The potential of La-containing spent catalysts from fluid catalytic cracking as feedstock of mullite based refractories

Abstract

The potential of La-containing spent FCC catalysts as feedstock of mullite refractories is discussed. A simple methodology to determine the maximum use temperatures is proposed. It combines the analysis of the microstructural evolution with temperature with strain-controlled (2 × 10−4s-1 to 3% maximum strain) and constant stress compressive creep tests at high stresses (15−30 MPa) at 1100–1200 °C. Complete reaction was assured by milling the waste before processing mullite materials. Phase and microstructural evolutions with temperature were established combining dynamic techniques (DTA-TG and dilatometry) with quenching experiments. Isothermal treatments at 1300 and 1400 °C allowed selecting the optimum thermal treatment: 1400 °C-3 h.The formation of a La2O3 rich Al2O3-SiO2 liquid at low temperatures ≈1200 °C leads to the development of a microstructure constituted by a skeleton of mullite tabular grains trapping the remaining glass. Such microstructure endows the material with sufficient creep resistance at temperatures 1100−1200 °C to be used as constituent of refractories for temperatures ≤1200 °C.