JPH0367551B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention involves fractionating the liquefied oil produced when coal is liquefied, and hydrocracking a part of the fraction with a boiling point of 200 to 350°C to remove normal paraffins in the fraction. The present invention relates to a coal liquefaction method for achieving stable operation of a coal liquefaction process and obtaining high-quality, high-yield liquefied oil products by removing a portion of the coal as light oil. (Prior Art) A coal liquefaction method involves heating ordinary coal and a solvent whose main components are medium to heavy oil produced from coal together with a catalyst under hydrogen pressure. At that time, the following ~ are required as a coal liquefaction solvent. In order to dissolve highly aromatic coal, a highly aromatic solvent is required. In order to suppress the recombination or polymerization of coal, which is prone to thermal decomposition, and to increase the liquid yield, a solvent with high hydrogen donating properties is required. Slightly polar solvents are required to promote coal pyrolysis and increase liquid yield. By the way, coal contains normal paraffin, which is thought to be derived from the wax of its source plants, and it is difficult to decompose when medium to heavy oil in liquefied oil is recycled as a liquefaction solvent. The normal paraffin gradually becomes thicker. When normal paraffin concentrates in the circulating solvent, it loses all of the properties necessary for a coal liquefaction solvent. That is, normal paraffin is an aliphatic compound and has a weak power to dissolve coal. As for hydrogen donating property, the bond dissociation energy of carbon-hydrogen bond can be cited as a measure of hydrogen donating property.
Normally, the bond dissociation energy of hydrogen-donating solvents is approximately
82Kcal/mol, but for normal paraffin it is approximately
90Kcal/mol, there is a difference of about 10Kcal/mol, and normal paraffin has a property that it is difficult to donate hydrogen. By concentrating the normal paraffin in the solvent, the hydrogen donating property is gradually impaired. Furthermore, since the normal paraffin itself is thermally decomposed, the hydrogen-donating solvent is consumed by the normal paraffin, and the hydrogen-donating ability of the solvent is further reduced. For, positive paraffin is non-polar,
Promotion of thermal decomposition cannot be expected. Therefore, reducing or eliminating normal paraffins from coal liquefaction solvents is an important requirement. Therefore, the present inventors previously published Japanese Patent Application Laid-Open No. 61-73794.
No. 61-101591, the boiling point is 350~
After removing the paraffin-rich fraction from the 450°C fraction,
A method of using a paraffin-poor fraction as part of a coal liquefaction solvent is provided. (Technical problem to be solved) However, the melting point of normal paraffin with a boiling point of 350°C or higher is 41°C, for example, heneicosane, which has a boiling point of 357°C, and is solid at room temperature. Furthermore, the liquefied oil fraction with a boiling point of 350° C. or higher is also semi-solid, and it is not easy to separate the solid fraction from the semi-solid fraction, which is a problem with the above method. The above method involves heating or diluting with a fraction with a boiling point of 350 or below to make it into a liquid state, and then separating the normal paraffin. On the other hand, normal paraffin has characteristics such as low odor, low toxicity, low viscosity, poor reactivity, and is easily decomposed by microorganisms. Because of this property, normal paraffin is widely used as it is in various solvents, lubricants, etc., and is also used as a raw material for various surfactants. In other words, normal paraffin with a boiling point of 350°C or higher is used in lubricants, paper processing agents, etc., and normal paraffin with a boiling point of 50°C or lower is used as a raw material for solvents and surfactants. Its usage is expected to increase as a raw material for higher alcohol-based detergents. In addition, normal paraffin is a clean fuel with a large calorific value, and is desired to be contained in large amounts in liquefied oil products, especially in light oil fractions (IBP ~ 200°C). (Purpose of the Invention) The present invention was made in view of the above circumstances, and is a method of reducing paraffin, which inhibits the liquefaction of coal, from a part of medium oil by hydrocracking using a relatively simple means. The purpose is to prevent a decrease in oil yield and obtain liquefied oil with high product value. (Structure of the Invention) The gist of the present invention is to fractionally distill coal liquefied oil, particularly by hydrocracking a part of the boiling point fraction (medium oil) of 200 to 350°C, and converting a part of normal paraffin into light oil. The removed fraction is mixed with a product obtained by hydrogenating the remainder of the fraction with a boiling point of 200 to 350°C and the fraction with a boiling point of 50°C or higher, and this mixture is used as a circulating solvent. 1st
The figure is a flow sheet of the present invention. The present invention will be explained with reference to the drawings. A slurry containing coal, a solvent, and a catalyst undergoes a coal liquefaction reaction in a liquefaction process. The product after the reaction is reduced to light oil (boiling point
200℃ or lower), medium oil (boiling point 200-350℃), and heavy oil (boiling point 350℃ or higher). Among these fractions, a part of the medium oil is hydrocracked and a part of the normal paraffin is removed as light oil, and the remainder of the medium oil and heavy oil are hydrogenated. The products obtained are mixed and the mixture is recycled as a liquefaction solvent. The medium oil and the heavy oil may be used by appropriately mixing the whole or a part thereof as necessary. The liquefaction conditions in the liquefaction process include the reaction temperature
430~470℃, reaction time 0.52.0 hours, hydrogen pressure 100~
^{Approximately} 200Kg/cm2 is desirable. As shown in Figure 2, when the reaction temperature is lower than 430℃, the target liquefied oil yield of coal liquefaction is low;
When the temperature exceeds 0.degree. C., the amount of gas and residue produced increases, the yield of liquefied oil decreases, and operational troubles due to coking and the like increase. Furthermore, when the hydrogen pressure is less than 100 Kg/cm ² , hydrogenation of aromatic rings and decomposition reactions following the hydrogenation are difficult to occur, resulting in a decrease in liquid yield. On the other hand, if the hydrogen pressure becomes higher than necessary, the amount of expensive hydrogen consumed increases and the cost required to manufacture pressure-resistant equipment becomes relatively high. The catalyst for coal liquefaction is not particularly limited, and easily available and inexpensive iron-based compounds can be used. Examples of iron-based catalysts include red mud, iron ore, steel mill waste such as converter dust, and waste from coal gasification processes, and the amount used may be 1 to 5% by weight based on coal. . Further, as with the iron catalyst, it is desirable to use a sulfur compound as a cocatalyst in an amount of 1 to 5% by weight based on the coal. When the catalyst concentration is less than 1%, the iron-based catalyst has little effect on improving the liquid yield, and when it exceeds 5%, the catalyst efficiency deteriorates. The obtained liquefied product is distilled by atmospheric distillation or vacuum distillation to produce light oil with a boiling point of up to 200℃, boiling point of 200℃~
It is fractionated into medium oil with a boiling point of 350℃ and heavy oil with a boiling point of 350℃ or higher. Light oil is taken out of the system as a product.
The present inventors have discovered that heavy oil that has undergone a hydrogenation process has extremely high hydrogen donating properties and is excellent in promoting the coal liquefaction reaction. That is, FIG. 3 shows the results of a coal liquefaction reaction with varying mixing ratios of heavy oil that has undergone a hydrogenation process and absorption oil that is by-produced in a coke factory and has poor hydrogen donating properties. The rate of increase in liquid yield is steep up to a heavy oil concentration of 30%, but is moderate at higher concentrations. Heavy oil concentration in solvent at steady state is approximately 25%
Therefore, it can be seen that although the hydrogen donating property is slightly insufficient with heavy oil alone, sufficient liquid yield can be obtained by supplementing with a portion of medium oil. Furthermore, according to experiments conducted by the present inventors, in the decomposition reaction of normal paraffin under liquefaction conditions (450°C, 1 hour), the average decomposition rate is about 50% for normal paraffin with a boiling point of 350°C or higher, and In normal paraffin at 350°C, it was about 10%. Therefore, normal paraffin that concentrates in the solvent under liquefaction conditions has a boiling point of 200-350
It is considered to be a normal paraffin with a boiling point of 200~
It was found that by hydrogenolyzing a portion of the 350°C fraction to reduce the amount of normal paraffins, it was possible to prevent the paraffins from inhibiting the liquefaction reaction. For hydrocracking of medium oil, Ni, Co, Mo, W,
A so-called hydrocracking catalyst supporting a metal such as Pt is used. Hydrocracking conditions include reaction temperature of 400℃ or higher, reaction time of 0.5 to 2.0 hours, and hydrogen pressure.
50-200Kg/ ^cm2 is desirable. If the reaction temperature is less than 400°C, decomposition of normal paraffin is difficult to occur. If the reaction time is less than 0.5 hours, sufficient decomposition reaction will not take place, and if it is more than 2 hours, the catalyst activity will be impaired due to concurrent polymerization reaction. In addition, if the hydrogen pressure is less than 50 kg/cm ² , the catalyst is likely to be poisoned;
If it exceeds Kg/cm ² , the cost required for the high-pressure container becomes relatively high. After the light oil content is removed from the medium oil that has undergone the hydrocracking process, it is mixed with the remaining medium oil and heavy oil that have undergone the solvent hydrogenation process, and is used as a solvent for coal liquefaction. In the solvent hydrogenation step of hydrogenating a portion of heavy oil and medium oil, hydrogen is added in an amount of 0.5 to 2.0% by weight per solvent using a hydrogenation catalyst such as Ni-Mo/Al ₂ O ₃ . If it is less than 0.5%, no effect of improving the hydrogen donating property of the solvent will be observed, and if it exceeds 2%, a large amount of expensive hydrogen will be consumed and the hydrogen donating property will be impaired due to excessive hydrogenation. The hydrogenation conditions are preferably a reaction temperature of 300 to 400°C, a reaction time of 0.5 to 2.0 hours, and a hydrogen pressure of 100 to 200 Kg/cm ² . If the reaction temperature is less than 300℃, the solvent will not be hydrogenated sufficiently, and if the reaction temperature exceeds 400℃,
The decomposition reaction of the solvent will proceed more easily, and the dehydrogenation reaction will also occur. Further, if the reaction time is less than 0.5 hours, sufficient hydrogenation reaction will not be carried out, and if the reaction time exceeds 2 hours, excessive hydrogenation will impair the hydrogen donating ability of the solvent. Further, if the hydrogen pressure is less than 100 Kg/cm ² , sufficient hydrogenation cannot be carried out, and if it exceeds 200 Kg/cm ² , the cost required for the high-pressure vessel becomes relatively high. After the light oil is removed from the medium and heavy oils that have undergone this hydrogenation process, they are again recycled to the liquefaction process as a liquefaction solvent together with the medium oil that has undergone the hydrocracking process. Next, the present invention will be explained with reference to examples. (Example) Wandouan coal was used as the liquefaction coal. The elemental analysis values are shown in Table 1. This Wandouan coal was processed using a continuous coal liquefaction unit with a processing capacity of 4/hr, a hydrocracking unit with a processing capacity of 2/hr, and a solvent hydrogenation unit with a processing capacity of 2/hr under the operating conditions shown in Table 2. The material balance when a steady state is reached by repeating liquefaction-hydrogenolysis-solvent hydrogenation is shown in Table 3 as an example. Table 3 shows a case where only liquefaction and solvent hydrogenation were repeated until a steady state was reached as Comparative Example 1. Further, as shown in FIG. 5, the material balance when normal paraffin is removed from heavy oil with a boiling point of 350° C. or higher is shown in Table 3 as Comparative Example 2. In addition, the separation of normal paraffin was performed as follows. At least 3 parts by weight of dimethyl sulfoxide (DMSO) and 1 to 3 parts by weight of cyclohexane are mixed with 1 part by weight of a fraction having a boiling point of 350° C. or higher, stirred, and allowed to stand still. After separating the lower DMSO layer, water is added to collect the fraction with a boiling point of 350°C or higher, which is mainly composed of aromatic compounds. Cyclohexane is recovered from the upper cyclohexane layer by distillation to recover a fraction with a boiling point of 350°C or higher, which is mainly composed of normal paraffin. According to this method, normal paraffin was separated from the fraction with a boiling point of 350°C or higher. From Table 3, in Comparative Example 2 in which normal paraffin was removed from heavy oil, the liquid yield (light oil + medium oil + heavy oil) improved from 48% to 50% due to the removal of normal paraffin. The target product, the yield of light oil, the concentration of normal paraffin in the light oil, and the calorific value of the light oil have been drastically reduced. However, in the case of an example in which a part of medium oil was hydrocracked, the liquid yield was 48%, but the light oil yield, the concentration of normal paraffin in the light oil, and the calorific value of the light oil were large. It has improved drastically. As the concentration of normal paraffin in the light oil increases, the concentration of aromatic compounds, oxygen-containing compounds, nitrogen-containing compounds, and sulfur-containing compounds in the light oil decrease. The reduction in aromatic compounds suppresses the generation of soot during combustion, and the reduction in heteroatom content reduces corrosion caused by liquefied oil, odor, NOx during combustion,
SOx generation is improved. Furthermore, when the normal paraffin contained in the light oil was analyzed, a peak was observed at a carbon chain number of 9, as shown in FIG. Although this light oil has a high octane number as a gasoline for automobiles as it is because it has a large amount of normal paraffin, it is expected that the octane number will be improved by using existing catalytic reforming technology. If this normal paraffin is separated using existing technology,
It can be used as an industrial gasoline, such as mineral spirits, as a paint solvent, etc.

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[Table] (Effects of the Invention) As is clear from the Examples, the present invention improves the liquefied oil yield. Light oil is obtained in high yield. High quality liquefied products are obtained. (High calorific value,
(Low sulfur) Application development will expand to automotive gasoline, industrial gasoline, etc. This invention has the following effects and is extremely useful industrially.

[Brief explanation of drawings]

FIG. 1 is a block diagram illustrating the method of the present invention. Second
The figure shows the relationship between reaction temperature and liquid yield in this method. FIG. 3 is a diagram showing the relationship between hydrogenated heavy oil concentration and liquid yield. FIG. 4 is a diagram showing the analysis results of normal paraffin in the light oil obtained in the example. FIG. 5 is a block diagram showing a conventional method.

Claims (1)

[Claims] 1 In a coal liquefaction method consisting of a coal liquefaction process using a solvent and a solvent hydrogenation process to regenerate the solvent, a part of the fraction with a boiling point of 200 to 350 °C after coal liquefaction is mixed with a fraction with a boiling point of 350 °C or higher, Distillate obtained by hydrogenation to remove light oil with boiling point below 200℃ and boiling point after coal liquefaction
The remainder of the 200-350°C fraction is hydrocracked and a portion of the normal paraffins contained in the fraction is removed as a light oil with a boiling point of less than 200°C, and the fraction is mixed and recycled to coal liquefaction. A method characterized by circulating coal as a solvent for liquefying coal in the process.