Published February 1991
Methylamines are produced conventionally by reacting gaseous methanol and ammonia in the presence of a catalyst such as silica-alumina. The reaction products have the thermodynamic equilibrium composition of monomethylamine, dimethylamine, and trimethylamine. To produce a product mix different from the equilibrium composition, unwanted methylamines recovered downstream must be recycled to the reaction to suppress their formation.
Nitto Chemical (Japan) has developed a process that can produce a non-equilibrium product mix having a high dimethylamine content, e.g., 86% dimethylamine and 7% each of mono- and trimethylamines. The process is based on zeolite-type catalysts. A commercial methylamines plant based on it has been in operation since 1984.
A conventional process to produce a product mix consisting of 34wt% monomethylamine, 46wt% dimethylamine, and 20wt% trimethylamine would require a total fixed capital about 14%higher and a product value about 7% higher than that of the Nitto Chemical process. To produce a product mix similar to the one prescribed for the Nitto Chemical process, the conventional process would be even more costly, because larger portions of the monomethylamine and trimethylamine product streams must be recycled to the reactor to suppress the formation of these two methylamines.