RU2144543C1 - Polyisobutylene production process - Google Patents

Abstract

FIELD: polymer production. SUBSTANCE: turbulent-type reactors are proposed to combine adiabatic and isothermal processes owing to in series connected reaction zones. Carrying out polymerization reaction in boiling reaction medium zone results in increased productivity of production of polyisobutylene with controlled molecular weight. EFFECT: reduced power and material consumption. 2 cl, 1 tbl

Description

 The invention relates to the field of technology of synthetic polymeric materials, in particular to a method for producing polyisobutylene, and may find application in the petrochemical industry.

 A well-known industrial method of producing polyisobutylene of the Wistanex type (Enjay company, USA) (in the book by V. S. Minsker, Yu. A. Sangalov "Isobutylene and its polymers". M: Chemistry, 1986, p. 151).

 The disadvantage of this process is that it is carried out in a perfect mixing reactor equipped with heat sink surfaces and a high-speed stirrer. The reactor is not optimal neither in design, nor in volume, nor in productivity. In addition, the process is characterized by high energy costs associated with the operation of the engine high-speed mixer. Attempts to increase the productivity of the reactor by increasing its volume complicate the thermostating of the polymerization process, which is accompanied by the appearance of temperature fields and a decrease in the molecular weight of the polymer.

Closest to the proposed (prototype) is a method for producing polyisobutylene by polymerization of isobutylene in the presence of a Friedel-Crafts catalyst in series-connected polymerization reactors, which are three vertical columns with a total volume of 5 m ³ • 3 and a liquid phase volume of 2.3 m ³ • 3 connected at the top of the condenser-refrigerator. Heat removal is carried out mainly due to the evaporation of the components of the reaction mixture. Mixing and removal of heat is carried out by an upward flow of boiling gases (isobutylene in a mixture with a low boiling fraction C ₃ - C ₄ ), which, condensing in the refrigerator, return to the reaction zone (in the book by V. S. Minsker, Yu. A. Sangalov "Isobutylene and its polymers ", M .: Chemistry, 1986, prototype).

 The disadvantage of the prototype method is its high material consumption and low productivity (per unit volume of the reactor), as well as the difficulty of regulating the molecular weight of the polymer.

 The objective of the invention is the creation of such a method of producing polyisobutylene, which can significantly reduce the consumption of materials and increase the productivity of the process, and also allows you to adjust the molecular weight of the polymer.

 The solution to this problem is achieved by the proposed method for the production of polyisobutylene by polymerization of isobutylene in the presence of a Friedel-Crafts catalyst in reactors connected in series, which provide the mixing of the reaction mixture and removal of the heat of reaction, followed by stopping the polymerization, desalting and isolating the polymer, in which the polymerization process is carried out first in a turbulent tubular reactor type in adiabatic mode, and then in the expander reactor in isothermal mode in bale boiling reaction medium.

 In the proposed method, boiling vapors of the reaction mixture are condensed and returned to the isothermal expander reactor.

 The combination in the proposed method of adiabatic and isothermal processes can significantly increase the flow rate of the monomer and, accordingly, increase the productivity of the polymerization process.

 At the initial stage of polymerization, when the conversion of isobutylene is small, the process is carried out in a tubular reactor of a turbulent type in adiabatic mode. Mixing in the reactor is due to the turbulence of the stream. The turbulence of the flows ensures, in turn, a gradientless distribution of the catalyst in the monomer volume and guaranteed stabilization of the thermal field of the reactor. The heat of reaction is removed by heating the reaction mass (which can be pre-cooled).

 Further, the polymerization process is continued in the expander reactor, which is a container of any shape, for example, cylindrical. When the reaction mixture enters the expander, a pressure drop occurs and the reaction mixture boils. The boiling of the reaction mixture provides heat removal of the polymerization reaction in the expander reactor. Vapors of unreacted monomer and solvent, condensing in the refrigerator, return to the reaction zone in the expander reactor and repeatedly participate in the heat scheme. Boiling the reaction medium ensures the isothermal process.

 The reaction mass, moving up the expander reactor, reaches the overflow pipe and flows through it to the stoppering unit for polymerization, desalination and polymer recovery.

It is proposed to use C ₃ -C ₄ fractions with isobutylene content from 5 to 60 wt.%, Or (iso) butane-butylene fractions saturated with isobutylene up to 50-80 wt.% At the stage of preparation of the charge, or isobutylene-butylene, as low-boiling solvents. a fraction containing from 5 to 50-80 wt. % isobutylene or any other isobutylene-containing products.

 The choice of a catalytic system is not critical and is associated with the need to maintain a certain temperature polymerization rate to obtain polyisobutylene with a given molecular weight. The examples used cationic catalytic systems based on compounds of aluminum, titanium and boron.

 A detailed description of the proposed method for producing polyisobutylene is given in the examples and in the table. Example 1 - comparative, polymerization is carried out in one reactor - in tubular adiabatic.

 Example 1

The polymerization of isobutylene is carried out in adiabatic and isothermal reactors connected in series. In a tubular reactor (adiabatic) through a special fitting located at the beginning of the reactor vessel, 5000 l / h of a 15% solution of isobutylene in propane-propylene fraction, pre-cooled to minus 60 ^o C. is fed. The solution contains 600 kg / h of isobutylene. Volume 20 L

40 l / hr of a toluene solution of the catalytic complex BF ₃ + polyaluminoxane + n. Butanol (molar ratio 2: 0) is fed into the same tubular (adiabatic) reactor through an internal pipe with numerous openings (which ensures crushing of the catalyst and contributes to its effective mixing with the charge) , 1: 1), which corresponds to a dosage of BF ₃ = 0.03 wt.% To isobutylene.

The polymerization in a tubular reactor takes 14 seconds, the conversion of isobutylene 15 wt.%. At the outlet of the reactor, the temperature of the reaction mixture is minus 45 ^o C.

Then the reaction mass enters the reactor expander with a volume of 1000 l in the liquid phase, where its boiling begins. The vapors of the low boiling hydrocarbon fraction and isobutylene condense in the refrigerator and flow into the reaction zone. In this case, the polymerization temperature is maintained by boiling the reaction mass minus 45 ^o C (isothermal process).

 After 720 seconds, the polymerizate reaches the overflow pipe and enters the tank, where the reaction is terminated (stoppering) with isobutyl alcohol in an amount of 0.1 wt. % to the catalyst. Then the polymerizate enters the site of desolation and degassing from residues of isobutylene and solvent.

 The conversion of isobutylene is 90 wt.%, The molecular weight of isobutylene is 50,000. The plant capacity is 540 kg / h.

 Example 2

The polymerization of isobutylene is carried out according to example 1. The difference is that in a tubular reactor with a volume of 20 l is fed 5000 l / h of a 15% solution of isobutylene in the propane-propylene fraction, previously refrigerated to minus 60 ^o C. The solution contains 60 kg / h of isobutylene. The volume of the reactor is 20 l.

40 l / h of a toluene solution of the catalytic complex BF ₃ + polyaluminoxane + n.butanol (molar ratio 2: 0, 1: 1), which corresponds to a dosage of BF ₃ = 0.03 wt.% To isobutylene, is fed into the tubular reactor through the inner pipe.

The polymerization in a tubular reactor takes 14 seconds, the conversion of isobutylene 15 wt.%. At the outlet of the reactor, the temperature of the reaction mixture is minus 45 ^o C.

Further, the reaction mass enters the reactor-splitter with a volume of 1000 l in the liquid phase, where its boiling begins. Vapors of the fraction and isobutylene condense in the refrigerator and flow into the reaction zone. In this case, the polymerization temperature is maintained by boiling the mass minus 45 ^o C (isothermal process).

 After 720 seconds, the polymerizate reaches the overflow pipe and enters the tank, where the reaction is terminated with isobutyl alcohol in an amount of 0.1 wt. % to the catalyst. The conversion of isobutylene is 90 wt.%, The molecular weight of polyisobutylene is 50,000. The polymerizate is fed to the anesthesia and degassing unit from isobutylene residues and fractions.

 Productivity of the installation is 540 kg / h.

 Example 3

The polymerization of isobutylene is carried out according to example 2. The difference is that a 50% solution of isobutylene in isobutylene-butylene fraction in the amount of 5000 l / h is fed into a 20 l tube reactor. The content of isobutylene in the solution is 1560 kg / h, the temperature of the mixture is minus 50 ^o C. The difference also lies in the fact that 40 l / h of a hexane solution of the TiCl ₄ + polyaluminoxane catalyst complex (molar ratio 1: 1) is fed into the pipe of the tubular reactor. dosage of TiCl ₄ = 0.05 wt.% to isobutylene. The polymerization time in the tubular reactor is 14 seconds. The conversion of isobutylene 10%, the temperature of the reaction mass at the exit is minus 10 ^o C.

In the reactor expander, the volume of the liquid phase in which is 180 l, the polymerization temperature is maintained at minus 10 ^o C due to the boiling phase. The polymerization time of 130 seconds, the conversion of isobutylene 98%, the molecular weight of polyisobutylene 25000, the installation capacity of 1528 kg / h.

 Example 4

The polymerization is carried out as in example 2. The difference is that an 80% solution of isobutylene in a butane-butylene fraction cooled to minus 50 ^o C is fed into a 4-liter tube reactor. The amount of charge fed is 2500 l / h, the amount of isobutylene in it is 1300 kg /hour.

As the catalyst used hexane complex BF ₃ + polyaluminoxane (molar ratio 1: 1) in an amount of 20 l / h, which is 0.07 wt. % BF ₃ to isobutylene. The polymerization time in the tubular reactor is 6 seconds. The conversion of isobutylene in it is 15%, the outlet temperature is minus 10 ^o C.

The polymerization of isobutylene continues in the expander reactor, the volume of the liquid phase in which is 1000 l. The polymerization temperature is maintained at minus 10 ^o C due to the boiling fraction, the polymerization time of 1440 seconds. The conversion of isobutylene 99%, a molecular weight of 10,000, the installation capacity of 1287 kg / h.

 Example 5

The polymerization is carried out as in Example 2. The difference is that an 80% solution of isobutylene in hexane is fed into a 28 L tube reactor. The amount of charge is 1000 l / h, while the amount of isobutylene is 500 kg / h. The temperature of the charge at the inlet of the reactor is +25 ^o C, and a toluene solution of the TiCl ₄ + triisobutylaluminium complex (molar ratio 4: 1) in an amount of 20 l / h, which is 0.1% TiCl ₄ wt. to isobutylene. At the exit of the tubular reactor during the polymerization time of 100 seconds, the conversion of isobutylene 38%, and the temperature of the reaction mass +70 ^o C.

In a reactor expander with a volume of 972 l, the polymerization of isobutylene continues, the temperature of +790 ^o C is maintained by boiling hexane. Polymerization time 3500 seconds. The conversion of isobutylene 95 wt.%. The molecular weight of polyisobutylene is 1200. The plant capacity is 475 kg / h.

 Example 6

The polymerization is carried out as in example 2. The difference is that the process is conducted in a mass of isobutylene. Isobutylene, cooled to minus 30 ^o C, is fed into a 4-liter tube reactor in an amount of 2880 l / h or 1800 kg / h. And as a catalyst, a solution of AlCl ₃ in chloroethyl is used. The supply of a catalyst solution of 50 l / h, which is 0.05 wt.% To isobutylene. At the outlet of the tubular reactor, the temperature of the polymerizate is minus 7 ^o C, the conversion of isobutylene 5%, the polymerization time in the tubular reactor 5 seconds.

The polymerization continues in the expansion reactor with a liquid phase volume of 44 l. The polymerization temperature is maintained at minus 7 ^o C due to the boiling of isobutylene. During the polymerization time of 55 seconds, the conversion reaches 30 wt.%. The molecular weight of polyisobutylene is 20,000. Productivity - 540 kg / h.

 Thus, the proposed method for the production of polyisobutylene by polymerization of isobutylene in the presence of various Friedel-Crafts catalysts in successive reactors of adiabatic and isothermal types allows us to solve the energy-intensive problems of existing plants and to obtain a polymer with a controlled molecular weight.

Claims (2)

 1. The method of producing polyisobutylene by polymerization of isobutylene in the presence of a Friedel-Crafts catalyst in reactors connected in series, which provide the mixing of the reaction mixture and removal of the heat of reaction, followed by stopping the polymerization, desalting and isolating the polymer, characterized in that the polymerization is carried out in a tubular turbulent reactor in an adiabatic mode, and then in the expander reactor in isothermal mode in a boiling reaction medium for 60 - 3600 s.  2. The method according to claim 1, characterized in that the heat is removed in the second reactor by condensing the vapor of the solvent and unreacted monomer and returning them to the expander reactor.

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