US2430416A - Aromatization of oil produced in low temperature carbonization of coal - Google Patents

Description

Patented Nov. 4, 1947 OFFICE AROMATIZATION or on. rnonucnn m LOW TEMPERATURE CABBONIZATION or COAL Charles Weizmann, London, England, asslgnor .to

Ketarome Limited, London, England No Drawing. Application May a, 1945, Serial No. 591,855

:3 Claims. (01. 260-4568) This invention, which is a continuation-1m part of application No. 363,381, filed on October 29, 1940, relates to the utilisation of a liquid product obtained in the carbonisation of coal. The method of carbomsing coal being dealt with is the low temperature carbonisation process to obtain smokeless coke which is normally carried out at about 600650 C. in retorts of the cokeoven type, which work on he batch or discomtinuous principle. The products of this method of carbonisatlon include a liquid usually called coal-oil. v

The invention deals with a particular fraction of this coal-oil, namely, the fraction which consists of products having boiling points of from 100 C. to 280 C., the preferred part of this range being from 100 C. to 180 C.

Further, from this fraction for its use for the purpose of the present invention, the acidic and basic constituents are'removed either before or after preparation of the fraction. In addition, any olefine constituents or part thereof may be removed leaving chemically saturated constituents thereof.

The object of the present invention is a process for the utilisation of the coal-oil fraction referred to above that is free from acidic and basic constituents by treating it to yield a mixture composed substantially of aromatic hydrocarbons, for example, benzene and toluene.

This object I find can be secured by a process according to the succeeding paragraph, in which all the features mentioned therein are essential to success, particular stress being laid on (a) the starting material; (b) the form in which the starting material is used; (c) the particular catalysts and (d) the particular temperature range. This is in contrast to processes in the prior art which have one or more of the features mentioned, but not all of them in combination, as a result of which the product obtained by the prior processes, differs from those according to the present application. 7

This can be seen for example with reference to Austrian patent Serial No. 101,681.

The Austrian process gives aromatics which are of the same molecular size only as the startlng material. A charging stock consisting of Ca hydrocarbons gives benzene only, for example,

contrast, applicant obtains a series of aromatics from any fraction, ranging from benzene to ethylbenzene and xylene. This is probably due to the fact that under applicants conditions the charge is completely broken down to small unsaturated molecules and that then re-synthesis takes place. At least the fact remains that applicant obtains a diflerent result.

The difference between these two processes is not a difference due to the range of boiling cuts used in the starting materials. In applicants case, the composition of the end product does not depend-on that of the charging stock.

The invention consists in a process for the preparation of a mixture comprised substantially of aromatic hydrocarbons from a fraction having boiling points between and 280 C. of the coal-oil produced in the low temperature carbonisation process to obtain smokeless coke and from which fraction the acidic and basic constituents have been removed, which process comprises submitting the aforesaid starting material in the form of its vapour to the action of a metallic catalyst of the kind known as hydrogenation-dehydrogenation catalysts at a temperature within the range 600 to 700 8., preferably at atmospheric pressure, and preferably at a space velocity of 0.1 to 0.5 litre of oil per hour, per litre active catalyst volume. r

The invention also consists in a process in accordance with the preceding paragraph in which the starting material employed is the coal-oil fraction aforesaid but limited to the boiling range of 100 to 180 C.

The invention also consists in a process in accordance with either of the preceding two paragraphs in which the catalyst is employed in a form presenting to the vapours a large and active surfac The invention also consists in a process in accordance with any of the preceding three paragraphs in which the product formed is separated into its gaseous and liquid constituents, for instance, by cooling or by adsorption or absorption in a selective solvent or by a combination of such methods.

The invention also consists in a process in accordance with any of the preceding tour paragraphs in which process the liquid resulting from while a C7 charging stock gives toluene only. In 50 the process is fractionated into practically pure arcane benzene (boiling point ao-ar' 0.), practically pure toluene (boiling point 111-112 C.) and an ethyl-benzene fraction (boiling point 135-146 The invention also consists in a process in accordance with any of the preceding flve paragraphs, in which process the gaseous constituent is utilised as starting material for chemical syntheses or as fuel for an evaporation unit and the catalyst furnace itself or as both a starting material and a fuel.

The invention also consists in a process in accordance with any of the preceding six paragraphs, specifically directed to the case in which any olefine constituents or part of them have been removed from the starting material.

The invention also consists in a process -in accordance with any of the preceding seven paragraphs, in which aromatised products thereby produced are returned into the process for a re-cycling treatment. v

The invention also consistsin a process in accordance with the preceding paragraph in which the products boiling between 145 C. and 195 C. are re-cycled to the reaction.

The invention also consists in processes in accordance with any of the preceding nine paragraphs, carried out as described in any of the examples given below.

The invention also consists in aromatic hydro-' carbons when prepared or produced by the methods or processes of manufacture particularly described and ascertained herein.

The invention also consists in an internal combustion engine fuel when produced in accordance with any of the preceding ten paragraphs.

Several ways of carrying this invention into effect will now be described by way of example.

EXAMPLE I This is an example of a process for the treatment of coal-oil under nickel catalyst conditions pared by reduction of copper oxide needles at 225. 300 gm. of the needles were placed in and filled the reaction tube described in Example I. The conditions of the reaction were the same as above. The total liquid obtained amounted to 54% of the original oil;.,-13.6% of this liquid obtained was benzene, 14.2% toluene and 14.8%

The coal-oil fraction, before entering the reaction tube, passed through a preheater, in which it was subjected to a temperature of 220, so that a substantial part of it was vaporised. The reaction products were cooled in an eflicient condenser to room temperature so that only their gaseous constituents were allowed to escape. The liquid condensate was fractionated and the fraction boiling above 140 subjected again to the above treatment. The total liquid obtained in the two treatments, which boiled up to 140, amounted to 53.1% of the original oil; of the products 10.8% were benzene, 16.1% toluene and 10% ethyl-benzene fraction. The remainder, boiling above 140 consisted of higher aromatic hydrocarbons, including, e. g., naphthalene. The space velocity employed in the above examples lies within 0.1 and 0.5 litre of oil per hour per litre active catalyst volume.

EXAMPLE II This is an example 0 the treatment of coal-oil under copper catalyst conditions The catalyst consisted of copper needles, preethylbenzene fraction.

Exnm'u: III

This is an example of the treatment of coal-oil under the conditions of a mixed iron and copper catalyst was benzene. 18.2% toluene and about 13.0%

ethylbenzene fraction.

EXAMPLE IV This a yurther example of the treatment of coal-oil under copper catalyst conditions In this example catalyst consisting of activated copper was heated at a temperature of 690. The total catalyst volume was 180 litres. With a speed of 25.3 litres per hour, 1. e., 20.8 kg. per hour, coal-oil of a boiling range to 230 was passed over the catalyst. The space velocity therefore was 0.1 litre per litre catalyst space and hour. The products formed were condensed continuously as far as possible and the escaping gases passed through a tower in which they were brought into intimate contact with an absorbing spindle oil. Per hour 15.3 litres=14.0 kg liquid product which was aromatic apart from a small head fraction, was condensed, and in the scrubbing installation 0.4 litre=0.3 kg. per hour was isolated in addition. .The gas amounted to 6.9 cbm. per'hour (calculated for normal temperature and pressure). As the density of the gas was 0.97 gm. per'litre, its weight was 6.9 kg. Expressed in weight 69% of the charging stock were recovered in liquid form, 31% in gaseous form. An inspection of the catalyst after the experiment which was continued for twelve hours showed that substantially no carbon deposition had taken place.

Fractionation of the liquid product yielded the following components, the quantities being calculated as per cent of the charging stock:

The fraction -180 was subjected to fractionation and from it was obtained the following principal constituents:

Boiling-point:

Isopropyl-benzene 151 The mixture of these substances can be used as such as ingredient for high-grade motor-fuel in view of its fairly high octane number, but it can Degrees also be degraded by re-cycling to substantial amounts or the low boiling aromatics as described below. l

6 Fractionation or the low fraction showed that it consisted of 1 Per cent A similar fractionation of the part of the prod- Head traction 0.7 not boiling under atmospheric pressure above 5 Benzene 3,5 180 and suitable purification by conventional Toluene 8.0 methods yielded led to the following substances: Ethylbenzene fraction 16.5

Percant Substance Boiling range Remarks Tetrahydronaphthalene nit-210. 5.0 Naphrhnlnnn gnu-225 l1. 3 amethyl-naphthalene hit-247 4.2 Pi czg te M. P. B-methylm 1 240247. 5.0 Pi 33 M. P. li dimethylnaphthalene 265-275" 4.2 ri a ii y. P. 1.2.64;ri-methyl-naphthaleno 195invacuo 2.1 Orange red pic- (probebly). rate M. P. 134. Anthmcene 240260 in vacuo..... 8.0 2methylanthracene 260-270 in vacuo--.. 4.0 Dihydropyrene 345-347invecuo 7.3 Dark-red plcrate M.P.l96198. Dibenzochrysene 350-410invacuo.--. 1.0 lPitch above 410 in vacuo- Substantial quantities of anthracene and espe- 25 The total amount of low boiling aromatics is cially chrysene may be isolated from the pitch.

The above last two lists contain only the substances which have been isolated in substantial quantities; they do not indicate that the tabulated compounds are the only products formed.

Examrnn V This icon example dealing with the re -cycling of the aromatised fraction boiling between 145- 195 were at the above indicated temperature, while the temperature decreased by about 15 towards the ends of the furnace. As the rate of throughput was 70 cc. per hour, the space velocity Was 0.16 litre per litre catalyst space and hour. 96% liquid products were recovered, while 4% of the charging stock was converted into gaseous products. 0f the liquid product 15% boiled up to a temperature of 1.452110% above 195, whilst 75% retained the original boiling range. Fractionation of this part showed that the proportion 01 trimethylbenzenes had increased; fractionation of the product boiling below 145 showed that it consisted of the following components expressed in oi the total charge:

Below benzene 1.3 Benzene 1.5 Toluene 1.51 Ethylbenzene fraction 12.0:

.Exanzrrn V1 This is o modification of the preceding example, the temperature of treatment being higher This example was carried out in a manner sim-- hill.

boiled below 18% boiled between l45-l90,

and 3d% boiled above 190". I

lit

therefore higher than at 600 and the increase in toluene is especially marked. In both cases, however, the xylene fraction is the principal constituout.

In the fraction boiling between -195,- 55% are mesitylene. 1

From the highest fraction inter alia naphthalene and anthracene were easily isolated; about 50% of this fraction consisted of chrysene.

, Esmurts 17K This is anexample applied to the saturated constituents of coal-oil The unsaturated constituents of coal-oil, which iorin usually 40 to 50% of it, may be used for other industrial purposes, such as the production of alcohols, bromides and the like. It is therefore important that the saturated constituents, after removal of the total quantity or of part of the clefines, can also be processed by the method described in this application. The charging stock for the following process was obtained by successive treatment of the coal-oil (boiling range 100-180") with sulphuric acid of increasing strength. The greater part of the olefines were thereby converted into alkyl hydrogen sulphates which were extracted with water. The residue was distilled and the part thereof boiling up to selected for the cracking process. 5% of the aforesaid residue boiled up to 123, 05% up to 173, its specific gravity was 0.807, its bromine number 19.5 g./l00 g., indicating an approximate olefine content of 17%. The aforesaid part was Per cent Light fraction (below benzene) 1.6 Benzene 1 3.3 Toluene 13.5 Ethylbenzene fraction 20.0

Alkylbenzenes, boiling between 145-l80.. 12.5 Heavy aromatics, boiling above l80 9.6

, components can GENERAL In general the reaction conditions involve a space velocity of 0.1-0.5 litre of oil per hour per litre active catalyst volume. By "active catalyst volume is meant the volume of the catalyst which is at the correct operating temperature.

The catalytic metals for use according to the present invention are such as catalyse hydrogenation and dehydrogenation reactions, e. g., iron, copper, nickel, cobalt, silver, chromium, molybdenum, tungsten or manganese. The catalyst need not consist of a single metal; mechanical mixtures or alloys of two or more metals may be used instead with equally favourable results. The metal catalyst may also be used in the form of a deposit on a suitable carrier such as pumice. The catalyst is conveniently contained in a tube made of metal or ceramic material.

The usual catalyst poisons, contained in the coal oil, are destroyed in the course of the aromatisation reaction. If, however, the activity of the catalyst decreases, it can easily be restored by successive treatment with air or pure oxygen and hydrogen. For the reactivation process, the cracking gases, which contain a certain percentage of hydrogen, may be used advantageously.

The pressure at which the conversion is carried out should preferably be near atmospheric, although this is not essential.

As regards the starting material the coal-oil may contain a percentage of aromatic compounds the amount depending upon the temperature at which each batch of coal-oil was produced. In general the lower the temperature of production the lower the content of aromatic compounds.

The present application is, however, independent of the actual composition of the coal-oil as regards these products.

A fuel for an internal combustion engine may be provided by the products of the processes range and the lower boiling point of an upper range are identical, some substance'may be common to both fractions but it is customary for all fractions to .be submitted toa simple refractionation process and by this means individual be isolated as far as may be desired.

I claim? 1. A process for the preparation of a mixture composed substantially of aromatic hydrocarbons from a fraction having boiling points between 100 and 280 C.- of the coal-oil produced in the 8 molybdenum, tungsten, manganese and alloys and mixtures of these metals, at a temperature within the range 600 to 700 C. I

2. A process as claimed in claim 1, in which the starting material employed is the coal-oil fraction aforesaid but limited to the boiling range of to 180 C.

3. A process as claimed in claim 1, in which the catalyst is employed in a, form presenting to the vapours a large and active surface.

4. A process as claimed in claim 1 in which the product formed is separated into its gaseous and liquid constituents by cooling.

5. A process as claimed in claim 1 in which process the liquid resulting from the process is fractionated into practically pure benzene (boiling point 80-81 C.), practically pure toluene (boiling point Ill-112 C.) and an ethyl-benzene fraction (boiling point -146 C.) which consists chiefly of ethylbenzene and styrene, but may also contain some xylene, and into a higher boiling part which is suitable for recycling over the catalyst.

6. A process as claimed in claim 1 specifically directed to the case in which olefine constituents have been removed from the starting material.

7. A process as claimed in claim 1 in which aromatised products produced in the process are returned to the process for a re-cycling treatment.

8. A process as claimed in claim 1, in which the products boiling between C. and C. are re-cycled to the reaction zone.

9. In the production of aromatics, the process which comprises removing acidic and basic constituents from a coal-oil fraction, produced in the low temperature carbonization of coal to obtain smokeless coke and having a boiling point range of from about 100 to 280 C., vaporizing said fraction, passing the vapors in contact with a finely-divided metallic hydrogenation-dehydrogenation catalyst selected from a group consisting of iron, copper, nickel, cobalt, silver, chromium, molybdenum, tungsten, manganese and alloys and mixtures of these metals, at a space velocity within the range of 0.1 to 0.5 liter per hour per literof active catalyst volume and at a temperature within the range of 600 to 700 C., separating the resulting products into a, liquid fraction and gases, distilling the liquid fraction to remove products boiling below about 145 C. and recycling the higher boiling fraction in contactwith said catalyst.

' CHARLES WEIZMANN.

REFERENCES CITED The following-references are of record [in the file of this patent:

[UNITED STATES PATENTS Austria Nov. 25, 1925