氧化铝和磷改性对非负载型催化剂结构和加氢脱硫性能的影响

采用共沉淀法制备了Ni-Mo非负载型加氢脱硫催化剂,利用X射线粉末衍射分析(XRD)、低温N₂吸附分析(BET)、红外光谱分析(Py-IR 、FT-IR)、氢气程序升温还原(H₂-TPR)、程序升温脱附分析(NH₃-TPD)、拉曼光谱分析(LRS)和气相色谱分析(GC-PFPD)等技术手段,考察了Al₂O₃和磷对催化剂结构性能的影响。 研究结果表明,Al₂O₃能够增加催化剂的孔容、孔径、比表面积,增加Lewis(L)酸酸量的同时形成了Brønsted(B)酸位。 在含有Al₂O₃的催化剂中加入磷会形成Al-P-O结构,阻止NiAl₂O₄尖晶石结构的形成,减小活性组分与Al₂O₃之间的作用;同时磷能够减少四面体配位Mo物种数量,增加八面体配位Mo物种数量。 催化剂具有较长的使用寿命;磷的加入使催化剂酸性由强酸性变成弱酸性,加氢脱硫活性由94%增加到99.8%。 在温度280℃,压力4.0 MPa、液时空速2.0 h^-1和氢油体积比500条件下,可将催化裂化柴油中的4-甲基二苯并噻吩(4-MDBT)、4,6-二甲基二苯并噻吩(4,6-DMDBT)和2,4,6-三甲基二苯并噻吩(2,4,6-TMDBT)深度脱除,硫含量由3950 μg/g降至7.9 μg/g。

Effect of Aluminium Oxide and Phosphorus Modification on Structure and Hydrodesulfurization Performance of Unsupported Catalysts

Unsupported Ni-Mo hydrodesulfurization catalysts were prepared by a coprecipitation method and characterized by X-ray diffraction(XRD), nitrogen physisorption measurement(BET), infrared spectroscopy(Py-IR, FI-IR), H₂-temperaure programmed reduction(H₂-TPR), temperature-programmed desorption of NH₃(NH₃-TPD), Laser Raman spectroscopy(LRS) and gas chromatography analysis(GC-PFPD) tests. The effects of Al₂O₃ and phosphorus addition on the structure of the catalysts were studied. The results indicate that the addition of Al₂O₃ greatly increases the pore diameter, specific surface area, the amount of the L acid sites and also promotes the formation of B acid sites. Addition of phosphorus leads to the formation of the Al-P-O structure instead of the NiAl₂O₄ structure, and weakens the interaction between active phase and Al₂O₃. The amount of tetrahedral Mo species decreases while the anount of octahedral Mo species increases. The catalysts has a longer service life. The catalyst acidity is changed from strong to weak by adding phosphorus. The hydrodesulfurization rate is increased from 94% to 99.8%. At 280 ℃, hydrogen pressure of 4 MPa, liquid hourly space velocity(LHSV) of 1.5 h^-1 and hydrogen-to-oil volume ratio of 500, 4-methyldibenzothiophene, 4,6-dimethyldibenzothiophene and 2,4,6-trimethyldibenzothiophene catalytic cracking are depthly removed in fluid catalytic cracking diesel oil; the sulphur concentration is decreased from 3950 μg/g to 7.9 μg/g.