Chemistry of hydrocarbon compounds – Adding hydrogen to unsaturated bond of hydrocarbon – i.e.,...
Reexamination Certificate
1999-01-22
2001-08-28
Killos, Paul J. (Department: 1621)
Chemistry of hydrocarbon compounds
Adding hydrogen to unsaturated bond of hydrocarbon, i.e.,...
C585S266000, C585S269000, C585S271000, C585S273000, C585S275000
Reexamination Certificate
active
06281397
ABSTRACT:
The present invention relates to a catalyst for the hydrogenation of olefinically unsaturated compounds, comprising at least one compound of titanium.
More specifically, the present invention relates to a process for the selective hydrogenation of unsaturated compounds containing at least one olefinic double bond, and a catalyst based on non-cyclopentadienyl derivatives of titanium combined with a suitable co-catalyst.
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.
Catalysts normally used comprise:
(1) supported heterogeneous catalysts consisting of inert materials (for example silica, alumina, carbon) onto which a metal such as nickel, platinum, palladium, etc. is deposited, and
(2) non-supported catalysts obtained by reacting an organometallic compound of nickel, cobalt, titanium, etc., 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 significant advantage as it allows blander hydrogenation conditions to be used, with smaller quantities of catalyst.
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-magnesium 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 catalysts based on titanium are characterized by the presence of groups of the cyclopentadienyl type coordinated to the metal 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 durability (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 complexes of the metallocene type are used as hydrogenation catalysts, a significant isomerization reaction of the unsaturated hydrocarbons 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.
Compositions are also known which are based on non-metallocene compounds of transition metals and alkyl derivatives of aluminum as activators, which have a certain catalytic activity in hydrogenation reactions. The publication Journal of the American Chemical Society, Vol. 85 (1963), page 4014 onwards., describes in particular catalytic compositions for the hydrogenation of unsaturated aliphatic substrates, based on titanium alkoxides and aluminum alkyls or lithium alkyls. The catalytic activity of these compositions however is insufficient for convenient use on an industrial scale. The same publication also mentions that the substitution of the aluminum alkyl activator with equivalent quantities of a Grignard reagent (butylmagnesium bromide) leads to the total deactivation of the catalyst.
The Applicant has now surprisingly found that it is possible to obtain a composition based on titanium or zirconium, which is capable of catalyzing the selective hydrogenation of olefinic double bonds and overcomes the above disadvantages, obtaining significantly higher catalytic activities than those so far registered in the known art for analogous systems. In addition, this composition does not contain metals with a high toxicity such as Cr, Pt, Ni, and can be used with fewer problems also in the food industry.
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 complex of a transition metal having the following general formula (I):
M(R
1
)(R
2
)(R
3
)(R
4
) (I)
wherein: M is selected from titanium and zirconium, preferably titanium;
each of the radicals R
1
, R
2
, R
3
or R
4
, independently, represents an organic or inorganic group of an anionic nature &sgr;-bonded to M, and may, particularly, be hydride, halide, a C
1
-C
10
alkyl group, a C
2
-C
15
alkylsilyl group, a C
5
-C
15
cycloalkyl group, a C
6
-C
15
aryl group, a C
1
-C
15
alkoxyl group, a C
1
-C
15
carboxyl group, a C
2
-C
15
dialkylamide group and a C
4
-C
20
alkylsilylamide group; on the condition that at least one, and preferably at least two, of these radicals is an organic group; and
(B) at least one organometallic compound of magnesium having the following formula (II):
Mg(R
5
)
n
(R
6
)
(2−n)
(II)
wherein: R
5
or R
6
each independently represent an aliphatic or aromatic hydrocarbon group having from 1 to 20 carbon atoms, and
“n” is a decimal number between 0 and 2.0.
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 an 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, optionally, an inert diluent which is normally a solvent of the substrate to be hydrogenated.
The compounds having formula (I) which form component (A) of the catalytic composition of the present invention belong to known groups of derivatives of titanium and zirconium and are normally in the solid or liquid state at room temperature. The methods for the preparation of many of these are described in specific literature together with the physico-chemical properties. However the compounds not described in literature can also be prepared analogously to the known methods.
According to the present invention, each R radical (R=R
1
, R
2
, R
3
or R
4
) in formula (I) may independently be of an organic or inorganic nature but must be bonded to the metal M with a covalent (or also covalent-ionic) bond of the “&sgr;” type, having a cylindrical symmetry.
Bonds of the “&pgr;” type are therefore excluded, such as, for example, the bond of a cyclopentadienyl group in a metallocene derivative. In addition, in the compound having formula (I), at least one R group of an organic nature must be present, i.e. c
Longhini Gianfranco
Masi Francesco
Santi Roberto
Enichem S.p.A.
Killos Paul J.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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