A method of preventing fouling in the polymerization reactors

 

(57) Abstract:

Describes a method of preventing fouling in the reactor circulation in the polymerization of alpha-olefins in the presence of a catalyst to obtain a product in the form of particles by introducing into the reactor agent that prevents fouling. It differs in that as an agent for preventing fouling, use a composition including a copolymer of alpha-olefin to Acrylonitrile and polyamine, which is a product of polymerization of aliphatic primary mono - or diamine with epichlorohydrin or a copolymer of alpha-olefin with maleic anhydride. The technical result is to simplify the process by using the proposed compositions. 2 S. and 3 C.p. f-crystals, 1 Il., table 1.

The invention relates to a method for preventing fouling in the polymerization reactors, in particular in the reactor circulation.

Developed different ways of obtaining solid and semi-solid polymers of hydrocarbons, for example of 1-olefins. In one such method olefins, such as ethylene, propylene or butene, are polymerized in the presence of catalysts in hydrocarbon solvent or by monomers acting as razbam the ion reactor. If the polymer is insoluble or only slightly soluble in the diluent, the polymer product is formed in the form of particles, and therefore the flow of the product consists of a suspension, formed polymer particles, solvents and monomers. This product flow is usually transported in the capacity of branch polymer, where the solid, liquid and gaseous constituents are separated from each other.

One type of reactor used in such ways, is a tubular reactor with continuous action, forming a loop, where the polymerization is carried out in a turbulent flow circulating in the loop. The product containing the polymer, the solvent and monomers derived from reactor circulation either continuously or, more usually, periodically through the discharge valve and is introduced into the separator, where the polymer is separated in the lower pressure.

A problem often encountered, especially in reactors with circulation, is the adhesion of polymer particles to the walls of the reactor. Even a small amount of the polymer cause the disappearance of the smooth interior surface of the reactor, when the adhesion is accelerated, and, in the worst case, cause clogging of the reactor. Polymer layer on the interior on the Naya bleeding the pump. At the same time decreases the efficiency of heat transfer of the reactor, and the temperature control is more difficult. If you use high temperature polymerization, this can lead to the melting of the polymer.

Further, the quality of the product is significantly reduced agglomeration of the polymer, which adheres to the inner wall of the reactor, and which comes out at some stage. Polymeric material that sticks and leaves later, has a different time and, hence, molecular weight than the molecular weight of the material which does not stick, resulting in the final product is not achieved the desired molecular structure.

Attempts have been made to avoid the harmful effects of fouling, as described above, by adding diluent antistatics, which make thinner more conductive and therefore prevent the formation of static electric charges, at least to some extent. However, the antistatic agents of this type are harmful to the catalyst of polymerization, because they are, at least to some extent as catalytic poisons, reducing the catalytic activity.

U.S. patent not as antistatic. U.S. patent 3995097 as antistatic offers a mixture of aluminum or chromium salts alkylsalicylate acid and alkylsulfonate alkali metal. U.S. patent 4012574 serves as antistatic surfactant that contains one or more perftoruglerodnykh groups. U.S. patent 4068054 as antistatic offers connection porphyrin separately or together with sulfosuccinates alkali metal. U.S. patent 4182810 as antistatic offers a mixture polysulfonamide polymer, polymer polyamine and soluble sulfonic acids.

The aim of the invention is to provide a method of preventing the harmful effects of fouling in the polymerization reactors. One object of the invention is a method of preventing the harmful effects of fouling, such that the catalytic activity decreases slightly. Another object of the invention is the provision of a method of preventing the harmful effects of fouling, such that the heat transfer polymerization reactor deteriorates slightly, and provides better time and molecular mass distribution of polymer particles.

Objectives of the invention are achieved when the COI is the region of the phenomenon of fouling in the polymerization reactor, in particular, in the reactor with circulation.

Such compositions known per se, and also known for their use as antistatic agents. For example, according to U.S. patent 4259087 these substances are used in small quantities to reduce the risk of ignition and explosion in hydrocarbon fuels due to electrostatic discharge. Other applications proposed in this patent, are solvents, cleaners, paint remover, fabric, liquid polishing agents and rubber compound.

In accordance with the invention it has been unexpectedly found that the use of these compositions as an agent for preventing fouling in the reactor circulation in the polymerization of alpha-olefins can effectively prevent the adhesion of polymer particles to the inner surface of the reactor and simultaneously avoid the harmful effects that are traditionally used for the appropriate purpose, the agents have on the activity of the catalyst. The amount of the composition may vary widely without adversely affecting the properties of the product.

Prevents fouling agents used in the invention consists of a composition, the cat is as discussed in U.S. patent 4259087, after complexation, per se known manner, Acrylonitrile, with a Lewis acid, such as AlCl3, ZnCl2and AlRnCl3-nand when the polymerization of the obtained complex material with limit olefin using a free radical initiator. The corresponding alpha-olefins are, for example, 1-hexene, 1-octene, 1-mission 1-dodecen, tetradecene, 1-hexadecene, achozen.

Polyamine components can also be obtained in a known manner, for example, by the polymerization of aliphatic primary mono - or diamine with epichlorohydrin or a copolymer of alpha-olefin with maleic acid anhydride. However, the applicants would like to emphasize that the expert can use in this invention and other polyamine obtaining describes the technical result of the catalyst. Especially it should be noted that the number of prevent the sticking agent used according to the invention, can be very high without simultaneous harmful effects on the catalytic activity.

Prevents fouling agent according to the invention can be introduced to the reactor in the flow of power coming into the reactor, or directly into the reactor. So, it can be in Leshey for submission of the catalyst. The introduction can be carried out either continuously or periodically, or only when needed.

According to the invention prevents fouling agent may be used, in particular, in the polymerization of alpha-olefins such as ethylene, propylene, BETEN, 4-methyl-1-penten or hexene, or liquid-phase or gas-phase method. Most preferred is its use for the polymerization of ethylene, propylene or butene or copolymerization reactor with circulation. Especially, prevent the sticking agent according to the invention is used for polymerization when used catalysts are susceptible to poisoning, such as Phillips catalysts or Ziegler catalysts. For example, when the Phillips catalysts can be used as catalysts, these catalysts are composed of chromium oxide deposited on an inorganic carrier such as silica, aluminum oxide and zirconium dioxide. The catalysts of the Ziegler-Natta usually consist of one or more transition metals belonging to groups IV to VI of the periodic system of elements, such as titanium, vanadium, zirconium or chromium, and ORGANOMETALLIC compounds of metals belonging to groups I-III and pressure 100-10000 kPa. The polymerization reactor may be a traditional type reactor vessel with stirring or tubular reactor, preferably the reactor with circulation or gas-phase reactor. The polymerization may be conducted periodically by the way, but the benefits of preventing fouling agent according to the invention become particularly clear in a continuous way, when problems caused by adhesion of polymer particles are more visible.

In the suspension polymerization of aliphatic hydrocarbons such as propane, butane, pentane, hexane, heptane or octene can be used as a diluent, although the use of preventing fouling agent according to the invention is not meant to limit only the listed examples.

The invention is described in detail with reference to the attached drawing, which schematically presents the traditional system of reactor circulation.

Figure 10 in the figure denotes a light curing device, in which in a reactor with a circulation of 15 monomer is introduced through the supply line 11 from line 12, the catalyst line 13 and the diluent through line 14. The suspension formed by the reactants and the resulting polymer circular the sa. The temperature of the reactor 15 can be adjusted by using a heating/cooling jacket 17. Supply of reagents described above is only illustrative, and thus, the reagents may be introduced into the reactor 15 in any desired manner either together or separately. Suspension polymer, diluent and monomer is withdrawn from reactor 15 through the valve 18. The valve 18 is opened periodically for a short period of time, such as every half a minute, and allows suspension of the product flowing through the pipe 19 into the separation tank 20. By reducing the pressure in the separation tank 20, the diluent contained in the suspension turns into a gas, while the solid polymer product is discharged through the pipe 21, and a gaseous phase containing the diluent and monomer, is displayed on the tube 22 and may be returned to the reactor 15 through the pipe 24 after raising the pressure with a compressor 23. Gas samples may be taken from the pipe 22 through the pipe 25 to the detector 26.

According to the invention the composition of the copolymer of alpha-olefin to Acrylonitrile and polymer polyamine is skipped, for example, along the line 14a in the flow of diluent 14 and then into the reactor with circulation 15. However, does this not mean that the thus, the composition may be introduced equally well, for example, on line 13.

Further, the invention is illustrated in the accompanying examples, in which as preventing fouling agents are used in the following industrial products:

- TOLD 511 - composition copolymer of alpha-olefin to Acrylonitrile and polyamine, where the polyamine is a product of the polymerization of aliphatic primary mono - or diamine with epichlorhydrine and qualified company manufacturer Petrolite Corporation, as the Quaternary polymer aminoamides. The composition of AC 3, produced by shell, is a xylene solution containing organic salts of chromium and calcium, stable polymer.

EXAMPLE 1

Homopolymerization ethylene is carried out in the laboratory in a suspension reactor of 3 l when using isobutane diluent and chromatiaceae catalyst deposited on a silica carrier. As to prevent fouling agent is used TOLD 511. The polymerization conditions and results are given in the table.

Introduction preventing fouling agent has no effect on the melt index of the polymer or activity the reactor circulation volume 86 m3when using chromatometer catalyst deposited on a silica carrier. As to prevent fouling agent is used ASA-3. In the polymerization process additive is gradually replaced by the additive in accordance with the invention TOLD 511. The electrostatic potential of the polymer powder obtained in the prevailing steady-state conditions, is reduced from the value of-4.3 to the value of-0.9, whereas the activity of the catalyst increases from values of 2.9 to a value of 3.6 kg/g catalyst. This illustrates the effectiveness of the additive according to the invention and the absence of toxic effect on the catalysts.

EXAMPLE 3

Repeated polymerization of example 2 using the agent of the invention TOLD 511 as preventing fouling agent. The additive of the invention abruptly replaced by another agent (ASA-3). The catalytic activity is sharply reduced, and the polymerization reaction is almost extinguished.

EXAMPLE 4

A copolymer of ethylene and 1-hexene is obtained on an industrial scale reactor with circulation volume 86 m3when using fluorinated chromium catalyst on a silica carrier. Multiple regression analysis demonstrared the 1,2oC above the use of additives TOLD 511 according to the invention instead of the other additives (AC-3). Despite the fact that according to the General knowledge that should lead to fouling of the walls of the reactor, the fouling phenomenon is not observed, such as increased load pump reactor or fluctuations of the reaction temperature.

EXAMPLE 5

The operation of the reactor with a circulation of 500 DM3is carried out at a temperature of 104oC when filing continuously 32 kg/h of isobutene, 4 g/h of catalyst for polymerization containing 0,98% chromium as the active metal, and ethylene, so that its content in the liquid phase is equal to 7.5 mol.%. To prevent fouling in the reactor is continuously injected solution TOLD 511 in isobutane. The amount of additive is equal to 11 g/h of pure TOLD 511. Polyethylene is continuously withdrawn from the reactor with a rate of 43 kg/h, which is normal for used catalyst. This confirms that the catalyst is not poisoned, despite the very large number of preventing fouling agent. Fouling of the reactor is not observed, and the polymer is free from static electricity. The melt index of the polymer I2is equal to 0.26 g/10 min and a melt index I21ravneet is the temperature value 95oC, is fed continuously 24 kg/h of propane, 30 g/h of polymerization catalyst containing 3% titanium as an active metal, ethylene, so that its content in the liquid phase is equal to 7.0 mol.%, and hydrogen so that its relation to ethylene equals 518 mol/KMOL. To prevent fouling in the reactor is continuously injected solution TOLD 511 in propane. The amount of additive is equal to 78 mg/h net TOLD 511. Polyethylene is displayed continuously from the reactor at a rate of 30 kg/h, which is a normal value for the used catalyst, and confirm that the catalyst is not poisoned. Fouling of the reactor is not observed, and the polymer is free from static electricity. The melt index of the polymer I2equal to 400 g/10 min.

EXAMPLE 7

In the first reactor with circulation, having a volume of 50 DM3and operating at a temperature of 70oC, is fed continuously 29 kg/h of propane, 11 g/h of catalyst polymerization, containing 2.6% of titanium as an active metal, 1.1 kg/h of ethylene, 50 g/h of 1-butene and hydrogen, so that its ratio to ethylene in the reactor is equal to 175 mol of KMOL. To prevent fouling in the reactor is continuously injected solution TOLD 511 in propane, calculated as 570 mg/h cisem 500 DM3and operating at a temperature of 95oC. In addition to the polymer slurry from the first reactor with circulation in the second reactor circulation is continuously fed 32 kg/h of propane and ethylene so that its content remains to 7.5 mol.%, and hydrogen so that its relation to ethylene equals 214 mol/KMOL. Polyethylene having a melt index I2115 g/10 min, continuously withdrawn from the reactor with a speed of 32 kg/h Samples of polymer powder are practically free from static electricity.

Then are irregularities in the operation of the pump, the feed TOLD, leading to power loss. The polymer samples taken within 2 h of the reactor, there is a significant static electricity. The polymerization rate does not increase, but remains at a value of 32 kg/hour, a Breach in the feed pump is corrected, and within 2 h of static electricity in polymer samples is reduced to extinction.

1. A method of preventing fouling in the reactor circulation in the polymerization of alpha-olefins in the presence of a catalyst to obtain a product in the form of particles by introducing into the reactor agent that prevents fouling of the emer alpha-olefin to Acrylonitrile and polyamine, representing the product of the polymerization of aliphatic primary mono - or diamine with epichlorohydrin or a copolymer of alpha-olefin with maleic anhydride.

2. The method according to p. 1, characterized in that as an agent for preventing fouling, use a composition including a copolymer of alpha-olefin to Acrylonitrile and polyamine in a mass ratio of 1 : 99 to 99 : 1, preferably 25 : 75 to 75 : 25.

3. The method according to p. 1 or 2, characterized in that the composition is administered in an amount of 0.001 to 3 g/g of catalyst, preferably from 0.01 to 0.7 g/g of catalyst.

4. The method according to PP.1 to 3, characterized in that as a polymerizable in the specified reactor alpha-olefin using ethylene, propylene, 1-butene, 1-hexene or mixtures thereof.

5. The use of a composition comprising a copolymer of alpha-olefin to Acrylonitrile and polyamine, which is a product of polymerization of aliphatic primary mono - or diamine with epichlorohydrin or a copolymer of alpha-olefin with maleic anhydride as an agent that prevents the formation in the reactor circulation in the polymerization of alpha-olefins.

 

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