US2242504A - Catalytic conversion of hydrocarbons - Google Patents

Description

May 20,` 1941- l w. l. BENEDICT Erm. 2,242,504 'I CATAJYTIC CONVERSION 0F HYDRCARBONS Filed April 29, 193s' l uen/07:9.'

f uff Patented May 2o, 1941 cArALmc ooNvEasroN or mnof cannons wayne L. Benedict and Jacob Eaton Amberg,

Chicago, lll., Company, ware mignon to Universal Oil Products Chicago, Ill., a. corporation of Dela- Appuesuon April zo, 1939, serai No. mosso (ci. 19e- 13) 11 Claims.

This invention relates to the catalytic conversion of heavy hydrocarbonaceous materials and more particularly, distillates which are vaporizable without substantial decomposition. More non-catalytic cracking of hydrocarbon oils is extensive, and because of the large amount of investigation has been developed to a point where the principles involved are fairly well understood. The principles of catalytic conversion of hydrocarbons, and more particularly the use of catalysts which assist the thermal cracking of higher-boiling hydrocarbon fractions to produce gasoline and gas, are not so well understood. Such explanations as have been given are largely empirical, and a discussion of the reactions is therefore best confined to a factual basis.

In one specific embodiment the present invention comprises a method for converting hydrocarbon fractions into high yields of gasoline and desirable gas which consists in'extracting said fractions with a selective solvent, contacting the raflinate with a dehydrogenation catalyst under conditions adequate to effect substantial dehydrogenation thereof, mixing the extract with a hydrogen-containing gas, contacting the mixture with a hydrogenation catalyst under conditions adequate to eiect substantial hydrogenation thereof, contacting the dehydrogenated reamnate and the hydrogenated extract in vaporous form with a cracking catalyst under conditions adequate to eiect catalytic cracking, separating the reaction products, returning a portion of the hydrogen-containing gas to the hydrogenation step,vcontacting a fraction of the normally gaseous hydrocarbons with a polymerization catalyst under conditions adequate to convert the olens therein substantially to the gasoline boiling range and recovering the polymer, recovering the catalytically cracked gasoline, and returning a portion of the unconverted fraction to the solvent extraction step.

It has been found that certain petroleum dis-v Vrailinate is relatively parafilnic.

tillates are rendered more susceptible to catalytic cracking after relatively minor portions of compounds of an unknown character have been removed' therefrom by solvent extraction. It has further been found that the unconverted fraction from the catalytic cracking step is similarly improved as a recycle stock when certain portions of it are removed by selective solvents. Proper solvents should have the property of selectively removing oleinic and aromatic hydrocarbons fromv mixtures thereof with saturated hydrocarbons. After solvent extraction the It has been found that partial dehydrogenation of the raffinate yields a stock which is substantially lmore amenable to catalytic cracking than the original oil. 'I'he extracted material is, per se, a relatively dicult stock to crack catalytically to produce high yields of motor fuel. It is improved, however, if it is subjected to a catalytic hydrogenation step `and then cracked either in a separate step or in the same step withthe dehydrogenated raffinate. The reaction products from the catalytic 'cracking step, or steps if the two stocks are cracked separately, are separated into unconverted oil which is returned to the solvent extraction step, a hydrogen-containing gas which is returned entirely or in part to the hydrogenation step, a fraction containing C: and C4 'olelns which are polymerized into substantial yields of gasoline boiling range material, and a finished gasoline of high octane number.

'Ihe solvents which may be used in the extraction step are not a special feature of the present invention, but may comprise any suitable selective solvent, among which are liquid sulfur dioxide,- furfural, dichlorethyl ether, nitrobenzene, glycol ethers, etc.

The catalysts used in the dehydrogenation step may comprise anysuitable dehydrogenation catalyst such as, for example, alumina or mag- .nesia to which have been added various other metal oxides to increase their dehydrogenating activity, including those of chromium, vanadium, iron, zinc, zirconium, molybdenum, tungsten, etc. The conditions for thel dehydrogenation step are substantially atmospheric pressure and temperatures within the range of 900-1l00 F.

'Ihe hydrogenation catalyst may comprise any suitable substance known to promote this reaction such aS, for example, molybdenum sulfide,

' molybdenum oxide, or, providing thesulfur content is'sufliciently low, the reduced metal catalysts such as nickel, copper, iron, cobalt, etc.

The conditions` of hydrcg'enation may include temperature ranges of 300-800 F. and pres-f 4sures of substantially atmospheric to 2000 pounds per square inch, depending to a certain` extent upon the catalyst used.

The present process may have more or less applicability when using cracking catalysts produced by the chemicaltreatment of naturallyoccurringA clays, or catalysts consisting of specially prepared silica-alumina, silica-zirconia,

thoria composites which have a highdegree of activity. These llattercomposites are prepared by combining the constituents in various ways such as mixing, coprecipitation an`d the like,

-under conditions whereby alkali metal ion's are excluded. It appears that no one component can be determined as that for which the remaining components may be considered as the promoter according to conventional terminology.

In the present invention the catalysts of the various steps are used in the form of sized silica-alumina.-

mary solvent extraction step 2. A portion ofthe unconverted fraction may be returned to catalytic cracking step 6 by means of lines I5, I5' and Separated hydrogen-containing gas passes through lines I8 and I1 .combining with line and thence to hydrogenation step I0. A portion of .the hydrogen-containing gas may be withdrawn through line I6 or, if so desired, the gas may be enriched with hydrogen from an outside source from line I8. The polymerization. oleiins from separation step 8 which include the Ca and C4 hydrocarbons pass through line I8 to polyparticles or formed shapes such'as pellets, produced by compression or extrusion methods.

The catalytic cracking step is carried out at temperatures within the range of approximately 8001200 F. and pressures sufficient to insure passage of the vapors through the plant.

The catalyst -used for the polymerization step may be sulfuric acid, the so-called solid phosphoric acid catalyst. or other suitable polymerization catalysts. When sulfuric acid is used the reaction is carried out with or stronger acid at a temperature within the range of approximately -250 F. The solid phosphoric acid catalyst consists of a mixture of liquid phosphoric acid catalyst with kieselguhr or similar suitable siliceous materials which is extruded' and may be'precalcined. The polymerization step using this catalyst is carried out at a tem# perature within the .range of approximately 250-450 F. and pressures of 100-1000 pounds .per square inch.

` The attached drawing diagrammaticall'y exemplifies one embodiment of the present invention. It should not be interpreted as lim'iting lthe invention to the exact conditions given therein.

The raw oil charge eli'ters the system through line I, passes into the solvent extraction step 2 wherein it is divided into a rafnate and an extract fraction. 'I'hese fractions are freed. of sol- 'vent by any convenient method. 'I'he raitlnatey is passed through line 3 to the dehydrogenation step 4 wherein it is contacted in vaporous form with a dehydrogenation catalyst under conditions adequate to effect partial dehydrogenation. The reaction products pass through line 5 to catalytic cracking step 6 wherein the oil is contacted in vaporous form with a cracking catalyst and partially converted to gasoline and gas. The reacmerizaticn step 20 where they are subjected to catalytic polymerization. v The gasoline boiling range polymer is recovered through line 2| and n may be blended with the iinishedv gasoline from the cracking step. Polymer of higher than gaso- 'line boiling range may be withdrawn through line 22 and returned by means not shown to the catalytic cracking step or maybe used for other purposes if so desired. The residual C3 and C4 hydrocarbons'are withdrawn through line 23.

The ilnished gasoline from the separation step 8 passes through line 24, combining with polymer from line 2I and passes to gasoline storage tion products leave the catalytic cracking step through lines 'l and 'I' and pass to separation step 8. The extract from thesplvent extraction 'step 2 passes through line 9 to hydrogenation step I0 wherein it is subjected to the action of hydrogen in the presence of `a catalyst under suitable conditions to effect hydrogenation. 'Ihe hydrogenated oil passes through lines Il' and I2 to catalytic cracking step I3, which is similar in character to catalytic cracking step 6. The reaction products leave the cracking step through line I4 and'enter the separation step 8 through line 1'. From the separation stepthe unconverted fractions from the catalytic cracking steps pass through line I5 to. line I and thence to pri- As'one alternative of the abovef-mentioned operation, the hydrogen-containing gas from dehydrogenation step 4 may be passed to hydrogenation step I0 by means of'line 26 which joins with line 9.

-In another alternative mode o'f operation, the hydrogenated oil from hydrogenation step I0 may pass through lines II and 21 to catalytic .cracking step' 6 in which case catalytic cracking step I3 is eliminated.

'l'he following example is given to illustrate the usefulness of the invention, but should not belinterpreted as limiting it to the exact conditions described therein.

A Mid-continent gas ou cf 35.9" A. P. I. gravity' was catalytically converted according to the above-described process after liquid sulfur dioxide was used in a primary selective solvent extraction s tep. The dehydrogenation lcatalyst consisted of activated alumina containing 8% oi chromia and dehydrogenation was carried out at 932 F. at substantially atmospheric pressure. The cracking,catalyst was a sodium-free syr.-

thetic silica-alumina composite and the cracking step was carried 'out at 932 F. and substantially atmospheric pressure. The hydrogenation catalyst was essentially molybdenum oxide, the operation being carried out at 1000 pounds pressure and 730 F. The polymerization step was carried out using a solid phosphoric acid catalyst at a temperature of 375 F. and pressure of 250 pounds per square inch.

p The total yield of 400 F. end-point, 81.5 octane number gasoline amounted to 86.5% of the original raw oil fraction charged.

We claim as our invention:

1.l A process for'tlie production of high antiwith a cracking catalyst under conditions adequate to eiect catalytic cracking, recovering the gas and gasoline, and returningthe insufficiently converted oil to the solvent extraction step.

2. A process for the production of high antiknock value gasoline which comprises extracting a hydrocarbon oil with a selective solvent, separating the ramnate and extract, contacting the rainate with a dehydrogenation catalyst under conditions adequate to eiect substantial dehydrogenation thereof, mixing the extract with a hydrogen-containing gas, and contacting the mixture with a hydrogenation catalyst under conditions adequate to eiect hydrogenation .ated oil in vaporous form with a cracking catalyst under` conditions adequate to effect catalytic cracking, mixing the extracted oil with a hydrogen-containing gas and contactingthe mixture with a hydrogenation catalyst under conditions adequate to effect substantial hydrogenation thereof, contacting the hydrogenated extract in vaporous form with a cracking catalyst under conditions adequate to effect catalytic cracking, combining the reaction products from the catalytic cracking steps, separating a hydrogen-'containing gas therefrom and returning a portion of it to the aforementioned hydrogenation step, recovering the catalytically cracked gasoline, and returning a portion of the insufflciently converted oil tothe solvent extraction step.

4. The process of claim 1 wherein the' cracking catalyst comprises a composite consisting essentially of a major portion of precipitated silica containing a minor portion of a compound selected from the group consisting of alumina and zirconia, said composite being substantially free of alkali metal compounds.

5. A process for the production of high antiknock value gasoline which comprises extracting a hydrocarbon fraction with a selective solvent, recovering the rafnate and extracted oil, contacting the rafllnate with a dehydrogenation' catalyst under conditions adequate to effect substantial dehydrogenation thereof, combining the extract with the hydrogen-containing gas produced in the dehydrogenation step, contacting the mixture with a hydrogenation catalyst under conditions adequate to eiect substantial hydrogenation thereof, contacting the dehydrogenated rafnate and the hydrogenated extract in vaporous fo'rm with a cracking catalyst under conditions adequate to eilect catalytic cracking, separating the reaction products, and returning the insumciently converted oil to the solvent extraction step.

6. A process for the production of high antiknock value gasoline which comprises extracting a hydrocarbon fraction with a selective solvent,

recovering the rainate and extracted oil, contacting the rainate with a dehydrogenation catalyst under conditions adequate to effect dehydrogenation thereof, mixing the extract with a hydrogen-containing gas, contacting the mixture with a hydrogenation catalyst under conditions adequate to eiect substantial hydrogenation thereof, contacting the dehydrogenated raffinate and the hydrogenated extract in vaporous form with a cracking catalyst under conditions adequate to effect catalytic cracking, separating the reaction products, returning the unconverted oil to the solvent extraction step, supplying hydrogen formed by the cracking to the hydrogenation step, and recovering the gasoline and gas. 7. The process of claim 1 wherein the solvent used in the extraction step is liquid sulfur dioxide.

8. A process for the production of high antiknock value gasoline which comprises extracting a hydrocarbon oil with a selective solvent, separating the rafiinate and extract, contacting -the ramnate with a dehydrogenation catalyst under conditions adequate to eiiect substantial dehydrogenation thereof, mixing the extract with a hydrogen-containing gas and contacting the mixture with a hydrogenation catalyst under conditions adequate to eifect substantial hydrogenation thereof, contacting the dehydrogenated rafnate and the hydrogenated extract in vaporous form with a cracking catalyst under conditions adequate to effect catalytic cracking, recovering the gas and gasoline, returning a portion of the insuiliciently converted oil to the catalytic crackin'g step, and returning a further portion of the insufliciently converted oil to the solvent extraction step.

9. A process for producing anti-knock gasoline which comprises extracting hydrocarbon oil with a selective solvent, separating the resultant rafnate and extract, subjecting the rafnate to dehydrogenation, hydrogenating the extract, cata.- lytically cracking the dehydrogenated raiinate and the hydrogenated extract, and recovering the resultant gasoline.

10. A process for producing anti-knock gasoline which comprises extracting hydrocarbon oil l supplying at least a portion of said gas to the" aforesaid hydrogenating step.

11. The process as dened in claim 9 further characterized in that hydrogen formed in the dehydrogenating step is supplied to the dehydrogenating step.

WAYNE L. BENEDICT. JACOB EISTON AHLBERG.

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