Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Plural component system comprising a - group i to iv metal...
Reexamination Certificate
1998-09-23
2001-01-30
Lipman, Bernard (Department: 1713)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Plural component system comprising a - group i to iv metal...
C502S117000, C502S152000, C502S155000, C525S338000, C525S339000
Reexamination Certificate
active
06180553
ABSTRACT:
The present invention relates to a process and a catalyst for the selective hydrogenation of olefinically unsaturated compounds.
More specifically, the present invention relates to a process for the selective hydrogenation of monomeric or polymeric unsaturated compounds containing at least one olefinic double bond, and a catalyst based on cyclopentadienyl derivatives of a metal of group 4 of the periodic table, which can be used in said process.
The hydrogenation of unsaturated substrates is a technology widely used for obtaining products which can be used in various fields, from the food industry to the field of plastic materials and the like. Several methods are known for the hydrogenation of olefinic double bonds (chemically a reduction by means of hydrogen), most of which use gaseous hydrogen in the presence of a suitable catalyst. The latter normally comprises a transition metal, usually a metal of group 10 of the periodic table, i.e. Ni, Pd or Pt. If these are present as impurities in the hydrogenated substrate, they can cause aging phenomena or toxicological problems in the case of food.
Hydrogenation catalysts based on other transition metals having fewer drawbacks than those listed above, are also known, but these also have a lower catalytic activity.
A particular aspect concerns the hydrogenation of polymeric unsaturated substrates, such as those obtained by the polymerization or copolymerization of conjugated dienes. In the polymeric chain, these polymers have double olefinic bonds which can be used for a possible vulcanization, but make the material unstable, particularly to oxidation, if left unaltered. In addition, with the hydogenation of these polymers, it is possible to obtain materials different from the normal rubbers, which can be used in various industrial fields.
In particular, block copolymers obtained starting from conjugated dienes and from vinyl-substituted aromatic hydrocarbons (especially styrene) can be used, in a non-vulcanized form, as thermoplastic elastomers or as impact-resistant transparent resins or as modifiers of styrene resins and olefinic resins. Owing to the presence of unsaturated double bonds in the polymeric chain, the above block copolymers have poor resistance to oxidation, ozone and atmospheric aging. This is a serious disadvantage for their application.
This lack of stability can be considerably reduced by selectively hydrogenating the olefinic double bonds of the above copolymers.
The known methods for hydrogenating polymers having olefinic double bonds are based on (1) supported heterogeneous catalysts which consist of inert materials (for example silica, alumina, carbon) onto which a metal such as nickel, platinum, palladium or the like is deposited and (2) non-supported catalysts obtained by reacting an organometallic compound of nickel, cobalt, titanium or the like, with a reducing compound such as an organoaluminum or an organolithium.
With respect to supported heterogeneous catalysts (1), non-supported catalysts (2) have the benefit of a greater activity. This is a considerable advantage as it allows blander hydrogenation conditions to be used, with smaller quantities of catalyst.
U.S. Pat. No. 4,501,857 describes a hydrogenation process of non-living polymers carried out in the presence of (A) a bis-(cyclopentadienyl) titanium derivative and (B) at least one organolithium derivative, the molar ratio between lithium atoms and titanium atoms being from 0.1 to 100.
EP-A-434.469 describes a catalytic composition which comprises (a) at least one titanium bis-cyclopentadienyl derivative and (b) at least one compound selected from those having general formula (i) M
1
(AlR
1
R
2
R
3
R
4
) and (ii) M
1
(MgR
5
R
6
R
7
), wherein M
1
, is selected from lithium, sodium and potassium. Compound (i) can be obtained by the reaction of an organic compound of an alkaline metal with an organometallic derivative of aluminum, whereas compound (ii) can be obtained by the reaction of an organo-alkaline compound with an organo-magnesia derivative.
EP-A-601.953 describes a hydrogenation process carried out in the presence of a catalyst having the general formula Cp
2
Ti(PhO)
2
or Cp
2
Ti(CH
2
PPh
2
)2, wherein Cp is C
5
H
5
.
The above metallocene catalysts of the known art are characterized by the presence of two groups of the cyclopentadienyl type co-ordinated to the titanium atom. In accordance with this it is generally thought that the active catalytic species consists of a stabilized titanium complex having a reduced oxidation state. These catalysts however have catalytic activities and a hardness (average life of the catalyst during the hydrogenation) which are still unsatisfactory for normal industrial processes, in many cases requiring the use of high quantities of metal with the consequent serious contamination of the hydrogenated product. This particularly occurs when the solvent in which the hydrogenation process is carried out is an aliphatic hydrocarbon, such as cyclohexane or heptane, which, on the other hand, is preferable as a solvent compared to aromatic hydrocarbons owing to its greater volatility and lower toxicity.
In addition, it has also been observed that, when the above bis-cyclopentadienyl complexes are used as hydrogenation catalysts, a significant isomerization reaction of the unsaturated hydrocarbons, including the polymers, especially if branched, parallelly takes place, obtaining at times high percentages of product different from that desired. This has the double disadvantage of a decrease in the selectivity and greater difficulty in separating the undesired products.
The Applicant has now found a catalytic composition which can be used in the selective hydrogenation of olefinic double bonds which overcomes the disadvantages mentioned above, as it is simple to prepare and allows significantly higher catalytic activities to be obtained than those achieved so far in the art.
In accordance with this, the present invention relates to a catalytic composition effective in the selective hydrogenation of olefinic double bonds, comprising the reaction product between:
(A) at least one cyclopentadienyl complex of a transition metal having the following general formula (I):
(R)M(R
1
)(R
2
)(R
3
) (I)
wherein:
M is selected from titanium, zirconium and hafnium, preferably titanium;
R is an anion containing an &eegr;
5
-cyclopentadienyl ring co-ordinated to M; and
each R
1
, R
2
or R
3
, independently, represents an organic or inorganic group of an anionic nature &sgr;-bound to M, and may, particularly, be hydride, halide, a C
1
-C
8
alkyl group, a C
3
-C
12
alkylsilyl group, a C
5
-C
8
cycloalkyl group, a C
6
-C
10
aryl group, a C
1
-C
8
alkoxyl group, a C
1
-C
8
carboxyl group, a C
2
-C
10
dialkylamide group and a C
4
-C
20
alkylsilylamide group;
the above compound (I) being solid, supported or dispersed in an inert liquid medium; and
(B) at least one organometallic compound of magnesium having the following formula (II):
Mg(R
4
)
n
(R
5
)
(2−n)
(II)
wherein:
R
4
is an aliphatic or aromatic hydrocarbon group having from 1 to 20 carbon atoms,
R
5
is halogen or a group such as R
4
, and
“n” is a decimal number between 0.5 and 2.0, preferably 2.
A second aspect of the present invention relates to a process for the preparation of said catalyst, comprising in particular putting the above compounds having formulae (I) and (II) in contact and reacting with each other, preferably in the presence of a liquid medium as diluent.
A further aspect of the present invention relates to a selective hydrogenation process of the olefinic double bonds of a monomeric or polymeric, olefinically unsaturated substrate, comprising putting said substrate in contact and reacting with hydrogen under appropriate conditions of pressure and temperature, in the presence of said catalyst and, preferably, an inert diluent which is normally a solvent of the substrate to be hydrogenated.
As described above, compound (I) in the formation of the catalytic composition of the present invention can be in soli
Longhini Gianfranco
Masi Francesco
Santi Roberto
Vallieri Andrea
Enichem S.p.A.
Lipman Bernard
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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