Interaction Between Potassium Carbonate and Carbon Substrate at Subgasification Temperatures. Migration of Potassium into the Carbon Matrix

The interaction between potassium carbonate and carbon substrate in an inert atmosphere was investigated by using carbon black with an amorphous structure and graphite. Qualitative and quantitative changes of potassium species on carbon in the course of heat treatment were monitored by means of atemperature-programmed reaction, extraction of potassium with a HCl solution, Auger electron spectroscopy, and electron probe microanalysis. Potassium carbonate impregnated on carbon black decomposed to give potassium oxide and CO₂ in the temperature range 470-900 K. We found that potassium species migrated into the carbon matrix in the temperature range 670-900 K. At higher temperatures potassium oxide remaining on the surface was reduced by reaction with carbon. Although metallic potassium on graphite was lost due to evaporation, no pronounced loss of potassium was observedfrom carbon black containing less than 5 wt% of potassium. The migration of potassium intobulk carbon was not observed on graphite.