US2781297A - Treatment of petroleum fractions - Google Patents

Description

United TREATMENT OF PETROLEUM FRACTIONS No Drawing. Application October 24, 1952, Serial No. 316,815

13 Claims. (Cl. 196-44) This invention relates to the treatment of petroleum fractions and more particularly to a novel method of removing arsenic from petroleum fractions containing the same.

Most crude oils contain arsenic in one form of another and, when the crude oil is fractionated or otherwise treated to separate petroleum fractions, the petroleum fractions contain arsenic. -In many cases the presence of arsenic in the petroleum fraction is not detrimental but in other cases, particularly when the petroleum fraction is subjected tofurther treatment and still more particularly when this treatment is efiected in the presence of a catalyst comprising a noble metal, the presence of arsenic is definitely objectionable and must be removed from the petroleum fraction before the latter contacts the catalyst.

The presence of arsenic is exceedingly harmful in the case of gasoline fractions which are subjected to reforming in the presence of a catalyst containing a noble metal. In the past few years reforming processes have been commercialized utilizing a catalyst containing platinum. It has been found that the arsenic contained in the gasoline fraction rapidly deactivates the platinum catalyst and thereby renders the reforming process inoperable.

The present invention is directed to a novel method of removing arsenic from petroleum fractions and, as hereinbefore set forth, is particularly applicable to the treatment of gasoline fractions prior to reforming thereof in the presence of a catalyst containing platinum.

In one embodiment the present invent-ion relates to a process for purifying an arsenic-containing petroleum fraction which comprises treating said petroleum fraction with a salt of a metal selected from the group consisting of copper and metals lower than copper in the electromotive series of metals, and recovering a purified petroleum fraction reduced in arsenic content.

. In a specific embodiment the present invention relates to a process for purifying an arsenic-containing gasoline fraction which comprises treating said gasoline fraction with copper sulfate composited with a porous silicaalumina support, and recovering a purified gasoline reduced in arsenic content.

As hereinbefore set forth, the novel method of the present invention is particularly applicable to the treatment of gasoline fractions containing arsenic prior to contact thereof with a catalyst containing platinum. The gasoline fraction generally will comprise a saturated gasoline fraction including straight run gasoline fraction, natural gasoline fraction, etc. Unsaturated gasolines including cracked gasoline, etc., and mixtures of unsaturated and saturated gasolines, may be treated in accordance with the present invention but not necessarily with equivalent results. The gasoline fraction may comprise a full boiling range gasoline, which generally has an initial boiling point of from about 50 to about 120 F. and an end boiling point of from about 375 to about 425 f F., or'it may comprise a selected fraction thereof, commonly referred to as naphtha including, for example, a naphtha having an initial boiling point of from about 150 to about 250 F. and an end boiling point of from about 300 to 425 F. or more. While the invention is particiittes Patent F 2,781,297 Patented Feb. 12, 1957 ularly applicable to the treatment of gasoline fractions, it is understood that it may be used for the treatment of other petroleum fractions, including kerosene, gas 011, marine oil, white oil, turbine oil, lubricating oil, etc.

One of 'the major difficulties encountered in the treatment of petroleum fractions containing arsenic is that the arsenic may be present in various forms and, while one form of arsenic may be easily removed, another form of arsenic may be very difiicult to remove. Another difliculty encountered in the treatment of petroleum fraction-s containing arsenic is that the form of arsenic in some cases changes during storage or transportation of the petroleum fraction, and a given process which is satisfactory for treating the petroleum fraction at one time is not effective in treating the petroleum fraction at a later date. A particular advantage to the process of the present invention is that it efficiently removes arsenic regardless of the form in which it is present in the petroleum fraction.

Because the exact state in which the arsenic is present in different petroleum fractions is varied and changeable, in the interest of simplicity, the present specification and claims refer thereto as arsenic. It is understood that the term arsenic is intended to include free arsenic and any combined forms thereof.

In accordance with the present invention the petroleum fraction containing arsenic is treated with a salt of a metal of copper and/or of metals lower than copper in the electromotive series of metals, thus including copper, mercury, silver, palladium, platinum, gold, and mixtures thereof. While reference is made to the electromotive series of metals in defining the metals which may be used in accordance with the present invention, it is understood that the process of the present invention does not function in the true manner of the metals of the electromotive series wherein, for example, arsenic would displace copper and the copper would appear in the effluent products. As will be shown in the examples at the end of the present specifications, copper is not displaced and does not appear in the efiluent product.

Any suitable salt of the foregoing metals may be employed. In general, salts of strong acids are preferred, including the sulfates, chlorides, bromides, fluorides, iodides, nitrates, etc. Other inorganic acid salts may be employed, as well as organic acid salts, but not necessarily with equivalent results. The organic acid salts include the formates, acetates, propionates, butyrates, valerates, etc. It is understood that a mixture of salts of different metals and/or different salts of the same metal may be employed in accordance with the present invention.

'While the hereinbefore mentioned metal salts may be utilized as such, it generally is preferred to composite the same with a support or carrier having a high surface area. Any suitable support may be employed and thus may include silica gel, alumina, magnesia, zirconia, thoria, zinc oxide, etc., or mixtures thereof, including, for example, silica-alumina, silica-zirconia, silicaalumina-zirconia, silica-magnesia, s,ilica-alumina-magnesia, etc., which composites may be naturally occurring or synthetically prepared. In. general, the synthetically prepared composites will be highly porous and thereby'of high surface area so that efiicient contacting of the petroleum fraction and metal saltis accomplished. Naturally occurring supports include clays, kieselguhr, fullers earth, pumice, bauxite, etc., which may be treated to increase the surface area thereof when desired. Other suitable supports include charcoal, cellulose fiber, sawdust, etc. As will be shown in the following example, sawdust proved to be very satisfactory for this purpose. In some cases, the support may havesome activity per se in removing arsenic compounds but, as will be shown in the following examples, this effect is small compared to the effect of the metal salt deposited thereon.

.Ihc quantity of metal s omposi d w h the support will vary over a wide range and may depend, for example, upon the arsenic content of the petroleum fraction being treated. Thus, the quantity of metal salt may range from about 0.1% to 20% by weight (calculated as the metal) or more up to the saturation point thereof and preferably is within the range of from about 1% to about 10% by-weight, calculated as the metal. For example, copper sulfate composited with silica-alumina preferably is utilized in an amount within the range of from about 1%. to about 10% by weight (calculated as copper).

When the metal salt is to be composited with a support, this may be accomplished in any'suitable manner. In general, this is-readily effected by wetting the support with an raqueousror organic solvent solution, including alcohols, ketones, etc., of the metal salt, stirring when necessary to insure intimate contact, and finally drying to evaporate the solvent. The wetting may be accomplished by soaking, immersing, suspending, dipping, etc., the support in the metal salt solution or by pouringor sprayingthe metal salt solution over the support. Excess solution may be drained and the composite then heated to remove further amounts of solvent and to fix the metal salt onto and within the support. The support may be in any suitable form including powders, pellets, granules, spheres, flakes, etc. The heating generally is effected at a temperature within the range of from about 150 to 300 F. or moreand for a time sufficient to efiect thedesired drying, which time, for example, may range from'about one hour to 24 hours or more.

Treatment of petroleum fractions may betetfected in any suitable manner. In a preferred embodiment a bed of the treating agent is disposed as .a fixed bed in a:confined zone, and the petroleum fraction is passed therethrough in either upward or downward flow. Other methods of treatment may include the fluidized operation in which the petroleum fraction and treating agent are maintained in' a state of turbulence under hindered settling conditions in a confined zone, the slurry type of operation in which the treating agent is carried as aslurry in the petroleum fraction into the treating zone, moving bed operations in which the treating agent passes asa moving bed countercurrently to or concurrently with the petroleum fraction, etc. Continuous processes are preferred but it is understood that the batch type operations may be employed when desired.

Treatment of the petroleum fraction may be effected at any suitable temperature. In general, satisfactory operation is effected in ambient temperatures, although higher temperatures which generally will not exceed about 500 F. may be employed, but not necessarily withthe. equivalent results. In fixed bed operations the pressurewillbe sufficient to force the petroleum fraction through the treating reagent and thus may range from about pounds to any. desired superatmospheric pressure whichusually will not be. inexcess of about 1000 pounds per square inch. "The liquid hourly space velocity, defined as' the volume of petroleum fraction per hour pervolume of treating reagent in the treating zone, will varyconsiderably and, because of the high efiiciency of the treating agentof the present invention, high space velocities may be used and thus may range up to an hourly space velocity .of 100 or more." Because of thesmall amount ofarsenic normally contained in the petroleum fraction, the treating reagent of the present invention will :have a considerably long life and may be utilized in mos't cases for-the treatment of petroleum fractions upflto or, ,even greater than 100,000 barrels of petroleum fraction per ton of treating agent. In view of the'large'quantities of petroleum fraction which may be treated'byagiven batch of treating reagent and in view of the comparatively small, amount of .metal salt contained in the :batch of treating reagent, it .will be seen that the present process is very economical and that it will be commercially feasible to dispose of the treating reagent after it has become spent rather than endeavor to reactivate the same.

However, it is understood that the treating reagent may be reactivated in any suitable manner and reused in the process when desired.

As hereinbefore set forth, the treatment of the gasoline fraction with the metal salt in particularly advantageous when the gasoline is subsequently subjected to reforming in the presence of a catalyst containing platinum. A particularly preferred catalyst comprises alumina, from about 07.01% to about 1% by weight of platinum and from about 0.1% to about 8% by weight of combined halogen. Another platinum-containing reforming catalyst includes a composite of silica-alumina-platinum. These catalysts generally are utilized for reforming of a gasoline fraction at a temperature of from about 800 to about 1000 F. and a pressure of from about pounds to 1000 pounds or more per square inch, although'higher or. lower temperatures and pressures may be employed in some cases.

The following examples are introduced to illustrate further the novelty and utility of the present invention, but not with the intention of unduly limiting the same.

EXAMPLE I A treating reagent was prepared as follows. 10 grams of a cellulose fiber sold commercially as Solka-Floc BW-40 was wetted with 7.5 cc. of a 5% alcohol solution of mercuric bromide, after which excess solution was removed by vacuum, and the composite was dried at 221 F..for 3 hours. This composite contained approximately 3% 'by weight of mercuric bromide (calculated as mercury).

A straight run naphtha having an arsenic content of about. parts per billion was passed at room temperature through a bed of the treating reagent prepared in the above manner at a liquid hourly space velocity of 30. The arsenic content of the treated naphtha was less than one partper billion until the equivalent of 66,000 barrels of naphtha-per ton of reagent were treated, at which time the arsenic'content of the treated naphtha was one part per billion.

It will be noted from the above data that the metal salt served to efficiently reduce the arsenic content of the naphtha and that the treating reagent reduced the arsenic content of the naphtha to 1 part per vbillion even after treating the equivalent of 66,000 barrels of naphtha per ton ofreagent.

EXAMPLE II A' treating reagent was prepared to comprise 3%mecuric chloride (calculated as mercury) composited with sawdust. This treating reagent was prepared by substantially the. same procedure as described in Example I.

When used for the treatment of another sample of the naphtha described in Example L-the arsenic content, after treating the equivalent of 21,000 barrels of naphtha per ton ofreagent, was 3.

In order to, compare the ability'of the sawdust alone to remove arsenic, another sample of the naphtha was passed through a bed of sawdust in substantially the same manner as was done with the reagent comprising mercuric chloride and sawdust. After the equivalent of 1000 barrels of naphtha per ton of sawdust were contacted with the sawdust, the arsenic content of the product was substantially the same as the arseniccontent of the charge. V Thisexample illustrates, notonly the necessity of using the metal salt, but also the high efficiencyof the reagent containingonly 3% by weight of mercuric chloride '(calculated'as mercury).

EXAMPLE 111 The treating reagent used in this example comprised a mixture of copper sulfate, mercuric chloride and silver nitrate composited with synthetically prepared silicaalumina microspheres. This reagent was prepared by dissolving 5.1 grams of copper sulfate, 0.013 gram of mercuric chloride and 0.016 gram of silver nitrate in 100 cc. of water, and pouring the resultant solution over 100 cc. of the silica-alumina microspheres. The composite was then dried for 4 hours at 230 F. This reagent contained 5% by weight of copper sulfate (calculated as copper), 0.02% by weight of mercuric chloride (calculated as mercury), and 0.02% by weight of slver nitrate (calculated as silver).

The reagent as prepared in the above manner was used for the treatment of another portion of the naphtha described in Example I. This run was made at a liquid hourly space velocity of 60. After the equivalent of 18,000 barrels of naphtha per ton of reagent were treated with the reagent at atmospheric temperature, the treated naphtha had an arsenic content of less than 2.

As hereinbefore set forth, the arsenic does not displace the metal salt from the reagent and the metal salt does not appear in the treated naphtha. The naphtha charge had copper content of 0.014 mg. per liter and the treated naphtha had a copper content of 0.011 mg. per liter. Thus, it is seen that the copperis not displaced by the arsenic and does not appear in the treated product.

EXAMPLE IV Another treating reagent was prepared comprising 5.09% of copper sulfate (calculated as copper) composited with sawdust. This reagent was prepared by the general procedure described in Example II.

After treating the equivalent of 90,000 barrels'of another portion of the naphtha described in Example H per ton of reagent, the arsenic content of the treated naphtha was 2 parts per billion. After treating the equivalent of 112,000 barrels of naphtha per ton of reagent, the arsenic content was 8 parts per billion. These runs were made at a liquid hourly space velocity of 35.

Here again it will be noted that the treating reagent of the present invention served to effectively reduce the arsenic content of the naphtha from 125 parts per billion to 2 parts per billion after treating the equivalent of 90,000 barrels of naphtha per ton of reagent and to 8 parts per billion after treating the equivalent of 112,000 barrels of naphtha per ton of reagent.

EXAMPLE V Another reagent was prepared to contain 3% by weight of mercuric bromide (calculated as mercury) composited with Attapulgus clay.

After treating the equivalent of 10,000 barrels of naphtha per ton of clay, the arsenic content of the treated clay was less than 2 parts per billion.

EXAMPLE VI Another treating reagent was prepared to contain 3% by weight of mercuric bromide (calculated as mercury) composited with alumina. In a single run which was concluded after the equivalent of 1500 barrels of naphtha per ton of reagent was treated, the treated naphtha had an arsenic content of less than 2 parts per billion.

EXAMPLE VII Another treating reagent was prepared comprising 2% by Weight of copper sulfate (calculated as copper) composited with silica-alumina cracking catalyst in the form of 20-50 mesh powder. This reagent was used to treat a naphtha having a boiling range of from about 100 to about 300 F. and an arsenic content of 33 parts per billion. This run was made at a liquid hourly space velocity of 30 and atmospheric temperature. The arsenic Table 1 Arsenic, parts per billion Equivalent barrels of naphtha per ton of reagent Less than 1. Less than 1.

The copper content of the naphtha charge was 0.012 mg. per liter, and the copper content of the treated naphtha was 0.006 mg. per liter. Here again it will be noted that the copper in the treating reagent was not displaced by the arsenic.

EXAMPLE VIII The silica-alumina cracking catalyst powder used to support the copper sulfate of Example VII was utilized alone; that is, without the copper sulfate composited therewith, in order to compare the results obtained with those obtained in Example VII. The results of using the silicaalumina alone are shown in the following table.

Table 2 Arsenic, Equivalent barrels of naphtha per ton of silica-alumina parts per billion From the data in the above table it will be noted that A EXAMPLE IX Another treating agent was prepared to comprise 2% by weight of copper acetate (calculated as copper) composited with sawdust. This reagent was prepared by the same general procedure as described in Example 11. After treating the equivalent of 8,000 barrels of another sample of the naphtha used in Example II per ton of treating agent, the arsenic content of the naphtha was reduced to about 4 parts per billion.

EXAMPLE X As hereinbefore set forth the metal salt for use in accordance with the present invention must not be above copper in the electromotive series of metals. A treating reagent comprising 2% by weight of nickel sulfate (calculated as nickel) composited with sawdust was prepared by the same general procedure as described in Example II. When utilized for the treatment of another sample of the naphtha used in Example I, and after treating the equivalent of 8,000 barrels of naphtha per ton of nickel sulfate, the treated naphtha had an arsenic content of parts per billion.

This example further illustrates the importance of utilizing a metal which is not above copper in the electromotive series of metals because, as noted from the results of this run, the nickel sulfate did not remove any arsenic from the naphtha.

EXAMPLE XI A treating reagent was prepared comprising 2% by weight of ferric chloride (calculated as iron) composited with sawdust and prepared by the same general procedure as described in Example II. When utilized for the treat ment'ofianother'sample'ofthe naphtha used in Example I, the treated naphtha :contained 50 parts per billion of arsenic after treating the equivalent of only 2800 barrels of naphtha per ton of ferricchloride. Here again it is noted that a metal above copper in the electromotive series of metals .is not satisfactory for the efficient removal of arsenicfrom naphtha.

EXAM E I As hereinbefore set forth the treating reagent of'the present invention must be a..salt.of the. metals hereinbefore setforth. The oxide:of the metal is'unsatisfactory as evidenced by the'treatment of another sample of the naphtha described in Example I witha reagent comprising 4%by weight .of copper oxide composited with sawdust and prepared by the same procedure as hereinbefore set forth. After treating the equivalent of 20,000 barrels of naphtha per ton of reagent, the treated naphtha had an arsenic content of 110 parts per billion. Thus, it will be seen that the copper oxide reagentis not satisfactory to effectively reduce the arsenic content of the naphtha.

I claim as my invention:

1. A combination processwhich comprises treating an arsenic-containing petroleum fraction with a reagent comprising a salt of a metal not higher than copper in the electromotive series of metals, recovering a purified petroleum fraction reduced in arsenic content, and subjecting saidpurified petroleum fraction to conversionwith a catalyst comprising a noble metal.

2. A combination process which comprises treating an arsenic-containing gasolinefraction with areagent .comprising a salt of arnetal not -higherthan copper in the electromotive scrim ofmetals, recovering a purifiedg'asoline fraction reduced'in arsenic content, and subjecting said purified gasoline fraction to reforming at reforming conditions witha catalyst comprising platinum.

3. The process of claim '2 further characterized in that said salt of a metal is composited in an amount of from about 0.1% to about 20% by weight (calculated as the metal) with a porous support.

4. The process of claim 2 further characterized in that said reagent comprises a salt of copper inan amount of from about 0.1% to about 20% by weight (calculated as copper) composited with a porous support.

5. 'Theprocess of claim 4 further characterized in that said reagent comprises copper sulfate in an amount of from about 1% to about 10% by weight-(calculated' as copper) composited with said support.

Q6. The process of claim 5 further characterized in that said support comprises silica-alumina.-

7. TTheprocess of claim 4 further characterized in that said :reagentcomprises copper chloride in an amount of from about.l% to about 10% by Weight (calculated as copper) composited-with said support.

8. The process of .claim 2 further characterized in that said. reagent comprises a salt of mercury in an amount of from about 0.1% to about 20% by weight (calculated as mercury)icomposited with a porous support.

9. Theprocess of claim 8 further characterized in that said reagent comprises mercuric chloride in an amount of from about 1% to about 10% by weight (calculated as mercury) composited with said support.

10; :The process of claim 8 further characterized in that said .reagent comprises mercuric bromide in an amountoffrom about 1% to about 10% by weight (calculatedas mercury) composited with said support.

11. The process of claim 2 further characterized in that said reagent comprises a salt of silver in an amount of from about 0.1% to about 20% by weight (calculated as silver) composited with a porous support.

.12. The process of claim 11 further characterized in that .said'reagent comprises silver nitrate in an amount ofz-fromabout 1% to about 10% by weight (calculated as silver) composited with said support.

13. Acombination process which comprises treating an arsenic-containing gasoline fraction with copper sulfate composited with a porous silica-alumina support, recovering a purified gasoline fraction reduced in arsenic content, andsubjecting said purified gasoline fraction to reformingat a temperature of from about 800 to about 1000.F,.in the presence of a catalyst comprising alumina, from about 0.01% to about 1% by weight of platinum and from about'0.1% to about 8% by weight of combined halogen.

References Cited in the "file of this patent UNITED STATES PATENTS 1,948,565 Day Feb. 27, 1934 2,042,052 Hoover May 26, 1936 2,479,110 Haensel Aug. 16, 1949 OTHER REFERENCES Lewis et al., Ind. and Eng. Chem, Anal. Ed, vol. 9, pages 405-406 (1937).

Thomas, The Science of Petroleum, vol. 11, Oxford University Press, page 1054 1 938).

Kalichevsky et al., Chemical Refining of Petroleum," 2nd Ed., Reinhold Pub. Corp., page 34 (1942).

Maxted, Journal of Chemical Society, vol. 119, pages 225-233 1920).

Claims (1)

1. A COMBONATION PROCESS WHICH COMPRISES TREATING AN ARSENIC-CONTAINING PETROLEUM FRACTION WITH A REAGENT COMPRISING A SALT OF A METAL NOT HIGHER THAN COPPER IN THE ELECTROMOTIVE SERIES OF METALS, RECOVERING A PURIFIED PETROLEUM FRACTION REDUCED IN ARSENIC CONTENT, AND SUBJECTING SAID PURIFIED PETROLEUM FRACTION TO CONVERSION WITH A CATALYST COMPRISING A NOBLE METAL.