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EP-3856796-B1 - METHODS FOR MAKING SUPPORTED CHROMIUM CATALYSTS WITH INCREASED POLYMERIZATION ACTIVITY

EP3856796B1EP 3856796 B1EP3856796 B1EP 3856796B1EP-3856796-B1

Inventors

  • MCDANIEL, MAX P.
  • CLEAR, Kathy S.

Dates

Publication Date
20260506
Application Date
20190919

Claims (19)

  1. A chromium/silica-coated alumina catalyst comprising: from 0.01 to 20 wt. % chromium, based on the weight of the catalyst; and a silica-coated alumina containing from 70 to 95 wt. % silica, based on the weight of the silica-coated alumina; wherein the catalyst has: a pore volume from 0.5 to 2 mL/g determined as set out in the description; and a BET surface area from 275 to 550 m 2 /g determined as set out in the description.
  2. The catalyst of claim 1, wherein: the catalyst contains from 0.2 to 10 wt. % chromium.
  3. The catalyst of claim 1 or claim 2, wherein: the pore volume is from 1 to 1.5 mL/g; and the BET surface area is from 300 to 525 m 2 /g.
  4. The catalyst of any one of claims 1 to 3 wherein the catalyst contains: from 0.5 to 5 wt. % chromium; and less than 0.5 wt. % fluorine.
  5. The catalyst of any one of claims 1 to 4, wherein the silica-coated alumina has been modified prior to combining with the chromium compound, wherein the modification is sulfation, phosphatation or titanation.
  6. An olefin polymerization process comprising contacting the catalyst of any one of claims 1-5 with an olefin monomer and an optional olefin comonomer in a polymerization reactor system under polymerization conditions to produce an olefin polymer.
  7. A process for preparing a supported chromium catalyst, the process comprising: (i) contacting a support comprising a silica-coated alumina containing from 70 to 95 wt. % silica with a chromium-containing compound in a liquid, and drying; and (ii) calcining at a peak temperature of at least 650 °C, optionally in an oxidizing atmosphere, to form the supported chromium catalyst.
  8. The process of claim 7, wherein: the peak temperature is in a range from 650 °C to 900 °C; and calcining is performed in the oxidizing atmosphere.
  9. The process of claim 7 or claim 8 , wherein: the supported chromium catalyst contains from 0.5 to 2.5 wt. % chromium; and the peak temperature is in a range from 650 °C to 900 °C.
  10. The process of any one of claims 7-9, wherein the supported chromium catalyst comprises chromium/sulfated silica-coated alumina, chromium/phosphated silica-coated alumina, or chromium/titanated silica-coated alumina.
  11. The process of claim 7, wherein the drying comprises spray drying.
  12. A process for preparing a supported chromium catalyst, the process comprising contacting a support comprising a silica-coated alumina with a chromium-containing compound while calcining at a peak temperature of at least 650 °C, optionally in an oxidizing atmosphere, to form the supported chromium catalyst, wherein the silica-coated alumina contains from 70 to 95 wt. % silica.
  13. The process of claim 12, wherein: the peak temperature is in a range from 650 °C to 900 °C; calcining is performed in the oxidizing atmosphere; and the supported chromium catalyst contains from 0.5 to 5 wt. % chromium.
  14. The process of claim 12 or claim 13, wherein a sulfur-containing compound is contacted with the support and the chromium-containing compound during calcining.
  15. An olefin polymerization process comprising: the process of any one of claims 7-14; and contacting the supported chromium catalyst with an olefin monomer and an optional olefin comonomer in a polymerization reactor system under polymerization conditions to produce an olefin polymer.
  16. The olefin polymerization process of claims 6, and 15, wherein the polymerization reactor system comprises a slurry reactor, a gas-phase reactor, a solution reactor, or a combination thereof.
  17. The olefin polymerization process of claim 16, wherein no co-catalyst is used in the olefin polymerization process.
  18. The olefin polymerization process of claim 16, wherein: the polymerization reactor system comprises a loop slurry reactor; and the olefin polymerization process is conducted in the presence of less than 5 ppm by weight of co-catalyst, based on diluent in the loop slurry reactor.
  19. The olefin polymerization process of any one of claims 16 to 18, wherein the olefin monomer comprises ethylene, and the olefin comonomer comprises 1-butene, 1-hexene, 1-octene, or a combination thereof.

Description

FIELD OF THE INVENTION The present disclosure generally relates to chromium catalysts, methods for preparing the chromium catalysts, and methods for using the chromium catalysts to polymerize olefins. More particularly, the present disclosure relates to methods of making a supported chromium catalyst containing a silica-coated alumina solid oxide support, and the subsequent use of the supported chromium catalyst in olefin polymerization processes. BACKGROUND OF THE INVENTION Chromium catalysts are among the most common catalysts used in olefin polymerizations. Supported chromium catalysts often are prepared by impregnating chromium onto a solid support, e.g., a solid oxide, followed by a calcining step. Generally, calcining is conducted in an oxidizing atmosphere, such that the chromium species within the supported chromium catalyst can be converted to hexavalent chromium. Hexavalent chromium/silica-coated alumina catalysts containing less than 20 wt. % silica were evaluated in U.S. Patent No. 5,401,820. However, these chromium/silica-coated alumina catalysts had poor catalyst activity and produced polymer of excessive molecular weight, making them inferior to traditional chromium/silica catalysts. A hexavalent chromium/silica-coated alumina catalyst also was evaluated in U.S. Patent Publication No. 2015/0191554 after calcination in dry air at 600 °C. This chromium/silica-coated alumina catalyst also had poor catalyst activity and produced high molecular weight. In view of these deficiencies, it would be beneficial to prepare chromium/silica-coated alumina catalysts with high catalytic activity for use in olefin polymerization processes. Accordingly, it is to this end that the present invention is generally directed. US 2012/0071614 A1 discloses a specified catalyst on silica clad alumina where there is 1 to 40 weight percent silica cladding. WO 2015/138673 A1 describes polymers with improved toughness and ESCR for large-part blow molding applications. US 2014/0242314 A1 discloses polymer resins with improved processability and melt fracture characteristics. SUMMARY OF THE INVENTION This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify required or essential features of the claimed subject matter. Nor is this summary intended to be used to limit the scope of the claimed subject matter. The subject matter of the invention is set out in the appended claims. Both the foregoing summary and the following detailed description provide examples and are explanatory only. Accordingly, the foregoing summary and the following detailed description should not be considered to be restrictive. Further, features or variations may be provided in addition to those set forth herein. For example, certain aspects may be directed to various feature combinations and sub-combinations described in the detailed description. BRIEF DESCRIPTION OF THE FIGURE FIG. 1 presents a plot of the molecular weight distributions of polymers produced using a Cr/silica-coated alumina catalyst, and titanated and sulfated modifications thereof. DEFINITIONS To define more clearly the terms used herein, the following definitions are provided. Unless otherwise indicated, the following definitions are applicable to this disclosure. If a term is used in this disclosure but is not specifically defined herein, the definition from the IUPAC Compendium of Chemical Terminology, 2nd Ed (1997), can be applied, as long as that definition does not conflict with any other disclosure or definition applied herein, or render indefinite or non-enabled any claim to which that definition is applied. To the extent that any definition or usage provided by any document herein disclosed conflicts with the definition or usage provided herein, the definition or usage provided herein controls. Herein, features of the subject matter are described such that, within particular aspects, a combination of different features can be envisioned. For each and every aspect and each and every feature disclosed herein, all combinations that do not detrimentally affect the catalysts, compositions, processes, or methods described herein are contemplated with or without explicit description of the particular combination. Additionally, unless explicitly recited otherwise, any aspect or feature disclosed herein can be combined to describe inventive catalysts, compositions, processes, or methods consistent with the present disclosure. Generally, groups of elements are indicated using the numbering scheme indicated in the version of the periodic table of elements published in Chemical and Engineering News, 63(5), 27, 1985. In some instances, a group of elements can be indicated using a common name assigned to the group; for example, alkali metals for Group 1 elements, alkaline earth metals for Group 2 elements, transition metals for Group 3-12 elements, and halogens or