US2042452A - Treatment of hydrocarbons - Google Patents

Description

Jun 2, 1936. H BOYD, JR 2,042,452

TREATMENT OF HYDROCARBONS Filed. Sept. 8, 1933 [nvenZor James H Boyd, cf]:

bis 1455077129 Patented June 2, 1936 UNITED STATES PATENT OFFICE TREATMENT OF HYDROCARBONS James H. Boyd, Jr., Philadelphia, Pa., assignor to The Atlantic Refining Company, Philadelphia, Pa., a corporation of Pennsylvania.

The present invention relates to a process ofl hydrocarbon oil conversion and more particularly to the polymerization of unsaturated gaseous hydrocarbons to form liquid hydrocarbons of the motor fuel boiling range.

A particular object of my invention is the polymerization of hydrocarbons containing from 2 to 5 carbon atoms to the molecule by subjecting the same to the action of heat and pressure in the reaction chamber of a pressure cracking apparatus, thereby to increase the yield of motor fuel produced.

A further object of my invention is the cooling of the cracked products issuing from the cracking furnace tubes during their introduction into the reaction chamber, said cooling being effected by the injection of liquefied gaseous hydrocarbons or liquefied gases in admixture with higher boiling hydrocarbons.

In many processes of pyrolytic decomposition of high boiling hydrocarbon oils to produce motor fuels, the oil is heated in tubes and rapidly raised to a cracking temperature, and subsequently the heated oil is maintained at the cracking tem- 25 perature for a period suflicient to permit the formation of appreciable quantities of hydrocarbons of the gasoline boiling range. Generally, in the operation of liquid phase cracking processes, the high boiling oil introduced from the heating 3o tubes into the reaction chamber will be at a temperature in excess of 850 F., and under a pressure in excess of 250 lbs./sq. in. Furthermore, in cracking processes where the oil in the heating tubes is raised to an abnormally high 85 temperature in order-to obtain high cracking rates, it is desirable to cool the oil to a certain extent before introducing it into the reaction chamber, to prevent the formation of relatively large amounts of carbon, which would occur at 40 such high temperatures, e. g., when cracking at temperatures above 950 F., in the heating tubes, it is desirable to cool the oil so that the temperature in the reaction chamber is not substantially in excess-of 900 F. J, 5 I propose to utilize the heat available in the reaction chamber for. the polymerization of the normally gaseous unsaturated hydrocarbons, particularly propylene and butylenes, or mixtures thereof occurring in' or produced from liquefied 5 gases from petroleum or natural gasoline refineries, and simultaneously to effect a partial cooling ofthe heated oil entering the reaction chamber by the introduction of the liquefied gas either alone or in admixture with higher boiling 5'5 hydrocarbons, as for example, gas 011.

My process is to be distinguishedfrom those processes of the prior art which suggest the recycling ofuncondensed gases to a cracking system for the purpose of reducing gas formation by operation of the law of mass action. 5

In the cracking of hydrocarbon oils, heat must be supplied to efiect'the decomposition of the higher boiling hydrocarbons into those of lower boiling range, i. e., the cracking is an endothermic reaction. However, it has been found that the l polymerization of unsaturated hydrocarbons to form higher boiling compounds is an exothermic reaction, i. e., when the unsaturates are heated to a temperature sufiicient to start the polymerization, the reaction takes place with the evolution 15 of heat. By introducing the relatively cool liquefied gases into the reaction chamber together with the heated products from the cracking tubes, a reduction in temperature is effected so that cracking and/or polymerization of the oil from the heating tubes is effected with the formation of less carbon, and simultaneously the liquefied gas is raised to a temperature sufllcient to initiate the polymerization of the components thereof.

For a further understanding of my invention,

reference is made to the accompanying drawing which illustrates an arrangement of apparatus suitable for carrying on my process. Hydrocarbon oil is withdrawn from storage (not shown) through pipe I and is forced by means of high pressure feed pump 2 through pipe 3, heat exchange coil 4 in the top of fractionating column l0, pipe 5, heat exchange coil 6 in the top of evaporating tower 2|, pipe I and pipe 8 into reaction chamber 9. Gas oil is drawn from storage (not shown) through pipe 36 and is passed by low pressure feed pump 31 through pipe 38 into a lower bubble plate section of the fractionating tower I 0. This gas oil is heated therein by con- 40 tact with the vapors of the incoming cracked products from pipe 22 of evaporator 2|, and such gas oil together with reflux condensate from column I0 is withdrawn from the bottom of the column through pipe II, and valve controlled pipe l2, and is passed by means of hot oil pump l3 through pipe l4 into heating tubes l5 of furnace l6. Herein the oil is heated to a temperature of the order of from about 940 F. to 960 F. and is passed through pipe l1 and pipe 8 into reaction chamber 9. Simultaneously a suitable quantity of liquefied gas is drawn from storage (not shown) through pipe 39 and is forced by means of high pressure pump 40 through valve controlled pipe 4] and-pipe} into reaction chamher 9. The heated oil from the tubes i5 is thus partially cooled in the reaction chamber, and the process of cracking, and of polymerization of the unsaturated components of the liquefied gas is efiected therein at a temperature of the order of from about 865 F. to 900 F., and under a pressure of about 750 lbs/sq. in.

The products from the reaction chamber 9 are withdrawn by means of pipe I8 and the pressure is reduced from about 750 lbs/sq. in. to about 70 lbs/sq. in. by means of valve l9, and the liquid-vapor mixture is introduced through pipe 20 into evaporator 2|. Due to the relatively low pressure, of the order of 70 lbs./sq. in., maintained in the evaporator, the lower boiling components of the mixture introduced pass as vapor from the upper portion of evaporator 2| through pipe-22 into fractionating column I0.- The tar and high boiling hydrocarbons which are stripped from the vapors in evaporator 2| are withdrawn from the bottom of the evaporator by means of valve controlled pipe 23. The vapors entering fractionating column III are stripped of their heavier components, such as, for example gas oil, in passing upwardly through the column in contact with reflux condensate and. gas oil introduced thereinto. The vapors passing from the top of column l comprises substantially the hydrocarbons of gasoline boiling range. These vapors are passed through pipe 24, partial condenser 24a and pipe 25a into reflux drum 25. A portion of the cracked distillate vapors which were condensed in partial condenser 24a. are withdrawn from drum 25 through valve controlled pipe 33 and are passed by means of reflux pump 34 and pipe 35 into column ID to serve as reflux in such column. The remaining condensate from the bottom of drum 25 and the vapors from the top of said drum are passed to condenser 28 through valve controlled pipe 21, and pipe 26 respectively.

- -In passing through condenser 23, substantially all the material which may be condensed, under the conditions of temperature and pressure therein, is condensed and passed through pipe 29 into gas separator 30. The condensate, i. e., cracked gasoline, is separated from the uncondensed gases, the gasoline being withdrawn from the bottom of the separator by means of valve controlled pipe 32, while the gases are passed from the top through valve controlled pipe 3|.

It may, in some cases, be preferable to admix the liquefied gas with the oil charged to the system through pipe I and pump 2 instead of introducing said liquefied gas directly to the reaction chamber through pipe 39 and pump 40. Or, it may be desirable to introduce the liquefied gas in admixture with heavier hydrocarbon oil, such as for example, gas oil, into the reaction chamber 9 by means of pipe 39, pump 40, valve 4| and pipe 8.

The operating conditions, i. e., temperature, pressure and time which may be given in the above description are merely exemplary, and'I do not intend to limit myself thereto, as my process is operable under various conditions of temperature, pressure and time depending upon the character of the oil charged, the composition of the liquefied gas and the properties of the gasoline desired. Furthermore, my process is equally applicable to vapor phase as well as liquid phase systems. a

Reference to the table given below shows th results obtained from actual operation of a liquid phase cracking system with and without the use of liquefied gas. The liquefied gas used had the following approximate composition: propane 8%, propylene 2%, butanes 45%, butylenes 45%.

From the above table it will be seen that by operating in accordance with my invention the yield of motor fuel was increased by 1.74%, the yield of tar was decreased by 0.20% and the yield of gas was decreased by 1.54%.

For brevity, in the appended claims the term liquefied gas is to be understood to comprehend low boiling hydrocarbons or mixtures of low boiling hydrocarbons containing from 2 to carbon atoms to the molecule. It is also to be understood that the liquefied gas after introduction into the cracking system, may or may not remain in the liquid phase, depending upon the operating conditions of temperature and pressure.

What I claim is:

1. The process of converting liquefied highly oleflnic gas into liquid hydrocarbons suitable for use as motor fuel, which comprises passing hydrocarbon oil through an elongated zone of restricted cross-sectional area under high superatmospheric pressure, heating the oil therein to a high cracking temperature, passing the products without substantial pressure reduction into a reaction zone, introducing a controlled amount of liquefied oleflnic gas, comprising principally hydrocarbons having from 2 to 5 carbon atoms per molecule and substantially free from hydrogen and methane, into said reaction zone whereby said reaction zone is maintained at a. lower cracking temperature sufficient" to efi'ect polymerization of oleflnic constituents of said gas, removing the reaction products from said lastmentioned zone and separating hydrocarbons of motor-fuel boiling range from lighter and heavier constituents of said reaction products.

2. The process of converting liquefied highly oleflnic gas into liquid hydrocarbons suitable for use as motor fuel, which comprises passing hydrocarbon oil through an elongated zone of restricted cross-sectional area under a superatmospheric pressure of the order of 750 pounds per square inch, heating the oil therein to a high cracking temperature, passing the products without substantial pressure reduction into a reaction zone, introducing a controlled amount of liquefied olefinic gas, comprising principally hy-' drocarbons having from 2 to 5 carbon atoms per molecule and substantially free from hydrogen and methane, into said reaction zone whereby said reaction zone is maintained at a lower temperature sufiiciently high to efiect polymerization of oleflnic constituents of said gas, removing the reaction products from said last-mentioned zone and separating hydrocarbons of motor-fuel boiling range from lighter and heavier constltuents of said reaction products.

3. The process of converting liquefied highly oleflnic gas into liquid hydrocarbons suitable for use as motor fuel, which comprises passing hydrocarbon oil through an elongated zone of restricted cross-sectional area under high superatmospheric pressure, heating the oil therein to a relatively high cracking temperature of the order of 950 F., passing the products without substantial pressure reduction into a reaction zone, introducing a controlled amo nt of iquefi d olefinic gas, comprising principally hydrocarbons having from 2 to carbon atoms per molecule and substantially free from hydrogen and methane, into said reaction zone whereby said reaction zone is maintained at a lower cracking temperature not substantially in excess of 900 F. sufiicient to effect polymerization. of olefinic r constituents of said gas, removing the reaction products from said last-mentioned zone and separating hydrocarbons of motor-fuel boiling range from lighter and heavier constituents of said reaction products.

4. The process of converting liquefied highly ole finic gas into liquid hydrocarbons suitable for use asmotorfueLwhichcomprisespassinghydrocarbon oil through an elongated zone of restricted crosssectional area under a pressure of the order of 750 pounds per square inch, heating the oil therein to a high cracking temperature of the order of 950 F., passing the products without substantial pressure reduction into a reaction zone, introducing a controlled amount of liquefied olefinic gas, comprising principally hydrocarbons having from 2 to 5 carbon atoms per molecule and substantially free from hydrogen and methane, into said reaction zone whereby said reaction zone is maintained at a lower cracking temperature not substantially in excess of-900 F. sumcient to efiect polymerization of olefinic constituents of said gas, removing the reaction products from said last-mentioned zone and separating hydrocarbons of motor-fuel boiling range from lighter and heavier constituents of said reaction products.

5. The process of converting liquefied highly olefinic gas consisting primarily of hydrocarbons of from 2 to 5 carbon atoms to the molecule into liquid hydrocarbons suitable for use as motor fuel, which comprises passing a non-residual hydrocarbon oil through an elongated zone of restricted cross-sectional area under high superatmospheric pressure, heating the oil therein to a high cracking temperature, passing the products without substantial pressure reduction into a reaction zone, introducing a controlled amount of liquefied olefinic gas, comprising principally hydrocarbons having from 2 to 5 carbon atoms per molecule and substantially free from hydrogen and methane, and relatively heavy hydrocarbon' oil into said reaction zone whereby said reaction zone is maintained at a lower cracking temperature suflicient to effect polymerization of olefinic constituents of said gas,vremoving the reaction products from said last-mentioned zone,

removing tarry residual constituents therefrom;

fractionating the remaining products to recover a clean condensate heavier thangasoline and recycling said condensate to the oil-cracking zone, removing the fractionated vapors and recovering motor fuel constituents therefrom.

JAMES H. BOVYD, JR.

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