【作者】 李雪芬；

【导师】 苏海全；

【作者基本信息】 内蒙古大学 ， 生态学， 2013， 博士

【摘要】 Co基催化剂是一种被大量研究的非贵金属催化剂,在F-T合成及CH4-CO2重整反应中均具有较好的催化活性。以不同形式的钴源作为前驱体制备催化剂,对催化剂的各种性质具有直接影响。由于钴羰基簇合物中的金属钴以零价态形式存在,以该簇合物为前驱体制备的催化剂具有良好的分散性和较高的催化反应活性。研究证明,助剂的添加能够有效改善钴基催化剂的反应活性、稳定性和选择性。稀土元素因其具有一定的碱性和给电子性能而成为催化反应中良好的助剂。本文通过钴羰基簇合物与稀土桥联将稀土助剂有效得引入催化剂,通过有机配体骨架使活性中心Co与稀土原子均匀分布,有利于在载体表面形成高分散的Ln-Co分布,稀土的存在降低了载体的酸性,促进了CO的解离,从而进一步提高了催化剂的反应活性。具体成果如下：1.合成了一系列不同核数(二核、三核、四核)的钴羰基簇合物,其中三核钴羰基簇合物为首次合成,并对其进行了结构表征和性质研究。2.通过配位取代法设计并合成了可控结构的三核钴簇与稀土(Ln=La、Ce、Sm、Eu)有机配体桥联配合物,并对合成的配合物进行了结构表征和性质研究。四种配位物均未见文献报道。3.以合成不同核数的钻羰基簇合物前驱体,以γ-Al2O3为载体制备一系列催化剂,对其进行性能表征,评价F-T反应催化活性及CH4-CO2重整催化活性。考察钴羰基簇合物在载体上的分布特征、表面性质及与载体之间的相互作用,分析了这些因素对F-T合成及CH4-CO2重整的影响。F-T反应评价结果表明,羰基簇合物为前驱体制备的催化剂与传统的硝酸钻为前驱体制备的催化剂相比,具有较高的催化反应活性,不同催化剂的CO转化率及C5+选择性顺序一致：Co3/γ-Al2O3>Co2/γ-Al2O3>Co4/γ-Al2O3>Co(N)/γ-Al2O3；CH4-CO2重整催化结果表明,以不同核数钴羰基簇为前驱体制备的催化剂具有不同的催化性能,其中10%Co(3)/γ-A1203具有优良的抗积炭性能。4.以合成的钴簇-稀土桥联配合物Ln-Co3(Ln=La、Ce、Sm、Eu)为前驱体,以γ-Al2O3为载体制备一系列催化剂,并评价其F-T反应催化活性及CH4-CO2重整催化活性。考察具有高度规则空间排布的钻簇-稀土桥联配合物在载体上的分布特征、表面性质及与载体之间的相互作用,分析了这些因素对F-T合成及CH4-CO2重整的影响。不同前驱体制备的催化剂F-T反应C5+选择性顺序为：Co-Ce/γ-Al2O3>Co-Eu/γ-Al2O3>Co-Sm/γ-Al2O3>Co-La/γ-Al2O3>Co+Ce/γ-Al2O3>Co(N)/γ-AlO3;对以四种钻簇-稀土桥联配合物为前驱体的催化剂进行CH4-CO2重整评价,发现在结构相似的情况下,原子序数相邻的稀土配合物催化剂活性差距不大,说明原子序数相邻的稀土具有相似的助剂效应。5.对以钴羰基簇合物为前驱体制备的催化剂及和以钴簇-稀土桥联配合物为前驱体制备的催化剂进行催化性能比较,结果如下：(1)F-T合成反应中,以钻簇-稀土桥联配合物为前驱体制备的催化剂CO转化率及C5+选择性均优于以钴羰基簇合物为前驱体制备的催化剂。(2) CH4-CO2重整反应中,以钴簇-稀土为前驱体制备的催化剂的催化活性高于以钴羰基簇合物为前驱体制备的催化剂,但其抗积炭能力要低于钴羰基簇合物为前驱体制备的催化剂。更多还原

【Abstract】 Supported cobalt is the preferred catalyst for the F-T synthesis and the CH4-CO2reforming, because of their high activity for catalytic reaction. The nature of the cobalt precursor has a large influence on various properties of the catalyst. The catalysts derived from cobalt carbonyl cluster with good dispersion and higher catalytic activities due to cobalt carbonyl clusters have provided zero valent metal particles. There is currently a consensus in the literature that promoter can improve the cobalt-based catalyst reactivity, stability and selectivity. Lanthanide is an excellent promoter for cobalt-based catalyst as a result of its unique properties.In this paper, catalysts were prepared by introduced lanthanide promoter into cobalt carbonyl clusters as precursors. The cobalt atoms and lanthanide, therefore, can be arranged in orderly rows on the supports by linked organic-ligand skeleton, leading to higher dispersion of cobalt-Ln on catalysts. Rare earth can reduce the acidity of the supports, promote the dissociation of CO and improve the activity of catalytic. Specific results are as follows:1. A series of cobalt carbonyl clusters with different cobalt atoms has been synthesized. The organometallic carboxylic cluster (CO)9Co3CCH2COOH was first synthesized and structure of Co3(CO)9CCH2COOH has been determined by X-ray diffraction.2. Four heterobimetallic complexes containing cobalt carbonyl cluster and lanthanide [Ln3{-OOCCCCo3(CO)9}(-OOCCF3)6(THF)3]2Co(-OH)6·THF (Ln=La,Ce, Sm, Eu) have been synthesized by reaction of Co4(CO)10HCCCOOH with Ln(-OOCCF3)3(Ln=La, Ce, Sm, Eu), and structurally characterized by single-crystal X-ray diffraction.3. New type of Co-based catalysts were prepared using Co2(CO)6HCCCOOH, Co3(CO)9CCH2COOH and Co4(CO)10HCCCOOH as precursors supported on γ-Al2O3. The Co(NO3)2can be used as precursor for preparing reference catalyst. The F-T synthesis and CH4-CO2reforming performance were investigated. The dispersion, metal particle size and interaction with support of metal cobalt derived from cobalt carbonyl catalysts were researched. The F-T synthesis results suggest that the CO conversion and C5+selectivity decreased in the following:Co3(CO)9CCH2COOH>Co2(CO)6HCCOOH>Co4(CO)10HCCCOOH>Co(NO3)2.. The CH4-CO2reforming results indicated that the catalyst prepared by the precursor of trinuclear cobalt carbonyl clusters exhibited a superior anti-coking property.4. Catalysts were prepared using lanthanide-cobalt clusters bridging complexes as catalyst precursors supported on γ-Al2O3. The F-T synthesis and CH4-CO2 reforming performance were explored. The dispersion, metal particle size and interaction with support of metal cobalt species derived from lanthanide-cobalt clusters bridging complexes were researched. The F-T synthesis results suggest that the CO conversion and C5+selectivity decreased in the order:Co-Ce/γ-Al2O3> Co-Eu/γ-Al2O3>Co-Sm/γ-Al2O3>Co-La/γ-Al2O3>Co+Ce/γ-Al2O3>Co(N)/γ-Al2O3； The CH4-CO2reforming results revealed that the catalysts prepared by the lanthanide-cobalt clusters bridging complexes with similar structures showed similar activity for the catalysts with adjacent atomic numbers.5. Comparisons of catalytic performance for lanthanide-cobalt clusters bridging complexes and cobalt carbonyl clusters as catalyst precursors were explored. The results as follows:(1) The catalytic activity and C5+selectivity of the catalysts prepared by the lanthanide-cobalt clusters bridging complexes were superior to those prepared by the cobalt carbonyl cluster and the mixture of cobalt carbonyl cluster with lanthanide salt.(2) The CH4-CO2reforming catalytic activity of the catalysts prepared by the lanthanide-cobalt clusters bridging complexes were better than that of those prepared by cobalt carbonyl cluster, but anti-carbon deposition of the catalysts prepared by lanthanide-cobalt clusters bridging complexes decreased on support.更多还原