JPH054998B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a binder pitch for electrodes from lime-based tar pitch from which fractions with a boiling point of 290° C. or lower have been removed, or a hydrocarbon material containing similar condensed cyclic aromatics. The properties of the binder pitch for electrodes vary depending on the type of electrode, etc., but it is generally known that they need to have the following characteristic values. Softening point (mercury method) 75-95℃ Benzene insoluble content 25-40% Quinoline insoluble content 5-20% Fixed carbon 55% or more Pitch produced by ordinary continuous tar distillation generally cannot satisfy the above characteristic values, so Modification operation is required. This modification method includes (1)
A simple heating method, (2) air or inert gas injection heating method, and (3) condensing agent addition heating method are known. However, these reforming operations are usually carried out at 250 to 420° C. for a long period of time, which requires a considerable amount of energy and time. Therefore, the present inventors have conducted repeated studies on a method for producing binder pitch for electrodes without carrying out the modification operation by heat treatment that is normally performed. The present invention was achieved by discovering that a pitch having characteristics as a binder pitch for an electrode can be obtained by adjusting the softening point of unused and inexpensive materials as necessary. That is, the gist of the present invention is that the boiling point is at least 290
Hydrocarbon substances, including lime-based tar pitch or similar condensed cyclic aromatic compounds from which distillations have been removed up to A solvent consisting of a hydrogen substance and/or an alicyclic hydrocarbon substance,
1 to 10 parts by weight of the solvent are mixed with 1 part by weight of the hydrocarbon substance, and then the mixture is allowed to stand for stratification separation, and the resulting lower layer is directly distilled or the lower layer is heated to a boiling point. A method for producing a binder pitch for electrodes, which comprises mixing tar-based oil at 290° C. or higher, followed by distillation, and distilling off the solvent to obtain pitch as a bottom fraction. The present invention will be explained in detail below. The hydrocarbon substance used as a starting material in the present invention is typically a bottom product obtained by distilling off a low-boiling fraction with a boiling point of at least 290°C or less from coal-based tar by atmospheric distillation, and is generally called road tar. Although the present invention is not limited to this, it includes fused cyclic aromatic compounds having properties similar to road tar that are obtained from various sources such as petroleum, shale oil, and tar sand through appropriate treatment. Hydrocarbon substances may be mentioned, among which rhodotar is most preferred. In addition, the above hydrocarbon substance has a boiling point of at least 290
Although the fraction up to 100°C is removed, it is also possible to have a configuration in which components with higher boiling points are also removed, depending on the case. When removing such higher boiling point components,
Usually, it is considered that the limit is to exclude fractions with a boiling point of up to 450°C, more preferably fractions with a boiling point of up to 400°C. Hereinafter, the case where rhodotar is used as a starting material will be explained. As the solvent, an aliphatic hydrocarbon substance and/or an alicyclic hydrocarbon substance having a boiling point or distillation temperature of 95% by volume of 65 to 290°C, preferably 80 to 250°C is used. These aliphatic hydrocarbon substances include _C6 to _C15 paraffins such as hexane, heptane, octane, decane, heptadecane, and mixtures thereof, naphtha kerosene, and the like. In addition, examples of alicyclic hydrocarbon substances include cyclohexane, methylcyclohexane, ethylcyclohexane, cycloheptane, methylcycloheptane,
Examples include C ₆ to _{C 10} alicyclic hydrocarbons such as ethylcycloheptane, cyclooctane, and decalin, alicyclic hydrocarbons having an alkyl group, and mixtures thereof, but naphtha is preferred from the viewpoint of economy and operability. Alternatively, it is preferable to use kerosene. These solvents should be selected so that their dry point (the upper limit of the boiling point range) is several degrees Celsius or more lower than the initial distillation temperature of the hydrocarbon material, depending on the type of hydrocarbon material used as the starting material. is preferred. This selection condition is especially important when the recovered solvent is recycled. If the recovered solvent contains a part of the hydrocarbon substance used as the starting material, the recovered solvent may be further purified by distillation and recycled. It is also possible to use a mixture of two or more of these solvents. If the amount of solvent used is too small, stratified separation in the next step will be difficult, and if too large is used, the cost of recovering the solvent from the stratified separation liquid will increase, making it uneconomical. 1 to 10 parts by weight, preferably 2 to 6 parts by weight, are used per part by weight of the hydrocarbon substance used. The starting hydrocarbon material and the solvent are mixed using a stirred tank axial flow mixer, a biaxial flow nozzle, an ejector, etc. at a temperature of room temperature to 200° C. for a period of several seconds to one hour. The resulting mixture is maintained at a temperature at which the upper layer separated by stratification from the mixture can be separated while maintaining a liquid state;
For example, it is allowed to stand at room temperature to 200° C. for several seconds to one hour under normal pressure or pressurization. Then, the solvent is stratified into an upper layer containing aromatic hydrocarbon substances with a reduced amount of benzene-insoluble matter and a lower layer where benzene-insoluble matter is concentrated. The above-mentioned mixture is allowed to stand still and separated using a container equipped with a heating jacket, a thickener, or the like. The solvent fraction is removed from the obtained upper layer by distillation under normal pressure or reduced pressure, or steam distillation using an evaporator or a distillation column. The distilled off solvent fraction is recycled as a solvent as it is or after being purified. In this distillation, the product obtained as a bottom fraction or bottom fraction differs depending on the type of hydrocarbon substance used as a starting material, but it usually has a boiling point of 260°C or higher, an average molecular weight of 200 to 300, and a benzene It is in the form of a pitch with an insoluble content of 0 to 5 wt% and a melting point of about room temperature to 50°C, and is effectively used as a pitch cut pack oil, a raw material for pyrolytic carbon materials, a raw material oil for carbon black, etc. On the other hand, the lower layer is obtained in the form of a pitch with very high viscosity. This lower layer material can be distilled as it is, or an appropriate amount of the bottom fraction obtained by removing the solvent from the upper layer material, or tar-based oil with a boiling point of 260°C or higher, is cut and mixed, and then an evaporator or distillation column is used. Then, all of the solvent and a part of the aromatic hydrocarbons are distilled off by distillation under normal pressure or reduced pressure, or by steam distillation in order to adjust the softening point of the resulting pitch, thereby obtaining a binder pitch for an electrode. Cutting back the tar-based oil to the stratified and separated lower layer material allows the pitch obtained as a product to have a well-balanced softening point and other physical properties (benzene insoluble content, quinoline insoluble content, etc.) as a binder pitch for electrodes. However, since the lower layer material is in the form of a very viscous pitch and is difficult to handle, it also serves to increase the fluidity of the lower layer material. In addition, when distilling off the entire amount of solvent and part of the aromatic compounds, by controlling the softening point as a guide, it is often possible to obtain a binder pitch for electrodes with well-balanced other physical properties. Confirmed by experimental results. Depending on the type of raw material, solvent, and extraction conditions, the tar-based oil may be directly distilled without being cut back into the lower layer after stratified separation, and the entire amount of the solvent and a portion of the aromatic hydrocarbon substances may be distilled off. It is also possible to obtain a binder pitch for electrodes, but in general,
The softening point tends to be too high compared to other physical property values. Therefore, as described above, the softening point is usually adjusted by cutting back the lower layer substance hetal oil and then distilling off the entire amount of the solvent and a part of the aromatic hydrocarbon substance in a distillation column or the like. In addition, the entire amount of the solvent and a part of the aromatic hydrocarbons are distilled off without cutting back the tar-based oil, which is the lower layer substance after stratified separation, and the tar-based oil is cut back into the resulting pitch to form an electrode pitch. It is also possible to obtain However, in this case, the boiling point of the cutlet oil is preferably 300°C or higher. The recovered solvent fraction is recycled as a solvent as is in the case of the upper layer, or if the recovered solvent contains aromatic hydrocarbon substances,
It is further purified using a distillation column, etc., and the solvent is recovered and recycled. Among the aromatic hydrocarbon substances, the fraction with a boiling point of 290°C or higher can also be used as cutback oil for lower layer substances. As detailed above, in the present invention, a hydrocarbon substance containing a road tar or a similar condensed cyclic aromatic compound from which at least a fraction of coal tar below 290°C has been removed is mixed with a specific solvent, and stratified. The separated lower layer can be distilled as it is, or the tar-based oil can be cut back and then distilled to remove the entire amount of solvent and part of the aromatic hydrocarbons. This is an extremely useful method that allows you to directly obtain a binder pitch for electrodes without the need for further operations. Next, the method of the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded. Examples 1 and 2 Coal tar obtained by carbonization of coal was continuously supplied to an atmospheric distillation column at 500 kg/Hγ, and gas oil,
Fractions with boiling points up to 290°C, such as carboxyl oil and naphthalene oil, were distilled off. The fraction (road tar) distilled from the bottom of the column was 400 Kg/Hγ. Then this road tar and boiling point range 160-260
800 kg/Hγ of kerosene at 130°C was introduced into a jacketed stirring tank and mixed for 30 minutes while maintaining the temperature at 130°C. The resulting mixture was introduced into a jacketed standing tank maintained at 130°C and allowed to stand for 15 minutes to obtain a stratified and separated lower layer at a ratio of 100 kg/Hγ. to this,
Tar-based cutback oil having an initial boiling point of 260°C or lower and a 95 volume % distillation point of 420°C was added at a rate of 20 kg/Hγ and introduced into the vacuum distillation column. A portion of the solvent and aromatic components were distilled off from the top of the vacuum distillation column under conditions of 50 mmHg and 200°C, and introduced into the next solvent recovery column, whereupon the solvent was recovered from the top and recycled to the stirring tank. Pitch was obtained from the bottom of the tower at a rate of 105 Kg/Hr. The physical property values are shown in Table 1. In addition, as Example 2, the physical properties of pitch produced under the same conditions as in Example 1 except that the layer-separated lower layer hetal oil was not cut back, and as a comparative example, pitch obtained from a regular continuous tar distillation column was investigated. Table 1 also shows the physical property values of those heat-treated at 380°C for 12 hours.

[Table] Compared to conventional products, the present product has lower benzene-insoluble content and quinoline-insoluble content, but when used as an electrode binder, it has been found that its characteristic values are actually better, as shown in the following reference example. There is. . Reference example 1 part by weight of pitches obtained in Examples 1, 2 and comparative examples and 3.8 parts by weight of needle coke were mixed in a kneader to 150 parts by weight.
After kneading at 60°C for 60 minutes, it was molded into a cylinder with a diameter of 25mm and a length of 100mm, fired at 800°C, and graphitized at 3000°C.The physical properties of the product are shown in Table 2. It is clear that graphitized products using the binder pitch of the present invention have superior characteristic values as electrodes compared to those using conventional pitch.

【table】

Claims (1)

[Scope of Claims] 1. A hydrocarbon substance containing a condensed cyclic aromatic compound from which a fraction with a boiling point of at least 290°C has been removed, and an aliphatic substance having a boiling point or a 95% distillation temperature of 65 to 290°C. A hydrocarbon substance and/or a solvent consisting of an alicyclic hydrocarbon substance are mixed in a ratio of 1 to 10 parts by weight of the solvent per 1 part by weight of the hydrocarbon substance, and then the mixture is left to stand. , stratified separation, and the resulting lower layer is directly distilled, or after mixing tar-based oil with a boiling point of 290°C or higher into the lower layer, distillation is performed, and the solvent is distilled off to obtain pitch as a bottom fraction. A method for manufacturing a binder pitch for electrodes, characterized by the following. 2. The method according to claim 1, characterized in that when tar-based oil is mixed into the stratified lower layer and distilled, all of the solvent and part of the aromatic hydrocarbons are distilled off.