US3654139A - Desulphurisation and de-aromatisation of petroleum distillates - Google Patents

Abstract

A PROCESS IS DISCLOSED IN WHICH A 60-250* C. DISTILLATE CONTAINING UP TO 2% WT. SULPHUR AND UP TO 25% WT. AROMATICS IS CATALYTICALLY DESULPHURISED WITH HYDROGEN IN A FIRST STAGE TO CONVERT THE MAJOR PROPORTION OF THE SULFUR TO HYDROGEN SULPHIDE. HYDROGEN SULFIDE IS REMOVED, THE FRACTION IS CONTACTED WITH SUPPORTED ELEMENTAL NICKEL TO REMOVE REMAINING SULPHUR IN A SECOND STAGE WITHOUT LIBERATION OF HYDROGEN SULPHIDE, WITHOUT AROMATICS HYDROGENATION, AND WITHOUT HYDROCRACKING, AND THE DESULPHURISED FRACTION IS HYDROGENATED OVER SUPPORTED ELEMENTAL NICKEL IN A THIRD STAGE.

Description

April 4, 1972 I J WINSQR E'l'AL 3,654,139

DESULPHURISATION AND DE-AHOMATISATION OF PETROLEUM DISTILLAIES Filed July 5, 1968 FEED PRODUCT I/V VEIV 7025 JOHN W/A/SOQ JOHN CARRU THERS United States Patent 3,654,139 DESULPHURISATION AND DE-AROMATISATION 0F PETROLEUM DIS'I'ILLATES John Winsor, 58 Giffard Drive, Famborough, Hampshire,

England, and John Carruthers, 42 Sandalwood Ave., Chertsey, Surrey, England Filed July 5, 1968, Ser. No. 742,733 Claims priority, application Great Britain, July 11, 1967, 31,770/ 67 Int. Cl. C10g 23/00; C07c /10 US. Cl. 208-89 14 Claims ABSTRACT OF THE DISCLOSURE The process is suitable for preparation of dearomatised SBP solvents, white spirits and high quality kerosine used as illuminating oil.

This invention relates to the desulphurisation and dearomatisation of petroleum distillates boiling within the range 60 to 250 C.

It is known that fractions of petroleum distillates used as solvents, white spirits, illuminating oil, and the like, all have a content, and sometimes a considerable content, of aromatic hydrocarbons which are harmful for certain uses. It has been previously proposed to convert these aromatic hydrocarbons by catalytic hydrogenation, and when the hydrogenation catalyst is a sulphur-sensitive reduced nickel catalyst, to give the feedstock a preliminary hydr-ocatalytic desulphurisation to reduce the sulphur content to not more than 50 ppm. wt. However, since the poisoning effect of sulphur on nickel is cumulative even small amounts of sulphur of the order of a few parts per million in a feedstock are harmful.

U.-K. Patent -No. 1,098,698 claims a process for the desulphurisation of a straight-run petroleum fraction containing up to 2.0% Wt. sulphur which comprises catalytically hydrodesulphurising the fraction in a first stage to convert the major proportion of the sulphur to hydrogen sulphide, removing the hydrogen sulphide, and contacting the fraction of reduced sulphur content with supported elemental nickel in a second stage under conditions such that residual sulphur is adsorbed by the nickel substantially without the liberation of hydrogen sulphide. Using this process sulphur levels can be reduced to 1 p.p.m. or less. The present invention combines a 2-stage desulphurisation similar to that of U.K. Patent No. 1,098,698 with a subsequent de-aromatisation process using a reduced nickel catalyst.

According to the present invention, therefore, a process for the desulphurisation and de-aromatisation of a pctroleum distillate boiling within the range 60 to 250 C. and containing up to 2% wt. sulphur and up to 25 wt. aromatics, comprises catalytically hydrodesulphurising the distillate in a first stage to convert the major proportion of the sulphur to hydrogen sulphide, removing the hydrogen sulphide, contacting the fraction of reduced sulphur content with supported elemental nickel in a second stage under conditions such that residual suplphur is adsorbed by the nickel without substantial liberation of hy- Patented Apr. 4, 1972 drogen sulphide, without substantial hydrogenation of the aromatics and without substantial hydrocracking of the feedstock, and hydrogenating the aromatics in a third stage over supported elemental nickel.

Any convenient petroleum fraction can be used, but de-aromatisation is particularly required with certain SBP solvents, white spirits and high quality kerosine used as illuminating oil. SBP solvents are produced to narrow boiling range specifications, e.g. 60-80 C., 60-90 0, -110" C. and -140 C. The feedstock can be fractionated into the required cuts either before or after processing according to the invention. If the whole feedstock is processed and then distilled only one distillation is necessary. If it is fractionated and the individual cuts processed, each cut must be individually stabilised.

The present invention proposes a two-stage desulphurisation operation because it is diflicult, using conventional catalytic hydrodesulphurisation techniques, to remove last traces of sulphur from a feedstock. These traces of sulphur are likely to be ring-type compounds such a thiophenes and substituted thiophenes. Conventional hydrodesulphurisation involves conversion of the sulphur present to hydrogen sulphide, which is then removed, and ring-type compounds are more resistant to such treatment.

The conditions used for the catalytic hydrodesulphurisation can follow established practice. Thus the fractions can be treated at 204-510 C. and 50-1500 p.s.i.g. at a space velocity of 0.1 to 20 v./y./hr. with 200-5000 s.c.f./ b.r.l. of hydrogen. Hydrogen may be recycled or passed once through. Catalysts suitable for use in such a process can comprise one or more oxides or sulphides of elements of Groups VIa and VIII of the Periodic Table on a support comprising one or more refractory oxides selected from oxides of elements of Groups II to V of the Periodic Tables, for example cobalt and molybdenum oxides supported on alumina.

The hydrogen sulphide produced during the catalytic hydrodesulphurisation stage is removed before the second desulphurisation stage so that the desulphurisation capacity of the nickel is not wasted on such easily removed sulphur. The majority of the hydrogen sulphide can be removed in the high pressure and low pressure separators which normally follow a catalytic hydrodesulphurisation reactor or zone. Alternatively, or in addition to such separators, hydrogen sulphide can be removed by any of the known ways, for example by stripping with inert gas, by washing with caustic soda, by adsorption on an adsorbent such as zinc oxide, clay, or molecular sieves, or by treatment with a solvent such as glycol amine soltion.

The product from the catalytic hydrodesulphurisation stage, free from hydrogen sulphide, is passed, in the second desulphurisation stage, over supported elemental nickel, which takes up residual sulphur and becomes progressively sulphided. It has been found that the presence of a small amount of hydrogen is beneficial even though the process is not a hydrodesulphurisation process because no hydrogen sulphide is produced. The hydrogen should of course be sulphur-free. The beneficial effect of hydrogen is believed to be due to the fact that the sulphur is present in organic sulphur compounds and that as the sulphur is adsorbed on the nickel unsaturated organic radicals are produced which tend to polymerise on the nickel surface and reduce its catalytic activity. If hydrogen is available these radicals are saturated to harmless saturated hydrocarbons. The amount of hydrogen to achieve this can be calculated and is very small, particularly since the product from the first stage contains only a small quantity of sulphur. Thus, for a feedstock containing 50 ppm. wt. sulphur the amount of hydrogen required is only 93x10 litres at N.T.P. per litre of feedstock. The amount of hydrogen present should not be excessive so as to avoid substantial hydrogenation of the aromatics present or pressure hydrocracking of the parafiins. Accordingly any large excess of hydrogen from the first stage must be removed before entry to the second stage. This can conveniently be done in the separators refered to above in connection with the removal of hydrogen sulphite. Alternatively, or additionally other means of stripping out the hydrogen can be used. If hydrogen recycle is employed in the catalytic hydrodesulphurisation stage there will be no gaseous hydrogen efiluent from that stage. In this case it is desirable that hydrogen be supplied separately to the second stage in an amount to prevent deactivation.

The amount of hydrogen supplied to the second stage should be controlled so that it is greater than the minimum necessary to prevent de-activation of the supported nickel, the maximum amount of hydrogen supplied depending on Whether the nickel is fresh, i.e. unsulphided, or other wise. The nickel may be regarded as fresh When the sulphurznickel ratio at any point in the catalyst bed is less than 0.06:1 atomic, i.e. when the nickel at any point in the bed has hydrogenation activity. When the catalyst is fresh the inlet hydrogen to hydrocarbon ratio (based on total feed) should not exceed 0.3:1 molar. During use the inlet hydrogenzhydrocarbon ratio based on total feed should not at any time exceed :1 molar. Preferably the inlet hydrogen-hydrcarbon ratio should be 0.001 to 0.221 molar.

The feedstock to the second stage can be in the vapour or liquid phase depending on whether or not the nickel is sulphided, the criterion being the above sulphurznickel ratio of 0.06:1 atomic. When the catalyst is unsulphided, the feedstock should be in the liquid phase, the amount of hydrogen supplied being limited to that which will saturate the feedstock at the operating temperature and pressure. In this situation there will be substantially no hydrogen partial pressure. As the catalyst becomes sulphided the amount of hydrogen supplied may be increased so that a hydrogen partial pressure exists,. The feedstocks in this latter case can be vapour or liquid, although liquid phase operation is preferred. When operating in liquid phase upward flow of the feedstock is desirable.

The solubility of hydrogen in the feedstock will depend on the nature of the feedstock, the ambient temperature and the ambient pressure. The following table shows the effect of increasing pressure within the range 100-1000 p.s.i.a. on the solubility of two pure paraffin hydrocarbons at a primary hydrogen-hydrocarbon ratio of 0.1 :1 molar.

Moi. traction of hydrogen in liquid phase Hg/butane at Ha /octane at Pressure, p.s.1.a. 110 F. 100 F.

M01. fraction of hydrogen in liquid phase Pressure, p.s.i.a. Hg/butane at 240 F. Hr/octane at 240 F.

100 System all vapour S stem all li uid. 400 0.018 y Do. q 1,000 System all liquid Do.

The table shows that the phase conditions change more readily at lower pressures and with lower boiling components. The feedstock will be a relatively complex mixture of components of different carbon number and molecular type and the effect of changes in reaction conditions will also be complex. However, if reaction condi- 4 tions are carefully chosen in relation to the nature of the feedstock it is possible to avoid a hydrogen vapour pressure in the system when the catalyst is fresh.

Naphthenes can be added to the second stage feedstock if the aromatic content of the feedstock is high, i.e. greater than 15% Wt. This is to avoid the rapid absorption of hydrogen that would result from the hydrogenation of such an amount of aromatic hydrocarbons, which might cause a considerable variation in the concentration of hydrogen present, and an excessive temperature rise. Naphthene addition can be by direct addition of suitable material or, more conveniently, by recycle from the third (bydrogenation) stage of the present process.

It was shown above that the temperature and pressure must be considered in relation to the hydrogenzhydrocarbon ratio. In addition it is desirable to operate the second stage at a fairly high temperature, since the sulphur capacity and desulphurisation activity of the supported nickel catalyst increase with temperature. In practice the upper limit of temperature is set by the onset of sidereactions such as cracking, isomerisation, and possible ring opening, the first of these being the most important. As the nickel becomes sulphided the operating temperature can be raised without by-product formation taking place. The space velocity of the second stage will depend on the amount of sulphur present and the level to which it is to be reduced, but subject to these requirements it should desirably be as high as possible.

Having regard to the foregoing, the reaction conditions, other than the inlet hydrogenzhydrocarbon ratio, can be selected from the following ranges.

Temperature, C.: 50 to 316 (preferably 75 to 250) Pressure, p.s.i.g.: 0 to 5000 (preferably to 2000) Liquid hourly space velocity (LHSV), v./v./hr.: 0.002 to 10 (preferably 0.1 to 5) The temperature rises occurring must be within the range given. Thus the second stage reactor exit temperature must not exceed the upper limit of the range and the range and the inlet temperature must be above the lower limit. The upper limit will apply also to the increased temperature possible when the nickel in the second stage is partly sulphided.

The sulphur content of the first stage product will depend on the original sulphur content and boiling range of the feedstock and on the hydrocatalytic desulphurisation conditions. Preferably the sulphur content is reduced as much as possible in this first stage, thus increasing the life of the nickel in the second stage. Suitably the sulphur content of the first stage product should not exceed 50 p.p.m. wt., preferably not more than 10 p.p.m. wt. The second stage product preferably has a sulphur content of less than 1 p.p.m. wt. particularly less than 0.5 p.p.m. wt. and it may be below 0.1 p.p.m. wt. The sulphur contents quoted refer to both combined and uncombined sulphur, but are expressed as the element.

The desulphurised product from the second stage is hydrogenated in the final stage of the process of the invention preferably in the vapour phase or mixed vapour/ liquid phase on entry to the final stage. The reaction conditions may be chosen from the following ranges.

Temperature, C.: 25 to 350 (preferably 50 to 300) Total pressure, p.s.i.g.: 25 to 2000 (preferably 100 to Liquid hourly space velocity (LHSV), v./v./hr.: 0.1 to

Excess hydrogen rate on total feed, s.c.f./b.r.l.: 50 to 5000 (preferably 200-1000) Liquid (product) recycle, can be employed to control the third stage temperature, particularly if the aromatic content of the feedstock to the stage is greater than 5% wt. The use of liquid recycle means that the volume of material passing through the reactor is increased, and to achieve the same contact time, the use of a larger reactor would be necessary. If cooling is necessary this can alternatively be achieved by using a cooled tubular reactor, with the catalyst in the tubes and a cooling agent being passed over them. In this type of reactor a higher average catalyst bed temperature can be obtained for a given level of hydrogenation than is possible with an adiabatic reactor. Any substance which is thermally stable within the temperature range of the process may be used as the cooling agent. If a cooled tubular reactor is used the third stage is preferably in the vapour phase throughout, as otherwise distribution difliculties may occur. If, however, product recycle is used the fact that this is in liquid phase at the reactor inlet means that the heat of vaporisation will assist the cooling effect and the minimum of liquid necessary to achieve the cooling effect may be used. This means that the total feed enters the final stage reactor at as low a temperature as possible, consistent with the temperature being high enough for the activity of the catalyst to be sufficient to hydrogenate the aromatics in the feedstock.

The process conditions chosen from the above ranges will depend on the extent of hydrogenation (i.e. dearomatisation) required, which in turn will depend on the aromatic content of the feedstock to the stage and the type of product required. Certain types of SBP solvents for example may require aromatic contents of less than 100 ppm. wt. and this can be achieved with feedstocks to the process containing up to 25 wt. aromatics. With kerosines the initial aromatic content can be up to 25% wt., and reduction to an aromatic content of less than 1% wt. is practicable. The final stage temperature can be increased during processing as necessary to allow for decrease in catalyst activity with time.

Although discussion has been confined to the use of single stages of catalytic hydrodesulphurisation, adsorption of sulphur on supported nickel, and hydrogenation, there can be more than one stage of each of these steps. In particular more than one stage of hydrogenation can be employed in the process of the invention. Moreover, any number of reactors can be employed in any one stage.

The accompanying drawing illustrates, schematically, a possible mode of operation of the second stage of the invention.

In the drawing a product from the first (catalytic hydrodesulphurisation) stage is pumped by pump 2 to a saturator 21. Valves 15, 17, 18, 24 and 25 are closed. Excess hydrogen leaves saturator 21 via lines 22, 26 and 28. Valves 23 and 27 are open, the latter acting as a pressure control valve, and the excess gas is vented off, desirably being used in the other stages of the invention. In the saturator 21 the feed is saturated with hydrogen, and the feed, containing dissolved hydrogen only, then leaves via lines 4 and 6 and open valve to reactor 7, containing fresh catalyst. Liquid leaving reactor 7 goes via lines 8, 10 and 12 and open valve .11 to open valve 13 where it is flow-controlled out to the final stage via line 14, cooling taking place in condenser 9.

When the activity of the catalyst has declined more hydrogen is admitted to reactor 7 by closing valves 6, 23 and 11 and opening valves 15, 17, 18, 24 and 25. In this situation feedstock passes through saturator 21 and thence through valve 24 to reactor 7. 'Excess hydrogen is not bled off as before via valve 23, but passes with the feedstock into the reactor. Liquid leaving the reactor is cooled in condenser 9 as before but instead of passing directly to product it enters a high pressure separator 16 via line 10 and valve 15. A secondary supply of hydrogen is supplied to separator 16 via valves 25 and 18 and lines 20, 26 and 19 to maintain the system pressure. Excess gas is pressurecontrolled out of the stage via valve 27. The liquid from separator 16 leaves via valve 17 and line 12 to flow control valve 13 and thence to product (i.e. to the final stage).

The supported nickel catalyst used in the second and third stages can incorporate any of the known natural or synthetic support materials, such as the refractory oxides of elements of Groups II to V of the Periodic Table, or

kieselguhr, pumice, or sepiolite. Sepiolite is the preferred material and the preferred catalyst for the second and third stages is nickel on sepiolite prepared and activated according to the disclosures of British Pat. No. 899,652. Sepiolite is the preferred support because it can withstand high temperatures under reducing or oxidising conditions, it holds the nickel in finely divided form and with a high surface area, and it is relatively cheap.

The supported nickel catalyst, preferably prepared and activated according to the above-mentioned British Pat. may contain from 1 to 50% wt. nickel (expressed as elemental nickel) and more particularly from 5 to 25% wt. Such a catalyst has high nickel surface area and has high activity and selectivity. We have found that it is capable of adsorbing sulphur up to a sulphurznickel atomic ratio of at least 0.75: 1. Since the sulphur capaacity of the support nickel material is high and is known it is possible to provide a sufficient amount of it to give an economic catalyst life.

The hydrogen used in all stages of the process of the invention can be commercially pure or it may be a mixed gas derived from a refinery process such as steam reformer tail gas, also containing methane, or catalytic reformer off-gas. It should, however, be sulphurfree. Catalytic re former off-gas is preferred, since operation in the liquid phase enables comparatively high pressures to be used, and catalytic reformer olf-gass is available at approximately 400 p.s.i.g. Preferably the gas contains at least 50 mol percent hydrogen, and more particularly from 70 to 99 mol percent hydrogen.

In accordance with conventional practice hydrogen may be supplied to each or every stage on a once-through or recycle basis. If a recycle method is used with a mixed gas, for example one containing methane, this can be removed by purging from the recycle gas or by separation from the liquid products.

The invention is illustrated by the following examples.

EXAMPLE 1 (a) first stage: catalytic hydrodesulphurisation Standard cobalt oxide-molybdenum oxide on alumina catalyst was pretreated with hydrogen at 332 C. and then presulphided at 332 C. with carbon disulphide in n-heptane. A straight-run C 140 C. distillate fraction derived from a Kuwait crude and containing p.p.m. weight sulphur was desulphurised over this catalyst under the following conditions:

Temperature, C.: 204-316 Pressure, p.s.i.g.: 400

H- recycle rate s.c.f./b.r.l.:

Make-up gas, percent mol: 70/30 H /CH The sulphur content of the product varied within the range 0.1 to 1.5 ppm weight.

(b) second stage: desulphurisation over supported nickel Straight run distillate, desulphurised as described in (a) was passed over fresh 10% wt. nickel on sepiolite catalyst in liquid phase using the flow system described and illustrated, and under the following conditions:

Temperature, C.: 204

Pressure, p.s.i.g.: 400

Make-up gas to saturator: Hydrogen Inlet hydrogenzhydrocarbon, ratio, molar: 0.02:1

In this operation the sulphur content of the straight run distillate was reduced from 1.1 to 0.1 ppm. weight.

The aromatic content of the distillate was 5 percent weight, comprising various quantities of C to C aromatics. No change in the aromatic content was detected by GLC analysis.

The run was still progressing satisfactory after 1000 hours operation.

() third stage: de-aromatisation In this way the aromatic content of the distillate was reduced to a very low level, namely 50 p.p.m. weight.

This operation was still progressing satisfactorily after 1500 hours.

EXAMPLE 2 (a) and (b) first and second stages: catalytic hydrodesulphurisation and desulphurisation over supported nickel A C 170 C. straight run distillate fraction was desulphurised over cobalt oxide-molybdenum oxide on alumina catalyst, using the operating conditions of Example 1(a). Thiophene was then added to increase the sulphur content to 22 p.p.m. weight. This material was then desulphurised over fresh wt. nickel on sepiolite in the liquid phase under the following conditions:

Temperature, 0 C.: 204-260 Pressure, p.s.i.g.: 400

Make-up gas to saturator: Hydrogen Inlet hydrogenzhydrocarbon ratio: molar 0.02:1

The sulphur content of the product was 0.2 p.p.m. wt. The catalyst retained its activity after a period of 700 hours.

EXAMPLE 3 (a) first stage: catalytic hydroesulphurisation The sulphur content of straight-run kerosine was reduced from 1700 p.p.m. wt. to 2.2 p.p.m. wt. by hydrodesulphurisation over cobalt oxide-molybdenum oxide on alumina catalyst,

(b) second stage: desulphurisa-tion over supported nickel The product from (a) was desulphurised over fresh 10% Wt. nickel on sepiolite catalyst in the liquid phase using the flow system described and illustrated, and under the following conditions:

Temperature, C.: 238

Pressure, p.s.i.g.: 400

Make-up gas to saturator: Hydrogen Inlet hydrogen: hydrocarbon ratio: molar 0.02:1

In this operation the sulphur content of straight-run kerosine was reduced from 2.2 to 0.3 p.p.m. wt.

The aromatic content of the kerosine was 18% wt., as determined by infra-red spectroscopy. Use of this technique failed to detect any change in aromatic content after desulphurisation.

This operation was still proceeding satisfactorily after 2233 hours on stream.

(c) third stage: de-aromatisation The product from (b) was hydrogenated over 10% wt. nickel on sepiolite to convert the aromatics to naphthenes in the liquid phase under the following conditions:

Temperature, C.: 218

Pressure, p.s.i.g.: 400

LHSV (fresh fee-d), v./v./hr.: 0.25

LHSV (product recycle), v./v./hr.: 05

Once through gas, percent mol: 70/ 30 H /Cl-l Inlet gas: total feed ratio, molar: 0.621

8 By this means the aromatic content of the kerosine was reduced from 18 to 0.8% wt.

The operation was still proceeding satisfactorily after 2200 hours on stream.

What we claim is:

1. A process for the desulphurisation and dearornatisation of petroleum distillate boiling Within the range 60 to 250 C. and containing up to 2% sulphur and up to 25% wt. aromatics, which process comprises:

(a) catalytically hydrodesulphurising the distillate in a first stage to convert the major portion of the sulphur to hydrogen sulphide;

(b) removing the hydrogen sulphide from the product of step (a);

(c) passing said distillate of reduced sulphur content, together with hydrogen, over a supported elemental nickel catalyst in a second stage operated under conditions such that residual sulphur in said product is absorbed by the nickel without substantial liberation of hydrogen sulphide, Without substantial hydrogenation of the aromatics, and without substantial hydrocracking of said distillate, said conditions being further defined by either (1) or (2):

(1) the second stage being operated in the liquid phase with substantially all of the hydrogen present being dissolved in said distillate and with substantially no hydrogen partial pressure, when the catalyst has a sulphurznickel ratio of less than 0.06:1 atomic, the amount of hydrogen present being (a) not more than the maximum that would dissolve in said distillate at the stage temperature and pressure, and

(b) not greater than that equivalent to an inlet hydrogemhydrocarbon ratio, based on total feed, of 0.0:1 molar,

(2) the second stage being operated in the liquid or the vapour phase and with a hydrogen partial pressure, when the catalyst has a sulphurznickel ratio equal to or in excess of 0.06:1 atomic, the amount of hydrogen present being (a) at a level at which a hydrogen vapour pressure exists at the stage temperature and pressure,

(b) but said amount of hydrogen being not greater than that equivalent to an inlet hydrogenzhydrocarbon ratio, based on total feed, of 10:1 molar, and

(d) passing said desulphurised second stage distillate to a third stage over a supported elemental nickel catalyst to hydrogenate the aromatics of said distillate.

2. A process as claimed in claim 1, in which the distillate is a naphtha boiling within the range 60-170" C. or a white spirit boiling within the range 15 0l90 C. or a kerosine boiling within the range 180250 C.

3. A process as claimed in claim 1, in which the first stage catalyst is cobalt oxide-molybdenum oxide on alumina.

4. A process as claimed in claim 1 in which the sulphur content of the distillate is reduced to not more than 50 p.p.m. wt. in the first stage.

5. A process as claimed in claim 1, in which the inlet hydrogemhydrocarbon ratio is 0.001 to 02:1 molar.

6. The process of claim 1 in which about 9.3 10 litres of hydrogen at N.T.P. per litre of feedstock are present in the second stage when the feedstock contains about 50 p.p.m. wt. sulphur.

7. A process as claimed in claim 1 in which the feedstock is flowed upwardly through the catalyst in said second stage.

9. A process as claimed in claim 1 in which the second stage reaction conditions, other than the hydrogenzhydrocarbon ratio, are selected from the following ranges: Temperature, C.: 50 to 316 Pressure, p.s.i.g.: to 5000 Liquid hourly space velocity, v./v./hr.: 0.002 to 10 10. A process as claimed in claim 9 in which the reaction conditions are selected from the following ranges Temperature, C.: 75 to 250 Pressure, p.s.i.g.: 100 to 2000 Liquid hourly space velocity, v./v./hr.: 0.1 to

11. A process as claimed in claim 1, in which the third stage is operated in vapour or mixed phase on entry to the stage and under conditions selected from the following ranges:

Temperature, C.: 25 to 350 Total pressure, p.s.i.g.: 25 to 2000 Liquid hourly space velocity, v./v.hr.: 0.1 to 10 Excess hydrogen rate on total feed, s.c.f./b.r.l.: 50 to 5000 12. A process as claimed in claim 11, in which the third stage is operated under conditions selected from the following ranges:

Temperature, C.: 50 to 300 Total pressure, p.s.i.g.: 100 to 1500 Excess hydrogen rate on total feed, s.c.f./b.r.l.: 200 to 1000 13. A process as claimed in claim 1 in which liquid 10 product from the third stage is recycled to the third stage reactor inlet to control the third stage temperature.

14. A process as claimed in claim 1 in which the supported nickel catalyst used in the second and third stages is nickel on sepiolite containing from 1 to Wt. nickel, expressed as elemental nickel.

References Cited UNITED STATES PATENTS 2,037,789 4/1936 Ipatietf 208213 2,037,790 4/1936 Ipatiefi 208213 2,273,299 2/1942 Szayna 2082l7 2,623,006 12/1952 McAlfee 208-217 2,921,022 1/1960 Sowerwine, Jr. 2082l7 3,190,830 6/1965 Rowland et a1. 208255 3,228,993 1/ 1966 Kozlowski, et al. 208210 3,258,431 6/1966 Fisher et al. 2082l7 3,347,779 10/ 1967 Groenendaal et a1. 20889 3,484,501 12/1969 Winsor et a1. 208143 DELBERT E. GANTZ, Primary Examiner G. J. CRASANAKIS, Assistant Examiner US. Cl. X.R. 260--667; 208212 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTEN Patent No. 3,654,139 Dated Agril 4, 1972 Inventor(s) John Winsor, et, a1.

It is certified that error appears in the aboveidentified patent and that said Letters Patentare hereby corrected as shown below:

golumn 1, in the heading, line 7, after England, insert assignors to The British Petroleum Company, Limited, London England Signed and sealed this 1st day of May 1973.

(SEAL) Attest:

' EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK l k ttesting Officer I Commissioner of Patents FORM P0710150 I uscoMM-oc 60376-P69 U.S. GOVERNMENT PRINTING OFFICE: I969 0*356-334.

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