Title of Invention

"A METHOD FOR THE PREPARATION OF THE GRANULES FROM PYROGENICALLY PREPRED SILICON DIEOXIDE"

Abstract

A method for the preparation of the granules from pyrogenically prepared silicon dioxide having the following physicochemical properties: Average grain size: 10 to 120 m BET surface area: 40 to 400 m2/g Pore volume: 0.5 to 2.5 ml/g Pore size distribution; less than 5% of the total pore volume exists of pored with a diameter < 5nm, rest meso- and macropores pH value; 3.6 to 8.5 Tapped density: 220 to 700 g/l characterized in that pyrogenically prepared silicon dioxide is dispersed In water and spray dried and the granules obtained are silanised in a manner as herein described.

Full Text

The invention relates to granules based on pyrogenically prepared silicon dioxide, the method for their preparation and the use thereof as catalyst supports. The preparation of pyrogenic silicas or silicon dioxides from SiCl4 by means of high-temperature-or flame hydrolysis is known (Ullmanns Enzyklopadie der technischen Chemie, 4th Edition, Volume 21, page 464 (1982)). Pyrogenic silicon dioxides are distinguished by having extremely fine particles, high specific surface (BET), very high purity, spherical particle shape and the absence of pores. On account of these properties pyrogenically prepared silicon dioxides are attracting increasing interest as supports for catalysts (Dr. Koth et al., Chem. Ing. Techn. 52, 628 (1980)). For this application the pyrogenically prepared silicon dioxide is shaped by mechanical means, for example, tabletting machines. The shaping of pyrogenically prepared silicon dioxide into sprayed granules also by means of spray drying, to obtain a starting material for sintered ceramic materials, is also known (DE-A.36 11 449). It is also known that silicon dioxide pyrogenically prepared in an electric arc may be shaped by means of spray drying into sprayed granules, which can be used as adsorption media or else as catalyst supports (DE-A 12 09 108). The subjection of pyrogenically prepared silicon dioxide to a gel process and the subsequent shaping into granules by means of spray drying is also known. These granules, after 2 coating with chromium oxide, are used in the polymerisation of ethylene (EP-A 0 050 902, US-A 4,386,016). Furthermore, the use of precipitated silicon dioxide as a catalyst support for the catalytic polymerisation of olefins is known (WO 91/09881). The known sprayed granules of pyrogenically prepared silicon dioxides have the disadvantage that they are not optimally suitable for use as catalyst supports, for example, in the production of polyethylene. The object was therefore the development from pyrogenically prepared silicon dioxide of sprayed granules which can be used as catalyst supports in _the production of polyethylene. The present invention provides granules based on pyrogenically prepared silicon dioxide and having the following physicochemical properties: Average grain size: 10 to 120 m 2 BET surface area: 40 to 400 m /g Pore volume: 0.5 to 2.5 ml/g Pore size distribution: less than 5 % of the total pore volume exists of pores with a diameter pH value: 3.6 to 8.5 Tapped density: 220 to 700 g/1 The granular material according to the invention can be prepared by dispersing pyrogenically prepared silicon dioxide in water, spray drying it and heating the granules obtained at a temperature of from 150 to 1,100 C for a period of 1 to 8 h. 3 The invention also provides granules based on pyrogenically prepared silicon dioxide and having the following physicochemical properties: Average grain size: 10 to 120 m BET surface area: 40 to 400 m2 /g Pore volume: 0.5 to 2.5 ml/g Pore size distribution: less than 5 % of the total pore volume exists of pores with a diameter pH value: 3.6 to 8.5 Tapped density: 220 to 700 g/1 The granular material according to the invention can be prepared by dispersing pyrogenically prepared silicon dioxide in water, spray drying it and silanising the granules obtained. Halosilanes, alkoxysilanes, silazanes and/or siloxanes can be used for the silanisation. The following substances in particular can be used as halosilanes: Haloorganosilanes of the type X3 Si(CnH2n+l) X = Cl, Br n = 1 to 20 Haloorganosilanes of the type X2 (R')Si(CnH2n+l) X = Cl, Br R' = alkyl n = 1 to 20 Haloorganosilanes of the type X(R')2 Si(CnH2n+l)x = Cl, Br R' = alkyl n = 1 to 20 4 Haloorganosilanes of the type X3 Si(CH2)m-R X = Cl, Br m , = 0.1 to 20 R' = alkyl, aryl (for example, -C6H5) -C4F9, -OCF2-CHF-CF3, -C6F13, -O-CF2-CHF2 -NH2, -N3, -SCN, -CH=CH2, -OOC(CH3)C = CH2 -OCH2-CH(O)CH2 -NH-C0-N-C0-(CH2)5 -NH-COO-CH3, -NH-COO-CH2-CH3, -NH-(CH2)3Si(OR)3 -Sx-(CH2)3Si(OR)3 Haloorganosilanes of the type (R)X2 Si(CH2)m-R' X = Cl, Br R = alkyl m = 0.1 to 20 R' = alkyl, aryl (for example, -C6H5) -C4F9, -OCF2-CHF-CF3, -C6F13, -O-CF2-CHF2 -NH2, -N3, -SCN, -CH=CH2, -OOC(CH3)C = CH2 -OCH2-CH(O)CH2 -NH-CO-N-CO-(CH2)5 -NH-COO-CH3, -NH-COO-CH2-CH3, -NH-(CH2)3Si(OR)3 -Sx-(CH2)3Si(OR)3 Haloorganosilanes of the type (R)2 x si(CCH2)m-R' X = Cl, Br R = alkyl m = 0.1 to 20 R' = alkyl, aryl (for example, -C6H5) -C4F9, -OCF2-CHF-CF3, -C6F13, -O-CF2-CHF2 -NH2, -N3, -SCN, -CH=CH2, -OOC(CH3)C = CH2 . -OCH2-CH(O)CH2 -NH-CO-N-CO-(CH2)5 -NH-COO-CH3, -NH-COO-CH2-CH3, -NH-(CH2)3Si(OR)3 -Sx-(CH2)3Si(OR)3 5 The following substances in particular can be used as alkoxysilanes: Organosilanes of the type (R0)3 Si(CnH2n+l) R = alkyl n = 1 to 20 Organosilanes of the type R'x (RO)y Si(CnH2n+l) R = alkyl R' = alkyl n = 1 to 20 x+y = 3 x = 1, 2 y = 1, 2 Organosiianes of the type (RO)3 Si(CH2)m-R R = alkyl m = 0.1 to 20 R' = alkyl, aryl (for example, -C6H5) -C4F9, -OCF2-CHF-CF3, -C6F13, -O-CF2-CHF2 -NH2, -N3, -SCN, -CH=CH2, -OOC(CH3)C = CH2 -OCH2-CH(O)CH2 -NH-CO-N-CO-(CH2)5 -NH-C00-CH3, -NH-COO-CH2-CH3, -NH-(CH2)3Si(OR)3 -Sx-(CH2)3Si(OR)3 Organosilanes of the type (R")x (RO)ySi(CH2)m-R' R" = alkyl x+y = 2 x = 1, 2 Y = 1, 2 R' = alkyl, aryl (for example, -C6H5) -C4F9, -OCF2-CHF-CF3, -C6F13, -O-CF2-CHF2 -NH2, -N3, -SCN, -CH=CH2, -OOC(CH3)C = CH2 -OCH2-CH(O)CH2 -NH-CO-N-CO-(CH2)5 -NH-COO-CH3, -NH-COO-CH2-CH3, -NH-(CH2)3Si(OR)3 -Sx-(CH2)3Si(OR)3 6 Preferably the silane Si 108 [ (CH3O) 3-Si-C8H17 ] , trimethoxyoctylsilane, is used as silanising agent. The following substances in particular can be used as silazanes: silazanes of the type R'R2Si- N -SiR2R' H R = alkyl R" = alkyl, vinyl as well as, for example, hexamethyldisilazane'. The following substances in particular can be used as siloxanes: cyclic polysiloxanes of the type D 3, D 4, D 5 for example, octamethylcyclotetrasiloxane = D 4 7 Polysiloxanes or silicone oils of the type The invention also provides granules based on pyrogenically prepared silicon dioxide and having the following physicochemical properties: Average grain size: 10 to 120 m o BET surface area: 40 to 400 m2/g Pore volume: 0.5 to 2.5 ml/g Pore size distribution: less than 5 % of the total pore volume exists of pores with a diameter Carbon content: 0.3 to 15.0 wt.% pH value: 3.6 to 8.5 Tapped density: 220 to 700 g/1 The granular material according to the invention preferably has meso- and macropores, with the volume of the mesopores constituting 10 to 80% of the total pore volume. The carbon content of the granular material according to the invention may be from 0.3 to 15.0 wt.%. 8 The particle size distribution of the granular material according to the invention may be 80 vol. % larger than 8 m and 80 vol. % smaller than 96 pun. In a preferred embodiment of the invention, the proportion of pores smaller than 5 m may be at most 5% referred to the total pore volume. The granular material according to the invention can be prepared by dispersing pyrogenically prepared silicon dioxide in water, spray drying it, heating the granules obtained at a temperature of from 150 to l,100°C for a period of 1 to 8 h and then silanising them. The same halosilanes, alkoxysilanes, silazanes and/or siloxanes described above can be used for the silanisation. The invention further provides a method for the preparation of granules based on pyrogenically prepared silicon dioxide, which is characterised in that pyrogenically prepared silicon dioxide, preferably silicon dioxide prepared from silicon tetrachloride, by means of- flame hydrolysis, is dispersed in water, spray dried, the granules obtained are optionally heated at a temperature of from 150 to l,100°C for a period of 1 to 8 h and/or silanised. The dispersion in water can have a silicon dioxide concentration of from 5 to 25 wt % The spray drying can be carried out at a temperature of from 200 to 600°C. Disc atomisers or nozzle atomisers can be used for this purpose. The heating of the granules can be carried out both in fixed beds, for example chamber kilns, and in moving beds, for example rotary dryers. 9 The silanisation can be carried out using the same halosilanes, alkoxysilanes, silazanes and/or siloxanes as described above, for which the silanising agent can be optionally dissolved in an organic solvent such as, for example, ethanol. Preferably the silane Si 108 [(CH3O)3-Si-C8H17], Jtrimethoxyoctylsilane, is used as silanising agent. The silanisation can be carried out by spraying the granular material with the silanising agent and subsequently heat-treating the mixture at a temperature of from 105 to 400°C over a period of 1 to 6 h. In an alternative method, the silanisation of the granules can be carried out by treating the granular material with the silanising agent in vapour form and subsequently heat-treating the mixture at a temperature of from 200 to 800 C over a period of 0.5 to 6 h. The heat treatment can take place under protective gas such as, for example, nitrogen. The silanisation can be carried out continuously or batchwise in heatable mixers and dryers equipped with spraying facilities. Examples of suitable devices are ploughshare mixers, disk dryers or fluidised bed dryers. ¦ The physicochemical variables of the granules, such as the specific surface, the particle size distribution, the pore volume, the tamped density and the silanol group concentration, the pore distribution and pH value can be altered within the specified limits by varying the starting materials and the conditions during-spraying-heating_and_ silanisation. 10 The granules according to the invention can be used as supports for polymerisation catalysts, in particular as supports for catalysts for the production of polyethylene. They have the advantage of possessing a high purity, a high thermostability, a low silanol group concentration, primary particles microspherical in shape and less than 5 % of the total pore volume exists of- pores with a diameter The invention further provides the use of the granules as catalyst supports, in particular for the production of polymerisation catalysts. In a preferred embodiment of the invention, the granules according to the invention can be used as catalyst supports for producing catalysts for the production of polyethylene. Examples The pyrogenically prepared silicon dioxides used are silicon dioxides having the physicochemical properties given below. J i 1) In accordance with DIN 66131 2) In accordance with DIN ISO 787/XI, JIS K 5101/18 (not screened) 3) In accordance with DIN ISO 787/II, ASTM D 280, JIS K 5101/21 4) In accordance with DIN 55921, ASTM D 1208, JIS K 5101/23 5) In accordance with DIN ISO 787/IX. ASTM D 1208, JIS K 5101/24 6) In accordance with DIN ISO 787/XVIII, JIS K 5101/20 7) Referred to the substance dried for 2 hours at 105°C 8) Referred to the substance calcined for 2 hours at 1000°C 9) Special moisture-resistant packaging 10) In water: ethanol 1:1 11) HCI content in constituent of the loss on ignition 12 To prepare the silicon dioxides, a liquid silicon compound is sprayed into an oxyhydrogen flame consisting of hydrogen and air. In most cases silicon tetrachloride is used. This substance is hydrolysed to silicon dioxide and hydrochloric acid by the action of the water formed during the hydrogen-oxygen reaction. After leaving the flame, the silicon dioxide enters a so-called coagulation zone, wherein the primary Aerosil particles and primary Aerosil aggregates agglomexate. The product, which exists at this stage as a kind of aerosol, is separated from the accompanying gaseous substances in cyclones and then aftertreated with moist heated air. By this process the residual hydrochloric acid content can be lowered to 0.025%. As the silicon dioxide obtained at the end of this process has a bulk density of only about 15 g/1, there is a subsequent vacuum compaction, whereby tamped densities of about 50 g/1 and more can be established. The particle si,zes of the silicon dioxides can be varied by means of the reaction conditions such as, for example, flame temperature, proportions of hydrogen and oxygen, quantity of silicon tetrachloride, residence time in the flame or length of the coagulation path. The BET surface area is determined using nitrogen in accordance with DIN 66 131. The pore volume is calculated from the sum of the micro-, meso- and macropore volumes. The micro- and mesopores are determined by recording an N2. isotherm and evaluation thereof by the methods of BET, de Boer and Barrett, Joyner and Halenda. The macropores D > 30 nm are determined by the Hg porosimetry method. For the determination of the macropores, the sample is dried for 15 h at 100O C in the drying oven and degassed at room temperature in a vacuum. 13 For the determination of the micro- and mesopores, the sample is dried for 15 h at 100 C in the drying oven and degassed for 1 h at 200°C in a vacuum. The silanol group concentration is determined by the lithium alanate method. Here the SiOH- groups are reacted with LiAlH4 and the quantity of hydrogen formed during this reaction is determined from the pressure. Principle of measurement The granular material is weighed into a four-necked flask. The flask is evacuated and an oil bath is heated to .150O C The temperature in the flask (controlled by an internal thermometer) rises with the temperature of the oil bath to about 130 C. The pressure during the preliminary treatment is recorded using a pressure measuring device PI2 (TM 210, 3 -3 from Leybold, measuring range 10 to 10 mbar) . The desorption of the water can be monitored from the pressure measurement. At the end of the preliminary treatment (30 min at the end temperature) a pressure of less than -2 10 mbar must have been achxeved. .After completion of the preliminary treatment, the evacuated flask is separated from the vacuum unit by closing the stop valve and is brought to normal temperature. The actual measurement is based on a measured quantity of LiAlH4 solution being introduced into the flask through the dropping funnel and the rise in pressure being measured from the hydrogen formed. If the volume of the flask is known, the quantity of H2 can be calculated from the ideal gas law. The pressure is recorded using a digital measuring device (PI1) (MKS Instruments PR-2000), having a measuring range of between 0 and 1 bar. The LiAlH4 solution used (2% LXALH4 in diethylene glycol dimethyl ether) is degassed prior to the experiment being 14 carried out, in order to remove readily volatile constituents, which distort the pressure measurement. For this purpose the pressure above the solution in the dropping funnel is lowered by a second vacuum pump to the vapour pressure (3.7 mbar at 22°C), so that the liquid boils. A blank measurement without a sample is taken to test whether the solution is sufficiently degassed. In the determination of the hydrogen pressure, a correction* is made using the vapour pressure of the solvent. Interpretation The apparatus is calibrated by first of all determining the volume of the dropping funnel provided with a ground-glass stopper, gauging the'capacity in litres. The volume of the reaction flask inclusive of all connections as far as the stop valve is obtained by the following experiment: The dropping funnel, filled with air at atmospheric pressure, is attached to the evacuated flask. A pressure compensation between the two volumes is then brought about by opening the tap of the dropping funnel. The pressure established is indicated by the digital measuring device. The volume of the reaction vessel is obtained from the mass balance. A volume VR equal to 243.8 ml is obtained with the present arrangement. vcorr. - VR - vsolids - vsolution The number of moles of hydrogen formed ,is obtained from the equations: 15 p is the increase in pressure in the reaction flask. This value is corrected by an amount corresponding to the vapour pressure of the solvent {3.7 mbar at 22 C). At room temperatures greatly differing from 22 C the vapour pressure is taken from the vapour pressure table. It is useful so to select the weighed sample, that a value for p of between 200 and-800 mbar is obtained. In this case minor changes in the vapour pressure owing to temperature variations have hardly any effect on the result. The volume of the reaction vessel is corrected by deducting the volume of solid matter and the volume of the solution introduced. The former is given from the weighed portion and the density and the latter is read from the dropping funnel. ¦ The density of silanol groups is finally obtained from the equation: NL: Lohschmidt number F: Surface of the weighed solid matter The samples are treated as follows: 1 h heating at 120°C and 0.2 mbar; cooling to 60°C; addition of LiAlH4; after 10 mins, reading the pressure difference which has arisen. The particle size distribution is determined by means of the laser optical particle size analyser Cilas Granulametre 715. 16 The rapped volume is determined in accordance with ASTM D 4164-88. Equipment: Tapping volumeter STA V 2003 from Engelsmann, in accordance with DIN 53194, section 5.2. b-f Measuring cylinder 250 ml, graduation marks every 2 ml Balance with limit of error of max. ± 0.1 g Procedure The counter of the tapping volumometer is set to 1000 strokes. The measuring cylinder is tared. The granular material is placed in the measuring cylinder up to the 250 ml mark. The weight of the sample is recorded (± 0.1 g). The measuring cylinder is placed in the volumeter and the apparatus is switched on. End of tapping: the apparatus automatically switches off after 1000 strokes The tapped bulk volumes are read to an accuracy of 1 ml. Calculation E: weighed portion of granular material in g V: volume read in ml The pH value is determined in 4% aqueous dispersion, in the case of hydrophobic catalyst supports in water:ethanol 1:1. W: water content in wt.% (determined in accordance with Specification P001) 17 Preparation of the granules according to the invention The pyrogenically prepared silicon dioxide is dispersed in completely demineralised water. A dispersing aggregate which operates according to the rotor/stator principle is used in the process. The suspensions formed are spray dried. The finished product is precipitated by a filter or cyclone. The sprayed granules are heated in a muffle furnace. The spray-dried and optionally heated granules are placed in a. mixer for the silanisation process and sprayed with intensive mixing optionally first of all with water and then with the silane Si 108 (trimethoxyoctylsilane) or HMDS (hexamethyldisilazane). After spraying has been completed, the material is mixed for 15 to 30 more minutes and then heated for 1 to 4 h at 100 to 400°C. The water used can be acidified with an acid, for example, hydrochloric acid, to a pH value of 7 to 1. The silanising agent used can be dissolved in a solvent such as, for example, ethanol. 18 19 20 21 The particle size distributions of the granules obtained -according to Examples 1 to 14 are represented in tabular and graphical form in Figures 1 to 4. Examples l, 5, 9, 11 and 13 are comparative Examples from prior art (DE-A 36 11 449 Liu). Examples of the use of the granules according to the invention as catalyst supports in the production of polyethylene Referred to the active component titanium, the catalysts achieved the following results in the polymerisation of ethylene: 22 We Claim: 1. A method for the preparation of the granules from pyrogenlcally prepared silicon dioxide having the following physicochemical properties: Average grain size: 10 to 120 urn BET surface area: 40 to 400 m2/g Pore volume: 0.5 to 2.5 ml/g Pore size distribution: less than 5% of the total pore volume exists of pores with a diameter pH value: 3.6 to 8.5 Tapped density: 220 to 700 g/l characterized in that pyrogenlcally prepared silicon dioxide Is dispersed In water and spray dried and the granules obtained are sllanised in a manner as herein described. 2. Method for the preparation of the granules are claimed in claim 1, wherein pyrogenlcally prepared silicon dioxide Is dispersed Jn water and spray dried and the granules obtained are heated at a temperature of from 150 to 1,100°C for a period of 1 to 8 h and subsequently silanised. A method for the preparation of the granules from pyrogenically prepared silicon dioxide having the following physicochemical properties: Average grain size: 10 to 120 m BET surface area: 40 to 400 m2/g Pore volume: 0.5 to 2.5 ml/g Pore size distribution; less than 5% of the total pore volume exists of pored with a diameter macropores pH value; 3.6 to 8.5 Tapped density: 220 to 700 g/l characterized in that pyrogenically prepared silicon dioxide is dispersed In water and spray dried and the granules obtained are silanised in a manner as herein described.

Documents:

00157-cal-2001-abstract.pdf

00157-cal-2001-clams.pdf

00157-cal-2001-correspondence.pdf

00157-cal-2001-description(complete).pdf

00157-cal-2001-drawings.pdf

00157-cal-2001-form-1.pdf

00157-cal-2001-form-18.pdf

00157-cal-2001-form-2.pdf

00157-cal-2001-form-3.pdf

00157-cal-2001-form-5.pdf

00157-cal-2001-g.p.a.pdf

00157-cal-2001-letters patent.pdf

00157-cal-2001-priority document others.pdf

00157-cal-2001-priority document.pdf

157-CAL-2001-CORRESPONDENCE 1.1.pdf

157-CAL-2001-CORRESPONDENCE.pdf

157-CAL-2001-FORM 27.pdf

157-CAL-2001-FORM-27.pdf

157-CAL-2001-PA.pdf