US2295752A - Conversion of hydrocarbon gases and liquids to motor fuels - Google Patents

Description

Sept. 15, 194.2.. c. L, PARKHURST I A.corwgasmn oF HYDRocARBoN GASES AND LIQUIDs To MOTOR FUELS 'r'iled June so', 1938 2 sheetssheet 1 Sept 15, 1942- G. L.. PARKHuRsT 2,295,752

CONVERSION OF' HYDROCARBON GASES AND LIQUIDS TO'MOTOR FUELS Filed June 30, 1938 2 Sheets-Sheet 2 Patented Sept. 15, 1942 CONVERSION F EYDROCARBON GASES AND LIQUIDS T0 MGTOR FUELS George L. Parkhurst, Chicago, Ill., assigner to Standard Oil Company, Chicago, Ill.,l a corporation of Indiana Application June 30, 1938, Serial No. lfil? 7 Claims. (Cl. 19d-liti) This invention relates to'an improved process and apparatus for converting hydrocarbon gases and liquids into high quality motor fuels.

One object of my invention is to increase the quality and yield of gasoline obtainable from hydrocarbon gases, petroleum oils, shale oils, oils obtained from carbonaceous materials-by hydrogenation or carbon monoxide synthesis, etc.

A further object is to provide `an improved method and means for utilizing both liquid and gaseous hydrocarbons in the most effective and eiiicient manner in the production of large yields of high octane number gasoline. A still further object is to provide a flexible integrated unit adapted to process all types of hydrocarbon materials, in which unit each of the materials is processed under conditions most suitable for that material. Another object is to provide an improved combination of systems for converting hydrocarbon gases and liquids into motor fuels and for -separating hydrocarbon gases into paraffinc and oleiinic fractions so that each fraction may be converted in the system most suited Vto that fraction. It is alsoran object to provide an integrated gas conversion unit including both thermal and catalytic systems, wherein one of said systems may be used for polymerization while the other system is used for gas reversion, the products from each system being `fractionated on the basis of relative saturation (i. e. into olefins and parafns) as well as on the basis of boiling point. A further object is to provide an improved and integrated unit for separately processing mixtures containing normally gaseous components and for blending both the liquid andthe gaseous reaction product for the most Aeffective utilization thereof.

It is also an object of the invention to provide an improved method and means for utilizing the heat of catalyst regeneration to supply a part f of the heat required for catalytic or thermal conversion. Other objects will become apparent as the detailed description of my invention proceeds.

'Thermal gas reversion or polymerization is capable of utilizing paraiiinic gasesin the manufacture of gasoline, while catalytic gas reversion or polymerization can best utilize the olefinic gases. In practising my invention I combine a catalytic gas reversion system with a thermal gas reversion system, segregate the C2 to Cr hydrocarbons (hydrocarbons having from'two to four carbon atoms per molecule) from the reaction products produced by .each system and then i'ractionate these Cz to C4 hydrocarbons on the basis of their saturation, the paranic fraction being returned to thethermal conversion process and the olenic fraction being returned to the catalytic conversion process. Since butanes are valuable components oi gasoline I prefer to segre= gate the butanes from the propane and ethane mal gas reversion system wherein normally liquid hydrocarbons are reacted with propane at a temperature of about 1000 to 1150 F., and wheretheir conversion into motor fuel.

in the C2 to C4 fraction of the reaction products is segregated from the other components of the reaction mixture. The combination also inf' cludes a catalytic system wherein olenic hydrocarbon gases are reacted with normally liquid products in the presence of a catalyst to effect The C2 to C4 raction from the gas reversion processes usually contains large amounts of parafnc hydrocarbons and in such cases l combine the C2 to C4 fraction from the thermal system with the C2 to C@ fraction from the catalytic system, and separate the parafnc from the oleinic gases in the combined fractions by means of a selective solvent such as phenol, cresylic acid, ntrobenzene, iuriural, dichlorethyl ether, sulfur dioxide, etc. From the rai'llnate which consists essentially of paranlc hydrocarbons I segregate the butane and return the propane and ethane for further thermal treatment. The unsaturated hydrocarbons which are freed from the solvent are recycled to the catalytic conversion process.

In the catalytic gas reversion process it is necessary from time to time to regenerate the catalyst by burning the carbon therefrom under controlled temperature conditions. From the standpoint of heat economy it is essential that the heat so generated be utilized and in practising my invention ll utilize this heat directly in either the thermal or catalytic furnace. l

prefer to mount the catalyst chambers in the convection section of the furnace above the convection tubes and at a point at which the temperature conditions are approximately those required for catalytic gas reversion. The lhot re-` generation gases may be employed for heating air or fuel charged to the furnace. it may ybe introduced directly into the combustion chamber of a furnace, or it may be introduced into the convection section for maintaining the tempera ture of the catalyst chambers and to supply heat in the convection furnace coils.

The invention will be more clearly understood from the following detailed description read in. connection with the accompanying drawings which form a part of the specification and in which similar parts are designated by like reference characters. In these drawings:

Figure 1 is a iiow diagramv of my improved gas gas reversion unit;

Figure 2 is a vertical section through a, combination thermal-catalytic furnace showing the position ci the catalyst chambers in the convection section; and

Figure 3 is a horizontal section of the furnace shown in Figure 2.

My invention will be described in connection with the manufacture of high octane gasoline from Mid-Continent gas oil and ordinary refinery gases, particularly cracking still gases. It should be understood, however, that other liquid charging stocks may be employed, ranging from n heavy naphthas to stocks which are even :more

viscous than gas oils. The gaseous hydrocarbons may be obtained from natural gas or from erably 1000, pounds per square inch. A liqueed gas mixture consisting chiey of propane, but also containing some ethane and butane is introduced through line i3 into line i0 or into another bank of tubes in the thermal conversion furnace, in which case the separately heated gases are preferably-combined with the heated gas oil charge at incipient gas reversion temperature. The mixture is then raised to gas reversion tern- ,perature--about 1000 to 11.50 F., preferably 1050 volume, but the amount of liquefied gas may range from 10% to 200% ci the volume of the liquid charging stock. `The amount of quench oli is usually rather small, about 5% to 10% of the combined charging stocks. The quench oil is preferably a gas oil, a portion of the charging Stoch or a cycle oil produced as hereinafter de-` scribed.

Debutanizer tower l0 is preferably operated with a bottom temperature of about 850 to 900 F, and at a pressure oi about 250 to 350, Dreierably about 300, pounds per square inch. By providing a sumcient amount of cooling in the upper part of this tower, either with cooling coils or by the introduction of a reilun liquid, as sharp a fractionation as possible is made between hydrocarbons from C; to C4 and hydrocarbons heavier than C4. The C1 to C4 fraction is withdrawn through line il to deethanizer tower it which is also operated at this high. pressure. The heavierfraction is withdrawn through pressurereducing valve 20 to fractionator 2l, which is per' part of the tower through line et.

preferably operated at about atmospheric to 50 pounds per square inch pressure, with a bottom temperature of about 750 to 900 F. Cycle stock is withdrawn as a side stream through line 22 and is returned by pump 23 back to line I0 for admixture with the gas oil feed, or preferably to the particular coils in the furnace in which the oil is at about the temperature of the recycle oil. Tar is withdrawn from the base of the fractionator through line 2d. It should be understood, however, that instead of using a single tower for separating tar and gas oil I may employ a separate tar flash tower, and withdraw the gas oil and gasoline fractions-from the top of the tar ash tower to a bubble tower fractionator.

The temperature in the top of fractionator 2! is regulated by cooling coils or the introduction of redux to take over substantially all of the gasoline fraction and to return substantially all of the gas oil as hereinabove described. The gasoline vapors are withdrawn through line 26 to condenser il and receiver 28 from which a. portion of the condensate may be recycled by pump 29 and line 30 as reux, and a portion withdrawn through line t! for storage or blending. Uncondensed gases from receiver 28 maybe withdrawn through line 32 to a suitable holder and/or compressed and introduced into the liquefied gas storage tank which will be hereinafter described.

As hereinabove described, the C1 to C4 fraction is introduced into deethanizer tower I8 at a pressure of about 300 pounds per square inch. The bottom temperature of this tower may range from about 150 to 250 F. but the top is preferably maintained at about F., by the use of cold reux. 'Methane and ethane are withdrawn from the top of the deethanizer through line 33, partially condensed in cooler, Sii and then introduced into receiver Q35, the methanewith some of the ethane being vented to suitable gas lines through valved line te, and the liqueed ethane being returned by pump 3l either to reflux line te or liquefied gas draw-on te. Ii'he C: and C4 hydrocarbons, with perhaps small amounts of C5 and C2 hydrocarbons are withdrawn from deethanizer i8 through line l0 to liqueiied gas storage tank d l. The gases in this storage tank consist essentially of a mixture of ethane, ethylene, propane, propylene, butano, iso-butano, buten'e-l, butene-2, iso-butylene and perhaps a very small amount of Cs hydrocarbons. The exact composition will vary throughout a relatively wide range, but it will usually be about 20% to 50% olens.

In order to separate the parainic from the olenic liqueed gases I introduce the liquefied gases by pump di, line i3 and heat exchanger ed to'solvent extraction tower d5 in which the liqueed gases are passed counter-current to a selective solvent which is introduced in the up- The temperature and pressure conditions in the tower will depend upon the particular solvent-employed. I prefer to use phenolic solvents such as phenol, cresylic acid, cresols, etc., or chlorinated phenolic solvents such as monochlorphenol, although it should be understood that any selective solvent may be used if the proper conditions are provided to eect the desired phase separation. The phenolic solvents may be used at about room temperatures and they offer the advantage of being easily separable from the extract and raiinate respectively, in the solvent recovery systems. Sulfur dioxide is an excellent solvent but its boiling range is so close to that of the gases assegna that separation is difficult. Chlorex (dichlorethyl ether) nitrobenzene, furfural, chloraniline, etc. are further examples of solvents which may be used.

Rafiinate from the extraction tower is withdrawn through line 41 and introduced by pump B8 into raiiinate still 49 which is provided with a suitable heating means 50. The solvent is withdrawn from the base of the still through line l and cooler 52 to solvent storage tank 53. Since butane and pentanes are valuable components or' motor fuels, such products are preferably removed as a side stream through line 5d. The remaining paraiilnic gases which consist chiefly of propane, smaller amounts of ethane and butanes are4 withdrawn from the top of the tower through line 55 and condenser 55 to re ceiver 51, uncondensed gases being vented throughlline 58, and the condensed parafnic gases being returned through line 59 by means of pump 60 to line I3 and furnace coils it.

The extract from tower 45 is withdrawn through line SI and heat exchanger 62 and is forced by pump 63 into extract still 6d which is likewise provided with suitable heating means 65. Solvent from the extract still is returned through line 66 and cooler tl' to solvent storage introduced by pump 12 and line lI-i into coils 14 of furnace 15. This furnace may be either a gas reversion, 'alkylation or polymerization furnace. If it is employed for gas reversion, gas oil is introduced through line 'it and the mixture of gas oil with olenic gases may be passed through the entire furnace concurrently or they may be heated in separate coils and combined after they have reached a temperature of incipient gas reversion, which for catalytic gas reversion is about 800 to 900 F.

In transfer line 11 the temperature is maintained at about 800 to 1000 F., preferably at about 900 F. At this temperature the mixture l:ls introduced through one or more or" the lines 18 into one or more of the catalyst chambers 19. The catalyst chamber is preferably a cylindrlcal vessel packed with any conventional catalyst such as activated hydrosilicate of alumina or acid-treated clay which has been formed into pellets and dried at'a temperature of about 1000 to 1050 F. Examples of suitable catalysts, either alone or in conjunction with thc heterogeneous catalysts hereinabove described. I do not limit myself to any particular catalyst and any known gas reversion catalyst may be employed.

-As hereinabove indicated, my process is not limited to gas reversion in the catalyst chambers--I may employ these catalyst chambers for polymerization, alkylation or other known contion of motor fuels.

If polymerization is to be eected an excellent catalyst is phosphoric acid onkieselguhr or clay, and with such a process and catalyst the temperature in transfer line 11 will be maintained at about 250 to 600 F., preferably about 450 F. and pressures of 100 to 1000 pounds per square inch. The gas oil charge is, of course, omitted.

For alkylation I may employ sodium aluminum chloride, phosphoric acid etc. as catalysts at a temperature of about 300 to 500 F., preferably 400 F. and pressures of 150 to 2000 pounds per square inch. A suitable liquid charging stock can be introduced through line 1B if desired.

In accordance with conventional practice one catalyst chamber is on stream while others are being purged, revivifled or recharged. The reactiornproducts leave the chambers through lines 8l! and thence through line 8| to debutanizer i6 or through line 82 to debutanizer B3. If a separate debutanizer 83 is employed it may be operated` at about atmospheric to 50 pounds per square inch pressure with a bottom temperature of about 400 to 450 F., sufficient cooling or reiiux being provided at the top to knock back any appreciable amounts of C5 or heavier hydrocarbons. The C4 and .light hydrocarbons may be Awithdrawn Ifrom the topv of this debutanizer through line 84 and introduced into'deethanizer do. It will be understood that if gases are transferred through lines 8l and 8d to debutanizer lo or'deethanizer I8, respectively, suitable compressors must be 4employed to boost the gas pressure to the required pressure.

Alternatively, the overhead from debutanizer 83 may be withdrawn through line 85, partially condensed in cooler 85 and introduced into receiver 81, the methanevand other uncondensed gases being vented through line 88, al part of the condensate being returned through line 89 for use as reflux, and the remainder of the condensate being introduced through line @0 to the liquefied gas storage tank di.

The heavy fractions from the base of debutanizer 03 are withdrawn through line 9i to iractionator column 92 which may operate under about the same conditions as tower 2l. Since the catalytic process produces substantially no tarry materials, the bottoms from this fractionator may be recycled through line 03 and 94 to the coils 14 in furnace 15 or preferably through line 05 to the coils li of furnace l2.

The overhead from fractionator Q2 is withdrawn through line 3S, condenser 01 to receiver 56, uncondensed gases being vented through linethe condensate from receiver` 98 may be recycled version .processes which utilize oleilnic hydrothrough line |00 as reflux and the rest of it withdrawn through line lol to storage or for blendmg.

From the above description it will appear that I have produced three different stocks for blending purposes: gasoline from the thermal conversion process (line 3|), gasoline from the catalytic conversion process (line I 0i) and butanes from` the raflinate still (line 5d). These three products have very dierent characteristics and may be blended in any desired amounts to produce motor fuel for particular purposes.

It should also be noted that any pentanes which are not knocked back in the debutanizers are eventually recovered with the butanes from the raillnate still (line 54) before the gases .are recarbons and hydrocarbon gases for the produc-` cycled. The withdrawal of butanes and pentanes at this point eilects a material savings in operat-l ing costs and provides valuable components in the iinal motor fuel blend.

Referring backto the catalytic conversion step-since most catalysts tend to lose their effectiveness after a certain period of use because of the deposition of carbon thereon, I revivify the catalyst periodically by burning out this carbon with air at a temperature which depends on the nature of the particular catalyst and which in the case of the hydrosilicate of alumina is preferably about 1000, but not above 1050 F. Air from line m2 is-forced by blower |93 through line |04 and the proper line |05 to the catalyst chamber undergoing reviviflcation, the combustion gases being withdrawn from the chamber through line |06 and recycled through line l'l and heat exchanger |08 by means of supplementary compressor |0811. The recycled gases are cooled in heat exchanger |08 and mixed with incoming air in such proportions as to maintain the,desired temperature during therevivication step.

Since large amounts of the hot gases are not required for recycling, I may utilize the heating value of such gases by introducing them through line |09 to the convection section or line |9a to the radiant section of furnace l2, as will hereinafter be described. When the gas contains. large amounts of carbon monoxide or 4other combustible material, it may well be introduced into the radiant section through line lSa, but ordinarily full advantage and benet may be taken of the sensible heat of these gases byintroducing them into the convection section through line its. Also, or alternatively, I may pass such hot gases through line H and heat exchanger iii to preheat incoming air which` passes through line i i2 to the furnace burners. 'or alternatively, be passed through heat exchanger H3 to preheat incoming charging stock to the furnace, the iinal cooled gases being vented The hot gases may also.'

through line i4. It should be understood that .as independent and separate units, they may be built as a single furnace M5 (Figures 2 and 3). Between outer walls i i6 are transverse bames lil and i i8. Spaceig, between baille lil and the outside Wall, forms the radiant section for the thermal heating step. Space |26, between barde H8 and the outside wall, forms the radiant section for the catalytic heating step.` Space ii, between bafiies ill and H8, may serve as a convectionsection for both the catalytic and ther mal heating steps, and since the temperature ai the top of this zone is about that which is employed for catalytic gas reversion, the catalytic vreaction chambers may be mounted in this convection section of the combination furnace. The flue gases leave the bottom of the convection section through flue |22. Heat is supplied for the thermal rafdiant section by burner |23 and to the catalytic radiant section by burner iid.

By mounting the catalytic reaction chambers the expense of insulation which would otherwise be required and at the same time I obtain eifective temperature regulation because this section of the furnace is held at substantially constant temperature. The hot gases which have been used to burn carbon" from the catalyst chambers may be passed directly into the convection section through line |09 or into one or both radiant sectionsthrough line "lila, as shown in Figure 3, or they may be used to preheat incoming air for supporting combustion, or to preheat charging stock. v

By employing a common convection section for both the thermal and catalytic heating systems I may connect any number oi tubes in the section with the system, and as shown in Figure 2, the thermal conversion heating step usually requires more tubes than the catalytic step.

It will thus be seen that the thermal and catalytic systems are integrated and interdependent in the heating step, as well as in the gas recovery and fractionation steps and the solvent extraction step. An outstanding feature of this combination is the treatment of gases from both the catalytic and thermal process in a common extraction system, so that the parafnic gases may be returned to the thermal process andthe oleilnic fraction to the catalytic process, respectively. By employing the solvent extraction step in conjunction with the inter-related conversion processes I can return those fractions to each system which are best adapted for conversion in that system. This is a feature of the invention which is impossible of accomplishment by any of the recycling system heretofore known.

While I have described in detail a preferred embodiment of my invention, it should be undern chambers 'thereby producing hot gases, and

means for utilizing the heat of said the radiant section of said f ace.

2. The apparatus of claim l which includes means for fractionating products leaving the catalyst chambers and for separately recovering a motor fuel fraction and a C2 to C4 fraction, means for solvent entr-acting said C3 to Cs -fraction and for separately recovering parainic and oleiinic Cz to Cs fractions, respectively,l and means for returning said oleiinic C2 to C4 fractions to the hot gases in l coils in said radiant section.

3. A hydrocarbon conversion system which comprises a furnace provided with a radiant section and a convection section, a bank of tubes in said radiant section, a bank of tubes in mid convection section, a plurality of catalyst chambers in said convection section, means for connecting said tubes and said catalyst chambers whereby hydrocarbons may be passed through the tubes in the convection section and the tubes in the radiant section respectively and then` introduced into oney of said catalyst chambers, means for transferring the introduction of hydrocarbons ii'rom said tubes into another of said catalyst chambers when the catalyst in one of said chambers has become spent, means for introducing an chambers, means for transferring the introduc-r tion of hydrocarbons from said tubes to another of said catalyst chambers when the catalyst in one orf said chambers has become spent, means for regenerating the spent catalyst in said cham'- ber wherebyhot regeneration gases are produced and means for transferring heat from said hot regeneration gases to said tubes in the radiant section of said furnace.

5. The apparatus of claim 4 wherein the furnace contains both aradiant section and a convection section and wherein the catalyst chamb ers are mounted in said convection section.

6. In a hydrocarbon conversion system a furnace provided with' a radiant section and a Vconvection section, banks of Vtubes in said radiant section and said convection section respectively,y

a plurality of catalyst chambers, means for connecting said tubes and said chambers whereby a hydrocarbon may be passed'through said tubes and thence into one of said catalyst chambers,

means for transferring the introduction of said hydrocarbon from said tubes into another of said catalyst chambers when the catalyst in one ofl said chambers has become spent, means for regenerating spent catalyst in said chambers whereby hot regeneration gases are produced andv means for transferring heat from said hot regeneration gases to the tubes in the radiant section of said furnace.

I'7. In a hydrocarbon conversion system a pipe Astill furnace, a lplurality of tubes in said furnace, a plurality of catalyst chambers, means for connecting said tubes with one of said catalyst chambers whereby hydrocarbons pass first through said tubes and thence into one of said catalyst chambers, means for transferring the introduction of hydrocarbons from said tubes to another of saidcatalyst chambers when the catalyst in one of said chambers has become spent, means for regenerating the spent catalyst in said cham' ber whereby hot regeneration gases are produced, a heat exchanger, means for passing said hot regeneration gases through said heat exchanger, means for passing air through said heat exchanger to be preheated by said hot regeneration gases and means for introducing said preheated air into said furnace for supporting combustion therein.

GEORGE L. PARKHURS'II

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