US2440258A - Refining of petroleum distillates - Google Patents

Description

April 27, l948- L. P. ELLIOTT ETAL 2,440,258

REFINING OF PETROLEUM DISTILLATES 4 Filed'Ag. 8, 1945 wad/mummy Nwwwwxw NOW ai .l

Paiented Apr. 27, 1948 REFINING F PETROLEUM DISTILLATES Laverne P. Elliott, Berkeley, and Melvin M. Holm, San Francisco. Calif., assignorato California Research Corporation, San Francisco, Calif., a

corporation of Delaware Application August 8, 1945, Serial No. 609,676 s s claims. (c1. 19e-1419)` f leum fractions for the production of lamp oils,

fuel oils and similar products composed of relatively more paraiiinic and naphthenic hydrocarbons substantially free of aromatic and unsaturated hydrocarbons, and containing only small amounts of such impurities as sulfur compounds,

nitrogen compounds, phenols, naphthenic acids,

asphaltic substances and inorganic matter.

Another objectv of the invention is to provide a process for the extraction of aromatic and olefin type hydrocarbons and sulfur containing components vfrom petroleum distillate fractions by extracting said fraction with sulfur dioxide, and then extracting the raiiinate of said'extraction with liquid hydrogen fluoride or hydrouoric acid.

An additional object of the invention is to produce highly refined lamp oils and fuel oils of superior quality with a minimum loss in oil and consumption of reagent materials.

Still` another object of the invention is to produce petroleum products of the distillate type composed substantially of parafiin and naphthene type hydrocarbons (saturated hydrocarbons) from a high sulfur content asphalt base or mixed base crude oil source, without the production of large quantities of acid sludge waste and thus avoid the related problem of sludge disposal.

In the production o f lamp oils or fuel oils from asphalt or mixed base crude petroleum oil the major refining problem is one of removal or separation of relatively large amounts of aromatic hydrocarbons and sulfur compounds to produce a product composed substantially of paraiiin and naphthene type hydrocarbons. Previous methods of accomplishing this refinement employed large amounts of sulfuricacid at 'elevated temperatures to cause a series of chemical changes to occur in a portion of the unsaturated, parailinic, naphthenic and` aromatic hydrocarbons and the sulfur containing compounds. The products of these chemical reactions, being soluble selectively in the resultant acid sludge layer, were removed by separation of the same from the unreacted oil layer. The chief disadvantage of this method was in the chemical action which degraded valuable hydrocarbon materials, consumed large amounts of sulfuric acidand posed a serious problem of reagent recovery and sulfuric` acid 'sludge disposal.

Another well-known method for refining petroleum oil distillates containing substantial amounts of unsaturated and aromatic type hydrocarbons and sulfur compounds is the sulfur dioxide extraction method in which a, parafilnic railinate is produced by selectively extracting the unsaturated, aromatic and sulfur-containing components of the stock. This method, however, does not completely or adequately separate the nonparainic and sulfur compounds from the parafilnic compounds desired in the lamp oils and fuel oils of this invention. Further treatment with sulfuric acid or fuming sulfuric acid has been applied to achieve more complete renement. These finishing methods also involve considerable losses of desired hydrocarbons due to oxidation and sulfonation.

This difficulty appears to be due in part to the use of reagents containing sulfur in performing the finishing treatment. Sulfuric acid, fuming sulfuric acid, other acids of sulfur and oxides of sulfur introduce into the oil reaction products containing sulfur. Although the use of these .reagents results in a net decrease in the natural sulfur content of the stocks treated, the sulfur containing products remaining in the finished oil are equally objectionable.

Small amounts of these residual impurities and reaction products may resultv in chimney deposits, crust formation on wicks and wick destruction in the case of lamp oils. In fuel oils, such as Diesel fuels, they cause corrosion, mineral deposits and plugging of the fuel injection system.

It has now been found that these difliculties are overcome and higher yields of finished lamp oils and distillate fuels of premium quality are obtained byemploying a hydrofiuoric acid treatment on the raiiinates obtained from sulfur dioxide extraction. A petroleum oil distillate obtained from an asphalt or mixed base crude petroleum oil is first treated by an extraction with liquid sulfur dioxide at reduced temperatures in the range of about 40 F. to about +70 F., but preferably in the region from about 10 F. to about 30 F. where substantially all of the sulfur dioxide is in the liquid form. Sufficient sulfur dioxide is employed to extract a maior portion of the undesirable components of the charge oil (aromatic l and unsaturated hydrocarbons, sulfur compounds,

nitrogen compounds, phenols, naphthenic acids, asphaltic substances, etc.) without extracting substantial amounts of the desirable components such as the paramn hydrocarbons. 'I'he amount of sulfur dioxide used is determined by the stock being treated and the degree of rennement des] sired. 'I'he treating conditions are chosen to allow a `minimum amount of aromatic hydrocarbons, consistent with th'e permissible smoke tendency, to remain in the raiiinate oil fraction of lamp oils.

The raffinate layer containing the desirable saturated hydrocarbons is separated from the extract layer and is freed of substantially all the dissolved sulfur dioxide by evaporation. This partially refined oil contains the sulfur compounds of the original charge which are the least susceptible to removal by sulfur dioxide, and also small amounts of sulfur compounds resulting from the sulfur dioxide extraction itself along with sulfur dioxide not removed by th'e evaporation step. 'If the partially refined oil goes to tankage before proceeding with the next step of refinement it is possible for a small but significant amount of oxygen to be absorbed. In order to avoid interfering effects of dissolved oxygen and sulfur dioxide in the final refining. the dissolved oxygen and sulfur dioxide are removed by distillation with reflux or by stripping prior to sending the partially rened oil to the next rening stage.

To completely refine this fraction a second extraction, employing liquid hydrofiuoric acid or hydrogen fluoride, is performed whereby these residual impurities, consisting mainly of sulfur compounds, are reduced to an insignificant proportion without the removal of appreciable amounts of desirable hydrocarbons, or th'e introduction of additional sulfur compounds or impurities. The extraction with liquid hydrofiuoric acid, which is performed in the proper manner to cooperate with the sulfur dioxide extraction in a combined refining process, is conducted at suitlable temperatures and pressures and employing suitable proportions of hydrofiuoric acid relative to the sulfur dioxide rainnate oil. The temperatures may be between about -50 and about 300 F. but conditions are usually chosen so that temperatures not far above nor below normal 'atmospheric values, namely, from about 30 F. to about 100 F., can be employed. The hydrofiuoric acid used may be diluted with water to the extent of as much as about 20% by weight in the mixture. However, treating acid containing not less than 90% hydrogen fluoride by weight is preferred to complete the refinement of most SO2 raffinate oil fractions. The hydrofiuoric acid is used in suiiicient amount to form a distinct liquid phase which will readily settle out to form a liquid hydrochlorie acid extract layer separable from the major portion of original oil charge contained in the rafiinate layer. The amount needed may vary with the content of residual impurities remaining after the SO2 extraction and the amount of water in the hydrofiuoric acid. For hydrofluoric acid containing -about 99% hydrogen fiuoride by weight an amount between about 5 and 200 percent by volume of the SO2 raffinate oil is generally satisfactory, but in cases where the content of sulfur-containing compounds is high' the amount of hydrofiuoric acid may greatly exceed 200% by volume of the oil extracted. The hydrofiuoric acid is removed from the raffinate layer by distillation with reflux and/or stripping and is thereby recovered for continuous use. p

Although very little fluorine is introduced into the finished oil by the hydrofiuoric acid treatment, objectionable amounts of fluorine may bereadily reduced to negligible proportions in the oil by any suitable means suoli' as passing the vaporized oil over lime or bauxite at elevated temperatures.

Catalytic defiuorination using etched aluminum rings to defiuorinate the oil vapor may also be used,

By the process just described the selective sol- -vent effects of liquid sulfur dioxide and liquid hydrogen fluoride or hydrofiuoric acid are combined to produce higher yields of more completely refined products (of extremely low sulfur content and controlled hydrocarbon type composition) than was possible by the processes described above. T'his result is achieved by choosing the sulfur dioxide extraction conditions so that all oi. th'e aromatic hydrocarbons are extracted except the small proportion that can be tolerated in the final lamp oil, for example, and then performing the hydrofiuoric acid extraction under the conditions for optimum selective extraction of the residual sulfur compounds with minimum extraction of aromatic hydrocarbons. The extract oils resulting from both extractions are readily recovered by evaporation and stripping operations which at the same time recover the sulfur dioxide and th'e hydrofiuoric acid solvents. The SO2 extract oil is a valuable source vof aromatic hydrocarbons and the HF extract oil contains sulfur compounds which are useful raw materials for the production of various chemicals such as odorants, perfumes, solvents, and lubricating oil additives.

The invention will now be more particularly Idescribed and illustrated in connection with the accompanying drawing which is a schematic flow diagram of a specific embodiment of the invention. Some auxiliary equipment such as condensers, reflux drums, exchangers, etc. which may be desirable or necessary for the operation of Ithe process, and the n'eed for which is obvious to anyone versed in the art, is not included in the diagram for the sake'of simplicity in describing the process.

'I'he charge oil is fed through line I into the bottom of SO2 extractor 2 where the oil is mixed With liquid sulfur dioxide entering the SO2 extractor at the top. The oil or raflinate phase, due to its lower density, moves toward the top of the extractor as the sulfur dioxide or extract phase drops to the bottom of the extractor where it is drawn off through line 3 leading to extract evaporator 4. The recovered sulfur dioxide is led back into SO2 extractor 2 through line 25 and the SO2 extract oil, composed chiefly of aromatic hydrocarbons, is withdrawn from the extract evaporator via line 6.

The raffinate phase is withdrawn from the top of SO2 extractor .2 through line 'I and introduced into rafiinate evaporator 8, Where the major portion of sulfur dioxide is separated from the oil by distillation. The rafiinate oil is passed to SO2 stripper I0 through line 9 and the remnants of sulfur dioxide are stripped from the raflinate oil by passing an oxygen-free stripping medium, such as a gaseous or 10W-boiling hydrocarbon fraction, through the heated oil.

After withdrawal from SO2 stripper I0, through line II, the SO2 raffinate oil is introduced into the bottom of HF extractor I 2 Where it is mixed with liquid hydrofiuoric acid being fed into the top of the HF extractor. As in the sulfur dioxide extraction just described, the

raflnate phase moves toward the top of the extractor and the extract phase settles to the bottom. The extract or hydrofiuoric acid phase is Withdrawn from HF extractor I2 via line I3 and is fed into HF regenerator I4. Hydro- .Iiuoric acid 1s recovered by distination and stripping in regenerator il and recycled to HF extractor i2 through line il. Fresh hydroiluoric acid make-up freed of omen and sulfur compounds may be fed to the system through line II. Anpoxygen-,free ystripping medium. Such as a low-boiling liquid hydrocarbon fraction, is '1sed. The HF' extract' oil, consisting of -a-high proportion of sulfur-containing compounds, is withdrawn through outlet Il.

The ramnate phase produced, which includes some of the stripping medium introduced into regenerator I4, is withdrawn through -line' i1 from the top of the extractor and fed' to HF stripper Il where the hydrogen fluoride and most of the stripping medium are separated from the rafllnate oil .by distillation under reilux and re cycled to HF extractor l2 through lines Il and I5. I'he bottoms from HF stripper Il is fed 1 nutte oil.

6 hydroilucric acidextractedoil andthefuming sulfurlcacidtreatedoilaswellas Color stability values were determined by measuring the color of the sample witha Saybolt'hromometer aftery keeping the sample in an oven at 212 l". for 1li-hours. To evaluate the burning characteristics of the samples A, B. T.M. lamp test method D-187 was used.

Comparison to-standard test-v results were obtained by comparing the burning qualities of the samples as determined by the lamp tests, with v the burning qualities of a sample of high-grade lamp oil prepared-from a parailin base crude petroleum source. and chosen as a standard becauseof its excellent burning characteristics.

The data obtained in these in the table below: l

through line 2l into kerosene stripper 2| where the remaining hydrocarbon stripping medium is stripped from the treated oil with steam, the nished oil being withdrawn through outlet 22. The wet stripping medium is passed overhead.

Although counterfiow through packed columns is shown in the extraction sections of the above illustration, other conventional means of contacting liquids such as mechanically driven agitators, circulating pumps, atomization of treating material into confined oil, etc., may be used with counterilow or conflow of liquid streams. Instead of continuous contacting, batch or combinations of batch and continuous treatments may be practiced =by methods well known in the art. Accelerated methods oi separating the mixed liquids, such as centrifuging', for example, may be applied with advantage in connection with some mixing apparatus.

Example The following example illustrates some of the many advantages obtained as a rf sult of'practicing the present invention. A lamp oil stock derived from a California crude lpetroleu-m oil having a gravity of 40.3 A. P. I., and containing 0.040 percent sulfur was extracted at F. with 70 percent by volume of sulfur dioxide" based on the oil charged. 'I'he yield' of SO2 raiiinate oil was 77.1 percent by volume of the charge. A portion of this raiilnate oil was extracted at 70 F. with 50 percent of its ownvolume of hydrotluoric acid containing 99 percent by weight of hydrogen uoride; A yield of 99 percent iinished oil, based on the SO: ramnate charged, was obtained.

For purposes of comparison, a second portion of the SO2 rafllnate oil was treated with commercial sulfuric acid at 70 F. using the equivalent of 0.15 pound of l5 percent turning sulfuric acid per gallon of oil. A yield of 96 percent by volume of acid treated oil was obtained.

A comparison of the results obtained on the finished oil prepared by sulfur dioxide extraction followed by hydroiluoric acid extraction (HF extracted) with those obtained on the SO: ramnate q,

The absence of appreciable chemical action between the SO2 raillnate oil and hydrofluoric acid accounts for the very high yield (99 percent based on the charge oil) obtained from the hydrofiuoric acid extraction as compared to the lower yield (96 percent based on the chargeoil') resulting from the 'filming sulfuric acid treatment. The ilumine content of the hydrouoric acid treated oil in the above example was found to be nil.

Since substantially no aromatic removal takes place during hydrofluoric acid extraction, the sulfur dioxide extraction preceding the same is performed under those conditions that will result in an SO2 railinate oil containing an aromatic content reduced to the desired degree. This concentration of aromatic hydrocarbons corresponds to thel maximum aromatic content permitted in the hydroiluoric acid finished oil. Thus substantially all the aromatic hydrocarbons to be removed are separated during the sulfur dioxide extraction andv can be readily recovered from' the SO: extract by simple physical processes. y sulfuric acid- -treatment of the SO; ralllnate, on the other hand, always involves the sulfonation of some of the aromatic, 'paraillnic and naphthenic hydrocarbons which are lost in anI acid Inspections and lamp tests were run on the sludge of relatively little value.

the somit-l tests are collected Y The combination of sulfur dioxide extraction (for the removal of the major portion of aromatic hydrocarbons and some of the sulfuir compounds from the original hydrocarbon oil) with hydrofiuoric acid extraction (for the purpose of removing the residual sulfur compounds) produces excellent results largely because of the high degree oi' selectivity that hydrofluoric acid shows toward the types of sulfur compounds remaining in the SO2 railinate oil. That these sulfur compounds may have a different distribution and composition than those contained in the original charge oil is illustrated by the greater selectivity exhibited by the liquid hydroiluoric acid toward the residual sulfur compounds in thepSOa raffinate than toward the sulfur compounds in the virgin oil.

A Midway stock for the production of mineral seal oil was extracted with sulfur dioxide to produce an SO2 rafhnate. The original stock and three portions of the SO2 raffinate were extracted with hydrofiuoric acid by thoroughly mixing the oil and acid for 20 minutes and then settling and separating the two .phases in each case. The sulfur contents of the HF rafilnates and acid phases were determined and the ratio of the percent by weight of sulfur in the acid phase to that in the raffinate phase (distribution ratio) was calculated for each experiment. A high ratio indicates relative ease of removal of sulfur from the oil by the hydrofiuoric acid. The data obtained in these experiments are tabulated below.

8 yield of a product of an extremely low sulfur content and oi' controlled hydrocarbon type composition, comprising first extracting said hydrocarbon oil with liquid sulfur dioxide to remove there-v from a desired maior amount of aromatics and some of said sulfur compounds, leaving in the rafiinate sulfur compounds which are more amenable to removal by liquid hydrogen fluoride than those in the hydrocarbon oil prior toliquid sulfur dioxide extraction, and subsequently extracting the raffinate obtained from said sulfur dioxide extraction with liquid hydrogen fluoride in the absence of added agents other than up to 10% Water to remove the remaining sulfur compounds substantially completely therefrom without appreciably changing the minor aromatic content of said raiiinate.

3. A process of refining a lamp oil stock containing aromatic and non-aromatic hydrocarbons and sulfur compounds to obtain therefrom a high The much higher distribution ratios obtained for the sulfur in extractions of the SO2 raiiinates, ranging from 13.4 to 21.9, compared to 6.87 obtained for the oniginal stock, illustrate the greater effectiveness of hydroiiuoric acid toward removal of sulfur compounds from the S02 raiiinates than from the stock, and indicate that either .the sulfur compounds in the SO2 raiiinates differ from those in the stock, or that lthe distribution of type of sulfur compounds in the SO2 rafnates differs from that in the stock, or both.

While the character of the present invention has been described and exemplified in detail by way of illustration, it will be understood that the invention embraces such other variations and modifications as come within its spirit.

We claim: I

l. A process of refining a hydrocarbon oil containing aromatic and non-aromatic hydrocarbons and sulfur compounds to obtain therefrom a high yield of a product of extremely low sulfur content and of controlled hydrocarbon type composition, comprising first extracting said hydrocarbon oil with liquid sulfur dioxide to remove the desired major amount of aromatic hydrocarbons therefrom, and subsequently extracting the rainate obtained from the sulfur dioxide extraction with liquid hydrogen fluoride in the absence of added agents other than up to 20% water to remove sulfur compounds substantially completely therefrom without appreciably changing the minor aromatic content of said raihnate.

2. A process of refining a hydrocarbon oil containing aromatic and non-aromatic hydrocarbons and sulfur compounds to obtain therefrom a high from the sulfur dioxide extraction with liquid hydrogen fluoride in the absence ofadded agents other than up to 20% water to remove the remaining sulfur compounds substantially completely therefrom without appreciably changing the minor aromatic content of said raiiinate.

4. A process for rening lamp oil stocks which comprises extracting the stock with liquid sulfur dioxide to obtain an extract containing a fraction of the sulfur compounds contained in said stock and a major fraction of the aromatic compounds in said stock and a rafilnate containing the remainder of the sulfur compounds of said stock, and also the sulfur compounds resulting from the contact of sulfur dioxide with the stock and aromatic compounds in amount slightly below the maximum consistent with permissible smoking tendency, and thereafter extracting the raffinate of the sulfur dioxide extraction step with hydrouoric acid under conditions adapted to remove 6. The process as defined in claim 1 wherein the step is conducted at 30-100' F., and water added to the hydrogen uoride does not exceed 10% by weight of the water-hydrogen fluoride mixture..

7. The process as deilned in claim 1 wherein the sulfur dioxide extraction step is conducted at 10-30 F., the hydrogen fluoride extraction step is conducted at 30-100" F., and the hydrogen fluoride employed is substantially anhydrous.

8. The process as denned in claim 4 wherein the sulfur dioxide extraction is conducted at 10-30' F., the raiiinate of the sulfur dioxide extraction is extracted with aqueous hydroiluoric acid containing at least 90% by weight of hydrogen fluoride, and the hydrouoric acid treating step is conducted at 30-100 F.

LAVIIRNE P. EILIUI'I. MELVIN M. HOIM.

REFERENCES crrnn The following references are of record in the file of this patent: 7

UNITED STATES PATENTS Number Name Date 911,553 Edeleanu Feb. 2, 1909 1,964,953v Lazar July 3, 1934 1,988,793 Haylett Jan 22, 1935 2,320,629 Matuszak June 1, 1943 2,343,744 Burk Mar. 7, 1944 2,343,841 Burk '.L. Mar. 7, 1944 2,349,473 Tannich May 23, 1944 2,366,743 Matusrak Jan. 9, 1945 2,375,675' Matuszak May 8, 1945 2,378,762

Frey June 19, 1945

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