Organic compounds -- part of the class 532-570 series – Organic compounds – Amino nitrogen containing
Patent
1998-01-06
2000-05-30
Dunn, Tom
Organic compounds -- part of the class 532-570 series
Organic compounds
Amino nitrogen containing
502 62, 502 63, 502 64, 502 85, 502 78, C07C20900
Patent
active
060692804
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for the preparation of a modified ammonium mordenite, and in particular to a catalyst comprising this modified ammonium mordenite prepared by said process, as well as to a process for the manufacture of methylamines by reaction of methanol with ammonia in the gas phase at elevated temperature, and optionally at elevated pressure, in which said catalyst is used.
In the catalytic synthesis of methylamines from ammonia and methanol, a vaporized mixture of methanol and ammonia is first prepared, which is next reacted in a reactor at temperatures of approximately 220 to approximately 500.degree. C. at pressures between atmospheric pressure and approximately 50 bars, by passing over a catalyst bed.
The product of the reaction between ammonia and methanol consists of a mixture of three amines, monomethylamine (abbreviated to MMA), dimethylamine (abbreviated to DMA), trimethylamine (abbreviated to TMA), water, ammonia and unreacted methanol. In addition, dimethyl ether (abbreviated to DME) may be formed as by-product. Among these products, dimethylamine is the amine most sought after as far as industry is concerned; it is actually used, as raw material for the manufacture of many commercial products such as solvents, pharmaceutical products, vulcanization accelerators, surfactants, fungicides (for example tetramethylthiuram disulphide) and the like. The production of dimethylamine from ammonia and methanol necessarily involves a step of separation of the products obtained after the reaction. However, isolation of dimethylamine by distillation from the mixture of methylamines is considerably complicated by the fact that residual ammonia and the methylamines produced form azeotropic mixtures.
At the present time, methylamines are manufactured on an industrial scale from methanol and ammonia, using in most cases amorphous silica-alumina catalysts, because these catalysts have outstanding catalytic properties.
However, the mixture of methylamines obtained in the presence of these catalysts contains a major proportion of trimethylamine and, consequently, the production of the desired dimethylamine is insufficient.
This is why many investigations have been carried out in order to find catalysts which allow to obtain dimethylamine selectively while suppressing the production of trimethylamine as much as possible. The quantities of the various methylamines in the reaction product are determined by the thermodynamic equilibrium of the reaction; these quantities depend, among other parameters, on the reaction temperature and on the molar ratio of the reactants. For example, in the case of a reaction temperature of 300.degree. C., an ammonia and methanol feed corresponding to an N/C atomic ratio of 2:1 and a methanol feed rate of 0.3 kg/h/kg of catalyst, the composition, in % by weight, of the mixture of methylamines at equilibrium is 20% MMA, 22.5% DMA and 57.5% TMA for an active but nonselective catalyst, when total conversion of methanol is achieved. This product composition corresponds to the thermodynamic equilibrium composition. Trimethylamine is thus produced predominantly under these conditions.
On the other hand, if the production of trimethylamine were suppressed, the composition in% by weight of the mixture of MMA and DMA at equilibrium would be 31.5% MMA and 68.5% DMA under the same conditions and when total conversion of methanol is achieved.
One can immediately see the interest in developping selective catalysts which prevent almost completely the production of trimethylamine.
A large number of catalysts have been proposed in order to reach this objective. The literature mentions, in particular, synthetic or natural zeolites like, for example, zeolites X, Y, ZK-5, ZSM-5, ZSM-12, FU-1, SK, erionite, ferrierite, faujasite, chabasite, clinoptilolite and more particularly mordenite. These zeolites have been used either as such or after having been subjected to various treatments in order to modify their characteristics, such as the number of acidic sites, the pore size or
REFERENCES:
patent: 5137854 (1992-08-01), Segawa et al.
patent: 5382696 (1995-01-01), Kiyoura et al.
Passelcq Jean
Van Gysel August
Dunn Tom
UCB S.A.
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