Potassium acetate-catalyzed acetylation of wood at low temperatures II: vapor phase acetylation at room temperature

Ezomatsu wood blocks were impregnated with potassium acetate (KAc) and then exposed to acetic anhydride vapor at 25°C and 120°C. The KAc-impregnated wood was rapidly acetylated at 120°C, and only 6 min was needed to achieve 20% weight percent gain (WPG). The WPG increased with increasing catalyst loading (CL), but it turned to decrease above 20% CL probably because the diffusion of acetic anhydride vapor was hindered by excess KAc depositing in the cell lumina. Thus, careful control of CL is necessary in the vapor-phase acetylation. KAc was also effective in catalyzing the vapor-phase acetylation at 25°C: the KAc-impregnated wood attained 20% WPG within 7 days, whereas the WPG did not exceed 10% even after 1 month in the uncatalyzed system. Irrespective of treatment methods, the hygroscopicity of wood was reduced and its dimensional stability was improved with an increase of WPG. These results confirm that the use of KAc simplifies the acetylation process at room temperature with minimal loss of acetic anhydride.