US2371616A - Production of valuable hydrocarbons - Google Patents

Description

3' Sheets-Shet 2 Wgaafng E. HALL PRODUCTION OF VALUABLE HYDROCARBONS Filed Jan. 27, 194D March 20, 1945.

March 20, 1945.

. L HALL PRODUCT-ION OF VALUABLE HYDROCARBONS 5 Sheets-Sheet 3 Filed Jan. 27, 1940 PsieniedMsr. zo, 1945 PRODUCTION F VALUABLE HYnRocARBoNs Edwin L nail, Philadelphie, Pn., assigner tn The. United Gas Improvement Company, a corporation of Pennsylvania 'ApplicationfJanuary 27, 1940, Serial No. 315,936

2 Claims. (Cl. 260-1-671) The present invention relates to the simultaneous production of manufactured gas rand valuable hydrocarbons, and relates more particularly to increasing the yield of certain of vide an improved methodof increasing the yield of alkylated aromatic hydrocarbons relative" to' the yield of benzene.

other features `of the inventienjresiie in the steps, combinations of steps and sequence of 55 steps, and in the construction, arrangement and combination .of parts, all of which together with other features will becomemore apparent to persons skilled in the art as the specication said hydrocarbons. proceedsand upon reference to the drawings in In'the usual manufacture of oil gas or carwhich: buretted water gas, a step in the processcom- Figure l'shows in elevation and partly in secprises cracking of vcrude petroleum oil or its less tion, a three Shell gas set chosen for illustration; costly portions, suchl as gas oil' and residuum Figure 2 shows a ow sheet illustrating the oil, under conditions which yield relatively large lo invention; and Y quantities of ixed or diicultly codensible Figure 3 is' an elevation, partly in section, diagases, suchas h'ydro,-'gen,methane, and ethylene grammatically illustrating apparatus'of the'contogether withl other gaseous' paraines and oletinuous or continual type. lines, and relatively -small quantities of more Referring Vmore'particularly to Figure 1, l inreadily condensible .hydrocarbons comprising is dicates'a. generator, 2 a-carburetter, s n supertar, drip oil and lower temperature condensates. heater and 4 a wash box. Broadly stated, the division between the gaseous Generator I is illustrated as having a fuel and' other products depends upon the `severity burner 5, an uprun air blast supply E, and an of cracking'and the severity of condensation. uprun steam 'supply 1'.

`It'has been proposed to modify' the usual conn 20 Superheater 3 is shown with a downrun steam ditions of cracking temperatures and time of' supply', contact and the temperature ofl condensation to Generator I is provided at its top with arr olfproduce andrecover smaller proportions o f the take 9 leading to the top of the carburetter 2, .original oil as gaseous products for distribution and carburetter 2" is provided at its base with as fuel and larger `Dr0portions as condensate 26 an olf-take I0, leading tothe base ol.' the supercontaining hydrocarbons morepvaluable for heater .3. t 1 other uses. Y Y Y Superheater' is shown with a stack vvalve Il AAmong the hydrocarbons so recoverable are and a gas odi-take- I2, the latter leading to wash saturated and unsaturated compounds suchas b ox 4 through valve |3 'f 1 benzene, toluene, xylene, naphthalene an- '.Generatoi-i hase',` gas off-.taken a1; its base thracene, idene, styrene, methyl styrene, cyclO- providedwith4 valve l5.-` Gas 'off-take I4 leads pentadiene, dicyclopenta'diene,`'butadiene, iso-V to wash b0x `4 1 mene,` pipery1ei1e,yetc Wash box' 4 is shown with th conventional Theusual condensation'in oil gas manufacgas'ofttake m turedown to atmospheric temperature removes Any other gas-making equipment employing from the gas Practically all 0f the Xylene.' naPharun with oil ht have been `substitnted'*for thalene, anthracene', indene, styrene, and the purposes of describing the'inventi0n methyl styrene. a Small part ofthe-benzene, and The operation'of the a' paretus will be' depossibly,half of the toluene. For 'the recovery scribed with an illustrative; cycle l of thc remainder of 'the benzene and toluene 40 v Liquid mgaseous fuel supplied tgbumer 5 i's and for the recoveryr of theD above mentionedA burned witharsupplied at t Y l conjugated dienes mueh. lower tempratures 0f 'The resuiting het blast gases pass up through condensation than usually employed ih gS mall- 1 the generator I, through olf-take '9, `dorm ufacture `are required. i V I through the carburetter Zand'up through super-- .Among the aI'OmallC hydIOUal'bOnS mitad 45 heater "3, raising the temperature of the carabove,l the alkylated' (including alkylenatd buretter and superheater and storing heat therearomatics are in general more valuable than'the in, and muy escp'e through stack valve. H 'or u', benzene. partiularl'y true. 0f 1118101116116, a waste heat boiler (not shownyor otherwise. xylene and styrene. f I f desired; secondary air may be introduced at An object of the present invention is to prol1 througli'pip II controlled byval've'l.

une blast is seconaueteq'as toobtain de.-

. sired distribution or heat througlout the {enr-l buretter and vsuperheater t lifter the l airlolasting operation the set Ais purged of 'blast gases by steam admitted at any convenient point, such as at I or at 23, whereupon stack valve II is closed, valve I3 is opened and a forward run with oil is made during which steam is preferably supplied, such as at 'I or at 23.

Supplying steam at 1 has the c lect of causing the steam to pass up through the generator whereupon it becomes highly superheated before reaching the carburetter, thus relieving th'e carburetter from the duty of furnishing this preheat.

It will, of course, be understood that a part -of the steam may be admitted at., 1 and a part at 23, thus making it possible to -regulate the temperature of lthe steam entering the top of carburetter 2, or all of the steam may be admitted at 1 or 23 with any desired degree of preheat. Reference is made to my copending application Serial No. 191,441, filed February 19, 1938.

y whether they include checkerbrick, or other construction or comprise merely the side walls. However, Whether coming into contact with the heated refractory surfaces or not this oil is subjected to the temperatures of the carburetter and superheater, and as it is carried down through the carburetter and up through the superheater along with the steam it is cracked into gas, coke, tar, drip oil and other condensates. The coke is usu ally deposited in the carburetter and superheater and the condensates are usually carried-out of the superheater in the vapor phase and are codensed at the wash box and further on in other condensing equipment. i

After the forward run, if desired, a back-run might be made as follows. Valve I3 is closed, valve I5 opened and steam is reversed through I the set by admitting it at 8, while injecting oil hydrogen and hydrocarbons which pass down retted water gas manufacture chosen for illustration since a carbonaceous fuel bed might be substituted in the generator I for burner 5. Any other appropriate cycle might be substituted. For

' instance, the reverse run might be omitted.

After passing through the off-take I6 the gas usually goes through water cooled condensers to a relief holder and from thence to the puriers for the removal of hydrogen sulfide, and thence to storage holders for release to the distribution system. l

The wash box 4 in which the gas comes in contact with water, and the water-cooled condensers cool the gas down to. approm'mately atmospheric temperature, lI Ilhe tar and oil condensed out in these vessels comprises a residual tar fraction boiling above 300 C., a dead oil fraction boiling between 200 C. and 300 C., and a light oil fraction boiling up to 200 C. and containing practically all of the styrene,'indene, and' xylene, possibly half or more of the toluene and some of the vbenzene and other miscellaneous hydrocarbons or benzol forerunnings. The individual compounds may be recovered from the light oil by fractional distillation.

Usual gas practice does not carry the condensation further. However, ifafter purification oil gas, for example, is cooled to approximately --c C., the remainder of the benzene and toluene as well as the dienes, cyclopentadiene, butadiene, is'oprene and piperylene, may be condensed out and recovered separately by fractional distillation, leaving the residual gas with hydrocarbons which are for the most part of less than four car bon atoms and which may also be recovered from the gas as will hereinafter appear.

Other condensate recovery means may be combined with or substituted for refrigeration, for example absorption such as in a scrubbing oil, adsorption such as on activated carbon, and/or compression.

By resorting to recovery by stages,'these materials may be removed from the gas in more or less concentrated form.

In the normal production of aromatics from the cracking of petroleum oils, the reaction is supposed to proceed generally as follows:

Paraflines-olefines and diolenes Cyclic olenes and naphthenes Aromatics Benzene-Ffree radicals-mlkylated aromatics.

As described and claimed in .copending application Serial Number 220,649, -led July 22, 1938 (now Patent Number 2,226,531, dated December 3l, 1940)', by Newcomb K. Chaney, by increasing the concentration of benzene and lower olel'lnes such as ethylene (but which term also includes propylene) above that caused by the concurrent formation of these materials in the oil cracking operation, the abovereaction of benzene with free radicals to form alkylated aromatica is favored.

Also the presence of an increased benzene and lower olenic concentration above the normal equilibrium concentration tends to oppose the formation of additional benzene and lower olenesby mass action. Thistends to suppress the breaking up of alkylated aromatics formed in the earlier stages to form benzene and lower olenes in the later stages of the cracking operation.

Whether the tlieory above set forth be correct or not, increasing the benzene and lower oleflnic concentrations above that produced by the normal formation of benzene and lower olenes from the oil in the cracking'operation favors an increase in the yield of alkylated aromatics relative to theyield of benzene.

'I'he increased concentration of benzene and lower olene or olenes maybe secured by introducing additional benzene and lowerolene or olenes into the cracking chamber during the cracking of the oil.

In accordance with this invention, all or part of the benzene and lower oleilnic material maybe separated from the products of cracking and recycled through the cracking chamber or chambers by scrubbing from the gas with the hydrocarbon feed oil benzene and lower olenic material in a two step operation, removing intermediate hydrocarbons separately. Benzene and lower olenic material are thus separated from the gas by absorption in the hydrocarbonoil prior to the admission of the oil into the cracking apparatus, as through supply means 2| or 24 in the drawings. However, as temperatures in the cracking apparatus, such as the carburetter and superheater `above described, maybe widely varied with different cycles and methods of operation, it will be understood that the oil with benzene and lower olefnic material inv admixture may be fed to the set at any other appropriate point or points.

The benzene and lower olenic material recycled in this manner need not be relatively rened, but may be crude cuts washed from 4the make gas in the manner described. In fact,..a very materially increased yieldl of styrene, a very valuable alkylated aromatic can be secured by washing Afrom the gas with make oil andrecycling a light oil cut containing considerable quantities of toluene, xylene, and styrene, in addition to benzene, and a light oil cut containing considerable quantities of butadiene, isobutylene, propylene and even cyclopentadiene and methane, in addition to ethylene.

However, it is preferred to separate from the gas after the initial scrubbing operations'for the absorption of benzene and prior to the scrubbing operation for the absorption of lower olenic material, substantial proportions of all hydrocarbons present of ve and four carbon atoms tothe molecule. It is to be understood that additional benzene or lower olefinic material orl both over and above that removed from the gas may, if desired, be added to the hydrocarbon oil prior to its admission to the cracking apparatus and/or' such additional benzene or lower olefinic material or both may be introduced separately to the same portion or portions of the cracking apparatus or to a dierent portion or portions. d

The invention will be further understood upon reference to Figure 2 of the.' drawings whichcomprises a ow sheet illustrating apparatus for carrying out the invention.

In Figure 2, 30 represents a gasset shown diagrammati-cally as comprising generator 3|, carburetter 32, superheater 33 and wash box 34 all `relief holder4| through line 42 through compressor or booster 43 andline 44 .toand through purifier system 45 of any suitable design and then through line46 into scrubber 41. The compressor ,or booster 43 may be placed either upstream or In dry purification for example, it is usually placed downstream from purier system 45.

downstream.

The purifier system 45, which may be of the dry purification or liquid purification or other type, serves to remove from the gas various impurities such as sulfur and cyanogen containing compounds of which hydrogen sulfldeand hydrogen cyanide'are examples. Since it is preferred not to build up a high concentration of these materials in the set by recycling, the `use of a purier system upstream from the scrubber 41, for example of the type used in ordinary gas manufacture, is recommended. i

' On the other hand, since condensation of hydrocarbons is undesirable invpurier systems and particularly in those of the oxide type, as a protection against any considerable condensation of higher boiling hydrocarbons in the purier system, a part or all of the purification may take place downstream of scrubber 41. A second purier system a has been illustrated for this purpose, the use of which is optional.

The apparatus described in Figure 2 up to scrubber 41 and its hook-up may be regarded as illustrative and any other suitable apparatus or system or hook-up might be substituted.

An oil supply for the set 30 is illustrated at 48 from which oil flows as through pump 49 and line 50 to scrubber 41, wherein oil and gas are `contacted' by any suitable means known in the art for the purpose of scrubbing higher boiling constituents from the gas. packer or bubble plate variety or otherwise are very suitable for this purpose. Other types of scrubbers will be found in the art.

As pointed out previously, there will be a higher percentage of total benzene present in the gas just prior to entering scrubber 41 than of higher boiling light oil constituents, such as toluene, styrene, xylene, etc., although there may be significant quantities of the latter substances present depending upon the temperature to which the gas has been reduced by the time it reaches scrubber ,41.

As an illustration, if the gas is reduced to a temperature of 95 F. prior to entering scrubber 41, it might have present of the Yorder of approximately 1/3 ofthe total toluene, 80% of the total benzene,l from 10 to,30% of the total xylene, and from 10 to 30% of the total styrene. Reference is made to my copending application Serial No.

301,330, led 'October 26, 1939.

These materials are washed from the gas in scrubber 41 to an extent dependent upon (l) the efciency of contact, and (2) the amount of wash oil employed per unit of gas scrubbed.

When the make-gas is substantially all oil gas gas. Thiswill, of course, vary with the B..t. u.

per cubic foot of the gas, or in other words, with the extent to which the oil is cracked to form gas.

l For instance, the more the oil is cracked, the

larger the volume of gas produced per unit of.oi1, and viceversa;

Assuming that all of `thevfeedol is contacted Towers whether of the amounts of benzene as well as other constituents l boiling in the neighborhood thereof.

Should it be desired to recover substantially all or a larger proportion of the xylene, styrene and toluene present in the gas prior to its entering scrubber -41, this may be done by any suitable means, such as by a further reduction in temv perature, for example at condenser 31, or by adding an additional condenser, recovering these constituents'as condensates.

Other means for regulating the proportion of the various constituents in the gas entering scrubber 41 will become apparent to persons skilled in the art upon becoming familiar herewith.

It will, of course, he understood that scrubber 41 is illustrated dically and may take any form, shape or construction suitable for the purpose and may comprise one or more imits as desired. 'Ihe same applies to scrubber 51.

While temperature regulating means for scrubber 41 have not been illustrated, it is to be understood that such may be provided, for instance or a control of the absorbing capacity of the oil- Decreased temperature will. of course, increase the absorbing capacity of the oil. Increased pressure might be employed for this purpose with or without decreased temperature.

The scrubbed gas, as leaves scrubber 41 through line 54 and passes through ai condensate recovery system 55 for the recovery` of Cs and C4 hydrocarbonsfrom which the residual gas iiows olf through linev 55 -to scrubber 51.

'I'he condensate recovery system 55 may be of any suitable design and its purpose is to take out of the gas hydrocarbons of ive and four carbon atoms, such as cyclopentadiene, butadiene, isobutylene,etc.

For the purpose of such further condensation b such as through bypass v64, shown controlledbyavalve55.

Ildesired apartofthe'oilfromsupply tankmaybebypasedtosetlthroughlinesil andiorlinesand'iorbothasdesired.

Means for feeding enriched feed oil to the Superheater 33 such as for reverse run purposes It will be tmderstood, however, that scrubber 41, extraction unit 55 and scrubber 51 may be operated continually, intermittently, or otherwise if desired, without departing from the broad concept of the invention.

Any desirable more or low temperature, or both may be employed in scrubber 51.

For example, when employing of the order of from12tolgallonsot'scrubbingoilperMCF` of gas. pressures of the order of 200 pounds per square inch at atmospheric temperature cause the absorption in the oil of the order of 25% of the propylene and 8% of the ethylene contained in the gas.

In view of the relatively large percentages of 35 propylene and ethylene in the gas, the hydrocarbon feed oil is thus charged with quantities thereof.

Any desired temperature and pressure in scrubber' 51 might be employed through an economic Substantial i0 balance between super-atmospheric pressure and prior to the entry of the gas into scrubber 51, or

' coming familiar herewith.

A In scrubber 51 the gas and hydrocarbon oil are contacted under conditions which increase the .absorptive capacity of the oil beyond that obtaining in scrubber 41. This is obviously necessary since lower olens in any substantial quantity were not removed in scrubber 41.

An increase in the absorptive capacity of the hydrocarbon oil in scrubber 51 may be obtained by increasing the preure in scrubber 51 such as by booster or compressor 58 and pump 5! in gas line 55anlioilline5l respectively,orbyare' duction in temperatuer in scrubber 51, or both.

vIntheeventofanincreaseinpressure in scrubber 51, control valve il in charged oil line l2 and valve 6|` in residual'gas line 53 are conveniently employed. l

Although it will usually be desired to bring all of the hydrocarbon feed oil into contact with the sub-'atmospheric temperature to obtain the desired absorption of lower olciinic material will usually be sought.

The nal. residual gas leaves scrubber 51 through line s: controlled by valve sl. and the hydrocarbon oil charged with benzene and lower oleiinic material leaves scrubber 51 through line 52 and ilows via surge chamber 56 and expansion valve 50 into gas-making set 3l, expansion valve 5I beingV operated intermittentlyas required in the operation of set 3l.

It is, of course, understood that, if desired, additional quantities of benzene and lower lenic materialmaybcchargedtotheseteitherviathe Afeedoilorotherwise.

Furthermore, whileit is desired to have the feed oil now serially through scrubber- s 41 and 51 because of the increased absorptive capacity ofthe oilinscnibber 51 dueto thepresenccofbenzene, the oil stream may be split ifdosdred. and caused to now m individual streams through the scrubbers, again lmited or fed separately to set 3l, or otherwise. Other variations may be made without departing from the broad concept of the invention. lThus separate streams of diierent types .of hydrocarbon oil might be employed, one. stream flowing through each scrubber and the streams then united or fed separately to the set. k

Line 53 leads to a storage holder for residual gas or to any other desired point not shown.

The residual gas is unusually low in illuminants and from this standpoint maybe substituted for natural gas for standbyor displacement or other .gas'inscrbber 5,ifdesiredaportofitmaybe V'us purposes. My proces hasmradded advantage poses.

from this standpoint in that upon analysis of a typical residual gas sample it was found to contain considerably more methane and considerably less hydrogen .than residual gas made without added benzene and lower oleflnes.

The three shell set and cycle earlier described were given merely for convenient illustration of apparatus adapted for use with my invention, and are subject to very wide modification. 'If a fuel bed is employed for heating the set, as in carburetted water gas practice, it may be preferable to curtail sharply or to omit the production of blue water gas, employing the fuel bed merely as a means of heating the carburetter and superheater. In such case, in the absence of the blue water gas and excess steam cracking atmosphere, it is desirable to admit steam or other diluent to the carburetter withthe hydrocarbon oil to reduce the partial pressures of the vapors andv products of cracking. This steam may be admitted through a supply means such as 23.V The fuel bed, of course, may be replaced by any other convenient means of heating such as an oil, tar, or gas burner as' illustrated at 5 in which case it is also desirable to admit steam or other diluent with the oil. The above modifications are merely illustrative. The invention is applicable to any process in which hydrocarbon oil is thermally cracked under temperature and contact conditions yielding relatively fixed gas and more readily condensible hydrocarbons including benzene, lower olenes and alkylated aromatics.

and the provision of taps 88 and Y9| on windings 81 and 80 respectively, make it possible to closely control temperature conditions within tube as well as to vary such conditions along tube 15, if and as desired;

Assuming that heaters 81 and 98 and cooler 89,

if necessary, are operating to establish desired `temperature conditions within tube 15, the opertial pressures of oil vapors and the surrounding temperatures are ordinarily suliicient to vaporize all ofthe oil.

The vaporized oil Vin passing through tube 15 is decomposed in a manner similar to that already described in connection with Figure 1.

The resin-forming hydrocarbons along with saturated aromatics, such as benzene, toluene,

' xylene, etc., because of the temperatures involved remain inthe vapor phase and pass off through delivery arm 82 with the gas.

Referring now to Figure 3 wherein cracking apparatus of the continuous or continual type is illustrated on a laboratory scale, 15 comprises a reaction tube which may be any suitable material l such asquartz, or any of the materials at present employed in continuous or continual cracking operations.

oil feeding tube 18 and steam feeding tube 18.'

Feeding tubes 18 and 19 pass through and form a gas-tight t with a closure member 80 for the inlet end of tube 15. t t

Tube 15 adjacent its outlet end 8| is provided with a gas deliveryY side arm 82 and a closure member 83, the latter being sufficiently below side arm 82 to form a well 84.

Tube 15 is also shown provided with an axially arranged tube 85 of small diameter.- Tube 85, as shown, projects through closure Amembers'illl and 83 and provides a convenient way Vof arranging thermocouple junctions for the measure of temperature. Tube 85 may be of any convenient material, such as quartz, or any other material suitable for continuous or continual cracking pur- Tube 15 may be of any convenient length which is usually correlated with the provisions Vfor feedingsteam and for feeding and vaporizing'oil in order to make it possible to obtain times of con# tact within a desired range. For temperature control purposes, tube 15 is shown surrounded'with a heating member `81 in theform of aresistancev winding which may be provided with several taps, as illustrated at 88; a-cooling coil Blof tubular construction for` the flow of cooling y,uid; and ,another resistance Temperatures between 1250 and 1550 F. are illustrative of those obtaining in tube 15, although any other desired temperature or temperatures suitable for the purpose may be employed.

Times of contact of from 0.5 to 3 seconds are illustrative, although any other desired time of contact suitable for the purpose may be employed. l

In substituting the apparatus of Figure 3 in Figure 2 for that of Figure l, elements 30 to 34 are eliminated, delivery arm 82 is connectedv to gas off-take 36, and line 52 is connected to oil feed tube 18, whereupon elements 36 to 6B are ing means may be employed.

winding so provided with suitabie taps, illustrated at 9|. Y

It will be seen that the provision of alcooling coil 88 between resistance windings 81 and,

IIf desired, `tube 15 may contain refractory material of suitable size and shape if suflicient free space is afforded for the flow of vapors, such additional refractory materials providing additional contact surfaces.` A

Small amounts of free carbon or other nonvaporizable substances tend tofcollect inwell 84 from which they may be removed during cleaning upon the removal of closure memberI 83.

When the walls of tube 15 become coated with a layer of carbon sufficientlyl thick to interfere with proper heat exchange, or otherwise, it may be removed by any suitable means such as by inor both,- the products of combustion being re`- moved through side arm 82.

of steam to one volume of trative.

- As above-stated, the yield of styrene.` a very valuable alkylated hydrocarbon, vmay be very materially increased by recycling'light oil and hydrocarbons of less :than f ourA carbon atoms separated from the gas the manner described. 'I'he feed oil, for example may contain ethylene, propylene, benzene, toluene, a smaller quantity of xylene and still smaller quantities of-indene'and styrene. f' l As exampIes of the increased yields of v1uab1e alkylated aromatic hydrocarbons in the labora- Any desired'proportion of steam to oil may be Aemployed inmy process of which two volumes` oil vapors is illust tory apparatus of Figure 3, the following may be given. r

EXAMPLE 1 To a mixture of a particular crude oil and benzol in proportions of two parts oil and one part benzol by volume was added 0.905 pound of ethylene per gallon of oil. The mixture of oil, benzol and ethylene was cracked under substantially similar conditions of temperature and contact as a control employing 100%. of the same crude oil in a quartz contact tube known commercially as Vitrosil."

The inside diameter of the tube was 11/8" and the length was 35.4".

In each case steam was admitted with the material cracked. The table below shows theincreased yields of certain valuable alkylated aromatic hydrocarbons, especially styrene when employing a mixture o! oil, benzene' and ethylene, the term alkylated being used herein and in the claims to include unsaturated as well as saturated hydrocarbon vside chains.

There were also obtained 0.173 pound per gallon of oil of dienes comprising butadiene, cyclopentadiene and dimer, isoprene and piperylene.

EXAMPLE2 To a mixture of a particular crude oil and benzol in proportions of 2 parts oil to one part benzol by volume wasV added 1.512 pounds of propylene per gallon of oil. 'I'he resulting mixture was cracked under substantially similar conditions of temperature and contact asa control employing 100% of the same crude oil in the tube of Example 1.

In each case steam was admitted with the material cracked. The table below shows the increased yields of certain 'valuable alkylated aromatic hydrocarbons, especially styrene when employing a mixture of oil, benzol and propylene.

Table II Mixture of oil, benzol 100% oil andpropylene LbsJg/al. of Lbalgal. of oil oil 0.206" 0.079 3'167 g' c2505 0134s There was also obtained 0.252 pound of dienes per gallon of oil comprising butadiene, cyclopentadiene anddimer, p iperylene and isoprene.

Other modifications in procedure in the performance of my invention than those set forth above will occur .to those skilled in the art upon becoming familiar herewith.

For instance, pyrolysis may be supplemented,

by other means for'decomposing the oil of which catalysis is an example. I'hus a combination of temperature and catalyst is within the purview of the invention.

The term hydrocarbon oil as-used herein embraces petroleum oil whether in the form of the crude or any liquid fraction thereof suitable for gas-making purposes.

Therefore, changes, omissions, additions, substitutions and/or modificationsmay be made within the scope of the claims without departing from the spirit of the invention.

I claim.

l. In the manufacture of combustible gas rich in methane and valuable saturated and unsaturated normally liquid aromatic hydrocarbons and valuable unsaturated hydrocarbons of at least 4 and less than 6 carbon atoms per molecule involving the vapor phase pyrolysis of petroleum oil in a heated petroleum oil pyrolyzing environment in the presence of added benzene and in the presence of atv least one added olene having less than 4 carbon atoms p ermolecule, with the production of gaseous products of pyrolysis containing benzene and saturated and; unsaturated hydrocarbons boiling higher and lowerthan benzene including hydrocarbon material boiling in the neighborhood of the boiling point of benzene, -said saturated and unsaturated hydrocarbons boiling higher than benzene including saturated and unsaturated. aromatic hydrocarbons, said hydrocarbon material boiling lower than benzene including unsaturated hydrocarbons of at least 4 and less than 6 carbon atoms per molecule and including olenes of less than 4 carbon atoms per moleculeA and methane; the steps of removing from said gaseous products of pyrolysis at least a substantial portion of said hydrocarbon material boiling higher than benzene; thereafter contacting the remaining gaseous products with petroleum o'il to absorb therein from said products benzene and hydrocarbon material boiling in the neighborhood of the boiling point of benzene, together with at least the bulk of any remaining hydrocarbon material boiling higher than benzene, leaving in said gaseous products unsaturated hydrocarbon material of at least 4 and less than 6 carbon atoms per molecule together witli oleflnes of less than 4 carbon atoms per molecule and methane; thereafter separately removing from the remaining gaseous products hydrocarbon material of at least 4 and less than 6 carbon atoms per molecule; thereafter contacting the yet remaining gaseous products with petroleum oil to absorb therein from said yet remaining gaseous products at least one olene of less than 4 carbon atoms per molecule, leaving a residual gas rich in methane; and introducing said petroleumv oil containing said absorbed benzene and hydrocarbon material boiling in the neighborhood of the boiling point of benzene, and said absorbed olene into said petroleum oil pyrolyzing environment for pyrolysis therein.

the manufacture of combustibile. gas rich inznethane as well as valuable saturated and un- "satilrated .normally liquidaromatic hydrocarbons and valuable unsaturated hydrocarbons of at least 4 and less than 6 carbon atoms per molecule by a cyclic processk in which heat is stored in a petroleumoil pyrolyzing zone during a heating period gi the cycle and in which petroleum oil is pyrol'yzedfin vapor phase in said heatedzone in `the presence of added benzene and in the presence of atleast oneadded olene of less than 4 carbon atoms per molecule during a petroleum oil pyrolyzing period of said cycle, with theproduction ofv gaseous products of pyrolysisl containing benzene as well as saturated and unsaturated aromatic hydrocarbons boiling higher than benzene and saturated and unsaturated hydrocarbons boiling lower than benzene, said hydrocarbons boiling higher and lower than benzene including hydrocarbon material boiling in the neighborhood of benzene and said hydrocarbon material boiling lower than benzene including unsaturated hydrocarbons of at least 4 and less than 6 carbon atoms per molecule as well as olefnes of less than 4 carbon atoms per molecule and methane; the steps comprising separating `from said gaseous products of Vpyrolysis at least a substantial portion of said aromatic hydrocarbon material boiling higher than benzene; thereafter contacting the remaining gaseous products of pyrolysis with petroleum oil to absorb in said oil from said products benzene and hydrocarbon material boiling in the neighborhood of the boiling point of benzene as well as at least the bulk of any remaining hydrocarbon material boiling higher than benzene While leaving in said gaseous products of -pyrolysis atleast a considerable portion of said saturated hydrocarbon material of at least 4 and less than 6 carbon atoms per molecule together with oleilnes of lessrthan `4 carbon atoms per molecule and methane; thereafter separately removing from the then remaining gaseous products of pyrolysis hydrocarbon material of at least 4 and less than 6 carbon atoms per molecule; thereafter contacting the yet remaining gaseous products of pyrolysis with petroleum oil to absorb in said oil from said products at least one oleiine of less than 4 carbon atoms per molecule leaving a residual gas rich in methane; and introducing said petroleum oil containingsaid absorbed benzene and said absorbed hydrocarbon material boiling in the neighborhood of the boiling point of benzene and said absorbed oleiine into said petroleum oil pyrolyzing environment for vapor phase pyrolysis.

EDWIN L. HALL.

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