Hydroxymethylation of Phenol Revisited: A Readjusted Mathematical Model

Abstract

The hydroxymethylation of phenol in alkaline conditions is the first step in the synthesis of resols, which must be later cured for the production of final articles. A mathematical model for the hydroxymethylation of phenol is presented. It is based on the kinetic mechanism by Freeman and Lewis (J. Am. Chem. Soc. 1954, 76, 2080−2087) and includes a set of side reactions. Arrhenius expressions for the seven hydroxymethylation kinetic constants at pH 8−10 and temperatures 30−57 °C, and in the absence of methanol, were recalculated from the constants reported by Zavitsas et al. (J. Polym. Sci., Part A-1: Polym. Chem. 1968, 6, 2541−2559), in order to take into consideration the hydration/dehydration of formaldehyde and other side reactions. The model adequately predicts the measurements in the mentioned publications and in Higuchi et al. (J. Wood Sci. 1999, 45, 306−312). All of the kinetic parameters were directly or indirectly taken from the literature and were not readjusted to the measurements.

Hydroxymethylation of technical lignins from South American sources with potential use in phenolic resins

“…The mechanism of hydroxymethylation of lignin, similar to that of P, is very complex. Even though the hydroxymethylation reactions are irreversible, the ionic species are in equilibrium with their corresponding neutral species . Besides, F can be consumed through undesirable reactions that include generation of aliphatic methylol groups (CH 2 OH) Al from the aliphatic hydrogens in lignin (H Al ) and the production of methanol and sodium formate by the Cannizzaro reaction at pH > 10 as shown in equations (3) and (4), respectively …”