Abstract:

The direct synthesis of olefins by CO₂ hydrogenation with iron-based catalysts is one of the best ways to achieve CO₂ emission reduction and CO₂ conversion and utilization. At present, the CO₂ hydrogenation activity and structural strength of the iron-based catalysts are still relatively low during CO₂ hydrogenation process, which has become an important challenge for the industrialization of CO₂ hydrogenation to olefins. In this work, a series of the supported iron-based catalyst was prepared by the impregnation method to study the influence of the properties of support materials on the structure of iron-based catalysts and the reactivities of the direct synthesis of olefins from CO₂ hydrogenation. This work found that the support induced the iron species formed during the process of CO₂ hydrogenation, simultaneously affected the order degree of carbon species on the surface of iron-based catalyst, and tuned the capability of CO₂ adsorption and the activities of CO₂ activation. The results shown that the Fe-based catalyst supported on ZrO₂ exhibited the best catalytic performance for CO₂ hydrogenation to olefins at 320℃ and 2.0 MPa. The CO₂ conversion (>30%) and the selectivity of olefins in C₂—C₇ hydrocarbon products were as high as over 85%, the ratio of olefins to paraffins was 8.2, and the CO selectivity was 17.1%.

Key words: carbon dioxide, hydrogenation, catalyst, support, olefins, iron species, alkali metal, Na, surface carbon species

摘要：

铁基催化剂CO₂加氢直接合成烯烃是实现CO₂减排及CO₂转化与利用的最佳途径之一。目前铁基催化剂的CO₂加氢活性及反应过程中铁基催化剂结构强度仍然较低，成为CO₂加氢制烯烃产业化生产的重要挑战。通过浸渍法制备一系列负载型铁基催化剂，研究载体材料性质对铁基催化剂结构及CO₂加氢直接合成烯烃的影响特性。研究发现，载体可诱导铁基催化剂在CO₂加氢反应过程中形成的铁物种，同时影响铁基催化剂表面碳物种的有序度，调变对CO₂吸附及活化能力；研究结果表明ZrO₂负载的Fe催化剂展现出最佳的CO₂加氢合成烯烃催化性能，在温度320℃和反应压力2.0 MPa时，CO₂转化率>30%，C₂~C₇烃类产物中烯烃选择性高达85%以上，烯烷比为8.2，且CO选择性较低为17.1%。

关键词: 二氧化碳, 加氢, 催化剂, 载体, 烯烃, 铁物种, 碱金属, 钠, 表面碳物种