Yoshihisa Tochihara

PdO/Al2O3 in catalytic combustion of methane: stabilization and deactivation

In the recently developed catalytically assisted combustors for gas turbines using natural gas, deactivation of the palladium oxide (PdO) catalyst needs to be prevented. The effects of additives such as lanthanum and neodymium in PdO/Al 2 O 3 on the catalytic durability at 1123 K were studied using a conventional fixed-bed flow reactor at atmospheric pressure. The surface properties of the catalysts were investigated using CO chemisorption, XRD, and TPD after CH 4 adsorption. The catalyst deactivation during CH 4 oxidation followed the equation Φ=r 1 [1/(1+α 1 t)] n1 +r 2 [1/(1+α 2 t)] n2 , where r, α and n are constants, subscripts 1 and 2 are the rapid and slow deactivation species, respectively, and t is time on stream. The PdO/Al 2 O 3 catalyst was rapidly deactivated by the transformation of PdO to metallic Pd and slowly deactivated by the particle growth of PdO. The addition of Nd 2 O 3 and La 2 O 3 to PdO/Al 2 O 3 prevented the particle growth of PdO as well as the transformation of PdO to Pd up to high temperature.

Effect of addition of Nd2O3 and La2O3 to PdO/Al2O3 in catalytic combustion of methane

Abstract The addition of both La 2 O 3 and Nd 2 O 3 strongly prevents the deactivation of the PdO/Al 2 O 3 catalyst during CH 4 combustion at 1123 K, compared with the addition of either La 2 O 3 or Nd 2 O 3 alone. This is not due to stabilization of the surface area of alumina but the prevention of the decrease in number of active sites as well as prevention of the transformation of PdO to Pd in the reaction.

High Pressure Test Results of a Catalytically Assisted Ceramic Combustor for a Gas Turbine

A catalytically assisted ceramic combustor for a gas turbine was designed to achieve low NOx emission under 5ppm at a combustor outlet temperature over 1300°C. This combustor is composed of a burner system and a ceramic liner behind the burner system. The burner system consists of 6 catalytic combustor segments and 6 premixing nozzles, which are arranged in parallel and alternately. The ceramic liner is made up of the layer of outer metal wall, ceramic fiber and inner ceramic tiles.Fuel flow rates for the catalysts and the premixing nozzles are controlled independently. Catalytic combustion temperature is controlled under 1000°C, premixed gas is injected from the premixing nozzles to the catalytic combustion gas and lean premixed combustion over 1300°C is carried out in the ceramic liner. This system was designed to avoid catalytic deactivation at high temperature and thermal and mechanical shock fracture of the honeycomb monolith of the catalyst.A combustor for a 10MW class, multi-can type gas turbine was tested under high pressure conditions using LNG fuel. Measurements of emission, temperature, etc. were made to evaluate combustor performance under various combustion temperatures and pressures.This paper presents the design features and the test results of this combustor.Copyright