US2411105A - Process for treating hydrocarbons - Google Patents

Description

Patented Nov. 12, 1946 UNITED STATES PATENT? cam- PROCESS FOR TREATING HYDROCARBONS Alan C. Nixon, Oakland, and David Louis Yabro'fl", Berkeley, Calif., assignors to 'Shell' Development Company, San' Francisco; Calif; a corporation of Delaware No Drawing; Application October-16,1943, Serial No. 506,612.

Claims. -(Cl. 196"-30)?= 1 This invention deals with a method for improvingvthe rate of separation of alkaline treating liquids or solutions from hydrocarbons or of facilitatingsteam strippingof the resulting fat alka-- line solution, if the latter is desired,- or both. This inventiontis a continuation-in-part of our. co-

pendingapplication SerialNo. 394,004 filed May It .is.we1l known that hydrocarbon oils are I mixtures of hydrocarbons and may contain compounds of ma-nyxdifierent degrees of saturation,

suchas paraffin's, olefins, polyolefins, acetylenes, i naphthenes; or aromatics It is also knownthat hydrocarbon :oils frequently. contain-weak acids e. g. havingrdissociation constants below about 10- such as hydrogen sulfida'mercaptans, alkyl phenols; etc. :It is often desirable to treat such hydrocarbon mixtures :to separatethe'm .intohydrocarbons' of different d'egreesof saturation'for to purify particular hydrocarbons,:such:.as hen-12: zene-,:-.toluene, xylene, butylenes, buta'dienasiso prene, ethylene; acetylene, etc.-; or to remove-weak acids of theztype-mentioned above from such:

hydrocarbons or mixtures.

Onemethod of carrying outsuch-a separatiorn or purification is by extracting one-or more-oi the components with an alkaline solution; whichhas a preferential solvent powerior one or moreof the components of the mixture, and there after saparating the resulting alkaline solution-' from the dissolved portion of the mixture.

The

extraction'maybe either-by liquid-liquid or by" vapor liqui'd contact, including extractive-distillation. "(In order'to achieve separation by eXtrac-" tive distillation the two or more compounds to be saparated from' one another should as a rule boil not'more than about20' C. apart'and preferably notmore thanabout=10 C, apart.) tractions are normally carried out in apparatus permitting contact of the alkaline treating solu--' tion and the mixture containing the hydrocarbons, usually. by counter-current flow, .either through a packed or a plate column, or through a series-of mixers and settlers, whereby two end phases are produced and separated, one of which is an extract comprising the fat alkaline treating solution containing theextracted portion of the mixture, and theother of which is the 'raffinate portion of themixturie. These two phases may be both liquid or one. may be liquid and the other may be aJVapor, For reasons of economy, the fat'alkalinesolutioh .is' usually regenerated such as by steam, stripping, air blowing or washing with a suitable wash liquid, etc, and theregen'erated These ex- J solution is then re-used for treatment of further quantitiesof the original mixture;

The mixtures. to which-this invention is applicableare either normally liquid or normally gaseous andip'referably have "an end boiling point of below about 200 C. They are comprised of hydrocarbons and must be substantially free'from sulfate ester acids, sulfonic' 3431618 01 other rela'-- tively strong acids because of the effect of these acids upon the alkaline treating solutionlby permanently poisoning or neutralizing it.

Alkaline treating liquids or solution which may be employed must be stable and'inert so as not to react irreversibly with the components of theimixtureunder'the conditions of the process? they mustihave a greatersolvent power for some" componentsthan for others; and they must be separablefrom the dissolved components by physical means such;as,.;by fractional distillation and/or washing out; either while they are in the form originallyabsorbed or else after they have been changed chemicall by a simple operation" such as air oxidation. If employed in liquid extraction,:they must be only partially miscible with inixtur'es'to be extracted. They maybe aqueous or non-aqueous;

amine, butyl amine, ethylene diamina-nionon di-,

or tri-ethanolamine, or quaternary ammonium. bases as tetra methyl, trimethyl benzyl, etci; am"- monium 'bases,.etc. In the extraction of weak acids normall associated with petroleum oils, alkaline treating solutions; such as tripotassium phosphate, sodium phenolate, sodium borate,'so- L dium. or potassium carbonate, organic bases, such as ethanolamine, diamino propanol, piperidine', etc:, or strong solutions of alkaline metal'hydroxides, preferably'having concentrations of 25 to 50%, or alkaline solutions containing solutizers may be employed.

Solutizers are known as organic substances which when in the liquid state are solvents forweak organic acids, are substantially insoluble in Water-immiscible: liquids, are soluble in aqueous strong bases, are chemically inert to the action of said bases even at elevated temperatures," and have boiling temperatures preferably substaniially higher than water. Solutizers are used to enhance the extractive powers of aqueous alkaline solutions for weak organic acids such as mercap- ;ans and phenols. The solutizer process and the various solutizers have been described in a series 3f patents and patent applications as well as in ;he general literature, for example, in the Yabroff at al. U. S. Patents 2,149,379, 2,149,380, 2,152,166, 2,152,720, 2,152,723, 2,164,851, 2,186,398, 2,202,039; applications Serials Numbers 255,684, filed Feb- ."uar 10, 1939; 271,962, filed May 5, 1939; Refiner and Natural Gasoline Manufacturer, May 1939, pages 171-176, and March 1940, pages 73-76, In- :lustrial Engineering and Chemistry, volume 32, pages 257-262, February 1940, etc.

In choosing one of the above alkaline treating liquids, sight must not be lost of the boiling temperature requirements relative to the boiling temperature of the mixtures. For example, in vaporliquid extraction, it is important that the solvent chosen have a boiling temperature higher than that of the mixture to be treated, and in the specific case of extractive distillation, it 'is desirable that the boiling temperature of the solvent be not less than about 50 C. higher than the boiling temperature of the mixture. Accordingly, the particular treating agent to be employed necessarily depends upon both the boiling temperature of the mixture to be treated,- and the: type of process to be used in the treatment.

Unfortunately, processes of this type often produce foam and/ or emulsions which greatly reduce the maximum throughput of a given treating unit. Emulsions, if formed, occur in liquid-liquid treating, and foaming may occur in vapor-liquid treating. Foaming may also occur if distillation, steam stripping, air blowing etc. is employed as a means for recovering the alkaline treating solution from the extract or rafl'inate.

The nature of the substances responsible for difficulties is not definitely established. It is believed though, that foam and emulsions are produced by small amounts of impurities, such as compounds related to gasoline gums or similar resinous materials formed by reaction of some of the components of the hydrocarbon mixtures with themselves or with the alkaline treating solution or a component thereof, particularly in the presence of oxygen. In many cases it is impossible to keep air away from such mixtures, since small quantities easily leak through joints of pumps and valves, etc.. Thus, most hydrocarbon ails contain small but definite amounts of dissolved oxygen. solutions with alkaline solutions containing ohenolates, a phenol type resinmay be formed, for instance, by the interaction of mercaptans, aldehydes or other impurities in the mixture ;reated.

Accordingly, it is the purpose of this invention ;0 provide means for improving, the rate of sepacation of aqueous alkaline treating liquids from ;he hydrocarbons which are being treated. Anither purpose is simultaneously or independently ;0 reduce the foaming tendency of the treating iquid, for example, when it is being regenerated )y steam stripping. Still another purpose is to provide means for preventing the formation of zmulsions caused by the presence of emulsifiers n the treating liquids, particularly those convaming impuritieswhich readily react to form emulsifiers. It is yet another purpose to provide t remedy for breaking emulsions formed in such reating processes.

.In the case of treating solutizer It has been discovered that the addition of relatively small amounts of a stable organic surfaceactive agent which contains at least 8 carbon atoms per molecule and has a molecular weight of below about 1000 (preferably below about 600) and which is dispersable in the alkaline treating liquid, results not only in reducing'foaming and in an improved rate of separation, but also in effective and rapid breaking of emulsions which may form between the two phases produced in the process. It is important that the agent be readily and completely dispersed through the treating solution so as to be continuously and evenly effective throughout the entire zone of contact and the surface-active agents used in the process are: those which form true solutions in the treating: solution or spontaneously form colloidal dispersions therein, i. e. form dispersions of at least colloidal dimensions.

The agents should be reasonably stable toward the action of oxygen in the presence of caustic. alkali and at elevated temperatures of steaming: if steam regeneration is employed as part of the process.

In a regenerative process wherein the spent treated solution is continuously regenerated and recirculated for further contact with the mixture to be treated, it is desirable that the surface-active agents, in order to be more or less permanently useful, should not be extracted from the treating solution when the latter is contacted with the hydrocarbon mixture. The presence of the agent in either of the separated components of the mixture may be undesirable, as it may interfere with their intended uses. Therefore, the surface-active agents should be substantially insoluble in hydrocarbon oils.

'In some cases, it may be desirable to remove these agents from the treating solution in which case they should have a property which makes possible such separation.

The organic surf ace-active agents of this invention are organic compounds containing at least one atom of sulfur and/or oxygen. Morespecifically they are members of the following groups: sulfonic or sulfuric acids having at least one alkyl radical of more than 4 carbon atoms, naphthenic acids having molecular weights between about 250/ and 500, fatty acids having between 8 and 14 carbon atoms per molecule, and the corresponding alkali and alkali-earth metal salts of each of the above free acids. Such surface-active compounds may be generally represented by the formula RY, wherein R is an organic radical and Y is a polar radical containing an atom selected from the group consisting of oxygen and sulfur.

Some of these agents are known to be more effective for breaking or settling emulsions, others are more effective for breaking or reducing foams, while still others are effective for both.

. Agents which are generally effective to prevent or break both foams and emulsions are the alkali and alkali-earth metal salts or free acids of sulfonic and sulfuric ester acids (containing an alkyl radical of more than 4 carbon atoms) ,.of naphthenic acids (having a molecular weight between 250 and 500), and of fatty acids (having between 8 and 14 carbon atoms per molecule).

The sulfonates and sulfates may, if desired, contain non-functional radicals such as halogen, ether, amino, imino, hydrosulfide, sulfide, ester, carboxyl amide, etc, radicals. Free carboxyl radicals should preferably be absent in the sulfates and sulfonates since some sulfated or sulfonated fatty acid soaps cause violent foaming.

Specific sulfonates which we have found to be suitable for our purpose are, for example, watersoluble alkali metal salts of petroleum sulfonic acids such as the salts of green acids produced in the manufacture of medicinal oils by acid treatment; or of th products of treating kerosene or lube oil extracts with strong sulfuric acid, etc.; or of various aliphatic or alicyclic sulfonic acids such as fatty sulfonic acids, fatty aromatic sulfonic acids, naphthene sulfonic acids; or of sulfonic acids of various alkylated (containing an alkyl radical of more than 4 carbon atoms) tenzenes, diphenyls, xylenes, diphenyl methanes, naphthalenes, anthracenes, phenanthrenes, tetralines; phenols (derived from petroleum or coal tar distillates) chlornaphthalenes, diphenyl oxides, chlorinated diphenyl oxides, diphenyl sulfides, diphenyl amines, phenyl naphthylamines, dinaphthyl oxides, sulfides or amines, pyridines, quinolines, isoquinolines, pyrroles, pyrrolidines, piperidine, thiophenes, thiophanes, etc.; or of various sulfonic acids of carboxylic acid esters or amides, such as for example, of the ester sulfocarboxylic acids or sulfonate amides having the general formulae:

(0:41-01? )n O=(|JR respectively, wherein the R radicals are organic radicals of more than 4 carbon atoms such as allphatic or cyclic hydrocarbon radicals, M is an alkali metal and n is an integer normally not greater than 2. g V

While the carboxylic acid esters and amides listed above are very effective for ou purpose, many of them have the disadvantage of being susceptible to hydrolysis during steam regeneration of the treating liquid forming free carboxylic acids upon decomposition, the salts of which may cause foaming unless they have 8 to 14 ca bon atoms.

It is of interest to note that the alkali metal salts of sulfonic acids possessing at least one alkyl radical of more than 4 carbon atoms, are in general far more effective than the salts of corresponding sulfonic acids not possessing them. For example, the alkali metal salts of naphthalene or anthracene sulfonic acids such as monoor dibutyl phenyl phenol sodium monoor disulfonates, sodium tetrahydro naphthalene sulfonate, i-sopropyl naphthalene sulfonate, etc., are only mildly beneficial if at all in carrying out the purpose of this invention, whereas the corresponding salts of higher alkylated naphthalene sulfonic acids are highly effective.

The sulfonates may be prepared in various ways. Aliphatic sulfonates may be obtained under some conditions by treating olefins 'or diolefins with strong sulfuric acid; or by treating organic acid sulfates with sodium sulfite so as to eliminate sodium sulfate; or by oxidation of mercaptans with nitric acid, etc.

Sulfate ester acids, the alkali salts of which are suitable for our purpose are, for example, the fatty sulfates, such as mono lauryl, cetyl, stearyl, etc., sulfate acids; or mono esters of sulfuric acid obtained by treating with strong to moderately strong sulfuric acid Various olefins or alcohols such as the long chain olefins obtained in the vapor phase cracking of wax at about 350-560 C., polymers obtained in the polymerization of normally gaseous olefins with inorganic polyoxy acids or Friedel-Crafts catalysts, fatty or naphthenic alcohols obtained in the catalytic reduction of fatty or naphthenic acids, alcohols ob,- tained by condensation of ketones or aldehydes followed by a hydrogenation; or alkyl aromatic mono esters of sulfuric acid, etc. A convenient source for many of the active sulfate ester acids are the sludges obtained in the acid treatment of cracked distillates, or the spent acids obtained in the polymerization of olefins or in the alkylation of isoparafiins with olefins with sulfuric acid.

The alkali or alkali-earth salts of naphthenic acids having a 'molecularweight between 250 and 0 may be derived from petroleum and may comprise a mixture of salts having molecule weights within this range.

The salts of the fatty acids containing between 8 and 14 carbon atoms per molecule such as sodium or potassium caprylate, pelargonate, caprate, undecylate, sabinate, laurate, tridecylate, myristate, etc., are effective both as demulsifiers and defoamers. However, the salts of lower fatty acids, those having less than 8 carbon atoms and those having more than 14 carbon atoms such as stearic acid, are substantially ineffective.

Amounts of the surface-active agents which need to be added to improve the rate of settling or breaking of the emulsion or foam or both, are insufficient to materially affect the action of the treating agent. This amount may vary between about .001% and 1%, and preferably between about .001% and .1% by volume of the treating agent. The different types of treating agents are capable of dissolving different amounts of the surface-active agents and different mixtures may require different amounts to reduce foaming and/or emulsification. This is probably due to the difference in reactivity of the ions of the respective agents and their effect on the hydrocarbon'mixtures treated. Therefore, actual laboratory tests within the above limitations may be required to accurately determine the amount of the agent or combination of agents for the most effective separation of the given mixture with a given alkaline treating solution.

It is desirable that the beneficial effect of the salt shallnot be restricted to and be dependent on a specific range of concentration substantially narrower than the limits indicated aboVe that is to say, there should not be a sudden reversal of the beneficial effect, 1. e., an increase in the emulsification or foaming tendencies or both, of the extracting solution upon addition of a slight excess of the salt over the optimum quantity. On the contrary, the beneficial effects should extend over substantially the entire range of concentration indicated, and changes in the effects due to-deviations from the optimum con- Example I In the table below, effects of a number of representative surface-active agents-are shown in a spent or contaminated aqueous copper ammonium acetate solution which when fresh had thefollowingcomposition: .25 mol/liter of cupric ions, 2.93 mols/liter of cuprous ions, 10.4 mols/liter of ammonia, and 4.0 mols/liter of acetic acid, Samples of this spent solution were subjected to an emulsion test in which they were agitated with an equal amount by volume of tertiary plete separation was noted, and whether'or not at the end of the settling time a rag was left at the interface.

'Other samples of the same solution were subjected to a distillation test in which their relao amylenes at a temperature of about 25 F. The tive foaming tendencies were observed. Results resulting emulsion was then allowed to settle and were as follows:

Ooncentra- Settling Addition compound on, cross-time in Rag Foaming mg./l cc. minutes None 30 Moderate. Sodi sulfate of higher secondary alcohol 50 6 d 100 Mildly positive. 500 6 Negative Sodium lauryl sulfate 67 6 134 6 D0. 375 5 No improvement. Sodium sulfonate ethyl methyl oleoamide 67 Improved. Sodium sulfonate ethyl oleoamidc 67 Do. Sodium petroleum sulfonate 67 Very much improved. Sodium hydrocarbon sulfonate 67 Slightly improved. Sodium alkyl aryl sulfonate 67 Much improved. Dioctyl ester of sodium sulfo sucemate 67 Mildly improved. Sodium sulfonate of complex stearyl alkyl compounds. 67 Do. Sodium salt of green acids 100 the time required for substantially complete sep- We claim as our invention: aration was noted and whether or not at the end 1. In a, process for treating a mixture comof the settling a residual rag (large globules of prising predominately hydrocarbons with an hydrocarbon surrounded by thin films of solution) aqueous alkaline treating liquid to effect the sep- Was left at the interface between the solvent aration of components of said mixture which are phase and the hydrocarbon phase. The results soluble in the .treatirv liquid from components were as follows: which are not soluble therein, in which process Gone. in Settling Vol. of Organic surface-active agent gin/100 cc. time in residual Remarks solvent minutes rag Fresh solution 0 1% 0 No foam. Spent solution 0 9 Stable foam. I. Salts of organic acids: A. Sulfonic acids Produced from transformer oil extract l 1% 2 No foam.

0 .01 9 2 Do. Commercial petroleum sulfonates 1 2% 0 Do. 0 O1 3 5 Do. Green acids 1 A 0 No foam, refused to emulsify. Sodium amyl alkyl poly-ether sulfonate l 1% 0 No foam. Dioetyl ester of sodium sulfo succinic acid 1 3 /1 0 Hydrolyzes rapidly.

D0 .01 5 0 No foam. B. Sulfuric ester 'acids Glyceryl rieinoleyl sulfate (Turkey red oil) 1 3 0 Do. Do .01 2 0 Do. Do 001 8 5 Do. Alkyl sulfate-i-NazSOi l 1% Trace Do. Do .01 4 8 Do.

(C4H9)CH O2H5 C2H4?HC2H4CH(C2H4)2 01 10 Trace DO.

(|) SOaNa Sodium alkyl sulfate 1 4 3% Do. 0. Naphthenic acids- Cyclic carboxylic acids 1 3 0 Do. Do 01 5% 2 Do. Naphthenic acids (equiv. wt. 332) 1 4 0 Do. Do .01 7 0 Do. D. Fatty acids- Larvic acid 1 9 0 No foam.

Do .01 l 5 Do.

Example 11 The following table discloses the effects of a number of representative surface-active salts covered by this invention when employed in a solutizer solution having the following composition:

KOI-I 6 normal Potassium isobutyrate 1.5 normal Potassium phenolate 1.0 normal two phases are produced, a first phase comprising predominately hydrocarbons and a second phase. comprising predominately aqueous alkaline treating liquid and at least a substantial portion of components of said mixture which are soluble therein, in which process a relatively stable dispersion of one phase in the other is produced, the improvement comprising the method of reducing the stability of such a dispersion which comprises efieoting said treatment in the presence of from about 0.001% to about 1% by volume of said treating liquid of an organic surface-active agent which forms a dispersion itself of particles at least as small as of colloidal dimensions in said aqueous treating liquid, which is substantially insoluble in said mixture and which is a salt of a naphthenic acid having a molecular weight between about 250 and 500.

2. The process of claim 1, wherein said mixture is a gasoline distillate.

3. The process of claim 1, wherein said mixture contains a substantial proportion of 04 diolefines.

4. The process of claim 1, wherein said treating process is a liquid-liquid phase separation process.

5. The process of claim 1, wherein the treating process is a vapor-liquid phase separation process.

6. The proces of claim 1, wherein said mixture contains diolefins and said alkaline treating solution is an aqueous copper ammonium acetate solution.

7. The process of claim 1, wherein the amount of the said surface-active agent is between about .001% and .1% by volume of said mixture.

8. The process of claim 1, wherein said surface-active agent is an alkali metal naphthemate.

9. The process of claim 1, wherein said dispersion is a foam.

10. In a process for contacting a hydrocarbon fraction containing substantial proportions oi hydrocarbons with difierent degrees of saturation and unsaturation with an aqueous copper ammonium acetate solution, whereby two phases are produced, a first phase comprising predominately hydrocarbons of a higher degree of saturation and a second phase comprising predominately said aqueous solution and dissolved therein a substantial proportion of the hydrocarbons of said fraction which have a higher degree of unsaturation, in which process a relatively stable dispersion of one phase in the other is produced by the action of impurities formed as a result of reactions of unsaturates in said mixture with each other and with oxygen, the method of preventing such a dispersion which comprises effecting said treating in the presence of from about 0.001% to about 1% by volume of said aqueous solution of an alkali metal salt of a petroleum naphthenic acid dispersable in said aqueous copper ammonium acetate solution, said naphthenate having a molecular Weight between about 250 and 500.

ALAN C. NIXON. DAVID LOUIS YABRO'FF.