Acetals selective etherification

Major and trace levels of metal initiators or catalysts can be present, such as Al, Ti, Fe, V, Cr, Fe, Cu, Ca, Zr, B, K, Na, Li and others which originate from organometallic salts. Catalysts may also include oxides and acetals that coordinate with such metals as Co, Zn, P, Pb, Co, Mn, Ge and Sb. Some of these metal salts can be used in the trans-etherification or polymerisation reactions to manufacture a range of polymers, e.g. metal acetals. Catalysts also play an important role in the selective PET polymerisation reactions. 

The catalyst can be recycled for 5 times without any loss of activity and selectivity. Apart from the ether or acetal production from bio-based carbohydrates, a strong interest has also been devoted to the etherification of glycerol, and in that context, the use of an acidic heterogeneous catalyst has proved to be successful. In particular, tertiobutanol/glycerol mixtures are transformed into the mono and diethers using Amberlyst-15 as well as H-Y and H-BETA large porous zeolites, the latter catalyst beeing... 

Another important optimization factor is the development of selective catalysts for the glycosidation process so that for example the formation of polydextrose and etherification reactions can be suppressed. As already mentioned, acetalization or transacetalization in the Fischer synthesis is catalyzed by acids. In principle, any acids with sufficient strength are suitable for this purpose, such as sulfuric acid, paratoluene- and alkylbenzene sulfonic acid, and sulfosuccinic acid. The reaction rate depends on the acidity and the concentration of the acid in the alcohol. 

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