US2319354A - Production of motor fuel of low sulphur content - Google Patents

Description

` May 1s, 1943 c. ci.4 sPERLlNG PRODUCTION'OF MOTOR FUEL 0F LOW SULPHUR CONTENT Filed Oct. 31, 1940 ATTORNEY.

-` Patented May 1s, 1943 UNITED STATES PATENT NOFFICE PRODUCTION OF MOTOR FUE'OF LOW J SULPHUB CONTENT Curren C. Sperling, Elizabeth, N.'J., assignor to Petroleum Conversion Corporation, Elizabeth, N. J., a corporation ot Delaware Application october 31, 194o,ser1 a1 No. 363,595'

'1 claims. `(c1. 19e-24) My invention relates to vapor phase cracking systems in which a hydrocarbon heat-carrier gas is commingled with a stream of sulphur-bearing hydrocarbon vapors -to produce cracking'thereof, and has foran object the provision ot a reliable and eective method and means for obtaining a substantially sulphur-free motor fuel therefrom.

Due to thecorrosi've action in an internal combustion engine of any sulphur compounds which may be contained in motor fuel, the permissible sulphur content, by present day standards, should not exceed about 0.2% by weight. Since many petroleum stocks are characterized by a relatively high sulphur content, from 0.5 to 5.0% by weight, the problem of removing the sulphur is very important, and one to which considerable time and research has been devoted. The sulphur removal Y problem is -cnplicated bythe fact the sulphur compounds may be exceedingly complex and because of their chemical and physical characteristics; for example, they may fall within the boil ing range of the motor fuel; they may not readily react with sulphur-removing agents or reagents which are inexpensive, and they mayrequire reagents which themselves produce material degradation of the motor fuel, or end products.

It is a further object of my inventionto prov ide a combination cracking and sulphur-removing system characterized by the conversion of the complex sulphur compounds into readily removable sulphides. which are then removed 'withou degradation of the end product.

In carrying outjmy invention in one form thereof, a stream of heated hydrocarbon vapors is com- Amingled with a high temperature stream of heatcarrier Sas and the mixture retained in a reaction chamber for the cracking of the vapors. The

temperature within the reaction chamber ranges from about 975 to 1075 1*".v To control the conversion of the sulphur compounds, a' substantial-` .ly sulphur-free heat-carrier gas .issupplied; and I in quantity such that the gas to oil vapor ratio is maintained high, as oi' the order of 1 to 3 by weight. The complex sulphur compounds then break down into removable sulphides, such as hy- 4 drogen sulphide, to the substantial exclusion of sulphur-compounds in the gasoline range. For' the removal of all of the sulphldes', all of the vaporizable reaction products are intimately contacted with a' sulphide removing agent. Preferably the sulphur-free heat-carrier gas is derived from the cracking system itself.-

For a more complete understandingl of my 'invention reference should now be had to the drawing, in which I have diagrammatically illustrated a system embodying a preferred form of my invention, the single lines symbolically representing .the connecting pipe lines.

Referring to the drawing, I have shown my invention in one form as applied to a vapor phase cracking process in which a charging stock, such for example as a sulphurbearing gasoil, is supplied by way of line Ill to a pump I I which forces it by way of lines I2 and I3" through the heating coil Il of a double end-fired heater I5. From transfer line I6 the oil, under the control of a pressure regulating valve I1, is discharged into a ash drum I8. To assist in vaporizing the heated gas oil, a heated ash gas from a supplyline 20 is through line 2l introduced into the lower part of the flash drum. The flash gas, substansisting of those having less than three carbon atoms per molecule. Additional flash gas is introduced into the upper part of the flash drum through line 22, the latter gas serving to dry the vapors withdrawn through the overhead outlet -line 23. The valves 2Ia and 22a are preferablyl included to control the quantity of flash gas entering the flash drum. T he derived stream of vapors along with the flash gas passes through line 2l to a heating coil 2l of the heater I I and under the control of valve 25 this heated stream of vapors enters the transfer line 26 at the mix point 21. Preferably the vapors 'are heated to within or just below the range of their cracking temperature (to about 900 F.) and during a timeinterval insuiiicient for material cracking to occur.

Concurrently with the foregoing operation, a heat carrier or cycle gas lslderived fromthe gas made in the cracking system, and as shown, a gas consisting chiey of hydrocarbon compounds having between 3yto 5 carbon atoms per molecule ilowrs through line III, is elevated in temperature by heat exch ger 3l, and through line 32 enters the heating cpil I3 of a double` end fired heater 34. At a temperature of 1200 F. or above the the cycle gas Vor heat-carrier gas is maintained cycle gas flows by way of line 35 and under the control of valve Il enters the transfer line 26 at the mix point 2l. The roof and :door tubes in j both the right and left hand iire chambers of the heater 34 are utilized in the heating of the cycle gas to its relatively` high temperature.

As will be explained'more in detail hereinafter;

substantially free of all sulphur compounds. In quantity it preferably bears a ratio of about 1 to 3 E; veiight to the ,vapors 'entering the transfer e V f Y high anti-knock characteristics.

gasoline range, and/or which are readily remov able without degradation of the final product of gasoline. A

vFrom my own investigation and research, I have found that as the sulphur content rises in the cycle and flash gases, more and more sulphur compounds are formed which fall within the gasoline range, which compounds cannot be.

easily and inexpensively removed from the gasoline. However, `by maintaining a substantially sulphur-free heatfcarrier or cycle and ash gas and by maintaining a relatively high ratio of gas to the oil vapors, the sulphur com unds Aare converted to the removable sulphides. 'I'he particular manner of removing the sulphides will be set forth in detail hereinafter.

The heat-carrier cracking system thus ,far described is characterized by agasoline yield comparable to and exceeding that of liquid phase cracking systems, and in particular is characterlzed by an end product 'having exceedingly For example, the typical range of the octane numbers of Supply tank 66. The agent, by pump 6l, may be introduced, under the control of valve 69, into the line 68 ahead of the-cooler or' main condenser 65; or, under the control of valve 10, it

vmay be introduced into the line 68 after the cracked products have passed through the cooler 65. In either case the sulphur removing l from any one of the numerous materials known gasoline is between 78 and 95, 1939l research Y method. Fln'ther in accord with my invention, there is no degradation oi end products either as to octane number or to yield as the result of the sulphur removal, in contrast with the material degradation resulting from conventional systems of removing sulphur from the end product of gasoline.

Again referring to the drawing, the mixture of heat-carrier gas and heated vapors is retained in a reaction chamber 38 for a suitable period of time (one of three minutes) and then discharged to a scrubber 39, preferably provided, with a number of bubble caps and trays (not shown) near the top thereof. The reaction products are scrubbed by a relatively large volume of scrubbingA medium comprising the residual oil from the flash drum I8 which through line 4l mixes with the residum from the bottom of the scrubberr39. The residuum is preferably cooled at 42 and by pump 43 forced into .the transfer line between the reaction chamber and scrubber for intimate mixture with the reaction products.

Residuum may be withdrawn from the under the control of .valve 44.

A vaporous overhead stream is taken from the scrubber 39 by way of line 45, the heat exchanger 3l included in the cycle gas line 30, and dissystem vcharged by line 46 into the lower portion of a bubble tower or Yi'ractionator 41. A relatively heavy fraction, such as gas oil, may be taken from the lower part of the bubble tower and by pump 48 introduced into the upper part of the scrubber 39' as reflux therefor. The bottoms from the bubble tower, iforming the recycle stock, pass by way of line 6|, valve 62, and pump 63, and in line I3 join with the charge. The overhead stream of vapors from the bubble tower 41 is reduced in temperature by heat exchanger,

a cooler, or by a condenser as indicated at 65.

In accordance with my invention, it is at this point that I prefer to introduce the sulphur removing agent, and for this purpose I provide a by those skilled in the art to be reasonably. ef= fective in chemically unitingwith the sulphides to produce products or precipitates which are heavier than the products suitable for inclusion in motor fuel.' I have found that awater wash including 10% by weight of sodium hydroxide (NaOH) is quite satisfactory. This 10% solution ofA sodium hydroxide maybe obtained from partially spent sodium hydroxide, iirst utilized for other purposes'in the refinery, and by partial recovery systems the same reagent may be used over and over again, thus reducing to a negligible amount the cost-of removing the sulphur from the system. As I have indicated, any suitable agent may be utilized and by way of further example the following agents will be satisfactory:

(1) Tri-potassium phosphate from which hy- ,drogen sulphide may be regenerated by heating the extracted medium;

(2) A concentrated aqueous solution of sodium phenolate or sodium salts of tar acids as extraction media from which the hydrogen sulphide can be regenerated and the media recycled. Other methods are known to the art and those most desirable are the regenerative and recycling operations which produce as a by-product, the hydrogen sulphide which may be used for the production of sulphuric acid.

Although I prefer to use an active agent, under some circumstances it may be practical to use water, into which the hydrogen sulphide may be dissolved, as suggested by Sachs Patent #1,872,349, dated August'16, 1932.

Regardless of which sulphur-removing agent is used it must be supplied in suilicient quantity to remove all of the hydrogen sulphide. For ex-` ample, 'if a solution of sodium hydroxide were used twomols of sodium hydroxide must be used for each mol of hydrogen sulphide removed from the cracking unit.

The desirability of sulphur removal is set forth in'said Sachs patent, but one material and essential diierence therefrom is the failure of thea Sachs disclosure to provide for the removal of sulphur compounds from both the condensate and the gas. In consequence, the end product of gasoline contained more than the permissible 'amount of sulphur for those crudes of relatively high sulphur content. Moreover, the Sachs disclosure failed to utilize rich Ca and C4 hydrocarbon gases for his heat-carrier, a matter of real importance to applicants invention. I have further determined that secondary reactions of the sulphur compounds can and do take place in low temperature zones, such as in the stabilizer, so that higher boiling sulphur compounds,

. 2,319,354 those within the boiling range of gasoline, arev formed and make the gasoline undesirable for motor fuel. In accordance with my `invention these sulphur compounds are removed while in their removablestate as sulphides and before any secondary reaction to high boiling compounds.

4 After the sulphur-removal treatment, `the reaction products and the sulphur removing agent flow through line 12 from the contacter or treater 1i and they pass together into a low pressure ac-` cumulator 13, having adequate capacity for the settling of the water and sulphur products from the hydrocarbon condensate. The water 'and sulphides are withdrawn by way of line 1|, un-

der the. control of valve 15, automatically operated by an interface controller 16 of any suitable type. The interface controller is an instrument well known to those skilled in the art and no furtherV explanation is needed herein other than to say that it functions in response to change in Alevel of the interface between the water and the valve join with the stabilizer tops which oomprise the ygases rich in Cas and 04's. The gas derived from the high pressure accumulator is known as the make gasand part of it under the control of valve l1 may be' discharged from the System through line- Il, while the remaining part thereof, under the control of valve 99, ilows by way of line lll to the convection bank III of the double end fired heater Il and forms the supply of the heated flash and. drying gas introduced by way of line 2l 4into the hash drum Il, as'above described.

In a system embodying my invention I have produced substantially sulphur-free gasoline from relatively high sulphur-bearingpetroieum fractions. And in those instances where" the sulphur content slightly exceeded the permissiblesulphur content in the end product or gasoline, I have by blending with a straight-run gasoline of low sulphur content, produced a highly satisfactory, marketable Vgasoline of high antiknock value, and of satisfactorily low sulphur l content, for example less than .2% by weightA of sulphur. Moreover, myinvention .has made possible the production of marketable gasoline,

-suiiiciently low in sulphur, from crudes having a sulphur content so high as to heretofore have Y beenconsidered of no value as charging stock 41h passes into the upper part of the bubble tower as reflux therefor. From the top of the low pressure accumulator, gas is withdrawn into a compressor 11, discharged therefrom at about 250# per square inch, reduced in temperature in cooler 19, and discharged into a high pressure accumulator 80. A second stream of coni densate is withdrawn from the accumlator 1I by pump 8l and joins with the compressed gas in line 18 and passes with it into 'the accumulator 80. In this manner condensable constituents in the gas withdrawn from the low pressure accumulator are removed as a condensate in the high pressure accumulator 80. It is to be understood a recovery system of the absorber type may be used instead of the compression type oi'- recovery system described and illustrated herein. Condensate from the high pressure accumulator passes by way of pump 83, under the control of valves 84 Aand 85, into a stabilizer 86, provided with a plurality of\bubble caps and trays (not shown).

In `the stabilizer', as is well understood in the art, heat is supplied to the lower part thereof as by a reboiler '81 and stabilized gasoline is withdrawn therefrom and sent to storage under oontrol of valve B8 and by way of line 89. The reboiler oil circuit is indicated at 90 andSl. The lighter constituents withdrawn from the top of the stabilizer 86 are reduced in temperatur@l by va cooler 92, and the resulting condensate collected in accumulator 93, from which it is returned by pump 94 to the stabilizer as redux therefor. The constituents removed in the sta'- `bilization of th cracked gasoline comprise hy- Idrocarbons having 3 to 4, and some 5 carbon atoms per molecule, more and less, and these' Allcgan Freeman Black Mt Charge at line 10 hllgiogcn Wyomiiiig crude crude sus 9 Gravity AP1 zz. s am 21.1 Sulphur wt. per ecnt 1.13 0. 82 2. 27, Cracking temp. F. in chainv ber 38 980 990 1000 Cracking pressure in chamber se 10o loo 10o Cracked qalnc leaning line 89 Volume per cent of charge.-. 49 70 55 Gravity API 57. 0 50. 0 56. 0, Octane MM. 72 70 i 79 Octane i939 res S5 85 95 Sulphur per cent by weight- 0.09 0.07 0. 32

Hydrogen sulphide removed in V 'une 74 Weight per cent of ch 0. 2 0. 7 0.v 8 Wght per cent oi ava bie phur. 20.0 aso a5. cv

col

-te'nt of the gasoilis 2.27 weight per cent, an

for cracking systems for the production of'gasoline. Thus, my invention has madefeasible the economic utilization of high sulphur-bearing 'charge oils which were hitherto considered of no value as charging stocks for the production of marketable gasoline.

v By way of further illustration and not of limitation, my invention has been applied to charge oils including those set forth in the following tabulation:

Taking -the Black Mountain Wyoming gas oil as illustrative it wi1lbeobserved the sulphur oo namountwhich has made this particular crude of littlevalue as a charging stock for the pro- L duction of cracked gasoline. In accord with my invention, this high percentage of sulphun'under the controlled .conditions of temperature and pressure and sulphur-free character of the heatrich gases pass by way of line 30 to.form the chief'supply of cycle or heat-carrier gas for the operations described above. In c'ase these gases are insuiiicient in quantity for the supply of the r quired amount of cycle gas, additional gas deriv d from the high pressure accumulator 80, by way of line 95, may, under the control -of carrier or cycle gas. was converted to removable sulphides to such a degree that only 0.32% by weight of sulphur appeared in the stabilized gasoline. Thus, by blending with low-sulphur gasoline a marketable, high octance gasoline was produced. Specifically by blending 33t/3% oi' straight run having a sulphur. content of, 0.1%

by weight, a gasoline was produced, having a sul-l removable sulphides.

phur content not above about .2% by weight.

More 'specically with respect to the Black Mountain Wyoming gas oil, the weight of a 42 gallon barrel is about 311 pounds. There is present therein around 7.07 pounds of sulphur. In line 'I4 therewill be removed about 2.49 pounds of hydrogen sulphide, which in terms of per cent of hydrogen sulphide removed against the total pounds of sulphur, comes to about 35%. A part of the remaining sulphur is removed with the residuum discharged under control of valve Il so that only the 0.32% by weight of sulphur remains inthe stabilized gasoline. For crudes having a sulphur content as high as 2% by weight, gasoline may be produced which, without further blending o'r treatment, will have a sulphur content not exceeding 0.2% by weight.

Moreover, by removing the sulphur from the cracked liquid products immediately after their exit fromA the bubble tower,v there, is no opportunity for secondary reactions of the sulphur compounds contained therein. These sulphur compounds as they-exist in the overhead stream from the bubble tower largely comprise readily they are not immediately removed, as by admixture vwith a sulphide removing agent either 4 ing in the usual stabilizing column such as column 86 are suiciently favorable for the occurrence of these .undesirable secondary reactions.

My invention is fu'rther characterized by the fact the sulphur is removed as a by-product of the system. Since the sulphur is in the form of sulphides (largely hydrogen sulphide) upon regeneration of the sulphur-removing agent the sulphides given oi therefrom may be used -for the production of sulphuric acid in manner well understood by those skilled in the art.

While I have shown a particular embodiment of ny invention, it will be understood that I do not limit myself thereto since many modifications may be made, and .I therefore contemplate by the appended claims to cover any such modifications as fall within the spirit and scope of my invention.

What I claim is:

l. In a vapor phase cracking system in which a gaseous hydrocarbon heat carrier lis commingled with and utilized forthe cracking of a stream of heated sulphur-bearing hydrocarbon vapors, the method of maintaining low the sulphur content of the end product which consists in maintaining a high ratio .of said gaseous heatcarrier to said hydrocarbon vapors during the cracking thereof, fractionatingn and cooling the cracked products, contacting both the gaseous and liquid constituents of said cracked products with a sulphide removing agent, separating said agent and said sulphides from said gaseous and liquid cracked products, separating from said products heat carrier gas having a sulphur content sufficiently low to promote the formation- 'of removable sulphides from said heated sulphur-bearing vapors, and separating from said liquid products a motor. fuel end-product characterized by its low sulphur content and its high anti-lmock value.

I have discovered that if 2. vIn avapor phase cracking systehiin-which/ a gaseous hydrocarbon heat carrier is commingled with and utilized for the cracking of a stream of-heated sulphur-bearing hydrocarbon said sulphides from said gaseous and liquid cracked products, separating from said products heat carrier gas having a sulphur content sutilciently low to spromote the formation of removable sulphides from said heated sulphur-bearing vapors, heating said separated cycle gas to a high temperature and commingling it with said stream of sulphur-bearing vapors .to promote cracking thereof and to convert'the contained c sulphur content into removable sulphides, and

separating from said products a motor fuel endproduct characterized by a sulphur content sufiiciently low for non-corrosive use in internal combustion-engines.

3. In a vapor phase cracking system in which a hydrocarbon heat carrier is commingled with a stream of heated sulphur-bearing hydrocarbon vapors to. assist in the cracking thereof, the method of maintaining low the sulphur content of the end product which consists in maintainy. said agent and sulphides, said gaseous constituing a ratio above unity by weight between said gaseous heat-carrier and said vapors, fractionating and'cooling the cracked products, in an elongated zone of restricted cross-sectional area intimately mixing a sulphide removing agent with the gaseous and liquid constituents of said 'cracked products, passing said mixture into an enlarged zone, separately withdrawing therefrom ents, and said liquid hydrocarbon constituents, supplying said agent in quantity to maintain the ratio of the agent to the cracked products sufficiently. high to produce substantially sulphur-free gaseous and liquid hydrocarbon constituents, and withdrawing said last-named constituents from said enlarged zone.

4. In a vapor phase cracking system in which a hydrocarbon heat carrier gas is commingled with and utilized for the cracking of a stream of heated sulphur-bearing hydrocarbon vapors,

the method of converting the sulphur compounds contained in said vapors into removable sulphides which comprises, maintaining a ratio of at least unity by weight between said gaseous heat-carrier and said vapors, fractionating and cooling the cracked products produced'as a result of\ the mixing of the vapors with the heatcarrier gas, in a conduit introducing into inti-I mate contact with said cracked products a sulphide removing agent, in an enlarged zone subdividing said mixture to provide further intimate contact of the agent with said products, in a second enlarged zone gravity-separating said agent and said sulphides from said gaseous and liquid products, recovering from said gaseous products constituents suitable for inclusion in tracking reaction to be converted into remov' able sulphides.

5p. In a vapor phase cracking system in which a hydrocarbon heat-carrier gas is commingled with a stream of heated sulphur-bearing hydrocarbon vapors to assist in producing cracking thereof, the method of converting the sulphur compounds contained in said vapors into removable sulphides, such as hydrogen sulphide; which comprises supplying a substantially sulphur-free heat carrier gas for mixture with said vapors to crack them, while maintaining high, on the order of 1 to 3 by weight the ratio of said gas to said vapors, cooling and fractionating the reaction products, intimately washing and scrubbing saidproducts with a sulphide removing agent, in an enlarged zone separating said agent and the removed sulphides from said cracked products, and Aseparating from said cracked products said substantially sulphur-free gas to form the supply of said heat-carrier gas, andlwithdrawing from the system a motor fuel end-product characterized by a sulphur content below about 0.2% by weight.

6. 'Ihe method of producing a gasoline having a sulphur content not exceeding 0.2% by weight from a crude having a sulphur content of about 2.0% by weight, which comprises deriving from the crude a stream of hot sulphur-bearing hydrocarbon vapors, commingling therewith a gaseous hydrocarbon heat carrier which supplies heat for the cracking of said vapors, maintaining a ratio of at least unity by weight between said gaseous heat-carrier and said vapors, tractionating and cooling the cracked products, contacting both Athe gaseous and liquidconstituents of said cracked products with a sulphide removsaid heated sulphur bearing vapors, and .sepa-' rating from said liquid products a motor ue'l characterized by a sulphur content not exceedi ing 0.2% by weight and by a high anti-knock value.

7. Themethod of producing from a charging stock having a high sulphurv content a` motor fuel having a low sulphur content, which comprises deriving a stream of heated sulphur-bearing hydrocarbon vapors from said charging stock, cracking the same by commingling therewith a high temperature gaseous hydrocarbon heatcarrier, maintaining a high ratio of said gaseous heat-carrier to said hydrocarbon vapors during the cracking thereof, fractionating and cooling the cracked products, preventing secondary reactions of the sulphur compounds in said cracked products with a sulphidevremoving agent, separating said agent and said sulphides from said 'gaseous and said liquid products, separating from said products4 said heat carrier gas with a sulphur content sulciently low to induce the formation of removable sulphides during the cracking of said sulphurbearing vapors and Y comprising a substantial proportion of C3 and C4 compounds, and in the substantial absence of secondary reactions of said sulphur compounds separating from said liquid products a-motor fuel characterized by a sulphur content not exceeding 0.2% by weight.

CURREN C. SPERLING.

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