Regeneration of spent bleaching earth by pyrolysis in a rotary furnace

A spent bleaching earth (SBE) from an edible oil refinery has been thermally regenerated by a rotary furnace under inert atmosphere (i.e. N-2). Under the experimental conditions investigated, pyrolysis temperature (500-660degreesC) is an important operating parameter. The effects of processing parameters such as pyrolysis temperature (>660degreesC) holding time and flowing gas (N-2 vs. CO2) on the characterizations of the resulting solids are negligible compared to the fresh bleaching earth. Results showed that these samples are type IV with hysteresis loops corresponding to type H3 from nitrogen adsorption isotherms, indicating slit-shaped mesoporous characteristics. The regenerated clays have smaller surface areas (approximate to100 vs. 268 m(2) g(-1)) and pore volumes (approximate to0.214 vs. 0.359 cm(3) g(-1)) than the fresh bleaching earth. In addition, this study clearly demonstrated that the porosities created in the samples without acid-washing are lower than those with acid washing due to the residues left in the pores. Thus, smaller pores, accompanied by an increase in surface area, were also obtained for all samples after acid washing treatments. (C) 2002 Elsevier Science B.V. All rights reserved.