Development of heat-resistant materials and high temperature catalytic combustor for combustion with no NOx formation

Catalytic activity of hexaaluminates Sr _<0.8>La_<0.2>Al_<12>O_<19> (SLA) and Sr_<0.8>La_<0.2>MnAl_<11>O_<19> (SLMA) impregnated with Pd (NO_3)_2 was investigated for combustion of CH_4.Although Pd-SLA showed a decrease in its activity at 700-800ﾟC due to reduction of PdO,high oxidation activity of SLMA compensated this influence, resulting in stable combustion by Pd-SLMA with no decrease in its activity at 700-800ﾟC.Improvement of low-temperature ignition activity for methane combustion was also investigated mainly on the catalyst systems Pd/mAl_2O_3-nMOx (M : metal elements) and Pd/mZrO_2-nMOx. The improved activity was found only for catalysts supported on Al_2O_3-NiO.With increasing amount of NiO in the support, the surface area of the catalysts monotonically decreased whereas their catalytic activity increased, resulting in the maximum activity at Pd/Al_2O_3-36NiO.Fabrication of SLMA thick films on SiC honeycomb supports with high thermal stability was also examined in order to overcome a poor heat shock resistance of the SLMA catalysts. Slurry coating of a mullite intermediate layr between SiC and SLMA was revealed to be useful for establishing honeycomb-shaped ceramic combustion catalysts using Mn-substituted hexaaluminates. We have further proceeded to evaluation of combustion durability of the catalysts, construction of a prototype catalytic combustor, and an installation test for a 150 kW-class gas turbine at an atmospheric pressure.Finally, the combustion test at 8.5 atm also resulted in almost the same as that at 1 atm, giving a bright perspective for practical application of high-temperature combustion catalysts for gas turbines.