US2671754A

US2671754A - Hydrocarbon conversion process providing for the two-stage hydrogenation of sulfur containing oils

Info

Publication number: US2671754A
Application number: US237934A
Authority: US
Inventors: Rosset Armand J De; Charles H Watkins
Original assignee: Universal Oil Products Co
Current assignee: Universal Oil Products Co
Priority date: 1951-07-21
Filing date: 1951-07-21
Publication date: 1954-03-09
Anticipated expiration: 1971-03-09

Description

Patented Mar. 9, 1954 UNITED STATES PATENT OFFICE HYDROCARBON CONVERSION PROCESS PROVIDING FOR THE TWO-STAGE HY- DROGENATION OF SULFUR CONTAIN- ING OILS Application July 21, 1951, Serial No. 237,934

4 Claims. (Cl. 196-28) The present invention relates to an improved process for converting a hydrocarbon oil stream in a series of cooperative steps to provide a desirable and low-boiling hydrocarbon fraction. The improvement is also particularly directed to a novel two-stage hydrogenation system for treating and upgrading an aromatic hydrocarbon oil fraction having a high sulfur content.

In petroleum processing, it is frequently desirable to effect the hydrogenation and saturation of naphtha and gasoline charge streams in order to efiect the conversion of olefins to more saturated materials, as well as the conversion of sulfur and nitrogen to hydrogen sulfide and ammonia respectively, prior to effecting a subsequent catalytic reforming of the naphtha stream. It is also frequently desirable to effect the hydrogenation of the unconverted gas oil in a catalytic cracking operation before it is recycled to the cracking zone, particularly aromatic oils and those containing sulfur. Such oils are in general refractory towards further cracking; however, unconverted gas oils, containing olefins as well as aromatics, are also undesirable in that they tend to form more coke on the cracking catalyst.

The hydrogenation of hydrocarbon oil over sulfur resistant catalysts streams may be carried out in a high pressure operation, above say about 2000 p. s. 1., so that the material is upgraded to provide a charge or cycle stock which is less carbon forming than the untreated material. However, a low pressure hydrogenation process, using a sulfur sensitive catalyst as provided by the present invention is of considerable advantage, in that it is easier to work at lower pressure and there is a lower initial expense in the cost of equipment. Hydrogenation operations may be uneconomical where there is no cheap supply or ready means of obtaining the hydrogen which is necessary for the process, but where hydrogen is available from an improved catalytic reforming operation, and where the latter is used in combination and in cooperation with catalytic cracking and hydrogenation steps, a particular advantage is obtained in the conversion of hydrocarbon oils.

It is thus one object of the present invention to provide a desirable improved combined operation wherein hydrogen produced in one stage thereof is utilized in another to in turn increase the quality and yields in gasoline which may be obtained from a wide boiling charge stream.

It is also an object of the present invention to provide an improved substantially low pressure 2 and two-stage hydrogenation operation having but a single hydrogen recycle system.

It is also an object of the present invention to take advantage of hydrocracking taking place during hydrogenation by providing means for separating and recovering low molecular weight hydrocarbons formed in the process.

It is a still further object of the present invention to provide a low pressure two-stage hydrogenation operation in which a sulfur containing aromatic oil stream is countercurrently contacted by the hydrogen stream.

It is still another object and feature of the present invention to provide in connection with a two-stage hydrogenation operation a substantially sulfur free hydrogen stream which has been used in one stage thereof to countercurrently strip and remove dissolved hydrogen sulfide from a hydro-desulfurized oil stream, prior to effecting the actual hydrogenation of the stream.

In one embodiment, the present invention provides for the treating of a hydrocarbon oil stream having a high sulfur content in a manner which comprises, passing the oil stream into contact with a sulfur resistant catalyst in the presence of hydrogen and under conversion conditions effecting the substantial desulfurization of the stream, without extensive saturation, separating a resulting hydrogen sulfide containing hydrogen stream-from the oil stream while passing the contacted oil stream into contact with a hydrogen stream, obtained as hereinafter set forth, and effecting the stripping of dissolved hydrogen sulfide from the oil stream, passing the resulting stripped and substantially sulfur free oil stream into contact with a hydrogenation catalyst in the presence ,of substantially sulfur free hydrogen and under conversion conditions effecting the hydrogenation of the oil stream, removing hydrogen sulfide from the separated hydrogen sulfidecontaining hydrogen stream, passing a resulting substantially sulfur free hydrogen stream into contact with the oil stream in the presence of said hydrogenation catalyst, and subsequently passing at least a portion of the latter hydrogen stream into contact with the substantially desulfurized oil stream to effect said stripping thereof.

This two-stage hydrogenation operation may be utilized in connection with low boiling hydrocarbon fractions, including naphtha and gasoline; however, it is particularly useful for improving the characteristics of residual oils and other relatively heavy stocks, such as unconverted gas oil from a catalytic cracking operation, so that substantially all sulfur may be removed and the aromatic content of the stream converted to provide a less refractory stock and a material with a low carbon-forming characteristic.

As a particular feature of the present invention, it is noted that while two different reactors or two catalytic contacting stages are provided for the oil stream, that in effect a single recycle stream of the hydrogen is provided for contacting the oil in the presence of the catalyst in each of the two zones. In other words, in the first zone or stage of contact the oil undergoes hydrodesulfurization in the presence of the catalyst and the hydrogen and a hydrogen stream containing hydrogen sulfide is separated from the contacted oil and treated with suitable washing or purifying medium to remove substantially all of the hydrogen sulfide therefrom. The resulting substantially sulfur free hydrogen stream is then passed to the hydrogenation zone where the substantially sulfur free oil contacts a hydrogenation catalyst in the presence of this substantially sulfur free hydrogen stream to provide a desirable hydrogenated product stream. The hydrogen stream that is separated from the hydrogenated oil stream is still substantially sulfur free, and thus at least a portion of this stream is used in a stripping zone to contact the once contacted oil stream to in turn remove substantially all dissolved hydrogen sulfide, prior to the oil undergoing the final hydrogenation contact. Normally, only a portion of the hydrogen stream need be used for the stripping operation and this portion may be added to the contaminated hydrogen sulfide containing hydrogen stream in orderthat it may be purified for recycling. The substantially sulfur free H2 stream from the hydrogenation state, which is not used for stripping, is passed back to the desulfurizing stage of contact.

The catalyst in the first stage of contact, effecting the hydro-desulfurization of the liquid hydrocarbon oil stream is a sulfur resistant catalyst and may be a sulfide of Group VI or Group VIII of the periodic system, or a mixture of the same, either as such or supported on an inert carrier which may be composed of alumina, silica, diatomaceous earth and the like. For example, molybdenum sulfide on activated alumina, or cobalt thio-molybdate supported on alumina or sulfided platinum or palladium supported on alumina may comprise a desirable catalyst for the first stage of contact. The pressure may be in the range of from about 100 to 1000 p. s. i. g., with temperatures of from the order of 500 to 900 F. but preferably of the order of about 700 to 850 F. An excess amount of hydrogen should be present and the feed rate of the oil stream, or weight hourly space velocity, defined as the weight of hydrocarbon charged per hour per weight of catalyst in the reaction zone, may lie within the range of from about 0.2 to about 20.

In the second stage of contact, a catalyst such as a supported metal of Group VIII of the periodic system may be used. For example, metallic nickel. platinum, or palladium on alumina may comprise a desirable catalyst. The temperature in the second stage of contact may be somewhat lower than that in the first and be of the order of {50 to 700 F., and preferably say of the order of about 600 F. The optimum operating temperature will increase as the hydrogen pressure is increased. Also, as in the first stage of contact, excess hydrogen should be present and the charge conditions may be as hereinbefore set forth for the first stage of contact.

A modified and simplified embodiment of the multiple stage low pressure hydrogenation operation of the present invention provides for treating an aromatic and sulfur containing aromatic oil stream in a manner which comprises, passing the oil stream downwardly through a desulfurization contacting zone having a sulfur resistant catalyst and contacting the latter in the presence of hydrogen passing upwardly therethrough countercurrently to the descending oil stream whereby to effect the substantial desulfurization of the latter, passing the resulting substantially desulfurized oil stream from said zone to a hydrogenation zone and contacting a hydrogenation catalyst in the presence of an upwardly countercurrently flowing substantially sulfur free hydrogen stream obtained as hereinafter set forth, withdrawing a hydrogen sulfide containing hydrogen stream and vaporized hydrocarbons of lower molecular weight than the charged oil from the upper portion of the first mentioned desulfurization contacting zone and removing hydrogen sulfide and hydrocarbons therefrom. passing the resulting substantially sulfur free hydrogen stream to the lower portion of the hydrogenation zone and passing it upwardly therethrough countercurrently to the descending oil stream as set forth, and subsequently passing the hydrogen stream from the upper portion of the hydrogenation zone into the lower portion of the desulfurization contacting zone as the substantially sulfur free hydrogen stream, and withdrawing an improved sulfur free oil hydrogenated stream from the lower portion of the dehydrogenation zone.

Also, in accordance with the desired embodiment, the substantially sulfur free hydrogen stream which is withdrawn from the hydrogenation zone is utilized to contact and strip dissolved H25 from the oil stream after the latter has been subjected to the first stage of contact in order that a substantially sulfur free stream is subsequently passed into the hydrogenation zone.

It is particularly desirable, as mentioned briefly hereinbefore, to obtain the hydrogen for a hydrogenation step as economically and advantageously as possible, thus it is desirable to utilize the present two stage hydrogenation operation in combination with a catalytic reforming operation which may be upgrading a straight run gasoline or naphtha fraction, or other such low boiling fraction having a boiling range up to the order of about 425 F., and which effects a net production of hydrogen.

Thus, in still another embodiment of the present invention, in converting a crude oil or other wide boiling range hydrocarbon stock having a high sulfur content, the improved processing operation comprises, fractionating the heavy hydrocarbon stream to form at least a low boiling naphtha-gasoline fraction and a higher boiling residual fraction effecting the catalytic contacting of said low boiling fraction in the presence of a reforming catalyst and hydrogen under reforming conditions providing an enhanced octane number gasoline stream and excess hydrogen, subjecting the higher boiling residual fraction to vacuum distillation and separating therefrom at least a lower boiling gas oil fraction and a residual fraction, subjecting the gas oil fraction to conversion in the presence of a catalyst at cracking conditions providing a cracked gasoline fraction and an unconverted heavier fraction, passing the unconverted hydrocarbon fraction into contact with a sulfur resistant catalyst in the presence of excess hydrogen withdrawn from the catalytic reforming stage and effecting the hydro-desulfurization of the unconverted fraction, separating a hydrogen stream containing hydrogen sulfide and hydrocarbons of lower molecular weight than the above mentioned unconverted hydrocarbon fraction from the desulfurized oil stream, subsequently passing the contacted oil stream into contact with a hydrogen stream obtained as hereinafter set forth in a manner eifecting the stripping and removal of absorbed and dissolved hydrogen sulfide, passing the resulting stripped and substantially sulfur free oil stream into contact with a hydrogenation catalyst in the presence of a substantially sulfur free hydrogen at conversion conditions effecting the hydrogenation and saturation of the oil stream, removing hydrogen sulfide and hydrocarbons from the hydrogen sulfide containing hydrogen stream separated from hydro-desulfurized oil stream, passing the resulting substantially sulfur free hydrogen stream into contact with the oil stream in the presence of the hydrogenation catalyst as set forth. separating hydrogen from the hydrogenated oil stream and passing a portion thereof into contact with the hydro-desulfurized stream to effect said stripping, withdrawing the hydrogenated oil stream from said hydrogenation zone and recycling at least a portion thereof to the catalytic cracking zone to combine with the gas oil stream from the vacuum distillation, whereby to provide an improved low carbon-forming cycle stock to the catalytic cracking zone, and an increased yield of desirable catalytically cracked gasoline.

Various reforming catalysts and reforming operations may be utilized in the foregoing improved operation in effecting the hydroforming of the straight run naphtha and gasoline fraction and the formation of excess hydrogen which is utilized in the hydrogenation steps, however, a preferred type of reforming catalyst utilizes at least one refractory oxide composited or associated with platinum or palladium, said catalyst being capable of promoting hydrocracking of paraflins and dehydrogenation of naphthenes, such as that described in U. S. Patent No. 2,479,109, issued August 16, 1949. These improved catalysts comprise alumina, platinum, and combined halogen, especially combined fluorine, and combined chlorine. The platinum-alumina-halogen catalyst has the halogen preferably in an amount from about 0.1 to about 2% by weight of the alumina on a dry basis, and the platinum in an amount of from about 0.1% to about 1%.

In effecting catalytic reforming with these platinum-alumina-combined halogen catalysts, the pressure may be in the range of about 50 to about 1200 p. s. i. g., although a total pressure at least 250 lbs. is ordinarily preferred. Temperatures may be of the order of about 600 F. to about 1000 F. but ordinarily will lie in the range of from about 750 F. to about 1000 F. The weight space velocity, defined as the weight of hydrocarbon charge per hour per weight of catalyst in the reaction zone, should lie within the range of from about 0.2 to about 40. The amount of hydrogen charge along with the hydrocarbon usually will be from about 0.5 to about moles per mole of hydrocarbon. After initial operation, the reforming operation will provide excess hydrogen which is utilized in the two stage hydrogenation operation as set forth.

Reference to the accompanying drawing and the following description thereof will serve to clarify the improved operation of the present invention, as well as point out further advantages obtained in connection therewith.

Figure 1 of the drawing indicates diagrammatically a process flow for converting a hydrocarbon charge stream in an improved multiple stage-operation providing greater and improved product yields.

Figure 2 of the drawing is a diagrammatic illustration of an improved and modified two-stage hydrogenation system, wherein there is countercurrent flow between the oil and hydrogen streams.

Referring now to Figure 1 of the drawing, a crude charge is passed by way of line I and control valve 2 into a fractionating zone 3 from which a light overhead cut, say of the naphtha-gasoline range, passes by way of line I and control valve 5 to a catalytic reforming zone 6. As noted hereinabove, various types of reforming catalyst and operations may be utilized within the zone 6, however, preferably an improved substantially non-regenerative catalytic reforming system utilizing the aforementioned platinum-aluminacombined halogen catalyst is utilized within the zone 6 to provide a high octane desirable gasoline product stream by way of line I and control valve 8. The improved reforming operation also provides excess hydrogen which may be withdrawn by way of line 9 and control valve l0, while of course a portion of the hydrogen stream is continuously recycled through line II and valve l2 to combine with the naphtha charge stream which is heated and catalytically reformed in zone 6.

The present arrangement indicates the topped crude being withdrawn by way of line [3 and valve l4 from the lower portion of the fractionating and separating zone 3, and this material is passed through a vacuum flashing zone l5 from which a suitable gas-oil stream may be withdrawn by way of line It and valve i! for cracking in the catalytic cracking zone l8. Heavy residual fuel oil is indicated as being withdrawn from the vacuum flashing or distillation zone by way of line If! and valve 20'.

The catalytic cracking zone i8 is indicated diagrammatically in the drawing and may comprise any one of the desired forms of operation, including the fluidized, fixed bed, moving bed or fluidized-fixed bed operation, and the unit may utilize a silica-alumina catalyst or any of the well known cracking catalysts commonly used in the petroleum arts. A catalytically cracked gasoline stock is continuously withdrawn through line l9 and valve 20 while unconverted gas oil is discharged by way of line 2i and valve 22. A portion of the unconverted gas oil may be withdrawn by way of line 23 and valve 24 and mixed with the heavy residual oil from the vacuum flashing zone IS in order to dilute the latter.

This unconverted oil from the catalytic cracking unit I8 is passing by way of line 2|, is in general a refractory material, particularly in the case of an oil stream containing a considerable quantity of aromatics, and has a tendency to produce large quantities of coke on the catalyst in the cracking zone. Also in a sulfur containing stock, it is desirable to remove the sulfur from the cycle material in order to prevent the buildup of excessive quantities thereof in the cracking zone. Thus, it is highly desirable to efl'ect the hydrogenation of the recycle stock to convert the aromatics and to saturate the olefins, as well as to provide means for efiecting the substantial desulfurization of those oils which have a high sulfur content and to lower the carbon-forming characteristics of the recycle material.

In accordance with one embodiment of the present invention, at least a portion of the unconverted gas oil in the cracking zone I8 is passed by way of line 2|, compressor 25 and line 26 to a heating zone 21. A hydrogen stream, obtained as will hereinafter be described more fully, is supplied from line 28 into admixture with the unconverted oil stream prior to being heated in heating zone 21 and prior to undergoing subsequent hydrogenation in the presence of a desirable catalyst. Also, as noted hereinbefore, the present two-stage hydrogenation system is Darticularly adapted for use in connection with those residual or unconverted gas oil stocks which have a relatively high sulfur content, thus the heated oil and hydrogen stream is passed from heater 2! by way of line 29 into the first stage hydrogenation reactor 30. The oil and hydrogen contact a sulfur resistant hydrogenating catalyst in reactor 30 at a temperature say of the order of 800 F. and at a pressure of about 700 p. s. i. g. and there is thus efiected a hydrodesulfurization of the oil stream in a substantially liquid phase operation. The desirable sulfur resistant catalyst may for example be a cobalt thio-molybdatealumina catalyst, while the weight hourly space velocity may be of the order of about .5 to 1, although a wider range may be utilized as hereinbefore noted, and a molal hydrogen to hydrocarbon ratio of the order of about 2, although here again a greater range of ratios may be utilized.

The resulting substantially desulfurized oil stream and gaseous components are passed by way of line 3 I, valve 32, cooler 33, and line 34 to a suitable separating and stripping zone 35. In the latter zone, the oil stream is separated from the hydrogen, hydrocarbon vapors, and resulting hydrogen sulfide, and the hydrogen sulfide and hydrocarbon vapor containing hydrogen stream is passed by way of line 36, cooler I and valve 31 to a suitable hydrocarbon vapor separator IOI, from. which condensed hydrocarbon vapors are drawn off by line I04 and valve I05. The resulting hydrogen sulfide containing hydrogen stream is assed by way of line I02 and valve I03 to a suitable hydrogen sulfide removal zone 38. In zone 38, the hydrogen sulfide may be substantially removed from the hydrogen stream by suitable water wash, Girbotol system, or the like, so that a resulting substantially sulfur free hydrogen stream may be returned by way of line 39 and valve 40 to the hydrogenation system. A suitable vent line 4| and valve 42 connects with line 36 in order that methane or other undesirable gases building up in the system may be gradually released and vented to prevent their build-up.

In a preferred arrangement of the present improved operation, the separating zone 35 also provides a stripping zone in which a substantially sulfur free hydrogen stream may countercurrently come into contact with the desulfurized oil stream entering zone 35. Thus, hydrogen is introduced by way of line 43 and effects the stripping of absorbed hydrogen sulfide and low molecular weight hydrocarbons from the oil stream in stripper 35 such that a substantially hydrogen sulfide free oil stream of approximately the same initial boiling point as the above mentioned unconverted oil may be withdrawn from separating and stripping zone 35 by way of line H and valve 45 for subsequent passage to the hydrogenation zone. Sulfur free hydrogen combines with the desulfurized oil stream, by means of line 39 connecting with the line 44, and the mixture is passed by way of pump or compressor 46 and line 41 into heater 48. Heater l0 heats the oil and hydrogen stream to a temperature somewhat lower than that first stage of hydrogenation, such that the material passes into reactor 50 by way of line 49 at a temperature .of the order of about 600 F. The catalyst in reactor 50, comprising the second stage of the hydrogenation system, may be a nickel catalyst as noted hereinbefore, or alternatively, in a desirable embodiment, a platinum-alumina-combined halogen catalyst similar to that used in the catalytic reforming zone 6 may be used. The catalyst must be capable of saturating and hydrogenating the aromatics in the oil stream, as well as saturating the olefin content of the stream.

The resulting hydrogenated oil stream and hydrogen passes by way of line 5I and valve 52 from reactor 50 to a suitable cooler 53 and from the latter by way of line 54 to a separating zone 55. In the latter, the hydrogen is separated from the hydrogenated oil stream and in view of the hydrogen sulfide removal step as provided by zone 38 is a substantially sulfur free hydrogen stream which may be withdrawn from the separator by way of line 56 and valve 51 for recycling to the first stage of the hydrogenation system by way of compressor 58 and line 28. However, in accordance with the particular feature of the present embodiment of the invention, at least a portion of this substantially sulfur free hydrogen stream is withdrawn from the separator 55 by way of line 59, valve 60, and pump SI such that the material may be introduced by way of the line 43 to the combined separating and stripping zone 35, in order to contact the substantially desulfurized oil stream therein as hereinbefore set forth. The improved hydrogenated stock is withdrawn from the lower portion of the separator or receiver 55 by way of line 52 and valve 63, with at least a portion of this improved oil stock being utilized as cycle stock for transfer by way of line 54 and pump 66 to line 61, which in turn discharges the cycle material into the catalytic cracking zone II. It has been found that by effecting the hydrodesulfurization and saturation of the recycle stock for a catalytic cracking stage, particularly for a sulfur containing aromatic gas oil charge, that the upgraded and improved cycle stock which is charged with the gas oil from the topped crude, by way of charge line IS in the present embodiment, will lower the coke formation to a great extent. The use of the improved hydrogenated cycle oil will also increase the cracking susceptibility of the entire charge stream to provide an increase in gasoline yield and a decrease in the yield of dry gas. For example, a cycle stock treated as set forth in the foregoing embodiment may effect the reduction of carbon formation from about 7 to say 1.3

It should also be pointed out the the present two-stage hydrogenation operation is of particular advantage in that it uses a lesser quantity of hydrogen that might be necessary for a highpressure hydrogenation operation of a topped crude. Also, in general, it is preferable to utilize the vacuum flashing or flash distillation treatment of the topped crude, such as provided by zone I5 in the present embodiment, in order to lessen the overall hydrogen requirements in the present combined and integrated conversion system, whereby excess hydrogen from the catalytic reforming unit 6, and passing by way of line 9 to line 39, is sufficient to sustain the present hydrogenation operation. For starting-up purposes, or under an operation where additional hydrogen may be required, such hydrogen may be introduced into the system by Way of line 68 and valve 69 into the hydrogen charge line 9.

Referring now to Figure 2 of the drawing, there is shown a special embodiment of the present invention, which. as mentioned hereinbefore, provides a two-stage hydrogenation operation wherein the oil stream flows countercurrently to the hydrogen stream in each of the two stages of catalytic hydrogenation. Thus, an unconverted oil stream from a catalytic cracking unit, or other such desired oil stream as it may be desired to hydrogenate, is charged by way of line In and valve H, and compressor or pump 12 into a suitable heating zone 13. The resulting heated oil stream passes by way of line H to a hydrodesulfurization reactor 15, and therein contacts a sulfur resistant hydrogenating catalyst at a temperature of the order of 800 F. and at a pressure of say 700-800 p. s. i. g., while in the presence of hydrogen which is moving upwardly through the catalyst, countercurrently to the descending oil stream, whereby the latter is partially saturated and substantially desulfurized. The hydrogen stream enters the lower end of the reactor '|5 by way of line 16 and is obtained as will hereinafter be set forth more specifically. Resulting hydrogen sulfide, hydrocarbon vapor, and hydrogen stream is discharged from the upper portion of the reactor 15 by way of line 11 and Y valve 18, to cooler I06. Condensed hydrocarbon vapors are collected in separator I01, and withdrawn by way of line I08 and valve I09. The hydrogen sulfide and hydrogen stream is discharged from separator I01 by line H and valve l l I, while a portion of the material may be vented through line 19 and valve 80 in order that methane or undesired gases may be prevented from building up in the system. The hydrogen sulfide in the hydrogen stream is substantially removed in a removal zone 8|, which as described in connection with Figure 1 of the drawing may be a scrubbing or Girbotol type of H25 removing unit, permitting a substantially sulfur free hydrogen stream to be withdrawn from unit 8| by way of line 82 and valve 83. free hydrogen stream subsequently passes by way of compressor 84 and line 85 to heater 86 wherein it is heated to a temperature of say of the order of 600 F. and passes by way of line 81 into the lower portion of the hydrogenation reactor 88. While the contacting temperature in the latter reactor is lower than that in reactor 15, a somewhat higher pressure say of the order of about 800 p. s. i. g. is maintained for effecting the contacting of the oil stream.

The desulfurized oil stream from reactor i passes downwardly by way of line 89, heat exchanger 90 and line 9| into the upper portion of the reactor 68. As in the first stage reactor, the oil stream effects the countercurrent contacting of the hydrogen stream which is rising through reactor 88 in the presence of a suitable hydrogenation catalyst. The heat exchanger 80 permits the hydrogen stream which is subsequently discharged from the upper end of the reactor 88 by way of line 92, to become heated to a temperature of say of the order of 700-800 F., by reason of the higher temperature oil stream being discharged from reactor 15. At the same time, the substantially desulfurized oil stream from the This sulfur upper reactor is cooled somewhat in exchanger 90 and enters the second hydrogenation stage of reactor 88 at a decreased temperature to be subsequently contacted in the presence of the hydrogenation catalyst at a temperature of the order of about 600 F.

Resulting hydrogenated oil withdrawn from the lower portion of reactor 88 may pass by way of line 93, valve 94, cooler and discharge line 96 to storage, or other such zone of use as may be desired. For example, in the case of recycle stock, the improved hydrogenated cycle oil may be returned to a catalytic cracking unit for improvement of the gasoline yield and quality from the latter zone. The improved hydrogenated oil may also be used to advantage for jet fuel and other relatively light fuel stocks. As in the embodiment of Figure 1 of the drawing, the hydrogen utilized in the two-stage countercurrent operation of Figure 2 of the drawing, may be supplied as excess hydrogen provided from a catalytic reforming unit, whereby there is an economical formation and supply of hydrogen available for use. The hydrogen supply to the hydrogenation unit of Figure 2 is indicated as being supplied through line 91 and valve 98, with this line connecting in turn with line 82 which carries the substantially sulfur free treated hydrogen stream passing from the top of the first stage reactor 15 to the lower end of the second stage reactor 88.

The embodiment of Figure 2 provides a very desirable simplification of a two-stage hydrogenation system and is particularly adaptable for use with aromatic sulfur containing streams which are to be upgraded by saturation, as well as by reducing their carbon formation characteristics and removing substantially all of the sulfur content thereof. The downward gravity flow of the oil stream through superimposed reactor zones, such as 15 and 88, effects the elimination of one of the pumps such as required in the two-stage arrangement of Figure 1 of the drawing. The heating load of the heater for the first stage, in

- this case heater I3, is reduced by virtue of not having to handle the hydrogen stream. The hydrogen stream is heated by countercurrent heat exchange with the oil stream between the separate hydrogenation zones as provided by the heat exchanger 90.

As a still further advantage of the countercurrent arrangement, the lower portion of reactor 15, or an additional contacting zone built into the lower portion thereof, provides for the countercurrent contacting between the substantially sulfur free hydrogen stream moving upwardly from the lower reactor to the upper and the descending substantially desulfurized oil stream such that the latter is substantially stripped of any hydrogen sulfide which may be dissolved or absorbed within the stream prior to its passing into the lower second stage reactor 88. In other words, a countercurrent stripping operation is effected between the hydrogen and oil streams intermediately between the desulfurization contacting and the saturation contacting and it is not necessary to use a separate separating and stripping chamber, such as 35 in Figure 1 of the drawing.

We claim as our invention:

1. A process for the treatment of hydrocarbon oil of high sulfur content which comprises contacting the oil in the presence of hydrogen with a sulfur resistant catalyst at desulfurizing conditions in a first conversion zone, introducing the effluent of the conversion zone to a stripping zone and therein separating from the treated oil a gaseous stream containing hydrogen and hydro;- gen sulfide, subjecting said gaseous stream to a purification treatment to remove hydrogen sulfide therefrom, supplying resultant purified hydrogen gas and said treated oil to a second conversion zone and therein contacting the same with a hydrogenation catalyst at hydrogenating conditions, removing a hydrogen-containing gas stream from said second zone and supplying a portion thereof to said first zone as the source of hydrogen for the first zone, and introducing another portion of the last-named stream to said stripping zone as a stripping medium therein.

2. A process for the treatment of hydrocarbon oil of high sulfur content which comprises contacting the oil in the presence of hydrogen with a sulfur resistant catalyst at desulfurizing conditions in a first conversion zone, separating from the treated oil a gaseous stream containing hydrogen and hydrogen sulfide while contacting the treated oil with a stripping gas, subjecting said gaseous stream to a purification treatment to remov hydrogen sulfide therefrom, supplying resultant purified hydrogen gas and said treated oil to a second conversion zone and therein contacting the same with a hydrogenation catalyst at hydrogenating conditions, removing a hydrogen-containing gas stream from said second zone and supplying at least a portion thereof to the first-mentioned separating step as said stripping gas.

3. A process for the treatment of hydrocarbon oil of high sulfur content which comprise countercurrently contacting a descending stream of the oil with an ascending stream of hydrogen'in the presence of a sulfur resistant catalyst at desulfurizing conditions in a first conversion zone, withdrawing from the upper portion of said zone a vaporous stream containing hydrocarbons, hydrogen and hydrogen sulfide, separating hydrocarbons and hydrogen sulfide from said vaporous stream, introducing resultant purified hydrogen gas to the lower portion of a second conversion zone disposed at a lower elevation than said first zone, removing desulfurized oil from the lower portion of said first zone and passing the same by gravity flow into the upper portion of said second zone, countercurrently contacting the desuifurized oil and the purified hydrogen gas in said second zone in the presence of a hydrogenation catalyst at hydrogenating conditions, re moving a hydrogen-containing gas stream from the upper portion of said second zon and introducing the same to the lower portion of said first zone as said ascending stream of hydrogen.

4. A process for the treatment of hydrocarbon oil of high sulfur content which comprises counter-currently contacting a descending stream of the oil with an ascending stream 01' hydrogen in the presence of a sulfur resistant catalyst at desulfurizing conditions in a first conversion zone, withdrawing from the upper portion of said zone a vaporous stream containing hydrocarbons, hydrogen and hydrogen sulfide, separating hydrocarbons and hydrogen sulfide from said vaporous stream, introducing resultant purified hydrogen gas to the lower portion of a second conversion zone disposed at a lower elevation than said first zone, removing desuli'urized oil from the lower portion of said first zone and passing the same by gravity flow into the upper portion of said second zone, countercurrentiy contacting the desulfurized oil and the purified hydrogen gas in said second zone in the presence of a hydrogenation catalyst at hydrogenating conditions, removing a hydrogen-containing gas stream from the upper portion of said second zone and passing the same in indirect heat exchange with said desulfurized oil flowing by gravity from the first zone to the second zone, and thereafter introducing said hydrogen-containing gas stream to the lower portion 01' said first zone as said ascending stream of hydrogen.

' ARMAND J.. or: ROSSET. CHARLES H. WATKINS.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,147,268 Pyzel Feb. 14, 1939 2,242,627 Strickland May 20, 1941 2,289,716 Marschner July 14, 1942 2,300,877 Drennan Nov. 3, 1942 2,332,572 Hepp et al. Oct. 26, 1943 2,376,086 Reid May 15, 1945 2,417,308 Lee Mar. 11, 1947 2,419,029 Oberfell Apr. 15, 1947

Claims

4. A PROCESS FOR THE TREATMENT OF HYDROCARBON OIL OF HIGH SULFUR CONTENT WHICH COMPRISES COUNTERCURRENTLY CONTACTING A DESCENDING STREAM OF THE OIL WITH AN ASCENDING STREAM OF HYDROGENN IN THE PRESENCE OF A SULFUR RESISTANT CATALYST AT DESULFURIZING CONDITIONS IN A FIRST CONVERSION ZONE, WITHDRAWING FROM THE UPPER PORTION OF SAID ZONE A VAPOROUS STREAM CONTAINING HYDROCARBONS, HYDROGEN AND HYDROGEN SULFIDE, SEPARATING HYDROCARBONS AND HYDROGEN SULFIDE FROM SAID VAPOROUS STREAM, INTRODUCING RESULTANT PURIFIED HYDROGEN GAS TO THE LOWER PORTION OF A SECOND CONVERSION ZONE DISPOSED AT A LOWER ELEVATION THAN SAID FIRST ZONE, REMOVING DESULFURIZED OIL FROM THE LOWER PORTION OF SAID FIRST ZONE AND PASSING THE SAME BY GRAVITY FLOW INTO THE UPPER PORTION OF SAID SECOND ZONE, COUNTERCURRENTLY CONTACTING THE DESULFURIZED OIL AND THE PURIFIED HYDROGEN GAS IN SAID SECOND ZONE IN THE PRESENCE