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首页> 外文期刊>Catalysis science & technology >Effects of CO2 on the deactivation behaviors of Co/Al2O3 and Co/SiO2 in CO hydrogenation to hydrocarbons
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Effects of CO2 on the deactivation behaviors of Co/Al2O3 and Co/SiO2 in CO hydrogenation to hydrocarbons

机译：二氧化碳的失活行为的影响Co /氧化铝和Co / SiO2 Co加氢碳氢化合物

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摘要

Different deactivation behaviors of the prototype Co/gamma-Al2O3 (CoAl) and Co/SiO2 (CoSi) catalysts under an excess CO2 environment were investigated in terms of the surface oxidation and aggregation of cobalt crystallites for the Fischer-Tropsch synthesis (FTS) reaction. The presence of excess CO2 in the syngas feed largely altered the catalytic activity and product distribution, especially on the CoAl catalyst. A relatively faster deactivation and lower C5+ selectivity under an excess CO2 environment were observed on CoAl compared with the CoSi, which also were fairly stable under the same reaction conditions. From measurements of the reduction-oxidation behaviors of the cobalt crystallites, it could be seen that CO2 molecules acted as a mild oxidant by partially oxidizing the exposed metallic cobalt surfaces. The dramatic decrease in CO conversion and an increase in CH4 selectivity under the CO2 environment over CoAl were mainly attributed to the irreducible oxidation of the metallic cobalt surfaces through strong interactions with the Al2O3 support. Meanwhile, the marginal deactivation rate and lower changes of selectivity on CoSi were mainly attributed to the reversible oxidation-reduction property of the metallic cobalt crystallites by forming larger cobalt crystallites with relatively weak interactions with the SiO2 support. An excess exposure to the mild oxidant of CO2 on the FTS catalysts generally decreased the catalytic activity irreversibly by forming strongly interacted large cobalt crystallites, which was more predominantly seen on the acidic Co/Al2O3 than on the Co/SiO2 catalyst. The easy reversibility of the oxidation-reduction of the surface metallic cobalt crystallites on SiO2 even in the presence of excess CO2 could prevent catalyst deactivation during the FTS reaction.
机译：不同的失活行为的原型催化剂过量二氧化碳环境下调查的表面氧化和聚合的微晶钴费托合成反应(FTS)。合成气饲料主要存在多余的二氧化碳改变了催化活性和产品分布,特别是在煤催化剂。相对更快的失活和C5 +低过量的二氧化碳环境下选择性观察到对煤炭与CoSi相比,哪个在同样的反应也相当稳定条件。reduction-oxidation钴的行为微晶,它可以看到二氧化碳分子作为一个温和的氧化剂,部分氧化裸露的金属钴表面。和一个戏剧性的减少公司转换增加二氧化碳甲烷选择性在煤炭主要是归因于环境的不可约氧化金属钴通过强相互作用的表面氧化铝的支持。失活率和低的变化CoSi主要归因于选择性可逆的氧化还原性质金属钴微晶的形成更大钴微晶相对较弱与二氧化硅的交互支持。暴露在二氧化碳的温和的氧化剂在罚球催化剂通常降低了催化活动由形成强烈的不可逆转相互作用大型钴微晶,这是更主要是在酸性有限公司/氧化铝比有限公司/二氧化硅催化剂。的氧化还原可逆性表面金属钴微晶二氧化硅在过量的二氧化碳的存在可以防止在FTS反应催化剂失活。

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