不同压力下 Ni/A12O3催化剂上CH4部分氧化制合成气反应比较

摘要

采用以质谱为检测器的程序升温和瞬变实验技术研究了0.1MPa和0.7MPa条件下CH4部分氧化制合成气反应。结果表明，与0.1 MPa条件下一样，在700℃、0.7MPa下CH4可以在金属镍活性中心上迅速分解生成H2和表面NixC，但CH4不能在NiO上分解，也不能被其氧化。CH4的分解，作为在Ni/Al2O3催化剂上进行部分氧化制合成气反应的第一步，是一个体积增大的反应，因而加压会抑制反应的进行。正是由于在加压条件下CH4的分解受到抑制，才使得在0.7MPa下CH4的转化率明显低于0.1 MPa。此外，加压有助于维持催化剂表面处于还原状态，这有利于反应高转化率、高选择性地进行。%Partial oxidation of CH4 to syngas was investigated under 0.1 MPa and 0.7MPa using temperature-programmed and transient experimental technique with MS as the detector. CH4 can decompose over metallic Ni sites rapidly and can not over NiO under 0.7 MPa, which is the same as that under 0.1 MPa. The decomposition of CH4 over the Ni/A12O3 catalyst, the first step of partial oxidation of CH4 to syngas, is a volume increase reaction and is restrained under 0.7 MPa. The conversion of CH4 is affected by pressure markedly. Higher pressure is favorable for keeping the catalyst in its reduced state that is necessary for the reaction to proceed with high conversion and selectivity.