Preparation of High-Performance Adsorbent from Coal for Adsorptive Denitrogenation of Liquid Hydrocarbon Streams

A high-performance adsorbent, CDA-C2, has been prepared from lignite by a chemical activation method with NaOH as an activation agent for removing nitrogen compounds from liquid hydrocarbon streams. The effects of coal ranks, activation agents (NaOH, KOH, NaOH + KOH, or H 3 PO 4 ), and activation methods (chemical and physical) on the adsorptive denitrogenation (ADN) performance of the coal-derived adsorbents (CDAs) were examined. ADN performance of the prepared CDAs was evaluated in a batch system using a model diesel fuel and in a flow adsorption system using a real coal liquid with a total N content of 980 ppmw. It was found that CDA-C2, which was prepared from a lignite by chemical activation using NaOH as an agent at 650 °C for 1 h with a yield of 47.8 wt %, gave a saturation capacity of 1.73 mmol of N/g of adsorbent for ADN of the real coal liquid, which is about 6 times higher than that of the best commercial activated carbon adsorbent. The higher ADN capacity and selectivity of CDA-C2 can be attributed to its significantly higher oxygen-containing functional groups (12 mmol/g of adsorbent) on the surface, as revealed by temperature-programmed desorption (TPD) analysis. In addition, the spent CDA-C2 can be regenerated by the toluene washing at 80 °C, followed by heating at 200 °C. On the basis of the present study, a new conceptual process for denitrogenation of liquid hydrocarbon streams was proposed, which can be operated at ambient conditions without using H 2 gas.