Methylamine Leonard

Leonard A process for making mixed methylamines by reacting ammonia with methanol over a silica-alumina catalyst at elevated temperature and pressure. Developed and licensed by the Leonard Process Company. In 1993, the installed worldwide capacity of this process was 270,000 tonnes/y. 

Mitsubishi Rayon (formerly Nitto Chemical) has operated a process since 1984 in which the equilibrium of methylamine formation is shifted to make more dimethylamine by use of an acid zeolite catalyst with a particular pore structure. The product stream contains 7 mol% MMA, 86 mol% DMA and 7 mol% TMA, and its investment as well as its operating costs are lower than the conventional Leonard process that is used by most companies. Since DMA has the highest sales volume, the process might be appealing246. 

The conversion of methanol and ammonia to methylamines is achieved over dehydration catalysts operated in the temperature range 300450°C and 0.12 MPa pressure. The reactions are exothermic, and excess ammonia is used to control the product distribution. The dehydration catalysts are generally promoted Si-Al composites. The promoters include molybdenum sulfide and silver phosphate [68]. In the commercial Leonard process, a gas-phase downflow catalytic reactor operating at about 350°C and 0.62 MPa is used [69]. Recovery of the desired product is achieved throu a series of four distillation and extractive distillation columns. Unwanted product is recycled, suppressing further formation of the undesired component in the reactor. A very small amount of methanol is lost to CO and H2, and yields from the commercial process based on methanol and anunonia are >97% [70]. 

Fig. 28.23. Leonard Process Co, process for methylamines. (Hydrocarbon Processing, Petrochemical Handbook, p. 114, Nov. 1383, Copyright 1983 by Guff Publishing Company and used by permission of the copyright...

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