Properties of Furfural

Molecular weight 96.082 g/mole Boiling point (760 mm Hg) 161.7 °C Freezing point -36.5 °C Specific gravity d 25 1.1610 Refractive index no 1.52608 

Furfural vapor is irritating to the mucous membranes, but the low volatility reduces the risk of 

Furfural was found to penetrate the skin of rabbits, but with no fatal effect up to 500 mg/kg. Several drops of furfural in standard eye tests with rabbits cause significant irritation but no irreversible damage. 

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The most important physical properties of furfural, as well as similar properties for furfuryl alcohol, tetrahydrofurfuryl alcohol and furan are given in Table 1. The tabulated properties of furfural are supplemented by a plot (Fig. 1) of the vapor—Hquid compositions for the system, furfural—water (15,16). 

Furfural is very thermally stable in the absence of oxygen. At temperatures as high as 230°C, exposure for many hours is required to produce detectable changes in the physical properties of furfural, with the exception of color (17). However, accelerating rate calorimetric data shows that a temperature above 250°C, in a closed system, furfural will spontaneously and exothermically decompose to furan and carbon monoxide with a substantial increase in pressure. The pressure may increase to 5000 psi or more, sufficient to shatter the container (18). 

Many industrial applications utilize the solvent properties of furfural and fur-furyl alcohol however, both chemicals also display unique features as monomers for condensation polymerization. Most of the furfuryl alcohol sold is used as monomer in the manufacture of resins for industrial application. 

The physical properties of finish removers vary considerably due to the diverse uses and requirements of the removers. Finish removers can be grouped by the principal ingredient of the formula, method of appHcation, method of removal, chemical base, viscosity, or hazardous classification. Except for method of apphcation, a paint remover formulation usually has one aspect of each group, by which it can be used for one or more appHcations. A Hst of the most common organic solvents used in finish removers has been compiled (3). Many are mentioned throughout this article others include ethyl lactate [97-64-3] propylene carbonate [108-32-7] furfural alcohol [98-01-1/, dimethyl formamide [68-12-2] tetrahydrofuran [109-99-9] methyl amyl ketone [110-43-0] dipropylene glycol methyl ether [34590-94-8] and Exxate 600, a trade name of Exxon Chemicals. 

Relatively pure xylan isolated from the holocellulose of aspen (Populus) wood is said to contain 85% of xylose residues.78 One of the characteristic properties of xylan is its ease of hydrolysis. Because it hydrolyzes much more readily than cellulose, mild acid treatment may be employed to bring about preferential hydrolysis of xylan from plant material. Xylose is ordinarily prepared in the laboratory by direct sulfuric acid hydrolysis of the native xylan in ground corn cobs.74 Hydrolysis in hydrochloric acid proceeds rapidly, but decomposition to furfural also occurs to some extent.76 A commercial method for the production of D-xylose from cottonseed hulls76 and straw77 and from corn cobs17 78 has been described. 

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. 

Furan resins are produced by the polymerization of furfural or furfuryl alcohol in the presence of acids (see Figure 15.8). The properties of these dark-colored resins are shown in Table 15.6. Furan resins have a relatively low heat deflection temperature (80 °C) and good mechanical properties. These materials, which are widely used as jointing materials for brick and tile, are characterized by excellent resistance to nonoxidizing acids, alkalis, and salts but are affected by the presence of oxidizing acids such as nitric acid. The furan plastics are also resistant at room temperature to nonpolar solvents, such as benzene, and to polar solvents, such as ethanol. 

Of the substances studied the most abundant in the Paleozoic rocks of the area are furfurals presumably derived from carbohydrates, higher molecular weight hydrocarbons, and in a few samples, amino acids. Acid and base soluble, low boiling substances having some properties of heterocyclic compounds, phenols, and organic acids exist in smaller amounts. 

Schiessler, R. W., Dixon, J. A., and others, "Properties of Hydrocarbons of High Molecular Weight", Research Project 42 of the A.P.I. at Pennsylvania State University Sept., 1958. Published with the permission of the Director, Professor Dixon. Aniline, Furfural. 

Even though 4a and its analogues are relatively simple compounds, they come to assume an importance which is quite disproportionate, when their origin is considered. Their two parts are derived differently the furfural resulting from 1,2-enolisa-tion of the Amadori compound and the furanone from 2,3-enolisation (see Chapter 2), the former being favoured by low pH and the latter by moderate pH. This means that for both components to be available for interaction, the reaction conditions, including pH, need to be carefully balanced. pH optimisation of the reaction will also be affected by the acid/base properties of the amino acid moiety of the Amadori compound. 

The effect of acetic acid on the distribution of furfural is significant as shown in figure 3. Acetic acid has modifier properties up to a concentration of 5 wt% and enhances furfural extraction. Further increase of acetic acid concentration results in a loss of these modifier properties. This effect is present at all studied temperature and pressure levels. The distribution of furfural was calculated with equation 2. 

Figure 4. Modifier properties of acetic acid for furfural by K value at 298 K REFERENCES...

Copolymers of furfural with phenol or phenol-formaldehyde polymers have been available commercially for many years. Since the acid-catalyzed reaction of furfural and phenol has been difficult to control, most industrial applications involve the use of alkaline catalysts. Furfural-phenol resins are used for their alkali resistance, enhanced thermal stability, and good electrical properties compared to phenol-formaldehyde resins. 

Anion-exchange resins with good heat and chemical resistance and high sorption rates have been prepared by polycondensation of furfural with polyethylenepolyamine and PVC. An increase in PVC content decreases the sorption properties of the resins... 

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