US2340922A - Desulphurization of hydrocarbon oils - Google Patents

Description

8, 1 R. D. BENT ETAL 22 DESULFHURIZATION 0F HYDROCARBON OILS Filed A rii 15, 1941 Inventors G263 Charles A. Pines M T By M a aw I Their Aflmrney Patented Feb. 8, i944 2,340,922 DESULPHURIZATIgfigF HYDROCARBON Robert D. Bent, Springfield, and Charles A. Pines, Upper. Darby, Pa., asslgnors to The Atlantic Refining Company, Philadelphia, Pa., a corporation of Pennsylvania Application April 15, 1941, Serial No. 388,570

8 Claims.

The present invention relates to the treatment of hydrocarbon oils, and more particularly to the production of gasoline of improved lead susceptibility and reduction in sulphur content of .higher boiling oil components. a

An object of this invention is the desulphuriza- 'tion of hydrocarbon mixtures, and particularly the catalytic desulphurization of hydrocarbon oils containing high boiling components, which, per se, are substantially unvaporizable at desulphurizing temperatures.

A further object of this invention is the desulphurization of relatively long boiling range petroleum distillates obtained by the straight-run distillation of crude petroleum, and comprising hydrocarbons boiling from 100 F. to 800 F. Such long boiling range distillate includes the hydrocarbons normally separated by fractifination into gasoline, kerosene, furnace oil, and gas oil.

A further object of this invention is the vapor phase desulphurization of a relatively long boiling I range distillate in the presence of a desulphurization catalyst, particularly fullers earth, at temperatures between 600 F. and 800 F., followed by the separation of the treated distillate into fractions, and the further treatment of a gasoline fraction to improve the lead susceptibility thereof. It has been proposed heretofore to desulphurize gasoline distillates by treatment in" the vapor phase with catalysts such as fullers earth or bauxite at temperatures of the order of 600 F. to 800 F. However, when this process of catalytic desulphurization was applied to higher boiling distillates, such as gas oil, considerable difilculty was encountered due to the fact that the higher boiling distillates could not be vaporized without decomposition at the temperature required for desulphurization, and as a result, the products of decomposition, particularly tarry matter and carbon, were deposited on the catalyst, thus reducing the useful life of the catalyst so greatly that the process became impractical. In our copending application Serial No. 386,972 we have disclosed a method whereby the above mentioned difllculties may be obviated, and that we were able to obtain substantial desulphurization of higher boiling hydrocarbon distillates without decomposition'by treating a relatively long boiling rangedistillate containing said higher boiling hydrocarbons. More particularly, we have disclosed that high boiling hydrocarbons may be catalytically desulphurized in the vapor phase by having present a quantity of lower boiling hydrocarbons suflicient to permit vaporization of the higher boiling hydrocarbons without substantial decomposition at the desulphurization temperature. In the event that the lower boiling hydrocarbons, such as gasoline, likewise contained sulphur compounds which it was desirable to remove,such lower boiling hydrocarbons were desulphurized simultaneously with the higher boiling hydrocarbons.

However, we have found that while we were able to obtain simultantously substantial desulphurization of both the gasoline and the higher boiling hydrocarbons in accordance with our process aforesaid, the lead susceptibility of the gasoline was not s'uillciently high to permit its use in the production of extremely high octane motor fuel, for example, aviation gasoline. By lead susceptibility we means the ability of the gasoline to respond to the addition of tetraethyl lead, as reflected in the increase in octane value. For example, two gasolines of substantially the same physical properties but differing in chemical composition or sulphur content may respond difierently to the addition of equal quantities of tetraethyl lead. In one case the addition of 3 cc. of tetraethyl lead may increase the octane value by 5 or 6 units, whereas in the second case, the increase may be only of the order of 2 to 3 units. In the manufacture of aviation gasoline of high octane value, for example, octane, where the quantity of tetraethyl lead permissible is limited to 3 cc. per gallon, it becomes necessary to employ, as a base, a gasoline of relatively high initial octane value and preferably of high lead susceptibility. In accordance with the present invention we are able to produce not only gasoline of high lead susceptibility but also substantial quantities of higher boiling hydrocarbons such as furnace oil and gas oil of reduced sulphur content.

In the practice of our invention, we produce a relatively long boiling range distillate, for example, a mixture of hydrocarbons boiling within the range of from 100 F. to 800 F. and containing objectionable-sulphur compounds, by distilling from crude petroleum the hydrocarbons norquantity really comprising gasoline, kerosene, furnace oil and gas oil. This hydrocarbon mixture is then vaporized by heating to a temperature oi from 608 F. to 800 F., preferably 750 F., the presence 01 the lower boiling hydrocarbons, i. e., gasoline and kerosene, assisting in the vaporization of the higher boiling hydrocarbons, particularly gas oil, and thereby preventing substantial decomposition of the gas oil. In the absence of the lower boiling hydrocarbons, the gas oil is incapable of being vaporized except at temperatures above those desired for desulphurization, and then only with excessive deccmpositionor cracking. The vaporized hydrocarbon mixture is thereafter brought into contact with a desulfurizing catalyst, such as fullers earth, at a temperature of from 600 F. to'800" R, and preferably at a temperature of from 700 F. to ?50 F., for a period of time sumcient to effect conversion of the sul-' phur compounds to lower mercaptans and Has without substantial decomposition of the hydrocarbons. Pressures employed in the desulphurizing operation may be atmospheric or superatmospheric, and we have found that pressures of the order of 30 to 50 pounds per square inch are quite suitable. The treated vapors, after removal from contact with the catalyst, are then separated by fractionation into distillates of desired boiling range, for example, gasoline, kerosene, furnace oil, and gas oil, and the mercaptans and ms thereafter removed from the distiliates by conventional methods. The gasoline fraction, after removal of H28, isthen vaporized and contacted with a. desulphurizing catalyst, such as fuliers earth, at a temperature between 600 F. and 800 F., and preferably between 700" F. and 750 F., in order to dissociate or convert residual sulphur compounds into dissociated, readily removable compounds such as HzS, whereby the lead susceptibility of the gasoline fraction is markedly improved. In producing the relatively long boiling range charging stock, it is preferable that such stock contain from about 20 per cent to about 80 per cent of hydrocarbons boiling within the gasoline boiling range, 1. e., from 100 F. to 400 F. However, we have found that very satisfactory results may be obtained by using in addition to the gasoline hydrocarbons, a suitable of hydrogen or normally gaseous hydrocomprising, for example, on or a mix= ture of two or more hydrocarbons containing from 1 to 4 carbon atoms per molecule. For instance, we may treat hydrocarbon mixtures comrising gasoline, kerosene, furnace oil, and gas oil to which have been added a suitable quantity of hydrogen or hydrocarbons of the nature of propane or butane, such added gas or gases comprising of the order of 5 per cent to 50 per cent of the mixture. In the practice of our invention, we have found that not all of the diflicultly-removable sulphur compounds contained in the charge oil are converted into HzS. For example, in many cases the sulphur compounds occurring in the higher boiling oil components are con. verted into low molecular weight mercaptans such as methyl and ethyl mercaptans, which appear as such in the gasoline fractions separated from the treated oil, and which may be removed by our second stage treatment with a desulphurlzing catalyst. Insofar as the desulphurizing catalysts are concerned, we prefer to employ fullers earth, for example, 30-60 mesh fullers earth which may or may not have been calcined by heating at temperatures of the order of 800 F. to 1100 F. Other desulphurlzing catalysts such carbons,

assume as bauxite, brucite, acid activated bentonite, not ural or synthetic silicates of aluminum, calcium, and magnesium, alumina-silica mixtures or complexes, metal oxides or sulphides, and the like may also be employed. These catalysts may be in the form of granules, of for example, 4 to mesh, or may be in the form of pellets or tablets of suitable size. In many cases the desulphurizing emciency of the catalysts may be enhanced bythe introduction of limited amounts of water or steam into the hydrocarbon vapors hem charged to the catalyst bed.

Our invention may be further understood with reference to the accompanying drawing which illustrates diagratically a system suitable for carrying out our process.

Referring to the drawing, crude petroleum containing a substantial quantity of lower boiling hydrocarbons is delivered, under a pressure of for example, 140 pounds per square inch, by pump 6 through pipe 2 to the tubular heater 8, wherein the crude oii is heated to a temperature of the order of 750 F. As a result of the heating, a substantial proportion of the crude oil is vaporized and the mixture of vaporized and unvap'orized oil is passed by means of pipe t to evaporator tower 5, wherein the unvaporized residual oil is separated from the vaporized oil which comprises, for example, the hydrocarbons normally constituting gasoline, kerosene, furnace oil, and gas oil. Such vaporized hydrocarbons may represent, for example, from 50 per cent to 70 per cent of the crude oil initially charged, and includes hydrocarbons and sulphur compounds boiling up to about 800 F. or slightly higher. A

suitable quantity of steam may be introduced into pipe l by means of valve-controlled pipe t, the

steam commingling with the hydrocarbon vapors passing through pipe d and later serving to enhance the desulphurizing emciency of the catalyst.

The unvaporized residual oil may be withdrawn from the evaporator by means of valve-controlled pipe '5 and disposed of as desired, while the hydrocarbon vapors, and sulphur compounds, are passed from the top of the evaporator through pipe 8 and valve-controlled pipe 9 into catalyst casing I0 provided with a bed of catalyst l I, such as granular fullers earth. In passing downwardly through the catalyst bed H, at a temperature of, for example, 750 F., the sulphur compounds contained in the hydrocarbon vapors are dissociated or converted into more easily removable compounds such as lower mercaptans and H23, without substantial decomposition of the hydrocarbons. The time of contact in the catalyst bed may be of the order of 1 to 60 seconds, and contact times of about 30 to 40 seconds have been found very satisfactory. A small amount of hydrocarbon gas and hydrogen may be formed during the conversion step, but extensive cracking of the hydrocarbons does not take place. The hydrocarbon vapors and H28 are drawn from the bottom of casing ID by means of valve-controlled pipe l2 and delivered by pipe l3 to fractionating tower ll provided with heating coil l5 and bubble trays I6. When the desulphurizing activity of the catalyst in casing Ill becomes exhausted, such casing may be cut out,

of the system by closing valve-controlled pipes 0 and I2, and upon opening valve-controlled pipes l1 and I8, the second casing I9 provided with catalyst bed 20 may be placed on stream. In this manner, continuous operation may be maintained, the spent catalyst H being regenerated or replaced while the catalyst bed 20 is in use. If desired, the catalyst casings may be operated in series, in which case three casings may be employed, two on stream and one on stream, to maintain continuous operation.

The treated hydrocarbon vapors and H28 introduced into fractionating tower l4 are subjected to fractionation, whereby hydrocarbon fractions of the desired boiling range are separated from one another. For example, gas oil may be withdrawn from the bottom of the tower through valve-controlled pipe 2|, a liquid side stream of furnace oil through valve-controlled pipe 22, and a liquid side stream of kerosene through valve-controlled pipe 23. All of these fractions may be subjected to conventional steam stripping, if desired, in order to remove traces of hydrocarbons boiling aboveor below the desired range for the particular fraction. Hydrogen sulphide may be removed from the fractions, for example, by washing with sodium hydroxide solution or equivalent reagent. The resulting fractions contained substantially less sulphur compounds than similar fractions which had not been subjected to treatment in accordance with our invention.

From the top of tower [4 are withdrawn the vapors comprising the lower boiling hydrocarbons, i. e., gasoline, admixed with hydrocarbon gases and H25. This mixture is delivered by pipe 24 to condenser 25, the hydrocarbon vapors are condensed, and the condensate together with the hydrocarbon gases and HaS are introduced into separator 26, wherein the gasoline condensate is separated from the gases. The gasoline condensate is drawn from the bottom of separator 26 and a portion thereof returned by valve-controlled pipe 21, pump 28, and pipe 29 to the top of tower I4 to serve therein as reflux. The re-. mainder of the condensate is passed by means of valve-controlled pipe 30 to the lower section of drawn from the upper section of tower 31 and delivered by pump 40 and pipe 4| to the tubular heater 42, wherein the gasoline is heated to a temperature between 600 F. and 800 F., and

preferably between 700 F. and 750 F. The gascline is thus substantially completely vaporized and the vapors are passed from the heater by means of pipe 43 and valve-controlled pipe 44 into catalyst casing 45 provided .witha bed of catalyst 46, such as granular fullers earth. A suitable quantity of steam may be introduced into pipe 43 ,by means of valve-controlled pipe 41, the steam commingling with the gasoline vapors passing through pipe 43 and later serving to enhance-the desulphurizing efiiciency of the catalyst. In passing downwardly through the catalyst bed 46, at a temperature of, for example, 750 F., the residual undissociated sulphur oom- -p0unds contained in the gasoline vapors are dissociated or converted into more easily removable compounds such as Has, without substantial decomposition of the gasoline. The time of contact in the catalyst bed may be of the order of 1 to 60 seconds, and contact times of about 5 to 20 seconds have been found-very satisfactory. A small amount of hydrocarbon gas and hydrogen may be formed during the conversion step, but extensive cracking of the gasoline does not take place. The gasoline vapors and HaS are drawn from the bottom of casing 45 by means of valve-controlled pipe 48 and delivered by pipe 49 to condenser 50,- wherein the vapors are conscrubbing tow'er 31 for treatment hereinafter described. The uncondensed hydrocarbon gases and Has are withdrawn from the top of separator 26 and may be passed from the system through valve-controlled pipe-3|, or a portion of the gases may be passed by valve-controlled pipe 32 and pump 33 through H2S scrubber 34, and the Has-free gas then recycled by pipe 35 to pipe 2 for admixture with the crude oil charged to tubular heater 3. Hydrocarbon gases or hydrogen supplied from an external source may be introduced into the oil charged to the system by means of valve-controlled pipe 36.

The gasoline condensate from separator 26 containing dissociated sulphur compounds, i. e., H28, and residual undissociated sulphur compounds, is passed upwardly through scrubbing tower 31 in intimate countercurrent contact with a solution of an alkaline agent, for example, sodium hydroxide, whereby the H28 is neutralized and removed from the gasoline. Fresh solution may be introduced into the top of tower 31 by means of valve=controlled pipe 38 and spent solution removed from the bottom of the tower by densed, and the condensate and H28 then passed from the system through valve-controlled pipe 5|. The gasoline condensate may be treated with an alkaline agent to remove H28, and a gasoin which case three casings may be employed,

means of valve-controlled pipe 39. In lieu of the two on stream and one off stream, to maintain continuous operation,

The following example will serve to illustrate the results which may be obtained in accordance with our invention, and is not to be construed as limiting the scope thereof.

A West Texas crude petroleum was heated in a pipe still to effect vaporization of a substantial proportion thereof, and the heated vapor-liquid mixture was charged to an evaporator tower wherein the vapor was separated from the unvaporized residuum} The vapor from this separation, representing approximately 70 per cent of the crude charged, was then passed through a bed of fullers earth at 750 ,F. and about 25 pounds per square inch pressure, and the treated vapors were then fractionated into'a light naphtha fraction, a reformer stock (heavy naphtha), a furnace oil fraction, and heavy gas oil. The

light naphtha fraction was treated for the removal of dissociated sulphur compounds, i. e.,

H25, and the treated naphtha was then vaporized and passed through a second bed of fullers earth at a temperature of 750 F. under a pressure of 50 pounds per square inch to efiect dissociation of residual sulphur compounds and to I improve the lead susceptibility of the naphtha. The sulphur content of all of the product fractions was determined on an HzS-iree basis.

Crude oil Light as- 011 stock... twat? 6 A. P. I. gravity ..degrees.- 36. Percent suliur l. 30 0. 044

0 ratin conditions:

Volur ne percent oil vaporized and charged to catalyst bed 69. 9 100. 0 Volume charge per volume catalyst per hour 0. 547 l. 81 Temperature oi catalyst bed.. 2 .F.. 750 760 Pressure ....pounds per square mch.. 25 50 Yield oi products, weight percent:

Light distillate Reformer stock Furnace 011..... Gas oil (heav Residuum.. Gas

Inspection oi products:

Light distlllate- A. P. I. gravity ..degrees.. Percent sulphur Distillation range F..

Reformer stock A. P. I. gravity ..degrees.. Percent sulphur Distillation range ..I"..

Furnace oil A. P. I. gravity ..degrees..

Percent sulphur... Distillation range.

Gas 011 (heavy)- A. P. I. gravity ..degrees.. Percent sulphur Distillation range .F

Reslduum- A. P. I. gravity ..degrees.. Percent sulphur Percent sulphur in total liquid products Percent sul hur removal from crude Percent su phur removal from catalytically treated products 1 The light distillate was that produced in the first run.

In the following/table are shown the relative lead susceptibilities of (1) untreated light naphthe. obtained by the straight-run distillation of the crude oil, (2) the treated light distillate from the first run, and (3) the treated light distillate From the above example, it will be seen that in accordance with our invention we are able to efiect a substantial decrease in the sulphur content of both the lower boiling and higher boiling components of a relatively long boiling range distillate without substantial decomposition or cracking of the components, and at the same time we have also obtained a substantial improvement in the lead susceptibility of the light naphtha distillate. By our method it is therefore possible to accomplish not only desulphurization and improvernent in lead susceptibility of the lower boiling hydrocarbons, but also desulphurization of high boiling components which are otherwise not amenable to desulphurization, per se, without substantial decomposition, and by thus avoiding decomposition we are able to extend the life of the catalyst and render the desulphurization-oi the higher boiling components commercially practicable.

What we claim is:

1. The method or treating hydrocarbon oil to produce gasoline of improved lead susceptibility and desulphurized higher boiling components, which comprises separating from crude petroleum a long boiling range distillate containing gasoline components and higher boiling components which are substantially unvaporizable at atmospheric pressure without decomposition, contacting said distillate substantially in the vapor phase with a desulphurizing catalyst at a temperature between 600 F. and 800 F. to dissociate the sulphur compounds contained in said distillate, separating from said distillate a gasoline traction containing dissociated and undissociated sulphur compounds and a fraction comprising higher boiling components having a reduced content of sulphur compounds, removing from said gasoline fraction the dissociated sulphur compounds, and contacting said gasoline fraction substantially in the vapor phase with a desulphurizing catalyst at a temperature between 600 F. and 800 F. to dissociate residual sulphur compounds and improve the lead susceptibility of said gasoline.

2. The method of treating hydrocarbon oil to produce gasoline of improved lead susceptibility.

and desulphurized higher boiling components, which comprises separating from crude petroleum a long boiling range distillate containing high boiling components readily susceptible of decomposition by heating at the normal vaporization temperature thereof and a quantity of gasoline components suflicient to permit substantially complete vaporization of the high boiling components together with the gasoline components at a temperature between 600 F. and 800 F. without substantial decomposition, contacting said distillate substantially in the vapor phase with a desulphurizing catalyst at a temperature between 600 F. and 800 F. to dissociate the sulphur compounds contained in said distillate, separating from said distillate a gasoline fraction containing dissociated and undissociated sulphur compounds and a fraction comprising higher boiling components having a reduced content of sulphur compounds, removing from said gasoline fraction the dissociated sulphur compounds, and contacting said gasoline fraction substantially in the vapor phase with a desulphurizing catalyst at a a temperature between 600 F. and 800 F. to dissociate residual sulphur compounds and improve the lead susceptibility oil-said gasoline.

3. The method of treating hydrocarbon 011 to produce gasoline of improved lead susceptibility and desulphurized higher boiling components, which comprises separating from crude petroleum a long boiling range distillate containing high boiling components readily susceptible of decomposition by heating at the normal vaporization temperature thereof and a quantity of gasoline components sumcient to permit substantially complete vaporization of the high boiling components' together with the gasoline components at a. temperature between 700 F. and 750 F. without substantial decomposition, contacting said distillate substantially in the vapor phase with fuller's earth at a temperaturebetween 700 F. and 750 F. to dissociate the sulphur compounds contained in said distillate, separating from said distillate a gasoline fraction containing dissociated and undissociated sulphur compounds and a fraction comprising higher boiling components having a reduced content of sulphur compounds, removing from said gasoline fraction the dissociated sulphur compounds, and contacting said gasoline fraction substantially in the vapor phase with fullers earth at a temperature between 700 F. and 750 F. to dissociate residual sulphur compounds and improve the lead susceptibility of said gasoline.

4. The method of treating hydrocarbon oil to produce gasoline of improved lead susceptibility and desulphurized higher boiling components, which comprises separating from crude petroleum a distillate boiling within the range of from 100 F. to 800 F. and containing high boiling, readily decomposable components, contacting said distillate substantially in the vapor phase with a desulphurizing catalyst at a temperature between 600 F. and 800 F. to dissociate the sulphur compounds contained in said distillate. separating from said distillate a gasoline fraction containing dissociated and undissociated sulphur compounds and a fraction comprising higher boiling components having. a reduced content of sulphur compounds, removing from said gasoline fraction the dissociated sulphur compounds, and contacting said gasoline fraction substantially in the vapor phase with a desulphurizing catalyst at a temperature between 600 F. and 800 F. to dissociate residual sulphurcompounds and improve the lead susceptibility of said gasoline. v

5. The method of treating hydrocarbon oil to produce gasoline of improved lead susceptibility and desulphurized higher boiling components, which comprises separating from crude petroleum a long boiling range distillate comprising hydrocarbons up to and including gas oil, contacting said distillate substantially in the vapor phase with a desulphurizing catalyst at a temperature between 600 F. and 800 F. to dissociate the sulphur compounds contained in said distillate, separating from said distillate a gasoline fraction containing dissociated and undissociated sulphur compounds and a higher boiling fraction having a reduced content of sulphur compounds, removing from said gasoline fraction the dissociated sulphur compounds, and contacting said gasoline fraction substantially in the vapor phase with a desulphurizing catalyst at a temperature between 600 F. and 800 F. to dissociate residualsulphur compounds and improve the lead susceptibility tialiy in the vapor phase with a desulphurizing catalyst at a temperaturebetween 600 F. and 800 F. to dissociate the sulphur compounds contained in said distillate, separating from the treated distillate a plurality of fractions at least one of which comprises gasoline containing dissociated and undissociated sulphur compounds,

removing from said gasoline fraction the dissociated sulphur compounds, and contacting said gasoline fraction substantially in the vapor phase with a desulphurizingicatalyst at a temperature between 600 'F. and 800 F. to dissociate residual sulphur compounds and improve the lead susceptibility of said gasoline.

7. The method of treating hydrocarbon oil to produce gasoline of improved lead susceptibility and desulphurized higher boiling components, which comprises separating from crude petroleum a distillate comprising gasoline, kerosene, furnace oil, and gas oil, contacting said distillate substantially in the vapor phase with a desulphurizing catalyst at a temperature between 700 F. and 750 F. to dissociate the sulphur compounds contained in said distillate, separating from the treated distillate a plurality of fractions at least one of whichcomprises gasoline containing dissociated and undissociated sulphur compounds, removing from said gasoline fraction the dissociated sulphur compounds, and contacting said gasoline fraction substantially in the vapor phase with a desulphurizing catalyst at a temperature between 700 F. and 750 F. to dissociate residual sulphur compounds and improve the lead susceptibility of said gasoline.

8. The method of treating hydrocarbon oil to produce gasoline of improved lead susceptibility and desulphurized higher boiling components, which comprises separating from crude petroleum a distillate comprising gasoline, kerosene, furnace oil, and gas oil, contacting said distillate substantially in the vapor phase with fullers earth at a temperature between 700 F. and 750 F. to dissociate the sulphur compounds contained in said distillate, separating from the treated distillate aplurality of fractions at least one of which comprises gasoline containing dissociated and undissociated sulphur compounds, removing from said gasoline fraction the dissociated sulphur compounds, and contacting said gasoline fraction substantially in the vapor phase with fullers earth at a temperature between 700 F. and 750 F. to dissociate residual sulphur compounds and improve the lead susceptibility of said gasoline.

\ ROBERT D. BENT.

CHARLES A. PINES.

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