[1]2 @ 7 0 0 , 6 1 2 ,United States Patent Office Patented Jan. 25, 1955 2,700,612 STABELIZATION OF ORGANIC MATERIALS 5 Joseph A. Chenicek, BensenviDe, ]M., assignor to Uni. versal OR Products Company, Chicago, Iff., a corporation of Delaware No Drawing. AppHeation January 31, 1951, , 10 Serial No. 208,852 18 CL-dim. (Cl. 99-8) This invention relates to a novel method of stabilizing 15 organic materials which tend to deteriorate in storage or in use due to undesirable oxidation reactions. Various organic compounds including mineral oils, motor fuels, lubricating oils, drying oils, rubber, etc. are adversely affected by oxygen with the resultant forrna- 20 tion of undesirable gums and usually with discoloration of the organic compounds, as well as other deleterious reactions. This is particularly true of motor fuels comprising olefinic gasolines, such as crac d gasoline an polymer gasoline. 2 5 . An object of the present invention is to prevent or at least substantially retard the undesirable deterioration of organic compounds, which may or may not be catalyzed by the presence of minute quantities of metals. Another object of the present invention is to provide 30 a novel method of adding an inhibitor-metal deactivator to organic compounds. 1 Another object of the invention is to provide a novel inhibitor-metal deactivator which will function to - stabilize organic compounds. 3 5 . Various inhibitors have heretofore been proposed to prevent or at least substantially retard the deterioration of, organic materials, and some of the more successful of these inhibitors are N,N'-dialkyl-p-phenylene diamines. While these inhibitors are highly satisfactory for the 40 stabilization of gasoline, they have the disadvantage that they themselves tend to undergo discoloration in the presence of oxygen and, if highly oxidized, may lose inhibitor potency. Discoloration of the inhibitor is also objectionable when the inhibitor is used in waterwhite 45 gasoline. . Similarly, various metal deactivators have heretofore been proposed to prevent or at least substantially retard the catalytic effect of minute quantities ofmetals, which metals catalyzed the oxidative deterioration of organic 50 materials. Examples of such metal deactivators Are ' ethylene diamine tetraacetic acid and related compounds, the reaction product obtained by the condensation of a mono- or a polyhydroxybenzaidehyde, which may or may not be substituted with alkyl groups, with anthranilic acid 55 which may or may not be substituted with alkyl groups, the reaction product obtained by the condensation of an alkali metal salt of an alpha primary amino - aliphatic carboxylic acid with an ortho-hydroxy aromatic aldehyde which may or may not be further substituted with hydroxy 60 or alkyl groups, and a-picolinic acid and related compounds such as (x-qliinoline carboxylic acid, etc. . The present invention offers a novel method of inhibiting organic compounds with phenylene diamine type inhibitors, freeing said organic compounds of deleterious 6 5 metals, and lowering said organic compounds in mercaptan and phenol content. In the past it has been necessary to retain the phenylene diamine type inhibitors in an inert atmosphere in order to avoid the undesirable oxidation thereof, and the necessity for the use of an inert 70 atmosphere is avoided by the novel features of the present invention. In one embodiinent the present invention comprises an grganic compound, which tends to undergo deterioration @y oxygen catalyzed b presence of minute quantities 75 y of certain metals, containing, as an inhibitormetal deactivator for said deterioration, an inhibitor-metal deactivator comprising the product formed by the reaction of a phenylene diamine type inhibitor wilh an acid type metal go deactivator. 2 Another embodiment @f the present invention relates to a method of stabilizing an organic material which comprises adding a phenylene diamine salt of an acid type metal deactivator to said organic material, and thereafter treating the same with an alkaline reagent. Another embodiment of the present invention relates to novel compositions of matter which comprise the products formed by the reaction of a phenylene diamine type inhibitor with an acid type metal deactivator. In a specific embodiment the present invention relates to a method of stabilizing olefinic gasoline containing hydrogen sulfide and phenols which comprises commingling therewith from about 0.0001% to about 0.1% by weight of an N,N'-di-sec-butyl-pphenylene diamine salt of an acid type metal deactivator, and thereafter treating the same with caustic to remove hydrogen sulfide and phenols and at the same time converting aid N,N'-disee-butyl-pphenylene diamine salt of an acid type metal deactivator to N,N'-di-see-butyl-p-phenylene diamine and the sodium salt of the said metal deactivator. The phenylene diamine type inhibitors to which the present invention is directed preferably are p-phenylene diamines and more preferably p-phenylene diamines in I one t e 9 s attac e to at east one of the nitrogen atoms is ed by an alkyl group and particularly propyl, butyl, and amyl radicals. Although the orthoand meta-phenylene diamines may be used, t genoral y o not possess I bitor potency of the p-substituted compounds. Similarly, while other alkyl radicals may replace one or more of the hydrogen atoms attached to the nitrogen atoms, the iso-propyl, secbutyl, tert-butyl, sec-amyl, and tort-amyl substituti@d compounds are preferred. A particularly preferred p-phenylene diamine inhibitor coniprises N,N'-di-seebutyl-p-phenylene diamine. In accordance with the present invention, the p-phen ylene diamine salt of the acid type metal deactivator is prepared. This salt is considerably more stable to atmospheric oxygen than is the corresponding phenylene diamine and, therefore, permits the transportation aiid storing of the inhibitor compound without the necessity of using an inert gas blanket. The phenylene diamine salt is readily obtained by reacting the phenylene diamine with a concentrated solution of the desired acid type metal deactivator. In gen6ral, it is preferred to add the inhibitor slowly with constant stirring to the metal deactivator or to a solution of the metal deactivator in a suitable solvent such as alcohol, ether, ketone, etc., The phenylene diamine salt of the metal deactivator may then be concentrated and recovered in any suitable manner, such as by washing under vacuum with a suitable solvent. in accordance with the invention, a solution of the phenylene diamine salt of the metal deactivator is added to the organic material to be stabilized before the latter is subjected to a refining treatment with an alkaline material. As applied to cracked gasoline, the gasoline generally contains hydrogen sulfide and phenois and is usually treated within a short time after it is produced in order to remove the hydrogen sulfide. It is objectionable to store cracked gasoline containing hydrogen sulfide for long periods of time because, the hydrogen sulfide will be oxidized to sulfur and thereby result in a corrosive mixture. Similarly, as applied to cracked gasoline, the gasoline generally contains minute quantities of metals such as copper, iron, cobalt, nickel, chromium, lead etc. which have a detrimental effect on the stabilizati@n of the gasoline. It is a particular feature of the present invention that the phenylene diamine salt of a metal deactivator be coinmingled with the gasoline prior to or simultaneously with the caustio,to remove hydrogen sulfide. The treatment of gasoline to remove hydrogen sulfide is generally effected by passing the gasoline through a body of caustic in a treating zone. The hydrogen sulfide reacts with the caustic to form sodium sulfide, and after the caustic solution has lost its activity, it is discarded. it is preferred to commingle the phenylene diamine salt of a metal deactivator with the gasoline on its way to the caustic treating zone. In view of the fact that the phenylene diamine salt of the metal deactivator is generally insoluble in gasoline, it may be necessary to utilize con-
[2]2,700,612 3 irentional mixers, orifices, and the like in order to effect' the desired mixing, and to pump an emulsion of gasoline and the phenylene diamine salt of the metal dezictivator into saidaasoline containin2 hydrogen sulfide and phenols. In the caustic treating zone, the caustic reacts with the 1)heAylene diamine salt of the metal deactivator to fmm the correspondin.- phenylene dianiine and an alkali metal salt of the metal deactivator, as for example, the tetra-sodium salt of . ethylene diamine tetraacetic acid from the phenylene diamine salt of ethylene diamine tetra-acetic acid. The phenylene diamine is soluble in the gasoline and will be retained therein, while the alkali metal salt of the metal deactivator will be distributed in bbth the gasoline and caustic solutions according to its solubility in each. - Immediately thereupon the alkdli metal salt of the metal deactivator wirt cliel;ite the minute quantities of metals presenti said metals otherwise tending to catalyze the oxidativedeterioration of the gasoline. Thus some of the chelated metals will undoubtedly be present in an inactive form in the gtsoline, while a major portion of the chelated metals, will be later discarded with the caustic solution which is itself discarded when sufficiently contaminated with sodium sulfide. In place of caustic any suitable alkaline agent that will remove hydrogen sulfide and which will react with the phenylene diamine salt of the metal deactivator to form the corresponding phenylene diamine and the inorganic salt of the metal deactivator may be used. Suitable alkaline reagents include potassium hydroxide, barium hydroxide, lithium hydroxide, sodium carbonate, etc. It has been found that the phenylene diamine compound is completely retained in the gasoline and that the inhibitor activity obtained through the use of the metal deactivator salt is high and will stabilize the gasoline to a great degree. The inhibitor-metal deactivator compound of the present invention will usually be added to gasoline in an amount less than 0.1% by weight and generally will be utilized in an amount from ,a.bout 0.0001% to about 0.01%. The exact amount required will depend upon the particular organic substance treated and upon the potency of the specific inhibitormetal deactivator selected. These inwbitorsmetal deactivators may also be employed in conjunction witli various dyes, antiknock agents such as tetraethyl lea,d, or other additives employed for specific purp<)ses in organic materials. While it has been fourld that the acid type metal deactivator is distributed between the gasoline and the caustic phase, the metal deactivation obtained through the use of the phenylene diamine salt of an acid type metal deactivator is high and chelation of the minute quantiti(-,s of metals present does occur. Selection of the specific phenylene diamine-metal deactivator salt as hereinbefore stated will depend both on the organic material to be stabilized and upon the amount of minute metals present in said organic material. A,nother important advantage to the features of the present invention is that the inhibitor-metal deactivator is added to the gasoline shortly after it is produced and generally not more than about three days thereafter. As hereinbefore set forth, the phenylene diamine salt of an acid type metal deactivator is added to the gasoline prior to caustic treating to remove hydrogen sulfide, vvhich treatment is effected shortly after the gasoline is produced. The inhibitor and metal deactivator are, therefore, incorporated into the gasoline before the gasoline is subjected to contact with air either in storage or during the@ subsequent treating operations to remo-,,e mercaptans. The subsequent treating opdrations may comprise a regenerative caustic treating process in which a solutizer is added to the caustic as, for example,_methyl alcohol, potassium isobutyrate, etc., the doctor treating process, etc' Particularly in the doctor.treating process, the treating reagent is air blown and the gasoline is contacted with the regenerated reagent, which means that the psoline is subjected to contict with the air entrained in the. treating solution. The fbllowing "amples are introduced to ilustrate further the novelty and utility of the. present invention, but not with the intention of unduly linliting the same. Example I 4 the orgam'c material in the following examples, I and II. The potency of the inhibitor and the metal deactivator is report6d in terms of iridudtion p6riod, which is an accelerated @test employed to evaluate the storage stability of gasoline. The cracked gasoline without added inhibitor has an induction period of 105 minutes. Upon the addition of one part per million of copper, as copper oleate, the induction period of this same gasoline drops to 55 min10 utes. Upon the addition of 0.003% by weight of an inhibitor consisting of N,N'-disec-butyl-p-phenylene diamine@, the induction period of the gasoline containing the copper is raised to 300 miniites, while a sample of 'the same gasoline in which no added copper is pres15 ent, has its iriduction period r@Lised to 450 minutes by the addition of the sa:rhe amount of the same inhibitor. The N,N'-di-sec-butyl-p-phenylene diamine salt of alpha-picolinic acid was prepared by slowly adding NN'di-sec-butyl-p-phenylene diamine to a solution of alpha20 pi(,olinic acid in methanol and constantly stirring the mixture. Upon evaporation of the methanol, a pinkish crystalline mass was formed and this material was washed in the Buchner funnel with acetone. The thus purified reaction prodlict consisted of oval transpar25 ent crystals, soluble in methanol, partially soluble in ace-tone, insoluble iri ethyl ether, benzene, and parblffins, and had a sharp melting point at 139' C. Alphapic,olinic adid melts from 137-139' C. A mixture of al,pha-picdlinic acid and of the N,N'-di-sec-butyl-p'30 pbenylene diamine salt of alpha-picolinic acid had a mixed melting point of 124' C., the melting point of each pure substance being lowered by the presence of the other. 0.005% by weight of the above mentioned crystals is added in methanolic solution (equivalent to 0.003% 35 by weight of the NIN'-di-sei@-butyl-p-phenylene diariiine inhibitor and 0.002% by weight of the alphd-picolinic acid metal deactivator) to another sample of the Pennsylvania cracked gasoline containing I part per million 40 of copper, and the product is washed with 10% by volume of 10% caustic solution. The induction period of the gasoline so treated is 460 minutes. In order to show that the results obtained by adding the inhibitor salt bf an acid type metal deactivator are 45 stiperior to the results obt@ined by adding the inhibitor directly and not because of the caustic wash itself, 0.003% by weight of N,N'-d i-see-butyl-p-phenylene diainine is added to ancither sample of the Penns@lvania cracked gasoline containing one part per million of 50 copper, the mixture is washed with 10% by volume of 10% sodium hydroxide solution. The induction period of the gasoline so treated is 300 minutes. Example 11 The NN'-di-see-butyl-p-phenylene diamine salt of 55 ethylene diamine tetra-acetic acid was prepared by slowly adding N,N'-di-sec-butyl-p-phenylene diamine to a solution of ethylene diamine tetraacetic acid in water and constantly @tirring the mixture. The mixture was 60 stirred for an additional hour and a clear pink solution was obtained. This sbluti6n was allowed to stand for 24 hours, after which the water was@ removed by evaporation on a steam bath. A crystalline mass was formed and this material was washed in a Buchner funnel with heptane and then with benzene. The thus puri65 fied reaction product consisted of prismatic crystals soluble in hot water, slightly soluble in methanol and acetone, aiid insoluble in ethyl ether, benzene, and paraffins, and had a melting point at 181' C. Ethylene diamine tetra-acetic acid melts at 238' C. A mixture of 70 ethylene diamine tetra@acetic acid and the N,N'- di-seebutyl-p-phenylene diamine salt of ethylene diamine tetraacetic acid had a mixed melting point of 205' C., the melting point of each pure substance being changed by the presence of the other. 75 0.007% by weight of the ab6ve mentioned crystals is added in an aqueous solution (equivalent to 0.003% by weight of the N,N'-di-secbtityl-p-phenylene diamine inhibitor and 0.004% by weight of the ethylene. diaminetetra-acetig acid metal deactivator) to another sample 80 of the Pennsylvania cracked gasoline containing one part per million of copper and the product is washed with 10% by volume of 10% caustic solution. The induction period of the gasoline so treated is 460 minutes. Similarly,. in order io show that the results obtained by Pennsylvania thermally cracked gasoline is utilized as 85 adding this inhibitor salt of an acid type meW deactiva-
[3]2,700,619 5 tor are superior to the results obtained by adding the inhibitor directly and not because of the caustic wash itself, 0.003,Yo by weight o' N ,N'-di-sec-butyl-p-phenylene diamine is added to another sample of the Pennsylvania cracked gasoene containing one part per mfllion of copper and the mixture is washed with 10% by volume of sodium hydroxide solution. The induction period of the gasoline so treated is 300 minutes. Exa.mple III As another example to demonstrate the utilit@ of these p-phenylene diamine salts of acid type metal deactivators, 0.029o of the N,N'-di -sec-butyl-p-phenylene diamine salt of alpha-picolinic acid, and 0.02% of the .N,N'-disec-butyl-p-phenylene diamine salt of ethylene diamine tetraacetic acid are slowly added to samples of lard. The development of rancidity in these two lard samples is followed by the so-called Active Oxygen Method, a standard test for following the development of rancidity of lard, in comparison to a control sample. The control sample becomes rancid in approximately three hours time, the sample containing 0.02% of the N,N'-di-sec-butyl-p-phenylene diamine salt of alphapicolinic acid becomes rancid in 21 hours, and the sample containing 0.02% of the N,N'-di-sec-butyl-p-phenylene diamine salt of ethylene diamine tetraacetic acid becomes rancid in 24 hours. Similarly, 0.02% of N,N'-disecbutyl-p-phenylene diamine is added to another sample of the same lard and rancidity, as measured by the Active Oxygen Method, is detected in 15 hours. Example IV As another example, to one sample of rubber contammg natural rubber, sulfur, zinc oxide, carbon black, synthetic rubber, pahn ofl, and hexamethylene tetraamine, is added 0.5% of the N,N'-di-sec-butyl-p-phenylene diamine salt of a-picolinic acid; to another sample of the same rubber is added 0.5% of the N,N' -di-seebutyl-p-phenylene diamine salt of ethylene diamine tetraacetic acid; to another sample is added 0.5% of N,N'- disec-butyl-p-phenylene diamine; and another sample is used as a control. After vulcanization in a press for 45 minutes at 294' F. to produce an optimum quality, the compositions containing the p-phenylene diamine salts of the acid-type metal deactivators deteriorate only approximately one-half as fast as the control composition when subjected to an accelerated ageing test such as the Greer oven test. The composition containing N,N'-disee-butyl-p-phenylene diamine deteriorates in a slightly but perceptibly faster rate than the compositions containing the p-phenylene diamine salts of the acid-type metal deactivators. Example V The following table illustrates the beneficial results obtained by treating alfalfa with the inhibitor-rnetal deactivators of the present invention. Inhibitor-metal deactivator A comprises the N,N'-di-sec-butyl-p-phenylene diamine salt of a-picolinic acid, inhibitormetal deactivator B comprises the N,N'-di-see-butyl-p-phenylene diamine salt of ethylene diamine tetraacetic acid, and inhibitor C comprises N,N'-di-sec-butyl-pphenylene diamine. The alfalfa used contains 28- milligrams of carotene per 100 grams of alfalfa. In order to assist in distributing the small amount of additive throughout the alfalfa, the additive is added as a solution in methanol. The sample of alfalfa to be used as a blank or control ran (no addition of inhibitor-metal deactivator or of inhibitor) is sirnilarly treated with the same amount of methanol in order to show that the improved results are not due to the methanol solvent used. Percent of Carotene Percent Active Lost at The End li2hibitor- of 7 Wks. Inhibitor-Metal Deactivator or Metal Deactivator or lnhibiInhibitor itor (Based on Temperature the Weight of Alfalfa) 751 F. 1251 F. - -None ------------------------ ----- ----------- 50.0 77 2 A ---------------------------- :7- 0.10 6.3 28:0 B --------------------------------- 0.10 6.5 30.2 --------------------------------- 0.10 6.1 35.0 6 The effectiveness of these p-phenytene diamine salts of acid-type metal deactivators for use for the retention of carotene in alfalfa is readily apparent by the data in the above table. 1
