoride, polychlorotrifluoroethylene, acrylonitrile-methyl (meth)acrylate copolymers, acrylonitrile-vinyl chloride copolymers, styrene-acrylonitrile copolymers, methacrylonitrile-styrene copolymers, polyalkyl (meth)acrylates, cellulose acetate, cellulose acetate butyrate, polycarbonates, polysulfones, polyphenylene oxide, polye
Ansmann Andreas
Benisch Christoph
Funke Frank
Merger Martin
Ohlbach Frank
BASF - Aktiengesellschaft
Davis Brian
Keil & Weinkauf
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