Portal de Periódicos da CAPES

Solid-state synthesis of mullite from spent catalysts for manufacturing refractory brick coatings

2017; Elsevier BV; Volume: 44; Issue: 4 Linguagem: Inglês

10.1016/j.ceramint.2017.11.044

1873-3956

Fabio Vargas, Edward Restrepo, Jhon Edison Rodríguez, Freddy Vargas, Lizeth Arbeláez, Pablo Caballero, Jhoman Arias, Esperanza López, Guillermo Latorre, Gloria Duarte,

Advanced materials and composites

This paper shows the results of the solid-state synthesis of mullite from spent catalysts discarded from fluid catalytic cracking (FCC); the catalysts are mainly composed of silica and alumina but are polluted with SOX, forming a non-crystalline network. The synthesized mullite was used as a feedstock to thermally spray a coating onto a silica-alumina refractory brick, and its chemical resistance at high temperature was subsequently evaluated by contact with K2CO3 at 950 °C. Initially, the spent catalyst was thermally treated for 2 h at 600, 900, and 1200 °C to eliminate the SOX pollutant. The heat treatment at 1200 °C completely removed the SOX in the sample. Additionally, four thermal processes were performed by heating the spent FCC catalyst in an electrical furnace to 1500 and 1600 °C and by using an oxyacetylene flame to synthesize mullite. Thermal treatments at 1500 °C were performed with and without alumina added to the spent FCC catalyst, whereas those conducted at 1600 °C and using a flame were performed using only added alumina. In the powders thermally treated at 1500 °C, silica-rich mullite (3Al2O3.2SiO2) accompanied by an excess of alumina or silica was obtained with or without alumina added, respectively. In contrast, the materials treated at 1600 °C formed alumina-rich mullite (2Al2O3.SiO2), which was accompanied by an excess of alumina. Mullite was not synthesized in the flame-heated powder. The silica-rich mullite accompanied by an excess of alumina was used as feedstock powder to modify the surface of a refractory brick, improving its resistance to chemical attack by K2CO3 at high temperature.