DE3208700A1 - Process for the preparation of methane by hydrogenolysis of hydrocarbon fractions - Google Patents

Description

The present invention relates essentially to a period of time for obtaining a charge with an increased calorific value, in particular a method for. Making a bath containing more than 95 wt% methane; the production is carried out by. Hydrogenolysis of a hydrocarbon fraction which, at atmospheric pressure, has a boiling temperature of less than about 400 ° C., in the presence of a special catalyst. ^:

It is known that from hydrocarbon- ' Fractions in the presence of hydrogen can obtain hydrocarbons that have a lower Have molecular weight as the starting product. This conversion can be thermal as well be catalyzed.

From an economic and commercial point of view however, it is less easy to find hydrocarbons with two or more carbon atoms per molecule. with high yields essentially in methane. convict. .

One of the objects of the present invention is that the conversion of hydrocarbons / with at least two carbon atoms per molecule mostly in high purity methane by -25. leads. . . .

The method according to the invention is in particular through the use of a special catalyst characterized specifically for the very selective extraction of high purity methane aligned by hydrogenolysis and hydrocarbons with more than two carbon atoms per molecule is.

The type of catalyst used in the present invention is not only characterized by a very selective behavior in carrying out this reaction, but also through a very high level of stability and service life. .

The reactions that cause the lowering of the molecular weight of hydrocarbon fractions and called degradation-hydrogenation or hydrocracking are generally known under elevated pressure with hydrocarbon products carried out that have high molecular weight $ they have been working von Bergius and then those of the I.G.-Farben-Industrie.

However, this work was particularly intended to obtain fractions that were easier than the batch treated are (fuels or liquid gasolines), being bituminous coal Subjected to printing from 2o to 3o MPa. Later has The petroleum industry uses this technique on converting heavier products with little Commercial value in lighter products, such as gas oil, naphtha, gasoline, LPG etc. is applied to the one considerably higher, have market value.

The aim of the present invention is the complete and profound hydrogenolysis of hydrocarbons and the recovery of mostly methane as a reaction product Batches of the type mentioned above. The gases obtained contain at least 95 wt .- # methane.

For this purpose a catalyst is used as a hydrogenolyeing agent or

to »■■ ■ · '*

ft · ·

several metals from group VIII of the periodic table, namely iron, cobalt or nickel are: ' holds.

The Group VIII metal or metals are on .throwed over a suitable carrier and you must according to the invention one or more metallic elements (or a derivative thereof) from the Group chromium, molybdenum, tungsten, titanium, zircon and hafnium, added

^ ° It was found that catalysts that at the same time on the one hand at least one metal from Group VIII and on the other hand at least one So-called additional element from the group of chromium, ■ molybdenum, tungsten, titanium, zircon and hafnium.

. contain their selectivity in the hydro

• to increase the genolysis reaction very considerably seem; this selectivity leads to the production of a very pure methane, with the catalysts at the same time have a considerably longer service life. As a result, the Regeneration of the catalyst at the end of the cycle is facilitated and becomes a regenerated «. Catalyst leads, the initial activity and selectivity of which is practically recovered.

It should be noted here that it does so in this way.

obtained methane as a gaseous fuel increased calorific value and for various other industrial purposes, e.g. for the synthesis of products such as carbon disulfide, Hydrocyanic acid, carbon tetrachloride, Chloroform, etc .; so there is an economic one Interest in a process and a catalyst according to the present invention,

• ··

after which one methane under satisfactory economic Conditions can receive.

The reaction consists in getting the hydrocarbon or the hydrocarbons which are the raw material to be converted, allowed to react with hydrogen in the presence of a suitable catalyst; under suitable The carbon-carbon bond is broken under pressure and temperature conditions and hydrogen attached to the free bond) it should be noted that this hydrogenolysis Eeaktion is strongly exothermic, as can be seen from the following examples:

C ₂ H ₆ + H ₂ -2H ₄ C + 65 * ooo joules / mole C ₅ H ₈ + 2H _{2 -5H 4} + 121,0OO joules / mole ^σ 4 ^Η 1ο ^{+ 5H} 2 '" ^4H 4 ^{C + 1} 73,000 joules / Mole etc.

This exotherm leads to a considerable Temperature increase through the catalytic bed -and can quickly deactivate the catalyst cause by destruction of the solid and consequently an increased drop in selectivity, from which the formation of more or less coked product precipitates on the catalyst surface and consequently a very strong deactivation results.

. . It is this considerable exothermicity that directs the conversion towards the production of carbon and hydrogen by thermal dissocitation of the Jo hydrocarbons from.

To avoid this sharp rise in temperature caused by the

To avoid catalytic bed, one must be special Take precautions to effectively remove the heat generated by the reaction.

For example, those commonly used in hydrocracking reactions can be used

Use reactors that allow the calories generated to be distributed, e.g. either a multi-tube reactor with external cooling or a series of small reactors with between-Ίο switched heat exchangers, or a reactor with several stages between the Includes stages cooling devices, etc .. As Means for releasing the calories formed. one can see the gases formed during the reaction . use after it has cooled down. This is done in such a way that one Cycle degree of these gases of at least 1o / 1 (molar) (cycle gas based on the total batch) guaranteed

The metals used in the catalyst. Group VIII does not belong to the precious metals of this group (metals of the platinum family), because the hydrogenolysing power of these noble metals less "profound" is what shows in a much lower methane yield than that · the is obtained with at least one metal from the iron, nickel and cobalt group, preferably nickel. However, small amounts of precious metals from the platinum group can be used as a second additional element as indicated later.

Iron, cobalt or nickel are coated on a suitable support, which is preferably has no acidic properties, e.g. aluminum oxide,

Silica-alumina, silica-magnesia, Coal and silicon dioxide etc.

A silica is preferably used with

ο a specific surface area of 5o to 4oo m / g, expediently 1oo to 3oo m / g, with a porous

. Total volume of ο.4 to 1.2 cnr / g, preferably 0.45 to 0.8o cnr / g, with the mean pore diameter generally between 5 and 15 mm and pores with a diameter of less than 2 mm are avoided

A particularly suitable catalyst contains nickel in conjunction with silicon dioxide. The silicon dioxide does not combine with the nickel or nickel oxide, and such a catalyst, the adding an additional metal, as mentioned above, is particularly effective in cracking of parai ^ .in or cycloparaffin molecules to Methane,

The iron and / or cobalt and / or nickel content (expressed as a metal element) is 0.5 to 50 wt .-%, based on the total mass of the ready-to-use catalytic converter. The content of. additional metal (expressed in metal elements) from the group consisting of chromium, molybdenum, tungsten, titanium, zirconium and hafnium is o, o1 to 2o wt .- #, preferably 0.1 to 10 wt .- ^, in particular 0.3 to 0.8 wt. If you use nickel, it amounts to the preferred nickel content 15 to 25 Gev »- #.

Moreover, the catalyst can as a second additional metal small amounts of precious metals from the platinum family include, for example, o, o1 to 5 wt -.% Platinum or palladium, or iridium, or rhodium

etc ·, preferably o, o1 to 1 wt .- ^ (expressed in metal elements).

The catalyst is generally by impregnating the selected support with a . prepared aqueous solution that contains the element or elements that one on the Wants to knock down the porter

Impregnation can be simple if one wants to introduce the chosen metals at once, whereby

"Io is one solution of the ingredients used. However, one can also apply the active elements separately in several successive impregnations used wobei.man different solutions containing 3 ^ewe ils one of the catalyst components contain ·

In the case of successive impregnations, one generally leaves on each impregnation a two-hour drying at about 100 to 110 ° C followed under dry air, after which the solid was two hours at a temperature of Calcined from 25o to 50o ° 0 in dry air Then the solid is left under drier Cool air to room temperature and then leads the following impregnation by

For example, the support can be in contact with the impregnating solution for 0.5 to 6 hours, preferably 1 to 2 hours stay.

For the following examples, a catalyst has been prepared whose support is a silica with a surface of 150 m / g, a porous Volume of 0.5o cmvg ^ a mean pore diameter

- 1ο -

knife of 14 mm, iet and that no porosity with pores with a diameter of less than 5 mm «

100 g of this carrier, in the form of beads with 2 mm in diameter, are impregnated at room temperature with 5o cm * of a solution of nickel nitrate, which contains 40 wt .- ^ nickel. The solid is left and the solution in contact for 2 hours and then pour the impregnated solid into a Drying cabinet, where you can put it under a stream of dry air for 2 hours at a temperature of 11o ° C dries.

The dry catalyst is then placed in an oven where it progressively (within an hour) brought to 450 ° C under a stream of air dried over activated alumina will; then it is left at this temperature for a further 2 hours.

The resulting product is then impregnated with 5o crn ^ of a solution containing 1 wt -.% Molybdenum in I'orm of ammonium molybdate contains Mo *. Then proceed as after the application of the nickel.

The calcined catalyst is then placed in the reactor under a stream of hydrogen at a temperature . reduced from 2oo to 5oo ° C within 1 to 6 hours; in the present example it was 2 Hours at 300 ° C.

The finished catalyst contains;

20% by weight of nickel and 0.5% by weight of molybdenum. ·.

You can then add the hydrocarbon charge Introduce simultaneously with hydrogen, in a sufficient amount so that all the hydrocarbons introduced can • be converted into methane; further a dilution gas is added at the same time, which may be methane to remove the calories formed during the reaction.

The amount of hydrogen introduced is essentially limited to what is absolutely necessary (theoretical Amount) for the total hydrogenolysis of the hydrocarbons to methane and for the hydrogenation olefins to paraffins and aromatic hydrocarbons to cycloparaffins (if those in the batch) are limited. However, the process requires large quantities Hydrogen: but the nuclear reactors can

'and indeed at night.

• These can be supplied cheaply by electrolysis of water.

• According to the invention, the conversion is preferably carried out at temperatures of about 34o to 50 ° C, expediently 35o to 4,000 ° C .; in any case to avoid the use of temperatures above 600 ⁰ C, since then reactions were strongly abound, which lead to coke formation.

If the catalyst surface is caused by coke formation is dirty, the catalyst can be regenerated by burning the coal precipitate removed with an oxygen-containing gas.

This oxidation phase is followed by rinsing with an inert gas, a reduction phase indicates the presence of hydrogen. This reduction will carried out in the same way as indicated above.

One holds in the reaction medium. a total pressure of 0.1 to 10 IPa, preferably 5 to 6 MPa upright

During the reaction, the flow rate of the reaction mixture through the catalytic bed about 0.1 to 10 parts by volume of batch, per part by volume of catalyst and per hour, preferably 0.5 to 4 parts by volume of batch per. Part by volume of catalyst and per hour

'.15 The amount of cycle gas to be introduced is adjusted so that you get too high temperature. Increases at any point in the catalytic bed avoids.

A part of the methane obtained can preferably be used as cycle gas,

example 1

1o cnr of the same as above are placed in a reactor described prepared catalyst

After v-uem the reactor at room temperature with a gas. (methane or nitrogen), the catalyst is reduced for 2 hours at a Temperature of 4-5o ° C with. Hydrogen·

Then bring the temperature of the catalytic

Bed to 37o ° C and the pressure to 5 MPa, whereby . the amount of hydrogen is 63 l / h.

A batch of the following composition is now initiated:

. Οξ paraffins. .32 wt .- ^. · Methylcyc lopent an 28 wt .- #

Cyclohexane. 35 wt .- #

Benzene 5 percent -.%

100 sulfur content about 1 ppm

Nitrogen content about 1 ppm

This batch is mixed in an amount of 2o cnr / h with nitrogen in an amount of I5o l / h initiated. This nitrogen will ■ used to remove the calories released during the reaction.

The flow rate is 2 and the hydrogen / hydrocarbons molar ratio equal to 1o, 3

The composition of the hydrocarbon product at the reactor outlet is as follows (after 50 hours):

^C 1 96.2o Weight # C ₂ o, 3o Weight % ^G 3 o, 2o Wt .- ^ C ₄ o, 3o Weight ίέ ° 5 o, 2o Weight # ° 6 1.2o Weight % ^C 7

Methylcyclopentane o, 55 wt -.% Cyclohexane o, 85

■ - 14 -

Benzene o _t 2o

Average molecular weight 16.5

The total degree of conversion is 97 »2 % and is distributed as follows:

^C 6 ⁹⁶ » ² #

Cr, 100 _t O %

Methylcyclopentane 98, oo

Cyclohexane. 97 “6o

Benzene 96.9

The selectivity of the conversion to methane is 98j 9 #.

Example 2 (comparative experiment)

In this example, the reaction temperature is fixed at 32o ° C while all conditions remain unchanged.

fixed at 32o ° C, while all other reaction

The hydrocarbon product leaving the reactor contains only 11.4% by weight of methane and the selectivity for conversion to methane is only 34.8 %.

Example 3

This example compares the development of two catalysts as a function of time. . One of the catalysts is that used in Example 1 (2o wt .- # nickel and 0.5 % molybdenum); it is referred to as A. The second catalyst contains only 20 % nickel and is designated as A *.

The test conditions are the same as in example 1.. .

The results obtained are shown in Table I.

Table I.

Test duration 5o 1oo 25o 5oo Catalyst A - methane am
Output (Gew # - #)
. selectivity 96.2
98.9 96.5
98.8 96.1
98.7 95.6
98.5 Catalyst A ¹ - methane am
Output TGew -%)
selectivity 96.4
98.8 96.2
98.7 9o, 4th
95.9 78.5
87.2

Example 4-

The following catalysts B to F are prepared by the method used for catalyst A.

All catalysts contain 2o wt .- # nickel and are distinguished by the additional element. Catalyst B contains o, 5 wt .- # chromium catalyst contains o C, 5 wt .- ^ tungsten catalyst D o contains 5 wt -% of the titanium catalyst E contains 0.5 wt .- # zircon. Catalyst F contains 0.5% by weight of hafnium

With these catalysts one leads long-term. search through.

The results obtained are given in Table II.

Test duration 5o 1oo 25o 5oo Catalyst B # methane am 96.3 96.3 96.2 95.9 exit selectivity 99.1 99.1 99 99 Catalyst 0 % methane am 96, -5 96.3 96.2 95.8 exit selectivity 99 .98.9 98.8 98.4 Catalyst D # methane am 96.4 96.2 96.3 95.9 exit selectivity 98.8 98.7 98.9 98.3 Catalyst E % methane am 96.6 96.4 96.4 95.9 exit selectivity 98.7 98.5 98.8 98.4 Catalyst F %> methane am 96.1 96.1 96.3 95.6 exit selectivity 98.4 .98.5 98.6 98.3

Example ^

Repeat Example 1 and uses a catalyst of 2o wt -.% Iron and o, 5 wt .- # molybdenum.

Contains the hydrocarbon product leaving the reactor after a test duration of 500 hours 95.1 wt .- ^ methane, the selectivity of the conversion in methane is 97.4. With a catalyst that contains only 20% iron without molybdenum, the Methane content of the hydrocarbon product leaving the reactor after a test duration of 500 hours 74.7 wt .- ^, the selectivity of the conversion in.

Methane is 58.8
Example 6

Repeat Example 1 and uses a catalyst of 2o wt, - # cobalt and o, 5 wt -.% Contains molybdenum.

The leaving the reactor after 5oo hours test duration hydrocarbon product contains 95 »4- weight _e -5l6 methane, the selectivity of the conversion is 97" 9 · with a catalyst containing only 2o% cobalt without molybdenum, the methane content of the the hydrocarbon product leaving the reactor after a test duration of 500 hours. 77 »6 wt« - #, the selectivity of the conversion to methane is 86.4 ·

Claims (1)

Claims Processes for the production of methane by hydrogenolysis a batch consisting of hydrocarbons with at least two carbon atoms per molecule consists,· characterized, that one works in the presence of a catalyst, which contains the following components: a) A carrier from the group of aluminum oxides, Silicon dioxide-aluminum oxides, silicon dioxide magnesia, carbon and silicon dioxide, ■ b) 0.5 to 50 wt .- # of at least one metal of Iron, nickel and cobalt group, as well as c) o, o1 to 20 wt. - # at least one so-called Additional metal from the group of chromium, molybdenum, tungsten, titanium, zircon and hafnium. 2. The method according to claim 1, characterized, ' that the catalyst 15 to 25 wt ..- # Nickel and 0.3 to 0.8 wt. # of the additional metal. 3. The method according to claims 1 and 2, characterized-, that the catalyst support is silicon dioxide '. . M-. Method according to claim 3 »
characterized, that the silicon dioxide has a specific surface from 50 to 4-oo m / g and a porous Total volume from 0.4 to 1.2 cnr / g, with the mean diameter of the pores between 5 and 15 mm and practically no pores Has a diameter of less than 2 mm. 5. Process according to Claims 1 to 4, characterized in that the catalyst also contains 0.01 to 5 % of a metal from the group of platinum, iridium, palladium and rhodium. 6. Process according to claims 1 to 5 » characterized, that one at a temperature of 34o to 5oo ° 0 is working· 7. Process according to Claims 1 to 6, characterized in that that the ready-to-use catalyst before. contact with the batch of hydrogen treatment is subjected.