Alkali-oxygen oxidation of coals to produce high-value benzene polycarboxylic acids (BPCAs) is a potential substitute for the petroleum route in the future. However, the high amount of alkali consumed in the process stands as a significant obstacle for the practical application of this approach In the present work, lignite, chosen as the raw material, was oxidized at temperatures higher than those reported so far. The results showed that, as the temperature increased, a gradually shortened reaction time and decreased alkali/coal mass ratio were required to obtain the maximum total yield of BPCAs, which remained about 20%. A total BPCA yield of 20.4% was obtained at conditions of 300 degrees C, 0.8/1 alkali/coal mass ratio, and 1 min, whereas the traditional method employs the conditions of 240 degrees C, 3/1 alkali/coal mass ratio, and 30 min to obtain a maximum BPCA yield of 20.5%. The distributions of BPCAs obtained by the two methods were found to be very close to each other. Excess alkali employed in the system can decrease the yield of BPCAs through the salting-out effect, with a more significant effect at higher reaction temperatures. The enhanced salting-out effect induced by excess alkali concentration delays the diffusion of intermediates formed on the lignite surface to the water phase, during which the parent structures for the BPCAs are possibly overoxidized to carbon dioxide. The high-temperature oxidation of lignite dramatically decreases the amount of alkali consumed and improves the production efficiency of BPCAs, which is very important for the industrialization of this process.