Abstract
Mixture of aluminum dross (AD) and coal fly ash (CFA) was used to produce high-temperature porous mullite for washcoat application. CFA is the combustion by-product of pulverized coal in a coal-fired power plant, while AD is a waste product produced in secondary aluminum refining. In this study, 80 wt% of AD and 20 wt% of CFA was used to prepare a mullite precursor (MP) via acid leaching and dry-milling. The precursor was coated on a substrate and subsequently fired at 1500 °C. The results showed that the precursor transformed to a hierarchical porous microstructure assembled by large interlocked acicular mullite crystals. The pore structures consisted of large interconnected open pores and small pores. The specific surface area of the mullite washcoat was 4.85 m2g−1 after heating at 1500 °C for 4 h. The specific surface area was compatible with the specific surface area of other high-temperature washcoats.
Highlights
High-temperature catalytic processes that aim at creating a more efficient and less polluting chemical process are being used in many applications
The unfired loaded-substrate was named as AS, the fired loaded-substrates were named as MA and MB, corresponding to substrates that were fired at 1200 ◦ C
There is a characteristic broad diffraction peak between 17° and 30°, centered at 2-theta angle of 22.5° in the XRD pattern, which attributed to amorphous phase in coal fly ash (CFA)
Summary
High-temperature catalytic processes that aim at creating a more efficient and less polluting chemical process are being used in many applications. The catalyst supports used in these processes basically consist of two components. The second component, a small weight fraction of the catalyst support, is a surface covering of washcoat impregnated with the active catalyst (platinum, palladium, or other noble metals). The washcoat is the crucial component of a catalyst support. It is where the catalytic reactions take place, as the main function of the washcoat is to provide high contact surface area between the catalyst and reacting gases for high reaction rates. The washcoat has to be thermally stable at Crystals 2020, 10, 178; doi:10.3390/cryst10030178 www.mdpi.com/journal/crystals
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