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Alkali Promotion in the Formation of CH4 from CO2 and Renewably Produced H2 over Supported Ni Catalysts
ChemCatChem ( IF 3.8 ) Pub Date : 2020-03-01 , DOI: 10.1002/cctc.202000327
Charlotte Vogt 1 , Jochem Wijten 1 , Chantal Leal Madeira 1 , Oscar Kerkenaar 1 , Kangming Xu 2 , Rupert Holzinger 2 , Matteo Monai 1 , Bert M. Weckhuysen 1
Affiliation  

In Power‐to‐Methane (PtM) plants, the renewable electricity supply can be stabilized by using green electrons to produce H2 via H2O electrolysis, which is subsequently used to hydrogenate CO2 into CH4. In this work PtM is studied in a cascade fashion, from simulated solar light to methane production in an all‐in‐one setup, which was newly developed for this work. This setup was used to assess the effects of H2 stream purity on the activity of Ni/SiO2 catalysts in CO2 methanation. An activity effect in downstream methanation is shown to be onset by aerosols that evolve from the electrochemical splitting of water. Small amounts of K are shown to affect CH4 production positively, but only if they are deposited in situ, via KOH aerosols. K‐doped Ni/SiO2 catalysts prepared in an ex situ manner, by impregnation with a KOH solution, showed a decrease in activity, while the same amount of KOH was deposited. Operando FT‐IR spectroscopy reveals that increased back‐donation to CO‐containing intermediates and carbonates formation likely causes catalyst deactivation in ex situ samples as often reported in literature for Ni/SiO2 catalysts. The mechanism for in situ promotion is either an increased rate in the hydrogenation of CHx (X=0–3) fragments, or a more facile water formation or desorption as CO‐containing reaction intermediates are unaffected by in situ promotion. These results are relevant to PtM from a fundamental standpoint explaining the effect of potassium on nickel methanation, but also from a practical standpoint as the presented effect of in situ promotion is difficult to achieve via standard synthesis methods.

中文翻译:

负载型Ni催化剂上碱促进从CO2形成CH4和可再生产生的H2

在沼气发电站(PtM)中,可通过使用绿色电子通过H 2 O电解产生H 2来稳定可再生电力供应,然后将其用于将CO 2加氢成CH 4。在这项工作中,对PtM进行了级联研究,从模拟太阳光到沼气的一体化生产,这是针对这项工作而新开发的。该设置用于评估H 2物流纯度对CO 2甲烷化中Ni / SiO 2催化剂活性的影响。下游甲烷化的活性效应被证明是由水的电化学分解产生的气溶胶引起的。少量K会影响CH肯定会产生4种产量,但前提是必须通过KOH气雾剂原位沉积。通过用KOH溶液浸渍以非原位方式制备的K掺杂Ni / SiO 2催化剂显示出活性降低,而沉积了相同量的KOH。Operando FT-IR光谱显示,向含CO的中间体的返碳和碳酸盐形成的增加可能会导致异位样品中催化剂失活,这在Ni / SiO 2催化剂的文献中经常有报道。原位促进的机理是CH x氢化的速率增加(X = 0–3)碎片,或者水更容易形成或脱附,因为含CO的反应中间体不受原位促进作用的影响。从基本的角度解释钾对镍甲烷化的影响,这些结果与PtM相关,但从实际的角度来看,由于难以通过标准合成方法实现现有的原位促进效果,因此与PtM相关。
更新日期:2020-03-01
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