Selective with methyldiethanolamine

When methyldiethanolamine is reacted with 1 mol of fatty acid, a mixture of di- and monoesteramine together with methyldiethanolamine is the reaction product [9]. The monoesteramine cannot be prepared selectively via this route as the reactivity of methyldiethanolamine and the monoesteramine is roughly the same, and thus statistic reaction mixtures are obtained. 

Lee et al. (1990) studied the PV of EtOH-water mixtures by cationic-anionic interpenetrating polymer network (IPN) membranes. The cationic PU prepared by quaternizing the tertiary amine from A -methyldiethanolamine and the anionic acrylic copolymer from acrylic acid were used as the cationic and anionic components. The separation factor increased as the content of the anionic component in the membrane increased. The ion content in the membrane was also found to be an important factor for the optimum permseparation of water. Better performance was achieved by PEG-based PU as the cationic component of the IPN membrane. The highest selectivity was observed for the IPN membrane with 10 wt% of PEG-based PU. 

There are a number of cases of industrial gas cleanups where two (A and B) or more gases are being simultaneously absorbed in the Uquid. The nature of mass transport, and therefore separation, will depend on how ficist each species reacts with the nonvolatile reactive species C (often the species C has some volatility, e.g. monoetha-nolamine). Each of gas species A and B can either react slowly or have a fast or instantaneous reaction with C. Thus, there can be a number of combinations, many of which are treated in Astarita et al. (1983). We consider here a particular case of considerable industrial importance, namely simultaneous absorption of H2S and CO2 into a reactive aqueous solution containing, say, methyldiethanolamine (MDEA). We want to show how the different rates of absorption lead to a high selectivity of H2S over CO2. The specific reactions are (Haimour et al, 1987)... 

Use of an aqueous methyldiethanolamine (MDEA) solution as a selective solvent (see Chapter 2) for hydrogen sulfide removal in tail gas cleanup has been described by Meissner (1983). With this solvent an overall conversion, including the Claus unit, of 99.9% of the H2S fed to the Claus unit is attainable. However, the treated gas contains some residual H2S, which may require incineration before discharge to the atmosphere. 

The Sulfinol solvent consists of sulfolane (tetrahydrothiophene dioxide) and an alkanolamine, usually diisopropanolamine (DIPA) or methyldiethanolamine (MDEA), and water. The solvent with DIPA is referred to as Sulfinol-D or simply as Sulfinol, and the solvent with MDEA is referred to as Sulfinol-M. Typically, Sulfinol-D is used when essentially complete removal of both hydrogen sulfide and carbon dioxide and deep removal of carbonyl sulfide is desired. Sulllnol-M is used for the selective removal of hydrogen sulfide over carbon dioxide and the partial removal of carbonyl sulfide (Nasir, 1990). Both Sulfinol solvents are reported to be capable of removing mercaptans and alkyl sulfides to very low levels. 

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