Isobutane-containing induced condensing agents in fluidized bed polymerization reactions
AssigneeExxonMobil Chemical Patents Inc.
InventorEric J. Markel
Life of this patent
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Abstract
Ethylene, alpha olefins, and other olefinically unsaturated monomers may be polymerized under fluidized bed polymerization reaction conditions in the presence of a Ziegler-Natta catalyst. A recycle stream featuring an induced condensing agent (ICA) comprising isobutane may increase catalyst productivity while maintaining quality of the polymer product, particularly when the recycle stream is delivered to a reactor containing the fluidized bed under conditions suitable to form a condensed or super-condensed mode in the recycle stream. The recycle stream may comprise unreacted olefinic monomers, and isobutane or a mixture of isobutane and isopentane.
Claims17
A method comprising:
- introducing to a reactor one or more olefinically unsaturated monomers in a continuous feed stream, the reactor having a fluidized bed comprising a Ziegler-Natta catalyst established therein;
- reacting the one or more olefinically unsaturated monomers under polymerization reaction conditions within the fluidized bed to form a plurality of polyolefin particulates;
- removing unreacted olefinically unsaturated monomers from the reactor, and returning continuously to the reactor a recycle stream comprising an induced condensing agent and the unreacted olefinically unsaturated monomers;
- wherein the recycle stream is returned to the reactor under conditions suitable to form a condensed mode or a super-condensed mode in the recycle stream prior to re-entering the reactor;
- wherein the induced condensing agent consists of a mixture of isobutane and isopentane, in which the isobutane is present in a molar excess relative to the isopentane and the isobutane is present in the recycle stream in an amount of 3 mol % or greater;
- and
- operating in the super-condensed mode with the recycle stream comprising at least 18 wt % liquid phase that re-enters the reactor.
A method comprising:
- introducing to a reactor one or more olefinically unsaturated monomers in a continuous feed stream, the reactor having a fluidized bed comprising a Ziegler-Natta catalyst established therein;
- reacting the one or more olefinically unsaturated monomers under polymerization reaction conditions within the fluidized bed to form a plurality of polyolefin particulates;
- removing unreacted olefinically unsaturated monomers from the reactor, and returning continuously to the reactor a recycle stream comprising the unreacted olefinically unsaturated monomers and an induced condensing agent consisting of isopentane;
- wherein the recycle stream is returned to the reactor under conditions suitable to form a condensed mode or a super-condensed mode in the recycle stream prior to re-entering the reactor;
- after a predetermined period of time, introducing isobutane into the recycle stream prior to the recycle stream re-entering the reactor, in which the isobutane is present in a molar excess relative to the isopentane and the induced condensing agent consists of isobutane and isopentane;
- and
- collecting at least a portion of the plurality of polyolefin particulates from the reactor.
Dependencies are inferred from the claim text.