PREPARATION OF N-PHENYL-BENZOQUINONEIMINE FROM HYDROXYDIPHENYLAMINES

Abstract: A hydroxydiphenylamine compound can be converted to an N-phenylquinoneimine by reacting the hydroxydiphenylamine with oxygen or an oxygen containing gas in the presence of a modified activated carbon catalyst, the catalyst having had surface oxides removed therefrom.

Description: PREPARATION OF N-PHENYL-BENZOQUINONEIMINE FROM HYDROXYDIPHENYLAMINES Field of the Invention. This invention relates to a no l process for the preparation of N-phenyl-benzoquinon'i'._.πines from their corresponding hydrαxydiphenylamines using an activated carbon catalyst which has had surϊacH* oxides removed therefrom. Background of the Inven on The class of cyclic eπone≤ xs well known in organic chemistry. Best known examples of cyclic-enones are quinones such as, for example, the benzoquinones , naphthoquinones,--. anthraquinones , phen πthraquinones, and the like. 1,4-Benzoquinone is comma.i y referred to as quinone. Quinones are generally brightly c:clored compounds and have versatile applications in chemical synthesis, biological uses, as redox materials, a-5 well as in industry. There are several review -articles on -the chemistry and applications of quinones ...neluding, for example, Klrk-Othmer Encyclopedia of Chemical Technology, Third ed., Vol. 19, pages 572-605, Johr Wiley & Sons, New York, 1932. The synthesis of quinones is: we ' ll documented. See, for example, J. Cason, Synthesis of. πtsnzoq inonea by Oxidation, in Organic Synthesis, Vol. IV, page 305, John Wiley & Sons, New York (1948) . Quincn≥s generally are prepared by oxidizing the appropriately disubstituted /36395 aromatic hydrocarbon derivatives, the ..υbstituents being hydroxyl or a ino groups in the ortho or para positions . 1, 4-Benzoquinone, for example, can be made from the oxidation of hydroquinone , -amin.-1phenol or p- phenylenediamine, or sometimes from qui ic acid. The reagents generally used for tlw oxidation are dichromate/sulfuric acid mixture, ferric chloride, silver (II) oxide or eerie ammonium nitrate. Such methods are generally performed in solvents which m y need elaborate waste disposal procedures- Some processes may also take several hours for completion of the re ction. Thus, some of the prior art processes utilize a catalytic agent to achieve an accep^αbl.. reaction rate while other processes proceed withou catalysts . The process according to the present invent.i on utilizes an oxidation mechanism which provide:.. extremely high conversion, high selectivity, and fast reaction rates. A prior art process which utilmes a catalyst in the preparation of an N-phenylquinane-im.i ne compound is disclosed by Destπurs, et al . in U.S. P tent No. 5,189,218. The process of Des urs, et al., which converts a N- (4- hydroxyphenyl) aniline into N-phenylb--.-.2oquinone-imine, utilizes a manganese, copper, cobalt. and/or nickel compound as a catalyst in an oxidation type reaction. Other processes which convert hydroxydiphenylamines to N-phenylqu i none-imines via stoichiσmetric oxidation using pot.3.-.-.-i.ιm or sodium dichromate catalysts are disclosed by Cottman in U.S. 4,968,463, U.S. 5,068,439, U.S. 5,053,540, U.S. 5,371,289, EP 448,899 and EP 617.-004. Denisov, et al . (Bu ll . Acad . L-'CJ . USSR Div. Chem . Sci . , 37 (10), 1988) disclose preparation of N- phenylquinone-imine by reacting -<milino-phenol (4- hydroxydiphenyla ine) with an Mn0 2 c talyst in a benzene solvent system. Ram et al . (Tetrahedron, 12 B ] , 887-90, 1977) teach a non-catalytic autoxidation relict ion process for conversion of p-hydroxydiphenylamiiis to N-phenyl-p- benzoquinone-imine . The above process of Desmurs , et al . , which uses a metal catalytic component, along with an other processes which utilize a metal catalyst, h v r.everal drawbacks. Not only are the metal catalysts relat:.-v..> Ly expensive, they raise important environmental conce n;] . For example, effluent streams and products can be contaminated by such metals. Further, recovery of the catalyst for reuse can be prohibitively expensive . Various non-heavy metal catalys s are known in the art. For example, activated carton catalysts, which are typically prepared by heating carbon to high temperatures (800°C to 900°C) with steam or with carbon dioxide to bring about a porous parti lat structure and increased surface area, are well known o idation catalysts. U.S. Patent No. 4,264,776, for exam le, discloses and claims a process for preparing se ondary amines by catalytic oxidation of tertiary amines using an activated carbon catalys . U.S. Patent No. 4,158,643 teaches a method for oxidation modification of an activated carbon support in which oxygen is added to the surface: of the activated carbon, and then the carbon support is ...nprαgnated with an inert hydrophobic compound. The carbon support, which may be any commercially available activated carbon for vapor phase activation use, is useful ir. oxidising carbon monoxide in the presence of sulfur dioxide for an extended period of time. U.S. Patent No. 4,624,937 provides a method for preparing activated carbon for cat IIy i cally oxidizing tertiary amines or secondary amines n the presence of oxygen or an oxygen-containing gas to .3-elactively produce secondary or primary amines. The me hod of 4,624,937 comprises the step of treating the arbon catalyst to remove oxides from the surface thereo . Thus, it can be seen that processes for preparing gninoneimines from hydroxydiphenylami neε are known. Additionally, the use of various carbon catalysts, including activated carbon, in chemical reactions is known. However, in the conversion of hydroxyd-.pr-t--.n lamine to an N- phenyl-benzoquinσnei ine, the use of modified activated carbon compound as an oxidation catalyst :; not heretofore been suggested. Summary of the Invention It has now been discovered that a hydroxydiphenylamine compound can be converted into its corresponding N-phenyl-benzoquinoneirn n.5 by reacting the hydroxydiphenylamine with oxygen or an oxygen containing ga3 in the presence of a modified activated carbon catalyst. The modified activated carbon catalyst of the present invention has been treated to remove oxides from the surface thereof- Such a modified carbon catalyst: allows the conversion of hydroxydiphenylamine to the corresponding N-phenyl-benzoquinonf.jmiπe in almost quantitative (HPLC) yields. In contrast to prior art, an advantage of using the process of the present invention is that the conversion of hydroxydiphenylamine to the corresponding N-phenyl- benzoquinoneimine is nearly quantitHLiW.. Thus, very little waste material remains upon completion of the reaction. Another advantage realized when using the modified activated carbon catalyst set E nh above is that the modified activated carbon catalyst, not only is recyclable, but it also avoids the drawbacks associated with metal catalysts which include h-i gh cost, product contamination and environmental waste c^ncsrns. -An additional advantage is that the modified activated carbon catalysts as set forth herein provide a faster, more complete reactioα compared to commercially available activated carbon catalysts :-r. the conversion of hydroxydiphenylamines to N-phenyl-bcnzoquinoneimines . Still further advantages of th≥ present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description of the preferred embodiment.'.. Detailed Description of the in e.ιijL s2ll The obj ect of the present invention is to provide an effective process fox conversion of hydroxy dip heny la mines to N-phenyl-benzoςp-i uioneimines . In accordance with the object of the invention, in a first embodiment, an o-rf-ho- or para - hydroxydiphenylamine according to Formula I : I wherein R-. and R 2 are independently selected from hydrogen; hydroxyl; C - C so alkyl, C : - C so alkox , C β - C i0 aryloxy, C 2 - C so alkenyl, C 3 - C aa cycloalkyl, C t - , 0 aryl, C 7 - C so aralkyl, C 7 - C 50 alkaryl, C L - C 30 ;J] >:y] amino, C fi - C 40 arylamino, wherein the alkyl moieties may be linear or branched; C 3 - C 30 heterocycle containing one or more nitrogen, sulfur, oxygen, and/or phosphorous atoms; C x - C so acyl; aroyl; cyano; halogen; thiol; C - Cς 0 thioalkyl; C 5 - C 40 thioaryl; amino; nitro; sulfonate having the formula S0 3 X wherein X is selected from sodium, , - C^ .-ilkyl or C s - C 40 aryl; and C x - C so alkyl ester or C 6 - C 40 aryl ester; wherein the above moieties may be further £.ub?;tituted, where appropriate; is reacted in the presence of oxygen or an oxygen containing gas and optionally, a solvent and heat, further in the presence of a modified activated carbon catalyst which has had the surfa;;ϋ oxides removed therefrom. More preferred embodiments for certain of the above identified R x and R 2 variables include C τ - C 10 alkyl, C - C 15 alkoxy-, C 6 - C 20 aryloxy, C 2 - C 6 Lkenyl, C 3 - C 10 cycloalkyl, C 6 - C, 0 aryl, C 7 - C iβ aralky] , G 7 - C 20 alkaryl, c ι - c ιo alkylamino, C s - C 2u arylamino, wherein the alkyl moieties may be linear or branched; (^ - c 20 heterocycle containing one or more nitrogen, sulE r, oxygen and/or phosphorous atoms; C x - C 20 acyl; d - C 15 thioalkyl; C 6 - C 20 thioaryl; sulfonate having the formula S0 3 X wherein X is selected from sodiucti, G, - C^ alkyl or C' ή - C 2α aryl; and C x - C 1U alkyl ester or C 5 - C ao aryl ester, wherein the above moieties may be further substituted, where appropriate. Exemplary variables for . and R 2 include, but are not limited to, hydrogen, hydro yl, methyl, ethyl, propyl, isopropyl, butyl, isobutyL, pentyl, 1,3- di ethylbutyl , hexyl, heptyl, octyl, ncnyl, decyl, dαdecyl, methoxy, ethoxy, propoxy, phenoxy, πthnnyl, propenyl, butenyl, cyclohexyl, σycloheptyl, 1, 3 -dimethyl-cyclohexyl, phenyl, phenol, benzyl, ethylbenzyl, xylyl, naphthyl, anthracyl, tolyl, toluene, xyleπe, ethylbenzene, nitrobenzene, chlorobenzene, me thyl-isobutyla ino, isopropylamino, aniline, 2, 4-dimethyl3niline, 1,3,5-sym- triazinyl, 2-beπzothiazolyl , mercaptopyridazyl , mercaptobenzothiazolyl, 2-benzim.idazolyl, 2-benzoxazolyl, 2-pyridyl, 2-pyrimidinyl, acetyl, caproyl, benzoyl, phthaloyl, terephthaloyl, fluoro, broitio, chloro, iodo, cyclohexylmercapto, ethylmercapto , phen/lmercapto, p- tolylsulfonate, methyl ester, ethyl eater, propyl ester, phenyl ester, allyl, iso-butenyl, adipyl, glutaryl, succinyl, malonyl, acrylyl, ruethacrylyl, 3- mercaptopropionyl, aminocarbonyl , carboethoxy, carbonyl, formyl, cyano, amino, nitro, thiol, and the like. These are merely exemplary radicals and are not in any way intended to limit the scope of the invention. In a most preferred embodiment, R j _ and R 2 in the compound of Formula I are both hydrogen, wherein the resulting compound is 4-hydroxydiphenylamine. The reaction produces a corπ-ioponding N-phenyl- benzoquinone-imine according to Formula IIA or IIB: IIA IIB The reaction is represented as follows: The modified activated carbon catalyst, described above, is prepared by removing both acidic and basic surface oxides from the surfaces of a carbon catalyst. A method for making the modified activated carbon catalyst is set forth in U.S. Patent No. 4,624,937. According to U.S. Patent No. 4, 624,937, a carbon material, such as Chose described :.r U.S. Patent No. 4,264,776, is initially provided. Ordinarily, the initial carbon catalyst used in preparing the modified carbon catalyse, is a commercially available activated carbon with a carbon content ranging from about 10% for bone charcoal to aboir: yy% for some wood chars and nearly 100% for activated carbons derived from organic polymers. The noncarbonaceous matter in commercial y available carbon materials will normally vary depending on such factors as precursor origin, processing, and activation method. The treatm-nr. process can be accomplished by a single or a multisc p scheme which in either case results in an overall chemical reduction of oxides on the carbon surface, i.e., a reduction or removal of acidic oxides from the carbon surf.ce . As used herein, the term "oxides" is intended to mean carbon functional groups which contain oxygen atoms as well as hetero-atom functional groups which contain oxygen atoms. Other hetero-atom functional groups which do not contain oxygen atoms may also be emov d :: ' roτn the surface of the carbon material during treatmer t . In a two-step scheme, the ca bon material can be first treated with an oxidizing agent s;uch as, for example, liquid nitric acid, nitrogen dioxide, 'rO- . j, air, oxygen, H 2 0 2 , hypochlorite, or a mixture of g.af es obtained by vaporizing nitric acid. The treatment ιan be accomplished using either a gas or a liquid oxidiz.iπci agent. Where a liquid is used, concentrated nitric acid containing from about 10 to about 80g. HN0 ? , per 10Og. of aqueous solution is preferred. Preferred gaseous oxidant s include oxygen, nitrogen dioxide, and nitric acid vapors. A particularly effective oxidant is nitric acid in the; vapor phase which includes nitric acid carried into th.?. vapor phase by an entraining gas as well as the vapors obt ined by distilling liquid nitric acid. With a liquid o. .dai.t, temperatures from about 60°C to about 90°C are appropriate, but with gaseous oxidants, it is often advantageous to use temperatures of about 50°C to about 500 'C or even higher for the treatment step. The treatment can be achieved by placing carbon from a manufacturer in a round bottom flas-k which contains a magnetic stirring bar- Liquid nitric c -.d is selected as the oxidizing agent for illustration. The amount of carbon used is determined by the percent carbon load desired (% carbon load = g. of carbon used per 100 τι.l of nitric acid solution) and the nitric acid solution volume to be used. Ordinarily, 1 to 200g. of carbon per 100 ml of nitric acid or other liquid oxidizing agent i.s satisfactory. Temperature control can be provided by any suitable means. A condenser and scrubber can be connected to the round bottom flask as desired. A calcula ~ e-d volume of water, preferably deionized water, is adde to the carbon, followed by sufficient (69-71%) nitric acid to achieve the desired nitric acid solution. The carbon and nitric acid solution are then stirred for the d-i-sir-d period at the desired temperature. After stirring, the carbon is filtered, and the resulting wet cake may or may not be washed and/or dried prior to pyrolysis. The time during which the carbon is treated with the oxidant can vary widely from about !> minutes to about 10 hours. Preferably, a reaction time, of about 30 minutes to about 6 hours is satisfactory- When concentrated nitric acid is the oxidant, a contact time OJ: about 30 minutes to about 3 hours is sat i-sPe-cL-ory - In a second step, the oxidiz i carbon material is pyrolyzed, i.e., heat treated, at a temperature in the range of about 500°C to about 1500°C, o «fr-rably from about 800 D C to 1200°C It is preferred to conduct the pyrolysis in an inert gas atmosphere, such as nitrogen, argon, or helium. Wet cake or dry carbon is placed in a ceramic pyrolysis dish which together are plaof. a quartz tube. Nitrogen is passed through water at about 70°C, then tlirough the quartz tube during pyrolysis. A dry, static nitrogen atmosphere is maintained after flushing the quartz tube with several tube volumes of dry nil rogeπ prior to pyrolysis. The quartz tube containing the pyrolysis dish is placed in a suitable pyrolyzer apparatus at about 930 U C for the desired period, followed by cooling while maintaining the nitrogen atmosphere . Pyrolysis can last anywhere Iron, about 5 minutes to 60 hours, although 10 minutes to 6 hours is normally satisfactory. The shorter times are pr fecred for economic reasons because, as might be expected, continued exposure of the carbon to elevated tempera ures for prolonged periods can result in a poor σarbi.n catalyst for the oxidation. Pyrolysis may be initiated in a slightly moist atmosphere or an atmosphere which contains NH 3 as this appears to produce a more active catalyst in a shorter time. Alternatively, the treatmer.t is accomplished in a single step by pyrolyzing the carbon material as described above while simultaneously passing a gas stream comprised of NH 3 and an oxygen-containing gas, e.g., H 2 0/NH 3 , through the carbon. The flow rate of the gas stream should be fast enough to achieve adequate contact between fresh gas reactants and the carbon surface, yet slow enough to prevent excess carbon weight loss and matecial waste. Many NH 3 /αxygen-containing gas mixtures can be used such as, for example, NH 3 /C0 2 , NH 3 /0 2 , NH^/H^O and NH,/NOx, provided the gas mixture achieves the desired result-. - Ordinarily, the oxygen-containing gas/NH 3 ratio can rang, from 0:100 to 90:10. Furthermore, ni rogen can be u,τed as a diluent to prevent severe weight loss of the carbon in high oxygen- containing gas concentrations. Ammonia is a basic gas, and, as such, is believed to assist the decomposition of the various oxide groups on the surface- of the carbon material. Any other chemical entity which will generate NH 3 during pyrolysis should also prove sa'X?; factory as an NH^ source. For economic reasons, an H 3 /-.XO qcι.s stream is most preferred. The carbon materials treat d according to the procedure set forth above, when used in the catalytic oxidation of a hydroxydiphenylamine to the corresponding N- phenyl-benzoquinoneimine, demonstrates fast, efficient conversion reaction without the drawhacks associated with using the heavy metal catalysts of the prior art processes. The catalyst loading concentrati n of the present invention is generally about 0.5% to about 25.0 % (wt/wt hydroxydiphenylamine) . Preferably, about 10% (wt/wt hydroxydiphenylamine) catalyst is us d in the reactions according to the present invention. Various solvents may be uεi d in any of the reactions in accordance with the s nt invention. Examples of solvents which may be u:3«.d in the reactions according to the present invention include, but are not limited , to, alcohols such as cnethanol, ethanol, isσprσpanol, methyl isobutyl carbine] , i-ϊthylene glycol, etc.; ketones such as acetone and methyl isobutyl ketone, cyclohexanσne , 5-methyl-2-hexanone, ϋ- met hyl-3-heptanone; aliphatic and/or aromatic hydrocarbons such as alkanes, alkenes, toluene and xylene; nitriles such as acetonitrile; halogenated solvents such as chloroform, methylene chloride, and carbontetrachloride; and other solvents such as N-methylpyrrolidon , THF, ethylacetate , dimethylformamide, and dimethylsulfoxide, water, or any mixture of solvents would also be usable. The starting material, a hydroxydiphenylamine (HDA) , may be present at concentrations from about 1.0% to about 75.0%. The reaction may take place at varying temperatures in a range of from about 0°C to about 150 °C. Preferably, the reaction temperature is in a range of from about 20 α C to about 80 3 C. The reaction of the present invention takes place in an oxygen system. Oxygen pressure can be varied with an effective range being between atmospheric psig and 1500 psig. Preferably, the system is between 20 and 500 psig 0 2 . Most preferably, the system is between 15 and 100 psig 0 2 . The oxygen concentration can range from about 100% 0 2 to about 2% 0 2 (using nitrogen or air dilution) . After completion of the oxidation reaction, the catalyst is filtered off and the N-phenylquinoneimine is isolated in a conventional manner, using a solvent if appropriate. It is also possible to utilize a tertiary a ine to accelerate the rate of reaction in the process of the present invention. Tertiary amines usable in the present invention include, but are not limited to, trialkyl- and triaryl-amines. The addition of a tertiary amine will result in a basic pH for the reaction. Preferably the pH is about pH8 to about pH . The present invention can b more clearly illustrated by the following example; (s) - The modified activated carbon catalyst used in the ex mples was prepared in accordance with the procedure set forth above- Example 1 A mixture of 5.0 g of -hydroxydiphenylamine (4- HDA) , 0.5 g modified carbon catalyst and 200 L methanol was charged to an autoclave. The react i-on mixture was stirred and the autoclave, purged with oxygen, was then charged to 30 psig of oxygen at 20-25 'C. The reaction mixture was then heated to 50 n C and π?ι Lutained at 50 °C until the reaction was complete. A 3 the reaction progressed, the oxygen pressure dropped. When oxygen pressure dropped to about 20 psig, more oxygen was charged to bring the pressure back to 30 psig. The reaction time was counted from the moment oxygen was charged to the autoclave. The reaction progress was monitored by analyzing samples using HPLC. When vcj.-y little or no oxygen uptake was detectable and the HPLC analysis indicated disappearance of starting material 4- hydroxydiphenylamine, the product was filtered to separate the catalyst. The reaction took about l hour and the HPLC analysis of the mixture indicated !-.'.-.7 area % of the product N-phenyl-p-benzαquinoneimine .NPQT) - The product can be isolated in greater than 90 % yr^id. The product is brown solids with a melting point of 100 -103 'C. Various isolation techniqu F wtjll known in the art may be used to isolate the product according to the present invention including, but not limited to, crystallization, concentration and/or precipitation. The catalyst and solvent recovered from the reaction can be recycled and reused in subsequent reactions . Example 2 This example teaches the (.affect of using triethylamine to increase the rate of reaction. In accordance with procedure set forth in Example 1, a mixture of 5.0 g of 4-hydroxydiphf- j nylamine (4-HDA) , 0.5 g modified carbon catalyst, 1.5 g ti -i .•=-. • hylamine and 200 ml methanol was charged to an autoclave. The same procedure as described in Example 1 was employed. The reaction took 20 minutes and the H.?L analysis of the mixture indicated 98.6 area % • of the ptoduct N-phenyl-p- benzoquinoneimine (NPQI) . Again, various isolation tec.--π.i.q'-.es well known in the art may be used to isolate the product according to the present invention including, but not limited to, crystallization, concentration and/or precipitation. The catalyst and solvent recovered from the reaction can be recycled and reused in subsequent reactions. Exam le 3 In accordance with procedure: set forth in Example 1, 5.0 g of 4-hydroxydiphenylamint. (4-HDA) in 200 mL toluene and 0.5 g modified carbon cat.lyst were charged to an autoclave . The same procedure as d<-.s.-:ribed in Example 1 was employed. The reaction was cari-ied out to completion in less than 1,25 hrs and the catalys was separated from the product by simple filtration. HPLC analysis of the mixture indicated greater than 95 area "s of the product N- phenyl- -benzoguinoneimine - A comparison of the following two examples clearly indicate the advantages of criei.hylan.ine on the rate of reaction. Λ mixture of 5.0 g of 4-hydroxydiphenylamine (4- HDA) , 0.5 g modified carbon catalyst .and 200 L methanol was charged to an autoclave. The ..-auction mixture waβ stirred and the autoclave, purged with oxygen, was then charged to 30 psig of oxygen at 21 °c. The reaction mixture was then maintained at 21 °C unt:.l the reaction was complete. As the reaction progressed, t e oxygen pressure dropped. When oxygen pressure dropped to 20 psig, more oxygen was charged to bring the pressure back to 30 psig. The reaction time was counted from the moment oxygen was charged to the autoclave. The re-action progress was monitored by analyzing samples using EP C. The following table summarizes the results : Table 1 When very little or no oxygen uptake was detectable and the HPLC analysis indicated disappearance of starting material 4-hydroxydiphenylarri , the product was filtered to separate the catalyst- The ; -ϊPLC analysis of the mixture indicated 98.6 area % ■ of the" product N-phenyl- p-benzoquinoneimine (NPQI) . Again, various isolation techniques well known in the art may be used to isolate the product according to the present invention including, but not limited to, crystallization, concentration and/or recipitation. The catalyst and solvent recovered from the reaction can be recycled and reused in subsequent reactions . Example 5 In accordance with procedure: sot forth in Example 4, a mixture of 5.0 g of 4-hydroxydiphenylamine (4-HDA) 0.5 g modified carbon catalyst, 200 ni, me-thanol and 1.5 g triethylamine was charged to an autoclave. The reaction mixture was stirred and the autoclave, pui-ged with oxygen, was then charged to 30 psig of oxygen at 21 °C. The reaction mixture was then maintained tc. 21 °C until the reaction was complete. As the reaction progressed, the oxygen pressure dropped. When oxygen ressu e dropped to 20 psig, more oxygen was charged to bring he pressure back to 30 psig. The reaction time was counted from the moment oxygen was charged to the autoclave. The reaction progress was monitored by analyzing sample:- using HPLC- The following table summarizes the result s : Table 2 When very little or no oxygen uptake was detectable and the HPLC analysis indicated disappearance of starting material 4-hydroxydiphenylamine , the product was filtered to separate the catalyst. Iho .IPLC analysis of the mixture indicated 99.2 area % of h product N-phenyl- p-benzoquinoneimine (NPQI) . This clearly indicates that the rate of reaction in the presence of triethylamine is exfre ely faster in comparison to the one without it. The N-phenyl-benzoquinoneimines αf the present invention may be used as starting materials in the production of aminodiphenylamines . Para -aminodiphenylamines are used in the production of numerous rubber chemicals including antidegradants, gel inhibitors and polymerization inhibitors. Further, the N-phenyl-be:-..oquinoneimines also exhibit performance enhancement properties when used as rubber additives. The invention has been des ' -:r---bt.d with reference to the preferred embodiments- Obviou.-ly, modifications and alterations will occur to others' upon reading and understanding the preceding detailed description- It is intended that the invention be construed -is including all such modifications and alterations in ;3θ tar as they come within the scope of the appended claims or the equivalents thereof .

Claims: Claims : 1- A process for preparing an N-phenylquinoneimine (NPQI) comprising oxidizing a corresponding hydroxydiphenylamine (HDA) in the pres-ence of oxygen and a modified activated carbon catalyst, itn said catalyst 5 having been modified by having surface oxides removed therefrom. 2. The process of clai.n 1 wherein the hydroxydiphenylamine (HDA) is 4-hydro>:ydiphenylamine . 3. The process of claim 1. whr.reiii the HDA is initially dissolved and/or mixed in solvent. 4. The process of claim :-; wherein the solvent is an alcohol, ketone, aromatic/ liphatic hydrocarbon, nitrile, halogenated solvent, N-methyl yrrolidone, THF, ethylacetate, di ethyl ormamide, dim chylr.ulfoxide, water, S or mixtures thereof . 5. The process of claim -l wherein the alcohol solvent is selected from methanol, 'r-t.hanol, isopropanol, methyl isobutyl carbinol and ethylen. glycol. 6. The process of claim 1 wherein a tertiary amine is further added to the reaction - 7. The process of claim wherein the tertiary amine is triethylamine. θ- The process of claim 1 wherein the oxides are removed from the modified activated carbon catalyst surface by subjecting activated carbcn to an oxidizing agent and then pyrolizing the activated carbon in an oxygen free atmosphere at a temperature in the range of about 500°C to about 1500°C. 9. The process of claim :- wherein the oxides are removed from the activated carbon catalyst surface by simultaneously pyrolizing the activated carbon in the presence of NH 3 and an oxygen containing gas that reacts with the oxides on the surface of the activated carbon at pyrolizing temperatures of about 500"C to about 1500°C. 10. The process αf claim 1 whe:. ein the pressure of the oxygen in the reaction is from ...bout 20 psig to about 500 psig 0 a .

Inventors: FIELDS DONALD L JR, LODAYA JAYANT S, STERN MICHAEL K, FIELDS, DONALD, L., JR., LODAYA, JAYANT, S., STERN, MICHAEL, K.
Applicants: FLEXSYS AMERICA LP, FLEXSYS AMERICA L.P.
Application year: 1999
Main classification: C07C251
IPC codes: B01J27, C07B61, C07C249, C07C251