(256u) Nanostructured Complex Oxides Catalysts for Reduction Soot Ignition Temperature

Nanostructured complex oxides for catalytic oxidation of various fuels are known to be promising and environmentally friendly catalysts that can be potentially used to increase efficiency of coal based power plants. The goal of this study is to identify nanostructured complex oxides catalysts such as LaCrO₃, PrCrO₃, La_0.8Cr_1-xLi_xO₃, CeCrO₃, Ce(Li)CrO₃ and Ce_1-xZr_xO₂ where x=0.1-0.7 that can be able to reduce coal ignition temperature actually to decrease combustion activation energy. These candidate catalysts were selected due to their high oxygen exchange and storage ability, high temperature stability, the ability to tune their properties by doping, and their low price relative to that of noble metals. An extensive set of complex oxides were synthesized and tested as potential catalyst for soot combustion. We synthesized powders of various complex oxides by two methods (i) Carbon Combustion Synthesis of Oxides (CCSO), which was developed and patented recently [1] and enables a rapid and easy synthesis; and (ii) Solution (metal nitrates-glycine) combustion synthesis (SCS) [2].  The catalytic activity of the as-synthesized powders was tested in a temperature-programmed combustion (TPC) apparatus. It consists of quartz fixed bed inserted in a reactor. The fixed bed was packed with a mixture of 0.1 g of amorphous carbon (45 nm), 1 g of the powdered catalyst and 10 g of silica pellets (0.3–0.7 mm in size). The catalyst/carbon/SiO₂ mixture was confined between two layers of quartz wool. A computer-regulated furnace heated the sample up to 700 °C at a heating rate of 5 °C/min. The effluent gas compositions were determined by a mass spectrometer. The Ce_0.5Zr_0.5O₂catalyst produced by CCSO and solution combustion shows the substantial performance with peak temperature of about 390 °C as opposed to the 670 °C of non-catalytic combustion. However, the preliminary experiments showed that the activity of the oxides synthesized by SCS was somewhat higher than those synthesized by CCSO.

References

1. K.S. Martirosyan and D. Luss, Carbon combustion synthesis of oxides, 2011, US Patent 7,897,135.
2. K.S. Martirosyan, and A.S. Mukasyan, Combustion Synthesis of Nanomaterials, In Dekker Encyclopedia of Nanoscience and Nanotechnology, Third Edition. CRC Press: New York, 2014, pp. 983–1001.