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 C₂–C₄ selectivity and decreased C₅₊ selectivity, 20 wt% zirconia displayed no effect on methane and increased C₂–C₄ 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 C₂–C₄ 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.

中文翻译：

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Si，Ti，Zr，Hf，Mn和Ce促进的K / Fe–Al–O尖晶石催化剂上CO ₂加氢成高级烃

在表面活性剂CTAB存在下通过共沉淀制备的接枝在K / Fe-Al-O尖晶石前体上的金属氧化物显示出对CO ₂加氢成烃的催化剂性能的显着影响。具体来说，二氧化钛的含量为20 wt％，氧化锆的含量为20 wt％，则增加了水煤气变换反应（RWGS）和费托合成（FTS）的速率，这反映在CO ₂转化率的增加和CO的减少上。选择性。尽管20 wt％的二氧化钛增加了甲烷和C ₂ -C _4的选择性，降低了C _5+的选择性，但是20 wt％的氧化锆对甲烷无影响，而C ₂ -C ₄和C _5+的增加选择性。5 wt％的氧化f和5 wt％的氧化锰对性能的影响很小，而5 wt％的二氧化铈提高了对甲烷和轻度C ₂ -C ₄的选择性，并显着降低了对C ₅₊的选择性。通过在Fe–Al–O表面以5 wt％的接枝率插入的二氧化硅起到了CO ₂转化的促进剂的作用，但在15 wt％的高负载量下，它是FTS的强抑制剂，增加了甲烷和CO的选择性并降低了CO _2。转换。尖晶石相和碳化铁相的纳米粒子都与氧化锆接触，导致表面铁原子的电子密度下降，这是由XPS检测到的Fe（2p）电子的结合能增加了0.7-0.8 eV所反映的。这可能是由于在Fe–Al–O尖晶石结构中掺入Zr引起的氧化铁与氧化锆的强相互作用，以及与ZrO ₂纳米颗粒接触的碳化物纳米晶体中近金属铁的强相互作用所致。电子受体路易斯酸并解释了CO ₂的增加转换。二氧化硅改性催化剂在FTS中的极低活性和甲烷化中的增强活性与用接枝二氧化硅部分选择性封闭Fe-碳化物组分的表面铁离子及其与钾促进剂的相互作用的模型相一致。