AU654757B2

AU654757B2 - Selective hydrogenation of C5 streams

Info

Publication number: AU654757B2
Application number: AU32803/93A
Authority: AU
Inventors: Robert P. Arganbright; Dennis Hearn; Edward M. Jones Jr; Lawrence A. Smith Jr.
Original assignee: Chemical Research and Licensing Co
Current assignee: Chemical Research and Licensing Co
Priority date: 1992-02-10
Filing date: 1993-02-04
Publication date: 1994-11-17
Anticipated expiration: 2013-02-04
Also published as: KR930017847A; MX9300698A; CA2089113C; KR100245018B1; CA2089113A1; AU3280393A; JPH05294851A; JP3224444B2; DE69315362T2; RU2120931C1; EP0556025A1; EP0556025B1; DE69315362D1; BR9300505A; MY116459A

Description

AUSTRALIA

Patents Act COMPLETE SPECIFICATION

(ORIGINAL)

654757 Class Int. Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority Related Art: Name of Applicant: Chemical Research Licensing Company Actual Inventor(s): Edward M. Jones, Jr.

Lawrence A. Smith, Jr.

Robert P. Arganbright Dennis Hearn Address for Service: PHILUPS ORMONDE FITZPATRICK Patent and Trade Mark Attorneys 367 Collins Street Melbourne 3000 AUSTRALIA r r Invention Title: SELECTIVE HYDROGENATION OF C5 STREAMS Our Ref 318117 POF Code: 64313/161121 The following statement is a full description of this invention, including the best method of performing it known to applicant(s): -1- 6006 CDT 1020B 1 SELECTIVE HYDROGENATION OF C 5

STREAM

2 BACKGROUND OF THE INVENTION 3 Related US Patent No. 5,087,780 discloses the 4 hydroisomerization of mixed C 4 streams and the hydrogenation of butadiene.

6 Field of the Invention 7 The present invention relates to the selective hydrogenation 8 of diolefins (dienes) contained in a refinery stream containing 9 predominantly C 5 's and more specifically olefinic C 5 More particularly the invention relates to a process for the selective 11 hydrogenation of the dienes utilizing a distillation column 12 reactor containing a hydrogenation catalyst which also acts as a :13 component in a distillation structure. Most specifically the 14 inven ion relates to the selective hydrogenation of a C 5 feed stream for the production of tertiary amyl methyl ether (TAME).

:16 Related Information 17 Mixed refinery streams often contain a broad spectrum of olefinic compounds. This is especially true of products from S".:19 either catalytic cracking or thermal cracking processes. These 20 olefinic compounds comprise ethylene, acetylene, propylene, .21 propadiene, methylacetylene, butenes, butadiene, etc. Many of 22 these compounds are valuable, especially as feed stocks for chemical products. Ethylene, especially is recovered.

24 Additionally, propylene and the butenes are valuable. However, the olefins having more than one double bond and the acetylenic \crt.pat\1020B.app 1 compounds (having a triple bond) have lesser uses and are 2 detrimental to many of the chemical process in which the single 3 double bond compounds are used, for example polymerization.

4 Refinery streams are usually separated by fractional distillation, and because they often contain compounds that are 6 very close in boiling points, such separations are not precise.

7 A C 5 stream, for instance, may contain C 4 's and up to C8's.

8 These components may be saturated (alkanes), unsaturated (mono- 9 olefins), or poly-unsaturated (diolefins). Additionally, the components may be any or all of the various isomers of the 11 individual compounds.

12 Hydrogenation is the reaction of hydrogen with a carbon- 13 carbon multiple bond to "saturate" the compound. This reaction .14 has long been known and is usually done at superatmospheric pressures and moderate temperatures using an excess of hydrogen 16 over a metal catalyst. Among the metals known to catalyze the 17 hydrogenation reaction are platinum, rhenium, cobalt, molybdenum, 18 nickel, tungsten and palladium. Generally, commercial forms of 19 catalyst use supported oxides of these metals. The oxide is reduced to the active form either prior to use with a reducing 21 agent or during use by the hydrogen in the feed. These metals also catalyze other reactions, most notably dehydrogenation at 23 elevated temperatures. Additionally they can promote the .24 reaction of olefinic compounds with themselves or other olefins to produce dimers or oligomers as residence time is 26 increased.

\crl.pat\1020B.app 1 Selective hydrogenation of hydrocarbon compounds has been 2 known for quite some time. Peterson, et al in "The Selective 3 Hydrogenation of Pyrolysis Gasoline" presented to the Petroleum 4 Division of the American Chemical Society in September of 1962, discusses the selective hydrogenation of C 4 and higher diolefins.

6 Boitiaux, et al in "Newest Hydrogenation Catalyst", Hydrocarbon 7 Processing, March 1985, presents an over view of various uses of 8 hydrogenation catalysts, including selective hydrogenation, 9 utilizing a proprietary bimetallic hydrogenation catalyst.

Isomerization can be achieved with the same family of 11 catalysts. Generally the relative rates of reaction for various 12 compounds are in the order of from faster to slower: 13 hydrogenation of diolefins 14 isomerization of the mono-olefins hydrogenation of the mono-olefins.

16 It has been shown generally that in a stream containing .17 diolefins, the diolefins will be hydrogenated before IS isomerization occurs.

19 The use of a solid particulate catalyst as part of a distillation structure in a combination distillation column 21 reactor for various reactions is described in U.S. Pat. No.s: (etherification) 4,232,177; 4,307,254; 4,336,407; 4,504,687; 23 4,918,243; and 4,978,807; (dimerization) 4,242,530; (hydration) S..:24 4,982,022; (dissociation) 4,447,668; and (aromatic alkylation) 4,950,834 and 5,019,669. Additionally U.S. Pat. No.s 4,302,356 26 and 4,443,559 disclose catalyst structures which are useful as \crl.pat\1020B.opp 1 distillation structures.

2 The C 5 refinery cut is valuable as a gasoline blending 3 stock or as source of isoamylene to form an ether by reaction 4 with lower alcohols. Tertiary amyl methyl ether (TAME) is rapidly becoming valuable to refiners as a result of the recently 6 passed Clean Air Act which sets some new limits on gasoline 7 composition. Some of these requirements are to include a 8 certain amount of "oxygenates", such as methyl tertiary butyl 9 ether (MTBE), TAME or ethanol, to reduce the amount of olefins in gasoline, and to reduce the vapor pressure 11 (volatility).

12 The C5's in the feed to a TAME unit are contained in a 13 single "light naphtha" cut which contains everything from C 5 's 14 through C8's and higher. This mixture can easily contain 150 to 15 200 components and thus identification and separation of the 16 products is difficult. Usually the C5's and a small part of the

C

6 gs are separated for use in the TAME process. However, the 18 incorporation of C 6 through C 8 tertiary olefins will allow the 19 production of other valuable ether products. For this reason the TAME is not separated from the heavier components, but all are 21 used directly as octane blending stocks.

Several of the minor components (diolefins) in the feed 23 will react slowly with oxygen during storage to produce "gum" and •*24 other undesirable materials. However, these components also react very rapidly in the TAME process to form a yellow, foul 26 smelling gummy material. Thus it is seen to be desirable to \crk .pat\1020B.app remove these components whether the "light naphtha" cut is to be used only for gasoline blending by itself or as feed to a TAME process.

It is an advantage of the present hydrogenation process which selectively hydrogenates diolefins that little if any saturation of the mono-olefins occurs. An additional feature of the process is that a portion of the mono-olefins contained within the stream or produced by the selective hydrogenation of the diolefins are isomerized to more desirable products.

SUMMARY OF THE INVENTION According to the present invention, there is provided a process for the selective hydrogenation of diolefins contained in a light naphtha having the steps of: feeding a first stream containing a light naphtha containing diolefins and a second stream containing hydrogen into a feed zone in a distillation column reactor; concurrently in said distillation column S 20 reactor contacting said first and second streams in a distillation reaction zone with a hydrogenation catalyst capable of acting as a distillation structure Sthereby reacting essentially all of said diolefins with 25 said hydrogen to form pentenes and other hydrogenated products in a reaction mixture, and (ii) operating the pressure of the distillation column reactor such that the temperature in said distillation reaction zone is in a selected range and 30 a portion of the mixture is vaporized by the exothermic heat of reaction; withdrawing the liquid portion from step (b) (ii) from said distillation column reactor as bottoms; and withdrawing the vaporous portion from step (b) (ii) along with any unreacted hydrogen from said distillation column reactor as overheads.

The present invention also provides a process for selective hydrogenation of diolefins and isomerization of mono-olefins contained within a light naphtha, having the SA 4a steps of: feeding a first stream containing a light naphtha and containing 3-methyl butene-l, 2-methyl butene-l, 2-methyl butene-2, 2-methyl butadiene-1,3, cis 1,3-pentadiene and trans 1,3-pentadiene and a second stream containing hydrogen into a feed zone in a distillation column reactor; concurrently in said distillation column reactor contacting said first and second streams in a distillation reaction zone with a hydrogenation catalyst acting as a distillation structure thereby reacting essentially all of said 2-methyl butadiene, cis 1,3-pentadiene and trans 1,3-pentadiene with said hydrogen to form pentenes and isomerizing a portion of said 3-methyl butene-l to form 2-methyl butene-2 in a reaction mixture, and (ii) controlling the overhead pressure of the distillation column reactor at a pressure of about 200 S 20 psig such that the temperature of the mixture within said distillation reaction zone is between 250-270 F and a :portion of the mixture is vaporized by the exothermic heat of reaction; withdrawing the liquid portion from step (b) 25 (ii) from said distillation column reactor as bottoms; and withdrawing the vaporous portion from step (b) (ii) along with any unreacted hydrogen from said distillation column reactor as overheads.

The present invention further provides a process for 30 the selective hydrogenation of diolefins contained in a light naphtha having the steps of: feeding a first stream containing a light naphtha containing diolefins and a second stream containing hydrogen into a feed zone in a distillation column reactor; concurrently in said distillation column reactor contacting said first and second streams in a distillation reaction zone with a hydrogenation S- 4b 1 g 17' catalyst including palladium oxide supported on alumina particles and said hydrogenation catalyst is contained in the pockets of a cloth belt which is twisted with distillation wire to form a catalytic distillation structure, thereby reacting essentially all of said diolefins with said hydrogen to form pentenes and other hydrogenated products in a reaction mixture, and (ii) controlling the overhead pressure of the distillation column reactor in the range of 130 to 210 psig such that the temperature in said distillation reaction zone is between 230 and 270°F and a portion of the mixture is vaporized by the exothermic heat of reaction; withdrawing a first portion of the liquid from step (ii) from said distillation column reactor as bottoms; withdrawing a second portion of the liquid from step as a side stream; withdrawing the vaporous portion from step (b) 20 (ii) along with any unreacted hydrogen from said distillation column reactor as overheads; cooling said overheads to condense all of the compounds that condense at that temperature and said overhead pressures of between 130 and 210 psig; separating said condensed material from any uncondensed material in said overheads and returning a portion of said condensed material to said distillation column reactor as reflux; withdrawing the remaining portion of said 30 condensed material as a distillate product; and recycling any unreacted hydrogen contained in said uncondensed material to said distillation column reactor.

Accordingly, there is provided a process including feeding a light 4c

'V

1 remove these components whether the "light naphtha" cut is toAe 2 used only for gasoline blending by itself or as feed a TAME 3 process.

4 It is an advantage of the present drogenation process which selectively hydrogenates dio fins that little if any 6 saturation of the mono-olefin occurs. An additional feature of 7 the process is that portion of the mono-olefins contained 8 within the strea or produced by the selective hydrogenation of 9 the diolef' s are isomerized to more desirable products.

SUMMARY OF THE INVENTION 1 Briefly, the present invention comprises feeding a light 12 naphtha cut containing a mixture of hydrocarbons along with a 13 hydrogen stream to a distillation column reactor containing a 14 hydrogenation catalyst which is a component of a distillation 15 structure and selectively hydrogenating the diolefins contained 16 in the light naphtha. Concurrently the lighter components, 17 including the unreacted hydrogen, are distilled and separated as 18 overheads from the partially hydrogenated light naphtha product.

19 Additionally and concurrently with the selective hydrogenation 20 and distillation, a portion of the C 5 mono-olefins are isomerized 21 to a more desirable feed for the TAME. Essentially all of the diolefins are converted to mono-olefins with very little 23 hydrogenation of the mono-olefins.

"24 In one embodiment where the feed is predominately a C stream the light naphtha product is withdrawn as bottoms. The 26 overheads are passed to a condenser in which all of the 1 condensibles are condensed and a portion refluxed to the top of 2 the column.

3 In a second embodiment where the feed comprises a broader 4 C 5 to Cg stream the C 5 's are separated from the C 6 components in the lower section of a distillation column reactor. The C 6 6 components are withdrawn as a bottoms stream while the C 5 's are 7 boiled up into the upper section of the distillation column 8 reactor which contains the catalytic distillation structure which 9 selectively hydrogenates the diolefins. The hydrogenated C 5 's are taken overheads along with the excess hydrogen and passed to 11 the condenser in which all of the condensibles are condensed and 12 subsequently separated from the uncondensibles (mostly 13 hydrogen), for example in a reflux drum separator. A portion of 14 the liquid from the separator is returned to the distillation column reactor as reflux and the remainder withdrawn as product 16 which may be directly charged to a TAME unit. If desired a 17 further inert distillation section may be utilized above the 18 catalytic distillation structure with a C 5 product side draw 19 below to fractionate out the excess hydrogen along with any other light components such as air, water, etc. which might be 21 troublesome in the downstream TAME unit.

Broadly the present invention is a process for the selective 23 hydrogenation of diolefins contained in a light naphtha i"24 comprising the steps of: feeding a first stream comprising a light naphtha 26 containing diolefins and a second stream containing hydrogen \cr.pat\1020.app 1 to a distillation column reactor into a feed zone; 2 concurrently in said distillation column reactor 3 contacting said first and second streams in a 4 distillation reaction zone with a hydrogenation catalyst capable of acting as a distillation structure, thereby reacting 6 essentially all of said diolefins with said hydrogen to form 7 pentenes and other hydrogenated products in a reaction mixture, 8 and 9 (ii) operating the pressure of the distillation column reactor such that a portion of the mixture is vaporized by the 11 exothermic heat of reaction; 12 withdrawing a portion of the liquid from step (ii) 13 from said distillation column reactor as bottoms; and 14 withdrawing the vapors from step (ii)along with any unreacted hydrogen from said distillation column reactor as 16 overheads.

17 Hydrogen is provided as necessary to support the reaction 18 and to reduce the oxide and maintain it in the hydride state.

19 The distillation column reactor is operated at a pressure such 20 that the reaction mixture is boiling in the bed of catalyst. A 21 "froth level" may maintained throughout the catalyst bed by 22 control of the bottoms and/or overheads withdrawal rate which 23 improves the effectiveness of the catalyst thereby decreasing the height of catalyst needed. As may be appreciated the liquid is boiling and the physical state is actually a froth having a 26 higher density than would be normal in a packed distillation \crl.pat\1020B .a p 1 column but less than the liquid without the boiling vapors.

2 The present process preferably operates at overhead 3 pressure of said distillation column reactor in the range between 4 0 and 250 psig and temperatures within said distillation reaction zone in the range of 100 to 300°F, preferably 130 to 6 270°F.

7 The C 5 feed and the hydrogen are preferably fed to the 8 distillation column rector separately or they may be mixed prior 9 to feeding. A mixed feed is fed below the catalyst bed or at the lower end of the bed. Hydrogen alone is fed below the catalyst 11 bed and the C 5 stream is fed below the bed to about the mid one- 12 third of the bed. The pressure selected is that which maintains 13 the dienes in the catalyst bed while allowing the propylene and 14 lighter to distill overhead.

BRIEF DESCRIPTION OF THE DRAWING 16 FIG. 1 is a simplified flow diagram of one embodiment of 17 the present invention.

18 FIG. 2 is a simplified flow diagram of a second embodiment 19 of the present invention.

FIG. 3 is a simplified flow diagram of a third embodiment of 21 the present invention.

e22 FIG. 4 is a simplified flow diagram of a fourth embodiment 23 of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT The advantages of utilizing a distillation column reactor in 26 the instant selective hydrogenation process lie in the better \crl .pat\102OB.app 1 selectivity of diolefin to olefin, conservation of heat and the 2 separation by distillation which can remove some undesirable 3 compound, e.g. heavy sulfur contaminants, from the feed prior to 4 exposure to the catalyst and the distillation can concentrate desired components in the catalyst zone. The diolefins contained 6 in the C 5 cut are higher boiling than the other compounds and 7 therefore can be concentrated in the catalyst zone while the 8 mono-olefins are isomerized and removed in the upper part of the 9 column. The reactions of the C 5 's of interest are: isoprene (2-methyl butadiene-1,3) hydrogen to 2- 11 methyl butene-l and 2-methyl butene-2; 12 13 cis- and trans 1,3-pentadienes (cis and trans 14 piperylenes) hydrogen to pentene-l and pentene-2; 3-methyl butene-1 to 2-methyl butene-2 and 2-methyl 16 butene-1; S 17 2-methyl butene-1 to 2-methyl butene-2; 18 2-methyl butene-2 to 2-methyl butene-l; and 19 1,3-butadiene to butene-1 and butene-2.

The first two reactions remove the undesirable components 21 while the third is advantageous for feed to a TAME reactor. The 22 3-methyl butene-1 does not react with methanol to produce TAME 23 over the sulfonic acid catalyst while the two 2-methyl butenes 24 do.

25 The catalytic material employed in the hydrogenation 26 process must be in the form to serve as distillation packing.

27 Broadly stated, the catalytic material is a component of a \crl .pat\102Q8.app 1 distillation system functioning as both a catalyst and 2 distillation packing, a packing for a distillation column 3 having both a distillation function and a catalytic function.

4 The reaction system can be described as heterogenous since the catalyst remains a distinct entity. The catalyst may be 6 employed as palladium oxide, preferably 0.1 to 1.0 weight 7 supported on an appropriate support medium such as alumina, 8 carbon or silica, preferably in containers as described herein or 9 as conventional distillation packing shapes as Raschig rings, Pall rings, saddles or the like.

11 It has been found that placing the supported catalyst into a 12 plurality of pockets in a cloth belt, which is supported in the 13 distillation column reactor by open mesh knitted stainless steel 14 wire by twisting the two together into a helix, allows the requisite flows, prevents loss of catalyst, allows for normal 16 swelling if any, of the catalyst and prevents breakage of the 17 extrudates through mechanical attrition. This novel catalyst 18 arrangement is described in detail in commonly owned US Patent 19 No. 4,242,530 and US Pat. No. 4,443,559 which are incorporated 20 herein.

21 The cloth may be of any material which is not attacked by "22 the hydrocarbon feeds or products or catalyst under the 23 conditions of the reaction. Cotton or linen may be useful, but fiber glass cloth or TEFLON cloth is preferred. A preferred catalyst system comprises a plurality of closed cloth pockets 26 arranged and supported in the distillation column reactor by wire \crl .pat\1020B.ap 1 mesh intimately associated therewith.

2 Another suitable container consists of metal or plastic 3 screen of suitable mesh size formed in a short cylinder, closed 4 at each end, in which the catalyst is retained. A plurality of these catalyst containing containers may be packed randomly or in 6 a regular fashion into a bed within the distillation column 7 reactor. There may be one or more of such beds, depending on the 8 catalyst requirements of the process.

9 The particulate catalyst material may be a powder, small irregular chunks or fragments, small beads and the like. The 11 particular form of the catalytic material in the containers is :12 not critical, so long as sufficient surface area is provided to 13 allow a reasonable reaction rate. The sizing of catalyst *14 particles should be such that the catalyst is retained within the containers.

16 A catalyst suitable for the present process is 0.34 wt% Pd on 3 to 8 mesh A1 2 0 3 (alumina) spheres, supplied by United 18 Catalysts Inc. designated as G-68C. Typical physical and .19 chemical properties of the catalyst as provided by the manufacturer are as follows: 21 TABLE I Designation G-68C 23 Form Sphere 24 Nominal size 5x8 mesh Pd. wt% 0.3 (0.27-0.33) 26 Support High purity alumina \cr.pat\10208.app 1 2 The catalyst is believed to be the hydride of palladium which is 3 produced during operation. The hydrogen rate to the reactor 4 must be sufficient to maintain the catalyst in the active form because hydrogen is lost from the catalyst by hydrogenation. The 6 hydrogen rate must be adjusted such that it is sufficient to 7 support the hydrogenation reaction and replace hydrogen lost from 8 the catalyst but kept below that which would cause flooding of 9 the column which is understood to be the "effectuating amount of hydrogen as that term is used herein. Generally the mole ratio 11 of hydrogen to diolefins in the feed to the fixed bed of the 12 present invention will be at least 1.0 to 1.0 preferably 2.0 to 13 :14 The present invention carries out the method in a catalyst packed column which can be appreciated ontain a vapor phase 16 ascending and some liquid phase as in any distillation. However ':17 since the liquid is held up within the column by artificial 18 "flooding", it will be appreciated that there is an increased density over that when the liquid is simply descending because of '20 what would be normal internal reflux.

21 Referring now to FIG. 1 there is shown a simplified flow 2 diagram in schematic of a preferred embodiment. There is shown 23 a distillation column reactor 10 containing a packing of suitable 24 hydrogenation catalyst as part of a distillation structure 12, as in the wire mesh arrangement described above, the column may 26 also have standard distillation structure 14. The light naphtha \crl.pat\1020B.app 1 is fed via line 1 to the distillation column reactor 10 below the 2 catalyst packing. The hydrogen is fed as a gas via flow line 2 3 at or near the bottom of the bed of catalyst packing. Heat is 4 added to the bottoms via flow line 4 by circulating through the reboiler 40 and back to the column via flow line 13. After the 6 reaction has started the heat of reaction, which is exothermic, 7 causes additional vaporization of the mixture in the bed. Vapors 8 are taken overhead through flow line 3 and passed to condenser 9 where substantially all of the condensible material is condensed to a temperature of 100*F. The overheads are then passed to 11 reflux drum 30 where the condensed material is collected and :12 separated from non condensibles, such as the unreacted hydrogen.

13 A portion of the condensed materials collected in the reflux drum S:14 are returned to the top of the distillation column reactor 10 via flow line 6. The distillate product, withdrawn through line 9, 16 is a suitable feed for a TAME reactor. The uncondensible :17 material is vented from the reflux drum via flow line 7 and for 18 economy the hydrogen can recycled to the reactor (not shown).

.19 Bottoms product containing essentially no C 5 diolefins is withdrawn via flow line 8 and may be sent to gasoline blending as stable gasoline. The process is advantageous because the high 22 heat of hydrogenation is absorbed by the vaporization of part of 23 the liquid, so temperature control is achieved by adjusting the 24 system pressure. All excess hydrogen is stripped from the bottoms product. In the case of C 5 the unhydrogenated 26 components are less volatile and tend to stay in the reactor for \crl.pat\1020B.app 1 a longer time assisting in more complete reaction.

2 In FIG. 2 there is shown a second embodiment of the 3 invention wherein the light naphtha is fed to the column 4 above the catalytic distillation structure 12 via flow line 1'.

Otherwise the arrangement is identical to FIG. 1. FIG. 3 6 illustrates a third embodiment wherein the column includes 7 additional conventional distillation structure 216 above the 8 catalytic distillation structure 12 to separate any C 4 and 9 lighter material, hydrogen, and other lower boiling components from the C 5 's which are withdrawn as side stream via flow line 11 209.

S12 EXAMPLE 1 13 A three inch diameter 30 foot tall steel column 310 with a :14 reboiler 340, condenser 320 and reflux system 330 and 306 is used as shown in FIG. 4. The middle 15 feet are packed with a 16 catalytic distillation structure 312 comprising 0.34 wt% S' :17 palladium on 1/8 inch alumina spherical catalyst which is 18 contained in the pockets of a fiber glass belt and twisted with 19 stainless steel wire mesh. The column is purged with nitrogen and pressure up to 20 psig. Light naphtha feed which has been prefractionated to remove most of the C 6 material is started to '.22 the column via line 301 at 50 Ibs/hr. When a bottom level is 23 obtained and the liquid is at the desired level in the column, 24 bottoms draw through line 308 is started and reboiler circulation began through line 304 and 313. Heat is added to the reboiler 26 340 until vapor is seen at the top of the column as evidenced by \crL.pat\1020.app 1 a uniform temperature of 130 0 F throughout the column. Hydrogen 2 flow is started to the bottom of the column at between 8 to 3 SCFH via line 302. The pressure on the column is then controlled 4 to maintain a bottoms temperature of about 320'F and a catalyst bed temperature of about 260°F. The overhead pressure was thus 6 maintained about 200 psig. The overheads are taken via line 303 7 and partially condensed in condenser 320 and all of the 8 condensibles collected in reflux drum 330 and returned to the top 9 of the column as reflux via line 306. Uncondensibles are vented from the drum via line 307. Liquid bottoms are withdrawn via 11 line 308. The results are shown in TABLE II below in which the :12 feed and bottoms analyses are compared.

i' 'crL.pat\1020B.app TABLE II Feed Bottoms Product Component, wt% Change Lights .0.073 0.000 -2100 Dimethyl ether 0.003 0.002 -36 isobutane 0.488 0.093 -81 methanol 0.058 0.000 -100 other C 4 's 4.573 3.304 -28 3-methyl butene-I 1.026 0.270 -74 isopentane 31.974 32.066 0 pentene-1 2.708 0.962 -64 2-methyl butene-l 6.496 4.012 -38 normal pentane 3.848 4.061 6 2-methyl butadiene-1,3 0.147 0.002 -99 trans pentene-2 6.995 9.066 Unknown 1 0.138 0.094 -32 cis pentene-2 3.886 3.723 -4 2-methyl butene-2 11.634 14.083 21 trans piperylene 0.142 0.002 -98 cis piperylene 0.095 0.003-9

C

6 25.603 28.198 Total 100.000 100.000 \crt .pat\10208.&p 1 Example 2 2 3 During the run the overhead pressure was adjusted to vary 4 the catalyst bed temperature. At lower temperatures the conversion of the diolef ins was lower, but the main difference 6 was that the isomerization of the 3-methyl butene-l was more 7 dramatically affected. Table III below compares the conversions 8 of the diolef ins and 3-methyl butene-l with the operating 9 temperature.

11 TABLE III 12 Conversion, Mole% 13 :14 Mid. OH Hrs isoprene t-Pin c-Pip 3-methyl--butene-l Temp Press on 16 OF psc STM :17 230 130 200 65 57 65 1.7 :-18 250 145 300 97 95 95 19 265 200 600 100 99 99 :20 \crt.pat\OZ0G.aFp

Claims

1. A process for the selective hydrogenation of diolefins contained in a light naphtha compricin \the steps of: feeding a first stream omprioing\a light naphtha containing diolefins and a second stream containing hydrogen vrt c ZOy're. &a distillation column reactor; nto t-£f a concurrently in said distillation column reactor contacting said first and second streams in a distillation reaction zone with a hydrogenation catalyst capable of acting as a distillation structure thereby reacting essentially all of said diolefins with said hydrogen to form S pentenes and other hydrogenated products in a reaction mixture, and (ii) operating the pressure of the distillation column S reactor such that the temperature in said distillation reaction zone is in a selected range and a portion of the mixture is S vaporized by the exothermic heat of reaction; withdrawing the liquid portion from step (ii) from said distillation column reactor as bottoms; and withdrawing the vaporous portion from step (b) S (ii)along with any unreacted hydrogen from said distillation column reactor as overheads.

2. The process according to claim 1 wherein said overheads are cooled to condense any condensible material and said condensible material is separated from said unreacted hydrogen and returned to the upper portion of said distillation column as .pat\10208.app reflux.

3. The process according to claim 2 wherein the vaporous portion from step contains substantially all of the C 5 and lighter boiling fraction and the liquid from step contains substantially all of the C 6 and heavier boiling fraction and said condensible material comprises C 5 's.

4. fThe process according to claim 2 or claim 3 wherein a portion of said condensible material is withdrawn as distillate product. The process according to any one of claims 2 to 4 wherein said separated hydrogen is recycled to said distillation column reactor.

6. The process according to any one of claims 1 to wherein said hydrogenation catalyst includes 0.34 wt% 20 palladium oxide supported on 1/8 inch alumina spheres and said hydrogenation catalyst is contained in the pockets of a cloth belt which is twisted with distillation wire to S. form a catalytic distillation structure and placed into said distillation column reactor.

7. The process according to any one of claims 1 to 6 wherein hydrogen is contained in said second stream in an amount to provide a mole ratio of hydrogen to said diolefins of from 1:1 to 2:1.

8. The process according to any one of claims 1 to 7 wherein the overhead pressure of said distillation column reactor is between 0 and 250 psig.

9. The process according to any one of claims 1 to 8 wherein the temperature within said distillation reaction zone is between 100 and 300 0 F. The process according to claim 9 wherein the etOb 19 temperature within said distillation reaction zone is between 100 and 300°F, said pentenes include 3-methyl butene-1 and 2-methyl butene-2, and a portion of said 3-methyl butene-1 is isomerized to 2-methyl butene-2 concurrently in said distillation reaction zone.

11. The process according to any one of claims 1 to wherein a distillate product containing C 5 's is with- drawn as a side stream below the top of said distillation column reactor.

12. A process for selective hydrogenation of diolefins and isomerization of mono-olefins contained within a light naphtha, having the steps of: feeding a first stream containing a light naphtha and containing 3-methyl butene-l, 2-methyl butene-l, 2-methyl butene-2, 2-methyl butadiene-1,3, cis 1,3-pentadiene and trans 1,3-pentadiene and a second stream containing hydrogen into a feed zone in a S 20 distillation column reactor; concurrently in said distillation column reactor contacting said first and second streams in a distillation reaction zone with a hydrogenation S 25 catalyst acting as a distillation structure thereby reacting essentially all of said 2-methyl butadiene, cis 1,3-pentadiene and trans 1,3-pentadiene with said hydrogen to form pentenes and isomerizing a portion of said 3-methyl butene-1 to form 2-methyl butene-2 in a reaction mixture, and (ii) controlling the overhead pressure of the distillation column reactor at a pressure of about 200 psig such that the temperature of the mixture within said distillation reaction zone is between 250-270 F and a portion of the mixture is vaporized by the exothermic heat of reaction; withdrawing the liquid portion from step (b) (ii) from said distillation column reactor as bottoms; and withdrawing the vaporous portion from step (b) S4d\ 20 (ii) along with any unreacted hydrogen from said distillation column reactor as overheads.

13. The process according to claim 12 wherein said overheads are cooled to condense any condensible material and said condensible material is separated from said unreacted hydrogen and returned to the upper portion of said distillation column as reflux.

14. The process according to claim 13 wherein said separated hydrogen is recycled to said distillation column reactor. A process for the selective hydrogenation of diolefins contained in a light naphtha having the steps of: feeding a first stream containing a light naphtha containing diolefins and a second stream containing hydrogen into a feed zone in a distillation column reactor; concurrently in said distillation column reactor contacting said first and second streams in a distillation reaction zone with a hydrogenation catalyst including palladium oxide supported on alumina particles and said hydrogenation catalyst is contained in the pockets of a cloth belt which is twisted with distillation wire to form a catalytic distillation structure, thereby reacting essentially 21 all of said diolefins with said hydrogen to form pentenes and other hydrogenated products in a reaction mixture, and (ii) controlling the overhead pressure of the distillation column reactor in the range of 130 to 210 psig such that the temperature in said distillation reaction zone is between 230 and 270'F and a portion of the mixture is vaporized by the exothermic heat of reaction; withdrawing a first portion of the liquid from step (b) (ii) from said distillation column reactor as bottoms; withdrawing a second portion of the liquid from step (b) as a side stream; withdrawing the vaporous portion from step (b) (ii)along with any unreacted hydrogen from said distillation column reactor as overheads; cooling said overheads to condense all of the compounds that condense at that temperature and said overhead pressures of between 130 and 210 psig; separating said condensed material from any uncondensed material in said overheads and returning a portion of said condensed material to said distillation column reactor as reflux; withdrawing the remaining portion of said condensed material as a distillate product; and recycling any unreacted hydrogen contained said uncondensed material to said distillation c n reactor. DATED: 3 February, 1993 PHILLIPS ORMONDE FITZPAT Attorneys for: recycling any unreacted hydrogen contained in said uncondensed material to said distillation column reactor.

16. A process for the selective hydrogenation of diolefins contained in a light naphtha, substantially as herein described with reference to any one of the embodiments of the accompanying drawings.

17. A process for the selective hydrogenation of diolefins contained in a light naphtha, substantially as herein described with reference to any one of the Examples. DATED: 13 September 1994 PHILLIPS ORMONDE FITZPATRICK Attorneys for: CHEMICAL RESEARCH LICENSING COMPANY S 23 ABSTRACT OF THE DISCLOSURE A process for the selective hydrogenation of diolefins contained in a refinery C 5 stream wherein the catalyst used is also a component in a distillation structure. Essentially no hydrogenation of the mono-olefins occurs. Additionally some of the mono-olefins may be isomerized to more valuable isomers of the mono-olefin. 0 i \crl.pat\102OB.app