US1995136A - Production of hydrocarbons rich in carbon from those poorer in carbon - Google Patents

Description

Patented Mar. 19,- 1935 PRODUCTION OF HYDBOOARBONS RICH IN CARBON FROM THOSE POORER 1N CAR- BON Fritz Winkler and Paul Feller, Lndwlgshafen-onthe-Rhine, Germany, asignors to I. G. Far-benindustrie Aktiengesellschaft,

the-Main, Germany art-on- No Application July is, 193:, Serial 4 Claims.-

The present invention relates to improvements in the production of hydrocarbons rich in carbon from those poorer in carbon, in particular to the production of acetylene from gaseous hydro- 5 carbons of the methane series.

It has already been proposed to convert gaseous or voporous hydrocarbons in particular those from the methane series, by incomplete combustion with gases comprising free oxygen, such as pure oxygen or gases containing or supplying the same into hydrocarbons richer in carbon, by

which term we mean hydrocarbons in which the percentage of the carbon in the molecular weight amounts higher than with the initial hydrocarbons, as for example into acetylene. The high temperature necessary for the formation of the hydrocarbons richer in carbon is produced by the combustion of a part of the gas. The hydrocarbons or the oxygen or both (separately) may be preheated.

We have now found that considerably greater yields of hydrocarbons richer in carbon are obtained from methane or vaporized homologues of methane by preheating the said methane or homologues thereof and then subjecting the resulting gases to incomplete combustion at a temperature above 1000 C., to such an extent that a substantial formation of olefines takes place. By incomplete combustion we mean a combustionwith such amounts of free oxygen that hydrocarbons still remain in the gas. Preferably from 5 to parts of oxygen are employed for each parts by volume of hydrogen contained in the free or combined state inthe gases to be subjected to incomplete combustion. The particular amount of oxygen depends on the nature of the hydrocarbons to be converted and on the content thereof in the gas. At least 5 per cent of the methane hydrocarbons should be converted into olefines in the preheating step. The term vaporized hydrocarbons is intended to include not only gaseous or vaporous hydrocarbons but also liquid hydrocarbons in the form of mist. When starting from coke oven gases or natural gases containing more or less large amounts of homologues of methane, it is necessary to employ a temperature of from about 800 to about 900 C. during the preheating, when starting from crackinggases or mineral oil distillation gases containing larger amounts of gaseous methane homologues suchas propane and butane a temperature of from about 500 to about 800 C. is usually sufiicient and when starting from gaseswhich mainly or exclusively consist-of higher homologues of methane than butane a tempera- In Germany July 26, 1932 ture of from about 400 to about 600 C. suffices.

When employing pure methane or gases containing methane as sole hydrocarbon considerably higher temperatures, namely from 1000 to 1200 C. or more are necessary for the preheating.

The particular temperature to be selected in each case is dependent on the partial pressure of the hydrocarbons, such as methane, present in the gas and may be easily determined by'a preliminary test. Under the said temperature conditions, considerable amounts of olefines are formed during the preheating and in the subsequent incomplete combustion considerably higher yields of acetylene are obtained than by an incomplete combustion without preheating or while preheating to lower temperatures. Moreover, the process according to this invention has the advantage that inorder to obtain the reaction temperature only a small amount 4 of gas need be burned and, furthermore, it is the hydrogen and methane present in the initial gases and/or formed during the preheating which mainly feed the'combustion. The higher yields of acetylene are probably due to the facts that firstly the materials are already in a preheated state and that therefore not so much heat is tion of a great heat and that thirdly the olefinesformed are more readily converted into acetylene than are the methane hydrocarbons. The waste heat of the reaction gases may be employed for the preheating.

The oxygen or the gas containing oxygen is also preferably preheated in order to obtain temperatures as high as possible and small combustion zones. The preheating of the gases or vapours containing hydrocarbons is preferably carried out in pipes having walls constructed of materials which do not give rise to the formation of deposits of carbon at high temperatures, as for example carborundum or other silicides orsteels coated with chromium oraluminium, or ceramic materials provided with glazes ofinorganic salts, and the incomplete combustion is preferably carried out in pipes or in heat-accumulators (discontinuously) while producing an inverted flame or by surface combustion; it is of advantage to of carbon black during the incomplete combustion, to dilute the methane hydrocarbons to be converted with inert gases; for this purp se a part of the reaction gases freed from acetylene may be employed. g

In all cases it is advantageous so to work that the reaction products are cooled rapidly.

The gases richer in carbon, as for example the acetylene formed, may be recovered'irom the gas mixtures obtained by the incomplete combustion by washing with organic solvents as for example with hydrocarbon oils or with liquid ketones such as cyclohexanone'; the gases-may also be directly further worked up, as for example into acetaldehyde or benzene.

In the incomplete combustion of gaseous or liquid hydrocarbons, such as methane and its homologues or olefines, with oxygen or gases containing oxygen for the preparation of hydrocarbons richer in carbon, in particular acetylene, the high temperatures of more than 1000.C. necessary for carrying out the reaction cause a far-reaching decomposition of the non-oxidized higher hydrocarbons into hydrogen, methane and carbon, 1. e. into less valuable products.-

We have further found that in the process hereinbefore described the incomplete combustion is rendered far more economical and more advantageous technically by exposing the initial hydrocarbons as such, before the incomplete combustion, to such high temperatures that not only olefines but also substantial amounts of liquid, in particular aromatic hydrocarbons are formed, the liquid hydrocarbons being separated and recovered as such before the further treatment. Preferably more than 20 com. of liquid hydrocarbons are formed from each cubic metre of initial hydrocarbons, but the advantages gained by this manner of working are also remarkable if smaller amounts of liquid hydrocarbons are formed.

This modification of the process according to the present invention is also applicable with great advantage to gaseous or vaporized olefinic hydrocarbons, such as ethylene, propylene and butylenes or gases containing the same, such as cracking gases, oil gas, coke oven gases, and gases obtained by the low temperature carbonization of brown coal. The particular temperatures employed for bringing about the said formation of liquid hydrocarbons depend on the nature of the initial hydrocarbons and also on the pressure used. At ordinary pressure methane, for example, is converted into liquid hydrocarbons at temperatures between about 900 and l00O 0., ethane, propane, and butane are converted at between about 550 and 900 C., ethylene, propylene and butylenes also at between about 550 and 900 C. Under pressures between 5 and 300 atmospheres ethylene, propylene and butylene are converted, depending on the height of the pressure, at temperatures between 250 and 600 C. Dilute gases are converted at higher temperatures than concentrated gases. At higher rates of flow higher temperatures are required.

The process according to this invention ofiers various advantages.

Not only acetylene, but considerable amounts of valuable liquid, in particular aromatic, hydrocarbons are obtained from cheap initial materials, such as methane, its homologues, olefines and gases containing the same, such as natural gases, cracking gases, distillation gases, waste gases from the destructive hydrogenation of coals, tars and oils, coke oven gases, vaporized (which term also includes nebulized) cheap oils and oil residues, a much better exploitation of the first stage and diluted with hydrogen, may.

by reason of but slight deposition 5f carbop'black, be carried out more readily industrially and with practically the same yields as when working with undiluted hydrocarbons.

The process may be carried out for example by heating the hydrocarbons in the form of gas, vapour or mist at ordinary or increased pressure either continuously, for example in pipes, or discontinuously in Cowper apparatus, which are preferably provided with wall material which does not lead to the deposition of carbon, until considerable amounts of liquid hydrocarbons are formed. The reaction products are then cooled, the liquid hydrocarbons removed by known methods, as for example with washing oil, by compression, with active, carbon or with active silica, and the gas mixture consisting of olefines. methane and hydrogen subjected to incomplete combustion with oxygen or gases containingoxygen. The incomplete combustion is effected, preferably with as great a speed of flow as possible, in pipes or heat-accumulators, with inverted flame, by surface combustion or, preferably, as hereinbefore described. In all cases the heat produced by the incomplete combustion may serve for the heating in the first stage of the process. The gases formed in the first stage may also be diluted as desired with inert gases.

The following examples will further illustrate the nature of this invention but the invention is not restricted to these examples.

Example 1 10 litres of oxygen per hour are passed through one arm of a forked quartz pipe having an internal diameter of 2 millimetres while through the other arm are passed 20 litres per hour of a mixture of homologues of methanehaving the following composition:-

Per cent CH4--- 8.0 ("one 14.2 C3Hs 51.9 CsHm 11.9 can 4,5 P1: 4.8 CLHR 0.9 N i 3.8

Per cent COz 2.0

Conn C2H4 9.8 CO 10.0 Hz... 30.5 CH4--- 33.5

Example 2 A gas containing mainly homologues of methane and having the composition:

Per cent CH4 8.0 C2He 14.2 Cs'Hs 51.9 C4H10 11.9 C2H4 4.5 CsHe 4.8 C4112..- 0.9 N 3.8

is passed at a speed of flow of 20 litres per hour and at a temperature of 850 C. through a pipe of V2A-stee1 having an internal diameter of 15 millimetres which has been coated with molybdenum by decomposition of a volatile compound of said metal, as described for example in application Ser. No. 656,630, filed 13th February 1933. While the volume increases by about 50 per cent, a gas mixture having the following composition is obtained:---

Per cent CaHs and C4Hs- 1 Col-I4 34.4

CnH2n+2 (n-being on the average equal to Per cent CO2 2.4

(one 10,2 C2H4 15.4 C0 12.4 H: 28.2 (r-n 28.9 N2- 2.5

The acetylene formed may be recovered by known methods, as for example by washing with organic liquids, or the gas may be further worked up into acetaldehyde or benzene. The heating for the first stage of the process may be effected by the waste heat from the second stage.

' 'What we claim is:--

1. A process for the conversion of a hydrocarbon into a hydrocarbon richer in carbon which comprises heating a gas essentially comprising a vaporized hydrocarbon of the methane series to such a temperature that at least 5 per cent of said vaporized hydrocarbon is converted into olefines, and then subjecting the resulting gas containing olefines to incomplete combustion at a temperature above 1000 C., hydrocarbons richer in carbon thereby being obtained.

2. A process for the conversion of a hydrocarbon into acetylene which comprises heating a gas essentially comprising a gaseous hydrocarbon of the methane series to such a. temperature that at least 5 per cent of said gaseous hydrocarbon is converted into olefines, and then subjecting the resulting gas containing olefines to incomplete combustion at a temperature above 1000 0., acetylene thereby being obtained.

3. A process for the conversion of a hydrocarbon into a hydrocarbon richer in carbon which comprises heating a gas essentially comprising a gaseous hydrocarbon of the methane series to such a temperature that at least 5 per cent of said gaseous hydrocarbon is converted into olefines, and that in addition normally liquid hydrocarbons are formed, removing these liquid hydrocarbons, and then subjecting the resulting gas containing olefines to incomplete combustion at a temperature above 1000 C., hydrocarbons I richer in carbon thereby being obtained.

4. A process for the conversion'of a hydrocarbon into acetylene which comprises heating a gas essentially comprising a vaporized hydrocarbon of the methane series to such a temperature that r acetylene thereby being obtained.

FRITZ WINKLER. mm. FEILER.