US2146154A - Inhibitor - Google Patents

Description

Feb 7, l939- H. F. MERRIAM ET AL 2,146,154

INHIBITOR Filed Oct. 15, 1936 `Patented Feb. 7, 1939 UNITED STATES PATENT FFICE INHIBITOR Application October 15, 1936, Serial No. 105,652

11 Claims.

This invention relates to corrosion inhibitors, to inhibited acid compositions, to methods for pickling metals for the removal of oxides or mill scale. and to pickling baths. The invention is more particularly directed to inhibitors, inhibited acid solutions and pickling baths comprising or containing sulfur bearing oils derived from sludges formed in oil rening processes in which sulfuric acid is employed. 'Ihe invention is also especially directed to metal pickling processes carried out with the utilization of such sulfur bearing oils as corrosion inhibitors.

Pickling solutions for removing oxides or mill scale from the surface of metals ordinarily consist largely of a dilute solution of an inorganic acid such as sulfuric acid. The acid, although it dissolves the oxides and scale, also attacks the metal to some extent so that acid is consumed, and a certain amount of metal is lost. It also appears that the hydrogen liberated by the action of the acid on the metal has a serious embrittling effect upon the metal being treated. Inhibitors are used not only for the reasons noted but also to prevent pitting and corrosion Where the metal is not covered by scale. Inhibitors are commonly employed in such solutions to decrease the activity of the acid with respect to the metal without greatly affecting the solvent action of the solution with respect to the oxides.

The principal objects of the invention are directed to improvements in inhibited acid compositions, methods for pickling metals, pickling baths, and to the provision of markedly effective sulfur bearing oil corrosion inhibitors for these purposes. It is a further aim of the invention to provide sulfur bearing corrosion inhibitor oils having a relatively high sulfur content substantially all of which is in strong chemical combination, and which oils are stable and do not become ^turbid on standing.

In oil refining processes, involving treatment of petroleum distillate oils with sulfuric acid, large quantities of sludges are produced. When destructively decomposed by heating, these sludges form gas mixtures containing water vapor and l condensable hydrocarbon vapors, and gases such as sulfur dioxide, carbon dioxide, nitrogen and l uncondensable hydrocarbons. When sludge material, resulting from treat- 5() ment with sulfuric acid of relatively light hydro- 1 carbon oil dlstillates containing substantial quantities of sulfur compounds is dissociated preferably by destructive decomposition by heating to form a hot gas mixture containing hydrocarbon vapors and the gas mixture is cooled, for example to about normal temperature, an oily condensate is obtained which is a sulfur bearing oil. A sulfur oil of this type is of such nature that it may be treated, for example as with sulfuric acid, in such a way as to effect a selective separation of a large portion of certain sulfur inhibitor constituents from other sulfur and nonsulfur constituents. The invention comprises corrosion inhibitors, inhibited acid compositions, and particularly metal pickling processes and pickling baths. In accordance with the present invention, it has been found that sulfur bearing oils containing said certain sulfur constituents and resulting from suchv sulfuric acid treatment, possess properties rendering these oils especially suited for inhibiting the corrosive action of acids on metals. The oils so produced are stable, as a general rule higher in sulfur than the initial oily condensate, and do not deposit free sulfur or become less effective on standing.

A further appreciation of the objects and advantages of the invention may be had from a consideration of the following description of the oils constituting the improved corrosion inhibitors, of inhibited acid compositions and pickling baths containing the improved inhibitors, of pickling methods involving use of the improved sulfur bearing oil inhibitors, and of methods for making the improved inhibitors. 'I'he accompanying drawing illustrates diagrammatically apparatus by which the improved sulfur bearing oil inhibitors may be made.

Referring to the drawing, I0 indicates the combustion chamber of a furnace adapted to burn coal, coke, oil, natural gas or other fuel. Mounted in chamber I0 is a decomposing kiln or retort II of any desirable construction, for example a fixed shell provided with suitable mechanism such as a screw conveyor, not shown, to facilitate discharge of coke. A rotary retort may also be employed if desired. Preferably an externally heated kiln adapted to substantially exclude admission of air is used. One end of kiln II communicates with a gas outlet I3, and the opposite end projects into a header I4 into which the solid residue of the decomposition of the acid sludge is continuously discharged. Header I4 empties into airlock I5 through which coke may be discharged without admitting air to the kiln. Acid sludges, constituting sources of the sulfur bearing inhibitor oils of the invention, are run into the kiln from supply tank I'I through a valve-controlled pipe I8. Gas outlet I3 is connected to the lower end of a cooler or condenser 20 of any suitable construction, either air or water cooled, and opi in erated so as to reduce the temperature of the gas stream to substantially normal to condense the bulk of the water vapor and a major portion of condensable hydrocarbons contained in the gas. Condensate from the cooler drains into a separator or collecting tank 2| through a pipe 22 having a liquid seal.

The gases uncondensed in cooler 20, containing principally sulfur dioxide, are discharged through gas line 23, and may be used as desired, for example in the manufacture of sulfuric acid by the contact process.

Separator 2| may be a tank or vat large enough to permit continuous gravity separation of water and oil contained in the condensate discharged from condenser 20. The sulfur bearing hydrocarbon oils of the condensate rise to the top of the mass in the separator, and may be Withdrawn continuously or intermittently through pipe 25 discharging into a collecting tank 26. Water settling to the bottom of the separator may be drawn oi through pipe 21, controlled by valve 28. and discharged to Waste or otherwise disposed of.

The still 30, of any approved construction, may be externally heated by hot combustion gases generated in brick-work setting 3| Raw condensate from collecting tank 26 is run into the still through pipe 38, controlled by valve 39. Vapors generated in the still flow through line 4| to a condenser 43, the condensate of which drains through pipes 45 and 46, into receivers 50 and 5|.

The inhibitor oils of the invention may be made in apparatus such as illustrated in the drawing and described above by operating substantially as follows.

In producing the improved sulfur bearing oil inhibitors, acid sludges which may be employed are those resulting from sulfuric acid treatment of light distillate oils obtained from petroleum crudes containing sulfur. The acid sludges employed in making the inhibitors of the invention are preferably sludges resulting from treatment with sulfuric acid of light hydrocarbon oil distillates such as gasolene and kerosene, containing not less than about 0.15% sulfur, although distillates containing less sulfur may be employed if desired. Illustrative examples of distillate oils from which sludges are produced of a character suitable for use in the present invention are straight-run gasolene distillates containing about 0.15% sulfur or more, and cracked distillate averaging 0.25 to 0.30% sulfur or more.

Sludge material of the type indicated and which may have for example a titratable acidity of 40% to 60% expressed as H2SO4 is continuously fed into kiln from supply tank I1. The burners in furnace |0 are adjusted to maintain within the kiln temperatures desirably not in excess of about 750 F., as above this temperature the sulfur oils constituting the basis of the improved inhibitors tend to be decomposed. The preferred temperatures are about 250 F. at the sludge inlet end, and about 500 F. to 600 F. at the coke outlet end of the kiln.

The sludge, gradually passed through the retort, is relatively gradually heated through the preferred temperature range and is decomposed by the action of heat. and the free and/or combined sulfuric acid of the sludge is reduced to sulfur dioxide by the hydrogen of the hydrocarbons and/or by the carbonaceous matter contained in the sludge. The sludge material is thus dissociated, as by the destructive distillation method indicated, with production of water vapor, and hydrocarbon vapors and sulfur compounds are formed. Residual coke is continuously discharged from the kiln through air-lock l5. The major part of the sulfur appears to have been evolved by the time the sludge has reached a temperature of S50-400 F.

The gas resulting from the decomposition of the sludge contains principally water vapor and sulfur dioxide, substantial amounts of condensable hydrocarbons and sulfur compounds and smaller quantities of uncondensable hydrocarbons and gases such as carbon dioxide. carbon monoxide, and nitrogen. For example, one representative sludge having a titratable acidity of about 50% expressed as H2SO4 yielded on decomposition by destructive distillation about 28% residual coke and a retort gas which, after cooling to about normal temperature, produced about 6% condensable oil, about 35% Water, based on the weight of the sludge, the balance of the retort gas comprising sulfur dioxide, carbon dioxide, carbon monoxide, nitrogen and uncondensable hydrocarbons and water vapor. As previously noted, according to the preferred method for making the sulfur bearing oils, decomposition of sludges is effected in the kiln substantially in the absence of oxygen and in the absence of other extraneous gases. When so operating, the volume of gas formed is lessened and loss of sulfur oil by volatilization is decreased.

The hot gaseous and vaporous products of decomposition of the sludge are discharged from the kiln and passed through conduit I3 into condenser 20 in which the gases are cooled to substantially normal temperatures. Cooling may be accomplished by circulating through the condenser in indirect heat exchange relation with the retort gas mixture any suitable cooling liquid or gas. In place of the condenser illustrated in the drawing, a vertical tower having a spray head at the top for introduction of water may be employed. In such cases, the retort gas mixture is introduced into the bottom of the tower and flows upwardly, intimately contacting and mingling with the downwardly directed spray of water fed in at the top of the tower. The amount of cooling water introduced is so controlled as to cool the exit gases leaving the top of the tower to about normal atmospheric temperatures.

During cooling of the retort gas mixture in the condenser 20. substantially all of the water vapor and the major portion of the condensable hydrocarbon vapors and sulfur compounds are condensed out of the gas stream. The condensate of cooler 20, containing varying proportions of water and liquid hydrocarbons and sulfur compounds is drained through pipe 22 into separator 2|. In the latter, the oils rise to the top of the liquid mass in the tank. and may be intermittently or continuously withdrawn through pipe 25 into tank 26 for collecting what may be termed a raw condensate or initial sulfur oil. The water settling to the bottom of the separator 2| may be discharged from the system through pipe 21.

Ihe oil collecting in tank 26 is an oil containing generally from about 3 to about 22% sulphur, apparently in strong chemical combination. It will be understood the sulfur content of this condensate may vary considerably in accordance with the characteristics of the initial crude oils and of the acid sludges produced on treatment of the hydrocarbon oil distillates with sulfuric acid. For example, an acid sludge formed though sulfuric acid treatment of a straight-run gasolene yielded an oil condensate of 12% by weight 0f the sludge, the condensate analyzing 14.8%

sulfur. A cracked distillate sludge yielded 10% by weight of oil condensate having a sulfur content of 7.5%. In another instance, a cracked distillate averaging about .25 to .30% sulfur produced on treatment with sulfuric acid a sludge which, on treatment in accordance with the present method, yielded 10.8% by weight of oil condensate analyzing 20.8% sulfur. For convenience in the following discussion, crude sulfur bearing oils of the kind just described are referred to herein as initial sulfur oils.

Initial sulfur oils of the type described apparently contain sulfur constituents and non-sulfur constituents and are of such nature that they may be treated, for example with sulfuric acid, in such a way as to bring about a selective separation of certain sulfur constituents from the other sulfur and non-sulfur constituents. Such separation treatment in most instances results in production of oils having substantially higher sulfur content than the initial sulfur oils and containing all or almost all of the said certain surfur constituents of the initial sulfur oils. 'I'he high sulfur oils resulting from such treat ment for convenience may be termed refined oils, or purified or concentrated or extracted oils. In accordance with the present invention, it has been found that these refined oils, or purified or concentrated or extracted high sulfur oils possess properties making such oils especially suited for inhibiting the corrosive action of acids on metals.

'I'he separation treatment of an initial sulfur oil to produce a refined oil (one such treatment being hereinafter described in detail) may be applied if desired directly to an initial sulfur oil as recovered in tank 26. However, the initial oil in this state contains appreciable quantities of foreign matter, such as coke-dust and tars, which under most circumstances may be desirably removed. Separation of foreign matter from the initial oil may be eiected by distilling the initial oil producing a coke or asphalt-like still residue and distillate or condensate which may be termed an unstabilized distillate oil. If desired, the separation treatment referred to may be applied to the sulfur bearing oil of tank 26 after removal of the foreign matter such as cokedust and tars (as by the distillation operation mentioned) that is, to the unstabilized distillate oil. Further, the initial sulfur oil in tank 26 and the unstabilized distillate oil usually contain substances such as mercaptans and pyridines which impart to the oil an undesirable odor and may tend to render the ultimate product oil unstable. Hence, according to the more satisfactory procedure for making the refined inhibitor oils of the invention, it is preferred to (1) remove from the initial sulfur oil of tank 26 the foreign matter as coke and tars as by distillation; (2) simultaneously fractionate the initial oil during the distillation operation, (since different fractions, e. g. a light fraction or a heavy fraction, may be suited for diierent purposes; (3) stabilize the fractions (to remove mercaptons, pyridines, etc.); and (4) then treat the stabilized oils or if desired the oils in unstabilized condition to produce the refined or purified or concentrated or extracted high sulfur oils.

Removal of foreign matter from the raw condensate of tank 26 and splitting of the condensate into two or more fractions may be done by distillation. For this purpose, oils from tank 26 are run into still 30 through line 38. The distillation operation may be carried out in any suitable still, preferably one provided with equipment for collecting separate fractions of distillate. It will be understood distillation of the raw condensate is principally for two purposes, first. to remove coke and tars from the oil, and second, to produce preferably two fractions, one having a relatively low boiling point range, and another having a higher boiling point range. Distillation may be effected for example by external heating of still 30. If desired, distillation of the crude condensate may also be accomplished at temperatures lower than those hereinafter mentioned by introducing live steam directly into the oil body while externally heating the same. Distillation may also be effected, though possibly less desirably, by superheated live steam. using steam at slightly above atmospheric pressure and heated to say 22B-250 F. before introduction into the oil. Vacuum distillation may be employed if desired.

Still 30 may be operated to produce a first cut including all the oils distilling over at temperatures up to about 350 F. at normal pressure. Vapors generated within this temperature range are liqueed in condenser 43, and are run into receiver 50. This relatively low boiling fraction may for example constitute approximately 20% by weight of the raw initial sulfur oil condensate fed into still 30. When removal of these low boiling fractions from the oil in still 30 is substantially complete, the temperature is raised to distill over oils having boiling points ranging from about 350 F. up to about 650 F. Vapors formed are condensed in cooler 43, and may be recovered in receiver 5i. This high boiling fraction may comprise for example 60-66% by weight of the raw condensate introduced into still 30. Approximately 10% by weight of tbe original raw condensate withdrawn from tank 26 may remain as a coke or asphalt residue in the still, and around 5-10%by weight of the original raw condensate may be lost in the distillation operation as uncondensable vapors and gases. The law boiling cut recovered in receiver 50 contains a slightly higher percentage of sulfur than the higher boiling fraction collected in receiver 5I. If desired, all of the vapors evolved in still 30 may be condensed and collected in a single receiver instead of in two receivers as 50 and 5i. In this situation, while there is some decomposition with liberation of HzS, the condensate collected corresponds in a general way with the condensate collected in tank 26 except that foreign matter, such as coke-dust and tars has been removed.

As indicated above, the hereinafter described sulfur constituent separation treatment may be applied directly to the raw condensate collecting in tank 26, or to the fractions collecting in receivers 50 and 5I, or to the condensate collecting in a single receiver used in place of receivers 50 and 5|. 'I'he oils, in most cases apparently contain substances such as pyridines and mercaptans which impart to the oils undesirable odors and which tend to render the oils somewhat unstable on standing. Accordingly, in mest instances it is preferred to further treat the abovementioned oils to stabilize the same and remove odors. This may be accomplished by treating the oils with a solution of sulfuric acid or caustic soda or both. When employing caustic alkali, as is preferred, the oil may be agitated with a 20% caustic soda solution at temperatures of about F. until reaction appears complete.

'I'he reaction products are allowed to settle. and 75 are withdrawn. 'I'he oil may then be washed with water to remove traces of alkali, and brightened as by blowing with air.

'I'he oils are preferably stabilized by treating with relatively low concentration sulfuric acid, say about equal volume, separating reaction products, and washing the oils with water and alkali to remove traces of acid. For this stabilization treatment, it is preferred to use acid of concentration not in excess of about 60% H2SO4, since acid of this or less concentration, while suitable for removing odor-imparting substances, does not appear to have appreciable effect on the desired sulfur compounds which should be left in the oils at this stage and recovered by the subsequent sulfur constituent separation treatment. If desired, the oils may be stabilized by using acid of greater concentration, say up to about 93.2% H2804 (66 B.) in which case the amount of stronger acid should not desirably exceed about 7% by volume of the oil treated.

Treatment of the oils with either caustic alkali or sulfuric acid notably improves the odor and increases the stability of the oils. In some instances, it is desirable to subject the oils to treatment with both caustic alkali and sulfuric acid In this case, after subjecting the oils to the caustic soda treatment noted above, and removing the alkali extract, the oils are washed with water to remove the alkali, and then treated with one or more washes of equal volume of dilute sulfuric acid, for example 30% H2SO4. The final oil products may be washed with water to remove traces of acid, and then brightened by blowing with air, or by othermethods.

In the case of a raw condensate from tank 26, or where the foreign matter is removed from the condensate of tank 26, as by distillation and collection of all the distillate in a single receiver, the resulting oil may be stabilized as described.

The oils stabilized, for example as mentioned above, are sulfur bearing mineral oils, light bodied, and have a relatively high sulfur content, substantially all of which is in strong chemical combination. It appears substantial amounts of the contained sulfur is present as alkyl sulfldes and possibly also some disuldes and other sulfur bearing compounds. The sulfur content of the oils at this stage may vary from about 3 to about 22%, and on standing the oils do not become turbid or deposit sulfur. The oils are a light straw color. The specific gravity of a representative oil is about 0.98. 'Ihe viscosity is low, about 32 to 34 Saybolt at 100 F.

The oils in unstabilized and stabilized condition appear to comprise mixtures of sulfur constituents especially adapted for use as inhibitors, and other less valuable sulfur and non-sulfur constituents. The ultimate refined oils, used in accordance with the invention as inhibitors, are obtained by selectively separating the sought for sulfur constituents from other sulfur and nonsulfur constituents. The separation may be effected for example by treatment of unstabilized or stabilized oils with relatively strong sulfuric acid which does not appear to react to any great extent with the non-sulfur constituents but which does appear to have the property of dissolving or combining with the sought for sulfur inhibitor constituents and forming an acid sludge containing such sulfur constituents.

On treatment of raw condensate or any of the fractions mentioned, in stabilized or unstabilized condition, with acid, as in tank or vat 55, there is formed a sludge which contains substantially all of the desired sulfur constituents of the oil. A preferred procedure for carrying out the sulfur constituent separation treatment is as follows. The particular oil being handled is treated with sulfuric acid of concentration preferably from about to about 93.2% H2804 in two equal dumps, each dump of acid representing about 50% by volume of total acid used. The rst dump of acid is added with agitation to the initial sulfur` oil in tank or vat 55. If heat of reaction is severe, the reaction mass may be cooled, since the temperature should preferably not exceed about F. The acid is added to the oil gradually say over a period of about 15 minutes or more. The reaction mass is allowed to settle for say 30 minutes or more, after which time the acid sludge formed is withdrawn from tank 55 by gravity through line 5l and fed into hydrolyzer 58. The acid insoluble oil from the first dump remaining in tank 55 is treated with a second dump of acid (about 50% by volume of the total acid used) in the same manner as with the first dump, allowed to settle, and the acid sludge withdrawn through line 51 and added to the sludge already in hydrolyzer 58 from the first dump. If desired, all of the acid used to treat the oil may be added thereto in one dump, although it is preferred to employ two or more dumps since this procedure brings about more complete extraction of sulfur inhibitor constituents from the oil. The sludge in hydrolyzer 58 is treated with about twice the volume of water and is hydrolyzed, resulting in breaking up of the sludge and a separation of the sulfur oil constituents extracted out of the stabilized or unstabilized oil from the acid which was used to effect this extraction of sulfur constituents from the stabilized or unstabilized oil. During hydrolysis, the temperature is preferably not permitted to exceed about F. The oil formed on hydrolysis of the sludge is generally lighter than the acid which settles and forms a layer of acid in the bottom of the hydrolyzer. After settling, the acid is drawn OIT through line 59, and the oil discharged through pipe 60 is preferably given alight wash for example with caustic alkali, or several washes with water to neutralize traces of acid which may remain in the oil on account of imperfect separation of oil and acid in the hydrolyzer. The oil may be brightened by filtering. Oils recovered in this way are the oils referred to herein as the refined oils, or puried or concentrated or extracted oils.

The sulfuric acid used to effect extraction of the sulfur inhibitor constituents should be of strength desirably not less than about 70% H2SO4, although it is preferred to use stronger acids. Satisfactory extraction may be obtained by utilizing 93.2% acid (66 B.) although indications are that acid of around 85% strength is more selective than the 93.2% acid. The amount of acid used to bring about separation of inhibitor sulfur constituents from other sulfur and non-sulfur constituents depends upon the amount of soluble sulfur constituents contained in any given oil and the strength of the acid used. Acids of 'Z5-85% strength have less solvent power than stronger acids of the order of 93%. As to the total amount of acid used in the separation operation it is preferred to employ acid in amount corresponding to not less than about one volume of acid to one volume of refined sulfur oil, since experience indicates about such amount of acid is desired to dissolve or extract the sulfur constituents from the initial stabilized or unstabilized 252. UUMVUSI l IUNS,

oil. That is, for any given volume of the refined high sulfur oil recovered, preferably not less than about an equal volume of acid was used in one or more dumps to treat the stabilized or unstabilized oil to bring about separation of the sulfur constituents from the non-sulfur .constituents. In practice, the amount of acid needed may be determined by taking a sample of the oil and adding thereto successive small amounts of acid until on further addition of sulfuric acid to the sample, further solution or dissolving of the oil ceases.

On hydrolysis of the acid sludges produced by the sulfuric acid treatment of stabilized or unstabilized oils generally 8590% as much oil is recovered as was removed from the stabilized or unstabilized oils on treatment with sulfuric acid, and the refined oils recovered on hydrolysis are as a rule considerably higher in sulfur content than the unextracted stabilized or unstabilized oils. For example, on treating a heavy fraction, stabilized by treatment with caustic alkali and weak sulfuric acid and boiling approximately within the range S50-650 F. and containing about 11.6% sulfur, with about twice the volume of 93.2% sulfuric acid (66 B.), the sulfur content of the unreacted oil after separation of the acid sludge formed was about 1.9%, and the sulfur content oi the refined extracted oil obtained on hydrolysis of the acid sludge was about 19%. In another instance, on treating an unstabilized heavy fraction, boiling approximately Within the range S50-650 F. and containing about 2.8% sulfur, with about one volume of 93.2% sulfuric acid, the sulfur content of the unreacted oil after separation of the acid sludge formed was about 0.6%, and the sulfur content of the rened extracted oil obtained on hydrolysis was about 8.9%. On treating an unstabilized light oil fraction, boiling at temperatures less than about 350 F. and containing about 18% sulfur, with about one volume of 93.2% sulfuric acid, the sulfur content of the unreacted oil after separation of the acid sludge formed was about 5.3% and the sulfur content of the refined extracted oil obtained on hydrolysis of the acid sludge was about 23%.

Instead of decomposing the acid sludge by heating as described in connection with the drawing, the original acid sludge may be subjected to hydrolysis as by steaming with live steam, for say an hour, until separation of weak acid (sludge acid) and an upper acid tar layer takes place. The weak acid may be drawn oif and the resulting acid tar or sludge material treated as by heating as in a retort Il. The only distillate may be taken in two or more cuts if desired, although it is preferred to collect the oily distillate as in a tank 26. During steaming of the acid sludge a light colored distillate may be recovered in a suitable condenser. This distillate and the condensate collected in tank 26 may be separately treated as already described to produce high sulfur rened oils, or may be combined and then so treated.

In accordance with the invention, refined high sulfur oils obtained as described above may be used to marked advantage as inhibitors in picking baths and acid solutions, and in metal pickling processes.

The acid pickling baths with which the improved sulfur oil inhibitors of the invention are used may be acid baths having an H2504 concentration of say 6 to 10%, such as are customarily employed for pickling and cleaning iron or steel. Other acid baths, such as acid sulfate Lxamme baths may be used if desired. The amount of the sulfur bearing oil inhibitor added to the bath for carrying out the pickling or cleaning operation may be varied. As a rule only a small amount of the sulfur bearing oil inhibitor is required. For example, the bath may contain from about 1 to about 20 pounds of the inhibitor per ton of 66 B. sulfuric acid.

The pickling or cleaning operation may be carried out as in usual practice. The metal may be completely immersed in the acid or a solution of the pickling bath may be sprayed onto the surface of the metal and subsequently removed with a water spray. The concentration of the acid bath and the temperature of the solution may be varied as desired and the inhibitors may be added to the pickling baths in greater or less proportion than mentioned above. Sulfuric and hydrochloric acids are generally employed in pickling operations although any other non-oxidizing acid may be substituted in Whole or in part. Pickling solutions may contain acids such as phosphoric or hydrouoric acids. Acid concentrations usually employed in commercial practice, for example 6 to 12%, are generally preferred in carrying out the present invention. After the pickling operation if the inhibitor oils of the invention are used, the metal treated has a bright surface finish.

The inhibitor oils of the invention may be introduced into pickling baths or other acid solutions in several ways. The inhibitor oils may be introduced directly into a sulfuric acid bath of the strength used in a pickling operation.

To provide for more ready mixing of the inhibitor oils with the acid of the pickling bath, the oils may be dissolved by the user or prior to delivery to the user, and the resulting mixture either diluted with water to the desired pickling strength, say 6% H2504, or added to a previously prepared pickling bath. For example, the inhibitor oils may be dissolved by the user in relatively strong sulfuric acid say 66 B. (93.2%) in the proportion of l:1.5-1.6 by volume, and the product so obtained then added to the pickling bath. It will be recalled from foregoing discussion that the total volume of acid used in the acid treatment in tank 55 is preferably not less than the volume of refined product oil recovered in line 60. Hence it will be appreciated the sludge recovered in line 5l comprises a mixture or composition consisting of a given volume of product oil and preferably not less than an equal volume of dissolving acid. This mixture possesses marked inhibiting properties and in some respects is similar to that obtained where the refined product oil of line 60 was dissolved in at least about an equal amount of strong acid for the purpose of making a pickling bath base, and such mixture may be employed in some cases as a pickling bath base. Hence, in some instances, where a desired product of the process is a pickling bath base comprising for example a mixture of a given volume of high sulfur oil dissolved in at least about an equal volume of strong acidI such product may be obtained by tapping the same off line 51, in which case the sludge mixture is not subjected to hydrolysis. Manufacture of a product or pickling bath base of this nature is one feature of the invention.

If desired, the inhibitor oils may be incorporated with a solid or liquid carrier and the carrier introduced into the pickling bath. For example, the oil may be added to dehydrated ferrous sulfate to form a dry powder containing 20% of the inhibitor oils, the dry powder being added to a sulfuric acid pickling bath of the desired strength. The oil may also be dissolved in relatively strong sulfuric acid say 66 B. and the acid containing the dissolved oil may be mixed with ferrous sulfate to form a dry powder which is added to the pickling bath or other acid solution. An emulsion of the oil with triethanolamine and water may be made and the resulting mixture added to a sulfuric acid pickling bath of any desired strength.

The inhibiting properties of the improved sulfur oil inhibitors of the invention are demonstrated by the following. In one series of tests the pickling bath comprised a 5% H2804 solution containing 0.1% by volume of the inhibitor. Mild steel strips of M; inch thickness were used, and the temperature of the pickling solution maintained at 160 F. The strips were subjected to a half hour preliminary pickling treatment and, after drying and weighing, were subjected to a further pickling treatment in the same solution for an hour and a half, dried and again weighed. Results obtained were as follows:

Inhibitor A was refined heavy fraction high sulfur oil obtained by distilling raw condensate of collector 26, recovering the heavy fraction, and treating the fraction with 66 B. HzSOr by the method described to recover dened oil. When no inhibitor was used, a steel strip was treated under the same conditions except that the pickling solution contained no inhibitor.

In another series of tests, the pickling solution contained 1.50 pounds of inhibitor per ton of 66 B. H2804 in the solution. Treatment was continued for two and one-half hours, and the metal strips dried and weighed at the end of each half hour. Loss of weight indicated below is the average loss of weight for the ve immersions to which each strip was subjected.

Inhibitor B was a refined heavy fraction high sulfur oil obtained by distilling raw condensate of collector 26, recovering the heavy fraction, and treating the fraction with 66 B. H2SO4 by the method described to recover the oil. Inhibitor D was a light fraction of the raw condensate refined with 66 B. HzSOi as described, and inhibitor C was a combined light and heavy fraction refined with 66 B. H2504. When no inhibitor was used, a steel strip was treated under the same conditions except that the pickling solution contained no inhibitor.

'I'he sulfur bearing oil inhibitors described are suited for use as corrosion inhibitors in arts other than pickling of metals. One phase of the invention involves provision of acid solutions inhibited sufficiently to prevent corrosion of metal surfaces by the acid. For example, in the transportation or storage of corrosive mineral acids in metal containers or pipe lines, a relatively small amount of inhibitor may be added to the acid to prevent corrosion of confining metal surfaces. The

amount of inhibitor used will depend upon the nature and concentration of the acid solution.

We claim:

1. The process of pickling metals which com prises subjecting the metal to the action of a bath containing a solution of a mineral acid and a relatively small amount of a corrosion inhibitor comprising a relatively light-bodied, lightcol ored, low viscosity sulfur oil boiling at temperatures less than about 650 F., stable with respect to sulfur deposition, substantially free of free sulfur, containing alkyl suldes, having a sulfur content not less than about 3% and formed by dissociating sludge material, resulting from sulfuric acid treatment of hydrocarbon distillate oils obtained from sulfur containing erudes, with aid of heat at temperatures not more than about 750 F. to break up the sludge under conditions to form a hot gas mixture containing water and hydrocarbon vapors, cooling the mixture to form a condensate comprising water and oil, separating water from oil, treating the oil with sulfuric acid of concentration not less than about 70% H2804 and in quantity suicient to effect extraction of sulfur bearing oil constituents from said oil, separating the resulting sludge reaction product from said oil, subjecting said resulting sludge to hydrolysis to separate sulfur oil and acid, and recovering sulfur oil from the reactio product resulting from said hydrolysis.

2. The process of pickling metals which comprises subjecting the metal to the action of a bath containing a solution of a mineral acid and a relatively small amount of a corrosion inhibitor comprising a relatively light-bodied, lightcolored, low viscosity sulfur oil boiling at temperatures less than about 650 F., stable with respect to sulfur deposition, substantially free of free sulfur, containing alkyl suldes, having a sulfur content not less than about 3% and formed by dissociating sludge material, resulting from sulfuric acid treatment of hydrocarbon distillate oils obtained from sulfur containing crudes, with aid of heat at temperatures not more than about '750 F. to break up the sludge under conditions to form a hot gas mixture containing water and hydrocarbon vapors, cooling the mixture to form a. condensate comprising water and oil, separating Water from oil, distilling the oil, recovering as condensate oil boiling at temperatures less than about 650 F., treating the oil with sulfuric acid of concentration not less than about 70% H2804 and in quantity sufficient to effect extraction of sulfur bearing oil constituents from said oil, separating the resulting sludge reaction product from said oil, subjecting said resulting sludge to hydrolysis to separate sulfur oil and acid, and recovering sulfur oil from the reaction product resulting from said hydrolysis.

3. The process of pickling metals which comprises subjecting the metal to the action of a bath containing a solution of a mineral acid and a relatively small amount of a corrosion inhibitor comprising a relatively light-bodied, light-colored, low viscosity sulfur oil boiling at temperatures less than about 650 F., stable with respect to sulfur deposition, substantially free of free sulfur, containing alkyl suldes, having a sulfur content not less than about 3% and formed by dissociating sludge material, resulting from sulfuric acid treatment of hydrocarbon distillate oils obtained from sulfur containing crudes, with aid of heat at temperatures not more than about 750 F. to break up the sludge under conditions to form a hot gas mixture containing water and UL- bUlVlT'UDI I IUNO,

hydrocarbon vapors, cooling the mixture to form a condensate comprising water and oil, separating water from oil, distilling the oil, recovering as condensate oil boiling at temperatures less than about 650 F., stabilizing the oil, treating the oil with sulfuric acid of concentration not less than about H2S04 and in quantity sufiicient to effect extraction of sulfur bearing oil constituents from said oil, separating the resulting sludge reaction product from said oil, subjecting said resulting sludge to hydrolysis to separate sulfur oil and acid, and recovering sulfur oil from the reaction product resulting from said hydrolysis.

4. The process of pickling metals which comprises subjecting the metal to the action of a bath containing a solution of a mineral acid and a relatively small amount of a corrosion inhibitor comprising a relatively light-bodied, lightcolored, low viscosity sulfur oil boiling at temperatures less than about 650 F., stable with respect to sulfur deposition, substantially free of free sulfur, containing alkyl suldes, having a sulfur content not less than about 3% and formed by dissociating sludge material, resulting from sulfuric acid treatment of hydrocarbon distillate oils containing not less than about 0.15% sulfur, with aid of heat at temperatures not more than about '750 F. to break up the sludge under conditions to form a hot gas mixture containing water and hydrocarbon vapors, cooling the mixture to form a condensate comprising water and oil, separating water from oil, treating the oil with sulfuric acid of concentration not less than about 70% H2504 and in quantity suiiicient to effect extraction of sulfur bearing oil constituents from said oil, separating the resulting sludge reaction product from said oil, subjecting said resulting sludge to hydrolysis to separate sulfur oil and acid, and recovering sulfur oil from the reaction product resulting from said hydrolysis.

5. The process of pickling metals which comprises subjecting the metal to the action of a bath containing a solution of a mineral acid and a relatively small amount of a corrosion inhibitor comprising a relatively light-bodied, lightcolored, low viscosity sulfur oil boiling at temperatures not more than about 350 F., stable with respect to sulfur deposition, substantially free of free sulfur, containing alkyl suldes, having a sulfur content not less than about 3% and formed by dissociating sludge material, resulting from sulfuric acid treatment of hydrocarbon distillate oils obtained from sulfur containing crudes, with aid of heat at temperatures not more than about '750 F. to break up the sludge under conditions to form a hot gas mixture containing water and hydrocarbon vapors, cooling the mixture to form a condensate comprising water and oil. separating water from oil, distilling y the oil, and recovering as condensate a fraction boiling at temperatures not more than about 350 F., treating the fraction with sulfuric acid of concentration not less than about 70% H2504 and in quantity sufficient to eiect extraction of sulfur bearing oil constituents from said fraction, separating the resulting sludge reaction product from said fraction, subjecting said resulting sludge to hydrolysis to separate sulfur oil and acid, and recovering sulfur oil from the reaction product resulting from said hydrolysis.

6. The process of pickling metals which comprises subjecting the metal to the action of a bath containing a solution of a mineral acid and a relatively small amount of a corrosion inhibitor comprising a relatively light-bodied, light-colored. low viscosity sulfur oil boiling substantially within the range 350 F. to 650 F., stable with respect to sulfur deposition, substantially free of free sulfur, containing alkyl suldes, having a sulfur content not less than about 3% and formed by dissociating sludge material, resulting from sulfuric acid treatment of hydrocarbon distillate oils obtained from sulfur containing crudes, with aid of heat at temperatures not more than about 750 F. to break up the sludge under conditions to form a hot gas mixture containing water and hydrocarbon vapors, cooling the mixture to form a condensate comprising water and oil, separating water from oil, distilling the oil, recovering as condensate a fraction boiling substantially within the range 350 F. to 650 F., treating the fraction with sulfuric acid of concentration not less than about 7% H2804 and in quantity sumcient to eiect extraction of sulfur bearing oil constituents from said fraction, separating the resulting sludge reaction product from said fraction, subjecting said resulting sludge to hydrolysis to separate sulfur oil and acid, and recovering sulfur oil from the reaction product resulting from said hydrolysis.

7. A pickling bath for metals comprising a solution of mineral acid and a relatively small amount of a corrosion inhibitor comprising a relatively light-bodied, light-colored, low viscosity sulfur oil boiling at temperatures less than about 650 F., stable with respect to sulfur deposition, substantially free of free sulfur, containing alkyl suldes, having a sulfur content not less than about 3% and formed by dissociating sludge material, resulting from sulfuric acid treatment of hydrocarbon distillate oils obtained from sulfur containing crudes, with aid of heat at temperatures not more than about 750 F. to break up the sludge under conditions to form a hot gas mixture containing water and hydrocarbon vapors, cooling the mixture to form a condensate comprising water and oil, separating water from oil, treating the oil with sulfuric acid of concentration not less than about 70% H2804 and in quantity sunicient to effect extraction of sulfur bearing oil constituents from said oil, separating the resulting sludge reaction product from said oil, subjecting said resulting sludge to hydrolysis to separate sulfur oil and acid. and recovering sulfur oil from the reaction product resulting from said hydrolysis.

8. A pickling bath for metals comprising a solution of mineral acid and a relatively small amount of a corrosion inhibitor comprising a relatively light-bodied, light-colored, low viscosity sulfur oil oiling at temperatures less than about 650 F., stable with respect to sulfur deposition, substantially free of free sulfur, containing alkyl suldes, having a sulfur content not less than about 3% and formed by dissociating sludge material, resulting from sulfuric acid treatment of. hydrocarbon distillate oils obtained from sulfur containing crudes, with aid of heat at temperatures not more than about 750 F. to break up the sludge under conditions to form a hot gas mixture containing water and hydrocarbon vapors, cooling the mixture to form a condensate comprising water and oil, separating water from oil, distilling the oil, and recovering as condensate oil boiling at temperatures less than about 650 F., treating the oil with sulfuric acid of concentration not less than about 70% HzSO4 and in quantity sumcient to effect extracresulting from said hydrolysis.

9. A pickling bath for metals comprising a solution of mineral acid and a relatively small amount of a corrosion inhibitor comprising a relatively light-bodied, light-colored, low viscosity sulfur oil boiling at temperatures not more than about 350 F., stable with respect to sulfur deposition, substantially free of free sulfur, containing alkyl suliides, having a sulfur content not less than about 3% and formed by dissociating sludge material, resulting from sulfuric acid treatment of hydrocarbon distillate oils obtained from sulfur containing crudes, with aid of heat at temperatures not more than about '750 F. to break up the sludge under conditions to form a hot gas mixture containing water and hydrocarbon vapors. cooling the mixture to form a oondensate comprising water and oil, separating water from oil, distilling the oil, and recovering as condensate a fraction boiling at temperatures not more than about 350 F., treating the fraction with sulfuric acid of concentration not less than about H2504 and in quantity sufficient to e'ect extraction of sulfur bearing oil constituents from said fraction, separating the resulting sludge reaction product from said fraction, subjecting said resulting sludge to hydrolysis to separate sulfur oil and acid, and recovering sulfur oil from the reaction product resulting from said hydrolysis.

10. A pickling bath for metals comprising a solution of mineral acid and a relatively small amount of a corrosion inhibitor comprising a relatively light-bodied, light-colored, low viscosity sulfur oil boiling substantially within the range 350 F. to 650 F., stable with respect to sulfur deposition, substantially free of free sulfur, containing alkyl suldes, having a sulfur content not less than about 3% and formed by dissociating sludge material, resulting from sulfuric acid treatment of hydrocarbon distillate oils obtained from sulfur containing crudes, with aid of heat at temperatures not more than about '750 F. to break up the sludge under conditions to form a 5 hot gas mixture containing water and hydro- Patent No. 2,1ii6,l5ii.

CERTIFICATE OF CORRECTION.

carbon vapors, cooling the mixture to form a condensate containing water and oil, separating water from oil, distilling the oil, recovering as condensate a fraction boiling substantially within the range 350 F. to 650 F., treating the fraction with sulfuric acid of concentration not less than about 70% H2504 and in quantity sufficient to eiect extraction of sulfur bearing oil constituents from said fraction, separating the resulting sludge reaction product from said fraction, subjecting said resulting sludge to hydrolysis to separate sulfur oil and acid, and recovering sulfur oil from the reaction product resulting from said hydrolysis.

ll. A mineral acid solution substantially noncorrosive to metals comprising mineral acid of concentration corrosive to metal and containing a sulfur bearing oil corrosion inhibitor, said solution being adapted for utilization in operations comprising metal pickling, storage of said solution within coniining metal surfaces, and passage of said solution through confining metal surfaces, and said solution containing said oil in quantity suiiicient to substantially inhibit corrosive action of the acid on metal; said inhibitor comprising a relatively small amount of a relatively lightbodied, light-colored, low viscosity sulfur oil boiling at temperatures less than about 650 F., stable with respect to sulfur deposition, substantially free of free sulfur, containing alkyl sulfides, having a sulfur content not less than about 3% and formed by dissociating sludge material, resulting from sulfuric acid treatment of hydrocarbon distillate oils obtained from sulfur containing crudes, with aid of heat at temperatures not more than about 750 F. to break up the sludge under conditions to form a hot gas mixture containing Water and hydrocarbon vapors, cooling the mixture to form a condensate comprising water and oil, separating water from oil, treating the oil with sulfuric acid of concentration not less than about 70% H2SO4 and in quantity suicient to effect extraction of sulfur bearing oil constituents from said oil, separating the resulting sludge reaction product from said oil, subjecting said resulting sludge to hydrolysis to separate sulfur oil and acid, and recovering sulfur oil from the reaction product resulting from said hydrolysis.

HENRY F. MERRIAM. THEODORE V. FOWLER. JR.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 5, first column, line 55, for only read oily; page 6, firstI column, line 3?, Afor the word defined read refined; page 'Z second co1u1'nn,' line 19, claim 6, for "7S" read T01; and that the said Letters Patent should be readwith this correction therein that the same my conform to `the record of the case in the Patent Office.

Signed and sealed this 28th day of'liarch, A. D. 1959.

Henry Van Arsdale Patents Acting Comissioner of v M f Nw February 7, 1959, ///f' ff) BEST AVAILABLE COP\ CERTIFICATE OF CORRECTION.. Patent No. 2,ll|.6,l5h.. February 7, 1959.

HENRY F. MERRIAM, ET ALa It is herebr certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 5, first column, line 55, for "only" read oily; page 6, first column, line 57, for the word "defined" read refined; page Y, second column,' line 19, claimy 6, for "7%" read 70%; and' that the said Letters .Patent should be readwith this correction therein that the same may conform to the record of the oase in the Patent Office.

Signed and sealed this 28th day of-March, A. D., 1959.

Henry Van Arsdale (Seal) Acting Commissioner of Patents.,

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