US3758604A - Isomerization-fractionation process - Google Patents

Isomerization-fractionation process Download PDF

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Publication number
US3758604A
US3758604A US00234734A US3758604DA US3758604A US 3758604 A US3758604 A US 3758604A US 00234734 A US00234734 A US 00234734A US 3758604D A US3758604D A US 3758604DA US 3758604 A US3758604 A US 3758604A
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Prior art keywords
isomerization
process according
catalyst
butene
continuous process
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Expired - Lifetime
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US00234734A
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English (en)
Inventor
N Sprecher
J Cotter
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ExxonMobil Technology and Engineering Co
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Exxon Research and Engineering Co
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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C11/00—Aliphatic unsaturated hydrocarbons
    • C07C11/02—Alkenes
    • C07C11/08—Alkenes with four carbon atoms
    • C07C11/09—Isobutene
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C5/00—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms
    • C07C5/22—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms by isomerisation
    • C07C5/23—Rearrangement of carbon-to-carbon unsaturated bonds
    • C07C5/25—Migration of carbon-to-carbon double bonds
    • C07C5/2506—Catalytic processes
    • C07C5/2562—Catalytic processes with hydrides or organic compounds
    • C07C5/2581—Catalytic processes with hydrides or organic compounds containing complexes, e.g. acetyl-acetonates
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C7/00—Purification; Separation; Use of additives
    • C07C7/005—Processes comprising at least two steps in series

Definitions

  • the present invention relates to a continuous process of separating isobutylene from mixtures containing in addition butene-l.
  • This process comprises a limited number of isomerization steps and accompanying separation steps, each of the isomerization steps being conducted under such conditions and with such catalysts as to maximize the desired type of double bond isomerization and optimize separation of the desired product in a substantially pure form.
  • this invention contemplates a multistage isomerization-fractionation process where the isomerization steps are directed to isomerize hydrocarbons having boiling points near those of the desired product, to produce hydrocarbons having boiling points more removed from those of the desired product, hence facilitating the separation of the desired product from the hydrocarbon mixture.
  • the efficiency of the process depends very much on the quality of the isomerization catalyst, whichshould enable high conversion and high isomerization rate at low temperatures as well as-a long life-time. Even if such a catalyst is available, it is necessary to use the catalyst in a manner that will assure the most economic process which yields high purity isobutylene from various feeds and thus requires optimization regarding the number of isomerization and distillation steps.
  • -It is another object of the present invention to provide such a process wherein the isomerization steps may be conducted in either vapor or liquid phase operation at temperatures from about -50 C to about 200 C, at space velocities from about 0.4 to about 40 liquid volumes of olefin per volume of catalyst per hour, at pressures from about atmospheric toabout 250 psig.
  • this invention contemplates double bond isomerization reactions which are carried out at relatively low temperatures conditions, which are favourable to obtain a low butene-l level according to the thermodynamic equilibrium. Catalysts of high isomerization activity are generally applicable. Thus lowtemperature active isomerization catalysts are preferred which are active at temperatures below 200C,
  • the invention provides a continuous process for separating isobutylene from C,-mixtures containing butene-l insubstantial proportions, which process comprises the following steps:
  • the initial isomerization is carried-out in two steps, the first step under such-conditions that the butene-l level is substantially reduced and the second step under more favourable'conditions to reduce the butene-l level as far as possible, preferably below 5 or 4 percent from the butene-l content of the effluent' of the first reactor.
  • the catalysts employed in both steps need not be identical. It is possible to use in the first step a catalyst which is sufficiently active to lower the butene-l level to a value ,in the range of 5 15 percent of the original part of the isomerized content. With a'suitable catalyst this reaction may be conducted a wide temperature range from -50 C to +200 C. Conveniently, however, is a range from 0 C C; Preferably, however, the catalysts employed in both steps are identical and only the temperatures of both steps are different, higher in the first one.
  • the two-step isomerization process offers the advantage that one is less dependant on fluctuations in the catalyst and feed composition and heat of reaction is more easy removed.
  • the isomerizations can be carried out in one vessel with temperature control but it is preferred to carry them out in two separate vessels separated by a heat-exchanger.
  • the isomerization is exothermic and heat of reaction released will raise the temperature and affect the performance of the catalyst. Increasing temperature directionally limits the equilibrium butene-l conversion. Thus it is preferred to run the two stages substantially adiabatically with cooling between them.
  • the first stage will preferably be run in such a way that substantially 90 100 percent of the isomerization (compared with the thermodynamic equilibrium values) and correspondingly of the heat generation will occur.
  • the finishing operation will be conducted in the second stage where only a moderate temperature increase will be allowed, of no more than say C.
  • the two-stage initial isomerization provides an efficient way to reach the very high purity requirements which are at present demanded, that is the benefit of the invention will be especially obtained if butene-l levels of lower than 3 percent, down to 0.1 percent and even lower are desired.
  • the temperature in the first stage can be increased, if necessary, to. compensate for declining catalyst activity with time, provides a buffer zone to catch possible catalyst poisons and allows for flexibility in operation (spare first stage may be provided).
  • the isomerization of the top fraction is conveniently carried out at low temperatures with a low temperature active catalyst to ob-' tain optimal results.
  • the process is also applicable to feeds containing beside isobutylene and butene-l, isobutane and butadiene.
  • a separate fractionating step will be included after the initial isomerization and fractionation to remove the afore-mentioned components. Their presence during the initial isomerization and fractionation steps does not affect the efficiency of the process.
  • the composition of the feed, in particular, the ratio of isobutylem: to butene-l does not have an effect on the efficiency of the process. It is an advantage that in principle any feed with varying ratios of isobutylene to bu,- tene-i can be handled. For instance, refinery stream containing usually 50 wt of butene-l in combination with isobutylene which may vary in the same range can be treated according to the process of the inwere as follows:
  • the feed, a C blend, is introduced at 1 and pumped by means of pump 2 in the first isomerization reactor 3.
  • the reactor is filled with the isomerization catalyst (in this case a solid, heterogeneous catalyst) and operated at temperatures in the. range of -50 C to+200C but preferably in the range of 0 C C. This temperature as well as the throughput is adjusted to isomerize a substantial part of the butene-l, that is up to the equilibrium position at the given temperature, which is not the optimal one reachable with the lowtemperature active catalyst.
  • Heat exchanger 4 cools the effluent of reactor 3 to the desired low temperature for carrying out the second isomerization in reactor 5.
  • the isomerized stream is then introduced through pipes 6 and 7 into the fractionator 8.
  • the cis and trans butenes- 2 are removed in the bottom fraction at 9 and the top fraction 10 containing mainly isobutylene. and butene-l is cooled by cooler 11, condensed in condensor 12 and subjected to isomerization in the reactor 13.
  • Reactor 14 is a spare reactor which can be used if, for instance, the reactor 13 has operated a long time and the catalyst activity has decreased.
  • the effluent ofreactor 13 is partly recirculated through pipe 15 which is connected to pipe 7 to the fractionation tower 8.
  • the other part is fed through pipe 16 to fractionator 17 where isobutane is removed as the top-product at 18.
  • the heavier fraction containing isobutylene is fed by pipe 19 into fractionator 20, where 1 purified isobutylene is withdrawn at 21.
  • the heavy ends can be recirculated to fractionator 8 if desired (through pipe 22).
  • the catalyst consisted of. cobalt-lI-acetylacetonate, supported on Si0 and reduced by triisobutylaluminium, preferably in the presence of the olefins, as described in our copending Ser. No. application 54,162/70.
  • Another possible catalyst is sodium on alumina.
  • a pure butene-2 stream is available at 9, which is essentially free of isobutylene and butene-l'.
  • the isomerization conditions in the three reactors Iso-l Reactor 1 5215151 -2 Reactor Stage 1 Stage 2 Stage 3" Temperature ZO C KO C fi fi C- 45C 38C.
  • SpaceVelocity l7 VVH l7 VVH l3 VVH The fractionation temperature may be in the range of 40 C 150 C. and in this example was 65 C.
  • a continuous process for separating isobutylene from C mixtures containing butene-l comprising the following steps:

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Analytical Chemistry (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Water Supply & Treatment (AREA)
  • Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
US00234734A 1971-03-19 1972-03-15 Isomerization-fractionation process Expired - Lifetime US3758604A (en)

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GB730971 1971-03-19

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US (1) US3758604A (enrdf_load_stackoverflow)
DE (1) DE2212845A1 (enrdf_load_stackoverflow)
FR (1) FR2130387B1 (enrdf_load_stackoverflow)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2528033A1 (fr) * 1982-06-08 1983-12-09 Exxon Research Engineering Co Procede de traitement d'une charge d'isobutylene
EP0129900A3 (en) * 1983-06-25 1985-10-02 Basf Aktiengesellschaft Process for the recovery of 1-butene from mixtures of hydrocarbons containing 2-butenes
US4777322A (en) * 1984-07-28 1988-10-11 Basf Aktiengesellschaft Obtaining but-2-enes from C4 -hydrocarbon mixtures which contain but-1-ene and may or may not contain but-2-enes

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4104321A (en) * 1977-03-18 1978-08-01 Uop Inc. Process for the separation of olefins
CA1179291A (en) * 1981-10-30 1984-12-11 David T. Ahlberg Distillation apparatus
FR2757506B1 (fr) * 1996-12-23 1999-02-19 Inst Francais Du Petrole Procede de production d'isobutene de haute purete combinant une distillation reactive d'hydroisomerisation et une isomerisation squelettale
FR2757505B1 (fr) * 1996-12-23 1999-02-19 Inst Francais Du Petrole Procede de production d'isobutene de haute purete combinant une distillation reactive d'hydroisomerisation, une distillation et une isomerisation squelettale

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3235471A (en) * 1962-03-16 1966-02-15 Phillips Petroleum Co Purification of c4-c6 1-olefins by extractive distillation
US3265591A (en) * 1962-11-15 1966-08-09 Du Pont Separation of butadiene from butenes by distilling in the presence of an aqueous solution of silver salts
US3284535A (en) * 1963-05-10 1966-11-08 Exxon Research Engineering Co Production of 3-methyl-1-butene

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3235471A (en) * 1962-03-16 1966-02-15 Phillips Petroleum Co Purification of c4-c6 1-olefins by extractive distillation
US3265591A (en) * 1962-11-15 1966-08-09 Du Pont Separation of butadiene from butenes by distilling in the presence of an aqueous solution of silver salts
US3284535A (en) * 1963-05-10 1966-11-08 Exxon Research Engineering Co Production of 3-methyl-1-butene

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2528033A1 (fr) * 1982-06-08 1983-12-09 Exxon Research Engineering Co Procede de traitement d'une charge d'isobutylene
US4435609A (en) 1982-06-08 1984-03-06 Exxon Research & Engineering Co. Isomerization of butene-1 to butene-2 in isobutylene
EP0129900A3 (en) * 1983-06-25 1985-10-02 Basf Aktiengesellschaft Process for the recovery of 1-butene from mixtures of hydrocarbons containing 2-butenes
US4777322A (en) * 1984-07-28 1988-10-11 Basf Aktiengesellschaft Obtaining but-2-enes from C4 -hydrocarbon mixtures which contain but-1-ene and may or may not contain but-2-enes

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Publication number Publication date
DE2212845A1 (de) 1972-09-28
FR2130387B1 (enrdf_load_stackoverflow) 1975-04-25
FR2130387A1 (enrdf_load_stackoverflow) 1972-11-03

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