Preparation of nitric humic acid by catalytic oxidation from Guizhou coal with catalysts

Nitric humic acid was prepared by catalytic oxidation between nitric acid and Guizhou coal, with added catalysts. We investigated catalytic oxidation processes and the factors that affect the reactions. The effects of different catalysts, including NiSO4 support on active carbon (AC-NiSO4), NiSO4 support on silicon dioxide (SiO2-NiSO4), composites of SO4 (2)/Fe2O3, Zr-iron and vanadium-iron composite were studied. As well, we investigated nitric humic acid yields and the chemical structure of products by element analysis, FT-IR and E4/E6 (an absorbance ratio at wavelengths of 465 and 665 nm of humic acid alkaline extraction solutions). The results show that the catalytic oxidation reaction with added catalysts can increase humic acid yields by 18.7%, 16.36%, 12.94%, 5.61% and 8.59%, respectively. The highest yield of humic acid, i. e., 36.0%, was obtained with AC-NiSO4 as the catalyst. The amounts of C and H decreased with the amount of nitrogen. The increase in the E-4/E-6 ratio in catalytic oxidation of (Guizhou) coal shows that small molecular weights and high yields of nitric humic acid can be obtained by catalytic oxidation reactions. (C) 2012 Published by Elsevier B. V. on behalf of China University of Mining & Technology.