US2429875A - Production of gasoline and diesel fuel by catalytic cracking and solvent extraction - Google Patents

Description

Oct. 28, 1947.

G. M. GOOD ErAL PRODUCTION 0F GASOLINB AND DIESEL FUEL BY CATALYTIC CRACKING AND SOLVENT EXTRACTION Filed 061;. 25, 1946 IWW @Www/My.; @di v Patented Oct. 28, 19.47

FUEL BY CATALYTIC CRACKING AND SOLVENT EXTRACTION George M. Good, Albany, Hervey H. Voge, Berkeley, and Bernard S. Greensfelder, Oakland.. Calif., assignors to Shell Development Company, San Francisco,

Delaware Calif., a corporation of Application October 25, 1946, Serial No. 705,682

This invention relates to a new and improved process for the production of useful products and in particular gasoline and Diesel fuel of high quality from petroleum oils.

While gasoline is by far the most important product of petroleum, there are various other use- .i'ul products. In the attempt to produce the maxi lmum amount of gasoline from petroleum, many of these desirable secondary products are either destroyed or produced in small quantities or suffer in quality. One such'product is Diesel fuel. The properties desired in fuels for Diesel engines are to a large extent diametrically opposite to those desired in gasoline. This is due largely to the fact that Otto cycle engines are spark-ignited and require a -f-uel which does noteasily preignite, whereas in Diesel engines a fuel which pre` ignites readily is desired.

In the past few years, catalytic cracking of heavy petroleum oils has become widely adopted,

mingled with the flrst catalytic gas oil .to increase y primarily because through this process excellent l yields of gasoline of superior quality may be produced. This process, however, requires a rela-V tively clean feed stock, and up to the present, at least, the favored feed stock has been the virgin gas oil which heretofore represented the best It is not surprising, there.

source of Diesel fuel. fore. that the adoption of the catalytic cracking process results in the'improvement in quantity and quality of gasoline largely at the expense of the quantity and quality of Diesel fuel.

Some combination processes utilizing catalytic cracking have been proposed for the production of Diesel fuel of at leastaverage quality. However, as far as known, no process has hitherto been invented or developed which is capable of producing superior quality Diesel fuel without.

is, briefly, carried out as follows:

A petroleum oil boiling above the gasoline boiling range is vcracked under conditions to produce a substantial yield of olenic gasoline. In general, this is best effected `by the use of temperatures and space` velocities in the higher end of the known applicable range. The product from this first step catalyticcracking is separated by distillation into normally gaseous products, olefinic gasoline, catalytic gas oil and usually a heavy bottom fraction. The catalytic gas oil is subjected to a suitable solvent treatment to separate a fraction rich in unsaturated and aromatic components of the ,gas oil. The raffinate 4is a high quality Diesel fuel, and is removed as a product of the process. The extract is hydrogenated, blended with the olefinic gasoline, and the mixture is eatalytically cracked in a second catalytic cracking step operating under a somewhat lower temperature than in the first catalytic cracking step. The product of the second cracking step is separated into normally gaseous products,gasoline and catalytic gas oil. This catalytic gas oil from the second cracking step is advantageously comthe yield of Diesel fuel or cycled to the ilrst catalytic'cracklng step to increase the yield of gasoline,

In the present process, Diesel fuel of excellent quality is separated from a, catalytic gas oil fraction between two consecutive catalytic cracking steps. This not only allows the production of a superior` Diesel fuel, but also does so without material decrease in the plant capacity. The separation of Diesel fuel in this manner and at this point contributes to the eillciency of the subsequent hydrogenation treatment by removing hydrocarbon constituents which it has been found are not particularly amenable to the hydrogenation treatment. Also, the separation of a Diesel fuel in this manner contributes to the efficiency of the second catalytic cracking step. firstly in providing a cracking feed` consisting largely of similar hydrocarbon typesA for which the cracking conditions may be adjusted to give optimum results, and secondly by providing a'particularly excellent source of hydrogen forv the second catalytic cracking step. The catalytic cracking at a relatively high temperature, followed by the treatment of the olenic gasoline under the lower temperature cracking conditions in the presence of the hydrogenated fraction of the gas oil. Droduces gasoline of excellent quality and in good yield.y While it is not considered a unique fea-` ture, it should be mentioned that the high tempcrature catalytic cracking in the rst step also produces gaseous products particularly rich in desirable olefins.

The process will be described in further particular in connection with the attached drawing wherein a plant adapted .for the present operation is illustrated diagrammatically by means of conventional figures not drawn to scale. Re-

ferring to this drawing, the feed to the plantentering via line I and pump 2 is passed to a scrubber 3 where it removes small amounts of entrained catalyst from the spent regeneration gas and at the same time is preheated. The feed may be any hydrocarbon oil boiling substantially above the gasoline boiling range. Apreferred feed is a. relatively clean gas oil fraction such as a virgin, gas oil fraction. The preheated feed is passed by pump 4 via lines 5 and 6 to reactor 1. Prior to entering reactor 1, it is mixed with a catalytic gas oil fraction entering via line 8 and hot freshly regenerated cracking catalyst is introduced from standpipe 9 of regenerator I0. The catalyst may be anyione. of the numerous known solid cracking catalysts. Examples of suitable catalyst types are forinstance the natural and treated clay cracking catalysts and the synthetic silica-alumina, s'ilica-magnesia, aluminaboric oxide cracking catalysts. In' the process illustrated, the catalytic cracking is carried out using the uidized catalyst technique. However, other techniques such as' the fixed bed, moving bed and suspensoid techniques as well as other modifications of the uidized catalyst technique, may be utilized. In the fiuidized catalyst technique, the catalyst is used in the form of a powder substantially passing a 1D0-mesh seive. The amount of catalyst introduced into the oil feed via standpipe 9 is usually between 3 and 30 parts by weight with respect to the oil feed. Reactor 1 is a conventional, fluidized catalyst cracking reactor, and is operatedin the conventional manner to eiiect a substantial cracking of the charge stock, for instance a depth of cracking of from about 30% to about 60%. The pressure may be any desired pressure, but is usually very moderate, for example, 1 to 5 atmospheres absolute. The temperature is usually between about 800 F. and 1050 F. Partially spent catalyst is continuously recycled from reactor 1 via lines I3 and III,

to a conventional fluidized catalyst regenerator I0, wherein it is regenerated in the conventional manner.

The reaction' product from reactor 1 is withdrawn via line II and passed to fractionator I2, wherein it is separated into the lower boiling fraction consisting of gasoline and gas which is removed overhead, a catalytic gas oil fraction which is withdrawn as aside stream via line I and a bottom fraction which is withdrawn. The overhead product is cooled; uncondensed gas is withdrawn via line i1 and olenic gasoline is collected in surge tank I8 to be treated as hereinafter specied. The bottom fraction consists of tarry material containing a small amount of catalyst and is usually discarded. The catalytic gas oil fraction boiling for example substantially within 400 F. and 750 F. is passed to extractor -I6 wherein it is extracted with a solvent having a preferential solubility for unsaturated and aromatic type components. Any one of the numerous solvents known to be suitable for this is recovered overhead and returned to the extractor. The extract phase consisting largely o! unsaturated and aromatic type components or the gas oil is passed via line 2l to a hydrogenation reactor 25 wherein it is hydrogenated with hydrogen entering via line 26. Any one oi' a large mimber of hydrogenation catalysts may be used in reactor 25. Examples of suitable catalysts are, for instance, nickel sulfide deposited upon diatomaceous earth, a pilled mixture of suldes of nickel and tungsten, molybdenum sulfide, alumina impregnated with molybdenum oxide, and cobalt molybdate supported by an activated alumina. The hydrogenation is otherwise carried out in the conventional way, The hydrogenated product is separated from unreacted hydrogen in separator 21 and the hydrogen yis Withdrawn via line 28. The liquid hydrogenated product is commingled with the oleflnic gasoline fraction from surge tank I8 and the mixture is passed via line 29 to reactor 30. This reactor,`lilre reactor 1, is a conventional, fiuidized catalyst cracking reactor and is operated in the conventional manner. The conditions in reactor 30 approximate those in reactor 1, except that the temperature and space velocity are preferably somewhat lower. In reactor 30 the olenic gasoline is catalytically treated simultaneously with the catalytic cracking of the hydrogenated gas oil fraction. For further details regarding the conditions, etc. which may be used in reactor 30 reference may be had to United type of operation may be used. Examples of suitable solvents are furfural, sulfur dioxide, methyl ethyl ketone plus water and 2,2' dichlorethyl ether. The raiiinate passes overhead via line I9. Smallamounts of solvents are recovered in stripping column 20 and recycled .to the extractor. The raffinate, free of solvent, is lrecovered via line 2 I. This product is a high grade Diesel fuel.

The extract-phase from the extractor is passed via line 22 to a stripping column 23 wherein the extract is separated from the solvent which latter States Patent No. 2,326,705.

The product from'reactor 30 is passed via line 3i to fractionator 32. Gasoline and gaseous products pass overhead and are cooled. The uncondensed gases are recovered by line 33 and gasoline of high quality is removed by line 34. In one modification the unconverted oil is passed by lines 35, 8, 36 and 6 to the rst cracking reactor 1, wherein it is again subjected to catalytic cracking under the somewhat higher temperature conditions therein prevailing. This allows an appreciable increase in the yield of gasoline. On the other hand the yield of Diesel fuel may be increased by combining part or all of the unconverted oil with the rst gas oil fraction. Line 31 is provided for this purpose.

The invention claimed is:

l. Process for the simultaneous production of quality gasoline and qualityDiesel fuel from hydrocarbon oils boiling above the, gasoline boiling range which comprises subjecting the hydrocarbon oil to catalytic cracking under conditions to produce a substantial quantity oi oleinic gasoline, separating from the product an olefinic gasoline fraction and a catalytic gas oil fraction, separating the catalytic gas oil fraction into a hydrogen-rich Diesel fuel fraction and a hydrogenpoor fraction (extract) by means of solvent extraction, hydrogenating said extract, commingling the hydrogenated extract with the above said olefinic gasoline fraction and .subjecting the mixture to catalytic cracking, and separating the product of saidv latter catalytic cracking step into ai gasoline fraction and a catalytic gas oil frac- 2. Process for the simultaneous lproduction of quality gasoline and quality Diesel fuel from hydrocarbon oils boiling above the gasoline boiling range which comprises subjecting the hydrocarbon oil simultaneously with a catalytic gas oil produced as hereinafter specified to catalytic cracking under conditions to produce a substantial quantity of oleiinic gasoline, separating from the z5 product an olenic gasoline fraction and a catalytic gas oil fraction, separating the catalytic gas oil fraction into a hydrogen-rich Diesel fuel fraction and a hydrogen-poor fraction (extract) by means of solvent extraction, hydrogenating said extract, commingling the hydrogenated extract with the above said olefinic gasoline fraction and subjecting the mixture to catalytic cracking, separating the product of said latter catalytic cracking step into a gasoline fraction and acatalytic gas oil fraction, and subjecting said latter catalytic 'gas oil fraction to catalytic cracking with the above said hydrocarbon oil as specified above.

3. Process according to claim 2, in which the rst specified catalytic cracking step is carried out, at a. higher temperature than the second specified catalytic cracking step.

4. Process for the simultaneous production of quality gasoline and quality Diesel fuel from hydrocarbon oils boiling above the gasoline 'boiling range which comprises subjecting the hydrocarbon oil to catalytic cracking under conditions to 6 Y produce a substantial quantity of oleiinic gasoline. separating from the product an oleflnic gasoline traction and a catalytic gas oil fraction, commingling said catalytic gas oil fraction with a second catalytic gas oil fraction produced as hereinafter speciiied, separating the mixed gas oil fractions into a hydrogen-rich Diesel fuel fraction GEORGE M. GOOD. HERVEY H. VOGE. BERNARD S. GREENSFELDER`

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