Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
  • B01J27/02—Sulfur, selenium or tellurium; Compounds thereof
  • B01J27/053—Sulfates
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
  • B01J21/02—Boron or aluminium; Oxides or hydroxides thereof
  • B01J21/04—Alumina
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F10/00—Homopolymers and copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
  • C08F10/02—Ethene
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F4/00—Polymerisation catalysts
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/16—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
  • B01J23/24—Chromium, molybdenum or tungsten
  • B01J23/26—Chromium
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F110/00—Homopolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
  • C08F110/02—Ethene

Definitions

• the present invention generally relates to catalysts for polymerizing oleffns, and more particularly to methods of preparing active catalysts by treating a chromium-based catalyst having an alumina support with sulfate.
• the present invention generally further relates to polymers, and more particularly to polymers having relatively low levels of long chain branching and methods of making the same using sulfate treated chromium-based catalysts having alumina supports.
• Supported chromium oxide catalysts are commonly employed to prepare polyolefins having desirable characteristics.
• Various supports for chromium oxide catalysts have been disclosed in the art. The particular support used for the chromium oxide strongly affects the properties of the polymer being formed.
• Silica supports have primarily been used due to their ability to form highly active polymerization catalysts. However, silica supports do not provide for the production of ultra high molecular weight polymers when hexavalent chromium is formed during the catalyst activation, which often occurs.
• Aluminum phosphate supports are similar to silica supports in that they form highly active catalysts. However like the silica supports, they also do not have the ability to produce very high molecular weight polymers.
• the polymers produced using the aluminum phosphate supports tend to contain relatively high amounts of long chain branching, which is not always a desirable property during processing of the polymer.
• Alumina supports desirably have relatively high surface areas and are very porous; however, chromium oxide catalysts supported by alumina are not sufficiently active to be considered commercially viable.
• the activity of such catalysts can be improved by adding fluoride to the alumina support. It is believed that the fluoride replaces surface hydroxide groups, which are believed to interfere with polymerization. Unfortunately, the addition of too much fluoride tends to sinter the alumina, resulting in the deactivation of the catalysts.
• a need therefore exists to develop a method for increasing the activity of chromium catalysts supported by alumina without being concerned that the alumina might be sintered.
• methods of preparing a polymerization catalyst include contacting a support comprising alumina with a sulfating agent and with chromium.
• the chromium is provided from a chromium compound such as chromium oxide
• the support can be calcined to activate the catalyst after loading the sulfating agent and the chromium on the support.
• the sulfating agent can be loaded on the support while calcining it.
• the support can be calcined after contactmg it with the sulfating agent and before contacting it with the organochromium compound.
• catalyst compositions for polymerizing oleffns comprise chromium and a sulfate treated alumina support.
• the catalyst compositions have an activity for ethylene polymerization that is at least 25% greater than an activity of the same catalyst without sulfate. Further, they have a surface area greater than 100 m 2 /g and a pore volume greater than 0.8 cc/g.
• a resin made using a catalyst as described herein is also advantageously provided.
• Methods of producing a polymer include contacting at least one oleffn with a catalyst prepared by contacting a support comprising alumina with a sulfating agent and with chromium.
• Polymer compositions produced in this manner can exhibit relatively low levels of long chain branching. Such low levels of long chain branching are indicated by the high weight-average molecular weight (Mw) values combined with the low zero shear viscosity (E 0 ) values of the polymers.
• Mw weight-average molecular weight
• E 0 zero shear viscosity
• polymer compositions with polydispersity index values (i.e., M W /M N ) in a range of from 6 to 15 have M w values greater than 300,000 g/mol and Eo values less than 1x10 Pa-s.
• the low levels of long chain branching are also indicated by the narrow rheological breadths combined with the high M w values of the polymer compositions.
• the polymer compositions have rheological breadths greater than 0.25.
• the high Mw values combined with the low relaxation times of the polymers further indicate the low chain branching of the polymers.
• polymer compositions have relaxation times less than 10 seconds.
• Figure 1 depicts a graph illustrating the activity of a cteomium/alumina catalyst treated with sulfate as a function of the amount of ammonium sulfate added to the catalyst.
• Figure 2 depicts the molecular weight distributions of polyethylene resins formed using a chromium/alumina catalyst treated with sulfate.
• Figure 3 depicts the molecular weight distributions of polyethylene resins formed using chromium/alumina catalysts treated with sulfate and not treated with sulfate.
• Figure 4 depicts an Arnett plot showing the linearity of polyethylene resins formed using chromium/alumina catalysts treated with sulfate and not treated with sulfate.
• Figure 5 depicts the molecular weight distributions of polyethylene resins formed using chromium/alumina catalysts treated with different amounts of ammonium sulfate.
• Figure 6 depicts the molecular weight distributions of polyethylene resins formed using organochromium/alumina catalysts treated with sulfate.
• Figures 7 and 8 depict the molecular weight distributions of polyethylene resins formed using chromium alumina catalysts, some of which were treated with varying amounts of phosphate, fluoride, and sulfate.
• Figure 9 depicts an Arnett plot of molecular weight distributions of polyethylene resins formed using chromiunValuminophosphate catalysts treated with sulfate and not treated with sulfate.
• a chromium-based catalyst having an alumina (Al 2 O 3 ) support can be treated with sulfate (i.e., sulfate anions) to enhance the activity of the catalyst, making its use in the production of polymers commercially viable.
• the alumina support primarily comprises alumina.
• the amount of alumina present in the support is at least 50% by weight of the total support.
• the alumina support can be made using methods known in the art.
• Examples of such methods include: reacting sodium aluminate, which is basic, with aluminum sulfate, which is acidic; neutralizing an aluminum salt with a base such as ammonia or ammonia hydroxide; performing flame hydrolysis of an aluminum compound; or performing hydrolysis of an organic solution of an aluminum compound by, e.g., adding water to an alcohol solution of aluminum isopropoxide (Al(OC3H 7 )3).
• sources of alumina include a crystalline form and a hydrated form of alumina. More specific examples include aluminum hydroxide (Al(OH) 3 ), boehmite (AIOOH) and gamma alumina (Al 2 O 3 ).
• the alumina support can also contain minority amounts of other materials that can be added for various reasons, such as fluoride, phosphate, silica, magnesia, boria, or titania. These materials can be added in the form of cogellation or by surface treatment.
• the alumina support can be calcined prior to any treatment by, e.g., heating in air at a temperature in arange of from 300°C to 900°C or from 500°C to 800°C.
• the chromium and the sulfate can be loaded on the alumina support before subjecting the support to a final calcination step for activating the catalyst.
• the chromium can be loaded before the sulfate, after the sulfate, or concurrently with the sulfate.
• the support can also be subjected to an initial calcination step to dehydrate it prior to further treatment with sulfate and chromium. This step converts hydrated forms of alumina precursors, such as Al(OH) 3 and A1OOH, to less hydrated forms.
• the initial calcining step can be accomplished by heating the support in an oxidizing, reducing, or inert atmosphere, which can be dry or can contain substantial amounts of humidity.
• Such initial dehydration can be carried out at a temperature ranging from 150°C to 900°C; alternatively, from200°C to 800°C; or alternatively, from 300°C to 700°C.
• the dehydration step can last for a duration of from a few minutes to 24 hours.
• the support can be given a sulfate and chromium treatment, followed by the final calcination or activation step.
• the sulfate can be loaded on the alumina support during the calcination step and after loading the chromium.
• the chromium can be loaded on the support using incipient wetness impregnation with a solution in which a chromium compound is dissolved.
• the chromium compound can be one or more compounds suitable for conversion to the hexavalent state of chromium. Examples of suitable chromium compounds include tertiary butyl chromate in a hydrocarbon liquid, chromium trioxide in water, chromium acetate in water, chromium nitrate in alcohol, or combinations thereof The chromium is added in an amount sufficient to ensure that the final catalyst contains a desired level of chromium
• the sulfate can be loaded on the support by contacting it with a sulfating agent.
• sulfating agent is defined as a material capable of providing a sulfate ion to an alumina support, wherein the sulfating agent can be in the form of a solution, a gas, or combinations thereof
• the sulfating agent is a solution, it can be applied to the support via incipient wetness impregnation.
• the sulfating agent is a gas such as SO 3 , it can be introduced to a vessel in which the support is positioned during the calcination of the support.
• sulfating agents include: SO 3 gas; H 2 SO in water or an organic liquid such as an alcohol; aqueous solutions comprising at least one of the following compounds: (NH 4 ) 2 S0 4 , A1 2 (S0 4 ) 3 , CuSO 4 , ZnSO 4 , KAl(SO 4 ) 2 , ZrOSO 4 , TiOSO 4 , MgSO 4 , (NH 4 )HSO 4 , NaHS0 4 , (NH 4 )HS0 3 , CaSO 4 and Cr 2 (SO 4 ) 3 , and combinations thereof Sulfur containing materials that are capable of further oxidation to sulfate during the calcination step can also serve as the sulfating agent.
• sulfur containing materials include sulfite salts, sulfurous acid, organic sulfides, sulfoxides, and SO 2 .
• Additional examples of sulfating agents include sulfur halides such as thionyl chloride and sulfuryl chloride.
• the sulfate is loaded on the alumina support before performing a calcination step to activate the support, followed by treating the support anhydrously with the organochromium compound. No further calcination of the organochromium compound is required to activate the catalyst.
• organochromium compounds include zerovalent compounds such as pi bonded chromium complexes, for example, dicumene chromium and dibenzene chromium Pi bonded chromium complexes are described in U.S. Patent No. 3,976,632, which is incorporated by reference herein in its entirety.
• Other examples include divalent and trivalent organochromium compounds such as chromocene (bis(cyclopentadienyl)chromium (II)), and substituted derivatives thereof in which the cyclopentadienyl rings contain one or more substituents, chromium diallyl and triallyl, bis(2,4 dimethyl pentdienyl) chromium, and amidochrornium compounds.
• the calcination step for activating the catalyst is performed by heating it in an oxidizing atmosphere, for example, in the presence of oxygen (O 2 ), at a temperature in a range of from 200°C to 1,000°C; alternatively, from 300°C to 800°C; or alternatively, from 400°C to 700°C.
• the calcining treatment can also involve reducing or other steps, such as treatment with carbon monoxide, hydrogen, or haliding agents.
• the chromium compound is converted to the hexavalent state as a result of being calcined.
• a substantial portion of the sulfate remains on the support during the calcination step in both embodiments, resulting in an increase in the activity of the chromium-based catalyst.
• the sulfate bonds with aluminum and replaces hydroxide groups at the surface of the support that hinder the activity of the catalyst.
• the sulfate also provides greater acidity to the chromium active sites.
• the introduction of the sulfate to the support causes little or no sintering of the alumina such that its relatively high surface area and porosity only decline by small amounts.
• the activated catalyst formed in the two embodiments described above optionally can be reduced.
• the support is reduced by heating it in the presence of carbon monoxide at a temperature in the range of from 100°C to 900°C; alternatively, from 200°C to 500°C; or alternatively, from 300°C to 400°C.
• Catalyst compositions for polymerizing olefins can be formed in the manner described above.
• Such catalyst compositions can include chromium and aluminum sulfate on an alumina support.
• the chromium is present in such catalyst compositions in an amount of from 0.01% to 10%; alternatively, from 0.1% to 10%; alternatively, from 0.5% to 5%; or alternatively, from 0.8%> to 3%, all percentages being by total weight of the final catalyst composition
• the sulfate is present in an amount of from 1% to 50%; alternatively, from 5% to 40%; or alternatively, from 10% to 30%, all percentages being by total weight of the final catalyst composition.
• a catalyst composition is formed that has an activity at least 25% greater than the activity of the same catalyst composition (based on the weight of the alumina support) without sulfate treatment, where the catalyst compositions are run under control conditions to polymerize olefins.
• the catalyst composition has an activity more than 25%; alternatively, more than 50%; or alternatively, more than 100%, greater than the activity of the same catalyst composition without sulfate treatment.
• the catalyst composition has a surface area greater than 50 m 2 /g; alternatively, greater than 100 m 2 /g; or alternatively, greater than 200 m 2 /g.
• the catalyst composition has a pore volume greater than 0.5 cc; alternatively, greater than 0.8 cc; or alternatively, greater than 1 cc.
• a resin made using a catalyst as described herein is also advantageously provided.
• the catalyst can be made in accordance with any of the methods described herein.
• a polymer composition can be formed by polymerizing at least one monomer in the presence of the foregoing sulfate treated chromium-based catalyst having an alumina support.
• suitable monomers include mono-olefins containing 2 to 8 carbon atoms per molecule such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, and 1-octene.
• the chromium-based catalyst is particularly suitable for producing polyethylene homopolymers and copolymers of ethylene and mono-olefins containing 3 to 8 carbon atoms per molecules. Any polymerization reactor known in the art that is capable of polymerizing olefin monomers to produce the homopolymers or copolymers described herein also can be used.
• Such reactors can comprise slurry reactors, gas-phase reactors, solution reactors or any combination thereof
• Gas phase reactors can comprise fluidized bed reactors or tubular reactors.
• Slurry reactors can comprise vertical loops or horizontal loops.
• Solution reactors can comprise stirred tank or autoclave reactors.
• Such reactors can be combined into multiple reactor systems operated in parallel or in series.
• the catalyst also can be used to produce ethylene polymers in a particle form process as disclosed in U.S. Patent Nos. 3,624,063, 5,565,175, and 6,239,235, which are incorporated by reference herein in their entirety.
• hydrogen (H 2 ) also can be introduced to the reaction zone to reduce the molecular weight of the polymer formed.
• the amount of catalyst present in the reaction zone can range from 0,001% to 1% by weight of all materials in the reaction zone.
• a slurry polymerization process is employed in which the catalyst is suspended in an inert organic medium and agitated to maintain it in suspension throughout the polymerization process.
• the organic medium can, e.g., be a paraffin, a cycloparaffin, or an aromatic.
• the slurry polymerization process can be carried out in a reaction zone at a temperature of from 50°C to 110°C and at a pressure in the range of from 100 psia to 700 psia or higher. At least one monomer is placed in the liquid phase of the slurry in which the catalyst is suspended, thus providing for contact between the monomer and the catalyst.
• the activity and the productivity of the catalyst are relatively high. As used herein, the activity refers to the grams of polymer produced per gram of solid catalyst charged per hour, and the productivity refers to the grams of polymer produced per gram of solid catalyst charged.
• the monomer also can be contacted with a cocatalyst in addition to the chromium-based catalyst.
• the cocatalyst can be contacted with the catalyst either before or after entry into the reaction zone.
• the catalyst and cocatalyst can each be fed independently into a mixing vessel ahead of the reactor where they are allowed to pre-contact each other in a hydrocarbon solvent for a period of from 1 minute to 10 hours at temperatures ranging from -20°C to 100°C. After this duration, the contacted catalyst and cocatalyst are both fed to the reaction zone. Since each feed stream can be measured and controlled independently, pre-contacting the catalyst and the cocatlayst provides a method of continuously controlling the composition of the catalyst and thereby the properties of the polymer produced.
• the catalyst and cocatalyst can also be fed directly into the reaction zone where they contact each other for the first time in the presence of the monomer.
• suitable cocatalysts include organoaluminum compounds such as triethyl uminum, organoboron compounds such as triethylboron, tri-n-butylborane, and tripropylborane, and combinations thereof
• organoaluminum compounds include aluminum alkyls such as R 3 A1, R 2 4 A1X, and R 4 A1X 2 compounds where R 4 is a 1 to 12 carbon atom hydrocarbyl radical and X is a halogen such as chlorine.
• the cocatalyst can, for example, be triethylaluminum chloride or diethylaluminum chloride.
• suitable organoboron compounds include trialkyl boron compounds, particularly those having alkyl groups of 1 to 12 carbon atoms or 2 to 5 carbon atoms, triaryl boron compounds such as triphenylborane, alkyl boron alkoxides such as B(C 2 H5) 2 OC 2 H 5 and halogenated alkyl boron compounds such as BC 2 H 2 C1 2 .
• Alkyls of lithium, magnesium, zinc, and other metals and organohydrosilanes can also be used as a cocatalyst.
• the cocatalyst can be premixed with the catalyst, or alternatively it can be introduced into the reaction zone as a separate stream.
• the amount of cocatalyst present in the reaction zone can be in the range of from 0.2 to 25 or from 0.2 to 10 parts per million by weight based on the weight of the solvent or diluent in systems employing such solvent or diluent.
• the catalyst can be impregnated with the cocatalyst in an amount that provides for a cocatalyst to chromium mole ratio in the range of from 0.1:1 to 100:1; alternatively, from 0.5:1 to 50:1; or alternatively, from 1:1 to 10:1.
• the monomer can be contacted with another catalyst simultaneously with the sulfated chromium-based catalyst and the cocatalyst if one is used.
• the sulfated chromium-based catalyst can be used in conjunction with a Ziegler-Natta catalyst to produce a bimodal polymer in a single reactor using one set of polymerization conditions.
• Suitable Ziegler-Natta catalyst are disclosed in U.S. Patent Nos. 5,275,992, 5,237,025, 5,244,990, 5,179,178, 4,855,271, 5,179,178, 5,275,992, and 4,607,019, each of which is incorporated by reference herein in its entirety.
• the sulfated chromium/alumina catalyst also can be used with another chromium-based catalyst such as a chromium/silica catalyst.
• a bimodal polymer has both relatively high and low molecular weight distributions and thus exhibits physical properties characteristic of both such as stress crack resistance and good pro cessability.
• Polymers such as polyethylene homopolymers and copolymers of ethylene with other mono-olefins can be produced in the manner described above to have unique properties. For instance, the polymers exhibit relatively low levels of long chain branching. Such low levels of long chain branching are indicated by the narrow rheological breadths combined with the high Mw values of the polymers.
• Rheological breadth refers to the breadth of the transition region between Newtonian and power-law type shear rate for a polymer or the frequency dependence of the viscosity of the polymer.
• the rheological breadth is a function of the relaxation time distribution of a polymer resin, which in turn is a function of the resin molecular structure or architecture.
• the polymers exhibit a narrow rheological breadth even when the polymers have low high load melt index (HLMI) values.
• the HLMI represents the rate of flow of a molten resin through an orifice of 0.0825 inch diameter when subjected to a force of 21,600 grams at 190°C.
• the HLMI values are dete ⁇ nined in accordance with ASTM D1238 condition E.
• the polymers have HLMI values less than 5 g/10 rnin; alternatively, less than 3 g 10 min; or alternatively, less than 2 g/10 rnin.
• the low levels of long chain branching of the polymers are also indicated by the high weight-average molecular weight (Mw) values combined with the low zero shear viscosity (E 0 ) values of the polymers.
• Mw weight-average molecular weight
• E 0 zero shear viscosity
• the polymers have Mw's greater than 300,000 grams/mole (g/mol); alternatively, greater than 400,000 g/mol; or alternatively, greater than 500,000 g/mol.
• E 0 values less than 5x10 6 Pa-s, less than lxl 0 6 Pa-s, or less than 5x10 5 Pa s.
• the high Mw values combined with the low relaxation times (T ⁇ ) of the polymers further indicate the low chain branching of the polymers.
• the polymers have relaxation times less than 10 seconds; alternatively, less than 7 seconds; or alternatively, less than 5 seconds.
• the polymers further have high tan delta values. Tan delta is the ratio of the loss modulus to the elastic modulus measured at a particular frequency on an oscillating viscometer as described above.
• the polymers have tan delta values, measured at 0.1 radians/second (very low shear rates), greater than 1.5; alternatively, greater than 1.7; or alternatively, greater than 1.9 when the Mwis above 300,000 g/mol.
• polyethylene resins produced using the sulfate treated chromium/alumina catalyst are unique in their molecular weight distributions.
• the molecular weight distribution (MWD) can be described by a parameter known as the polydispersity index (PDI), which indicates the breadth of the molecular weight distribution and is equivalent to the weight- average molecular weight of a polymer divided by the number-average molecular weight of the polymer (i.e., Mw/M N ).
• the polyethylene resins have PDI values greater than 4; alternatively, greater than 6; alternatively, greater than 8; or alternatively, greater than 10.
• the PDI values of such polyethylene resins also are often less than 20; alternatively, less than 17; alternatively, less than 15; or alternatively, even less than 12.
• the polyethylene resins have PDI values in the range of from 6 to 15.
• the M z (z-average molecular weight)/Mw ratios of the polymer compositions are less than 10; alternatively, less than 6; or alternatively, less than 5 and thus indicate a relatively high tail in the MWD.
• the molecular weights and molecular weight distributions are obtained using gel permeation chromatography (GPC).
• the GPC is performed using a Waters 150 CV gel permeation chromatograph with trichlorobenzene (TCB) as the solvent, with a flow rate of 1 milliliter/minute at a temperature of 140°C.
• 2,6-Di-t-butyl-4-methylphenol (BHT) at a concentration of 1.0 gram per liter is used as a stabilizer in the TCB.
• An injection volume of 220 liters is used with a nominal polymer concentration of 0.3 gram/liter at room temperature.
• Dissolution of the sample in stabilized TCB is carried out by heating at 160-170°C for 20 hours with occasional, gentle agitation.
• the gel permeation chromatograph includes two Waters HT-6E columns (7.8 mmx300 mm). The columns were calibrated with a broad linear polyethylene standard (Chevron Phillips Chemical Company Marlex® BHB 5003) for which the molecular weight has been determined.
• Polymer resins having the previously described properties can be formed into articles of manufacture or end use articles using techniques known in the art such as extrusion, blow molding, injection molding, fiber spinning, thermoforming, and casting.
• a polymer resin can be extruded into a sheet, which is then thermoformed into an end use article such as a container, a cup, a tray, a pallet, a toy, or a component of another product.
• end use articles into which the polymer resins can be formed include pipes, films, bottles, fibers, and so forth. Additional end use articles would be apparent to those skilled in the art.
• the alumina support was then impregnated with various amounts of ammonium sulfate in aqueous solution as shown in Table 1 below, followed by drying the support in a vacuum oven at 100°C for 10 hours.
• the support was then impregnated with a methanolic solution of C ⁇ (N03) 3 to incorporate chromium therein, followed by drying it in a vacuum oven at 100°C for 10 hours.
• the resulting catalyst precursor was then activated by calcination in dry air for 3 hours at 600°C.
• Table 1 shows several physical properties of the activated catalyst samples and the compositions of the catalyst samples. Table 1 further provides the weight percent of sulfate added to each alumina support and the weight percent of sulfate actually found by X-ray fluorescence analysis in each catalyst sample after the calcination step, all weight percentages being by total weight of the catalyst. Based on the results depicted in Table 1, all or a substantial portion of the sulfate added to the support was retained on the catalyst during the calcination. For samples 1 and 2, the amount of sulfate measured after calcining was slightly larger than the actual amount of sulfate added.
• the measured surface area and pore volume, expressed per gram of the finished catalyst, are also shown in Table 1.
• the measured surface area and pore volume were corrected for the additional weight of the sulfate as shown in Table 1 and are also expressed in Table 1 per gram of the original alumina support. In view of these corrected values, surface area and pore volume did not significantly decline as the amount of sulfate added was increased. Rather, they surprisingly stayed about the same.
• Example 2 Catalyst samples (samples 4-9) were prepared in the same manner as described in Example 1 with different amounts of sulfate except that catalyst sample 4 contained no sulfate. The amount of sulfate added to each catalyst sample and the weight percent of hexavalent chromium (Cr VI) contained in each sample by total weight of the sample are shown in Table 2 below.
• a polymerization run using each catalyst sample was made in a 2.2 liter steel reactor equipped with a marme stirrer rotating at 400 rpm.
• a steel jacket containing boiling methanol with a connection to a steel condenser surrounded the reactor.
• the boiling point of the methanol was controlled by varying nitrogen pressure applied to the condenser and jacket, which permitted precise temperature control to within half a degree centigrade, with the help of electronic control instruments.
• a small amount (0.04 to 0.10 grams) of the catalyst sample was first charged under nitrogen to the dry reactor. Next 1.2 liter of isobutane liquid was charged to the reactor, and the reactor was heated up to 95°C.
• Triethylboron (TEB) cocatalyst was added in a heptane solution midway during the isobutane addition.
• the amount of TEB cocatalyst added was equal to 8 ppm of the isobutane diluent by weight.
• ethylene was added to the reactor to equal a fixed pressure of 550 psig (3792 kPa), which was maintained during the experiment. The stirring was allowed to continue for one hour, and the activity was noted by recording the flow of ethylene into the reactor to maintain the set pressure.
• EXAMPLE 3 A catalyst treated with 20 parts of ammonium sulfate per 100 parts by weight of alumina was made according to the procedure described in Example 1. The catalyst contained 2 % Cr by weight of the alumina. It was calcined at 600°C for activation, and then it was used to polymerize ethylene at 95°C and 550 psig, (3792 kPa) according to the procedure described above, with the exception of two changes. First, two of the runs were performed using 8 ppm of triethylaluminum (TEA) as the cocatalyst, and two runs were performed using 8 ppm of triethylboron (TEB) as the cocatalyst.
• TEA triethylaluminum
• TEB triethylboron
• Figure 3 compares the molecular weight distribution of one of the foregoing polymers formed using the sulfate treated Cr/alumina catalyst (treated with 14% SO by weight of the catalyst) and the TEB cocatalyst to the MWD of a polymer formed using a Q-/alumina catalyst containing no sulfate but otherwise prepared, activated, and run identically.
• Figure 3 again illustrates the narrowing effect of the sulfate on the MWD.
• EXAMPLE 4 Catalysts treated with 0 to 40 parts ammonium sulfate per 100 parts alumina by weight were made as previously described in Example 1. These catalysts contained 2% Cr by weight of the alumina and were calcined at 600°C for activation. These catalysts were then allowed to polymerize ethylene at 95°C and 550 psig (3792 kPa) as previously described, except that 175 psig (1207 kPa) of hydrogen gas was added to decrease the molecular weight of the polymer formed. The cocatalyst used was 8 ppm by weight (based on the isobutane diluent) of a mixture of 3 parts TEB and 1 part TEA.
• the melt index (MI) which represents the rate of flow of a molten resin through an orifice of 0.0825 inch diameter when subjected to a force of 2,160 grams at 190°C, was deteixnined in accordance with ASTM D1238. As shown in Table 3, despite the large amount of H 2 added, the polyethylene resins had low HLMI values, which indicate that they had high molecular weights. Further, as the amount of sulfate increased, the HLMI dropped, indicating that the presence of the sulfate caused the molecular weights to increase. The measured molecular weights also increased as the amount of sulfate increased.
• the polydispersity index values (Mw/M N ) of the polyethylene resins were surprisingly narrow, with M W /M N values ranging from 8 to 13.
• the resins also unexpectedly exhibited Mz/Mw values of around 4.
• the Mz/Mw is another measure of molecular weight breadth, which is particularly sensitive to the highest molecular weight components of the distribution.
• a distinctive feature of the polymer resins was their low degree of long chain branching, as indicated by several of the results in Table 3.
• the HLMI/MI ratio values were much lower than those of polymers produced by other chromium-based catalysts at such high Mw- Despite having Mw values in the range of 300,000 to over 500,000 g/mol, the relaxation times of the resins were only 2 to 6 seconds, which is also unique for polymers in general, and especially for polymers produced by chromium-based catalysts.
• the resins also exhibited high tan delta (measured at 0.1 rad/sec) values and rheological breadth parameters unprecedented by other chromium-based catalysts.
• the addition of sulfate caused those values to go up, indicating a decrease in long chain branching.
• the catalyst containing the largest amount of sulfate produced a polyethylene resin having a Mw of over half a million and a rheological breadth parameter of 0.38.
• a parameter of 0.38 is above that expected from even a Ziegler- Natta catalyst at the same Mw-
• the high tan delta values exhibited by the polyethylene resins also indicate that the resins were essentially linear.
• Figure 5 shows the molecular weight distribution of some of the polymers in Table 3.
• sulfate is added to the catalyst, the molecular weight distribution narrows, eliminating especially the low molecular weight end of the curve.
• EXAMPLE 5 The following run was performed twice and demonstrates the use of an organochromium compound with the sulfated alumina support.
• Alumina A from W.R. Grace was again obtained and impregnated with an aqueous solution of ammonium sulfate to incipient wetness.
• the total amount of ammonium sulfate added was equivalent to 20 wt.% based on the weight of the alumina (calculated as Al 2 O 3 ). After being dried in a vacuum oven for 12 hours, this powder was then calcined in dry air for 3 hours at 600°C.
• EXAMPLE 6 The following runs demonstrate the use of sulfate to modify the molecular weight distribution on an aluminophosphate catalyst.
• Alumina A having a surface area of 300 m 2 /g and a pore volume of 1.5 cc/g was obtained from W.R Grace. It was calcined in flowing dry nitrogen at 600°C for 1 hour. At this point some of the alumina was treated with sulfate and the rest was not. The alumina to be sulfated was then impregnated to incipient wetness with water containing sulfuric acid in an amount equivalent to 7.3% by weight of the dry alumina to be used (calculated as Al 2 O 3 ). The damp powder was then dried at 110°C for 8 hours and again calcined in nitrogen at 600°C for an hour.
• Triethylaluminum or triethyboron cocatalyst was used, along with 50 psig (345 kPa) H2. Ethylene was supplied on demand at 550 psig (3792 kPa) for 60 minutes.

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