Organic compounds -- part of the class 532-570 series – Organic compounds – Nitriles
Reexamination Certificate
2001-02-09
2003-02-11
McKane, Joseph K. (Department: 1626)
Organic compounds -- part of the class 532-570 series
Organic compounds
Nitriles
C502S301000
Reexamination Certificate
active
06518449
ABSTRACT:
The present invention relates to a process for regenerating a hydrogenation catalyst, and to hydrogenation processes carried out with a catalyst comprising at least the regenerated catalyst.
The invention relates more particularly to a process for regenerating catalysts of Raney type used in processes for the total or partial hydrogenation of compounds comprising nitrile functions into amine functions.
The hydrogenation of compounds comprising nitrile functions into amine compounds has been carried out industrially for a long time.
Thus, hexamethylenediamine, a compound used in particular for the manufacture of polyhexamethyleneadipamide, also referred to as PA66 and known as “Nylon”, is manufactured industrially by hydrogenation of adiponitrile in the presence of a Raney nickel catalyst. This process is described in particular in U.S. Pat. No. 3,821,305. Other processes for hydrogenating nitrile or polynitrile compounds into amine compounds are described in U.S. Pat. Nos. 3,372,195, 2,287,219, 2,449,036, 3,565,957, 3,998,881, 4,188,146, 4,235,521, 4,254,059 and WO 95/17959.
These documents relate to the hydrogenation of various aliphatic, aromatic, substituted, unsaturated, etc. nitrile compounds.
These patents also relate to processes which are carried out in the presence of solvent, sodium hydroxide and ammonia. They are generally carried out with Raney-type catalysts such as Raney nickel or Raney cobalt.
The preparation of these Raney catalysts has been described for a long time, and in particular in U.S. Pat. No. 1,638,190 and in J.A.C.S. 54, 4116 (1932). A preparation process starting with nickel, molybdenum and aluminium alloy is described in U.S. Pat. No. 2,948,887.
Raney-type hydrogenation catalysts whose catalytic effect is improved by doping with other metal elements have also been proposed. For example, U.S. Pat. No. 4,153,578 describes a Raney nickel catalyst comprising molybdenum. This catalyst is used in particular for reducing aldehydes to alcohols.
Processes for hydrogenating polynitrile compounds by reduction of certain nitrile functions to give compounds comprising nitrile and amine functions have also been proposed. One application developed is the partial hydrogenation, known as the semi-hydrogenation, of aliphatic dinitriles such as adiponitrile into aminonitriles such as aminocapronitrile. Thus, U.S. Pat. No. 4,389,348 describes the semi-hydrogenation of dinitrile into &ohgr;-aminonitrile with hydrogen, in an aprotic solvent and ammonia medium and in the presence of rhodium deposited on a basic support. U.S. Pat. No. 5,151,543 describes the semi-hydrogenation of dinitriles into aminonitriles in a solvent in a molar excess of at least 2/1 relative to the dinitrile, comprising liquid ammonia or an alkanol containing a mineral base in the presence of a catalyst such as Raney nickel and Raney cobalt.
Similarly, patent application WO 93/16034 describes a process for the semi-hydrogenation of adiponitrile into aminocapronitrile in the presence of a Raney nickel catalyst, a base and a transition metal complex.
In the documents cited, the problem of reducing the consumption of catalyst, either by better recovery or by recycling, is not envisaged.
The recovery of the hydrogenation catalyst is envisaged in the case of complete hydrogenation by U.S. Pat. No. 4,429,159, which describes a process for pretreating Raney nickel catalyst with a carbonate to reduce the entrainment of this catalyst in the hexamethylenediamine flow. The catalyst thus recovered can be recycled after washing with water, as a mixture with fresh catalyst.
Processes for regenerating the catalysts used in semi-hydrogenation processes have also been described in patent applications WO 97/37964 and WO 97/37963. The catalysts are treated with a flow of nitrogen at a temperature of between 150° C. and 400° C., in the absence of any liquid or solvent. After regeneration by treatment with hydrogen, the catalysts are washed with water to neutral pH and optionally conditioned with liquid ammonia. These regeneration processes use a high-temperature treatment which can give rise to partial sintering of the catalyst. In addition, these processes do not make it possible to recover total catalytic activity, in particular when the process for hydrogenating the nitrile compounds is carried out in liquid medium, and more particularly in the presence of a basic compound.
One of the aims of the present invention is to propose a process for regenerating a hydrogenation catalyst of the Raney catalyst type which makes it possible to recover an activity substantially equivalent to that of a fresh catalyst.
To this end, the invention proposes a process for regenerating a catalyst of the Raney catalyst type for the total or partial hydrogenation of nitrile functions into amine functions on organic compounds, characterized in that it consists in mixing the spent catalyst, separated from the hydrogenation reaction medium, with an aqueous solution of a basic compound having an anion concentration of greater than 0.01 mol/l, in maintaining the mixture at a temperature below 130° C. and then in washing the treated catalyst with water or a basic aqueous solution until the final pH of the washing waters is between 12 and 13.
According to another preferred characteristic of the invention, the process for regenerating the catalyst can comprise a hydrogenation of this catalyst, carried out by treating the catalyst under a hydrogen atmosphere and at a temperature below 130° C.
According to the invention, the catalyst can be placed under a hydrogen atmosphere before maintaining the spent catalyst/basic solution mixture at the reaction temperature. In this case, the basic treatment and the hydrogenation of the spent catalyst are carried out simultaneously.
In another embodiment, the catalyst is hydrogenated before the step of mixing with the basic aqueous solution. Finally, it is also possible to subject the catalyst, treated with a basic solution and optionally washed, to the hydrogenation step.
From the point of view of cost-effectiveness and ease of implementation, the process consisting in simultaneously carrying out the treatment with a basic a solution and hydrogenation is preferred.
The various characteristics and definitions of the products or operating conditions described below are applicable to all the embodiments mentioned above.
The regeneration process of the invention can be carried out in batchwise or continuous mode.
The process of the invention allows a regeneration of the hydrogenation or semi-hydrogenation catalyst at low temperature, thus avoiding deterioration of the catalyst, more particularly a reduction in the doping effect of the metal elements contained in the Raney catalyst.
According to the invention, the catalysts which can be regenerated by the process described above are Raney-type catalysts such as, for example, Raney nickel and Raney cobalt. These catalysts can advantageously comprise one or more other elements, often referred to as dopants, such as, for example, chromium, titanium, molybdenum, tungsten, manganese, vanadium, zirconium, iron, zinc and more generally the elements from groups IIB, IVB, IIIB, VB, VIB, VIIB and VIII of the Periodic Table of the Elements. Among these dopant elements, chromium, iron and/or titanium or a mixture of these elements are considered as being the most advantageous and are usually present at a concentration by weight (expressed relative to the Raney nickel or Raney cobalt metal) of less than 10%, preferably less than 5%.
Raney catalysts often comprise traces of metals present in the alloy used to prepare the said catalysts. Thus, aluminium is especially present in these catalysts.
According to one preferred characteristic of the invention, the basic aqueous solution used to treat the catalyst is a solution of alkaline base or aqueous ammonia. The basic compound preferably has a high solubility in water.
Mention may be made of sodium hydroxide, potassium hydroxide, lithium hydroxide or caesium hydroxide as basic compounds that are suitable.
The concentration of an
Boschat Vincent
Leconte Philippe
Anderson Rebecca
Burns Doane Swecker & Mathis L.L.P.
McKane Joseph K.
Rhodia Fiber & Resin Intermediates
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