US1594666A - Process for cracking oil - Google Patents

Description

Aug.- 3 '1926. 1,594,666

` P. DANCKWARDT PRocEssFoR GRACKING oIL' Filed Oct. e, 1924 Q tez Paul anclfward.

abtoz 1 w14 Patented Aung. 3, 1926.'

UNITED STATES V. 41,594,666 PATENT oFI-lca PAUL DA'NCKWARDT," 0F DENVER, COLORADO.

PROCESS FOR CRAGKING OIL.

Application led October 6,

It is well known that the products of the cracking processes now employed for the production of gasoline from heavy hydro-Y carbons have a disagreeable odor and are different in 'character from gasoline derived from crude oil by distillation carried on at l .atmospheric pressure.

. It is the object of this invention to producel a method whereby `a gasoline superior to that obtainable by present cracking meth# ods can be'produced.

These improvedfresults lare attained by a method in which the cracked vapors and gases are exposed to the action of a nickel catalyzer as they emanate from the cracking still. By this means the unsaturated hydrocarbons and the otheringredients' that areresponsible for the disagreeable odors and other undesirable qualities, are made to combine with hydrogen, which may be formed from a part of the oil during the cracking process itself, or which may be introduced from an extraneous source. Nickel has long been known as a catalyzer for unsaturated hydrocarbons, but, so far, it has not been employed successfully in a commercial way with mineral oils, for the reason that ity soon. becomes inactive, a condition referred -to by chemists as poisoned, The inactive or poisoned nickel can be revivilied, but only by an expensive process, which makesit impracticable.

"I obtain my improved results by employing-nickel in conjunction with an alkalijor, alkali earthemetal hydroxide, which absorbs the ixnpiirities'directly from the oil and from the nickel, as will be hereinafter more fully ex lained.

y process further diEers from mostl ,other processes of this nature in this,'that itemploys Quo direct application of fireto the still and thereby avoids overheating and the consequent production of free carbon.

My process, briefly described, consists in subjecting the oil to a'moderate temperature and to high pressures, either with or without the addition of hydro-gemfixed gases or steam from "an external source, usingl asmuch contact surface asv possible for, good economy; then bringing the gases-and vapors directly into contact with nickel held suspended in molten sodium hydroxide, or

jirst separating the heavier parts of the vapors of distillation by a partial condensation and then passing the lremaining light hydrocarbons and the iixed gases through a- 1924 serial No. 741,911.

mixture of molten sodium hydroxide and nickel.

which I prefer to employ in carrying it out. l

I may sta'tehere, however, that ra cracking still such'as described and claimed in my copendin'g application (Serial No. 625,697, JfiledMarchl'?, 1923) or any other of the many pipe stills in vcommon usey may be cmployed,

For-the purpose of more clearly describir ing lnyinvention, I' shall have reference to the accompanying drawing, which shows a longitudinal section through the apparatus.

Numerals 1, 2, 3, 4 and 5 .designate steel pipes or cracking tubeswhich are preferably placed vertically within brick or ceis surroundedby va jacket 8 of steel tubing. A pipe 9 is connected t'o the up er endr of the jacket surrounding pipe 1an connects the jacketsspace with a source of superheated fsteam.V The jackets surrounding pipes 1 and 2 are connected at their lower ends bv a pipe 10 and the upper ends of the jackets surrounding pi es 2 and 3 are connected at their upper en s by a pipe`1`1 and this is continued so'that all ofthe jacket spaces become connected in series. enters through'the pipe'Q Hows downwardly through the jacket :space about pipe 1 upwardly throughr the jacket space about pipe 2, etc. and finally leaves the lastl jacketspace through the ipe 12.` Extending vdownwardly from t e lower closed "ends of the The steam that tubes 1 to 5 are pipes 13, 14, 15, 16 and 17 of.

smaller diameter. These pipes, except pipe 17, have their lower ends closed.v by caps in the manner shown: Pipes 18, 19, 20 and 21 connectV pipes 13, 14, 15 and 16, respectively, with the tops of pipes 2 3, 4 and 5. A pipe v22 connects the pipe 17 with the high pressure pump 23, while pipe 17 extends to and is connected, with `,the delivery port of the compressor 24 by means of which hydrogen or other gases from an outside source may be supplied if and when desired. From the top of cracking tube 1-a pipe 25, provided with a valve 26, extends to a steel tank 27 which serves as a receiver for all of the oils and vapors coming from the cracking tubes. The tank.27, in addition to serving as a receiver, also serves as a separator. The lighter vapors andv gases are carried olf through a pipe 28', which connects with and extends into the tank 29, which contains the nickel catalyzer and the hydroxide. The. unvaporized oil passes from the tank 27 to the pump 23 through pipe 30. By means of the pump 23 'the unvaporizedy oil'that collects in the tank 27 may be forced into and caused to circulate through the cracking tubes in the direction of the arrows. Fresh oil is added to the liquid in tank 27 through a pipe 31. The tank 29, which contains the nickel catalyzer, has its lower end surrounded by a steam jacket 32, which may be connected to the steam sup ly for heating the contents thereof. In-order that the contents of the tank 29 may be dumped, I have provided it w-itlLtrunnions 33, about which it may be rotated. The tank 29 should be provided with a removable cover 29* 'to facilitate the dumping. The pipe 28 and 'the pipe n36 are provided with couplings or unions 34 and 35, respectively. Pipe 36 forms a condenser coil and is located principally within the tank 37 from which it extends to the collecting tank 38.

In the drawing, I have .shown only tive cracking tubes, but any number may be .used

r and they may be connected in series as tubes.

vshown or in parallel or in parallel groups of series connected tubes.

The larger the number of tubes, the better will the heat from the superheated steam be utilized and the more quickly will the crackmg proceed. It will be noted .that the -steam in the jacket spaces flows in the opposite direction from the oil in the cracking This allows theY o il to, be heated gradually and permits an eiiicient utilization of the heat. As the temperature to which the oil is raised is low (not over 800 F.) very little carbon is formed and for this reason, cleaning out is seldom required. It may be necessary, however, from time to time to remove the caps at the ends of ipes 13.-16 one at a time and blow or was the tubes out by means .of steam, which may be connected'at the pipe 39, which branches from the pipe 22. Thermometers and pressure ages may be connected wherever desired, ut as this does no t involve invention, they have not been shown.

In carrying out my process by means of i the above described apparatus, I fill tank 27 about-two-thirds (2X3) full of oil and start the pump 23 with valve 26 partly open.

Steam, superheated to a temperature of 1000--1100o F., is now\turned into the jackets, owing in through pipe 9 and leaving through pipe 12. The valve in pipe 12 is adjusted so that the steam, just before it leaves the outlet pipe, is under a pressure of 200 pounds per square inch, or moreif e process is to be carried out at higher pre sures, and at a temperature somewhat above the boiling point of water at that pressure s o that no condensation of steam will take place. If these directions are observed thesteam escaping from the pipe 12 may be used for other purposes, such 'as for driving engines4 or for heating. The pum 23 is operated at such a speed that theoil escaping from the top of the cracking tube 1 willhave a temperature of not more than 800 F. Valve 26 is now closed to such an extentthat the pressure of the oil within the cracking tubes is somewhere between 400 to 1000,pounds per square inch. The exact pressure to be used must be determined by trial, as it will diier for different grades of oil. In order that none of the` pipes shall be subjected to excessived strain, I aim to keep the steam pressure Within the jackets about one-half as great as the pressure of the oil withinthe cracking tubes. In this way the outer wallsI of the .steam jacket are subjected to strains due lto the steam pressure alone, while the walls of the cracking tubes are subjected to both an inner and' an outer pressure and the strains are therefore due to the difference of these op` posing pressures. If the steam pressure is one-half as great as the oil pressure, then the walls of the cracking tubes and of the steam jacket are subjected to the same effective 1 pressures. By this means the danger of entering the tank 27. After passing the valve 26, the pressure to which the gases and vapors are subjected, is greatly decreasedI whereby the heavier parts will be separated out. 'Ihe lighter parts will not condense in the tank 27, but will travel through the vpipe 28 into the container 29 Where theywill be-libera-ted near the bottom and will bubble upwardly through the molten mixture of sodium hydroxide in which the nickel catalyzer, either in the form of owder, wire, or cuttings, issuspended. Be ore'starting the operation the contents "of the tank 29 is heated by steam to such a temperature that it will melt. VHAfter the gases have started to.. flow from .the tank 27 into .tank 29 the sodiumq hydroxide is kept molten and iuid by heat from the wapors alone.

Sodiu hydroxide melts at about 210 C. when perfectly dehydrated and at a lower temperature' when it contains some Water. I .have/,found'that a `small amount of water the charge must finally be dumped and replaced by a new one. The 4time of usefulness of a chargeI can be prolonged somewhat by using mechanical stirrers. It is, however, better practice to provide tWo tanks 29 and connections by means of which the gases may be diverted into the reserve tank Whenever the'hydroxide in the first tank becomes too hard. This makes it possible to dump and recharge one tank at a time Without interrupting the operation.

The hydroxide that has become useless may be regenerated by leaching the charge with Water, filtering and treating t-he filtrate with caustic lime. -In this Way a solution of fresh sodium hydroxideis obtained, which. upon evaporation, yields dry hydroxide. When the `dry hydroxide Athus formed is mixed with nickel and melted down in one of the containers 29 by the application of\steam to the heating jacket, the mixture is ready for use.

The reaction, as far as the oil is concerned, Which takes place inthe catalytic cell or the tank29 that vcontains the hydroxide and nickel, consists very probably of a simple addition of hydrogen to the unsaturated hydrocarbons, which have been formed by the heat treatment. This is perhaps accompanied by a regrouping of the molecules of certain parts of the oil. This is indicated by the fact that the amount of light hydrocarbons formed by the catalytic treatment exceeds that. formed When the catalyzer is not used, so much that it can hardly be ex- `plained by the fact alone that the unsaturates are changed into saturates.

In other processes, using nickel as a catalyzer, it was found that the nickel soon lost its efficacy. In my method it does not. I may explain this on the theory that the molten alkali is continually .decomposing the layers of inactive substances formed on .the surface of the nickel or that it prevents its format-ion by absorbing the substances which poison the nickel When no hydroxide is used.

The vapors which leave the catalytic cell, pass through the condenser coil 36 Where they are condensed and flow thence to the reservoir 38' where the condensatecollects as a sweet smelling, clear liquid, practically -identical with natural gasoline.

As fast as the liquid in tank 27 is decreasing during the operation of the process, fresh oil is introduced through pipe 31. If this` oil contains natural gasoline, the latter will be evaporated by the heat of the oil and vapors in the tank as.they come from the cranking tubes. This gasoline will therefore not pass through the cracking tubes Where it mi ht be partly destroyed.

Alt ough I have referred specifically to sodium hydroxide, other oxides and hydroxides of the alkali or alkali-earth metals may be use-d. In case alkali-earth compounds or mixtures of these With compounds of the alkali metals are used, it Will be necessary to granulate lthem or to form balls containing nickel and to pass the vapors through the granules or over the surface of the granu les or balls as such mixtures cannot be rendered fluid.

I have also tried to substitute for the nickel other metals such as iron, manganese, copper, zinc and aluminum and have found that some reactions take place Which are similar to those that take place with nickel. When the oxides of the other etals Were employed, some of them Were educed and acted the same as the metals, others dissolved in the hydroxide, except when calcium hydrate was used, which seemed to form a hard hydrogen is formed by the cracking.- The use of hydro en is, hovvever, of considerable advantage w en Working under high pressure, when it seems to take part in the crack- Aing of the oil and almost entirely prevents the formation of carbon. The same applies to the use of steam, which, when introduced with the oil during the cracking phase, ap-

higher boiling points, which consists in passing the vapors and gases from a cracking still through a mixture of molten sodlum hydroxide and nickel.

2. The process of producing hydrocarbons of low boiling points from hydrocarbons of higher boiling points, Whichconsists 1n passing the vapors and gases from a crackin still through a mixture of molten alkali metal hydroxide and nickel. l

3. The process of producing hydrocarbons of'lovv boiling points from hydrocarbons of higher boiling points, which cons1sts 1n passing the vapors and gases from a cracking still into intimate contact with a `mixture composed of molten sodium hydrox1de and nickel.

4. The process of produclng hydrocarbons of low boiling points from hydrocarbons of higher boiling points, whlch consists 1n submitting'the hydrocarbons to a temperature and pressure high enough to cause the hydrocarbons'to disintegrate partially, bringlng the products formed into intimate contact with nickel and molten sodium hydroxide, and condensing the light hydrocar-` of 400-1000 pounds per square inch, passing the vapors and gases formed through molten sodium hydroxide in which metallic nickel is suspended, and condensing the vapors.

6. The process of producing hydrocarbons of low boiling points from hydrocarbons of higher boiling points, which consists in cracking the hydrocarborls` at a temperature not to exceed 800 F. and under a pressure of 400-1000 pounds per square inch, passing the vapors and gases formed through molten alkali metal hydroxide in which metallic nickel is suspended, and then condensing the vapors.

not to exceed 800,F. and under a pressure of L)COO-1000D pounds per square inch, passing the vapors and gases formed into intimate contact with molten sodiumlhydroxide in which metallic nickel is suspended, and then condensing the' vapors.

8. The process of producing hydrocarbons of low boiling points fromhydrocarbons of higher boiling points, Which consists in cracking the hydrocarbons at a temperature not to exceed 800 F. and-under a pressure of 40G-1000 pounds per square inch, introducing hydrogen, 'passing the vapors and gases formed into intimate contact with molten sodium hydroxide in which metallic nickel is suspended, and then condensing the vapors. l

In tesi ony whereof I aix my signature.

PAUL DANCKWARDT.

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