JP4863186B2 - Process for producing olefin polymer - Google Patents

Description

  The present invention relates to a method for obtaining an olefin polymer from a liquid hydrocarbon raw material mainly containing a olefin having 4 carbon atoms, which is obtained from a raffinate when a diene hydrocarbon is produced by an extractive distillation method.

Separation of dienes such as butadiene from hydrocarbon mixtures containing dienes, olefins and saturated aliphatic hydrocarbons, such as petroleum cracking products, is due to the close boiling points of many compounds and azeotropes Is not possible with simple distillation. Therefore, diene is widely obtained by extractive distillation using a solvent. To obtain an olefin polymer in the presence of a solid acid catalyst, a liquid hydrocarbon mainly containing olefins having 4 carbon atoms contained in raffinate when producing dienes by extractive distillation using diene hydrocarbon as an extract. Has been done in the past. In general, the solid catalyst is suspended in an organic solvent and injected into the polymerization reaction tank. When the solid acid catalyst remains in the olefin polymer as it is, characteristics such as transparency of the product are changed in the long term. In addition, when a halogen-containing catalyst such as aluminum chloride (AlCl ₃ ) is used as the solid acid catalyst, the residual catalyst in the polymer decreases the commercial value as a halogen-based impurity. Therefore, the catalyst is usually deactivated and removed after the polymerization, but these treatment steps are complicated steps including extraction, separation, purification, filtration and the like with an alkaline aqueous solution.

  Increasing the efficiency of the solid acid catalyst and reducing the amount of use is not only a catalyst cost reduction, but also reduces the burden of the catalyst deactivation process and removal process, which is one of the fundamental solutions. . For this purpose, it is effective to use a solid acid catalyst having a small particle diameter in order to increase the surface area per unit volume of the catalyst. However, according to the study of the present inventor, when the particle size of the solid acid catalyst is decreased, the ability to adsorb impurities in the reaction system to the surface increases, and in order to adsorb impurities in the raw material, It turned out that effects, such as a surface area increase, are not fully acquired.

In order to solve this problem, it is conceivable to remove impurities (compounds) adsorbed on the solid acid catalyst contained in the raw material before the polymerization reaction. However, it is not clear what impurities should be removed, and the specific means of course is not clear. As a related technique, in a method for producing tertiary butanol from isobutylene in raffinate by using a raffinate of extractive distillation method using diene hydrocarbon as an extract, the residual dimethylformamide in the raw material is a strongly acidic ion exchange resin. There is a method of carrying out an adsorption treatment using a material (for example, see Patent Document 1). However, since the olefin according to the present invention undergoes a polymerization reaction in contact with a strongly acidic ion exchange resin, this proposed means cannot be diverted in order to solve the above-mentioned problems in olefin polymerization technology.
JP 2000-34242 A

  An object of the present invention is a raffinate of an extractive distillation method using a diene hydrocarbon as an extract, the raw material being a liquid hydrocarbon mainly containing an olefin having 4 carbon atoms as an olefin, and a solid acid having a small particle size. In a method for producing an olefin polymer using a catalyst, a compound that decreases the catalyst efficiency by adsorbing to a catalyst such as an extractive distillation solvent in raffinate is adsorbed and removed, and the solid acid catalyst is maintained by maintaining a high catalyst efficiency. It is to provide a method of reducing the amount of addition and reducing the extraction burden due to an alkaline aqueous solution or the like in the deactivation treatment and removal treatment of the catalyst.

The first of the present invention is a hydrocarbon containing 5 to 95 mass% of olefins containing 50 mass% or more of olefins having 4 carbon atoms, including hydrocarbons obtained from raffinate of extractive distillation method using diene hydrocarbon as an extract, and 4 carbon atoms. After contacting liquid hydrocarbons consisting of 95 to 5% by mass of saturated aliphatic hydrocarbons containing 50% by mass or more of saturated aliphatic hydrocarbons (100% by mass together) with activated alumina , The present invention relates to a method for producing an olefin polymer, wherein olefin is polymerized in the presence of aluminum chloride containing 60% by mass or more of particles having a diameter of less than 1400 μm.

The second of the present invention, Oite to a first aspect of the present invention, a process for producing an olefin polymer, wherein the aluminum chloride is intended to include particles of size less than 850 .mu.m 60% by mass or more.

A third aspect of the present invention relates to a method for producing an olefin polymer according to any one of the first or second aspects of the present invention, wherein the olefin having 4 carbon atoms is isobutene.

A fourth aspect of the present invention relates to a method for producing an olefin polymer according to any one of the first to third aspects of the present invention, wherein the organic solvent used for the extractive distillation is dimethylformamide.

  According to the method of the present invention, an aliphatic hydrocarbon containing a olefin having 4 carbon atoms obtained from extractive raffinate is used as a raw material, and in the presence of a granular solid acid catalyst containing 60% by mass or more of particles having a particle diameter of less than 1400 μm. In the method for producing an olefin polymer, the efficiency of the catalyst can be increased, the amount of the catalyst used can be reduced, the production cost for the catalyst can be reduced, and the subsequent catalyst deactivation and / or removal process can be simplified. Or can be omitted. Moreover, the catalyst residue in the obtained olefin polymer is small. In particular, when a halogen-containing catalyst is used, even when a lubricating oil additive such as a detergent composed of the derivative is burned, the release of halogen into the atmosphere is small, and thus it is useful in terms of environmental conservation. is there.

Hereinafter, the present invention will be described in detail.
The olefin polymer of the present invention means a polymer containing a C4 olefin having a double bond at the terminal as a main constituent component. In the present invention, as a starting material for obtaining an olefin polymer, 5 to 95% by mass of olefin mainly containing carbon 4 olefin obtained from raffinate of extraction distillation method using diene hydrocarbon as an extract and mainly carbon A liquid hydrocarbon composed of 95 to 5% by mass of a saturated aliphatic hydrocarbon containing a saturated aliphatic hydrocarbon of formula 4 (both are 100% by mass in total) is used. Here, “mainly” means 50% by mass or more. That is, it means that 50 mass% or more of olefins having 4 carbon atoms are contained in the olefin, and 50 mass% or more of saturated hydrocarbons having 4 carbon atoms in the saturated hydrocarbon.

  Examples of the raw material for extractive distillation include a mixture of diene, olefin and saturated aliphatic hydrocarbon obtained in the petroleum refining or petrochemical industry. For example, as a raw material for obtaining butadiene, it is mainly referred to as a C4 fraction (C4 fraction, crude butadiene, BB fraction, etc.) produced when ethylene / propylene or the like is produced by naphtha decomposition. Are preferred). In addition to this, the same fraction obtained by high-temperature cracking of gas oil, or the one obtained from cracked products of petroleum by fluid catalytic cracking (FCC), the catalytic dehydrogenation reaction product of butane, butene, etc. can be used. . When obtaining isoprene which is a diene having 5 carbon atoms, a raw material fraction having 5 carbon atoms is used.

  The extractive distillation method used in the present invention is not particularly limited, and any known extractive distillation method using a diene hydrocarbon as an extract can be preferably used. Specific examples of the extractive distillation method for producing butadiene will be given below, but isoprene is also carried out in the same manner.

  When the vaporized C4 fraction is fed from the bottom of the extraction tower and the extraction solvent is added from the top of the tower, the apparent boiling point of butadiene rises due to the interaction between the solvent and butadiene and moves to the bottom of the tower, containing olefins. The hydrocarbon to be discharged flows out from the top of the column as raffinate containing the extraction solvent, and the extract containing butadiene and the like flows out from the bottom of the column. The extraction solvent that accompanies the raffinate is recovered from the raffinate by a method such as washing with water in a water washing tower. However, even after such treatment, the raffinate usually contains a trace amount of a degradation product such as an extraction solvent and an oxide of the extraction solvent. The content is usually on the order of several tens of mass ppb to 10 mass ppm. Further, it is preferable to appropriately remove dienes and hydrocarbons having an acetylene bond contained in a small amount in the raffinate by hydrogenation by a known method if desired. Hereinafter, in the present specification, the term “raffinate” means a product obtained from an extractive distillation column and then subjected to an extraction solvent separation step and a desired hydrogenation step, unless otherwise specified.

  Preferred extraction solvents in the extractive distillation of the present invention include furfural, acetonitrile, dimethylacetamide, dimethylformamide, N-methylpyrrolidone and the like. The extraction efficiency is preferably one that contains nitrogen, which is a highly polar organic solvent that has little interaction with olefins, etc., and its boiling point is sufficient compared to hydrocarbons in raffinate because of the ease of separation of hydrocarbons and solvents. Is preferably high. Therefore, among these, dimethylformamide and N-methylpyrrolidone are most preferable.

  As the olefin, those having a vinyl group, that is, those having a double bond at the terminal are particularly preferred. For example, 1-butene and 2-methyl-1-propene (isobutene) are preferable as the olefin having 4 carbon atoms. Of the olefins having 4 carbon atoms, isobutene is particularly preferable. In the present invention, it is not prohibited to contain an olefin having 5 carbon atoms in addition to the olefin having 4 carbon atoms. As olefins having 5 carbon atoms, 3-methyl-1-butene, 1-pentene, 1-hexene, vinylcyclohexane, 4-methyl-1-pentene, 2,4,4-trimethyl-1-pentene, 1 -Decene, 1-dodecene and the like. The olefin having 4 carbon atoms is most preferable in view of the ease of keeping the reaction system containing the produced polymer and the raw material hydrocarbon in a liquid state, the reactivity of the olefin, and the like.

  When the olefin content is less than 5% by mass, the production efficiency of the olefin polymer is not commercial, and when it exceeds 95% by mass, the viscosity of the reaction system becomes too high particularly when producing an olefin polymer having a large molecular weight. Therefore, the process may not be performed smoothly. The content of olefin is, for example, in the step of producing a polymer of polyolefin having 4 to 3500 carbon atoms (polybutene) from hydrocarbon containing isobutene which is olefin having 4 carbon atoms, the isobutene concentration is 20 to 20%. It is preferably in the range of 80% by mass, and more preferably in the range of 25-60% by mass.

  Hydrocarbons mainly containing olefins with 4 carbon atoms are easily obtained from the market as raffinates when butadiene is produced by extractive distillation from C4 fractions distilled from naphtha cracking equipment that produces lower olefins such as ethylene and propylene. can do. The raffinate usually contains as olefin 40 to 55% by weight of isobutene and 20 to 35% by weight of 1-butene, and additionally 7 to 8% by weight of 2-butene. Butadiene is 0.5 mass% or less and contains a trace amount of extraction solvent. The balance is saturated hydrocarbons such as butane and isobutane. Of course, other raffinates or saturated hydrocarbons can be added to the raffinate.

  Since the polymerization raw material of the present invention contains a hydrocarbon obtained from a raffinate of an extractive distillation method using a diene hydrocarbon as an extract, a small amount of extraction solvent is inevitably accompanied even through the extraction solvent removal step. The extraction solvent can interact with any compound present in the polymerization reaction system. In particular, those containing nitrogen which is preferable as an extraction solvent, such as dimethylformamide, N-methylpyrrolidone and the like, have strong basicity, and therefore are highly likely to cause preferential and strong interaction with the solid acid catalyst. The present inventor has found that a particulate solid acid catalyst containing 60% by mass or more of particles having a particle size of less than 1400 μm has a particularly high adsorption ability with respect to these extraction solvents, and these adsorbates reduce the catalyst efficiency.

In the present invention, the raw material hydrocarbon is brought into contact with a treatment agent containing aluminum atoms before the polymerization step, and the extraction solvent is adsorbed on the treatment agent. The treatment agent containing an aluminum atom is preferably an inorganic solid treatment agent containing a component represented by the composition formula Al ₂ O ₃ . As long as the component represented by Al ₂ O ₃ is included, a natural or synthetic inorganic substance can be used. Specific examples of the inorganic solid treatment agent include activated alumina, silica / alumina, molecular sieve and the like. Preferably it is activated alumina. These may be molded using an appropriate binder.

For example, commercially available alumina can be appropriately pulverized and classified for use. Although the specific surface area as a solid processing agent is not specifically limited, Usually, it is the range of 1-500 m < ² > / g. In addition, as long as the effect of the present invention is not hindered, the alumina is modified by appropriately impregnating an alkali metal, alkaline earth metal or other metal in an oxide, hydroxide or other form or by appropriately supporting it by other methods. Things can also be used. However, usually, such support / modification is not particularly necessary, and alumina having an alkali metal or alkaline earth metal content such as sodium of 0.5% by mass or less is used. Thus, alumina with little or no loading / modification is inexpensive, and the present invention is an advantageous method also in this respect. In addition, the alumina which can be preferably used in the present invention is preferably activated alumina, particularly alumina having high chlorine adsorption ability. It is. Further, a compound containing a component represented by Al ₂ O ₃ is known to have the properties of amphoteric compound.

  The present inventor has found that the treatment agent containing an aluminum atom in the present invention has the characteristics of an amphoteric compound as an aluminum compound and the adsorptive power as an adsorbent. By this unique property, the olefin is substantially polymerized. It is considered that the residual extraction solvent in the raw material is physically adsorbed, or is adsorbed and removed particularly by the action of forming a coordination compound with a lone electron pair in the compound as the extraction solvent. That is, the residual extraction solvent can be adsorbed and removed without substantially proceeding with the polymerization reaction of olefins as compared with the adsorption removal by the strongly acidic ion exchange resin proposed in Japanese Patent Application Laid-Open No. 2000-34242.

  The temperature at which the aluminum atom-containing treatment agent is brought into contact with the liquid hydrocarbon raw material varies depending on the combination of the treatment agent and the type of olefin in the raw material hydrocarbon. If the treatment temperature is too high, the olefin polymerization reaction may proceed. If it is too low, the treatment effect cannot be sufficiently exhibited, and the subsequent polymerization process temperature is taken into consideration, and the temperature is set to -30 ° C to 100 ° C. It is preferable that the temperature is in the range of −10 ° C. to 50 ° C. In order to sufficiently obtain the effects of the present invention, it is preferable to bring the raw material hydrocarbon into contact with the aluminum atom-containing treatment agent in the liquid phase, and the treatment is performed while applying pressure as necessary.

  The contact time between the aluminum atom-containing treating agent and the raw material hydrocarbon is not particularly limited as long as the removal of the extraction solvent is achieved, but it is usually preferably in the range of about 1 minute to 10 hours. When the length is shorter than this range, the contact is generally insufficient, and thus the extraction solvent is not sufficiently removed. As a method for contacting, either a batch type or a continuous type is possible. In the case of a continuous type, a fixed bed type, a fluidized bed type or the like can be used. As the flow direction, either an upflow or a downflow can be adopted.

The inventor has previously filed a patent application by finding that the treatment of the raw material olefin with an aluminum atom-containing treating agent as a pretreatment of the olefin polymerization with an acid catalyst has an effect on improving the efficiency of the acid catalyst. No. 2004-245716), the present application is based on the finding that this effect is very remarkable in a granular solid acid catalyst containing 60% by mass or more of particles having a particle size of less than 1400 μm. That is, the solid acid catalyst in a granular form containing particles having a particle size of less than 1400 μm is 60% by mass or more, and has excellent catalytic efficiency. Since it receives greatly, the effect by the combination of the process of this invention is acquired notably. In particular, since the solid acid catalyst having a particle diameter of less than 850 μm (20-mesh sieve particles) has a high ability as an adsorbent, the effect of the present invention is remarkable in a solid acid catalyst containing more than 60 mass% of these. A solid acid catalyst (12 mesh sieve impervious particles) having a particle size of 1400 μm or more has a relatively low adsorption capability, and the effect of the present invention is obtained, but is relatively low. The solid acid catalyst in the present invention is not particularly limited as long as it is a known solid acid catalyst for olefin polymerization, but aluminum chloride (AlCl ₃ ) is preferable from the viewpoint of catalytic activity.
The size of the granular material in the present invention is based on the mesh opening size defined in JISZ8801 (ISO3310) “Test sieve”. Specifically, the 12 mesh sieve impervious particles are particles having a particle size of 1400 μm or more, and the particles passing through the 12 mesh sieve are particles having a particle size of less than 1400 μm. Similarly, 20-mesh sieve particles have a particle size of less than 850 μm.

The above solid acid catalyst is usually put into a suitable solvent such as normal hexane, normal heptane, isooctane, cyclohexane, cyclododecane, toluene, benzene, dichloromethane, methyl chloride, ethyl chloride, and stirred to be suspended. Pour into the reaction vessel. You may use together as a complex using the compound used as a well-known ligand. If necessary, for example, HCl, t-butyl chloride, water or the like may be supplied as an activator. The amount used is preferably 0.5 × 10 ^{−5 to} 1.0 × 10 ⁻² (mol / mol) with respect to the olefin having a terminal double bond in the raw material.

  The polymerization reaction is carried out in a liquid phase using raw material hydrocarbons and catalyst that have been treated with an aluminum atom-containing treating agent. The reaction can be carried out by either a batch method or a continuous method, but a continuous method is preferred. A well-known thing can be used for a reaction apparatus. The raw material hydrocarbon and catalyst are supplied by a known method. The polymerization temperature and pressure are not particularly limited as long as the reaction system is maintained in a liquid phase, but a preferred temperature is −100 to + 10 ° C. and a pressure is 0.1 to 2 MPa.

  There is no restriction | limiting in particular in the number average molecular weight of an olefin polymer. That is, the olefin polymer is dissolved in the unreacted olefin and saturated aliphatic hydrocarbon in the polymerization reaction system, and can be separated from the unreacted olefin and saturated aliphatic hydrocarbon by distillation or the like. If there is a range, for example, a dimer, a trimer to an oligomer having a number average molecular weight of 500 or less, a viscous polymer having a number average molecular weight in the range of 1,500 to 50,000, and a number average molecular weight of 100, All isobutene polymers of more than 000 polymeric polymers can be obtained.

  After the polymerization, a catalyst deactivation step and / or a catalyst extraction / removal step is performed according to a known method. However, since the amount of the catalyst added is reduced, the load of these steps is larger than that of the conventional method. Become smaller. In addition, the target polymer is obtained by appropriately distilling before and after these steps to remove unreacted olefins and the like. Further, the polymer thus obtained can be further appropriately distilled to be separated into an olefin polymer having a desired number average molecular weight. In the present invention, since the catalyst addition amount is reduced, a polymer having a halogen concentration of 5 mass ppm or less can be easily obtained by installing a dehalogenation tower (for example, an alumina packed tower). .

  As mentioned above, although the explanation has been given mainly using the butene-based olefin polymer as an example, the effect according to the present invention is not limited to the butene-based olefin polymer.

Hereinafter, although an example is given and explained, the present invention is not limited to an example.
<Preparation and production of raw material A>
A raffinate of an extractive distillation method (extraction solvent: dimethylformamide) using butadiene as an extract was prepared from a C4 fraction from an ethylene cracker. Hereinafter, it is referred to as “raw material A”. Table 1 shows the hydrocarbon composition of the raw material A. The dimethylformamide concentration in the raw material A was 0.7 mass ppm. The concentration of dimethylformamide in the raw material was measured using a GC-FTD (thermal ionization detector) after extracting the dimethylformamide in the raw material with water and concentrating it by evaporation. Asked.

<Preparation and production of raw material B>
A C4 mixture (but not containing dimethylformamide) having the same hydrocarbon composition as that of “Raw material A” was prepared from a commercially available special grade reagent, and 1.5 mass ppm of N-methylpyrrolidone was added thereto. Hereinafter, it is referred to as “raw material B”.

<Aluminum atom-containing treatment agent>
Activated alumina (UOP LLC, trade name: A203-CL) was pulverized and the particle size was classified from 0.5 mm0 to 1.0 mm as an aluminum atom-containing treatment agent. 10 g of this was filled in a fixed bed container having an internal volume of 15 ml. For the purpose of comparison, a container having the same shape filled with a reagent-grade calcium chloride (manufactured by Tokyo Chemical Industry Co., Ltd.) and classified to a particle size of 0.5 to 1.0 mm was prepared.

<Catalyst>
Aluminum chloride was used as the particulate solid acid catalyst. As shown in Table 2, seven types of catalysts were used depending on the particle size distribution. Catalysts 1 to 5 are the catalysts of the present invention. Reference catalysts 1 and 2 have particle size distributions outside the scope of the present invention.

<Pretreatment of raw materials>
The raw material A and the raw material B maintained in a liquid state under a pressure of 0.3 MPa are separately injected into a container filled with the aluminum atom-containing treatment agent, and the conditions are + 20 ° C. and WHSV = 1h ⁻¹ for 60 minutes. Pre-processed.

<Polymerization reaction>
In an autoclave with an internal volume of 200 ml, the above pretreated raw material is 240 g / hr, and aluminum chloride having a particle size distribution shown in Table 2 as a granular solid acid catalyst is suspended in hexane and fed separately. Polymerization was continuously performed for 120 minutes at a temperature of -15 ° C and 0.19 MPa. The addition amount of the catalyst was 0.5 mmol with respect to 1 mol of isobutene in each raw material.

<Calculation of conversion of isobutene to polyisobutene>
The raw material before the polymerization reaction and the polymer after the polymerization reaction (polyisobutene) are sampled in sealed containers, neutralized with an aqueous sodium hydroxide solution to deactivate the catalyst, and kept at room temperature and normal pressure. The isobutene mol% was analyzed by gas chromatography. The reduced amount of isobutene in the evaporated gas component was defined as the conversion rate (%) of isobutene to polyisobutene. The results are shown in Table 3.

  First, in each raw material pretreated with activated alumina, both the raw material A and the raw material B are compared with the case where the pretreatment is not performed and the case where the same treatment is performed with calcium chloride and molecular sieve. It can be seen that a high conversion was obtained even with the same catalyst addition amount. Moreover, when the increase rate of the conversion rate in the raw material A and the increase rate in the raw material B are compared, the increase rate in the raw material A is larger, and this invention is more effective with respect to the raffinate which uses dimethylformamide as an extraction solvent. I understand.

  Next, the rate of increase (%) in the conversion rate when the raw material A was pretreated with activated alumina, in relation to the particle size of the catalyst, is a reference catalyst 1 consisting of aluminum chloride of 2000 μm or more and less than 2800 μm. In the reference catalyst 2 made of aluminum chloride of only 1400 μm or more and less than 2000 μm, the increase rate is almost the same at 200%, but the catalyst 1 containing 60% by mass or more of particles less than 1400 μm according to the embodiment of the present invention. 5, the increase rate increases to 300% or more, and it can be seen that a remarkable effect is obtained in this range. In particular, the increase rates of the catalyst 3 and the catalyst 4 containing 60% by mass or more of particles less than 850 μm are remarkable at 370% and 400% or more.

Claims (4)

5 to 95% by mass of olefins containing 50% by mass or more of olefins having 4 carbon atoms and saturated aliphatic hydrocarbons having 4 carbon atoms, including hydrocarbons obtained from raffinate of extractive distillation method using diene hydrocarbon as an extract After contacting a liquid hydrocarbon composed of 95 to 5% by mass of saturated aliphatic hydrocarbon containing 50% by mass or more (100% by mass together) with activated alumina , 60 particles having a particle size of less than 1400 μm are obtained. A method for producing an olefin polymer, comprising polymerizing an olefin in the presence of aluminum chloride containing at least mass%. 2. The method for producing an olefin polymer according to claim 1, wherein the aluminum chloride contains 60% by mass or more of particles having a particle diameter of less than 850 μm.   The method for producing an olefin polymer according to claim 1, wherein the olefin having 4 carbon atoms is isobutene. The method for producing an olefin polymer according to any one of claims 1 to 3 , wherein the organic solvent used for the extractive distillation is dimethylformamide.