A desirable process for realizing a low-carbon society is the direct conversion of dilute CO₂ from flue gases or air into highly concentrated hydrocarbons without a need for separate CO₂ capture and purification processes. In this study, we investigated the performance of integrated CO₂ capture and reduction to CH₄ over Ni-based dual-functional catalysts promoted with Na, K, and Ca. Ni/Na-γ-Al₂O₃ exhibited the highest activity for integrated CO₂ (5% CO₂) capture and reduction, achieving high CO₂ conversion (>96%) and CH₄ selectivity (>93%). In addition, very low-concentration CO₂ (100 ppm CO₂) was successfully converted to 11.5% CH₄ at the peak point (>1000 times higher concentration than that of the supplied CO₂) over Ni/Na-γ-Al₂O₃. The Ni-based dual-functional catalyst exhibited a high CO₂ conversion exceeding 90%, even when 20% O₂ was present during CO₂ capture. Furthermore, an increased operation pressure had positive impacts on both CO₂ capture and CH₄ formation, and these advantageous effects were also observed when CO₂ concentration was at the level of atmospheric CO₂ (100–400 ppm). As the pressure increased from 0.1 to 0.9 MPa, CH₄ production capacity with 400 ppm CO₂ was enhanced from 111 to 160 μmol g_cat^–1. This approach in combination with the efficient catalyst shows encouraging potential for CO₂ utilization, enabling direct air capture-conversion to value-added chemicals.

中文翻译：

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在加压条件下向大气中利用CO _2时，集成的CO ₂捕集和还原为CH _4的活性增强

实现低碳社会的理想方法是将稀薄的CO ₂从烟道气或空气直接转化为高浓度的碳氢化合物，而无需单独的CO ₂捕获和纯化过程。在这项研究中，我们调查了用Na，K和Ca促进的Ni基双功能催化剂对集成CO ₂捕集和CH ₄还原的性能。的Ni /钠的γ-Al ₂ ö ₃表现出最高的活性集成CO ₂（5％CO ₂）捕获和降低，实现高CO ₂转化率（> 96％）和CH ₄选择性（> 93％）。另外，极低浓度的CO₂（100ppm的CO ₂）被成功地转化为11.5％CH ₄在峰值点（>比所提供的CO的1000倍浓度高₂）在Ni / NA的γ-Al ₂ ö ₃。即使在CO ₂捕获期间存在20％的O ₂，Ni基双功能催化剂也表现出超过90％的高CO ₂转化率。此外，增加的操作压力对CO ₂捕获和CH ₄形成均具有积极影响，并且当CO ₂浓度处于大气CO ₂水平时也观察到这些有利影响。（100-400 ppm）。随着压力从0.1 MPa增加到0.9 MPa，具有400 ppm CO _2的CH ₄生产能力从111μmolg _cat ^–1增加到160μmolg _cat ^–1。这种方法与高效催化剂的结合显示出令人鼓舞的CO ₂利用潜力，使直接的空气捕集转化为增值化学品成为可能。