Abstract:
Gasoline motor fuel compositions which contain minor amounts of an aryl o-aminoazide, such as o-azidoaniline, to impart improved antiknock characteristics and greater oxidation stability to the gasoline.

Description:
This is a continuation-in-part of our patent application Ser. No. 83,297, filed Oct. 10, 1979, now abandoned. 
    
    
     SUMMARY OF THE INVENTION 
     This invention relates to gasoline motor fuel compositions of improved antiknock characteristics and greater oxidation stability. 
     DESCRIPTION OF THE INVENTION 
     We have discovered a class of metal-free antiknock agents which are capable of substantial improvement in the antiknock properties of a motor gasoline and which also provide a surprising improvement in the oxidation stability of the motor fuel. 
     The antiknock agents and antioxidants of our invention are aryl o-aminoazides. Surprisingly, we have discovered that the meta- and para-aminoazides as well as the N-substituted o-aminoazides are proknocks, that is, they increase the knocking characteristics of motor gasoline. The o-aminoazides have the following general formula ##STR1## wherein each R group is independently selected from hydrogen, alkyl having from one to about four carbon atoms, alkenyl having from two to about four carbon atoms, haloalkyl having from one to about four carbon atoms, aryl having from six to about ten carbon atoms, cycloalkyl having from five to about eight carbon atoms, alkoxy having from one to about four carbon atoms, carbalkoxy having from two to about five carbon atoms, carbaryloxy having from seven to about nine carbon atoms, alkylamino having from one to about four carbon atoms, acyl having from two to about five carbon atoms, hydroxyl, amino, cyano, nitro, halo and halophenyl, or wherein any two adjacent R groups containing a total of four carbon atoms are joined together in a saturated or unsaturated ring. 
     Compounds which are useful gasoline additives in accordance with our invention in addition to o-azidoaniline include the following: 
     2-Azido-3-methylaniline 
     2-Azido-4-methylaniline 
     2-Azido-5-methylaniline 
     2-Azido-6-methylaniline 
     2-Azido-3,4-dimethylaniline 
     2-Azido-4,5-dimethylaniline 
     2-Azido-5,6-dimethylaniline 
     2-Azido-3,5-dimethylaniline 
     2-Azido-3,4,5-trimethylaniline 
     2-Azido-3,4,6-trimethylaniline 
     2-Azido-3,5,6-trimethylaniline 
     2-Azido-4,5,6-trimethylaniline 
     2-Azido-3,4,5,6-tetramethylaniline 
     2-Azido-3-ethylaniline 
     2-Azido-4-isopropylaniline 
     2-Azido-4-tert.butylaniline 
     2-Azido-5-propylaniline 
     2-Azido-5-tert.butylaniline 
     2-Amino-3-azidostyrene 
     3-Amino-4-azidostyrene 
     3-Amino-4-azidoisopropenylbenzene 
     2-Azido-4-methoxyaniline 
     2-Azido-5-methoxyaniline 
     2-Azido-6-methoxyaniline 
     2-Azido-4,5-dimethoxyaniline 
     2-Azido-5,6-dimethoxyaniline 
     2-Azido-3,5-dimethoxyaniline 
     2-Azido-5-isopropoxyaniline 
     2-Azido-5-ethoxyaniline 
     2-Azido-4-n-butoxyaniline 
     2-Azido-4-isobutoxyaniline 
     2-Azido-4-fluoroaniline 
     2-Azido-4-chloroaniline 
     2-Azido-4-bromoaniline 
     2-Azido-4-iodoaniline 
     2-Azido-5-chloroaniline 
     2-Azido-6-fluoroaniline 
     2-Azido-3-fluoroaniline 
     2-Azido-4,5-difluoroaniline 
     2-Azido-5,6-dichloroaniline 
     2-Azido-4,5,6-trichloroaniline 
     2-Azido-3,4,5,6-tetrachloroaniline 
     2-Azido-4,5-diiodoaniline 
     2-Azido-3,4-diiodoaniline 
     2-Azido-4-chloro-5-methylaniline 
     2-Azido-5-chloro-6-methylaniline 
     2-Azido-3-fluoro-5-methylaniline 
     2-Azido-3-fluoro-4-isobutylaniline 
     2-Azido-4-iodo-5-methylaniline 
     2-Azido-4-bromo-5-ethylaniline 
     Useful gasoline additives in accordance with our invention additionally include the following: 
     2-Amino-3-azidobiphenyl 
     3-Methyl-2&#39;-amino-3&#39;-azidobiphenyl 
     3-Methyl-3&#39;-amino-4&#39;-azidobiphenyl 
     3-tert.Butyl-3&#39;-amino-4&#39;-azidobiphenyl 
     2,2&#39;,4-Trimethyl-3&#39;-amino-4&#39;-azidobiphenyl 
     2,4-Dichloro-2&#39;-amino-3&#39;-azidobiphenyl 
     4-Fluoro-2&#39;-iodo-3&#39;-amino-4&#39;-azidobiphenyl 
     2-Azido-4-cyclohexylaniline 
     2-Azido-5-cyclohexylaniline 
     2-Azido-5-(2-methylcyclopentyl)aniline 
     Methyl-3-amino-4-azidobenzoate 
     Ethyl-4-amino-5-azidobenzoate 
     Propyl-2-amino-3-azidobenzoate 
     Phenyl-3-amino-4-azidobenzoate 
     2-Azido-1-naphthylamine 
     3-Azido-2-naphthylamine 
     1-Azido-2-naphthylamine 
     2-Azido-1,3-diaminonaphthalene 
     1-Azido-2-aminotetrahydronaphthalene 
     3-Amino-4-azidophenol 
     4-Amino-3-azidophenol 
     3-Amino-4-azidobenzyl alcohol 
     1-Amino-2-Azido-4-naphthol 
     1,3-Diamino-2-azidobenzene 
     1,4-Diamino-2-azidobenzene 
     1,5-Diamino-2-azidobenzene 
     1,6-Diamino-2-azidobenzene 
     1-Amino-4-(N,N-dimethylamino)2-azidobenzene 
     2-Amino-3-azido-acetophenone 
     3-Amino-4-azido-acetophenone 
     4-Amino-5-azido-acetophenone 
     4-Amino-5-azido-n-butyrophenone 
     2-Azido-4-nitroaniline 
     2-Azido-4-trifluoromethylaniline 
     2-Azido-5-trifluoromethylaniline 
     2-Azido-4,6-bis(trifluoromethyl)aniline 
     2-Azido-4-cyanoaniline 
     2-Azido-5-cyanoaniline 
     The gasoline fuel composition desirably contains from about 0.1 to about 50 grams of the aryl o-aminoazide antiknock and oxidation stabilizing agent per gallon and preferably from about 0.5 to about 15 grams per gallon. 
     The aryl o-aminoazides can be prepared by the method of Smith et al, J. Am. Chem. Soc. 84, 485 (1962). Thus, in order to product o-azidoaniline, o-nitroaniline is used as the initial reactant. In producing the ring-substituted o-azidoanilines, o-nitroaniline containing the desired ring substituent or substituents is used. In like manner, the polynuclear aryl o-aminoazides are prepared from the corresponding o-nitronaphthyl amines and the o-nitrotetrahydronaphthyl amines. A typical preparation is set out in Example 1. 
    
    
     EXAMPLE 1 
     Preparation of 2-Azido-4-fluoroaniline. 
     A 25 gram portion (0.16 mol) of 2-nitro-4-fluoroaniline was mixed with 24 grams of phthalic anhydride and the mixture was heated at 180°-210° C. for two hours with slow stirring. After evolution of water was complete, the mixture was allowed to cool. It was ground to a powder and treated with three 100 cc. portions of boiling ethanol. The residue was crude N(2-nitro-4-fluorophenyl)phthalimide (mp. 238°-240° C.). A 36 gram (0.126 mol.) portion of this product was dissolved in one liter of acetone containing 108 cc. of acetic acid and 108 cc. of water. The solution was refluxed and treated with a total of 84 grams of iron powder added in small portions. After three hours refluxing, the mixture was filtered while hot and the filtrate was neutralized with saturated sodium carbonate solution. The mixture was filtered and the filtrate poured into about three liters of ice water. N(2-Amino-4-fluorophenyl)phthalimide precipitated out. This product melted at 190°-193°  C. The amine was diazotized in 1500 cc. of water containing 200 cc. concentrated hydrochloric acid by treating with a solution of 12 grams of sodium nitrite in 50 cc. of water at 0°-5° C. After stirring three hours at 0°-5° C., the solution was filtered and the filtrate was treated dropwise with a solution of 8.2 grams of sodium azide in 50 cc. of water. After about one hour, evolution of nitrogen had stopped. The white solid was removed on a filter, washed with water, and vacuum dried. The product, N(2-azido-4-fluorophenyl)phthalimide decomposed with the evolution of nitrogen at 200°-205° C. 
     This material was suspended in 325 cc. of 95 percent ethanol and treated with 4.0 grams of 95 percent hydrazine. The mixture was stirred for two hours at room temperature. The addition of 160 cc. of water and 50 cc. of 20 percent sodium hydroxide solution caused the solid to dissolve. This mixture was filtered into about two liters of ice water. The precipitate of 2-azido-4-fluoroaniline was removed on a filter, washed with water and vacuum dried (mp. 44° C.). It decomposes with evolution of nitrogen between 75° and 100° C. 
     EXAMPLES 2-7 
     A series of motor fuel compositions were tested for octane ratings by the motor method (MON by ASTM D2700) and the research method (RON by ASTM D2699) using a clear commercial automotive gasoline having a MON of 84.4 and an RON of 92.6. In these experiments various o-azidoanilines were tested using four grams of the additive per gallon of gasoline in each test. The results of these experiments are set out in Table I in which each listed difference in octane numbers is based on consecutive, matched determinations with the o-azidoaniline and the substituted o-azidoanilines present and absent. 
     
                       TABLE I______________________________________Example   2-azidoaniline                ΔMON  ΔRON______________________________________2         unsubstituted                +0.5        +1.23         4-methyl   +0.3        +0.84         6-methyl   0           +0.65         4,5-dimethyl                +0.4        +1.46         4-methoxy  +0.2        +1.17         4-fluoro   +0.3        +1.0______________________________________ 
    
     EXAMPLES 8-10 
     Example 2 was repeated using different test gasolines. The Primary Reference Fuels (PRF) are combinations of isooctane and heptane. Indolene is a standard test gasoline of Standard Oil Company of Indiana which is in general use in the industry. Four grams of o-azidoaniline were added per gallon of gasoline. The octane numbers of the fuels and the test results are set out in Table II. 
     
                       TABLE II______________________________________Ex.   Gasoline   MON      RON    ΔMON                                   ΔRON______________________________________2     commercial 84.4     92.6   +0.5   +1.28     80 PRF     80.0     80.0   +0.8   +1.39     90 PRF     89.7     89.8   +0.6   +1.010    Indolene   88.6     98.4   +0.4   +0.8______________________________________ 
    
     EXAMPLES 11-13 
     The octane rating of several commercial gasolines containing a known metallic antiknock compound were compared before and after the addition of four grams of o-azidoaniline per gallon of gasoline. The results are set out in Table III. 
     
                       TABLE III______________________________________Metallic     Before        AfterEx.     antiknock            MON      RON    ΔMON                                   ΔRON______________________________________2       none     84.4     92.6   +0.5   +1.211      TEL      86.5     93.6   +0.7   +0.512      MMT      84.6     94.8   +0.4   +0.713.sup.a   Ce(tod).sub.4            84.9     94.6   +0.1   +0.7______________________________________ TEL tetraethyl lead, 1.5 g.Pb/gal. MMT manganese methylcyclopentadienyl tricarbonyl, 0.0625 g. Mn/gal. Ce(tod).sub.4 tetrakis(2,2,7trimethyl-3,5-octanedianato)-cerium, 0.3 g. Ce/gal. .sup.a also contained 4 g./gal. of 2,2,7trimethyl-3,5-octanedione. 
    
     EXAMPLES 14-23 
     The experiments of Examples 2-7 were repeated in the same gasoline using different aryl azido compounds which were found to be proknocks. These compounds were added in an amount of four grams per gallon of gasoline. The results of these tests are set out in Table IV. 
     
                       TABLE IV______________________________________Ex.    Aryl azide          ΔMON                               ΔRON______________________________________14     3-azidoaniline      -0.7     +0.115     4-azidoaniline      -0.7     -0.416     2-methoxy-5-azidoaniline                      -1.1     -2.017     o-azidonitrobenzene -0.4     -0.218     o-azidotoluene      -0.6     -1.519     3-azido-4-methoxytoluene                      -0.3     -0.920     o-azidochlorobenzene                      -0.6     -1.521     2-azido-N-methylaniline                      -0.6     -0.822     2-azido-N,N-dimethylaniline                      -1.1     -2.623     2-azido-N-methylacetanilide                      -0.2     -0.5______________________________________ 
    
     EXAMPLES 24-28 
     A series of experiments were carried out to compare o-azidoaniline with other nonmetallic octane improvers on a weight basis, including one antiknock agent and three antiknock blending agents. The comparison is made at that concentration in weight percent for each agent at which the average increase of ΔMON and ΔRON, that is (ΔMON+ΔRON)/2, is one octane number. The results are set out in Table V which also lists the relative activity on a weight basis with N-methylaniline normalized to an activity of 1.0. 
     
                       TABLE V______________________________________                           RelativeEx.     Additive        Wt. %   activity______________________________________24      o-azidoaniline  0.17    3.625      N-methylaniline 0.62    1.026      methanol        2.8     0.2027      ethanol         2.5     0.2228      methyl t-butyl ether                   4.2     0.14______________________________________ 
    
     In further exemplification of this invention, the above listed compounds are separately added to motor gasoline in appropriate amount and are found to significantly improve the octane rating of the gasoline. 
     EXAMPLE 29 
     The antioxidant properties of the o-azidoanilines were studied in two gasoline base stocks. Pertinent data on these base stocks are set out in Table VI in which gasoline base stock A is a light fluid catalytic cracking fraction and gasoline base stock B is a commercial unleaded gasoline. 
     
                       TABLE VI______________________________________              A       B______________________________________API gravity          62.8      67.9Hydrocarbon analysis aromatics, % by vol.                17.0      12.5 olefins, % by vol.  35.0      14.5 saturates, % by vol.                48.0      73.0Knock ratings RON, ASTM D2699     92.1      92.6 MON, ASTM D2700     80.5      84.4Distillation overpoint, ° F.                103       78 10%                 132       110 50%                 184       199 90%                 285       310 endpoint            356       401Sulfur, ppm.         184       185Bromine No.          70        --______________________________________ 
    
     These two gasoline base stocks were tested for oxidation stability in accordance with ASTM D525. The data is set out in Table VII in which 0.10 weight percent is 2.76 grams per gallon of the o-azidoaniline. The test was not extended beyond 1,440 minutes (24 hours). 
     
                       TABLE VII______________________________________          Amount, MinutesAntioxidant      wt. %     A        B______________________________________none             --        60       720o-azidoaniline   0.01      60       --o-azidoaniline   0.05      150      --o-azidoaniline   0.10      &gt;1,440   --o-azidoaniline   0.15      --       &gt;1,4402-azido-4-methylaniline            0.10      585      --2-azido-6-methylaniline            0.10      1,050    --2-azido-4-methoxyaniline            0.10      &gt;1,440   --______________________________________ 
    
     It is to be understood that the above disclosure is by way of specific example and that numerous modifications and variations are available to those of ordinary skill in the art without departing from the true spirit and scope of the invention.