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US3449461A - Dehydrocyclization of paraffins - Google Patents

Dehydrocyclization of paraffins Download PDF

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Publication number
US3449461A
US3449461A US596456A US3449461DA US3449461A US 3449461 A US3449461 A US 3449461A US 596456 A US596456 A US 596456A US 3449461D A US3449461D A US 3449461DA US 3449461 A US3449461 A US 3449461A
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United States
Prior art keywords
catalyst
dehydrocyclization
sulfur
aromatics
platinum
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Expired - Lifetime
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US596456A
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English (en)
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John W Jenkins
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Shell USA Inc
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Shell Oil Co
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Classifications

    • 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
    • C07C5/32—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms by dehydrogenation with formation of free hydrogen
    • C07C5/373—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms by dehydrogenation with formation of free hydrogen with simultaneous isomerisation
    • C07C5/393—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms by dehydrogenation with formation of free hydrogen with simultaneous isomerisation with cyclisation to an aromatic six-membered ring, e.g. dehydrogenation of n-hexane to benzene
    • C07C5/41—Catalytic processes
    • C07C5/415—Catalytic processes with metals
    • C07C5/417—Catalytic processes with metals of the platinum group
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
    • C10G35/00—Reforming naphtha
    • C10G35/04—Catalytic reforming
    • C10G35/06—Catalytic reforming characterised by the catalyst used
    • C10G35/085—Catalytic reforming characterised by the catalyst used containing platinum group metals or compounds thereof

Definitions

  • This invention relates to a process for the dehydrocyclization of paraffins to aromatics.
  • Aromatics can be produced by a thermal treatment of light hydrocarbon gases at high temperatures according to the Fischer process. This process requires temperatures in the neighborhood of 1830 F. to 2370 F. and the use of a large number of expensive alloy reaction tubes of extremely small dimensions.
  • aromatic hydrocarbons may be synthesized by catalytic dehydrocyclization of open chain hydrocarbons.
  • Catalysis VI pp. 553542, edited by P. H. Emmett, Reinhold Publishing Co., New York, 1958.
  • This procedure allows aromatic hydrocarbons to be produced from relatively inexpensive and readily available hydrocarbons.
  • paraflins which, in view of their poor octane number, are least desirable for gasoline fuels may advanta geously be utilized to obtain aromatic hydrocarbons, which can be used as a high octane gasoline component, solvent, or starting material for the chemical and plastic industry.
  • dehydrocyclization catalysts are the oxide catalysts such as molybdena-alumina and chrorniaalumina, the latter catalyst generally being considered about the best catalyst.
  • oxide catalysts such as molybdena-alumina and chrorniaalumina
  • Doelp US 3,272,760
  • platinum chromia-alumina catalyst for dehydrocyclization.
  • Platinum catalysts have been known and used for years in the reforming of naphthenic fractions where aromatics are produced primarily by dehydrogenation of naphthenes.
  • extensive Work has been done on catalytic dehydrocyclization, the present processes are not entirely nltfid States Patent 0 Patented June 10, 1969 satisfactory for one reason or another and elforts have been continued to provide a new or improved process.
  • parafiins can be dehydrocyclized to aromatics by means of certain noble metal catalysts which are active, stable, and selective.
  • the parafiin to be converted is contacted under dehydrocyclization conditions with a sulfided Group VIII noble metal catalyst.
  • the dehydrogenation is effected in the presence of minor amounts of sulfur. This is surprising since noble metals such as platinum are considered to be very strong hydrogenation-dehydrogenation catalysts when in the reduced form and sulfur is known to "be a noble-metal poison.
  • the catalyst employed in the process of the invention comprises a minor amount, e.g., 0.01-5 w. of one or more Group VIII noble metals, i.e., platinum, palladium, rhodium, ruthenium, osmium and iridium.
  • Group VIII noble metals i.e., platinum, palladium, rhodium, ruthenium, osmium and iridium.
  • the preferred metals are iridium, palladium, and platinum, with platinum being particularly preferred.
  • other transition metals having dehydrogenation activity can be incorporated into the catalyst together with the noble metal.
  • the noble metal advantageously is supported on a suitable support such as activated carbon, refractory oxides and the like.
  • Porous refractory oxides such as silica, alumina, magnesia and the like, e.g., substantially nonacidic, are highly suitable. These carriers are widely available commercially and their preparation is well known. Should a refractory oxide tend to be acidic, the acidity can be reduced by any suitable means, e.g., by the addition of alkali metal.
  • Preferred carriers are alumina and silica, with silica being especially preferred.
  • the silica has a high surface area, Le, a surface area of about 300 to 750 sq. m./g.
  • any suitable method for adding the metal component to the support can be used.
  • Highly suitable catalysts can be prepared by impregnating the noble metal on the support, or ion-exchanging metal with an appropriate support such as a refractory oxide.
  • Any suitable metal compound preferably Water soluble, can be used.
  • suitable platinum compounds which can be used include chloroplatinic acid, platinous tetrammine compounds such as platinous tetrammine chloride, platinuous tetrammine nitrate or platinous tetrammine hydroxide.
  • the metal component can be provided by mixing an aqueous dispersion of a sulfide such as platinum sulfide with the refractory oxide.
  • the catalyst is usually dried and preferably is calcined in air. Calcination in air, of course, decomposes the metal salt and converts the metal to the oxide form.
  • a calcin-ation temperature in the range from about 600-900 F. is highly advantageous, although higher or lower temperatures can be used if desired.
  • the catalyst is sulfided to provide high activity, stability and selectivity. Sulfiding can be carried out in a known manner, such as by passing a mixture of hydrogen and hydrogen-sulfide over the catalyst at a temperature of about 500750 F. for a suitable length of time.
  • the catalyst can be sulfided by adding sulfur, hydrogen sulfide, or a decomposable sulfur compound such as mercaptans, disulfides, thiophene and the like to the feed.
  • Suitable concentrations of sulfur range from about 50 to 10,000 ppm. by weight sulfur based on the hydrocarbon. Preferably, rather high concentrations of sulfur,
  • the catalyst is ordinarily used in granular or pelleted form in fixed beds. Fairly uniform particles of about inch to about inch in size are satisfactory. If desired, the dehydrogenation may be effected with finely divided catalyst to provide a fluidized catalytic process.
  • Dehydrocyclization of paraffins to aromatics is carried out at a temperature in the range from about 750-1200 F. and preferably from about 9001100 F.
  • the pressure is relatively low and can be in the range from a subatmospheric pressure of about 2 p.s.i.a. to an elevated pressure of about 100 p.s.i.a. or more.
  • Preferred pressure are in the range from about 5 p.s.i.a. to 50 p.s.i.a. Low pressure tends to favor dehydrocyclization.
  • Weight hourly space velocity can vary over a considerable range, such as from about 0.1 to about and preferably from about 0.25 to 5.
  • the molar ratio of hydrogen to hydrocarbon can vary from as low as about 0.1:1 to as high as 5:1, although lower and higher ratios can be used if desired. Low hydrogen/oil ratios tend to favor dehydrocyclization.
  • Recycle hydrogen can be used.
  • paraffins which can be dehydrocyclized by the process of the invention comprise paraffins ranging from C C individually or in a mixture
  • the process of the invention is particularly suitable for lower paraffins, e.g., C C paraflins.
  • the lower parafiins are generally considered to be more difficult to dehydrocyclize than higher molecular weight paraffins.
  • the parafiin can also be in admixture with other hydrocarbons.
  • Suitable feeds can range from hexane, heptane, or other individual hydrocarbon fractions available in a petroleum refinery to mixed hydrocarbon fractions comprising 60% v., preferably 70% v. or more, paraffins.
  • Such fractions can be straight-run fractions, raflinates, e.g., C -C raffinates resulting from solvent extraction of aromatic hydrocarbons, molecular sieve or other processes for the separation of normal paraffins from non-normal paraflins and the like.
  • raflinates e.g., C -C raffinates resulting from solvent extraction of aromatic hydrocarbons, molecular sieve or other processes for the separation of normal paraffins from non-normal paraflins and the like.
  • the hydrocarbon feed can contain cyclic paraffins. Unlike chromia-alumina, catalyst stability is little affected by cyclopentane structures. Indeed, methylcyclopentane is a significant product of normal hexane dehydrocyclization in the present process. Also, in contrast, it may be noted that in conventional catalytic reforming of naphthas with a catalyst of platinum on halogenated alumina, there is some cyclization to five membered rings followed by dehydroisomerization to aromatics. However, since the ratio of ring opening of five-membered rings to ring closure to five-membered rings is governed by an equilibrium constant, any increase in cyclization rate automatically increases ring opening rate. The net result, then, with practical reforming feeds containing methylcyclopentane is that five-membered rings are usually destroyed faster than they are produced.
  • aromatic hydrocarbons produced in the dehydrocyclization reaction comprise at least about 15% by weight and usually at least about 25% by Weight of the liquid hydrocarbon product.
  • the aromatics can be recovered by any suitable separation process, e.g., extraction by means of an aromatic selective solvent.
  • EXAMPLE I A catalyst comprising 2% w. platinum impregnated on silica gel (Davison grade was tested with and without sulfur for the dehydrocyclization of n-dodecane. For the test with sulfur, the catalyst was presulfided by passing hydrogen and n-dodecane with added dimethyl disulfide over the catalyst While slowly heating the catalyst to operating temperature, and conducting the conversion with 1360 p.p.m. w. sulfur as dimethyl disulfide added to the feed. Operation was conducted at 860 F., 15 p.s.i.g., 2 WHSV, and 3 H /oil mol ratio. Results are given below for an interval between the second and third hour of the process period.
  • Various noble metal catalysts were prepared by impregnating silica gel (Davison grade 950) with an aqueous solution of an appropriate salt of the particular metal.
  • the catalystmetal salt solution mixture was dried at 250 F. with frequent agitation for at least 5 hours and further dried at 700 F. for 1 hour.
  • Each catalyst was sulfided with n-hexane containing 1000 p.p.m. S as dimethylsulfide at 700 F. for 2 hours.
  • the sulfided catalyst was tested for dehydrocyclization of n-hexane at 20 p.s.i.g. pressure, 1 WHSV, 1 H /oil molar ratio, with 1000 p.p.m. w. sulfur as dimethyl disulfide added to the feed.
  • Conversion of n-hexane to benzene represents the most difficult dehydrocyclization case and thus provides a good test of catalyst activity. Results are given below at a catalyst age of 25 hours.
  • Aromatics Other 0,; Aromatics 6. 2 Total Aromatics 9. 2 31. 5 44. 0 44. 1 22.0
  • EXAMPLE V This example demonstrates the stability of the catalyst.
  • a catalyst of 1% w. platinum impregnated on silica (Davison grade 950) was presulfided and tested for the dehydrocyclization of hexane with dimethyl disulfide added to provide 1000 p.p.m. by weight sulfur..
  • Reaction conditions were 20 p.s.i.g., 1 WHSV, 1 H /oil mol ratio, and temperature adjusted as necessary to provide a benzene yield of 32% w., basis feed.
  • Temperature increase was substantially linear throughout the 100 hour test period from 978% F. to 1008 R, an activity decline rate of 0.3 F. per hour.
  • catalyst decline rate was substantially constant at slightly over 1 F/ hour up to about hours (at which time the temperature demand was 951 F.) and began to accelerate thereafter.
  • the catalyst was subjected to a simple carbon burn-off with dilute air and tested again without sulfur.
  • the regenerated catalyst was very unstable, temperature demand increasing very rapidly from about 900 F. at the end of the two hours to 1000 F. at the end of twenty-two hours.
  • a fresh portion of the catalyst (presulfided at 700 F. with n-hexane containing 1000 p.p.m. S as dimethyl disulfide) was tested under similar conditions but with dimethyl disulfide added to the feed to provide 1000 p.p.m. by weight sulfur.
  • the catalyst was quite stable, as indicated by a gradually decreasing temperature demand in the period from 10 hours (975 F.) to 84 hours (987 F.).
  • the catalyst was subjected to a simple carbon burn identical to that for the unsulfided catalyst, and was tested again with normal hexane containing 1000 p.p.m. sulfur. Again good stability was demonstrated, the temperature demand curve being substantially the same as in the first cycle but at a 35 F. higher level.
  • the sulfur is not only beneficial to catalyst stability but is also beneficial to regenerability of the catalyst.
  • a process for dehydrocyclization of a parafiin having from 6 through 20 carbon atoms which comprises contacting said paraffin at a temperature of about 750 F. to 1200 F. with a sulfided Group VIII noble metal catalyst, the catalyst being in the sulfided state prior to contact with the paraffin.
  • the catalyst comprises from about 0.01 to 5% by weight noble metal on a substantially non-acidic porous refractory oxide.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Engineering & Computer Science (AREA)
  • General Chemical & Material Sciences (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
  • Production Of Liquid Hydrocarbon Mixture For Refining Petroleum (AREA)
  • Catalysts (AREA)
  • Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)
US596456A 1966-11-23 1966-11-23 Dehydrocyclization of paraffins Expired - Lifetime US3449461A (en)

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US59645666A 1966-11-23 1966-11-23

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US (1) US3449461A (de)
BE (1) BE706811A (de)
DE (1) DE1618982C3 (de)
GB (1) GB1143147A (de)
NL (1) NL6715757A (de)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4304658A (en) * 1979-12-13 1981-12-08 Texaco Inc. Dehydrocyclization to aromatic hydrocarbons over rhodium catalyst
US4320240A (en) * 1979-12-13 1982-03-16 Texaco Inc. Steam dehydrocyclization of paraffinic hydrocarbons in the presence of catalyst containing Group VIII metal and an activating amount of a Group I B metal
US4644089A (en) * 1986-07-10 1987-02-17 Phillips Petroleum Company Catalytic reforming of hydrocarbons
US6653518B2 (en) 2001-06-15 2003-11-25 Exxonmobil Chemical Patents Inc Reforming process for manufacture of para-xylene
US20090326287A1 (en) * 2006-07-03 2009-12-31 Basf Se Method for producing o-xylene
US9091433B2 (en) 2009-05-20 2015-07-28 Basf Se Monolith catalyst and use thereof

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2317683A (en) * 1941-02-27 1943-04-27 Shell Dev Cyclization of hydrocarbons
US2378209A (en) * 1942-11-17 1945-06-12 Shell Dev Process for the production of aromatic hydrocarbons
GB1024326A (en) * 1961-09-25 1966-03-30 Engelhard Ind Inc Improvements in or relating to the preparation of aromatic hydrocarbons

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2317683A (en) * 1941-02-27 1943-04-27 Shell Dev Cyclization of hydrocarbons
US2378209A (en) * 1942-11-17 1945-06-12 Shell Dev Process for the production of aromatic hydrocarbons
GB1024326A (en) * 1961-09-25 1966-03-30 Engelhard Ind Inc Improvements in or relating to the preparation of aromatic hydrocarbons

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4304658A (en) * 1979-12-13 1981-12-08 Texaco Inc. Dehydrocyclization to aromatic hydrocarbons over rhodium catalyst
US4320240A (en) * 1979-12-13 1982-03-16 Texaco Inc. Steam dehydrocyclization of paraffinic hydrocarbons in the presence of catalyst containing Group VIII metal and an activating amount of a Group I B metal
US4644089A (en) * 1986-07-10 1987-02-17 Phillips Petroleum Company Catalytic reforming of hydrocarbons
US6653518B2 (en) 2001-06-15 2003-11-25 Exxonmobil Chemical Patents Inc Reforming process for manufacture of para-xylene
US20090326287A1 (en) * 2006-07-03 2009-12-31 Basf Se Method for producing o-xylene
US9091433B2 (en) 2009-05-20 2015-07-28 Basf Se Monolith catalyst and use thereof

Also Published As

Publication number Publication date
GB1143147A (en) 1969-02-19
BE706811A (de) 1968-05-21
NL6715757A (de) 1968-05-24
DE1618982C3 (de) 1978-07-20
DE1618982B2 (de) 1977-11-24
DE1618982A1 (de) 1971-01-21

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