US2276081A - Conversion of hydrocarbons - Google Patents

Description

March 1o, 194,2.l E, H 'MCGREw 2,276,081v coNvERsIroN oF HYDRocARBoNs Filed Aug. 12, v1959 lll wm; Wb\

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,Q5 MM lll Patented Mar. 10, 1942 CONVERSION or HYDRocARBoNs Edwin H. McGrew, Chicago, Ill., assignor to Universal Oil Products Company, Chicago, Ill., a corporation cf Delaware Application August 12, 1939, Serial No. 289,725

Claims.

This invention concerns a process for manufacturing substantially olefin-free gasoline by the catalytic conversion of hydrocarbon oils. More particularly, the process relates to the conversion of distillate fractions of hydrocarbon oil having substantially no material of the gasoline boiling range present therein.

Although the process may apply to the production of motor fuels for use in any type of internal combustion engine, it fndsspecial application-in the manufacture of fuels for use in airplane motors. This is true because of the highly stable character of the finished product, as well as its great susceptibility to increases in antiknock value by the addition of tetraethyl lead.

Numerous processes have been developed for the production of increased yields of motor fuel from crude petroleum and other hydrocarbon sources. Among these is the non-catalytic thermal cracking process whereby heavy oils are converted to substantial yields of gasoline having relatively high antiknock value. Straight-run gasoline and naphthas which may have poor antiknock properties are non-catalytically reformed to produce gasoline of improved octane number. This process also yields substantial quantities of gases containing polymerizable oleflns, and various polymerization processes mayv be used in conjunction therewith to augment the yields of valuable motor fuel produced.

Another process of more recent development is the catalytic cracking process whereinhydrocarbon fractions containing substantially no gasoline are converted to high yields 0f premium grade motor fuel.

The octane numbers obtainable by commercial non-catalytic cracking and reforming processes are relatively limited, since improved antiknock properties beyond a certain point can be gained only at the expense of yield of gasoline, so that eventually a pointis reached wherein it is no longer economical to increase the octane rating in this manner. Catalytic cracking and polymerization processes may be used to produce motor fuel of higher octane rating than is economically feasible according to the non-catalytic methods of operation.

However, the products of cracking processes have a common characteristic in that all of them contain considerable percentages of olenic hydrocarbons. Cracked and reformed gasolines have not been considered suitable for use in the aviation industry, because of the unsaturated hydrocarbons present. Moreover, cracked gasolines, because of these olenic hydrocarbons, are usu` ally less susceptible to improvements in octane rating by the addition of substances suchl as` tetraethyl lead, than the saturated straight-run gasolines of similar boiling range and antiknock value.

Various methods have been practiced for increasing the stability of cracked gasoline, including treatment with sulfuric acid, metal salts, clays, and/or inhibitors, in order to prevent gum formation and the development of undesirable color during storage. However, chemical treatment, such as with sulfuric acid, metal salts, and` the like, results in removal of part or all of the oleinic constituents of the gasoline with consequent loss in antiknock properties ofthe nished gasoline. Inhibitors prevent the formation of gum, but have no effect on the olen the gasoline.

It is with methods of catalytically producing and increasingy the saturation of catalytically cracked gasoline which is olefinic in character in order to increase storage stability, decrease color and gum content, improve the color, and increase susceptibility to the addition of tetraethyl lead that the present invention isconcerned.

In one specic embodiment the present invention comprises a .process for converting hydrocarbon oils into substantially saturated gasolines suitable for use as aviation base fuels, which comprises contacting said hydrocarbon oil witha cracking catalyst at a temperature within the range of approximately 80G-1200" F., and substantially atmosphericpressure, fractionatlng the reaction products, separating the gasoline into a low-boiling` fraction and a higher-boiling fraction, mixing the low-boiling fraction with hydrogen, contacting it with a hydrogenation catalyst under conditions adequate to eifect substantial hydrogenation of the oleflns contained therein, contacting Athe higher-boiling fraction of catalytically cracked gasoline with or without a portion of the original hydrocarbon oil admixed therewith, with a catalytic mass selected from the group consisting of silica-alumina, silica-zirconia, and silica-alumina-zirconia, at a temperature of G-900 F. and a pressure of substantially atmospheric to 1000 pounds per square inch, and

combining it with the hydrogenated low-boiling fraction of catalytically cracked gasoline to form a substantially saturated finished gasoline.

The catalysts which are useful in the present process may include cracking catalysts of vari ous types. such as synthetic precipitatedA composites consisting essentially of a major portion of precipitated and washed silica hydrogel havcontent of ing added thereto minor proportions of precipitated hydrogels to form masses consisting of silica-alumina, silica-zirconia, silica-alumina-zirccnia, etc., said composites being substantially free of alkali-metal compounds.

ln the following specification the terms silicaalumina, silica-zirconia, and silica-alumina-zirconia masses are used in a broad sense. Inasmuch as the chemical knowledge of the solid state has notfbeen developedperfectly, it is not possible to give' the structure of all solid substances. All that can be said deiinitely concerning these masses is that they contain silicon, oxygen, aluminum, and/or zirconium in combination. Generally speaking, however, all these components indicate more or less low catalytic activity individually but in the aggregate display high activity. This activity is not an additive function, it being relatively constant for a wide range of proportions of the components, whether in molecular yor ,fractions of myoleculavpropor-v tions. No one component can be determined as the one for which the remaining components may be considered as the promoters according to conventional'terminology, nor can any components be' determined as the support and the others the catalyst proper.

According to the description of the preparation of the preferred catalysts given below, precipitated hydrated alumina and/or hydrated zirconia are composited with precipitated hydrated silica gel, otherwise known as silica hy- 4`drogel, and then the composite is washed,dried, and calcined, producing a catalyticL mass. However, the diierent catalysts which may be so produced therefrom do not necessarily give equivalent results.

The primary catalytic cracking step may be carried out at a temperature within-*the range of /approximately 800-1200 F. and a pressure of substantially atmospheric or slightly superatmospheric,'say of the order of 50-200 pounds per square inch, using any suitable cracking catalyst such as acid-treated clays, and preferably catalysts of the type describedin a general way as f silica-alumina, silica-zirconia, and silica-alumina-zirconia catalyst. The operating conditions under which the high-boiling fraction of gasoline is treated include temperatures within" the range of approximately 60o-900 F., and presf sures of substantially atmospheric to 1000 pounds per square inch, employing a silicaalumina, silica-zirconia or silica-alumina-zirconia catalyst. The operation is carried out for a time suilicient to obtain substantial conversion of the olefins to saturated compounds.

The catalytic masses employed in both conversion steps undergo an accumulation of carbonaceous deposits which must be removed from time to time, and this is suitably done by heating in the presence of oxygen-containing gases at a temperature of 1000 F. or higher.

The hydrogenation step wherein the lowerboiling fractionof catalytically cracked gasoline is saturated may be preceded by a desulfurization step such as, for example, treatment with sodium hydroxide -or various metals or 'metal oxides, such as those of copper, iron, and the like. The low-boiling fraction of gasoline is mixed with hydrogen or hydrogen-containing gas and contacted with a suitable hydrogenation catalyst at a temperature of approximately 250-500 F., and substantially atmospheric'pressure.

prise nickel, or mixed nickel-copper catalyst,

The catalytic mass employed may comdrawing, which is not ,valve 2, pump 3,

although other hydrogenation catalysts may sometimes be employed, such as copper, iron, cobalt, chromium, molybdenum oxide, nickel thio-molybdate, etc.

One embodiment of the present invention is illustrated diagrammatically in the attached drawn to scale nor has 'any attempt been made to proportion the equipment. It should not be interpreted as limiting the invention to the exact apparatus or conditions indicated therein.

Hydrocarbon -oil is charged through line I, valve 4, line 5, valve 6, line 1, valve 8, pumpS, valve I0 to coil II which is disposed in heater l2. At with a high-boiling fraction of catalytically cracked gasoline obtained as hereinafter described which enters through line I3 and valve I4, combining with line 1. The mixture is heated to a temperature of approximately GOO-900 F., and passed through line I5, valve I8 into catalytic reactor I1 which may comprise any suitablev type of reactor, such as manifolded tubes disposed in a heated zone, reaction chambers, etc., and' is normally provided in duplicate or triplicate, iriorder to permit' continuous operation, one set 'of reactors being used for hydrocarbon conversion, while the others lare being reactivated. The reaction products leavethe systemy through line I8 and-valve I9, entering secondary fractionator 20. The nished gasoline is taken overhead through line 2l and valve 22 through stabilizers] condensers, etc.,l not shown, to suitable storage. The insumciently converted oil passes through lines 23 'and 24 and valve 25, line 26, line 21, valve 28, pump 23, and valve 30 to coil 3| which is disposed in heater 32. The heated oil is passed throughline 33, valve 34 to catalytic reactor 35, which may "/A sure. The reaction products pass through line 36, valve 31, to primary fractionator 38. A part of the. insufficiently converted oil may be withdrawn through line 39 and valve 40, and a part or all of the oil may be passed through line 4I, valve 42 to line 21, and thence by previously described routes returned to the catalytic cracking step. A part or all of the original charging stock may be passed through line 43, valve 44, line 26 and line 21 to the high-temperature catalytic cracking step.

A higher-boiling fraction of the catalytically cracked gasoline may bek removed through line I3 and valve I4, and passed by previously described routes to catalytic reactor I1. Theend point vof this product is normally within the limits of approximately 30D-400 F. A lowerboiling fraction of cracked gasoline is removed through line 45, valve 48 to stabilizer 41. The gaseousk products are removed through line 43 and valve 49. The stabilized gasoline lpasses vthrough line 50, vvalve 5I, pump 52, valve 53 to desulfurizer 54 whereinl hydrogen sulfide and other sulfur compounds, such as mercaptons, may be removed.

Any suitable type of desulfurizing agent may be used at this point, including alkali-metal hydroxides or metals or ,metal oxides, such as l those of copper, iron, nickel,lead, etc. The gasoline` then passes through line 55, valve 53 this point the oil is mixed may be used. The mixture from line 51 passes through valve 60, heat exchanger 6I and thence to catalytic hydrogenator B2 wherein the olefins are hydrogenated to the corresponding parafn hydrocarbons at a temperature within the range of approximately Z50-500 F., and a pressure of substantially atmospheric or slightly superatmospheric, such as 50-100 pounds per square inch. The hydrogenated fraction passes through line 63 and valve` 64 and may be sent to fractionator by way of line 65 and valve I6. A part or all of the hydrogenated fraction may be withdrawn through line `6*'1 and valve 68 ethyl lead per gallon. The bromine number of through suitable stabilizers, condensers, etc.,

not shown in the interests of simplifying the drawing.

Lines `69 and valve draining fractionator 20 orv of removing a part of the insuiiiciently converted oil at this point.

As will be seen from the drawing-a part or all of the original charging stock may be mixed with 'l0 serve as a means of the high-boiling fraction of catalytically cracked gasoline and sent to the low-temperature conversion stage. However, in certain instances it is more desirable to pass a part or al1 of the charging stock to thehigh-temperature catalytic cracking step, and in this case, the high-boiling fraction of catalytically cracked gasoline is processed in the low-temperature stage by itself.

The following examples are given to illustrate the usefulness and practlcability of this invention, but should not be construed as limiting it to the exact conditions given therein.

Eample 1 lA/Mid-Continent gas oil was blended with a fraction of the catalytically cracked gasoline produced as hereinafter described. The fraction boiled within the range of 200-300 F. The mixture was contacted with a silica-alumina-zirconia cracking catalyst at a temperature of 750 F., and alpressure of 100 pounds per square inch. The reaction products were separated and the product having an end point of 300 F. was recovered. The insumciently converted oil was passed to a high-temperature catalytic cracking .step where it .was converted to motor fuel at a temperature of 950 F. The reaction products were separated in a fractionator, the major portion of the insufliciently converted oil being recycled to the catalytic cracking step. The side cut of gasoline reaction products from this step were fractionated in the fractionator used for the conversion step at 750 F., so that the final gasoline consisted of a blend of hydrogenated low-boiling fraction and substantially saturated gasoline from the low-temperature catalytic converter. The iinished gasoline had a bromine number of 2, indicating substantially no olefins (present.

'I'he octane number of the products stabilized to 7 pounds Reid vapor pressure was '10, which was increased to 91 by the addition of 6 cc. of tetra- 75 catalytic cracking step alone was 110, indicating a highly` oleiinic material.

The sulfur content ofthe gasoline was 0.02%.

The copper dish gum content was 1 mg.v The gasoline had an oxygen bomb induction period in excess of 12 hours.

Example 2 A Pennsylvania gas oil was contacted with silica-alumina-zirconia cracking catalyst at a.

temperature of 950 F., whereby it was converted into substantial yields of gasoline. The gasoline was separated into a fraction boiling within the-limits of -200" F., and a fraction boiling up tov 350 F. The lower-boiling fraction was hydrogenated as previouslyl described. The

higher-boiling fraction was contacted with the silica-alumina-zirconia catalyst at a temperature of 750 F. IIfhe final blend of gasolinefhad an octane number of '17, which was increased by the addition of` 6'cc. of tetraethyl lead per gallon to 93.

I claim as my invention:

1. A process of hydrocarbon oil gconversion which comprises combining a portion of said hydrocarbon oilwith a higher-boiling lfraction of catalytically cracked gasoline obtained as hereinafter described, lcontacting the mixture with a cracking catalyst at a temperature within the range of approximately 600900 F., and a pressure of substantially atmospheric to 1000 pounds per square inchI recovering the gasoline fraction, mixing heavier insumciently converted products of the catalytic cracking with another portion of the original hydrocarbon oil, passing the mixture to a second catalytic cracking step wherein it is contacted with a cracking catalyst at a temperature within the range of 800-1200 F., and a pressure of substantially atmospheric to pounds per square inch, recovering a highboiling fraction of catalytically cracked gasoline from said second catalytic cracking step, combining it as hereinbefore described with the firstmentioned portion of the original hydrocarbon oil, separating a low-boiling fraction of the catalytically cracked gasoline `from the products of said second cracking step, mixing it with hydrogen, contacting the mixture with a hydrogenation catalyst, under conditions adequate to effect substantialhydrogenation'of the oleflns contained therein, and combining the thus hydrogenated gasoline fraction with the gasoline fraction recovered from the rst-rnentioned cracking step with a heavy gasoline fraction formed as hereinafter set forth, contacting the resultant mixture with a cracking catalyst at a temperature in the approximate range of GOO-900 F., separating gasoline from insuiliciently converted oil, catalytically cracking at least a portionl of the latter at higer temperature than said mixture, separating the resultant catalytically cracked gasoline into a lightv fraction and a heavy fraction, combining the latter with said hydrocarbon oil as aforesaid, subjecting said light fraction to hydrogenation and thereafter combining the samewith gasoline products of the first-mentioned catalytic conversion step.

3. A process for Vhydrocarbon oil conversion which comprises mixing said hydrocarbon oil with a fraction of catalytically cracked gasoline obtained as hereinafter described, contacting the mixture with a catalytic mass selected from the group consisting of silica-alumina, silica-zirconia, and silica-alumina-zirconia. at a temperature within the range of approximately GOO-900 F. and a pressure of substantially atmospheric to 1000 pounds per square inch, to produce a sub; stantially olen-free gasoline, separating the reaction products, recovering the gas and gasoline, contacting fractions of said reaction products heavier than gasoline in vaporous form with a cracking catalyst under conditions of temperature and pressure adequate to effect substantial catalytic cracking thereof, separating the reaction products, recovering a high-boiling fraction of catalytically cracked gasoline, combining it withthe original hydrocarbon oil charge as heretofore described, recovering a lower-boiling fraction of catalytically cracked gasoline, removing a portion of the sulfur contained therein, mixing the fraction with hydrogen, contacting the mixture with a hydrogenation catalyst under conditions of temperature and pressure adequate to effect substantial hydrogenation of theolens contained therein, recovering the hydrogenated fraction, and combining it with the olefin-free gasoline produced in the primary conversion step.

4. A conversion process which comprises combining hydrocarbon oil heavier than gasoline lil with hydrocarbons boiling in the gasoline range, formed as hereinafter set forth, subjecting the resultant mixture to the action of a cracking catalyst at a temperaturein the approximate range of 60G-900 F., separating gasoline from insufliciently converted oil, catalytically cracking at least a portion of the latter at higher temperature than said mixture to convert a substantial portionthereof into gasoline, and combining heavier fractions of the last-named gasoline with said hydrocarbon oil as aforesaid.

5. A conversion process which'comprises com. bining hydrocarbon oil heavier than gasoline with hydrocarbons boiling in the gasoline range, formed as hereinafter set forth, subjecting the resultant mixture to the action of a cracking catalyst at a temperature in the approximate -range of GOO-900 F., separating gasoline from insufficiently converted oil, catalytically cracking at least a portion of the latter at higher temperature than said mixture to convert a substantial portion thereof into gasoline, separating the lastnamed gasoline into a light fraction and a` heavy fraction, and combining the latter with said hydrocarbon oil as aforesaid.

EDWIN H. MCGREW..

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