US1651114A - Process of cracking hydrocarbon oils and manufacturing cyanides - Google Patents

Description

Patented Nov. 29, 1927- UNITED STATE$ PATENT OFFICE.

PROCESS OF CRACKING HYDROCARBON No Drawing.

molten alkalinous metal cyanide reagent in which is capable of holding in suspension or forming a molten magma with carbon separated out or freed during the formation of the lower boiling hydrocarbons which result from such pyrolytic treatment'of the oil, and in this connection involves the employment or combination therewith of a cyanide making process, through the intermediacy of which, any cyanide decomposed in the disi tilling and cracking step is thereafter reconstituted from the coky residuum or molten magma comprising the distillation residues and the recovery of the cyanide from the latterautomatically effected, by utilizing the said residues in the manufacture of additional cyanide.

The object of this invention is to obtain from the aforesaid hydrocarbon material, hi her percentages of desulphurized lower bo iling oils or refined lighter distillates than 3 are obtained by any of the hitherto practised processesof distilling and cracking oils, and to reclaim the cyanide reagent from the distillation residues while utilizing the latter in the manufacture of additional. cyanide that the cost, not only of the cyanide recovery step, but also that of the distilling and cracking operation is thereby very much reduced in that it enables the profitable production of desulphurized lower boiling oils from higher boiling hydrocarbon oils containin considerable percentages of sulphur and also other like hydrocarbon material not heretofore successfully treated by known cracking or oil converting processes.

In my copending application entitled: Process of cracking oils, Serial No. 586,029; filed Sept. 2nd, 1922, I have described the use of molten cyanide in the treatment of hydrocarbon material, such as heavy hydrocarbon oils for the production of lower boilin g oils therefrom. In operating the process as described in said application, I separated the coky residuum or finely divided carbon contained in the distillation residues or fusion reaction products by filtration of the latter through iron turnings. On continued OILS AND MANUFACTURINGOYANIDES.

Application filed December 28, 1925. Serial No. 78,003.

use of this method, however, a difficulty became apparent, unforseen when operating on the small scale; namely that the increasing mass of coky residuum absorbs large quantities of the sodium cyanide reagent, and even after filtering or liquating out the surplus cyanide from the coky residuum at a red heat, as much as 20-25% of the cyanide is still trapped in the coky residuum. Obviously of course this may be recovered from the coky 'mass by suitable leaching, but any such procedure, obviously involves considerable expense, imposed upon a process already burdened by the relatively low market Value of some or all of its reaction products;

I have therefore sought and have found such a combination of steps as will not only permit of the economical utilization of cyanide for the production of lower boiling oils from higher boiling oils as disclosed in mysaid copending case; but which will further afiord'an efficient recovery of said cyanide, moreover, while satisfactorily accomplishing these results, I have succeeded in going still further, in that my present process not alone afiords liberation of the cyanide trapped in the coky mass, but actually gives far more than 100% of cyanide yield therefrom.

In brief, I do not remove the cyanide from the coky mass but rather I remove the coky mass from the cyanide by fixing the carbon thereof in the form of additional cyamde.

According to my invention, hydrocarbon 011 stock either in the form of the various high boiling coal tar distillates (solvent naptha), gas oil, solar oil, topped crude petroleum, petroleum residuums, fuel oil, and particularly the latter high boilin oil stock, is commingled with a molten a1 ali metal cyanide reagent and distilled'under cracking temperature and under pressure which can be regulated so as to produce from such oil a large proportion of desulphurized lower boiling oils. The sulphur or sulphur compounds in the oil during treatment combines with a portion of the cyanide to form alkali metal sulphocyanide. Any moisture contained in such oil stock reacts with the molten cyanide to form ammonia which in part decomposes and tends to hydrogenate some of the unsaturated hydrocarbons formed in the process. Oil vapors or permanent gases;

tageously bubbled through the molten cyanide to aid in the comminglement of the 011 therewith. The evolved hydrocarbon vapors and gases are suitably col ected.

The fusion residues left in the still, comprising coky residuum, alkali metal cyanide and its decomposition products,are discharged from the still, preferably as a free flowing molten magma, which is thereafter treated to reconstitute the cyanide decomposed by the sulphur and moisture content of the oil, that is, if the oil contains moisture, and to recover the cyanide from said magma and also to utilizethe latter in'the manufacture of additional cyanide in the manner hereinafter described.

In carrying my process into practice; I first charge molten cyanide into a closed vessel or still made of any suitable material, such as iron. The charging is continued until the still is about half filled with said cyanide. The cyanide used may be sodium cyanide of commercial purity, with a melting point around 550 C. or lower; the low melting oint of the latter compound being due to lmpurities such as sodium sulphocyanide, and other alkali metal com-' pounds. The cyanideis maintained in the moltencondition within the still by the application of heat thereto. The oil stock, under as much pressure as may be desired, and advantageously in a preheated condition, is introduced at a low point in the still "so that it enters well below thesur'faoe of the bath or depth of molten cyanide. As the oil is injected, the pressure inside the .still rises while the oil is commingled with the molten cyanide by the agitation of the bubbling of the generated oil vapors through the depth or bath of molten cyanide. If desired, permanent gases, such as hydrogen, or still gases may be introduced together with the oil so as to bubble through the molten bath and further aid in comminglement of the oil therewith. The pressure is regulated according to the temperature desired in the still. A convenient pressure, and one which gives good results, as when operating on higher boiling oils, such as fuel oil, is about 100 lbs. per square inch, but this pressure may be varied up or down during the operation of the process. The

rate of the oil flow injected into the still and the temperature of the molten cyanide being so adjusted as to prevent accumulat1on of asphalt or oil inside the still. As the oil is first commingled with the molten cyanide in the lower portion of the still, the liberated vapors pass upwardly in contact with the overlying continuum of the molten cyanide bath and therein are subected to a temperature between 550600f G. which is high enough to insure cracking,

\ with the resulting formation of a vapor mixture which upon condensation under pressure maintained on the system, yields a distillate of much less specific gravity than the original oil. After the cyanide in the still has engaged its quota of oil; namely, in the case of fuel oil, a proportion of the latter approximately equal to about ten times the volume of the cyanide filled into the still I gradually release the pressure and" carry on the distillation of any remaining volatilizable hydrocarbons either under atmospheric pressure or in a vacuum, but preferably around atmospheric pressure. During the latter operation I prefer to gradually increase the temperature to say around 700 0.; the vapors evolved during the distilling operation being suitably collected and condensed.

When operating with lighter oils than fuel oil, for instance, gas oil, a much greater quantity of this oil can be engaged by the, molten cyanide before the latter becomes too concentrated in coky residuum for continued use. In practise, I have used as much as fifty times the volume .of gas oil to a proportion of one volume of molten sodium cyanide and obtained a resulting distillation residue capable of being discharged from the still as a free flowing mol ten magma. It may be seen therefore that molten cyanide may be used in the treatment of a very large variet dro'carbons which vary consi erably in quantity of coke forming residues.

A convenient form of still is a cylinder or a tube with an agitator or with a worm or spiral agitator moving the mixture forward to the discharge end but any ordinary still of suitable material such as iron may also be used with or without an agitator.

After the completion of distillation, the

of liquid hycarbon or finely divided coke left in the still, remains largely in suspension in-"the molten c anide mixed with its decomposition pro ucts. To insure suspension of the coky residuum in the molten bath I continue the bubbling of still gases therethrough until the molten magma thereby formed is ready for discharging. If insuf ficient cyanide in proportion to the oil treated'had been used, the residual products anide from the fusion residues or molten magma might be resorted to; provided that such fusion residueshad not been allowed to become too concentrated in coky residuum. However, as such an operation does not reconstitute the cyanide decomposed the moisture or sulphur content of the 011, nor does it recover the cyanide absorbed or trapped in the coky mass,it is preferable not to'undertake such filtratlon or hquation, in view of my discovery of the practicability of so treating these residues as to, 111 efiect, separate these coky residues themselves from the cyanide entrapped therein, rather than to remove the said cyanide from the said residues. In other words, I have found it to be the much more economical course, to remove the trap-constituting residuum, so to speak, from the entrapped sub stance, in contradistinction to any attempt to remove the latter from the former.

I have made the discovery that the coky residuum in question admixed as it is, with cyanide and with the decomposition products of cyanide,is peculiarly well adapted to participate in a reaction with an alkali metal carbonate, such as sodiuin carbonate, and

nitrogen or a nitrogenous gas to not alone,

reconstitute the decomposed cyanide, but to further form additional cyanide, the carbon of the distillation or fusion residues being the source of the carbon supply for such additional cyanide.

This reaction is effected at a cyanide forming temperature, the sodium carbonate, advantageously in the molten state, being admixed with the still molten and hence highly heated residues aforesaid, and nitrogen or its equivalent being contacted with or absorbed by the molten mixture, in a suitable reaction chamber, for instance, a revolving nichrome metal tube inclined slightly to the horizontal, such as is generally used in known processes for manufacturing cyanide through the absorption of nitrogen by a molten magma of alkali and carbon heated to a temperature between 800 and 1200 0.

Thus, the very substance which would ordinarily be regarded as a source of trouble and expense, and from which the trapped cyanide could normally be separated only at considerable expense,is caused to free this trapped cyanide by being itself combined with othersubstances to form an additional and auxiliary quantity of the substance be-. ing freed, to wit,cyanide.

It is obvious that, the cyanide reclaimed and manufactured in the cyanide forming step of the described process may contain appreciable quantities of alkali metal sulphocyanide, the percentage of the latter substance varying with the percentage of sulphur in the oil treated. The accumulation of such sulphocyanide beyond prescribed tillation.

fresh cyanide produced by this reaction issuflicient to reduce or maintain the perccntage of alkali metal sulphocyanide more or less constant in any portion of this cyanide which maybe used as the cyanide reagent in the treatment of oil aforesaid.

It will be understood that, the additional cyanide produced in the cyanide forming step of the described process may be marketed as commercial cyanide or it may be steamed to produce ammonia, by the usual methods employed for this purpose. The residue resulting from the steaming operation, namely, commercial soda ash, that is, if the said. steaming operation is conducted at temperatures higher than 500 C. sodium carbonate will be produced instead of sodium formate, which former compound is at once utilizable as the alkalibase-supplying compound in the aforesaid cyanide forming step of my process.

It may be stated that, a cyanide reagent containing a proportion of twenty parts sodium sulphocyanide and eighty parts sodium cyanide remains molten below 400 0.; such a cyanide reagent may be used advantageously, when operating under high pressure, as at this temperature, say around 400 C. does not reduce the mechanical strength of the steel retorts now generally used for high pressure oil cracking dis- I have successfully treated, in one of such retorts, higlrboiling hydro carbon oils by injecting the same into a bath of the aforesaid low melting point cyanide reagent while maintaining the latter under a pressure of over 600 lbs. per square inch, and obtained extraordinary high yields of low boiling oils having 'a greater volatility than gasolene of corresponding specific gravity.

In connection with the use of oil vapors cyanide reagent, there is the advantage that t I some portion of them may be reconverted into liquefiable hydrocarbon oils by the operation itself. In the case of hydrogen there is the advantage that it may take part to some extent in the actions in producing saturated bodies. Hydrogen rich gases suitable for this purpose may be made by breaking up still gases or other hydrocarbon gases or vapors by the aid of a high heat. The introduction of more or less hydrogen together with the hydrocarbon gases during the treatment of the oil with the molten cyanide aids materially in hydrogenating fresh molten cyanide reagent and hydrogen are evolved and carbon disappears on con-*- bubbled through the same,hydrocarbons tinued bubbling of the hydrogen therethrough under superatmospheric pressure viz 500 lbs. per square inch;

The hydro-gen, still gases etc. employed for agitating the oil with the molten cyanide reagent or for commingling the residual carbon therewith may be replaced in part with a quantity of steam, such as to provide water vapor up to 540% of the weight of the oil charged into the still. However, the addition of Water or steam is optional as the oil stock, unless previously dehydrated, usually contains moisture suflicient to promote hydrogenating reactions which tend to increase the percentage of liquid aromatic hydrocarbons in admixture with the other lower boiling hydrocarbon oils produced in the distilling and cracking step of the process.

As indicated, sodium carbonate or soda ash is the preferred alkali base-supplying agent employed in the process principally because it gives satisfactory results and is inexpensive. Instead of sodium carbonate 1 may employ other metal carbonates such as potassium carbonate, or the alkali metal hydroxides or formates and perhaps other metal compounds or mixtures of a plurality of different compounds of one or more alkali metals.

' What I claim is:

1. The method of cracking hydrocarbon oils and manufacturing cyani es which comprises,distillingsuc'h oils in contact with a molten alkali'metal cyanide reagent under superatmospheric pressure, collecting the evolved hydrocarbon vapors and gases, reconstituting the cyanide decomposed in the distilling step and liberating the cyanide trapped in the distillation residues, by subjecting the latter to a cyanide forming reaction in which participate alkali and nitrogen to combine with a part at least of the car on content of said residues to form additional alkali metal cyanide, thereby reclaiming the cyanide reagent in admixture with the additional cyanide produced through the intermediacy of said cyanide forming reaction.

2. The process of cracking high boiling hydrocarbon oils and manufacturing cyanidewhich comprises, engaging such oils with a bath ofmolten alkali metal cyanide, to produce low boiling hydrocarbons which are liquid at normal pressure and temperature,

and a fusion residue containing coky residuum, mixin the said fusion residue with soda ash, su jecting the so formed mixture to the action of a nitrogenous gas under alkali metal cyanide forming conditions to fix the carbon of said fusion residues in the form of additional sodium cyanide and to reconstitute the cyanide decomposed in the distilling step, thereby reclaiming the originally used lation residues, by subjecting the latter to a cyanide formin reaction in which participate sodium car onate and nitrogen to combine with the carbon using, in part at least, the so liberated cyanide for treating additional quantities of oil.

4. The process of cracking hydrocarbon oils and manufacturing cyanides which comprises, distilling such oils in contact with an alkali metal'cyanide under suitable pressure and'temperature to produce low boiling hydrocarbons which are liquid at normal pressure and temperature, and subjecting the quantity of sodium cyanide inadmixture with the additional cyanide pro-' content thereof, and redistillation residues to a cyanide forming reaction to reconstitute the cyanide decomposed in the distilling step and to form additional cyanide.

5. A process 1n accordance with claim 4 in I which the distillation residues are mixed with an alkali metal carbonate and heated in contact with nitrogen, to a temperature sufiicient to effect a reaction between the carbon of said residues and the said alkali metal carbonate to form'an alkali metal cyanide.

6. A process of cracking hydrocarbon oils and manufacturing cyanides which comprises, distilling such oils in contact with molten alkali metal cyanide, collecting the volatile reaction products and mixing the resulting distillation residues with an akali metal compound, heating this latter mixture in contact with a nitrogen containing gas, to a temperature sufficient to efiect a reaction between the carbon contained in said distillation residues and the said alkali metal compound to. form an alkali metal cyanide.

In testimony thereof, I aflix my-signature hereto.