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
2000-07-28
2003-03-18
Pezzuto, Helen L. (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...
C502S104000, C502S103000, C502S115000, C502S125000, C502S126000, C526S209000, C526S124300, C526S158000, C526S142000, C526S137000
Reexamination Certificate
active
06534433
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a process for preparing a catalyst support for (stereospecific) polymerization of alpha-olefins, in particular propylene, and to the support thus obtained.
BACKGROUND OF THE INVENTION
Alpha-olefin polymerization in general is carried out using Ziegler-Natta type catalysts. The Ziegler-Natta type catalyst system is generally constituted by two non-dissociable elements: a transition metal-based catalytic component deposited on a magnesium chloride-based support and a co-catalyst generally based on an aluminum compound. Numerous patents describe these catalyst components and their supports.
European patent application EP-A-0,239,475 discloses a controlled morphology catalyst spherical support for alpha-olefin polymerization. The catalyst support is obtained by reacting a chlorine-containing organic compound in the presence of an electron donor and a prior mixture of an alkylmagnesien and an aluminoxane and/or aluminosiloxane and, optionally, an electron donor. The support is then subjected to an activation step using a chlorine-containing compound prior to impregnation by a transition metal halide. This process leads to effective catalysts for ethylene polymerization. They have however proved to be less effective in particular for polymerization of propylene.
Activation of catalyst supports by treatment with cyclic monoethers for ethylene polymerization catalysts is known. European patent application 0,554,141 discloses, for example, a process for activating a magnesium chloride-based support that enters into the manufacture of the ethylene catalytic polymerization component. This process comprises activating the support in suspension in an inert liquid using a cyclic mono-ether. That patent does nevertheless not disclose nor suggest the possibility of such activation for controlled morphology catalyst supports adapted to propylene polymerization.
U.S. Pat. No. 3,642,746 discloses a Ziegler-Natta catalyst system useful to reduce the ash content of the obtained polymer. The catalyst is prepared by pretreatment of a divalent metal dihalide with en electron donor and impregnation of the obtained support with a transition metal halide.
A process for polymerization of ethylene in the gas phase leading to a linear polyethylene with a narrow weight distribution is known from U.S. Pat. No. 5,055,535. This process uses a Ziegler-Natta catalyst in presence of an alkylaluminium and a monoether. According to this document, the monoether should not be in contact with the catalyst in absence of the cocatalyst in the medium. The monoether constitues therefore an external Lewis Base and intervenes only during the polymerization. Further the monoether does not act as a polymerization activator and does therefore not allow to enhance productivity.
It is known that stereospecific polymerization of &agr;-olefins beyond ethylene such as propylene requires a stereospecific type catalyst. Indeed, contrary to polymerization of ethylene, which is a symmetrical molecule, the polymerization of an asymmetric &agr;-olefin, such as propylene, can lead to isotactic, syndiotactic or atactic chaining. The use of a stereospecific catalyst can then ensure that polymers of the desired structure, such as predominantly syndiotactic or isotactic, for example, are obtained. This explains why catalysts employed for ethylene polymerization are not necessarily suitable for polymerizing polypropylene.
SUMMARY OF THE INVENTION
It has now been surprisingly found that activation adapted to ethylene can be applied to a support adapted to propylene.
The invention makes it possible to obtain catalysts which are both highly effective and highly stereospecific for the polymerization of &agr;-olefins with at least 3 carbon atoms, in particular propylene.
The invention consequently provides a process for preparing a catalyst support for polymerizing &agr;-olefins comprising the steps of:
(i) reacting, in the presence of a first electron donor, a chlorine-containing organic compound and a prior mixture of an alkylmagnesien and an aluminoxane and/or aluminosiloxane and/or alkylaluminum and, optionally, a second electron donor; and
(ii) activating the product from step (i) in suspension in an inert liquid by means of an activation electron donor.
The invention also provides a catalyst support obtainable by the process according to the invention.
DETAILED DESCRIPTION OF THE INVENTION
The invention will now be described in more detail below.
According to the invention, the spherical catalyst support is prepared by reacting, in the presence of an electron donor, a chlorine-containing organic compound with a prior mixture of an alkylmagnesien and an organic compound of aluminium, aluminoxane and/or aluminosiloxane and/or alkyl-aluminum. The chlorine containing organic compound is caused to react in the prior mixture of alkylmagnesien and organic compound of aluminium, the reaction taking place in the presence of a first electron donor. The prior mixture of alkyl magnesien and organic compound of aluminium can also comprise a second electron donor, which, generally, (but not necessarily) is of the same type as the first electron donor.
The reaction is carried out in the presence of a donor, which can be introduced:
through previous mixing of the chlorine-containing organic compound with this (first) donor, or
through previous mixing of the alkylmagnesien and aluminium organic compound (aluminoxane and/or aluminosiloxane and/or alkylaluminum) in this (first) donor; or
both through previous mixing of the chlorine-containing organic compound in this (first) donor and previous mixing of the alkylmagnesien and organic compound of aluminium (aluminoxane and/or aluminosiloxane and/or alkylaluminum) in this (second) donor. In this case, the second donor can be identical to or different from the first donor; it is preferably identical.
According to one embodiment, the chlorine-containing organic compound is mixed with at least a portion of the first electron donor prior to the reaction of step (i), this portion being preferably at least 50%.
According to one embodiment, the amount of first electron donor mixed with the chlorine-containing organic compound prior to the reaction of step (i) represents, in moles, more than 50% of the total of the first and second electron donors present during the reaction of step (i).
In a further embodiment, the reaction of step (i) takes place in the presence of a first electron donor, the prior mixture of an alkylmagnesien and an aluminoxane and/or aluminosiloxane and/or alkylaluminum comprising a second electron donor, identical to the first electron donor.
At the end of step (i), the solid obtained is generally substantially spherical.
The alkylmagnesien is previously mixed with the aluminoxane and/or aluminosiloxane and/alkylaluminium, preferably in solution in an inert solvent such as a hydrocarbon, for example hexane or heptane, preferably in the presence of an electron donor, which can be the first or second donor depending on the case. Once the mixture has been made, the chlorine-containing organic compound, generally (but not necessarily) diluted in a (first) electron donor and optionally in an inert solvent such as hydrocarbon like hexane or heptane is made to react. At the end of the reaction, the support formed, in suspension in the reaction medium, is filtered and optionally washed with inert liquid. The support, in suspension in an inert solvent such as a hydrocarbon like hexane or heptane, is then brought into contact with a so-called activation electron donor, preferably a cyclic ether. This activation operation can be carried out before or after the preceding filtration and washing operations. The support formed is filtered and optionally washed with an inert liquid if the cyclic ether treatment took place after the first filtration and first washing operations. One thus obtains a support the particle diameter of which is generally comprised between 5 and 150 microns and more generally between 10 and 100. The supports and, consequently the sub
Cochard Daniel
LaCombe Jean-Loup
Malinge Jean
Saudemont Thierry
Violle Henri
Atofina
Choi Ling-Siu
Pezzuto Helen L.
Smith , Gambrell & Russell, LLP
LandOfFree
Process for preparing a catalyst support for polymerization... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for preparing a catalyst support for polymerization..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for preparing a catalyst support for polymerization... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3025606