Preparation of nitrogen-enriched activated carbons from brown coal

Nitrogen-enriched activated carbons were prepared from a Polish brown coal. Nitrogen was introduced from urea at 350 C in an oxidizing atmosphere both to carbonizates obtained at 500- 700 degrees C and to activated carbons prepared from them. The activation was performed at 800 degrees C with KOH in argon. It has been observed that the carbonization temperature determines the amount of nitrogen that is incorporated (DC5U, 8.4 wt % N-daf; DC6U, 6.3 wt % N-daf; and DC7U, 5.4 wt % N-daf). X-ray photoelectron spectroscopy (XPS) measurements have shown that nitrogen introduced both at the stage of carbonizates and at the stage of activated carbons occurs mainly as N-6, N-5, and imine, amine and amide groups. On the other hand, the activation of carbons enriched with nitrogen results in the formation of pyridonic nitrogen and N-Q. The introduction of nitrogen at the activated carbon stage leads to a slight decrease in surface area. It has been proven that the most effective way of preparing microporous activated carbons enriched with nitrogen to a considerable extent and having high surface area ( similar to 3000 m(2)/g) is the following: carbonization --> activation --> reaction with urea.