Patent GB-802036-A (GB)
Title: Improvements in aromatic amines
Inventor: DENT WALTER THEODORE
IPC: C07C215/76
Filed: 1956-07-13
Abstract: Oxidation, peroxidation and/or polymerization of petrol is reduced by the addition of at least one aromatic amine of the formula I, where X is hydroxyl <FORM:0802036/III/1> or NHR1, where R1 and R2 are hydrocarbon radicals and where R3 is hydrogen or a hydrocarbon radical and at least one aliphatic aldehyde having an a b  double bond, the aldehyde being present to the extent of not more than 5 per cent by weight of the aromatic amine.  The aromatic amines I are treated to reduce the content of any primary amine impurity to less than 10 per cent, preferably less than 1 per cent, and not more than 5 per cent, preferably not more than 1 per cent of an a b unsaturated aliphatic aldehyde is then added to the amine. These steps may be carried out by distillation followed by the addition of aldehyde or by N-alkylation of the primary amine with a primary or secondary alcohol in the presence of a hydrogenation catalyst followed by the addition of aldehyde; if a primary alcohol is used the a b  unsaturated aldehyde may be formed in situ (see Group IV (b)).  Typical amines of formula I are N-n-butyl-p-aminophenol, 4-isopropyl-aminodiphenylamine, N : N1 - di - sec - butyl - p-phenylenediamine and N : N-dimethyl-N1-di-sec - butyl - p - phenylenediamine. Typical aldehydes are those containing at least one hydrogen on the b  carbon atom and up to eight carbon atoms in the molecule such as acrolein, a -methyl-acrolein and crotonaldehyde. The examples describe the colour stabilization of N : N1 - di - sec - butyl - p - phenylenediamine which may contain N-sec-butyl-p-phenylenediamine as impurity.  The antioxidant is added to olefine-free petrol and the colour and optical density at 470 mm is given.  In examples: (2) an antioxidant containing 0.7 per cent impurity is added 0.1 gm. to 100 mls. of petrol and is stabilized before addition by distillation followed by addition of crotonaldehyde or crotonized nonaldehyde; (2) an antioxidant containing 0.5 per cent impurity is distilled and 5 samples prepared, some containing crotonaldehyde and some being distilled again after addition of the aldehyde.  The antioxidant is added to petrol at a concentration of 70 mgs./l.; (3) using a sample of antioxidant similar to that used in (2) obtained on a plant scale, several runs are described to find the effect of varying the order of distillation and aldehyde addition, results are given using 70 mg./l. of petrol which is equivalent to 25 lbs. per 1000 U.S. barrels; (4) compares a freshly prepared sample of antioxidant in petrol with one that had been stored for 12 months; (5) describes the stabilization of an antioxidant by heating with various alcohols and hydrogenating catalysts and the various samples are then dissolved in petrol to the extent of 0.1 per cent.ALSO:Aromatic amines of the general formula I <FORM:0802036/IV (b)/1> where X is -OH or -NHR1 and R1 and R2 are hydrocarbon radicals and R3 is hydrogen or a hydrocarbon radical, and which contain as an impurity at least one aromatic compound having a primary amine group, are colour stabilized by reducing the content of the primary amine impurity to less than 1 per cent by weight and adding not more than 5 per cent by weight, preferably not more than 1 per cent, of an aliphatic aldehyde containing an a b  double bond. The invention also includes (a) compositions comprising at least one aromatic amine of the general formula I and at least one unsaturated aldehyde, (b) compositions comprising (a) associated with a primary amine impurity, and (c) compositions comprising an organic material liable to oxidation, peroxidation and/or polymerization, e.g. petrol and an antioxidant composition such as (a) or (b).  Typical amines of the formula I are those where R2 is alkyl or aralkyl such as N-n-butyl-p-aminophenol and 4-isopropylamino-diphenylamine, where R1 and R2 are alkyl such as N : N1-di-isopropyl-p-phenylenediamine and N : N1-di-sec.-butyl-p-phenylenediamine and where R1, R2 and R3 are alkyl such as N : N-dimethyl-N1-sec.-butyl-p-phenylenediamine.  The preferred aldehydes are those containing up to eight carbon atoms and having at least one hydrogen attached to the b  carbon atom and acrolein, a -methyl-acrolein and crotonaldehyde are mentioned.  N : N1-di-sec.-butyl-p-phenylenediamine may be used as an antioxidant in petrol and when prepared by reductive alkylation of p-nitrianiline, is known to contain N-sec.-butyl-p-phenylenediamine, p-phenylenediamine and p-nitroaniline as impurity.  The mono-alkylated diamine, even when present in small amounts, is found to increase the colour instability of the dialkylated diamine and its concentration may be reduced by a fractional distillation in which case the distillation is preferably carried out before addition of the olefinic aldehyde.  The concentration of the primary amine may also be reduced by heating the impure product with a primary or secondary alcohol and a metal catalyst capable of dehydrogenating the alcohol to the corresponding aldehyde or ketone and capable of hydrogenating the resulting Schiffs base, formed from the primary amine and the aldehyde or ketone, to give an alkylated secondary amine.  Preferably the alcohol used is a primary alcohol of the general formula RCH2CH2OH so that the resulting aldehyde RCH2CHO is crotonized under the reaction conditions to form in situ the desired olefinic aldehyde RCH2CH=CRCHO. Raney nickel and foraminate nickel are found to be suitable catalysts for this reaction.  In the examples: (1), (2), (3), (4) N : N1-di-sec.-butyl-p-phenylenediamine containing N-sec.-butyl-p-phenylene-diamine as impurity is colour stabilized by the distillation and addition of aldehyde method.  The antioxidant is added to olefinicfree petrol under various conditions and the results are tabulated to give the optical density and colour after various exposures.  (5) describes the stabilization of the same compound by refluxing with various alkanols and catalysts and the results of 17 runs are tabulated as before.