Catalytic cracking of residual palm oil and regeneration of spent bleaching earth

Abstract

Bleaching earth is used to remove colour, phospholipids, oxidized products, metals and residual gums in the palm oil process refinery. Once adsorption process ends, the spent bleaching earth (SBE) which contains approximately 20-40 wt. % of the adsorbed oil is usually disposed to landfills. This study was carried out to recover the residual palm oil and regenerate the SBE. The oil content in SBE was recovered by catalytic cracking method using transition metal (Cuprum, Zinc, Chromium and Nickel) doped HZSM-5. Transition metal was introduced in HZSM-5 zeolite using incipient wetness impregnation method. The physicochemical properties of the catalysts were characterized using X-ray diffraction, Fourier transform infrared, nitrogen adsorption and temperature programmed desorption of ammonia. Liquid products obtained from cracking were analyzed by gas chromatography-mass spectrometry. The Ni/HZSM-5 zeolite exhibited the highest yields of alkenes. The performance of Ni loaded (5 wt. %, 10 wt. %, 15wt. %) on HZSM-5 zeolite for cracking of residual oil in SBE then was investigated for further study. The 15 wt. % of Ni doped on HZSM-5 zeolite exhibited the highest yields of alkenes and alkanes. Response surface methodology was employed to study the relationships of catalytic cracking of residual palm oil in SBE such as temperature, heating time and nitrogen flow rate on liquid products yield over 15%Ni/HZSM-5 catalyst and the optimization of the process have been carried out. The optimum liquid products yield of catalytic cracking of residual palm oil in SBE was 12.91 wt. % and achieved at 452 oC, 160 min of heating time and 86 mL/min of nitrogen flow rate. The regeneration of SBE by pyrolysis at high temperature (500 oC) followed with sulphuric acid (H2SO4) solution treatment at different concentration (0.5-3.0 M) for the crude palm oil and methylene blue decolourisation was also investigated. The results showed that the regenerated SBE using 1.5 M H2SO4 was identified as an optimal concentration of H2SO4 treatment.