고체산화물 연료전지용 메탄 개질 촉매에 관한 연구

Abstract

In order develop methane reforming catalysts for SOFC application, several catalysts such as Ni-YSZ anode with K2Ti2O5 additive and Ni supported on several perovskites have been examined. Ni-YSZ cermet was prepared by physical mixing of NiO and YSZ. Potassium titanates, for enhancing the reforming performance over Ni-YSZ cermet, were synthesized by solid state reaction. They were mixed thoroughly using a ball mill. Perovskite structured materials were synthesized through Pechini method and used as support. The reaction was carried using a tubular cell having a length of 20cm, a diameter of 0.6cm and a wall thickness of 0.2cm after 0.1 g of catalyst was coated uniformly onto the inner wall of the tube. Methane conversion was monitored by on-line GC. To investigate the alterations of catalytic activity, various characterizations have been conducted by means of XRD, BET and etc. Total amounts of carbon species formed on the catalyst surface during the reforming reaction were measured by TGA and TPO analysis. Among the potassium titanates promoted catalysts, 10 wt.% K2Ti2O5+Ni-YSZ catalyst shows the high reforming activity with methane conversion around 86%. It also suppresses carbon deposition to some degree to show a durability for ~50 hrs until plugging occurs, but not so effective. Perovskites-support catalysts show superior durability as long as ~100 hrs to the potassium titanates-promoted catalysts. Ni-SrTiO3 demonstrates 82% methane conversion with best durability of the all catalysts examined in the present study. Moreover, no carbon deposition was found in Ni-SrTiO3 catalysts after the course of reaction around 100 hrs. Measurements of the concentration and temperature profiles along the Ni-SrTiO3–coated tube have shown that, at 10% point from the entrance, 85% of the methane conversion was already observed and temperature was decreased sharply due to heat consumption by the endothermic reaction. From the 10% point till the gas exit, mole fraction of product was not changed while the temperature increased gradually. Kinetic simulations in the tubular reactor have shown good matches between experimental and simulation results in terms of the conversion, mole fractions of each reactants and products along the tube.