Kazunari Komatsu

Zeolite-supported precious metal catalysts for NOx reduction in lean burn engine exhaust

The effects of the zeolite-supported precious metal catalysts on NOx reduction in oxygen-rich exhaust have been investigated. It became clear that NOx conversion related the number of NO adsorption sites of precious metal and the number of HC (C3H6) adsorption of support (zeolite). PtIrRh/MFI zeolite catalyst showed higher performance and durability than the current PtRh supported on alumina and ceria catalyst.

Development of lean NOx catalyst for lean burn gasoline engine

Abstract Lean NOx catalyst for a lean burn gasoline engine was developed. This catalyst could constantly reduce NOx under lean burn driving condition by using hydrocarbon as a reducing agent. This catalyst consists of platinum (Pt), iridium (Ir) and rhodium (Rh) as active metals and H-MFI type zeolite as a support material. This catalyst had high thermal durability that was caused by Pt-Ir-Rh composite that suppressed the growth of particle size of itself during thermal aging and MFI zeolite that had high thermal durability and HC trap activity. Lean burn vehicle with this developed catalyst achieved emission legislation limit after an engine endurance test and improved 16% of fuel economy at JPN 10-15 mode.

Sulfur Poisoning of Palladium-based Catalysts Using Cerium Oxide.

酸化セリウムを酸素貯蔵材として使用したパラジウム担持触媒の二酸化硫黄 (SO2) ガスによる被毒現象を検討した. 還元雰囲気下において, 酸化セリウムに担持したパラジウムに吸着した硫黄の脱離温度は, 酸化アルミニウムに比較して高温化しており, 被毒状態からの触媒活性の回復に影響を与えていることが判明した. この高温化は, 吸着した硫黄量と触媒の状態変化の解析から, 還元されたパラジウムと酸化セリウム間における酸化セリウムの還元性に基づく栢互作用が原因であると推察された. また, 573Kにおける, パラジウム担持酸化セリウムのSO2被毒に対する酸化, 還元雰囲気の影響を検討した結果, 酸化雰囲気では, SO2の吸着が酸化セリウムの酸素貯蔵を阻害し, 還元雰囲気では, パラジウム表面を不活性化しているものと推論した.