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首页> 外文期刊>Catalysis science & technology >CO2 hydrogenation to higher hydrocarbons on K/Fe-Al-O spinel catalysts promoted with Si, Ti, Zr, Hf, Mn and Ce
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CO2 hydrogenation to higher hydrocarbons on K/Fe-Al-O spinel catalysts promoted with Si, Ti, Zr, Hf, Mn and Ce

机译：二氧化碳加氢更高的碳氢化合物K / Fe-Al-O尖晶石催化剂与Si提拔,Ti,Zr、高频、Mn, and Ce

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摘要

Metal oxides grafted on K/Fe-Al-O spinel precursors prepared by co-precipitation in the presence of the surfactant CTAB displayed significant effects on the performance of the catalysts in CO2 hydrogenation to hydrocarbons. Specifically, 20 wt% titania and 20 wt% zirconia increased the rates of both the reverse water gas shift reaction (RWGS) and the Fischer-Tropsch synthesis (FTS), as reflected in the increase of the CO2 conversion and the decrease of CO selectivity. While 20 wt% titania increased methane and C-2-C-4 selectivity and decreased C5+ selectivity, 20 wt% zirconia displayed no effect on methane and increased C-2-C-4 and C5+ selectivity. 5 wt% hafnia and 5 wt% manganese oxide had little effect on performance and 5 wt% ceria enhanced the selectivity to both methane and light C-2-C-4 and significantly decreased the selectivity to C5+. Silica inserted by grafting at the Fe-Al-O surface at 5 wt% acted as a promoter of CO2 conversion but at high loading of 15 wt% was a strong inhibitor to FTS, increased methane and CO selectivity and decreased CO2 conversion. Nanoparticles of both spinel and Fe-carbide phases in contact with zirconia caused a decline in the electron density of surface iron atoms, as reflected by the increase of the binding energy of Fe (2p) electrons by 0.7-0.8 eV as detected by XPS. This may be a result of a strong interaction of iron oxide and zirconia due to incorporation of Zr in the Fe-Al-O spinel structure and a strong interaction of near metallic iron in carbide nanocrystals in contact with ZrO2 nanoparticles that plays a role of an electron acceptor as a Lewis acid and explains the increase of CO2 conversion. The extremely low activity of the silica modified catalyst in FTS and enhanced activity in methanation are consistent with the model of selective blocking of the surface iron ions of the Fe-carbide component with grafted silica moieties and their interaction with the potassium promoter.
机译：金属氧化物嫁接在K / Fe-Al-O尖晶石前体共同沉淀的准备表面活性剂CTAB的显示重大影响的性能催化剂在二氧化碳加氢碳氢化合物。具体来说,20 wt %二氧化钛和20 wt %氧化锆增加了利率的反向水煤气转变(RWGS)和费托反应合成(FTS),反映在增加减少的二氧化碳转换和有限公司选择性。甲烷和C-2-C-4选择性和C5 +下降选择性,20 wt %氧化锆显示没有影响对甲烷和增加C-2-C-4和C5 +选择性。氧化对性能影响很小,5 wt %二氧化铈都提高了选择性甲烷和轻型C-2-C-4并显著降低了选择性C5 +。在Fe-Al-O表面5 wt %了但在高负载的启动子的二氧化碳转换15 wt %是一个强有力的抑制剂FTS,增加甲烷和一氧化碳选择性和减少二氧化碳转换。Fe-carbide阶段接触氧化锆表面铁的电子密度的下降了原子的增加铁(2 p)电子的结合能0.7 - -0.8 eVXPS探测到。强相互作用的氧化铁和氧化锆掺入Fe-Al-O Zr的尖晶石结构和附近的强相互作用金属铁碳化物纳米晶体在接触与氧化锆纳米颗粒,扮演的角色电子受体作为路易斯酸和解释道增加的二氧化碳转换。在FTS活性二氧化硅改性催化剂甲烷化和增强的活动与选择性阻塞的模型一致Fe-carbide表面的铁离子组件与接枝硅及其半个与钾交互促进剂。

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