Furfural, intermediate extraction

The most import uni cyclic ethers arc (he furan compounds Furfural is manufactured by treating pentosan with sulfuric acid and steam stripping mil the furfural a n is formed The sources of pentosan arc such agricultural products uv comet tbs. oat hulls, and hagavtc Furfural is used to produce furan and tetrahydro furan fTHF) These products are used as organic intermediates, extraction solvent, polymer solvents, and in polyurethane applications... 

The concept of extractive reaction, which was conceived over 40 years ago, has connections with acid hydrolysis of pentosans in an aqueous medium to give furfural, which readily polymerizes in the presence of an acid. The use of a water-immiscible solvent, such as tetralin allows the labile furfural to be extracted and thus prevents polymerization, increases the yield, and improves the recovery procedures. In the recent past an interesting and useful method has been suggested by Rivalier et al. (1995) for acid-catalysed dehydration of hexoses to 5-hydroxy methyl furfural. Here, a new solid-liquid-liquid extractor reactor has been suggested with zeolites in protonic form like H-Y-faujasite, H-mordenite, H-beta, and H-ZSM-5, in suspension in the aqueous phase and with simultaneous extraction of the intermediate product with a solvent, like methyl Aobutyl ketone, circulating countercurrently. 

Furfural is obtained commercially by mealing pentosan-rich ugricullural residues (corncobs, oat hulls, cottonseed hulls, hagasse. rice hulls) with a dilute acid and removing the furfural by steam distillation. Major industrial uses of furfuraldehyde include (1) the production of t urnns and tetrahydrofurans where the compound is an intermediate (2) Ihc solvent refining of petroleum and rosin products (3) the solvent binding of bonded phenolic products and (4) the extractive distillation of butadiene from other C4 hydrocarbons. 

Reactive extraction uses liquid ion exchangers that promote a selective reaction or separation. The solutes are very often ionic species (metal ions or organic/inorganic acids) or intermediates (furfural phenols, etc.), and the extraction chemistry is discussed elsewhere (11-13). Reactive extraction can be used for separation/ purification or enrichment or conversion of salts (14). A 2001 review on reactive phase equilibria, kinetics, and mass transfer and apparative techniques is given in Ref. 8. Reactive extraction equipment is discussed in detail in Ref. 15, and recent advances are given in Ref. 16. 

Fig. 25. In situ extraction of intermediate furfural (desirable product) by means of hydrocarbon solvent (tetralin).

QO Furfural. [QOCheitL] 2-Furalde-hyde chemical intermediate solvent used in petrol, luimcating oil, gas oil, and diesel fuel extractive distillatitm of... 

It is used also as a secondary decolorizing agent for crude wood rosin and a selective solvent for extraction and crystallization of anthracene from crude anthracene oils. Furfural is used as an intermediate in pharmaceutical, herbicide, fragrance and flavoring applications. 

The oxidation proceeds by the two-step catalytic process indicated above, without the isolation of the intermediate acrolein. Acrylic acid, obtained in high yield based on propylene, is isolated as an aqueous solution and purified by extraction and distillation. The principal impurities in the commercial monomer, termed glacial acrylic acid, that may affect subsequent polymerization reactions include acetaldehyde, acrolein, furfural, benzaldehyde, and acrylic acid dimer, 3-acryloxypropionic acid. Since these impurities are inhibitory in polymerization. 

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