Untitled record

15

Process for producing polyisobutylene using a diluent of 1-alkene

Polyisobutylene Production Process with 1-Alkene Diluent

Full description

Background of the invention

The invention described herein relates to improvements in the isobutylene polymerization process. In particular, the invention relates to processes for preparing polyisobutylene (PIB) products having improved properties. More specifically, the invention relates to techniques used to manipulate and control liquid-phase processes for the production of polyisobutylene, with polyisobutylene products having preselected properties, in a manner that improves the operation and control of polyisobutylene reactors.

U.S. Patent No. 6,562,913 issued on May 13, 2003, entitled “Process For Producing High Vinylidene Polyisobutylene” (referred to here as Patent 931), relates, among other things, to liquid-phase polymerization processes used to prepare low-molecular-weight polyisobutylene products. (have a numerical average molecular weight (MN) of less than 10,000), and are highly reactive (have a content of terminal double bonds of at least about 70%). As disclosed in Patent 931, both a catalytic composition, which may desirablely comprise a complexing agent of BF3, a complexing agent such as methanol, and a feedstock containing isobutylene, are introduced into a reaction zone where they are intimately mixed with Residual reaction mixture To obtain a reaction mixture in a state in which it is closely intermixed in the reaction zone. The closely mixed reaction mixture is maintained in the state it is in and at a relatively constant temperature, not less than approximately 0 degrees Celsius. While in the reaction zone, isobutylene is polymerized to form a polyisobutylene product with a high degree of non-toxicity.

Terminal saturation (vinylidene). A crude product stream containing the remaining catalytic composition, unreacted isobutylene and polyisobutylene is then withdrawn from the reaction zone. Both the introduction of the feedstock into the reaction zone and the withdrawal of the product stream from it are controlled so that the residence time of the isobutylene undergoing the polymerization process in the reaction zone does not exceed about 4 minutes, and thus the product stream contains a highly reactive polyisobutylene product. It is preferable that the reaction area represents the tubular side of the heat exchanger consisting of a shell-and-tube exchanger, where refrigerant is circulated on the side of the shell. A recirculation loop may preferably be used to circulate the reaction mixture through the reaction zone on the tube side at a linear speed sufficient to stabilize and maintain a closely coupled intermixed state in the mixture and to remove the heat generated by the exothermic polymerization reaction.

US Patent No. 7,037,999 issued on May 2, 2006 (US Patent Publication No. 040587/2003), entitled “Mid-Range Vinylidene Content Polyisobutylene Polymer Product And Process For Producing The Same” (referred to here as Patent No. 999), describes Among other things, a PIB polymeric product with medium-range vinylidene content and a process for its manufacture. As disclosed in Patent No. 999, at least about 90% of the PIB molecules in the product are polyisobutylene with double bonds in the alpha or beta position. The content of the vinylidene double bond in the alpha (or terminal) site in the product may range from 20% to 70%, and the content of the internal double bonds bearing four substituents is very low, preferably less than about 5% and typically less than About 1-2%. Polymeric products of PIB with intermediate-range vinylidene content are preferably prepared by a liquid-phase polymerization process in a cyclic reactor similar to the reactors described in Patent No. 913 at a temperature that may preferably be about 16°C (60°F) or Top using a catalytic compound consisting of BF3/methanol and a contact time of no more than about 4 minutes.

U.S. Patent No. 6,992,152 issued on January 31, 2006, entitled “Apparatus and Method for Controlling Olefin Polymerization process” (referred to here as Patent No. 152), relates, among other things, to a method for controlling the operation of reactors such as that described in Patent No. 999. And 913 in order to achieve effectiveness values when running the process and better homogeneity of the process product. In particular, Patent 152 describes a method for controlling the ratio of BF3 to catalyst composition and thus controlling the reactivity (terminal double bond content) of the product. In particular, this control is achieved by allowing the introduction of the catalyst modifying agent separately from the input to the catalyst composition itself.

US Patent No. 6,844,401 issued on January 18, 2005, entitled “Apparatus for Preparing Polyolefin Products and Methodology for Using the Same” (referred to here as Patent No. 401), relates, among other things, to procedures, etc. Used to optimize the processes described above. In particular, Patent No. 401 describes an olefin reactor system that includes at least two separate regions in the reactor that operate together. This multi-reactor system provides process efficiency values and advantages in particular regarding conversion rates and polymer polydispersity. In addition, Patent No. 401 describes downstream systems used to quench the remaining escaping catalyst with the crude product to prevent further reaction from occurring rapidly, to remove residual material from the catalyst by washing, and to separate the product from unreacted monomer, dimers, oligomers and other undesirable contaminants. Such as diluents and the like.

According to certain preferred embodiments of Patent Nos. 913, 999, 152 and 401, polyisobutylene products may be manufactured by processes involving liquid-phase polymerization carried out using a cycloreactor at a temperature of -1 to 32°C (30 to 90°F). The preferred catalyst may be a BF3/methanol catalyst complex and the reactor residence time may typically be no more than about 4 minutes. A preferred product may have a relatively low molecular weight, and a PIB polymer with a double bond content in the alpha (vinylidene) site in the middle range (50-60%) has a relatively low molecular weight. At least about 90% of the PIB molecules in the product are in the form of double bonds in the alpha site (vinylidene) or double bonds in the beta site. Other polyisobutylene groups generally constitute less than 10% and typically less than 5% of the molecules.

International Patent Application No. 77056/00 discloses a gas phase process for preparing polyisobutylene, whereby the average molecular mass viscosity of the resulting polyisobutylene is maintained at a desired value by measuring the partial pressure of isobutylene in the gas phase in the reactor and correcting the partial pressure value. Using media selected from the polymerization temperature and concentration of at least one of the components of the hydrocarbon feed mixture. The corrected partial pressure of isobutylene is maintained constant at around a target value by regulating the flow rate of the catalyst introduced into the reactor and/or the flow rate of the hydrocarbon feed mixture introduced into the reactor. International Patent Application No. 96426/01 also describes adjusting the flow rate of the catalyst or feedstock as a function of measurements of the partial pressure of isobutene in the gas phase of a multiphase reactor to control the viscosity or average molecular mass of the desired product.

US Patent No. 2,815,335 discloses low-reactivity polyisobutylene structures at low polymerisatrion temperatures. US Patent No. 2,852,500 describes molecular weight processing for the preparation of high molecular weight copolymers of styrene and isobutylene using methyl chloride as a diluent.

Table 1 below shows structures of possible isomers that may be found in low molecular weight polyisobutylene products. Other groups are likely to be present in trace amounts and should not affect the overall reactivity of the PIB molecule.

In general, the reactivity of the olefinic double bond is directly related to the degree of its substitution. This means, the greater the degree of substitution of the olefinic double bond, the lower its reactivity. Therefore, because structure I (the phenylidene double bond or alpha site) of Table 1 is only bisubstituted, it is more reactive than structures II, III or IV where the double bond is in the beta site. Structures II and III each have three substitutions at positions 1, 2, 2 and are less reactive than structure I, but due to the availability of a hydrogen atom on the terminal carbon, they are more reactive than structure IV, which has three substitutions at positions 1, 1. , 2 1,1,2-trisubstituted devoid of a terminal hydrogen. Structure V has four substituents and is the least reactive of all the groups shown.

In general, PIB products produced according to the processes described in Patent Nos. 913, 999, 152 and 401 described above contain mainly structures I and IV, with the other two being present in only trace concentrations. Highly reactive (HR) polyisobutylene products (see Patent No. 913) may generally contain about 80-85 mol% of structure I (where the double bond is in the alpha position) and about 15-20 mol% of structure IV ( Where the double bond is in the beta position. PIB polymeric products with an intermediate vinylidene content (see Patent No. 999), which may sometimes be referred to as “improved” products, typically consist mostly of structures I and IV only, but typically about 55-60 mol% of Structure I and about 35-40 mol% of structure IV, respectively, in the presence of trace concentrations of other oligomers.

Table 1: Structures of PIB leaders

<img file="SA3692B1_D0001.tif" />

I. Bi-substitutions at positions 2-2

<img file="SA3692B1_D0002.tif" />

II. Three-substituted adjacency at positions 1, 2, 2

<img file="SA3692B1_D0003.tif" />

III. Opposite of the three substitutions at positions 1, 2, and 2

<img file="SA3692B1_D0004.tif" />

IV. Three substitutions at positions 1, 1, and 2

<img file="SA3692B1_D0005.tif" />

V. Quadruple substituents at positions 1, 1, 2, 2

When performing the processes described above, highly specialized procedures and equipment may often be used to optimize the operation or control of the polymerization reactions within which they are carried out. Furthermore, as in any industrial procedure, a method and/or equipment used to improve efficiency and productivity is constantly being sought. In particular, when producing polyisobutylene, the ability to control (optimize) the conversion rate of isobutylene to polyisobutylene (conversion rate) is often considered. In many cases, the ability to carefully control (optimize) the polydispersity index (PDI) and/or the numerical average molecular weight (MN) of the polyisobutylene product is also of great importance. More particularly, it is highly useful in many commercial applications to be able to carefully control the concentration of active double bonds in a polyisobutylene product.

General description of the invention

In accordance with the concepts and principles of the invention described herein, a method for producing polyisobutylene is provided which is directed toward topics raised in connection with processes according to the prior art such as those described above. In particular, in one of several important aspects, the invention described herein provides a process for the production of polyisobutylene comprising exposing a reaction mixture containing isobutylene, An isobutylene diluent comprising a C1-C16 alkene and a catalytic composition of reaction conditions suitable for subjecting at least a portion of the isobutylene to a polymerization process to form a polyisobutylene product comprising polyisobutylene molecules, wherein at least a portion includes polyisobutylene molecules The polyisobutylene produced in this way contains double bonds in the alpha position (vinylidene). The polyisobutylene product has a numerical average molecular weight and an index Dispersion polymerization. The process of the invention also includes manipulating the concentration of the diluent in the mixture so as to control any one or more properties of (a) the relative size of a portion of the polyisobutylene thus produced which includes double bonds in the alpha position, (b) the numerical average molecular weight of the product, (c) ) Evidence of dispersive polymerization of the product and (d) relative size of the fraction of isobutylene that is converted to polyisobutylene.

Also in accordance with the concepts and principles of the invention, the diluent may preferably comprise isobutylene and the catalyst composition may comprise a compound of BF3 and a compounding agent of a primary alcohol. Typically, the compound-forming agent may be methanol.

Also according to the invention, the reaction mixture may preferably be exposed to suitable reaction conditions in a reaction zone where the reaction mixture is maintained in a closely mixed state. Typically, the area may include a reaction zone in a loop reactor.

Also in accordance with the concepts and principles of the invention, it is found that the relative size of the fraction of isobutylene that is converted to polyisobutylene is considered a direct function of the concentration of the diluent, and that the index of dispersive polymerization of the product is considered an indirect function of the concentration of the diluent, and the numerical average of the molecular weight of the product is considered an indirect function of the concentration. diluent, The relative size of the fraction of polyisobutylene molecules produced that contain double bonds in the alpha site is a direct function of the concentration of the diluent. Accordingly, in accordance with the concepts and principles of the invention, the concentration of the diluent in the mixture may increase such that the relative size of the portion and/or the aforementioned portion increases, the concentration of the diluent in the mixture may increase and thus the evidence of dispersion polymerization of the product is reduced, and the concentration of the diluent in the mixture may decrease, which increases the average Numerical molecular weight of the product.

Desirably, the concentration of diluent in the mixture should not exceed about 50% by weight, and preferably the concentration of diluent in the mixture should not exceed 30% by weight, and typically, the concentration of diluent in the mixture should range from about 8 to about 15% by weight.

Also in accordance with the concepts and principles of the invention, a process is provided which may include a step consisting of selecting a diluent concentration of the mixture corresponding to a specified relative volume of said portion, and a processing step may include maintaining the diluent content of the mixture at the chosen concentration and thus keeping the relative volume of said portion substantially constant . In addition, the process may include a step consisting of selecting a diluent concentration of the mixture corresponding to the amount of the specified dispersion polymerization index, and the processing step may include maintaining the diluent content of the mixture at the chosen concentration such that the dispersion polymerization index is maintained substantially constant. Also, the process may include a step consisting of selecting a diluent concentration for the mixture corresponding to the specified relative volume of said fraction, and the processing step may include maintaining the diluent content in the mixture at the chosen concentration and thus keeping the relative volume of the fraction essentially constant. Of course, as is readily understood by those skilled in olefin polymerization technology, it is often necessary to determine the specific numerical correspondence between the diluent concentration and one or more properties of the dispersive polymerization index, molecular weight, section size and/or fragment volume in advance to obtain On a set of set values from which a pre-determined concentration of the diluent is chosen. Conversely, the content and/or properties of the product can be simply controlled and the concentration of the diluent changed as needed in response.

Also according to the invention, the process may include steps consisting of treating the product to remove the diluent and unreacted isobutylene therefrom and recycling at least one diluent and unreacted isobutylene back to the reaction zone.

Furthermore, the invention provides a process for producing polyisobutylene comprising exposing a reaction mixture comprising isobutylene, An isobutylene diluent comprising a C1-C16 alkene and a catalytic composition of reaction conditions suitable for subjecting at least a portion of the isobutylene to a polymerization process to form a polyisobutylene product, wherein at least a portion of the polyisobutylene molecules comprise double bonds. On site alpha, Said polyisobutylene product has a numerical average molecular weight and an index of dispersion polymerization, wherein said polyisobutylene product has at least one variable, which is considered to vary as a function of the concentration of the diluent in the mixture, wherein the at least one variable includes (a) the relative volume of said portion; (b) number average molecular weight of the product, (c) evidence of dispersion polymerization of the product, or (d) relative size of the fragment. According to this aspect of the invention, the process may include steps consisting of selecting a diluent concentration corresponding to a preselected value of at least one of said variables and then maintaining the mixture at said selected diluent concentration such that said variable remains at the preselected value. Also according to this aspect of the invention, the variable may include the relative size of said fraction, the numerical average molecular weight of the product, the index of dispersive polymerization of the product and/or the relative size of said fraction.

The invention also provides an improved process for the production of polyisobutylene wherein a reaction mixture containing isobutylene, an isobutylene diluent comprising a C1-C16 alkene and a catalytic composition is subjected to reaction conditions suitable for subjecting at least a portion of the isobutylene to a polymerization process to form a polyisobutylene product which includes molecules of polyisobutylene, Where at least a portion of the polyisobutylene molecules comprise double bonds in the alpha position and the polyisobutylene product has a numerical average molecular weight and evidence of dispersion polymerization, the improvements include increasing the concentration of the diluent in the mixture and thus increasing the relative volume of said portion. , reducing the numerical average molecular weight of the product, and/or reducing the evidence of dispersion polymerization of the product.

Conversely, the invention provides an improved process for the production of polyisobutylene wherein a reaction mixture comprising isobutylene, an isobutylene diluent comprising a C1-C16 alkene and a catalytic composition is subjected to reaction conditions suitable for subjecting at least a portion of the isobutylene to a polymerization process to form a polyisobutylene product. polyisobutylene, which includes molecules of polyisobutylene, Where at least a portion of the polyisobutylene molecules comprise double bonds in the alpha position and the polyisobutylene product has a numerical average molecular weight and evidence of dispersion polymerization, the improvements include reducing the concentration of the diluent in the mixture and thereby reducing the relative size of said portion. , increasing the numerical average molecular weight of the product, and/or increasing the index of dispersive polymerization of the product.

The invention also provides new polyisobutylene products which are produced by the processes described above.

Brief explanation of the drawings

Figure 1: represents a schematic drawing showing the preparation of a laboratory reactor arrangement for performing isobutylene polymerization processes in accordance with the invention;

Figure 2: A graph showing the variation in the content of double bonds (vinylidene) in the alpha site of the polymer with changing diluent concentration (data collected at 4°C (40°F));

Figure 3: represents a graph showing the slope of the molecular weight (MN) and the slope of the dispersion polymerization index (PDI) with changing diluent concentration (data were collected at 4°C (40°F). (Filled symbols show MN values - axis left; unfilled symbols show the PDI–right axis);

Figure 4: represents a graph showing the conversion tendencies with changing diluent content;

Figure 5: A schematic diagram showing the PIB production process with continuous recycling of isobutylene and/or diluent;

Figure 6: represents a graph that shows the differences in MN with changing the concentration of the diluent (isobutane);

Figure 7: represents a graph that shows the differences in viscosity (v) with changing the concentration of the diluent (isobutane);

Figure 8: represents a graph that shows the differences in the PDI with changing the concentration of the diluent (isobutane); And

Figure 9: represents a graph that shows the differences in the content of the double bond (vinylidene) in the alpha position with changing the concentration of the diluent (isobutane).

Detailed description

The concepts and principles of the invention can generally be applied in accordance with both the various PIB reactors and PIB production processes described in Patents Nos. 913, 999, 152 and 401 described above, and should be applied in accordance with all reactors and reactor systems used to produce highly reactive and/or PIB polymeric products. Or with medium-range vinylidene content using liquid-phase polymerization procedures. In this regard, it should be noted that the feedstock for these reactors may include isobutylene or a mixture of isobutylene and an appropriate non-reactive diluent (solvent). Suitable feedstocks are generally described in Patent Nos. 999, 152 and 401 described above. The particularly preferred feedstock includes a high-purity isobutylene monomer having a composition as shown below in Table 2.

Table 2: Concentrations of independent components in the isobutylene stream

the components

% by weight

Methane

0.026

Ethan

0.0006

Propane

0.0024

Propylene

0.027

Isobutane

0.064

p-butane

0.010

Biotin-1

0.016

Isobutylene

99.84

th-butin-2t

0.010

ThN-Biotin-2

0.063

1, 3 butadiene

0.007

C5+

0.007

According to the concepts and principles of the invention, in the liquid-phase production process of polyisobutylene, an important and previously unknown relationship was discovered between the concentration of the diluent and the vinylidene content in the alpha position of the product. That is, according to the concepts and principles of the invention, it was discovered that an increase in the concentration of the diluent in the reaction mixture generally causes an increase in the concentration of the double bonds (vinylidene) in the alpha position in the product. Moreover, by the same token, increasing the diluent concentration generally results in significantly improved (narrower) dispersion polymerization guides. In connection therewith, further according to the invention, the diluent content in the reaction mixture may not exceed 50% by weight, it may be desirable not to exceed 30% by weight, and typically not more than 10% by weight. However, more generally, the desired diluent should be able to simply dissolve both isobutylene and polyisobutylene and should be inert to the polymer formation reactions occurring in the reactor. In this latter regard, a C3-C16 alkene, or a mixture of a C3-C16 alkane and a C3-C16 alkene, may be used as a diluent. Desirably, the diluent may be a C3-C16 1-alkene such as, for example, butene-1. In other words, the diluent may usefully comprise a mixture of hydrocarbons such as, for example, C4 hydrocarbons and other lightweight hydrocarbons.

As noted above, the processes according to the present invention can generally and conveniently be used in conjunction with the equipment and processes described in Patent Nos. 913, 999, 152 and 401. However, for further clarification, the invention will be described in conjunction with a simplified experimental reaction system 10 shown as Schematic in Figure 1.

Referring to Figure 1, the experimental reaction system 10 may preferably include a loop reactor 10, a recirculation pump 12, an isobutylene monomer inlet 14, which may include a pump 16, a diluent inlet 18, and may also include a pump. 20 diluent pump, an inlet 22 for the catalytic compound (initiator), and a cooling system 24 to remove the heat of the exothermic polymerization reaction. As shown, the annular reactor 10 may include parts 10a, 10b and 10c and also a pipe 26 which serves to interconnect parts 10a and 10c as shown and provides a place for connecting the pump 12. As can be seen in Fig. 1, the cooling system 24 for the system may include a Cooling jackets 24A, 24B and 24C are desired, respectively, for reactor parts 10A, 10B and 10C, 28 chilling fluid inlet and 30 chilling fluid outlet. In addition, the system may also include a feedstock inlet 32, where the isobutylene monomer and diluent are received and mixed for introduction into the reactor, and a product outlet 34, where the resulting polymeric product 42 is withdrawn from the system via a pressure gauge 40 .

In the process of operation, the reaction mixture comprising isobutylene, isobutylene diluent and catalyst composition is recirculated by pump 12 through reactor parts 10a, 10b and 10c and pipe 26 when the reaction conditions are suitable for at least a portion of the isobutylene to be subjected to a polymerization process to form a polyproduct. Polyisobutylene including polyisobutylene molecules maintained in Reactor 10. Meanwhile, isobutylene and the diluent are introduced into reactor 10 through inlet 32, the catalyst composition (starting material) is introduced into the reactor through inlet 22, and the remaining product is withdrawn from the system through outlet 34.

Using system 10, experiments were conducted while maintaining a total flow rate of monomer into the cyclic reactor at 100 ml/min. The reactions were carried out at temperatures between 4°C and 16°C (40°F and 60°F). The pressure in the annular reactor is maintained at 14 bar (200 psi). The inner diameter of the reactor tubes is 0.775 cm (0.305 in) and the total reactor volume is 228 cm3. The flow of catalyst (starting material) is set at 0.02 ml/min so that the reaction set position is maintained. The recycling rate in the annular reactor is 2 gallons/minute. The catalyst composition includes a composite of BF3 and methanol such that the molar ratio of BF3 to methanol is 1:1. No modifying agent (methanol) is added to the reactor separately from the catalyst composite, although this step may be desirable under conditions Certain. In this latter regard, the process of adding the modifier is described separately in detail in Patent No. 152 described above. High-purity isobutylene (purity &gt; 99.5% by weight) was used as the feedstock and relatively high-purity isobutane (purity ranging from 95 to 98% by weight) was used as the diluent.

Experiments were conducted at different concentration levels of the diluent to study the effect of the concentration of the diluent on the content of the double bond in the alpha site, the molecular weight (MN) and the dispersion polymerization index (PDI) of the product. In these experiments, the level of the diluent varies between 0 and 27% by weight.

Concentrations at the ends of the chains were measured using 13C NMR spectroscopy. Molecular weight measurements were carried out using size exclusion chromatography (SEC).

The experimental results are shown in Figures 2, 3 and 4. Figure 2 shows the variations in the content of the isobutylene isomer with double bonds in the alpha position with changes in the concentration of the isobutane diluent at 4°C (40°F). As can be seen in Figure 2, the alpha isomer content increases with increasing concentration of the diluent. Therefore, it is clear that the alpha isomer content in the product can be increased simply by increasing the concentration of the diluent in the reaction mixture. It is also clear that if other conditions are imposed, the alpha isomer content in the product can simply be reduced by lowering the concentration of the diluent in the reaction mixture.

Referring to Figure 3, the effect of diluent concentration on the numerical average molecular weight (MN) and the dispersion polymerization index (PDI) can be seen. In Figure 3, the MN values appear on the left axis and are represented by filled symbols, while the PDI values appear on the right axis and are represented by unfilled symbols. The significant decrease in PDI values at an almost constant molecular weight between 0 and 10% by weight of the diluent concentration (isobutane) is of particular importance. This may be of particular benefit in meeting commercially valuable scattering polymerization specifications for PIB polymers. Therefore, it is clear that the PDI values of the product may decrease simply by increasing the concentration of the diluent in the reaction mixture. It is also clear that, if other conditions are unavoidable, the PDI values of the product can simply be reduced by lowering the concentration of the diluent in the reaction mixture. On the other hand, it is clear that the molecular weight of the product can be reduced simply by increasing the concentration of the diluent in the reaction mixture. It is also clear that, if other conditions are necessary, the molecular weight of the product can simply be increased by reducing the concentration of the diluent in the reaction mixture.

Referring to Figure 4, it can also be noted that the rate of conversion of isobutylene to polyisobutylene can be increased by increasing the diluent content. This can likely be attributed to the fact that higher concentrations of diluent in the reactor can provide improved heat transfer properties.

As noted from the above, the alpha isomer content increases, scattering polymerization decreases, the conversion rate increases and the molecular weight decreases with the increase in the concentration of the isobutane diluent. Tendencies similar to those observed at 4°C (40°F) were also observed when polymerization reactions were performed at 16°C (60°F). The tabulated experimental data are recorded in Tables 3 and 4 below. As can be seen, these tables also show the concentration of alpha and beta in the polyisobutylene product obtained.

Table 3: Data showing the effect of diluent concentration on the properties of PIB at 4°C (40°F)

Concentration of the diluent of isobutane

(% by weight)

Numerical average molecular weight (MN)

Dispersion polymerization index (PDI)

Alpha isomer concentration (structure I)

Beta isomer concentration (structure IV)

The other Zamara

Conversion rate

zero

3318

3.81

54.2

NA

NA

17.9

3288

3.31

56.5

33.6

9.9

22.1

3155

2.47

59.9

32.3

7.8

24.6

2909

2.25

65.4

32.5

2.1

27.2

2724

2.22

73.41

18.1

8.4

29.1

1785

2.19

75.3

20.3

4.4

33.4

Table 4: Data showing the effect of diluent concentration on PIB properties at 16°C (60°F)

Concentration of the diluent of isobutane

(% by weight)

Numerical average molecular weight (MN)

Dispersion polymerization index (PDI)

Alpha isomer concentration (structure I)

Beta isomer concentration (structure IV)

The other Zamara

Conversion rate

zero

2249

2.71

53.0

NA

NA

48.3

2373

2.23

54.4

34.8

10.8

52.3

2217

2.17

63.1

30.7

6.2

51.5

1637

1.91

69.5

25.3

5.2

57.5

1389

1.89

70.0

22.9

7.1

57.7

1109

1.85

73.3

17.6

9.1

62.3

According to the concepts and principles of the invention, the process may also ensure continuous recycling of the diluent and/or unreacted isobutylene. This process is shown schematically in Figure 5. Referring to Figure 5, the reaction mixture comprising isobutylene, the isobutylene diluent (usefully isobutane) and a catalyst composition (preferably a complex of BF3 and a complex forming agent such as methanol) in reactor 200 is subjected to appropriate reaction conditions to subject a portion of the isobutylene to The least polymerization process to form a polyisobutylene product including isobutylene molecules. Conditions in Reactor 200 are such that at least a portion of the polyisobutylene molecules thus produced in the product contain double bonds in the alpha site and the polyisobutylene product has a numerical average molecular weight and evidence of dispersion polymerization. Upon exiting reactor 200, the crude polyisobutylene product is washed in the scrubber 202 to remove any remaining catalyst and is flashed in the crude flash zone 204 to remove the diluent and unreacted isobutylene. The product is then conveniently captured in flash unit 212 and subsequently transported by outlet 24. Any oligomer may be removed by 222. At least a portion of the diluent and unreacted isobutylene flashed in region 204 can then be continuously recycled to the upper portion back to the reactor 200 by lines 206 and 208 while being passed through the impurity removal device 220. The 224 indicates perfusion stream. The concentration of the diluent in the reaction mixture in reactor 200 can be manipulated as desired and/or maintained constant at any given time at a level that ensures maximum benefit to the process in maintaining the desired alpha isomer content and also maintaining a low PDI value. This can of course be done by adding a diluent via line 216. The feed rate of the new isobutylene transported by line 210 can then be determined using the isobutylene conversion rate in the reactor, i.e., the higher the conversion rate, the greater the isobutylene feed rate. In addition, when desired, the concentration of the diluent can be varied to change the alpha isomer content in the product, the PDI value of the product, the molecular weight of the product and/or the conversion rate. Regarding what was mentioned last, it is worth noting that the alpha isomer content in the product and the conversion rate change directly with the concentration of the diluent, while the molecular weight of the product and the PDI value change directly with the concentration of the diluent.

Additional experimental data have been collected for studies involving the fabrication of PIB of the highly active variety (alpha-site double bond content greater than 80%) using a scale-up form of the reactor that is constructed essentially identical to that of reactor10. For these studies, an additional modifying agent is introduced essentially as described in Patent No. 152. These studies reveal that it is highly beneficial to operate the reactor using an isobutane diluent concentration of about 8-15% by weight. The following description is based on the data obtained from it.

In these studies, the temperature was maintained at about -3°C (27°F) using a cooler at about -15°C (5°F). The inlet flow rate (isobutylene + diluent) was approximately 26 gallons/minute and the volumetric flow rate of the recirculation pump was approximately 1260 gallons/minute.

The catalyst flow rate is adjusted (typically 0.03 to 0.05% by weight of the feed rate) so that the operating temperature is maintained constant. According to Patent No. 152, the modifying agent is introduced separately into the reactor to maintain the methanol to catalyst ratio at 0.63:1 to manufacture a highly effective PIB product (with a high vinylidene content). In a highly effective product, it is desirable for the molecular weight (MN), the PDI value and the viscosity to be within specific ranges, usually imposed by the product specifications. One such product can have the following specifications: MN-2100 to 2500, PDI-1.6 to 2.2; Kinematic Viscosity (v) - from 1500 to 1750, and the content of double bonds in the alpha site - exceeds 80 mol%. The usual goal of the manufacturing process is for all of these specifications to be met together.

In connection with the above, kinematic viscosity (v) was measured using Fensk tubes manufactured by Canon immersed in a viscosity bath (Kohler type KV3000). MN and PDI measurements were obtained using SEC measurements as previously described. The values obtained for the different variables are as shown in Figures 6 to 9. The thick, dark lines shown on the graphs indicate the desired specification variables.

An essentially pure isobutane stream with a composition as shown in Table 5 below was obtained from ISGAS for use in an attempt to isolate the effects on the P113 production process with trace impurities in the isobutane diluent, although in an actual practical sense It is generally not feasible to use this material in a commercial operation. The total content of oxygenates in the pure diluent stream is less than about 5 ppm (about 3.4 ppm for methanol, and about 1.4 ppm for MTBE).

Table 5: Purity of the separate components in the diluent of isobutane (which has a purity of 99.8%)

the components

% by weight

Propane

0.02

Isobutane

99.79

p-butane

0.18

The experimental setup and conditions in these attempts are essentially identical to those described above in conjunction with Reaction System 10. The experimental data obtained as a result of these attempts are recorded in Table 6 below.

Table 6: Properties of the product obtained using high purity isobutane

Diluent concentration of isobutane (% by weight)

MN

PDI

kinematic viscosity

Content of double bonds in alpha site (% mol)

zero

3292

3489

61.4

3197.7

2.55

2693

58.5

2946.9

2.48

2637

59.9

2883

2.43

2628

60.1

2751

2.29

2213

60.3

It can be seen from Table 6 that the main benefit of workability is achieved so that a PIB with a low dispersion polymerization index is produced. This means that a significant decrease in PDI and viscosity can be achieved simultaneously with increasing diluent concentration, while keeping the molecular weight approximately constant. This makes commercial sense to meet MN and PDI/viscosity specifications at the same time. However, there is often no change in the double bond content in the alpha site with increasing diluent concentration of isobutane as observed in the case of low-purity isobutane.

In light of the above, it is clear that the present invention provides a mechanism for significantly reducing both PDI and viscosity by increasing the concentration of the diluent without any significant corresponding reduction in molecular weight. In addition, both viscosity and PDI can be maintained within specifications while achieving the target molecular weight. This is particularly important in the production of HR grade PIB (high vinylidene content) where controlling dispersion polymerization and viscosity to keep within specifications is critical. Moreover, the use of a low-purity isobutane diluent results in a higher content of double bonds in the alpha site compared to that of a high-purity isobutane diluent. This can be caused by the presence of other hydrocarbon components in the feed stream or can be due to the presence of oxygenated compounds other than methanol. With regard to what was mentioned previously, it is more likely that other oxygenated compounds play a role in increasing the vinylidene content. According to studies conducted by the inventors, the main potential compound is dimethyl ether. These oxygenated compounds have a role similar to that of additional methanol, which is added as a modifying agent. As is known, methanol is also an oxygenated compound that can be added in a controlled manner to regulate the vinylidene content.

It appears that the invention provides the maximum benefit when operating the PIB production process using a diluent concentration that ranges from about 8 to about 15% by weight, since above this range the amount of products obtained decreases when the value of the MN begins to decrease, especially when Use a low-purity isobutane diluent (synthetic grade).

Although the content of double bonds in the alpha site increases with increasing dilution of isobutane (in the example of impure isobutane), controlling the content of double bonds in the alpha site by adjusting the appropriate methanol-to-catalyst ratio is considered more desirable. This results from the fact that there is usually minimal control over the industrial process compared to feedstock composition.