AU696287B2 - Process of coal liquefaction - Google Patents

Description

RogtulatAoli) 3.2

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

SName of Applicant: NIPPON BROWN COAL LIQUEFACTION CO., LTD.

Actual Inventor(s): Kenji Uesugi; Kazuharu Tazawa; Takao Kaneko; and Masaaki Tamura method of performing it known to me:method of performing it known to me:- -1- I

I,

PROCESS OF COAL LIQUEFACTION BACKGROUND OF THE INVENTION This invention relates to a process for coal liquefaction and more particularly, to a process Lor coal liquefaction including the hydrogenation step of hydrogenating coal in the presence of solvent and catalyst.

The recent resources and energy situation urgently require the development of a liquid fuel as a substitute for petroleum. In view of abundant coal reserves, it is important to establish techniques of efficiently liquefying coal to obtain a liquid fuel.

There have been proposed a variety of processes for coal liquefaction. A typical process of coal •liquefaction includes mixing dry pulverized coal with a solvent to give a slurry mixture, adding hydrogen gas to the mixture, rapidly heating in a preheater, and performing hydrogenation under high temperature and high pressure conditions. For the improveiment in yield of liquefied oil, there is mentioned a process wherein the oeo dissolution (or conversion into low molecular weight fractions) of coal is initially promoted by a procedure *of keeping at a low temperature or a procedure of I-I- -C--l gradually heating from low temperature, followed by hydrogenation at high temperature.

Relatively low coalification coal such as brown coal is very reactive and its thermal decomposition starts with the decomposition of oxygen-containing functional groups in the vicinity of 200 0 C. The thermal decomposition becomes relatively violent from 250 0 C and then violent from about 350 0 C along with the generation of carbon monoxide and hydrocarbon gases, and thermally decomposed radicals generate considerably from the coal, and the concentration of the radicals in the coal increases rapidly. By the term the concentration of radicals in coal" is meant a concentration of radicals generating from coal in the course of the thermal i decomposition of coal (hereinafter referred to thermal deicomposition radicals of coal).

In the prior art processes of coal liquefaction, it is difficult to adequately add hydrogen to (or to hydrogenate) the thermal decomposition radicals of coal in a temperature range of 250 0 C, at which the thermal decomposition of coal becomes relatively violent, to 400 0 C. Therefore, the mutual recombination of the thermal decomposition radicals of coal takes place, causing the coal (starting coal) to be polycondensed.

_F 11__1_ -3- Ultimately, a coke-like heavy material which is difficult to decompose with hydrogen (hydrogenate) even at h'nigh temperatures is formed.

Eventually, the reactivity for liquefaction of coal lowers. While the heavy material is formed, the yield of gaseous components such as methane increases. Thus, the yield of the intended liquefied oil lowers. The hydrogen gas added for the hydrogenation is consumed for the formation of gases from coal and is not effectively utilized for the formation of liquefied oil. This leads to the rise of the production cost of liquefied oil.

The present invention was accomplished in view of the foregoing. It is an object of the present invention to provide a piucess for coal liquefaction which is able to reduce the consumption of hydrogen gas and wherein fiquefied oil can be obtained in high yield over the prior art processes of coal liquefaction .:o.oi by suppressing undesirable reactions derived from the thermal decomposition of S coal.

:l tI In order to achieve the above object, the present invention provides in a broad embodiment a process for coal liquefaction which comprises the step ol of hydrogenation of coal in the presence of solvent and catalyst, characterised in that an iron containing compound capable of conversion into pyrrhotite at a S temperature of not higher than 250C is used as the catalyst, and the coal is 0o 0: subjected to low temperature hydrogenation at a temperature ranging 250- 400 0 C and then to high temperature hydrogenation at a temperature higher than in the low temperature hydrogenation.

In accordance with a first embodiment of the invention there is _21 IO7198L'9242. PGS.3 s IP _II_ -4provided a process for coal liquefaction as set out in the preceding paragraph, wherein prior to the high temperature hydrogenation, part of the solvent i:, separated from the mixture of coal, solvent and catalyst resulting from the low temperature hydrogenation step, such that the concentration of coal in the mixture subjected to the high temperature hydrogenation is from 40 to percent by weight of the mixture.

In accordance with a preferred embodiment of the invention the iron containing compound catalyst is composed mainly of iron hydroxide.

In a further preferred embodiment of the invention the coal is brown coal.

0 0 I O1/7;98LP9242.PGS,4 BhIEF DESCRIPTION OF THE DRAWING Fig. 1 is a schematic view showing an example of a process for coal liquefaction according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention pertains to a process for coal liquefaction, which is carried out in the following manner.

A solvent is added to coal, to which an iron compound capable of conversion into pyrrhotite at a temperature of not higher than 250 0 C is further added as a catalyst to obtain a slurry mixture. Hydrogen is added to the slurry mixture wherein low temperature hydrogenation is effected at a temperature, TI, of 250 400°C, followed by high temperature hydrogenation at a temperature, T 2 which is higler khan the temperature, TI, in the low temperature hyl. ,ena4'on. The temperature, T2, for the hLgh emp. *'-ure hydrogenation is one at which the hydrogenation takes place satisfactorily, and is usually in the range of 400 500 0 C. These hydrogenation temperatures are, respectively, selected properly. For instance, the low temperature hydrogenation temperature, TI, is set at I

II

350 0 C and the high temperature hydrogenation temperature, T2, is set at 450 0

C.

In doing so, the undesirable reactions derived from the thermal decomposition of coal can be suppressed, resulting in the reduction in consumption of hydrogen gas over the case using the known processes of coal liquefaction, with a higher yield of liquefied oil.

More particularly, since an iron compound capable of conversion into pyrrhotite at a temperature not higher than 250°C is added as a catalyst, the added iron compound is converted to pyrrhotite at a temperature not higher than 250 0 C. As a result, the catalyst is present as pyrrhotite at the stage of the low temperature hydrogenation at a temperature, T 1 (250 400 0 When the catalyst is present as pyrrhotite, hydrogen can be sufficiently supplied to the thermal decomposition radicals of coal, also in the temperature range of 250 0 C at which the thermal decomposition of coal becomes relatively violent to 400°C. This means that in the stage of the low temperature hydrogenation using the temperature, T 1 (250 400°C), the thermal decomposition radicals of coal is sufficiently supplied with hydrogen.

a a -6- I- Thus, the mutual recombination of the thermal decomposition radicals of coal is suppressed. This, in turn, suppresses the de-hydrogenation and the polycondensation reaction of coal, resulting in supressing the formation of coke-like heavy material which is difficult to decompose with hydrogen (hydrogenate) even at high temperatures.

After completion of the low temperature hydrogenation, the high temperature hydrogenation is performed at a temperature, T 2 higher than the temperature, TI, in the low temperature hydrogenation.

Therefore, in this stage of the high temperature hydrogenation, the decomposition with hydrogen (hydrogenation) smoothly proceeds, so that the hydrogen gas is effectively utilized for the formation of liquefied oil.

The consumption of hydrogen gas can be reduced, and liquefied oil can be obtained in high yield on comparison with conventional processes of coal liquefaction.

As will be apparent from the embodiments of the invention, the undesirable reactions derived from the thermal decomposition of coal can be suppressed according to the coal liquefaction process of the s

S

S.

*i 5*55 Si S S -7-

L-

invention. This enables the reduction in consumption of hydrogen gas and the liquefied oil can be obtained in high yield over the case using conventional processes of coal liquefaction.

The invention is described in more detail.

We have made intensive studies on the thermal decomposition behavior of coal, the behavior of the radicals formed through the thermal decomposition, and the stabilization of the thermal decomposition radicals with hydrogen, As a result, it has been found that the thermal decomposition of coal starts from about 200 0

C,

and becomes relatively violent from 250 0 C, especially violent at about 350 0 C or higher, at which the concentration of the thermal decomposition radicals of I coal sharply increases. When using, as a catalyst, a catalyst which exists as pyrrhotite at 250 0 C or above, it is possible to effectively add hydrogen sufficient for reaction with the thermal decomposition radicals of coal, also in the temperature range of 250 4000C.

,ooQ Thus, the thermal decomposition radicals of coal at temperatures ranging 250 4000C can be suppressed from a. mutual recombination.

This, in turn, suppresses the occurrence of undesirable reactions such as de-hydrogenation reaction 4**o -8-

I

and polycondensation reaction of coal. Therefore, the formation of polycondensates which are poor in reactivity is suppressed, e.g. coke-like heavy material which is difficult to decompose through hydrogenation (hydrogenate), also at high temperatures is not formed.

This leads to the reduction in amount of hydrocarbon gases being produced in the course of hydrogenation at high temperatures and allows the hydrogenation to proceed smoothly. Hydrogen gas is effectively used for the production of liquefied oil, with reducing consumption of hydrogen gas. In addition, the useful liquefied oil can be obtained in high yield.

The invention has been accomplished based on the above finding. More particularly, the process of coal liquefaction according to the invention (first invention) comprises, as defined before, the hydrogenation step of hydrogenating coal in the presence •:00 of solvent and catalyst, characterized in that an iron compound capable of conversion into pyrrhotite at a :00.0.

temperature of not higher than 250 0 C is used as the catalyst, and the coal is subjected to low temperature hydrogenation at a temperature of 250 4000C and then to high temperature hydrogenation at a temperature •higher than in the low temperature hydrogenation.

-9- Therefore, accoding to this coal liquefaction process of the invention, undesirable reactions derived from the thermal decomposition of coal can be suppressed. As a result, the consumption of hydrogen gas can be reduced, with the liquefied oil being obtained in high yield over the case using the conventional processes of coal liquefaction as having set out before.

In the practice of the invention, the low temperature hydrogenation should be effected at a temperature of 250 400 0 C. In other words, the temperature for the low temperature hydrogenation should be in the range of 250 400 0 C. The reason for this is described below.

Where the temperature for the low temperature hydrogenation is lower than 250 0 C, the thermal decomposition of coal proceeds very gently. Therefore, the concentration of the resultant thermal decomposition radicals is low, so that hydrogen can be satisfactorily supplied by transfer of hydrogen in the coal itself. No .fl, polycondensate is produced. More particularly, since the amount of hydrogen necessary for the stabilization of the thermal decomposition radicals is very small within a temperature range lower than 250 0 C, it is not necessary to supply hydrogen through the low temperature hydrogenation. In this temperature range, even if the low temperature hydrogenation is carried out, little effect of the hydrogenation can be expected. On the other hand, the thermal decomposition of coal becomes too vivlent at temperatures higher than 400 0 C, and the concentration of the thermal decomposition radicals of coal increases sharply. Therefore, hydrogen is in short supply to the thermal decomposition radicals of coal and becomes insufficient for stabilization of the thermal decomposition radicals. The consumption of hydrogen gas cannot be reduced, and a high yield of liquefied oil cannot be attained. Accordingly, the temperature should be in the range of 250 400 0 C within which the formation rate of the thermal decomposition radicals of coal and the hydrogen supply rate against the thermal decomposition radicals of coal are well balanced. In the temperature range of 250 400 0 C, the hydrogen is satisfactorily supplied to the thermal decomposition radicals of coal and the formation of heavy material through the recombination of the thermal decomposition radicals of coal is suppressed.

The low temperature hydrogenation time is appropriately in thm range of about 10 60 minutes. A higher treating temperature results in a shorter time.

j6 -11- The treatment at 350 0 C for about 30 minutes is preferably used.

The catalyst plays an important role in the practice of the invention as defined before. The iron compound added for use as a catalyst should be converted to pyrrhotite at a temperature of 250 0 C or below.

The reason why the temperature at which thb iron compound is converted to pyrrhotite is defined at 250 0

C

or below is as follows. The thermal decomposition of coal starts to take place relatively violent from 250'C.

If the conversion temperature of an iron compound to pyrrhotite is higher than 250 0 C, hydrogen cannot be sufficiently supplied to the thermal decomposition radicals generated between 250 0 C and the conversion temperature, resulting in the formation of polycondensates. Therefore, even when the temperature of the low temperature hydrogenation is high, the temperature of conversion of an iron compound to pyrrhotite should be 250 0 C or below.

The iron compounds capable of conversion to pyrrhotite at 250 0 C or below can be checked and confirmed in the following manner.

More particularly, in general, iron compounds are readily sulfided with sulfur or sulfur compounds and -12converted to iron sulfide compounds. The iron sulfide compounds can be classified, depending on the types thereof, into pyrrhotite (Fei-xS), troilite (FeS), and pyrite (FeS 2 When subjected to the powder X-ray diffractometry, these compounds exhibit different peak positions and are readily determined, respectively.

Accordingly, iron compounds which are to be checked and confirmed are sulfided at a temperature of 250 0 C or below and are subjected to the powder X-ray diffractometry thereby checking and confirming intended compounds. When the sulfiding temperature is changed, the temperature at which an iron compound is converted to pyrrhotite can be determined.

We made use of the above checking and confirming method to check the behavior of sulfiding an iron 't compound into pyrrhotite and the catalytic rction of the pyrrhotite. As a result, it has been found that the catalytic action and activity of the pyrrhotite, and the temperature of conversion of an iron compound into an iron sulfide compound and the temperature of conversion to pyrrhotite depend on the type of iron compound.

Especially, it has been found that an iron compound mainly composed of iron hydroxide is sulfided an changed (converted) into pyrrhotite at a low temperature of -13-

I-,

I I I 250 0 C or below, and exhibits a high catalytic activity.

In view of this, it is preferred that an iron compound composed mainly of iron hydroxide is used as the catalyst (third invention).

In the practice of the invention, the catalyst plays an important role as stated before and is able to supply hydrogen to the thermal decomposition radicals of coal from 250°C at which the thermal decomposition of coal starts to occur relatively violently and stabilizes the thermal decomposition radicals of coal, thereby suppressing the recombination thereof. The low temperature hydrogenation at a temperature ranging 250 400 0 C causes solid coal to be solubilized. This promotes the catalyst to be well dispersed, thus ensuring good contact between the catalyst and the reactant (coal). This ends up with the high temperature 4 hydrogenation proceeding efficiently, which is considered to result from the low temperature hydrogenation.

The hydrogen supply to the thermal decomposition radicals of coal relies on the hydrogen contained in the solvent and the hydrogen activated by means of the catalyst. Tnerefore, a higher hydrogenation activity of a catalyst allows the hydrogenation from solvent to -14proceed more efficiently, resulting in a better supplying effect of hydrogen on the thermal decomposition radicals of coal.

The amount of the catalyst is generally in the range of 0.5 10.0 wt% on dry ash-free basis of coal.

A higher catalytic activity results in a smaller amount with good economy. In case of this invention, the activity of this catalyst is high, it is preferred that the catalyst is used in such a way that an amount of iron in the catalyst is in the range of 0.5 5.0 wt% based on dry ash-free coal. In order to permit high dispersion of the catalyst in a solvent, it is preferred to use a finely pulverized catalyst having an average particle size of 2 um or below.

~In the practice of the invention, hydrogen added t oOr to a slurry mixture containing coal, solvent and catalyst at the time of the low temperature hydrogenation is Cissolved in the solvent of the mixture and is activated by means of the catalyst, thereby e stabilizing the thermal decomposition radicals of coal.

Besides, hydrogen serves to cause part of the solvent to hydrogenate thereby keeping the capability of hydrogen rroc supply of the solvent. For the hydrogenation, it is not limit to add only pure hydrogen, the addition of a gas i containing hydrogen is sufficient for this purpose.

Mixed gases of hydrogen and hydrocarbon gases may be added.

The solvent not only dissolves the coal, but also serves to rapidly supply hydrogen to the thermal decomposition radicals of coal. The solvent is not limited with respect to the type thereof. Usually, mixtures of middle and heavy oils produced during the coal liquefaction reaction, residues after the liquefaction, and de-ashed materials of the residues are used by recycling in a coal liquefaction process.

The mixing of solvent with coal and catalyst is conventionally performed. In prior art, such mixing is for the purpose of dehydration of coal or feed, to a liquefaction reactor, of a stable coal slurry after its adjustment in viscosity to a level at which the slurry is ready to handle. In contrast, one of the objects of the invention is to suppress undesirable reactions derived from the thermal decomposition of coal. As stated before, the solvent is used to quickly supply hydrogen to the thermal decomposition radicals of coal.

Thus, the optimum mixing conditions of solvent the type and amount of solvent) differ from those of the prior art. Therefore, in the practice of the invention, -16- Y 9 the mixing of solvent should preferably be performed while taing the objects of the invention and the effect of a solvent into account.

After completion of the low temperature hydrogenation at a temperature of 250 400 0 C, even if part of the solvent is separated from the mixture containing coal, solvent and catalyst slurry mixture) to increase the concentration of coal in the mixture to 40 60 wt%, the mixture is low in viscosity and is easy to handle without any hindrance.

Accordingly, the concentration of coal in the mixture obtained after the completion of the low temperature hydrogenation is increased to 40 60 wt%, followed by high temperature hydrogenation. By this, the efficiency of contact between the coal and the catalyst is improved in the high temperature hydrogenation. This, in turn, affords an improved yield of liquefied oil. And, the treating amount of coal per unit time and unit capacity increases at the stage of the high temperature hydrogenation (second invention). This is described in more detail.

to*" In a coal liquefaction process, in general, it is more beneficial in economy to use a higher concentration of coal in the slurry mixture. A higher -17g coal concentration leads to a higher viscosity of the slurry mixture, resulting in making it difficult to handle. Therefore, the coal concentration in the slurry mixture is set at a level enough not to impede the handling of the mixture. In conventional coal liquefaction processes, the coal concentration is low.

Especially, when using brown coal which has a developed fine pore structure, part of a solvent is absorbed in the fine pores of the brown coal, thereby increasing the viscosity of the slurry mixture. Accordingly, the coal concentration in the slurry mixture is often limited to a level as low as 25 35 wt% and, in fact, should be inevitably set at such a low concentration. This permits only a reduced amount of coal being treated per unit capacity of reactor, coupled with a low capacity ror.

efficiency, a low contact efficiency of coal and catalyst, and a low yield of liquefied oil.

In contrast thereto, in the practice of the invention, coal is heated at a temperature of 250 oeo 4000C at the stage of the low temperature hydrogenation, during which the coal is modified by shrinkage of fine pores in the coal. Therefore, after completion of the low temperature hydrogenation, the slurry mixture considerably lowers in viscosity. This unnecessitates -18part of a solvent which is necessary for keeping the viscosity of the slurry mixture. All or part of the unnecessary solvent may be separated without hindrance.

By the separation, the concentration of the coal in the mixture can be increased to 40 60 wt%. It should be noted that if the solvent is separated in an amount exceeding the unnecessary amount, the concentration of the coal can exceed 60 wt%. Nevertheless, such a slurry mixture becomes so high in viscosity as to impede the handling thereof. Therefore, the concentration of the coal after the separation of the solvent should be wt% or below.

Accordingly, when the concentration of coal in the mixture obtained after the low temperature hydrogenation is increased to 40 60 wt% and the slurry is subjected to the high temperature hydrogenation, the 4r "efficiency of the contact between the coal and the isoe: catalyst is improved in the high temperature hydrogenation. Therefore, the hydrogen activated by the catalyst is efficiently supplied to the coal for hydrogenation thereby improving the yield of liquefied oil. In addition, since the coal concentration in the mixture is as high as 40 60 wt%, the amount of coal to be treated in the high temperature hydrogenation per -19unit time and unit capacity increases, compared to the prior art processes of coal liquefaction. A greater amount of coal can be treated per reactor capacity, along with an increasing reactor capacity efficiency.

Moreover, even if a reactor capacity is made small, a satisfactory amount of treated coal can be obtained, ensuring the use of a smaller-size reactor.

The coal liquefaction process of the invention is particularly performed using an apparatus and a process flowchart, for example, shown in Fig. 1. This is described in detail with reference to Fig. 1.

First, dry, pulverized coal is fed to a coal slurry making vessel along with a recycle solvent recovered from a gas-liquid separator and a distillation column a catalyst an iron compound capable of conversion into pyrrhotite at a temperature of 250°C or below), and a co-catalyst such as sulfur, in which they are mixed together. The slurry mixture is transported through a preheater or heat exchanger to a low temperature hydrogenation reactor In the course of the transportation, hydrogen gas or a hydrogen-containing mixed gas is aJiIed as a hydrogen source, and the catalyst is converted to pyrrhotite.

In the low temperature hydrogenation reactor the low temperature hydrogenation is carried out under conditions including a temperature of 250 400 0

C

and a time of approximately 10 60 minutes. In this stage, part of the coal is thermally decomposed to generate carbonic acid gas and water, and hydrogen is added to the coal hydrogen is supplied to the thermal decomposition radicals of coal). The heavy material in the coal undergoes extraction and dissolution with the solvent for coal liquefaction (recycle solvent), and the extracted heavy material is converted into oil fractions along with the shrinkage of fine pores in the coal.

After completion of the low temperature hydrogenation, a gas component and part of the solvent uO are recovered from the top of the low temperature hydrogenation reactor and separated into the gas :..component and the solvent by means of the gas-liquid separator Thereafter, the solvent was fed to the Cee.4.

coal slurry making vessel and the hydrogencontaining gas component is fed into a high temperature hydrogenation reactor On the other hand, a slurry mixture including unreacted coal, reaction product, the other solvent and the catalyst is withdrawn from the -21lower portion of the low temperature hydrogenation reactor and introduced into the high temperature hydrogenation reactor It will be noted that hydrogen may be freshly fed in the course of the introduction. The high temperature hydrogenation reactor may be of the -ontinuous stirred tank type, the flow tubular type or the bubble column type.

In the high temperature hydrogenation reactor the high temperature hydrogenation (i.e.

liquefaction reaction) is carried out at a temperature of 400 500 0 C higher than the low temperature hydrogenation. In this stage, the coal undergoes extraction and dissolution with the recycle solvent, and hydrogenation and decomposition with the catalyst to give lighter oil fractions, turning into the desired product.

0 After completion of the high temperature

S

hydrogenation, the reactor effluent is introduced into a gas-liquid separator wherein the gas component is separated. The remaining liquid and solid components are separated into liquid and solid components by means of a solid-liquid separator such as for the solvent de-ashing process, followed by feeding the liquid component into a distillation column followed by *-2 -22separation into light oil product and middle and heavy oil product. %trL of the middle and heavy oils is recovered as a recycle solvent for coal liquefaction and is recycle and fed to the coal slurry making vessel In the practice of the invention, coals include, aside from low coalification coals such as brown coal, sub-bituminous coal and bituminous coal. Especially, the process of the invention is beneficially applicable to brown coal (fourth invention). This is because brown coal is likely to generate thermal decomposition radicals of coal as having set out hereinbefore. In prior art processes, undesirable reactions are liable to take place owing to the thermal decomposition radicals of coal. In the present invention, such a reaction can be appropriately suppressed and this suppressing effect is remarkable. In view of this, among brown coals, coal which belongs to brown coal whose heating value is 7300 Kcal/kg (dry, mineral-free basis) defined in JIS M 1002 can be appropriately treated. These coals are usually 0* S.00t dried to a moisture content of 15% or below and pulverized into pieces having a size as small as about 60 mesh. These pieces can be liquefied more efficiently according to the piocess of the invention.

-23- The separation procedures of solvent, oil or solids such as separation of solvent or separation of oil are not critical and include, aside from distillation, filtration. With the distillation, distillation conditions which are suited for the intended product should be properly selected.

Examples of the invention are described, which should not be construed as limiting the invention thereto. In Examples and Comparative Examples, the conversion and yield are those determined on dry, ashfree basis.

[Check test on the temperature of conversion of a catalyst (iron compound) to pyrrhotite] Hydrogen was added, in an autoclave, to a slurry mixture containing an iron compound as a catalyst, sulfur in an amount corresponding to 2.0 times by atomic .6 ratio the content of iron present in the catalyst, and a distillate obtained by liquefaction reaction (hereinafter referred to as process solvent, followed by sulfidait at a temperature of 150 450 0 C for minutes. Thereafter, the conversion of the catalyst (iron compound) into pyrrhotite was determined, from Ros s which the temperature for 100% conversion of the *catalyst (iron compound) into pyrrhotite was checked.

-24- The catalyst (iron compound) used included yiron oxyhydroxide, limonite iron ore, pyrite iron ore and basic oxygen furnace dust (iron oxide) which were, respectively, used singly. The conversion of the catalyst (iron compound) into pyrrhotite was determined in the following manner. According to a solvent extraction technique using tetrahydrofuran (THF), a catalyst was separated and collected, as a THF insoluble material, from the slurry mixture obtained a2ter the sulfidation treatment. The catalyst was dried and subjected to measurement of pyrrhotite according to the powder X-ray diffractometry, from which the conversion of the catalyst (iron compound) into pyrrhotite was calculated.

The results are shown in Table 1. The temperature for the 100% conversion of the catalyst (iron compound) to pyrrhotite is 350 0 C for pyrite iron ore and 400°C for basic oxygen furnace dust. In contrast thereto, with y-iron oxyhydroxide and limonite iron ore, the conv rsion temperature is lower, i.e. the 100% conversion temperature is 200°C. Thus, both y-iron oxyhydroxide and limonite iron ore are iron compounds which are able to convert into pyrrhotite at a

I

temperature of 250 0 C or below and are usable as a catalyst in the practice of the invention.

to. 0 too* -26- Table 1 I Temperature for 100% No. Catalyst (iron compound) Te f conversion to pyrrhotite 1 y-iron oxyhydroxide 200 2 limonite iron ore 200 3 pyrite iron ore 350 4 basic oxygen furnace dust 400 (iron oxide) Low temperature High temperature hydrogenation Hydrogenation Catalyst Starting Cat t Concen- Concenc c al on tration Temp- tration Temp- ime comptund) -,ime Time of coal erature ,im of coal erature m 0 (min.) 0 (min.) (wt (wt Example 1 Yallourn y-iron oxy- 28 350 30 28 450 coal hydroxide Example 2 Yallourn y-iron oxy- 28 350 30 50 450 coal hydroxide Example 3 Yallourn limonite 28 350 30 50 450 coal iron ore Example 4 Banko coal y-iron oxy- 28 350 30 28 450 hydroxide Example 5 Banko coal y-iron oxy- 28 350 30 50 450 hydroxide Comp. Ex. Yallourn pyrite iron 28 350 30 28 450 1 coal ore Comp. Ex. Yallourn r-iron oxy- 28 450 2 coal hydroxide *2 *2 *2

C

C

CC

C

CCC

:..Note) Concentration of coal in a mixture of solvent and coal (dry not hydrogenated at low temperature ash-free basis) 27 Table 3 Conerson iel ofgas Consumption Utilization of coal*l 1 Oiel*1 component*1ofeicny *2 hydrogen*1 of hydrogen *3 Example 1 98.5 66.5 16.0 5.5 12.1 Example 2 100.0 77.0 14.7 6.1 12.6 Examrpl1e 3 100.0 75.0 15.0 6.1 12.3 Example 4 100.0 75.2 17.4 5.2 14.4 Examale 5 100.0 80.1 12.0 5.5 14.7 Comp. Ex. 1 97.0 59.6 18.3 5.0 11.9 Comp. Ex. 2 97.0 1 56.3 17.9 5.5 10.2 Note) *1 Dry, ash-free basis *2 Yield of n-hexane soluble material *3 Oil yield (wt%)/hydrogen consumption (wt%)

S

.5S*

S

S

28 Example 1 The types of starting coal, catalyst (iron compound), low temperature hydrogenation conditions and high temperature hydrogenation conditions are shown in Table 2.

First, Yallourn brown coal of Australia (with a heat value of 5930 Kcnl/kg (dry, mineral-free basis and a fuel ratio of 0.89) was provided as a starting coal and a process solvent was provided as a solvent. Both were so xed that the concentration of the coal on dry, ash-free basis was adjusted to 28 wt%. y-Iron oxyhydroxide having an average particle size of 0.5 pm was added, as a catalyst, to the mixture in an amount of 4.8 wt% of the coal on the dry, ash-free basis, followed by further addition of sulfur in an amount of 2.0 times

S

by atomic ratio as great as the content of iron in the catalyst to obtain a slurry mixture. Subsequently, the slurry mixture was introduced into an autoclave (inner capacity of 30 cc), into which hydrogen was further introduced to an initial hydrogen pressure of 15.0 MPa to carry out low temperature hydrogenation under conditions of a temperature of 350 0 C and a timer of minutes. Thereafter, the temperature was raised to 450 0 C, followed by high temperature hydrogenation under -29conditions of a temperature of 450 0 C and a time of minutes.

After completion of the high temperature hydrogenation, the hydrogenation reaction product was separated and subjected to solvent extraction to determine the conversion of the coal and the yield of oil. The results are shown in Table 3. As will be apparent from Table 3, the conversion of coal was 98.5 wtq and the yield of oil (n-hexane-soluble material) (hereinafter referred to as oil yield) waG 66.5 wt%.

The yield of a gas component was 16.0 wt% and the consumption of hydrogen was 5.5 wt%. The utilization efficiency of hydrogen oil yield/hydrogen consumption, or an oil yield per hydrogen consumption) was 12.1.

Example 2 .In the same manner (conditions and procedure) as o5*o in Example 1, a slurry mixture having a similar .composition was obtained, followed by low temperature hydrogenation in the same manner (conditions, reactor and procedure) as in Example 1. After completion of the low temperature hydrogenation, an n-hexane insoluble material (including coal and catalyst) in the slurry mixture was separated and recovered from an n-hexane soluble material. A process solvent was added to the nhexane insoluble material in an amount of 100 wt% of the starting coal (on dry, ash-free basis) to obtain a slurry mixture so that the coal concentration in the slurry mixture was adjusted to 50 wt%. Subsequently, hydrogen was again introduced to an initial hydrogen pressure of 15.0 MPa, followed by heating to 450 0 C and high temperature hydrogenation under conditions of a temperature of 450 0 °C and a time of 60 minutes. After completion of the high temperature hydrogenation, the conversion of the coal was determined in the same manner as in ExampLa 1, with the results shown in Table 3.

It will be noted that Example 2 substantially corresponds to an example of the second invention (a ^process of coal liquefaction recited in Claim In the second invention, part of the solvent is separated from the slurry mixture obtained after completion of the low temperature hydrogenation so that the concentratior of coal is made to 40 60 wt%, followed by high temperature hydrogenation. In Example 2, since an autoclave was used as an apparatus, it is difficult to separate part of the solvent from the slurry mixture after the low temperature hydrogenation. Accordingly, after completion of the low temperature hydrogenation, -31n-hexane soluble material (solvent) and n-hexane insoluble material in the slurry mixture were separated from each other and recovered. Then, a process solvent is added to the n-hexane insoluble material to obtain a slurry mixture having a coal concentration of 50 wt%.

Subsequently, hydrogen is again introduced, followed by high temperature hydrogenation. As will be apparent from the foregoing, part of the solvent is not separated from the slurry mixture in Example 2. A procedure of separating the solvent and adding a fresh process solvent is included. This procedure differs from the process of the second invention. However, this is ascribed to the use of the autoclave as an apparatus and is only for experimental reasons. Substantially, the above procedure oi Example 2 corresponds to the ~separation of part of the solvent from the slurry mixture. In this manner, Example 2 substantially corresponds to an example of the second invention.

The slurry mixture having a coal concentration O~cO of 50 wt% obtained in Example 2 is substantially the same as a slurry concentration having a coal concentration of 50 wt% which is obtained by separating part of a solvent in an actual apparatus. It was confirmed that the slurry mixture was still low in -32viscosity and was easy to handle without involving any hindrance in handling. It will be noted that the slurry mixtures after the low temperature hydrogenation and the adjustment of the coal concentration in Examples 3 and appearing hereinafter are similar to the slurry mixture of Example 2 and are so low in viscosity that they do not involve any hindrance in handling.

In Example 2, the addition of a fresh process solvent after separation of a solvent is included owing to the use of an autoclave as an apparatus as set out above. In addition, the step of freshly introducing hydrogen for the high temperature hydrogenation is also included. In an actual apparatus as shown in Fig. 1, part of a solvent is continuously separated from a oi slurry mixture subsequently to the low temperature S. hydrogenation to make a coal concentration of 40 wt%. Thereafter, the mixture is fed to a high temperature hydrogenation step wherein the high temperature hydrogenation is carried out without further introduction of hydrogen.

Example 3 Limonite iron ore (a kind of iron hydroxide) was used as a catalyst in place of y-iron oxyhydroxide. The procedure of Example 2 was repeated except the catalyst -33for the preparation of a slurry mixture, the low temperature hydrogenation, the adjustment of a coal concentration and the high temperature hydrogenation.

Thereafter, the conversion of coal and the like were determined in the same manner a& in Example 1. The results are shown in Table 3.

Example 4 Banko Coal of Indonesia (with a heating value of 6640 Kcal/kg (dry, mineral-free basis) and a fuel ratio of 0.94) was used as starting coal in place of the Yallourn brown coal of Australia. In the same manner as in Example 1 except the starting coal, a slurry mixture was prepared and low temperature and high temperature hydrogenations were carried out. In the same manner as in Example 1, the conversion of coal and the like were determined. The results are shown in Table 3.

Example eao Banko Coal of Indonesia (with a heating value of 6640 Kcal/kg (dry, mineral-free basis) and a fuel ratio of 0.94) was used as starting coal in place of the Yallourn brown coal of Australia. In the same manner as in Example 1 except the starting coal, a slurry mixture was prepared and low temperature and high temperature hydrogenations were carried out. In the same manner as -34in Example i, the conversion of coal and the like were determined. The results are shown in Table 3.

Comparative Example 1 Finely pulverized natural pyrite iron ore having an average particle size of 0.5 pm was used as a catalyst in place of y-iron oxyhydroxide and was added in an amount of 7.0 wt% of coal (dry, ash-free basis).

In the same manner as in Example 1 except the starting coal, a slurry mixture was prepared and low temperature and high temperature hydrogenations were carried out.

In the same manner as in Example i, the conversion of coal and the like were determined. The results are shown in Table 3.

Comparative Example 2 The general procedure of Example 1 was repeated ~except that the low temperature hydrogenation was not carried out. More particularly, a slurry mixture was prepared in the same manner as in Example i, and was then introduced into an autoclave (inner capacity of cc). Hydrogen was further introduced to an initial hydrogen pressure of 15.0 MPa., followed by high temperature hydrogenation under conditions of a temperature of 450 0 C and a time of 60 minutes. In the same manner as in Example i, the conversion of coal and the like were determined, with the results shown in Table 3.

From the examples and the comparative examples, the following information is obtained.

The procedure of Example 1 is better in the conversion of coal, the oil yield and the utilization efficiency of hydrogen than that of Comparative Example 1. This reveals that y-iron oxyhydroxide (whose temperature of conversion to pyrrhotite is 250 0 C or below) is able to reduce the consumption of hydrogen gas and to obtain liquefied oil in a higher yield with better results of the liquefaction reaction on comparison with the pyrite iron ore (whose temperature of conversion to pyrrhotite is 350 0

C).

i The procedure of Example 1 is better in the

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conversion of coal, the oil yield and the utilization efficiency of hydrogen than that of Comparative Example 2. This demonstrates that the case where the high temperature hydrogenation is carried out subsequently to 9999 the low temperature hydrogenation is better in the results of the liquefaction reaction than the case wherein the high temperature hydrogenation is performed without any low temperature hydrogenation.

-36- Example 2 is better in the conversion of coal, the oil yield and the utilization efficiency of hydrogen than Example 1. This demonstrates that the results of the liquefaction reaction is improved when increasing the coal concentration in the slurry mixture to 50 wt% after completion of the low temperature hydrogenation.

Example 3 is substantially the same as Example 2 with respect to the conversion of coal, the oil yield and the utilization efficiency of hydrogen, with similar results of the liquefaction reaction. This reveals that when using limonite iron ore (a kind of iron hydroxide) as a catalyst, such good results as with the case of yiron oxyhydroxide are obtained.

The comparison between Examples 4 and 5 reveals that Example 5 is better in the conversion of coal, the oil yield and the utilization efficiency of hydrogen.

This reveals that when increasing the coal concentration in the slurry mixture to 50 wt% after completion of the low temperature, good results of the liquefaction reaction are obtained not only using, as a starting coal, the Yallourn brown coal of Australia, but also using the Batn.o Coal of Indonesia.

-37- Where the terms "comprise", "comprises", "comprised" or "comprising" are used in this specification, they are to be interpreted as specifying the presence of the stated features, integers, steps or components referred to, but not to preclude the presence or addition of one or more other feature, integer, step, component or group thereof.

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Claims (6)

1. A process for coal liquefaction which comprises the step of hydrogenation of coal in the presence of solvent and catalyst, characterized in that an iron containing compound capable of conversion into pyrrhotite at a temperature of not higher than 250 0 C is used as the catalyst, and the coal is subjected to low temperature hydrogenation at a temperature of 250-400 0 C and then to high temperature hydrogenation at a temperature higher than in the low temperature hydrogenation.

2. A process for coal liquefaction as claimed in claim 1, wherein prior to the high temperature hydrogenation, part of the solvent is separated from the mixture of coal, solvent and catalyst resulting from the low temperature hydrogenation step, such that the concentration of coal in the nmixture subjected to the high temperature hydrogenation is from 40 to is.

3. A process for coal liquefaction as claimed in claim 1 or 2, wherein the iron containing compound used as the catalyst is composed mainly a o of iron hydroxide.

4. A process for coal liquefaction according to any one of the preceding claims wherein the coal is brown coal. o DATED this 10th day of July, 1998. NIPPON BROWN COAL LIQUE T CO., LTD By their Patent Attorneys, CALLINAN LAWRIE Z*ro~ -I I II I II ABSTRACT A process for coal liquefaction is provided wherein undesirable reactions derived from the thermal decomposition of coal are suppressed whereby the consumption of hydrogen gas is reduced and liquefied oil can be obtained in a higher yield as compared with the case using a conventional process of coal liquefaction. A process for coal liquefaction which comprises the hydrogenation step wherein coal such as brown coal is hydrogenated in the presence of solvent and catalyst, characterized in that an iron compound capable of conversion into pyrrhotite at a temperature of 250 0 C or below is used as a catalyst, and low temperature hydrogenation is carried out at a temperature of 250 400 0 C, followed by high temperature hydrogenation at a temperature which is higher than the temperature in the low temperature hydrogenation.

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