JPH0367552B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention improves the stable operation of the coal liquefaction process by hydrogenating the fraction with a boiling point of 200°C or higher after liquefaction, and then hydrocracking the boiling point fraction of 200 to 350°C. , Concerning a coal liquefaction method to obtain high quality, high yield liquefied oil products. (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 is provided for using a paraffin-poor fraction as part of a liquefaction solvent. (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° C. or less to make it liquid, 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. That is, normal paraffin with a boiling point of 350°C or higher is used as a lubricant, paper processing agent, etc., and normal paraffin with a boiling point of 350°C or lower is used as a raw material for solvents and surfactants.
It is expected that its usage will increase in the future as a raw material for soft detergents or higher alcohol 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). (Objective of the Invention) The present invention has been made in view of the above-mentioned circumstances, and uses relatively simple means to reduce or remove normal paraffin, which inhibits coal liquefaction, from a liquefaction solvent, thereby increasing the liquefied oil yield. The purpose is to prevent deterioration and obtain liquefied oil with high product value. (Structure of the Invention) The gist of the present invention is to hydrogenate a fraction with a boiling point of 200°C or higher after liquefaction, and then to hydrogenate a fraction with a boiling point of 200°C or higher obtained by hydrocracking the fraction with a boiling point of 200 to 350°C; The point is to mix the added fraction with a distillate with a boiling point of 350°C or higher and use this mixture as a solvent for coal liquefaction. FIG. 1 is a flow sheet of the present invention. Describing the present invention with reference to the drawings, a slurry containing coal, a solvent, and a catalyst undergoes a coal liquefaction reaction in a liquefaction process. The products after the reaction are liquefied light oil (boiling point below 200℃) and liquefied medium oil (boiling point 200℃ or less) in the distillation process.
~350℃) and liquefied heavy oil (boiling point 350℃ or higher). The liquefied medium oil and liquefied heavy oil are then hydrogenated to increase their hydrogen donating ability. This product is again fractionated into hydrogenated light oil, hydrogenated medium oil, and hydrogenated heavy oil. Of these, the hydrogenated medium oil is hydrocracked to remove a portion of the normal paraffin as light oil. After that, it is mixed with hydrogenated heavy oil and used as a liquefaction solvent. During this time, the light oil fractionated in each process is taken out of the system as a product. Note that the distillation cut temperature in the hydrogenation step is the same as in the liquefaction system. The liquefaction conditions in the liquefaction process include the reaction temperature
430-470℃, reaction time 0.5-2.0 hours, hydrogen pressure 100
~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 at atmospheric pressure or under reduced pressure to produce liquefied light oil with a boiling point of up to 200℃,
It is fractionated into liquefied medium oil with a boiling point of ~350℃ and liquefied heavy oil with a boiling point of 350℃ or higher. Light oil is taken out of the system as a product. The amount of medium oil necessary to secure the entire amount of heavy oil and the solvent for liquefaction is sent to a solvent hydrogenation process. In the solvent hydrogenation step, 0.5 to 2.0% by weight of hydrogen is added to the 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. As hydrogenation conditions, the reaction temperature is 300
~400℃, reaction time 0.5~2.0 hours, hydrogen pressure 100~
200Kg/cm ² is desirable. If the reaction temperature is less than 300°C, the solvent will not be sufficiently hydrogenated, and if it exceeds 400°C, the decomposition reaction of the solvent will tend to proceed and a 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 it exceeds 2 hours, the hydrogen donating property of the solvent will be impaired due to excessive hydrogenation. 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. The medium and heavy oils that have gone through the above solvent hydrogenation process are again distilled at normal pressure and under reduced pressure to produce hydrogenated light oil with a boiling point of up to 200℃, hydrogenated medium oil with a boiling point of 200 to 350℃, and water with a boiling point of 350℃ or higher. Fractionated into added heavy oil. The present inventors have discovered that heavy oil that has undergone a solvent hydrogenation process has an extremely high hydrogen donating property compared to medium oil, and has an excellent effect of promoting the liquefaction reaction of coal. Figure 3 shows the results of a coal liquefaction reaction by varying the mixing ratio of hydrogenated heavy oil and absorption oil with poor hydrogen-donating properties produced as a by-product in a coke factory. The rate of increase in liquid yield is steep up to a heavy oil concentration of 30%, but is moderate at higher concentrations. Since the concentration of heavy oil in the solvent in a steady state is about 25%, heavy oil alone is insufficient for hydrogen donating properties. The inventors further hydrocracked the hydrogenated medium oil to remove the light oil, and found that the medium oil still had hydrogen-donating properties, although it was slightly inferior to the hydrogenated medium oil. I found out that This medium oil after hydrocracking contains 75% in the solvent in a steady state, making up the majority of the solvent, so by mixing it with the heavy oil that has excellent hydrogen donating properties mentioned above, It was found that when the heavy oil concentration exceeds 30%, the liquid yield can be brought into the region where it moderately increases. Moreover, according to this method, light oil is processed through the liquefaction process.
Produced in 3 steps: hydrogenation step, hydrocracking step,
The proportion of light oil in the product will increase significantly. Furthermore, since the medium oil that has undergone the hydrogenation process contains more hydrogenated aromatic ring compounds than the medium oil that has undergone the liquefaction process, it is possible to improve the yield of light oil by hydrocracking and improve the yield of light oil by hydrocracking. Effective in preventing caulking in the process. It is known that hydrogenated aromatic ring compounds have better hydrogen donating properties than aromatic ring compounds and are easily thermally decomposed. In addition, the inventors conducted a decomposition reaction of normal paraffin under liquefaction conditions (450°C, 1 h), and found that the average decomposition rate of normal paraffin with a boiling point of 350°C or higher was approximately 50%.
The average decomposition rate of normal paraffin with a boiling point of 350℃ or less is approximately
10%, it was found that the normal paraffin that thickens during the liquefaction process is a normal paraffin with a boiling point of 350°C or lower. Based on these findings, the boiling point after hydrogenation is 200-350.
The present invention is accomplished by further hydrocracking the °C fraction to decompose normal paraffins and produce light oil. In the hydrocracking process, Ni, Co, Mo, W,
A so-called hydrocracking catalyst on which a metal such as Pt is supported 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. At reaction temperatures below 400°C, normal paraffin is difficult to decompose and the yield of light oil is low. Further, if the reaction time is less than 0.5 hours, sufficient decomposition reaction is difficult to occur, and if it exceeds 2 hours, the catalyst is likely to deteriorate due to concurrent polymerization reactions, etc., and the hydrogen donating property of the produced medium oil is impaired. Furthermore, if the hydrogen pressure is less than 50 kg/cm ² , the polymerization reaction will proceed more easily and the catalyst will be more likely to be poisoned.
If it exceeds Kg/cm ² , the cost required for the high-pressure container becomes relatively high. From the hydrogenated medium oil that has undergone this hydrocracking process, light oil containing the decomposition products of normal paraffins with a boiling point of 200°C or lower is removed by atmospheric distillation, and the fraction with a boiling point of 200°C or higher is removed after the hydrogenation process described above. It is recycled and used as a liquefaction solvent together with heavy oil. 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 coal liquefaction unit with a processing capacity of 4/hr, a solvent hydrogenation unit with a processing capacity of 2/hr, and a hydrocracking unit with a processing capacity of 2/hr, as shown in Table 2. Table 3 shows the material balance when a steady state is reached by repeating liquefaction-solvent hydrogenation-hydrogenolysis under operating conditions as an example. Comparative Example 1 shows the material balance when only liquefaction-solvent hydrogenation is repeated, and the material balance when liquefaction-solvent hydrogenation-separation of normal paraffin from heavy oil is repeated as shown in Figure 5. The income and expenditure are also listed in Table 3 as Comparative Example 2. Note that the separation of normal paraffin was performed as follows. At least 3 parts by weight of dimethyl sulfoxide (DMSO) per 1 part by weight of the fraction with a boiling point of 350°C or higher.
After mixing and stirring 1 to 3 parts by weight of cyclohexane, the mixture is 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. From the upper cyclohexane layer, cyclohexane is recovered by distillation, and a fraction with a boiling point of 350°C or higher containing normal paraffin as a main component is recovered. According to this method, normal paraffin was separated from the fraction with a boiling point of 350°C or higher. As is clear from Table 3, when normal paraffin is separated from heavy oil (Comparative Example 2), the liquefied oil yield (light oil + medium oil + heavy oil) increases, but the coal liquefaction process The purpose is Light oil yield decreases. In addition, the concentration of normal paraffin contained in the light oil product and the calorific value of the light oil have also been significantly reduced. However, in the case of the example in which hydrogenated medium oil is hydrocracked, the liquefied oil yield increases as in the case of separating normal paraffins from heavy oil, and in particular, the light oil yield and normal paraffin increase. The paraffin concentration and calorific value have significantly improved. As the concentration of normal paraffin contained in light oil increases, the concentration of aromatic compounds, nitrogen-containing compounds, sulfur-containing compounds, and oxygen-containing compounds decrease. The reduction in the concentration of aromatic compounds suppresses the generation of soot during combustion, and the reduction in the concentration of heteroatom-containing compounds improves corrosion caused by liquefied oil, odor, and the generation of NOx and SOx during combustion. Furthermore, when normal paraffin contained in the light oil was analyzed, it was found that it had a peak at carbon chain number 9, as shown in FIG. This light oil has a high content of normal paraffin, so
As it is, it will be a gasoline for automobiles with a low octane number, but it is expected that the octane number will be improved by known catalytic reforming technology. If this normal paraffin is separated using existing techniques, it can be used as industrial gasoline, for example, mineral spirits, and as paint solvents.

【table】

【table】

【table】

[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 products are obtained (high calorific value, low sulfur). Applications are being developed to include automobile 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 that consists of a coal liquefaction process using a solvent and a solvent hydrogenation process that regenerates the solvent, the fraction with a boiling point of 200 to 350°C after solvent hydrogenation is further hydrocracked to reduce the amount contained in that fraction. A part of the normal paraffin that had been removed is removed as a light oil with a boiling point of less than 200℃, and the fraction with a boiling point of 350℃ or more after solvent hydrogenation is mixed and recycled to the coal liquefaction process as a coal liquefaction solvent. A method characterized by: