Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C4/00—Preparation of hydrocarbons from hydrocarbons containing a larger number of carbon atoms
  • C07C4/02—Preparation of hydrocarbons from hydrocarbons containing a larger number of carbon atoms by cracking a single hydrocarbon or a mixture of individually defined hydrocarbons or a normally gaseous hydrocarbon fraction
  • C07C4/04—Thermal processes
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G2400/00—Products obtained by processes covered by groups C10G9/00 - C10G69/14
  • C10G2400/24—Acetylene and homologues

Definitions

• This invention relates generally to the pyrolysis of hydrocarbons preferably diluted or admixed with hydrogen to give relatively uncontaminatedmixtures of acetylene and hydrogen as the sole gaseous products. More particularly, the present invention relates to an improved pyrolytic method of obtaining acetylene and hydrogen as essentially the only products of pyrolysis of non-aromatic hydrocarbons having from two to ten carbon atoms by employing a combination of carefully controlled and critical operating conditions.
• a process employing electrical energy has been in commercial operation at the acetylene plant of Chemische 'Werke Huls in Germany. 'This process employs an electric are for heating the gaseous hydrocarbon feed.
• this reactor it isnot precisely known at What temperature the acetylene actually forms from the hydrocarbon; however, it is known that the core of the arc burns at about 3000 C. while at the end of'the reactor tube the temperature is between 1600 and 2000 C. It is readily apparent that while a portion of the reacting feed gases is subjected to are temperature, i.e., around 3000 C., a substantial portion bypasses this hottest part of .the arc and is pyrolyzed at substantially lower temperatures.
• the over-all process involves anessentially uncontrolled time-temperature pyrolysis.
• the high temperatures leads to. the production of higher acetylenichydrocarbons such as diacetylene and other alkynes in substantial amounts, and atthe same time, the lower temperatures leave a considerable portion of incompletely pyrolyzed hydrocarbon feedrin the efiluent gases.
• a gas containing substantially pure methane is sometime-s not available as a feed stock.
• non-aromatic hydrocarbons as ethane, propane, the butanes, the heptanes, and the like, ethylene, propylene, butenes, and higher olefins and cyclohexane, and mixtures thereof can be advantageously used in this newly discovered process.
• the control of the hydrogen to carbon ratio has another unique advantage; i.e., the process itself produces acetylene and essentially pure hydrogen containing small amounts of methane; methane is also hydrogen rich relative to other hydrocarbons.
• the process itself produces acetylene and essentially pure hydrogen containing small amounts of methane; methane is also hydrogen rich relative to other hydrocarbons.
• no elaborate separation procedure is necessary for the removal of acetylene from the process efiluent gas
• no elaborate separation procedure is necessary for the removal or recovery of any other hydrocarbons from this gas. That is, can be recycled directly to dilute the hydrocarbon feed in an amount necessary to give a hydrogen to carbon ratio which is within the limits required to yield the outstanding results of this invention.
• the process of the invention can also be operated so that the effluent gases from the reactor, after removal of acetylenes, will consist of essentially pure hydrogen.
• the hydrogen to carbon ratio is chosen in the upper ranges of the limits, that is from 15 to 30, then the eflluent gas, after removal of acetylenes consists of up to 98% hydrogen with methane as the only principal contaminant.
• Another alternate method is to first pyrolyze a stream wherein the hydrogen to carbon ratio is in the lower ranges of the limit, that is, from 6 to 20. This will yield an eflluent which, after the removal of acetylene hydrocarbons has a hydrogen to carbon ratio in the upper ranges of the limits.
• This product stream, after acetylene removal can if desired, be further processed in a second reactor to yield a second efiluent stream consisting of essentially pure hydrogen and acetylene.
• the process of this invention comprises introducing a mixture of at least one non-aromatic hydrocarbon and hydrogen preferably continuously into a reaction zone wherein the maximum temperature within the effective reaction zone is above 1400 C.; withdrawing the effluent from said reaction zone and, at the point of withdrawal, quenching the eflluent to a temperature of 600 C. or less; lower quench temperatures are operable, e.g., 350 C. or less.
• the hydrocarbon used may have two to ten carbon atoms. Since the gas is primarily being heated during its passage through the reactor, and is being heated and cracked during its passage through the effective reaction zone, the temperature of the gas reaches a maxi mum temperature during its passage through the reaction zone at a point prior to the quench.
• the space velocity, Sv is stated as:
• V flow rate of feed gases, ftfi/sec. measured at 0 C.
• Hg abs. and V reaction zone volume, ft.
• Effective space velocity wherein P is the total reactor pressure in atmosphere absolute.
• the foregoing formula for efifective space velocity is the definition of the effective space velocity for the reaction zone.
• the range of effective space velocity which can be employed over the temperature and hydrogen to carbon ratio, as defined above is 1.0 to 400 SC.1 atm.- and is preferably in the range 2.5 to 300 sec? atm.
• reaction zone in which the principal part of the pyrolysis reaction occurs, and to which defined zone it is in fact desired to confine the pyrolysis reaction.
• the beginning of the reaction zone is taken to be that point at which the temperature of the reacting gases first reaches a level of about 250 C. below the maximum temperature in the reactor; the end of the reaction zone is considered to be the point of quenching or start of quenching.
• the gas temperature is estimated to be within 100 C. of the wall temperature.
• This isothermal reaction zone is very important. If substantial amounts of decomposition of the feed occur prior to this reaction zone, a tenacious carbon deposit forms in this part of the reactor causing increased pressure drop and decreased acetylene yields. In fact, operation may be stopped entirely because of blockage. On the other hand, if substantial reaction occurs within the quench zone, soot will form due to acetylene degradation. This carbon, which is soft, represents a loss in yield. It does not necessarily produce blockage of the reactor and is usually carried out of the reactor zone with the gas as soot.
• the efl'luent can be quenched for instance through a De Laval nozzle so as to secure a rapid drop in temperature.
• the high velocity efliuent gases thus attained can then be mixed with water or another quenching medium, or, they can be passed through a turbine to extract a portion of their energy.
• the pressure employed within the reaction zone is essentially atmospheric, but pressures from 130 mm. Hg. abs. up to five atmospheres abs. can be employed, five atmospheres being a convenient pressure level in commercial recovery operations. Yields will vary with hydrogen dilution. Where reaction zone pressures, other than atmospheric are employed, an effective hydrogen to carbon ratio as previously described, can be used to define the elfect of pressures on the extent of hydrogen dilution desired.
• the feed material to the reactor for the production of acetylene need not be any one pure hydrocarbon, i.e., prior to hydrogen dilution.
• Commercial sources of hydrocarbons of 2 to carbon atoms and containing mixtures of parafiinic, alicyclic, olefinic and other types of non-aromatic hydrocarbons are suitable as feedstocks as long as they can be volatilized into a hydrogen stream under the conditions of the process. If pure hydrocarbons of this type are available these would also be suitable feedstocks.
• Varying amounts of gases such as nitrogen can also be present in the feed stream and/or in the hydrogen dilution stream. Small amounts of gases such as for example, oxygen, carbon monoxide and carbon dioxide may also be present.
• gases such as for example, oxygen, carbon monoxide and carbon dioxide may also be present.
• the aforementioned contaminants will show up in the product stream as nitrogen and/ or carbon monoxide and water. Although these cannot be used to advantage in subsequent reactions with hydrogen, they have little or no effect
• the products of such pyrolysis normally include methane as is well known.
• methane As is well known.
• the decomposition of methane so formed proceeds to the formation of acetylene and hydrogen when carried out under the herein described conditions.
• the decomposition of hydrocarbons heavier than methane proceeds more rapidly than the cracking of methane itself, and the decomposition of methane is in fact the rate controlling step in the overall decomposition of the heavier hydrocarbons to acetylene and hydrogen.
• a carefully metered hydrocarbon feed suitably diluted with hydrogen, is caused to pass through an electrically heated reaction chamber and is rapidly quenched.
• the maximum temperature within the reaction zone will be for example, about 1750 C.
• the hydrocarbon feed and the hydrogen diluent are withdrawn from storage, metered, and passed through suitable control valves. At this point, the desired concentration of the hydrogen diluent is provided by a metered amount of hydrogen being incorporated into the feed stream of hydrocarbon.
• the pressure of the feed material is measured and the feed stream proceeds to the electrically heated reactor.
• the hydrocarbon stream and hydrogen diluent would be metered separately and passed as separate streams into the reactor, i.e., the gas feed entering the furnace can be a premixed stream of hydrogen and hydrocarbon or the components can be fed separately.
• the hydrocarbon is of high molecular 'weight so that it must be vaporized by the addition of heat to bring it to the gaseous state at the temperature and pressure conditions at the reactor inlet.
• the hydrocarbon containing feed passes through the length of the reactor zone and thereby into contact with the themocouple which measures temperatures within the reactor.
• the thermocouple arrangement is for example composed of an alumina thermocouple protection tube and a platinum-platinum-10% rhodium thermocouple protection tube. This thermocouple protection tube is disposed within and along the length of the larger reactor tube.
• the thermocouple is employed to measure a longitudinal temperature profile. This profile can be measured in two ways i.e., with the thermocouple and/ or with the pyrometer. However, above 1650 C., only the pyrometer is used. The profiles, so obtained establish the extent of the reaction zone.
• thermocouple protection tube is maintained within the reactor tube is made of alumina and positioned within the graphite resistance element designed to use a low voltage electrical current up to 3 k.v.a., thus providing sufficient heat to effect the maximum temperature within the reactor tube.
• the adnulus positioned between the large diameter reactor tube and the smaller diameter thermocouple protection tube thus constitutes the reactor cross section.
• refractory walls of zirconia and aluminum silicate together with an intermediate radiation shield of stainless steel and a furnace wall of copper, are desirably employed.
• the outer wall of the reactor is desirably water cooled.
• a window is preferably positioned in the outer wall of the reactor to permit, if desired, observation by an optical pyrometer sighting on the reactor tube (through a slit in the graphite resistance element), thus providing means for determining the temperature thereof.
• the gaseous eflluent stream Upon leaving the reaction zone, the gaseous eflluent stream enters the quenching chamber where rapid cooling of the hot product gas to a temperature in the range of at least 600 C. down to 300 C. or less is caused to occur as described above.
• quenching is effected most desirably at this point by cold fluid injection, either gaseous or liquid.
• the hot efiiuent product gases are quenched with a portion of the effluent which has been withdrawn, cooled and recycled by the recycle pumps to the quench chamber. This is one preferred method for cooling. Additional cooling may be achieved by water cooling of the outer metallic surface of the quenching chamber. Analysis of the gaseous components in the product efiluent is accomplished by gas chromatograph and/ or mass spectroscopy.
• any suitable systems and reactors may be employed for the practice of this invention so long as they provide for adequate heat transfer rates into the gaseous feed phase for controlling the temperatures in the reaction zone, and adequate and immediate quenching of the reaction following the reaction zone of the reactor.
• Suitable devices may include among others those containing a reactor formed of: a space between narrow, heated channels of high temperature refractories; a space between regularly disposed heated rods of carbon or high temperature refractory; or a space between previously heated small particles in a moving stream, as well as the type of annulus reactor employed in the present description of the invention.
• a product gas can be obtained consisting substantially of acetylene and hydrogen, with the total of all other hydrocarbons, including methane generally less than to 7% (volume).
• feed disappearance inclusive of any methane present in the feed
• feed disappearance is in a range of 95 to 100%.
• the maximum in feed conversion to acetylene occurs as Se substantially lower than that required to give 100% feed disappearance.
• the maximum conversion of hydrocarbon to acetylene per pass will occur at values of Se substantially lower than those required to give complete hydrocarbon feed disappearance, exclusive of methane in the feed.
• the most common solid substance to be removed from the product effluent by a solids trap is carbon in the form of small flakes formed in the reactor as a product of the pyrolysis. Soot in the eflluent gas is trapped in the oil system of the compressors. Only minute amounts of condensible liquid product have been found and therefore no provision for handling such product has been considered necessary.
• a main pump may be employed to draw the feed and hydrogen diluent and product gases through the reactor and the quenching chamber.
• a recycle pump may be employed to recycle a part of the product through a cooler and back to the quenching chamber for the rapid and immediate cooling of the newly produced effluent product leaving the reactor.
• a gas sampling system may be provided downstream of the main pump and will include a volumetric gas meter and gas sample valve.
• Equivalent hydrocarbon is that single hydrocarbon which at the same mole percent in the feed as the summation of all percentages of hydrocarbons present in the feed would yield, per mols of feed, the same number of atoms of hydrogen and of carbon as are present in the feed (exclusive of hydrogen molecules present in the gas).
• the empirical formula and the average molecular weight of the mixture are only necessary to know the empirical formula and the average molecular weight of the mixture. Then for pure hydrocarbon diluted with hydrogen:
• product analyses do not include other bydrocarbons some of which appeared in all runs, but to the extent generally of less than 0.5% (mole) each, and which, in total, are generally about 1% (mole) or less. Dilueuts, other than hydrogen, and solid carbon are also not shown.
• Example 1 A gas mixture wherein the H/C is 7.3/1 consisting of 81.2% hydrogen, 18.6% ethane and about 0.2% methane was passed continuously through a pyrolysis reactor of the type described hereinabove.
• the reaction zone is taken as that zone which starts at a temperature about 250 C. below the maximum temperature observed in the reaction zone, and ends at the point of quench.
• the volume of the reaction zone is V the space velocity, S is taken as the total flow of gas measured at C., 7 60 mm. Hg abs. pressure in cubic feet/sec, fed to this defined reaction zone, divided by the reaction zone volume in cubic feet.
• Effective space velocity, S is taken as:
• the product gas has the following analysis:
• Example 5A Under otherwise the same conditions as in Example 5, but with the maximum reaction zone temperature at 1750 C., the product gas analyzed as follows:
• Example 5B As in Example 5A, but with the maximum reaction zone temperature at 1795 C., the product gas analyzed which corresponds to:
• Example 8A A substantially the same condition as Example 8, but with the maximum temperature at 1604 C. and Se 64.9 secatmr the product gas analyzed as follows:
• a process for the pyrolysis of mixtures containing substantially non-aromatic hydrocarbons having 2 to 10 carbon atoms admixed with hydrogen which comprises heating said mixture of hydrocarbons and hydrogen within a substantially isothermal pyrolysis reactor zone at a maximum temperature within said reaction zone of at least 1450 C. up to 2000 C., the effective space velocity of said mixture through said reaction zone being within the range 1.0 to 400 sec:- atm.-
• a process for the pyrolysis of mixtures containing at least 65 mole percent of at least one non-aromatic hydrocarbon having from 2 to 10 carbon atoms and hydrogen to produce acetylene and hydrogen which comprises heating the mixture of hydrocarbon and hydrogen within a substantially isothermal pyrolysis reactor zone at a maximum temperature within said reaction zone of at least 1450 C. up to 2000 C., the eflective space velocity of said mixture through said reaction zone being within the range 1.0 to 400 sec.” atm.- the effective hydrogen to carbon ratio in said mixture of hydrocarbon and hydrogen being from 6.0 to 30.0.
• a process for the pyrolysis of a mixture of nonaromatic hydrocarbons having from 2 to 10 carbon atoms and hydrogen to produce acetylene and hydrogen which .comprises heating said mixture of hydrocarbons and hydrogen within a pyrolysis reactor zone at a maximum temperature within the reaction zone of said reactor of at least 1450 C. up to 2000 C., the etfective space velocity of said mixture through said reaction zone being within the range 1.0 to 400 sec.- atm.- the beginning of the pyrolysis reactor zone being defined as that point at which .15 the temperature of the reacting gases first reaches a temperature level of about 250 C. below the maximum temperature and the end of said zone being defined as the point of quenching of the product gases.
• a process for the pyrolysis of mixtures of hydrogen and non-aromatic hydrocarbons having from 2 to 10 carbon atoms to produce acetylene which comprises heating a mixture of hydrogen and said hydrocarbons having an effective hydrogen to carbon atomic ratio in the range 6.0 to 30.0, within a substantially isothermal pyrolysis reactor at a maximum temperature within said reaction zone of at least 1450 C. to 2000 C., the efiective' space velocity through said reaction zone being in the range of 2.5 to 300 sec. atrnr 6.
• a process for the isothermal pyrolysis of non-aromatic hydrocarbons having 2 to 10 carbon atoms, to produce acetylene and hydrogen which comprises heating a mixture of hydrogen, hydrocarbons and inert gases within a pyrolysis reactor at a maximum temperature within the reaction zone of said reactor of at least 1450 C. up to 2000" C., the effective space velocity of said mixture through said reaction zone being in the range of 2.5 to 300 sec.- atm. and thereafter rapidly quenching the product gases to a temperature of at least 600 C.

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  • CA CA835434A patent/CA835434A/en not_active Expired
• 1964
  • 1964-11-09 US US409944A patent/US3227771A/en not_active Expired - Lifetime
• 1965
  • 1965-11-08 NL NL6514454A patent/NL6514454A/xx unknown
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  • 1965-11-09 FR FR37847A patent/FR1492803A/fr not_active Expired
  • 1965-11-09 DE DEH57630A patent/DE1296618B/de active Pending
  • 1965-11-09 JP JP6831865A patent/JPS4517405B1/ja active Pending
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