POLYMERIZATION CATALYST SYSTEMS, METHODS OF MAKING AND USES THEREFOR

Abstract: A novel magnesium treated silica-containing compound that is useful as a support for chromium based olefin polymerization catalyst systems is provided which produces ethylene polymers having with MWD's that promote good properties particularly in HMW film applications.

Description: POLYMERIZATION CATALYST SYSTEMS, METHODS OF MAKING AND USES THEREFOR This invention relates to polymerization catalyst systems and polymerization processes. By "consisting essentially of" herein it is intended to mean that the substance or combination of substances recited after this phrase does not include any further components which would materially affect the properties of the substances or combination of substances recited after this phrase. Supported chromium oxide catalyst systems long have been used to prepare olefin polymers in hydrocarbon solution or slurry processes to give products having excellent characteristics from many standpoints. A number of supports have been broadly disclosed in the art for the support of chromium oxide catalyst systems including, silica, alumina, boria, zirconia, silica-alumina, and other refractory metals. In order to obtain a polymer product with easy processing characteristics, catalyst systems preferably have a low pore volume and high surface area. Generally, it is recognized that catalyst systems having a low pore volume and high surface area can result in a higher melt index and produce an olefin polymer that is easier to process. Unfortunately, it also has been found that decreasing the catalyst system pore volume usually corresponds to a decrease in the catalyst system surface area. These catalyst systems provide polymers with extraordinarily good properties which can only be achieved presently on the commercial scale by making bimodal polymers from two reactors. Thus the first benefit is one of economics. With the magnesia modified silica catalyst we get polymers with fabulous properties more cheaply than our competitors. For our HMW film it is necessary to add a fluoro- polymer to process the resin when it is blown into film. So processing is not the real forte for this particular catalyst system. These characteristics are contrary to what is desired for polymer processability. It is also known that catalyst systems need to be dry for best polymerization productivity and activity. Therefore, catalyst systems are heated and dried prior to use. Unfortunately, heating of catalyst systems can cause problems with catalyst system integrity. For example, if a catalyst system uses a silica-based inorganic oxide support, heat can cause the silica to melt, or sinter, and therefore decrease the surface area of the resultant catalyst system If alumina is selected as a support material, heating of the alumina can cause the alumina to fracture and create uneven and rough catalyst system particulates which can result in a polymer product that is difficult to handle SUMMARY OF THE INVENTION Therefore, it is desirable to provide improved silica-containing inorganic oxide catalyst system supports Again it is desirable to provide a silica-containing inorganic oxides having a high surface area Yet again it is desirable to provide novel silica-containing inorganic oxides that either retain or increase surface area upon heating. Once again it is desirable to provide an improved chromium catalyst system. Again it is desirable to provide a catalyst system suitable for use in polymerization processes. Once more it is desirable to provide a chromium catalyst system that can produce an olefin polymer having a decreased melt index. In accordance with one embodiment of this invention a process is provided to prepare a magnesium treated silica-containing composition comprising contacting a silica-containing inorganic oxide with a magnesium-containing compound and converting said magnesium-containing compound to a magnesium oxide to produce a magnesium treated silica-containing composition. In accordance with another embodiment of this invention a process is provided to contact said magnesium treated silica-containing composition with a chromium compound to produce a catalyst system composition. In accordance with yet another embodiment of this invention a polymerization process is provided using a catalyst system comprising chromium supported on a magnesium treated silica-containing composition. DESCRIPTION OF THE PREFERRED EMBODIMENTS In accordance with the present invention, a predominately silica-containing compound is contacted with at least one magnesium compound convertible to the oxide form, and then calcined The essence of this invention is either precipitating, or doping, magnesium within the pores of a silica-containing compound. Magnesium treatment of the silica-containing compound can be done in accordance with different embodiments of the invention, discussed in detail below. The resultant magnesium treated silica-containing compound can be used as a catalyst system support. As used in this disclosure, the term "support" refers to a carrier for another catalytic component. However, by no means, is a support necessarily an inert material; it is possible that a support can contribute to catalytic activity and selectivity. Silica-containing compounds employed to prepare polymerization catalyst systems of the present invention must contain a major proportion of silica. Preferred silica-containing compounds contain a substantial proportion of silica, e.g., at least about 50% by weight of silica, preferably at least about 70%, and most preferably 90%, by weight of silica, although still larger proportions of silica can be used. The preferred predominantly silica-containing compounds of the present invention consist essentially of less than about 50% by weight of at least one additional metal oxide such as, for example, alumina, boria, magnesia, titania, zirconia and mixtures of any two or more thereof. Generally, the silica-containing compound employed has a surface area, prior to magnesium treatment, of at least about 10 square meters per gram (m 2 /g). Preferably, the initial surface area of the silica-containing compound, prior to treatment with a magnesium compound, can be at least 50 m 2 /g, and most preferably, any silica-containing compound employed is a high surface area silica, i.e., support, with a surface area in excess of about 100 m7g. In accordance with one embodiment of this invention, a magnesium salt can be used in a very concentrated aqueous solution and precipitated within the pores of a silica-containing compound. Exemplary magnesium salts include, but are not limited to, magnesium nitrate, magnesium chloride, magnesium acetate, and mixtures thereof. The concentrated aqueous solution of the magnesium salt is mixed with the silica-containing compound. Mixing can occur by spraying the aqueous solution containing the magnesium salt onto the silica-containing compound, or by slurrying the aforementioned components together. The concentration of the aqueous magnesium solution can be any amount sufficient to deposit enough magnesium into the pores of the silica-containing compound to increase the surface area of the silica-containing compound and yet, not significantly decrease the pore volume of the silica-containing compound. Usually, concentrations of about 125 millimoles of the magnesium salt per l OOg (mmol/ 1 OOg) of support are sufficient. Preferably, concentrations within a range of about 200 to about 700 mmol/lOOg of support and most preferably, within a range of 250 to 400 mmol/ 1 OOg of support, are preferred. Higher or lower magnesium salt concentrations do not have significant, beneficial effects on surface area. Contacting conditions of the silica-containing compound and the magnesium compound are not critical. Any temperature and any period of time can be suitable. For convenience, contacting generally is carried out at about room temperature, although higher or lower temperatures, within a range of about 4.4°C to about 38°C (about 40°F to about 100°F), can be used. A time period sufficient to allow the support and magnesium compound to come into intimate contact is all that is necessary. Thus, the silica-containing compound and the magnesium salt solution can be brought into contact for as little time as a few seconds to several hours or more, such as, for example, about 5 seconds to about 24 hours, as convenient. After sufficient contact time, any basic compound can be added to the magnesium/silica-containing compound slurry to precipitate the magnesium within the pores of the silica-containing compound. Exemplary basic compounds include, but are not limited to hydroxides, such as for example, sodium hydroxide, potassium hydroxide, ammonium hydroxide, and mixtures thereof. Preferably, the basic compound is ammonium hydroxide (NH 4 OH), due to availability and ease of use. Heat and increased times can increase effectiveness of introducing and/or precipitating magnesium into the pores of the silica-containing compound. Optionally, the magnesium treated silica-containing support can be heated to temperatures within a range of about 30°C to about 90°C and aged for times of up to eight hours. Preferably a temperature range of 50°C to 60°C and an aging time of about one hour is sufficient. Following precipitation of magnesium within the pores of the silica- containing compound, a substantial portion of excess liquid can be removed by any suitable means, such as, foi example, decantation, filtiation, 01 any othei method known in the art Aftei lemoval of excess liquid, the magnesium-tieated sihca- contaming compound is nnsed with a dilute basic solution, such as, for example, ammonium hydi oxide and washed with deionized The solid then is dried in any manner known in the art to remove any residual liquid Any suitable means can be employed, such as, for example, oven drying, vacuum drying, alcohol washing, and/or passing of vigorous steam of dry (moisture-free) gas over the magnesium treated silica-containing compound Preferably, for ease of use, the magnesium treated silica-containmg compound is washed with an alcohol Any alcohol that can remove residual liquid, l e , water, can be used to wash the magnesium-treated sihca-contammg compound Exemplary alcohols include, but are not limited to, methanol, ethanol, propanol and mixtures thereof The partially dried, magnesium-treated sihca-contammg compound then is further dried to remove any remaining absorbed solvent and subjected to calcination conditions Calcination can be conducted by heating the magnesium treated sihca-contammg compound m the presence of a dry, oxygen- containing gas, such as, for example, air, under conditions sufficient to convert any magnesium to an oxide Generally, temperatures within a range of about 300°C to about 800°C, for a time withm a range of about 0 5 to about 20 hours are sufficient Typically, less time is required at higher calcination temperatures and more time is required at lower calcination temperatures Preferably, heating occurs at a temperature of around 350°C to about 450°C (about 662°F to about 842°F) for a period of two to four hours, depending upon the amount of compound being calcined, and then raised to a temperature in the range from 400°C to 800°C and held and this temperature from 3 to 15 hours dependmg on the amount of compound being calcined In accordance with a second embodiment of this invention, magnesium treatment can comprise coprecipitatmg magnesia with a silica-containmg compound This coprecipitation method can be as equally effective in increasing the surface area of silica containing compounds As used in this disclosure, coprecipitation is preparation of a catalyst system wherein a magnesium compound is copiecipitated with a silica-containing compound and then ch omium can be added Anothei method of copiecipitation can be piepaiation of a catalyst system wheiem a magnesium compound is copiecipitated with a silica-containmg compound and a chiomium compound The magnesium treated silica-containing support, after calcination, must be contacted with any chromium compound in oi dei to produce a polymerization catalyst system The chromium compound can be added in accoi dance with any method known in the art Exemplary methods include starting with a sihca/chiomium cogel-containing compound and then ti eating with a magnesium- containing compound Another exemplary method is to add a chromium compound with the magnesium salt and precipitate both chromium and magnesium withm the pores of the silica-containmg compound Another embodiment of the invention comprises adding chromium in conjunction with an alcohol solution prior to calcination of the silica-containmg support A further embodiment of this invention is to add the chromium after the support has been calcined Addition of chromium also can be done after the magnesium-treated silica-containmg compound has been dried by combining additional magnesium with a solution of a chromium compound Commonly used polymerization cocatalysts can be used, if desired, but are not necessary Exemplary cocatalysts include, but are not limited to, metal alkyl, or organometal, cocatalysts, l e , alkyl boron and/or alkyl aluminum compounds The term "metal" in organometal is intended to include boron Often these cocatalysts can alter melt flow characteristics (melt index or high load melt index) of the resultant polymer While not wishing to be bound by theory, it is believed a cocatalyst can act as a scavenger for catalyst system poisons If the cocatalyst is an alkyl boron compound, trihydrocarbylboron compounds are preferred and tπalkyl boron compounds are most preferred Preferably, the alkyl groups have from about 1 to about 12 carbon atoms and preferably, from 2 to 5 carbon atoms per alkyl group Tπalkyl boron compounds, such as, for example, tπ-n-butyl borane, tπpropylborane, and tπethylboran (TEB) are preferred cocatalysts because these compounds are effective agents to improve polymer properties, such as, for example, to reduce melt flow and retard polymer swelling during polymerization Other suitable boron compounds include tπhydrocarbyl boron compounds broadly, tπaryl boron compounds, such as, for example, triphenylborane, boron alkoxides, such as, for example, B(OC 2 H 5 ),, and halogenated alkyl boron compounds, such as, for example, B(C 2 H 5 )C1 2 By far, the most preferred cocatalyst is tπethylboran, for the reasons given above Other suitable cocatalysts can be aluminum compounds of the formula AIR',^.,, where X is a hydride or halide, R' is a 1 to 12 carbon atom hydrocarbyl radical and n is an integer of 1 to 3 Tπethylaluminum (TEA) and diethylaluminum chloride (DEAC) are particularly suitable A cocatalyst, when used, usually can be used in an amount within a range of about 1 to about 20 parts per million (ppm), or milligrams per kilogram (mg/kg), based on the mass of the diluent in the reactor Preferably, cocatalyst is used in an amount within a range of 1 to 12 mg/kg, for cost effectiveness and best resultant polymer properties Expressed in other terms, a cocatalyst can be present in an amount so as to give an atom ratio of cocatalyst metal to chromium within a range of about 0 5 1 to about 10 1, preferably 2 1 to 8 1 The cocatalyst either can be premixed with a catalyst system or added as a separate stream to the polymerization zone, the latter being preferred Reactants and Reaction Conditions The polymers produced in accordance with the process of this invention are homopolymers of ethylene and copolymers of ethylene and higher alpha-olefin comonomers Preferably, the ethylene concentration in the polymerization reactor is within a range of from about 2 weight percent to about 20 weight percent, based on the total liquid contents of the reactor. Most preferably, the ethylene concentration in the polymerization reactor is within a range of from about 4 to about 15 weight percent Measured in another manner, ethylene concentration in the polymerization reactor flash gas is within a range of from about 5 weight percent to about 12 weight percent Most preferably, the ethylene concentration in the polymerization reactor flash gas is within a range of from about 6 5 to about 10 weight percent While ethylene concentration does not significantly affect the molecular weight of the resultant polymer, higher or lower ethylene concentration can effect catalyst activity The alpha-olefin comonomeis used in the piesent invention must be selected fiom the gioup consisting of 1-butene, 1 -hexene, and mixtuies theieof in oi dei to pioduce a copolymei with desn ble pioperties as well as ease of use in a loop/slurry polymeuzation leaction piocess The most piefeπed comonomei is 1 - hexene to pi oduce a copolymei with the best product pioperties If a comonomer is present duπng polymeuzation, the comonomei concentration in the polymerization reactoi is within a range of from about 0 5 to about 20 mole percent Most preferably, comonomer is present withm a range of about 1 to about 15 weight percent As used in this disclosuie the term "polymer" includes both homopolymers and copolymers Polymerization can be carried out in any manner known in the art, such as gas phase, solution or slurry conditions, to effect polymerization A stirred reactor can be utilized for a batch process, or the reaction can be carried out continuously m a loop reactor or in a continuous stirred reactor A preferred polymerization technique is that which is referred to as a particle form, or slurry, process wherein the temperature is kept below the temperature at which polymer goes into solution Such polymerization techniques are well known in the art and are disclosed, for instance, in Norwood, U S 3,248,179, the disclosure of which is hereby incorporated by reference The preferred temperature in the particle form process is within a range of about 185 to about 230°F (about 85 to 110°C), although higher or lower temperatures can be used Two preferred polymerization methods for the slurry process are those employing a loop reactor of the type disclosed m Norwood and those utilizing a plurality of stirred reactors either in series, parallel or combinations thereof wherein the reaction conditions can be different in the different reactors The molecular weight of the polymer can be controlled by various means known in the art such as adjusting the temperature (higher temperature giving lower molecular weight) and introducing, or varying the amount of, hydrogen to alter the molecular weight, or varying the catalyst compounds POLYMER CHARACTERISTICS Polymers produced in accordance with this invention have increased density, broadened molecular weight distribution especially on the high molecular weight end, decreased MI, and decreased HLMI, as compared to polymers prepared from conventional supported chromium catalyst systems be they chromium on silica or chromium on a silica-titania matrix. It is believed that the uniqueness of this catalyst system is derived from the formation of a catalyst with a large surface area and unique polymerization sites. These characteristics can produce a polymer, or resin, which has an increase in the molecular weight region which promotes good properties in resins while not enhancing the very high molecular weight tail or long chain branching which characterizes chromium based catalysts. While not wishing to be bound by theory, it is believed that polymers produced in accordance with this invention are unique in that the polymer chains are intertwined in each polymer particle; each polymer particle can be considered "all-inclusive" as to polymer characteristics. This catalyst system composition most preferably is applicable for use with ethylene polymerization. The resultant ethylene polymer usually can have a density within a range of about 0.91 to about 0.975 g/cc, and preferably within a range of about 0.945 to about 0.96 g/cc. The polymer melt index (MI) usually is within a range of about 0.015 to about 0.7 g/10 min and preferably within a range of about 0.02 to about 0.5 g/10 min. The polymer high load melt index (HLMI) of the resultant polymer usually is within a range of about 1 to about 175 g/10 min and preferably within a range of about 4 to about 70 g/10 min. The shear ratio (HLMI/MI) is usually within a range of about 40 to about 250, and preferably within a range of about 50 to 200. Polymers having characteristics within the given ranges are especially useful for applications of blow molding and/or film production. The uniqueness of the disclosed and claimed catalyst system is the ability to make polymers with a molecular weight distribution (MWD) that promotes good properties particularly dart impact in high molecular weight (HMW) film applications. While not wishing to be bound by theory, it is believed that these property improvements result from the lessening of long chain branching (LCB) and/or the reduction in HMW tails as a result of the increased surface area. A further understanding of the invention and its advantages is provided by the following examples. EXAMPLES The following Examples lllustiate vanous aspects of the invention Data aie included foi each example about polymeuzation conditions, as well as the lesultant polymei All chemical handling, including leactions, preparation and storage, was performed undei a dry, inert atmospheie (usually nitrogen) In geneial, catalyst systems used for polymerization in the Examples weie prepared as described in this application All laboratory polymerization tests were done m a steam-jacketed, 2 65 htei, stiπed, stainless steal vessel In a typical run, 40 to 100 mg of catalyst system were added to the reactoi followed by hydrogen, if used, then 600 ml of isobutane If a cocatalyst, such as a metal alkyl, was utilized, catalyst was flushed into the reactor with an additional 600 ml of isobutane When hexene- 1 oi any other comonomer was used then comonomer was added just before the system was pressured to 3 89 MPa (550 psig) with ethylene Ethylene was added on demand as the reaction proceeds Pilot plant polymerizations were done in a 87 litre (23-gallon) slurry loop reactor at a production rate of approximately 1 1 3 kg (25 pounds) of polymer per hour General procedures for preparation of catalyst systems m the following Examples is as follows This also is referred to as an AESOP (Alkaline Earth Standard Oxide Poregel) preparation First, a concentrated solution of a magnesium salt is prepared by dissolving the salt and chromιum(III) nitrate in a minimum amount of deionized water This solution, called a "syrup," was heated to about 50 to about 55°C to dissolve the salts Chromium was added m the amount of one weight percent of the MgO formed from the dehydration of the Mg(OH) 2 to ensure that some chromium will be available to bond to the surface of the MgO Then, the syrup and ammonium hydroxide were sprayed onto the support Alternatively, only the syrup can be sprayed onto the support and then the support comprising the sprayed syrup can be combined with an aqueous solution of ammonium hydroxide This technique is preferred when the support has insufficient pore volume to contain both the syrup and required volume of ammonium hydroxide If this alternative method is used, it is possible to have up to a 30% loss of MgO in the final magnesium-treated silica-containing support Preferably, the catalyst system is aged at temperatures within a range of about 50°C to 60°C in 0 7 to 1 0 molar ammonium hydroxide (NH 4 OH) solution for about one hour The NH 4 OH is removed and the catalyst system is washed two to three times in water heated to about 50 to 60°C for about 30 minutes and filtered Then, one to three n-propanol washes followed the water washes The catalyst system was dried in a vacuum oven for at least 24 to about 48 hours at about 120°C to 125°C More than 95% of the volatile material was lost during the first 10 to 15 hours of drying The catalyst was kept in a vacuum oven until no further weight loss was observed, about one day Although the amount of volatile material lost during the second day of drying is less than 5 wt%, it is believed that this additional drying time can avoid poor catalyst system activation. The dried catalyst was screened through a 35-mesh (0.50mm) screen and stored. Catalyst systems generally were prepared as described above. Specific variations to the above-discussed preparation are listed below. Analyses of the resultant polymers were conducted according to the following procedures: Density (g/ml) - ASTM D 1505-68 and ASTM D 1928, Condition C Determined on a compression molded sample, cooled at about 15°C per minute, and conditioned at room temperature for about 40 hours. Fluff Bulk Density (g/ml) - ASTM D 1895, the apparent density test. High Load Melt Index (HLMI)(g/10 min) - ASTM D 1238. Determined at 190°C with a 21,600 gram weight. Melt Index (MI)(g/10 min) - ASTM D 1238. Determined at 190°C with a 2,160 gram weight. Surface Area and Pore Volume Measured by BET nitrogen sorption using a Quantachrome Corporation, Autosorb-6b instrument. Throughout the Examples, "est" means the weight percent estimated from ingredients of the preparation, assuming 100 % recovery. EXAMPLE 1 Run 101 : 10 to 15 g of 964Magnapore ® , Lot 2633, obtained from W R Grace of Baltimore, Md was activated by calcination in air at a rate of approximately 6°C/mιn to a hold temperature of 593°C and held at this temperature for about three hours Airflow was 1 2 to 1 6 SCFH at ambient temperature After cooling, the system was flushed with nitiogen to remove all traces of air The catalyst was stored under nitrogen until use This catalyst is designated as a control and called 964 Magnapore ® Run 102 1025g (4 0 moles) of Mg(NO 3 ) 2 « 6H 2 O and 13 3 g of Cr(NO,),»9H 2 O were dissolved in 400 ml of deionized water with stirring and heating The warm syrup was sprayed onto 800g of 964 Magnapore ® (Lot 2633) followed by 670 ml of cone NH 4 OH The mixture was divided into 2 equal portions with each being aged for 1 hour at about 50 to 60°C in 2 6 liters of deionized water containing 135 ml of cone NH 4 OH The solids were filtered and then slurried in 2 6 liters of water at about 50 to 60°C for 30 min This wash process was repeated Each batch then was washed three times in 2 6 liters of 50 to 60°C) n-propanol for 30 minutes, filteπng after each wash Both batches were dried in vacuum oven at about 120 to 130°C for about 48 hours Fifteen grams of this catalyst was calcined in air heated at a rate of l°C/min to 400°C and held there for two hours Heating then was continued at the same rate to a final temperature of 593°C and held there for about three hours The activated catalyst was recovered and stored under nitrogen until use This catalyst system is designated as AESOP preparation of 964 Magnapore ® /MgO catalyst system Run 103 A methanolic solution containing 28 g of Mg(NO 3 ) 2 # 6H 2 O was added to 40g of 964 Magnapore ® (Lot 2633) This was dried in vacuum oven at about 1 10°C for about 16 hours 0 34 g of Cr(NO 3 ) 3 «9H 2 O in methanol was added to the dried solid and then dried again To this twice-dried solid was added a methanolic solution of 14 2g of Mg(NO 3 ) 2 «6H 2 O and 0 21g Cr(NO 3 ) 3 » 9H 2 O and re- dried in the vacuum oven at about 110°C for about 72 hours The resulting solid was calcined as described in Run 102 In a similar fashion, catalysts were prepared from the chloride and acetate salts of magnesium These catalyst systems are described as impregnation of the 964 Magnapore ® , i e , 964 Magnapore ® /Mg(NO 3 ) 2 , 964 Magnapore ® /Mg(C 2 H 3 O 2 ) 2 , and 964 Magnapore ® /MgCl 2 Properties of the catalyst systems are provided in Table 1 TABLE 1 Run Catalyst Activation Surface Pore Wt % Number Temperature Area Volume MgO a (°C) (m7g) (cmVg) 101 964 Mag 570 2 3 0 0 102-a 964 Mag/MgO 593 71 1 1 14 15 6 102-b 964 Mag/MgO 649 701 1 5 18est 102-c 964 Mag/MgO 760 590 1 3 18est 103-a 964 Mag/Mg(NO,) 2 593 388 1 04 12 8 103-b 964 Mag/Mg(C 2 H 3 O 2 ) 2 593 420 1 32 13 4 103-c 964 Mag/MgCl 2 593 392 1 15 12 9 d Weight percent oxides were calculated in their most common forms from x-ray fluorescence spectrometπc results of the elements EXAMPLE 2 This example illustrates other examples of the enhancement of surface area by using the AESOP procedure as described in Example 1 Designations 952, HA30W, HPVSiO2, and XPO-7003 are different silicas made by the Davison Catalyst Division of W R Grace Co of Baltimore, Md TABLE 2 Run Support Catalyst Activation Surface Pore Wt % Wt % No Matrix Description Temp (°C) Area Volume MgO TiO, (m 2 /g) (cm7g) 201 Silica 952 SiO 2 300 1 5 202 Silica 952 SiO 2 /MgO 400 461 1 29 14 6 203 Silica- 963 Magnapore ® 649 491 2 35 3 4 Titania 204 Silica- 963 Mag/ MgO 704 589 1 57 17 4 3 4 Titania 205 Silica HA30W 593 479 1 55 0 0 206 Silica HA30W/MgO 593 638 1 18 14 1 0 207 Silica HA30W/MgO/TiO 2 593 599 1 29 15 3 0 208 Silica HPVSiO 2 400 277 2 58 0 0 209 Silica HPVSiO 2 /MgO 400 535 1 68 14 6 0 210 Silica HPVSIO 2 /TiO 2 593 268 2 26 0 9 1 211 Silica HPVSiO 2 /MgO/TiO 2 593 482 1 47 14 6 9 7 212 Silica XPO-7003 Run Support Catalyst Activation Surface Pore Wt. % Wt. % No. Matrix Description Temp. (°C) Area Volume MgO TiO 2 (m 2 /g) (cm7g) 213 Silica XPO-7003/MgO 593 461 1.29 14.4 214 Silica XPO-7003/MgO/TiO 2 593 643 1.29 12.6 8.5 EXAMPLE 3 This Example demonstiates the impiovement of catalyst system support and catalyst system suiface aiea fiom cogellation of silica and a magnesium compound to form a catalyst system support Run 301 64 g Mg(NO,),»6H 2 O weie dissolved in 150 ml deionized watei to which 2 ml cone HNO, had been added While stirring continuously, 149 ml of tetraethoxysilane (Strem, 98%, density = 0 9356 g/cc) were added over a period of 45 minutes To this mixtui e were added dropwise a solution containing 100 ml of water and 10 ml of concentiated NH 4 OH Some white precipitate formed during the addition of the base The mixture gelled after the addition of 37 ml of the dilute NH 4 OH The gel was aged in 2 liters of water containing 25 ml of concentrated NH 4 OH at 80°C for about one hour after which it was filtered and washed twice at 80°C for about 30 minutes with two two-liter portion of water containing 5 ml of cone NH 4 OH The gel then was washed twice with n-propanol at about 70°C for about 30 mm After a final filtration, the solid was recovered and dried m a vacuum oven at about 110°C for about 24 to 72 hours 1 wt% chromium from a methanol solution of Cr(NO 3 ) 3 *9H 2 O was added to a 20g portion of the catalyst and re-dπed overnight at about 1 10°C under vacuum The catalyst was sieved through a 35-mesh screen and calcined in the manner described m Run 102 Run 302 Catalyst preparation, work-up and calcination were as described in Run 301, except 100 ml of tetraethoxysilane was used Run 303 Catalyst preparation, work-up and calcination were as described in Run 301, except 50 ml of tetraethoxysilane was used Run 304 Catalyst preparation, work-up and calcination were as descnbed in Run 301, except that a magnesium salt was not used Gelation occurred after the addition of 30 ml of dilute NH 4 OH solution Table 3 Examples illustrating the enhancement of catalyst surface area from the cogelation of silica and magnesia TABLE 3 Run Catalyst Activation Surface Poie Volume Wt % No Description Temperature Area (cmVg) MgO (°C) (m 2 /g) 304 SιO 2 /MgO 593 649 1 54 1 1 6 305 SιO 2 /MgO 593 676 1 18 16 7 306 SιO 2 /MgO 593 712 1 45 25 2 307 SiO, 593 424 1 95 0 The uniqueness of the catalyst is illustrated by a comparison among Examples 1, 2 and 3 EXAMPLE 4 The enhancement of surface areas of a variety of supports by means of the porgelation of magnesium hydroxide followed by calcination to form MgO apparently is a unique phenomena among the alkaline earth oxides as illustrated by data of Table 4 Run 401 10 to 15 g 964 Magnapore ® (Lot 2622) were calcined at about 704°C for about three hours as described in Run 101 This catalyst system is designated as a control, 964 Magnapore ® Run 402 120g (0 25 moles) of Mg(NO 3 ) 2 » 6H 2 O were dissolved in 100ml of deionized water Then, 0 91g of Cr(NO 3 ) 3 # 9H 2 O were dissolved in 104 ml of this magnesium salt solution and sprayed onto 50g of 964 Magnapore ® The solid mixture was added to a solution containing 80 ml of cone NH 4 OH and 100 ml H 2 O, after which it was washed three times with two-liter portions of about 80 to 90° C water This was followed by two two-liter n-propanol washes as described in Run 102 A solid was recovered and dried in vacuum oven at 100°C for about 48 hours Then, 15 g was calcined by heating in air at a rate of l°C/min to 400°C, held there for about two hours Heating then was continued at the same rate to the final temperature of 704°C and held there for about three hours These catalysts are designated as 964 Mag/MgO Run 403 16 5g of Ca(NO 3 ) 2 «4H 2 O and 0 639 g Cr(NO 3 ) 3 »9H 2 O of were dissolved in deionized water This solution was sprayed onto 50 g of 964 Magnapore ® . The damp solid was added to a solution containing 67 ml of concentrated NH 4 OH and 100 ml H 2 O. Rinsing, drying, and calcination were as described in Run 402. This catalyst system is designated as 964 Mag/CaO. Run 403: 93g of Sr(NO 3 ) 2 «4H 2 O were dissolved in 125ml of deionized water. Then, 1 .58 g of Cr(NO 3 ) 3 » 9H 2 O were dissolved in 104 ml of this solution and sprayed onto 50 g of 964 Magnapore ® . The solid mixture was added to a solution containing 57 ml of cone NH 4 OH and 100 ml H,O. Rinsing, drying, and calcination were as described in Run 402. This catalyst system is described as 964 Mag/SrO. Run 405: 15.3 g of Ba(CH3CO2)2»4H 2 O and 0.707 g Cr(NO 3 ), # 9H 2 O were dissolved in deionized water. This solution was sprayed onto 50 g of 964 Magnapore ® after which the solid mixture was added to a solution containing 54 ml of cone NH 4 OH and 100 ml H 2 O. Rinsing, drying, and calcination were as described in Run 405. The data in Table 4 shows the properties of AESOP catalyst systems based on a 964 Magnapore ® matrix. TABLE 4 Run Catalyst Activation Surface Pore Wt.% Wt. c No. Description Temperature Area Volume MgO" TiO 2 (°C) (m7g) (cm7g) 401 964 Mag 704 593 2.26 0.0 7est 402 964 Mag/MgO 704 701 1.50 18est 5est 403 964 Mag/CaO 704 415 1.84 6.6 5.4 404 964 Mag/SrO 704 339 1.54 15.4 7.1 405 964 Mag/BaO 704 323 1.35 11.4 6.4 EXAMPLE 5 Poregelation of MgO (AESOP preparation) into a commercial chromium polymerization catalyst makes a unique polyethylene as shown by the data in Table 5. The data in Table 5 compares poregellation techniques with impregnation techniques of a magnesium compound. This uniqueness becomes apparent when the molecular weight and tau-eta (tau-eta is derived from the Caireau-Yasuda Model of curve fitting dynamic rheology data at 190°C) parameters are compared. Tau-eta is related to the molecular weight and molecular weight distribution of the polymer. The higher Mw and broader the MWD on the high molecular weight end the larger is tau-eta. Tau-eta also increases as the amount of long chain branching in the polymer increases. Thus, the decrease in tau-eta at a higher M w for a resin made by the AESOP catalyst can be inteφreted as less long chain branching and or less very high molecular weight molecules, i.e. those greater than several 964 Mag/Mg(NO 3 ) 2 million. Polymerization reactions were carried out to an activity of 2500 gPE/gcat in the presence of 2 ppm TEB, 2.0 wt% 1 -hexene, 0.2 mole percent of hydrogen and a reactor pressure of 3.89 MPa (550 psig). TABLE 5 Run Catalyst Wt. % Wt. °/ Reaction Activity HLMI Mw Taueta No. Type MgO TiO 2 Temp. °C gPE/gcat hr g/lOmin xlO " (s) 101 964 Mag 0 7est 80 5490 7.5 348 63 102 964Mag/Mg(NO 3 ) 2 12.8 6.1 90 3200 5.7 332 21 103 964 Mag/MgO 12.3 5.5 100 3880 5.6 410 t EXAMPLE 6 Uniqueness of AESOP catalysts derives from the increase in the molecular weight region centered around 500,000 - 1 ,000,000 as illustrated by the following SiO 2 /MgO cogel data of Table 6. The data in Table 6 show resins made from silica magnesia cogels with varying amounts of MgO. Polymerization reactions were carried out to an activity of 2500 g/g in the presence of 4.0 wt% hexene-1 and at a reactor pressure of 3.89 MPa (550 Psig). TABLE 6 Run Catalyst Wt. % Reaction Activity Density HLMI Mw M-/M- No. Type MgO Temp. °C gPE/gcat/hr g/cm 3 g/lOmin xlO "3 601 SiO 2 0 98 1920 0.922 6.4 294 19 602 SiO 2 /MgO 11.6 98 3180 0.934 1.8 421 21 603 SiO 2 /MgO 16.7 98 2160 0.934 0.6 429 19 604 SiO 2 /MgO 25.2 98 2430 0.933 0.5 551 21 EXAMPLE 7 Uniqueness of the MgO AESOP as compared to other Group II oxides is illustrated by the data in Table 7 The data in Table 7 show 20 HLMI resins made from the poregelation of alkaline earth oxides into 964 Magnapore ® starting material. The M w of 964 Mag/MgO is greater than that of the control but with a much smaller tau-eta value M w for CaO and SrO AESOPs of 964 Magnapore ® are less than that of the control for an equivalent HLMI The retention of M w while having a very low tau-eta may reflect the diminishing of the very high molecular weight components and/or lessening of long chain-branching typically present in conventional supported chromium catalyst systems. Laboratory polymerizations were run to an activity of 2500 gPE/gcat with temperature and pressure regulated to achieve the target HLMI of 20. All reactions were done in the presence of 1 wt.% hexene-1 but without any hydrogen or added cocatalyst. TABLE 7 Run Catalyst Wt. % Temp. Pres. Activity HLMI HLMI/MI Mw Mw/Mn Tau-eta, No. Type MO °C psig g/g/hr g/10min xlO "3 (s) 701 964 Mag 0 88 550 3810 20.8 125 189 30 6.91 702 964 Mag/MgO 13est 102 400 3050 18.7 72 211 12 0.91 703 964 Mag/CaO 7est 97 500 4850 20.9 56 145 8 0.19 704 964 Mag/SrO 15est 100 450 1960 21 44 132 7 0.08 EXAMPLE 8 The unique HMW peak in the molecular weight distribution appears to give resin properties that provide advantages in the film market as illustrated by the data in Table 8. The data in Table 8 provide a comparison of film properties between a commercial high molecular weight (HMW) bimodal film made in dual reactors versus that made from the poregelation of MgO onto either 964 Magnapore ® or HA30W. TABLE 8 Run 801 802 803 Catalyst 964 Mag/MgO HA30W/MgO/TiO 2 Lynx ® - 100 d Activation Temp., °C 593 593 Wt. % MgO 13est 15.3 Wt. % TiO 2 5est 9.4 SA, m 2 /g 678 599 PV, cnrVg 1.2 1.3 Resin Properties Density, g/cc 0.949 0.948 0.951 HLMI, g/10 mins 6.5 5.8 8.0 HLMI/MI 130 142 127 M w x 1000 352 415 303 M w /M. 30 36 32 Film Properties Tau 5 10 5 Dart Impact 390 354 372 MD 34 21 33 TD 184 84 143 Reactor Conditions Reactor Single Slurry Single Slurry Loop Dual Reactors Loop Ethylene, mol % 7.6 9.5 ? Hexene-1, mol % 0.03 0.10 ? Hydrogen, mol % 0.54 0.47 ? Temperature, °C 106 106 ? Pressure, psig 560 560 ? TEB, ppm 3.2 4.2 a Lynx ® -100 is a titanium-magnesium chloride type catalyst commercially available from Catalyst Resources, Inc. While this invention has been described in detail for the puφose of illustration, it is not to be construed as limited thereby but is intended to cover all changes and modifications within the spirit and scope thereof.

Claims: C L A I S 1 A process to prepare a treated silica-containing composition comprising a) contacting a silica-containing inorganic oxide with a magnesium- containing compound, and b) converting said magnesium-containing compound to a magnesium oxide 2. A process according to claim 1 , wherein said silica-containing composition further comprises a titanium compound 3. A process according to claim 1, further comprising introduction of a chromium compound onto said treated silica-containing composition. 4. A process according to claim 3, further comprising subjecting said chromium/silica-containing composition to activation in an oxidizing ambient at a temperature within a range of about 500 to about 800°C to convert at least a portion of the chromium component to the hexavalent state. 5. A process according to claim 1 wherein said silica-containing support is selected from the group consisting of silica, silica-alumina, phosphated silica, silica-titania, coprecipitated silica/titania, fluorided/silated alumina, and mixtures thereof. 6. A process according to claim 5, wherein said support is essentially silica. 7. A polymerization process comprising contacting in a reaction zone, at a temperature within a range of about 85°C to about 110°C (about 185°F to about 230°F) in the presence of a hydrocarbon diluent: a) ethylene monomer; b) a catalyst system comprising chromium supported on a magnesium treated silica-containing compound; and c) an aluminum alkyl cocatalyst; and recovering a polymer of ethylene. 8. A process according to claim 7, comprising the presence of higher alpha-olefin comonomer selected from the group consisting of 1-butene, 1 -hexene and mixtures thereof in said reaction zone. 9. A process according to claim 7, wherein said aluminum alkyl cocatalyst has the general formulae AIR,, A1R-X, and/or A1RX-, wherein R is an alkyl group having from about 1 to about 12 carbon atoms per molecule and X is a halogen atom. 10. A process according to claim 7, wherein said aluminum alkyl cocatalyst is selected from the group consisting of triethyl aluminum, triisobutylaluminum chloride, diethyl aluminum chloride, ethylaluminum sesquichloride, and mixtures thereof. 1 1. A process according to claim 7, wherein said aluminum alkyl cocatalyst is selected from the group consisting of triethyl aluminum, triisobutyl aluminum and mixtures thereof. 12. A process according to claim 7, wherein said diluent is isobutane. 13. A process according to claim 7, wherein said copolymer of ethylene comprises a polymer having: a) a broadened molecular weight distribution; b) a decreased melt index; and c) a decreased high load melt index, compared to polymers made in the absence of magnesium impregnation of a catalyst system comprising chromium supported on a magnesium treated silica-containing compound.

Inventors: BENHAM ELIZABETH A, COLLINS KATHY S, EATON ANTHONY P, MARTIN SHIRLEY J, MCDANIEL MAX P, SHVEIMA JOSEPH, SUKHADIA ASHISH M, BENHAM, ELIZABETH, A., COLLINS, KATHY, S., EATON, ANTHONY, P., MARTIN, SHIRLEY, J., MCDANIEL, MAX, P., SHVEIMA, JOSEPH, SUKHADIA, ASHISH, M.
Applicants: BENHAM ELIZABETH A, COLLINS KATHY S, EATON ANTHONY P, MARTIN SHIRLEY J, MCDANIEL MAX P, PHILLIPS PETROLEUM CO, SHVEIMA JOSEPH, SUKHADIA ASHISH M, BENHAM, ELIZABETH, A., COLLINS, KATHY, S., EATON, ANTHONY, P., MARTIN, SHIRLEY, J., MCDANIEL, MAX, P., PHILLIPS PETROLEUM COMPANY, SHVEIMA, JOSEPH, SUKHADIA, ASHISH, M.
Application year: 2000
Main classification: B01J31
IPC codes: B01J21, C08F4, C08F10, C08F110, C08F210