Furfural solvent action

Early methods of separation employed such solvents as oleic acid/ crude coal-tar solvent naphtha, light pyridine,5 etc. Based on the selective solution of phenanthrene by the coal-tar naphtha, and of carbazole liy the light pyridine, Clark proposed a complicated scheme for the separation and recovery of all three of these constituents. Recently, organic liquid compounds containing the furan nucleus have been found to have a highly selective solvent action on phenanthrene and carbazole." Thns, furfural while dissolving phenanthrene and carbazole does not have a marked solvent action on anthracene at low temperatures. However, at elevated temperatures it does dissolve anthracene with the result that it is possible... 

Furans are volatile, fairly stable compounds with pleasant odours. Furan itself is slightly soluble in water. It is readily available, and its commercial importance is mainly due to its role as the precursor of the very widely used solvent tetrahydrofuran (THF). Furan is produced by the gas-phase decarbonylation of furfural (2-formylfuran, furan-2-carboxaldehyde), which in turn is prepared in very large quantities by the action of acids on vegetable residues mainly from the manufacture of porridge oats and cornflakes. Furfural was first prepared in this way as far back as 1831 and its name is derived from furfur which is the latin word for bran in due course, in 1870, the word furan was coined from the same root. 

Among the various derivatives of biomass, furan compounds obtained from furfural are important (200 000 t year ). A new family of furan diethers has been obtained by alkylation of 2,5-furandimethanol or furfuryl alcohol under the action of microwave irradiation with PTC solvent-free conditions (Scheme 10.79) [154]. Reaction times were improved by use of microwave irradiation, and the same conditions were extrapolated to the synthesis of a series of new furan diethers by alkylation of furfuryl alcohol by dihalides. 1,4-Diketones substituted by furans or thiophenes were synthesized by conjugate addition of aldehydes to a,j8-unsaturated ketones by irradiation without solvent in the presence of thiazolium halides and DBU adsorbed on alumina [155]. 

N-methyl-2-pyrrolidone, a solvent used as an alternate to furfural and phenol for the extraction of lubricating oil fi-actions. 

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