Amines and Nitrogen-Containing Intermediates

Aliphatic amines are classified in primary amines (RNH2), secondary amines (R2NH), and tertiary amines (R3N), with R representing in this very general scheme an alkyl chain of any length and further functionalization. Technically interesting classes of amines are short hain alkyl amines (primary, secondary, and tertiary), fatty amines, di- and polyamines, as well as aromatic amines. Table 5.3.8 highlights 

N H 2 hexamethylene diisocyanate, urethanes isocyanates, antioxidants, dyes, agrochemicals, pharmaceuticals 

Methylamine, dimethylamine and trimethylamine are produced by reaction of methanol vith ammonia [route (a) in Topic 5.3.4]. The reaction proceeds as a continuous gas-phase catalysis using form-selective, acidic silicon/aluminum oxides (mordenite, chabasite) as catalyst contacts. This catalyst choice favors formation of the most desired product dimethylamine ( 10% trimethylamine) in contrast to the earlier applied amorphous silicon/aluminum oxide contacts. The reactor temperature is kept betv een 250 and 300 °C and the reaction pressure is betv een 10 and 30 bar. 

The production of tert-hutylamine is interesting for the fact that this amine has been used to demonstrate the technical potential of hydroamination in commercial amine production [route (b) in Topic 5.3.4]. BASF introduced in the early 1990s the first process that operates vith a zeolite catalyst and converts isobutene directly with ammonia. The reaction is carried out by contacting the supercritical reaction mixture with the catalyst at temperatures between 250 and 300 °C and at pressures between 200 and 350 bar. Under equilibrium conversion conditions tert-butylamine forms in 95% selectivity. 

Fatty amines are manufactured industrially in most cases by hydrogenation of the fatty acid nitriles [route (c) in Topic 5.3.4]. The latter are formed before by reaction of fatty acids with ammonia in a catalytic dehydratization reaction. The fatty nitrile hydrogenation is preferentially carried out as a liquid-phase reaction using nickel or cobalt contacts as heterogeneous catalysts. 

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