Furans Furfural, Table

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). 

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. 

To optimize the operating conditions for the detoxification of the hydrolysates with resins, experiments were carried out with synthetic solutions. Table 3 shows how the detoxifying efficiency of the anionic resin Dowex 1 diminished with increasing treated volume. Aliquots of the solution eluted through the column were sampled after 120,230, and 250 mL. As a whole, after the early 600 mL, the column still had a fair cleaning efficiency for acids but a reduced removal efficiency toward the furan compounds the data show that the cleaning efficiency of the column was 99% for formic acid, 87% for acetic acid, 40% for HMF, and 46% for furfural. An optimized resin/solution ratio of 0.14 g/g was thus extrapolated. The addition of a subsequent detoxification step with the cationic resin Dowex-50W left the concentrations of the acids almost unchanged whereas it further reduced those of HMF and furfural by 14 and 26%, respectively. The detoxification of the hydrolysate was performed on the basis of this optimized detoxification setup. 

Analysis of the volatile compounds of tamarind revealed the presence of more than 80 compounds. Aromatic and furan derivatives were dominant. The major constituents were 2-phenyl acetaldehyde (25.4% of total volatiles), which has a fruity and honey-like odour, 2-furfural (20.7%), having a caramel-like flavour, followed by hexadecanoic acid (18.1%) and limonene, which has a citrus flavour. A list of the volatile compounds detected in tamarind is given in Table 20.5. 

Furan has also been labeled with heavy water on supported catalysts (chromium, zinc, and manganese oxides promoted with K2C03) at a temperature of 350°.117 Deuterated furan has also been obtained from the vapor phase decarbonylation of furfural over mixed oxide catalysts in the presence of heavy water. Both of these systems utilize extreme experimental conditions and the methods outlined in Table XII are to be preferred for preparative labeling. 

The cracking of furfural to furan and carbon monoxide was carried out in an adiabatic reactor using a pelleted catalyst. Data from a large reactor operating at 1.5 atmospheres are given in Tables 1.4 and 1.5. Six moles of steam were used per mole of furfural to decrease the temperature rise in the bed. Analysis of the exit stream showed less than 0.01% of the furfural was unreacted. 

Table II shows a sensory evaluation after adding each component to fresh beer. No change in the aroma after adding 2-methyltetrahydro-furan-3-one, 3-methyl-2-buten-l-ol or 2-acetylfuran to fresh beer was apparent The aroma was distinguishable between the control beer and the beer samples with ethyl lactate, furfural, linalool, 5-methyl-furfural, and y -nonalactone respectively added, but no stale flavor was detected in each beer sample. An astringent note, this being part of the stale flavor, appeared after adding 2-furfuryl ethyl ether (2-FEE) to the control beer. 2-FEE is considered to have been partly respon-sible for the stale flavor, although it was not completely reproduced by the addition of 2-FEE...

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