DE1954221A1 - Silica-supported catalyst for polymerisation of olefins - Google Patents

Abstract

Supported catalyst for the polymerisation of l-olefins has a support consisting of a silica xerogel having a pore diameter of 300-500 A and a specific surface of 200-500 m2/g, this support being stable up to 1,100 C when it is calcined in a fluidised bed.

Description

Polymerization Process and Catalyst Therefor The present invention relates to catalysts with a silica kero support that has a narrow pore diameter distribution in the range from 300 to 600 i, a surface area in the range from 200 to 500 m² / g and Stability at temperatures up to 1100 ° C tears when calcined in a fluidized bed is, with a metal-containing catalytic material such as chromium oxide on the carrier or another metal oxide. is deposited. The present invention relates to further a polymerization process in which such a catalyst for the Manufacture of polyolefins with lower molecular weights and high melt indices is used without loss of catalyst activity, especially for manufacture of polymers and copolymers of olefins with a maximum 8 carbon atoms in the chain and with no branch closer to the double bond than the 4 position.

The present invention thus relates to a method for polymerization of l-olefins with a maximum of 8 carbon atoms in the chain and no branching closer to the double bonds than the 4-position. The invention also relates to Silica xerogel supported catalysts useful in such processes.

In recent driving have new processes and catalysts for the stereospecific polymerization has received considerable attention. The catalysts with stereospecific effect contain deposited metal-containing catalytic material on a support, the catalytic system acting in a heterogeneous phase. Described in the literature: Catalysts of this class include, for example Chromium oxide on a support made of aluminum or silicon oxides and by oxidation Silicon oxide activated with air at about 500 ° C.

Using supported chromium oxide catalysts of the above Type polymerizations can be carried out with monomer concentrations of about 2 to 7% will. The conditions can be varied by varying the temperature and the solvent be chosen so that the reaction in solution or suspension (as a slurry process) can be carried out. Polymerization processes of this type allow manufacture of polymers with a varied range of molecular weights., depending of temperature, pressure, solvent and other reaction conditions, including the way in which the catalyst is activated. 3, for example, can in the production of polyethylene polymers with high molecular weight (low Melt indexes) using a slurry process with a speed of about 5000 to 15,000 kg of polyethylene: en per kg of catalyst are obtained. In a solution process, polymers can with low molecular weight (high melt indices) can be obtained, but with a Conversion rate below about 1000 kg of polyethylene per kg of catalyst. To the Protection of the grain and appearance of the resin product must be the chromium content in the resin are below 2.5 ppm.

When the supported chromium oxide catalyst in the solution polymerization is used, the catalyst must be stripped off prior to use of the resin will.

In contrast, the slurry process, in which no Stripping the catalyst is required and the conversion rates are much higher provides considerable economic advantages and is therefore large commercially more interesting than the solution method. However, slurry processes have been heretofore at high conversion values of around 5000 kg of polyethylene and more per kg of catalyst limited to the production of polymers with melt indexes below about 2. The use of modifiers, such as hydrogen, lowers the molecular weight and increases the melt index of the polymer product, the benefits of such Modifying agents, however, are limited because they reduce catalyst activity.

Although the variation in the chromium oxide content of the catalyst, the addition of different metal oxide promoters, the combination of different carriers, like silicon dioxide or

Silica, alumina, zirconium diocide and the like, as well as the Use of different activation temperatures for a given catalyst activity have been extensively studied, so far are only minor improvements been received.

Numerous unsuccessful attempts have thus already been made been To obtain polymers with lower molecular weights and higher melt indices, the attempts have been made at the expense of the catalyst activity. The desired Low molecular weight, high melt index polymers have significant Applications for films and foils, extrusion coating, injection molding and rotary pressing and the same. Accordingly, the primary object of the present invention is to provide of catalysts and polymerization processes that include such catalysts, which facilitate the production of low molecular weight and high molecular weight polyolefins Allow melt index at high conversion values.

The present invention thus relates to a new polymerization catalyst and a new polymerization method using such a catalyst. The catalyst comprises a silica xerogel support on which a metal-containing catalytic Material is deposited. The silica xerogel carrier is characterized by a narrow pore diameter distribution mainly in the range of 300 to 600 Å, a surface area in the range of 200 to 500 m² / g and a stability at temperatures up to 1100 ° C when in a fluidized bed is calcined, characterized. The metalliferous deposited on the carrier catalytic material is preferably a metal oxide, especially chromium oxide or another metal oxide, such as cobalt, nickel, vanadium, molybdenum or tungsten oxide.

The polymerization process according to the invention comprises contacting an 1-olefin with a maximum of 8 carbon atoms in the chain and no branches closer to the double bond than the 4-position with the catalyst described above under polymerization conditions to create polyolefin products with high Melt index and low molecular weight.

The manufacture of silica xerogel material of this type which is used for the Use as a support for catalysts according to the invention is suitable in the USA patent application Ser. No.

766 693+) dated October 11, 1968 with the title flpreparation of silica Gels ".

The metal-containing catalyst material can be used in any suitable manner deposited on the silica xerogel support. For example, the silica xerogel base be coated with a metal oxide, in which the finely ground metal oxide with the silica base is shear mixed at room temperature. The metal oxide generally makes up to 5% by weight, preferably 1 to 3% by weight, of the catalyst the end.

Similar results can be obtained by using the metal oxide and the carrier under vacuum conditions and / or under a nitrogen atmosphere 2000C to be mixed. Activation of the catalyst takes place in air in a fluidized bed at temperatures between about 81,500 and 11000C and preferably at about 996 ° C carried out. The activation period is on the order of 2 to 10 Hours and preferably from about 6 hours at the above Temperaturbe conditions. Activation is achieved without physical stimulation in the wearer.

The process is based on the polymerization of l-olefins with a maximum 8 carbon atoms in the chain and no branch closer to the double bond applicable than the 4 position.

The process is also useful for the interpolymerization of two or more 1-olefins of the above type.

In the slurry or suspension polymerization described above of 1-olefins, the molecular weights of the polymer products are much lower than the molecular weights with other available supported chromium catalysts can be obtained at the same activity values. the Polymers are characterized by the fact that they have a low molecular weight, which can be seen from melt indices between 2 and 20 for polyethylene, and low chromium concentrations, less than 2.5 ppm without stripping the catalyst.

Example 1 Into a 333 liter (88 gallons) loop reactor are continuously monomeric ethylene, isobutane solvent and the catalyst fed to the ethylene saturation at 5 ffi j 1% and the solids between Hold 15 and 25%. The reactor temperature is 110.4 ° C and the reactor pressure is maintained at 45.7 kg / cm² (650 psig) and the resulting slurry becomes at a speed of 4.57 to 7.62 m (15 to 25 ft) / sec. circulates.

Available, known catalysts with optimal melt index / synthesis temperature ratios are in a stream of air in a fluidized bed at a temperature between 871 and. 982 ° C activated. This is done to the optimal activation temperature for maximum Determine melt index.

The already known catalysts used are chromium oxide catalysts on silica gel supports, which are commercially available. These catalysts on silica supports have an average pore volume of 1.6 cm3 / g, an average of -2 Surface of 300 m / g and a resulting mean pore diameter of 213 i as determined by nitrogen absorption. They are coated with 2.1 CrO3 and are considered to be the optimal catalysts in terms of maximum melt index Resin products have been found.

250 g of this catalyst are in a fluidized bed at (a) 8710C, (b) 9260C and (c) 982 ° C using an air flow of 11.3 liters (0.40 ft3) / min. calcined in a 4 inch diameter activator. The maximum temperature is maintained in the reactor for 6 hours. The catalysts are then stored in a nitrogen atmosphere until used.

Synthesis conditions, catalyst properties after activation and polymer properties are given in Table I below.

The maximum melt index is, as can be seen, with comparable Activity values (about 5000 kg polyethylene / kg catalyst) obtained when the catalyst is activated at 9260C.

At higher temperatures, the catalyst support shrinks sharply on and the melt index falls.

T a b e l l e I synthesis conditions activated catalysis. Polymeric Ownership Properties Properties Synthe- Catalysts- Catalysts- through- pores- surface- grinded, ashes set tem- per- tor type gate activation cut volume che rer Po- MI2 * (ppm) tem- perature, ° C Liche (cm3 / g) (m² / g) flow rate, ° C ethylene knife, saturation # 110.0 chromium oxide 871 5.1 not activated not not activated 1.3 211 activated activated activated 110.4 "926 5.0 1.44 226 225 1.8 184 110.5 "982 4.9 1.25 193 259 1.6 330 * MI2 = Melt Index according to ASTM D-1238-54T (condition E) Example 2 10 080 g Sodium silicate solution containing 28.7% SiO2 and 8.9% Na20 are added with stirring added to 12 720 g of water and cooled to 5 C. Then 11,200 g of H2S04 (12.75 % By weight) are added as follows: (a) 4,480 g are added at a constant rate added over 1 hour and (b) the remainder is added over 45 minutes added. The final pH of the precipitate is 6.2 and the SiO2 content is around 8.5%.

The slurry is then heated to 95 ° C and held for 3 hours Temperature held. The slurry is then treated with a solution of 1113 g of NH4NO3 in 170 liters (45 gallons) water and then washed with deionized water until the filtrate has a titer below 20 ppm Na2SO4.

The product is reslurried in acetone and washed with water, until the water in the acetone is below 1%.

The product is then homogenized and the acetone is distilled off, in order to reduce the acetone content to below 1% by weight.

The cooled silica gel is in one for 4 hours before evaluation Oven calcined at 5380C. The physical properties of the silica kerogel thus obtained are a pore volume (PV) of 2.66 cm3 / g, a surface area (OF) of 307 m2 / g and an average pore diameter (d.PD) of 347 The xerogel is 2.1 % CrO3 plated to have a chromium concentration that is commercially available available Chromoxydkatalysatosi: is comparable.

The coating is then carried out by adding 813 g of dry xerogel carrier and 16.45 g of dry powdery chromium oxide are placed in a ribbon mixer. A vacuum of 711 mm (28 inches) Hg is applied to the mixer and it is so Heat supplied so that a temperature of 2500C is obtained in 3 hours. The heat is held for 2 hours and the catalyst is then brought to room temperature brought and stored in airtight containers.

These catalysts are in a fluidized bed using Air flow rates of 5.65 liters (0.2 ft3) / min. In an activator with a diameter of 10.2 cm (4 inches) and at temperatures of (a) 9540C and (b) 996 0C calcined. The maximum temperature is maintained for 6 hours. then the catalysts are stored in a nitrogen atmosphere until use. The evaluation of these catalysts in the loop reactor is carried out on the same Conditions as in example 1.

Synthesis conditions, catalyst properties after activation and polymer properties are summarized in Table II.

Comparing the results of Table I with the results of It can be seen from Table II that the reactor conditions are the same, but are there is a very significant increase in melt index when using the invention Catalysts can be used at the same level of activity.

T a b e l l e II Synthesis conditions activated catalyst polymer properties properties Synthe- Catalyst- Catalyst- through- pore- surface- a- mah- density, Ash setem- tor type toracti- cut volume of larger pores, tempered- (ppm) temperature, fourth (cm3 / g) diameter MI2 pert ° C temperature ethylene ser, Å saturation 110.4 Example 2 954 ° C 5.2 2.14 252 340 3.2 0.9645 164 110.3 Example 2,996 ° C 4.8 2.23 251 356 4.2 0.9647 184 Example 3 In the present A catalyst prepared as in Example 2 and activated at 982 ° C. is used as an example rated in the loop reaction, using hydrogen as a modifier is added in the reactor. This experiment is compared with the results obtained with an optimal chromium oxide catalyst.

Synthesis conditions, catalyst properties after activation and polymer properties are compared in Table III.

With the catalyst according to the invention it can be seen in the same Activity level obtained a much higher melt index.

T a b e l l e III Synthesis conditions activated catalyst polymer properties Properties Synthe- Catalyst Activation H2 Conc. Pore Vo- Surface Average MI2 Density, Ash set- tempter type average lumen pore tem- Ratio (cm3 / G) (m² / g) diameter ° C tur, ° C H2 / ethylene ser, Å 111.5 Example 2 982 1 x 10-2 2.20 253 347 12.2 0.09668 305 111.1 Chromium oxide 843 1 x 10-2 1.55 234 260 3.2 0.09699 238 B e i s p i e-l 4 In the present example ethylene / 1-hexene copolymers are used in the loop reactor the catalyst prepared according to Example 2 and the chromium oxide catalyst prepared.

Even at a lower synthesis temperature, there is obviously a very high significant increase in the melt index when the catalyst according to the invention at the same level of activity is used.

T a b e l l e IV Synthesis conditions activated catalyst copolymer properties properties Synthe- Catalyst- Catalyst- Hexene, Porenvo- surface- Density, ash setter- toracti- weight-% lumen pores- (ppm) temperature, four- (cm3 / g) (m² / g) diameter MI2 pert ° C tempera- ture, Å tur, ° C 106 Chromium Oxide 954 0.5 1.44 226 225 1.0 0.956 150 105.2 Example 2 996 0.5 2.48 251 305 330 4.0 0.956 250 B e i s p i e 1 5 In the present example in the loop reactor ethylene / -l-butene copolymers using the Catalyst prepared according to Example 2 and the chromium oxide catalyst prepared.

Synthesis conditions, catalyst properties and copolymer properties are compared in Table V.

Again, when using the catalyst according to the invention, the same level of activity (about 14,000 kg of polyethylene per kg of catalyst) Product obtained with a considerably higher solubility index (2.50 versus 0.14).

T a b e l l e V Synthesis conditions Catalyst properties Copolymer properties Synthe- cata- cata- 1-butene pore- surface- mah- density, ash setempe- gate type gate activation weight% volume pore size, temperature (ppm) temperature, (cm3 / g) (m² / g) diameter MI2 pert ° C temperature, ° C ser, Å 101 chromium oxide 843 1.7 1.60 300 213 0.14 0.9425 70 102 Example 2 982 1.6 2.12 242 335 2.50 0.9430 72

Claims (14)

N e u e P a t e n t a n s p r ü c h e 1. Supported catalyst, consisting of a catalytic material deposited on a carrier, characterized that the carrier is made of a silica xerogel with a pore diameter distribution mainly in the range from 300 to 500 R, a surface area in the range from 200 to 500 m² / g and Stability at temperatures up to about 1100 ° C when calcined in a fluidized bed becomes, exists, stands. 2. Catalyst according to claim 1, characterized in that the catalytic Material is a metal oxide. 3. Catalyst according to claim 2, characterized in that the catalytic material is chromium oxide. 4. Catalyst according to claim 1, characterized in that the catalytic Material constitutes up to 5% by weight of the total weight of the supported catalyst. 5o Use of a catalyst according to Claims 1 to 4 for polymerizing of a 1-olefin with a maximum of 8 carbon atoms and no branching closer to of the double bond than the 4-position. 6. Use according to claim 5, characterized in that the one 1-olefin containing monomer feed contains ethylene 7. Use according to claim 5, characterized in that the 1-olefin-containing monomer feed Contains propylene. 8. Use according to claim 5, characterized in that the one t-oletin-containing monomer feed is a mixture of at least two interpolymerizable contains l-olefin. 9. Use according to claim 5, characterized in that the one t-oletin containing monomer feed a mixture of 1-hexene and xethylene contains. 10. Use according to claim 5, characterized in that the one S-Qlerin containing monomer feed a mixture of 1-butene and xethylene contains. 11. Use according to claim 5, characterized in that the catalytic Material is a metal oxide. 12. Use according to claim 5, characterized in that the catalytic Material up to 5 wt.% Of the total weight of the catalyst susmacht. 13. Use according to claim 12, characterized in that the catalytic material is chromium oxide. 14. Use according to claim 5, characterized in that the polymerization is carried out in suspension.