US2584248A - Recovery of sulfur compounds from petroleum - Google Patents

Description

Feb. 5, 1-952 R. E. BARIEAU RECOVERY OF SULFUR COMPOUNDS FROM PETROLEUM Filed July 15, 1948 2 SHEETS-SHEET l m 3.": 3m .0 FIUUZ w 5 w 0 L .n m m m GII'P E E W N D H M Y. a R A w w w a S c I T H m, f E w v 0 m w 0 E w l 2O MOLES HF PER GRAM ATOM OF SULFUR CHARGED INVENTOR ROBERT E. BARIEAU FIG. 1

ATTORNYS/ Feb. 1952 R. E. BARIEAU 2, 8

RECOVERY OF SULFUR COMPOUNDS FROM PETROLEUM Filed July 15, 1948 2 SHEETSSHEET 2 .97 .96 'l .95 l0 0 N 94F T 0/4 I 5.93 5 l :5 Q. a Li. 5' .9! w

NIL

l .9 \N l-r o v :1 I00 0 l0 3 u m z I-- 2 Q HF STRENGTH WEIGHT 7 INVENTOR ROBERT E. PSARIEAU 2 mam r ATTORNEY Patented Feb. 5, 1952 UNITED RECOVERY OF SULFUR COMPOUNDS FROM PETROLEUM Application July 13, 1948, Serial No. 38,397

8 Claims.

This invention relates to a method of extractmg sulfur compounds from crude petroleum oils or from distillation fractions of these crude oils. More particularly, this invention relates to a method of separating sulfur compounds from petroleum crude oils or fractions thereof having a medium to high sulfur content by a two-stage acid extraction process.

An object of this invention is to recover a concentrate consisting predominantly of organic sulfur compounds from crude petroleum oils or fractions of crude petroleum oils.

A further object is to effect a substantial degree of desulfurization of crude petroleum or fractions of crude petroleum by concentrating the sulfur compounds contained therein in an extract by means of a two-stage acid extraction process.

A variety of sulfur compounds have been identified in petroleum oils and crude concentrates of these compounds are known to be useful in the preparation of weed-killing compositions and surface-active agents. Such concentrates may be further processed to separate sulfur compounds individually or according to chemical type.

It has been discovered that an extract consisting predominantly of organic sulfur compounds can be obtained from crude petroleum oils or petroleum fractions by a method comprising a two-stage acid extraction wherein the concentration of the acid used in the first extraction step is lower than that of the acid used in the second extraction step.

It has also been discovered that the acid of lower concentration used in the first extraction step removes from petroleum stocks of medium to high sulfur content, components of these stocks which are of a non-sulfurous nature. The extract containing the non-sulfurous components is, small in volume and has a relatively low overall sulfurcontent. Thus, the acid of lower concentration effects a selective removal of the nonsulfurous components, which would be. removed together with and as an impurity in such sulfur compounds that might be extracted in a single extraction employing a more concentrated acid.

Extraction of the rafiinate of the first extraction step with an acid of higher concentration has been found to produce an extract containing a higher percentage of sulfur compounds than it is possible to obtain in a single extraction.

Further, it has been discovered that there exist preferred acids and acid concentration ranges for both extraction steps.

The mineral acids are particularly suitable for use in the first extraction step; especially strong mineral acids such as hydrofluoric, perchloric, and sulfuric acids. From data gathered in the extraction of Santa Maria gas oils with these acids, concentrations of between about to about per cent in the first extraction step can be used with the preferred concentrations being:

Per cent Hydrofluoric acid 80 Sulfuric acid 80 Perchloric acid 70 Hydofluoric acid is employed in the second extraction step at a concentration of at least per cent and preferably at a concentration of about 8586%.

The first extraction step in the process of the invention produces an extract consisting principally of readily extractable non-sulfur compounds, while the second step produces an extract consisting predominantly of sulfur compounds.

The three acids which may be employed in the first extraction step are approximately equivalent in their extractive action; however, the preferred concentrations .difier for the acids as shown above.

Generally it is preferredto conduct both extraction steps under normal conditions of temperature and under sufficient pressure to maintain the materials in liquid phase. However, it is possible to conduct the extractions at reduced or elevated temperaturesprovided the pressure The contact time in both extraction steps is ordinarily short, being on the order of ten minutes; however, some stocks may require a longer period of contact for successful extraction.

The ratio of acid to oil in the first extraction is preferably between about 0.05 and 0.3 volume of acid per volume of oil.

The ratio of hydrofluoric acid to oil in the second extraction step may vary from about 2 to 20 mols of acid per gram-atom of extractable sulfur contained in the rafi'inate of the first extraction step but it is preferred to use a ratio of 14-16 moles of HF per gram-atom of extractable sulfur contained in the raffinate of the first extraction step.

Both extraction steps may be conducted in either batchwise or continuous operation, and the conventional apparatus of the solvent extraction art may be readily adapted for use in the process of the invention. One of the methods of conducting this two-step extraction process, when using hydrofluoric acid in both steps, is to use the acid phase from the second extraction step, after it has been suitably purified and diluted, as the solvent-extractive phase for the first extraction step; then purifying and concentrating the acid from this latter step to a suificient strength and purity so that it can be recycled and used as the acid for the second ste thereby eliminating the necessity of two acid concentration units. Such util zation of hydrofluoric acid in both extraction steps permits more efiioient use of the acid solvent and sim lifies solvent recovery and purification. Accord n ly,

the modification of the process of the inv ntion is preferred over mo ifications employing different acids in the two extraction steps.

The second extract from either cont nu us or batch-type operation may be further treated to separate the sulfur com ounds individually or acc rd ng to chemical type.

Of the appended drawin s, Fi ure 1 is a g aphical re resentation of the variations of the cha acter of the extract obtained from a highsulfur gas oil with quantity of acid employed in the extraction step. Figure 2 is a graph cal rep esentation of the variation in the pro erties of the extract with the concentration of the acid employed.

Referring now to Figure 1. the data upon which the graph is based was gathered in a series of experiments to which a Santa Maria gas oil havin a sulfur content of 2.46 per cent was extracted with varying Quantities of 99.4 per cent hydrofluoric acid. The acid quantity is expressed in mols of acid per gram-atom of sulfur in the oil being extracted. It is seen that the extract yield rises sharply as the quantity of ac d employed is increased, this sharp rise continues until a ratio of 14-16 mols of acid per gram-atom of sulfur is reached. The employment of higher acid to sulfur ratios produces only a slight increase in the yield of extract. The weight per cent of sulfur in the extract similarly shows a sharp rise as the ratio of acid to sulfur is increased from to 8 mols of acid per gram-atom of extractable sulfur. The rise continues less sharply until a ratio of about 1 1 mols of acid per gram-atom of sulfur is reached after which further increases in the acid ratio produce little gain in the sulfur content of the extract. It is found that most efficient use of the acid in the extraction of sulfur compounds is obtained by employing 14-16 mols of acid per gram-atom of extractable sulfur in the extraction.

In Figure 2 of the appended drawings, data accumulated in a series of extractions of Santa Maria gas oil containing 2.46 per cent sulfur is summarized. A ratio of 14.8 mols of acid to each gram-atom of sulfur in the oil was maintained in each extraction and the concentration of hydrofluoric acid was varied from to 99.4 per cent by weight. It is seen from this figure that the extract yield increased slowly with acid con centration until a concentration of -80 per cent was reached and then the yield increased much more rapidly with further increases in concentration. The per cent of sulfur in the extracted material also increased slowly with acid concen tration until a concentration of about per cent was reached and then rose abruptly to reach a maximum at about 86 per cent. As acid concentration was increased above 86 per cent and particularly as it was increased above 90 per cent, the percentage of sulfur in the extract declined. The extract obtainedat acid concentrations from 50 to 80 per cent is small in volume and low in sulfur content indicating the presence in the oil of some non-sulfurous material, which is rather easily extractable. The decline in per cent sulfur content of the extract obtained at acid concentrations above about 90 per cent indicates the probability that some difficultly extractable non sulfurous materials are removed by hydrofluoric acid at 90-100 per cent concentrations. Operation according to the process of the invention in its preferred modification employing hydrofluoric acid at about 80 per cent concentration in a first extraction step makes possible the removal of readily extractable non-sulfurous compounds in. this step, then a second extraction step employing hydrofluoric acid at a concentration of -90 per cent makes possible the removal of an extract consisting essentially of sulfur compounds without the inclusion of the difficultly extractable non-sulfurous material which would be removed if acid at concentrations above per cent were employed. While acid concentrations of 85-90 per cent are preferred in the second extraction step, the process may be conducted employing more concentrated or even substantially anhydrous hydrofluoric acid in the second extraction step in order to obtain the advantage of greater concurrent desulfurization of the oil in addition to the recovery of an extract consisting predominantly of sulfur compounds.

The process of the invention is illustrated by the following examples:

EXAMPLE I Santa Maria oil was extracted according to the process of the invention employing perchloric; acid of 70-72 per cent concentration in the first extraction step and hydrofluoric acid of 85.7 per cent concentration in the second extraction step. Properties of this gas oil are shown in the following Table I. The gas oil and perchloric acid were shaken in a laboratory separatory funnel for 5-10 minutes. After standing, the extract layer was separated. The rafiinate was washed with water, then with caustic, and then with water again. After washing, the rafdnate was filtered. andinspected. Following inspection, the raffinate was extracted with 85.7 per cent hydrofluoric acid in a manner similar to that of the first extraction step. The raflinate and extract of the second extraction were washed and inspected. Data from this experiment are sum-- manned in the following Table I. Y

more I Extraction 1 Extraction 2 Substance treated Santa Maria gas oil Rai'linate of Extractions. A d Perchlorlc. Hydrogen Fluoride. Acid Strength (Wt per cent) 70-72 85.7. Pretreatment Caustic Wash" Contact time. 5-10 minutes minutes. Temperature 7 79-84. Moles of HF per g. atom of S 15.7. Vol. acid per Vol. Charge 0.100

Inspections Charge Extract Rafiinate Charge Extract Raflinate Actual Recovery (Wt. per cent). Yield Density (Wt. per cent) Yield from Wt. (Phase separation) Density (/4) 0.8811 Refractive Index (N a). 1. 4887 Aniline Point F.)... r 127 Molecula'rWt.-' Carbon (Wt. per cent). 84. 63 Hydrogen (Wt. per cent) 12.50 Suhur (Wt. per cent) 2. i6 Nitrogen 0. O5 C+H+S (Av. per cent).. C+H+S+N (Av. per ent)..... 99.64 Per Cent Sulfur Compounds..

Note: 1 Yield from Density (Wt. per cent) is calculated in the following manner:

where:

D.,: density of charge. Dr=density of rafliuate. D. density of extract.

2 ll'lolecular weights were determined from observations of the freezing point lowering of benzene in benzene solutions of the materials whose molecular weight is being determined.

The method is set forth in Physical Methods of Organic Chemistry, by Weissbcrgcr, Inter-s ien e Press, 1945, at page et seq.

It is seen from Table I that an extract containing 81.3 per cent sulfur compounds was ob- :15

tained in the sccondextraction step and that a substantial degree of desulfurization of the gas oil was concurrently obtained.

EXAMPLE II A quantity of Santa Maria gas oil was subjected to a two-stage acid extraction employing hydrofluoric acid as the extractive solvent in both stages, the acid concentration was 80.4 per cent in the first stage and 85.9 per cent in the second stage. The results of the extractions are pcrchloric acid of '70 per cent concentration are approximately equivalent in the first extraction step of the process of this invention and it has similarly been found that sulfuric acid of about 88 per cent concentration is approximately equivalent to hydrofluoric and perchloric acids at their respective preferred concentrations in the first extraction step.

It is not intended that this invention be limited to the examples given for the sake of illustration but rather to extend it to such modifications Within the skill of the art as are within the scope of the appended claims.

summarized in the following Table II: I claim:

Table II Extraction 2 Extraction 1 Raflinate of Extraction 1 Substance treated Santa Maria gas oil Santa Maria gas oil, pretreated with 80.4% HF. HF Strength (Wt. Per Cent) 4 85.9. Pretreatment Contact time Temperature E)... Moles of HF per g. atom of S Inspection Charge Extract Railinate Charge Extract Raflinate Actual Rccovery (wt. per cent)..-" 4. 16 81. 7 100 5. 33 80. 4 Yield from Density (wt. per cent) 100 7. 3 92. 7 100 9. 37 90.63 Yield from HF balan e (wt. per

cent) 6. 7 93. 3 100 Yield from Wt. 5.0 95. 0

Density (20/4) 9336 .8772

Refractive Index (N 5135 .4869

Aniline Point F.) Molecular Weight Carbon (Wt. Per Cent C+H+S (Av. Per Cent). Per Cent Sulphur Compounds" See Remarks following Table I.

It is seen from Examples I and II that hydrofluoric acid of 80 per cent concentration and 1 The method of separating a. concentrate of 7 organic sulfur compounds from sulfur-containing petroleum oils which comprises first extracting said oil with a mineral acid having a concentration not exceeding 80 per cent by weight and thereafter extracting the raifinate of the first extraction with hydrofluoric acid having a concen' tration of at least 85 per cent by weight.

2. The method of separating a concentrate of organic sulfur compounds from petroleum oils of medium to high sulfur content which comprises first extracting the oil with a strong mineral acid at a concentration not exceeding about 80 per cent by weight to remove readily extractable non-sulfur compounds from the oil and thereafter extracting the rafiinate of the first extraction step with hydrofluoric acid at a concentration of at least per cent by weight to separate an extract consistingpredominantly of organic sulfur compounds.

3. The method of separating a concentrate of organic sulfur compounds from petroleum oils of medium to high sulfur content which comprises first extracting one volume of oil with 0.05 to 0.3 volumes of a strong mineral acid at a concentration of per cent to per cent by weight to remove readily extractable non-sulfur compounds from the oil and thereafter extracting the rafi'lnate of the first extraction with hydrofluoric acid at a concentration of at least per cent by weight to separate an extract consisting predominantly of organic sulfur compounds.

4. The method of separating a concentrate of organic sulfur compounds from petroleum oils of medium to high sulfur content which comprises first extracting one volume of oil with 0.05 to 0.3 volumes of a strong mineral acid at a concentration of about 50 to 80 per cent by weight to remove readily extractable non-sulfur compounds from the oil, thereafter extracting the raffinate of the first extraction with hydrofluoric acid at a concentration of at least 85 per cent by weight to separate an extract consisting predominantly of organic sulfur compounds and em ploying in the second extraction step 14-16 mols of hydrofluoric acid per gram-atom of extractable sulfur contained in the rafiinate of the first extraction step.

5. The method of separating a concentrate of organic sulfur compounds from petroleum oils of medium to high sulfur content which comprises first extracting one volume of oil with 0.05 to 0.3 volumes of hydrofluoric acid having a concentration of about 80 per cent to remove readily extractable non-sulfur compounds from the oil, thereafter extracting the raifinate of the first extraction step with hydrofluoric acid having a concentration of about'85-90 per cent and employing in the second extraction 14-16 mols of hydrofluoric acid per gram-atom of extractable sulfur contained in the raifinate of the first extraction step.

6. The method as defined in claim 5 wherein the acid employed in the first extraction step is perchloric acid at a concentration of about per cent.

7. The method as defined in claim 5 wherein the acid employed in the first extraction step is sulfuric acid at a concentration of about per cent.

8. The method as defined in claim 5 wherein the petroleumoil is a Santa Maria gas oil.

ROBERT E. BARIEAU.

REFERENCES CITED The following references are'of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,957,840 Lewis May 8, 1934 2,440,258 Elliott et al Apr. 27, 1948 2,449,463 Evering et a1 Sept. 14, 1948 2,465,964 Brooke et a1 Mar. 29, 1949 FOREIGN PATENTS Number Country Date 345,596 Great Britain Mar. 26, 1931

Claims (1)

1. THE METHOD OF SEPARATING A CONCENTRATE OF ORGANIC SULFUR COMPOUNDS FROM SULFUR-CONTAINING PETROLEUM OILS WHICH COMPRISES FIRST EXTRACTING SAID OIL WITH A MINERAL ACID HAVING A CONCENTRATION NOT EXCEEDING 80 PER CENT BY WEIGHT AND THEREAFTER EXTRACTING THE RAFFINATE OF THE FIRST EX-

Images