Modification reaction, phenolysis

Choice of the Lignin Modification Reaction. The phenolysis reaction was selected as a means of modifying the structure and reactivity of the ammonium lignin sulfonate for three main practical reasons. First, because this lignin derivative is soluble in (and will ultimately be used in conjunction with) liquid phenol itself second, because unreacted phenol, unlike other reaction solvents, would not have to be removed from the phenolated product after reaction and before conversion to the adhesive resin and third, because lignins and carbohydrates are known to react with phenols under acidic conditions (6,7). 

Functionality Measurement of Phenolated Lignin. It is important to have knowledge of the functionality of the phenolated lignin from the point of view of further chemical modification. The amount of bound phenol in the phenolysis reaction has been measured by titrating the phenol extracted from the reaction mixture (15). This indirect method measures the unreacted phenol and determines bound phenol as the difference between the initial charge and the titrated phenol. This is sometimes misleading. 1H NMR spectroscopy is another candidate for the determination of the amount of bound phenol. However, this calculation is difficult since the number of protons before and after the phenolysis reaction is unknown. 

From the data in Table II, it seems that the pressures involved in carrying out the phenolysis modification do not pose any special engineering problems since the maximum encountered is only 45 psi. Subsequently, however, in another set of experiments that were carried out for longer heating periods, the pressures observed rose to much higher levels (cf. Table VIII). This may be due to the presence of water generated by dehydration reactions. 

---