螯合剂对Co-Mo/Al2 O3成型加氢脱硫催化剂性能的影响

摘要

以拟薄水铝石为原料，添加有机溶剂，经挤条成型、干煅、焙烧制备了比表面积大、孔分布宽的柱状γ-Al2 O3载体；采用共浸渍法制备了系列Co-Mo/Al2 O3催化剂( CoO和MoO3质量分数分别为2%和8%)。利用低温氮吸附、XRD和H2-TPR技术对催化剂进行了表征，考察了螯合剂柠檬酸( CA)、草酸( OA)和乙二胺四乙酸( EDTA)对成型催化剂粗苯加氢脱硫活性的影响。结果表明，添加螯合剂后，催化剂的前驱体主要沉积在载体的3~10 nm中孔内，活性组分以无定形态高度分散在载体上。添加CA可提高催化剂的还原性，显著降低Mo6+的还原温度。在300℃、3.0 MPa、液体空速( LHSV)为2 h-1和氢油体积比为600的条件下，噻吩硫的脱除率可达到99.9%以上。%γ-Al2 O3 monolith support with high surface area and wide pore size distribution was obtained by extruding the mixture of pseudo boehmite and organic additives, as well as subsequent drying and calculation;a series of Co-Mo catalysts with ca. 8% molybdenum and 2% cobalt were prepared through co-impregnation of the support with solutions of ammonium heptamolybdate, cobalt nitrate and the chelating agent of citric acid ( CA) , oxalic acid ( OA ) and ethylenediamine tetraacetic acid ( EDTA ) . The Co-Mo/Al2 O3 catalysts were characterized by nitrogen sorption, XRD and H2-TPR; the effect of chelating agents on their textural properties and activity in hydrodesulphurisation ( HDS ) of a commercial crude benzol was investigated. The results indicated that the catalyst precursors were mostly deposited over the surface of the mesopores with a diameter between 3 and 10 nm; the addition of chelating agent results in a high dispersion of Co-Mo species on the alumina support. The H2-TPR results revealed that the addition of CA is able to improve the catalyst reducibility and shift the reduction temperature of Mo6+to lower temperature. For the HDS reaction of the real-feedstock in a down-flow tubular reactor under 300 ℃, 3. 0 MPa, a liquid hourly space velocity (LHSV) of 2 h-1, and a hydrogen/oil volume ratio of 600 , the removal of thiophene sulfur reaches 99 . 9% over the CA-promoted Co-Mo/Al2 O3 catalyst.