US3190830A - Two stage hydrogenation process - Google Patents

Description

United States Patent 3,190,830 TWO STAGE HYDROGENATION PROCESS John Rowland and Warren Nevin Norton Knight, Sunbury-on-Thames, England, assignors to The British Petroleum Company Limited, *London, England, a British joint-stock corporation No Drawing. Filed Feb. 26, 1963, Ser. No. 261,224 Claims priority, application Great Britain, Mar. 7, 1962,

Claims. (Cl. 208-255) This invention relates to a multi-stage hydrogenation process. I

It is known that aromatic hydrocarbons may be recovered from hydrocarbon mixtures, containing aromatic and non-aromatic hydrocarbons, by solvent extraction.

We have found that it is desirable to remove at least part of the olefin content of such mixtures before solvent extraction; this may be effected by hydrogenation in the presence of a catalyst, cobalt molybdate catalyst being particularly suitable. However, hydrocarbon mixtures obtained by the cracking of petroleum fractions usually contain gum-forming constituents which adversely effect the performance of many hydrogenation catalysts; cobalt molybdate catalyst in particular is adversely effected.

In accordance with the present invention there is provided a process which comprises contacting a feedstock comprising a major proportion of aromatics and monoolefins and a minor proportion of gum-forming constituents, at elevated temperature and in the presence of hydrogen with a supported nickel catalyst which, under operating conditions, contains a major proportion of the nickel in elemental form, whereby at least a substantial proportion of the gum-forming constituents are destroyed and thereafter, in an olefin-removing stage, contacting the product or a fraction thereof and hydrogen at elevated temperature with a hydrogenation catalyst, preferably cobalt molybdate catalyst, whereby at least a substantial proportion of the mono-olefins is converted into paraflins, and thereafter recovering the aromatics.

The process may be carried out in batchwise or continuous manner.

A suitable feedstock to the process of the invention is a steam cracked gasoline produced by cracking, in the presence of steam, petroleum distillate fractions, for example primary flash distillate of naphthas, fractions preferably boiling within the range 50 C. to250 C. Preferred cracking temperatures for the production of gasolines for use in the process of the invention exceed 1100 F. (593 C.); suitable temperatures lie in the range 1100 F, to 1400 F. (593760 C.) and suitable cracking pressures lie in the range 0 to 60 lbs./ sq. in. gauge. Preferably the gas-olines have a total sulphur content of 0.005 to 0.2% by weight.

A suitable feedstock to the process of the invention is a narrow cut of steam cracked gasoline.

Thus according to one aspect of the invention there is provided a process which comprises distilling a raw steam cracked gasoline and recovering a fraction which predominates in hydrocarbons having 6-8 carbon atoms per molecule, said hydrocarbons being predominantly aromatics and mono-olefins with a minor proportion of gumforming constituents, thereafter contacting said fraction at elevated temperature and in the presence of hydrogen, with a supported nickel catalyst which, under operating conditions, contains a major proportion of the nickel in elemental form, whereby at least a substantial proportion of the gum-forming constituents are destroyed and, thereafter, in an olefin-removing stage, contacting the product or a fraction thereof in the presence of hydrogen, at elevated temperature, with a hydrogenation catalyst, where- 3,19%,830 Patented June 22, 1965 forming constituents at elevated temperatures and in the presence of hydrogen, with a supported nickel catalyst which under the operating conditions, contains a major proportion of the nickel in elemental form, whereby at least a substantial proportion of the gum-forming constituents are destroyed and thereafter contactingthe product or a fraction thereof in the presence of hydrogen at elevated temperature with a hydrogenation catalyst whereby at least a substantial proportion of the mono-olefins are converted into paraffins, and thereafter recovering the aromatics.

If desired the steam cracked gasoline may be given a mild hydrogenation treatment to remove part of the gumforming constituents before a distillation stage and thereafter a narrow cut, obtained by distillation, fed to a second hydrogenation over a nickel catalyst for the removal of substantially all of the remaining gum-forming constituents.

According to one manner of operation, separate hydrogen feed is maintained to each of the two hydrogenating stages, thereby facilitating reaction control. In this case the hydrogen feed to each stage is slightly in excess of stoichiometric requirements. Thus the feedstock may be passed over the nickel catalyst while said feedstock is in admixture with a slight excess of hydrogen over that required for the destruction of the gum-forming constituents. However, when using a substantial excess of hydrogen over the nickel catalyst, the required reaction't-emperature is lower than is the case when the amount of hydrogen approximates to the stoichiometrical quality for reaction with the gum-forming constituents.

If desired, all of the hydrogen required in the hydrogenati-on stages may be passed with the feedstock over the nickel catalyst and the product of this stage together with the excess hydrogen passed over the catalyst of the olefin removing stage.

The preparation of the nickel catalyst and its activation may be carried out in any convenient manner, the following three methods being merely illustrative.

. (a) The catalyst may be prepared on the base by an impregnation technique by dissolving in water a nickel salt, for example nickel nitrate, and impregnating the support material with it. The support material may be conveniently in the form of granules or pellets of any desired size formed from groundsupport material. After impregnation, the catalyst is dried and is then in a form in which it can be stored for long periods Without deterioration. In order to use the catalyst, it must be activated by heating to decompose the salt; in the case of the nitrate this required a temperature of about 500-550 0., and the nickel will be converted to the oxide. Final activation by reduction to metallic nickel can be carried out in a stream of hydrogen or hydrogen-containing gas at a temperature of to 600 C. and at a pressure of 0200 lbs./sq in. gauge. The time of treatment depends upon the temperature. Typical conditions using a sepiolite catalyst support are 16 hours at 500 C. and atmospheric pressure; no damage results to the sepiolite however, if it is heated at a temperature above 600 C.

(b) The catalyst may be prepared by milling dry nickel formate with powdered catalyst support, and the mixture 3 subsequently pelleted. The advantage of this method of preparation is that a salt such as nickel formate reduces directly to nickel (without going through the oxide state) in a non-oxidising atmosphere, for example in an inert gas or hydrogen stream at a temperature of 150 C. to 300 C. At 250 C. treatment for 4 hours will usually be appropriate. This method has the advantage that it is not necessary to heat large quantities of catalysts to temperatures of 500 C. and higher.

The catalyst may be prepared by a technique which utilises the water soluble complex formed when nickel formate dissolves in ammonia. This complex breaks down on heating to give nickel formate again. By using this water-soluble complex, catalysts may be prepared by the impregnation technique from normally water insoluble compounds such as nickel formate. The compound is dissolved in ammonia solution and the solution used for the impregnation of granules or pellets of the support material; the catalyst is then dried, and activation is carried out by the method described under (b).

After the reduction, the nickel catalyst should not be allowed to come into contact with air or spontaneous oxidation of the nickel to nickel oxide may occur.

Preferably the activated catalyst contains 2 to 50% by wt. of elemental nickel, based on the total weight of catalyst.

Suitable catalysts for treatment with a sulphur-containing material and use in the process of the invention are nickel supported on alumina, kieselguhr, chalk or silica gel.

A preferred catalyst is nickel supported on sepiolite, containing 2 to by wt. of nickel. Another preferred catalyst contains circa 33% by wt. of nickel and circa 3% by wt. of cobalt supported on an aluminum silicate base.

A suitable catalyst is Nickel Kuhlmann catalyst.

The first and second stage reactors may be isothermal or adiabatic in manner of operation. The heat of reaction in the process of the invention is considerable; if adiabatic reactors are employed in either or both stages it will be desirable, to assist in temperature control in the two hydrogenation steps, to recycle part of the liquid product of the second hydrogenation step to the first hydrogenation step.

Preferably hydrogenation over the nickel catalyst is carried out at a temperature in the range 50250 C. at any pressure, being subatmospheric, atmospheric or superatmospheric. Usually it will be desirable to maintain liquid phase conditions and the pressure will be selected accordingly.

Suitably hydrogen absorption is maintained at circa 350 s.c.f./b.

A major constituent of the gum-forming material will usually be in the form of dienes; these, under the hydrogenating conditions for the removal of gum-forming materials, will be mainly converted to mono-olefins.

If desired hydrogenation may be carried out using a gas consisting of hydrogen together with inert constituents. Preferably, when inert constituents are present, the gas contains at least mol percent of hydrogen, the proportion suitably lying within the range 2590 mol percent of hydrogen.

A preferred gas is a platforrner tail gas. Suitably a gas is employed containing 70 mol percent of hydrogen. A typical gas will consist of 70 mol percent of hydrogen and mol percent of methane. Other suitable gases are steam cracker tail gas, catalytic cracker tail gas and tail gas derived from the dehydrogenation of hydrocarbons.

Preferably the olefin-removing stage is carried out in the presence of a catalyst comprising cobalt oxide and molybdenum oxides on a support. Preferably the support is alumina. Suitably the catalyst contains 1 to 10% Wt. of cobalt oxide, expressed as C00 and 5 to wt. of molybdenum oxide, expressed as M00 The catalyst comprising cobalt oxide and molybdenum oxide is preferably used within the following ranges:

Pressure 100 to 1000 p.s.i.g. Temperature 150 to 480 C. Space velocity 0.5 to 8.0 v./v./hr. Gas recycle rate 500 to 8000 s.c.f./b.

Usually hydrogen adsorption in this step will he circa 250 s.c.f./b.

Preferably when using a sulphur-containing feedstock, the conditions of operation of the olefin-removing stage, are selective to favour the desulphurisation of the feedstock which is fed to this stage.

The product, being mainly a mixture of parafiins and aromatics, is very suitable for further treatment by solvent extraction, for example, by means of dior tri-ethylene glycols, for the recovery of an extract of high aromatic content.

The invention is illustrated but not limited with reference to the following examples.

EXAMPLE 1 The feedstock to the first stage hydrogenation was a C -C cut of steam cracked gasoline obtained under the following conditions:

A straight-run naphtha, having a specific gravity 60/ 60 F. of 0.767 and an ASTM boiling range 79198 C. was passed through a steam cracker at a steam: feed weight ratio of 0.45:1 and a coil out-let temperature of 1310" F. The stabilised gasoline product had the following characteristics: Spccific gravity 60/60 F 0.817. ASTM distillation:

I.B.P. 45 C.

5% wt. recovered at 64 C.

10% wt. recovered at 72 C.

50% Wt. recovered at 138 C.

% wt. recovered at 178 C.

F.B.P. wt. recovered at 207 C. Total sulphur 0.029% wt. Existent gum 15 mg./ ml. Accelerated gum min.) 28 mg./ 100 ml. Accelerated gum (240 min.) 176 mg./100 ml. Induction period (ASTM) 285 min. Bromine number 86.3 min. Diene index 4.67 min.

The C -C cut was prepared from this material by distillation in a =14-plate continuous column at ca 2: 1 reflux ratio. An analysis of the C C cut is given in Table 1.

This feedstock was passed continuously with hydrogen over a catalyst having the following characteristics:

Type: Nickel and cobalt hydroxides supported on aluminium silicate.

Chemical analysis (percent wt. on material stable at 950 F.):

Nickel 33.1

Cobalt 2.95

Iron 0.22 Si0 14.0

Reaction conditions and an analysis of the feedstock and product are given in Table 1.

At 393 hours on stream, the gas rate was increased to 795 s.c.f./b. of hydrogen. The Diene Index remained satisfactory despite a reduction in reaction temperature to 300 F.

The product obtained from the period 0-260 hours on stream was passed with fresh hydrogen over a catalyst having the following characteristics:

Type: Cobalt and molybdenum oxides on alumina. Chemical analysis (percent wt. on material stable 1020 F.):

M003 15.7 Na 0.029

Operating conditions and an analysis of the product for the period 18-370 hours on stream is given in Table 2.

Diene contents were assessed by use of the Diene Index.whioh is described in detail in British patent specification 660,155. The method is based on the assumption that acidified mercuric nitrate will react with conjugated dienes to form insoluble complexes which can be removed by filtration. As conjugated dienes absorb strongly in the ultra-violet region of the spectrum at 2350 A., the differences in the absorbances measured at 2350 A. on a sample before and after washing with mercuric nitrate will be a measure of the conjugated diene content of the sample. However, styrene is also removed by the mercuric nitrate washing and as styrene also absorbs at 2350 A., a correction must be made for the styrene absorption. It is known that the styrene absorbance .at 2350 A. is 1.3 times the absorbance at 2580 A. and since the conjugated dienes do not absorb at 2580 A., the difierence in-absorbance measured at 25 80 A. on the washed and unwashed sample enables a correction to be made for the styrene contribution to the absorbance at 2350 A.

6 weight ratio of 0.39:1 and a coil outlet temperature of 1350 F. The stabilised gasoline product has the following characteristics:

Diene inrleY 4.9.

This gasoline product was passed continuously with a hydrogen containing gas over a nickel-on-sepiolite catalyst containing 10% by wt. of nickel. Reaction conditions were as follows:

A straight-run naphtha having :a specific gravity 60/ 60 of 0.711 and an ASTM boiling range 42-153 C.

'Was passed'through' a steam-cracker at a steamgfeed Table 1 Hours on stream Feedstock Pressure, p sl Q 450 450 450 450 450 Space velocity, v./v./hr 2.0 2.0 2.0 2.0 2.0 Once-through gas rate, s.c.f. Hg/b g 422 2 Product gas rate, s.0.f. E2).-. 13 12 10 11 11 Mid catalyst bed temp., 1 205 270 315 315 300 Hydrogen absorbed, s.0.f./b 357 231 278 351 510 Inspection data: Specific ravity,.60/fi0 F--- 0.8172 0.8102 0.8130

Total sulphur, percent wt 0.023 Bromine No.' 42.4 32.0 29.2 24.7 27.3 t Diene index 5. 0. 84 0. 0. 10 0. 11 4. 54 1. 20 0. 95 0. 42 0. 34

16. 3 15. 6' 10. 3 15.1 15. 5 15. 2 15. 6 14. 7 Ethyl benzene 2.1 4. 4 4. 5 4.8 m-Xylene 6. 0 5. 9 6. 1 5. 9 p-Xylene 2. 9 2. 9 3. 1 3. 0 O-xylene 4. 6 4. 4 4. 4 4. 4

Reaction pressure 445 lbs./s in. gauge. Table 2 o q Mean catalyst bed temperature--- 223 F. 1 Space velocity t 1.75 v./v./hr.

2 Hours on stream 13 27 31 90 216-2 5 361 370 Recycle gas rate 11170 Make-up gas rate 292 s.-c.f./b. Mid. catal st bed tern "F 780 780 780 780 Pressure, 551g .31 450 450 450 450 P gas analyslsipace velogity, v lv ll r n 3- 8 3 2 5- 8 5 g Hydrogen 73.3 m-ol percent.

ec cerae,s.c.. Makyeqlp gas rate, 3 m 2g 11g 2i: Methane D101 percent. P d t te,s.c.f. H b H ;d1%?ge1 1 b lnbed,sari nab.--" .231 201 177 242 'The product obtained was distilled 1n two stages to re- Ins ection data: p I. I pspecific gravity 60.76001? 0.7955 0.8078 0.8086 0.8065 cover a C -C out. Other distillation fractions whlch Total sulphur, percent wt 0.0014 0.0001 0.0001 0. 0001 W thus o talned were employed to produce a motor Bromine N0 0- 4 8 O- 3 3 gasoline Dione index 0.1 0.01 0.01 0.01 Styrene correction 0.2 0. 01 0.01 0.01 'Th1s fraction was passed with .a hydrogen containing m fi s .1 15.2 148 gas over a nickel-on-sepiolite catalyst containing 10% by ToluenefIIQ .5 14.9 14.0 15.3 wt. of nickel. Reaction conditions and ins ecti-on data 4 9 5 0 5 0 p gg gl g :8 5 of feed and product for the penods 636-641 hours on m-x lenlilj .1 3.0 2.0 3.0 stream and 1 3 95 1400 hours on stream are given in O-xylene 4-4 7 '3-9 Table 3 The product of this treatment was assed with h d-rogen Y EXAMPLE 2 over a catalyst cons sting of cobalt and molybdenum modes on alumina having the composition given in Example 1.

Reaction conditions and product inspection data for the Table 3 Hours on stream 636-641 1,395-1A00 Reactor pressure, p.s.i.g 403 400 5 Mid catalyst bed temperature,

F 225 223 Space velocity, v.lv./hr 2.0 1. 97 Make-up gas rate, s.c.f./b 143 171 Make-up gas hydrogen content,

percent mol 67 70 Net hydrogen consumption, 1

s.c.f./b 25 51 Inspection data Food Product Feed Product Specific gravity, 60I60 F 0.7602 0.7590 0.7637 0 7619 ASTM distillation: 0 BP, C 67 65 66 65 FPB, C 119 115 121 124 Total sulphur, percent wt 0. 015 0. 015 0.018 0. 016 Bromine number 40. 2 39. 2 43. 7 37. 8 Dione index 0. 54 0. 04 0. 47 0. 03 Styrene correction 0. 31 0. 05 0.28 0. 04 Benzene content, percent wt 24. 4 24. 2 24. 4 24. 7 2O Toluene content, percent wt 11. 9 12. 1 12. 1 12. 3

Table 4 Catalyst Cobalt and molybdenum oxides on alumnia Hours on stream 169-178 265-274 Reactor pressure, p.s.i.g 450 450 90 Mid catalyst bed temperature, F. 700 700 0 Space velocity, v./v./hr 2.02 2.0 Gas recycle rate, s.c.f./b 850 850 Net hydrogen consumption, s.c.f. 221 260 Product inspection data: Specific gravity, 60l60 F 0. 7582 0. 7567 Total sulphur, percent wt 0.0010 0.0001 Bromine number 0.7 0. 6 3g Benzene content, percent wt. 24. 7 25.0 Toluene content, percent wt 12.8 13.1

EXPERIMENT The following experiment is provided for purposes of comparison only and does not constitute operation =according to the invention.

The feedstock employed was a raw de-but-anised steamcracked gasoline having the following inspection data:

This feedstock was processed with hydrogen over the catalyst containing cobalt oxide and molybdenum oxide described in Example 1.

Process conditions were as follows:

Reactor inlet pressure 100-110 p.s.i.g.

Temperature 500 F.

Space velocity 2 v./v./hr.

Gas recycle rate 2000-2500 s.'c.-f./h.

Recycle gas hydrogen content (H 3 free) 92-95 percent mol.

Hydrogen consumption was initially 160 s.c.f./b.; this value declined rapidly to zero at 336 hours on stream. During this run the pressure differential across the catalyst bed increased rapidly until the termination of the run at 336 hours. On examination of the reactor it was found that substantial blockage had occurred in the pre-heating zone prior to the catalyst bed. The catalyst was coated with polymer which probably accounted for the nil hydrogen consumption immediately prior to shut-down.

We claim:

1. A process for the separation of aromatics from a feedstock mixture containing, in a major proportion, said aromatics and mono-olefins, and a minor proportion of gum-forming constituents, comprising the steps of: contacting said feedstock in a first hydrogenation stage with a supported nickel catalyst which, under operating conditions, contains a major proportion of nickel in elemental form, in the presence of a gas in which the reactant thereof consists essentially of hydrogen and at an elevated temperature, whereby at least a substantial proportion of the gum-forming constituents are destroyed; passing at least a portion of the product stream from said first stage to a second, olefin removing, hydrogenation stage and contacting said portion with a hydrogenation catalyst difierent from said supported nickel catalyst of said first stage in the presence of hydrogen and at an elevated temperature whereby at least a substantial proportion of the monoolefins in said portion are converted into paraffins; and recovering the aromatics from the product stream of said second stage.

2. A process according to claim 1, wherein a separate hydrogen feed is maintained to each of said hydrogenation stages.

3. A process according to claim 1, wherein all of the hydrogen required in said two hydrogenation stages is passed through the first hydrogenation stage and wherein excess hydrogen from the first stage is passed to the second stage.

4. A process according to claim 1, wherein the supported nickel catalyst is nickel-on-sepiolite.

5. A process according to claim 1, wherein the olefin removal in said second hydrogenation stage is carried out in the presence of a. cobalt oxide and molybdenum oxide-containing catalyst.

6. A process for the separation of aromatics from a feedstock consisting of a raw steam cracked gasoline, comprising the steps of: distilling said raw steam cracked gasoline and recovering a fraction therefrom predominating in hydrocarbons having 6-8 carbon atoms per molecule, said hydrocarbons being predominantly aromatics and mono-olefins with a minor proportion of gum-forming constituents; passing said fraction to a first, hydrogenation stage and contacting said fraction with a supported nickel catalyst which, under operating conditions, contains a major proportion of nickel in elemental form, in the presence of a gas in which the reactant thereof consists essentially of hydrogen and at an elevated temperature whereby at least a substantial proportion of said gumforming constituents are destroyed without substantial hydrogenation of the aromatic and mono-olefin constituents; passing at least a portion of the product stream from said first stage to a second, olefin removing, stage and contacting said portion with a hydrogenation catalyst different from said supported nickel catalyst of said first stage in the presence of hydrogen and at an elevated temperature to convert the said mono-olefins of said fraction to paraffins; and, thereafter recovering the aromatics from the product stream of said second stage.

7. A process for the separation of aromatics from a feedstock consisting of raw steam cracked gasoline containing predominantly aromatics and mono-olefins with a minor proportion of gum-forming constituents, comprising the steps of: contacting said feedstock with a sup ported nickel catalyst which, under operating conditions, contains a major proportion of nickel in elemental form, in the presence of a gas in which the reactant thereof consists essentially of hydrogen and at an elevated temperature, whereby at least a substantial proportion of the gum-forming constituents are destroyed; passing at least a portion of the product stream from said first stage to a second, olefin removing, hydrogenation stage and contacting said portion with a hydrogenation catalyst different from said supported nickel catalyst of said first stage in the presence of hydrogen and at an elevated temperature tions, contains a major proportion of nickel in elemental form, in the presence of a gas in which the reactant thereof consists essentially of hydrogen and at an elevated temperature, whereby at least a portion of said gum-forming constituents are destroyed; distilling the product stream from said first stage and recovering a fraction therefrom predominatingin hydrocarbons having 6-8 carbon atoms per molecule; passing said fraction to a second stage and contacting said fraction with a supported nickel catalyst which, under operating conditions, contains a major proportion of nickel in elemental form, in the presence of a gas in which the reactant thereof consists essentially of hydrogen and at an elevated temperature, whereby substantially all of the remaining gum-forming constituents are destroyed; passing at least a portion of the product stream to a third stage and contacting the product stream in said third stage with a hydrogenation catalyst different from said supported nickel catalyst of said first stage in the presence of hydrogen and at an elevated temperature to convert at least a substantial proportion of the monoolefins in said product stream in said third stage to paraflins; and thereafter recovering the aromatics from the product stream'from said third stage.

9. A process according to claim 8, wherein the feedstock is a steam cracked gasoline having a sulphur content in the range 0.005-0.2% by weight.

10. A process for the separation of aromatics from a feedstock mixture containing aromatics and mono-olefins in major proportions and gum-forming constituents in a minor proportion which comprises contacting said feedstock in a first hydrogenation stage with a supported nickel catalyst which, under operating conditions, contains a major proportion of nickel in elemental form, in the presence of a gas in which the reactant thereof consists essentially of hydrogen and at a temperature in the range -250 0, whereby at least a substantial proportion of the gum-forming constituents are destroyed, passing the product stream from said first stage to a second olefin removing hydrogenation stage and contacting said product stream in the presence of hydrogen with a cobalt oxide-molybdenum oxide catalyst on a support, at a pressure in the range to 1000 p.s.i.g., a temperature in the range -480 C., and at a space velocity of 0.5 to 8.0 v./v./hr., whereby at least a substantial proportion of the mono-olefins in said product stream are converted into paraflin, and recovering the aromatics from the product stream of said second stage.

References *Cited by the Examiner UNITED STATES PATENTS 2,872,492 2/59 Donaldson et a1. 260-667 2,953,612 9/60 Haxton et al 260683.9 3,004,914 10/61 White 208-255 3,098,829 7/63 White et al. 208-255 3,113,096 12/63 White 208-255 3,113,097 12/63 White et al. 208-255 3,116,233 12/63 Dovrnes et a1. 208-255 ALPHONSO D. SULLIVAN, Primary Examiner.

Claims (1)

1. A PROCESS FOR THE SEPARATION OF AROMATICS FROM A FEEDSTOCK MIXING CONTAINING, IN A MAJOR PROPORTIONS, SAID AROMATICS AND MONO-OLEFINS, AND A MINOR PROPORTION OF GUM-FORMING CONSTITUENTS, COMPRISING THE STEPS OF: CONTACTING SAID FEEDSTOCK IN A FIRST HYDROGENATION STAGE WITH A SUPPORTED NICKEL CATALYST WHICH, UNDER OPERATING CONDITIONS, CONTAINS A MAJOR PROPORTION OF NICKEL IN ELEMENTAL FORM, IN THE PRESENCE OF A GAS IN WHICH THE REACTANT THEREOF CONSISTS ESSENTIALLY OF HYDROGEN AND AT AN ELEVATED TEMPERATURE, WHEREBY AT LEAST A SUBSTANTIAL PROPORTION OF THE GUM-FORMING CONSTITUENTS ARE DESTROYED; PASSING AT LEAST A PORTION OF THE PRODUCT STREAM FROM SAID FIRST STAGE TO A SECOND, OLEFIN REMOVING, HYDROGENATION STAGE AND CONTACTING SAID PORTION WITH A HYDROGENATION CATALYST DIFFERENT FROM SAID SUPPORTED NICKEL CATALYST OF SAID FIRST STAGE IN THE PRESENCE OF HYDROGEN AND AT AN ELEVATED TEMPERATURE WHEREBY AT LEAST A SUBSTANTIAL PROPORTION OF THE MONOOLEFINS IN SAID PORTION ARE CONVERTED INTO PARAFFINS; AND RECOVERING THE AROMATICS FROM THE PRODUCT STREAM OF SAID SECOND STAGE.