US2207552A - Manufacture of aromatic hydrocarbons from petroleum oil - Google Patents

Description

J. W. PUTT Filed Dec. 8, 19436 July 9, 1940.

I MANUFACTURE 0F AROMATIC HYDROCARBONS FROM PETROLEUM OIL aggA/JoA/oa Patented July 9, 1940 AUNITI-:D STATI-:s i PATENT OFFICE"- MANUFACTURE Oil' AEOMATIC HYDRO- CABBONS FBDM PETBOLEUBI 011 James W. Putt, Beverly Hills, Calif. Application December 8, 1938. Serial No. 114.813

' 6 Claims. (Cl. 26o-868) This invention pertains generally to the manuvfacture from petroleum.- of diluents, solvents, plasticizers, aromatic hydrocarbons, spray oils, Diesel oils, high grade petroleum distillates, etc.

'The invention has to do particularly with processes for chemically converting lmineral oils to produce aromatic hydrocarbons as well as base materials for the manufacture oit dyes, chemicals,

essential oils, resins,varnishes, etc. Byfchemlo ically converting Imean the transforming of hydrocarbons to compounds of diii'erent chemical structure or formulae,

In the past, thevproduction and derivation o! aromatic hydrocarbons for such uses has for the d most part been confined to coal tar produced by thev pyrolosis of coal in by-product coke ovens,'

and for practical and commercial reasons to the coal producing regions. As compared to my process, the cost of manufacturing aromatic hydrocarbons from coal tars is high, and the cost .is substantially increased by the cost of trans-` portation to points distant from the sources of coal supply. Petroleum oils constitute another' Vsource of aromatic hydrocarbons for industrial uses, and from a commercial standpoint they' are highly advantageous as base materials because of their lower cost on the basis of, potential aromatics. The availability of andthe wide distribution of oil production minimizes expensive `3b transportation. l f

From a theoretical4 standpoint, the desirability of utilizing petroleum oils as a base material for the production of aromatic hydrocarbons has beenrealized, but no successful method has been proposed. whereby it is possibleto obtain from petroleum oils, aromatic hydrocarbons in commercial quantities that are of a quality comparable with those derived from the coal tars and at 'costs suiiiciently low to render such manufac- 40 ture commercially feasible. Accordingly, my' primary object is to provide a process whereby aromatic hydrocarbons can be produced at .costs materially below the costs of producing aromatic hydrocarbons from coal tars or other sources.

Crude petroleum oils (such as California crude i oil) contain paraflinic and napthenic hydrocarbonsand from a refining and commercial standpoint in most cases a percentage .of tars or waxes which are objectionable. Petroleum oils such as those produced from a so-called cracking process contain paraiiinic, olenic and napthenic hydrocarbons. 'I'he paraiilnic hydrocarbons, when separated from the napthenic and olenic hydrocarbons and fractionated to the proper boiling Y 55, range, are desirable for use -as Diesel oils, spray arrangement into aromatic hydrocarbons under' the conditions later described.

oils, or any oil which requires a high concentration of paraiilnic hydrocarbons. The paramnic, oleiinic and napthenic hydrocarbons have dissimilar chemical characteristics pertaining to their solubility in organic solvents such as liquid sulphur dioxide, furfural, acrolein, etc., the parafiinic being insoluble andthe olenic and napthenic being soluble.

In accordance with the invention I am able to convert into aromatic hydrocarbons the nap- 10 thenic portion of any suitable petroleum distillate. This napthenic portion is that portion which is soluble in an organic solvent such as liquid sulphur dioxide, furfural, acrolein, etc. 'I'his distillate may be' the vaporizable portion of any 15 suitable crude oil from which the tars, waxes, or heavy residuum has been removed. 'I'his distillate may have a boiling range from approximately 100 F. to 800 F. and it may consist of any' suitable fraction, say one having a boiling 20 range o1'. 100 F. more or lesswithin these limits, if desirable. y

V I am able to convert into aromatic hydrocarbons the napthenic and olenic portions of any suitable distillate produced from a so-called 25 cracking plant. This napthenic and olenic portion is that portion which is soluble in an organic solvent such as liquid sulphur dioxide, furfural, acro1ein,etc. This distillate maybe the Vaporizable portion of the product produced from the 30 cracking plant and may have a boiling range. from approximately 100 F. to 800 F. and it may consist of. any suitable fraction say one having a boiling range-of 100" F. more or less Within these limits if desirable. 35

In accordance with the invention, in the manufacture of aromatic hydrocarbons, .diluents, solvents and plasticizers, the presence of paraflinic hydrocarbons is undesirable in that, being saturated, they d o not respond to molecular reo However, in stating that the saturated paraiinic hydrocarbons are undesirable, it is tobeunderstood'they are undesirable onlynas charging stock'for that 45 part of my process involving more directly the conversion of the charging stock into aromatic hydrocarbons, diluents, solvents and plasticizers. These parailinic hydrocarbons when separated from the napthenic and olenic hydrocarbons by 50 use of a selective solvent such' as herein mentionedare highly desirable for use as Diesel oils, spray oils, high grade distillate or any petroleum product which requires a high concentration of paraiilnic hydrocarbons. The charging stock may a distillateproduced from a crude oil 4 or a distillate produced from a synthetic oil from suitable predetermined boiling range.

a so-called cracking plantyor any fraction of lStarting with a petroleum oil distillate as chargingfstock, the distillate first is subjected to 'l a ,solvent treatment in which the parainic hydrocarbons are separated fromthe napthenic by reason of the selective solubility of the napthenes in the solvent. Starting with a synthetic dis tillate or charging stock produced from a crack.

ing plant, the synthetic distillate rst is subjected to a solvent treatment in which the paraf' nn hydrocarbons are separated from the napthenic and olenic .by reason of the selective solubility of the napthenes and olenns in the solvent.

After separating the parailiriic hydrocarbons from thel small amount of solvent entrained therein I have stock suitable in accordance with the process for high grade spray oils, Diesel. oils or any high grade' oil requiring a large concen-,vv

tration of parainic hydrocarbons. In most cases it being only necessary to fractionate these paraff rlnic hydrocarbons to the proper boiling range and passing same to storage for sale.A Then after separating the lsolvent from either or both the napthenes and oleflns, as the case may be, I have a` stock suitable in accordance with the process for the production of aromatic hydrocarbons,

diluents, solvents andrplasticizers. The `solvent may be recovered by the usual methodsl of distillation. The, portion of .the distillate or charging stock soluble in the -solvent will be referred to as the soluble oil. This vsoluble oil being either the soluble portion secured from the crude hydrocarbons. In this respect the invention is distinguished from the mere cracking of a solvent extractl as has heretofore been proposed for vthe purpose of obtaining lighter and more rvolatile fuels, from a relatively heavy oil obtained by` a solvent treatment.A Such processes as have been' proposed may incidentally result vin the production of some aromatics, but they are distinguished in that they are incapable of producing aromatic hydrocarbons alone or in commercial quantities from an Yeconomical standpoint. The known processes of vapor phase cracking in tubes have the disadvantage of producing excessive quantities of fixed gases, due to the extreme vapor temperatures (around-1500 F.) required. Also such vapor phase cracking processes require a high ratio of fuel-to-charging stock and high heating gas velocities acrossbthe tubes, which give large -heat losses up the stack. These are all conditions which produce heavy coke deposits in the tubes, and shorten the life of the equipment, maln'ng the whole operation uneconomical for the production of aromatic hydrocarbons.

I have found-that in order to bring about.

molecular. rearrangement of the soluble oil into aromatic hydrocarbons, it is necessary to avoid excessive temperatures and to effect the molecu- .lar rearrangement of the soluble oil vapors under."

conditions of relatively low" oilr vapor pressure.

In order to establish the conditions conducive to aaomca I the formation of laromatic-fhydrocarbons I subject the soluble oilvapors to a lmolecular rearrangement directly admixed with a suitable low molecular weight heatedu gas, the proportions of gas and vapors being such that in accordance with the laws of partial pressures, the actual or effective vapor pressure of the soluble oil vapors undergoing molecular rearrangement, is substantially reduced below the normal gaugefpressure at the existenttemperature. By directly admixing relatively high proportions of the heated low molecular weight gases with the soluble oil vapors in suitable -equipment,.I amable to produce aromatic hydrocarbons from petroleum without the characteristic Adiiilculties that have been ex,-

perienced in the past. Y g

In the nal steps of thel process, the converted oil vapors are subjected to suitable fractional condensation to obtain products having boiling ranges suitable for the particular purposes forV whichthefractions are to kbe used.

The invention, and thecomplete process, 'will perhaps be more fully understood and explained `to best advantage by reference to the accompanying ilow sheet illustrating diagrammatically and conventionally the various stages of the process. It will beunderstood that any suitable apparatus may beemployed for carrying out the invention,"-

and-that the drawing is to be regarded merely asillustrative of the invention in 'one-of its typical and preferred embodiments.

Assuming the initialy oil or charging stock to be processed, toconsist of a California type crude oil` containing both saturated and naphthenic hydrocarbons, the oil first may be topped in a.

skimming plant I0, the heavier endsbeing sent to storage through line II, and suitable lighter fractions within the desired lboiling range, after removal ofy terry bodies,l taken through line I 2 to a suitable. solvent extraction plant, diagrammatically indicated at I3, ..Where the crude oil has a high saturated hydrocarbon content and it is desired to convert the saturated compounds version into aromatics, I may rst subject the crude, before pr after being topped, to cracking in -a plant I4, running the residuum to storage through line Illa, and conducting the lighter fractions, consisting mainly of parains, naphthenes and olens, after removal of tars, through line I5 for treatment inthe solvent extraction plant I3.

lAs previously'mentioned, the purpose of the solvent extraction plant I3 is to separate the naphthenic and olelnic (or either when only one type is present) constituents of Athe charging stock from the saturated hydrocarbons. Solvent extraction systems of this character are well known and. require' no detailed explanation or showing. It will suce to state that any suitable,

process may be employed for accomplishing the extraction. Likewise, I may employ. any suitable solvent, such as liquid sulphur dioxide, croton4 under pressure and proper conditions of temperature however is preferred as a selective solvent. In the extraction plant I3, the naphthenic and olenic hydrocarbons are dissolved in the sulphur .into unsaturated compounds' suitable for,con v dioxide, and thereby separated from the insoluble parainic hydrocarbons. The latter may be removed through line I5 for any desired further treatment and for such uses as Diesel, spray oils, or any other uses for which an oil is particularly suited byumn or its-him ment or u napthenic and^olefinic hydrocarbons in proper condition for conversion into aromatica. At this point itmay be observed that the o il thus obtained bythe solvent extraction process preferably will have an approximate boiling range within the limits of 100" F. to 800 F., andI it may consist of any suitable fraction',.say one having a boiling range of 100 F., more or less, within these limits. In general. the particular boiling range of the separated soluble oil will be selected in accordance with the type of 'nal (aromatic) product being manufactured, and of course the type and characteristics ofthe oil treated in the solvent extraction plant will be predetermined accordingly. In most instances it is advisable to..

use as a charging stock for the conversion unit. fractions having relatively narrow boiling ranges since, by using such stocks, I reduce the amount of fixed gases produced, and secure a higher recoveryi of liquid products. The lower boiling charging stocks give higher percentages of lower boiling aromatic hydrocarbons in the flnished products than Iare obtained when high boiling range charging stocks .are used'. Charging stocks ofdiiferent boiling points may require slight variations in operating conditions, but these variations pertain to slight changes in temperature,

time of reaction, pressure and volume of combus-Y tion gases, and do not alter the'process.,

From the "sulphur dioxide separation plant 'I8 the oil passes through line to a/vaporizing retort or pipe still Il wherein the oil is heated to vaporizing temperature under a suitable pressure, for example 60 pounds gauge orover, or under, as may be determined jby a back pressure the fundamentals of valve, 22 in thevapor ,discharge line 23.l The vapors are discharged intol an enlarged zone Within the flash drum 24, with suiiicient pressure drop at the valve 22 to facilitate vaporization of any unvolatilized oil. Any unvaporizfableresidue l may be drained from the ash chamber through line 24a. For the purpose of insuring complete vaporization of the oil and'to reduce coke formation in the superheater, I preferably inject super.-

heated steamthrough line 25 into the ilash drum, the steam commingling with the vapors and the mixture owing through line 26 `to a tubular superheater 21 in which the oil vapor and steam mixture is heated to a suitable temperature preferably Within the range of 900 F. to 1l50 F. The oil vapors, together with the admixed steam when used, are next combined by suitable means with a heated low molecular weight gas that may be generated by any suitable means, for example in a combustion chamber 28 within which fuel such as distillate or natural gas supplied via line 29 from a compressor or pressure container 30, is burned in the presence of an air stream being discharged by a compressor 3l through line 32 into the combustion chamber.

The fuel is burned with a relatively high proportion of air, `for example 'in a ratio of 14 pounds of air to 1 pound of Iiuel, or in excessy thereof. The combustion gases, consisting mainly of -car- 'bon monoxide, leave the combustion chamber under pressure through passage 33 and are mixed therein with the superheated oil vapors 76 from line 34 leading from thesuperheater 21.

per sq. in. gauge.

partial pressure effect on the oil vapors by admix general practice,

. the oil vapors.

The temperature of the outlet combustion gases is controlled so` that the temperature of the gas andoil'vapormixtureordinarilywillbeinthe .neighborhood of 1200 1"., and preferably not substantiallyin excess of 1350' F. In the treatment of many` oils. it has been found that a maximum conversion to`aromatics requires a reaction chamber temperature not substantially below 1100 F. and this may be regarded as a preferred minimum conversion temperature. It maybe that other oils will respond to lower temperatures, but jas stated, a temperature of 1100 F. may be given as preferred. The gas and oil vapor mixture enters a suitable reaction chamber 35 containing an enlarged zone within whichV the oil vapors undergo molecular rearrangement into aromatic hydrocarbons at the temperatures stated, the rate of ow through the reaction chamber being regulated'so. that the vapors remain therein the length of time required for maximum conversion and reformation. Ordinarily the vapors will be held in the reaction chamber for a period approximating two minutes, which period however may vary in accordance with the characteristics' of the charging stock. and nal product to-be made. A

Preferably the conversion will be caused tovdeterminable in accordance with the nature of the charging sto'ck and -products desired. As illustrative, the reaction chamber pressure may vary within the range of from 15 to 100 pounds In'order to obtain the desired ture with thelow molecular Weight gas, the proportion of'gas in the mixture will greatly exceed the proportion Aof oil vapo'rs and at any time the proportion of lgas may be changed '-as it is desired to further reduce the partial pressure of Vthe oil vapors to the lowest practical limit.. As a I prefer to admix around 4 volumes of the combustion gas (inclusive o'r exclusive offsteam, if present) with 1 volume of In these proportions, the partial premure of the combustion or uncondensible gas constituents ofthe mixture will substantially exceed the partialpressure of the oil vapors. However, as stated the gas-to-oil vapor ratio may be varied from this preferred ratio to obtain an oil vapor partial pressure most suitablefor the de sired results. Again, these proportions may be variedin accordance with the characteristics of the charging stock'and the properties desired in thenished product. Tests have indicated that by maintaining the proper conditions, i. e., temperature, pressure and gas-to-oil vapor ratio in the reaction. chamber, it is possible to obtain pure aromatic hydrocarbons. 1

.Thus by controlling the volumes of combustion gases to volumes of superheated soluble oil vapors I am able to eifect the molecular rearrangement of the soluble oil vapors at pressures considerably below the gauge pressure and am able to convert the superheated soluble oil vapors to 'aromatic hydrocarbons at temperature lower than thought possible heretofore. In other words the gauge pressure may show 40 pounds within the reaction chamber but due to the lawsy (Daltons) of par-l tial pressures the soluble oil vapors are underl going molecular rearrangement atY a much lower fro 4 Y rthrough une s's into 'a scrubbing tower :1, une

purpose of which is. to cool the reformed prodthrough line 40,. If desiredl a stripping action ucts to the extent necessary "to retard polymerization and to prevent excessive formation of coke. .The gas and vapors risingfthrough the scrubber may be chilled or partiallycooled by the use of a volatile reflux, as -may' be supplied through line 39 from the base of the fractionating column 39. Any'condensate or heavy tarswithln the bottom of the scrubber may be drawn oil on the condensate in the scrubber may be had by injecting steam into the base through line 31a. After being cooled in the scrubber, the gas and vapor are discharged through line.4l to a Jiractionating apparatus, typically indicated generallyat 42, and which may be of any suitable type capable of separating or fractionallycondensing the aromatic vapors into the .desired fractions or cuts. By means of a back pressure valve 43 ln the vapor line 4I, or at any other suitable location, the proper operating pressure `-may be maintained within the reaction chamber 35and scrubber 31.

The fractionatingv column 39 may operate Ito fractionally condense and Separate one or a series of the aromatic fractions,`according to the desired boiling range of the product. For example,

- a heavier fraction may be taken from the base 572 F., was subjected of the column through line 44, and successively lighter fractions drawn oi at intermediate points through outlets 45 and 46. -Vaporsleaving' the fractionating column via line 41 are subjected to final condensation within condenser 48,` the conv densate, together `with the uncondensed gases, thence flowing through line 49 vinto accumulator 50,' from which the gases are exhaustedthrough line 5l arid the liquid product passed through line 52 to treaters or storage.

In a typical run, an initial charging stock consisting of a California distillate derived from a California crude oil having a gravity of 35.4 A. P. I., initial boiling point 420 F. and end point liquid sulphur dioxide, andafter separation from the insoluble, constituents-of the crude distillate,

the soluble oil showed the following boiling temperature and gravity properties by Hemple distillation:

Table I Gravity ol oil Percent distilled over- Tggm Spe A- P' I'. 60 Ff/co" F.

This oil, after vaporization with steam and being subjected to conversion by admixture with heated combustion gases as described in the foregoing, produced a total nal liquid condensate yield of 76.2 parts (by Weight based on the soluble extract), 16.4 parts otxed gas and casing head gasoline, and 3.9 parts of carbon. 1in the following table the results `of the Hemple distillation of the. total (reformed) condensate are given: Y

l0 32 oil 1865 20 25 gong 904 30 16. 955 4o- 11. a f .991 50 10.0 LM 60. 9. 6 1.1113 70 9. 2 LMS 80 9.0 1.001 87.5 6. 2 1.027

to solvent extraction by resultant Percent distilled over- V'is indicated by the following table showing the comparative results' of such standard tests as determination of the dilution ratio, solubility in From Table III it will be noted that the products of the present process are of high quality for uses as solvents with resins in the manufacture of varnishes and paints, as shown by the very high kauri butanol value; also that the `products are highly suitable for the manufacture of lacquers', as Ashown by the high dilution ratio values. In these regards, among others, the product is superior to any of the usual diluentsv or solvents now being made from petroleum oils alone. It willbe noted that the products are particularly suitable for use as paint thinners or carriers due to their high specic gravity and ability to hold paint pigments in suspension. As` further indications ofthe type of products capable of being produced by the in-v vention, it may be observed that tests made by a refractometer (specific refractor dispersion method of Ward and Fulweiler, Industrial and Engineering .Chemistry Analytical Edition of 1934, pages 396-400)v indicate that th'e products are substantially100% aromatic hydrocarbons andpossess the qualities of those aromatics d erived from the coal tars. The products are found to be completely soluble in three volumes-of 98% sulphurlc acid, and they are completely soluble in equal volumes of dimethyl sulphate.

In stating that the process 1s capable of producing products that according to the tests as described in the foregoing, are substantially entirely aromatic innature, it is to be understood that the invention Iis not to be regarded as limited to the making of products .100% aromatic. I have found that superior diluents, solvents, plasticizers,- etc., may be made that contain substantial or high percentages of aromatics, but

which need not be entirely aromatic in their colnposition.v

low molecular weight withl the /heated oil vapors of coal, which comprises treating a petroleum oil containing paraiiinic and non parafiinio hydrocarbons with a selective solvent to remove the paraiiinic hydrocarbons, recovering the non paraillnic'soluble'portion of the oil from the selective solvent by distillation, vaporizing and heating the non parainic portion of the oil, admixing and proportioning a heated gas of relatively so that according to the laws of' partial pressure .the actual vapor pressure of the admixed voil vapors undergoing conversion is substantially reducedbelow the gauge pressure oi' the mixture, V.maintaining the mixture at a temperature and time of reaction causing chemical conversion of the oil vapors to substantially and predominantly aromatic hydrocarbons, and finally subjecting the .converted oil vapors to fractionation, cooling, and condensation.

2. A method of producing aromatic hydrocar' bons and diluents and solvents of a predominant-y 1yA aromaticl hydrocarbon content whose dilution ratio, kauri butanol, and dimethyl sulfate values closely approach or equal those of coal tar aromatic hydrocarbons, produced by the pyrolysis of coal, consisting in subjecting a petroleum oil to conditions of cracking to produce a crackedy distillate, separating by distillation a desired fraction boiling within the limits from 100 degrees F. to 800 degrees F., contacting the desired fraction with a selective solvent to remove undesirable insoluble paraiiinic hydrocarbons from said distillate, recovering the soluble portion of the distillate from the selective solvent by distillation, vaporizing and heating the soluble portion of the distillate, admixing and proportioning a. heated gas of relatively low molecular weight with the heated oil vapors so that according to the laws of partial pressure the actual vapor prsure of the admixed oil vapors undergoing conversion is substantially reduced below the gauge pressure of the mixture, maintaining the mixture I at a temperature and time of reaction causing chemical conversion of the oil vapors to substantially and predominantly aromatic hydrocarbons. and nally subjecting the converted oil vapors to fractionation, cooling, and condensation.

. `3. A method'of producing aromatic hydrocar- 4bons and diluents and solvents of a predominantly aromatic hydrocarbon content whose dilution ratio, kauri butanol," and dimethyl sulfate values closely approach or 'equal those of coal tar aromatic hydrocarbons, produced by the pyrolysis of coal, which comprises heating and vaporizing a petroleum oil that has been solvent treated to remove undesirable paraiiinic hydrocarbons, admixing and proportioning a heated gas of relatively low molecular weight with the heated oil vapors kso that according to the laws of partial pressure the actual vapor pressure of the admixed oil vapors undergoing conversion is substantially reduced below the gauge pressure of the mixture, maintaining the mixture at a temperature and time' of reaction causing chemical conversion of the oil vapors to subs'tantiallyand predominantly aromatic hydrocarbons, and iinally subjecting the converted oil vapors to fractionation, cooling, and condensation.

4. In a method such as that described in claim 1 wherein the selective solvent is SO2.

5. In a method such as that described in claim 1 wherein a narrow and low boiling fraction of a petroleum' oil is treated to produce a high percentage yield of low boiling diluents, solvents and aromatic hydrocarbons.

6. In a method such as that described in claim 1 wherein a narrow and high boiling -fraction of a petroleum oil is treated to produce a high percentage yield of high boiling diluents, solvents and aromatic hydrocarbons.

JAMES W. PU'I'I'.

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