无额外供氢体下负载型MoFeO_x催化剂催化甘油制丙烯醇

采用浸渍法制备MoFe/X(X=SnO_2,ZrO_2,CeO_2,TiO_2,CNTs,MgO)以及MoFe氧化物催化剂用于甘油气-固相催化转化制丙烯醇。通过XRD、BET、XPS、H_2-TPR和NH_3-TPD表征,MoFe主要由晶相Fe_2O_3和Fe_2(MoO_4)_3组成而MoFe/X主要为高分散态的Fe、Mo氧化物(Fe~(3+)、Mo~(6+)),其表面均只存在弱酸中心;所采用载体由于自身性质(比表面积和酸碱性)差异与Mo、Fe氧化物之间存在不同的相互作用,进而有效地调控了MoFe/X的表面弱酸强度、酸浓度和可还原性能。所制备催化剂对甘油制丙烯醇的催化性能(收率)依次为:MoFe/TiO_2MoFe/CeO_2MoFe/ZrO_2MoFe/CNTsMoFe/SnO_2MoFeMoFe/MgO。340°C时,MoFe/TiO_2上甘油的转化率达到83.4%,丙烯醇的选择性和收率分别达到26.7%和22.3%;同时其展现出优于MoFe/CeO_2、MoFe/ZrO_2和MoFe/CNTs的稳定性。甘油转化率与催化剂表面弱酸中心浓度呈正相关性,而丙烯醇的生成则与氧化中心(非酸中心)密切相关。甘油转化率和丙烯醇选择性在MoFe/X上随反应温度变化而呈现相悖的变化趋势。

MoFeOx-Supported Catalysts for the Catalytic Conversion of Glycerol to Allyl Alcohol without External Hydrogen Donors

Supported MoFe/X (X=SnO₂, ZrO₂, CeO₂, TiO₂, CNTs (Carbon nano-tubes)), MgO and MoFe oxide catalysts were prepared for use in the catalytic conversion of glycerol to allyl alcohol. The prepared catalysts were characterized by XRD, BET, XPS, H₂-TPR, and NH₃-TPD. The results showed that Fe and Mo oxides with high chemical value (Fe³⁺ and Mo⁶⁺) predominated in MoFe/X MoFe oxide catalysts, which exhibited only weakly acidic properties. The applied supports with different physicochemical characteristics showed distinct interactions with Mo and Fe oxides, modifying the concentration of surface weak acid site, acid strength, and reducibility of MoFe/X oxide catalysts. The catalysts, based on their catalytic performance for glycerol conversion to allyl alcohol, can be ranked in terms of allyl alcohol yield as MoFe/TiO₂ > MoFe/CeO₂ > MoFe/ZrO₂ > MoFe/CNTs >> MoFe/SnO₂ > MoFe >> MoFe/MgO. Over the MoFe/TiO₂, a maximum allyl alcohol yield of 22.3% was from glycerol conversion of 83.4%, which had a selectivity of 26.7%. The MoFe/TiO₂ also showed higher catalytic stability than the MoFe/CeO₂, MoFe/ZrO₂, and MoFe/CNTs oxide catalysts. The glycerol conversion showed positive relationship with the surface weak acid concentration of MoFe and MoFe/X catalysts, while the allyl alcohol was produced over the redox sites (non-acid sites) of catalysts. With increasing reaction temperature, the glycerol conversion increased, while the allyl alcohol selectivity decreased, over the MoFe/X oxide catalysts.