Spent Fluidized Catalytic Cracking Catalyst Enhances Pyrolysis Of Petrochemical Waste Activated Sludge

Large quantities of solid waste are generated in the petroleum refining process.They can cause serious environmental effects for the existence of toxic and harmful substances such as petroleum and heavy metals.How to achieve the harmless treatment and resource utilization has become a problem that must be solved.In this study,the catalytic pyrolysis as a promising technology was used for the treatment of typical refining wastes such as spent fluidized catalytic cracking catalyst(s FCCc)and waste activated sludge(WAS).Different dosage of s FCCc was added in WAS to investigate its effects on pyrolysis performance in terms of product yields,quality,possible reaction mechanisms and kinetics at a series of temperatures.The volatiles(60.75%)and oxygen content(17.44%)in WAS are relatively high,which implied a considerable value for energy recovery and utilization.The metal oxides such as Al₂O₃,Fe₂O₃and Ca O deposited in s FCCc provide active sites for the vapor reforming.The obtained thermogravimetric(TG)and derivative thermogravimetric(DTG)analysis indicated that the WAS pyrolysis process may be made up of 4 stages,and compared with no catalyst,s FCCc could reduce the average activation energy of stage II and stage III sections by 12.93%and 6.63%respectively.The catalytic pyrolysis was via carbocation mechanism.It was also found that both the high terminate temperature and s FCCc can significantly improve the sludge pyrolysis conversion rate.When the temperature was increased from 650?to 850?,the yield of non-condensable gas increased from 21.40%to 24.82%,and the residue yield decreased to a minimum of 44.48%.However,the yields of pyrolytic liquid reached a maximum of 31.90%at 750?.Under the synergistic effect of s FCCc and high temperature,as the s FCCc addition ratio increased from 1:0(WAS:s FCCc)to 1:1,the total yields of pyrolytic liquid and gas increased by more than 7%,and the yield of pyrolytic residue reached a minimum of 40.62%.In addition,s FCCc effectively improves the quality of pyrolytic bio-oil and non-condensable gas.The content of H₂in non-condensable gas increased from 29.26%to 38.35%.The content of saturates in pyrolytic bio-oils increased to a maximum 45.69%and H/C molar ratios increased from1.43 to 1.53.The O mobility from WAS to pyrolytic bio-oil decreased from 22.08%to14.91%,and pyrolytic bio-oil tended to be lightening.Moreover,the residue was low environmental risk and had the ability to catalytic ozonation,and shows an effective mineralization effect on the refractory organics in refining wastewater treatment.With the strategy of"treating waste with waste",the study provides a feasible reference for the resource utilization and reduction treatment for refinery waste.