DE1265728B - Process for the hydrogenative isomerization of n-pentane - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. α .:

C07c

German: 12 ο -1/01

Number: 1265 728

File number: G 22507IV b / 12 ο

Filing date: July 10, 1957

Open date: April 11, 1968

The subject of patent 1171 892 is a process for the hydrogenative isomerization of naphthene-free or very low-naphthenic hydrocarbons with at least 85 percent by volume of C ₃ and / or C ₆ paraffins over a supported platinum catalyst with 0.1 to 5.0 percent by weight Pt at temperatures im Range from 315 to 480 ⁰ C under increased pressure at a throughput rate of at least 5 parts by volume of liquid feed per volume of catalyst-filled space per hour, which is characterized in that the feed is filled with catalyst together with hydrogen at a throughput rate of 5 to 25 parts by volume per volume Room per hour and at the same time a low hydrogen-hydrocarbon ratio between 0.9 and 8.4 Nm ³ per 1001 liquid hydrocarbons is passed over the catalyst.

Preferably, in the process of the main patent, the throughput rate is between 8 and 12 held, and a halogen-containing platinum-on-alumina catalyst is preferably used as the supported catalyst. sator used.

In the process according to the main patent, the hydrogen-hydrocarbon ratio is preferably kept close to, but still above 1.8 Nm ³ H ₂ per 1001 hydrocarbons, and according to a particularly expedient embodiment of the main patent, the critical hydrogen-hydrocarbon ratio is determined by preliminary tests , below which larger amounts of carbon are rapidly deposited on the catalyst, and the process then works close to this, but still above this critical ratio.

The catalytic hydrogenating isomerization is known to be an equilibrium reaction, with the result that, even under the most favorable conditions of the ideal case, no more than the equilibrium conversion of n-pentane to isopentane corresponding to the reaction temperature in question can be achieved in a single pass. In the examples the main patent n-pentanoic sales are up to 50.3% was obtained at the applied where high throughput speeds and a reaction temperature of 443 ⁰ C in a single pass. Is carried out at much lower flow rates (1 part per volume of catalyst-filled space per hour), so at a reaction temperature of 432 ⁰ C to reach the equilibrium conversion of 6O ° / o (see FIG. Industrial and Engineering Chemistry, Vol. 43, 1951, P. 2103).

If now, as in most cases, the technical objective goes as follows: the starting material used is a process for hydrogenating isomerization
of n-pentane

Addendum to the patent: 1171892

ίο applicant:

GuIf Research & Development Company,
Pittsburgh, Pa. (V. St. A.)

Representative:

Dr.-Ing. B. Bloch and Dr. K. Jacobson,

Patent attorneys,

8042 Schleissheim, Freisinger Str. 38

Named as inventor:

Richard Graham,

William Richard, Penn Township, Pa. (V. St. A.)

^a 5 Claimed priority:

V. St. v. America July 11, 1956 (597131) - -

To convert as completely as possible into the desired process product, the person skilled in the art makes use of the known means of circulating the contained in the drain from the isomerization device, not converted part of the starting material. Since isopentane has a lower boiling point than n-pentane, offers The most obvious method to the person skilled in the art is to obtain isopentane by fractional distillation and the circulation of the distillation residue.

It has now been found that such a procedure is used in the case of the main patent low hydrogen concentrations and high flow rates to a proportionate rapid deactivation of the platinum catalyst results in the catalyst often being an expensive one

so y g p

Must be subjected to regeneration. It was also recognized that for this rapid deactivation of the platinum catalyst are those contained in the distillation residue of the effluent from the reaction vessel, higher boiling hydrocarbons than n-pentane are responsible, on the one hand from impurities

809 538/536

3 4

In terms of the n-pentane used as starting material, the feed contains higher-boiling impurities and on the other hand, originating from side reactions is plotted;

men that take place during isomerization, and FIG. 4 explains deactivation studies at

which is when the distillation residue of the iso- the hydrogenating isomerization of n-pentane at merization product continuously in a cycle, single pass or partial cycle; will enrich in the original material. F i g. 5 is a similar diagram for the hydraulic

The invention is based on the object of this yielding isomerization in a single pass or Disadvantage of the process of the main patent fractionation and recycling, occurs when from the course of the isomerization In the circuit device described in Example 1 the isopentane fractionated distillate is driven according to FIG. 2 worked. This method lation separated and the distillation residue is referred to as partial circulation. According to Cycle is performed to eliminate. F i g. 2 a refinery pentane fraction is used as fresh

It has been found that the life of the platinum charge fed through line 20 after catalyst is no longer significantly impaired, it has been preheated to the reaction temperature. if one takes care of it in this cycle process, 15 Through the line 21 a cycle flow is in the that the fresh feed fed into the isomerization device is introduced. The total load Charge not more than 3 mole percent and preferential mixed with a preheated one, through line22 wise no more than 1.5 mole percent hydrocarbon-fed hydrogen-containing gas stream and is in contains substances with a boiling point above about 36 ° C. the isomerization vessel 23 passed. The product The process of the invention for hydrogenating 20 flows through line 24 into a high pressure stripping isomerization of n-pentane in the presence of 0.1 to that in which the liquid products from the gases 5 percent by weight of platinum can be separated on a carrier as a cata-. The withdrawing through line 25 lysator at temperatures of 315 to 480 ° C under gas flow is after passage through (not increased Printing according to patent 1171892 is therefore provided) cleaning devices, such as a characterized in that the discharge from the 25 light oil scrubber into the hydrogen line 22 back-isomerization device after disconnecting the headed. The liquid product flows through line 27 isopentane by fractional distillation in the stabilizing column 28, from which the gaseous Is circulated in a manner that is drawn off as loading component from the head through line 29 Charge is passed into the isomerization device. The stabilized liquid product is through n-pentane fraction not more than 3 mol percent, upstream 30 line 30 in the fractionation column 31 for removal not more than 1.5 mole percent, carbon of the isopentane passed. The column 31, of Hydrogen with a boiling point above about 36 ° C whose head has an isopentane fraction with about 95% contains. Isopentane through line 32 as isomerized

According to the invention, this can be deducted from two different finished products which ways are reached, namely referred to as an "isopentane column" for the sake of simplicity. Embodiment of the invention in that the bottom fraction of the isopentane column that .aus only a corresponding part of that of isopentane n-pentane and higher-boiling hydrocarbons The freed effluent from the isomerization device is discharged through line 33. A part leads in the circuit, and after a second execution of this distillation residue is through line 34 Approximate form of the invention in that one subtracts from 40 and the remainder through line 21 in the circular isopentane The freed outflow of the isomerization forerun is fed back into the fresh feed line 20, direction through a fractional distillation to reduce the concentration of higher-boiling impurities

The n-pentane fraction is processed and recycled (mainly hexane isomers and cyclofour. pentane) is in the withdrawn from the isopentane column

In a particularly preferred embodiment, the distillation residue is considerably higher than that of the invention at low hydrogen levels in the fresh feed. In this embodiment, hydrocarbon ratios of about 6.5 Nm ^{3 of} the process of the invention have a higher content of above n-pentane (36 ° C. ) share liquid pentane per volume with catalyst 50 boiling hydrocarbons as the fresh charge-filled space per hour (V / V / h) and above the kung. The respective concentration of this higher cycle of the unconverted part of the boiling hydrocarbons in the feed discharge from the reaction vessel according to one of the two depends on how much material is circulated in the above-mentioned methods is carried out in this way. As will be described in more detail in Example 1, according to the invention, tests with partial circulation feed not more than 0.5 mol percent coal feed in which the feed hydrogen with a boiling point above 36 ⁰ C kung have been carried out according to the invention of the isomerization vessel contains 5.0 or 3.1 mol, percent higher than n-pentane boiling hydrocarbons

To further explain the invention is contained on substances Reference is made to the drawings. 60 The cycle process described in Example 2

Fig. 1 is a highly schematic flow diagram one is in F ig. 1 shown. This procedure enables hydrogenating isomerization according to the invention, the concentration of higher than n-pentane boiling with fractionation and recycling; Hydrocarbons in the feed

F i g. 2 is a corresponding flow diagram of a hydraulic control. According to FIG. 1 is the fresh load, The isomerization process according to the invention 65 refinery n-pentane fraction, through line 40 manure with partial circulation; the fractionation column (isopentane column) 41 to

F i g. 3 is a diagram showing the deactivation of the isopentane fed. Simultaneously rate of the catalyst against the gel becomes the stabilized liquid isomerization product

withdrawn from the stabilizing column 42 through line 43, mixed with the fresh feed, and this mixture is fed through line 44 into the isopentane column 41. From the top of the column 41 is withdrawn through line 45 as a Isomerisationsprodukt Isopentanfraktion which contains 95 ° / ₀ or more isopentane. The hydrocarbons boiling above isopentane, which mainly consist of n-pentane and higher-boiling hydrocarbons, flow from the bottom of column 41 through line 46. This stream passes into the fractionation column (pentane column) 47, from the top of which a highly purified n-pentane fraction is drawn off through line 48. The hydrocarbons boiling above 36 ^° C. leave column 47 through line 49. The n-pentane withdrawn through line 48 forms the feed to isomerization vessel 50 and is made up of the n-pentane from the fresh feed and the circulated, unconverted n -Pentane from the outlet from the isomerization vessel. The purity of the feed can be controlled by the severity of the fractionation in columns 41 and 47. As Example 2 shows, this "circulating fractionation process" can be carried out in such a way that the feed to the isomerization vessel contains only 0.4 mol percent of hydrocarbons with boiling points above 36.degree. Referring to Figure 1, this feed is mixed with the hydrogen containing gas supplied through line 49 '. The mixture passes through the isomerization vessel 50, and the reaction mixture drawn off through the line 51 is separated into a gaseous and a liquid phase in the high pressure separator 52. The gases withdrawn through line 53 are after a cleaning treatment to reduce the hydrocarbon content, e.g. B. a light oil scrubbing, returned to the hydrogen line 49 '. The liquid product occurring in the separator 52 flows through line 54 into the stabilizing column 42, from the top of which through line 55 the gaseous fraction is discharged. The stabilized liquid product flows off through line 43 and is mixed with the fresh feed in the manner described and fed to the isopentane column.

In the examples below, pentane fractions are isomerized, which are used in a refinery as Direct distillates arise and consist mainly of n-pentane. The middle composition and some analytical values for these refinery fractions are given in Table I.

Table I.

Average composition and analysis values
of the refinery pentane fractions

Composition by volume

Isopentane 7 to 9

n-pentane 88 to 91

Pentenes 1 to 2

Cyclopentane 0 to 11 im

2,2-dimethylbutane 0 to 1 medium

2,3-dimethylbutane 0 to 1J 1.5%

Analysis values

Sulfur, weight percent ... 0.003

Bromine number .., 4

Water, weight percent 0.001 to 0.003

A commercially available platinum-alumina catalyst in quiescent bed is used. Table II gives the properties of a typical catalyst sample.

Table II
Properties of the catalyst

Shape chopsticks

Diameter, mm less than 1.7

Bulk density, g / cm ³ 0.83

analysis

specific surface,

m ^a / g 296

Platinum, weight percent 0.57
Chlorine, weight percent

after 2 or 10 or

20 hours of treatment

at 540 ^° C. in air 0.77; 0.64; 0.36
Total sulfur,

Weight percent 0.06

Spectrographic Analysis

Main component Al

1 to 10% -

0.1% to 1% Pt ₃ Si

0.01% to 0.1% Na ₃ Fe

less than 0.01% Cu ₃ Ca, Mn, Mg ₃ Cr, B

example 1

The platinum-alumina catalyst described in Table II is placed in the reaction vessel in a quiescent bed. The catalyst has already been used several times for the hydrogenating isomerization of n-pentane in a single pass and has been regenerated twice by oxidizing the carbon-containing deposits. The reaction pressure is 28 atm, the feed rate of the feed 9 V / V / hr, and the hydrogen-hydrocarbon ratio in the feed 6,5Nm about ^3/1001 of liquid hydrocarbons. The hydrogen-containing gas consists of 80 mol percent hydrogen, 18 mol percent and methane, the remainder being ethane and heavy hydrocarbons. The hydrogen and hydrocarbon feed streams are preheated to the reaction temperature. This temperature is chosen so that the degree of conversion is maintained at such a level that the stabilized liquid isomerization product contains 40 to 50% isopentane. The reaction temperature is readjusted several times during the process. From time to time samples of the stabilized liquid isomerization product of 10 to 15 ml each are taken from line 30 of stabilizing column 28 (FIG. 2). To determine the rate of deactivation of the catalyst, the samples are examined for their isopentane content. In Fig. 4 the isopentane content of these samples is plotted against the age of the catalyst. The catalyst age is the amount of liquid charge in units of 1001 which has passed through 1 kg of the catalyst since the start of the experiment.

During the initial period of this example up to a catalyst age of 525 l / kg, the

Activity of the catalyst previously regenerated twice, Example 2

determined at temperatures of 435 and 446 ° C. The platinum-alumina used in Example 1

The catalyst age of 525 l / kg is then used, while the catalyst is used for the third time before this test, as shown in FIG. 4 as phase I designated operating period oxidatively regenerated. The results of the experiment selected the partial cycle ratio so that the loading 5 are shown in FIG. 5 plotted graphically. The catalyst charge constantly having a content of above 36 ° C. is used for the hydrogenating isomerization of the n-pentane fraction described in Table I in boiling hydrocarbons of 5.0 mol percent. This concentration of higher-boiling hydrocarbons in the feed up to a catalyst age of 1925 l / kg is again maintained in a single-pass procedure that uses the iso- io passage from the sump. During the first portion penta column 31 through line 34 (Fig. 2) constantly this period of operation the reaction temperature is a product amount of 9.5 percent by volume, based 429 ⁰ C; in the second section the temperature is deducted on the fresh batch. Fig. 4 443 ⁰ C increased. To determine the deactivation, it shows that the catalyst activity drops rapidly during this speed of the catalyst for a single working phase I. The deactivation cycle will again speed up product samples of the catalyst during phase I. It is found that the rate of conversion corresponds to a decrease in the degree of conversion of the catalyst, that of a 3.14% / 100% charge per kilogram of catalyst. 1001 loads per kilogram of catalyst

Following phase I, an experiment on zo speaks very precisely corresponds to the previously determined determination of the deactivation rate at deactivation rate for a single operation with a single passage and passage of material (0.4%). When using a catalyst feed with 1.5 mol percent age of 1925 l / kg, the reaction temperature of hydrocarbons boiling above 36 ° C is increased to 468 ° C and controlled with the fractionation cycle " The run control method according to Fig. 1. This operating period can also be seen from Fig. 4 for fresh charge and the stabilized liquid product, specifically for the catalyst age of 41 and 825 to 1400 l / kg together in the isopentane column higher fraction of the pentane column 47, and from the top of the pentane column 47 than during phase I, and the rate of the pentane column 47 is a charge for the deactivation goes back to the value withdrawn from the 30 isomerization vessels, which last 0.4 mole percent previously in deactivation attempts with long - Hydrocarbons boiling above 36 ⁰ C contains the single pass as normal deactivation This work Partly was determined with fractionation and circulation rate, namely a discharge is at 468 ⁰ C up to a total catalysis. would take the degree of conversion by 0.4% per 1001 age of 3500 l / kg. Thereby loading and per kilogram of catalyst. 35 from time to time samples of the stabilized isomeric

The next phase of the under part-circuit transit sationsproduktes taken and analyzed, the process carried out, the phase II, is expressed with a Isopentangehalte of these samples as a content of the feed to above 36 ⁰ C boiling mole percent of the total pentanes, are in Fig. 5 Hydrocarbons of no more than 3 mol- plotted against the age of the catalyst. The percentage slope carried out, i.e. in the vicinity of the upper 40 of this curve, shows that the catalyst is deactivated considerably at the limit of the inventive range, phase II is more slowly deactivated than when the partial cycle begins at a catalyst age of 1400 l / kg, proceed according to Example 1. the Entaktivierungsdie reaction temperature is 471 ⁰ C. the upflow velocity of the catalyst corresponds to only a fraction from the Isopentankolonne 31 is guided in a decrease in the degree of conversion by 0.23% for each such an amount in the circuit, that the sawn 1001 45 feed per kilogram of catalyst . It is about 3.1 moles in the isomerization vessel, which means that it is considerably lower than the percentage of deactivation of the hydrocarbon boiling above 36 ° C, both when working with constituent substances. The amount of the cycle required for this, as well as when working with one-time cycle material, is obtained by the passage. With such a low deactivation bottom fraction of the column 31 at 29.9 volume speeds, a service life of the catalysis percent of the fresh feed of the corresponding partial sator between 32000 and 460001 per kilogram can be deducted through line 34. Even while the catalyst can be reached. Even with application phase II, samples of the stabilized liquid of the high throughput rates are taken and analyzed in terms of the product. The main isopentane patent means that the catalyst life of these samples is shown in Fig. 4 for a catalyst duration of 4 to 6 months. ^! satoraltei from 1400 to 2100 l / kg. In addition to the studies on catalyst deactivation, the results show that during phase II with a stabilized content of 3.1 mole percent in the charge of superfluous product according to Examples 1 and 2 and with periodic sampling of the charge Fi g. 4 hydrocarbons boiling at half a temperature of 36 ° C, and 5 the properties of the various activation rates of the catalyst, although 60 reaction products are also determined over long periods of operation than during the working period. The compositions and times through, but much lower than in the properties of the products and the ingredients phase L The deactivation rate during the loading are together with the operation of phase II corresponds to a decrease in the conditions in Table III for the operation with degree of conversion by 1, 05% per 1001 per kilogram of Sg partial circulation (phases I and II of Example 1) catalyst; with a single pass and for the working method with fractionation and cycle this decrease is 0.4%, during phase I however running (phase III of example 2) together -3.14%. posed

Table III example 1 Example 2

Work phase according to
F i g. 4 or 5

Catalyst age
(in 100 l / kg)
Beginning of the trial period

End of the trial period

Composition of the refinery n-pentane fraction (fresh feed),
Volume percentage

Isopentane

n-pentane

Pentenes

2,2-dimethylbutane .. cyclopentane

Composition of
liquid charge, percent by volume

Isopentane

n-pentane

Pentenes

2,2-dimethylbutane .. cyclopentane
2,3-dimethylbutane .. 2-methylpentane

3-methylpentane

benzene

toluene

Composition of
Gas charging,
Mole percent

hydrogen

methane

Ethane and higher hydrocarbons.

Work phase according to
F i g. 4 or 5

working conditions
Average reaction temperature ^{, 0 C}

Reaction pressure, atmospheric flow rate, V / V / h

Hydrogen to hydrocarbon ratio in the feed,

Nm ^3/1001

Gas charging,
Nm ^3/1001 Fresh feed

Amount of liquid feed added to the reaction vessel, percent by volume the fresh load

Isopentane content in
stabilized liquid product, mole percent

I. Π m 5.9 18.6 21.0 7.8 20.4 24.2 9.2
87.8
1.0
1.2
0.8 ö, 7
88.7
0.9
1.0
0.7 9.5
87.1
2.6
0.0
0.8 0.6
86.6
2.2
0.5
ι 6.1
89.3
1.5
0.5 6.1
90.8
2.7
0.4 3.0 1.6 - J
1.1
0.2
0.2 0.6
0.2
0.2 - 80.3
18.4 79.6
18.5 80.6
18.2 1.3 1.9 1.2 I. II III 457
28 471
28 468
28 9.0 9.0 8.9 6.15 6.15 6.15 18.8 16.0 15.0 215 181 166 40 40 50

ΠΙ

31.2 34.0

88.5 1.0 1.3 0.4

4.2

92.6

2.8

0.4

174 47 10

Table III (continued)

example 1 Example 2

80.9 18.0

1.1 III

468 28

9.0

6.15 15.0

Product yields reactor gas Nm ^3/1001 Fresh loading ... stabilizer gas Nm ^3/1001 Fresh feed

Light liquid product (iC ₅ ), volume percentage of fresh charge ... Higher-boiling liquid product, volume percentage of fresh charge ...

Work phase according to F i g. 4 or 5

Product composition

Light liquid product, percent by volume

n-butane

Isopentane

n-pentane

Pentenes

2,2-dimethylbutane ..

Higher boiling liquid product, percent by volume

Isopentane

n-pentane

Pentenes

2,2-dimethylbutene .. cyclopentane
2,3-dimethylbutane 2-methylpentane 3-methylpentane ....

η-hexane

Methylcyclopentane ..

Cyclohexane

Saturated C ₇ carbon

hydrogen

benzene

toluene

Aromatic
C ₈ hydrocarbons

fabrics

Aromatic
C ₉ hydrocarbons

fabrics

Aromatic
C ₁₀ hydrocarbons

18.6 15.9 14.7 3.22 2.85 3.63 84.2 64.3 87.6 9.5 29.9 3.7 I. II III 0.1
93.2
6.6
0.1
0.0 0.2
96.5
2.6
0.5
0.2 0.3
94.3
4.4
0.8
0.2 6.5
83.7
1.6
1.5 6.7
86.2
1.8
2.1 1.5
32.9
0.3
3.4 H 1.9 27.7 j
0.8
1.4
track
track 0.3
0.4
track
track 4.2
4.3
2.6
6.3 track
0.5
0.6 track
0.1
0.4 10.3
0.4
3.3 0.2 0.1 1.0 - - 0.9 0.9

95.2 3.8 0.7 0.2

37.6 0.2 3.7

26.2

10.4 0.3 3.7

Table III illustrates the results obtained by the cycle processes according to the invention will. The table shows that the stabilized reaction product has higher-boiling hydrocarbons contains that were not included in the fresh batch. These hydrocarbons must thus formed as by-products during the isomerization process. According to Table III contains

809 538/536

the refinery pentane fraction used as fresh feed practically no higher-boiling hydrocarbons except for 2,2-dimethylbutane and cyclopentane. The through line 49 in FIG. 1 and line 34 in FIG. 2 withdrawn higher boiling liquids However, the product contains significant amounts of the higher-boiling hydrocarbons of 2,2-dimethylbutane up to Cm-aromatics. With the partial cycle process according to FIG. 2 and to an even greater extent in the fractionation cycle process according to FIG. 1 becomes a feed with a considerably lower content of higher boiling hydrocarbons than it was when the entire product distillation residue was recirculated to the isomerization vessel it is possible. Therefore, the method according to the invention enables a significant to be achieved longer catalyst life than when the entire product distillation residue is recycled could be achieved.

F i g. 3 shows a graphic comparison of the catalyst deactivation rates in the isomerization with and without the use of the cycle process according to the invention. In Fig. 3, the deactivation rates (in percent decrease in the degree of conversion per 100 liters of feed per kilogram of catalyst) are plotted against the concentrations of hydrocarbons boiling above 36 ° C in the feed, expressed in mole percent, for four different modes of operation. Points indicates the deactivation speed for the working method with fractionation and circulation, period !? the Entaktivierungsgeschwindigkeit for single pass, point C has Entaktivierungsgeschwindigkeit for the sub-circuit method, in which the feed contains 3 mole percent above 36 ⁰ C boiling hydrocarbons, and point D is the Entaktivierungsgeschwindigkeit for the circulation method in which the feed 5 mole percent above 36 ⁰ C. contains boiling hydrocarbons. The curve connecting the four points illustrates the considerable increase in the deactivation rate of the catalyst when the catalyst is recirculated without adequate purification of the recycled product stream. The method of working with a single pass according to point i? Although leads to a relatively low deactivation rate; However, this advantage is masked by the fact that the total yield of isopentane is limited in a single pass through the equilibrium concentration. In the case of circulation, on the other hand, it is possible to convert all of the n-pentane contained in the fresh charge, apart from minor operating losses, into isopentane.

The method of the invention can be modified in various respects. The n-pentane can be separated from the higher-boiling hydrocarbons, for example, by chromatographic adsorption, with the aid of molecular sieves or by selective chemical treatment. The distillation columns 41 and 47 in FIG. The isopentane is withdrawn as product from the head, while the as feed serves for the Isomerisierungsgefäß n-pentane fraction as a side stream and-the above 36 ⁰ C boiling hydrocarbons are withdrawn from the bottom of the column 1 are replaced by a single column,

Claims (3)

Patent claims: 1. A process for the hydrogenative isomerization of n-pentane in the presence of 0.1 to 5 percent by weight of platinum on a support as a catalyst at temperatures of 315 to 480 ⁰ C under increased pressure according to patent 1171892, characterized in that the flow from the isomerization device according to separating the isopentane by fractional distillation is circulated in such a way that the n-pentane fraction passed into the isomerization device as feed does not exceed 3 mol percent, preferably no more than 1.5 mol percent, of hydrocarbons with a boiling point above about 36 ° C contains. 2. The method according to claim 1, characterized in that that only a corresponding part of the isopentane-freed effluent from the isomerization device leads in a cycle. 3. The method according to claim 1, characterized in that the freed from isopentane The isomerization device proceeds through fractional distillation to an n-pentane fraction processed and circulated. Considered publications:
Canadian Patent No. 487,392;
Industrial and Engineering Chemistry, 43, 1951, 2103. 1 sheet of drawings 809 538/536 4.68 © Bundesdruckerei Berlin