Salt reagent recycle

Of the removal processes that have attained commercial status, the current favorite employs a shiny of lime or limestone. The activity of the reagent is promoted by the addition of small amounts of carboxylic acids such as adipic acid. The gas and the shiny are contacted in a spray tower. The calcium salt is discarded. A process that employs aqueous sodium citrate, however, is suited for the recoveiy of elemental sulfur. The citrate solution is regenerated and recycled. (Kohl and Riesenfeld, Gas Purification, Gulf, 1985, p. 356.)... 

Primary waste generation is small because of the high density nature of the fused salt operations. Nearly all primary waste residues show excellent potential for recycle. (The present main processing sequence for plutonium does not include significant reagent and residue recycle). 

Process Schematic. The final installation in our main production sequence will be the recycle of reagent salts. There are quite a number of options involved in recycling reagents from nearly every operation. Figure 12 shows the process schematic where the three major salt recycle steps are highlighted by heavy lines. 

The goal in any salt recycle system is to keep the system as simple as possible and to use compatible reagents for each of the steps processing, recovery, and reprocessing. In evaluating potential recycle schemes, these two considerations will play an important role. 

The need for optically pure materials for pharmaceuticals, agrochemicals, aroma chemicals, etc. has been emphasized (see Sections 2.8.8 and 4.5.8). Diastereisomeric salt formation is commonly employed, but this method is expensive as it involves the use of chirally pure reagents. It is also inefficient, since the unwanted isomer cannot be readily recycled. (Davey, 1994). 

As reagents causing intramolecular recyclizations of 2-benzopyrylium salts, nucleophiles centered at nitrogen, oxygen, sulfur, or carbon atoms were used. As a fairly general rule, the ring opening of the heterocyclic moiety leads to an orf/io-quinonoid structure, as shown in more detail in Section III,C,4,iv (Structure 201). 

Heating anhydrobases 212 without any external reagent at elevated temperature gives rise to a-naphthols 104 (86KGS276). Therefore, a real isomeric recyclization of 2-benzopyryIium salts (cf. Section III,C,4,a,ii) may occur and is carried out in two steps, with the last one requiring severe conditions. 

The Anelli oxidation of alcohols to aldehydes and ketones has been accomplished using polymer-supported nitroxyl radical catalysts. The practicality of removing polymer-supported reagents by filtration to simplify product purification is highlighted by these examples. Bolm and coworkers11 demonstrated that a silica-supported nitroxyl catalyst is easily filtrated after use from the reaction solution, recovered and recycled, and the residual inorganic salts present in the reaction mixture are separated from the organic product by aqueous extraction (Table II, entry 7). 

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