US2157220A - Method of converting hydrocarbons - Google Patents

Description

May 9, 1939. H. c. scHUTT METHOD 0F CONVERTING HYDROCARBONSv Filed March 26d, 1934,

Ill'.

Patented May 9, 1939 UNITED STATES i l2,157,220 l PATENT OFFICE 2,151,220vr o Mn'rnoo oF coNvEarlNe mnocAaBoNs Application March 2s, 1934, serial No. 717,456

17 Claims.

My invention relates to a method of converting` hydrocarbons and more particularly to a method of producing a blended stabilized motor fuel comprising both cracked distillate, that is, 5 distillate obtained by converting hydrocarbons of higher molecular weight into lower molecular Weight, and polymerized distillate, that is distillate obtained by converting hydrocarbons of lower molecular weight into hydrocarbons of higher molecular weight.

In a vapor' phase process s uch as disclosed in co-pending application to John Wycliffe Throckmorton, Serial No. 687,985, filed September 2, 1933, in which hydrocarbon oils are -converted into hydrocarbons of lower molecular Weight, a considerable volume of gaseous and low boiling hydrocarbons is formed. The formation of light hydrocarbons is more or less inherent to a vapor phase process of this type. The application of John Wycliffe Throckmorton, above referred to,

lis an improved form of what is known to the art as the gyro process. In actual practice, reflners who make motor fuel by converting the hydrocarbon oil using the gyro process employ a polymerization unit in conjunction with the gyro cracking unit in order to recover a polymerized distillate. This polymerized distillate not only represents a distinct advantage in increasing yields by the conversion of light hydrocarbons which could not be used as motor fuel, but the polymerized distillate has an extremely high octane number of antiknock value.

In a polymerization process such as is disclosed inthe co-pending application of Karl Finsterbusch, Serial Number 693,463 led October 13, 1933, the lighter hydrocarbons such as methane, ethylene, and ethane are substantially eliminated from the polymerization feed to increase the percentage of unsaturates` in the feed and give a more ideal charging stock. In this Way the polymerization feed may be converted to a liquidy state to reduce the volume and horsepower that would be required to deliver the feed at polymerization pressures if it were in the vapor3 or gaseous state in which it leaves the cracking unit.

Although the above method provides for a most efficient conversion of those unsaturated constituents fed to the polymerizing unit, it

5 nevertheless sacrifices the yields which could be u process for polymerizing gases produced by a cracking operation or from other suitable sources to increase the yield of motor fuel distillates.

It isV a further object of my invention to provide a process for polymerizing gases produced fromv a cracking operation or other suitable 5 sources by converting all the polymerizable constituents of the gas at the optimum rate and conditions for each constituent or each group of constituents.

Another object of my invention is to provide a process for -polymerizing gases produced by a cracking operation or other suitable sources which will substantially prevent the overpolymerization of any constituents and therefore reduce the formation of heavy polymers which require recycling in the main cracking'system and which reduce the yield of motor fuel distillates.

Another object of my invention is to provide a combined cracking andpolymerizing operation which will avoid gumming or coking up of the polymerizing reaction chamber with its attendant increased formation of coke or gum.

A further object of my invention is to provide a cracking and polymerizing operation in which the polymerization feed is split into fractions having different reaction-velocities and in which the fractions, each consisting of constituents of substantially the same reaction velocity characteristics are separately polymerized and combined to produce a greater yield of motor fuel distillate.

A still further object of my invention is to provide ra multi-stage polymerization process in which the heavier saturated hydrocarbons such as butane, pentane, etc. which do not polymerize directly, are in part converted together with the unsaturates such as butylene, which are being polymerized in a lower reaction-velocity coil and in which the conversion products are subsequently recycled for complete polymerization with the lighter molecular weight unsaturates in. a higher reaction-velocity coil.

It is a still further object of my invention to provide a polymerization process in which a part of the heavier saturated hydrocarbons such as butane, pentane, etc. which do not polymerize directly, are converted together with the unsaturates such as propylene and butylene whichv are being polymerized in a lower reaction-velocity coil, the remainder of the saturates being substantially completely converted in a separate cracking coil and subsequently recycled for complete polymerization with the lighter molecular weight unsaturates in a higher reaction-velocity coil.

Other and further objects of my invention'will appear from the following description.

The accompanying drawing represents a diagrammatic view of one form of apparatus capa-' ble ofcarrying out the process of my invention.

In general, pyrolytic conversion of propane, propylene, butane, butylene, etc., into heavier hydrocarbon constituents is characterized by successive steps of decomposition and polymerization at a rate of reaction entirely different from that for ethylene and its closely related compounds under the same temperature and pressure conditions. Therefore, if a mixture of hydrocarbon gases ranging from ethane, ethylene to butane, butylene and heavier compounds is treated in the same reaction coil, all compounds will be subjected to the same temperature effect which leads to overcracking or polymerization of one constituent and undercracking and polymerization of another constituent. Such conditions seem to exist in the processing systems used at present unless -some system such as that disclosed in the above mentioned-application of Karl Finsterbusch is utilized wherein the lightest hydrocarbons of the order of methane, ethane and ethylene are separated from the heavier hydrocarbons ranging from propylene and heavier constituents.

The reaction velocity of a hydrocarbon not only is abfunction of the temperature but also a function of its concentration in a complex mixture. Therefore, variations in the composition of the gas mixture charged to the polymerization plant require simultaneously corresponding variations of the operating conditions if operation is to continue at the same rate. Overpolymerization of ethylene leads .to the formation of heavy polymers with reduction in yield of motor fuel constituents. Overcracking and polymerization may cause increased formation of coke or gum and consequent fouling of the reaction chamber or may even form heavy polymers which must be recycled in the main cracking system to avoid a loss in producible or recoverable endpoint gasov line distillate.

In order to more or less overcome the present diillculties and deficiencies it is proposed to process the lighter and heavier fractions of the gas to be polymerlzed in separate reaction coils at the proper time-temperature factor governed by the reaction-velocity at which the reactant undergoes conversion. Ideal conditions would exist if all constituents be separated from each other and be treated in a pure state. 'I'his is practically impossible in a commercial operation. However, the separate treatment of the two fractions will considerably improve the operation and yield, being closer to ideal` conditions.

If the ethylene is treated with the lighter fractions the conditions for this coil .can be so -l adjusted that maximum conversion of ethylene into useful motor fuel is obtained, while the accompanying methane, ethane and some propane having a much lower reaction-velocity constant will be only slightlyl affected. Propylene and butylene have a very similar reaction-velocity characteristic and, if treated together in the second separate coil at their optimum rate of temperature and time, will yield a maximum amount of gasoline distillate at a minimum rate of formation of heavy polymers. If, for example, one fraction consisting of propane, buta'ne, and their corresponding unsaturated compounds such as propylene and butylene, is' exposed to tmperature pressure conditions determinedby the my process is based upon the physical effect,

that the reaction-velocity constant, as far as cracking operation is concerned, varies directly as a function of the molecular weight, but as far as polymerization reaction is concerned, varies inversely as a function of the molecular weight.

Close separation of the fractions is not necessary since the reaction-velocity decreases with the concentration. For example, if a minor portion of ethylene is treated in the presence of heavier fractions, its reaction velocity is lower, due to its low degree of concentration, and the reaction-velocity will fall within the reaction rate characteristics of the heavier constituents, such as propylene and butylene and consequently the danger of overpolymerization is remote.

Under some conditions, it may happen that the feed to the low reaction-veloci@ coil will contain a relatively high percentage of the heavier saturated hydrocarbons such as butane and pentane, for example, and due to the time-temperaturepressure conditions existing in the coil, a small fraction of these heavier saturates will be cracked into light unsaturates such as ethylene. In such case, it may be desirable to provide a separate cracking unit to which the remaining uncracked heavier saturates such as butane and propane may be charged together with the light unsaturates of predominantly ethylene-like characteristics. The cracked products from this cracking coil will include gasoline-like hydrocarbons formed by the ethylene polymerization in the coil and a relatively high percentage of unsaturates such as ethylene, which may then be combined with the rst separated low molecular weight ethylene fraction to form the feed to the high reaction-velocity polymerization coil.

It is well known that the gas produced in the gyro cracking system is subject to wide variations in quantity and quality especially if the cracking unit is not Very closely controlled. Suchvariations will throw a single coil polymerization unit immediately out of balance. It is evident that in lmy proposed method of operation such changes will hardly affect theoperation of the polymerization system as the respective concentration of each of the two gas fractions will not materially change. The quantity only may change. This will necessitate merely slight ad- Yjustments in the temperature conditions to compensate for the change in the time element.

More particularly referring now to the drawing, I charge a mixture of gaseous and low boiling hydrocarbons recovered, for example, from the fractionating tower of a gyro process system or from any other suitable source, through a condenser to a compressor (not shown) from which a liquid and gas feed is taken ofi". The liquid feed is charged through a line I to a high pressure fractionator or rectifying column 2 equipped with suitable trays for separating the hydrocarbon vapors into the desired fractions.

- desired vapor pressure specications.

This column may be operated at pressures of from 250 to 400 pounds per square inch and at suitable temperatures in order that the desired endpoint gasoline may be withdrawn from the bottom of the tower and a desired mixture of low boiling and gaseous hydrocarbons withdrawn from the top of the tower. The operating conditions of this tower are such that the liquid hydrocarbons having 5 and more carbon atoms per molecule are withdrawn from the bottom of the tower together with sufficient liquid hydrocarbons having 4 atoms per molecule to give the gasoline the The remainder of the C4 fraction and all the lighter fractions are taken off overhead through the line 3 and cooled in the condenser 4. The mixture of liquid and gaseous hydrocarbons is led through the line 5 to the gas separator 6 where the lighterV hydrocarbons of the order of methane, ethylene and ethane are separated and vented rthrough the line 1 and valve 1a to join the gas to the convection section Ill of the furnace setting II- In general, I may refer to different hydrocarbon compounds having the same number of carbon atoms but a varying number of hydrogen atoms by assigning to the hydrogen of tbe compound a value :r representing the number of hydrogen atoms present. For example, propane CaHs and propylene CaHe would be represented as CsHx. After the initial heating in the convection section I0, the liquid hydrocarbons pass through the radiantly heated coil I2 of the furnace where they are rapidly brought up to the required reaction temperature for polymerization prior to introduction to the low reaction velocity reaction chamber I3. In this chamber, as a result of an exothermic reaction, a conversion of the propylene, butylene, etc., into hydrocarbons of higher molecular weight, i. e., `gasoline-like hydrocarbons, takes place while propane, butane and other saturates having a much higher reaction constant will be in part converted into lower molecular weight unsaturated and saturated compounds. The reactant withdrawn from the reaction chamber I3 through aline I4 is conducted to an arrestor I5 where it is quenched with a light distillate recovered in a later step in this cycle and introduced through the line I6. The

I mixture of quenched products and light distillate .Y is withdrawn vfrom the arrestor through the line I1 and introduced to a high pressure separator I8 from which a small amount of heavy polymers and gums is withdrawn through a line I3 for removal from the process,- or recycle .to the cracking system. The uncondensed vapors and gases are withdrawn from the high pressure separator I8 through a line 2B, cooled and 'condensed in a condenser 2I and charged througha line 22 having a back pressure control valve 22a to a low pressure separator 23. The constituents not condensable under these conditions pass off overhead through a line 24 and compressor 24' and combined with the 'gas feed from line 8 and the gas feed in line 1 from the gas separator 6 for introduction to the absorber 25 by means of the line 26. A portion of the liquid products of gasoline boiling range from the lo'w pressure separator 23 are charged through a. line I 6 to the arrestor I5 as a quenching medium while the remainder of these products is fed through the line 21 by means of the pump 21a to the high pressure fractionator or rectifying column 2.

The lighter hydrocarbons of the order of methane, ethylene, ethane, together with smaller amounts of propane, propylene and heavier hydrocarbons passing through the line 3 from the compressor (not shown), the line 1 from the gas separator 6, and the line 24 from the low pressure separator 23, are combined for introduction to the high pressure absorber 25 through the line 2G. Absorption `oil is introduced through the line 28 to the top' of the absorption tower 25 and ows downward in intimate contact with the hydrocarbon gases and vapors rising upward through the tower to remove the heavier hydrocarbons from the gas vapor mixture. The absorption oil and heavier hydrocarbons carried l thereby are removed from the bottom of the absorption tower through the line 29 and may be returned to the main fractionating tower of the cracking plant for separation from the a/bsorption oil. The light gaseous hydrocarbons/of predominantly ethylene-like characteristics, together with methane, ethane, propane and propylene in minor amounts are taken oi overhead through the line 30 and fed at the absorber pressure or pumped at a higher pressure by means of the compressor 30a to the radiantly heated coil 3| of the furnace setting II. In this coil the mixture is rapidly heated to polymerizing conditions of temperature for most favorable ethylene conversion and then charged to the higher reaction velocity reaction chamber 32 wherein, as a result of the exothermic reaction the ethylene is converted to hydrocarbon constituents of gasoline boiling range. The minor quantities of methane, ethane, and propane which have a much lower reaction constant will be only slightly affected. The reactant is withdrawn from the reaction chamber 32 through theline 33 and charged to the arrestor 34 wherein it is quenched with a light distillate separated in a later step of this cycle and introduced to the arrestor 34 through the line 35. The quenched products and light distillate are withdrawn from the arrestor 34 through a line 36 and introduced to a high pressure separator 31 from which any heavy polymers formed are withdrawn as a bottom product through the line 38 for recycle to the cracking system or removal, in conjunction with theheavy polymers withdrawn from the separator I8 through the line I9. The uncondensed vapors and gases withdrawn from the separator 31 through the line 39 are cooled` and then condensed in a condenser 4I! and fed through a line 4| and back pressure control valve 4Ia to a low pressure separator 42 where constituents of gasoline boiling range are separated from residual gas which is removed as an overhead product through the line 43 and back pressurecontrol valve 43a. A portion of the liquid hydrocarbons in the separator 42 is utilized as a quenching medium and charged to the arrestorv 34 through the line 35. 'I'he remainder of the liquefied hydrocarbons of gasoline boiling range passes through the line 44 to the line 21 and combines with the liquid therein for introduction to the high pressure fractionator 2.

It is to be noted that a portion of the feed from polymerization feed lines 9 and 30 may be bypassed through the lines and 41 to the reaction chambers i3 and 32-respectively for controlling the temperature in these reaction chambers inasmuch as the time is a xed characteristic.

' In order that I may satisfactorily convert the greatest possible amount of saturated hydrocarbons which may be fed to the polymerizing coil 3| with the unsaturates such as propylene. I have provided a cracking coil in conjunction with the gas feed line 24 from the low pressure separator 23. The line 24 may be tapped at any suitable place by means of a branch line 48 having a shut-off valve 49 leading to a convection section 5U of a cracking furnace 5I. The line 24 may be cut oif in this alternative mode of operation by means of a shut-off valve 24a located as shown in drawing. TheA hydrocarbon vapors and gas passing through the line 48 will contain not only polymerization products such as ethylene, which will polymerize in this coil to produce gasoline-like hydrocarbons, but will also contain unconverted saturated hydrocarbons such as propane and butane whose conversion to low molecular weight unsaturates will be effected in the coils of the cracking furnace 5i. The gases from the convection section 50 pass through a radiantly heated section 52 and at their exit from the soaking tubes of this section are quenched in the arrester 53 by means of the cool light distillate recovered as will be more fully explained hereinafter. The quenched products pass through a cooler 54 wherein their temperature is lowered before introduction to a separator 55. From this separator there is taken oif overhead through the line 56 having a valve 5l and compressor 56a, lower molecular weight hydrocarbons, both saturates and unsaturates of which the latter are of predominantly ethylene characteristics. These overhead products.- are then combined with the light gas fractions from the lines lI and 8 and delivered through the line 2Q to the absorber 25 from which the ethylene and fixed gas is removed throughV the line 30 to the polymerization coil 3|. The liquid, which will be substantially gasoline distillate, which accumulates in the separator 55, is forced under pressure through the line 58 by means of the pump 59a for return to the high pressure fractionator or rectifying column 2. VA portion of this liquid is pumped through the line 59 by means of pump 60 to the arrestor 53 for the purpose described above.

It is believed that the operation of my process will be clear from the foregoing description.

It will be observed that I have accomplished the objects of my invention. I have provided a polymerization system in which the ethylene is polymerized separately from the propylene and butylene in order to increase the yield of motor fuel dstillates from gases produced by a cracking operation.

I have further provided a polymerization system in which the saturates such as butane and pentane, for example, are converted at least in part to unsaturates in a lower reaction velocity polymerization coil as an incident to propylenebutylene polymerization and. in which the polymerization of these converted saturates is effected in conjunction 'with other light unsaturates in a subsequent higher reaction velocity polymerization coil in order that a maximum yield of motor fuel distillate may be obtained.

aioaaao Although I have shown and described/a 2- stage system of polymerization, it is to be understood that this is by .way of example only and my process may be expanded to include am' desired number of stages.

It will be understood that certain features and sub-combinations are of utility and may be employed without'reference to other features and sub-combinations. This is contemplated by and is within the scope of myclaims. It is further obvious that various changes may be made in details within the scope of my claims without departing from the spirit of my invention. It is, therefore, to be understood that my-invention is not to be limited to the specific details shown and' described.

Having thus described my invention, what I claim is:

1. A method of polymerizing a mixture of normally gaseous unsaturated hydrocarbon compounds of the methane series including the steps of separating the mixture of compounds into fractions differing as to the average reactionvelocity of the unsaturates in each, subjecting each fraction to a separate polymerizing reaction most favorable to the average reaction-velocity of the unsaturates of the fraction and recovering a distillate of gasoline boiling range from the reaction products of the polymerization steps. f

2. A method of polymerizing a mixture comprising normally gaseous and very low boiling saturated and unsaturated hydrocarbon compounds of the methane series including the steps of separating the mixture according to the molecular weight of the compounds into fractions differing as to the average reaction-velocity of the unsaturates in each, subjecting each fraction to a separate polymerizing reaction most favorable to the average reaction-velocity of the unsaturates of the fraction and recovering a distillate of gasoline .boiling range from the products of reaction.

3. A method of polymerizing a mixture of normally gaseous and very low boiling unsaturated hydrocarbon compounds of the methane series, including the steps of separating the mixture into a liquid fraction and a vapor fraction differing as to the averagereaction-velocity of the unsaturates in each, polymerizing the liquid fraction at one set of temperature pressure conditions most favorable to the average reaction velocity of the unsaturates of that fractlonsep arately polymerizing the vapor fraction at a different set of temperature pressure conditions most favorable to the average reaction velocity of the unsaturates of that fraction, and recovering a distillate of gasoline boiling range from the reactant from the polymerizationsteps.

4. A method of polymerizing a mixture comprising normally gaseous. and very low boiling saturated and unsaturated hydrocarbon compounds of the methane series including the steps of separating the mixture according to the moi leeular weight of the compound into a liquid fraction and a vapor fraction differing as to average reaction-velocity, subjecting the liquid fraction to polymerization at one set of temperature pressure conditions most favorable to the average reaction velocityv of the unsaturates of that fraction, separately subjecting the vapor fraction to polymerization at a different set of temperature pressure conditions most favorable vto the average reactionvelocity of the unsaturates of that fraction, and recovering a distillate of substantially gasoline boiling range from the reaction products of the polymerization steps.

5. The method of treating a mixture of liquid hydrocarbons of the nature of motor fuel and a hydrocarbon gas containing unsaturates of the4 methane series comprising the steps of rectifying the mixture to stabilize the motor fuel, subjecting the overhead products from the rectification step to a condensing operation to condense the heavier gaseous hydrocarbons, separating the uncondensed gases from the condensate, removing the gases from the separating zone, subjecting the condensate to polymerization by heat and pressure to form hydrocarbons of the nature of motor fuel, separately subjecting the gases removed from the separating zone to polymerization by heat and pressure to form hydrocarbons of the nature of motor fuel, subjecting the products withdrawn from the polyrnerization zones vto condensation to condense hydrocarbons of the nature of motor fuel, separating the uncondensed vapors and gases from the condensates in separating zones, passing a portion of the respective condensates from each separatingA zone to the rectication zone and withdrawing a stabilized motor fuel therefrom.

V6. In a polymerization process in which a low boiling hydrocarbon voil distillate and a stream of -normally gaseous saturated and unsaturated hydrocarbons of the methane series are operated on to obtain a polymerization feed, the steps of separating in a rectification step, the liquid hydrocarbons into two classes, namely, class G, comprising a portion of those hydrocarbons having the formula 04H10 and all lighter hydrocarbons, and class L comprising the remainder of those. hydrocarbons having the formula 04H10 and all heavier hydrocarbons, separately withdrawing hydrocarbons of class L and classG, from the rectication step, subjecting the hydrocarbons of class G to a condensing operation so that the majority of the hydrocarbons of the formula CaHs, Cal-Ia, 04H8 and C4H1o will be in the liquid phase and the majority of the hydrocarbons of the formula CzHs, 02H4 and Cl-Ir will be in the gas phase, separately withdrawing the liquid and the gaseous hydrocarbons, combining the gases so withdrawn with the rst mentioned stream of hydrocarbon gases, substantially separating in an absorption step` gaseous hydrocarbons having the formula CaHs, C21-I4 and Cl-Ir from the heavier hydrocarbons in the combined gases, withdrawing the lighter gaseous hydrocarbons and the uncondensable gases from the absorption step, polymerizing the liquid hydrocarbons of the formula CsHs, C3Ha, C4Ha and Cil-Im, separately polymerizing the gaseous hydrocarbons of the formula CaHe, 02H4 and CH4, and introducing the polymerized products into the rectication step.

7. A process for producing a hydrocarbon motor fuel, including the steps of taking a very lowboiling distillate recovered from gases of a) hydrocarbon cracking operation, and a stream of uncondensed gases of the methane series, substantially eliminating from the liquid a portion of the hydrocarbons having the formula. 04H10 and all heavier hydrocarbons ina rectication step, separately withdrawing overhead the remajority of the 02H: and CH; hydrocarbons are in the gas phase, combining the C21-L: and CH4 gaseous hydrocarbons with the said stream of uncondensed gases, eliminating most of the heavier hydrocarbons from thecombined streams 5 in anv absorption step, passing the remaining gaseous CzHI and CH.;V hydrocarbons to a polymerization zone and there polymerizing the same under heat and pressure, passing the liquid Celi-Im and Cri-I1 hydrocarbons to a separate polymerization zone and there polymerizing the same under heat and pressure, introducing a portion of the I polymers Withdrawn from each polymerizing zone into the rectication zone and passing the hydro-- carbons in the gas phase Vfrom said last' polymerization step into the absorption zone.

8. A process for converting a. mixture of normally gaseous and very low boiling saturated and unsaturated hydrocarbon compounds of the methane series including the steps of recovering from the mixture of compounds a fractionhaving a relatively low average reaction-velocity with respect to the unsaturates therein, subjecting the fraction to polymerizing conditions of heat and pressure mostl favorable to the average reaction velocity of the fraction, recovering a first distillate oi" gasoline boiling range from the reaction products of the polymerization step, subjecting the remainder of the reaction products of the polymerization step to cracking conditions of heat and pressure, recovering a second distillate of gasoline boiling range from the reactant from the cracking step, recovering from the remainder of the reaction products of the cracking operation a fraction having a relatively high average reactionvvelocity with respect to the'unsaturates therin,separately subjecting this"last mentioned fraction to polymerizing conditions of heat and pressure most favorable to the average reaction velocity of the fraction and recovering a third distillate of gasolineboiling range from the reactant from the last mentioned polymerization step.

9. In a polymerization process, in which normally gaseous and very low boiling saturated and unsaturated hydrocarbon .compounds of the methane series are operated'upon to obtain a polymerization feed, the steps including separating from the compounds arst reactant having an average reaction-velocity substantially equivalent to that of propylene, 'subjecting the rst reactant to temperature and pressure conditions Aoptimum for polymerization oipropylene and unsaturates whose reaction-velocity rate due to` their concentration in the reactant is substantally that of propylene while atleast a part pf the saturates such as propane and butane are -cracked, separating from the reaction -product a rst distillate of substantially gasoline boiling range, subjecting the 'remainderof the reaction product to temperature and Pressure conditions optimum for cracking of the remainder o1' the saturates to form lower molecular weight unsaturates, separating from the reaction products of the cracking'operation a second distillate of substantially gasoline boiling rangerecovering from the remainder of the reaction products of the cracking operation and the remainder oi'- the rst mentioned compounds a 'second reactant having an average reaction-velocity substantially equivalent to Vthat of ethylene, separately subjecting the second reactant to` temperature and pressure conditions optimum for polymerization of unsaturates of predominantly ethylene-like characteristics and separating from the retactant 7 from the last mentioned polymerization operation a third distillate of substantially gasoline boiling range.

10. A method of polymerizing a mixture of normally gaseous and very low boiling hydrocarbon compounds ofthe methane series including the steps of separating from the mixture according to the molecular weight of the compounds a first reactant comprising hydrocarbon unsaturates and saturates, said reactant having a relatively low average reaction-velocity with respect to the unsaturates therein, heating the reactant under pressure, passing the heated reactant to a reaction zone and permitting polymerization to take place as an exothermic reaction under conditions most favorable to the average reaction velocity of the fraction, separating from the reaction products of the polymerization zone. a rst distillate of substantially gasoline boiling range, separating from the-remainder of the reaction products and the remainder of the original compounds according to molecular Weight a second reactant having with respect to the rst reactant a relatively higher average reactionvelocity, heating the second reactant under pressure, passing the second reactant to a separate reaction zone and permitting polymerization to take place as an exothermic reaction under conditions most favorable to the average reaction velocity of the reactant and separating from the.

reaction products of the last mentioned polymerizing zone a second distillate of substantially gasoline boiling range.

11. A method of polymerizing normally gaseous and very low boiling hydrocarbon compounds as .in claim 10 wherein the separation of the second reactant is eiected by intimately commingling the remainder of the first reaction product and the remainder of the original .compounds with an absorption menstruum in the absorption zone and removing the unabsorbed hydrocarbons from `the absorption zone as the second reactant.

,.-sisting chiefly of propane, propylene, butane and butylene, and into another gas fraction consisting chiefly of hydrocarbons of less molecular weight than propylene. l

14. Av method for' converting olefin-containing hydrocarbon gases to gasoline boiling range hydrocarbons which comprises separating said gas into a fraction consisting chiefly of low molecular weight hydrocarbon gases and a fraction consisting chiefly of high molecular weight hydrocarbon gases, subjecting said fractions to diierent time-temperature conversion conditions favorable to the conversion of the oleflnic hydrocarbons contained'therein to gasoline boiling range hydrocarbons, and recovering a distillate oi' gasoline boiling range from the combined reaction. products.

15. Method in accordance with claim 14 in which the high molecular weight fraction consists chiefly of propane, propylene, butane and butylene, and the low molecular weight fraction consists chiefly of hydrocarbons of lower molecular Weight than propylene.

16. Method in accordance with claim 14 in 'which gases resulting from the conversion of the HERMANN C. SCHU'T.

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