With the growing demand for paper pulp in developing countries such as China, production of paper using reed as a resource is regarded as one of the most profitable approaches for high-value conversion of biomass due to the shortage of wood-derived resources in China.1,2 However, the major technical hurdle of non-wood pulping is the severe environmental pollution caused by the black liquid due to poor performance of alkaline recovery.3 Exploring new approaches besides alkaline recovery for effective utilization of this hazardous material has attracted much attention. Processing routes, such as steam water gasification,4 supercritical water gasification5 and pyrolysis6 have been extensively studied. Among those processes, hydrothermal carbonization of black liquor is an approach to effectively decrease COD (Chemical Oxygen Demand) and biomass content in black liquor with relatively little environmental impact.7 The obtained carbons from hydrothermal carbonization have been reported to be utilized as solid fuels.8 Preparation of adsorbents from hydrothermal carbonization is also a good approach for high-value conversion of biomass in aqueous solution.7 However, the specific surface area of the carbon from hydrothermal reaction is generally low, which significantly limits its application.7 In order to further increase the specific surface area of adsorbent, the thermal carbonization treatment will be generally applied. The most common reactor for thermal carbonization is the fixed bed reactor, which usually has rather high carbonization temperature and long reaction time. In the present work, the fluidized bed reactor was employed for thermal carbonization due to its yielding of uniform product, because of its efficient heat and mass transfer that minimize temperature variation and ensure good mixing.9 These advantages are so compelling that the application of a fluidized bed reactor for the carbonization step can be very attractive for carbon-based adsorbent production. In addition, to the best of our knowledge, the study of a fast approach for preparation of carbon adsorbents from reed black liquor with large specific surface area and their direct application for gas separation has not been reported as yet.