Methanol Synthesis
Methanol Synthesis
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DOI：
10.1007/s10562-012-0905-2
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发表时间：
2012
影响因子：
2.8
通讯作者：
K. C. Waugh
中科院分区：
文献类型：
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作者：
K. C. Waugh
甲醇和氨一样，是通过多相催化生产的关键工业化学品之一。与最初的氨催化剂（Fe/K/Al 2 O3）一样，对于甲醇，最初的甲醇合成催化剂ZnO由Alwin Mittasch发现。这被转化为工业过程，其中在400 °C和200 atm下由CO/H2生产甲醇。同样，与氨催化剂一样，目前使用的最终催化剂只有在彻底筛选推定的“促进剂”后才能获得，因此对于甲醇，对添加剂进行了彻底筛选以促进ZnO的活性。早期成功的促进剂是Al_2O_3和Cr_2O_3，它们提高了ZnO的稳定性，但没有提高其活性。发现CuO的加入提高了ZnO的活性，但如此制备的催化剂寿命短。目前的甲醇合成催化剂基本上是Cu/ZnO/Al 2 O3，具有约60%的高CuO含量，ZnO约30%，Al 2 O3约10%。这些Cu/ZnO/Al_2O_3催化剂的活性组分是Cu金属，而ZnO只是作为优选的载体，而不是通过掺入CuO来促进ZnO的活性。也可以使用Cu金属的其它载体，例如Al 2 O3、MgO、MnO、Cr2 O3、ZrO 2和甚至SiO2。在所有这些催化剂中，活性与Cu金属面积成比例。最初的进料现已从CO/H2变为CO/CO2/H2（10：10：80），放射性标记研究提供了不太可能的发现，即CO 2分子被氢化为甲醇; CO分子充当还原剂。CO2通过吸附的甲酸盐物种的中间作用在Cu上转化为甲醇。这些Cu/ZnO/Al 2 O3催化剂现在在~230°和50 - 100 atm之间操作。甲醇合成活性的这一重要步骤变化导致生产甲醇所需的能量显著降低。然而，“阶跃变化”是渐进的。它是基于由表面科学技术的组合提供的基础知识而获得的，所述表面科学技术例如LEED、扫描隧道显微镜、TPD、程序升温反应光谱，与催化机理研究（包括放射性标记研究）和化学吸附研究（包括反应性化学吸附研究，例如N2 O反应性前沿色谱法）相结合。
Methanol, like ammonia, is one of the key industrial chemicals produced by heterogeneous catalysis. As with the original ammonia catalyst (Fe/K/Al2O3), so with methanol, the original methanol synthesis catalyst, ZnO, was discovered by Alwin Mittasch. This was translated into an industrial process in which methanol was produced from CO/H2at 400 °C and 200 atm. Again, as with the ammonia catalyst where the final catalyst which is currently used was achieved only after exhaustive screening of putative “promoters”, so with methanol, exhaustive screening of additives was undertaken to promote the activity of the ZnO. Early successful promoters were Al2O3and Cr2O3which enhanced the stability of the ZnO but not its activity. The addition of CuO was found to increase the activity of the ZnO but the catalyst so produced was short lived. Current methanol synthesis catalysts are fundamentally Cu/ZnO/Al2O3, having high CuO contents of ~60 % with ZnO ~ 30 % and Al2O3~ 10 %. Far from promoting the activity of the ZnO by incorporation of CuO, the active component of these Cu/ZnO/Al2O3catalysts is Cu metal with the ZnO simply being involved as the preferred support. Other supports for the Cu metal, e.g. Al2O3, MgO, MnO, Cr2O3, ZrO2and even SiO2can also be used. In all of these catalysts the activity scales with the Cu metal area. The original feed has now changed from CO/H2to CO/CO2/H2(10:10:80), radiolabelling studies having provided the unlikely discovery that it is the CO2molecule which is hydrogenated to methanol; the CO molecule acts as a reducing agent. The CO2is transformed to methanol on the Cu through the intermediacy of an adsorbed formate species. These Cu/ZnO/Al2O3catalysts now operate at ~230° and between 50 and 100 atm. This important step change in the activity of methanol synthesis has resulted in a significant reduction in the energy required to produce methanol. The “step change” however has been incremental. It has been obtained on the basis of fundamental knowledge provided by a combination of surface science techniques, e.g. LEED, scanning tunnelling microscope, TPD, temperature programmed reaction spectroscopy, combined with catalytic mechanistic studies, including radiolabelling studies and chemisorption studies including reactive chemisorption studies, e.g. N2O reactive frontal chromatography.