Process for preparing an olefin polymer including withdrawing a gaseous sample for analysis - Patents.com

Abstract

A method for preparing an olefin polymer in a polymerization apparatus in the presence of a solid particulate polymerization catalyst and an organometallic compound, comprising the steps of withdrawing a gaseous stream from said polymerization apparatus, passing said gaseous stream through a bed of a particulate solid having chemical groups on its surface which are reactive with said organometallic compound, and supplying a sample of said gaseous stream to an analytical apparatus.

Description

[Technical field]

[0001] The present disclosure provides a process for preparing an olefin polymer, in particular a process for preparing an olefin polymer in which a gaseous sample is withdrawn from a polymerization apparatus, including a polymerization reactor or a combination of polymerization reactors, and fed to an analytical apparatus. [Background technology]

[0002] Polyethylene is a widely used commercial polymer. Suitable processes for producing polyolefins include suspension polymerization processes and gas-phase polymerization processes in the presence of a solid polymerization catalyst and an organometallic compound as a cocatalyst and / or scavenger. Suspension polymerization is usually carried out in a stirred tank reactor or a loop reactor. Suitable reactors for carrying out gas-phase polymerization are, for example, a fluidized bed reactor, a stirred gas-phase reactor or a multi-zone loop reactor having two different gas-phase polymerization zones connected to each other. For example, polymerization of olefins in a fluidized bed reactor and a multi-zone loop reactor series is disclosed in EP 3524343 A1, WO 2018 / 115236 A1 and WO 2016 / 150997 A1.

[0003] To control the polymerization reaction, information is required about the composition of the reaction mixture in the polymerization reactor, or in each polymerization reactor if a combination of polymerization reactors is used. This is generally achieved by withdrawing a gaseous sample from the polymerization reactor or combination of polymerization reactors, or from one of the polymerization units where a gas phase is present, and analyzing the composition of the gaseous sample, for example by gas chromatography. US Pat. No. 4,469,853 discloses a process for preparing polyolefins having predetermined properties by detecting parameters that determine those properties by gas chromatography, generating signals corresponding to the detected parameters, comparing those signals with predetermined values, and controlling the parameters. US Pat. No. 2012 / 0283395 A1 discloses a gas phase polymerization reactor system and a loop slurry polymerization reactor system, each reactor system including a measurement system that can be used to control and / or monitor the reaction conditions in the reactor. This document discloses that the analytical device for determining the composition of the gaseous sample can be a chromatographic analytical device, such as a gas chromatograph, a mass spectrometer, or a Raman probe.

[0004] To improve the quality of gas analysis and to extend the life of analytical equipment, gaseous samples are frequently passed through a filter before being fed to the analyzer. For example, U.S. Patent No. 3,556,730 discloses that such a filter can be a chamber filled with glass fibers or a filter using a paper element. However, analysis of the gas components of samples taken from olefin polymerization reactors often produces unreliable results, requiring recalibration of the analyzer or cleaning of the sample dispenser. Summary of the Invention [Problem to be solved by the invention]

[0005] Therefore, there is a need to provide an improved process for preparing olefin polymers that can reliably measure the composition of the reaction mixture in the polymerization reactor and reduce the maintenance costs of the analytical equipment.

[0006] The present disclosure provides a process for preparing an olefin polymer, comprising: feeding a solid particulate polymerization catalyst, an organometallic compound, and an olefin or a combination of an olefin and one or more other olefins to a polymerization apparatus comprising a polymerization reactor or a combination of polymerization reactors; homopolymerizing an olefin or copolymerizing an olefin with one or more other olefins in the presence of a polymerization catalyst and an organometallic compound at a temperature of 20 to 200°C and a pressure of 0.1 MPa to 20 MPa; withdrawing a gaseous stream from the polymerization apparatus; passing the gaseous stream through a bed of particulate solids having chemical groups on their surfaces which react with organometallic compounds; Gaseous Stream providing a sample of the gaseous stream to an analytical device for analyzing the sample. fruit , the results of analyzing the sample of the gaseous stream are provided as measurement signals to a controller for controlling a process for preparing an olefin polymer; Provide a process.

[0007] In some embodiments, the analytical device is a gas chromatograph.

[0008] In some embodiments, the organometallic compound is an aluminum alkyl.

[0009] In some embodiments, the particulate solid is an oxide or mixed oxide of the elements calcium, aluminum, silicon, magnesium, or titanium, or the particulate solid is ZrO2 or B2O3.

[0010] In some embodiments, the chemical groups on the particle solid surface that react with the organometallic compound are OH groups, adsorbed water or distorted Si-O-Si bridges.

[0011] In some embodiments, the particulate solid is a silica gel equipped with a humidity indicator.

[0012] In some embodiments, the gaseous stream withdrawn from the polymerizer is a continuous gaseous stream withdrawn from the polymerizer at a flow rate of from 1 Nl / h to 500 Nl / h.

[0013] In some embodiments, the analyzer is provided with samples of the gaseous stream at regular intervals.

[0014] In some embodiments, two or more gaseous streams are withdrawn at different locations from the polymerization apparatus and then samples of some or all of the two or more gaseous streams are fed to a single analytical device for analyzing the samples, or some or all of the two or more gaseous streams have a dedicated analytical device that is provided with only a sample of one of the gaseous streams withdrawn from the polymerization apparatus.

[0015] In some embodiments, the particulate solid bed is 50 cm 3 ~10000cm 3 The liquid is contained in a container having a volume of 1000 g.

[0016] In some embodiments, the particulate solid bed is contained within a vessel comprising a pipe having a diameter between 6 mm and 100 mm, an inlet for introducing a gaseous stream into the pipe, and an outlet for withdrawing the gaseous stream from the pipe, the distance between the inlet and the outlet being between 0.2 m and 10 m.

[0017] In some embodiments, the vessel further comprises a first valve at one end of the pipe for introducing the particulate solids bed into the pipe and a second valve at the other end of the pipe for removing the particulate solids bed from the pipe; and / or At the inlet and outlet of the pipe, there are 35 μ A screen having a mesh size of 100 mm to 2 mm is provided.

[0018] In some embodiments, the results obtained from analyzing the gaseous sample are provided as a measurement signal to a controller for controlling a process for preparing an olefin polymer.

[0019] The present disclosure also provides a method for producing a gaseous solids bed comprising: a pipe having a diameter of 6 mm to 100 mm; an inlet for introducing a gaseous stream into said pipe; an outlet for withdrawing the gaseous stream from said pipe; a first valve at one end of said pipe for introducing a bed of particulate solids into said pipe; and a second valve at the other end of said pipe for removing the bed of particulate solids from said pipe, said inlet and said outlet of said pipe having a diameter of 35 mm to 100 mm. μ The vessel is provided with a screen having a mesh size of 0.2 m to 2 mm, and the distance between the inlet and the outlet is 0.2 m to 10 m.

[0020] The present disclosure also relates to a method for controlling an olefin polymerization process comprising homopolymerizing an olefin or copolymerizing an olefin with one or more other olefins in a polymerization apparatus comprising a polymerization reactor or a combination of polymerization reactors at a temperature of 20-200° C. and a pressure of 0.1 MPa-20 MPa in the presence of a solid particle polymerization catalyst and an organometallic compound, the method comprising: - withdrawing a gaseous stream from the polymerization apparatus; - passing the gaseous stream through a bed of particulate solids having chemical groups on their surfaces which react with the organometallic compound; - supplying the gaseous sample to an analytical device for analyzing the gaseous sample; - analyzing the sample to obtain information about the conditions in the polymerization apparatus; - adapting polymerization conditions in a polymerization device to predetermined values ​​based on information obtained by analysing the sample. [Brief description of the drawings]

[0021] [Figure 1]FIG. 1 shows a schematic of a polymerization apparatus set-up comprising a series of polymerization reactors in which the process of the present disclosure can be carried out. [Diagram 2] FIG. 2 shows a schematic diagram of a vessel for containing a bed of particulate solids according to the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] The present disclosure provides a process for preparing an olefin polymer. The olefins for preparing the olefin polymer are in particular, but not limited to, 1-olefins, i.e., hydrocarbons having terminal double bonds. Non-polar olefinic compounds are preferred. Particularly preferred 1-olefins are linear or branched C2-C 12 -1-Alkenes, in particular linear or branched C2-C such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, and 1-decene 10 -1-Alkenes or 4-methyl-pentenes, linear or branched C2-C 10 -1-alkenes; conjugated and non-conjugated dienes such as 1,3-butadiene, 1,4-hexene, 1,7-octene. Mixtures of different 1-olefins can also be polymerized. Suitable olefins also include olefins in which the double bond is part of a ring structure which may have one or more ring systems. Examples are cyclopentene, norbornene, tetracyclododecene or methylnorbornene, or dienes such as 5-ethylidene-2-norbornene, norbornadiene or ethylnorbornadiene. It is also possible to polymerize mixtures of two or more olefins, for example mixtures of two, three or four olefins.

[0023] The olefin polymers can be obtained by homopolymerization of an olefin or by copolymerization of an olefin with one or more other olefins. The olefin polymers can be obtained in particular by homopolymerization or copolymerization of polyethylene or propylene, in particular by homopolymerization or copolymerization of polyethylene. The preferred comonomers in the propylene polymerization are ethylene, 1-butene and / or 1-hexene in an amount of at most 60% by weight, preferably 0.5 to 35% by weight. As comonomers in the ethylene polymerization, it is preferred to use C3 to C8-1-alkenes, in particular 1-butene, 1-pentene, 1-hexene and / or 1-octene in an amount of at most 20% by weight. Particularly preferred are olefin polymers in which ethylene is copolymerized with 0.1% by weight to 12% by weight of 1-hexene and / or 1-butene.

[0024] In the process of the present disclosure, an olefin is homopolymerized or an olefin is copolymerized with one or more other olefins in the presence of a solid particle polymerization catalyst and an organometallic compound which are fed to a polymerization apparatus comprising a polymerization reactor or a combination of polymerization reactors together with an olefin or a combination of an olefin and one or more other olefins at a temperature of 20 to 200°C, preferably 30 to 150°C, particularly preferably 40 to 130°C, and at a pressure range of 0.1 MPa to 20 MPa, particularly preferably 0.3 MPa to 5 MPa.

[0025] The polymerization catalyst may be any conventional solid particle polymerization catalyst that can be used in combination with an organometallic compound as a cocatalyst to polymerize olefins. This means that the polymerization can be carried out using Ziegler or Ziegler-Natta catalysts, Phillips catalysts based on chromium oxide, or single-site catalysts. For the purposes of this disclosure, single-site catalysts are catalysts based on chemically uniform transition metal coordination compounds. Furthermore, mixtures of two or more of these catalysts can also be used to polymerize olefins. Such mixed catalysts are generally called hybrid catalysts. The preparation of these catalysts and their use in olefin polymerization is known.

[0026] Preferred catalysts are of the Ziegler or Ziegler-Natta type, preferably comprising a titanium or vanadium compound, a magnesium compound and, optionally, as support material, an electron donor compound and / or a particulate inorganic oxide. As titanium compounds, halides or alkoxides of trivalent or tetravalent titanium are generally used, but titanium alkoxyhalides and mixtures of various titanium compounds are also conceivable. It is preferred to use titanium compounds containing chlorine as the halogen. For the preparation of the solid component, it is preferred to use, in addition, at least one magnesium compound. Suitable compounds of this type are magnesium halides, in particular halogen-containing magnesium compounds such as chlorides or bromides, and magnesium compounds, which can be obtained in a conventional manner, for example by reaction with a halogenating agent. As magnesium compounds for the preparation of the particulate solid, in addition to magnesium dichloride or magnesium dibromide, di(C1-C 10 -alkyl)magnesium compounds are preferably used. Suitable electron donor compounds for preparing Ziegler or Ziegler-Natta type catalysts are, for example, alcohols, glycols, esters, ketones, amines, amides, nitriles, alkoxysilanes and fatty ethers. These electron donor compounds can be used alone or in mixtures with other electron donor compounds. Preferred electron donor compounds are selected from the group consisting of amides, esters and alkoxysilanes.

[0027] Also preferably, the Phillips type chromium catalyst is prepared by applying a chromium compound to an inorganic support, followed by activating the catalyst precursor at a temperature in the range of 350 to 1000 ° C, thereby converting chromium less than 6-valent to the hexavalent state. In addition to chromium, other elements such as magnesium, calcium, boron, aluminum, phosphorus, titanium, vanadium, zirconium, zinc, etc. can be used. In particular, it is preferable to use titanium, zirconium or zinc. Combinations of the above elements are also possible. The catalyst precursor can be doped with fluorides before or during activation. Supports for Phillips type catalysts include alumina, silica (for example in the form of silica gel), titania, zirconia or mixed oxides or gels thereof, aluminum phosphate. More suitable support materials can be obtained by modifying the pore surface area, for example, by compounds of the elements boron, aluminum, silicon or phosphorus. It is preferable to use silica gel. It is preferably spherical or granular silica gel, the former also being spray-driable. The activated chromium catalyst can be subsequently prepolymerized or prereduced. The pre-reduction is usually carried out at 250-500° C., preferably 300-400° C., using cobalt or via hydrogen in an activator.

[0028] The preferred catalysts for use in the method of the present disclosure are also supported single-site catalysts. Particularly suitable are those that contain large volumes of σ- or π-bonded organic ligands, such as catalysts based on mono-Cp complexes, catalysts based on bis-Cp complexes, commonly designated as metallocene catalysts, or catalysts based on late transition metal complexes, especially iron-bisimine complexes. Further preferred catalysts are mixtures of two or more single-site catalysts, or mixtures of heterogeneous catalysts containing at least one single-site catalyst. Materials suitable as supports for Phillips-type chromium catalysts are also useful as supports for single-site catalysts.

[0029] The solid particle polymerization catalyst used in the process of the present disclosure is used in combination with an organometallic compound.Preferred organometallic compounds are organometallic compounds of metals of Groups 1, 2, 12, 13 or 14 of the Periodic Table of the Elements, especially organometallic compounds of metals of Group 13, especially organoaluminum compounds.Preferred cocatalysts are, for example, organometallic alkyls, organometallic alkoxides, organometallic halides.

[0030] Organometallic compounds are used on the one hand as cocatalysts for solid particle polymerization catalysts and on the other hand as scavengers which react with polar compounds which may be entrained in the polymerization reactor and act as catalyst poisons.

[0031] Preferred organometallic compounds include lithium alkyls, magnesium or zinc alkyls, magnesium alkyl halides, aluminum alkyls, silicon alkyls, silicon alkoxides and silicon alkyl halides. More preferably, the organometallic compounds include alkylaluminums and alkylmagnesiums. Even more preferably, the organometallic compounds include alkylaluminums, most preferably trialkylaluminum compounds, or compounds of this type in which the alkyl groups are replaced by halogen atoms, such as chlorine or bromine. Examples of such aluminum alkyls are trimethylaluminum, triethylaluminum, triisobutylaluminum, tri-n-hexylaluminum or diethylaluminum chloride, or mixtures thereof.

[0032] The process of the present disclosure can be carried out using all low pressure polymerization methods known industrially in polymerization equipment including a polymerization reactor or a combination of polymerization reactors. These polymerization reactors can be, for example, stirred tank reactors or loop reactors, or the polymerization reactors can be fluidized bed reactors, stirred gas phase reactors or multi-zone loop reactors with two different gas phase polymerization zones connected to each other. The polymerization can be carried out batchwise or, preferably, continuously in one or more stages, for example 1, 2, 3 or 4 stages. Solution, suspension and gas phase processes are all possible. This type of process is usually known to the person skilled in the art. In the above polymerization processes, gas phase polymerization, especially in a gas phase fluidized bed reactor or a multi-zone circulating gas phase reactor, and suspension polymerization, especially in a loop reactor or a stirred tank reactor, are preferred.

[0033] In a preferred embodiment of the present disclosure, the polymerization process is a suspension polymerization in a suspension medium, preferably a mixture of inert hydrocarbons such as isobutane or a hydrocarbon, and in the monomer itself. The suspension polymerization temperature is usually in the range of 20°C to 115°C, and the pressure is in the range of 0.1 MPa to 10 MPa. The solid content of the suspension is usually in the range of 10% to 80% by weight. The polymerization can be batch-wise, such as in a stirred autoclave, or continuous, such as in a tubular reactor, or preferably in a loop reactor. It can be carried out by the Phillips PF process described in U.S. Pat. No. 3,242,150 and U.S. Pat. No. 3,248,179.

[0034] Suitable suspension media are all media commonly known for suspension reactors. The suspension medium should be inert, liquid or supercritical under the reaction conditions and have a boiling point significantly different from that of the monomers and comonomers used in order to make it possible to recover these starting materials by distillation from the product mixture. Common suspension media are saturated hydrocarbons with 4 to 12 carbon atoms, such as isobutane, butane, propane, isopentane, pentane and hexane, or mixtures of these, also known as diesel oil.

[0035] In a preferred suspension polymerization process, the polymerization is carried out in a series of two, preferably three or four, stirred vessels. The molecular weight of the polymer fraction prepared in each reactor is preferably set by adding hydrogen to the reaction mixture. The polymerization process is preferably carried out by setting a maximum hydrogen concentration and a minimum comonomer concentration based on the amount of monomer in the first reactor. In the subsequent further reactors, the hydrogen concentration is gradually decreased and the comonomer concentration is modified, in each case again based on the amount of monomer. Ethylene or propylene are preferred as monomers and 1-olefins with 4 to 10 carbon atoms as comonomers.

[0036] A further preferred suspension polymerization process is suspension polymerization in a loop reactor, in which the polymerization mixture is continuously pumped through a tubular reaction tube. As a result of the pumping circulation, a continuous mixing of the reaction mixture is achieved and the introduced catalyst and the fed monomer are distributed in the reaction mixture. The pumping circulation also prevents settling of the suspended polymer. The removal of the reaction heat through the reactor wall is also promoted by the pumping circulation. In general, these reactors are essentially composed of a loop reactor tube with one or more up-legs and one or more down-legs surrounded by a cooling jacket to remove the reaction heat, and a horizontal tube section connecting the vertical legs. The impeller pump, the catalyst and monomer feeding equipment, as well as the discharge equipment, i.e. usually the settling leg, are usually installed in the lower tube section. However, the reactor can also have two or more vertical tube sections to obtain a serpentine arrangement.

[0037] The suspension polymerization is preferably carried out in a loop reactor with an ethylene concentration of at least 5% by mole, preferably 10% by mole, relative to the suspending medium. By suspending medium here we do not mean the feed suspending medium, for example isobutane alone, but a mixture of the feed suspending medium and the monomers dissolved therein. The ethylene concentration can be easily determined by gas chromatographic analysis of the suspending medium.

[0038] In a particularly preferred embodiment of the present disclosure, the polymerization process is carried out as a gas phase polymerization, i.e., a process for obtaining a solid polymer from the gas phase of the monomers. Such a gas phase polymerization is usually carried out under a pressure of 0.1 MPa to 20 MPa, preferably 0.5 MPa to 10 MPa, in particular 1.0 MPa to 5 MPa, and at a polymerization temperature of 40 to 150°C, preferably 65°C to 125°C.

[0039] Suitable gas-phase polymerization reactors are horizontal or vertical stirred reactors, fluidized-bed gas-phase reactors or multi-zone circulating reactors, preferably fluidized-bed gas-phase reactors or multi-zone circulating reactors.

[0040] A fluidized bed polymerization reactor is a reactor in which polymerization takes place in a layer of polymer particles, characterized in that the layer is kept in a fluidized state by introducing gas into the lower end of the reactor, usually below a gas distribution grid, which functions to distribute the gas flow, and discharging the gas again at the upper end. The reactor gas is then returned to the lower end of the reactor via a gas recycle line equipped with a compressor and a heat exchanger. The loop reactor gas is usually a mixture of the olefin to be polymerized with an inert gas such as nitrogen and / or a lower alkane such as ethane, propane, butane, pentane or hexane, and optionally with a molecular weight regulator such as hydrogen. It is preferred to use nitrogen or propane as the inert gas, optionally in combination with a further lower alkane. The velocity of the reactor gas must be high enough, firstly to fluidize the mixed bed of fine polymer present in the tubes that function as the polymerization zone, and secondly to effectively remove the heat of polymerization. The polymerization can also be carried out by condensation or hypercondensation, in which a portion of the circulating reaction gas is cooled below the dew point and returned to the reactor as liquid and gas phases, respectively, or as a two-phase mixture, and additionally utilizes the enthalpy of vaporization to cool the reaction gas.

[0041] A multi-zone circulation reactor is a gas-phase reactor in which two polymerization zones are connected to each other and the polymer passes through them alternately multiple times. This reactor is described, for example, in WO 97 / 04015A1 and WO 00 / 02929A1 and has two interconnected polymerization zones, a riser through which the growing polymer particles flow upwards under fast-flow or transport conditions, and a downcomer through which the growing polymer particles flow in a dense form under gravity. The polymer particles leaving the riser enter the downcomer, and the polymer particles leaving the downcomer are introduced back into the riser, so that a polymer circulation is established between the two polymerization zones and the polymer passes through the two zones alternately multiple times. The two polymerization zones of one multi-zone loop reactor can also be operated under different polymerization conditions by setting different polymerization conditions in the riser and the downcomer. For this purpose, the gaseous mixture leaving the riser and entraining the polymer particles can be partially or totally prevented from entering the downcomer. This can be achieved, for example, by feeding a barrier fluid in the form of a gas and / or liquid mixture into the downcomer, preferably at the top of the downcomer. The barrier fluid should have a suitable composition different from that of the gaseous mixture present in the upcomer. The amount of added barrier fluid can be adjusted to generate an upward gaseous stream opposite to the flow of polymer particles, especially at its top, acting as a barrier for the particle-entrained gaseous mixture from the upcomer. In this way, it is possible to obtain two different gas composition zones in one multi-zone loop reactor. Furthermore, it is also possible to introduce supplemental monomers, comonomers, molecular weight regulators such as hydrogen and / or inert fluids at any point of the downcomer, preferably below the barrier feed point. Different monomer, comonomer, hydrogen concentrations are thus also easily generated along the downcomer, which allows for even greater differentiation of the polymerization conditions.

[0042] The gas phase polymerization method according to the present invention is preferably carried out in the presence of a C3 to C5 alkane as a polymerization diluent, and particularly in the case of homopolymerization or copolymerization of ethylene, it is more preferably carried out in the presence of propane.

[0043] If desired, different or identical polymerization reactors can be connected in series to form a polymerization cascade. It is also possible to arrange reactors using two or more different or identical polymerization processes in parallel.

[0044] In a particularly preferred embodiment of the present disclosure, the process for preparing olefin polymers is carried out in a series of two or more gas phase reactors. More preferably, the polymerization of olefins is carried out in a series comprising a fluidized bed reactor and a multi-zone circulating reactor. Preferably, the fluidized bed reactor is located upstream of the multi-zone loop reactor. Such a series of gas phase reactors may further comprise additional polymerization reactors. These additional reactors may be any type of low pressure polymerization reactor, such as a gas phase reactor or a suspension reactor, and may include a prepolymerization stage.

[0045] In the process of the present disclosure, the gaseous stream is withdrawn from a polymerization apparatus including a polymerization reactor or a combination of polymerization reactors. If the polymerization is a gas phase polymerization, the gaseous stream can be withdrawn from any position in the polymerization apparatus. Preferably, the gaseous stream is withdrawn from a position in the polymerization apparatus where the reaction gas is present. This means that if the polymerization is a gas phase polymerization, the gaseous stream may be withdrawn directly from the reactor, or, for example, in the case of polymerization in a fluidized bed reactor or a multi-zone loop reactor, the gaseous stream may be withdrawn from a gas recycle line. If the polymerization is a suspension polymerization carried out in a polymerization reactor that is not completely filled with suspension, the gaseous stream is preferably withdrawn from a vapor section in the polymerization reactor that is higher than the suspension level in the reactor. In particular, if the polymerization is carried out in a fully filled polymerization reactor such as a loop reactor, the gaseous stream may be withdrawn from a part of the polymerization apparatus where the gas phase is present, rather than directly from the polymerization reactor. Such a device may be, for example, a flash vessel installed downstream of the polymerization reactor, or a device connected to the flash vessel.

[0046] FIG. 1 shows a schematic of a polymerization apparatus set-up comprising a series of polymerization reactors, including a fluidized bed reactor and a multi-zone circulating reactor, in which the process of the present disclosure can be carried out.

[0047] The first gas-phase reactor, the fluidized bed reactor (1), contains a polyethylene particle fluidized bed (2), a gas distribution grid (3), and a velocity reduction zone (4). The diameter of the velocity reduction zone (4) is generally increased compared to the diameter of the fluidized bed section of the reactor. Upward gas supplied through the gas distribution grid (3) located at the bottom of the reactor (1) keeps the polyethylene layer in a fluidized state. The gaseous stream of the reaction gaseous mixture leaving the top of the velocity reduction zone (4) through the recycle line (5) is compressed by a compressor (6) and transferred to a heat exchanger (7), where it is cooled and then recycled to the bottom of the fluidized bed reactor (1) at a point below the gas distribution grid (3) at location (8). If necessary, the recycle gas can be cooled below the dew point of one or more recycle gas components in the heat exchanger in order to operate the reactor in a condensed material, i.e., condensed, mode. In addition to unreacted monomers, the recycle gas can contain inert condensable gases, such as alkanes, and inert non-condensable gases, such as nitrogen. Make-up monomer, hydrogen gas, and any inert gas or process additives can be fed to the reactor (1) at various locations, for example, via line (9) upstream of the compressor (6). Generally, the catalyst is fed into the reactor (1) via line (10), preferably located below the fluidized bed (2).

[0048] The polyethylene particles obtained in the fluidized bed reactor (1) are discontinuously discharged through a line (11) to prevent the gaseous mixture from the fluidized bed reactor (1) from entering the second gas phase reactor, and are supplied to a solid-gas separator (12). The gas leaving the solid-gas separator (12) leaves the reactor as exhaust gas through a line (13), and the separated polyethylene particles are supplied to the second gas phase reactor through a line (14).

[0049] To analyze the composition of the reaction gas in the fluidized bed reactor (1), a gaseous stream is withdrawn from the recycle line (5) at a location between the compressor (6) and the heat exchanger (7) via a sampling line (15).

[0050] The second gas phase reactor is a multi-zone loop reactor (21) including a riser (22) and a downcomer (23) through which the polyethylene particles pass repeatedly. In the riser (22), the polyethylene particles flow upwards in the direction of arrow (24) under fast fluidization conditions. In the downcomer (23), the polyethylene particles flow downwards by gravity in the direction of arrow (25). The riser (22) and downcomer (23) are suitably in communication with each other via interconnecting bends (26), (27).

[0051] The polyethylene particles and reactant gaseous mixture flow through the riser (22) and then exit the riser (22) and are sent to a solid-gas separation zone (28). Such solid-gas separation may be accomplished using conventional separation equipment such as a centrifuge, such as a cyclone. From the separation zone (28), the polyethylene particles enter the downcomer (23).

[0052] The reaction gaseous mixture leaving the separation zone (28) is recycled to the riser (22) via a recycle line (29) equipped with a compressor (30) and a heat exchanger (31). Between the compressor (30) and the heat exchanger (31), the recycle line (29) branches and the gaseous mixture is divided into two separate streams: line (32) sends one part of the recycle gas to the interconnecting bend (27) and line (33) sends the other part of the recycle gas to the bottom of the riser (22), where fast fluidization conditions are established.

[0053] The polyethylene particles from the first gas phase reactor enter the multi-zone loop reactor (21) through the line (14) at the interconnecting bend (27) at the position (34). The polyethylene particles obtained in the multi-zone loop reactor (21) are continuously discharged from the bottom of the downcomer (23) via the discharge line (35).

[0054] A portion of the gaseous mixture leaving the separation zone (28), after passing through a compressor (30), exits through a recycle line (29) and is sent through a line (36) to a heat exchanger (37) where it is cooled to a temperature where the monomers and any inert gases are partially condensed. A separation vessel (38) is disposed downstream of the heat exchanger (37). Separated liquid is withdrawn from the separation vessel (38) through a line (39) and fed by a pump (44) through lines (40), (41), (42), (43) into the downcomer (23), where the feed stream introduced through line (40) is fed to create a barrier to prevent the reaction gas mixture in the riser (22) from entering the downcomer (23). Make-up monomer, make-up comonomer, and any inert gas and / or process additives may be introduced into lines (41), (42), (43) via lines (45), (46), (47) and fed into the downcomer (23) at monomer feed points (48), (49), (50). Make-up monomer, make-up comonomer, and any inert gas and / or process additives may further be introduced into the recycle line (29) via line (51). The gaseous mixture obtained in the vapor phase in the separation vessel (38) is recycled to the recycle line (29) through line (52).

[0055] At the bottom of the downcomer (23) is attached a control valve (53) having an adjustable opening for regulating the flow of polyethylene particles from the downcomer (23) through the interconnecting bend (27) to the riser (22). Above the control valve (53), a quantity of recycle gaseous mixture provided through line (54) from the recycle line (29) is introduced into the downcomer (23) to encourage the polyethylene particles to flow through the control valve (53).

[0056] To analyze the composition of the reaction gases in the riser (22) and downcomer (23), a gaseous stream is withdrawn from the recycle line (29) through sampling line (55) and from the downcomer (23) through sampling line (56) at a location between the compressor (30) and the heat exchanger (31).

[0057] In the process of the present disclosure, the gaseous stream withdrawn from the polymerization apparatus is fed to an analytical apparatus. The analytical apparatus may be a gas chromatograph, It may be a Raman probe, an infrared detector, a mass spectrometer, or a thermal conductivity detector. Preferably, the analytical instrument is a gas chromatograph.

[0058] Before entering the analytical instrument, the gaseous stream is passed through a bed of particulate solids having chemical groups on their surfaces which react with organometallic compounds.

[0059] In a preferred embodiment of the present disclosure, the particulate solid having chemical groups on its surface that react with organometallic compounds is a porous material such as talc, layered silicates, inorganic oxides, and the like.

[0060] Inorganic oxides suitable as particulate solids can be found among the oxides of elements of groups 2, 3, 4, 5, 13, 14, 15 and 16 of the periodic table. Preference is given to oxides or mixed oxides of the elements calcium, aluminum, silicon, magnesium or titanium. Other inorganic oxides can be used alone or in combination with the above oxides, for example ZrO2 or B2O3. Preferred oxides are silica, in particular in the form of silica gel or pyrogenic silica, alumina or silicon-aluminium mixed oxides. Preferred mixed oxides are, for example, calcined hydrotalcites. It is also preferred to use silica of formula SiO2·aAl2O3, where a is between 0 and 2, preferably between 0 and 0.5. The particles of the particulate solid may be in granular or spray-dried form, the particles of the particulate solid consisting of smaller primary particles, for example with an average particle size of 5 nm to 5 m.

[0061] The particulate solid having a surface having a chemical group reactive with an organometallic compound has an average particle size of 50 mm to 10 mm, more preferably 200 mm to 5 mm. The specific surface area of ​​the particulate solid is 200 m2 or less as measured by a gas adsorption method according to the BET method specified in ISO 9277:2010. 2 / g~1000m2 / g, more preferably 500m 2 / g~800m 2 / g range.

[0062] The chemical groups on the surface of the particulate solid which react with the organometallic compound are preferably OH groups, adsorbed water or distorted Si-O-Si bridges, especially of the calcined solid.

[0063] By reacting with the organometallic compound, the active chemical groups on the surface of the particulate solid are consumed. Thus, the zone in the particulate solid bed where the reaction between the organometallic compound and the active surface groups occurs passes through the particulate solid bed. Preferably, before all of the reactive surface groups of the particulate solid bed through which the gaseous stream withdrawn from the polymerization apparatus passes have reacted with the organometallic compound, the particulate solid bed is replaced by a new particulate solid bed having chemical groups on its surface which react with the organometallic compound.

[0064] In a preferred embodiment of the present disclosure, the particulate solid having chemical groups on its surface that react with organometallic compounds is a silica gel equipped with a humidity indicator. When the gaseous stream withdrawn from the polymerization apparatus passes through a bed of silica gel particles equipped with a humidity indicator, the organometallic compound can react with the humidity indicator, which is usually colored, to change the color of the silica gel particles. This allows easy monitoring of the consumption of the reactive surface groups by reaction with the organometallic compound.

[0065] In a preferred embodiment of the present disclosure, the gaseous stream withdrawn from the polymerization apparatus is a continuous gaseous stream withdrawn from the polymerization apparatus at a flow rate of 1 Nl / h to 5000 Nl / h, preferably 1 Nl / h to 500 Nl / h, more preferably 5 Nl / h to 350 Nl / h, in particular 10 Nl / h to 250 Nl / h. The unit "Nl" should be understood as standard liter, which is the amount of gas per liter of volume under standard conditions of 101325 Pa (=1.01325 bar) and 0°C.

[0066] In a preferred embodiment of the present disclosure, the analyzer is provided with samples of the gaseous stream at regular intervals.

[0067] In a preferred embodiment of the present disclosure, two or more, e.g., two, three, four or five, gaseous streams are withdrawn from the polymerization apparatus at different locations and some or all samples of the two or more gaseous streams are provided to one analytical device for analyzing the samples, or some or all of the two or more gaseous streams have a dedicated analytical device that is provided with only a sample of one of the gaseous streams withdrawn from the polymerization apparatus.

[0068] To analyze the material composition in a polymerization apparatus according to the present disclosure, a gaseous stream is withdrawn from the polymerization apparatus. The gaseous stream is preferably fed into a sampling loop that is adjacent to or preferably located in an analysis apparatus such as a gas chromatograph. The sampling loop provides a predetermined volume of gaseous sample, which is then transported into an analysis unit, for example by an inert carrier gas. The analysis apparatus is usually calibrated so that the sum of all measured components is 100%. However, it has been found that when a gaseous stream is withdrawn from a polymerization apparatus carrying out the polymerization of olefins in the presence of a polymerization catalyst and an organometallic compound, this calibration value becomes unstable and the measured sum of all components continues to decrease. It has been found that the accumulation of fine solid particles in the sample loop causes the volume of the sample loop to slowly shrink, which in turn reduces the volume added to the analysis apparatus, distorting the analysis value. The further away the sum of the measured components is from 100%, the less accurate the measurement becomes. Furthermore, recalibration of the analysis apparatus can bring the sum of the measured components back to 100%, but with each recalibration, it takes less and less time to reach an unacceptable deviation. After recalibrating the analyzer 5-10 times, cleaning the sample loop and sampling valve is inevitable. During cleaning, the analyzer cannot be used. Operating the polymerization unit without control is generally avoided, since such operation may result in the polymer product not reaching the specified property profile or in serious process incidents. As a result, the polymerization in the polymerization unit may have to be stopped during cleaning, resulting in production losses, or the need for alternative analyzers and additional efforts.

[0069] By passing the gaseous stream withdrawn from the polymerization apparatus through a bed of particulate solids having chemical groups on their surface that react with organometallic compounds, the deposition of fine solid particles in the sampling device of the analyzer is avoided and the measured total of all components is kept stable. By passing the gaseous stream through a bed of particulate solids having chemical groups on their surface that react with organometallic compounds, the concentration of the organometallic compounds in the gaseous stream leaving the bed of particulate solids is preferably less than 99%, more preferably less than 99.5%, more preferably less than 99.8%, and especially less than 99.9% of the concentration of the organometallic compounds in the gaseous stream withdrawn from the polymerization apparatus.

[0070] The bed of particulate solids having chemical groups on their surface that react with organometallic compounds is placed in a 50 cm 3 ~1000cm 3 , preferably 100 cm 3 ~5000cm 3 , more preferably 200 cm 3 ~2500cm 3 It is preferable that the liquid is contained in a container having a volume of 1000 g.

[0071] FIG. 2 shows a schematic diagram of a vessel for containing a bed of particulate solids according to the present disclosure.

[0072] The vessel comprises a vertical tube (101) with flanges (102), (103) at the top and bottom. Attached to the flange (102) is a first short tube element (104) with a ball valve (105) for filling the tube (101) with a bed of particulate solids, such as silica, having chemical groups on its surface that react with organometallic compounds. Attached to the flange (103) is a second short tube element (106) with a ball valve (107) for emptying the tube (101).

[0073] The vertical pipe (101) includes a short horizontal pipe (108) terminating in a flange (109) near the upper end of the pipe (101) and a short horizontal pipe (110) terminating in a flange (111) near the lower end of the pipe (101). A capillary tube (112) is connected to the flange (111) for supplying a gaseous stream to the pipe (101). A capillary tube (113) is connected to the flange (109) for withdrawing the gaseous stream from the pipe (101) after it has passed through the pipe (101). The connections between the flange (111) and the pipe (112) and between the flange (109) and the pipe (113) are provided with steel screens (114), (115) to retain the bed of particulate solids within the pipe (101).

[0074] In a preferred embodiment of the present disclosure, the particulate solid bed is contained in a vessel comprising a pipe having a diameter of 6 mm to 100 mm, preferably 10 mm to 80 mm, in particular 15 mm to 50 mm, the pipe having an inlet for introducing a gaseous stream into the pipe and an outlet for withdrawing the gaseous stream from the pipe, the distance between the inlet and the outlet being 0.2 m to 10 m, preferably 0.3 m to 5 m, in particular 0.4 m to 2 m.

[0075] Preferably, the vessel further comprises a first valve at one end of the pipe for introducing the bed of particulate solids into the pipe, and a second valve at the other end of the pipe for removing the bed of particulate solids from the pipe. In a preferred embodiment, the inlet and outlet of the pipe are provided with 35 pressure valves for retaining the bed of particulate solids within the pipe. μ m~2mm, preferably 50 μ m~1.5mm, especially 100 μ Preferably, the vessel is provided with a screen having a mesh size of 1 mm to 1 mm. In a particularly preferred embodiment, the vessel comprises first and second valves at the ends of the pipes, the inlets and outlets of which are provided with screens.

[0076] Thus, in one embodiment, the disclosure provides a method for producing a gaseous stream comprising the steps of: a pipe having a diameter of 6 mm to 100 mm, preferably 10 mm to 80 mm, in particular 15 mm to 50 mm; an inlet for introducing a gaseous stream into the pipe; an outlet for withdrawing the gaseous stream from the pipe; a first valve at one end of the pipe for introducing a bed of particulate solids into the pipe; and a second valve at the other end of the pipe for removing the bed of particulate solids from the pipe; μ m~2mm, preferably 50 μ m~1.5mm, especially 100 μ A screen having a mesh size of 0.2 m to 1 mm is provided, the distance between the inlet and the outlet being 0.2 m to 10 m, preferably 0.3 m to 5 m, in particular 0.4 m to 2 m.

[0077] In a preferred embodiment of the polymerization process of the present disclosure, the results obtained from analyzing the gaseous sample are provided as a measurement signal to a controller for controlling the process for preparing an olefin polymer.

[0078] Thus, in one embodiment, the present disclosure provides a method for controlling an olefin polymerization process comprising homopolymerizing an olefin or copolymerizing an olefin with one or more other olefins in a polymerization apparatus comprising a polymerization reactor or a combination of polymerization reactors in the presence of a solid particle polymerization catalyst and an organometallic compound at a temperature of 20-200° C. and a pressure of 0.1 MPa-20 MPa, comprising: - withdrawing a gaseous stream from the polymerization apparatus; - passing the gaseous stream through a bed of particulate solids having chemical groups on their surfaces which react with the organometallic compound; - supplying the gaseous sample to an analytical device for analyzing the gaseous sample; - analyzing the sample to obtain information about the conditions in the polymerization apparatus; - adapting polymerization conditions in a polymerization device to predetermined values ​​based on information obtained by analysing the sample. Thus, the present disclosure also provides methods for preparing olefin polymers, including such processes for controlling an olefin polymerization process.

[0079] The results obtained from the analysis of the gaseous stream samples provide information about the conditions in the polymerization equipment. These data can be used to determine the polymerization conditions for a particular grade or condition, on the one hand, and to adapt the measured polymerization conditions to predetermined values. This adaptation can be performed manually by an operator, or automatically. In a preferred embodiment of the present disclosure, the results obtained from the analysis of the gaseous stream samples are provided as measurement signals to a controller for controlling the olefin polymerization process. Working Example Comparative example A

[0080] As shown in Figure 1, a series of fluidized bed reactors and a multi-zone loop reactor (MZCR) with two reaction zones connected together produced multiple grades of ethylene 1-hexene copolymers with 1-hexene contents ranging from 0 wt% to 4 wt% with an average yield of 100 kg / h at temperatures ranging from 60°C to 110°C and pressures ranging from 1 MPa to 10 MPa. The catalyst system used to carry out the polymerization was a Ziegler-Natta catalyst system containing a catalytic solid consisting of TiCl4 supported on a MgCl2 support. Triisobutylaluminum was used as a cocatalyst and was fed to the polymerization at a feed rate of 25 g / h to 50 g / h.

[0081] The polymerization was controlled by withdrawing the reaction gases via sampling lines (15), (55), (56) and transferring them to a MAXUM Edition II gas chromatograph (Siemens AG, RNberg, Germany; not shown in FIG. 1 ) to measure the gas composition in the riser (22) and downcomer (23) of the fluidized bed reactor (1) and the multizone loop reactor (21). The gas chromatograph was alternately fed with the reaction gases via lines (15), (55), (56). After selecting the polymerization zone for determining the composition of the reaction gas and thus the appropriate sampling line, the reaction gases were continuously withdrawn through one of the sampling lines (15), (55), and (56) and first passed through an in-line 15M particulate filter (Swagelok The reaction gas was passed through a pressure reducer (Fuji Electric Co., Ltd., Solon, Ohio, USA) and then the pressure was reduced to 0.17 MPa (abs) by a pressure reducer. The flow rate of the reaction gas measured after the pressure reducer at 0.17 MPa was 30 Nl / h for all selected sampling lines (15), (55) and (56). In the space close to the gas chromatograph, a side stream with a flow rate of 5 Nl / h was branched off to feed the sample valve containing the injection loop while sending the remaining part of the reaction gas extracted through lines (15), (55), (56) into the exhaust gas. The working sampling lines (15), (55), (56) with a flow rate of the reaction gas higher than the flow rate of the gas actually fed to the sample valve were selected to reduce the dead time between the extraction of the gas from the polymerization apparatus and its final introduction into the gas chromatograph.

[0082] To perform the measurements, the sample valve was switched to its position, the injection loop, through which the reactant gas to be analyzed had previously been passed, was then incorporated into the carrier gas line, and the contents of the injection loop were then transferred by the carrier gas to the gas chromatograph. To obtain the next GC chromatogram, the sample valve was switched back to its original position, and the reactant gas to be analyzed was again passed through the injection loop. Flushing of the injection loop with the reactant gas continued for at least 1 minute before the injection loop was again incorporated into the carrier gas stream. The gas chromatograph was operated at a rate of 20 gas chromatograph readings per hour, on average.

[0083] The sum of all measured components periodically decreased, eventually requiring the injection loop and sample valve to be cleaned. After such cleaning operations, the gas chromatograph was calibrated so that the sum of all measured components was 100%. This value is unstable. The sum of all measured components continued to drop. After 2 weeks, the sum of all measured components was below 80%, and the accuracy of the gas chromatographic measurement was significantly reduced. By recalibrating the gas chromatograph, the sum of all measured components could be reset to 100%, and the gas chromatograph could be reused with sufficient accuracy for 10 days, until the sum of all measured components continued to drop and again fell below 80%, requiring further recalibration. After 1 week, the sum of all measured components was again below 80%. If the measurement accuracy of the GC is acceptable, the polymerization was terminated, the gas chromatograph was removed, the injection loop and sample valve were cleaned, and then the polymerization was resumed, avoiding further shortening in order not to cause a polymerization interruption of 2 days on average. Example 1

[0084] The series of polymerizations carried out in Example A are continued, on average, under the same conditions, but with a vessel containing a silica bed installed in the sampling line between the pressure reducing device and the position where the side stream branches off to the sample valve of the gas chromatograph, as shown in FIG. 2. The vessel is equipped with a tube (101) with an inner diameter of 25 mm and a length of 850 mm from flange (102) to flange (103). The vessel is filled with silica equipped with a humidity indicator (silica gel orange, 2-5 mm, with indicator, pearls, Carl Roth GmbH+Co KG, Karlsruhe, Germany). The screens (114), (115) were chosen as 20 mesh screens (mesh size 850 μm).

[0085] The polymerization was carried out for 4 weeks, with the sum of all measured components remaining above 99% throughout the entire period. After 4 weeks, the polymerization was interrupted and the vessel (101) was emptied. Approximately one-quarter of the silica had changed color from orange to dark brown. Example 2

[0086] Example 1 was repeated with new silica. The polymerization was carried out for 3 months. The sum of all measured components was reduced to 95%, but it was still possible to control the polymerization with high precision. The silica bed was then removed from the vessel (101). A small part of the silicon dioxide had not yet changed from orange to dark brown. Example 3

[0087] Example 2 was repeated, but using another silica with a humidity indicator (Silica gel orange, granular, 0.2-1 mm, Sigma-Aldrich, Merck KGaA, Darmstadt, Germany) and the screens (114), (115) being 100 mesh screens (mesh size 150 μm).

[0088] The sum of all measured components was reduced to 96%, still allowing for highly accurate control of the polymerization. Emptying of the vessel (101) after three months showed that most of the silica had turned dark brown, although some was still orange.

[0089] Examples 1-3 demonstrate that by providing a bed of particulate solid having chemical groups on its surface that react with organometallic compounds, a gas chromatograph in an olefin polymerization apparatus can be operated with high accuracy in the presence of an alkylaluminum cocatalyst without repeated cleaning of the gas chromatograph dispenser and / or without recalibrating the gas chromatograph.

Claims

1. 1. A process for preparing an olefin polymer comprising: feeding a solid particulate polymerization catalyst, an organometallic compound, and an olefin or a combination of an olefin and one or more other olefins to a polymerization apparatus comprising a polymerization reactor or a combination of polymerization reactors; homopolymerizing said olefin or copolymerizing said olefin with said one or more other olefins in the presence of said polymerization catalyst and said organometallic compound at a temperature of 20-200° C. and a pressure of 0.1 MPa-20 MPa; withdrawing a gaseous stream from the polymerization apparatus; passing said gaseous stream through a bed of particulate solids having chemical groups on their surfaces which react with said organometallic compound; providing a sample of the gaseous stream to an analytical device for analyzing the sample of the gaseous stream; A process wherein the results obtained from analyzing the sample of said gaseous stream are provided as a measurement signal to a controller for controlling the process for preparing an olefin polymer.

2. 2. The process of claim 1, wherein the analytical device is a gas chromatograph and / or the gaseous stream withdrawn from the polymerizer is a continuous gaseous stream withdrawn from the polymerizer at a flow rate of from 1 Nl / h to 5000 Nl / h.

3. the organometallic compound is an aluminum alkyl; and / or The particulate solid is an oxide of the elements calcium, aluminum, silicon, magnesium, or titanium or a mixed oxide of the elements calcium, aluminum, silicon, magnesium, or titanium, or the particulate solid is ZrO ２ Or B ２ O ３ 3. The process according to claim 1 or 2,

4. 3. A process according to claim 1 or 2, wherein the chemical groups on the surface of the particulate solid which react with the organometallic compound are OH groups and / or the particulate solid is a silica gel provided with a humidity indicator.

5. 3. The process of claim 1 or 2, wherein two or more of the gaseous streams are withdrawn at different locations in the polymerization apparatus and then samples of some or all of the two or more of the gaseous streams are fed to one of the analyzers for analyzing the samples, or some or all of the two or more of the gaseous streams are each analyzed in a dedicated analyzer provided with only a sample of one of the gaseous streams withdrawn from the polymerization apparatus.

6. The particulate solid bed is 50 cm ３ ~10000cm ３ 3. The process according to claim 1 or 2, wherein the bed of particulate solids is contained in a vessel comprising a pipe having a diameter of between 6 mm and 100 mm, an inlet for introducing the gaseous stream into said pipe, and an outlet for withdrawing the gaseous stream from said pipe, the distance between said inlet and said outlet being between 0.2 m and 10 m.

7. the vessel further comprises a first valve at one end of the pipe for introducing the bed of particulate solids into the pipe and a second valve at the other end of the pipe for removing the bed of particulate solids from the pipe; and / or 7. The process of claim 6, wherein the inlet and the outlet of the pipe are provided with screens having a mesh size of between 35 μm and 2 mm to retain the particulate solid bed within the pipe.

8. 1. A vessel comprising a pipe having a diameter of 6mm to 100mm, an inlet for introducing a gaseous stream into said pipe, an outlet for withdrawing said gaseous stream from said pipe, a first valve at one end of said pipe for introducing a bed of particulate solids into said pipe and a second valve at the other end of said pipe for removing said bed of particulate solids from said pipe, said inlet and said outlet of said pipe are provided with screens having a mesh size of 35μm to 2mm, and the distance between said inlet and said outlet is 0.2m to 10m.

9. A method for controlling an olefin polymerization process comprising homopolymerizing an olefin or copolymerizing an olefin with one or more other olefins in a polymerization apparatus comprising a polymerization reactor or a combination of polymerization reactors in the presence of a solid particle polymerization catalyst and an organometallic compound at a temperature of 20-200° C. and a pressure of 0.1 MPa to 20 MPa, comprising: - withdrawing a gaseous stream from said polymerization apparatus; - passing said gaseous stream through a bed of particulate solids having chemical groups on their surfaces which react with said organometallic compound; - supplying a sample of said gaseous stream to an analytical device for analyzing the gaseous sample; - analyzing said sample to obtain information about the conditions in said polymerization apparatus; - adapting the polymerization conditions in said polymerization device to predetermined values ​​based on the information obtained by analysing said sample.

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