碳纳米管的高温处理及表征

用真空高温炉对在纳米聚团流化床中用催化裂解法大批量制备的多壁碳纳米管进行了1500～2150℃的真空高温处理,并用高分辨透射电镜、激光拉曼、X射线晶体衍射及热重分析表征热处理效果.结果证明,高温处理对碳纳米管具有显著的整形作用,激光拉曼光谱可以有效地表征高温整形效果,但是管壁的大缺陷很难得到修复.经过1800℃处理以后,碳纳米管中的金属催化剂和载体得到有效去除,产品纯度高达99%以上.     

Study of Carbon Nanotube Supported Co-Mo Selective Hydrodesulphurization Catalysts for Fluid Catalytic Cracking Gasoline

In this paper, carbon nanotube supported Co-Mo catalysts for selective hydrodesulphurization （HDS） of fluid catalytic cracking （FCC） gasoline were studied, using di-isobutylene, cyclohexene, 1-octene and thiophene as model compounds to simulate FCC gasoline. The results show that the Co-Mo/CNT has very high HDS activity and HDS/hydrogenation selectivity comparing with the Co-Mo/γ-Al2O3 and Co-Mo/AC catalyst systems. The saturation ratio of cyclohexene was lower than 50%, and the saturation ratio of 1,3-di-isobutylene lower than 60% for the Co-Mo/CNT catalysts. Co/Mo atomic ratio was found to be one of the most important key factors in influencing the hydrogenation selectivity and HDS activity, and the most suitable Co/Mo atomic ratio was 0.4. Co/CNT and Mo/CNT mono-metallic catalysts showed lower HDS activity and selectivity than the Co-Mo/CNT bi-metallic catalysts.     

XPS Characterization of Carbon Nanotube Supported CoMo Hydrodesulfurization Catalysts

In this paper, the effect of catalytic support and sulfiding method on the chemical state of supported Co-Mo catalysts is studied by XPS. After sulfidation with in-situ method, the majority of molybdenum in CNT supported CoMo catalyst is transferred to a species with a formal chemical state Mo(Ⅳ) in MoS2 phase, and the rest to Mo(Ⅴ) which consists of Mo coordinated both to O and S, such as MoO2S2^2- and MoO3S^2-. In case of CoMo/γ-Al2O3 catalyst sulfided with in-situ method, a fraction of molybdenum is transferred to formal state Mo(Ⅳ) in the form of MoS2, but there is still a mount of unreduced Mo(VI) phase which is difficult to be sulfided. In CoMo/CNT catalyric system sulfided with ex-situ method, Mo(IV) in the form of MoS2 is detected along with a portion of unreduced Mo(VI) phase, suggesting that not all the Mo phases are reduced and sulfided by ex-situ method. As for CoMo/γ-Al2O3, a portion of molybdenum is sulfided to intermediate reduced state Mo(V) which consists of Mo coordinated both to O and S, such as MoO2S2^2- and MoO3S^2-, in addition, there is still a fraction of unreduced Mo(Ⅵ)phase. XPS analyses results suggest that CNT support facilitates the reduction and sulfidation of active species to a large extent, and that alumina support strongly interacts with active species, hereby producing a fraction of phase which resists complete sulfiding. Catalytic measurements of catalysts in the HDS of dibenzothiophene (DBT) show that CoMo/CNT catalysts are of higher HDS activity and selectivity than CoMo/γ-Al2O3 catalyst, which is in good relation with the sulfiding behavior of the corresponding catalyst.     

不同结构碳纳米管的电磁波吸收性能研究

研究了单壁、多壁碳纳米管(聚团状、阵列状)以及未纯化与纯化后碳纳米管在2～18 GHz范围内的电磁波吸收性能. 通过测定不同结构碳纳米管粉体的介电常数以及磁导率, 得到损耗因子及衰减常数大小顺序为: 阵列状多壁碳纳米管>原生聚团状多壁碳纳米管>纯化聚团状多壁碳纳米管>原生单壁碳纳米管>纯化后单壁碳纳米管. 相比多壁碳纳米管, 单壁碳纳米管衰减常数随频率变化较小, 且具有较宽的吸收峰. 模拟计算和实验测试结果都表明, 碳纳米管/聚合物复合材料具有优良的电磁吸波性能.     

甲醇芳构化反应中Ag/ZSM-5催化剂的失活特性

通过四次连续反应-再生循环实验对甲醇芳构化催化剂Ag/ZSM-5进行了失活再生研究,结果表明催化剂通过烧碳可以得到部分再生.对反应-再生后的催化剂进行了X射线衍射(XRD)、透射电子显微镜(TEM)表征,证实芳构化过程中催化剂的ZSM-5骨架结构保持完好,金属烧结也不严重.傅里叶红外光谱(FTIR)和氨-程序升温脱附(NH3-TPD)实验证实了反应生成的水使催化剂在475℃发生水热脱铝,进而导致Brφnsted酸流失及催化剂的芳构化反应能力不可逆下降.     

稠油的可控氧化热采：MnO2催化剂上的重油低温氧化分解行为

采用MnO2纳米催化剂促进稠油重组分的低温氧化裂解及高温氧化生热,进而促进火烧油层技术在超稠油油藏开发中的应用,提高火烧油层技术的采收率.结果表明, MnO2促进了稠油的低温裂解,高温生热量并不随燃料沉积量的减少而降低. MnO2的加入促进了低温下小分子的生成,并使高温氧化反应更加温和,提高了高温产物的氧化度.相比无催化剂的氧化反应, MnO2使稠油的低温氧化和高温氧化的表观活化能分别降低了10–30 kJ/mol和20–40 kJ/mol.     

催化剂对纳米聚团床法制备的纳米碳材料形貌的影响

 在纳米聚团床中用催化化学气相沉积法批量制备了碳纳米管，研\r\n究了过渡金属催化剂对碳纳米管形貌和产量的影响．实验结果表明，含\r\n铁催化剂的活性较低，产率较低，但产品质量较好；含镍催化剂的活性\r\n较高，产率较高，但产品质量较差；在钴催化剂作用下发现了一种新型\r\n的针状纳米碳材料．用含载体较少的铁催化剂可以得到纯度较高且微观\r\n结构较好的碳纳米管，但产率较低；不含任何载体的纯镍催化剂则不能\r\n得到碳纳米管．适宜的催化剂组成、催化剂活性点的均匀分布和裂解速\r\n度的控制等构成了纳米聚团床大批量制备碳纳米管技术的关键．     

水热改性对氧化铝载体织构和表面性质的影响

The alumina support was treated in the moderate aqueous hydrothermal condition to avoid from the excess growth of boehmite (AlOOH) crystals which usually results in the obvious decrease of the specific surface area (BET). The experimental results indicated that the hydrothermal treatment of the alumina support at 140 ℃ for 2 hours promoted the formation of the plate-like AlOOH crystallites on the surface of the support via dissolution-precipitation route. The occurrence of the nano plate-like structure led to the improvement in the structural and surface properties, such as the increase of the specific surface area, the surface hydroxyl concentration and the surface acidity.     

拉曼描述碳纳米管系统:缺陷探测,产物热处理,过程分析和催化剂(英文)

利用拉曼散射技术从多角度研究了碳纳米管合成系统。发现拉曼散射技术不仅可表征碳纳米材料本身的特性,而且可分析宏观的多壁碳纳米管与单壁碳纳米管的生长过程。针对不同的碳纳米材料的生长特性提出了催化剂与反应器设计及过程控制的研究方向。同时还发展了一种基于拉曼光谱法的定量测定单壁碳纳米管含量的方法。     

碳纳米管的宏量制备及产业化

作为纳米材料的代表之一,碳纳米管因其独特的一维结构具备了优异的力学、电学、热学、光学和反应性能,使其在能源存储与转化、复合材料、多相催化、环境保护及生物医药等领域具有大量的应用潜力.本文总结了多种类型碳纳米管宏量制备的化学及工程原理,并对多壁碳纳米管、单壁碳纳米管、双壁碳纳米管、定向碳纳米管、超顺排碳纳米管、水平超长碳纳米管、掺杂碳纳米管、螺旋碳纳米管、碳纳米管结及碳纳米管/石墨烯杂化物的宏量制备方法进行了评述.同时,对碳纳米管产业化中新的工程问题,如工业标准、环境评估以及产业化进展进行了分析.目前,碳纳米管已经具有成千吨的产能,并广泛应用于锂离子电池电极、导电复合材料、汽车配件和体育用品等领域.尽管如此,高性能的碳纳米管的宏量制备及其配套产业化技术仍有待深入开发,产品需要进一步丰富、市场需要进一步拓展,以望形成大规模纳米产业,促进社会的可持续发展.