Furfuryl alcohol, produced by Silvateam, is a clear colorless organic liquid when pure, but becomes amber upon prolonged exposure to light and air. Furfuryl alcohol, produced in Argentina, is produced using a catalytic hydrogenation process at high pressure, starting from furfural. Furfuryl alcohol has a purity of 98.5%. Furfuryl alcohol reacts with formaldehyde and leads to the formation of resinous condensation products that are widely used in the production of thermosetting resins and is particularly resistant to chemicals and solvents. It is also used for:
Manufacture of foundry resins, characterized by low viscosity, good mechanical strength at metal melting temperature and low gas emission. Production of corrosion resistant resins with a very competitive price. Production of abrasive wheels and adhesives based on urea-formaldehyde resin due to its wetting - dispersant properties. Production of tetrahydrofurfuryl alcohol (THFA) used as a solvent in the pharmaceutical industry. Furfuryl alcohol is delivered by tank trucks, in 240kg steel drums, in 1,000kg tanks and in tank container holding 21 to 23t each and by tanker (300 ~ 400t). The packaging used is made of steel and in an inert nitrogen gas atmosphere (N2), oxygen-free to prevent oxidation during transportation.
Chemistry and Resinification of Furan Resins
Furfuryl alcohol-based resins are the most important industrial furan resins in terms of usage and volume. The final cross-linked products exhibit outstanding properties and characteristics. Furfural replaces formaldehyde in the conventional production of phenolic resins. It reacts easily with phenol in the presence of an alkaline catalyst to form a novolac phenol-furfural resin. (Novolac phenolic resin requires an acid catalyst.) Furfuryl alcohol readily resinifies or homopolymerizes in the presence of an acid catalyst [such as mineral acids, organic acids, Lewis acids, and acyl halides] to produce liquid linear chains (oligomers). These chains consist primarily of dimers and trimers that have methylene linkages between the furan rings.
The process essentially is a methylolation involving the condensation of the methylol group of one furfuryl alcohol molecule with another molecule at the fifth position. The furfuryl alcohol resinification process is highly exothermic; the necessary temperature control is accomplished by cooling via either reflux or an external cooling fluid. The process is carried to a predetermined viscosity end point, and the reaction is stopped by adjusting the pH to between 5 and 8. The resulting liquid resin has a shelf life of more than 6 months. Furfuryl alcohol also undergoes copolymerization with aldehydes such as formaldehyde and furfural, and with phenols and urea in the presence of an aldehyde.
Achmatowicz oxidative rearrangement of furfuryl alcohols 52 in planetray ball mill provided 6-hydroxy-2H-pyrane-3(6H)-ones 53, via mechanism starting with transient furan epoxide formation by Prilezhaev reaction. K?nig et al. established that mCPBA was the most efficient among variety of oxidants, when added in excess. Quartz sand was employed as solid support and reactants milled in planetary mill in agate beaker and balls for 15–30 min to achieve high reaction yields. The conditions for the solid starting material 52d were modified, and simultaneous use of choline chloride and quartz sand reached 63% yield. Upon the commencement of the grinding, the reaction mixtures were simply diluted with water and filtered, thus entirely organic solvent-free synthesis was achieved. For comparison, the best yield obtained by mCPBA reaction with furfuryl alcohol in classical solvent reactions was 88%.
The two intermediates of commercial furan resins are furfural and furfuryl alcohol. Furfural occurs in the free state in many plants but is obtained commercially by degradation of hemicellulose constituents present in these plants. There are a number of cheap sources of furfural, and theoretical yields of over 20% (on a dry basis) may be obtained from both corn cobs and oat husks. In practice yields of slightly more than half these theoretical figures may be obtained. In the USA furfural is produced in large quantities by digestion of corn cobs with steam and sulphuric acid. The furfural is removed by steam distillation.
Furfural is a colourless liquid which darkens in air and has a boiling point of 161.7°C at atmospheric pressure. Its principal uses are as a selective solvent used in such operations as the purification of wood resin and in the extraction of butadiene from other refinery gases. It is also used in the manufacture of phenol-furfural resins and as a raw material for the nylons. The material will resinify in the presence of acids but the product has little commercial value. Catalytic hydrogenation of furfural in the presence of copper chromite leads to furfuryl alcohol, the major intermediate of the furan resins.
