DE1418654C - - Google Patents

Description

1 2

The isomerization of paraffin hydrocarbons which can be removed is the process according to FIG

In the gasoline boiling range, a known method of the invention is relatively simple, but has considerable

Increasing the octane number of gasoline fractions. Remaining advantages. Since methylcyclopentane and cyclo-

Hexane hexane isomers are particularly suitable for this treatment, a reversible reaction takes place

or pentane-hexane fractions. These fractions are held which show the proportions of each compound in the

But not only normal and inoparaffins hold, reaction zone determined; the removal of cyclo-.

but also CycloparafTine, which does not improve hexane out of the system, shifts the reaction in

and can even be disadvantageous in the isoineri direction of a further conversion of methyl

affect the sation process. From the following cyclopentane in cyclohexane. In this way, the

led to boiling points of various C ₆ carbon io enrichment of methylcyclopentane and slowed down

Hydrogen can be seen, however, that methylcyclo- even effectively kept below an upper limit

Pentane boils so close to η-hexane that a separation will be caused by the equilibrium between the

of the two compounds by fractional distillation two cycloparaffins under the iso-

tion is practically impossible. merization conditions is determined. At one too

λ -, ι-, · u it. . ". _On is strong accumulation of cycloparaffins can

2'2-Dimethy butane 49.7 C cycle can be interrupted for a time.

<? {"i ü τ ^hylbutane <n-JO ^ The method is suitable for the treatment of

2-Methy pentane ^ '^ substitute materials, their content of methylcyclopentane

I-methylpentane £ s7 ° r is ^{less than 10} percent by weight. Fractionation

» '. , ^Kd , ⁿ ', t, oo ^ X ²⁰ to remove cyclohexane from the product

Methylcyclopentane 71.8 C _{is advantageous} with one in one or more

_r ^en f ⁰ '·· ^' Lp fractionation columns carried out fractionation

Cyclohexane 8U, 7 C _{for the} separation of the desired isoparaffins combined

If, therefore, an isomerization process does not work together. For example, if a C _e fraction is treated in a process for the separation of hydrocarbons, the product can be combined into an overhead fraction that contains substance types, for example with selective adsorption on dimethylbutane, an intermediate fraction, the molecular sieves, finds the isomeric η -Hexane and any existing methylcyclopentanization instead of in the presence of cycloparaffins, and, contains and which is recycled, and a bottom fraction consisting of what is more important when the unreacted products cyclohexane are separated, are recycled, the cyclo- 30 The methylpentanes can be found in the head or intermediate paraffins in the system. This problem has already been dealt with in a fraction - preferably the latter - in the USA. Patent 2 9Ü5 736 described. To the detriment, since they can be further converted into the higher octane dimethylbutanes, preventing the undesired build-up of cyclo-. A complete separation of paraffins is proposed there, so much hydrocarbon material is not possible from the material cycle between the dimethylbutanes and methylpentanes, since the boiling points can be separated close together that the range is undesirably higher, so that the fractions are not pure in practice CycloparafTinen concentrations are not reached.

will. According to this U.S. patent proposal The feed to the isomerization process

However, not only is cycloparaffin, but can also be fractionated to remove

mix with it also a proportion of the non-cyclic Pa- 40 cyclohexane and optionally of isoparaffins, the

Refined hydrocarbons are in the process cycle and do not require conversion, e.g. B. of dimethyl

then withdrawn from the sanitary proceedings. This will cause butanes to be subjected. In this case, before

inevitably a reduction in the yield of the desired isomerization zone, a single fractionation system

th connections. used in which the insert is introduced and

In contrast, the invention proceeds from the task to which the reaction product is returned. There

position, by taking suitable measures to build up the boiling points of cyclohexane and benzene tightly

an undesirably high concentration of cyclo- lie together, there is the possibility that a

paraffincn to prevent without doing desired pa-. certain amount of benzene from use with the cyclo-

refined hydrocarbons are removed from the process cycle hexane if the feed contains benzene,

to have to remove. 50 The removal of benzene by fractionation is

The invention therefore relates to a process, however, through the formation of an azeotropic mixture

for isomerizing up to H) weight percent Me- complicated, and the insert is before the fractionation

Ce paraffin hydrocarbons containing ethylcyclopentane. treatment preferably by other methods,

Steffen by heating in the presence of hydrogen to remove any benzene present. On that

and catalysts, with unconverted Pa- 55 being discussed in more detail below.

The preferred catalysts for the isomerization

dcn and an enrichment of the isomerization process of the invention are an aluminum

slufe present Mcthyicyclopcntans is prevented, halide and a hydrogenating metal on a heat-

which is characterized by the fact that the permanent oxide is used as a carrier. The procedure is in

starting material is isomerized at 65 to 177 "C and the 60 presence of hydrogen carried out,

the resulting product by distillation into an aluminum chloride is preferably used as the halide

essentially only cyclohexane-containing soil used in the catalyst, but aluminum can also be used

fraction, an η-hexane and methylcyclopentane ent- nium bromide are needed. The aluminum halo-

Haltendc Mittclfruklion and one the Dimethylbutane genid is preferably used in an amount of 3 to

containing top fraction separates and the n-hexane 65 to 20 percent by weight, based on the catalyst,

and methylcyclopentane existing middle fraction in turns. The halide can be incorporated into the catalyst

recirculates the isomerization stage. by working with aluminum halide

Because cyclohexane is brought into contact by known fractionation method steamers. A roughly-

iger excess of aluminum halide can then can be removed by heating.

All metals of groups VIa and VIII of the Periodic Table can be used as the hydrogenation metal known to be effective. Preferred is a platinum group metal, e.g. B. Platinum or palladium, which is present in an amount of 0.01 to 5.0 percent by weight.

The heat-resistant oxide used as the carrier is aluminum oxide, which is expediently made from an aluminum alcoholate will be produced. The hydrogenation metal can be used during or after the preparation of the aluminum oxide be incorporated into the catalyst, for example during hydrolysis, in a slurry or in a gel of hydrated alumina or after calcination. Becomes a If the metal of the platinum group is used as the hydrogenation metal, it is preferably added by precipitation Metal from a solution with hydrogen sulfide.

The. Isomerization is carried out in the liquid or vapor phase under the following conditions:

Temperature 65 to 177 ° C

Pressure normal pressure

up to 141 kg / cm ² ,
preferably 16.8
up to 41 kg / cm ²
Room flow velocity - 0.05 to 10, preferably

speed, V / V / h 0.2 to 5

Molar ratio of hydrogen 0.01 to 20: 1, preferably 1.5 to 15: 1 in front of hydrocarbon

In addition to the C ₆ hydrocarbons, the insert can also contain C ₅ and / or C ₄ hydrocarbons. It is useful if the insert is practically free from benzene, since this is a catalyst poison. The benzene content of the insert is preferably below 0.1 percent by weight, especially below 0.01 percent by weight. The benzene can be removed by acid treatment or other known methods or converted to cyclohexane by hydrogenation. When the benzene is converted to cyclohexane it is particularly convenient to use the process according to the invention. It is also advantageous if the insert is practically free from water and sulfur, the sulfur content preferably being below 0.001 percent by weight. These two substances can be removed by any suitable method.

Example ^:

A dry, desulphurized and dearomatized hexane cut from a light gasoline that is made from crude oil from the Middle East was obtained, was isomerized over a platinum-aluminum oxychloride catalyst, the Contained 0.56 percent by weight platinum and 15 percent by weight aluminum chloride. The following working conditions were applied:

Temperature 149 ° C

Pressure 36 kg / cm ²

Space flow rate 1.0 V / V / h

Molar ratio hydrogen
to hydrocarbon 3.5: 1

The key figures of the use and the product are listed in Table 1 below:

Table 1

propane

Isobutane

η-butane

Isopentane

n-pentane

2,2-dimethylbutane

2,3-dimethylbutane

Cyclopentane

2-methylpentane.

3-methylpentane

η-hexane

Methylcyclopentane

Cyclohexane

The product obtained in a yield of 95.5 percent by weight was in a column with 40 trays separated into a top product and a bottom fraction at a reflux ratio of 20: 1. The soil product was further distilled in a second column with 40 plates at a reflux ratio of 20: 1, with a top fraction, which is suitable for recycling into the isomerization reactor, and one out Cyclohexane was obtained, which was suitable for the production of benzene. The values for these distillations are listed in Table 2 below.

mission product track Weight percent track track - 1.5 track 0.5 0.5 21.0 1.5 36.0 track 17.5 28.5 18.0 22.5 2.5 41.0 3.0 4.0 2.0

Table 2

Column I | Column 2

fraction

Head product | Soil product | Head product | Bottom Product Yield in percent by weight based on input 3J, 6 I 66.4 J 97.0 | 3.0

Composition in percent by weight

propane

Isobutane

n-üutan

Isopentane

n-pentane

2,2-dimethylbutane

2,3-dimethylbutane

Cyclopentane

2-methylpentane

3-methylpentane

n-I lexan

Methylcyclopentane

Cyclohexane

track
1.0

track
5.0
3.0

59.0

30.5
1.5

2.0
43.5

26.0

22.0

3.5

3.0

2.0 45.0

26.5

23.0

3.5

track

Lane 100.0

From table 1 it can be seen that the methylcyclopcntane is converted to cyclohexane under the isomerization conditions, and Table 2 shows that virtually all of the cyclohexane can be removed from the product by fractionation. Table 2 also shows that the distillation also resulted in an overhead product rich in 2,2-dimethylbutane and a recycle stream mainly containing n-oxane and methyl pentanes can be obtained.

IO

Claims (1)

Claim: Process for isomerizing up to 10 percent by weight Methylcyclopentane-containing paraffinic hydrocarbons by heating in Presence of hydrogen and catalysts, with unconverted paraffins in the isomerization stage be recycled and an enrichment of the present in the isomerization stage Methylcyclopentane is prevented, characterized in that one the starting material is isomerized at 65 to 177 ° C and the resulting product by distillation into a bottom fraction containing essentially only cyclohexane, an η-hexane and methylcyclopentane containing middle fraction as well as a top fraction containing the diniethylbutane separates and the middle fraction consisting of η-hexane and methylcyclopentane in the isomerization stage returns.