Phenols half-neutralization

In collaboration with Jon Belisle, octanol pKa values were measured for a series of benzoic acids and phenols. A coupled electrode calibrated in aqueous buffers was used. The haIf-neutralization potential was measured since the Renderson-Hasselbalch equations would not apply. The titrant was 0.1 sodium hydroxide in isopropanol methanol 4 1. The titrant was only 6% of the total volume at half-neutralization, so the medium was essentially octanol-like. The results are listed in Table I and some benzoic acid values are plotted in Figure 6. 

That is, hox(AtXH)= - / (ArX ). For this type of reaction, E (ArX ) is positive. Hence, the more positive this value, the more difficult it is to oxidize the compound. For many phenols and anilines, polarographic half-wave potentials, Zs1/2(ArX"), determined at pH values where the compound is present in its neutral form, are available. These values should reasonably parallel the oxidation potentials of the compounds, and therefore can also be used to relate oxidation rate constants ... 

Novolaks were prepared using a phenol-to-formaldehyde molar ratio of 4 1 with 5 mole percent of H2SO4 added as a catalyst. Typically, 47 g liquid phenol (91.7% assay), 3 g paraformaldehyde, and 30 mL water plus the required acid catalyst were added to a three-neck, 250-mL round bottom flask. The flask was fitted with a reflux condenser and stirrer. The mixture was refluxed for 2 to 4 hours with the oil bath at 115 °C then, the mixture was neutralized with 50% (w/w) NaOH and the excess phenol removed by steam distillation for 5 to 6 hours. The remaining viscous oily residue was washed repeatedly with boiling water. A novolak with the P/N fraction was prepared as described above with 1 1 by volume phenol and P/N fraction and half of the amount of formaldehyde. Initial wood-gluing testing with this novolak indicates wood failure rather than glueline failure. 

Sulfuric acid hydrolyzed samples were neutralized with CaO and then approximately 10% of monomeric phenol was added. The mass was "cooked", dried and pressed producing a strong board resistant to six weeks water immersion (Table 2). This result was most encouraging since phenol costs less than half the selling price of commercial phenol/formaldehyde B-stage resins. Combinations of nitric and sulfuric acids were at least no better than sulfuric acid alone (Table 2). 

Bio-oil chemical properties vary with the feedstock but woody biomass typically produces a mixture of 30% water, 30% phenolics, 20% aldehydes and ketones, 15% alcohols, and 10% miscellaneous compounds. As a fuel, bio-oil has environmental advantages when compared to fossil fuels, producing half the NO and no SO. As a fuel derived from a renewable resource, bio-oil is considered carbon dioxide neutral (Mukaney et al., 2002). 

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