Organic compounds -- part of the class 532-570 series – Organic compounds – Unsubstituted hydrocarbyl chain between the ring and the -c-...
Reexamination Certificate
2001-06-04
2002-11-12
Solola, T. A. (Department: 1626)
Organic compounds -- part of the class 532-570 series
Organic compounds
Unsubstituted hydrocarbyl chain between the ring and the -c-...
C540S534000
Reexamination Certificate
active
06479658
ABSTRACT:
The invention relates to a process for the cyclizing hydrolysis of an aminonitrile compound into a lactam in the presence of a catalyst.
The invention relates more particularly to a process for the cyclizing hydrolysis of an aminonitrile compound in the presence of a macroporous particulate catalyst obtained by deposition/impregnation or adsorption of an oxidized compound onto a macroporous support.
Lactams, such as &egr;-caprolactam, are base compounds for the manufacture of polyamides and in particular PA 6.
Among the various known processes for synthesizing these lactams, one of the processes is the cyclizing hydrolysis of the corresponding aminonitrile, and more particularly of a corresponding aliphatic aminonitrile, in the presence of water and a catalyst.
Thus, U.S. Pat. No. 2,357,484 describes a process for the vapour-phase preparation of lactam, with activated alumina, silica in gel form or borophosphoric acid as catalyst.
U.S. Pat. No. 4,628,085 also describes a process for preparing lactams by vapour-phase cyclizing hydrolysis in the presence of a silica-based catalyst with a specific surface of greater than 250 m
2
/g. This reaction is performed in the presence of hydrogen and ammonia.
Patent application WO 98/0669 proposes catalysts based on hydrated or non-hydrated metal oxides, the metals being chosen from the group comprising tin, zirconium, hafnium, bismuth, vanadium, niobium and tantalum or mixtures thereof. These catalysts are of bulk type and have no macroporosity. Their cycle time is very short and incompatible with an industrial exploitation of the lactam manufacturing process.
a process for the vapour-phase cyclizing hydrolysis of aminonitrile using, as catalyst, an alumina which has domains of determined specific surface and pore volume.
The lactams produced are generally used for the manufacture of polymer, such as, for example, &egr;-caprolactam for the manufacture of PA 6. The applications of these polymers are many and varied.
However, one of the most important applications is the manufacture of yarns, filaments or fibres in particular for the textile industry.
These varied applications, and in particular the one described above, require the use of a polyamide which has very specific physicochemical and chemical properties. To obtain such properties, it is necessary to synthesize these polymers from monomers or lactams which also have very strict purity properties.
Thus, the caprolactam must generally satisfy the following specifications:
permanganate index (according to ISO standard 8660): <5
free bases: <0.1 milliequivalent (meq)/kg of CPL
volatile bases (according to ISO standard 8661): <0.5 meq/kg
UV absorbance at 290 nm (according to ISO standard 7059): <0.05
To obtain these specifications, it is necessary to carry out complex purification processes. Such processes have many economic drawbacks, in particular large energy consumption and heavy investment in materials.
One of the reasons for the need to purify the crude lactam produced by the known processes is the presence of side reactions which arise in particular during the step of cyclizing hydrolysis of the aminonitrile.
To avoid these side reactions, it is thus necessary for the catalyst to promote the main reaction of formation of the lactam. This property of the catalyst can be illustrated by the selectivity of the process towards crude lactam. The quality of crude lactam can also be assessed by titrating it with an aqueous 0.2 N potassium permanganate solution (permanganate index).
In addition, in order for the purity of the crude lactam produced to be high and continuous, it is necessary for the level of selectivity of the catalyst to be conserved throughout the catalyst's cycle time.
The aluminas proposed in the Applicant's patent application WO 96/22974 represents the start of a solution to this problem by proposing a highly active and selective catalyst which has a long cycle time.
However, it appears necessary to further improve the performance levels of the catalysis for the cyclizing hydrolysis of lactams, in order to improve the initial selectivity of the catalyst as well as the purity of the crude lactam, while at the same time maintaining this high level throughout the catalyst's cycle time.
One of the aims of the present invention is to propose a solution for improving the catalysis for the cyclizing hydrolysis of aminonitriles, and in particular the selectivity of this catalysis to produce a crude lactam in a high degree of purity. Thus, the crude lactam produced can be used for the manufacture of polymer with high chemical and physicochemical properties, after carrying out a purification process which is simpler and more economical than those currently used.
The expression “crude lactam” refers to the product from the cyclizing hydrolysis reaction after removal of the ammonia and any solvents such as water, for example.
The expression “purified lactam” denotes the lactam obtained by purification of the crude lactam.
To this end, the invention proposes a process for the cyclizing hydrolysis of an aminonitrile compound into a lactam by reaction of an aminonitrile of general formula (I) below:
N≡C—R—NH
2
(I)
in which:
R represents a substituted or unsubstituted aliphatic, cycloaliphatic or arylaliphatic radical comprising from 3 to 12 carbon atoms, with water, in the presence of a solid catalyst, characterized in that the catalyst is a particulate catalyst obtained by deposition and/or adsorption of at least one oxygenated compound of at least one element chosen from the group consisting of the elements belonging to groups 1 to 16 of the universal classification of the elements (new classification), this list also including rare-earth metals, on a particulate support made of simple or mixed inorganic oxide of at least one element chosen from the group consisting of silicon, aluminium, titanium, zirconium, vanadium, niobium, tantalum, tungsten, molybdenum, iron and rare-earth metals, or by mixing together at least one of the said oxygenated compounds or a precursor of the said oxygenated compounds with the inorganic oxide(s) forming the support before shaping them.
According to the invention, the particulate catalyst comprises at least one macroporosity characterized by a pore volume, corresponding to pores greater than 500 Å in diameter, of greater than or equal to 5 ml/100 g.
This macroporosity is advantageously formed during the process for shaping the particles by the techniques described below, or like, for example, the addition of porogen.
The catalyst can be used in various forms, such as beads, grindings, extrudates in the form of hollow or solid cylindrical granules, honeycombs or pellets, the shaping optionally being carried out using a binder.
They can be, firstly, beads of inorganic oxides derived from an oil-drop shaping (or drop coagulation). Beads of this type can be prepared, for example, by a process similar to the one described for the formation of alumina beads in patents EP-A-0,015,801 or EP-A-0,097,539. Control of the porosity can be achieved in particular, according to the process described in patent EP-A-0,097,539, by drop coagulation of an aqueous suspension or dispersion of inorganic oxide.
The beads can also be obtained by a process of aggregation in a rotating drum or granulator.
They can also be extrudates of inorganic oxides. These can be obtained by blending and then extrusion of a material based on the inorganic oxide. Controlling the porosity of these extrudates can be achieved by the choice of oxide used and by the conditions for preparing this oxide or by the conditions for blending this oxide before extrusion. The inorganic oxide can thus be mixed with porogens during the blending. By way of example, the extrudates can be prepared by the process described in U.S. Pat. No. 3,856,708.
Similarly, beads of controlled porosity can be obtained by addition of porogen and aggregation in a rotating bowl or granulator or by the “oil drop” process.
These shaping processes can be carried out by using a mi
Brunelle Jean-Pierre
Seigneurin Aline
Sever Lionel
Burns Doane Swecker & Mathis L.L.P.
Rhodia Fiber & Resin Intermediates
Shameem Golam M M
Solola T. A.
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