Synthesis of C_<2+> Alcohols from Syngas over Supported Metal Catalysts Containing Small Amounts or Rh

单金属催化剂Ir和Mo活性极低，主要产物为烃类。另一方面，Ir-Mo双金属催化剂表现出高活性，对C_<2+>醇的选择性提高。氧化钼在Mo单金属催化剂中生成，金属Mo在Ir-Mo催化剂中生成。这表明Mo是被从Ir金属中迁移过来的氢所还原的。TPR实验表明，吸附在Ir上的CO也会迁移到Mo上，CO和氢在Mo金属上发生反应。结果表明，含少量Rh的二氧化硅负载Ir-Mo-Rh催化剂的Co加氢活性远高于Ir-Mo双金属催化剂。Rh的加入对不同醇的选择性变化不大。催化剂制备过程中金属的浸渍工艺对催化剂的活性有很大影响。研究了对C_<2+>醇的选择性提高，发现氧化锆载体的使用和Li的加入提高了C_<2+>醇的选择性。提出了一种利用微乳液制备负载型金属催化剂的新方法。结果表明，该方法制备的硅负载铑催化剂具有极小的铑颗粒，且其尺寸分布明显狭窄。该催化剂的CO加氢活性明显高于浸渍法制备的常规催化剂，对C_<2+>醇具有较高的选择性。

Monometallic catalysts, Ir and Mo, were extremely low in activity and yielded hydrocarbon as main products. On the other hand, Ir-Mo bimetallic catalyst exhibited an high activity, and an increase in the selectivity to the C_<2+> alcohols was observed on the bimetallic catalyst. Mo dioxide was formed in the Mo monometallic catalyst while Mo metal was formed in the Ir-Mo catalyst. This suggests that Mo was reduced with hydrogen species migrated from Ir metal. From the TPR experiment, it was suggested that CO adsorbed on Ir also migrates onto Mo, and that CO and hydrogen reacted over Mo metal.It was found that Ir-Mo-Rh supported on silica containing small amounts of Rh exhibited much higher activity for Co hydrogenation than Ir-Mo bimetallic catalyst. The selectivity to various alcohols did not change very much upon the addition of Rh. The activity was greatly affected by the impregnation procedure of the metals in the catalyst preparation. The increase of selectivity to C_<2+> alcohols was investigated, and it was found that use of zirconia support and the addition of Li enhanced the selectivity of C_<2+> alcohols.We proposed a novel preparation method of supported metal catalysts using microemulsions. It was found that silica-supported Rh catalyst prepared by this method had extremely small rhodium particles, and that their size distribution was appreciably narrow. This catalyst exhibited much higher activity for the CO hydrogenation than the conventional catalysts prepared by impregnation, and showed high selectivity to C_<2+> alcohols as well as the conventional catalysts.