US1661565A - Process for the conversion of high-boiling hydrocarbons into low-boiling hydrocarbons - Google Patents

Description

March 6, 1928.

OCARBONS L. EDELEANU PROCESS FOR THE CONVERSION OF HIGH BOILING HYDE HYDROCARBONS INTO LOW BOILING Filed June 28. 1926 bmw,

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Patented Mar. 6, 1928.

UNITED STATES PATENT OFFICE.-

LAZLB EDELEANU, OF BERLIN-CHARLOTTENBURG, GERMANY, ASSIGNOB TO ALLGE- MEINE GESELLSCHAFT FUR CHEMISCHE INDUSTRIE, F BERLIN, GERMANY.

PBbC'ESS FOR THE CONVERSION OF HIGH-BOILIN G HYDROCARBONS INTOT-OW-BOILING HYDROCARBONS.

Application filed June as, 1926. Serial No. 119,242.

My invention comprises a treatment of petroleum distillates prior to their further fractional distillation by the cracking process, by which treatment objectionable byproducts are eliminated or reduced in quantity and a higher proportion of commercially valuable products secured. I

The known cracking processes which consist in the conversion of hydrocarbons of 1 high boiling point into those of low boiling point, increase the yield of light distillates in the fractional distillation of crude oil, at either atmospheric or increased pressure, by causing the oil vapors to remain in contact with the superheated metallic surface of the still. The su erheating of the oil vapors causes a splitting of the high boiling hydrocarbons, eonvertmg them into lower boiling hydrocarbons. Under very high tem erature, the splitting of the molecules 0 the hydrocarbons is pushed too far, resulting in the formation of fixed gases and a large amount of coke, in addition to the light hydrocarbons. M

Based on'these facts a great number of processes have been devised for producing gasoline from the hi h boiling hydrocarbons which processes iifer only in the 0011- ditions under which temperature and pressure are applied, or in the arrangement of the equipment in which the cracking is carried out.

All of these processes have certain drawbacks in common, which react unfavorably on their commercial value for producing gasoline from high boiling hydrocarbons. The main disadvantages are:

The asphaltum and the substances rich in carbon always present in the cracking stocks,

produce during the cracking operation, a

largeamount of coke which adheres to the walls of the apparatus. Its removal is dif-- ficult and necessitates frequentshutting .down of the still for cleaning. "The residuum 4 oil which has not entered into the reaction and which remains as. a by-product generphur dioxide prior to submitting it to the cracking process. It is knownthat the sulphur dioxide is a good solvent for tlie"nitrogen and sulphur bearing compounds as well as for asphaltum and substances rich in carbon. Separation of these injurious sub-. stances by liquid sulphur dioxide removes the causes of the disadvantages enumerated above.

Methods of treatment of petroleum oils with liquid sulfur dioxide for removing substances soluble therein are described in my United States Patents Nos. 911,553 and 1,526,665. A preferred method is illustrated in'the accompanying drawing, showing diagrammatically an arrangement of apparatus suitable forearrying out the invention.

Referring to the drawing, the untreated cracking stock is supplied from a convenient source, shown as the tank 1, to a pump 2 by which it is passed through a precooler 3 and the cooler 4 to the lower part of the mixer 5. Both the precooler 3 and the cooler 4 are of the double pipe type. As a low temperature in the mixer 5 is desirable, the cracking oil should be well cooled before entering the mixer 5. In the precooler 3 the oil is precooled by the cold treated oil leaving the mixer 5, and in the cooler 4 it is cooled to the desired low temperature by means of evaporating sulfur dioxide. 6

The liquid sulfur dioxide re uired for the treatment of the cracking oi is supplied from a storage tank 6 and passed through a precooler 7of the double pipe type to the cooler 8. In the precooler 7 the sulfur dioxide is precooled by the cold extract consisting of liquid sulfur dioxide which has dissolved constituents of the oil after leaving the mixer 5; in the cooler 8 it is cooled by evaporating a part of itself at low pressure. This cold sulfur dioxide is taken by a pump 9 and passed to the top of the mixer 5.

The process of mixing the oil and the sulfur dioxide is a continuous one.

The oil passing through the mixer 5 first dissolves the sulfur dioxide. As soon as the oil is saturated, the sulfur dioxide is extracting the heavy hydrocarbon from the oil. This extract is settling in the lower part of the mixer 5 and drawn off into the extract tank 10. The refined oil is drawn off from the upper part of the mixer 5 into the refined oil tank 11.

The extract is taken from the extract tank 10 by the pump 12 and passed through the precooler 7 and preheater 13 to the evaporators 14, 15 and 16. In the precooler 7 the extract is precooling the sulfur dioxide, heating up itself. In the preheater 13 the extract is heated to a higher temperature by the finished hot' extract leaving the last evaporator 16.

In the evaporator 14 the sulfur dioxide contained in the extract is evaporated by heating, by means of heating pipes 25, and passes to the condenser 17, where it is condensed. As the sulfur dioxide contained in the extract cannot be expelled completely only by heating, the remaining extract is passed to the vacuum evaporators 15 and 16 after the greater part of the sulfur dioxide in the first evaporator has been removed; in

. the vacuum evaporators 15 and 16 the last traces of sulfur dioxide are drawn off by the sulfur dioxide gas pump 26 and vacuum pump 27 and forced into the condenser 17.

The refined oil is taken from the raffinate tank 11 by the pump 28 and passed throu h the precooler 3 and the preheater 18 to t e evaporator-s 19, 20 and 21. In the precooler 3 the rafiinate is precooling the untreated cracking stock, heatin up itself, and in the preheater 18 the rafiinate is heated to a higher temperature by the finished rafiinate coming from the last evaporator 21.

In the evaporator 19 the sulfur dioxide dissolved in the refined oil is removed mainly by means of heating pipes 24, the last traces of sulfur dioxide are drawn off by gas pump 26 and vacuum pump 27 from the vacuum evaporators 20 and 21.

The finished hot extract is discharged from the last evaporator 16 by the pump 22 and passed through the preheater 13 to the storage tank. In the preheater 13 the finished extract is heating up the extract going to the first evaporator 14 at the same time cooling down itself.

The finished hot rafiinate is taken from the last evaporator 21 by the pump 23 and passed through the preheater 18 to the storage tank. In the preheater 18 the finished raffinate is heating up the raftinate going to the first evaporator 19 and at the same time cooling itself down.

The vacuum pump 27 draws off the last traces of sulfur dioxide from the last evaporators 16 and 21 under high vacuum and pushes the vapors to the gas pump 26.

The gas pump 26 draws off that part of sulfur dioxide which cannot be driven out only by heating, from the evaporators 15 and 20. At the same time it draws o fi vapors of sulfur dioxide from the cooler 8. It compresses all the vapors and pushes them to the condenser 17 in which they are liquefied.

The liquid sulfur dioxide is collected in the tank 6 and used again.

For cooling the cracking stock, part of the liquid sulfur dioxide is branched off before entering the cooler 8 and passed through the c0010! 4. In the cooler 4 the liquid sulfur dioxide comes in contact with the cracking stock having a higher temperature than the sulfur dioxide and a part of the sulfur dioxide vaporizes at a rather low temperature as the pressure is kept low at the sulfur dioxide side. Thus the cracking stock passing the cooler is cooled to the desired temperature.

The vapors of sulfur dioxide are drawn off through the cooler 8 to the gas pump 26.

As one illustration of the advantages of my invention I give the following: By the treatment with llquid sulphur dioxide of a Texas Luling gas oil having a specific gravity of 0.889 and a sulphur content of 0.8%, a gas oil with a specific gravity of 0.865 and sulphur content of 0.24% is obtained. If both gas oils are cracked separately under equal conditions of pressure (about 85 lbs.) and temperatures (about 770 F.) the following products result:

Non-

treated Treatfid gas oil 0 P21 cent P I Cracked distillate n 6 Gasoline 4!) 53. 7 Coke 4. G i. 5 Sulphur in the cracked distillate 0. 34 0.09 Sulphur in gasoline 0. l 0. 06

In non-treated gas oil which remains as a by-product there will form after a while a sediment of about 6% of carbon and asphaltic matter, while in the treated gas oil there will appear only traces of sediment.

If the cracking of gas oil into gasoline is affected by pressure andcatalytic action, as for instance by means of any of the known catalysts for aiding in the conversion of hydrocarbons, the advantages of using a gas oil preliminarily treated with liquid sulphur dioxide are more striking.

The invention is not restricted to any particular oil or cracking process but pertains generally to the use of liquid sulphur dioxide fortreetingthematerialsto' cracked prior to subjecting them-to What-I claim is:

v 1. An im roved recess for the cracking 5 of high boi ng hy ing hydrocarbons which consists in'submitting to a p cracking process the portion of-the distillats which remains undissolved after being treated with liquid sul- I phur dioxide. v

2. An im roved process for the cracking of high hydrocarbons into low boiling hydrocarbons by removing from the cracking st'ock the-.nitrogenand sulphur com- 15 pounds as well as the asphaltum by meansof v rbons into low boil-- li uid sulphur dioxide and by afterwards mitting the cracking 'stockto a pressure cracking process. n

3. An improved process for cracking hydrocarbons aving a high boiling point into hydrocarbons having a lower boiling point b3 treating them with li uid sulphur dioxi e, separating the li sulphur dioxide and hydrocarbons dim ved therein, and subjecting the undissolved hydrocarbons to pres- 2 sure cracking in the presence of a catalyst.

Intestiinony whereof, I have signed my name to this specification. 1

LAZAR EDELEANU.

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