磷、柠檬酸改性对MoW/Ni/Al2O3催化剂性质及加氢脱氮性能的影响

采用等体积浸渍法制备了以γ-Al₂O₃为载体，Ni、Mo、W为活性金属组分的三金属催化剂，考察了磷改性、柠檬酸改性以及磷-柠檬酸组合改性对催化剂性质、加氢脱氮性能和脱氮选择性的影响。通过NH₃-TPD、Py-IR、H₂-TPR、XPS和HRTEM对催化剂进行表征，结果表明：磷改性不但提高了催化剂的表面弱酸量，而且提高了金属的硫化性能，促进碱性氮和非碱性氮的脱除，但磷改性导致金属活性相的堆垛层数偏高、分散度下降；柠檬酸改性降低了催化剂活性金属氧化物的硫化温度，提高了催化剂的加氢活性，但对氢解性能基本没有影响，表现为非碱性氮脱除性能的提高；而磷-柠檬酸组合改性，不但提高了催化剂的氢解性能，而且改善了其加氢活性，使催化剂对焦化蜡油中碱性氮和非碱性氮的脱除率均得到大幅提升，分别达到80.1%、54.9%。

Effect of citric acid and phosphorus on properties and hydrodenitrogenation performance of MoW/Ni/Al2O3 catalysts

The trimetallic catalysts were prepared by the iso-volume impregnation method using nickel-molybdenum-tungsten as active metals and γ-Al₂O₃ as support. The properties of the catalysts modified by phosphorus, citric acid and phosphorus in cooperation with citric acid, as well as the catalytic performance of hydrodenitrogenation and denitrogenation selectivity were examined. The catalysts were characterized with NH₃-TPD, Py-IR, H₂-TPR, XPS and HRTEM. The results indicated that on the surface of the catalyst modified by phosphorus the amount of weak acid was increased. Also phosphorus promoted the sulfidation of active metals and improved the rate of removal of basic nitrogen and non-basic nitrogen. But phosphorus resulted in the increase of the stacked layers and decreased the dispersion of active metals. Citric acid added in the catalysts could lower the sulfuration temperature of the active metallic oxide, and improve the hydrogenation performance of catalysts; but it had no effect on hydrogenolysis activity, and focused on the removal of non-basic nitrogen. Phosphorus in cooperation with citric acid could not only improve the hydrogenolysis activity of catalysts, but also improve the hydrogenation performance of catalysts. As a result the rate of removal of basic nitrogen and non-basic nitrogen of the catalyst modified by phosphorus in cooperation with citric acid for coker gas oil was remarkably promoted, reaching 80.1% and 54.9% respectively.