Research On Harmlessness And The Water Treatment Of Waste FCC Catalysts

Fluid catalytic cracking (FCC) catalyst is one of the mostly used catalyst in petroleum processing. During the cracking reactions, the converted coke deposits on the catalyst and results in the activity loss of FCC catalyst, as the steam of high temperature could destroy the active constituent and heavy metals in the crude oil such as Ni, V, Fe could deactivate the active sites of the catalyst by absorption and reaction. In recently years, there are tens of thousands waste FCC catalysts, and irrationally emission could cause pollution to the environment since the waste FCC catalysts contain many heavy metal elements. Therefore, it is still an urgent problem to deal with the waste FCC catalysts. Currently, the main solution is to bury the waste catalysts, but they would be discriminated as dangerous wastes when the concentration of leaching solution of nickel in solid waste exceeds 5mg/L by Chinese standard. Therefore, how to perform immobilization treatment of Ni in the waste FCC catalysts such that they can be discharged safely is the main problem in the research. In the research, we first explore the deactivation mechanism of the waste catalyst, by analyzing the existence and distribution of the heavy metal elements in the waste catalyst through a series of analyzing methods, such as infrared. XRD, XPS, SEM, and exploring the migration path of Ni.Then, we conduct harmless treatment of Ni in the waste catalyst through high temperature calcination and microwave curing. We study the impact of two methods with different temperatures and different Ni additions. The results show that these two methods could both immobilize Ni efficiently and the degree of immobilization decreases as the Ni addition increases, while increases as the treatment time increases.The Ni content of leachate is much lower than 5mg/L byhigh temperature calcination, which could effectively achieve the harmlessness of Ni.Finally, we conduct both harmless and resource oriented treatment to the waste FCC catalyst. Through mixing nano TiO2 with Ni element could realize harmlessness. Meanwhile, producing Ni-TiO2-FCC on the basis of waste FCC catalyst, the carrier of Ni-TiO2, could re-utilize the resource. We study the impact of Ni immobilization with different Ni additions and different leaching periods, and we analyze the photocatalytic degradation of methyl orange by the modified catalysts. The experiment results show that mixing TiO2 with Ni could achieve Ni-harmlessness, and the degradation effect of methyl orange by Ni-TiO2-FCC waste catalystis up to 90%.