JPS61203198A - Liquefaction of coal - Google Patents

Abstract

PURPOSE:To prepare high-quality coal liquefaction products with a good yield consistently in a simple process, by mixing a product of hydrocracking of medium oil obtained by hydrogenation of a solvent fraction after coal liquefaction, with a heavy oil and using the mixt. as solvent for coal liquefaction. CONSTITUTION:A slurry consisting of coal, solvent and catalyst is made to undergo liquefaction reaction at 430-470 deg.C under H2 pressure of 100-200 kg/cm<2> for 0.5-2.0 hr and is distilled to obtain a light oil with a boiling point of below 200 deg.C, a medium oil with a boiling point of 200-350 deg.C and a heavy oil with a boiling point of above 350 deg.C. A mixed solvent consisting of the medi um oil and heavy oil is hydrogenated in the presence of a hydrogenation catalyst such as Ni-Mo/Al2O3 to add 0.5-2.0 wt% H2 to the solvent. The solvent is distilled for separation into light, medium and heavy oils. The medium oil is subjected to hydrocracking at above 400 deg.C under H2 pressure of 50-200 kg/cm<2> for 0.5-2.0 hr to crack n-paraffin and after removal of light oil, medium oil is mixed with the heavy oil after hydrogenation for recycling as solvent for coal liquefaction.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention provides hydrogenation of a liquefied solvent fraction with a boiling point of 2.
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 hydrocracking a 00-350°C fraction.

(Prior Art) A method for liquefying coal 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 ■
~■ is needed.

■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.

(■ In order to accelerate the thermal decomposition of coal and increase the liquid yield, a slightly polar solvent is required.

By the way, coal contains normal paraffin, which is thought to be derived from the wax content of its source plants, and if medium-e heavy oil in liquefied oil is recycled as a liquefaction solvent, it will be difficult to decompose. The normal paraffin gradually becomes thicker.

When normal paraffins are concentrated in the circulating solvent, all of the properties (1) to (3) necessary for a solvent for coal liquefaction are lost.

That is, regarding (■), normal paraffin is an aliphatic compound and has a weak power to dissolve coal.

(Regarding ri, the bond dissociation energy of carbon-hydrogen bonds can be cited as a measure of hydrogen donating property.

Normally, the bond dissociation energy of hydrogen-donating solvents is approximately 82 Kc.
al/mol, but for normal paraffin it is about 90Kca.
There is a difference of about 10 Kcal/so I, and normal paraffins have a property of being difficult to donate hydrogen.

As the normal paraffins become concentrated in the solvent, hydrogen donating properties are 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.

Regarding (2), normal paraffin is non-polar and cannot be expected to promote thermal decomposition.

Therefore, reducing or eliminating normal paraffins from coal liquefaction solvents is an important requirement.

Therefore, the inventors of the present invention first applied for patent application No. 59-195833.
No. 59-221345, boiling point 35
After removing the paraffin-rich fraction from the 0-450°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 paraffins 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, and the above method has a problem in this respect. The above method involves heating or diluting with a fraction with a boiling point of 350° C. or lower to make it liquid, and then separating the normal paraffins.

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 paraffins with a boiling point of 350°C or higher are used in lubricants, paper processing agents, etc., and normal paraffins with a boiling point of 350°C or lower are used as raw materials for solvents and surfactants. The amount used as a raw material for detergents is expected to increase.

In addition, normal paraffin is a lean fuel with a large calorific value, and in liquefied oil products, it is especially suitable for light oil fractions (IBP ~ 200℃).
) is desired to be included in large amounts.

(Object of the Invention) The present invention has been made in view of the above circumstances, and uses relatively simple means to reduce or remove normal paraffins that inhibit coal liquefaction from a liquefaction solvent, thereby reducing the yield of liquefied oil. The purpose is to prevent this and obtain liquefied oil with high product value.

(Structure of the Invention) The gist of the present invention is that after hydrogenating the solvent fraction after liquefaction,
The product obtained by hydrocracking a fraction with a boiling point of 200 to 350°C to reduce the amount of normal paraffins is mixed with a fraction with a boiling point of 350°C or higher, and this mixture is used as a solvent for coal liquefaction.

FIG. 1 is a flow sheet of the present invention.

To explain this using 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 fractionated into light oil (boiling point 200°C or lower), medium oil (boiling point 200-350°C), and heavy oil (boiling point 350°C or higher) in a distillation process. Medium oil and heavy oil are hydrogenated to increase their hydrogen donating ability. This product is again fractionated into light oil, medium oil, and heavy oil. Of these, the medium oil is hydrocracked to reduce normal paraffins, and then mixed with heavy oil and used as a circulating solvent. Use as.

During this time, the light oil fractionated in each process is taken out of the system as a product.

The liquefaction conditions in the liquefaction process are 1 reaction source degree 430~
470℃, reaction time 0.5-2.0 hours, hydrogen pressure 100
~200Kg/crn' is desirable.

As shown in Figure 2, if the temperature per reaction is less than 430°C, the liquefied oil yield, which is the goal of coal liquefaction, will be low, and if it exceeds 470°C, the amount of gas and residue produced will increase and the liquefied oil yield will decrease. At the same time, operational troubles due to kneeing, etc. increase.

In addition, when the hydrogen pressure is less than 100 Kg/ctn', the hydrogenation reaction of the aromatic ring and the decomposition reaction that is associated with the hydrogenation reaction 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. Good.Also, it is desirable to use a sulfur compound as a cocatalyst in the same way as an iron catalyst, at a ratio of 1 to 5 weight 2 based on coal.If the catalyst concentration is less than 1$, there is almost no effect of improving liquid yield by iron-based catalysts. If it exceeds 5z, the catalyst efficiency will deteriorate.

The obtained liquefied product is distilled under normal pressure or reduced pressure to produce light oil with a boiling point of up to 200°C, boiling point between 200 and 350°C.
It is fractionated into medium oil and heavy oil with a boiling point of 350°C or higher. The light oil is taken out of the system as a product.The entire amount of heavy oil and the amount of medium oil necessary to secure the liquefaction solvent are sent to a solvent hydrogenation process.

In the solvent hydrogenation step, 0.5 to 2.0 weight 2 of hydrogen is added per solvent using a hydrogenation catalyst such as Xl-No/A2207. If it is less than 0.5X, no effect of improving the hydrogen donating property of the solvent will be observed, and if it exceeds 2z, a large amount of expensive hydrogen will be consumed and the hydrogen donating property will be impaired due to excessive hydrogenation. The hydrogenation conditions include a reaction temperature of 300 to 400°C and a reaction time of 0.
．． Hydrogen pressure of 100 to 200 kg/c for 5 to 2.0 hours 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 easily proceed, resulting in simultaneous dehydrogenation reactions. No hydrogenation reaction takes place, and if the reaction time exceeds 2 hours, the hydrogen donating ability of the solvent will be impaired due to excessive hydrogenation. Furthermore, if the hydrogen pressure is less than 100 kg/crrr', sufficient hydrogenation cannot be carried out, and if it exceeds 200 kg/cm', the cost required for a high-pressure vessel becomes relatively high. Light oil with boiling point up to 200℃ by atmospheric distillation or vacuum distillation, boiling point 200-350
℃ medium oil, fractionated into heavy oil with a boiling point of 350℃ or higher
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 absorbent oil with poor hydrogen donating properties produced as a by-product in a coke pot. The rate of increase in liquid yield is steep up to a heavy oil concentration of 30 ml, 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 has insufficient hydrogen donating properties.

The inventors further hydrocracked the medium oil after hydrogenation, and the medium oil from which the light oil was removed still had hydrogen donating properties, although it was slightly inferior to the medium oil after hydrogenation. I found out that there is. This medium oil after hydrocracking is in a solvent at a steady state of 75%
1 and occupies the majority of the solvent, so when mixed with the heavy oil that has excellent hydrogen donating properties,
It has been found that the liquid yield can be brought into a region where the liquid yield increases moderately when the heavy oil concentration is 30% or more.

Moreover, according to this method, light oil is produced in three steps: liquefaction, hydrogenation, and hydrocracking, and the proportion of light oil in the product increases significantly.

Furthermore, the medium oil that has undergone the hydrogenation process contains more hydrogenated aromatic ring compounds compared to the medium oil that has undergone the liquefaction process.
It is effective in improving the yield of light oil by hydrocracking and preventing coking in the hydrocracking 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 paraffins under liquefaction conditions (450°C, 1 h), and the average decomposition rate of normal paraffins with a boiling point of 350°C or higher was about 5 oz.

The average decomposition rate of normal paraffins with a boiling point of 350℃ or less is approximately 10
It was found that the normal paraffin that thickens in 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 involves hydrocracking a fraction to decompose normal paraffins and produce light oil.

In the hydrocracking process, a so-called hydrocracking catalyst is used in which a metal such as Go, Go, Ni, W, or Pt is supported on a carrier such as zeolite, silica gel, or alumina. Hydrocracking conditions include 1 reaction temperature of 400°C or higher;
Reaction time 0.5-2.0 hours, hydrogen pressure 50-200Kg
/ crn” is desirable at a reaction temperature of less than 400°C.
Normal paraffin is difficult to decompose and has a low light oil yield. Also, if the reaction time is less than 0.5 hours, sufficient decomposition reaction is difficult to occur, and if it exceeds 2 hours, polymerization reaction etc. occur simultaneously.
The catalyst tends to deteriorate, and the hydrogen donating ability of the produced medium oil is impaired. Furthermore, hydrogen pressure 50Kg/crn
If the pressure is less than 200 kg/cm, the polymerization reaction tends to proceed easily and the catalyst is likely to be poisoned. If the pressure exceeds 200 kg/cm, the cost required for the high-pressure vessel becomes relatively high.

From the hydrogenated medium oil that has undergone this hydrocracking process, light oil with a boiling point of 200° C. or lower is removed by atmospheric distillation.

The fraction with a boiling point of 200° C. or higher is recycled and used as a liquefaction solvent together with the above-mentioned hydrogenated heavy oil.

Next, the present invention will be explained by examples.

(Example) Wandouan coal was used as the liquefaction coal. The elemental analysis values are shown in Table 1.

This Wandoan charcoal is 4! Using a coal liquefaction equipment with a processing capacity of J,/hr, a solvent hydrogenation equipment with a capacity of 2 har, and a hydrocracking unit with a processing capacity of 21 hr, the operating conditions shown in Table 2 are carried out. The material balance when liquefaction-solvent hydrogenation-hydrogenolysis is repeated and a steady state is reached is shown in Table 3 as an example.The material balance when only liquefaction-solvent hydrogenation is repeated is shown in Table 3 as a comparative example. In addition, as shown in FIG. 5, the material balance in the case of repeating liquefaction, solvent hydrogenation, and separation of normal paraffin from heavy oil is also shown in Table 3 as Comparative Example 2.

As is clear from Table 3, when normal paraffins are separated from heavy oil (Comparative Example 2), the liquefied oil yield (light oil +
The light oil yield, which is the target of the coal liquefaction process, will decrease, although the medium-quality yuzu heavy oil) will increase.

In addition, the concentration of normal paraffin contained in the product light oil,
The calorific value of light oil has also decreased significantly.

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 #, the light oil yield, The concentration of normal paraffin and calorific value are greatly 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 reduces corrosion caused by liquefied oil, odor, and NO during combustion.
x, SOx generation is improved. Furthermore, when we analyzed the normal paraffins contained in light oil, we found that
As shown in the figure, it was observed that there was a peak at the number of carbon chains of 9.

Since this light oil has a high content of positive paraffins, it becomes automobile gasoline with a low octane number as it is, but it is expected that the octane number can be improved by existing catalytic reforming technology. ``If this normal paraffin is separated using existing technology, it can be used as an industrial gasoline, such as mineral spirit, as a paint solvent.

Table 2 (Effects of the Invention) As is clear from the Examples, according to the present invention (1) the liquefied oil yield is improved.

■Light oil can be obtained in high yield.

(■High quality products can be 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 Description of the Drawings] Figure 1 is a block diagram showing the method of the present invention, Figure 2 is a diagram showing the relationship between reaction temperature and liquid yield in this method, and Figure 3 is a diagram showing the relationship between hydrogenated heavy oil concentration and FIG. 4 is a diagram showing the relationship between liquid yields, FIG. 4 is a diagram showing the analysis results of normal paraffins in light oil obtained in Examples, and FIG. 5 is a block diagram showing the conventional method.

Claims (1)

[Claims] After hydrogenating the solvent fraction after liquefaction, the boiling point is 200-35
A method for liquefying coal, which comprises mixing a product obtained by hydrocracking a 0°C fraction to reduce normal paraffins and a fraction with a boiling point of 350°C or higher, and using this mixture as a solvent for coal liquefaction. .