Furfural source

Cottonseed Hulls. Hulls are used as roughage in animal feed and as mulch and soil conditioner. Additional uses for cottonseed hulls include fuel, insulation, and a xylose and furfural source. Raffinose derived from cottonseed hulls is used in culture media (50). 

Manufacture. Furfural is produced from aimually renewable agricultural sources such as nonfood residues of food crops and wood wastes. 

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 com 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 com cobs with steam and sulphuric acid. The furfural is removed by steam distillation. 

JR Schwier, GG Cooke, KJ Hartauer, LYu. Rayon a source of furfural—a reactive aldehyde capable of in-solubilizing gelatin capsules. Pharm Technol 17(5) 78-79, 1993. 

Although highly reactive, 2/7-azirines are of considerable synthetic interest and serve as a source of the 3-fluoro-4//-l, 3-diazepines 86. Reaction of 80 with difluorocarbene in the presence of furfural gave 86, rather than the expected furfural-derived products 83. Rearrangement of the initial 1,3-dipolar intermediate 81 to 84 and then cycloaddition of 84 with 80 are proposed as key steps in the reaction the intermediate cycloadduct 85 gave 86 on base-induced elimination of HF. Nucleophilic displacement of the fluoro group in 86 provided access to further substituted 1,3-diazepines <06TL639>. 

Pure xylan is not employed in industry. but crude xylan or pentosans are of industrial importance. Xylan has been proposed as a textile size but is not employed as yet for this purpose.130 Perhaps the largest use of pentosans is in their conversion to furfural, which has many applications and serves as the source of other furan derivatives. At the present time, large quantities of furfural are used in the extractive purification of petroleum products, and recently a large plant has been constructed to convert furfural by a series of reactions to adipic acid and hexamethylene-diamine, basic ingredients in the synthesis of nylon. In commercial furfural manufacture, rough ground corn cobs are subjected to steam distillation in the presence of hydrochloric acid. As mentioned above, direct preferential hydrolysis of the pentosan in cobs or other pentosan-bearing products could be used for the commercial manufacture of D-xylose. 

Recent work on the synthesis, structure and some properties of macromolecules bearing furan rings is discussed. Two basic sources of monomers are considered, viz. furfural for monomers apt to undergo chain polymerization and hydroxymethylfurfural for monomers suitable for step polymerization.Within the first context, free radical, catiomc and anionic systems are reviewed and the peculiarities arising from the presence of furan moieties in the monomer and/or the polymer examined in detail. As for the second context, the polymers considered are polyesters, polyethers, polyamides and polyurethanes. Finally, the chemical modification of aU these oligomers, polymers and copolymers is envisaged on the basis of the unique reactivity of the furan heterocycle. 

The MCR toward 2//-2-imidazolines (65) has found apphcation in the construction of A(-heterocyclic carbene (NHC) complexes (74). Alkylation of the sp Af-atom with an alkyl halide followed by abstraction of the proton at C2 with a strong base (NaH, KOtBu) resulted in the formation of the free carbene species, which could be trapped and isolated as the corresponding metal complexes (Ir or Rh) [160]. The corresponding Ru-complexes were shown to be active and selective catalysts for the transfer hydrogenaticm of furfural to furfurol using iPrOH as hydrogen source [161]. 

Bagasse in admixture with molasses has also been suggested as a cattle food. Bagasse, because of its pentosan content, may also be used as a source of furfural. - ... 

Scheme 6 Fructose can be transformed into 5-hydroxymethyl furfural (HMF) via acid-catalyzed dehydration. Solid acid catalysts applied to facilitate the reaction are zeolites, ion-exchange resins and solid inorganic phosphates. With sporadic success, notably with inorganic phosphates, other carbohydrate sources such as inulin can also be transformed into HMF.

Furfural is such a reactive, volatile, and water-soluble compound that its loss could be due to several causes. Oxidation and volatilization from eluates, especially from the column effluent, are the most likely sources of loss. Humic acid seemed to affect the recovery of only two solutes caffeine and 2,4-dichlorophenol. 

Furan-2-carbaldehyde (furfural) is widely used in the vegetable oil, plastics, rubber and petroleum industries as well as being a versatile starting material for furan syntheses. It is the major source of commercial furans. It is used to extract unsaturated hydrocarbons from hydrocarbon mixtures, a process important in the purification of petroleum and vegetable oils. The chemistry of furfural has been extensively studied because of its industrial importance and availability. 

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 major soluble components of acid hydrolysates are sugars, such as xylose, glucose, and cellobiose furfurals, such as furfuraldehyde and hydroxymethyl furfural and organic acids, such as levulinic acid, formic acid, and acetic acid (13). When natural sources of cellulose are acid-hydrolized, numerous products can result, largely because of the hemicellulose materials. These make it difficult to produce a relatively pure sugar product and limit the utility of the acid hydrolysis process. 

Hot Pressing of Felted Mats. An experiment intended to identify which of thetwo mechanisms is operative was designed and executed. The approach taken was based on the argument that each mechanism requires certain cell wall components be present and that removal of all or most of the component will be detrimental to wet-strength development. The phenol-furfural condensation mechanism requires hemicellulose as a source of furfural. The thermoplasticity of lignin mechanism requires lignin. Consequently, three pulps were prepared containing ... 

It is concluded that all of the results presented above discredit the phenol-furfural condensation mechanism and that the source of wet strength in hardboards is thermoplastic-fusion of lignin concentrated on the surfaces of the fibers. 

Wood is the source of a large number of chemicals and pharmaceuticals, and a number of lower-volume chemicals can be obtained from wood hydrolysis (Fig. 2). Furfural is formed from the hydrolysis of some polysaccharides to pentoses, followed by dehydration. 

Another predominant furan, namely furfural, is described as sweet and bread-like caramellic. This furan can interact with hydrogen sulfide of juice to produce thiofurfural, a compound with a skunky odor (35). Furfural has an important role in the monitoring of citrus juice quality (36), and has an especially significant relationship to browning (34). The main source of furfural in aged citrus products is by oxidative degradation of ascorbic acid. Furans, such as deoxyfuroin, furoin and furil are probably formed by self-condensation of furfural (37). 

In 1895 Dull,9 who was studying inulin and its products of hydrolysis, found that when either fructose or sorbose was treated with an aqueous solution of oxalic acid under pressure, a substance was obtained which had the formula CeHeOa and resembled furfural in its properties. This substance was further investigated by Kiermayer4 who found that fructose and sucrose were the best sources when they were heated with 0.3% aqueous oxalic acid at 120°. It was however only the fructose portion of the sucrose molecule which was transformed since the glucose moiety was recovered unchanged. Kiermayer prepared several derivatives of CeH Os and from its reactions concluded that its structure was probably /3-hydroxy-S-methylfurfural (III). Van Ekenstein and... 

In principle, monosaccharides and their conversion products including furfural can be isolated from sulfite spent liquors. Because of the complicated separation technique needed and since alternative raw material sources, such as wood and agricultural wastes are available, these processes have so far been of very limited practical interest. Because of their carbohydrate content, sulfite spent liquors find use either directly or after some fractionation as a feed component for cattle. 

While there are many chemicals possessing the furan nucleus, furfural and furfuryl alcohol are of major industrial significance. The chief source of furfural in plant materials is the pentosan fraction, predominantly xylan (Scheme 1). 

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