JPH0639405B2 - Method for separating and purifying n-paraffin from ethylene low polymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a method for economically separating and purifying n-paraffin from a low ethylene polymer by-produced during the production of Ziegler polyethylene.

<Conventional Technology and Problems to Be Solved> Conventionally, a molecular sieve method, a perspiration method, and a solvent crystallization method have been used as methods for separating and purifying n-paraffins from petroleum-based or synthetic oil raw materials. Mainly carbon number C
For molecular weight of 22 or less, use molecular sieve method for n-
Paraffin is separated, and the perspiration method and the solvent crystallization method are often used for carbon numbers of C23 or more. In the molecular sieve method, it is industrially difficult to separate a high content of n-paraffin, and the carbon number is C30. Further, although the perspiration method and the solvent crystallization method can treat C23 or more, the content of the obtained n-paraffin is generally about 75%, and the limit is about 85%. Therefore,
If the carbon number becomes C20 or more, n-
It was extremely difficult to separate paraffin from individual products.
On the other hand, ethylene low-polymerization products produced as a by-product during Ziegler process polyethylene production include fuel, additive raw materials for fluid catalytic cracking of gasoline and light oil, hot melt adhesives, rubber anti-aging agents, resin modification and weight increase. It is used as an agent, an additive for plastic paints, a lubricant for polyvinyl chloride, a dispersant for pigments, and a modifier for paraffin wax. By the way, since this is a by-product by nature, the physical properties vary from lot to lot, but the fact is that the user accepts this because it is cheap.

On the other hand, recently, bio-related products such as pharmaceuticals and fragrances, special solvents, and n-paraffin, which is a standard substance for analytical instruments, have been marketed up to 22 carbon atoms, and the demand has been further expanded. It's starting.

Furthermore, for C24 and above, attention has been paid to the thermal stability and thermal reactivity, which are the characteristics of high-quality n-paraffins, and the market for n-paraffins having no transition point has been newly developed. ing. The so-called sensor wax is used. In other words, the object of the present invention is to solve the problem that the physical properties and composition control have not been made more strict, and to provide homogeneous n-paraffins suitable not only for conventional applications but also for novel applications. It is in.

<Means for Solving the Problems> In view of the above situation, the present inventor has found that the ethylene low-polymerization product produced as a by-product during the production of Ziegler polyethylene basically has an even carbon number, It should be noted that the composition contained in is mainly n-paraffin and i-paraffin having a limited molecular structure, and is a waxy solid having a carbon number of C6 to C400.
Economically advantageous compared to the purification method and C6 to C400
We have succeeded in establishing a technology to separate and purify n-paraffins with a purity of 93% or higher in the range up to the order.

That is, a low ethylene polymer by-produced during the Ziegler method polyethylene production is used as a raw material, and in addition to the following step (a), it is treated using any one of the steps (b), (c) and (d). The method for separating and purifying n-paraffins from a low ethylene polymer is characterized by:

(A) A step of separating the catalyst residue by passing it in a molten state at a temperature of about 130 ° C or higher.

(B) n by carbon number of C6 to C24 by vacuum precision distillation
-A step of separating and purifying paraffin.

(C) A step of separating and purifying n-paraffins having a carbon number of C20 to C400 by crystallization using a hydrocarbon solvent, a ketone solvent, or a mixed solvent thereof.

(D) C20 to C400 by appropriately combining the above steps (a), (b) and (c).
Step of separating and purifying n-paraffin up to the position.

The raw material ethylene low-polymerization product used here has different component compositions and physical properties depending on the polymerization conditions of polyethylene, but one example is as follows.

Composition: C6 to C400 carbon number distribution, C10 to C80 about 70
%, There is a peak near C50. n-paraffin is
80-96% with an even number of carbons.

Physical properties: Softening point 85-130 ℃ Viscosity 6-300 (10-60) CPS / 130 ℃ Flash point 100-230 ℃ Penetration 1-30 (6-20) dmm / 25 ℃ Ash content 0.01-1.5% Generally Ziegler Since a low ethylene polymer produced as a by-product during the production of polyethylene by method contains a catalyst residue, the catalyst residue is first removed by the step (a) in order to use this as a raw material. By-product ethylene low-polymerization product has a melting point of approximately 130 ° C.
Because of the following, the temperature of the melt is maintained at 130 to 140 ° C. in the melt tank in the presence of the super-auxiliary agent while being sufficiently stirred. After pre-coating the reactor with Celite or the like, the melt is charged into the reactor and filtered to remove catalyst residues and traces of unsaturated hydrocarbons. Alternatively, the melt and the alkali 2-6% aqueous solution are sufficiently contacted with stirring in a pressure tank at about 150 ° C. under stirring to dissolve impurities such as catalyst residues in the alkaline aqueous solution or remove them as an inorganic substance. After removing impurities such as catalyst residues, it becomes a white solid wax at room temperature.

By-product ethylene low-polymerization products from which impurities such as catalyst residues have been removed in the above step (a) are transferred to the step (b). In the step (b), vacuum precision distillation is performed to separate and purify n-paraffins having carbon numbers C6 to C24. The conditions for vacuum precision distillation are usually 280 ° C or higher and a vacuum degree of 0.1 mmHg or lower. The vacuum distiller usually has more than 30 stages.

The step (c) is crystallization.

Hydrocarbons as solvents for crystallization separation are petroleum hydrocarbons,
For example, petroleum benzine, ligroin, n-hexane, etc., as well as aromatic hydrocarbons such as benzene, toluene,
Xylene, anthracene, etc. can also be used. For ketones, methyl ethyl ketone (MEK), methyl isopropyl ketone (MIPK), methyl isobutyl ketone (MIBK),
Methyl amyl ketone (MAK), methyl hexyl ketone (M
HK), diisobutyl ketone (DIBK), isophorone and the like are preferable. A mixed system of the above hydrocarbons and ketones is also preferable, for example, MEK-toluene, MIBK-toluene, MEK-n.
-Hexane mixed system etc. are mentioned.

When crystallization is performed using a polar solvent, a product having a composition having a narrow molecular weight distribution and having sharp physical properties such as a melting point can be obtained. On the other hand, a non-polar solvent such as an aromatic hydrocarbon has a wide molecular weight distribution range to be separated, but can produce a product having high physical properties such as a melting point and hardness. Therefore, by changing the type and mixing ratio of the solvent, the composition of the obtained product can be freely changed by utilizing the difference in the selective separation ability of the solvent, and the product having the desired physical property value can be manufactured. .

Furthermore, in the crystallization method, the difference in the crystallization rate of each component during crystallization is incorporated into the fractionation method to further enhance the separation effect.

The resin component having a molecular weight of about 30,000 or more contained in the ethylene low-polymerized product has a remarkably large molecular weight as compared with paraffin and wax, and therefore has a very low solubility especially in a polar solvent as compared with paraffin and wax. Therefore,
Prior to crystallization, the paraffin and wax are dissolved, and the amount of solvent and the melting temperature are set so that the resin does not dissolve,
The resin content can be efficiently separated by the passage.

As described in (d), the above (b) and (c) are appropriately combined to obtain a highly pure product.

The product obtained by the method of (b) and (c) at the finishing stage,
It is decolorized and deodorized by treating with activated carbon and activated clay. Further, in the case of C22 or less, a product from which trace impurities such as unsaturated hydrocarbons are removed by a sulfuric acid washing step is manufactured.

<Operation> The polyethylene low polymer obtained by removing the polyethylene high polymer, the solvent, and the catalyst residue from the polyethylene polymer in the step (a) is an aggregate of saturated or unsaturated hydrocarbons such as linear, branched, or cyclic. However, as described above, most of them are n-paraffins and basically have an even number of carbon atoms, so that even in the vacuum precision distillation of (b), a sufficiently high purity can be obtained. .

By this vacuum precision distillation, each boiling point is fractionally distilled to obtain C6 ~
Separate up to C30. Usually, it is easy to fractionate C6 to C24.

Then, C20 or more, particularly C30 or more and C50 or so, can be fractionated to a considerably sharp component ratio by vacuum thin film distillation.

When it becomes C30 or more, separation by vacuum thin film distillation becomes difficult, but the crystallization separation method of (c) is adopted here. As a solvent for crystallization separation, a mixed system of a non-polar hydrocarbon solvent and a polar ketone solvent has an action of facilitating the precipitation of straight-chain hydrocarbons and preventing crystallization and mixing of branched and cyclic hydrocarbons. It seems to do. Crystallization is an operation in which a substance having a desired molecular weight is precipitated by keeping it at a predetermined temperature for a certain period of time.

In the low-polymer polyethylene as a raw material, when there are many branched or cyclic hydrocarbons, it is also optional to perform the crystallization operation before the precision distillation or thin-film distillation, and a combination of these operations, that is, ( By using the step (d), a hydrocarbon having a sharp composition can be further isolated.

Hereinafter, the present invention will be described in more detail with reference to Examples.

<Example 1> The by-product ethylene low-polymerization product usually contains a catalyst residue,
The mixture was heated and melted at about 160 ° C., and the catalyst residue was removed to obtain a raw material. The raw material from which this catalyst residue was removed was distilled using a single distillation apparatus under the conditions of 2 mmHg to 10 mmHg and 280 ° C. The distillate is n having a carbon number of C6 to C30.
-A paraffin and i-paraffin-based mixture. Using this C6 to C30 distillate as a raw material, 0.1 mmHg, 280 ° C
Precision distillation under the conditions made it possible to obtain n-paraffins having a purity of 97% or more and close to a single product in the range of C6 to C24. Table 1 shows the n-paraffin content of the raw materials after simple distillation and the products A to D obtained therefrom.

<Example 2> A mixture of the distillation residue after simple distillation and the distillation residue after precision distillation of Example 1 is a waxy solid having carbon numbers of C20 to C400 and is basically n-paraffin and i. -Mainly contains paraffin. The carbon of the n-paraffin obtained by separating n-paraffin by crystallization using a mixture of the distillation residues having C20 to C400 carbon atoms as a raw material and a hydrocarbon solvent, a ketone solvent, or a mixed solvent thereof. The number distribution is about ± C10 and the molecular weight distribution is extremely narrow, and n-
The paraffin content is about 93% or more. When the thin film distillation apparatus is used under high vacuum and high temperature conditions and the raw material is divided into a distillate and a distillation residue and then crystallized, n-paraffin separation,
Purification operation becomes easy.

Table 2 shows the raw materials after the treatment of Example 1 and the n-paraffin content of the products E and F obtained by crystallization and separation using the raw materials.

<Effects of the Invention> C20 or lower products obtained by the method for separating and purifying n-paraffin from the ethylene low-polymerization product of the present invention are high-purity n-paraffins, and therefore, fine chemical-related products such as pharmaceuticals and fragrances, special solvents, Alternatively, it can be widely used as a standard substance for analytical instruments (for example, n-hexadecane C16 is a standard fuel for cetane number measurement) and the like.

Further, n-paraffin wax having a C20 or more is remarkably superior to conventional petroleum paraffin wax, microcrystalline wax or coal synthetic wax, has a sharp melting point, high latent heat of fusion, good thermal stability and is chemically stable. Therefore, in the fields of heat storage materials, thermosensors, thermal papers, thermal transfer inks, and hot melt adhesives, it was possible to obtain high-performance crystalline products that were unprecedented.

Claims (1)

[Claims] 1. A low-polymerization product of ethylene, which is a by-product during the production of Ziegler-method polyethylene, as a raw material, and in addition to the following step (a), any one of the steps (b), (c), and (d) A method for separating and purifying n-paraffin from an ethylene low-polymerized product, which comprises treating with an ethylene low polymer. (A) A step of separating the catalyst residue by passing it in a molten state at a temperature of about 130 ° C. or higher. (B) n by carbon number of C6 to C24 by vacuum precision distillation
-A step of separating and purifying paraffin. (C) A step of separating and purifying n-paraffins having a carbon number of C20 to C400 by crystallization using a hydrocarbon solvent, a ketone solvent, or a mixed solvent thereof. (D) Above (a), (b),
A step of separating and purifying n-paraffin from C20 to C400 positions by appropriately combining the steps of (c).