US2279547A - Hydrocarbon conversion - Google Patents

Description

April 14, 1942. -G. B. ZIMMERMAN HYDROCARBON CONVERSION Filed June 9, 1939 INVENTOR GORDON ZIMMERMAN ATTORNEY mobzozbb.

Patented Apr. 14, 1942 UNITED STATES PATENTOFFl-CE "2,279,547 it Y HYDROCARBON CONVERSION Application June 9, 1939, Serial No. 278,203

6 Claims.

The invention relates to the conversion of hydrocarbon oil into substantial yields of high octane rating gasoline. More specifically it is concerned with a process for treating a wide boiling range hydrocarbon oil wherein the gasoline mixture, comprising the straight-run product, the gasoline produced in catalytically cracking the gas-oil fraction, and the gasoline from thermally cracking the crude bottoms, is subjected to aromatizationtreatment to produce a final product with a relatively high concentration of aromatic.

hydrocarbons of relatively low olefin content and of high octane rating.

The invention particularly involves thermal cracking treatment of the heavy bottoms of the crude oil, catalytic cracking treatment of the straight-run intermediate fraction, separation of the straight run distillate fraction and the distillate fractions from the thermal and the catalytic cracking treatments intoa fraction consisting essentially of hydrocarbons containing 'five carbon atoms and less to the molecule and a fraction containing the higher molecular weight hydrocarbons, catalytic aromatization. treatment of the higher molecular weight hydrocarbons and blending of the conversion products from the aromatization treatment with the hydrocarbon fraction containing five carbon atoms and less to the molecule.

In one specific embodiment the invention com prises fractionally distilling a wide boiling range hydrocarbon oil into a light fraction consisting essentially of hydrocarbons boiling in the range of gasoline, an intermediate fraction consisting essentially of hydrocarbons boiling in the range of gas-oil, and a heavy residual fraction containportion into gasoline boiling range hydrocarbons,

separating liquid residue from the catalytlcally cracked vaporous conversion products and recovering the former as a product of the process, subjecting said catalytically cracked vaporous conversion products to fractionation to separate fractionated vapors of. the desired end boilin point from the heavier vaporous conversion products, condensing the latter as refiux condensate in the fractionating zone and subjecting the same to further cracking treatment, cooling and condensing the fractionated vapors and collecting the resulting distillate and gas, commingling the light fraction from the fractional distillation. the distillate fractions from the thermal cracking and catalytic cracking treatments and subjecting the mixture to fractionation to separate hydrocarbons containing 5. carbon atoms and less to the molecule from the heavier components, subjecting said heavier components toaromatization treatment to convert a substantial portion of the aliphatic and naphthenic hydrocarbons to aromatic hydrocarbons, commingling the conversion products from the aromatizationtreatment with the overhead fractions from the last mentioned fractionation, cooling and condensing the mix ture and recovering the resulting distillate and gas as products of the process.

Straight-run gasoline ordinarily is composed of paraffinic and/or naphthenic hydrocarbons and,

depending upon the concentration of each, its

ing hydrocarbons boiling above said intermediate 1 fraction, subjecting said heavy residual fraction to thermal cracking treatment to convert a substantial portion to gasoline boiling range hydrocarbons, separating the non-vaporous cracked liquid residue from the thermally cracked vaporous conversion products and recovering the for-' mer as a product of the process, subjecting said thermally cracked vaporous conversion products to fractionation to separate fractionated vapors of the desired end boiling point from the heavier octane rating may vary over a relatively wide range. For example, the/octane rating may be relatively low when it is highly parafiinic, increasing gradually as the concentration of naphthe'nic hydrocarbons increases. Although the gasolines, having a relatively high concentration of naphthenic hydrocarbons, have a high octane rating as comparedwith straight-run gasolines with a higher concentration of paraflinie hydrocarbons, the octane ratings of these mixtures is still below those of the gasolines presently employed in the automotive industry. The addition of small amounts of antiknocking agents, such as lead tetraethyl, improves the gasoline to some extent, but as yet no material has been found that will improve the antiknock properties of the straight-run gasolines sufiiciently for them to become equivalent to or compare favorably with those gasolines produced by catalytic or pyrolytic means.

Thermally cracked gasoline, on the other hand, is highly olefinic, and although the olefins tend to increase the octane rating of the final gasoline,

they also increase the potential gum-forming properties of the gasolineand, in addition, the gasoline has a high acid heat test as compared with that of a paraffinic or aromatic gasoline;

- Catalytically cracked gasoline, like thermally taneously in the same reaction zone to produce a gasoline containing a relatively high percentage of aromatic hydrocarbons. The invention therefore involves a series of steps combined in a novel and advantageous manner to produce a final product of the desired characteristics.

ple, from 100 to 500 pounds per square inch, and. is directed through line It! and valve l9 into reaction chamber 20 wherein the oil undergoes substantial further conversion by means of its contained heat. Reaction chamber 20 is preferably maintained at substantially the same or at a slightly reduced pressure relative to that employed on the outlet of'the heating coil and is preferably insulated to reduce the radiation losses therefrom, although insulation is not shown in the accompanying drawing.

The term aromatization as used through the I specification and claims refers to the conversion of aliphatic and/ or naphthenic hydrocarbons into aromatic hydrocarbons. The conversion of aliphatic to aromatic hydrocarbons involves dehydrogenation followed by cyclization, whereas the conversion of naphthenic to aromatic hydrocarbons merely involves dehydrogenation. Catalytic cracking refers principally to the splitting of carbon-to-carbon bonds in the presence of catalytic masses, whereas thermal cracking refers principally to the splitting of carbon-to-carbon bonds by heat and pressure.

The accompanying diagrammatic drawing illustrates generally in side. elevation the apparatus in which the process of the invention may be accomplished. The fact is recognized, however, that various modifications may. be made, such as the addition of stabilizing and condensing thereto.

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equipment where needed or the utilization of other cracking procedures, when desired, but it is the purpose of this invention to cover such modifications within its broad scope. I

Referring to the drawing, charging stock for the process, comprising a wide" boiling range hydrocarbon oil, such as crude oil, is introduced through line I and valve 2 to pump 3, which discharges through line 4 and valve 5 into heating coil 6. The oil in passing through heating coil 6 is raised to a temperature in the range of 400 to 700 F. by means of heat supplied from furnace I, and is discharged therefrom through line D 8 and valve 9 into fractionator I0 maintained at a pressure varying from substantially atmospheric to 100 pounds or more per square inch.

The heated oil introduced to fractionator I0 is separated by fractionation into a light fraction consisting essentially of hydrocarbons boiling in the range of gasoline and preferably boiling below 475 F., an intermediate fraction consisting essentially of hydrocarbons boiling above said light fraction and substantially below 750 F., and a heavy residual fraction containing hydrocarbons boiling above said intermediate fraction.

The heavy fraction from fractionator I0 is directed through line H and valve l2 to pump l3,

which discharges through line l4 and valve l5 into heating coil I6. I The oil in passing through heating coil I6 is raised to the desired cracking temperature, which may vary, for example, from 850 to 1000 F. by means of heat supplied from furnace I1, and is discharged therefrom under a superatmospheric pressure ranging, for exam- The resulting conversion products after their prolongedconversion in chamber" 20 are discharged from the lower portion thereof through line 2| and valve 22 into the separating zone of fractionator and separator 23. Valve 22 is preferably a pressure control valve by means of which a substantial superatmospheric pressure is maintained in the heating coil and communicating reaction chamber, the pressure on the downstream side of the valve being somewhat lower than that maintained in said heating coil and said reaction chamber. Chamber 23 is preferably maintained at a lower pressure than that maintained in reaction chamber 20 ranging, for example, from 50 to 250pounds per square inch in order to effect substantial further vaporization of the liquid conversion products introduced In the separating zone of chamber 23 the vaporous conversion products introduced thereto and evolved therein are separated from the non-vaporous liquid residue, the latter being discharged from the lower portion thereof through line 24 and valve 25 to cooling and storage or to further treatment as desired. The vaporous conversion products introduced to the separating zone, together with the vapors evolved within the same zone, are introduced to the fractionatingzone situated in the upper portion of chamber 23. Fractionated vapors of the desired end boiling point are separated from the heavier vaporous conversion products in the fractionating zone, the latter being condensed therein as reflux condensate and the former being withdrawn as an overhead vaporous fraction. The fractionated vapors are directed through line 26 and valve-21 to cooling and condensation in condenser 28. The resulting distillate and gas from condenser 28 is directed through line 29 and valve 30 to collectionand separation in receiver 3|. The normally gaseous hydrocarbons remaining uncondensed and undissolved in receiver 3| are directed from the upper portion thereof through line 32 and valve 33 to collection and storage or to further treatment. The distillate collected and separated in receiver 3| is directed from the 'lower portion thereof through-line 34 and valve 35 into pump 36, which discharges through line 31 and valve 38 into line for treatment as hereinafter described. The reflux condensate collected in the lower portion of the fractionating zone in chamber 23 is directed therefrom through line 39 and valve 40 into pump 4|, which discharges through line 42 and valve 43 into line l4 wherein said reflux condensate commingles with the heavy fraction from fractionator I 0 prior to its conversion in heating coil l6 and reaction chamber 20.

. The intermediate fraction from fractionator I0 is directed through line 44 and valve 45 to pump 46,- which discharges through line 4'! and valve 48 into heating coil 49. The oil in passing through heating coil 49 is substantially completely vaporized therein and is raised to a temperature within the range of 800 to 1200 F. without condensate in the fractionating zone.

substantial pyrolytic cracking thereof by means of heat supplied from furnace 59. The heated marily with a combination of steps ratherthan with the design of any particular piece of equipment, no attempt will be made to describe in detail the features of the various reactors that may be employed.

A reactor which may be employed and one which has found wide application in the field of catalysis isthat which contains a plurality of relatively small diameter reactor tubes supported within an enclosed zone, preferably equipped for alternate processing and reactivation. It is also of particular importance that provisions be made for introducing heat to the reactor during the processing cycle and for cooling the reactor during the reactivation cycle, catalytic cracking being an endothermic reaction and reactivation an exothermic reaction. During the .cracking re-' action carbon deposits upon the surface and within the pores of the catalyst lowering its catalytic activity, and in order to restore the catalyst to its active state frequent reactivations are necessary. In order to accomplishcontinuous operation, a plurality of reactors are preferably employed so that at least one or more may be employed for processing while the other or others is undergoing reactivation.

Catalysts which may be employed in the catalytic cracking treatment may consist of pellets or granules of an inert siliceous and refractory material, such as silica composited with compounds selected from the group consisting of alumina, zirconia, vanadia, and thoria, or the sidered exactly equivalent in their catalytic effeet, for certain of these catalysts, such as the silica-alumina catalyst, are known to give better results than the others, This fact,however, is not to be considered as a limiting feature to the broad scope of the invention, for it is thoroughly recognized that other catalysts not mentioned may also be employed to obtain favorable results.

The conversion products from reactor 58 are directed through line 54 and valve 55 into and through cooler 55 wherein the conversion products are cooled to the desired temperature by indirect heat exchange with a cooling medium introduced to cooler 55 by way of closed coil 51. Cooled conversion products leaving cooler 55 are directed through line 58 into the separating zone of fractionator and separator 59. The vaporousconversion products are separated from the nonvaporous liquid residue in the separating 'zone and the latter removed by way of line 69 and valve 5| to cooling and storage or to further treatment as desired. The vaporous conversion products from the separating zone areintroduced to the fractionating zone situated in the, upper portion of fractionator and separator 59 wherein fractionated vapors of the desired end'boiling point are separated from the higher boiling hydrocarbons and the latter condensed as reflux The fractionated vapors separated in chamber 59 are di- .rected from the upper portion thereof through line 52 and valve 98 and subjected to cooling and condensation in condenser 94. The resulting distillate and uncondensed and undissolved gases are directed through line 85 and valve to collection and separation in receiver 51. Normally gaseous hydrocarbons collected and separated in receiver 51 are directed through line 58 and valve 89 to collection and storage or to further treatment as desired. Distillate collected in the lower portion of receiver 61 is directed through line I9 and valve II to pump 12, which discharges through line 13 and valve H into line 85 for treatment as hereinafter described.

Reflux condensate from the fractionating zone of chamber 59'is directed through line 15 and valve 15 to pump 11, which discharges through line 18 and valve 19 into line fl-for subsequent conversion in commingled statewith the intermediate fraction from fractionator 19. When once-through catalytic'cracking is desired, or

when it is desired to reduce the amount of rether cracking in commingled state with the heavy fraction from fractionator I9.

The light fraction from fractionator I9 is directed through line 82 and valve 88 to pump 84,

which discharges through line 85 and valve 89,

and said light fraction commingled in line 85 with the distillate fractions from thermal and catalytic cracking treatments introduced as previously described. The mixture in line 85 is then directed through line 81 and valve 88 into free-- tionator 89 wherein the combined distillates are subjected to fractionation to separate a fraction consisting essentially 'of hydrocarbons containing 5 atoms of carbon and less to the molecule from the heavier higher boiling components, the

former being removed as a vapor and the latter as a liquid. Provision is made for reboiling the distillate collected in the lower portion of fractionator 89 by means of indirect heat exchange with a suitable heating medium introduced by way of closed coil 1 l3. The heavier higher boiling portion of the distillate collected in the lower portion of fractionator 89 is directed through line 99 and valve 9| to pump 92, which discharges through line 93 and valve 94 into heating coil 95. -When the distillate in line 85 contains relatively minor amounts of hydrocarbons containing raised to a temperature in the approximate range of 800 to 1209 F. by means of heat supplied from furnace 91. The heated vapors discharged from heating coil 95, under a pressure varying from substantially atmospheric to pounds or more per square inch. are directed through line 98 and valve 99 into reactor I99. Reactor I99 may be of substantially the same design as reactor 58, because although diflerent catalysts are employed in the aromatization reaction thereaction is similar in many respects to the catalytic cracking rethe reactivation of catalysts involves an exothermic reaction.

Catalysts which have been found to be highly eflicient for converting aliphatic and/or naphthenic hydrocarbons to aromatic hydrocarbons consist in general of pellets or granules of alumina or inert siliceous and refractory materials composited with compounds of the elements selected from the group consisting of the elements in the left hand columns of groups 4, 5, and 6 in the periodic table. Although these catalysts are the preferred catalysts, various other catalysts not mentioned which are capable of promoting the desired reaction may be employed within the broad scope of the invention.

The conversion products from reactor I are directed through line IIII and valve I 02, and, when fractionator 89 is employed, commingle'd with the light hydrocarbons removed therefrom as an overhead fraction through line I03 and valve I04 and the mixture thereafter subjected to cooling and condensation in condenser I05. The resulting distillate, together with uncondensed and undissolved gases, is directed through I line I06 and valve I01 to receiver I08. Uncondensed and undissolved gases collected and separated in receiver I08 are directed from the upper portion thereof through line I09 and valve III! to collection and storage. ed in the lower portion of receiver I08 is directed through line III and valve II 2 to storage or to further treatment as desired.

The following is an example of one specific operation of the process as it may be accomplished in an apparatus such as illustrated and above described when using the preferred catacontaining gasoline and naphtha having an end point of approximately 450 R, an intermediate fraction equal to approximately by volume of the charge and consisting essentially of hydrocarbons boiling above said light fraction and below 700 F., and a bottoms fraction comprising the balance of the charging stock containing hydrocarbons boiling above said intermediate fraction.

The bottoms fraction was subjected to thermal.

cracking treatment in a conventional full flashing coil and chamber unit at a temperature of 935 F. and at a superatmospheric pressure of approximately 150 pounds per square inch on the reaction chamber. The conversion products from the reaction chamber were introducedto a vaporizing and separating zone maintained at a superatmospheric pressure of 75 pounds per square inch wherein the vaporous conversion products were separated from the liquid conversion prodnets and said liquid conversion products subject'- ed to substantial further vaporization to separate a non-vaporous liquid residue which was recovered as a product of the process. The vaporous conversion products, together with the vapors evolved in the separating zone, were subjected Distillate collect- 2,279,547 the aromatization reaction is endothermic while to fractionation to separate fractionated vapors of the desired end boiling point from the higher boiling hydrocarbons, the latter being condensed as reflux condensate in the fractionating zone and returned to the heating coil for further thermal cracking treatment. The fractionated vapors were subjected to cooling and condensation and the resulting distillate and uncondensed and undissolved gases collected and separated into their respective fractions.

The intermediate fraction from the fractional distillation was subjected to catalytic cracking treatment in the presence of a silica-alumina cracking catalyst at a temperature of 932 and at a superatmospheric pressure of pounds per square inch. The conversion products from this zone were introduced to a separating zone. maintained at a superatmospheric pressure of 40 pounds per square inch wher .n the liquid residue was separated from the aporous conversion products and the former recovered as a product of the process. The vaporous conversion products were subjected to fractionation to separate es being withdrawn as a product of the process.

The distillate produced in the thermal cracking and the catalytic cracking treatments were commingled with the light fraction from the fractional distillation and subjected to fractionation to separate a light vaporous fraction containing hydrocarbons having 5 carbon atoms and less to the molecule from the higher boiling hydrocarbons containing 6 and more carbon atoms to the molecule. The latter fraction was subjected to aromatization treatment in the presence of an alumina-chromia catalyst at a temperature of 932 F. and at a superatmospheric pressure of 40 pounds per square inch to convert a substantial portion to unsaturated cyclic compounds. The products from the aromatization treatment were commingled with the light vaporous fraction from the last mentioned fractionation, the mixture subjected to cooling and condensation and the resulting distillate and gases collected and separated.

Thisoperation on the basis of 1000 barrels of crude oil charged per 24 hour day resulted in a yield of gasoline equivalent to approximately 67.5% by volume of the charging stock having an cctane rating of 75, the remaining 32.5% being liquid residue, gas and loss.

I claim as my invention:

1. A process which comprises fractionating 'crude petroleum to form a residual fraction, 9.

- light fraction containing straight-run gasoline components, and an intermediate fraction heavier 2,279,547 than gasoline, thermally cracking said residual fraction, catalytically cracking said intermediate fraction, combining said light fraction with gasoline products of said thermal andcatalytic treatments', aromatizing the resultant mixture in the presence of a dehydrocyclization catalyst, and

recovering the aromatized gasoline.

3. A process which comprises fractionating crude petroleum to form a residual fraction, a light fraction containing straight-run gasoline components, and an intermediate fraction heavier than gasoline, thermally cracking said residual fraction,catalytically cracking said intermediate fraction, combining said light fraction with gasoline products of said thermal and catalytic treat ments, fractionating the resultant mixture to separate therefrom the hydrocarbons of less than six carbon atoms to the molecule, subjecting the remainder of said mixture to aromatization, and blending the resultant gasoline boiling products 5. A process forproducing anti-knockmotor fuel from crude petroleum which comprises topping the crude to separate straight-run gasoline fractions therefrom, cracking portions of the crude heavier than gasoline to produce cracked gasoline, combining the-latter with said straightrun gasoline fractions, fractionating the resultant mixture to separate therefrom the hydrocarbons of less than six carbon atoms to the molecule,

subjecting the remainder 'of said mixture to aromatization in the presence of a dehydrocyclization catalyst, and blending the resultant gasoline with said hydrocarbons of less than six carbon atoms.

4. A process for producing anti-knock motor fuel from crude petroleum which comprises top-' ping the crude to separate straight-run gasoline fractions therefrom, cracking portions of the boiling products with said hydrocarbons of less than six carbon atoms.

6. The process as defined in claim 3 further characterized in that said remainder of said mixture is subjected to arcmatization in the presence of a dehydrocycliza'tion catalyst. I

GORDON B. ZIMMERMAN.

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