MECHANISTIC INVESTIGATION INTO THE DECARBOXYLATION OF AROMATIC CARBOXYLIC ACIDS AND THEIR ROLE IN RETROGRESSIVE REACTIONS

摘要

In the past, it had been proposed that carboxylic acids and their alkali and alkaline earth metal salts, which are prevalent in low-rank coals, are major contributors to retrograde reactions that inhibit efficient thermochemical processing of low-rank coals. In the pyrolysis and liquefaction of low-rank coals, low-temperature (T <400 °C) cross-linking reactions have been correlated with the loss of carboxyl groups and the evolution of CO2 and H2O.1,2,3 Pretreatments such as methylation or demineralization reduce crosslinking and CO2 evolution in pyrolysis.3,4,5 Exchange of Na+, K+, Ca++, or Ba++ into demineralized coals increase cross-linking and CO2 evolution in pyrolysis and liquefaction.3,6