Alloying Effect of Nickel–Cobalt Based Binary Metal Catalysts Supported on α-Alumina for Ammonia Decomposition

The development of a base metal catalyst which shows high performance for the ammonia (NH3) decomposition have been conducted. For the Ni and Co based catalysts using α-Al2O3 as a support, the performance of the single metal catalysts was lower than that of the γ-Al2O3 supported catalysts. However, its performance was greatly improved by using a binary metal catalyst system. Based on the XRD analysis, it was found that Ni and Co supported on α-Al2O3 were alloyed. TEM observation confirmed that the metal particle size in the α-Al2O3 supported Ni-Co catalyst is smaller than that of the single metal catalysts (Ni/α-Al2O3 or Co/α-Al2O3). Furthermore, in-situ XRD and H2-TPR measurements revealed that the Ni-Co alloy forms during the reduction process. The optimum mixing ratio of Ni and Co components was 1:1, and the optimum pre-reduction temperature before the performance test was 600 °C. Studies on the differences of support oxides proved that the improvement effect by alloying can be similarly obtained with the SiO2 supported catalyst, indicating that the catalyst using the support with less interaction between the active metal and the support is more likely to obtain the performance improvement effect by alloying

Study on the synthetic methods of layered and microporous aluminosilicates

制度:新 ; 文部省報告番号:乙1426号 ; 学位の種類:博士(工学) ; 授与年月日:1999-02-4 ; 早大学位記番号:新2751 ; 理工学図書館請求番号:2304早稲田大

硫黄を含むメタン水蒸気改質反応でのアルミナ担持白金触媒の炭素析出と活性点

Effect of sulfur poisoning on Pt/α-Al2O3 catalysts in steam methane reforming (SMR) was investigated using dimethyl sulfide (DMS). SMR with and without 10 ppm DMS addition was performed over 0.1-2.0 wt% Pt/α-Al2O3 catalysts. Catalyst deterioration occurred at an early stage, but not inactivation in the presence of DMS. Moreover, after the supply of DMS was stopped, the activity was completely restored. DMS in the reaction gas also caused severe sintering of the Pt particles and promoted carbon formation on the 1.0-2.0 wt% Pt catalysts. On the other hand, carbon formation did not occur on the 0.1 wt% Pt catalysts. The Pt sintering and carbon formation behaviors were independent of the SMR activity. These results suggest that three different active sites are formed on the Pt/α-Al2O3. The first is a SMR active site not affected by DMS. The second is an active site that loses activity due to DMS, but completely regenerates after the supply of DMS is stopped. The third is not an active site of SMR but where sintered Pt accelerates methane decomposition to produce carbon.メタン水蒸気改質(SMR)反応を0.1～2.0 wt% Pt/α-Al2O3触媒を用いて10 ppmのジメチルスルフィド（DMS）を含む条件と含まない条件で行った。DMSを含む場合は初期に劣化が生じるが失活には至らなかった。DMSの供給を停止すると活性は完全に元に戻った。DMSを含むガスの場合は1.0～2.0 wt% Pt/α-Al2O3触媒上のPtはシンタリングして炭素析出を促進した。このシンタリングと炭素生成挙動はSMR反応と無関係であった。一方，Pt担持量が0.1 wt%だと炭素析出は起こらなかった。これらの結果からPt/α-Al2O3触媒上には三つの活性サイトが形成されたと考えた。一つ目はDMSの影響を受けない活性点，二つ目はDMSにより活性を失うがDMSの供給を停止すると完全に再生する活性点，三つ目はSMRの活性点ではなくシンタリングしたPtがメタン分解を促進して炭素を生成する活性点である