a Per cent primary and secondary amines calculated as monoethylaniline. Alkylation with Amines. During the course of some later investigations, in which it was attempted to identify the various by-products formed in the methylation of aniline to give dimethylaniline, traces of diphenylamine were found. This led to the discovery that diphenylamine may be produced from aniline in appreciable amounts at temperatures from 360°to 500°C ., with optimum temperatures of 440°to 460°C. ( 5). This reaction has been reported recently by other investigators (7). In the present work it was found that other aryl amines responded to this type of reaction, considered to be alkylation with amines.Among them were o-toluidine, p-toludine, (3-naphthylamine, and 2-aminopyridine, giving the corresponding diarylamines-di-otolylamine, di-p-tolylamine, di-^-naphthylamine, and 2,2'-dipyridylamine. It is planned to present more of the related findings in a later paper.
CONCLUSIONSThe following conclusions may be drawn with regard to the catalytic vapor phase alkylation of aniline with alcohols.Supported aluminum oxide was found to be the most efficient catalyst for nitrogen alkylation. Other metal oxides, aluminum salts, and phosphoric acid were either less active or caused excessive nuclear alkylation.There are an optimum space velocity and an optimum temperature for maximum tertiary amine formation. Products containing at least 90% tertiary amine are obtainable from methanol and aniline, o-toluidine, or p-toluidine. With higher alcohols, nitrogen alkylation becomes more difficult and rearrangement to nuclear alkylated products occurs more readily. A more active, or more selective, catalyst than those investigated here, probably to be used at lower temperatures, would be needed to permit the preparation of AjiV-dimethylaniline in a reasonably high degree of purity.
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