负载型P-Mo-V/SBA-15催化剂上的甲烷选择氧化反应

以磷钼钒杂多酸(H₅PMo₁₀V₂O₄₀)为前驱体、介孔SBA-15为载体, 采用浸渍法制备不同负载量的P-Mo-V氧化物催化剂. 在甲烷选择氧化反应中, 考察了负载量、反应温度、空速等对甲烷转化率和产物选择性的影响. 结果表明, 催化剂对甲烷选择氧化制甲醛具有较高活性, 甲烷转化率随负载量的增大和反应温度的升高而提高, 甲醛的选择性随负载量的增大先升后降. 反应温度为640 ℃、空速为48300 L•kg^－1•h^－1、氧化物负载量w＝2.89%时, 甲醛的时空产率最高(295 g•kg_cat^－1•h^－1). 多种表征表明, 氧化物负载量w≤2.89%时, P-Mo-V氧化物在载体介孔孔道内以高分散形式存在. 催化剂的酸性和氧化还原性质与负载量相关, NH₃-TPD和H₂-TPR的测试结果表明, 较弱的酸性位和较低还原温度的活性组分有利于甲烷选择氧化制甲醛.

Selective Oxidation of Methane on SBA-15 Supported P-Mo-V Oxide Catalysts

A series of catalysts with different contents of P-Mo-V mixed oxide supported on SBA-15 have been prepared by an impregnation method using H₅PMo₁₀V₂O₄₀ (HPA) as a precursor. The effects of P-Mo-V mixed oxide loading, reaction temperature and space velocity (GHSV) on the catalytic performance of selective oxidation of methane were investigated. The results indicate that the catalysts exhibit high selectivity to HCHO. CH₄ conversion increases with increasing the loading of P-Mo-V mixed oxide and reaction temperature. The selectivity to HCHO reaches a maximum at certain loading of P-Mo-V mixed oxide. A space time yield of 295 g•kg_cat^－1•h^－1 was obtained over the catalyst of 2.89PMoV/SBA-15 under the optimum condition of 640 ℃ and GHSV of 48300 L•kg^－1•h^－1. The characterization results of the catalysts suggest that the P-Mo-V mixed oxides with the mass loading ≤2.89% are highly dispersed in the channels of SBA-15. The oxides with weak acidity and low reduction temperature are favorable to the selective oxidation of CH₄ to HCHO.