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Characterization and catalytic activity of soft-templated NiO-CeO 2 mixed oxides for CO and CO 2 co-methanation
Frontiers of Chemical Science and Engineering ( IF 4.3 ) Pub Date : 2020-08-12 , DOI: 10.1007/s11705-020-1951-8
Luciano Atzori , Maria Giorgia Cutrufello , Daniela Meloni , Barbara Onida , Delia Gazzoli , Andrea Ardu , Roberto Monaci , Maria Franca Sini , Elisabetta Rombi

Nanosized NiO, CeO2 and NiO-CeO2 mixed oxides with different Ni/Ce molar ratios were prepared by the soft template method. All the samples were characterized by different techniques as to their chemical composition, structure, morphology and texture. On the catalysts submitted to the same reduction pretreatment adopted for the activity tests the surface basic properties and specific metal surface area were also determined. NiO and CeO2 nanocrystals of about 4 nm in size were obtained, regardless of the Ni/Ce molar ratio. The Raman and X-ray photoelectron spectroscopy results proved the formation of defective sites at the NiO-CeO2 interface, where Ni species are in strong interaction with the support. The microcalorimetric and Fourier transform infrared analyses of the reduced samples highlighted that, unlike metallic nickel, CeO2 is able to effectively adsorb CO2, forming carbonates and hydrogen carbonates. After reduction in H2 at 400 °C for 1 h, the catalytic performance was studied in the CO and CO2 co-methanation reaction. Catalytic tests were performed at atmospheric pressure and 300 °C, using CO/CO2/H2 molar compositions of 1/1/7 or 1/1/5, and space velocities equal to 72000 or 450000 cm3·h−1·gcat−1. Whereas CO was almost completely hydrogenated in any investigated experimental conditions, CO2 conversion was strongly affected by both the CO/CO2/H2 ratio and the space velocity. The faster and definitely preferred CO hydrogenation was explained in the light of the different mechanisms of CO and CO2 methanation. On a selected sample, the influence of the reaction temperature and of a higher number of space velocity values, as well as the stability, were also studied. Provided that the Ni content is optimized, the NiCe system investigated was very promising, being highly active for the COx co-methanation reaction in a wide range of operating conditions and stable (up to 50 h) also when submitted to thermal stress.



中文翻译:

软模板NiO-CeO 2混合氧化物的表征及对CO和CO 2共甲烷化的催化活性

采用软模板法制备了不同Ni / Ce摩尔比的纳米NiO,CeO 2和NiO-CeO 2混合氧化物。所有样品均通过不同技术对其化学组成,结构,形态和质地进行了表征。在用于活性测试的相同还原预处理催化剂上,还测定了其表面基本性能和比金属表面积。无论Ni / Ce的摩尔比如何,都可获得尺寸约为4nm的NiO和CeO 2纳米晶体。拉曼和X射线光电子能谱结果证明在NiO-CeO 2处形成缺陷部位界面,其中Ni物种与支持物强烈相互作用。还原样品的微量热分析和傅立叶变换红外分析结果表明,与金属镍不同,CeO 2能够有效吸附CO 2,形成碳酸盐和碳酸氢盐。在400°C下H 2还原1 h后,研究了CO和CO 2共甲烷化反应的催化性能。在大气压力和300°C下使用1/1/7或1/1/5的CO / CO 2 / H 2摩尔组成和空速等于72000或450000 cm 3 ·h -1 ·进行催化测试g-1。在任何研究的实验条件下,CO几乎都被氢化,而CO 2转化率受CO / CO 2 / H 2比和空速的强烈影响。鉴于CO和CO 2甲烷化的不同机理,解释了更快和绝对优选的CO加氢。在选定的样品上,还研究了反应温度和更高数量的空速值以及稳定性的影响。只要优化Ni含量,研究的NiCe系统就很有前景,对CO x具有高活性 共甲烷化反应在宽范围的操作条件下也很稳定(长达50小时),即使受到热应力也是如此。

更新日期:2020-08-12
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