US3168592A

US3168592A - Manufacture of acetylene by two stage pyrolysis under reduced pressure with the first stage pyrolysis conducted in a rotating arc

Info

Publication number: US3168592A
Application number: US210890A
Authority: US
Inventors: Mario T Cichelli; Schotte William
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 1962-07-19
Filing date: 1962-07-19
Publication date: 1965-02-02
Anticipated expiration: 1982-02-02

Description

Feb. 2, 1965 M. "r. CICHELLI ETAL 3,153,592

MANUFACTURE OF ACETYLENE BY TWO STAGE PYROLYSIS UNDER REDUCED PRESSURE WITH THE FIRST STAGE pyaomsxs CONDUCTED IN A ROTATING ARC Filed July 19, 1962 NYDROOARBON FEED OOOLINO WATER OUTLET POST-ARC HYDROOARBON 35 INLET POST-ARC NYOROGARBON INLET COOLING WATER INLET PRODUCT GAS T INVENTORS MARIO T. CICHELLI OIJENCH WATER WILLIAM SCHOTTE BY whrw ATTORNEY United States PatentO 3,168,592 MANUFACTURE 9F ACETYLENE BY TWO TAGE PYROLYSES UNDER REDUCED PRESSURE Wl'lll THE FIRST STAGE PYROLYSHS CQNDUCTED EN A ROTATHNG ARC Mario T. Cichelli and William Schotte, Wilmington, Del., assignors to E. I. du Pont rle Nemours and Company, Wilmington, Del, a corporation of Delaware Filed .luly 19, 1962, Ser. No. 210,890 Claims. (Cl. 260-679) This invention relates to an improved process for the manufacture ofacetylene, and particularly to a two stage pyrolysis under reduced pressure in which a lower hydrocarbon .is pyrolyzed to acetylene in a rotating electric are as a first stage, and part of the heat of the hot output gases thereafter is immediately utilized to pyrolyze a hydrocarbon of higher molecular weight to acetylene by the post-arc injection of the higher hydrocarbon, followed quickly by quenching to a low temperature at which the individual integrity of the products is preserved.

The pyrolysis of hydrocarbons to form acetylene is well known in the art and there are numerous ways of accomplishing the heat transfer, such as by contact of the feed stock with combustion products, as described in US. Patent 2,790,838, or by the arc-heating of a carrier gas such as hydrogen, as taught in US. Patent 2,916,534. In both of these approaches, however, non-essential gases are present in the reaction zone, and this is objectionable because the equipment size must be increased proportionately. Moreover, operating temperatures must be very high in processes relying on thermal dissociation of gases such as hydrogen or nitrogen as the heat transfer agency,

and this is accompanied by excessive heat requirements together with high thermal stressing of apparatus components. Hydrocarbon synthesis by methane pyrolysis followed by reaction within 2-8 seconds time with various hydrocarbons is taught in US. Patent 2,197,257; however, acetylene per se is apparently not obtainable as a product.

A primary object of this invention is to provide a process for the manufacture of acetylene which operates throughout at least one stage at a relatively low temperature and thus is conservative in heat demand. Another object of this invention is to provide a process for the manufacture of acetylene which utilizes the available heat more efficiently than has hitherto been possible. Another object of this invention is to provide a process for the manufacture of acetylene which is accompanied by a lower carbon monoxide adulterationas a result of the terminal quenching of products. The manner in which these and other objects of this invention are obtained will become clear from the following detailed description and the drawing, which shows schematically apreferred apparatus for carrying out the process of the invention.

Generally, the process of this invention comprises,

(a) Passing a feed of gaseous hydrocarbon of l-3 carbon atoms through a rotating electric are having a frequency of rotation in excess of 2000 rev./sec. at a rate sufiicient to pyrolyze said hydrocarbon to acetylene and produce hot reaction gases having a temperature in excess of 1700 C.;

.(b) Admixing with said hot reaction gases leaving said electric are a second gaseous hydrocarbon which has a molecular weight higher than the molecular weight of said feedrhydrocarbon but not higher than about 150 at a rate sufficient to pyrolyze said second hydrocarbon to acetylene and produce a mixture of hot gaseous reaction products having a temperature at least about 200 C. below the temperature of the hot reaction gases leaving the electric are but not below 1300 C.;

3,168,592 Patented Feb. 2, 1965 (c) Maintaining the pressure in the reactor at less than 500 mm. Hg during said pyrolyses;

(d) Quenching the mixture of hot gaseous reaction products to a temperature below about 300 C.; and

(e) Employing a residence timefrom arc to quench of less than 0.01 second.

By such process, a high conversion of feed hydrocarbon to acetylene is produced in the first stage pyrolysis by passage of the feed hydrocarbon through the rotating arc, and additional acetylene, equal to at least about 8% of the total acetylene, is formed by pyrolysis of at least part of the second hydrocarbon in the second stage, concomitant with the cooling of the are product to an interim temperature level, followed by a quick cooling of the entire effluent to below about 300 C. to forestall intercombination or polymerization reactions involvingacetylene. Due to the combination of conditions, there is obtained good conversion of the second hydrocarbon in the second stage pyrolysis to acetylene with the formation of little or no ethylene and like olefins. Thus, a sig-' nificant part of the energy, required to produce the high conversions of feed hydrocarbon to acetylene in the first stage, is recovered in the production of additional amounts of acetylene in the second stage, resulting in an over-all economy in the utilization of electric power per unit weight of acetylene. Also, the combination of conditions has the further advantages of decreasing the formation of by-product CO, carbon, and losses of acetylene through side reactions and. polymerization.

It is essential to good result that there be careful maintenance of a temperature above a first high level of about 1700 C., preferably at about 2000" C. to about 2800 C., adapted to pyrolyze the pre-arc hydrocarbon feed. to acetylene in the first stage and above a second interim level above about 1300 C., preferably above 1600 C., in the second stage but lower than the first to effect an eflicient pyrolysis of the post-arc feed to the second hydrocarbon to acetylene and to cool in large part the products of the first pyrolysis, and finally that there be rapid quenching of the full effiuent to a. temperature below about 300 C, Consequently, the proportion of the second hydrocarbon employed in the second stage or post-arc feed must be such thatthe sum of its sensible heat demand and the heart of cracking it to acetylene does not exceed that which will bring the temperature of the products from the upstream pyrolysis down to an interim temperature about 1300" C., preferably in the range of about 1600 C. to about 2000 C. Also, the amount of the hydrocarbon employed in the post-arc feed should be sufficient to bring the temperature of the pyrolysis products down by at least about 200 C. below the temperature of the gas leaving the arc, which usually will result in the production of at least about an 8% additional amount of acetylene. Preferably, the amount of post-arc hydrocarbon will be sulficient to bring the temperature down by about 400 C. to about 900 C. The amount of post arc hydrocarbon required will vary with its temperature, the other conditions of operation, the loss of heat from the reactor, and the like. Once the reduction in temperature in the second stage pyrolysis is effected, it is necessary to bring the total product efilu-ent to nonreactive temperatures as quickly as possible to prevent losses of acetylene by both reaction and polymerization.

It has been found that the rapid mixing afforded by the rotating electric arc, having a frequency of rotation in excess of 2000 rev./ sec. (revolutions per second), is necessary to the secondary pyrolysis stage in the manufacture levels of turbulence which promote rapid mixing. In addition, the arc imparts a high swirling velocity, typically 200 to 400 ft./sec., to the arc gas, which further improves the mixing with the hydrocarbon added below the arc. Such rapid mixing is necessary to bring the arc-gas and post-arc feed to thermal equilibrium in a very short period of time, thereby yielding a high conversion to acetylene. Electric arcs rotated by permanent magnet assemblies, or arcs which, in effect, rotate, as in the case of the so-called polyphase traveling arcs" which strike in sequence from one pair of electrodes to a neighboring pair, with all of the electrodes arranged in a circular pattern, are also operable and the term rotating arc as used in the claims is intended to encompass all of these together with their equivalents. At the same time, it is intended to exclude therefrom arcs displaced primarily by impingement of the gas streams, as these are altogether too erratic to be of use.

The pre-arc hydrocarbon feed to the rotating electric arc can be any saturated or unsaturated hydrocarbon having from one to three carbon atoms, or mixtures thereof, although methane and propane individually are particularly preferred as a matter of current economics. The second hydrocarbon, employed in the post-arc feed, is of even wider selection and, in general, includes any hydrocarbon having a higher molecular Weight, a larger number of carbon atoms, than the hydrocarbon constituting the principal part of the pre-arc feed up to, and including, a molecular weight of 150, either solely or in admixture one with another. Usually, the post-arc hydrocarbon will have a molecular weight in the range of 44 to 150.

'The purpose of the post-arc hydrocarbon feed is twofold, i.e., (1) to utilize part of the heat of the product leaving the arc to produce additional amounts of acetylene by pyrolysis of the hydrocarbon in the post-arc feed and (2) to cool the product gases from the arc. Both of these objectives can be attained to a high degree by employing a relatively hot post-arc feed which, advantageously, can have a temperature up to about 1100 C. In this manner, it is possible to introduce a high proportion of post-arc hydrocarbon compared to the arc eflluent gas volume and, where the post-arc feed is brought to temperature by waste heat, or at least by other heating means such as oil or gas burners or the like, which are usually lower in cost than are heating, there is realized an over-all heating economy. It will be understood that the heating of the post-arc hydrocarbon should be conducted at temperatures below those giving troublesome coke formation or uncontrolled cracking as a side reaction and this imposes a practical limit on the heat content imparted to the post-arc hydrocarbon. Under some circumstances, it is desirable to employ either a cold (room temperature) post-arc hydrocarbon or a heated hydrocarbon to which is added a portion of room temperature hydrocarbon as a means of effecting close heat control for the entire process, and this is entirely feasible and within the contemplation of this invention. In addition, there can be a preselected pattern of introductions of different post-arc hydrocarbons or mixed post-arc hydrocarbons, either at the same or different temperatures, so as to obtain a thermodynamic balance in time with respect to the progressive thermal demands of the process, as can be advantageous in going from start-up to steady state operation, or in going from one feed gas to a different feed gas, or the like.

Typical examples of suitable hydrocarbons for use in the post-arc feed include, but are not limited to, propane, butane, toluene, divinylacetylene, and natural gasoline. For economic reasons, the post-arc hydrocarbon, as well as the pre-arc hydrocarbon, should be gaseous, that is it should be in the form of a gas or vapor. Thus, if the hydrocarbon is liquid at standard conditions of temperature and pressure, it should be vaporized and fed into the reactor in vapor (gaseous) form.

The process of this invention is conducted at an absolute pressure below about 500 mm. Hg, preferably at about 100 to about 350 mm. Hg. Such low pressures produce high conversions of the hydrocarbons to acetylene, minimize carbon formation and avoid losses of acetylene through side reactions and polymerization.

Also, it is vital that the terminal quenching of the entire process efliuent to temperatures below 300 C. be effected as quickly as practicable, with a residence time of gas between arc and quench of less than 0.01 second, preferably of about 0.001 to about 0.003 second. Quenching by cold water spray has proved eifective and convenient; however, other methods of quenching, as by contact with solids or through the conjoint use of solids and liquids or the like, are also suitable.

Referring to the drawing, a small scale reactor utilized a 1.75" I.D. copper pipe shell 10 measuring 12" long from the top end to the upper end of quench nozzle 37, shell 10 abutting annular copper flanges 18 at the top and 28 at the bottom. The spacing of quench nozzle 37 above flange 28 was several inches; however, this distance is not critical. Companionate copper flanges 20 and were provided at the top and bottom, respectively, electrically insulated from their adjacent flange elements by

gaskets

21 and 29, which also sealed the interior of shell 10 against vacuum leakage, and the assembly held together by conventional means, not shown, preserving the individual electrical isolation of at least the two upper flanges.

Shell 10 was enclosed within a concentric cooling jacket 25 provided with water inlet and

outlet connections

26 and 27, respectively. Cathode 15 was a graphite electrode which, in various runs, ranged from "V2" in diameter carried by a water-cooled copper holder, indicated generally at 16, mounted centrally of flange 20 and coaxial of shell 10. Negative terminal 19 attached to flange 20 provided an electrical connection with holder 16 and cathode 15. Shell 10 constituted the anode, which was in electrical connection through flange 18 with positive terminal 17.

Inlet pipe 11 discharging into shell 10 radially of flange 18 constituted the feed port for hydrocarbon passed to the electric arc, the flow of which was distributed evenly throughout the full cross-section of 10 bypassage through the multiple holes of distributor plate 12, fabricated from ceramic or equivalent high temperature electrical insulator.

A pair of post-arc hydrocarbon injection tubes 35 diametrically opposed one to another was provided opening into shell 10 about 1" below the locus of rotating arc termination a, hereinafter described. A water quencher was used, consisting simply of upstanding water supply tube 36 entering shell 10 at the lower end coaxially thereof, providedwith a spray nozzle 37 located about 7" below region a, adapted to discharge water substantially evenly in a generally radial direction across the shell. Product gases were removed from the apparatus through connection 38 in open communication with the bottom end of shell 10 leading to conventional separation equipment, not shown, disposed downstream.

Arc rotation was effected electromagnetically to give the electric are a frequency of about 4000 to about 8000 rev./sec. through the agency of 5 /2" inside diameter field coil 31 through which was passed a direct current. Coil 31 was disposed coaxially with respect to cathode 15 at a radial clearance of approximately 1% with respect to jacket 25, in a lengthwise position such that the midpoint of the arc struck was located approximately midlength of the coil.

In operation, using methane as the hydrocarbon feed to the arc and propane at room temperature as the postare feed supplied through tubes 35, the pyrolysis will be conducted at a reduced pressure within the reactor of about mm. Hg absolute, which was found to give good conversions and, at the same time, minimized carbon formation. The apparatus hereinbefore detailed had a power consumption of about 50 kw. and the arc zone ending at region a measured about 1" long. The are Was ingabout 7000 revolutions/sec. under a field strength or" coil 31 of 600 gauss. The evenness of arc contacting is an important factor in itself, since we have found that an appreciably higher acetylene yield of the order of 7085% conversion of methaneptypically, to acetylene is thereby obtained independent of other considerations.

In the case of methane, good pyrolysis is obtained at a temperature above 1700 C., whereas propane readily pyrolyzes to acetylene at temperaturesabove 1300 C. Accordingly, methane Was projected through the rotating are at an entering flow velocity of about 7 meters per second (measured at 150 mm. Hg pressure absolute, and 25' C.) into contact with suflicientpropane to bring the over-all temperature to above about 1300 C. prior to water quenching. A limitation of the residence time between arc and water spray of 0.001 to 0.003 second gave good results. The conversion of propane to acetylene varied from 47% to 70%, which thus constituted added production resulting from-utilization of the sensible heat of the products of the upstream arc pyrolysis of the methane. Inaddition, the two stage pyrolysis reduced the amount of carbon monoxide formed during the terminal water quenching, which was very advantageous.

A larger reactor, similar in design to that hereinbefo-re described, also has been used. In this larger reactor, the copper pipe shell had an internal diameter (I.D.) of 3.5 inches; the post-arc injection tubes 35 were. positioned about 2% inches below the locus of the rotating arc termination a; and the quencher spray nozzle 37 was located about 12 inchesfbelow region a; the other dimensions of the equipment'being generally twice those of the smaller reactor. This larger reactor operated with field strengths of up to 1800 gauss, the frequency of rotation of theelec'tric arc also beingin to about8000 rev./sec.

In summary, the pyrolysis of this invention realizes the followingimprovements: (1) a reduction of by-product CO concentrations from a level of /s% with conventional processes to about 0.5 1%, (2) an increase in acetylene concentration from the usual maximum level of 20% to about21-22%, and (3) a reduction in power consumption of about 1 kw.'-hr./lb. C H

The following examples carried out in the apparatus detailed furnish numerical'data comparative of operation with and without post-arc hydrocarbon feed:

EXAMPLE I.EFFECT OF POST-ARC ADDITION OF PROPANE IN 1.75-1N. I.D. REACTOR Case I. Without post-arc addition of propane A flow of 11.4 1b./hr. of commercial grade methane (analyzing 94.1% CH 4.4% C H and 1.5% C H was passed through a 51.8-kw. rotating arc (7000 rev./ sec.)

operated at 320 amp, 162 v., and about 600 gauss. The

pressure maintained in the reactor was 143 mm. Hg absolute. The water-quenched product contained 20.2% C' H 0.2% C H4, and 246% CO. The carbon conversion of methane to acetylene was 80% with apower consumption of 7.0 kW.-hl./1l'). of C H produced.

The net heat input to the gas was 64% of the power supplied or 33.2 kw., the remaining 18.6 kw. being lost to cooling water. The temperature of the hot gas leaving thearc was calculated to be about 2420 C. Under these "conditionathe residence time of the hot gas between arcand quencher was 0.0013 second.

the range of about 4000 i i Case 2. With post-arc addition of propane A flow of 12.0 lb./hrof commercial grade methane (same analysis as above) was passed through a 58.0-kw. rotating are operated at 325 amp., 178 v., and about 600 gauss. The pressure was -9 mm. Hg absolute. Natural grade propane (analyzing 0.3% CH 8.0% C H ,'90.8% C l-I and 0.9% C H was introduced at a rate of 3.1 lb./hr. as a room-temperature gas through two inlets disposed adistanc'e of 1" below the arc. The product gas analyzed 22.5% C H 0.9% C H and 0.5 CO, corresponding to an over-all carbon conversion to acetylene for both the methane and the propane =of 77.8%. If 80% conversion of methane to acetylene is assumed on the basis of operation without propane addition, .the propane to acetylene conversion calculates to about 70%. The power consumption was 6.0 kw.-hr./lb. C H as com pared with 7.0 kW.-hr./lb. for Case 1.

Based on a net heat input to the methane of 64% of the power input, the temperature of the hot gas leaving the att c was calculated to be amout 2800 C. The correspondi'ng residence time between the arc and thejlocation ofthepost-arc addition points was 0.0002 second. With postarc addition of propane, the (temperature of the resulting mixture of hot gaseous reaction products wascalculated to be about .1930 C. A further residence time of 0.0013 second was calculated for the distance between the post-arc addition points and the quencher, giving an over-all residence time of 0.0015 second,

EXAMPLE 2.EFFECT OF POST-ARC ADDITION OF NATURAL GASOLINE IN 3.5-IN. LD. REACTOR Case 3. Without. posture addition of natural gasoline A flow of 170 lb./hr. of natural gas (analyzing 93.2%

CH 3.5% C H 0.1% C H 0.9% C H 0.5% C H 0.8% CO and 1.0% N was passedthrough a 528-kw.

residence time of 0.0011 second for the 12-iI1fldlStanC between the arc and the quencher.

i 0 Case 4. With postarc addition of natural gasoline A how of 170 lb./hr. of natural gas (same analysis as for Case 3) was passed through a 529-kw. rotating are operated at 1150 amp, 460 v., and 1450 gauss. A pressure of 225 mm. Hg absolute was maintained in the reactor. Vaporized natural gasoline (corresponding to 50 mole percent C l-I and 50 mole percent C H at 500 C. was introduced at a rate of 48 lb./hr. through inlets disposed a distance of 2% in. belowthe arc. The product gas analyzed 20.8% .C H 0.4% (1 1-1 and 1.1% CO, corresponding to an overall carbon conversion to acetylene for both the naturalgas and the natural gasoline of 69.4%.

- gas toacetylene on the basis of-operationessentially. identical with Case 3, the natural gasoline to acetylene conversion calculates to 56%. r The power consumption was 4.3 kw.-hr./lb. C H as compared to 5.3 kw.-hr./lb. C H

with a power cons'umptionof 5.3

This corresponds to a temperature of i I about 2200 C. for the hot gases leaving the arc, and a Assuming 73.7% conversion of natural residence time of 0.001 second was calculated for the 9% in. distance between the post-arc addition points and the quencher, giving an over-all residence time of 0.0012 second.

From the foregoing, it will be understood that our invention can be modified extensively without departure from its essential spirit, and it is therefore intended to be limited only by the scope of the appended claims.

This application is a continuation-in-part of our copending application Serial Number 18,956 filed March 31, 1960, now abandoned.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. .A process for the manufacture of acetylene in a reactor, which process comprises (a) passing a feed of gaseous hydrocarbon of 1-3 car- .bon atoms through a rotating electric are having a frequency of rotation in excess of 2000 rev./see. at a rate sufficient to pyrolyze said hydrocarbon to acetylene and produce hot reaction gases having a temperature in excess of 1700 C.; (b) admixing with said hot reaction gases leaving said electric are a second gaseous hydrocarbon which has a molecular weight higher than the molecular weight of said feed hydrocarbon but not higher than about 150 at a rate suflicient to pyrolyze said second hydrocarbon .to acetylene and produce a mixture of hot gaseous reaction products having a temperature at least about 200 C. below the temperature of the hot reaction gases leaving the electric are but not below (c) maintaining the pressure in the reactor at less than 500 mm. Hg during said pyrolyses;

(e) employing a residence time from arc to quench of less than 0.01 second. 2. A process for the manufacture of acetylene in a reactor, which process comprises (a) passing a feed of gaseous hydrocarbon of 1-3 carbon atoms through a rotating electric arc having a frequency of rotation in excess of 2000 rev./sec. at a rate sufiicient to pyrolyze said hydrocarbon to acetylene and produce hot reaction gases having a temperature of about 2000 C. to about 2800 C.; (b) admixing with said hot reaction gases leaving said electric are a second gaseous hydrocarbon which has a molecular weight higher than the molecular weight of said feed hydrocarbon but not higher than about 150 at a rate sufficient to pyrolyze said second hydrocarbon to acetylene and produce a mixture of hot gaseous reaction products having a temperature about 400 C. to about 900 C. below the temperature of the hot reaction gases leaving the electric arc but not below 1600 C.;

(c) maintaining the pressure in the reactor at about 100 to about 350 mm. Hg during said pyrolyses;

(d) quenching the. mixture of hot gaseous reaction products to a temperature below about 300 C.; and

(e) employing a residence time from are to quench of less than 0.01 second.

3. A process for the manufacture of acetylene in a reactor, which process comprises (a) passing a feed of gaseous hydrocarbon of 1-3 carbon atoms through a rotating electric are having a frequency of rotation in excess of 2000 rev./sec. at a rate sufficient to pyrolyze said hydrocarbon to acetylene and produce hot reaction gases having a temperature of about 2000 C. to about 2800 C.; (b) admixing with said hot reaction gases leaving said electric are a second gaseous hydrocarbon which has a molecular weight higher than the molecular weight of said feed hydrocarbon but not higher than about 150 at a rate sufiicient to pyrolyze said second hydrocarbon to acetylene and produce a mixture of hot gaseous reaction products having a temperature in the range of about 1600 C. to about 2000 C. which is about 400 C. to about 900 C. below the temperature of the hot reaction gases leaving the electric are;

(c) maintaining the pressure in the reactor at about to about 350 mm. Hg during said pyrolyses;

(e) employing a residence time from are to quench of about 0.001 to about 0.003 second.

4. A process for the manufacture of acetylene in a reactor, which process comprises (a) passing a feed of gaseous hydrocarbon which consists essentially of methane through a rotating electric are having a frequency of rotation in excess of 2000 rev./ sec. at a rate sufficient to pyrolyze said hydrocarbon to acetylene and produce hot reaction gases having a temperature in excess of 1700 C.;

(b) admixing with said hot reaction gases leaving said electric are a second gaseous hydrocarbon which has a molecular weight in the range of 44 to at a rate sufiicient to pyrolyze said second hydrocarbon to acetylene and produce a mixture of hot gaseous reaction products having a temperature at least about 200 C. below the temperature of the hot reaction gases leaving the electric arc but not below 1300 C.

(c) maintaining the pressure in the reactor at less than 500 mm. Hg during said pyrolyses;

(e) employing a residence time from are to quench of less than 0.01 second.

5. A process forv the manufacture of acetylene in a reactor, which process comprises (a) passing a feed of gaseous hydrocarbon which consists essentially of methane through a rotating electric are having a frequency of rotation in excess of 2000 rev./sec. at a rate suflicient to pyrolyze said hydrocarbon to acetylene and produce hot reaction gases having a temperature of about 2000 C. t about 2800 C.;

(b) admixing with said hot reaction gases leaving said electric are a second gaseous hydrocarbon which has a molecular weight in the range of 44 to 150 at a (e) employing a residence time from are to quench of less than 0.01 second. 6. A process forthe manufacture of acetylene in a reactor, which process comprises (a) passing a feed of gaseous hydrocarbon which consists essentially of methane through a rotating electric arc having a frequency of rotation of about 4000 to about 8000 rev./ sec. at a rate sufficient to pyrolyze said hydrocarbon to acetylene and produce hot reaction gases having a temperature of about 2000 C. to about 2800 C.;

(b) admixing with said hot reaction gases leaving said electric are a second gaseous hydrocarbon which has a molecular weight in the range of 44 to 150 at a rate sufficient to pyrolyze said second hydrocarbon to acetylene and produce a mixture of hot gaseous reaction products having a temperature in the range of about 1600 C. to about 2000 C. which is about 400 C. to about 900 C. below the temperature of the hot reaction gases leaving the electric arc;

7. A process for the manufacture of acetylene in a reactor, which process comprises (a) passing a feed of gaseous hydrocarbon which consists essentially of methane through a rotating electric are having a frequency of rotation in excess of 2000 rev./sec. at a rate sutficient to pyrolyze said hydrocarbon to acetylene and produce hot reaction gases having a temperature in excess of 1700 C.;

(b) admixing with said hot reaction gases leaving said electric are a second gaseous hydrocarbon which consists essentially of propane at a rate sufiicient to pyrolyze said second hydrocarbon to acetylene and produce a mixture of hot gaseous reaction products having a temperature at least about 200 C. below the temperature of the hot reaction gases leaving the electric are but not below 1300 C.;

(e) employing a residence time from are to quench of less than 0.01 second.

8. A process for the manufacture of acetylene in a reactor, which process comprises (a) passing a feed of gaseous hydrocarbon which consists essentially of methane through a rotating electric are having a frequency of rotation of about 4000 to about 8000 rev/sec. at a rate sufficient to p yrolyze said hydrocarbon to acetylene and produce hot reaction gases having a temperature of about 2000 C. to about 2800 C.

(b) admixing with said hot reaction gases leaving said electric are a second gaseous hydrocarbon which consists essentially of propane at a rate suflicient to pyrolyze said second hydrocarbon to acetylene and produce a mixture of hot gaseous reaction products having a temperature at least about 200 C. below the temperature of the hot reaction gases leaving the electric are but not below 1600 C.;

(c) maintaining the pressure in the reactor at about 100 to about 350 mm. Hg during said pyrolyses; (d) quenching the mixture of hot gaseous reaction products to a temperature below about 300 C.; and

actor, which process comprises (a) passing a feed of gaseous hydrocarbon which consists essentially of methane through a rotating electric are having a frequency of rotation in excess of 2000 rev/sec. at a rate sufficient to pyrolyze said hydrocarbon to acetylene and produce hot reaction gases having a temperature in excess of 17 00 C.;

(b) admixing with said hot reaction gases leaving said electric are a second gaseous hydrocarbon which consists essentially of natural gasoline at a rate sufiicient to pyrolyze said second hydrocarbon to acetylene and produce a mixture of hot gaseous reaction products having a temperature at least about 200 C. below the temperature of the hot reaction gases leaving the electric are but not below 1300 C.;

(e) employing a residence time from are to quench of less than 0.01 second.

10. A process for the manufacture of acetylene in a reactor, which process comprises (a) passing a feed of gaseous hydrocarbon which consists essentially of methane through a rota-ting electric are having a frequency of rotation of about 4000 to about 8000 rev/sec. at a rate sufiicient to pyrolyze said hydrocarbon to acetylene and produce hot reaction gases having a temperature of about 2000 C. to about 2800 C.;

(b) admixing with said hot reaction gases leaving said electric are a second gaseous hydrocarbon which consists essentially of natural gasoline at a rate sufiicient to pyrolyze said second hydrocarbon to acetylene and produce a mixture of hot gaseous reaction products having a temperature at least about 200 C. below the temperature of the hot reaction gases leaving the electric are but not below 1600 C.;

References (Iited in the tile of this patent UNITED STATES PATENTS 2,074,530 Baumann et al. Mar. 23, 1937 2,256,174 Schilling et al Sept. 16, 1941 2,985,698 Pechtold et al May 23, 1961 3,073,769 Doukas Jan. 15, 1963

Claims

1. A PROCESS FOR THE MANUFACTURE OF ACETYLENE IN A REACTOR, WHICH PROCESS COMPRISES (A) PASSING A FEED OF GASEOUS HYDROCARBON OF 1-3 CARBON ATOMS THROUGH A ROTATING ELECTRIC ARC HAVING A FREQUENCY OF ROTATION IN EXCESS OF 2000 REV./SEC. AT A RATE SUFFICIENT TO PYROLYZE SAID HYDROCARBON TO ACETYLENE AND PRODUCE HOT REACTION GASES HAVING A TEMPERATURE IN EXCESS OF 1700*C.;