JPS61203197A - Liquefaction of coal - Google Patents

Abstract

PURPOSE:To prepare high-quality coal liquefaction products with a good yield consistently in a simple process, by using as solvent for coal liquefaction a mixt. of a product obtained by hydrocracking of a part of medium oil in coal liquefaction oil, a remainder of the medium oil and a hydrogenation product of heavy oil. 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. The light oil is taken out of the system as final product and a part of medium oil is subjected to hydrocracking at above 400 deg.C under H2 pressure of 50-200kg/cm<2> for 0.5-2.0 hr in the presence of a catalyst for hydrocracking to reduce the n-paraffin content and remove the light oil and is used as solvent for coal liquefaction. Then a mixed solvent consisting of the remainder of the medium oil and the heavy oil is hydrogenated at 300-400 deg.C under H2 pressure of 100-200 kg/cm<2> fro 0.5 to 2.0 hr in the presence of a hydrogenation catalyst such as Ni-Mo/Al2O3 to add 0.5-2.0 wt% H2 to the mixed solvent and the resulting product is also used as solvent for coal liquefaction.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention involves fractionating liquefied oil produced when coal is liquefied, and hydrocracking a portion of the fraction with a boiling point of 200 to 350°C. 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 reducing the amount of normal paraffins in the 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.

(■ Suppresses recombination or polymerization of coal that is easily decomposed,
In order to increase the liquid yield, a solvent with high hydrogen donating properties is required.

<φ 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 paraffins, which are thought to originate from the wax content of its source plants, and if medium-diameter heavy oil in liquefied oil is recycled as a liquefaction solvent, it is 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 (2), the bond dissociation energy of carbon-hydrogen bonds is cited as a guideline for hydrogen donating property, and the bond dissociation energy of normal hydrogen donating solvents is about 82 Kcal/mol, but for normal paraffin it is about 90 Kcal/mol. ,
There is a difference of about 10 Kcal/+sol, and normal paraffins have a property of being difficult to donate hydrogen. As the normal paraffin becomes 1 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 heating agent 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 tree 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. Normal paraffins with a boiling point of 350°C or lower are used as raw materials for solvents and surfactants, and in the future will be used as soft detergents or higher alcohols. 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.

(Objective of the Invention) The present invention has been made in view of the above circumstances, and it is possible to recover liquefied oil by reducing normal paraffins, which inhibit the liquefaction of coal, from a part of medium oil by hydrocracking using 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, and in particular to
A product obtained by hydrocracking a part of the ~350°C fraction (medium oil) to reduce normal paraffins, and a product with a boiling point of 200~350°C
The remainder of the fraction and the fraction with a boiling point of 350° C. or higher are mixed with a product obtained by hydrogenation, and this mixture is used as a circulating solvent. FIG. 1 is a flow sheet of the present invention.The present invention will be explained with reference to the drawings.2 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) fractions in a distillation process. Among these fractions, a product obtained by hydrocracking a portion of medium oil to reduce normal paraffins and a product obtained by hydrogenating the remainder of medium oil and heavy oil are mixed. Then, this mixture is recycled as a liquefaction solvent. The medium oil and the heavy oil may be used by appropriately mixing all or part of them as necessary.

The liquefaction conditions in the liquefaction step include a reaction temperature of 430~
470°C, reaction time 0.5-2.0 hours, hydrogen pressure 100
~200Kg/ctn' is desirable.

As shown in Figure 2, if the reaction temperature is less than 430°C, the liquefied oil yield aimed at by coal liquefaction will be low, and if it exceeds 470°C, the amount of gas and residual liquid produced will increase and the liquefied oil yield will decrease. At the same time, operational troubles due to caulking, etc. increase.

Furthermore, if the hydrogen pressure is less than 100 kg/cm'', the hydrogenation reaction of the aromatic ring and the decomposition reaction following the hydrogenation reaction will be difficult to occur, resulting in a decrease in liquid yield.On the other hand, if the hydrogen pressure is higher than necessary, expensive hydrogen As the consumption of pressure increases, 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 parts by weight per coal. In addition, it is desirable to use a sulfur compound as a cocatalyst in a ratio of 1 to 5 weight 2 based on coal, similar to the iron catalyst.If the catalyst concentration is less than 1, the iron-based catalyst has little effect on improving the liquid yield, and 5z If it exceeds this, the catalyst efficiency will deteriorate.

The obtained liquefied product is fractionated by atmospheric distillation or vacuum distillation into light oil with a boiling point of up to 200°C, medium oil with a boiling point of 200 to 350°C, and heavy oil with a boiling point of 350°C 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 highly effective in promoting the coal liquefaction reaction. .

That is, FIG. 3 shows the results of a coal liquefaction reaction by changing the mixing ratio of heavy oil that has undergone a hydrogenation process and absorption oil that is a by-product in a coke factory and has poor hydrogen donating properties. The rate of increase in liquid yield is steep up to 30% heavy oil concentration, but is moderate at higher concentrations.

Since the concentration of heavy oil in the solvent in a steady state is approximately 252, the hydrogen donating property is somewhat insufficient with just one heavy oil, but sufficient liquid yield can be obtained by replenishing some of the medium oil. I know that it will happen.

Furthermore, according to the experiments of the present inventors, under liquefaction conditions (450
℃, 1 hour), the average decomposition rate of normal paraffins with a boiling point of 350℃ or higher is about 502℃.
It was about 10% in the case of pure grain rough-in with a boiling point of 200 to 350°C. Therefore, it is thought that the normal paraffins that concentrate in the solvent under liquefaction conditions are normal paraffins with a boiling point of 200 to 350°C. It was found that the inhibition of normal paraffin on the reaction could be prevented.

For the hydrocracking of medium oil, a so-called hydrocracking catalyst is used, in which a metal such as Ni, Go, No, W, or ρ is supported on a carrier such as zeolite, silica gel, or alumina. Hydrocracking conditions include reaction temperature of 400°C or higher, reaction time of 0.5 to 2.0 #, and hydrogen pressure of 50 to 200 K.
g/c go is preferable.

- If the reaction temperature is less than 400°C, decomposition of normal paraffins 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/am'', the catalyst is likely to be poisoned, and if it exceeds 200 kg/crn', the cost required for a high-pressure vessel becomes relatively high.The medium oil that has undergone this hydrocracking process has light oil components removed. After that, it is mixed with the remaining medium oil and heavy oil that went through the solvent hydrogenation process to form 1
Used as a solvent for coal liquefaction.

Part of heavy oil and medium oil is hydrogenated. In the solvent hydrogenation step, hydrogen is added in an amount of 0.5 to 2.0 weight 2 per solvent using a hydrogenation catalyst such as old-No/A 12 07, for example.

If it is less than 0.5z, 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, a reaction time of 0.5 to 2.0 hours, and a hydrogen pressure of 100 to 200 kg/
If am' is less than 300° C., the solvent will not be sufficiently hydrogenated, and if the reaction temperature exceeds 400° C., the decomposition reaction of the solvent will tend to proceed, 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. Furthermore, if the hydrogen pressure is less than 100 kg/crn', sufficient hydrogenation cannot be carried out, and if it exceeds 200 kg/cm', the cost required for a high-pressure vessel becomes relatively high.The medium and heavy oils that have undergone this hydrogenation process are converted into light oils. After removing the oil, it is recycled to the liquefaction process as a liquefaction solvent together with the medium oil that has passed through the hydrocracking process.

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.

A continuous coal liquefaction unit with a processing capacity of 4fL/hr for this Wandouan coal, a hydrocracking unit with a processing capacity of 2 cycles/hr, 29. Liquefaction-hydrocracking- under the operating conditions shown in Table 2 using a solvent hydrogenation equipment with a processing capacity of /hr.
The material balance when the solvent hydrogenation is repeated and a steady state is reached is shown in Table 3 as an example.Table 3 shows the case where only liquefaction-solvent hydrogenation is repeated and a steady state is reached as a comparative example 1. .

Further, as shown in FIG. 5, the material balance when normal paraffin is removed from heavy oil having a boiling point of 350° C. or higher is shown in Table 3 as Comparative Example 2.

From Table 3, in Comparative Example 2 in which normal paraffin was removed from 1 heavy oil, the liquid yield (light oil + medium yuzu heavy oil) improved from 481 to 501 by removing normal paraffin, but the target product was A certain light oil yield, normal paraffin concentration in the light oil,
The calorific value of light oil has been drastically reduced.

However, in the case of the 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 normal paraffin concentration in the light oil increases, the aromatic compound concentration, oxygen-containing compound concentration, nitrogen-containing compound concentration, and sulfur-containing compound concentration 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, and SO! occurrence is improved.

Further, when the normal paraffin contained in the light oil was analyzed, a peak was observed at a carbon chain number of 8, as shown in FIG. This light oil has a large amount of normal paraffins, so its octane number is low for use as automotive gasoline. However, it is expected that the octane number will improve using existing catalytic reforming technology. It can be used as a paint solvent, for example, as a mineral spirit.

(Effects of the Invention) As is clear from the examples, according to the present invention, (1) the liquefied oil yield is improved;

(Phi light oil can be obtained in high yield.

■High quality liquefied products can be obtained. (High calorific value, low sulfur) ■ Application development is expanding to automobile gasoline, industrial gasoline, etc.

This invention has the following effects and is extremely useful industrially.

[Brief explanation of 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 liquid yield. 4 is a diagram showing the analysis results of normal paraffins in the light oil obtained in the example, and FIG. 5 is a block diagram showing the conventional method.

Claims (1)

[Claims] A product obtained by hydrocracking a part of the fraction with a boiling point of 200 to 350 °C in coal liquefied oil to reduce normal paraffins, the remainder of the fraction with a boiling point of 200 to 350 °C, and a fraction with a boiling point of 350 °C or higher. A method for liquefying coal, which comprises mixing a product obtained by hydrogenating and using this mixture as a solvent for coal liquefaction.