JPH05294851A - Selective hydrogenation of diolefins - Google Patents

Abstract

PURPOSE: To selectively hydrogenate diolefins contained in C₅ flow of rifinery by using a distillation column reactor contg. hydrogenation catalyst capable of acting as a set of distillation structure.

CONSTITUTION: A light naphtha contg. diolefins is introduced via a line 1 to the distillation column rector 10 contg. a packed substance of proper hydrogenation catalyst as a part of a distillation structure 12 and a standard distillation structure 14, hydrogen is supplied via a line 2, and the light naphtha and hydrogen are brought into contact with hydrogenation catalyst in a distillation reaction zone to allow essentially all of diolefins contained in a lightnaphtha to react with hydrogen to form pentenes and other hydrogenated products in reaction mixture. By operating the pressure of the reactor, the temp. in the reaction zone is made in a selected range and a portion of the reaction mixture is vaporized. The liq. portion contg. no C₅ diolefins is withdrawn as bottoms via a line 8, the vaporous portion is withdrawn as overheads together with unreacted hydrogen and the condensed portion is supplied to the production process of t-amyl-methyl ether.

COPYRIGHT: (C)1993,JPO

Description

Detailed Description of the Invention

Related US Pat. No. 5,087,780 is
Mixed C ₄ discloses hydroisomerization and hydrogenation of butadiene stream (mixed C ₄ streams).

[0002]

BACKGROUND OF THE INVENTION The present invention mainly comprises a C ₅ component,
More specifically, it relates to the selective hydrogenation of diolefins (dienes) contained in refinery streams containing olefinic C ₅ components. More specifically, the present invention relates to a process for selectively hydrogenating dienes using a distillation column reactor containing a hydrogenation catalyst that also acts as a component of a distillation structure. More particularly, the present invention is to produce a tert- amyl methyl ether (TAME), it relates to the selective hydrogenation of C ₅ feed stream.

[0003]

2. Description of the Prior Art Refinery mixed streams often contain a wide variety of olefinic compounds. This is especially true for products from catalytic cracking and pyrolysis processes. Examples of these olefin compounds include ethylene, acetylene, propylene, propadiene, methylacetylene, butenes, and butadiene. Many of these compounds are useful as feedstocks for obtaining various chemicals. Particularly important ethylene has been recovered. Furthermore, propylene and butenes are also important. However, olefins having two or more double bonds and acetylene-based compounds (having triple bonds) are poorly used, and many chemical processes (for example, polymerization) in which a compound having only one double bond is used. It is harmful to them.

Refinery streams are usually separated by fractional distillation, but such separations are not precise because they often contain compounds with boiling points that are fairly close together. For example, the C ₅ stream may include C ₄ components up to C ₈ components. These components are saturated compounds (alkanes)
, Unsaturated compounds (monoolefins), or polyunsaturated compounds (diolefins). These components may also be different isomers of individual compounds.

Hydrogenation is the reaction of carbon-carbon multiple bonds with hydrogen to saturate a compound. This reaction is
This reaction is well known in the art, and is usually carried out in the presence of a metal catalyst using excess hydrogen at an overpressure and a suitable temperature. Metals known to catalyze hydrogenation reactions include platinum, rhenium, cobalt, molybdenum, nickel, tungsten, and palladium. Commercially available catalysts are usually in the form of supporting oxides of these metals. This oxide is reduced to the active form by a reducing agent prior to use or by hydrogen in the feed during use. These metals also catalyze other reactions (most notably dehydrogenation at high temperatures). Furthermore, these metals are
If the residence time is increased, the reaction between the olefin compounds or the reaction between the olefin compound and another olefin compound may be promoted.

Selective hydrogenation of hydrocarbon compounds is also a well known reaction. "Selective hydrogenation of pyrolysis gasoline" in September with the American Chemical Society Journal of the oil sector in 1962 by me of Peterson et al., Describes the selective hydrogenation of C ₄ or more diolefins. Boit
iaux et al., "The Latest Hydrogenation Catalyst", Hydrocarbon
Carbon Processing , March 1985 ”, reviews various applications of hydrogenation catalysts, including selective hydrogenation, using bimetal hydrogenation catalysts.

Isomerization can occur using the same series of catalysts. In general, the relative reaction rates for the various compounds slow down in the order described below.

(1) Hydrogenation of diolefins (2) Isomerization of monoolefins (3) Isomerization of monoolefins Generally, in a stream containing diolefins,
It has been found that diolefins are hydrogenated before isomerization occurs.

Combined distillation column reactor (a combi
national distribution column
The use of a solid particulate catalyst in an n reactor as part of a distillation structure to effect various reactions is described in US Pat. No. 4,232,177, 4,307,254.
No.4,336,407,4,504,687
No. 4,918,243, and 4,978,8
No. 07 (etherification); No. 4,242,530 (dimerization); No. 4,982,022 (hydration); No. 4,447,668 (dissociation);
950,834 and 5,019,669 (aromatic alkylation); and the like. Further, U.S. Pat. Nos. 4,302,356 and 4,443,559 disclose catalytic structures useful as distillation structures.

The refinery C ₅ cut is useful as a feedstock for gasoline blends or as a feedstock for isoamylene to form ethers by reaction with lower alcohols. For oil refiners, the Air Purification Ordinance (Cl
ean Air Act) was recently passed,
Tert-amyl methyl ether (TAME) is becoming increasingly useful. Some of these requirements are: (1) a certain amount of "oxygenate (oxyg
enates) "[eg, methyl tert-butyl ether (MTBE), TAME, or ethanol]
(2) reducing the amount of olefins in gasoline; and (3) lowering the vapor pressure (volatility).

In a simple distillation "light naphtha" fraction containing all components from C _{5 to} C ₈ and above, T
It contains the C ₅ component in the feedstock to the AME unit. The mixture may contain 150-200 components, thus making product identification and separation difficult. Normally, for use in the TAME process, C
_{The 5} components and a small amount of C ₆ components are separated. However,
The introduction of third-olefin C ₆ -C _8, other useful ether product. Therefore, TAME is not separated from the heavier components, but either can be used directly as a raw material for octane blending.

Minor components (diolefins) in the feedstock
Some of the “gum” reacts slowly with oxygen during storage.
And other undesirable substances. These ingredients also react rapidly in the TAME process to form a yellow, off-flavor gum. Therefore,
It has been found desirable to remove these components, whether the "light naphtha" cut is used by itself only for gasoline blends or as a feed to the TAME process.

An advantage of the hydrogenation process of the present invention, which selectively hydrogenates diolefins, is that there is little saturation of monoolefins. A further feature of the process of the invention is that some of the monoolefins contained in the stream, or some of the monoolefins produced by the selective hydrogenation of diolefins, are isomerized to more desirable products. Is to be done.

[0014]

Briefly, the present invention provides a light naphtha fraction containing a mixture of hydrocarbons,
The process includes supplying a distillation column reactor containing a hydrogenation catalyst (which is one component of the distillation structure) with a hydrogen stream, and selectively hydrogenating the diolefin contained in the light naphtha. At the same time, lighter components, including unreacted hydrogen, are distilled and separated from the lightly naphtha product that has been hydrogenated to some extent as overhead. Simultaneous with selective hydrogenation and distillation, some of the C ₅ monoolefins are isomerized to a more desirable feed to obtain TAME. Substantially all of the diolefins are converted to monoolefins with little hydrogenation of the monoolefins. In one embodiment, where the feed is predominantly a C ₅ stream, the light naphtha product is withdrawn as bottoms. The overhead is passed to a condenser where all of the condensable material condenses and some of it refluxes to the top of the column.

In another embodiment, where the feed comprises a broader C _{5 to} C ₈ stream, the C ₅ component is separated from the C ₆₊ component in the lower section of the distillation column reactor. The C ₆₊ component is withdrawn as a bottoms liquid stream, the C ₅ component is boiled,
Proceed to the upper section of the distillation column reactor containing the catalytic distillation structure that selectively hydrogenates diolefins. The hydrogenated C ₅ component is taken off overhead with excess hydrogen, passed through a condenser in which all of the condensable material is condensed, and subsequently, for example in a reflux drum separator, the non-condensed material (mostly Hydrogen)). Part of the liquid from the separator is returned to the distillation column reactor as reflux and the rest is taken off as product. This product can be fed directly into the TAME unit. If desired, further inert distillation sections may be provided above the catalytic distillation structure.
section) is used to drive the C ₅ product side draw downwards and excess hydrogen to other light components such as air and water, which are detrimental in the downstream TAME unit. Can be distilled with.

Broadly speaking, the present invention is a method for selectively hydrogenating diolefins contained in light naphtha, comprising: (a) (1) a light olefin containing diolefins. Supplying a feed zone with a first stream containing naphtha and (2) a second stream containing hydrogen to a distillation column reactor; (b) (i) in the distillation reaction zone, wherein The first and second streams are contacted with a hydrogenation catalyst, which can act as a distillation structure, thereby reacting essentially all of the diolefins with the hydrogen to give pentenes in the reaction mixture. And (ii) forming other hydrogenation products, and (ii) operating the pressure of the distillation column reactor such that a portion of the reaction mixture is vaporized by the heat of reaction. Steps to be performed simultaneously in c) removing the liquid portion from step (b) (ii) from the distillation column reactor as a bottoms liquid; and (d) vapor from step (b) (ii) with unreacted hydrogen as described above. Withdrawing from the distillation column reactor as overhead.

Hydrogen is optionally supplied to maintain the reaction and reduce the oxide to keep it in the hydride state. The distillation column reactor is operated at a pressure such that the reaction mixture boils in the catalyst bed. By controlling the bottoms and / or overhead withdrawal rates, a "fross level" can be maintained throughout the catalyst bed. Such adjustments improve the effectiveness of the catalyst and thus require lower catalyst bed heights. Needless to say, the liquid is boiling and its physical state is effectively froth, and the density of the froth is higher than the normal density in a packed distillation column, but lower than the liquid without boiling vapor. ..

The process of the present invention employs an overhead pressure of 0 to 250 psig in the distillation column reactor and 100 to 300 ° F. in the distillation reaction zone.
It is preferred to operate at a temperature (preferably 130-270 ° F).

The C ₅ feed and hydrogen may be fed separately to the distillation column reactor, or they may be mixed and fed. In the case of mixed feed, below the catalyst layer,
Alternatively, it is supplied to the lower end of the catalyst layer. If fed separately, hydrogen is fed below the catalyst bed, and a C ₅ stream is fed below the catalyst bed around about the center of about 1/3 of the catalyst bed. The pressure selected is such that propylene and lighter components can be distilled off as overhead while retaining the dienes in the catalyst layer.

The advantages of using a distillation column reactor in the selective hydrogenation process of the present invention are better selectivity of diolefins to monoolefins, preservation of heat, and separation by distillation. This distillative separation allows removal of certain unwanted compounds (eg, heavy sulfur contaminants) from the feed prior to exposure to the catalyst. Distillation can further concentrate desired components in the catalyst zone. The diolefin contained in the C ₅ cut has a higher boiling point than the other compounds. It is thus possible to isomerize the monoolefins and remove them at the top of the column while concentrating the diolefins in the catalytic zone. The reactions of the important C ₅ components are as follows.

(1) Isoprene (2-methyl butadiene-1,3) + hydrogen → 2-methyl butene-1 and 2-methyl butene-2; (2) cis and trans-1,3-pentadiene ( (Cis and trans-piperylene) + hydrogen → pentene-1 and pentene-2; (3) 3-methylbutene-1 → 2-methylbutene-2 and 2-methylbutene-1; (4) 2-methyl -Butene-1-> 2-methyl butene-2; (5) 2-methyl butene-2-> 2-methyl butene-1; and (6) 1,3-butadiene-> butene-1 and butene-2 The two reactions remove unwanted components, while the third reaction favors the feed to the TAME reactor. 3-Methylbutene-1 does not react with methanol by a sulfonic acid catalyst to produce TAME, but two 2-methylbutenes react with methanol by a sulfonic acid catalyst to produce TAME.

The catalytic material used in the hydrogenation process must be in a form that will function as a distillation packing. Broadly speaking, the catalytic material is one component of the distillation system that acts as both a catalyst and a distillation packing (ie, packing for a distillation column that has both distillation and catalytic functions).

The reaction system can be described as being a heterogeneous system. This is because the catalyst exists as an independent substance. The catalyst comprises palladium oxide (preferably 0.1 to 1.0 wt%) supported on a suitable support (eg, alumina, carbon, or silica), preferably in a container as described herein. Alternatively, it can be used in the form of being housed in a conventional distillation packing shape (for example, Raschig ring, pole ring, or saddle).

Placing the supported catalyst in the pockets of the cross belt (supported in the distillation column reactor by twisting two open mesh braided stainless steel wires in a spiral) provides the required flow. Has been found to be possible, prevent catalyst loss, allow normal swelling of the catalyst (if swelling occurs), and prevent extrudate breakage due to mechanical friction. This new catalyst assembly is described in US Pat.
242,530 and 4,443,559, which are incorporated herein by reference.

The cloth can be any material that is unaffected by the hydrocarbon feed, product, or catalyst under the reaction conditions. Cotton and linen are useful, but glass fiber cloth and TEFLO are preferred.
It is N cross. A preferred catalyst system comprises a plurality of closed cross pockets arranged and supported in a distillation column reactor by closely connected wire mesh.

Another suitable container consists of a metal or plastic screen of suitable mesh size formed in a short cylinder, which screen is closed at each end holding the catalyst. The plurality of vessels containing the catalyst can be packed randomly or regularly in the bed in the distillation column reactor.
There may be more than one such layer, depending on the catalytic requirements of the process.

The particulate catalytic material may be a powder, small irregular chunks or fragments, or small beads. The morphology of the catalytic material in the vessel is not critical as long as it provides sufficient surface area to allow the appropriate reaction rate. The sizing of the catalyst particles should be done so that the catalyst is retained in the vessel.

A suitable catalyst for the process of the present invention is a 3-8 mesh Al ₂ O ₃ (alumina) sphere loaded with 0.34% by weight of Pd.
Commercially available from Lyst as G-68C. Typical physical and chemical properties of the catalyst reported by the manufacturer are as follows.

[0029] The catalyst is believed to be the palladium hydride produced during operation. The hydrogen feed rate to the reactor must be sufficient to keep the catalyst in its active form. This is because hydrogenation loses hydrogen from the catalyst. The hydrogen feed rate must be adjusted to hold the hydrogenation reaction and replace the hydrogen lost from the catalyst, but at a rate that causes flooding of the column [this is the "effect amount of hydrogen"].
"amount of hydrogen)"].
The molar ratio of hydrogen to diolefin in the feed to the fixed bed of the present invention is at least 1.0 to 1.0 (preferably 2.0 to 1.0).

The process of the present invention is carried out in a catalyst packed column containing a liquid phase and an ascending vapor phase. However, since the liquid is retained in the column by artificial "flooding", the liquid at this time has a density increase that exceeds that when it simply descends because the liquid is the normal internal reflux.

Referring to FIG. 1, there is shown a simplified schematic flow diagram of the preferred embodiment. A distillation column reactor 10 is shown that includes a charge of a suitable hydrogenation catalyst as part of a distillation structure 12 (such as the wire mesh assembly described above). The distillation column also has a standard distillation structure 14. Light naphtha is fed to the distillation column reactor 10 via the flow line 1 under the catalyst packing. Hydrogen is supplied as gas to the bottom of the catalyst packed bed via the flow line 2. Circulating the reboiler 40, flow line 13
The heat is applied to the bottom liquid via the flow line 4 by returning to the column via the flow line 4. When the reaction is initiated, the heat of reaction, which is an exothermic reaction, causes further vaporization of the mixture in layers. The vapor is withdrawn as overhead via flow line 3 and is sent to condenser 20 where substantially all of the condensable material is 100 ° F.
Is condensed to the temperature of. The overhead is then sent to a reflux drum 30 where condensed material is collected and separated from uncondensed material (eg unreacted hydrogen). A part of the condensed matter collected in the reflux drum is
It is returned to the distillation column reactor 10 via the flow line 6.
The distillation product taken off via line 9 is TAME
A suitable feed for the reactor. The non-condensed material is discharged from the reflux drum via the flow line 7, where hydrogen can be recycled to the reactor (not shown) for improved economy.

The bottom product, which is essentially free of C ₅ diolefins, is withdrawn via flow line 8 and can be sent for gasoline blending to obtain stable gasoline. The process is advantageous because the high exotherm of hydrogenation is absorbed by the vaporization of a portion of the liquid, thus temperature control is achieved by adjusting the system pressure. All excess hydrogen is withdrawn from the bottom product. In the case of the C ₅ component, the non-hydrogenated component is less volatile and thus tends to stay in the reactor for a longer period of time, promoting a more complete reaction.

Another embodiment of the invention is shown in FIG. 2, where light naphtha is fed to column 10 over catalytic distillation structure 12 via flow line 1 '. The other arrangements are the same as in FIG. FIG. 3 illustrates yet another embodiment in which the column 10 further includes a conventional distillation structure 216 on top of the catalytic distillation structure 12 to allow the C ₄ component and lighter material, hydrogen. , And other lower boiling components are separated from the C ₅ component which is withdrawn as a sidestream via flow line 209.

[0034]

EXAMPLES Example 1 Reboiler 340, condenser 320, and reflux system 33.
A 3 inch diameter, 30 foot tall steel tower 310 equipped with 0 and 306 was used as shown in FIG. Catalyst containing 0.34% by weight of palladium on 1/8 inch alumina spheres (encased in a pocket of a glass fiber belt and twisted using a stainless steel wire mesh) Distillation structure 312
Was filled over a central area of 15 feet. Up to 20
The column was purged with nitrogen at pressures up to psig. The light naphtha feed, which had been prefractionated to remove most of the C6 ₊ material, was fed via line 301 at a rate of 50 lbs / hr. When the bottoms liquid level is obtained and the liquid is at the desired level in the column, bottoms draining via line 308 is initiated, lines 304 and 31.
Reboiler circulation via 3 was started. Until steam becomes visible at the top of the column (as seen by a uniform temperature of 130 ° F throughout the column)
Heat was applied to the reboiler 340. 8 through line 302
At 10 SCFH, a hydrogen stream was started to feed the bottom of the column. Then, the pressure of the tower is adjusted to adjust the temperature of the bottom liquid to about 3
The temperature of the catalyst bed was maintained at 20 ° F and the temperature of the catalyst layer at about 260 ° F. Overhead pressure was maintained at about 200 psig. The overhead is withdrawn via line 303, partially condensed in condenser 320, all condensable material is collected in reflux drum 330, and line 3
Returned as reflux to the top of the column via 06. Material that did not condense was discharged from the reflux drum via line 307. The bottom liquid was taken out via a line 308.
The results obtained are shown in Table II. In Table II, the feed and bottoms analysis results are compared.

[0035] Example 2 During operation, the overhead pressure was adjusted to change the temperature of the catalyst layer. At lower temperatures the conversion of diolefins was less, but the main difference was
This is because the isomerization of 3-methyl butene-1 was greatly affected. Table III below compares the conversion of diolefin and 3-methylbutene-1 with operating temperature.

[0036]

[Brief description of drawings]

FIG. 1 is a simplified flow chart of one embodiment of the present invention.

FIG. 2 is a simplified flow chart of another embodiment of the present invention.

FIG. 3 is a simplified flowchart of yet another embodiment of the present invention.

FIG. 4 is a simplified flow chart of yet another embodiment of the present invention.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical indication location // C07B 61/00 300 (72) Inventor Lawrence Alfred Smith, Junia USA Texas 77401, Hughston, Pine Street 5009 (72) Inventor Dennis Hahn, USA Texas 77062, Hughston, Thunder Bay 16326 (72) Inventor Robert Phillip Argan Bright, USA Texas 77586, Seabrook, Devonport 814

Claims (15)

[Claims] 1. A first stream comprising (a) (1) a light naphtha containing diolefins, and (2).
Supplying a second stream containing hydrogen to a distillation column reactor to a feed zone; (b) (i) in the distillation reaction zone, said first and second streams acting as distillation structures A hydrogenation catalyst, which is capable of reacting essentially all of the diolefins with the hydrogen to form pentenes and other hydrogenation products in the reaction mixture, and (Ii) operating the pressure of the distillation column reactor such that the temperature in the distillation reaction zone is within a selected range and a portion of the reaction mixture is vaporized by the heat of reaction. A step carried out simultaneously in the reactor; (c) withdrawing the liquid portion from step (b) (ii) as bottom liquid from the distillation column reactor; and (d) from step (b) (ii). Steam part Step with hydrogen taken as an overhead from the distillation column reactor; including, a method of selectively hydrogenating the diolefins contained in the light naphtha. 2. The overhead is cooled to condense condensable material and the condensable material is separated from the unreacted hydrogen and returned as reflux to the top of the distillation column. the method of. 3. The vapor portion from step (b) contains substantially all of the boiling fraction of C ₅ or less, and the liquid portion from step (b) contains substantially all of the boiling fraction of C ₆ or more. Contains everything,
And the condensable substance comprises a C ₅ component.
The method described. 4. The method of claim 3, wherein a portion of the condensable material is removed as a distillation product. 5. The method of claim 2, wherein the separated hydrogen is recycled to the distillation column reactor. 6. The hydrogenation catalyst comprises 0.34% by weight of palladium oxide on ⅛ inch alumina spheres, and the hydrogenation catalyst forms a catalytic distillation structure. 2. The process of claim 1 wherein said distillation column is housed in a pocket of a cross belt made of twisted wire and placed in said distillation column reactor. 7. Hydrogen in the second stream is 1: 1 to 1: 1.
The method of claim 1 included in an amount to provide a hydrogen to diolefins molar ratio of 2: 1. 8. The method of claim 1, wherein the overhead pressure of the distillation column reactor is 0 to 250 psig. 9. The temperature in the distillation reaction zone is 100 to 100.
The method of claim 8 at 300 ° F. 10. The temperature in the distillation reaction zone is 100.
˜300 ° F., the pentenes include 3-methyl butene-1 and 2-methyl butene-2, and a portion of the 3-methyl butene-1 is 2-methyl butene-
The method according to claim 9, wherein the method is isomerized to 2. 11. The process of claim 1 wherein the distillation product containing the C ₅ component is withdrawn as a side stream below the top of the distillation column reactor. 12. (a) (1) 3-methyl butene-1,2-methyl butene-1,2-methyl butene-
2,2-methyl butadiene-1,3, cis-1,3-
Feeding a first stream containing pentadiene and light naphtha containing trans-1,3-pentadiene, and (2) a second stream containing hydrogen to a distillation column reactor to a feed zone. (B) (i) in the distillation reaction zone, contacting said first and second streams with a hydrogenation catalyst capable of acting as a distillation structure, whereby said 2-methyl butadiene, Reacting substantially all of the cis-1,3-pentadiene and trans-1,3-pentadiene with the hydrogen to form pentenes, and
-Isomerizing a portion of methylbutene-1 to form 2-methylbutene-2 in the reaction mixture,
And (ii) the overhead pressure of the distillation column reactor is about 200 psig so that the temperature of the reaction mixture in the distillation reaction zone is 250-270 ° F. and a portion of the reaction mixture is vaporized by the heat of reaction.
And (d) withdrawing the liquid portion from step (b) (ii) as a bottom liquid from the distillation column reactor; and (d) Selectively hydrogenating the diolefins contained in the light naphtha, including the step of withdrawing the vapor portion from step (b) (ii) with the unreacted hydrogen as overhead from the distillation column reactor, And a method for isomerizing mono-olefins contained in light naphtha. 13. The method of claim 12, wherein the overhead is cooled to condense condensable material and the condensable material is separated from the unreacted hydrogen and returned to the top of the distillation column as reflux. the method of. 14. The method of claim 13, wherein the separated hydrogen is recycled to the distillation column reactor. 15. A first stream containing (a) (1) light naphtha containing diolefins and (2) a second stream containing hydrogen to a distillation column reactor. (B) (i) In the distillation reaction zone, a cross-belt containing palladium oxide supported on alumina particles and twisted with a distillation wire to form a catalytic distillation structure. Contacting the first and second streams with a hydrogenation catalyst contained in a pocket, thereby reacting essentially all of the diolefins with the hydrogen,
Forming pentenes and other hydrogenation products in the reaction mixture, and (ii) the temperature in the distillation reaction zone is 230-270 ° F. and a portion of the reaction mixture is vaporized by the exotherm of the reaction. So that the overhead pressure of the distillation column reactor is 130-210 psig.
In the distillation column reactor at the same time; (c) removing a first portion of the liquid from step (b) (ii) as a bottoms liquid from the distillation column reactor. Step; (d) withdrawing the second portion of the liquid from step (b) (ii) as a side stream; (e) the vapor portion from step (b) (ii) together with unreacted hydrogen Removing from the tower reactor as overhead; (f) cooling the overhead to a temperature of 1
Condensing all of the compounds that condense at the overhead pressure of 30-210 psig; (g) separating the condensate from unreacted material in the overhead and a portion of the condensate into the distillation column reactor. Returning as a reflux; (h) removing the rest of the condensed material as a distillation product; and (i) recycling unreacted hydrogen contained in the non-condensed material to the distillation column reactor. And a method for selectively hydrogenating diolefins contained in light naphtha.