CA1196027A - Method of dehydrocyclizing alkanes - Google Patents

Method of dehydrocyclizing alkanes

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Publication number
CA1196027A
CA1196027A CA000420636A CA420636A CA1196027A CA 1196027 A CA1196027 A CA 1196027A CA 000420636 A CA000420636 A CA 000420636A CA 420636 A CA420636 A CA 420636A CA 1196027 A CA1196027 A CA 1196027A
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Prior art keywords
zeolite
method
catalyst
large
barium
Prior art date
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CA000420636A
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French (fr)
Inventor
Waldeen C. Buss
Thomas R. Hughes
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Chevron Research and Technology Co
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Chevron Research and Technology Co
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Priority to US06/344,572 priority Critical patent/US4435283A/en
Priority to US344,572 priority
Priority to US06/393,160 priority patent/US4631123A/en
Priority to US393,160 priority
Priority to US42054082A priority
Priority to US420,540 priority
Application filed by Chevron Research and Technology Co filed Critical Chevron Research and Technology Co
Application granted granted Critical
Publication of CA1196027A publication Critical patent/CA1196027A/en
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Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01JCHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J29/00Catalysts comprising molecular sieves
    • B01J29/04Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
    • B01J29/06Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
    • B01J29/064Crystalline aluminosilicate zeolites; Isomorphous compounds thereof containing iron group metals, noble metals or copper
    • B01J29/068Noble metals
    • CCHEMISTRY; METALLURGY
    • C10PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10GCRACKING 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
    • C10G35/00Reforming naphtha
    • C10G35/04Catalytic reforming
    • C10G35/06Catalytic reforming characterised by the catalyst used
    • C10G35/095Catalytic reforming characterised by the catalyst used containing crystalline alumino-silicates, e.g. molecular sieves

Abstract

ABSTRACT OF THE DISCLOSURE

A method of dehydrocyclizing alkanes is disclosed wherein the alkanes are contacted with a catalyst containing a large-pore zeolite, a Group VIII metal, and an alkaline earth metal.

Description

~19t~Z/j~

A METHOD OF DEHYDROCYCI,IZING ALKANES
BACKGROUND OF T}l _ NVENTION
The invention relates to a new catalyst and a new method of dehydrocyclizing acrylics more particularly dehydrocyclizing alkanes containing at least 6 carbon atoms to form the corresponding aromatic hydrocarbons.
Catalytic reforming is well known in the petroleum industry and reEers to the treatment of naphtha fractions to improve the octane rating. The more important hydrocarbon reactions occurring d~lring reforming operation include dehydrogenation of cyclohe~anes to aromatics, dehydro-isomeriæation of alkylcyclopentanes to aromatics, and dehydrocyclization of parafEins to aromatics. Hydrocracking reactions which produce high yields of light gaseous hydrocarbons, e.g., methane, ethane, propane and butane, are to be particularly minimized during reforming as this decreases the yield of gasoline boiling products.
Dehydrocyclization is one of the main reactions in the reforming process. The conventional methods of performing these dehydro-cyclization reactions are based on the use of catalysts comprising a noble metal on a carrier. Known catalysts oE this kind are based on alumina ; ~ 20 carrying 0.2% to 0.8% by weight of platinum and preferably a second auxiliary metal.
The possibility of using carriers other than alumina has also been studied and it was proposed to use certain molecular sieves such as X
and Y zeolites, which appeared suitable provided that the reactant and product molecules were sufficiently small to pass through the pores of the zeolite. However, catalysts based upon these molecular sieves have not been commercially successful.
ln the conventional method of carrying out the aforementioned dehydrocyclization, paraffins to be converted are passed over the catalyst, in the presence of hydrogen, at temperatures of the order of 500C and pressures of from 5 to 30 bars. Part of the paraffins are ~,~

:~9~0~7 converted into aromatic hydrocarbons, and the reaction is accompanied by isomeriæation and cracking reactions which also convert the paraEfins into isoparaffins and lighter hydrocarbons.
The rate of conversion of the hydrocarbons into aromatic hydrocarbons varies with the reaction conditions and the nature of the catalyst.
The catalysts hitherto usecl have given moderately satisfactory results w:lth heavy paraffins, but less satisfactory results wLth C6-C8 paraffins, particularly C6 paraffins. Catalysts based on a type 1 zeolite are more selective with regard to the dehydrocyclization reaction; can be used to improve the rate of conversion to aromatic hydrocarbons without requiring higher temperatures, which usually have a considerable adverse effect on the stability of the catalyst; and produce excellent results with C6-C8 paraffins. However, run length and regenerability are problems and satisEactory regeneration procedures are not known~
In one method of dehydrocyclizing aliphatic hydrocarbons, hydrocarbons are contacted in the presence of hydrogen with a catalyst consisting essentially of a type L zeolite having exchangeable cations of which at least 90% are alkali metal ions selected from the group consisting of ions of sodium, lithium, potassium, rubidium and cesium and containing at least one metal selected from the group which consists of metals of Group VIII of the Periodic Table of Elements, tin and germanium, said metal or metals includi~g at least one metal from Group VIII of said Periodic Table having a dehydrogenating effect, so as to convert at least part of the feedstock into aromatic hydrocarbons.
A particularly advantageous embodiment of this method is a platinum/alkali metal/type L ~eolite catalyst because of its excellent activity and selectivity for converting hexanes and heptanes to aromatics, but run length remains a problem.

~3~ '7 SUMM~RY OF THE INVENT:[ON
__ _ _ The present invention overcomes the deficiencies of the prior art by using a catalyst comprising a large-pore zeolite, an alkaline earth metal and a Group VIII metal to reform hydrocarbons at an extremely high selectivity for converting alkanes to aromatics. The hydrocarbons are contacted with a catalyst comprising a ]arge-pore æeolite, at least one Group VIII metal(preferably platinum), and an alkaline earth metal selected from the group consisting oE barium, strontium and calcium (preferably varium). In one aspect of the present invention, the process conditions are afljusted so that the selectivity for n-hexane dehydro-cycllzation is greater than 60%. In another aspect, the Selectivity Index of the catalyst is greater than 60%. The catalyst gives satisfactory run length.
Preferably, the large pore zeolite is a type L zeolite which contains from 0.1% to 5% by weight platinum and 0.1% to 35% by weight barium. The hydrocarbons are contacted with the barium-exchanged type zeolite at a temperature of from 400C to 500C (preferably 430C to 550C); an LHSV of from 0.3 to 5; a pressure of from 1 atmosphere to 500 psig ~preferably from 50 to 300 psig); and an H2/HC ratio of from 1:1 to 10:1 (preferably from 2:1 to 6:1).
DF,SCRIPTION OF THE PREFERRED EMBODIMENTS
In its broadest aspect, the present invention involves the use of a catalyst comprising a large-pore zeolite, an alkaline earth metal and a Group VIII metal in the reforming of hydrocarbons, in particular, the dehydrocyclization of alkanes, at an extremely high selectivity for converting hexanes to aromatics.
The term "selectivity" as used in the present invention is defined as the percentage of moles of paraffin converted to aromatics relative to moles converted to aromatics and cracked products, 100 x moles of paraffins i.e., Selectivity = converted to arom tics _ _ moles of paraffins converted to aromatics and cracked products i' .

:~~

Isome-rization reactions and alkylcyclopentane formation are not considered in determining selectivity.
The term "selectivity for n-hexane" as used in the present invention is defined as the percentage of moles of n-hexane converted to aromatics relative to moles converted to aromatics and cracked products.
The selectivity for converting paraffins to aromatics is a measure of the efficiency oE the process in converting paraEfins to the desired and valuable products: aromatics and hydrogen, as opposed to the less desirable productsof hydrocracking.
An inherent characteristic of any dehydrocyclization catalyst is its ~electivity Index. The Selectivity Index is defined as the "selectivity for n~hexane" using n-hexane as feed and operating at 490C, 100 psig, 3 LElSV
and 3 H2/HC after 20 hours.
Highly selective catalysts produce more hydrogen than less selective catalysts because hydrogen is produced when paraffins are converted to aromatics and hydrogen is consumed when paraffins are converted to cracked products. Increasing the selectivity of the process increases the amount of hydrogen produced (more aromatization) and decreases the amount of hydrogen consumed (less cracking).
Another advantage of using highly selective catalysts is that the hydrogen produced by highly selective catalysts is purer than that produced by less selective catalysts. This higher purity results because more hydrogen is produced, while less low boiling hydrocarbons (cracked products) are produced. The purity of hydrogen produced in reforming is critical if, as is usually the case in an integrated refinery, the hydrogen produced is utilized in processes such as hydrotreating and hydrocracking, which require at least certain minimum partial pressures of hydrogen. If the purity becomes too low, the hydrogen can no longer be used for this purpose and must be used in a less valuable way, for example as fuel gas.

',~

'7 In the method according to the invention, the feed hydrocarbons preferab:ly comprise nonaromatic hydrocarbons containing at least 6 carbon atoms. Preferably, the feedstock is substantially free of sulfur, nitrogen, metals and other known poisons for reforming catalysts.
The dehydrocyclization is carried out in the presence of hydrogen at a pressure adjusted so as to favor the reaction thermodynamically and limit undesirable hydrocracking reactions by kinetic means. The pressures used preferably vary from 1 atmosphere to 500 psig, more preferably from 50 to 300 psig, the molar ratio of hydrogen to hydrocarbons preferably being from 1:1 to 10:1, more preferably from 2:1 to 6:1.
In the temperature range of from ~l00C to 600C, the dehydrocyclization reaction occurs with acceptable speed and selectivity.
If the operating temperature is below 400C, the reaction speed is insufficient and consequently the yield is too low for industrial purposes. Also, the dehydrocyclization equilibria is unfavourable at low temperatures. When the operating temperature is above 600C, interfering secondary reactions such as hydrocracking and coking occur, and sub-stantially reduce the yield and increase the catalyst deactivation rate.
It is not advisable, therefore, to exceed the temperature of 600C.
The preferred temperature range (~30C to 550C) of dehydrocyclization is that in which the process is optimum with regard to activity, selectivity and the stability of the catalyst.
The liquid hourly space velocity of the hydrocarbons is preferably between 0.3 and 10.
The catalyst according to the invention is a large-pore zeolite charged with one or more dehydrogenating constituents. The term "large-pore zeolite" is defined as a zeolite having an effective pore diameter of 6 to lS Angstroms.
Among the large-pored crystalline zeolites which have been found to be useful in the practice of the ,L, ' :,

2'~' --6~

present lnventlon, type L zeolite and syn-thetic zeolites having the faujaslte structure such as zeolite X and zeolite Y
are the most important and have apparent pore sizes on the order of 7 to 9 Angstroms.
A con:~position o:f type L zeolite, expressed in terms of mole ratios of oxides, may be represen ted as follows (0.9-1.3)M2/nO:A12O3(5.2 6.9)SiO2:y 2 wherein M designates a cation, n represents the valence of M, and y may be any value from 0 to about 9. Zeoli te L, its X-ray diffraction pattern, its properties, and method for its preparation are described in detail in Uni-ted States Pa-tent No. 3,216,789. United States Patent No. 3,216,789 descrihes the preferred zeolite of the present invention. The real formula may vary without changing the crystalline struc-ture;
for example, the mole ratio of silicon to aluminum (Si/Al) may vary from 1.0 to 3.5.
The chemical formula for zeolite Y expressed in terms of mole ratios of oxides may be written as:
(0.7-l.l)Na2O:A12O3:xsiO2:YH2O
wherein x is a value greater than 3 up to about 6 and y may be a value up to about 9. Zeolite Y has a characteristic X-ray powder diffraction pattern which may be employed with the above formula for identification. Zeolite Y is described in more detail in United States Patent 21O. 3,130,007. United States Patent No. 3,130,007 describes a l~eolite useful in -the present invention.
Zeolite X is a synthetic crystalline zeolitic molecular sieve which may be represented by the formula:
(0.7-l.l)M2/nO.A12O3:(2.0-3)SiO2:y 2 it3~

wherein M represents a metal, par-ticularly alkali and alkaline earth metals, n is the valence of M, and y may have any value up to about 8 depending on the identity of M and the degree of hydration of the crystalline zeolite. Zeolite Y~, its X-ray diffraction pattern, its properties, and method ~or its preparation are described in detail in United States Patent No. ~,882,244. United States Patent No. 2,~82,2~ describes a zeolite useEu:L in the present invention.
The preferred catalyst according to the invention is a type L zeolite charged with one or more dehydrogenating constituents.
An essential element of the present inven-tion is the presence of an alkaline earth metal in the large-pore zeolite.
That alkaline earth metal must be either barium, strontium or calcium, preferably barium. The alkaline earth metal can be incorporated into the zeolite by synthesis, impregnation or ion exchange. Barium is preferred to the other alkaline ear-ths because it results in a somewhat less acidic catalyst. Strong acidity is undesirable in the catalyst because it promotes cracking, resulting in lower selectivity.
In one embodiment, at least part of the alkali meta]
is exchanged with barium, using techniques known for ion exchange of zeolites. This involves contacting the zeoli-te with a solution containing excess Ba ions. The barium should constitute from 0.1% to 35% of the weight of the zeolite.
The dehydrocyclization catalysts according to the invention are charged with one or more Group VIII metals, e.g., nickel, ruthenium/ rhodium, palladium, iridium or pla-tinum.

. -7a-The preferred Group VIII metals are iridium and par-ticularly platinum, which are more selective with regard to dehydrocyclization and are also more stable ~mder -the dehydro cyclizatlon reaction condi-tions -than o-ther Group VIII metals.
The preferred percen-tage of platinum in the ca-talyst is between 0.1% and 5%.
Group VIII rnetals are introduced in-to the large-pore zeoli-te by syn-thesis, impregna-tion or exchanye in an aqueous solution of an appropriate sal-t. When i-t is desired -to introduce two Group VIII metals in-to -the ~ (3~ ~

zeolite, the operation may be carried out simultcmeously or sequentlally By way of example, platinum can be introduced by impregnating the zeolite with an aqueous solution of tetrammineplatinum (II) nitrate, tetrammineplatinum ~II) hydroxide, dinitrodiamino-platinum or tetrammineplatinum (II) chloride. In an ion exchange process, platinum can be introduced by using cationic platinum comp]exes such as tetramrnine-platinllm (II) nitrate.
An inorganic oxide may be used as a carrier to b-ind the large-pore zeolite containing the Group VIII metal and alkaline earth metal.
The carrier can be a natural or a synthetically produced inorganic oxide or combination of inorganic oxides. Typical inorganic oxide supports wl~ich can be used include clays, alumina, and silica, in which acidic sites are preferably exchanged by cations which do not impart strong acidity (such as Na, K, Rb, Cs, Ca, Sr, or Ba).
The catalyst can be employed in any of the conventional types of equipment known to the art. It may be employed in the form of pills 9 pellets, granules, broken fragments, or various special shapes, disposed as a fixed bed within a reaction zone, and the charging stock may be passed therethrough in the liquid, vapor, or mixed phase, and in either upward or downward flow. Alternatively, it may be prepared in a suitable form for use in moving beds, or in fluidized-solid processes, in which the charging stock is passed upward through a turbulent bed of finely divided catalyst.
After the desired metal or metals have been introduced, the catalyst is treated in air at about 260C and then reduced in hydrogen at temperatures of from 200C to 700C, preferably 400C to 620C.
At this stage it is ready for use in the dehydrocyclization process. In some cases however, for example when the metal or metals have been introduced by an ion exchange process, it is preferable to eliminate any residual acidity of the zeolite by treating the catalyst ~1 _9~

with an aqueous solution o~ a salt or hydroxide of a suit-able alkali or alkaline earth element in order to 05 neutralize any hydrogen ions formed during the reduction of metal ions by hydrogen.
In order to obtain optirnum selectivity, tempera~ure should be adjusted ~o that reaction rate is appreciable, but conversion is les.s than 98~, as excessive temperature and excess reaction can have an adverse affect on selectivity. Pressure should also be adjusted within a proper range~ Too high a pressure will place a thermo-dynamic (equilibrium) limit on the desired reaction, especially for hexane aromatization, and too low a pres-sure may result in coking and deactivation, Although the primary benefit of this inventionis in improving the selectivity for conversion of paraf-fins (especially C6-C8 paraffins) to aromatics, it is also surprisingly found that the selectivity for conversion of methylcyclopentane to benæene is excellent. This reac tion, which on conventional reforming catalysts based on chlorided alumina involves an acid catalyzed isomerization step, occurs on the catalyst of this invention with selec-tivity as good as or better than on the chlorided alumina based catalysts of the prior art. Thus, the present invention can also be used to catalyze the conversion of stocks high in 5-membered-ring alkyl naphthenes to aromatics.
Another advantage of this invention is that the catalyst of the present invention is more stahle than prior a~t zeolitic catalysts. ~tability of the catalyst, or resistance to deactivation, determines its useful run length. Longer run lengths result in less down time and expense in regenerating or replacing the catalyst charge.
In one embodiment o~ the present invention, a hydrocarbon feed is contacted with a first catalyst which is a conventional refor~ing catalyst and a second catalyst which is a dehydrocyclization catalyst comprising a large-pore zeolite~ an alkaline eartil metal and a ~roup VI-[ r metal.

3~i{~
t --10--The use oE a reEorming catalyst comprising an alumina support, platinum, and rhenium is cliscussed fully in United States Patent 3,415,737, whlch describes -the use of an advan-tageous conventional reforming catalyst. Other advantageous bimetallic catalysts include platinum--tin, platinum-germanium, platinum-lead and pla-tinum-iridium.
The hydrocarbons can be contacted with the two cata-lysts in series, with the hydrocarbons first being contacted with the first (conventional) reforming catalyst, and then with the second (dehydrocyclization) catalyst; or with the hydro-carbons first being contacted wi-th the second catalyst; and then with the first catalyst. Also the hydrocarbons can be contacted in parallel with one fraction of the hydrocarbons being contacted wlth the first catalyst and another fraction of the hydrocarbons being contac-ted with the second catalyst.
Also the hydrocarbons can be contacted with both catalysts simultaneously in the same reactor.

EXAMPLES
The invention will be further illustrated by the following examples which set forth a particularly advantageous method and composition embodiments. While the examples are provided to illustrate the present invention, they are not intended to limit it.
Example I
An Arabian Light straight run which had been hydro-fined to remove sulfur, oxygen and nitrogen was reformed at 100 psig, 2 LHSV, and 6 H2/HC by three different catalysts.
The feed contained 80.2v~ paraffins, 16.7v~ naphthenes, and ~l~g~
~lOa-3.1v% aromatics, and it contained 21.8v% C5, 52.9v% C6, ~1.3v%
C7, and 3.2v% C8.
In the first run, the Arabian Light straight run was reformed at 499C using a commercial sulfided platinum~
rhenium-alumina catalyst discl.osed in United States Patent No. 3,415,737.
In the second run, the Arabian Light straight run was reformed at 493~C using a platinum-potassi.um-type L zeolite catalyst formed by~ Lmpregnat:ing a potassium-type I. æeolite with 0.8% platinum using tetrammineplatinum (Il) nitrate; (2) drying the catalyst; (3) calcining the catalyst at 260C; and (4) reducing the catalyst at 480C to 500C for 1 hour.
In the third run, the process of the present invention, the Ara~ian l.ight straight run was reformed at 493C u.sing a platinum-barium-type L zeolite catalyst Eormed by: (1) Lon exchanging a potassium-type L
zeolite with a suEficient volume of 0.17 molar barium nitrate solution to contain an excess of barium compared to the ion exchange capacity of the zeolite; (2) drying the resulti}lg bar:Lum-exchanged type L zeolite catalyst; (3) calcining ~he catalyst at 590C; (4) impregnating the catalyst with 0.8% platinum using tetrammineplatinum (II) nitrate; (5) drying the catalyst; (6) calcining the catalyst at 260C; and (7) reducing the catalyst in hydrogen at 480C to 500C for 1 hour.
The results of these three runs are shown in Table I.

TABLE I

Pt/Re 493C 493C
Feed Alumina Pt/K/LPt/Ba/L
__ _ _ Cl Wt % Fd 2.8 5.5 3.6 C2 6.6 2.5 1.3 3 9.3 3.2 1.5 iC4 0.1 5.8 0.9 0.5 NC4 0.5 6.8 3.8 2.4 iC5 5.1 13.6 6.7 5.6 NC5 11.3 9.8 12.6 12.6 C6~ P-~N 81.3 13.4 7.8 9.3 Benzene 1.5 15.1 40.6 43.8 C7+ Aromatics .8 15.8 12.7 15.0 C5~ LV % Yield 63 69.9 74.4 Hydrogen, SCF/B 470 1660 2050 Selectivity,~ole % 20 72 87 C6~ P --> Aromatics This series of runs shows that the use of a platinum-barium-type L zeolite catalyst in reforming gives a selectivity for , ~ ,, 3~

converting hexanes to benzene markedly superior to that of the prior art.
Not:Lce that associated with this superior selectivity is an increase in hydrogen gas producti.on which can be used in other processes. Notice also that the hydrogen purity is higher for the Pt/Ba/L run since more hydrogen is produced and less Cl plus C2 are produced.
EXAMPLF._[I
A second series of runs were made to show that the present invention would work with other large--pore zeolites in aclditlon to type L æeolite. The Selectivity Index was measured for four catalysts.
this second ser:ies of runs was made using n-hexane as feed.
All runs in this series were made at 490C, 100 psig, 3 LHSV and 3 H2/HC.
In the first run, a platinum-potassium-type L zeolite was used which had been prepared by the procedures shown in the second process of Example I.
In the second run, a platinum-barium-type 1. zeolite was used which had been prepared by the procedures shown in the third process of Example I except that the barium nitrate solution was 0.3 molar instead of 0.17 molar.
In the third run, a platinum-sodium-zeolite Y was used which had been prepared by impregnating a sodium-zeolite Y with Pt(NH3)4(N03)2 to give 0.8% platinum, then drying, calcining the catalyst at 260C and reducing in hydrogen at 480-500C.
In the fourth run, a pl.atinum-barium-zeolite Y was used which had been prepared by ion exchangingasodium-zeolite Y with 0.3 molar barium nitrate at 80C, drying, and calcining at 590C, then impregnating the æeolite with Pt(NH3)4(N03)2 to give 0.8% platinum, then drying, calcining the catalyst at 260C, and reducing in hydrogen at 480-500C.
The results of these runs are given below in Table II.

~.

3~ 7 TABIE II

Conver ion Selectivity ` 5 hrs. 20 hrs. Index _ Pt/K/L 70 59 79 Pt/Ba/L 85 85 92 Pt/Na/Y 82 79 54 Pt/Ba/Y 74 68 66 Thus, in operation, the incorporation of barium into a large-pore zeol:ite, such as type Y zeolite, causes a dramatic improvement in selectivity for n-hexane. Notice that the stability of the platinum-barium-type L zeolite is excellent. After 20 hours, there was no drop in conversion when platinum-barium-type L zeolite catalyst was used.
EXAMPLE III
A third series of runs was made to show the effect of adding additional ingredients to the catalyst.

This third series of runs was made using a feed, which had bee~ hydrofined to remove sulphur, oxygen and nitrogen, containing 80.9v% paraffins, 16.8v% naphthenes, and 1.7v% aromatics. The feed also contained 2.$v% C5, 47.6v% C6, 43.4v% C7 and 6.3v% C8. All runs in this series were made at 490C, 100 psig, 2.0 LHSV and 6.0 H2/HC.
In the first run, a platinum-sodium-zeolite Y was prepared by the procedures shown in the third process of Example II.
In the second run, a platinum-barium-zeolite Y was prepared by the procedures shown in the fourth process of Example II.
In the third run, a platinum-rare earth-æeolite Y was prepared by impregnating a commercial rare earth zeolite Y obtained Erom Strem Chemicals Inc. to give 0.8% Pt using Pt~NH3)4(N03)2, then the zeolite was dried, calcined at 260C and reduced at 480-500C.
In the fourth run, a platinum-rare earth-barium-zeolite Y
was prepared by ion exchanging a commercial Strem Chemicals Inc. rare earth zeolite Y with a 0.3 molar .~

;C~2~

~l -14-Ba(~O3)2 solution at 80C, drying and calcining the zeolite at 590C, impregnating the zeolite with 05 Pt(NH3)4(NO3)2 to give 0.~ Pt, tilen drying, calcining the zeolite at 260C, and reducing at 430-500C. The results of these runs are given below in Table III.

TABLE III

Activity Aromatics @ 3 Hrs, C5~ Selectivity, _ Mole ~ of Feed % @ 3 Hrs P~/Na/Y 36 46 Pt/~a/Y 54 68 Pt/Rare E~rth/Y 22 ~Too Low to Measure) Pt/Ba/Rare Earth/Y 36 27 This series oE runs shows that the addition of ~U rare earth to the catalyst has an adverse effect on selectivity.
Example IV
An Arabian Naphtha which had been hydrofined to remove sulfur, oxygen and nitrogen was reformed at 100 psig, 3 ~HSV, and 3 H2/HC to produce a C5+ product having an aromatlcs content of 82 wt % by two different processes.
The feed was a hydrofined Arabian Naphtha containing 67.9 paraffins, 23.7% naphthenes, and 8.4~ aromatics.
Distillation results by D86 method were: start - 203F, 5~-219, 10~-224, 30%-243, 50~-265, 70~-291, 90?~321, 9~-337, EP 370F.
In the first process, the Arabian ~aphtlla was reformed at 516C in a reactor using a conventional reforming catalyst comprising 0.3 Pt, 0.6 Re, 1.0 Cl (wt %) on alumina. It was presulfided separately.
In the second process, the Arabian Naphtha ~las reformed at 493C in the same reactor wherein the top half of the reactor contained the same type of catalyst as t`na.
of the first process and the bottom half of the reactor contains a platinum-barium-type L zeolite catalyst Eor~e~
by the procedures shown in Example I.

The results of these two runs are shown in Table IV.
TABLE IV

Pt/Re/1/2 Pt/Re/Alumina Alumina1/2 Pt/Ba/L
Deactivation Rate 2.0 1.9 C5~ yield r LV~ yield 68.9 71.0 Hydrogen, SCF/D 950 1050 While ~he present invention has been described with reference to specific embodiments, this application is intended to cover those various changes and substitu-~ions which may be made by those skilled in the art with-out departing from the spirit and scope of the appended claims.

~)

Claims (23)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of reforming hydrocarbons comprising contacting said hydrocarbons with a catalyst comprising a large-pore zeolite containing:
(a) at least one Group VIII metal; and (b) an alkaline earth metal selected from the group consisting of barium, strontium and calcium, wherein the Selectivity Index of the catalyst is greater than 60%.
2. A method of reforming hydrocarbons according to Claim 1 wherein said alkaline earth metal is barium and wherein said Group VIII
metal is platinum.
3. A method of reforming hydrocarbons according to Claim 2 wherein said catalyst has from 0.1% to 35% by weight barium and from 0.1% to 5%
by weight platinum.
4. a method of reforming hydrocarbons according to Claim 1 wherein said large-pore zeolite has an apparent pore size of from 7 to 9 Angstroms.
5. A method of reforming hydrocarbons according to Claim 4 wherein said large-pore zeolite is selected from the group consisting of zeolite X, zeolite Y, and type L zeolite.
6. A method of reforming hydrocarbons according to Claim 5 wherein said large-pore zeolite is zeolite Y.
7. A method of reforming hydrocarbons according to Claim 6 wherein said large-pore zeolite is a type L zeolite.
8. A method of reforming hydrocarbons according to Claim 7 wherein said contacting occurs at a temperature of from 400°C to 600°C; an LHSV
of from 0.3 to 5; a pressure of from 1 atmosphere to 500 psig; and an H2/HC
ratio of from 1:1 to 10:1.
9. A method of reforming hydrocarbons according to Claim 8 wherein said contacting occurs at a temperature of from 430°C to 550°C; a pressure of from 50 to 300 psig; and an H2/HC ratio of from 2:1 to 6:1.
10. A method of reforming hydrocarbons comprising contacting said hydrocarbons with a catalyst comprising a large-pore zeolite containing:
(a) at least one Group VIII metal; and (b) an alkaline earth metal selected from the group consisting of barium, strontium and calcium, wherein the process conditions are adjusted so that the selectivity for n-hexane dehydrocyclization is greater than 60%.
11. A method of reforming hydrocarbons according to Claim 10 wherein said alkaline earth metal is barium and wherein said Group VIII
metal is platinum.
12. A method of reforming hydrocarbons according to Claim 11 wherein said catalyst has from 0.1% to 35% by weight barium and from 0.1% to 5% by weight platinum.
13. A method of reforming hydrocarbons according to Claim 10 wherein said large-pore zeolite is selected from the group consisting of zeolite X, zeolite Y and type L zeolite.
14. A method of reforming hydrocarbons according to Claim 13 wherein said large-pore zeolite is zeolite Y.
15. A method of reforming hydrocarbons according to Claim 14 wherein said large-pore zeolite is a type L zeolite.
16. A method of reforming hydrocarbons according to Claim 15 wherein said contacting occurs at a temperature of from 430°C to 550°C;
a pressure of from 50 to 300 psig; and an H2/HC ratio of from 2:1 to 6:1.
17. A hydrocarbon conversion process comprising:
(a) contacting said hydrocarbons at reforming conditions and in the presence of hydrogen with a first catalyst comprising a metallic oxide support having disposed therein in intimate admixture platinum and rhenium; and (b) contacting said hydrocarbons with a second catalyst comprising a large-pore zeolite containing at least one Group VIII metal; and an alkaline earth metal selected from the group consisting of barium, strontium and calcium.
18. A hydrocarbon conversion process according to Claim 17 wherein said alkaline earth metal is barium and wherein said Group VIII
metal is platinum.
19. A hydrocarbon conversion process according to Claim 18 wherein said dehydrocyclization catalyst has from 0.1% to 35% by weight barium and from 0.1% to 5% by weight platinum.
20. A hydrocarbon conversion process according to Claim 17 wherein said large-pore zeolite is selected from the group consisting of zeolite X, zeolite Y and type L zeolite.
21. A hydrocarbon conversion process according to Claim 20 wherein said large-pore zeolite is zeolite Y.
22. A hydrocarbon conversion process according to Claim 21 wherein said large-pore zeolite is a type L zeolite.
23. A hydrocarbon conversion process according to Claim 17 wherein said contacting in step (b) occurs at a temperature of from 430°C; a pressure of from 50 to 300 psig; and an H2/HC ratio of from 2:1 to 6:1.
CA000420636A 1982-02-01 1983-01-31 Method of dehydrocyclizing alkanes Expired CA1196027A (en)

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US06/393,160 US4631123A (en) 1982-02-01 1982-06-28 Method of dehydrocyclizing alkanes
US393,160 1982-06-28
US42054082A true 1982-09-20 1982-09-20
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