镁改性FCC催化剂抗铁污染性能和机理研究

Study on anti-iron contamination performance and mechanism of magnesium-modified FCC catalyst

采用原位加入的改性方式,制备了镁改性FCC催化剂,利用N_(2)吸附-脱附、XRD、SEM、FTIR、循环老化装置及先进催化裂化评价装置等对催化剂的性质及抗铁污染性能进行了研究,并探讨了催化剂的抗铁污染机理。实验结果表明,镁改性对FCC催化剂的理化性质没有不利影响,反而可显著提高铁污染后催化剂比表面积和孔体积的保留率。铁污染的镁改性FCC催化剂的表面酸中心具有更高的大分子可接近性,有利于重油大分子在孔道内的裂化,相比常规铁污染的FCC催化剂,显示了更低的油浆产率和更高的汽油产率、总液收率及转化率。改性镁物种与铁物种能形成高热稳定性的镁-铁尖晶石,进而提高FCC催化剂的抗铁污染性能。

Magnesium-modified FCC catalyst(MgO-Cat)were prepared by in-situ modification method,and further characterized through N_(2) adsorption-desorption,XRD,SEM,FTIR,cyclic deactivation unit and advanced cracking evaluation unit to study its physiochemical properties and anti-iron contamination performance.Also,the anti-iron contamination mechanism of MgO-Cat was discussed.The experimental results indicate that magnesium-modification has no negative effect on the physiochemical properties of MgO-Cat,inversely can increase the retention rate of specific surface area and pore volume of iron-contaminated MgO-Cat obviously.The iron-contaminated MgO-Cat possessed much higher acid sites accessibility for big molecules,which is greatly helpful for the cracking conversion of heavy oil molecules.Compared with iron-contaminated traditional FCC catalyst,iron-contaminated MgO-Cat exhibits much lower slurry yield and much higher gasoline yield,total liquids yield and conversion.The magnesium species for modification can form highly-stable Mg-Fe spinel with iron species,and thus can improve the anti-iron contamination performance of FCC catalyst.