催化学报

催化学报 ›› 2006, Vol. 27 ›› Issue (11): 1019-1027.

• 研究论文 • 上一篇    下一篇

碳纳米管促进的Co-Mo-K硫化物基催化剂用于合成气制低碳混合醇

马晓明,林国栋,张鸿斌   

  1. 厦门大学化学化工学院, 固体表面物理化学国家重点实验室, 福建厦门 361005
  • 收稿日期:2006-11-25 出版日期:2006-11-25 发布日期:2006-11-25

Co-Mo-K Sulfide-Based Catalyst Promoted by Multi-walled Carbon Nanotubes for Higher Alcohol Synthesis from Syngas

MA Xiaoming, LIN Guodong, ZHANG Hongbin*   

  1. College of Chemistry and Chemical Engineering, State Key Laboratory of Physical Chemistry of Solid Surfaces, Xiamen University, Xiamen 361005, Fujian, China
  • Received:2006-11-25 Online:2006-11-25 Published:2006-11-25

PDF

925

被引次数

74

摘要： 以自行制备的多壁碳纳米管(CNT)作为添加剂,制备共沉淀型CNT促进的Co-Mo-K硫化物基催化剂. 实验发现,与未添加CNT的催化剂相比,添加少量CNT可显著提高CO的加氢转化活性和生成低碳醇的选择性. 在5.0 MPa, 623 K, V(CO)∶V(H2)∶V(N2)=45∶45∶10, GHSV=3600 ml/(g·h)的反应条件下, Co1Mo1K0.3-10%CNT催化剂上CO的转化率达21.6%, 相应的总醇(C1～4醇)时空产率为241.5 mg/(g·h), 产物中C2+醇/C1醇=1.39 (C基选择性比). 添加少量CNT并不会导致Co1Mo1K0.3硫化物基催化剂上CO加氢反应表观活化能发生明显变化,但却导致工作态催化剂表面催化活性Mo物种(Mo4+)的摩尔百分率有所提高; 另一方面, CNT促进的催化剂对H2有更强的吸附活化能力,并能在相当大程度上抑制水煤气变换副反应的发生. 这些因素有利于提高催化剂的活性和选择性.

关键词: 多壁碳纳米管, 助剂, 钴, 钼, 钾, 硫化物基催化剂, 一氧化碳, 加氢, 低碳醇合成

Abstract: Using home-made multi-walled carbon nanotubes (CNT) as the promoter, sulfurized Co-Mo-K catalysts (denoted as CoiMojKk-x%CNT) were prepared by the co-precipitation method. Their catalytic performance for higher alcohol synthesis from syngas was evaluated and compared with that of the CNT-free counterpart (CoiMojKk). Appropriate incorporation of a minor amount of CNT into CoiMojKk led to a significant increase in CO conversion and selectivity for the higher alcohols. Under the reaction conditions of 5.0 MPa, 623 K, V(H2)∶V(CO)∶V(N2)=60∶30∶10, and GHSV=3600 ml/(g•h), the observed space-time-yield of total (C1-4) alcohols reached 241.5 mg/(g•h) with CO conversion of 21.6% over the Co1Mo1K0.3-10%CNT catalyst, which was 1.84 times that over Co1Mo1K0.3. Ethanol became the dominant product of the CO hydrogenation under the conditions mentioned above. The water-gas-shift (WGS) side reaction was inhibited to a greater extent over the CNT-promoted catalyst. The results of catalyst characterization indicated that the addition of a minor amount of CNT into the Co1Mo1K0.3 catalyst did not cause an obvious change in the apparent activation energy for the conversion of CO but led to an increase in the molar percentage of catalytically active Mo-species (Mo4+) in the total Mo amount at the surface of the functioning catalyst. Based on the temperature-programmed desorption results, it could be inferred that, under the conditions of the higher alcohol synthesis, there existed a considerably larger amount of reversibly adsorbed H-species on the CNT-promoted catalyst, which would generate a surface micro-environment with high stationary-state concentration of the adsorbed H-species on the catalyst and thus increase the rate of a series of surface hydrogenation reactions. In addition, high stationary-state concentration of adsorbed H-species on the surface of catalyst would effectively inhibit the WGS side reaction. These factors contribute considerably to the increase in the main product yield.

Key words: multi-walled carbon nanotube, promoter, cobalt, molybdenum, potassium, sulfide-based catalyst, carbon monoxide, hydrogenation, higher alcohol synthesis