Phenolation of wood using oxalic acid as a catalyst: Effects of temperature and hydrochloric acid addition

Abstract

Birch wood meal has been phenolated in the presence of oxalic acid alone or its mixture with hydrochloric acid (HCl) at various temperatures ranging from 150 to 250°C under high pressure. The effects of high temperature, high pressure, and the addition of HCl in conjunction with oxalic acid on the amounts of wood residue and combined phenol have been investigated. In the case of the oxalic acid-catalyzed process, by increasing reaction temperature from 180 to 250°C, the amounts of wood residue could be considerably reduced, but the amount of combined phenol decreased. In comparison to a noncatalyzed process in the absence of water, the catalyzed one offered a relatively lower amount of wood residue and a higher amount of combined phenol. However, compared to a noncatalyzed process with water, particularly at a high temperature of 250°C, the catalyzed process gave significantly larger amounts of wood residue. In addition, with a small addition of HCl to an oxalic acid catalyzed system, the amount of wood residue was remarkably reduced compared to that of oxalic acid alone, and the amount of combined phenol could be increased significantly. Furthermore, the mechanical properties of the moldings prepared from the phenolated wood were sufficiently improved by the addition of a small amount of HCl to the oxalic acid-catalyzed system. © 1996 John Wiley & Sons, Inc.