不同炭载体上碳化钼催化剂的合成

Synthesis of Molybdenum Carbide Catalysts over Different Carbon Supports

在三种不同炭材料上用程序升温还原法成功制备了负载型Mo2C催化剂,并用X射线衍射和程序升温还原-质谱检测了合成过程中Mo2C的形成历程.结果显示,炭材料的性质及合成条件均对Mo2C的形成温度及合成过程有着显著的影响.以纯氢为反应气体时,石墨化程度较高的炭黑载体上钼物种可被还原为金属Mo,再与碳物种直接碳化生成Mo2C;在碳纳米管载体上Mo2C的生成温度较炭黑上低;在活性炭载体上钼物种只被还原到较低的氧化态,之后与碳反应生成Mo2C.当氢气不足或在惰性气氛下,炭载体在高于700℃时还原钼物种并使之发生碳化生成Mo2C.

Molybdenum carbide catalysts were successfully prepared using three types of carbon materials as supports and carbon sources （carburizers） by the hydrogen or carbothermal reduction method. The results of X-ray diffraction and temperature-programmed reduction-mass spectroscopy showed that the nature of the carbon materials and synthetic conditions influenced the formation of molybdenum carbide. The molybdenum species could be reduced to metallic molybdenum over the graphitic carbon （carbon black） material in hydrogen atmosphere, and then the metallic molybdenum was carbonized directly by carbon to molybdenum carbide. The formation temperature for molybdenum carbide over carbon nanotubes was lower than that over carbon black. Under the condition of hydrogen insufficiency or inert gas, the molybdenum species was reduced and carbonized by carbon to molybdenum carbide at above 700 ℃.